Manufacturing method for semiconductor device

Abstract

To provide a semiconductor device with less variation in transistor characteristic.SOLUTION: A manufacturing method for a semiconductor device includes the steps of: forming an opening that reaches an oxide semiconductor device in a structure including the oxide semiconductor device; filling the opening with a first conductor; forming a second conductor in contact with an upper surface of the first conductor; forming a first barrier insulating film by a sputtering method so as to cover the structure, the first conductor, and the second conductor; and forming a second barrier insulating film on the first barrier insulating film by an ALD method. The first barrier insulating film and the second barrier insulating film have a function of suppressing hydrogen diffusion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] 1. Field of the Invention

[0003] One embodiment of the present invention relates to a transistor, a semiconductor device, and an electronic device. Another embodiment of the present invention relates to a manufacturing method of a semiconductor device. Another embodiment of the present invention relates to a semiconductor wafer and a module.

[0002] In this specification and the like, a semiconductor device refers to any device that can function by utilizing semiconductor characteristics. Semiconductor elements such as transistors, semiconductor circuits, arithmetic devices, and memory devices are all embodiments of semiconductor devices. Display devices (liquid crystal display devices, light-emitting display devices, etc.), projection devices, lighting devices, electro-optical devices, power storage devices, memory devices, semiconductor circuits, imaging devices, electronic devices, and the like may be considered to include semiconductor devices.

[0003] Note that one aspect of the present invention is not limited to the above technical fields. One aspect of the invention disclosed in this specification relates to an object, a method, or a manufacturing method. Another aspect of the present invention relates to a process, a machine, a manufacture, or a composition of matter. [Background technology]

[0004] In recent years, the development of semiconductor devices has progressed, and LSIs, CPUs, and memories are mainly used. A CPU is a collection of semiconductor elements that have semiconductor integrated circuits (at least transistors and memories) separated from a semiconductor wafer and on which electrodes serving as connection terminals are formed.

[0005] Semiconductor circuits (IC chips) such as LSIs, CPUs, and memories are mounted on circuit boards, such as printed wiring boards, and are used as components of various electronic devices.

[0006] Furthermore, technology for constructing transistors using semiconductor thin films formed on substrates with insulating surfaces has attracted attention. Such transistors are widely used in electronic devices such as integrated circuits (ICs) and image display devices (also simply referred to as display devices). Silicon-based semiconductor materials are widely known as semiconductor thin films applicable to transistors, but oxide semiconductors have also attracted attention as other materials.

[0007] Furthermore, transistors using oxide semiconductors are known to have extremely low leakage current in a non-conducting state. For example, a low-power CPU utilizing the low leakage current characteristic of transistors using oxide semiconductors has been disclosed (see Patent Document 1). Also, for example, a memory device capable of retaining stored data for a long period of time utilizing the low leakage current characteristic of transistors using oxide semiconductors has been disclosed (see Patent Document 2).

[0008] Furthermore, in recent years, with the trend toward smaller and lighter electronic devices, there has been an increasing demand for higher density integrated circuits, and there is also a demand for improved productivity in semiconductor devices including integrated circuits. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-257187 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-151383 Summary of the Invention [Problem to be solved by the invention]

[0010] An object of one embodiment of the present invention is to provide a semiconductor device with little variation in transistor characteristics. Another object of one embodiment of the present invention is to provide a semiconductor device with favorable electrical characteristics. Another object of one embodiment of the present invention is to provide a semiconductor device with favorable reliability. Another object of one embodiment of the present invention is to provide a semiconductor device with high on-state current. Another object of one embodiment of the present invention is to provide a semiconductor device with high field-effect mobility. Another object of one embodiment of the present invention is to provide a semiconductor device with favorable frequency characteristics. Another object of one embodiment of the present invention is to provide a semiconductor device that can be miniaturized or highly integrated. Another object of one embodiment of the present invention is to provide a semiconductor device with low power consumption. Another object of one embodiment of the present invention is to provide a method for manufacturing the semiconductor device.

[0011] Note that the description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily solve all of these problems. Note that problems other than these will become apparent from the description of the specification, drawings, claims, etc., and it is possible to extract other problems from the description of the specification, drawings, claims, etc. [Means for solving the problem]

[0012] One embodiment of the present invention is a method for manufacturing a semiconductor device, the method including the steps of: forming an opening in a structure including an oxide semiconductor device, the opening reaching the oxide semiconductor device; filling the opening with a first conductor; forming a second conductor in contact with a top surface of the first conductor; forming a first barrier insulating film by a sputtering method to cover the structure, the first conductor, and the second conductor; and forming a second barrier insulating film over the first barrier insulating film by an ALD method, wherein the first barrier insulating film and the second barrier insulating film have a function of suppressing diffusion of hydrogen.

[0013] In the above, the first barrier insulating film is preferably silicon nitride. In the above, the second barrier insulating film is preferably silicon nitride. In the above, the hydrogen concentration of the first barrier insulating film is preferably lower than the hydrogen concentration of the second barrier insulating film.

[0014] In the above, it is preferable that the second barrier insulating film is formed by a PEALD method.In the above, it is preferable that the precursor used in forming the second barrier insulating film does not contain an organic substance.

[0015] In addition, in the above, before the step of forming the structure, the method may include a step of forming a third barrier insulating film by an ALD method and a step of forming a fourth barrier insulating film on the third barrier insulating film by a sputtering method, and the third barrier insulating film and the fourth barrier insulating film may have a function of suppressing hydrogen diffusion.

[0016] In the above, the third barrier insulating film is preferably silicon nitride. In the above, the fourth barrier insulating film is preferably silicon nitride. In the above, the hydrogen concentration of the fourth barrier insulating film is preferably lower than the hydrogen concentration of the third barrier insulating film.

[0017] In the above, it is preferable that the third barrier insulating film is formed by a PEALD method.In the above, it is preferable that the precursor used in forming the third barrier insulating film does not contain an organic substance.

[0018] In the above, the oxide semiconductor film included in the oxide semiconductor device is preferably formed by a sputtering method using a target containing one or more selected from In, Ga, and Zn. [Effects of the Invention]

[0019] According to one embodiment of the present invention, a semiconductor device with little variation in transistor characteristics can be provided. According to one embodiment of the present invention, a semiconductor device with favorable electrical characteristics can be provided. According to one embodiment of the present invention, a semiconductor device with favorable reliability can be provided. According to one embodiment of the present invention, a semiconductor device with high on-state current can be provided. According to one embodiment of the present invention, a semiconductor device with high field-effect mobility can be provided. According to one embodiment of the present invention, a semiconductor device with favorable frequency characteristics can be provided. According to one embodiment of the present invention, a semiconductor device that can be miniaturized or highly integrated can be provided. According to one embodiment of the present invention, a semiconductor device with low power consumption can be provided. According to one embodiment of the present invention, a manufacturing method of the semiconductor device can be provided.

[0020] Note that the description of these effects does not preclude the existence of other effects. Note that one embodiment of the present invention does not necessarily have all of these effects. Note that effects other than these will become apparent from the description in the specification, drawings, claims, etc., and it is possible to extract other effects from the description in the specification, drawings, claims, etc. [Brief explanation of the drawings]

[0021] [Figure 1] 1A to 1C are schematic diagrams of a semiconductor device according to one embodiment of the present invention. [Figure 2] 2A to 2C are schematic views illustrating a method for manufacturing a semiconductor device according to one embodiment of the present invention. [Figure 3] 3A to 3C are schematic views illustrating a method for manufacturing a semiconductor device according to one embodiment of the present invention. [Figure 4] 4A and 4B are a top view and a cross-sectional view of a semiconductor device according to one embodiment of the present invention. [Figure 5] 5A and 5B are cross-sectional views of a semiconductor device according to one embodiment of the present invention. [Figure 6]Figure 6A is a diagram explaining the classification of IGZO crystal structures, Figure 6B is a diagram explaining the XRD spectrum of a CAAC-IGZO film, and Figure 6C is a diagram explaining the electron microbeam diffraction pattern of a CAAC-IGZO film. [Figure 7] Fig. 7A is a plan view of a semiconductor device according to one embodiment of the present invention, and Figs. 7B and 7C are cross-sectional views of the semiconductor device according to one embodiment of the present invention. [Figure 8] FIG. 8 is a cross-sectional view illustrating a configuration of a memory device according to one embodiment of the present invention. [Figure 9] FIG. 9 is a cross-sectional view illustrating a configuration of a memory device according to one embodiment of the present invention. [Figure 10] 10A and 10B are block diagrams illustrating a configuration example of a storage device according to one embodiment of the present invention, and perspective views illustrating a configuration example of a storage device according to one embodiment of the present invention. [Figure 11] 11A to 11H are circuit diagrams illustrating configuration examples of a memory device according to one embodiment of the present invention. [Figure 12] 12A and 12B are schematic diagrams of a semiconductor device according to one embodiment of the present invention. [Figure 13] 13A and 13B are diagrams illustrating an example of an electronic component. [Figure 14] 14A to 14E are schematic diagrams of a memory device according to one embodiment of the present invention. [Figure 15] 15A to 15H are diagrams illustrating electronic devices according to one embodiment of the present invention. [Figure 16] FIG. 16 is a graph according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments will be described with reference to the drawings. However, it will be readily understood by those skilled in the art that the embodiments can be implemented in many different ways and that various changes in form and details can be made without departing from the spirit and scope of the present invention. Therefore, the present invention should not be interpreted as being limited to the description of the following embodiments.

[0023] In addition, in the drawings, sizes, layer thicknesses, or regions may be exaggerated for clarity. Therefore, the drawings are not necessarily limited to the scale. The drawings are schematic representations of ideal examples and are not limited to the shapes or values ​​shown in the drawings. For example, in actual manufacturing processes, layers or resist masks may be unintentionally thinned by processes such as etching, but this may not be reflected in the drawings to facilitate understanding. In addition, in the drawings, the same reference numerals may be used in common between different drawings for identical parts or parts having similar functions, and repeated explanations may be omitted. When referring to similar functions, the same hatch pattern may be used and no particular reference numeral may be assigned.

[0024] In order to make the invention easier to understand, particularly in top views (also called "plan views") or perspective views, some components may be omitted from the drawings. Also, some hidden lines may be omitted from the drawings.

[0025] In addition, in this specification, ordinal numbers such as first, second, etc. are used for convenience and do not indicate the order of processes or stacking. Therefore, for example, "first" can be appropriately replaced with "second" or "third," etc. in the description. Furthermore, the ordinal numbers used to identify one embodiment of the present invention may not match the ordinal numbers used in this specification.

[0026] Furthermore, in this specification, terms indicating arrangement such as "above" and "below" are used for convenience in describing the positional relationship between components with reference to the drawings. Furthermore, the positional relationship between components changes as appropriate depending on the direction in which each component is depicted. Therefore, the terms are not limited to those described in the specification, and can be rephrased appropriately depending on the situation.

[0027] For example, if it is explicitly stated in this specification that X and Y are connected, it is assumed that the specification also discloses cases in which X and Y are electrically connected, cases in which X and Y are functionally connected, and cases in which X and Y are directly connected. Therefore, it is not limited to a specific connection relationship, for example, a connection relationship shown in a figure or text, and it is assumed that connections other than those shown in a figure or text are also disclosed in a figure or text. Here, X and Y are assumed to be objects (e.g., devices, elements, circuits, wiring, electrodes, terminals, conductive films, layers, etc.).

[0028] In this specification and the like, a transistor is an element having at least three terminals including a gate, a drain, and a source. A transistor has a region (hereinafter also referred to as a channel formation region) where a channel is formed between the drain (drain terminal, drain region, or drain electrode) and the source (source terminal, source region, or source electrode), and a current can flow between the source and the drain through the channel formation region. In this specification and the like, the channel formation region refers to a region through which a current mainly flows.

[0029] Furthermore, the functions of the source and drain may be interchanged when transistors of different polarities are used, or when the direction of current flow changes during circuit operation, etc. For this reason, the terms source and drain may be used interchangeably in this specification and the like.

[0030] Note that the channel length refers to, for example, a region where the semiconductor (or a portion in the semiconductor through which current flows when the transistor is on) and the gate electrode overlap in a top view of a transistor, or the distance between the source (source region or source electrode) and the drain (drain region or drain electrode) in the channel formation region. Note that the channel length of one transistor does not necessarily have the same value in all regions. That is, the channel length of one transistor may not be fixed to a single value. Therefore, in this specification, the channel length is defined as any one value, maximum value, minimum value, or average value in the channel formation region.

[0031] The channel width refers to, for example, the length of a channel formation region in a region where a semiconductor (or a portion of the semiconductor through which current flows when the transistor is on) and a gate electrode overlap in a top view of a transistor, or the length of the channel formation region in a direction perpendicular to the channel length direction in the channel formation region. Note that the channel width of a single transistor does not necessarily have the same value in all regions. That is, the channel width of a single transistor may not be determined to a single value. Therefore, in this specification, the channel width refers to any one value, maximum value, minimum value, or average value in the channel formation region.

[0032] In this specification and the like, depending on the structure of a transistor, the channel width in a region where a channel is actually formed (hereinafter also referred to as an "effective channel width") may differ from the channel width shown in a top view of the transistor (hereinafter also referred to as an "apparent channel width"). For example, when a gate electrode covers the side surface of a semiconductor, the effective channel width may be larger than the apparent channel width, and the influence thereof may not be negligible. For example, in a fine transistor in which a gate electrode covers the side surface of a semiconductor, the proportion of the channel formation region formed on the side surface of the semiconductor may be large. In such a case, the effective channel width is larger than the apparent channel width.

[0033] In such cases, it may be difficult to estimate the effective channel width by actual measurement. For example, in order to estimate the effective channel width from the design value, it is necessary to assume that the shape of the semiconductor is known. Therefore, if the shape of the semiconductor is not accurately known, it is difficult to accurately measure the effective channel width.

[0034] In this specification, when simply referred to as a channel width, it may refer to an apparent channel width. Alternatively, when simply referred to as a channel width, it may refer to an effective channel width. Note that values ​​of the channel length, channel width, effective channel width, apparent channel width, etc. can be determined by analyzing a cross-sectional TEM image, etc.

[0035] Note that impurities in a semiconductor refer to, for example, anything other than the main component constituting the semiconductor. For example, an element with a concentration of less than 0.1 atomic % can be considered an impurity. The presence of impurities can, for example, increase the defect state density of the semiconductor or reduce the crystallinity. When the semiconductor is an oxide semiconductor, impurities that change the characteristics of the semiconductor include, for example, Group 1 elements, Group 2 elements, Group 13 elements, Group 14 elements, Group 15 elements, and transition metals other than the main components of the oxide semiconductor, such as hydrogen, lithium, sodium, silicon, boron, phosphorus, carbon, and nitrogen. Note that water can also function as an impurity. For example, the inclusion of impurities can cause oxygen deficiency (V) in the oxide semiconductor. O :oxygen vacancy) may be formed.

[0036] In this specification and the like, silicon oxynitride refers to a material whose composition contains more oxygen than nitrogen, and silicon nitride oxide refers to a material whose composition contains more nitrogen than oxygen.

[0037] In this specification and the like, the term "insulator" can be replaced with an insulating film or an insulating layer, the term "conductor" can be replaced with a conductive film or a conductive layer, and the term "semiconductor" can be replaced with a semiconductor film or a semiconductor layer.

[0038] Furthermore, in this specification, "parallel" refers to a state in which two straight lines are arranged at an angle of -10 degrees or more and 10 degrees or less. Therefore, it also includes cases in which the angle is -5 degrees or more and 5 degrees or less. Furthermore, "substantially parallel" refers to a state in which two straight lines are arranged at an angle of -30 degrees or more and 30 degrees or less. Furthermore, "perpendicular" refers to a state in which two straight lines are arranged at an angle of 80 degrees or more and 100 degrees or less. Therefore, it also includes cases in which the angle is 85 degrees or more and 95 degrees or less. Furthermore, "substantially perpendicular" refers to a state in which two straight lines are arranged at an angle of 60 degrees or more and 120 degrees or less.

[0039] In this specification and the like, the term "metal oxide" refers to an oxide of a metal in a broad sense. Metal oxides are classified into oxide insulators, oxide conductors (including transparent oxide conductors), oxide semiconductors (also referred to as "oxide semiconductors" or simply as "OSs"). For example, when a metal oxide is used in a semiconductor layer of a transistor, the metal oxide may be referred to as an oxide semiconductor. In other words, an OS transistor can be rephrased as a transistor including a metal oxide or an oxide semiconductor.

[0040] Furthermore, in this specification and the like, normally off means that when no potential is applied to the gate or when a ground potential is applied to the gate, the drain current flowing through the transistor per 1 μm of channel width is 1×10 -20 A or less, 1 x 10 at 85°C -18 A or less, or 1 x 10 at 125°C -16 This means that it is A or below.

[0041] (Embodiment 1) In this embodiment, an example of a semiconductor device according to one embodiment of the present invention and a manufacturing method thereof will be described with reference to FIGS. 1A to 3C.

[0042] <Configuration example of semiconductor device> 1A is a schematic diagram of a semiconductor device 10 according to one embodiment of the present invention. The semiconductor device 10 according to one embodiment of the present invention includes an element layer 13 formed on a substrate (not shown), an oxide semiconductor element 12 included in the element layer 13, a conductor 14 disposed in an opening formed in the element layer 13, a conductor 15 disposed on the conductor 14, an insulator 11a disposed to cover the element layer 13, the conductor 14, and the conductor 15, and an insulator 11b on the insulator 11a. Note that in this specification and the like, the oxide semiconductor element may be referred to as an oxide semiconductor device. Also, in this specification and the like, the element layer 13 may be referred to as a structure.

[0043] The element layer 13 has an interlayer insulating film laminated above or below the oxide semiconductor element 12. Examples of interlayer insulating films that can be used include silicon oxide, silicon oxynitride, silicon oxide doped with fluorine, silicon oxide doped with carbon, silicon oxide doped with carbon and nitrogen, and silicon oxide having vacancies. Note that while FIG. 1A illustrates a state in which the element layer 13 includes one oxide semiconductor element 12, the present invention is not limited to this. The element layer 13 may also include a plurality of oxide semiconductor elements 12.

[0044] The conductor 14 is disposed in an opening formed in the interlayer insulating film of the element layer 13. The opening reaches the oxide semiconductor element 12, and the conductor 14 is electrically connected to the oxide semiconductor element 12. In other words, the conductor 14 functions as a plug that electrically connects the conductor 15 to the oxide semiconductor element 12. The conductor 14 can be, for example, a metal element selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, lanthanum, or the like, an alloy containing the above-mentioned metal element, or an alloy combining the above-mentioned metal elements. Furthermore, conductive materials that are resistant to oxidation, such as tantalum nitride, titanium nitride, tungsten, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, and oxides containing lanthanum and nickel, or materials that maintain conductivity even when absorbing oxygen, may also be used.

[0045] The conductor 15 is provided in contact with the upper surface of the conductor 14. The portion of the conductor 15 that does not overlap with the conductor 14 is in contact with the uppermost interlayer insulating film of the element layer 13. The conductor 15 functions as a wiring, an electrode, a terminal, or the like that is electrically connected to the oxide semiconductor element 12. The conductor 15 can be formed using a conductive material that can be used for the conductor 14. Note that although FIG. 1A shows two conductors 14 and two conductors 15, the present invention is not limited to this. The conductors 14 and 15 can be provided as appropriate depending on the configuration of the oxide semiconductor element 12, etc.

[0046] The oxide semiconductor element 12 includes at least one of circuit elements such as a switch, a transistor, a capacitor, an inductor, a resistor, and a diode. Furthermore, an oxide semiconductor film is provided in at least a part of these circuit elements. For example, the oxide semiconductor element 12 may be a transistor including a channel formation region in an oxide semiconductor film. Specific examples of the oxide semiconductor element 12 and the like will be described in the following embodiments.

[0047] For example, a metal oxide such as In-M-Zn oxide containing indium, an element M, and zinc (the element M is one or more selected from aluminum, gallium, yttrium, tin, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, etc.) may be used as the oxide semiconductor film. Alternatively, In-Ga oxide, In-Zn oxide, or indium oxide may be used as the oxide semiconductor film.

[0048] The above oxide semiconductor film has a band gap of 2 eV or more, preferably 2.5 eV or more. By using an oxide semiconductor film with such a wide band gap, the off-state current of a transistor can be reduced.

[0049] The oxide semiconductor film preferably has crystallinity. In particular, it is preferable to use a c-axis aligned crystalline oxide semiconductor (CAAC-OS) as the oxide semiconductor film.

[0050] CAAC-OS has a highly crystalline and dense structure, and is free of impurities and defects (e.g., oxygen vacancies (V OThe CAAC-OS is a metal oxide with a low oxygen vacancy. In particular, after the formation of the metal oxide, heat treatment at a temperature at which the metal oxide does not become polycrystallized (for example, 400°C or higher and 600°C or lower) can give the CAAC-OS a more highly crystalline and dense structure. In this way, the density of the CAAC-OS can be increased, thereby further reducing the diffusion of impurities in the CAAC-OS.

[0051] On the other hand, since it is difficult to identify clear grain boundaries in CAAC-OS films, it is unlikely that a decrease in electron mobility due to grain boundaries occurs. Therefore, oxide semiconductor films containing CAAC-OS films have stable physical properties. Therefore, oxide semiconductor films containing CAAC-OS films are heat-resistant and highly reliable.

[0052] An oxide semiconductor film with a low carrier concentration is preferably used for a region where a channel of a transistor is formed. To reduce the carrier concentration of an oxide semiconductor film, the impurity concentration in the oxide semiconductor film may be reduced to reduce the density of defect states. In this specification and the like, a low impurity concentration and a low density of defect states are referred to as a highly pure intrinsic or substantially highly pure intrinsic oxide semiconductor. Examples of impurities in an oxide semiconductor include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, and silicon.

[0053] In particular, hydrogen contained in the oxide semiconductor film reacts with oxygen that bonds with metal atoms to form water, which causes oxygen vacancies (V O ) may be formed. Furthermore, defects in which hydrogen enters oxygen vacancies (hereinafter referred to as V OH.) may function as a donor and generate electrons as carriers. In addition, some of the hydrogen may bond with oxygen that is bonded to a metal atom to generate electrons as carriers. Therefore, a transistor using an oxide semiconductor film containing a large amount of hydrogen is likely to have normally-on characteristics (a channel exists and current flows through the transistor even when no voltage is applied to the gate electrode). Furthermore, if the in-plane distribution of the hydrogen concentration varies, the electrical characteristics of the transistor may vary according to the in-plane distribution of the hydrogen concentration. Furthermore, because hydrogen in an oxide semiconductor film is easily moved by stress such as heat or an electric field, the reliability of the transistor may be reduced if the oxide semiconductor film contains a large amount of hydrogen. Therefore, in the region where a channel is formed in the oxide semiconductor film, impurities, oxygen vacancies, and V O It is preferable that H be reduced as much as possible. In other words, it is preferable that the region in the oxide semiconductor film where a channel is formed has a reduced carrier concentration and is i-type (intrinsic) or substantially i-type.

[0054] However, even if the oxide semiconductor film is formed with reduced hydrogen in the oxide semiconductor film, hydrogen may diffuse from the outside. For example, when an organic resin such as polyimide is provided on the oxide semiconductor element 12, hydrogen contained in the organic resin may diffuse.

