Semiconductor equipment

Abstract

It provides materials suitable for semiconductor applications such as transistors and diodes. - Using large substrates such as glass to mass-produce highly reliable semiconductor devices. The present invention provides a semiconductor device that can perform the following: an oxide semiconductor film and a gate in contact with the oxide semiconductor film. The present invention provides a semiconductor device having a transistor with a good electronic state at the interface with an insulating film. By providing stable electrical characteristics to transistors using oxide semiconductor films as channels, reliability is improved. To manufacture high-performance semiconductor devices. [Solution] C-axis oriented and triangular or hexagonal when viewed from the direction of the surface or interface A semiconductor device using an oxide material containing crystals that have an atomic arrangement and are rotated around the c-axis.

Description

[Technical Field]

[0001] This relates to a semiconductor device having a circuit including semiconductor elements such as transistors, and a method for manufacturing the same. For example, power devices, memory, thyristors, converters, etc., that are mounted in power supply circuits. Semiconductor integrated circuits including image sensors, electro-optical devices such as liquid crystal display panels, This relates to electronic devices that incorporate light-emitting devices such as light-emitting displays as components. It also relates to semiconductors. Regarding oxides used in the device.

[0002] In this specification, a semiconductor device refers to a device that can function by utilizing semiconductor properties. This term encompasses all types of electronic devices, including electro-optical devices, light-emitting devices, semiconductor circuits, and electronic equipment. That is the case. [Background technology]

[0003] As exemplified by liquid crystal displays, many transistors formed on glass substrates, etc., are ammonia. It is composed of materials such as crystalline silicon and amorphous silicon. Transistors using this method have low field-effect mobility, but can be used to create large-area glass substrates. This is possible. Also, the field-effect mobility of transistors using polycrystalline silicon is high, but glass It has the disadvantage of not being suitable for increasing the surface area of ​​the substrate.

[0004] In addition to transistors made from silicon, in recent years transistors have been made using oxide semiconductors. The technology for manufacturing and applying these materials to electronic and optical devices is attracting attention. For example, oxide semiconductors As a base material, a transistor was fabricated using zinc oxide and an In-Ga-Zn-O system oxide, and the table Patent documents 1 and 2 disclose technologies used for switching elements of pixels in display devices. is provided.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] One aspect of the present invention is to provide a material suitable for semiconductor applications such as transistors and diodes. This is one of the problems.

[0007] Another problem is to provide a semiconductor device that can be mass-produced with high reliability using a large substrate such as a mother glass. This is one of the problems.

[0008] The electrical characteristics of a transistor are easily affected by the electronic state at the interface between an oxide semiconductor film and a gate insulating film in contact with the oxide semiconductor film. During or after the fabrication of the transistor, if the interface between the oxide semiconductor film and the gate insulating film is in an amorphous state, the defect density at the interface is large, and the electrical characteristics of the transistor tend to be unstable. Moreover, the electrical characteristics of a transistor using an oxide semiconductor film as a channel change when irradiated with visible light or ultraviolet light.

[0009] In view of such problems, one aspect of the present invention is to provide a semiconductor device having a transistor with a good electronic state at the interface between an oxide semiconductor film and a gate insulating film in contact with the oxide semiconductor film. This is one of the problems.

[0010] This is one of the problems. This is one of the problems. This is one of the problems.

[0011] Furthermore, by providing stable electrical characteristics to transistors using oxide semiconductor films as channels, One of our goals is to manufacture highly reliable semiconductor devices. [Means for solving the problem]

[0012] Atoms that are c-axis oriented and have a triangular or hexagonal shape when viewed from the direction of the ab-plane, surface, or interface. An oxide material is used that has an arrangement and contains crystals in which the orientation of the a-axis or b-axis is different in the ab-plane. Yes, they are.

[0013] Furthermore, the aforementioned oxide material may contain zinc. By including zinc, it becomes c-axis oriented, The ab plane, when viewed from the direction of the surface or interface, has a triangular or hexagonal atomic arrangement, On the b-plane, it becomes easier to form oxide materials containing crystals with different orientations of the a-axis or b-axis. .

[0014] Alternatively, the aforementioned oxide materials include indium, gallium, zinc, tin, titanium, and aluminum. It consists of a material containing two or more elements selected from Um.

[0015] The aforementioned oxide materials are produced by sputtering, molecular beam epitaxy, atomic layer deposition, or It can be formed by the Ruth laser deposition method.

[0016] The aforementioned oxide material is obtained by laminating two films with different compositions, or by heat treatment after lamination. It can be formed by crystallizing it.

[0017] One aspect of the present invention has a plurality of metal oxide layers, wherein the metal oxide layers are separated from each other by 4-coordinate oxygen atoms It is an oxide material bonded via (four-coordinate oxygen). Also, one metal oxide layer is , a central metal atom with 4 coordination, a central metal atom with 5 coordination, or both 5-coordinate and 6-coordinate It has a central metal atom, and via a 3-coordinate oxygen atom (hereinafter referred to as 3-coordinate O) or 4-coordinate O This forms a layer that spreads out in a planar manner.

[0018] If the aforementioned oxide material is conductive, it can be used as the material for the gate electrode of a transistor. This can be achieved. The gate electrode is formed by laminating a film made of the aforementioned oxide material and a metal film. It is permissible.

[0019] Alternatively, if the oxide material is conductive, the source electrode and drain electrode of the transistor... It can be used as the electrode material. The source electrode and drain electrode are made of the aforementioned oxide. A film made of a material and a metal film may be formed by laminating them together.

[0020] If the aforementioned oxide material has semiconducting properties, the active layer of the transistor may be made of the aforementioned oxide material or Various films can be used. In that case, for example, the source electrode and the film of the transistor. It is provided in contact with a conductive film that functions as a rain electrode and an insulating film. The aforementioned insulating film is It functions as a gate insulating film, underlayer insulating film, or interlayer insulating film of a transistor. [Effects of the Invention]

[0021] According to one aspect of the present invention, a semiconductor device having excellent electrical properties can be manufactured.

[0022] Furthermore, using large substrates such as mother glass, it is possible to mass-produce highly reliable semiconductor devices. It is possible to do so. [Brief explanation of the drawing]

[0023] [Figure 1]A diagram illustrating the structure of an oxide material according to one aspect of the present invention. [Figure 2] A top view and a cross-sectional view showing an example of a semiconductor device according to one aspect of the present invention. [Figure 3] A top view and a cross-sectional view showing an example of a semiconductor device according to one aspect of the present invention. [Figure 4] A top view and a cross-sectional view showing an example of a semiconductor device according to one aspect of the present invention. [Figure 5] A top view and a cross-sectional view showing an example of a semiconductor device according to one aspect of the present invention. [Figure 6] A top view and a cross-sectional view showing an example of a semiconductor device according to one aspect of the present invention. [Figure 7] A top view and a cross-sectional view showing an example of a semiconductor device according to one aspect of the present invention. [Figure 8] A circuit diagram showing an example of a liquid crystal display device using a transistor, which is one aspect of the present invention. [Figure 9] A circuit diagram showing an example of a semiconductor memory device using a transistor, which is one aspect of the present invention. [Figure 10] A circuit diagram and a diagram showing electrical characteristics illustrating an example of a semiconductor memory device using a transistor, which is one aspect of the present invention. [Figure 11] A circuit diagram and a diagram showing electrical characteristics illustrating an example of a semiconductor memory device using a transistor, which is one aspect of the present invention. [Figure 12] A perspective view showing an example of an electronic device according to one aspect of the present invention. [Figure 13] Planar and cross-sectional images of an oxide film containing CAAC, obtained by HAADF-STEM. [Figure 14] Planar and cross-sectional images of an oxide film without CAAC, obtained by HAADF-STEM. [Figure 15] XRD spectrum of an oxide film containing CAAC after as-depo. [Figure 16] XRD spectrum after heat treatment of an oxide film containing CAAC. [Figure 17] XRD spectrum of an oxide film containing CAAC after as-depo. [Figure 18]XRD spectrum after heat treatment of an oxide film containing CAAC. [Figure 19] XRD spectrum of an oxide film containing CAAC after as-depo. [Figure 20] XRD spectrum after heat treatment of an oxide film containing CAAC. [Figure 21] A graph showing the Vg-Id curve of a transistor. [Figure 22] Graphs showing the results of the +BT and -BT tests. [Figure 23] Graphs showing the results of the +BT test and -BT test performed while irradiating the transistor with light. [Figure 24] A graph showing the time dependence of the change in threshold voltage Vth (ΔVth) under various stress conditions. [Figure 25] A schematic diagram illustrating the mechanism of optical negative bias degradation. [Modes for carrying out the invention]

[0024] The embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is... Not limited to the following description, the form and details can be modified in various ways, as any person skilled in the art would know. This is easily understood. Furthermore, the present invention shall be interpreted as being limited to the contents of the embodiments described below. It is not the case that the same thing is referred to. Furthermore, when explaining the structure of the invention using drawings, the same thing is referred to. The symbols are used consistently across different drawings. Note that the same term "hatch pattern" is used when referring to similar items. They are the same, and sometimes no sign is added.