[0055] Therefore, in one embodiment of the present invention, insulators 11a and 11b that function as barrier insulating films against impurities such as hydrogen are provided over the element layer 13 and the conductor 15. Providing such insulators 11a and 11b can reduce the diffusion of impurities such as hydrogen into the oxide semiconductor film from above the element layer 13. Furthermore, providing insulators 11a and 11b to cover not only the element layer 13 but also the conductor 15 that functions as a wiring can reduce the diffusion of impurities such as hydrogen into the oxide semiconductor film through the conductor 15 and the conductor 14. Note that hereinafter, insulators 11a and 11b may be collectively referred to as insulator 11.

[0056] In this specification, a barrier insulating film refers to an insulating film having barrier properties. In this specification, the barrier properties refer to a function of suppressing the diffusion of a corresponding substance (also referred to as low permeability) or a function of capturing and fixing a corresponding substance (also referred to as gettering).

[0057] As described above, the insulator 11 is preferably an insulator that has the function of suppressing hydrogen diffusion, and preferably has lower hydrogen permeability than at least one of the interlayer insulating films included in the element layer 13. For example, aluminum oxide, magnesium oxide, hafnium oxide, gallium oxide, indium gallium zinc oxide, silicon nitride, or silicon nitride oxide can be used as the insulator 11. In particular, it is preferable to use silicon nitride, which has a high hydrogen barrier property.

[0058] The insulator 11a is disposed in contact with the upper surface of the interlayer insulating film at the top of the element layer 13 and the upper surface and side surfaces of the conductor 15. Furthermore, if a pattern shift or the like occurs in the conductor 15, the insulator 11a may come into contact with part of the conductor 14. Therefore, if the insulator 11a itself contains a high concentration of hydrogen, there is a risk that hydrogen will diffuse into the oxide semiconductor element 12 via the interlayer insulating film, the conductor 14, or the conductor 15.

[0059] Therefore, it is preferable that the insulator 11a has a low hydrogen concentration. The insulator 11a preferably has a lower hydrogen concentration than at least one of the interlayer insulating films included in the element layer 13, and more preferably has a lower hydrogen concentration than the insulator 11b. Therefore, it is preferable that the insulator 11a is deposited by a method that does not use a gas containing hydrogen as a deposition gas. For example, the insulator 11a may be deposited by a sputtering method.

[0060] Furthermore, since the insulator 11a is formed to cover the conductor 15, the surface underlying the insulator 11a has relatively pronounced irregularities, which may cause pinholes or discontinuities to form in the insulator 11a. In this case, the pinholes or discontinuities formed in the insulator 11a may become paths through which hydrogen diffuses into the element layer 13.

[0061] Therefore, it is preferable that the insulator 11b has better covering properties than the insulator 11a. With this configuration, even if a pinhole or a step is formed in the insulator 11a, the insulator 11b can cover the pinhole or step, thereby preventing hydrogen from entering.

[0062] The insulator 11b is preferably formed by a method with good coating properties, such as atomic layer deposition (ALD). In particular, it is preferably formed by using the plasma-enhanced ALD (PEALD) method, which allows film formation at relatively low temperatures. Furthermore, when forming the film by the PEALD method, it is preferably formed using a precursor that does not contain organic substances. This allows the hydrogen concentration in the insulator 11b to be reduced.

[0063] By providing such an insulator 11, it is possible to reduce the diffusion of hydrogen from above the insulator 11 and from the insulator 11 itself to the element layer 13, thereby reducing the hydrogen concentration in the channel formation region of the oxide semiconductor element 12. As a result, a semiconductor device with little variation in transistor characteristics can be provided. Also, a semiconductor device with good reliability can be provided. Also, a semiconductor device with good electrical characteristics can be provided.

[0064] 1A shows a configuration in which the insulator 11 functioning as a barrier insulating film is provided on the element layer 13, but the present invention is not limited to this. As shown in FIG. 1B, the insulator 18 functioning as a barrier insulating film may be disposed below the element layer 13.

[0065] Insulator 18 has a layered structure of insulator 18b and insulator 18a on insulator 18b. Here, insulator 18a is preferably made of a barrier insulating film that can be used for insulator 11a, and insulator 18b is preferably made of a barrier insulating film that can be used for insulator 11b. In other words, the layered structure of insulator 18 is preferably provided upside down with respect to insulator 11.

[0066] With this stacked structure, the insulator 18a in contact with the interlayer insulating film below the element layer 13 has a reduced hydrogen concentration, similar to the insulator 11a, and therefore it is possible to reduce the diffusion of hydrogen from the insulator 18 itself to the interlayer insulating film. Furthermore, even if the base of the insulator 18 is uneven and pinholes or discontinuities are formed in the insulator 18a, the insulator 18b can close the pinholes or discontinuities, thereby reducing the penetration of hydrogen from below the element layer 13.

[0067] 1C, the insulator 11 may be provided so that the insulator 11a contacts the side surface of the element layer 13. Furthermore, the insulator 11a may be configured to contact the insulator 18a in a region where it does not overlap with the element layer 13. In this case, it is preferable that the region where the insulator 11a and the insulator 18a contact each other is formed so as to surround the element layer 13. With this configuration, it is possible to reduce the diffusion of hydrogen from the outside into the element layer 13 not only from the top and bottom surfaces of the element layer 13 but also from the side surfaces.

[0068] <Method for manufacturing semiconductor device> Next, a manufacturing method of the semiconductor device 10 according to one embodiment of the present invention, which is shown in FIG. 1A, will be described with reference to FIGS. 2A to 3C.

[0069] In this specification, insulating materials for forming insulators, conductive materials for forming conductors, or semiconductor materials for forming semiconductors can be formed as films by using a sputtering method, a chemical vapor deposition (CVD) method, a molecular beam epitaxy (MBE) method, a pulsed laser deposition (PLD) method, an ALD method, or the like, as appropriate.

[0070] There are three types of sputtering methods: RF sputtering, which uses a high-frequency power supply for sputtering; DC sputtering, which uses a direct current power supply; and pulsed DC sputtering, which changes the voltage applied to the electrode in a pulsed manner. RF sputtering is mainly used to deposit insulating films, while DC sputtering is mainly used to deposit metal conductive films. Pulsed DC sputtering is mainly used to deposit compounds such as oxides, nitrides, and carbides using reactive sputtering.

[0071] CVD methods can be classified into plasma-enhanced CVD (PECVD), which uses plasma, thermal CVD (TCVD: Thermal CVD), which uses heat, and photo-CVD (Photo-CVD), which uses light. They can also be further divided into metal CVD (MCVD: Metal CVD) and metal-organic CVD (MOCVD: Metal Organic CVD) depending on the source gas used.

[0072] The plasma CVD method can produce high-quality films at relatively low temperatures. Furthermore, because the thermal CVD method does not use plasma, it is a film formation method that can minimize plasma damage to the workpiece. For example, wiring, electrodes, elements (transistors, capacitors, etc.) included in a semiconductor device may become charged up by receiving electric charge from the plasma. In this case, the accumulated electric charge may destroy the wiring, electrodes, elements, etc. included in the semiconductor device. On the other hand, the thermal CVD method, which does not use plasma, does not cause such plasma damage, and therefore can increase the yield of semiconductor devices. Furthermore, because the thermal CVD method does not cause plasma damage during film formation, it can produce films with fewer defects.

[0073] As the ALD method, a thermal ALD method in which a reaction between a precursor and a reactant is carried out using only thermal energy, a PEALD method in which a plasma-excited reactant is used, or the like can be used.

[0074] CVD and ALD differ from sputtering, which deposits particles emitted from a target. Therefore, they are film formation methods that are less affected by the shape of the workpiece and have good step coverage. ALD, in particular, offers excellent step coverage and thickness uniformity, making it suitable for coating the surfaces of openings with high aspect ratios. However, because ALD has a relatively slow film formation rate, it may be preferable to use it in combination with other film formation methods, such as CVD, which has a faster film formation rate.

[0075] Furthermore, the CVD method allows deposition of a film with any composition by adjusting the flow rate ratio of the source gases. For example, the CVD method allows deposition of a film with a continuously changing composition by changing the flow rate ratio of the source gases during deposition. When deposition is performed while changing the flow rate ratio of the source gases, the time required for deposition can be shortened compared to deposition using multiple deposition chambers because no time is required for transport and pressure adjustment. Therefore, the productivity of semiconductor devices can be improved in some cases.

[0076] Furthermore, in the ALD method, a film of any composition can be formed by simultaneously introducing multiple different precursors or by controlling the number of cycles of each precursor.

[0077] First, a substrate (not shown) is prepared, and an element layer 13 including an oxide semiconductor element 12 is formed on the substrate. The interlayer insulating film of the element layer 13 can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like. For example, a silicon oxide film may be formed as the interlayer insulating film by a sputtering method.

[0078] Next, an opening 19 is formed in the interlayer insulating film of the element layer 13, reaching the oxide semiconductor element 12 (see FIG. 2A). The opening can be formed by lithography. Although wet etching may be used to form the opening, dry etching is preferable for fine processing.

[0079] Next, the conductor 14 is embedded in the opening 19 (see FIG. 2B). A conductive film that can be used for the above-mentioned conductor 14 is formed so as to embed the opening 19, and the conductive film is subjected to a chemical mechanical polishing (CMP) process or the like to form the conductor 14. The conductive film can be formed using a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like.

[0080] By performing CMP on the conductive film until the upper surface of the interlayer insulating film at the top of the element layer 13 is exposed, the conductive film remains only in the opening 19, thereby forming a conductor 14 with a flat upper surface. Note that the CMP process may remove part of the upper surface of the interlayer insulating film.

[0081] Next, a conductive film 15A is formed to cover the element layer 13 and the conductor 14 (see FIG. 2C). The conductive film 15A may be any conductive film that can be used for the above-mentioned conductor 14. The conductive film 15A can be formed by a sputtering method, a CVD method, an MBE method, a PLD method, an ALD method, or the like.

[0082] Next, the conductive film 15A is processed by lithography to form the conductor 15 that contacts the upper surface of the conductor 14 (see FIG. 3A). At this time, a part of the interlayer insulating film of the element layer 13 may be removed in a region where the conductor 15 does not overlap with the interlayer insulating film. As a result, the height of the region of the top surface of the element layer 13 that overlaps with the conductor 14 may become higher than the other regions.

[0083] Next, the insulator 11a is formed to cover the element layer 13, the conductor 14, and the conductor 15 (see FIG. 3B). The insulator 11a may be formed using any of the insulating materials having the above-mentioned hydrogen barrier properties, and is preferably formed using a nitride containing silicon, such as silicon nitride. The insulator 11a is preferably formed using a sputtering method. By using a sputtering method that does not require the use of hydrogen-containing molecules in the film formation gas, the hydrogen concentration in the insulator 11a can be reduced.

[0084] Next, insulator 11b is deposited on insulator 11a (see FIG. 3C). The insulator 11b may be made of any of the insulating materials having hydrogen barrier properties described above, and is preferably made of a silicon-containing nitride, such as silicon nitride. The insulator 11b is preferably deposited by the ALD method, which provides good coverage, and more preferably by the PEALD method.

[0085] When forming the insulator 11b by the PEALD method, it is preferable to use a precursor that does not contain organic substances such as hydrocarbons (hereinafter referred to as an inorganic precursor). By forming the insulator 11b using an inorganic precursor, the hydrogen concentration in the insulator 11b can be reduced. The inorganic precursor may contain silicon and may further contain a halogen element. If the inorganic precursor contains a halogen element, the halogen element may be contained as an impurity in the insulator 11b. The amount of impurities can be determined using secondary ion mass spectrometry (SIMS) or X-ray photoelectron spectroscopy (XPS).

[0086] However, the present invention is not limited to the ALD method using inorganic precursors, and precursors containing organic substances may also be used in some cases.

[0087] Furthermore, when forming a silicon nitride film by the PEALD method, nitrogen radicals are used as a reactant. Nitrogen radicals are obtained by converting nitrogen gas into plasma. Nitrogen plasma contains nitrogen in the form of molecules, radicals, ions, or the like. For example, nitrogen plasma containing nitrogen radicals can be generated by applying high frequency waves such as RF or microwaves to nitrogen gas. In this case, it is preferable that the reactant does not contain hydrogen. This allows the hydrogen concentration in the insulator 11b to be reduced.

[0088] In this manner, the semiconductor device 10 shown in FIG. 1A can be fabricated.

[0089] 1B, before forming the element layer 13 shown in FIG. 2A, the insulator 18b is formed, the insulator 18a is formed on the insulator 18b, and the element layer 13 is formed on the insulator 18a. The insulator 18a can be formed by the same method as the insulator 11a. The insulator 18b can be formed by the same method as the insulator 11b.

[0090] 1C, in the method for fabricating the semiconductor device 10 shown in FIG. 1B, the element layer 13 may be etched before the insulator 11a is formed so that the insulator 11a covers the side surfaces of the element layer 13. By exposing the top surface of the insulator 18a in this etching, a region where the insulators 11a and 18a are in contact with each other can be formed outside the element layer 13. This allows the element layer 13 to be sealed with the insulators 11a and 18a.

[0091] In the above description, the insulator 11 has been shown as having a laminated structure of the insulators 11a and 11b, but the present invention is not necessarily limited to this. For example, if the coverage of the insulator 11a is sufficiently good and no pinholes or discontinuities are formed, it is possible to provide only the insulator 11a without providing the insulator 11b. Also, for example, if the hydrogen concentration of the insulator 11b is sufficiently low, it is possible to provide only the insulator 11b without providing the insulator 11a. Similarly, the insulator 18 can be provided with only the insulator 18a or only the insulator 18b.

[0092] According to one embodiment of the present invention, a novel semiconductor device can be provided. Alternatively, according to one embodiment of the present invention, a manufacturing method of a novel semiconductor device can be provided. Alternatively, according to one embodiment of the present invention, a semiconductor device with little variation in transistor characteristics can be provided. Alternatively, according to one embodiment of the present invention, a semiconductor device with favorable electrical characteristics can be provided. Alternatively, according to one embodiment of the present invention, a semiconductor device with favorable reliability can be provided.

[0093] At least part of the structures, methods, and the like described in this embodiment mode can be implemented in appropriate combination with other embodiment modes and examples described in this specification.

[0094] (Embodiment 2) In this embodiment, a semiconductor device including a transistor 200 will be described as a specific example of the semiconductor device 10 described in Embodiment 1 with reference to FIGS. 4A to 7C.

[0095] <Configuration example of semiconductor device> The configuration of a semiconductor device corresponding to the semiconductor device 10 shown in FIG. 1B will be described with reference to FIGS. 4A and 4B. FIGS. 4A and 4B are a top view and a cross-sectional view, respectively, of a semiconductor device having a transistor 200. FIG. 4A is a top view of the semiconductor device. FIG. 4B is a cross-sectional view of the portion indicated by the dashed dotted line A1-A2 in FIG. 4A, and is also a cross-sectional view of the transistor 200 in the channel length direction. Note that some elements are omitted from the top view of FIG. 4A for clarity.

[0096] A semiconductor device of one embodiment of the present invention includes an insulator 212 over a substrate (not shown), an insulator 214 over the insulator 212, a transistor 200 over the insulator 214, an insulator 280 over the transistor 200, an insulator 282 over the insulator 280, an insulator 283 over the insulator 282, an insulator 288 over the insulator 283, an insulator 274 over the insulator 288, and an insulator 285 over the insulator 283 and the insulator 274. Here, the insulator 212 preferably has a stacked structure of an insulator 212b and an insulator 212a over the insulator 212b.

[0097] 4A and 4B. Insulator 283 contacts a portion of the top surface of insulator 214, the side surfaces of insulator 216, insulator 222, insulator 275, insulator 280, and insulator 282, as well as the side surfaces and top surface of insulator 282. The heights of the tops of insulators 283, 288, and 274 are approximately the same.

[0098] The transistor 200 also includes a conductor 240 (conductor 240a and conductor 240b) that is electrically connected to the transistor 200 and functions as a plug. Note that an insulator 241 (insulator 241a and insulator 241b) is provided in contact with the side surface of the conductor 240 that functions as a plug. Furthermore, a conductor 246 (conductor 246a and conductor 246b) that is electrically connected to the conductor 240 and functions as a wiring is provided on the insulator 285 and the conductor 240. Furthermore, an insulator 286 is provided to cover the conductor 246 and the insulator 285. The insulator 286 preferably has a stacked structure of an insulator 286a and an insulator 286b on the insulator 286a.

[0099] Here, the transistor 200 corresponds to the oxide semiconductor element 12 described in Embodiment 1. The insulator 212 (insulator 212a, insulator 212b) corresponds to the insulator 18 (insulator 18a, insulator 18b) described in Embodiment 1. The conductor 240 corresponds to the conductor 14 described in Embodiment 1. The conductor 246 corresponds to the conductor 15 described in Embodiment 1. The insulator 286 (insulator 286a, insulator 286b) corresponds to the insulator 11 (insulator 11a, insulator 11b) described in Embodiment 1. Therefore, for these, the description of Embodiment 1 can be referred to in addition to the description of this embodiment.

[0100] Insulator 241a is provided in contact with the inner walls of the openings of insulators 275, 280, 282, 283, and 285, and conductor 240a is provided in contact with the side surfaces of insulator 241a. Insulator 241b is provided in contact with the inner walls of the openings of insulators 275, 280, 282, 283, and 285, and conductor 240b is provided in contact with the side surfaces of insulator 241b. Note that insulator 241 has a structure in which a first insulator is provided in contact with the inner walls of the openings, and a second insulator is provided further inward. Note that conductor 240 has a structure in which a first conductor is provided in contact with the side surfaces of insulator 241, and a second conductor is provided further inward. Here, the height of the top surface of conductor 240 and the height of the top surface of insulator 285 in the region overlapping with conductor 246 are approximately the same.

[0101] Although the transistor 200 has been described as having a stacked structure of the first insulator of the insulator 241 and the second insulator of the insulator 241, the present invention is not limited to this. For example, the insulator 241 may be provided as a single layer or a stacked structure of three or more layers. Furthermore, the transistor 200 has been described as having a stacked structure of the first conductor of the conductor 240 and the second conductor of the conductor 240, but the present invention is not limited to this. For example, the conductor 240 may be provided as a single layer or a stacked structure of three or more layers. When a structure has a stacked structure, ordinal numbers may be assigned to indicate the order of formation to distinguish the structures.

[0102] [Transistor 200] As shown in FIGS. 4A and 4B , the transistor 200 includes an insulator 216 on an insulator 214, a conductor 205 (conductor 205a and conductor 205b) disposed so as to be embedded in the insulator 214 or the insulator 216, an insulator 222 on the insulator 216 and on the conductor 205, an insulator 224 on the insulator 222, an oxide 230a on the insulator 224, an oxide 230b on the oxide 230a, a conductor 242a on the oxide 230b, an insulator 271a on the conductor 242a, and an oxide 271b on the oxide 271b. 30b, conductor 242b on oxide 230b, insulator 271b on conductor 242b, insulator 252 on oxide 230b, insulator 250 on insulator 252, insulator 254 on insulator 250, conductor 260 (conductor 260a and conductor 260b) located on insulator 254 and overlapping with part of oxide 230b, and insulator 275 arranged on insulator 222, insulator 224, oxide 230a, oxide 230b, conductor 242a, conductor 242b, insulator 271a, and insulator 271b. Here, insulator 252 contacts the upper surface of insulator 222, the side surface of insulator 224, the side surface of oxide 230a, the side surface and upper surface of oxide 230b, the side surface of conductor 242, the side surface of insulator 271, the side surface of insulator 275, the side surface of insulator 280, and the lower surface of insulator 250. Furthermore, the upper surface of conductor 260 is disposed so as to be at approximately the same height as the top of insulator 254, the top of insulator 250, the top of insulator 252, and the upper surface of insulator 280. Furthermore, insulator 282 contacts at least a portion of the upper surfaces of conductor 260, insulator 252, insulator 250, insulator 254, and insulator 280.

[0103] In the following, the oxide 230a and the oxide 230b may be collectively referred to as the oxide 230. The conductor 242a and the conductor 242b may be collectively referred to as the conductor 242. The insulator 271a and the insulator 271b may be collectively referred to as the insulator 271.

[0104] Openings are provided in the insulator 280 and the insulator 275, reaching the oxide 230b. The insulator 252, the insulator 250, the insulator 254, and the conductor 260 are disposed in the openings. In addition, the conductor 260, the insulator 252, the insulator 250, and the insulator 254 are disposed between the insulator 271a and the conductor 242a and the insulator 271b and the conductor 242b in the channel length direction of the transistor 200. The insulator 254 has a region in contact with the side surface of the conductor 260 and a region in contact with the bottom surface of the conductor 260.

[0105] The oxide 230 preferably includes an oxide 230a disposed on the insulator 224 and an oxide 230b disposed on the oxide 230a. By providing the oxide 230a below the oxide 230b, it is possible to suppress the diffusion of impurities from structures formed below the oxide 230a to the oxide 230b.

[0106] Note that in the transistor 200, the oxide 230 has a two-layer structure of the oxide 230a and the oxide 230b, but the present invention is not limited to this. For example, the oxide 230b may have a single layer or a stacked structure of three or more layers, or each of the oxide 230a and the oxide 230b may have a stacked structure.

[0107] The conductor 260 functions as a first gate (also referred to as a top gate) electrode, and the conductor 205 functions as a second gate (also referred to as a back gate) electrode. The insulators 252, 250, and 254 function as first gate insulators, and the insulators 222 and 224 function as second gate insulators. The gate insulators may also be referred to as a gate insulating layer or a gate insulating film. The conductor 242a functions as either a source or a drain, and the conductor 242b functions as the other. At least a part of a region of the oxide 230 that overlaps with the conductor 260 functions as a channel formation region.

[0108] FIG. 5A shows an enlarged view of the vicinity of the channel formation region in FIG. 4B. When oxygen is supplied to the oxide 230b, a channel formation region is formed in the region between the conductor 242a and the conductor 242b. Therefore, as shown in FIG. 5A, the oxide 230b includes a region 230bc that functions as the channel formation region of the transistor 200, and regions 230ba and 230bb that are provided on either side of the region 230bc and function as source and drain regions. At least a portion of the region 230bc overlaps with the conductor 260. In other words, the region 230bc is located in the region between the conductor 242a and the conductor 242b. The region 230ba overlaps with the conductor 242a, and the region 230bb overlaps with the conductor 242b.

[0109] The region 230bc, which functions as a channel formation region, has fewer oxygen vacancies or a lower impurity concentration than the regions 230ba and 230bb, making it a high-resistivity region with a low carrier concentration. Therefore, the region 230bc can be said to be i-type (intrinsic) or substantially i-type. The region 230bc can be easily formed, for example, by microwave treatment in an oxygen-containing atmosphere. Here, microwave treatment refers to treatment using, for example, an apparatus with a power source that generates high-density plasma using microwaves. Furthermore, in this specification and elsewhere, microwaves refer to electromagnetic waves having a frequency of 300 MHz or more and 300 GHz or less.

[0110] Furthermore, the regions 230ba and 230bb, which function as source and drain regions, have many oxygen vacancies or high concentrations of impurities such as hydrogen, nitrogen, and metal elements, which increases the carrier concentration and reduces resistance. That is, the regions 230ba and 230bb are n-type regions with a higher carrier concentration and lower resistance than the region 230bc.

[0111] Here, the carrier concentration of the region 230bc that functions as a channel forming region is 1×10 18 cm -3 Preferably, it is 1×10 or less.17 cm -3 More preferably, it is less than 1×10 16 cm -3 More preferably, it is less than 1×10 13 cm -3 More preferably, it is less than 1×10 12 cm -3 The lower limit of the carrier concentration of the region 230bc that functions as a channel formation region is not particularly limited, but is preferably, for example, 1×10 -9 cm -3 It can be said that:

[0112] Furthermore, a region may be formed between region 230bc and region 230ba or region 230bb, whose carrier concentration is equal to or lower than that of region 230ba and region 230bb, and equal to or higher than that of region 230bc. That is, this region functions as a junction region between region 230bc and region 230ba or region 230bb. The junction region may have a hydrogen concentration equal to or lower than that of region 230ba and region 230bb, and equal to or higher than that of region 230bc. The junction region may also have oxygen vacancies equal to or lower than those of region 230ba and region 230bb, and equal to or higher than those of region 230bc.

[0113] 5A shows an example in which the regions 230ba, 230bb, and 230bc are formed in the oxide 230b, but the present invention is not limited to this. For example, each of the above regions may be formed not only in the oxide 230b but also in the oxide 230a.

[0114] Furthermore, it may be difficult to clearly detect the boundaries between regions in the oxide 230. The concentrations of metal elements and impurity elements such as hydrogen and nitrogen detected in each region may not necessarily vary stepwise from region to region, but may also vary continuously within each region. In other words, it is sufficient that the concentrations of metal elements and impurity elements such as hydrogen and nitrogen decrease in regions closer to the channel formation region.

[0115] In the transistor 200, the oxide 230 including the channel formation region (the oxide 230a and the oxide 230b) is preferably a metal oxide that functions as a semiconductor (hereinafter also referred to as an oxide semiconductor).

[0116] The metal oxide functioning as a semiconductor preferably has a band gap of 2 eV or more, preferably 2.5 eV or more. By using such a metal oxide with a wide band gap, the off-state current of the transistor can be reduced.

[0117] For example, a metal oxide such as In-M-Zn oxide containing indium, element M, and zinc (element M is one or more elements selected from aluminum, gallium, yttrium, tin, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, etc.) may be used as oxide 230. Alternatively, In-Ga oxide, In-Zn oxide, or indium oxide may be used as oxide 230.

[0118] Here, it is preferable that the atomic ratio of In to element M in the metal oxide used for oxide 230b is greater than the atomic ratio of In to element M in the metal oxide used for oxide 230a.

[0119] In this way, by placing oxide 230a below oxide 230b, it is possible to suppress the diffusion of impurities and excessive amounts of oxygen from structures formed below oxide 230a into oxide 230b.

[0120] Furthermore, since the oxide 230a and the oxide 230b have a common element other than oxygen (as a main component), the defect state density at the interface between the oxide 230a and the oxide 230b can be reduced. Because the defect state density at the interface between the oxide 230a and the oxide 230b can be reduced, the effect of interface scattering on carrier conduction is reduced, and a high on-current can be obtained.

[0121] The oxide 230b preferably has crystallinity. In particular, it is preferable to use CAAC-OS as the oxide 230b.

[0122] CAAC-OS has a highly crystalline and dense structure, and is free of impurities and defects (e.g., oxygen vacancies (V O In particular, the CAAC-OS can be made to have a dense structure with higher crystallinity by heat-treating the formed metal oxide at a temperature (for example, 400°C or higher and 600°C or lower) at which the metal oxide does not polycrystallize. In this way, the density of the CAAC-OS can be increased, thereby further reducing the diffusion of impurities or oxygen in the CAAC-OS.

[0123] On the other hand, since it is difficult to identify clear grain boundaries in CAAC-OS, it is said that the decrease in electron mobility due to grain boundaries is unlikely to occur. Therefore, metal oxides with CAAC-OS have stable physical properties. As a result, metal oxides with CAAC-OS are heat-resistant and highly reliable.

[0124] Furthermore, in a cross-sectional view of the transistor 200 in the channel width direction, a curved surface may be formed between the side surface of the oxide 230b and the top surface of the oxide 230b. That is, the end of the side surface and the end of the top surface may be curved (hereinafter also referred to as rounded).

[0125] The radius of curvature of the curved surface is preferably greater than 0 nm and smaller than the film thickness of the oxide 230b in the region overlapping with the conductor 242, or smaller than half the length of the region not having the curved surface. Specifically, the radius of curvature of the curved surface is greater than 0 nm and smaller than 20 nm, preferably greater than 1 nm and smaller than 15 nm, and more preferably greater than 2 nm and smaller than 10 nm. This shape can improve the coverage of the oxide 230b with the insulators 252, 250, 254, and conductor 260.

[0126] The oxide 230 preferably has a stacked structure of multiple oxide layers with different chemical compositions. Specifically, in the metal oxide used for the oxide 230a, the atomic ratio of the element M to the metal element that is the main component is preferably larger than the atomic ratio of the element M to the metal element that is the main component in the metal oxide used for the oxide 230b. Furthermore, in the metal oxide used for the oxide 230a, the atomic ratio of the element M to In is preferably larger than the atomic ratio of the element M to In in the metal oxide used for the oxide 230b. Furthermore, in the metal oxide used for the oxide 230b, the atomic ratio of In to the element M is preferably larger than the atomic ratio of In to the element M in the metal oxide used for the oxide 230a.

[0127] The oxide 230b is preferably a crystalline oxide such as CAAC-OS. Crystalline oxides such as CAAC-OS have few impurities and defects (such as oxygen vacancies), a highly crystalline, and a dense structure. This can prevent the source or drain electrode from extracting oxygen from the oxide 230b. This reduces the extraction of oxygen from the oxide 230b even during heat treatment, making the transistor 200 stable against high temperatures (so-called thermal budget) during the manufacturing process.

[0128] Here, the conduction band minimum changes gradually at the junction between the oxide 230a and the oxide 230b. In other words, the conduction band minimum at the junction between the oxide 230a and the oxide 230b changes continuously or can be said to be a continuous junction. To achieve this, it is advisable to reduce the defect level density of the mixed layer formed at the interface between the oxide 230a and the oxide 230b.

[0129] Specifically, when the oxide 230a and the oxide 230b contain a common element other than oxygen as a main component, a mixed layer with a low density of defect states can be formed. For example, when the oxide 230b is an In-M-Zn oxide, the oxide 230a may be an In-M-Zn oxide, an M-Zn oxide, an oxide of element M, an In-Zn oxide, an indium oxide, or the like.

[0130] Specifically, the oxide 230a may be a metal oxide having an atomic ratio of In:M:Zn=1:3:4 or a similar composition, or an atomic ratio of In:M:Zn=1:1:0.5 or a similar composition. The oxide 230b may be a metal oxide having an atomic ratio of In:M:Zn=1:1:1 or a similar composition, an atomic ratio of In:M:Zn=1:1:2 or a similar composition, or an atomic ratio of In:M:Zn=4:2:3 or a similar composition. Note that a similar composition includes a range of ±30% of the desired atomic ratio. Gallium is preferably used as the element M.

[0131] Here, the oxide 230a and the oxide 230b are preferably formed by sputtering. Oxygen or a mixed gas of oxygen and a rare gas is used as the sputtering gas. The oxygen content in the formed film can be increased by increasing the proportion of oxygen contained in the sputtering gas. Note that the method for forming the oxide 230a and the oxide 230b is not limited to sputtering, and CVD, MBE, PLD, ALD, etc. may also be used as appropriate.

[0132] When a metal oxide film is formed by sputtering, the atomic ratio is not limited to the atomic ratio of the formed metal oxide film, but may be the atomic ratio of a sputtering target used to form the metal oxide film.

[0133] By configuring the oxide 230a and the oxide 230b as described above, the defect state density at the interface between the oxide 230a and the oxide 230b can be reduced, which reduces the influence of interface scattering on carrier conduction, and the transistor 200 can achieve a large on-state current and high frequency characteristics.

[0134] At least one of the insulators 212, 214, 271, 275, 282, 283, 288, and 286 preferably functions as a barrier insulating film that suppresses the diffusion of impurities such as water and hydrogen from the substrate side or from above the transistor 200 into the transistor 200. Therefore, at least one of the insulators 212, 214, 271, 275, 282, 283, 288, and 286 is preferably an insulating material that suppresses the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (NO, NO, NO, etc.), and copper atoms (i.e., through which the above impurities are less likely to permeate). Alternatively, it is preferably an insulating material that suppresses the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, etc.) (i.e., through which the above oxygen is less likely to permeate).

[0135] For the insulators 212, 214, 271, 275, 282, 283, 288, and 286, it is preferable to use insulators that have the function of suppressing the diffusion of impurities such as water and hydrogen, and oxygen. For example, aluminum oxide, magnesium oxide, hafnium oxide, gallium oxide, indium gallium zinc oxide, silicon nitride, or silicon nitride oxide can be used. For example, it is preferable to use silicon nitride, which has a high hydrogen barrier property, for the insulators 212, 275, 283, 288, and 286. Furthermore, it is preferable to use aluminum oxide or magnesium oxide, which has a high function of capturing and fixing hydrogen, for the insulators 214, 271, and 282. This can suppress the diffusion of impurities such as water and hydrogen from the substrate side to the transistor 200 side through the insulators 212 and 214. Alternatively, it is possible to suppress the diffusion of impurities such as water and hydrogen toward the transistor 200 from an interlayer insulating film disposed outside the insulator 285. Alternatively, it is possible to suppress the diffusion of oxygen contained in the insulator 224 or the like toward the substrate through the insulators 212 and 214. Alternatively, it is possible to suppress the diffusion of oxygen contained in the insulator 280 or the like toward an upper side of the transistor 200 through the insulator 282 or the like. In this way, it is preferable to have a structure in which the transistor 200 is surrounded by the insulators 212, 214, 271, 275, 282, 283, 288, and 286, which have the function of suppressing the diffusion of impurities such as water and hydrogen, and oxygen.

[0136] As shown in FIG. 4B , the semiconductor device including the transistor 200 is sandwiched between the insulators 286 and 212, which have hydrogen barrier properties, thereby reducing hydrogen diffusion into the transistor 200. Furthermore, the insulator 286 is provided to cover the insulator 285 and the conductor 246, thereby reducing hydrogen diffusion into the transistor 200 via the conductor 246. Furthermore, the transistor 200 is sealed by the insulators 283 and 288, which have hydrogen barrier properties, and the insulator 212 on the inner side. This further reduces hydrogen diffusion into the transistor 200. Furthermore, the insulators 214, 271, and 282, which have high hydrogen capturing and hydrogen fixing properties, are provided on the inner side, thereby preventing low-concentration hydrogen near the transistor 200 from diffusing into the oxide 230.

[0137] It is also preferable to use an oxide having an amorphous structure as the insulators 214, 271, 275, and 282. For example, AlO x (x is any number greater than 0), or MgO y It is preferable to use a metal oxide such as y (where y is any number greater than 0). In such metal oxides having an amorphous structure, oxygen atoms have dangling bonds, and the dangling bonds may have the property of capturing or fixing hydrogen. By using such a metal oxide having an amorphous structure as a component of the transistor 200 or providing it around the transistor 200, hydrogen contained in the transistor 200 or hydrogen present around the transistor 200 can be captured or fixed. In particular, it is preferable to capture or fix hydrogen contained in the channel formation region of the transistor 200. By using a metal oxide having an amorphous structure as a component of the transistor 200 or providing it around the transistor 200, a highly reliable transistor 200 and a semiconductor device can be manufactured that have excellent characteristics.

[0138] Furthermore, the insulators 214, 271, 275, and 282 preferably have an amorphous structure, but may have a polycrystalline structure region formed in a portion thereof. The insulators 214, 271, 275, and 282 may have a multilayer structure in which an amorphous layer and a polycrystalline layer are stacked. For example, they may have a stacked structure in which a polycrystalline layer is formed on an amorphous layer.

[0139] The insulators 212a, 214, 271, 275, 282, 283, and 286a can be deposited by, for example, sputtering. Sputtering does not require the use of hydrogen-containing molecules in the deposition gas, and therefore can reduce the hydrogen concentrations of the insulators 212a, 214, 271, 275, 282, 283, and 286a. Furthermore, the insulators 212b, 288, and 286b are preferably deposited by ALD, particularly PEALD. This allows the insulators 212b, 288, and 286b to be deposited with good coverage, thereby improving the hydrogen barrier properties of the insulators 212, 286, 283, and 288.

[0140] However, the film formation method is not limited to the sputtering method and the ALD method, and the CVD method, the MBE method, the PLD method, etc. may also be used as appropriate.

[0141] It may also be preferable to reduce the resistivity of the insulators 212, 275, 283, and 286. For example, it may be preferable to reduce the resistivity of the insulators 212, 275, 283, and 286 to approximately 1×10 13 By setting the resistivity to Ωcm, the insulators 212, 275, 283, and 286 may be able to reduce charge-up of the conductor 205, the conductor 242, the conductor 260, or the conductor 246 during treatment using plasma or the like in the semiconductor device manufacturing process. The resistivity of the insulators 212, 275, 283, and 286 is preferably 1×1010 Ωcm or more 1×10 15 Ωcm or less.

[0142] Furthermore, the insulators 216, 274, 280, and 285 preferably have a lower dielectric constant than the insulator 214. Using a material with a low dielectric constant as an interlayer film can reduce parasitic capacitance between wirings. For example, silicon oxide, silicon oxynitride, silicon oxide to which fluorine has been added, silicon oxide to which carbon has been added, silicon oxide to which carbon and nitrogen have been added, silicon oxide having vacancies, or the like can be used as the insulators 216, 274, 280, and 285 as appropriate.

[0143] The conductor 205 is arranged so as to overlap the oxide 230 and the conductor 260. Here, the conductor 205 is preferably provided by being embedded in an opening formed in the insulator 216. Also, a part of the conductor 205 may be embedded in the insulator 214.

[0144] The conductor 205 includes a conductor 205a and a conductor 205b. The conductor 205a is provided in contact with the bottom surface and sidewall of the opening. The conductor 205b is provided so as to be embedded in a recess formed in the conductor 205a. Here, the height of the upper surface of the conductor 205b is approximately the same as the height of the upper surface of the conductor 205a and the height of the upper surface of the insulator 216.

[0145] Here, the conductor 205a is preferably made of a conductive material that has the function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules (NO, NO, NO, etc.), copper atoms, etc. Alternatively, it is preferably made of a conductive material that has the function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.).

[0146] By using a conductive material for the conductor 205a that has the function of reducing hydrogen diffusion, it is possible to prevent impurities such as hydrogen contained in the conductor 205b from diffusing into the oxide 230 via the insulator 224 or the like. Furthermore, by using a conductive material for the conductor 205a that has the function of suppressing oxygen diffusion, it is possible to suppress oxidation of the conductor 205b and a decrease in conductivity. Examples of conductive materials that have the function of suppressing oxygen diffusion include titanium, titanium nitride, tantalum, tantalum nitride, ruthenium, and ruthenium oxide. Therefore, the conductor 205a may be formed as a single layer or a multilayer of the above conductive materials. For example, the conductor 205a may be made of titanium nitride.

[0147] The conductor 205b is preferably made of a conductive material containing tungsten, copper, or aluminum as a main component, for example, tungsten.

[0148] The conductor 205 may function as a second gate electrode. In this case, the threshold voltage (Vth) of the transistor 200 can be controlled by changing the potential applied to the conductor 205 independently of the potential applied to the conductor 260. In particular, applying a negative potential to the conductor 205 can increase the Vth of the transistor 200 and reduce the off-state current. Therefore, applying a negative potential to the conductor 205 can reduce the drain current when the potential applied to the conductor 260 is 0 V compared to not applying a negative potential to the conductor 205.

[0149] The electrical resistivity of the conductor 205 is designed taking into consideration the potential applied to the conductor 205, and the film thickness of the conductor 205 is set to match this electrical resistivity. The film thickness of the insulator 216 is approximately the same as that of the conductor 205. Here, it is preferable to make the film thicknesses of the conductor 205 and the insulator 216 thin within the range permitted by the design of the conductor 205. By making the film thickness of the insulator 216 thin, the absolute amount of impurities such as hydrogen contained in the insulator 216 can be reduced, thereby reducing the diffusion of the impurities into the oxide 230.

[0150] As shown in FIG. 4A, the conductor 205 is preferably larger than the area of ​​the oxide 230 that does not overlap with the conductors 242a and 242b. The conductor 205 also preferably extends beyond the channel width direction ends of the oxide 230a and the oxide 230b. That is, the conductor 205 and the conductor 260 preferably overlap with each other via an insulator outside the side surfaces of the oxide 230 in the channel width direction. This structure allows the channel formation region of the oxide 230 to be electrically surrounded by the electric field of the conductor 260, which functions as the first gate electrode, and the electric field of the conductor 205, which functions as the second gate electrode. In this specification, a transistor structure in which the channel formation region is electrically surrounded by the electric fields of the first and second gates is referred to as a surrounded channel (S-channel) structure.

[0151] In this specification and the like, a transistor with an S-channel structure refers to a transistor structure in which a channel formation region is electrically surrounded by the electric fields of one and the other of a pair of gate electrodes. The S-channel structure disclosed in this specification and the like differs from a fin structure and a planar structure. By adopting the S-channel structure, the transistor can be made more resistant to the short-channel effect, in other words, less susceptible to the short-channel effect.

[0152] The conductor 205 is also extended to function as a wiring. However, the present invention is not limited to this, and a conductor functioning as a wiring may be provided below the conductor 205. Furthermore, it is not necessary to provide one conductor 205 for each transistor. For example, the conductor 205 may be shared by multiple transistors.

[0153] Note that although the transistor 200 illustrates a structure in which the conductor 205 has a stacked structure of the conductor 205a and the conductor 205b, the present invention is not limited to this. For example, the conductor 205 may have a single layer structure or a stacked structure of three or more layers.

[0154] Insulator 222 and insulator 224 function as gate insulators.

[0155] The insulator 222 preferably has a function of suppressing the diffusion of hydrogen (e.g., at least one of hydrogen atoms, hydrogen molecules, etc.). The insulator 222 also preferably has a function of suppressing the diffusion of oxygen (e.g., at least one of oxygen atoms, oxygen molecules, etc.). For example, the insulator 222 preferably has a function of suppressing the diffusion of one or both of hydrogen and oxygen more than the insulator 224.

[0156] The insulator 222 may be an insulator containing an oxide of one or both of aluminum and hafnium, which are insulating materials. Aluminum oxide, hafnium oxide, or an oxide containing aluminum and hafnium (hafnium aluminate) is preferably used as the insulator. When the insulator 222 is formed using such a material, the insulator 222 functions as a layer that suppresses oxygen release from the oxide 230 to the substrate and the diffusion of impurities such as hydrogen from the periphery of the transistor 200 to the oxide 230. Therefore, the insulator 222 can suppress the diffusion of impurities such as hydrogen into the inside of the transistor 200 and the generation of oxygen vacancies in the oxide 230. Furthermore, the conductor 205 can be prevented from reacting with oxygen contained in the insulator 224 or the oxide 230.

[0157] Alternatively, the insulator may contain, for example, aluminum oxide, bismuth oxide, germanium oxide, niobium oxide, silicon oxide, titanium oxide, tungsten oxide, yttrium oxide, or zirconium oxide. Alternatively, these insulators may be nitrided. Furthermore, the insulator 222 may be formed by stacking silicon oxide, silicon oxynitride, or silicon nitride on these insulators.

[0158] The insulator 222 may be a single layer or a multilayer insulator containing a so-called high-k material, such as aluminum oxide, hafnium oxide, tantalum oxide, or zirconium oxide. As transistors become smaller and more highly integrated, thinning of the gate insulator can lead to problems such as leakage current. Using a high-k material as the gate insulator can reduce the gate potential during transistor operation while maintaining the physical film thickness. Alternatively, the insulator 222 may be made of a material with a high dielectric constant, such as lead zirconate titanate (PZT), strontium titanate (SrTiO3), or (Ba,Sr)TiO3 (BST).

[0159] The insulator 224 in contact with the oxide 230 may be made of, for example, silicon oxide, silicon oxynitride, or the like, as appropriate.

[0160] In addition, during the manufacturing process of the transistor 200, it is preferable to perform heat treatment while the surface of the oxide 230 is exposed. The heat treatment may be performed, for example, at a temperature of 100°C or higher and 600°C or lower, more preferably 350°C or higher and 550°C or lower. Note that the heat treatment is performed in an atmosphere of nitrogen gas or an inert gas, or an atmosphere containing an oxidizing gas at 10 ppm or higher, 1% or higher, or 10% or higher. For example, the heat treatment is preferably performed in an oxygen atmosphere. This supplies oxygen to the oxide 230, thereby eliminating oxygen vacancies (V O) can be reduced. The heat treatment may be performed under reduced pressure. Alternatively, the heat treatment may be performed in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas after the heat treatment in a nitrogen gas or inert gas atmosphere to compensate for the desorbed oxygen. Alternatively, the heat treatment may be performed in an atmosphere containing 10 ppm or more, 1% or more, or 10% or more of an oxidizing gas, and then the heat treatment may be performed in a nitrogen gas or inert gas atmosphere.

[0161] By subjecting the oxide 230 to oxygen addition treatment, oxygen vacancies in the oxide 230 are repaired by the supplied oxygen. In other words, "V O Furthermore, the reaction of the hydrogen remaining in the oxide 230 with the supplied oxygen can be removed as H2O (dehydration). As a result, the hydrogen remaining in the oxide 230 recombines with the oxygen vacancies to form V O The formation of H can be suppressed.

[0162] Furthermore, by carrying out the heat treatment as described above, it is possible to give the oxide 230 a more highly crystalline and dense structure. In this way, by increasing the density of the oxide 230, it is possible to further reduce the diffusion of impurities or oxygen in the oxide 230.

[0163] The insulators 222 and 224 may have a stacked structure of two or more layers. In this case, the stacked structure is not limited to a stacked structure made of the same material, and may be a stacked structure made of different materials. The insulator 224 may be formed in an island shape by overlapping with the oxide 230a. In this case, the insulator 275 is configured to contact the side surface of the insulator 224 and the top surface of the insulator 222.

[0164] The conductor 242a and the conductor 242b are provided in contact with the top surface of the oxide 230b. The conductor 242a and the conductor 242b function as a source electrode and a drain electrode of the transistor 200, respectively.

[0165] As the conductor 242 (conductor 242a and conductor 242b), it is preferable to use, for example, a nitride containing tantalum, a nitride containing titanium, a nitride containing molybdenum, a nitride containing tungsten, a nitride containing tantalum and aluminum, or a nitride containing titanium and aluminum. In one embodiment of the present invention, a nitride containing tantalum is particularly preferable. Also, for example, ruthenium oxide, ruthenium nitride, an oxide containing strontium and ruthenium, or an oxide containing lanthanum and nickel may be used. These materials are preferable because they are conductive materials that are resistant to oxidation or that maintain conductivity even when they absorb oxygen.