[0025] The present invention will be described below, but the terms used in this specification will be briefly explained. First, In this specification, the source and drain of a lampistor will be referred to as the drain. Then the other is used as the source. That is, they are not distinguished by their potential. Therefore In this specification, the term "source" may also be interpreted as "drain."

[0026] Furthermore, voltage is the potential difference between a certain potential and a reference potential (for example, ground potential). It is often used to indicate these things. Therefore, voltage, potential, and potential difference are often rephrased as potential, voltage, and voltage difference, respectively. It is possible to do so.

[0027] In this specification, even when the term "connect" is used, in actual circuits... However, this may only apply if there are no physical connections and the wiring is simply running along the surface.

[0028] The ordinal numbers "1st" and "2nd" are used for convenience only and do not necessarily indicate the order of processes or stacking. This does not indicate that. Furthermore, in this specification, the proper nouns used to specify the invention are not used to indicate that. This does not indicate a title.

[0029] (Embodiment 1) In this embodiment, the c-axis orientation is used, and the ab-plane, surface, or interface is triangular when viewed from that direction. Alternatively, it has a hexagonal atomic arrangement, and along the c-axis, the metal atoms are layered or metal atoms and oxygen Atoms are arranged in layers, and at the ab plane (or surface or interface), the a axis and These are crystals with different b-axis orientations (rotated around the c-axis) (CAAC: C Axis Ali This section describes a method for forming an oxide film containing (also known as gned crystal).

[0030] CAAC-containing oxides, in a broad sense, are non-single crystals that can be viewed from a direction perpendicular to their ab-plane. It has an atomic arrangement of triangles, hexagons, equilateral triangles, or regular hexagons, and is perpendicular to the c-axis. When viewed from a straight direction, the metal atoms are arranged in layers, or the metal atoms and oxygen atoms are arranged in layers. This refers to materials containing CAAC. Furthermore, oxide films containing CAAC may have a new structure that exhibits grain boundaries. It is a structured film and is not necessarily aligned with respect to the ab plane.

[0031] CAAC is not a single crystal. Furthermore, oxide films containing CAAC are formed solely from amorphous material. It's not something that's always there. Also, oxide films containing CAAC contain crystalline parts (crystalline portions). However, it can sometimes be difficult to clearly distinguish the boundary between one crystalline region and another.

[0032] Some of the oxygen constituting the oxide film containing CAAC may be replaced with nitrogen. The c-axis of each individual crystal portion that makes up C is in a certain direction (for example, the substrate surface supporting CAAC or They may be aligned perpendicular to the surface of the oxide film containing CAAC. Alternatively, CAA The normals of the ab-planes of the individual crystal portions that make up C are in a certain direction (for example, supporting CAAC). It may be oriented perpendicular to the substrate surface or the surface of the oxide film containing CAAC.

[0033] Depending on its composition, an oxide film containing CAAC can be a conductor or a semiconductor. They can be insulators. Furthermore, depending on their composition, they can be transparent or opaque to visible light. It is clear.

[0034] Examples of such CAAC-containing oxides include those formed in film form, on the film surface, substrate surface, or When observed from a direction perpendicular to the interface, a triangular or hexagonal atomic arrangement is observed, and Observing the cross-section of the film reveals a layered arrangement of metal atoms or metal atoms and oxygen atoms (or nitrogen atoms). You can also list the materials that are recognized as being in a row.

[0035] CAAC will be explained in detail using Figure 1. Unless otherwise specified, Figure 1 is shown above. The direction is defined as the c-axis, and the plane perpendicular to the plane shown in Figure 1 is defined as the ab plane. Note that this is simply the upper half, the lower half. When we say "half," we mean the upper half and the lower half when the ab side is used as the dividing line.

[0036] Figure 1(A) shows one 6-coordinate metal atom M_1 and six 4-coordinate metal atoms adjacent to metal atom M_1. This shows a structure containing O and . For each such metal atom, only the adjacent oxygen atom is shown. The resulting structure is called a subunit here. The structure in Figure 1(A) takes the form of an octahedron, For simplicity, it is shown as a planar structure. Note that the upper and lower halves of Figure 1(A) are respectively There are 3 oxygen atoms in each of the 4-coordinate groups. The subunit typically shows only one metal atom. However, in reality, multiple subunits interact with each other in a planar manner via 3-coordinate or 4-coordinate oxygen. It forms an extended metal oxide layer.

[0037] Figure 1(B) shows one 5-coordinate metal atom M_2 and three 3-coordinate metal atoms adjacent to the metal atom M_2. The structure shows an oxygen atom and two adjacent 4-coordinate oxygen atoms. All 3-coordinate oxygen atoms are ab It exists on the surface. In the upper and lower halves of Figure 1(B), there is one 4-coordinate oxygen atom each. ru.

[0038] Figure 1(C) shows one 4-coordinate metal atom M_3 and four 4-coordinate atoms adjacent to the metal atom M_3. The structure of O is shown. The upper half of Figure 1(C) has one 4-coordinate O, and the lower half There are three 4-coordinate oxygen atoms in the minute.

[0039] Metal atoms with these coordination numbers are bonded via 4-coordinate oxygen atoms. Specifically, 4-coordinate A bond is formed when the total number of oxygen atoms is four. For example, a 6-coordinate metal atom M_1 forms a bond with the upper half of the 4-coordinate atom. When bonding via oxygen at position 1, there are three 4-coordinate oxygen atoms, so the 5-coordinate metal atom M_2 The upper half consists of 4-coordinate oxygen atoms, the lower half consists of 4-coordinate oxygen atoms or 4-coordinate metal atoms M_2 with 5-coordinate oxygen atoms. It will bond with one of the four-coordinate oxygen atoms in the upper half of the metal atom M_3.

[0040] In addition, subunits bond together such that the total charge of the layered structure becomes zero. .

[0041] Here, for 3-coordinate oxygen and 4-coordinate oxygen, the charge per bond is -0.6, respectively. 67, -0.5 can be considered. For example, In (6-coordinate or 5-coordinate), Zn (4 The charges of Ga (5-coordinate) and Sn (5-coordinate or 6-coordinate) are +3, +2, respectively. Since it is +3 and +4, it consists of a subunit made of In, a subunit made of Zn and G A subunit consisting of 'a' has a charge of 0. Therefore, any combination of these forms a layer. The total charge of the structure is always 0. On the other hand, the subunit made of Sn has a charge of +1. Therefore, in order to form a layered structure containing Sn, a charge of -1 is needed to cancel out the charge of +1. This is the result. An example of a structure that takes on a charge of -1 is a structure in which two Zn subunits are bonded together. For example, if one subunit made of Sn is bonded to two subunits of Zn If there is even one such structure, the charges cancel each other out, so the total charge of the layered structure can be made zero. Cut.

[0042] Figure 1(D) shows the layered structure of the In-Sn-Zn-O system. For simplicity, the three-coordinate oxygen atoms are omitted. Only the number of O atoms in 4-coordinate systems is shown. In atoms can take on either 5-coordinate or 6-coordinate configurations. This will be assumed. By using the structure shown in Figure 1(D) which repeats one period, In-Sn-Z nO-based crystals (In2SnZn3O8) can be obtained. -O layer structure is In2SnZn2O7(ZnO) m (m is 0 or a natural number.) It can be represented by a chemical formula. In addition, there are In-Sn-Ga-Zn-O type materials, In -Ga-Zn-O type materials, In-Si-Zn-O type materials, In-Al-Zn-O type Materials, Sn-Ga-Zn-O system materials, Al-Ga-Zn-O system materials, Sn-Al-Z nO-based materials, In-Zn-O-based materials, Sn-Zn-O-based materials, Al-Zn-O Materials in the Zn-Mg-O system, materials in the Sn-Mg-O system, and materials in the In-Mg-O system. In-Ga-O based materials, In-O based materials, Sn-O based materials, Zn-O based materials The same applies when using other methods.

[0043] Next, a method for forming an oxide film containing CAAC will be described.