[0166] Note that hydrogen contained in the oxide 230b and the like may diffuse into the conductor 242a or the conductor 242b. In particular, by using a nitride containing tantalum for the conductor 242a and the conductor 242b, hydrogen contained in the oxide 230b and the like is likely to diffuse into the conductor 242a or the conductor 242b, and the diffused hydrogen may bond with nitrogen contained in the conductor 242a or the conductor 242b. In other words, hydrogen contained in the oxide 230b and the like may be absorbed by the conductor 242a or the conductor 242b.

[0167] Preferably, no curved surface is formed between the side surface of the conductor 242 and the top surface of the conductor 242. The conductor 242 having no curved surface can increase the cross-sectional area of ​​the conductor 242 in the cross section in the channel width direction. This increases the conductivity of the conductor 242 and the on-state current of the transistor 200.

[0168] The insulator 271a is provided in contact with the top surface of the conductor 242a, and the insulator 271b is provided in contact with the top surface of the conductor 242b. The insulator 271 preferably functions as a barrier insulating film against oxygen. Therefore, the insulator 271 preferably has a function of suppressing oxygen diffusion. For example, the insulator 271 preferably has a function of suppressing oxygen diffusion more than the insulator 280. For example, a nitride containing silicon, such as silicon nitride, may be used as the insulator 271. The insulator 271 preferably has a function of capturing impurities such as hydrogen. In this case, the insulator 271 may be an insulator such as a metal oxide having an amorphous structure, such as aluminum oxide or magnesium oxide. In particular, using aluminum oxide having an amorphous structure or aluminum oxide having an amorphous structure as the insulator 271 is preferable because it may be able to more effectively capture or fix hydrogen. This enables the manufacture of a transistor 200 and a semiconductor device with excellent characteristics and high reliability.

[0169] The insulator 275 is provided to cover the insulator 224, the oxide 230a, the oxide 230b, the conductor 242, and the insulator 271. The insulator 275 preferably has the function of capturing and fixing hydrogen. In this case, the insulator 275 preferably includes an insulator such as silicon nitride or a metal oxide having an amorphous structure, such as aluminum oxide or magnesium oxide. Alternatively, for example, the insulator 275 may be a stacked film of aluminum oxide and silicon nitride on the aluminum oxide. For example, aluminum oxide may be deposited by sputtering, and silicon nitride may be deposited by PEALD.

[0170] By providing the insulators 271 and 275 as described above, the conductor 242 can be wrapped in an insulator that has a barrier property against oxygen. That is, it is possible to prevent the oxygen contained in the insulators 224 and 280 from diffusing into the conductor 242. This makes it possible to suppress the conductor 242 from being directly oxidized by the oxygen contained in the insulators 224 and 280, which would increase the resistivity and reduce the on-current.

[0171] The insulator 252 functions as part of the gate insulator. A barrier insulating film against oxygen is preferably used as the insulator 252. Any of the insulators that can be used for the insulator 282 described above may be used as the insulator 252. An insulator containing an oxide of one or both of aluminum and hafnium may be used as the insulator 252. Examples of the insulator that can be used include aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), and an oxide containing hafnium and silicon (hafnium silicate). In this embodiment, aluminum oxide is used as the insulator 252. In this case, the insulator 252 is an insulator containing at least oxygen and aluminum.

[0172] The insulator 252 is preferably provided in contact with the top surface and side surfaces of the oxide 230b, the side surfaces of the oxide 230a, the side surfaces of the insulator 224, and the top surface of the insulator 222 in the channel width direction as well. In other words, the regions of the oxide 230a, the oxide 230b, and the insulator 224 that overlap with the conductor 260 are covered with the insulator 252 in the cross section in the channel width direction. This allows the insulator 252, which has a barrier property against oxygen, to block oxygen from being released from the oxide 230a and the oxide 230b when a heat treatment or the like is performed. Therefore, oxygen vacancies (V O ) can be reduced. O ), and V OH can be reduced. Therefore, the electrical characteristics of the transistor 200 can be improved, and the reliability can be improved.

[0173] Conversely, even if the insulators 280 and 250 contain excessive amounts of oxygen, the oxygen can be prevented from being excessively supplied to the oxides 230a and 230b. Therefore, the regions 230ba and 230bb can be prevented from being excessively oxidized via the region 230bc, which can cause a decrease in the on-state current or the field-effect mobility of the transistor 200.

[0174] 4B, the insulator 252 is provided in contact with the side surfaces of the conductor 242, the insulator 271, the insulator 275, and the insulator 280. This reduces the oxidation of the side surface of the conductor 242 and the formation of an oxide film on the side surface. This reduces the decrease in the on-state current or the field-effect mobility of the transistor 200.

[0175] Furthermore, the insulator 252, together with the insulator 254, the insulator 250, and the conductor 260, must be provided in an opening formed in the insulator 280 or the like. To miniaturize the transistor 200, it is preferable that the insulator 252 be thin. The thickness of the insulator 252 is 0.1 nm or more and 5.0 nm or less, preferably 0.5 nm or more and 3.0 nm or less, and more preferably 1.0 nm or more and 3.0 nm or less. In this case, the insulator 252 only needs to have a region with the above-described thickness in at least a portion thereof. Furthermore, it is preferable that the thickness of the insulator 252 is thinner than the thickness of the insulator 250. In this case, it is preferable that the insulator 252 only needs to have a region with a thickness thinner than the insulator 250 in at least a portion thereof.

[0176] To form the insulator 252 into a thin film as described above, it is preferable to use the ALD method. The ALD method includes the thermal ALD method, in which the reaction between a precursor and a reactant is carried out using only thermal energy, and the PEALD method, in which a plasma-excited reactant is used. The PEALD method may be preferable because it uses plasma, allowing film formation at a lower temperature.

[0177] The insulator 250 functions as part of the gate insulator. The insulator 250 is preferably disposed in contact with the upper surface of the insulator 252. The insulator 250 can be made of silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide doped with fluorine, silicon oxide doped with carbon, silicon oxide doped with carbon and nitrogen, silicon oxide having vacancies, or the like. Silicon oxide and silicon oxynitride are particularly preferred because they are stable against heat. In this case, the insulator 250 is an insulator containing at least oxygen and silicon.

[0178] As with insulator 224, insulator 250 preferably has a reduced concentration of impurities such as water and hydrogen. The thickness of insulator 250 is preferably 1 nm or more and 20 nm or less, and more preferably 0.5 nm or more and 15.0 nm or less. In this case, insulator 250 only needs to have a region with the above-mentioned thickness in at least a portion thereof.

[0179] 4A and 4B show a configuration in which the insulator 250 is a single layer, but the present invention is not limited to this and the insulator 250 may have a laminated structure of two or more layers. For example, as shown in Fig. 5B, the insulator 250 may have a two-layer laminated structure of an insulator 250a and an insulator 250b on the insulator 250a.

[0180] As shown in FIG. 5B , when the insulator 250 has a two-layer stacked structure, it is preferable that the lower insulator 250a be formed using an insulator that is easily permeable to oxygen, and the upper insulator 250b be formed using an insulator that suppresses oxygen diffusion. This configuration can suppress the diffusion of oxygen contained in the insulator 250a into the conductor 260. In other words, it can suppress a decrease in the amount of oxygen supplied to the oxide 230. It can also suppress oxidation of the conductor 260 due to the oxygen contained in the insulator 250a. For example, the insulator 250a may be formed using a material that can be used for the insulator 250 described above, and the insulator 250b may be formed using an insulator containing one or both of aluminum and hafnium oxides. Examples of the insulator that can be used include aluminum oxide, hafnium oxide, an oxide containing aluminum and hafnium (hafnium aluminate), and an oxide containing hafnium and silicon (hafnium silicate). In this embodiment, hafnium oxide is used as the insulator 250b. In this case, the insulator 250b contains at least oxygen and hafnium. The thickness of the insulator 250b is 0.5 nm to 5.0 nm, preferably 1.0 nm to 5.0 nm, and more preferably 1.0 nm to 3.0 nm. In this case, the insulator 250b only needs to have a region with the above-described thickness in at least a portion.

[0181] When silicon oxide or silicon oxynitride is used for the insulator 250a, the insulator 250b may be an insulating material, such as a high-k material with a high dielectric constant. By forming the gate insulator as a stacked structure of the insulators 250a and 250b, a thermally stable stacked structure with a high dielectric constant can be achieved. This allows the gate potential applied during transistor operation to be reduced while maintaining the physical thickness of the gate insulator. Furthermore, the equivalent oxide thickness (EOT) of the insulator functioning as the gate insulator can be reduced. This allows the dielectric strength of the insulator 250 to be increased.

[0182] The insulator 254 functions as part of the gate insulator. A barrier insulating film against hydrogen is preferably used as the insulator 254. This can prevent impurities such as hydrogen contained in the conductor 260 from diffusing into the insulator 250 and the oxide 230b. The insulator 254 may be any of the insulators that can be used for the insulator 283 described above. For example, silicon nitride formed by the PEALD method may be used as the insulator 254. In this case, the insulator 254 is an insulator containing at least nitrogen and silicon.

[0183] Furthermore, the insulator 254 may further have a barrier property against oxygen, which can prevent oxygen contained in the insulator 250 from diffusing into the conductor 260.

[0184] Furthermore, the insulator 254, together with the insulator 252, the insulator 250, and the conductor 260, must be provided in an opening formed in the insulator 280 or the like. To miniaturize the transistor 200, it is preferable that the insulator 254 be thin. The thickness of the insulator 254 is 0.1 nm or more and 5.0 nm or less, preferably 0.5 nm or more and 3.0 nm or less, and more preferably 1.0 nm or more and 3.0 nm or less. In this case, the insulator 254 only needs to have a region with the above-described thickness in at least a portion thereof. Furthermore, it is preferable that the thickness of the insulator 254 is thinner than the thickness of the insulator 250. In this case, it is preferable that the insulator 254 only needs to have a region with a thickness thinner than the insulator 250 in at least a portion thereof.

[0185] The conductor 260 functions as a first gate electrode of the transistor 200. The conductor 260 preferably includes a conductor 260a and a conductor 260b disposed on the conductor 260a. For example, the conductor 260a is preferably disposed so as to surround the bottom and side surfaces of the conductor 260b. As shown in FIG. 4B, the top surface of the conductor 260 is generally aligned with the top of the insulator 250. Although the conductor 260 is shown in FIG. 4B as having a two-layer structure of the conductor 260a and the conductor 260b, it may have a single-layer structure or a stacked structure of three or more layers.

[0186] The conductor 260a is preferably made of a conductive material that has the function of suppressing the diffusion of impurities such as hydrogen atoms, hydrogen molecules, water molecules, nitrogen atoms, nitrogen molecules, nitrogen oxide molecules, copper atoms, etc. Alternatively, it is preferably made of a conductive material that has the function of suppressing the diffusion of oxygen (for example, at least one of oxygen atoms, oxygen molecules, etc.).

[0187] Furthermore, since the conductor 260a has the function of suppressing oxygen diffusion, it is possible to suppress a decrease in conductivity due to oxidation of the conductor 260b caused by oxygen contained in the insulator 250. As a conductive material having the function of suppressing oxygen diffusion, it is preferable to use, for example, titanium, titanium nitride, tantalum, tantalum nitride, ruthenium, ruthenium oxide, or the like.

[0188] Furthermore, since the conductor 260 also functions as wiring, it is preferable to use a conductor with high conductivity. For example, the conductor 260b can be made of a conductive material containing tungsten, copper, or aluminum as a main component. The conductor 260b may also have a layered structure, such as a layered structure of titanium or titanium nitride and the above conductive material.

[0189] Furthermore, in the transistor 200, the conductor 260 is formed in a self-aligned manner so as to fill an opening formed in the insulator 280 or the like. By forming the conductor 260 in this manner, the conductor 260 can be reliably placed in the region between the conductor 242a and the conductor 242b without alignment.

[0190] In addition, in the channel width direction of the transistor 200, the height of the bottom surface of the conductor 260 in a region where the conductor 260 and the oxide 230b do not overlap, relative to the bottom surface of the insulator 222, is preferably lower than the height of the bottom surface of the oxide 230b. When the conductor 260, which functions as a gate electrode, covers the side and top surfaces of the channel formation region of the oxide 230b via the insulator 250 or the like, the electric field of the conductor 260 can be easily applied to the entire channel formation region of the oxide 230b. This increases the on-state current of the transistor 200 and improves its frequency characteristics. The difference between the height of the bottom surface of the conductor 260 and the height of the bottom surface of the oxide 230b in a region where the oxides 230a and 230b do not overlap with the conductor 260, relative to the bottom surface of the insulator 222, is 0 nm or more and 100 nm or less, preferably 3 nm or more and 50 nm or less, and more preferably 5 nm or more and 20 nm or less.

[0191] The insulator 280 is provided on the insulator 275, and openings are formed in the regions where the insulator 250 and the conductor 260 are to be provided. The top surface of the insulator 280 may be flattened.

[0192] The insulator 280, which functions as an interlayer film, preferably has a low dielectric constant. Using a material with a low dielectric constant as the interlayer film can reduce the parasitic capacitance that occurs between wirings. The insulator 280 is preferably formed using, for example, the same material as the insulator 216. In particular, silicon oxide and silicon oxynitride are preferred because they are thermally stable. In particular, materials such as silicon oxide, silicon oxynitride, and silicon oxide with vacancies are preferred because they can easily form regions containing oxygen that is released by heating.

[0193] The insulator 280 preferably has an excess oxygen region or excess oxygen. Furthermore, the concentration of impurities such as water and hydrogen in the insulator 280 is preferably reduced. For example, the insulator 280 may be formed using silicon oxide, silicon oxynitride, or the like as appropriate. The insulator 280 containing excess oxygen can be formed by depositing the insulator 280 by a sputtering method in an oxygen-containing atmosphere. Providing the insulator 280 containing excess oxygen reduces oxygen vacancies in the oxide 230, thereby improving the reliability of the transistor 200. Furthermore, the hydrogen concentration in the insulator 280 can be reduced by using a sputtering method that does not require hydrogen as a deposition gas. Alternatively, the insulator 282 in contact with the top surface of the insulator 280 may be deposited by a sputtering method in an oxygen-containing atmosphere, and oxygen may be added to the insulator 280. When oxygen is added to the insulator 280 in forming the insulator 282, the method for forming the insulator 280 is not limited to sputtering, and CVD, MBE, PLD, ALD, or the like may be used as appropriate. For example, the insulator 280 may have a layered structure of silicon oxide formed by sputtering and silicon oxynitride formed by CVD on top of it. Silicon nitride may also be further layered on top of that.

[0194] The insulator 282 preferably functions as a barrier insulating film that suppresses the diffusion of impurities such as water and hydrogen from above into the insulator 280 and preferably has a function of capturing impurities such as hydrogen. The insulator 282 also preferably functions as a barrier insulating film that suppresses oxygen permeation. The insulator 282 may be an insulator made of a metal oxide having an amorphous structure, such as aluminum oxide. In this case, the insulator 282 contains at least oxygen and aluminum. By providing the insulator 282 in contact with the insulator 280 in the region between the insulators 212 and 283 and having a function of capturing impurities such as hydrogen, the insulator 282 can capture impurities such as hydrogen contained in the insulator 280 and maintain a constant amount of hydrogen in the region. In particular, using aluminum oxide having an amorphous structure as the insulator 282 is preferable because it may be able to more effectively capture or fix hydrogen. This enables the manufacture of a highly reliable transistor 200 and semiconductor device with excellent characteristics.

[0195] The insulator 282 is preferably formed by a sputtering method. By forming the insulator 282 by a sputtering method, oxygen can be added to the insulator 280. However, the method for forming the insulator 282 is not limited to a sputtering method, and a CVD method, an MBE method, a PLD method, an ALD method, or the like may also be used as appropriate.

[0196] The insulator 283 functions as a barrier insulating film that prevents impurities such as water and hydrogen from diffusing from above into the insulator 280. The insulator 283 is disposed over the insulator 282. The insulator 283 is preferably a nitride containing silicon, such as silicon nitride or silicon nitride oxide. For example, silicon nitride formed by a sputtering method can be used as the insulator 283. By forming the insulator 283 by a sputtering method, a high-density silicon nitride film can be formed. Furthermore, by using a sputtering method that does not require the use of molecules containing hydrogen in the deposition gas, the hydrogen concentration in the insulator 283 can be reduced.

[0197] It is preferable to use a nitride containing silicon, such as silicon nitride, as the insulator 288. For example, silicon nitride formed by the PEALD method may be used as the insulator 288. By improving the coverage of the insulator 288, the hydrogen barrier properties of the stacked structure of the insulators 283 and 288 can be improved. Here, the insulators 283, 288, and 274 are subjected to CMP processing until the top of the insulator 283 is exposed. Therefore, the tops of the insulators 283, 288, and 274 are roughly aligned.

[0198] The conductors 240a and 240b are preferably made of a conductive material containing tungsten, copper, or aluminum as a main component. The conductors 240a and 240b may have a layered structure.

[0199] Furthermore, when the conductor 240 has a layered structure, it is preferable to use a conductive material that has the function of suppressing the permeation of impurities such as water and hydrogen for the first conductor arranged near the insulators 285, 283, 282, 280, 275, and 271. For example, it is preferable to use tantalum, tantalum nitride, titanium, titanium nitride, ruthenium, ruthenium oxide, etc. Furthermore, the conductive material that has the function of suppressing the permeation of impurities such as water and hydrogen may be used in a single layer or a layered structure. Furthermore, it is possible to suppress impurities such as water and hydrogen contained in layers above the insulator 283 from mixing into the oxide 230 through the conductors 240a and 240b.

[0200] The insulators 241a and 241b may be a barrier insulating film that can be used for the insulator 275, etc. For example, the insulators 241a and 241b may be made of an insulator such as silicon nitride, aluminum oxide, or silicon nitride oxide. The insulators 241a and 241b are provided in contact with the insulators 283, 282, and 271, and therefore can prevent impurities such as water and hydrogen contained in the insulator 280 from mixing into the oxide 230 through the conductors 240a and 240b. Silicon nitride is particularly suitable because it has a high blocking property against hydrogen. Furthermore, it can prevent oxygen contained in the insulator 280 from being absorbed by the conductors 240a and 240b.

[0201] When insulators 241a and 241b are formed into a layered structure as shown in FIG. 4B, it is preferable that the first insulator in contact with the inner wall of an opening such as insulator 280 and the second insulator inside it be formed by combining a barrier insulating film against oxygen and a barrier insulating film against hydrogen.

[0202] For example, the first insulator may be aluminum oxide formed by ALD, and the second insulator may be silicon nitride formed by PEALD. This configuration can suppress oxidation of the conductor 240 and reduce hydrogen contamination of the conductor 240.

[0203] Conductors 246 (conductors 246a and 246b) may be disposed in contact with the upper surfaces of the conductors 240a and 240b, functioning as wiring. Conductor 246 is preferably made of a conductive material containing tungsten, copper, or aluminum as its main component. The conductor may have a layered structure, for example, a layered structure of titanium or titanium nitride and the above-mentioned conductive material. The conductor may be formed so as to be embedded in an opening provided in an insulator.

[0204] Note that in this embodiment, as shown in FIG. 4A, the transistor 200 including the conductor 260 functioning as a first gate electrode and the conductor 205 functioning as a second gate electrode has been described; however, the present invention is not limited thereto. Any structure may be used as long as the transistor uses an oxide semiconductor film, and may be appropriately designed depending on the characteristics required of the semiconductor device. For example, the transistor may have a top-gate structure or a bottom-gate structure.

[0205] <Materials for semiconductor devices> The following describes constituent materials that can be used in semiconductor devices.

[0206] <<Substrate>> The substrate on which the transistor 200 is formed may be, for example, an insulating substrate, a semiconductor substrate, or a conductive substrate. Examples of insulating substrates include glass substrates, quartz substrates, sapphire substrates, stabilized zirconia substrates (e.g., yttria-stabilized zirconia substrates), and resin substrates. Examples of semiconductor substrates include semiconductor substrates made of silicon or germanium, or compound semiconductor substrates made of silicon carbide, silicon germanium, gallium arsenide, indium phosphide, zinc oxide, and gallium oxide. Examples of semiconductor substrates include those having an insulating region within the semiconductor substrate, such as an SOI (Silicon-On-Insulator) substrate. Examples of conductive substrates include graphite substrates, metal substrates, alloy substrates, and conductive resin substrates. Other examples include substrates having a metal nitride and a metal oxide. Examples of other substrates include a substrate in which a conductor or semiconductor is provided on an insulating substrate, a substrate in which a conductor or insulator is provided on a semiconductor substrate, and a substrate in which a semiconductor or insulator is provided on a conductive substrate. Alternatively, a substrate provided with elements may be used, such as a capacitor element, a resistor element, a switch element, a light-emitting element, a memory element, and the like.

[0207] <<Insulators>> Examples of the insulator include oxides, nitrides, oxynitrides, nitride oxides, metal oxides, metal oxynitrides, and metal nitride oxides, all of which have insulating properties.

[0208] For example, as transistors become more miniaturized and highly integrated, thinner gate insulators can cause problems such as leakage current. Using a high-k material for the gate insulator allows for lower voltage operation of the transistor while maintaining the physical film thickness. On the other hand, using a material with a low dielectric constant for the interlayer insulator can reduce the parasitic capacitance between wiring. Therefore, it is best to select materials based on the insulator's function.

[0209] Furthermore, examples of insulators with a high relative dielectric constant include gallium oxide, hafnium oxide, zirconium oxide, oxides containing aluminum and hafnium, oxynitrides containing aluminum and hafnium, oxides containing silicon and hafnium, oxynitrides containing silicon and hafnium, and nitrides containing silicon and hafnium.

[0210] Examples of insulators with a low dielectric constant include silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide with fluorine added, silicon oxide with carbon added, silicon oxide with carbon and nitrogen added, silicon oxide with voids, and resin.

[0211] Furthermore, a transistor using a metal oxide can have stable electrical characteristics by being surrounded by an insulator that has a function of suppressing the permeation of impurities such as hydrogen and oxygen. Examples of insulators that have a function of suppressing the permeation of impurities such as hydrogen and oxygen include insulators containing boron, carbon, nitrogen, oxygen, fluorine, magnesium, aluminum, silicon, phosphorus, chlorine, argon, gallium, germanium, yttrium, zirconium, lanthanum, neodymium, hafnium, and tantalum, and can be used in a single layer or a stacked layer. Specifically, examples of insulators that have a function of suppressing the permeation of impurities such as hydrogen and oxygen include metal oxides such as aluminum oxide, magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, hafnium oxide, and tantalum oxide, and metal nitrides such as aluminum nitride, silicon nitride oxide, and silicon nitride.

[0212] The insulator functioning as the gate insulator is preferably an insulator having a region containing oxygen that is released by heating. For example, by using a structure in which silicon oxide or silicon oxynitride having a region containing oxygen that is released by heating is in contact with the oxide 230, oxygen vacancies in the oxide 230 can be compensated for.

[0213] <<Conductors>> The conductor is preferably a metal element selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, iridium, strontium, lanthanum, etc., or an alloy containing the above metal elements as a component, or an alloy combining the above metal elements. For example, tantalum nitride, titanium nitride, tungsten, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, oxides containing lanthanum and nickel, etc. Furthermore, tantalum nitride, titanium nitride, nitrides containing titanium and aluminum, nitrides containing tantalum and aluminum, ruthenium oxide, ruthenium nitride, oxides containing strontium and ruthenium, and oxides containing lanthanum and nickel are preferred because they are conductive materials that are resistant to oxidation or maintain conductivity even when absorbing oxygen. Furthermore, semiconductors with high electrical conductivity, such as polycrystalline silicon containing impurity elements such as phosphorus, and silicides such as nickel silicide may also be used.

[0214] Furthermore, a plurality of conductive layers formed from the above materials may be stacked. For example, a stacked structure may be formed by combining the above-described material containing a metal element and a conductive material containing oxygen. A stacked structure may be formed by combining the above-described material containing a metal element and a conductive material containing nitrogen. A stacked structure may be formed by combining the above-described material containing a metal element, a conductive material containing oxygen, and a conductive material containing nitrogen.

[0215] When an oxide is used for the channel formation region of a transistor, a conductor functioning as a gate electrode preferably has a stacked structure in which a material containing the metal element and a conductive material containing oxygen are combined. In this case, the conductive material containing oxygen is preferably provided on the channel formation region side. By providing the conductive material containing oxygen on the channel formation region side, oxygen released from the conductive material is easily supplied to the channel formation region.

[0216] In particular, as a conductor functioning as a gate electrode, it is preferable to use a conductive material containing oxygen and a metal element contained in the metal oxide in which the channel is formed. Alternatively, a conductive material containing the aforementioned metal element and nitrogen may be used. For example, a conductive material containing nitrogen, such as titanium nitride or tantalum nitride, may be used. Alternatively, indium tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide, or indium tin oxide doped with silicon may be used. Furthermore, indium gallium zinc oxide containing nitrogen may be used. Using such a material may allow hydrogen contained in the metal oxide in which the channel is formed to be captured. Alternatively, hydrogen introduced from an external insulator or the like may be captured.

[0217] <<Metal oxides>> It is preferable to use a metal oxide (oxide semiconductor) that functions as a semiconductor as the oxide 230. Metal oxides that can be used as the oxide 230 according to the present invention will be described below.

[0218] The metal oxide preferably contains at least indium or zinc. It is particularly preferable that it contains indium and zinc. It is also preferable that it contains aluminum, gallium, yttrium, tin, or the like in addition to these. It may also contain one or more elements selected from boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, cobalt, and the like.

[0219] Here, we consider a case where the metal oxide is an In-M-Zn oxide containing indium, element M, and zinc. The element M is aluminum, gallium, yttrium, or tin. Other elements that can be used for element M include boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and cobalt. However, there are cases where a combination of the aforementioned elements can be used as element M.

[0220] In this specification and the like, nitrogen-containing metal oxides may also be collectively referred to as metal oxides. Nitrogen-containing metal oxides may also be referred to as metal oxynitrides.

[0221] <Classification of crystal structures> First, classification of crystal structures in oxide semiconductors will be described with reference to Fig. 6A. Fig. 6A is a diagram illustrating classification of crystal structures of oxide semiconductors, typically IGZO (a metal oxide containing In, Ga, and Zn).

[0222] As shown in FIG. 6A, oxide semiconductors are broadly classified into "amorphous," "crystalline," and "crystal." "Amorphous" includes completely amorphous. "Crystalline" includes c-axis-aligned crystalline (CAAC), nanocrystalline (nc), and cloud-aligned composite (CAC). The "Crystalline" classification excludes single crystal, polycrystal, and completely amorphous (excluding single crystal and polycrystal). "Crystal" includes single crystal and polycrystal.

[0223] The structure within the bold frame in Figure 6A is an intermediate state between "amorphous" and "crystal," and is a structure that belongs to a new boundary region (new crystalline phase). In other words, this structure can be said to be completely different from the energetically unstable "amorphous" and "crystal."

[0224] The crystalline structure of a film or substrate can be evaluated using X-ray diffraction (XRD) spectroscopy. Figure 6B shows the XRD spectrum obtained by GIXD (Grazing-Incidence XRD) measurement of a CAAC-IGZO film classified as "Crystalline." The GIXD method is also known as the thin-film method or the Seemann-Bohlin method. Hereinafter, the XRD spectrum obtained by GIXD measurement shown in Figure 6B will be simply referred to as the XRD spectrum. The composition of the CAAC-IGZO film shown in Figure 6B is approximately In:Ga:Zn = 4:2:3 [atomic ratio]. The thickness of the CAAC-IGZO film shown in Figure 6B is 500 nm.

[0225] In Figure 6B, the horizontal axis is 2θ [deg.] and the vertical axis is intensity [au]. As shown in Figure 6B, a peak indicating clear crystallinity is detected in the XRD spectrum of the CAAC-IGZO film. Specifically, a peak indicating c-axis orientation is detected near 2θ = 31° in the XRD spectrum of the CAAC-IGZO film. Furthermore, as shown in Figure 6B, the peak near 2θ = 31° is asymmetrical with respect to the angle at which the peak intensity is detected.

[0226] The crystalline structure of a film or substrate can be evaluated by the diffraction pattern (also called the nanobeam electron diffraction pattern) observed using nanobeam electron diffraction (NBED). Figure 6C shows the diffraction pattern of a CAAC-IGZO film. Figure 6C shows a diffraction pattern observed using NBED, in which an electron beam is incident parallel to the substrate. The composition of the CAAC-IGZO film shown in Figure 6C is approximately In:Ga:Zn = 4:2:3 [atomic ratio]. In the nanobeam electron diffraction method, electron diffraction is performed using a probe diameter of 1 nm.

[0227] As shown in Figure 6C, multiple spots indicating c-axis orientation are observed in the diffraction pattern of the CAAC-IGZO film.

[0228] <<Oxide semiconductor structure>> Note that oxide semiconductors may be classified differently from those shown in FIG. 6A when focusing on their crystal structures. For example, oxide semiconductors are divided into single-crystal oxide semiconductors and other non-single-crystal oxide semiconductors. Examples of non-single-crystal oxide semiconductors include the above-mentioned CAAC-OS and nc-OS. Non-single-crystal oxide semiconductors include polycrystalline oxide semiconductors, amorphous-like oxide semiconductors (a-like OSs), amorphous oxide semiconductors, and the like.

[0229] Here, the above-mentioned CAAC-OS, nc-OS, and a-like OS will be described in detail.

[0230] [CAAC-OS] CAAC-OS is an oxide semiconductor having multiple crystalline regions, each with its c-axis aligned in a specific direction. The specific direction can be the thickness direction of the CAAC-OS film, the normal direction to the surface on which the CAAC-OS film is formed, or the normal direction to the surface of the CAAC-OS film. A crystalline region is a region with periodic atomic arrangement. If the atomic arrangement is considered as a lattice arrangement, a crystalline region can also be a region with a uniform lattice arrangement. Furthermore, CAAC-OS has a region where multiple crystalline regions are connected in the ab-plane direction, and the region may have distortion. Note that distortion refers to a location where the lattice arrangement changes between a region with a uniform lattice arrangement and a region with a different uniform lattice arrangement in the region where multiple crystalline regions are connected. In other words, CAAC-OS is an oxide semiconductor with a c-axis aligned but no clear orientation in the ab-plane direction.

[0231] Each of the multiple crystalline regions is composed of one or more minute crystals (crystals with a maximum diameter of less than 10 nm). When a crystalline region is composed of one minute crystal, the maximum diameter of the crystalline region is less than 10 nm. When a crystalline region is composed of many minute crystals, the size of the crystalline region may be several tens of nm.

[0232] In an In-M-Zn oxide (wherein M is one or more elements selected from aluminum, gallium, yttrium, tin, titanium, etc.), the CAAC-OS tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium (In) and oxygen (hereinafter referred to as an In layer) and a layer containing M, zinc (Zn), and oxygen (hereinafter referred to as an (M, Zn) layer) are stacked. Note that indium and the element M are mutually substituted. Therefore, the (M, Zn) layer may contain indium. The In layer may contain M. The In layer may contain Zn. The layered structure is observed as a lattice image in a high-resolution TEM image, for example.

[0233] When the CAAC-OS film is subjected to structural analysis using, for example, an XRD apparatus, a peak indicating c-axis orientation is detected at or near 2θ=31° in out-of-plane XRD measurement using θ / 2θ scan. Note that the position of the peak indicating c-axis orientation (2θ value) may vary depending on the type and composition of the metallic elements constituting the CAAC-OS.

[0234] Furthermore, for example, in the electron diffraction pattern of the CAAC-OS film, multiple bright spots are observed, and the spots are observed at positions that are point-symmetric with respect to the spot of the incident electron beam that has passed through the sample (also called the direct spot).

[0235] When the crystalline region is observed from the specific direction, the lattice arrangement within the crystalline region is basically a hexagonal lattice, but the unit cell is not necessarily a regular hexagon and may be non-regular hexagonal. Furthermore, the distortion may have a pentagonal, heptagonal, or other lattice arrangement. In the CAAC-OS, no clear grain boundaries are observed even near the distortion. This indicates that the formation of grain boundaries is suppressed by the distortion of the lattice arrangement. This is thought to be because the CAAC-OS can tolerate distortion due to the lack of close-packed oxygen atom arrangement in the ab-plane direction or the change in interatomic bond distance caused by metal atom substitution.

[0236] A crystal structure with clear grain boundaries is called polycrystalline. Grain boundaries act as recombination centers, trapping carriers and potentially causing a decrease in the on-state current and field-effect mobility of a transistor. Therefore, CAAC-OS, which lacks clear grain boundaries, is one of the crystalline oxides with a crystal structure suitable for use in the semiconductor layer of a transistor. Zn is preferred for use in CAAC-OS. For example, In-Zn oxide and In-Ga-Zn oxide are suitable because they can suppress the generation of grain boundaries more effectively than In oxide.

[0237] CAAC-OS is an oxide semiconductor with high crystallinity and no clear grain boundaries. Therefore, it can be said that the decrease in electron mobility due to grain boundaries is unlikely to occur in CAAC-OS. Furthermore, since the crystallinity of oxide semiconductors can be reduced by impurities or defects, CAAC-OS can be said to be an oxide semiconductor with few impurities and defects (such as oxygen vacancies). Therefore, oxide semiconductors with CAAC-OS have stable physical properties. Therefore, oxide semiconductors with CAAC-OS are heat-resistant and highly reliable. Furthermore, CAAC-OS is stable even under high temperatures (so-called thermal budgets) during the manufacturing process. Therefore, using CAAC-OS for OS transistors allows for greater flexibility in the manufacturing process.

[0238] [nc-OS] The nc-OS has periodic atomic arrangement in a microscopic region (e.g., a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). In other words, the nc-OS has microcrystalline structures. The size of these microcrystalline structures is, for example, 1 nm to 10 nm, particularly 1 nm to 3 nm, and therefore these microcrystalline structures are also called nanocrystalline structures. Furthermore, the nc-OS exhibits no regularity in the crystal orientation between different nanocrystalline structures. Therefore, the entire film lacks orientation. Therefore, depending on the analytical method, the nc-OS may be indistinguishable from an a-like OS or an amorphous oxide semiconductor. For example, when a structural analysis of an nc-OS film is performed using an XRD system, no peaks indicating crystallinity are detected in out-of-plane XRD measurements using θ / 2θ scanning. Furthermore, when electron diffraction (also known as selected-area electron diffraction) is performed on an nc-OS film using an electron beam with a probe diameter larger than that of nanocrystalline structures (e.g., 50 nm or larger), a halo-like diffraction pattern is observed. On the other hand, when electron diffraction (also called nanobeam electron diffraction) is performed on an nc-OS film using an electron beam with a probe diameter close to or smaller than the size of the nanocrystals (for example, 1 nm to 30 nm), an electron diffraction pattern can be obtained in which multiple spots are observed within a ring-shaped region centered on the direct spot.

[0239] [a-like OS] The a-like OS is an oxide semiconductor having a structure between the nc-OS and the amorphous oxide semiconductor. The a-like OS has a pore or low-density region. That is, the a-like OS has lower crystallinity than the nc-OS and CAAC-OS. Furthermore, the a-like OS has a higher hydrogen concentration in the film than the nc-OS and CAAC-OS.

[0240] <<Oxide semiconductor structure>> Next, the above-mentioned CAC-OS will be described in detail, which relates to the material composition.

[0241] [CAC-OS] CAC-OS is a material structure in which elements constituting a metal oxide are unevenly distributed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or a similar size range. Hereinafter, a metal oxide in which one or more metal elements are unevenly distributed and the regions containing the metal elements are mixed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or a similar size range, is also referred to as a mosaic or patch state.

[0242] Furthermore, CAC-OS has a mosaic structure in which the material is separated into first and second regions, and the first regions are distributed throughout the film (hereinafter also referred to as a cloud structure). That is, CAC-OS is a composite metal oxide having a structure in which the first and second regions are mixed.

[0243] Here, the atomic ratios of In, Ga, and Zn to the metal elements constituting the CAC-OS in the In-Ga-Zn oxide are denoted as [In], [Ga], and [Zn], respectively. For example, in the CAC-OS in the In-Ga-Zn oxide, the first region is a region where [In] is larger than [In] in the composition of the CAC-OS film. The second region is a region where [Ga] is larger than [Ga] in the composition of the CAC-OS film. Alternatively, for example, the first region is a region where [In] is larger than [In] in the second region and [Ga] is smaller than [Ga] in the second region. The second region is a region where [Ga] is larger than [Ga] in the first region and [In] is smaller than [In] in the first region.

[0244] Specifically, the first region is a region whose main component is indium oxide, indium zinc oxide, or the like. The second region is a region whose main component is gallium oxide, gallium zinc oxide, or the like. In other words, the first region can be rephrased as a region whose main component is In. The second region can be rephrased as a region whose main component is Ga.

[0245] It should be noted that there are cases where a clear boundary between the first region and the second region cannot be observed.

[0246] For example, in the case of CAC-OS in In-Ga-Zn oxide, EDX mapping obtained using EDX (Energy Dispersive X-ray spectroscopy) confirms that the CAC-OS has a structure in which a region mainly composed of In (first region) and a region mainly composed of Ga (second region) are unevenly distributed and mixed.

[0247] When CAC-OS is used in a transistor, the conductivity due to the first region and the insulating property due to the second region act in a complementary manner, thereby providing the CAC-OS with a switching function (the ability to turn on and off). In other words, CAC-OS has a conductive function in part of the material and an insulating function in part of the material, and the material as a whole functions as a semiconductor. By separating the conductive function from the insulating function, both functions can be maximized. Therefore, by using CAC-OS in a transistor, a high on-current (I on ), high field-effect mobility (μ), and good switching behavior can be achieved.

[0248] Oxide semiconductors have a variety of structures, each with different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, a CAC-OS, an nc-OS, and a CAAC-OS.

[0249] <Transistors containing oxide semiconductors> Next, a case where the oxide semiconductor is used in a transistor will be described.

[0250] By using the oxide semiconductor for a transistor, a transistor with high field-effect mobility and high reliability can be realized.

[0251] An oxide semiconductor with a low carrier concentration is preferably used for a channel formation region of a transistor. For example, the carrier concentration of the channel formation region of an oxide semiconductor is 1×10 17 cm -3 Less than 1 × 10 15 cm -3 or less, more preferably 1 × 10 13 cm -3 Less than or equal to 1×10 11 cm -3 or less, more preferably 1 × 10 10 cm -3Less than 1 x 10 -9 cm -3 The above is the case. Note that in order to reduce the carrier concentration of an oxide semiconductor film, the impurity concentration in the oxide semiconductor film may be reduced to reduce the density of defect states. In this specification and the like, a semiconductor having a low impurity concentration and a low density of defect states is referred to as a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor. Note that an oxide semiconductor having a low carrier concentration may also be referred to as a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor.

[0252] Furthermore, a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has a low density of defect states, and therefore the density of trap states might also be low.

[0253] Furthermore, charges trapped in the trap states of an oxide semiconductor take a long time to dissipate and may behave like fixed charges. Therefore, a transistor in which a channel formation region is formed in an oxide semiconductor with a high density of trap states may have unstable electrical characteristics.

[0254] Therefore, in order to stabilize the electrical characteristics of a transistor, it is effective to reduce the impurity concentration in the oxide semiconductor. Furthermore, in order to reduce the impurity concentration in the oxide semiconductor, it is preferable to also reduce the impurity concentration in the adjacent film. Examples of impurities include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, and silicon.

[0255] <Impurities> Here, the influence of each impurity in an oxide semiconductor will be described.

[0256] When an oxide semiconductor contains silicon or carbon, which is one of the Group 14 elements, defect levels are formed in the oxide semiconductor. Therefore, the concentration of silicon or carbon in the channel formation region of the oxide semiconductor and the concentration of silicon or carbon near the interface with the channel formation region of the oxide semiconductor (concentration obtained by secondary ion mass spectrometry (SIMS)) are calculated to be 2×10 18atoms / cm 3 Less than or equal to 2 x 10 17 atoms / cm 3 The following applies.

[0257] Furthermore, when an oxide semiconductor contains an alkali metal or alkaline earth metal, defect states may be formed and carriers may be generated. Therefore, a transistor using an oxide semiconductor containing an alkali metal or alkaline earth metal is likely to have normally-on characteristics. For this reason, when the concentration of the alkali metal or alkaline earth metal in the channel formation region of the oxide semiconductor obtained by SIMS is set to 1×10 18 atoms / cm 3 Less than or equal to 2 x 10 16 atoms / cm 3 Do the following:

[0258] Furthermore, when nitrogen is contained in an oxide semiconductor, electrons serving as carriers are generated, the carrier concentration increases, and the semiconductor is likely to become n-type. As a result, a transistor using an oxide semiconductor containing nitrogen as a semiconductor tends to have normally-on characteristics. Alternatively, when nitrogen is contained in an oxide semiconductor, trap states may be formed. As a result, the electrical characteristics of the transistor may become unstable. For this reason, the nitrogen concentration in the channel formation region of an oxide semiconductor obtained by SIMS is set to 5×10 19 atoms / cm 3 Less than 5 x 10 18 atoms / cm 3 Less than or equal to 1×10 18 atoms / cm 3 Less than 5 × 10, more preferably 17 atoms / cm 3 Do the following:

[0259] Furthermore, hydrogen contained in an oxide semiconductor may react with oxygen bonded to a metal atom to form water, which may form an oxygen vacancy. When hydrogen enters the oxygen vacancy, electrons serving as carriers may be generated. Furthermore, some of the hydrogen may bond with oxygen bonded to a metal atom to generate electrons serving as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen is likely to have normally-on characteristics. For this reason, it is preferable to reduce the amount of hydrogen in the channel formation region of the oxide semiconductor as much as possible. Specifically, the hydrogen concentration measured by SIMS in the channel formation region of the oxide semiconductor is 1×10 20 atoms / cm 3 Less than 5 x 10 19 atoms / cm 3 less than 1×10 19 atoms / cm 3 less than 5×10 18 atoms / cm 3 less than 1×10 18 atoms / cm 3 Make it less than.

[0260] When an oxide semiconductor with sufficiently reduced impurities is used for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0261] <<Other semiconductor materials>> The semiconductor material that can be used for the oxide 230 is not limited to the metal oxides described above. A semiconductor material having a band gap (a semiconductor material that is not a zero-gap semiconductor) may also be used for the oxide 230. For example, it is preferable to use a semiconductor of a simple element such as silicon, a compound semiconductor such as gallium arsenide, or a layered material that functions as a semiconductor (also called an atomic layer material or a two-dimensional material). In particular, it is preferable to use a layered material that functions as a semiconductor.

[0262] In this specification and the like, a layered material is a general term for a group of materials having a layered crystal structure. A layered crystal structure is a structure in which layers formed by covalent or ionic bonds are stacked via bonds weaker than covalent or ionic bonds, such as van der Waals forces. A layered material has high electrical conductivity within a unit layer, that is, high two-dimensional electrical conductivity. By using a material that functions as a semiconductor and has high two-dimensional electrical conductivity in the channel formation region, a transistor with a large on-current can be provided.

[0263] Layered materials include graphene, silicene, and chalcogenides. Chalcogenides are compounds containing chalcogen. Chalcogen is a general term for elements in Group 16, including oxygen, sulfur, selenium, tellurium, polonium, and livermorium. Chalcogenides also include transition metal chalcogenides and Group 13 chalcogenides.

[0264] It is preferable to use, for example, a transition metal chalcogenide that functions as a semiconductor as the oxide 230. Specific examples of transition metal chalcogenides that can be used as the oxide 230 include molybdenum sulfide (typically MoS2), molybdenum selenide (typically MoSe2), molybdenum tellurium (typically MoTe2), tungsten sulfide (typically WS2), tungsten selenide (typically WSe2), tungsten tellurium (typically WTe2), hafnium sulfide (typically HfS2), hafnium selenide (typically HfSe2), zirconium sulfide (typically ZrS2), and zirconium selenide (typically ZrSe2).

[0265] <Application examples of semiconductor devices> An example of a semiconductor device according to one embodiment of the present invention will be described below with reference to FIG.

[0266] FIG. 7A shows a top view of the semiconductor device 500. The x-axis in FIG. 7A is parallel to the channel length direction of the transistor 200, and the y-axis is perpendicular to the x-axis. FIG. 7B is a cross-sectional view corresponding to the portion indicated by the dashed dotted line A1-A2 in FIG. 7A, and is also a cross-sectional view of the transistor 200 in the channel length direction. FIG. 7C is a cross-sectional view corresponding to the portion indicated by the dashed dotted line A3-A4 in FIG. 7A, and is also a cross-sectional view of the opening region 400 and its vicinity. Note that some elements have been omitted from the top view in FIG. 7A for clarity.

[0267] 7A to 7C, the same reference numerals are used to designate structures having the same functions as those constituting the semiconductor device shown in <Configuration Example of Semiconductor Device>. Also in this section, the materials described in detail in <Configuration Example of Semiconductor Device> can be used as the materials constituting the semiconductor device.

[0268] 7A to 7C is a modified example of the semiconductor device shown in FIGS. 4A and 4B. The semiconductor device 500 shown in FIGS. 7A to 7C differs from the semiconductor device shown in FIGS. 4A and 4B in that an opening region 400 is formed in the insulator 282 and the insulator 280. The semiconductor device 500 also differs from the semiconductor device shown in FIGS. 4A and 4B in that a sealing portion 265 is formed to surround the plurality of transistors 200.

[0269] The semiconductor device 500 has a plurality of transistors 200 and a plurality of opening regions 400 arranged in a matrix. A plurality of conductors 260 functioning as gate electrodes of the transistors 200 are provided extending in the y-axis direction. The opening regions 400 are formed in regions that do not overlap with the oxide 230 and the conductors 260. A sealing portion 265 is formed to surround the plurality of transistors 200, the plurality of conductors 260, and the plurality of opening regions 400. Note that the number, arrangement, and size of the transistors 200, the conductors 260, and the opening regions 400 are not limited to the structure shown in FIG. 7 and may be set appropriately according to the design of the semiconductor device 500.