[0044] First, the first oxide film is deposited on the substrate using sputtering, molecular beam epitaxy, or atomic layer deposition. Alternatively, the film is deposited by pulsed laser deposition. Note that heating the substrate during film deposition allows for... An oxide film with a high proportion of crystalline regions to amorphous regions can be obtained. For example, substrate temperature The temperature should be between 150°C and 450°C. Preferably, the substrate temperature should be between 200°C and 35°C. Keep the temperature below 0°C.

[0045] By increasing the substrate temperature, the oxide film containing CAAC can be further crystallized. ru.

[0046] Next, the substrate may undergo a first heat treatment. By performing the first heat treatment, the substrate becomes more amorphous. An oxide film can be formed in which the proportion of crystalline regions is large relative to the crystalline regions. The first heat treatment is, for example, For example, the process should be carried out at a temperature above 200°C but below the strain point of the substrate. Preferably, it should be between 250°C and 450°C. The following conditions apply. The atmosphere is not limited, but it may be carried out in an oxidizing atmosphere, an inert atmosphere, or a reduced pressure atmosphere. The processing time should be between 3 minutes and 24 hours. The longer the processing time, the more crystals will form in the amorphous region. While it is possible to form oxide films with a large proportion of the region, heat treatment exceeding 24 hours is not productive. This is undesirable because it leads to a decrease in [something].

[0047] An oxidizing atmosphere is an atmosphere containing oxidizing gases. Oxidizing gases include oxygen, ozone, or It is preferable that the substance is nitrous oxide or the like, and does not contain water, hydrogen, etc. For example, heat treatment equipment The purity of the oxygen, ozone, and nitrous oxide introduced into the system must be 8N (99.999999%) or higher. Preferably 9N (99.9999999%) or higher (i.e., impurity concentration is 1 ppm or less, preferred (The concentration should be less than 0.1 ppm). The oxidizing atmosphere is created by mixing an oxidizing gas with an inert gas. It may be used in this way. In that case, it shall contain at least 10 ppm or more of oxidizing gas. .

[0048] Here, an inert atmosphere refers to nitrogen, noble gases (helium, neon, argon, krypton, This is an atmosphere primarily composed of inert gases such as xenon. Specifically, oxidizing gases, etc. The reactive gas concentration should be less than 10 ppm.

[0049] The first heat treatment is performed using an RTA (Rapid Thermal Annealing) apparatus. This is possible. By using RTA, heat treatment can be performed at a temperature above the strain point of the substrate for a short period of time. Therefore, it is possible to form an oxide film in which the proportion of crystalline regions is large compared to amorphous regions. This can shorten the time required to do so.

[0050] As an oxide, its chemical formula is InMO3(ZnO) m You may also use materials denoted as (m>0). Here, M is one or more metallic elements selected from Ga, Al, Mn, and Co. For example, M can be Ga, Ga and Al, Ga and Mn, or Ga and Co You may also use the following:

[0051] Also, nitrogen 5 × 10 19 atoms / cm 3 Preferably 1 × 10 20 atoms / cm 3 In Ga-Zn-O-based materials containing less than 7 atomic percent of the above form c-axis oriented hexagonal crystals. It becomes an oxide containing a crystalline structure, with In-O crystal planes (crystal planes containing indium and oxygen) and In -A layer of Ga and Zn is present between the O crystal plane (a crystal plane containing indium and oxygen). It comprises a layer containing nitrogen within the above range. In this case, multiple layers of Ga and Zn are present between the In-O crystal planes. It's acceptable to include layers.

[0052] Next, a second oxide film may be deposited on the first oxide film to form an oxide laminate. The first oxide film and the second oxide film can be formed using the same method.

[0053] When forming the second oxide film, the first oxide film is seeded by forming it while heating the substrate. A second oxide film can be crystallized in the crystal. At this time, the first oxide film and the second The phenomenon where an oxide film is composed of the same element is called homogeneous growth. Alternatively, the first oxide film and The second oxide film is composed of at least one different element, and this is called hetero-growth. say.

[0054] Furthermore, a second heat treatment may be performed after the formation of the second oxide film. The second heat treatment is The same method as in heat treatment 1 should be used. By performing the second heat treatment, the amorphous region In contrast, an oxide laminate with a high proportion of crystalline regions can be formed. Alternatively, a second heat treatment can be performed. By doing so, the first oxide film can be used as a seed crystal, and the second oxide film can be crystallized. This is done. At this time, the first oxide film and the second oxide film are composed of the same element in a homo-grown form. It is also acceptable to do so. Alternatively, the first oxide film and the second oxide film may be of at least one type. It can also be a heterogeneous growth composed of different elements.

[0055] An oxide film containing CAAC can be formed using the method described above.

[0056] This embodiment can be used in appropriate combination with other embodiments.

[0057] (Embodiment 2) In this embodiment, the transient is used with the oxide film containing CAAC as shown in Embodiment 1. An example of this will be explained using Figure 2.

[0058] Figure 2(A) is a top view of the transistor. The dashed line AB and the one shown in Figure 2(A) The dashed line CD represents the AB section shown in Figure 2(B) and the CD section shown in Figure 2(C), respectively. It corresponds to a surface.

[0059] Here, we will explain the AB section shown in Figure 2(B) in detail.

[0060] The AB cross section shows the substrate 100, the gate electrode 104 on the substrate 100, and the substrate 100 and the gate A gate insulating film 112 covers the gate electrode 104, and the gate electrode 1 is connected to the gate insulating film 112. The semiconductor film 106 is located on 04, and the semiconductor film 106 is located on the semiconductor film 106 and is in partial contact with the semiconductor film 106. A pair of electrodes 116, a gate insulating film 112, a semiconductor film 106, and the pair of electrodes 116 are covered This is a cross-section of a transistor having an interlayer insulating film 118.

[0061] The gate electrode 104 can be a single layer or a multilayer structure, and can be made of Al, Ti, Cr, Co, or Ni. Cu, Y, Zr, Mo, Ag, Ta, and W, their nitrides, oxides, and alloys You may select and use one or more of them. Also, the gate electrode 104 is the CA shown in Embodiment 1. The configuration can include a conductive film (oxide conductive film) made of an oxide film containing AC. The work function can be controlled by the composition of the oxide conductive film.

[0062] When an oxide conductive film is used for the gate electrode 104, the oxide conductive film has higher resistance compared to a metal film. Therefore, in order to reduce the resistance of gate electrode 104, the sheet resistance becomes 10Ω / sq or less. It is preferable to use it in lamination with a low-resistance film selected from the aforementioned materials. However, oxide conductive A stacked structure is selected so that the film is on the gate insulating film side 112.

[0063] In Figure 2, the gate electrode 104 is greater than the semiconductor film 106 in the top view, both vertically and horizontally. By making the shape larger, photodegradation of the semiconductor film 106 and charge generation are suppressed. However, it is not limited to this. The semiconductor film 106 is higher than the gate electrode 104 in the top view. It is acceptable for the shape to be large in both length and width.

[0064] There are no major restrictions on the substrate 100, but it should at least have enough heat resistance to withstand subsequent heat treatment. It is necessary to do so. For example, glass substrates, ceramic substrates, quartz substrates, sapphire substrates These may be used as the substrate 100. Alternatively, single crystal semiconductors such as silicon or silicon carbide may be used. Conductor substrates, polycrystalline semiconductor substrates, compound semiconductor substrates such as silicon germanium, SOI ( It is also possible to apply a silicon-on-insulator (SIO) substrate, etc. A substrate 100 may be used in which semiconductor elements are provided on these substrates.

[0065] Alternatively, a flexible substrate may be used as the substrate 100. In that case, directly on the flexible substrate This involves fabricating a transistor. Note that in order to mount a transistor on a flexible substrate, A non-flexible substrate 100 is used, and after a transistor is fabricated on it, Another method involves peeling off the zista and transferring it to a flexible substrate. In that case, the substrate 100 and the transistor... It is advisable to provide a release layer between the zista and the other components.

[0066] The semiconductor film 106 is a silicon film, germanium film, silicon germanium film, silicon carbide From a film or gallium nitride film, or an oxide film containing CAAC as shown in Embodiment 1 A suitable semiconductor film (oxide semiconductor film) can be used. Oxide semiconductor films are easy to deposit and Because it has high field-effect mobility even without laser beam processing, the semiconductor film 106 It is preferable as a material to be used in the oxide semiconductor film and the gate in contact with the oxide semiconductor film. This makes it possible to obtain transistors with fewer interface states at the interface with the insulating film.

[0067] The gate insulating film 112 and the interlayer insulating film 118 are, for example, silicon oxide, silicon oxide nitride. silicon nitride, silicon nitride, aluminum oxide, hafnium oxide, yttrioxide Aluminum or zirconium oxide may be used, and it can be provided in a laminated or single layer. For example, heat The gate insulating film 112 and The interlayer insulating film 118 may be a film that releases oxygen upon heating. By using this film, defects occurring in the semiconductor film 106 can be repaired, and transistor This can suppress the deterioration of its electrical properties.

[0068] Here, silicon oxidizride is defined as a substance whose composition contains more oxygen than nitrogen. This indicates, for example, oxygen at 50 atomic% to 70 atomic% and nitrogen at 0.5 atomic% to 15 atomic%. % or less, silicon is 25 to 35 atomic percent, and hydrogen is 0 to 10 atomic percent. It refers to substances included within a certain range. Furthermore, silicon nitride, in its composition, is composed of more oxygen than This also indicates a high nitrogen content; for example, oxygen is 5 atomic% or more and 30 atomic% or less, and nitrogen is 20 to 55 atomic percent, silicon 25 to 35 atomic percent, hydrogen 10 atoms This refers to substances containing between % and 25 atoms. However, the above range is defined as the Rutherford period. Rutherford Backscattering Spectrometer (RBS) (rometry) and hydrogen forward scattering (HFS) This is the result of measurements using cattering spectrometry. Furthermore, the content ratio of the constituent elements shall not exceed 100 atomic percent in total.

[0069] The gate insulating film 112 and the interlayer insulating film 118 are made of the same material as the pair of electrodes 116, which is a semiconductor film 10 If it diffuses to 6 and may adversely affect transistor characteristics, an insulating film with a small diffusion coefficient of the material of the pair of electrodes 116 may be used. The interlayer insulating film 118 functions as a protective film for the semiconductor film 106. When "oxygen is released by heating" means that in TDS (Thermal Desorption S pectroscopy: temperature-programmed desorption gas spectroscopy) analysis, the amount of oxygen released in terms of oxygen atoms is 1.0×10

[0070] atoms / cm or more, preferably 3.0×10 atoms / cm 18 or more. 3 Here, the method for measuring the amount of oxygen released in terms of oxygen atoms in TDS analysis will be described below. 20 ato ms / cm 3 or more.

[0071] Here, regarding the method for measuring the amount of oxygen released in terms of oxygen atoms in TDS analysis, it will be explained below. to.

[0072] The amount of gas released during TDS analysis is proportional to the integrated value of the spectrum. Therefore, the amount of gas released can be calculated by the ratio of the integrated value of the measured spectrum to the reference value of the standard sample. The reference value of the standard sample is the ratio of the density of atoms to the integrated value of the spectrum of a sample containing a predetermined atom. For example, from the TDS analysis results of a silicon wafer containing hydrogen with a predetermined density as a standard sample and the TDS analysis results of the insulating film, the amount of oxygen molecules released from the insulating film (N ) can be obtained by Equation 1. Here, it is assumed that all of the spectrum detected at mass number 32 obtained by TDS analysis is derived from oxygen molecules. Although there is CH3OH as a substance with mass number 32, it is not considered here as it has a low possibility of existence. Also, for isotopes of oxygen atoms with mass number ...

[0073] For example, from the TDS analysis results of a silicon wafer containing hydrogen with a predetermined density as a standard sample and the TDS analysis results of the insulating film, the amount of oxygen molecules released from the insulating film (N ) can be obtained by Equation 1. Here, it is assumed that all of the spectrum detected at mass number 32 obtained by TDS analysis is derived from oxygen molecules. Although there is CH3OH as a substance with mass number 32, it is not considered here as it has a low possibility of existence. Also, for isotopes of oxygen atoms with mass number O2 it can be obtained by Equation 1. Here, it is assumed that all of the spectrum detected at mass number 32 obtained by TDS analysis is derived from oxygen molecules. Although there is CH3OH as a substance with mass number 32, it is not considered here as it has a low possibility of existence. Also, for isotopes of oxygen atoms with mass number ... 32, although there is CH3OH, it is not considered here as the possibility of its existence is low. Also, for isotopes of oxygen atoms with mass number 32, although there is CH3OH, it is not considered here as the possibility of its existence is low. Also, for isotopes of oxygen atoms with mass number Regarding oxygen molecules containing 17 oxygen atoms and 18 oxygen atoms with a mass number, in nature... Its relative abundance is extremely small, so it will not be considered.

[0074] N O2 =N H2 / S H2 ×S O2 ×α (Equation 1)

[0075] N H2 This value represents the density of hydrogen molecules detached from a standard sample. H2 The standard test This is the integral value of the spectrum when the sample is analyzed using TDS. Here, the reference value of the standard sample is N H2 / S H2 Let's assume that. S O2 This is the integral value of the spectrum obtained when the insulating film is analyzed by TDS. α is a coefficient that affects the spectral intensity in TDS analysis. (See details of Equation 1.) For further information, please refer to Japanese Patent Publication No. 6-275697. The amount of oxygen released from the insulating film is as follows: Using the EMD-WA1000S / W temperature-controlled desorption analyzer manufactured by Denshi Kagaku Co., Ltd., a standard sample and and 1 x 10 16 atoms / cm 3 Measurements were taken using a silicon wafer containing hydrogen atoms. .

[0076] Furthermore, in TDS analysis, some oxygen is detected as oxygen atoms. Oxygen molecules and oxygen atoms The ratio of these can be calculated from the ionization rate of oxygen molecules. Note that α above represents the oxygen component. Because it includes the ionization rate of the oxygen atom, by evaluating the amount of oxygen molecule released, the amount of oxygen atom released is determined. Even if they are present, it can still be estimated.

[0077] Note N O2 This is the amount of oxygen molecules released. The amount released when converted to oxygen atoms is the amount of oxygen molecules. This will be twice the amount released.

[0078] In the above configuration, the film that releases oxygen upon heating is silicon oxide (SiO2), which has an excess of oxygen. X (X>2)) is also acceptable. Silicon oxide (SiO2) has an excess of oxygen. X (X>2) means, It contains more than twice the number of oxygen atoms per unit volume compared to the number of silicon atoms. The number of silicon atoms and oxygen atoms per atom were measured using the Rutherford backscattering method. be.

[0079] From the gate insulating film 112 or the interlayer insulating film 118 to the semiconductor film 106 which is an oxide semiconductor film When oxygen is supplied, the interface state density between the semiconductor film 106 and the gate insulating film 112, and This can reduce the interface state density between the semiconductor film 106 and the interlayer insulating film 118. As a result, Due to the operation of the zistor, etc., the interface between the semiconductor film 106 and the gate insulating film 112, or the semi The ability to suppress carrier trapping at the interface between the conductive film 106 and the interlayer insulating film 118 is This allows us to obtain transistors with minimal degradation of electrical characteristics.

[0080] Furthermore, electric charge can be generated due to oxygen vacancies in oxide semiconductor films. Generally, oxide semiconductors Oxygen deficiencies in a conductive film cause some of them to act as donors, releasing electrons which are carriers. As a result, The threshold voltage of the transistor shifts in the negative direction. The gate insulating film 112 also This ensures that oxygen is sufficiently supplied from the interlayer insulating film 118 to the semiconductor film 106, which is an oxide semiconductor film. This causes the threshold voltage to shift in the negative direction, which is due to the acidity of the oxide semiconductor film. This can reduce the density of primary defects.

[0081] In other words, a film that releases oxygen upon heating is provided on the gate insulating film 112 or the interlayer insulating film 118. By doing so, the interface state density at the interface between the semiconductor film 106 and the gate insulating film 112, or the semiconductor The interface state density at the interface between film 106 and interlayer insulating film 118, and the semi-oxide semiconductor film The oxygen vacancy density of the conductive film 106 is reduced, and the semiconductor film 106, which is an oxide semiconductor film, is gate-insulated. To reduce the effect of carrier trapping at the interface with the edge film 112 or interlayer insulating film 118. It is possible.

[0082] The pair of electrodes 116 are made of the metal, metal nitride, metal oxide, or alloy indicated by the gate electrode 104. Gold and other materials can be used as appropriate.

[0083] Using a Cu-containing film on a pair of electrodes 116 can reduce the resistance of the wiring, making it suitable for large display devices and other applications. However, this can reduce the occurrence of wiring delays, etc. When using Cu for the pair of electrodes 116, Depending on the material of the substrate 100, adhesion may be poor, so the layer of substrate 100 and a film with good adhesion A layered structure is preferable. A film with good adhesion to the substrate 100 can be made of Ti, Mo, Mn, etc. Alternatively, a film containing Al or similar material can be used. For example, a Cu-Mn-Al alloy may be used.