[0270] As shown in FIGS. 7B and 7C , the sealing portion 265 is provided to surround the multiple transistors 200, the insulators 216, 222, 275, 280, and 282. In other words, the insulator 283 is provided to cover the insulators 216, 222, 275, 280, and 282. In the sealing portion 265, the insulator 283 is in contact with the upper surface of the insulator 214. In the sealing portion 265, the insulators 288 and 274 are provided between the insulators 283 and 285. The tops of the insulators 288 and 274 are approximately at the same height as the top of the insulator 283. The insulator 274 may be made of the same insulator as the insulator 280.

[0271] With this structure, the multiple transistors 200 can be enclosed by the insulators 283, 214, and 212. Here, it is preferable that one or more of the insulators 283, 214, and 212 function as a barrier insulating film against hydrogen. This can prevent hydrogen contained outside the region of the sealing portion 265 from mixing into the region of the sealing portion 265.

[0272] Note that a configuration may be adopted in which openings are formed in insulators 283, 288, 274, and 285 outside sealing portion 265, and a sealing portion is formed where insulator 286 contacts insulator 214. Alternatively, a configuration may be adopted in which openings are formed in insulators 214, 283, 288, 274, and 285 outside sealing portion 265, and a sealing portion is formed where insulator 286a contacts insulator 212a. In other words, the configuration shown in FIG. 1C may be adopted.

[0273] 7C , insulator 282 has an opening in opening region 400. In addition, insulator 280 may have a groove overlapping the opening of insulator 282 in opening region 400. The depth of the groove in insulator 280 may be at most deep enough to expose the top surface of insulator 275, and may be, for example, approximately ¼ to ½ of the maximum film thickness of insulator 280.

[0274] 7C , insulator 283 contacts the side surface of insulator 282, the side surface of insulator 280, and the top surface of insulator 280 inside opening region 400. In addition, a portion of insulator 274 may be formed in opening region 400 so as to fill a recess formed in insulator 283. In this case, the height of the top surface of insulator 274 formed in opening region 400 may roughly match the height of the top surface of insulator 283.

[0275] By performing heat treatment with the opening region 400 formed and the insulator 280 exposed through the opening of the insulator 282, oxygen can be supplied to the oxide 230 while some of the oxygen contained in the insulator 280 diffuses outward from the opening region 400. This allows sufficient oxygen to be supplied from the insulator 280, which contains oxygen released by heating, to a region in the oxide semiconductor that functions as a channel formation region and its vicinity, while preventing excessive oxygen from being supplied.

[0276] At this time, the hydrogen contained in the insulator 280 can be bonded with oxygen and released to the outside through the opening region 400. The hydrogen bonded with oxygen is released as water. Therefore, the hydrogen contained in the insulator 280 can be reduced, and the hydrogen contained in the insulator 280 can be prevented from mixing with the oxide 230.

[0277] 7A, the shape of the opening region 400 in a top view is substantially rectangular, but the present invention is not limited to this. For example, the shape of the opening region 400 in a top view may be rectangular, elliptical, circular, diamond-shaped, or a combination thereof. The area and spacing of the opening regions 400 can be appropriately set in accordance with the design of the semiconductor device including the transistors 200. For example, in a region where the density of the transistors 200 is low, the area of ​​the opening regions 400 can be increased or the spacing between the opening regions 400 can be narrowed. For example, in a region where the density of the transistors 200 is high, the area of ​​the opening regions 400 can be narrowed or the spacing between the opening regions 400 can be widened.

[0278] According to one embodiment of the present invention, a novel semiconductor device can be provided. According to one embodiment of the present invention, a novel manufacturing method for a semiconductor device can be provided. According to one embodiment of the present invention, a semiconductor device with little variation in transistor characteristics can be provided. According to one embodiment of the present invention, a semiconductor device with favorable electrical characteristics can be provided. According to one embodiment of the present invention, a semiconductor device with favorable reliability can be provided. According to one embodiment of the present invention, a semiconductor device with high on-state current can be provided. According to one embodiment of the present invention, a semiconductor device with high field-effect mobility can be provided. According to one embodiment of the present invention, a semiconductor device with favorable frequency characteristics can be provided. According to one embodiment of the present invention, a semiconductor device that can be miniaturized or highly integrated can be provided. According to one embodiment of the present invention, a semiconductor device with low power consumption can be provided.

[0279] At least part of the structures, methods, and the like described in this embodiment mode can be implemented in appropriate combination with other embodiment modes and examples described in this specification.

[0280] (Embodiment 3) In this embodiment, one mode of a semiconductor device will be described with reference to FIGS.

[0281] [Storage device 1] 8 illustrates an example of a semiconductor device (memory device) according to one embodiment of the present invention. In the semiconductor device according to one embodiment of the present invention, a transistor 200 is provided above a transistor 300, and a capacitor 100 is provided above the transistors 300 and 200. Note that the transistor 200 described in the above embodiment can be used as the transistor 200.

[0282] The transistor 200 is a transistor in which a channel is formed in a semiconductor layer containing an oxide semiconductor. The transistor 200 has a low off-state current; therefore, when used in a memory device, the stored data can be retained for a long time. That is, a refresh operation is not required or the frequency of the refresh operation is extremely low; therefore, the power consumption of the memory device can be sufficiently reduced.

[0283] 8, a wiring 1001 is electrically connected to the source of a transistor 300, and a wiring 1002 is electrically connected to the drain of the transistor 300. A wiring 1003 is electrically connected to one of the source and drain of a transistor 200, a wiring 1004 is electrically connected to a first gate of the transistor 200, and a wiring 1006 is electrically connected to a second gate of the transistor 200. The gate of the transistor 300 and the other of the source and drain of the transistor 200 are electrically connected to one electrode of a capacitor 100, and a wiring 1005 is electrically connected to the other electrode of the capacitor 100.

[0284] Moreover, the memory device shown in FIG. 8 can be arranged in a matrix to form a memory cell array.

[0285] <Transistor 300> The transistor 300 is provided on a substrate 311 and includes a conductor 316 functioning as a gate, an insulator 315 functioning as a gate insulator, a semiconductor region 313 formed of part of the substrate 311, and low-resistance regions 314a and 314b functioning as source and drain regions. The transistor 300 may be either a p-channel type or an n-channel type.

[0286] In the transistor 300 shown in FIG. 8, a semiconductor region 313 (a part of a substrate 311) where a channel is formed has a convex shape. A conductor 316 is provided to cover the side and top surfaces of the semiconductor region 313 with an insulator 315 interposed therebetween. The conductor 316 may be made of a material that adjusts the work function. Such a transistor 300 is also called a FIN transistor because it utilizes the convex portion of the semiconductor substrate. An insulator may be provided in contact with the top of the convex portion and function as a mask for forming the convex portion. While the case where the convex portion is formed by processing a part of the semiconductor substrate has been described, a semiconductor film having a convex shape may also be formed by processing an SOI substrate.

[0287] Note that the transistor 300 illustrated in FIG. 8 is just an example, and the structure is not limited thereto. An appropriate transistor may be used depending on the circuit configuration or driving method.

[0288] <Capacitor element 100> The capacitor 100 is provided above the transistor 200. The capacitor 100 includes a conductor 110 functioning as a first electrode, a conductor 120 functioning as a second electrode, and an insulator 130 functioning as a dielectric. An insulator 287 is preferably provided to cover the insulator 130.

[0289] For example, the conductor 112 and the conductor 110 can be formed simultaneously over the conductor 240. Note that the conductor 112 functions as a plug or a wiring electrically connected to the capacitor 100, the transistor 200, or the transistor 300. The conductor 112 may be covered with the insulator 287, similar to the conductor 130. The conductor 112 corresponds to the conductor 246 described in the above embodiment, and the description of the conductor 246 can be referred to for details.

[0290] 8, the conductor 112 and the conductor 110 are shown as having a single layer structure, but are not limited to this configuration and may have a stacked structure of two or more layers. For example, a conductor having barrier properties and a conductor having high adhesion to the conductor having high conductivity may be formed between a conductor having barrier properties and a conductor having high conductivity.

[0291] The insulator 130 can be made of, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, aluminum oxide, aluminum oxynitride, aluminum nitride oxide, aluminum nitride, hafnium oxide, hafnium oxynitride, hafnium nitride oxide, hafnium nitride, or the like, and can be formed as a stacked layer or a single layer.

[0292] For example, it is preferable to use a layered structure of a material with high dielectric strength, such as silicon oxynitride, and a high dielectric constant (high-k) material for the insulator 130. With this configuration, the capacitor 100 can ensure sufficient capacitance by having an insulator with high dielectric constant (high-k), and the capacitor 100 can improve its dielectric strength by having an insulator with high dielectric strength, thereby preventing electrostatic breakdown of the capacitor 100.

[0293] Examples of high-dielectric-constant (high-k) materials (materials with a high relative dielectric constant) insulators include gallium oxide, hafnium oxide, zirconium oxide, oxides containing aluminum and hafnium, oxynitrides containing aluminum and hafnium, oxides containing silicon and hafnium, oxynitrides containing silicon and hafnium, and nitrides containing silicon and hafnium.

[0294] Alternatively, a ferroelectric material may be used as the insulator 130. For example, a mixed crystal of hafnium oxide and zirconium oxide (also referred to as "HZO"), or a material in which element X (element X is silicon (Si), aluminum (Al), gadolinium (Gd), yttrium (Y), lanthanum (La), strontium (Sr), etc.) is added to hafnium oxide. Alternatively, a piezoelectric ceramic having a perovskite structure may be used as the insulator 130. For example, lead zirconate titanate (PZT), strontium bismuthate tantalate (SBT), bismuth ferrite (BFO), or barium titanate may be used.

[0295] The insulator 287 is preferably an insulator that has the function of capturing and fixing hydrogen, which can be used for the insulator 214 or the insulator 282. For example, it is preferable to use aluminum oxide. By providing such an insulator 287 on and in contact with the insulator 130, the hydrogen contained in the insulator 130 can be captured and fixed, thereby reducing the hydrogen concentration in the insulator 130. This allows the leakage current between the conductor 110 and the conductor 120 to be reduced.

[0296] 8, the shape of the capacitor 100 is a planar type, but the shape of the capacitor 100 in the memory device described in this embodiment is not limited to this. For example, the shape of the capacitor 100 may be a cylindrical type.

[0297] On the other hand, materials with high dielectric strength (materials with low dielectric constant) include silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, silicon oxide with fluorine added, silicon oxide with carbon added, silicon oxide with carbon and nitrogen added, silicon oxide or resin with pores, etc.

[0298] <Wiring layer> Between each structure, a wiring layer provided with an interlayer film, wiring, plugs, etc. may be provided. Furthermore, multiple wiring layers may be provided depending on the design. Here, for a conductor functioning as a plug or wiring, the same reference numeral may be used to refer to multiple structures. Furthermore, in this specification and the like, the wiring and the plug electrically connected to the wiring may be integrated. That is, there are cases where a part of the conductor functions as the wiring, and cases where a part of the conductor functions as the plug.

[0299] For example, an insulator 320, an insulator 322, an insulator 324, and an insulator 326 are stacked in this order as an interlayer film over the transistor 300. Conductors 328 and 330 electrically connected to the capacitor 100 or the transistor 200 are embedded in the insulators 320, 322, 324, and 326. The conductors 328 and 330 function as plugs or wirings.

[0300] The insulator functioning as an interlayer film may also function as a planarizing film that covers the underlying unevenness. For example, the top surface of the insulator 322 may be planarized by a planarization process using a chemical mechanical polishing (CMP) method or the like to enhance flatness.

[0301] A wiring layer may be provided over the insulator 326 and the conductor 330. For example, in FIG. 8, an insulator 350, an insulator 352, and an insulator 354 are stacked in this order. A conductor 356 is formed in the insulator 350, the insulator 352, and the insulator 354. The conductor 356 functions as a plug or a wiring.

[0302] Similarly, a conductor 218, a conductor constituting the transistor 200 (the conductor 205), and the like are embedded in the insulator 210, the insulator 212 (the insulator 212a and the insulator 212b), the insulator 214, and the insulator 216. Note that the conductor 218 functions as a plug or wiring electrically connected to the capacitor 100 or the transistor 300.

[0303] Here, similar to the insulator 241 described in the above embodiment, the insulator 217 is provided in contact with the side surface of the conductor 218 that functions as a plug. The insulator 217 is provided in contact with the inner wall of the opening formed in the insulators 210, 212, 214, and 216. In other words, the insulator 217 is provided between the conductor 218 and the insulators 210, 212, 214, and 216. Note that the conductor 205 can be formed in parallel with the conductor 218, and therefore the insulator 217 may be formed in contact with the side surface of the conductor 205.

[0304] The insulator 217 may be, for example, an insulator such as silicon nitride, aluminum oxide, or silicon nitride oxide. The insulator 217 is provided in contact with the insulators 210, 212, 214, and 222, and therefore can prevent impurities such as water or hydrogen from the insulator 210 or the insulator 216 from mixing into the oxide 230 through the conductor 218. Silicon nitride is particularly suitable because it has a high blocking property against hydrogen. In addition, the insulator 217 can prevent oxygen contained in the insulator 210 or the insulator 216 from being absorbed by the conductor 218.

[0305] The insulator 217 can be formed by a method similar to that of the insulator 241. For example, a silicon nitride film is formed by a PEALD method, and an opening reaching the conductor 356 is formed by anisotropic etching.

[0306] As in the previous embodiment, an insulator 286 (insulator 286a, insulator 286b) functioning as a barrier insulating film is provided on the conductor 112 and the conductor 110 corresponding to the conductor 246. The insulator 286 is provided so as to cover the insulator 287. Furthermore, the insulator 150 is provided on the insulator 286. The conductor 158 is formed so as to be embedded in the insulator 150.

[0307] A conductor 162 is provided on an insulator 150, and an insulator 160 is provided covering the conductor 162. Furthermore, a conductor 166 is provided on the insulator 160, and an insulator 164 is provided on the conductor 166. The insulators 160 and 164 can be made of an organic resin such as polyimide. The conductors 162 and 166 can be made of a low-resistance conductive film such as aluminum.

[0308] Here, part of the conductor 166 is electrically connected to the wiring 1001 and is electrically connected to the transistor 300 through the conductor 162, the conductor 158, the conductor 112, and the like. Part of the conductor 162 is electrically connected to the wiring 1005 and is electrically connected to the conductor 120 of the capacitor 100 through the conductor 158.

[0309] As described above, many interlayer insulating films, wirings, and the like are provided over the transistor 200, and these films contain impurities such as hydrogen that affect the oxide semiconductor film. In particular, the insulators 160 and 164 made of organic resins are prone to hydrogen diffusion. However, covering the insulator 287 with the insulator 286, which is an insulating film having hydrogen barrier properties, can reduce the diffusion of hydrogen into the transistor 200 and the like. Furthermore, covering most of the conductor 120 with the insulator 286 can significantly reduce hydrogen diffusing into the transistor 200 through the conductor 112, which functions as a wiring.

[0310] 9, a configuration may be adopted in which insulators 168a and 168b are provided to cover the insulator 150 and the conductor 162 and function as a barrier insulating film against hydrogen. The insulator 168a has a similar structure to the insulator 286a, and therefore the description of the insulator 286a can be referred to for details. The insulator 168b on the insulator 168a has a similar structure to the insulator 286b, and therefore the description of the insulator 286b can be referred to for details. Note that hereinafter, the insulators 168a and 168b may be collectively referred to as the insulator 168.

[0311] In this way, by providing the insulator 168 in contact with the lower surface of the insulator 160 made of organic resin, it is possible to further reduce hydrogen diffusing downward from the insulator 160.

[0312] Examples of insulators that can be used as the interlayer film include insulating oxides, nitrides, oxynitrides, nitride oxides, metal oxides, metal oxynitrides, and metal nitride oxides.

[0313] For example, by using a material with a low dielectric constant for the insulator that functions as an interlayer film, the parasitic capacitance that occurs between wirings can be reduced. Therefore, it is advisable to select a material depending on the function of the insulator.

[0314] For example, the insulators 150, 210, 352, and 354 preferably have an insulator with a low dielectric constant. For example, the insulators preferably include fluorine-doped silicon oxide, carbon-doped silicon oxide, carbon- and nitrogen-doped silicon oxide, pore-containing silicon oxide, or resin. Alternatively, the insulators preferably have a layered structure of silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, fluorine-doped silicon oxide, carbon-doped silicon oxide, carbon- and nitrogen-doped silicon oxide, or pore-containing silicon oxide, and resin. Silicon oxide and silicon oxynitride are thermally stable, and therefore, combining them with resin can provide a thermally stable layered structure with a low dielectric constant. Examples of resins include polyester, polyolefin, polyamide (e.g., nylon, aramid), polyimide, polycarbonate, and acrylic. These resins may also be used for the insulators 160 and 164.

[0315] Furthermore, the electrical characteristics of a transistor including an oxide semiconductor can be stabilized by surrounding the transistor with an insulator that has a function of suppressing the permeation of impurities such as hydrogen and oxygen. Therefore, the insulators 350, 212, 214, 282, 283, and 286 can be insulators that have a function of suppressing the permeation of impurities such as hydrogen and oxygen.

[0316] Examples of insulators that can suppress the permeation of impurities such as hydrogen and oxygen include insulators containing boron, carbon, nitrogen, oxygen, fluorine, magnesium, aluminum, silicon, phosphorus, chlorine, argon, gallium, germanium, yttrium, zirconium, lanthanum, neodymium, hafnium, and tantalum, and can be used in a single layer or a stacked layer. Specifically, examples of insulators that can suppress the permeation of impurities such as hydrogen and oxygen include metal oxides such as aluminum oxide, magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, hafnium oxide, and tantalum oxide, silicon nitride oxide, and silicon nitride.

[0317] Conductors that can be used for wiring and plugs include materials containing one or more metal elements selected from aluminum, chromium, copper, silver, gold, platinum, tantalum, nickel, titanium, molybdenum, tungsten, hafnium, vanadium, niobium, manganese, magnesium, zirconium, beryllium, indium, ruthenium, etc. Also usable are semiconductors with high electrical conductivity, typified by polycrystalline silicon containing impurity elements such as phosphorus, and silicides such as nickel silicide.

[0318] For example, conductors 328, 330, 356, conductor 218, conductor 112, conductor 110, conductor 120, and conductor 158 can be formed using conductive materials such as metal materials, alloy materials, metal nitride materials, or metal oxide materials, either in a single layer or in a stacked layer, formed from the above materials. High-melting-point materials such as tungsten or molybdenum, which have both heat resistance and conductivity, are preferably used, and tungsten is preferred. Alternatively, they are preferably formed from low-resistance conductive materials such as aluminum or copper. Using a low-resistance conductive material can reduce wiring resistance. Conductors 162 and 166 are preferably formed from low-resistance conductive materials.

[0319] <Wiring or plug in layer provided with oxide semiconductor> When an oxide semiconductor is used for the transistor 200, an insulator having an excess oxygen region may be provided near the oxide semiconductor. In that case, an insulator having a barrier property is preferably provided between the insulator having the excess oxygen region and a conductor provided in the insulator having the excess oxygen region.

[0320] 8, for example, an insulator 241 may be provided between the insulator 224 and the insulator 280 containing excess oxygen and the conductor 240. By providing the insulator 241 in contact with the insulator 222, the insulator 282, and the insulator 283, the insulator 224 and the transistor 200 can be sealed with an insulator having barrier properties.

[0321] That is, the insulator 241 can prevent excess oxygen contained in the insulator 224 and the insulator 280 from being absorbed by the conductor 240. Furthermore, the insulator 241 can prevent hydrogen, which is an impurity, from diffusing into the transistor 200 through the conductor 240.

[0322] The insulator 241 may be an insulating material that has the function of suppressing the diffusion of impurities such as water or hydrogen, and oxygen. For example, it is preferable to use silicon nitride, silicon nitride oxide, aluminum oxide, or hafnium oxide. Silicon nitride is particularly preferable because it has a high blocking property against hydrogen. Other examples that can be used include metal oxides such as magnesium oxide, gallium oxide, germanium oxide, yttrium oxide, zirconium oxide, lanthanum oxide, neodymium oxide, and tantalum oxide.

[0323] As described in the above embodiment, the transistor 200 may be sealed with the insulators 212, 214, 282, 283, and 286. Such a structure can reduce the intrusion of hydrogen contained in the insulators 274, 150, and the like into the insulator 280 and the like.

[0324] Here, the conductor 240 penetrates the insulators 283 and 282, and the conductor 218 penetrates the insulators 214 and 212. As described above, the insulator 241 is provided in contact with the conductor 240, and the insulator 217 is provided in contact with the conductor 218. This makes it possible to reduce hydrogen that gets mixed into the inside of the insulators 212, 214, 282, and 283 via the conductors 240 and 218. In this way, the transistor 200 is sealed with the insulators 212, 214, 282, 283, 241, and 217, making it possible to reduce the intrusion of impurities such as hydrogen contained in the insulator 274 from the outside.

[0325] <Dicing line> The following describes dicing lines (sometimes called scribe lines, dividing lines, or cutting lines) that are provided when dividing a large-area substrate into individual semiconductor elements to extract multiple semiconductor devices in chip form. As a dividing method, for example, first, grooves (dicing lines) for dividing the semiconductor elements are formed in the substrate, and then the substrate is cut along the dicing lines to divide (divide) the multiple semiconductor devices.

[0326] 8, for example, it is preferable to design the insulator 282, the insulator 280, the insulator 275, the insulator 222, and the insulator 216 so that the area where the insulator 283 and the insulator 214 contact each other overlaps with the dicing line. That is, openings are provided in the insulators 282, 280, 275, 222, and 216 near the area that will become the dicing line provided on the outer edge of the memory cell having multiple transistors 200.

[0327] That is, insulator 214 and insulator 283 come into contact with each other through openings provided in insulators 282 , 280 , 275 , 222 , and 216 .

[0328] Furthermore, for example, openings may be provided in the insulators 282, 280, 275, 222, 216, and 214. With this configuration, the insulators 212 and 283 are in contact with each other through the openings provided in the insulators 282, 280, 275, 222, 216, and 214. In this case, the insulators 212 and 283 may be formed using the same material and the same method. Providing the insulators 212 and 283 using the same material and the same method can improve adhesion. For example, it is preferable to use silicon nitride.

[0329] With this structure, the transistor 200 can be surrounded by the insulator 212, the insulator 214, the insulator 282, and the insulator 283. At least one of the insulators 212, 214, 282, and 283 has a function of suppressing diffusion of oxygen, hydrogen, and water. Therefore, even when the substrate is divided into a plurality of chips by dividing the substrate into each circuit region in which the semiconductor element described in this embodiment is formed, impurities such as hydrogen or water can be prevented from entering from the side surface of the divided substrate and diffusing into the transistor 200.

[0330] Furthermore, this structure can prevent excess oxygen in the insulator 280 and the insulator 224 from diffusing to the outside. Therefore, the excess oxygen in the insulator 280 and the insulator 224 is efficiently supplied to the oxide in which a channel is formed in the transistor 200. The oxygen can reduce oxygen vacancies in the oxide in which a channel is formed in the transistor 200. This allows the oxide in which a channel is formed in the transistor 200 to be an oxide semiconductor with a low density of defect states and stable characteristics. That is, fluctuations in the electrical characteristics of the transistor 200 can be suppressed and reliability can be improved.