[0084] As described above, a transistor with controlled threshold voltage and excellent electrical characteristics can be obtained. This allows for low power consumption and excellent electrical characteristics, as well as highly reliable semiconductor equipment. The device can be manufactured with high productivity.

[0085] This embodiment can be used in appropriate combination with other embodiments.

[0086] (Embodiment 3) In this embodiment, a transistor with a different structure from the transistor shown in Embodiment 2 is used. I will explain about this.

[0087] Figure 3 shows a top view and a cross-sectional view of a transistor according to one embodiment of the present invention. As shown in Figure 3(A) The dashed lines AB and CD shown below represent the cross-section of AB shown in Figure 3(B), respectively. This corresponds to the CD cross-section shown in Figure 3(C).

[0088] The AB section shown in Figure 3(B) will be described in detail below.

[0089] The AB cross section shows the substrate 100, the gate electrode 104 on the substrate 100, and the substrate 100 and the gate A gate insulating film 112 covers the gate electrode 104, and a pair of electrodes 116 are located on the gate insulating film 112. Then, a portion of the pair of electrodes 116 on the gate electrode 104 are in contact via the gate insulating film 112. The semiconductor film 106, the gate insulating film 112, the pair of electrodes 116 and the semiconductor film 106 This is a cross-section of a transistor having an interlayer insulating film 118 covering it.

[0090] In this embodiment as well, the gate electrode 104 and the semiconductor film 106 are the same as in Embodiment 2. The configuration is as follows: Using a gate electrode having an oxide film containing CAAC as shown in Embodiment 1. By doing so, the work function can be controlled, and the threshold voltage of the transistor can be controlled. Furthermore, by using the oxide semiconductor film shown in Embodiment 1 for the semiconductor film 106, Transients with low interface state density at the interface between the conductive film and the gate insulating film in contact with the oxide semiconductor film You can earn points.

[0091] Figure 4 shows a top view and a cross-sectional view of a transistor according to one embodiment of the present invention. As shown in Figure 4(A) The dashed lines AB and CD shown below represent the cross-section of AB shown in Figure 4(B), respectively. This corresponds to the CD cross-section shown in Figure 4(C).

[0092] The AB section shown in Figure 4(B) will be described in detail below.

[0093] The AB cross section shows the substrate 100, the underlayer insulating film 102 on the substrate 100, and the underlayer insulating film 102. A semiconductor film 106 and a pair of electrodes located on the semiconductor film 106 and partially in contact with the semiconductor film 106. 116, a gate insulating film 112 covering the semiconductor film 106 and the pair of electrodes 116, and gate A transistor having a gate electrode 104 on a semiconductor film 106 via an insulating film 112 This is a cross-section of the ta.

[0094] The base insulating film 102 has the same configuration as the gate insulating film 112 and the interlayer insulating film 118. It is possible.

[0095] Figure 5 shows a top view and a cross-sectional view of a transistor according to one embodiment of the present invention. As shown in Figure 5(A) The dashed lines AB and CD shown below represent the cross-section of AB shown in Figure 5(B), respectively. This corresponds to the CD cross-section shown in Figure 5(C).

[0096] The AB section shown in Figure 5(B) will be described in detail below.

[0097] The AB cross section shows the substrate 100, the underlayer insulating film 102 on the substrate 100, and the underlayer insulating film 102. A pair of electrodes 116 and a semiconductor that is located on the pair of electrodes 116 and is in partial contact with the pair of electrodes 116. A body film 106, a gate insulating film 112 covering the semiconductor film 106 and a pair of electrodes 116, and A transistor having a gate electrode 104 on a semiconductor film 106 via a terminal insulating film 112. This is a cross-section of the Zista.

[0098] In Figures 3 to 5, the gate electrode 104 is larger than the semiconductor film 106 in both length and width. This configuration suppresses photodegradation and charge generation of the semiconductor film 106, but is not limited to this. It is not determined. The semiconductor film 106 is longer vertically than the gate electrode 104 in the top view. It is also acceptable for it to be large in both width and height.

[0099] Figure 6 shows a top view and a cross-sectional view of a transistor according to one aspect of the present invention. As shown in Figure 6(A) The dashed lines AB and CD shown below represent the cross-section of AB shown in Figure 6(B), respectively. This corresponds to the CD cross-section shown in Figure 6(C).

[0100] The AB section shown in Figure 6(B) will be described in detail below.

[0101] The AB cross section shows the substrate 100, the underlayer insulating film 102 on the substrate 100, and the underlayer insulating film 102. A semiconductor film having regions 126 and 121, and a gate insulating film 112 on region 121 And, the gate electrode 104 on the gate insulating film 112, the underlying insulating film 102, region 126, gate An interlayer insulating film 118 covering the insulating film 112 and the gate electrode 104, and the interlayer insulating film 118 A pair of electrodes 116 that are in contact with region 126 through an opening that exposes the provided region 126 and This is a cross-section of a transistor having ,

[0102] Here, the gate insulating film 112 and the gate electrode 104 may have substantially the same upper surface shape. This shape is achieved by processing the gate electrode 104 and the gate insulating film 112 using the same mask. This is obtained by doing so. Note that after forming the gate electrode 104 and gate insulating film 112, plastic The width of the gate electrode 104 may be narrowed by Zuma treatment or chemical treatment.

[0103] Region 121 has a top surface shape that is substantially the same as that of the gate insulating film 112 or gate electrode 104. This is also good. This shape uses the gate insulating film 112 or gate electrode 104 as a mask for the semiconductor film. This is obtained by forming region 126. For example, gate insulating film 112 or gate electrode 1 Using O4 as a mask, impurities (boron, phosphorus, hydrogen, noble gases, nitrogen, etc.) are introduced into the semiconductor film. The region with reduced resistance can be designated as region 126. Region 121 is region 12 This is a region of the semiconductor film where layer 6 is not formed.

[0104] Region 121 functions as the channel region of the transistor. Region 126 is It functions as the source and drain regions of a transistor.

[0105] Figure 7 shows a top view and a cross-sectional view of a transistor according to one aspect of the present invention. As shown in Figure 7(A) The dashed lines AB and CD shown below represent the cross-section of AB shown in Figure 7(B), respectively. This corresponds to the CD cross-section shown in Figure 7(C).

[0106] The AB section shown in Figure 7(B) will be described in detail below.

[0107] The AB cross section shows the substrate 100, the gate electrode 104 on the substrate 100, and on the gate electrode 104 The gate insulating film 112 and region 1 on the gate electrode 104 via the gate insulating film 112 A semiconductor film having region 26 and region 121, and covering the semiconductor film and gate insulating film 112 The interlayer insulating film 118 and the opening that exposes the region 126 provided in the interlayer insulating film 118 This is a cross-section of a transistor having a pair of electrodes 116 in contact with region 126.

[0108] Figure 7 shows the gate insulating film 112 and gate electrode 104 and region 121 having substantially the same top surface shape. The diagram shows, but is not limited to, gate insulating film 112 and gate electrode 1 The shapes of 04 and region 121 may be different.

[0109] As described above, a transistor with controlled threshold voltage and excellent electrical characteristics can be obtained. This allows for low power consumption and excellent electrical characteristics, as well as highly reliable semiconductor equipment. The device can be manufactured with high productivity.

[0110] This embodiment can be used in appropriate combination with other embodiments.

[0111] (Embodiment 4) In this embodiment, the transistor shown in Embodiment 2 or Embodiment 3 was used for fabrication. The liquid crystal display device described below will be described. In this embodiment, the liquid crystal display device is equipped with the first invention of the present invention. Examples of applying the form will be explained, but it is not limited to these. For example, EL( One embodiment of the present invention can also be applied to an electroluminescence display device. This is something that can be easily conceived by someone skilled in the art.

[0112] Figure 8 shows the circuit diagram of an active-matrix driven liquid crystal display device. The liquid crystal display device is... Source lines SL_1 to SL_a, gate lines GL_1 to GL_b, and multiple pixels 200 The pixel 200 has a transistor 230, a capacitor 220, and a liquid crystal element 210. This includes the above. Multiple such pixels 200 are arranged to constitute the pixel section of a liquid crystal display device. When simply referring to a source line or gate line, it is written as source line SL or gate line GL. do.

[0113] Transistor 230 is the transistor shown in Embodiment 2 or Embodiment 3. By using a transistor according to one aspect of the present invention, power consumption is low and electrical characteristics are good. A good and reliable display device can be obtained.

[0114] The gate wire GL is connected to the gate of transistor 230, and the source wire SL is connected to transistor 23 The source of transistor 230 is connected to the drain of capacitor 220. The electrode is connected to one of the pixel electrodes of the liquid crystal element 210. The other capacitance of the capacitor 220 The electrode and the other pixel electrode of the liquid crystal element 210 are connected to the common electrode. The gate line GL may be provided in the same layer and made of the same material.

[0115] Furthermore, the gate wire GL is connected to the gate drive circuit. The gate drive circuit is as follows (Embodiment 2) Alternatively, it may include the transistor shown in Embodiment 3. The transistor is a threshold voltage Because the voltage is controlled, the off-current can be reduced, and the voltage required to turn it on can also be reduced. This allows for reduced power consumption.

[0116] Furthermore, the source line SL is connected to the source drive circuit. The source drive circuit is in Embodiment 2 Alternatively, it may include the transistor shown in Embodiment 3. The transistor is a threshold voltage Because the voltage is controlled, the off-current can be reduced, and the voltage required to turn it on can also be reduced. This allows for reduced power consumption.

[0117] Furthermore, either or both of the gate drive circuit and the source drive circuit may be provided separately. Formed on a plate, and then COG (Chip On Glass), wire bonding, or T Even if you connect using methods such as AB (Tape Automated Bonding) good.

[0118] Furthermore, since transistors are susceptible to damage from static electricity, it is advisable to include a protection circuit. It is preferable that the protection circuit be constructed using nonlinear elements.

[0119] When a potential is applied to the gate wire GL such that it is greater than or equal to the threshold voltage of transistor 230, The charge supplied from the source line SL becomes the drain current of transistor 230, which is the capacitance. Charge is accumulated in transistor 220. After charging one row, transistor 230 in that row turns off. In this state, voltage is no longer applied from the source line SL, but the electricity stored in capacitor 220 The required voltage can be maintained by the load. Then, the next row of capacitors 220 is charged. Next, we move to the electric side. In this way, we charge rows 1 to a.

[0120] Note that transistor 230 is a transistor with a controlled threshold voltage, therefore the capacitor The charge held in the lower 220 is less likely to escape, and the capacitance of the capacitor 220 can be reduced. This makes it possible to reduce the power consumption required for charging.

[0121] Furthermore, transistor 230 is a transistor with a small off-current (using an oxide semiconductor film). When using transistors (such as transistors), the period during which the voltage is maintained can be extended. This allows for a reduction in the display refresh rate for images with little movement (including still images). This makes it possible to further reduce power consumption. Also, the capacity of capacitor 220 can be made even smaller. This makes it possible to reduce the power consumption required for charging.

[0122] As described above, according to one aspect of the present invention, a highly reliable liquid crystal display device with low power consumption is provided. You can obtain this.

[0123] This embodiment can be used in appropriate combination with other embodiments.

[0124] (Embodiment 5) In this embodiment, the transistor shown in Embodiment 2 or Embodiment 3 is used to semicircular This section describes an example of fabricating a conductive memory device.

[0125] A typical example of a volatile semiconductor memory device is selecting transistors that constitute the memory element. By accumulating electric charge in a capacitor, information is stored using DRAM (Dynamic Radar). (NDOM Access Memory), using circuits such as flip-flops to store information in memory. The SRAM (Static Random Access Memory) that holds the data be.

[0126] Typical examples of non-volatile semiconductor memory devices include the gate electrode and channel formation region of a transistor. It has a floating gate between it and the region, and it holds charge in the floating gate. There is flash memory that stores data in this way.

[0127] Some of the transistors included in the semiconductor memory device described above are in Embodiment 2 or Embodiment The transistor shown in 3 can be applied.

[0128] First, a volatile memory using the transistor shown in Embodiment 2 or Embodiment 3. This will be explained using Figure 9.

[0129] The memory cell consists of a bit line BL, a word line WL, a sense amplifier SAmp, and a transistor It has a transistor (Tr) and a capacitor (C) (see Figure 9(A)).

[0130] The time variation of the voltage held in capacitor C is determined by the off-current of transistor Tr, as shown in Figure 9. As shown in (B), it is known to gradually decrease. Initially, charging from V0 to V1. The applied voltage decreases over time to VA, which is the limit point for reading data1. Let this period be called the retention period T_1. That is, in the case of a binary memory cell, during the retention period T_1 I need to refresh myself.

[0131] Here, the transistor Tr is the transistor shown in Embodiment 2 or Embodiment 3. By using this method, the threshold voltage is controlled, which allows the holding period T_1 to be extended. In other words, it becomes possible to reduce the frequency of refreshes, thereby reducing power consumption. It is possible.

[0132] When using a transistor with a small off-current, the period for maintaining the voltage is Because it can be made even longer, power consumption can be reduced even further. , highly purified and with an off-current of 1 × 10 -21 A or less, preferably 1 × 10 -24 A or lower When DRAM is constructed using transistors made of oxide semiconductor films, several units can be used without supplying power. It becomes possible to retain data for periods ranging from days to decades.

[0133] As described above, according to one aspect of the present invention, a volatile memory with high reliability and low power consumption can be obtained.

[0134] Next, a non-volatile memory applying the transistor shown in Embodiment 2 or Embodiment 3 will be described with reference to FIG. 10.

[0135] FIG. 10(A) is a circuit diagram of the non-volatile memory. The non-volatile memory includes a transistor Tr _1, a word line WL_1 connected to the gate of the transistor Tr_1, a source wiring SL_1 connected to the source of the transistor T r_1, a transistor Tr_2, a source wiring SL_2 connected to the source of the transistor Tr _2, a drain wiring DL_2 connected to the drain of the transistor Tr_2, a capacitor C, a capacitance wiring CL connected to one end of the capacitor C, and a floating gate FG connected to the other end of the capacitor C, the drain of the transistor Tr_1, and the gate of the transistor Tr _2. Note that the non-volatile memory shown in this embodiment utilizes the fact that the threshold voltage of the transistor Tr_2 varies according to the potential of the floating gate FG. For example,

[0136] FIG. 10(B) is a diagram for explaining the relationship between the voltage V CL of the capacitance wiring CL and the drain current I flowing through the transistor Tr_2. CL through the transistor Tr_2. flow I D _2.

[0137] Here, the floating gate FG can adjust the voltage via the transistor Tr_1. For example, the potential of the source wiring SL_1 is set to VDD. At this time, the potential of the word line WL_1 is set to a potential obtained by adding VDD to the threshold voltage Vth of the transistor Tr_1. WL_1 is set to a potential obtained by adding VDD to the threshold voltage Vth of the transistor Tr_1. By doing so, the potential of the floating gate FG can be set to HIGH. Also, By setting the potential of the word line WL_1 to be less than or equal to the threshold voltage Vth of transistor Tr_1 This allows the potential of the floating gate FG to be set to LOW.

[0138] Therefore, V shown as FG=LOW CL -I D _2 curve and V shown with FG=HIGH CL -I D You can obtain either of the two curves. That is, when FG=LOW, V CL Drain current I at 0V D Since _2 is small, the data is 0. Also, FG=HIGH So, V CL Drain current I at 0V D Since _2 is large, the data becomes 1. This allows data to be stored.

[0139] Here, transistor Tr_1 is the transistor shown in Embodiment 2 or Embodiment 3. When applied, the transistor can achieve extremely low off-current, thus flow The charge accumulated in the ting gate FG is transferred between the source and drain of transistor Tr_1. This helps prevent unintentional data leaks. Therefore, it allows for data retention over long periods of time. This is possible. Furthermore, by using one aspect of the present invention, the threshold voltage of transistor Tr_1 can be adjusted. Because the voltage is controlled, it is possible to reduce the voltage required for writing, flash memory Compared to other types of power sources, such as Mori, it can reduce power consumption.

[0140] Note that transistor Tr_2 is the transistor shown in Embodiment 2 or Embodiment 3. You may apply this.

[0141] Next, regarding the non-volatile memory shown in Figure 10, the configuration without a capacitor is shown in Figure 1 Let's explain using example 1.

[0142] Figure 11 is a circuit diagram of a non-volatile memory. The non-volatile memory consists of transistor Tr_1 and , the word line WL_1 which connects to the gate of transistor Tr_1, and transistor Tr_1 Source wiring SL_1 to connect to the source, transistor Tr_2, and transistor Tr The source wire SL_2 connects to the source of _2, and the drain of transistor Tr_2 is also connected. The drain wiring DL_2 is connected to the drain of transistor Tr_1. It has a gate Tr_2.

[0143] When using a transistor with a small off-current for transistor Tr_1, a capacitor should be provided. Even without it, charge can be held between the drain of Tr_1 and the gate of Tr_2. Because it does not include a capacitor, it is possible to reduce the area and integrate it compared to when a capacitor is included. It is possible.