[0331] In the above, an example has been shown in which the transistor 200 is sealed with the insulator 283 and the insulator 214 or the insulator 212, and a dicing line is formed in the region where they contact, but the present invention is not limited to this. For example, a configuration may be used in which the transistor 200 is sealed with the insulator 286 and the insulator 214 or the insulator 212, and a dicing line is formed in the region where they contact.

[0332] (Fourth embodiment) 10A, 10B, and 11A to 11H, a transistor including an oxide as a semiconductor (hereinafter also referred to as an OS transistor) and a memory device including a capacitor (hereinafter also referred to as an OS memory device) according to one embodiment of the present invention will be described. The OS memory device is a memory device including at least a capacitor and an OS transistor that controls charging and discharging of the capacitor. The off-state current of the OS transistor is extremely small, so the OS memory device has excellent retention characteristics and can function as a nonvolatile memory.

[0333] <Storage device configuration example> 10A shows an example of the configuration of an OS memory device. The memory device 1400 includes a peripheral circuit 1411 and a memory cell array 1470. The peripheral circuit 1411 includes a row circuit 1420, a column circuit 1430, an output circuit 1440, and a control logic circuit 1460.

[0334] The column circuit 1430 includes, for example, a column decoder, a precharge circuit, a sense amplifier, a write circuit, etc. The precharge circuit has a function of precharging the wiring. The sense amplifier has a function of amplifying a data signal read from a memory cell. Note that the above wiring is connected to a memory cell in the memory cell array 1470, and will be described in detail later. The amplified data signal is output to the outside of the memory device 1400 as a data signal RDATA via the output circuit 1440. The row circuit 1420 also includes, for example, a row decoder, a word line driver circuit, etc., and can select a row to access.

[0335] The memory device 1400 is supplied with a low power supply voltage (VSS) from the outside as power supply voltages, a high power supply voltage (VDD) for the peripheral circuit 1411, and a high power supply voltage (VIL) for the memory cell array 1470. Control signals (CE, WE, RE), an address signal ADDR, and a data signal WDATA are also input from the outside to the memory device 1400. The address signal ADDR is input to a row decoder and a column decoder, and the data signal WDATA is input to a write circuit.

[0336] The control logic circuit 1460 processes control signals (CE, WE, RE) input from the outside to generate control signals for the row decoder and column decoder. The control signal CE is a chip enable signal, the control signal WE is a write enable signal, and the control signal RE is a read enable signal. The signals processed by the control logic circuit 1460 are not limited to these, and other control signals may be input as needed.

[0337] The memory cell array 1470 has a plurality of memory cells MC arranged in a matrix and a plurality of wirings. The number of wirings connecting the memory cell array 1470 and the row circuit 1420 is determined by the configuration of the memory cells MC, the number of memory cells MC in one column, etc. The number of wirings connecting the memory cell array 1470 and the column circuit 1430 is determined by the configuration of the memory cells MC, the number of memory cells MC in one row, etc.

[0338] 10A shows an example in which the peripheral circuit 1411 and the memory cell array 1470 are formed on the same plane, but this embodiment is not limited to this. For example, as shown in FIG. 10B, the memory cell array 1470 may be provided so as to overlap a part of the peripheral circuit 1411. For example, a sense amplifier may be provided so as to overlap the memory cell array 1470 below.

[0339] 11A to 11H will be used to explain examples of the configuration of a memory cell that can be applied to the above-described memory cell MC.

[0340] [DOSRAM] 11A to 11C show circuit configuration examples of a DRAM memory cell. In this specification and the like, a DRAM using a memory cell with one OS transistor and one capacitor may be referred to as a DOSRAM (Dynamic Oxide Semiconductor Random Access Memory). The memory cell 1471 shown in FIG. 11A includes a transistor M1 and a capacitor CA. The transistor M1 includes a gate (sometimes referred to as a top gate) and a back gate.

[0341] A first terminal of the transistor M1 is connected to a first terminal of the capacitor CA, a second terminal of the transistor M1 is connected to a wiring BIL, a gate of the transistor M1 is connected to a wiring WOL, a back gate of the transistor M1 is connected to a wiring BGL, and a second terminal of the capacitor CA is connected to a wiring LL.

[0342] The wiring BIL functions as a bit line, and the wiring WOL functions as a word line. The wiring LL functions as a wiring for applying a predetermined potential to the second terminal of the capacitor CA. When writing and reading data, it is preferable to apply a low-level potential to the wiring LL. The wiring BGL functions as a wiring for applying a potential to the back gate of the transistor M1. The threshold voltage of the transistor M1 can be increased or decreased by applying an arbitrary potential to the wiring BGL.

[0343] 11A corresponds to the configuration of the memory device shown in FIG. 8 in which the conductor 110 is not electrically connected to the gate of the transistor 300. That is, the transistor M1 corresponds to the transistor 200, and the capacitor CA corresponds to the capacitor 100.

[0344] The memory cell MC is not limited to the memory cell 1471, and the circuit configuration can be changed. For example, the memory cell MC may have a configuration in which the back gate of the transistor M1 is connected to the wiring WOL instead of the wiring BGL, as in the memory cell 1472 shown in FIG. 11B. Furthermore, for example, the memory cell MC may be a memory cell configured with a single-gate transistor, that is, a transistor M1 without a back gate, as in the memory cell 1473 shown in FIG. 11C.

[0345] When the semiconductor device described in the above embodiment is used for the memory cell 1471 or the like, the transistor 200 can be used as the transistor M1 and the capacitor 100 can be used as the capacitor CA. By using an OS transistor as the transistor M1, the leakage current of the transistor M1 can be made very small. That is, written data can be held by the transistor M1 for a long time, so that the frequency of refreshing the memory cell can be reduced. Alternatively, the refresh operation of the memory cell can be made unnecessary. Furthermore, because the leakage current is very small, multilevel data or analog data can be held in the memory cell 1471, the memory cell 1472, and the memory cell 1473.

[0346] Furthermore, in the DOSRAM, if the sense amplifier is configured to overlap under the memory cell array 1470 as described above, the bit line can be shortened, which reduces the bit line capacitance and the storage capacitance of the memory cell.

[0347] [NOSRAM] 11D to 11G show circuit configuration examples of a gain cell type memory cell having two transistors and one capacitor. The memory cell 1474 shown in FIG. 11D includes a transistor M2, a transistor M3, and a capacitor CB. The transistor M2 has a top gate (sometimes simply referred to as a gate) and a back gate. In this specification and the like, a memory device having a gain cell type memory cell using an OS transistor as the transistor M2 may be referred to as a nonvolatile oxide semiconductor RAM (NOSRAM).

[0348] The first terminal of transistor M2 is connected to the first terminal of capacitor CB, the second terminal of transistor M2 is connected to wiring WBL, the gate of transistor M2 is connected to wiring WOL, and the back gate of transistor M2 is connected to wiring BGL. The second terminal of capacitor CB is connected to wiring CAL. The first terminal of transistor M3 is connected to wiring RBL, the second terminal of transistor M3 is connected to wiring SL, and the gate of transistor M3 is connected to the first terminal of capacitor CB.

[0349] The wiring WBL functions as a write bit line, the wiring RBL functions as a read bit line, and the wiring WOL functions as a word line. The wiring CAL functions as a wiring for applying a predetermined potential to the second terminal of the capacitance element CB. When writing data, while retaining data, and while reading data, it is preferable to apply a high-level potential to the wiring CAL. Also, while retaining data, it is preferable to apply a low-level potential to the wiring CAL. The wiring BGL functions as a wiring for applying a potential to the back gate of the transistor M2. By applying an arbitrary potential to the wiring BGL, the threshold voltage of the transistor M2 can be increased or decreased.

[0350] 11D corresponds to the memory device shown in Fig. 8. That is, the transistor M2 corresponds to the transistor 200, the capacitor CB corresponds to the capacitor 100, the transistor M3 corresponds to the transistor 300, the wiring WBL corresponds to the wiring 1003, the wiring WOL corresponds to the wiring 1004, the wiring BGL corresponds to the wiring 1006, the wiring CAL corresponds to the wiring 1005, the wiring RBL corresponds to the wiring 1002, and the wiring SL corresponds to the wiring 1001.

[0351] Furthermore, the memory cell MC is not limited to the memory cell 1474, and the circuit configuration can be changed as appropriate. For example, the memory cell MC may be configured such that the back gate of the transistor M2 is connected to the wiring WOL instead of the wiring BGL, as in the memory cell 1475 shown in FIG. 11E. Furthermore, for example, the memory cell MC may be configured as a memory cell including a transistor M2 with a single gate structure, that is, a transistor M2 without a back gate, as in the memory cell 1476 shown in FIG. 11F. Furthermore, for example, the memory cell MC may be configured such that the wiring WBL and the wiring RBL are combined into a single wiring BIL, as in the memory cell 1477 shown in FIG. 11G.

[0352] When the semiconductor device described in the above embodiment is used for the memory cell 1474 or the like, the transistor 200 can be used as the transistor M2, the transistor 300 can be used as the transistor M3, and the capacitor CB can be used as the capacitor CB. By using an OS transistor as the transistor M2, the leakage current of the transistor M2 can be significantly reduced. This allows written data to be held by the transistor M2 for a long time, thereby reducing the frequency of refreshing the memory cell. Alternatively, the refresh operation of the memory cell can be eliminated. Furthermore, since the leakage current is extremely small, multilevel data or analog data can be held in the memory cell 1474. The same applies to the memory cells 1475 to 1477.

[0353] Note that the transistor M3 may be a transistor having silicon in a channel formation region (hereinafter, may be referred to as a Si transistor). The conductivity type of the Si transistor may be either an n-channel type or a p-channel type. The Si transistor may have higher field-effect mobility than an OS transistor. Therefore, a Si transistor may be used as the transistor M3 functioning as a read transistor. Furthermore, by using a Si transistor as the transistor M3, the transistor M2 can be stacked on top of the transistor M3, thereby reducing the area occupied by the memory cell and achieving higher integration of the memory device.

[0354] Furthermore, the transistor M3 may be an OS transistor. When OS transistors are used for the transistors M2 and M3, the memory cell array 1470 can be configured as a circuit using only n-type transistors.

[0355] 11H shows an example of a gain cell type memory cell having three transistors and one capacitor. The memory cell 1478 shown in FIG. 11H includes transistors M4 to M6 and a capacitor CC. The capacitor CC is provided as appropriate. The memory cell 1478 is electrically connected to wirings BIL, RWL, WWL, BGL, and GNDL. The GNDL wiring is a wiring that applies a low-level potential. Note that the memory cell 1478 may be electrically connected to wirings RBL and WBL instead of wiring BIL.

[0356] The transistor M4 is an OS transistor having a back gate, and the back gate is electrically connected to the wiring BGL. Note that the back gate and the gate of the transistor M4 may be electrically connected to each other. Alternatively, the transistor M4 does not necessarily have a back gate.

[0357] Note that the transistors M5 and M6 may be n-channel Si transistors or p-channel Si transistors. Alternatively, the transistors M4 to M6 may be OS transistors. In this case, the memory cell array 1470 can be configured using only n-channel transistors.

[0358] When the semiconductor device described in the above embodiment is used in the memory cell 1478, the transistor 200 can be used as the transistor M4, the transistors M5 and M6 can be used as the transistors M5 and M6, and the capacitor 100 can be used as the capacitor CC. By using an OS transistor as the transistor M4, the leakage current of the transistor M4 can be made extremely small.

[0359] Note that the configurations of the peripheral circuit 1411, the memory cell array 1470, and the like shown in this embodiment are not limited to those described above. The arrangement or functions of these circuits, wirings connected to the circuits, circuit elements, and the like may be changed, deleted, or added as necessary. The memory device of one embodiment of the present invention has high operating speed and can retain data for a long period of time.

[0360] The structures and methods described in this embodiment can be used in appropriate combination with other structures and methods described in this embodiment or structures and methods described in other embodiments.

[0361] (Embodiment 5) 12A and 12B, an example of a chip 1200 on which a semiconductor device of the present invention is mounted is shown. A plurality of circuits (systems) are mounted on the chip 1200. A technology for integrating a plurality of circuits (systems) on a single chip in this manner is sometimes called a system on chip (SoC).

[0362] As shown in FIG. 12A, a chip 1200 includes a CPU 1211, a GPU 1212, one or more analog arithmetic units 1213, one or more memory controllers 1214, one or more interfaces 1215, one or more network circuits 1216, and the like.

[0363] 12B, the chip 1200 is provided with bumps (not shown), which are connected to a first surface of a package substrate 1201. In addition, a plurality of bumps 1202 are provided on the backside of the first surface of the package substrate 1201, which are connected to a motherboard 1203.

[0364] The motherboard 1203 may be provided with storage devices such as a DRAM 1221 and a flash memory 1222. For example, the DOSRAM described in the previous embodiment may be used as the DRAM 1221. Also, for example, the NOSRAM described in the previous embodiment may be used as the flash memory 1222.

[0365] The CPU 1211 preferably has multiple CPU cores. The GPU 1212 preferably has multiple GPU cores. The CPU 1211 and the GPU 1212 may each have a memory for temporarily storing data. Alternatively, a memory common to the CPU 1211 and the GPU 1212 may be provided on the chip 1200. The memory may be the NOSRAM or DOSRAM described above. The GPU 1212 is suitable for parallel calculation of a large amount of data and can be used for image processing or multiply-and-accumulate operations. By providing the GPU 1212 with an image processing circuit and a multiply-and-accumulate circuit using the oxide semiconductor of the present invention, it becomes possible to perform image processing and multiply-and-accumulate operations with low power consumption.

[0366] Furthermore, by providing the CPU 1211 and GPU 1212 on the same chip, the wiring between the CPU 1211 and GPU 1212 can be shortened, enabling high-speed data transfer from the CPU 1211 to the GPU 1212, data transfer between the memories of the CPU 1211 and GPU 1212, and transfer of the calculation results from the GPU 1212 to the CPU 1211 after calculation in the GPU 1212.

[0367] The analog calculation unit 1213 has one or both of an A / D (analog / digital) conversion circuit and a D / A (digital / analog) conversion circuit. The analog calculation unit 1213 may also be provided with the above-mentioned product-sum calculation circuit.

[0368] The memory controller 1214 has a circuit that functions as a controller for the DRAM 1221 and a circuit that functions as an interface for the flash memory 1222 .

[0369] The interface 1215 has an interface circuit with externally connected devices such as a display device, speaker, microphone, camera, and controller. Controllers include a mouse, keyboard, game controller, etc. As such an interface, a USB (Universal Serial Bus), HDMI (registered trademark) (High-Definition Multimedia Interface), etc. can be used.

[0370] The network circuit 1216 includes a network circuit such as a LAN (Local Area Network), and may also include a circuit for network security.

[0371] The above circuits (systems) can be formed in the same manufacturing process on the chip 1200. Therefore, even if the number of circuits required for the chip 1200 increases, there is no need to increase the manufacturing process, and the chip 1200 can be manufactured at low cost.

[0372] A package substrate 1201 on which a chip 1200 having a GPU 1212 is provided, a motherboard 1203 on which a DRAM 1221 and a flash memory 1222 are provided can be called a GPU module 1204.

[0373] The GPU module 1204 includes the chip 1200 using SoC technology, allowing for a small size. Furthermore, due to its superior image processing capabilities, it is suitable for use in portable electronic devices such as smartphones, tablet devices, laptop PCs, and portable (portable) game consoles. Furthermore, a multiply-and-accumulate circuit using the GPU 1212 can execute techniques such as deep neural networks (DNNs), convolutional neural networks (CNNs), recurrent neural networks (RNNs), autoencoders, deep Boltzmann machines (DBMs), and deep belief networks (DBNs). Therefore, the chip 1200 can be used as an AI chip, and the GPU module 1204 can be used as an AI system module.

[0374] At least part of the structures, methods, and the like described in this embodiment mode can be implemented in appropriate combination with other embodiment modes and examples described in this specification.

[0375] (Sixth embodiment) This embodiment mode will describe examples of electronic components and electronic devices in which the memory device or the like described in the above embodiment mode is incorporated.

[0376] <Electronic components> First, an example of an electronic component incorporating a memory device 720 will be described with reference to FIGS. 13A and 13B.

[0377] FIG. 13A shows a perspective view of electronic component 700 and a substrate (mounting substrate 704) on which electronic component 700 is mounted. Electronic component 700 shown in FIG. 13A has memory device 720 inside mold 711. FIG. 13A omits a portion of the interior of electronic component 700 to show it. Electronic component 700 has lands 712 on the outside of mold 711. Lands 712 are electrically connected to electrode pads 713, and electrode pads 713 are electrically connected to memory device 720 by wires 714. Electronic component 700 is mounted on, for example, a printed circuit board 702. A plurality of such electronic components are combined and electrically connected on printed circuit board 702 to complete mounting substrate 704.

[0378] The memory device 720 includes a driver circuit layer 721 and a memory circuit layer 722 .

[0379] 13B shows a perspective view of electronic component 730. Electronic component 730 is an example of a SiP (System in Package) or MCM (Multi Chip Module). Electronic component 730 has an interposer 731 provided on a package substrate 732 (printed circuit board), and a semiconductor device 735 and multiple memory devices 720 provided on interposer 731.

[0380] In the electronic component 730, an example is shown in which the storage device 720 is used as a high bandwidth memory (HBM). The semiconductor device 735 can be an integrated circuit (semiconductor device) such as a CPU, a GPU, or an FPGA.

[0381] The package substrate 732 may be a ceramic substrate, a plastic substrate, a glass epoxy substrate, etc. The interposer 731 may be a silicon interposer, a resin interposer, etc.

[0382] The interposer 731 has multiple wirings and functions to electrically connect multiple integrated circuits with different terminal pitches. The multiple wirings are provided in a single layer or multiple layers. The interposer 731 also functions to electrically connect the integrated circuits provided on the interposer 731 to electrodes provided on the package substrate 732. For these reasons, the interposer is sometimes called a "rewiring substrate" or "intermediate substrate." In some cases, through electrodes are provided in the interposer 731, and the integrated circuits and the package substrate 732 are electrically connected using the through electrodes. In addition, with a silicon interposer, TSVs (Through Silicon Vias) can also be used as through electrodes.

[0383] It is preferable to use a silicon interposer as the interposer 731. Since a silicon interposer does not require the provision of active elements, it can be manufactured at a lower cost than an integrated circuit. On the other hand, since the wiring formation of a silicon interposer can be performed using a semiconductor process, it is easy to form fine wiring that is difficult to form with a resin interposer.

[0384] HBM requires many interconnects to achieve a wide memory bandwidth. Therefore, the interposer that implements HBM requires fine and high-density interconnects. Therefore, it is preferable to use a silicon interposer for implementing HBM.

[0385] Furthermore, in SiP or MCM using silicon interposers, a decrease in reliability due to differences in the expansion coefficient between the integrated circuit and the interposer is unlikely to occur. Furthermore, because the silicon interposer has a highly flat surface, poor connection between the integrated circuit mounted on the silicon interposer and the silicon interposer is unlikely to occur. In particular, it is preferable to use silicon interposers in 2.5D packages (2.5-dimensional packaging), in which multiple integrated circuits are arranged horizontally on the interposer.

[0386] A heat sink (heat dissipation plate) may be provided over the electronic component 730. When a heat sink is provided, it is preferable to align the height of an integrated circuit provided on the interposer 731. For example, in the electronic component 730 shown in this embodiment, it is preferable to align the height of the memory device 720 and the height of the semiconductor device 735.

[0387] Electrodes 733 may be provided on the bottom of package substrate 732 in order to mount electronic component 730 on another substrate. Fig. 13B shows an example in which electrodes 733 are formed with solder balls. By providing solder balls in a matrix on the bottom of package substrate 732, BGA (Ball Grid Array) mounting can be achieved. Electrodes 733 may also be formed with conductive pins. By providing conductive pins in a matrix on the bottom of package substrate 732, PGA (Pin Grid Array) mounting can be achieved.

[0388] The electronic component 730 can be mounted on other substrates using various mounting methods, including but not limited to BGA and PGA, such as a staggered pin grid array (SPGA), a land grid array (LGA), a quad flat package (QFP), a quad flat J-leaded package (QFJ), or a quad flat non-leaded package (QFN).

[0389] The structures and methods described in this embodiment can be used in appropriate combination with other structures and methods described in this embodiment or structures and methods described in other embodiments.

[0390] (Embodiment 7) In this embodiment, an application example of a storage device using the semiconductor device described in the previous embodiment will be described. The semiconductor device described in the previous embodiment can be applied to storage devices of various electronic devices (e.g., information terminals, computers, smartphones, e-book readers, digital cameras (including video cameras), recording / playback devices, navigation systems, etc.). Note that the term "computer" here refers to a tablet computer, a notebook computer, a desktop computer, and a large-scale computer such as a server system. Alternatively, the semiconductor device described in the previous embodiment can be applied to various removable storage devices such as memory cards (e.g., SD cards), USB memories, and SSDs (solid-state drives). FIGS. 14A to 14E schematically show several configuration examples of removable storage devices. For example, the semiconductor device described in the previous embodiment can be processed into a packaged memory chip and used in various storage devices and removable memories.

[0391] 14A is a schematic diagram of a USB memory. The USB memory 1100 has a housing 1101, a cap 1102, a USB connector 1103, and a board 1104. The board 1104 is housed in the housing 1101. For example, a memory chip 1105 and a controller chip 1106 are attached to the board 1104. The semiconductor device described in the above embodiment can be incorporated into the memory chip 1105 or the like.

[0392] FIG. 14B is a schematic diagram of the appearance of an SD card, and FIG. 14C is a schematic diagram of the internal structure of the SD card. The SD card 1110 has a housing 1111, a connector 1112, and a substrate 1113. The substrate 1113 is housed in the housing 1111. For example, a memory chip 1114 and a controller chip 1115 are attached to the substrate 1113. The capacity of the SD card 1110 can be increased by providing a memory chip 1114 on the back side of the substrate 1113. Furthermore, a wireless chip with a wireless communication function may be provided on the substrate 1113. This enables reading and writing of data from and to the memory chip 1114 through wireless communication between a host device and the SD card 1110. The semiconductor device described in the above embodiment can be incorporated into the memory chip 1114 or the like.

[0393] FIG. 14D is a schematic diagram of the appearance of an SSD, and FIG. 14E is a schematic diagram of the internal structure of the SSD. SSD 1150 has a housing 1151, a connector 1152, and a board 1153. Board 1153 is housed in housing 1151. For example, memory chips 1154, 1155, and a controller chip 1156 are attached to board 1153. Memory chip 1155 is a work memory for controller chip 1156, and may be, for example, a DOSRAM chip. By providing a memory chip 1154 on the back side of board 1153, the capacity of SSD 1150 can be increased. The semiconductor device described in the previous embodiment can be incorporated into memory chip 1154 or the like.

[0394] At least part of the structures, methods, and the like described in this embodiment mode can be implemented in appropriate combination with other embodiment modes and examples described in this specification.

[0395] (Embodiment 8) A semiconductor device according to one embodiment of the present invention can be used in a processor such as a CPU or a GPU, or a chip. Specific examples of electronic devices including a processor such as a CPU or a GPU, or a chip according to one embodiment of the present invention are shown in FIGS. 15A to 15H.