[0144] Furthermore, although this embodiment shows a non-volatile memory using four or five wires, It is not limited to this. For example, source wiring SL_1 and drain wiring DL_2 are common It is also acceptable to configure it in this way.

[0145] As described above, according to one aspect of the present invention, a semiconductor with high long-term reliability and low power consumption is produced. Body memory can be acquired.

[0146] This embodiment can be used in appropriate combination with other embodiments.

[0147] (Embodiment 6) In this embodiment, an example of an electronic device to which Embodiment 2 or Embodiment 3 is applied will be described.

[0148] FIG. 12(A) shows a portable information terminal. It includes a housing 300, buttons 301, a microphone 302, a display unit 303, a speaker 304, and a camera 305, and has functions as a mobile phone. One aspect of the present invention can be applied to the display unit 303 and the camera 305. Although not shown, one aspect of the present invention can also be applied to an arithmetic unit, a wireless circuit, or a storage circuit inside the main body.

[0149] FIG. 12(B) shows a display. It includes a housing 310 and a display unit 311. One aspect of the present invention can be applied to the display unit 311. By using one aspect of the present invention, it is possible to obtain a display with high display quality even when the size of the display unit 311 is increased.

[0150] FIG. 12(C) shows a digital still camera. It includes a housing 320, buttons 321, a microphone 322, and a display unit 323. One aspect of the present invention can be applied to the display unit 323. Although not shown, one aspect of the present invention can also be applied to a storage circuit or an image sensor.

[0151] By using one aspect of the present invention, the cost of the electronic device can be reduced, and a display device with high display quality can be obtained.

[0152] This embodiment can be used in appropriate combination with other embodiments. Examples

[0153] High-angle scattering annular dark-field scanning transmission electron microscopy (HAADF-STE) of oxides containing CAAC M:High-Angle Annular Dark Field Scanning The flat surface obtained by Transmission Electron Microscopy Planar and cross-sectional views are shown in Figures 13(A) and 13(B), respectively. Similarly, amorphous The planar and cross-sectional images of the oxide obtained by HAADF-STEM are shown in Figure 14(A ) and Figure 14(B) are shown.

[0154] The sample is an InGa-Zn-O oxide film, which was obtained by DC sputtering using a quartz group The film was deposited on a plate. Other deposition conditions were: power 0.5 kW, deposition pressure 0.4 Pa, film deposition. The gases used were 35 sccm of Ar and 15 sccm of O2, with a target-substrate distance of 60 m. m was used. The target is an In-Ga-Zn-O target (molar ratio, In2O3: A Ga2O3:ZnO (1:1:2) substrate was used. The thickness was 100 nm.

[0155] Here, Sample 1 was set to a substrate temperature of 400°C, and Sample 2 was set to a substrate temperature of room temperature. No heat treatment was performed after the film was applied.

[0156] From the planar images shown in regions 1001 and 1002 of Figure 13(A), the ab plane, surface or It was found that the atomic arrangement has a triangular or hexagonal shape when viewed from the direction of the interface. From the cross-sectional image shown in Figure 13(B), it can be seen that the metal atoms are aligned in the direction indicated by the arrow. That is, metal atoms, or metal atoms and oxygen atoms, are arranged in layers along the c-axis. Understood. That means Sample 1 is an oxide film containing CAAC.

[0157] From the plan view shown in Figure 14(A), the shape is triangular or hexagonal when viewed from the direction of the surface or interface. The atomic arrangement could not be confirmed. Also, from the cross-sectional image shown in Figure 14(B), the metal atoms, It was found that the metal atoms and oxygen atoms were not arranged in layers. In other words, sample 2 is C It is clear that this is not an oxide film containing AAC.

[0158] As described above, we were able to obtain an oxide film containing CAAC. [Examples]

[0159] In this example, the crystalline state of the oxide film containing CAAC was determined by X-ray diffraction (XRD: X-Ray An example of evaluation using the Diffraction method will be explained.

[0160] In the sample, an InGa-Zn-O oxide film was obtained by DC sputtering, which removed silica groups. The film was deposited on a plate. Other deposition conditions were: power 0.5 kW, deposition pressure 0.4 Pa, and The get-substrate distance was set to 60 mm, and the substrate temperature to 400°C. The target was In-Ga -Zn-O target (molar ratio, In2O3:Ga2O3:ZnO=1:1:2) It was used. The thickness is 300 nm.

[0161] Here, in Sample 3, the film deposition gas is O2 = 40 sccm, and in Sample 4, the film deposition gas is N2 = 40 sccm.

[0162] Figures 15 and 16 show the XRD spectra measured using the out-of-plane method. Figure 15 shows the film after deposition (as-depo), and Figure 16 shows the film after deposition in an N2 atmosphere at 450°C for 1 hour. This shows the result after heat treatment. Here, solid lines 1101 and 1103 represent sample 3, and solid line 110 Lines 2 and 1104 show the XRD spectrum of sample 4.

[0163] From Figures 15 and 16, under both conditions there is a peak corresponding to (009), and the c-axis It was found that they were strongly oriented. That is, samples 3 and 4 are c-axis oriented. It was found that, in particular, there was a tendency for the peak intensity corresponding to (009) to be large in sample 4. Furthermore, in sample 3, the peak position corresponding to (009) was shifted to the lower angle side. I found out they were there.

[0164] Figures 17 and 18 show the XRD spectra measured using the in-plane method. Figure 18 shows the film after deposition (as-depo), and Figure 18 shows the film after heat treatment in an N2 atmosphere at 450°C for 1 hour. This shows that, here, solid lines 1111 and 1113 represent sample 3, and solid lines 1112 and The solid line 1114 shows the XRD spectrum of sample 4.

[0165] From Figures 17 and 18, under both conditions there is a peak corresponding to (009), and the c-axis It was found to be strongly oriented. Also, the peak corresponding to (110) and (119) It was also found to have a peak corresponding to [this value].

[0166] Next, Figures 19 and 20 show the peak (110) obtained by the in-plane method. The optical system was fixed at position (2θ), and the sample was rotated around the normal to the sample surface as the axis to obtain the XRD spectrum. This is the cult. Here, solid lines 1121 and 1123 represent sample 3, and solid line 1122 The solid line 1124 shows the XRD spectrum of sample 4.

[0167] Figures 19 and 20 show that no peaks were observed under any of the conditions.

[0168] Figures 15 to 20 show that the measured sample is non-single crystal and has properties different from polycrystalline. It was found that the CAAC exhibits the characteristics of having the following. In this example, In-Ga-Zn- Although this explanation describes O-based oxide films, it is not limited to this material, and also applies to In-Sn-Zn films. -O-based oxide films can also be obtained containing CAAC. [Examples]

[0169] On a 600mm x 720mm glass substrate, an In-Ga-Zn-O based acid containing CAAC was applied. A transistor was fabricated using a ionized film (thickness 35 nm), and its initial characteristics are shown in Figure 21. The fabricated transistor has a channel length L of 3 μm and a channel width W of 50 μm, as shown in Figure 2. This is a bottom-gate transistor with the structure shown. Also, the gate insulating film of the transistor The film thickness is 100 nm.

[0170] Figure 21 shows Vg-Id curve data (Vd=1V, Vd=1V) measured at 20 points on the substrate. Although it is 0V, the plots are almost the same and overlap, so from this result we can determine CAAC Transistors using an In-Ga-Zn-O oxide film containing the following have good uniformity. The upper Vg-Id curve in Figure 21 shows the value when Vd = 10V, and the lower Vg-Id curve in Figure 21 shows the value when Vd = 10V. The Vg-Id curve is the value when Vd = 1V.

[0171] The average threshold voltage Vth of these transistors is 1.34V, and the field effect transfer The average movement was 10.7 cm. 2 The threshold voltage Vth was / Vs. The curve obtained by taking the square root of Id in the Vg-Id curve measured with d set to 10V (hereinafter referred to as √ This value is calculated using the Id curve (also known as the Id curve).

[0172] Furthermore, in order to evaluate the reliability of the transistors, a new In-Ga-Zn- containing CAAC was developed. Multiple transistors were fabricated on a 5-inch substrate using an O-based oxide film (thickness 35 nm). BT testing was performed on those transistors. The channel length of the fabricated transistors was... L is 6 μm, channel width W is 50 μm, and the bottom-gate type transistor has the structure shown in Figure 2. It is a transistor. Also, the thickness of the gate insulating film of the transistor is 100 nm.

[0173] BT testing is a type of accelerated testing that tests for changes in transistor characteristics caused by long-term use. This can be evaluated in a short time. In particular, the transistor threshold before and after BT testing. The change in the voltage value Vth is an important indicator for examining reliability. Therefore, the smaller the change in threshold voltage Vth (ΔVth), the more reliable the transistor. It can be said that this is the case.

[0174] Specifically, the temperature of the substrate on which the transistor is formed (substrate temperature) is kept constant, The source and drain of the transistor are at the same potential, and the gate is at a different potential than the source and drain. Apply a certain potential for a certain period of time. The substrate temperature should be set appropriately according to the purpose of the test. The +BT test is defined as the case where the potential applied to the gate is higher than the potentials of the source and drain. i. When the potential applied to the gate is lower than the potentials of the source and drain, it is called a -BT test. say.

[0175] The test intensity of the BT test is determined by the substrate temperature, the electric field strength applied to the gate insulating film, and the electric field application time. This can be determined by the electric field strength applied to the gate insulating film, which is between the gate and the source. It is determined by dividing the potential difference between the drain and the gate insulator by the thickness of the gate insulator. For example, if the thickness is 100 If you want to apply an electric field strength of 2 MV / cm to a gate insulating film of nm thickness, the potential difference should be 20 V. That's all you need to do.

[0176] Voltage refers to the potential difference between two points, while electric potential refers to the potential difference between two points in an electrostatic field at a given point. It refers to the electrostatic energy (electrical potential energy) possessed by a unit charge within it. Generally, the potential difference between the potential at a certain point and a reference potential (e.g., ground potential) This phenomenon is simply called electric potential or voltage, and the terms electric potential and voltage are often used interchangeably. Therefore, unless otherwise specified in this specification, potential may be read as voltage, Voltage may be interpreted as electric potential.

[0177] The BT test was conducted with a substrate temperature of 80°C and an electric field strength of 3 MV / cm applied to the gate insulating film. The time (also called stress time) is divided into 100 seconds, 200 seconds, 500 seconds, 1000 seconds, and 150 seconds. +BT and -BT tests were conducted with settings of 0 seconds and 2000 seconds.

[0178] The results of the +BT test after 2000 seconds are shown in Figure 22(A), and the results of the -BT test after 2000 seconds are shown. The results are shown in Figure 22(B).

[0179] In Figure 22(A), the threshold voltage Vth after the +BT test is positive compared to the initial characteristics. The voltage changes by 0.63V in the direction shown in Figure 22(B) after the -BT test compared to the initial characteristics. The threshold voltage Vth is changing by 0.02V in the positive direction. In both BT tests... However, the change in threshold voltage Vth ΔVth is 1V or less, and In-G including CAAC It was confirmed that transistors fabricated using a-Zn-O oxide films have high reliability. Ta.

[0180] Furthermore, for the BT test, transistors that have never undergone BT testing before will be used. It is important to conduct tests. For example, using a transistor that has undergone a +BT test once, a -B test can be performed. When a T-test is conducted, the results of the -BT test are not properly evaluated due to the influence of the previously performed +BT test. It is not possible to perform a +BT test again using a transistor that has already undergone a +BT test. The same applies if such a test is conducted. However, taking these effects into consideration, if the BT test is deliberately repeated... This does not apply if you are returning it.

[0181] Furthermore, an LED light source (white light with an illuminance of 10,000 lux) was used, and the experiment was conducted while irradiating with light. The results of the BT test (also called photopositive bias degradation) are shown in Figure 23(A), using an LED light source. Figure 23(B) shows the results of the -BT test (also known as photo-negative bias degradation) conducted while irradiating with [a specific light source]. As shown in Figure 23(A), the threshold voltage Vth after the +BT test is compared to the initial characteristics. The voltage has changed by 0.27V in the positive direction, and in Figure 23(B), the voltage is -B compared to the initial characteristics. The threshold voltage Vth after the T test has changed by 0.23V in the negative direction. In this BT test as well, the change in threshold voltage Vth ΔVth was 1V or less, C Reliability of transistors fabricated using an In-Ga-Zn-O oxide film containing AAC It was confirmed that the value was high.

[0182] Furthermore, Figure 24 shows the time-dependent change in threshold voltage Vth ΔVth under various stress conditions. This shows the existence of the data. The vertical axis shows the change in threshold voltage Vth ΔVth on a linear scale. The horizontal axis shows stress time on a logarithmic scale.

[0183] Figures 25(A) and 25(B) show schematic diagrams illustrating the mechanism of photo-negative bias degradation. Figures 25(A) and 25(B) show the interface between the oxide semiconductor and the gate insulating film. As shown in Figure 25(A), when light shines on the transistor, a hole is created. The holes are trapped and detrapped. The holes are gate insulating films, as shown in Figure 25(B). By being attracted to it, it becomes a fixed charge, causing a negative shift in the threshold voltage Vth. Therefore, the absence of oxygen deficiency levels is crucial to eliminating photo-negative bias degradation. Reducing oxygen deficiency is effective in eliminating photo-negative bias degradation. Amorphous surface Because oxygen is less likely to escape from the crystal surface than from the surface, CAAC-containing In-Ga-Zn-O Transistors using oxide films of this system have high reliability. Furthermore, by reducing oxygen deficiency... Therefore, a film that releases oxygen upon heating is used as the gate insulating film and interlayer insulating film, Heat treatment in an oxidizing atmosphere is effective in improving reliability. [Explanation of symbols]

[0184] 100 circuit boards 102 Underlying insulating film 104 Guard gate 106 Semiconductor film 112 Gate Insulator 116 Electrode 118 Interlayer insulating film 121 areas 126 areas 200 pixels 210 liquid crystal elements 220 Capacitors 230 transistors 300 cabinets 301 button 302 Microphone 303 Display section 304 Speakers 305 Camera 310 cabinets 311 Display section 320 cabinets 321 buttons 322 Microphone 323 Display section 1001 area 1002 area 1101 Solid line 1102 Solid line 1103 Solid line 1104 Solid line 1111 Solid line 1112 Solid line 1113 Solid line 1114 Solid line 1121 Solid line 1122 Solid line 1123 Solid line 1124 Solid line

Claims

1. It comprises a gate electrode, a gate insulating film having a region above the gate electrode, an oxide semiconductor film having a region above the gate insulating film, and a conductive layer having a region above the oxide semiconductor film. The conductive layer has a region that functions as a source electrode or a drain electrode. The oxide semiconductor film comprises a first oxide film and a second oxide film having a region above the first oxide film. The first oxide film has an amorphous region, The second oxide film has regions in which, in cross-sectional view, metal atoms, or metal atoms and oxygen atoms, are confirmed to be arranged in layers. The oxide semiconductor film comprises indium, gallium, and zinc. Semiconductor equipment.

2. It comprises a gate electrode, a gate insulating film having a region above the gate electrode, an oxide semiconductor film having a region above the gate insulating film, and a conductive layer having a region above the oxide semiconductor film. The conductive layer has a region that functions as a source electrode or a drain electrode. The oxide semiconductor film comprises a first oxide film and a second oxide film having a region above the first oxide film. The first oxide film has regions in which, in cross-sectional view, metal atoms, or metal atoms and oxygen atoms, are not found to be arranged in layers. The second oxide film has regions in which, in cross-sectional view, metal atoms, or metal atoms and oxygen atoms, are confirmed to be arranged in layers. The oxide semiconductor film comprises indium, gallium, and zinc. Semiconductor equipment.

3. It comprises a gate electrode, a gate insulating film having a region above the gate electrode, an oxide semiconductor film having a region above the gate insulating film, and a conductive layer having a region above the oxide semiconductor film. The conductive layer has a region that functions as a source electrode or a drain electrode. The oxide semiconductor film comprises a first oxide film and a second oxide film having a region above the first oxide film. The first oxide film has regions in which, in cross-sectional view, metal atoms, or metal atoms and oxygen atoms, are not found to be arranged in layers. The first oxide film has regions in which a triangular or hexagonal atomic arrangement cannot be observed when viewed from above. The second oxide film has regions in which, in cross-sectional view, metal atoms, or metal atoms and oxygen atoms, are confirmed to be arranged in layers. The second oxide film, when viewed from above, has regions containing triangular or hexagonal atomic arrangements. The oxide semiconductor film comprises indium, gallium, and zinc. Semiconductor equipment.

4. In any one of claims 1 to 3, The gate insulating film comprises a first film having oxygen and silicon, and a second film having nitrogen and silicon, in a semiconductor device.

5. A semiconductor device in any one of claims 1 to 4, wherein the source electrode or the drain electrode is electrically connected to a pixel electrode.

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