[0396] <Electronic devices and systems> A GPU or chip according to one embodiment of the present invention can be mounted in various electronic devices. Examples of such electronic devices include electronic devices with relatively large screens, such as televisions, monitors for desktop or notebook information terminals, digital signage, and large game machines such as pachinko machines, as well as digital cameras, digital video cameras, digital photo frames, e-book readers, mobile phones, portable game machines, personal digital assistants, and audio playback devices. Furthermore, by providing an electronic device with a GPU or chip according to one embodiment of the present invention, it is possible to equip the electronic device with artificial intelligence.

[0397] The electronic device of one embodiment of the present invention may include an antenna. By receiving a signal through the antenna, images, information, or the like can be displayed on a display portion. When the electronic device includes an antenna and a secondary battery, the antenna may be used for contactless power transmission.

[0398] An electronic device according to one embodiment of the present invention may have a sensor (including a function for measuring force, displacement, position, velocity, acceleration, angular velocity, rotation speed, distance, light, liquid, magnetism, temperature, chemical substance, sound, time, hardness, electric field, current, voltage, power, radiation, flow rate, humidity, gradient, vibration, odor, or infrared rays).

[0399] An electronic device of one embodiment of the present invention can have various functions. For example, it can have a function of displaying various information (still images, videos, text images, etc.) on a display unit, a touch panel function, a function of displaying a calendar, date, time, etc., a function of executing various software (programs), a wireless communication function, a function of reading programs or data recorded on a recording medium, etc. Examples of electronic devices are shown in FIGS. 15A to 15H.

[0400] [Information terminal] 15A shows a mobile phone (smartphone), which is one type of information terminal. The information terminal 5100 has a housing 5101 and a display unit 5102. As input interfaces, a touch panel is provided on the display unit 5102 and buttons are provided on the housing 5101.

[0401] By applying the chip of one embodiment of the present invention, the information terminal 5100 can execute applications using artificial intelligence. Examples of applications using artificial intelligence include an application that recognizes a conversation and displays the conversation content on the display portion 5102, an application that recognizes characters, figures, or the like input by a user to a touch panel provided in the display portion 5102 and displays the characters, figures, or the like on the display portion 5102, and an application that performs biometric authentication such as fingerprint or voiceprint authentication.

[0402] 15B illustrates a notebook information terminal 5200. The notebook information terminal 5200 includes a main body 5201 of the information terminal, a display unit 5202, and a keyboard 5203.

[0403] The notebook information terminal 5200 can execute applications using artificial intelligence by applying a chip of one embodiment of the present invention, similar to the information terminal 5100 described above. Examples of applications using artificial intelligence include design support software, text correction software, and automatic menu generation software. Furthermore, new artificial intelligence can be developed by using the notebook information terminal 5200.

[0404] 15A and 15B, a smartphone and a notebook type information terminal are used as examples of electronic devices, but information terminals other than smartphones and notebook type information terminals can also be used. Examples of information terminals other than smartphones and notebook type information terminals include PDAs (Personal Digital Assistants), desktop type information terminals, and workstations.

[0405] [Game consoles] FIG. 15C illustrates a portable game console 5300, which is an example of a game console. The portable game console 5300 includes a housing 5301, a housing 5302, a housing 5303, a display unit 5304, a connection unit 5305, operation keys 5306, and the like. The housing 5302 and the housing 5303 can be detached from the housing 5301. By attaching the connection unit 5305 of the housing 5301 to another housing (not shown), the video displayed on the display unit 5304 can be output to another video device (not shown). In this case, the housing 5302 and the housing 5303 can each function as an operation unit. This allows multiple players to play a game simultaneously. The chips described in the above embodiments can be incorporated into the substrates of the housings 5301, 5302, and 5303.

[0406] 15D shows an example of a game machine, a stationary game machine 5400. A controller 5402 is connected to the stationary game machine 5400 wirelessly or via a wire.

[0407] A game machine with low power consumption can be realized by applying a GPU or a chip of one embodiment of the present invention to a game machine such as a portable game machine 5300 or a stationary game machine 5400. Furthermore, low power consumption can reduce heat generation from a circuit, thereby reducing the influence of heat on the circuit itself, peripheral circuits, and modules.

[0408] Furthermore, by applying the GPU or chip of one embodiment of the present invention to the portable game console 5300, the portable game console 5300 can have artificial intelligence.

[0409] Originally, the expression of the progress of a game, the behavior of creatures appearing in the game, and phenomena occurring in the game are determined by the program of the game, but by applying artificial intelligence to the portable game console 5300, it becomes possible to express things that are not limited to the game program. For example, it becomes possible to express things such as changes in the questions asked by the player, the progress of the game, the time, and the behavior of people appearing in the game.

[0410] Furthermore, when playing a game requiring multiple players on the portable game console 5300, the game players can be personified using artificial intelligence, so that the game can be played by one person by making the opponent a game player based on artificial intelligence.

[0411] 15C and 15D illustrate a portable game machine and a stationary game machine as examples of game machines, but game machines to which the GPU or chip of one embodiment of the present invention is applied are not limited to these. Examples of game machines to which the GPU or chip of one embodiment of the present invention is applied include arcade game machines installed in entertainment facilities (game centers, amusement parks, etc.) and pitching machines for batting practice installed in sports facilities.

[0412] [Mainframe Computer] The GPU or chip according to one embodiment of the present invention can be applied to a mainframe computer.

[0413] 15E is a diagram showing a supercomputer 5500, which is an example of a mainframe computer. FIG. 15F is a diagram showing a rack-mounted computer 5502 included in the supercomputer 5500.

[0414] The supercomputer 5500 includes a rack 5501 and a plurality of rack-mounted computers 5502. The plurality of computers 5502 are stored in the rack 5501. The computer 5502 is provided with a plurality of boards 5504, and the GPU or chip described in the above embodiment can be mounted on the boards.

[0415] The supercomputer 5500 is a large-scale computer primarily used for scientific and technological calculations. Scientific and technological calculations require high-speed processing of enormous amounts of calculations, resulting in high power consumption and large amounts of heat generated by the chip. By applying a GPU or chip according to one embodiment of the present invention to the supercomputer 5500, a supercomputer with low power consumption can be realized. Furthermore, low power consumption can reduce heat generation from circuits, thereby reducing the impact of heat generation on the circuits themselves, peripheral circuits, and modules.

[0416] 15E and 15F illustrate a supercomputer as an example of a mainframe computer, but the mainframe computer to which the GPU or chip of one embodiment of the present invention is applied is not limited to this. Examples of the mainframe computer to which the GPU or chip of one embodiment of the present invention is applied include a computer (server) that provides services, a large general-purpose computer (mainframe), etc.

[0417] [Moving object] The GPU or chip according to one embodiment of the present invention can be applied to automobiles, which are moving objects, and to the area around the driver's seat of an automobile.

[0418] Fig. 15G is a diagram showing the area around the windshield inside the interior of an automobile, which is an example of a moving body, showing display panel 5701, display panel 5702, and display panel 5703 attached to the dashboard, as well as display panel 5704 attached to a pillar.

[0419] The display panels 5701 to 5703 can provide various information by displaying a speedometer, tachometer, mileage, fuel gauge, gear status, air conditioning settings, etc. Furthermore, the display items or layout displayed on the display panels can be changed as appropriate to suit the user's preferences, allowing for improved design. The display panels 5701 to 5703 can also be used as lighting devices.

[0420] The display panel 5704 can complement the view (blind spot) blocked by the pillar by displaying an image from an imaging device (not shown) installed in the vehicle. That is, by displaying an image from an imaging device installed outside the vehicle, blind spots can be complemented and safety can be improved. Furthermore, by displaying an image that complements the invisible part, safety can be confirmed more naturally and without discomfort. The display panel 5704 can also be used as a lighting device.

[0421] Since the GPU or chip of one embodiment of the present invention can be used as a component of artificial intelligence, the chip can be used, for example, in an automatic driving system for automobiles. The chip can also be used in a system that provides road guidance, hazard prediction, etc. The display panels 5701 to 5704 may be configured to display information such as road guidance and hazard prediction.

[0422] Although an automobile is described above as an example of a moving body, the moving body is not limited to an automobile. For example, moving bodies can include trains, monorails, ships, and flying bodies (helicopters, unmanned aerial vehicles (drones), airplanes, and rockets), and the chip of one embodiment of the present invention can be applied to these moving bodies to provide a system using artificial intelligence.

[0423] [electric appliances] 15H shows an example of an electric appliance, an electric refrigerator-freezer 5800. The electric refrigerator-freezer 5800 includes a housing 5801, a refrigerator door 5802, a freezer door 5803, and the like.

[0424] The electric refrigerator-freezer 5800 having artificial intelligence can be realized by applying the chip of one embodiment of the present invention to the electric refrigerator-freezer 5800. By using artificial intelligence, the electric refrigerator-freezer 5800 can have a function of automatically generating a menu based on ingredients stored in the electric refrigerator-freezer 5800 and their expiration dates, a function of automatically adjusting the temperature to match the ingredients stored in the electric refrigerator-freezer 5800, and the like.

[0425] Although electric refrigerator-freezers have been described as an example of electrical appliances, other electrical appliances include, for example, vacuum cleaners, microwave ovens, electric ovens, rice cookers, water heaters, induction cookers, water dispensers, heating and cooling appliances including air conditioners, washing machines, dryers, and audio-visual equipment.

[0426] The electronic devices, functions of the electronic devices, application examples of artificial intelligence, and effects thereof described in this embodiment can be appropriately combined with descriptions of other electronic devices.

[0427] At least part of the structures, methods, and the like described in this embodiment mode can be implemented in appropriate combination with other embodiment modes and examples described in this specification. [Example]

[0428] In this example, the transistor described in the above embodiment was manufactured, and its electrical characteristics were measured.

[0429] In this example, transistors having the same configuration as the transistor 200 shown in FIG. 4 were arranged at 2.0 pieces / μm 2 Sample 1 was fabricated in which the insulators 212 were arranged at a density of 1000 times the density of the insulators 210a and 210b, and the electrical characteristics of Sample 1 were measured. Note that the transistor of Sample 1 differs from the transistor 200 shown in FIG. 4 in that the insulator 212 has a single-layer structure. Also, as shown in FIG. 5B, the transistor of Sample 1 has an insulator 250 having a stacked structure of insulators 250a and 250b.

[0430] Silicon nitride with a film thickness of 60 nm was used as the insulator 212. The insulator 212 was deposited by pulse DC sputtering using a silicon target. The deposition gases used for the deposition of the insulator 212 were argon gas at 30 sccm (25 sccm from the first gas supply port and 5 sccm from the second gas supply port) and nitrogen gas at 85 sccm, the deposition pressure was 0.5 Pa, the substrate temperature was 200°C, and the distance between the target and the substrate was 62 mm. The pulse DC power supply had a power of 1 kW, a frequency of 100 kHz, and an off time per cycle of 4016 nsec.

[0431] The insulator 214 was made of aluminum oxide with a thickness of 40 nm, formed by sputtering. The insulator 214 was first formed to a thickness of 5 nm without applying bias power, and then formed to a thickness of 35 nm with applying bias power of 50 W. The insulator 216 was made of silicon oxide with a thickness of 130 nm, formed by sputtering. The insulators 212, 214, and 216 were successively formed using a multi-chamber sputtering apparatus without being exposed to the outside air.

[0432] The conductor 205a was made of titanium nitride film formed by metal CVD, and the conductor 205b was made of tungsten film formed by metal CVD.

[0433] A hafnium oxide film having a thickness of 20 nm formed by the ALD method was used as the insulator 222. Furthermore, a silicon oxide film having a thickness of 20 nm formed by the sputtering method was used as the insulator 224.

[0434] The oxide 230a was a 10-nm-thick In-Ga-Zn oxide film formed by DC sputtering. The oxide 230a was formed using a target with an In:Ga:Zn atomic ratio of 1:3:4, oxygen gas at 45 sccm, a deposition pressure of 0.7 Pa, a deposition power of 500 W, a substrate temperature of 300°C, and a target-substrate distance of 60 mm. The insulator 224 and the oxide 230a were formed consecutively using a multi-chamber sputtering system without exposure to the air.

[0435] The oxide 230b was a 15-nm-thick In-Ga-Zn oxide film formed by DC sputtering. The oxide 230b was formed using a target with an atomic ratio of In:Ga:Zn=1:1:2, oxygen gas at 45 sccm, a deposition pressure of 0.4 Pa, a deposition power of 200 W, a substrate temperature of 300°C, and a target-substrate distance of 130 mm.

[0436] After the oxide film that becomes the oxide 230b is formed, a heat treatment is performed at 450° C. for 1 hour with nitrogen gas at 4 slm and oxygen gas at 1 slm.

[0437] The conductor 242 was made of tantalum nitride with a thickness of 20 nm, formed by sputtering. The insulator 271 was made of aluminum oxide with a thickness of 5 nm, formed by sputtering. The insulator 275 was a laminated film of aluminum oxide with a thickness of 5 nm, formed by sputtering, and silicon nitride with a thickness of 5 nm, formed thereon by PEALD. The insulator 280 was a laminated film of silicon oxide with a thickness of 5 nm, formed thereon by sputtering, and silicon nitride.

[0438] The insulator 252 was made of aluminum oxide with a thickness of 1 nm and formed by the ALD method. The insulator 250a was made of silicon oxynitride with a thickness of 5 nm and formed by the CVD method. The insulator 250b was made of hafnium oxide with a thickness of 1.5 nm and formed by the ALD method. The insulator 254 was made of silicon nitride with a thickness of 1 nm and formed by the PEALD method.

[0439] The conductor 260a was made of titanium nitride with a thickness of 5 nm and formed by metal CVD, and the conductor 260b was made of tungsten and formed by metal CVD.

[0440] A 40-nm-thick aluminum oxide film formed by sputtering was used as the insulator 282. The insulator 282 was formed to a thickness of 5 nm with a bias power of 300 W applied, and then to a thickness of 35 nm with a bias power of 100 W applied.

[0441] The insulator 283 was a silicon nitride film with a thickness of 25 nm formed by sputtering. The insulator 288 was a silicon nitride film with a thickness of 5 nm formed by PEALD. The insulator 274 was a silicon oxynitride film formed by APCVD. Here, the insulators 283, 288, and 274 were subjected to CMP processing until the top of the insulator 283 was exposed. Therefore, the tops of the insulators 283, 288, and 274 roughly coincide with each other.

[0442] The insulator 285 is made of silicon oxide with a thickness of 50 nm, deposited by sputtering. Openings reaching the conductor 242 are formed in the insulators 285, 283, 280, 275, and 271, and the insulators 241 and conductor 240 are disposed in the openings. The insulator 241 is made of aluminum oxide with a thickness of 5 nm, deposited by ALD, on the side of the opening, and silicon nitride with a thickness of 5 nm, deposited by PEALD, on the inside of the insulator 241. The conductor 240 is made of titanium nitride with a thickness of 5 nm, deposited by metal CVD, on the inside of the insulator 241, and tungsten with a thickness of 5 nm, deposited by metal CVD, on the inside of the titanium nitride.

[0443] A conductor 246 is disposed in contact with the upper surfaces of the conductor 240, the insulator 241, and the insulator 285. The conductor 246 is made of tungsten having a film thickness of 50 nm, which is formed by sputtering.

[0444] The insulator 286a is disposed covering the conductor 240 and the insulator 285. The insulator 286a is a 10-nm-thick silicon nitride film formed by sputtering. The insulator 286a is formed by pulsed DC sputtering using a silicon target. The deposition gases used for the deposition of the insulator 286a were argon gas at 30 sccm (25 sccm from the first gas supply port and 5 sccm from the second gas supply port) and nitrogen gas at 85 sccm. The deposition pressure was 0.5 Pa, the substrate temperature was 200°C, and the target-substrate distance was 62 mm. The pulsed DC power supply had a power of 1 kW, a frequency of 100 kHz, and an off time per cycle of 4016 nsec. Prior to deposition of the insulator 286a, a heat treatment was performed under reduced pressure at 350°C for 5 minutes. The deposition of the insulator 286a was then performed without exposure to the outside air.

[0445] The insulator 286b is disposed to cover the insulator 286a. The insulator 286b is a silicon nitride film with a thickness of 5 nm formed by the PEALD method. The insulator 286b is formed by repeatedly introducing an inorganic silicon precursor and applying plasma with a frequency of 13.56 MHz while introducing nitrogen gas into the chamber. The insulator 286b is formed at a substrate temperature of 350°C.

[0446] Sample 1 having the above configuration is a transistor with a channel length of 60 nm and a channel width of 60 nm, as designed values. Although not shown in the transistor 200 shown in FIG. 4, in Sample 1, a polyimide film with a thickness of 1.4 μm is formed on the insulator 286. After fabrication, Sample 1 was subjected to a heat treatment in a nitrogen atmosphere at a temperature of 400° C. for 8 hours.

[0447] The Id-Vg characteristics (drain current-gate voltage characteristics) of the nine devices of Sample 1 fabricated as described above were measured using a semiconductor parameter analyzer manufactured by Keysight Technologies. The Id-Vg characteristics were measured by setting the drain potential Vd to 0.1 V or 1.2 V, the source potential Vs to 0 V, the bottom gate potential Vbg to 0 V, and sweeping the top gate potential Vg from -4.0 V to 4.0 V in 0.1 V steps.

[0448] 16 shows the measurement results of the Id-Vg characteristics of Sample 1. In FIG. 16, the horizontal axis represents the top gate potential Vg (V), the first vertical axis represents the drain current Id (A), and the second vertical axis represents the field-effect mobility μFE (cm) at Vd=0.1 V. 2 / Vs). The drain current at Vd=0.1 V is shown by a thin solid line, the drain current at Vd=1.2 V is shown by a thick solid line, and the field-effect mobility at Vd=0.1 V is shown by a dashed line. As shown in FIG. 16, all nine transistors of Sample 1 of this example exhibited good electrical characteristics.

[0449] Furthermore, the shift voltage Vsh of each of the nine devices was calculated from the results of the Id-Vg measurements, and its median and standard deviation σ were determined. Here, the shift voltage Vsh is defined as the Vg at which the tangent to the maximum slope of the transistor's Id-Vg curve intersects with the line at Id = 1 pA. The median value of the shift voltage Vsh was 0.17 V, and the standard deviation of the shift voltage Vsh was 36 mV, both of which were good values.

[0450] By providing the insulator 286 having a barrier property against impurities such as hydrogen in this manner, a transistor with good electrical characteristics and little variation in transistor characteristics within the substrate surface can be provided.

[0451] At least a part of the configurations, methods, and the like shown in this embodiment can be implemented in appropriate combination with the embodiment modes and other embodiments described in this specification. [Explanation of symbols]

[0452] M1: transistor, M2: transistor, M3: transistor, M4: transistor, M5: transistor, M6: transistor, 10: semiconductor device, 11: insulator, 11a: insulator, 11b: insulator, 12: oxide semiconductor element, 13: element layer, 14: conductor, 15: conductor, 15A: conductive film, 18: insulator, 18a: insulator, 18b: insulator, 19: opening, 100: capacitance element, 110: conductor, 112: conductor, 120: conductor, 130: insulator, 150: insulator, 158: conductor, 160: insulator, 162: conductor, 164: insulator, 166: conductor Conductor, 168: insulator, 168a: insulator, 168b: insulator, 200: transistor, 205: conductor, 205a: conductor, 205b: conductor, 210: insulator, 212: insulator, 212a: insulator, 212b: insulator, 214: insulator, 216: insulator, 217: insulator, 218: conductor, 222: insulator, 224: insulator, 230: oxide, 230a: oxide, 230b: oxide, 230ba: region, 230bb: region, 230bc: region, 240: conductor, 240a: conductor, 240b: conductor, 241: insulator, 241a: insulator, 241b : insulator, 242: conductor, 242a: conductor, 242b: conductor, 246: conductor, 246a: conductor, 246b: conductor, 250: insulator, 250a: insulator, 250b: insulator, 252: insulator, 254: insulator, 260: conductor, 260a: conductor, 260b: conductor, 265: sealing portion, 271: insulator, 271a: insulator, 271b: insulator, 274: insulator, 275: insulator, 280: insulator, 282: insulator, 283: insulator, 285: insulator, 286: insulator, 286a: insulator, 286b: insulator, 287: insulator, 288: insulator , 300: transistor, 311: substrate, 313: semiconductor region, 314a: low resistance region, 314b: low resistance region, 315: insulator, 316: conductor, 320: insulator, 322: insulator, 324: insulator, 326: insulator, 328: conductor, 330: conductor, 350: insulator, 352: insulator, 354: insulator, 356: conductor, 400: opening region, 500: semiconductor device, 700: electronic component, 702: printed circuit board, 704: mounting board, 711: mold, 712: land, 713: electrode pad, 714: wire, 720: memory device, 721: drive circuit layer,722: memory circuit layer, 730: electronic component, 731: interposer, 732: package substrate, 733: electrode, 735: semiconductor device, 1001: wiring, 1002: wiring, 1003: wiring, 1004: wiring, 1005: wiring, 1006: wiring, 1100: USB memory, 1101: housing, 1102: cap, 1103: USB connector, 1104: substrate, 1105: memory chip, 1106: controller chip, 1110: SD card, 1111: housing, 1112: connector, 1113: substrate, 1114: memory chip ,1115: Controller chip, 1150: SSD, 1151: Housing, 1152: Connector, 1153: Board, 1154: Memory chip, 1155: Memory chip, 1156: Controller chip, 1200: Chip, 1201: Package board, 1202: Bump, 1203: Motherboard, 1204: GPU module, 1211: CPU, 1212: GPU, 1213: Analog calculation unit, 1214: Memory controller, 1215: Interface, 1216: Network circuit, 1221: DRAM, 1222 2: flash memory, 1400: storage device, 1411: peripheral circuit, 1420: row circuit, 1430: column circuit, 1440: output circuit, 1460: control logic circuit, 1470: memory cell array, 1471: memory cell, 1472: memory cell, 1473: memory cell, 1474: memory cell, 1475: memory cell, 1476: memory cell, 1477: memory cell, 1478: memory cell, 5100: information terminal, 5101: housing, 5102: display unit, 5200: notebook information terminal, 5201: main body, 5202: table display unit, 5203: keyboard, 5300: portable game console, 5301: housing, 5302: housing, 5303: housing, 5304: display unit, 5305: connection unit, 5306: operation keys, 5400: stationary game console, 5402: controller, 5500: supercomputer, 5501: rack, 5502: calculator, 5504: circuit board, 5701: display panel, 5702: display panel, 5703: display panel, 5704: display panel, 5800: electric refrigerator-freezer, 5801: housing, 5802: refrigerator compartment door, 5803: freezer compartment door,

Claims

[Claim 1] forming an opening in a structure including an oxide semiconductor device, the opening reaching the oxide semiconductor device; filling the opening with a first conductor; forming a second conductor in contact with an upper surface of the first conductor; forming a first barrier insulating film by a sputtering method to cover the structure, the first conductor, and the second conductor; forming a second barrier insulating film on the first barrier insulating film by an ALD method; the first barrier insulating film and the second barrier insulating film have a function of suppressing diffusion of hydrogen, The method for manufacturing a semiconductor device, wherein the hydrogen concentration of the first barrier insulating film is lower than the hydrogen concentration of the second barrier insulating film.

Images