Display device

Abstract

To increase the stability of a processing step for wires formed of copper, aluminum, gold, silver, molybdenum, or the like, reduce the impurity concentration of a semiconductor film, or improve the electric characteristic of a semiconductor device.SOLUTION: A semiconductor device includes a semiconductor film, a pair of first protective films in contact with the semiconductor film, a pair of conductive films containing copper, aluminum, gold, silver, or molybdenum in contact with the pair of first protective films, a pair of second protective films in contact with the pair of conductive films on the opposite surface of the pair of first protective film, a gate insulating film in contact with the semiconductor film, and a gate electrode overlapping with the semiconductor film through the gate insulating film. In a cross-sectional shape, side surfaces of the pair of second protective films exist outside the pair of conductive films.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a semiconductor device having a transistor and a manufacturing method thereof. [Background technology]

[0002] It is used in many flat panel displays, such as liquid crystal displays and light-emitting displays. The transistors used are made of amorphous silicon and single crystal silicon formed on a glass substrate. The silicon semiconductor is made of silicon semiconductor such as polycrystalline silicon or polysilicon. Transistors using semiconductors are also used in integrated circuits (ICs).

[0003] In addition, as flat panel displays become larger and higher resolution, the driving frequency becomes higher. As the wiring becomes larger, the resistance and parasitic capacitance of the wiring increases, causing wiring delays. In order to suppress this, a technique for forming wiring using copper is being investigated (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-133422 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the constituent elements of the wiring, such as copper, aluminum, gold, silver, and molybdenum, It is difficult to process and there is a problem that it diffuses into the semiconductor film during processing.

[0006] The wiring elements, such as copper, aluminum, gold, silver, and molybdenum, are It is one of the impurities that cause poor electrical characteristics. The semiconductor film becomes less resistant when exposed to heat and is easily damaged by aging or stress testing. However, there is a problem in that the amount of variation in the electrical characteristics of the transistor, typically the threshold voltage, increases. do.

[0007] Therefore, one embodiment of the present invention is a semiconductor device formed using copper, aluminum, gold, silver, molybdenum, or the like. Another object of the present invention is to improve the stability of a processing step of wiring to be formed. Another object of the present invention is to reduce the impurity concentration of a semiconductor film. Another object of the present invention is to improve electrical characteristics of a semiconductor device. Another object of the present invention is to improve the reliability of a semiconductor device. Another object of one embodiment of the present invention is to realize a power saving semiconductor device. Another object of one embodiment of the present invention is to provide a semiconductor device with excellent productivity. It is an object of the present invention to realize the above-mentioned. It is assumed that there is no need. [Means for solving the problem]

[0008] One embodiment of the present invention is a semiconductor film, a pair of first protective films in contact with the semiconductor film, and a pair of first A pair of conductive films having copper, aluminum, gold, silver, or molybdenum in contact with the protective film. and a pair of second protective films in contact with the pair of first protective films on the opposite side of the pair of conductive films. a gate insulating film in contact with the semiconductor film; and a gate insulating film overlapping the semiconductor film. and a pair of second protective films are disposed on the outer side of the pair of conductive films in a cross-sectional shape. The semiconductor device is located at

[0009] One embodiment of the present invention is a method for manufacturing a semiconductor film having a pair of first protective films, a copper film, an aluminum film, and a forming a conductive film having gold, silver, or molybdenum and a pair of films to be a second protective film; After forming a first mask on the film that will become the pair of second protective films, the pair is A part of the film to be the second protective film is etched to form a pair of second protective films, and the first After removing the mask, the conductive film and the pair of first protective films are removed using the pair of second protective films as a second mask. A pair of first protective films and a pair of conductive films are formed by etching a part of each of the protective films. The present invention relates to a method for manufacturing a semiconductor device in which a

[0010] One embodiment of the present invention is a method for manufacturing a semiconductor film having a pair of first protective films, a copper film, an aluminum film, and a forming a conductive film having gold, silver, or molybdenum and a pair of films to be a second protective film; After forming a first mask on the film that will become the pair of second protective films, the pair is The film to be the second protective film and the conductive film are each partially etched to form a pair of second protective films. After the first mask is removed, a pair of second protective films are formed. Then, a part of the film that will become the pair of first protective films is etched to form the pair of first protective films. The present invention relates to a method for manufacturing a semiconductor device.

[0011] The semiconductor film is made of a semiconductor such as silicon, germanium, gallium arsenide, or gallium nitride. Alternatively, the semiconductor film can be formed by using In, Ga, or The insulating film can be formed using an oxide semiconductor containing Zn.

[0012] In a transistor included in a semiconductor device according to one embodiment of the present invention, The laminated structure includes at least a first protective film and a conductive film, and the side surface is located on the outer side of the conductive film. The upper surface of the conductive film is covered with the second protective film, and the second Since the side surface of the protective film is located outside the conductive film, the conductive film is not exposed to plasma, for example. As a result, the conductive film is not easily damaged by the plasma irradiation. Since the generation of compounds of the constituent metal elements is reduced, the metal elements constituting the conductive film become semiconductors. It becomes difficult to move to the membrane.

[0013] In addition, when the conductive film constituting the pair of electrodes is processed, the semiconductor film is By covering the conductive film with the first protective film, the metal elements that make up the conductive film are blocked by the first protective film. This makes it difficult for the hydrogen to migrate into the semiconductor film.

[0014] As a result, the components of the wiring and electrodes, copper, aluminum, gold, silver, molybdenum, It is possible to suppress the diffusion of impurities such as ions into the semiconductor film. The concentration of impurities in the semiconductor substrate can be reduced. Effect of the Invention

[0015] According to one embodiment of the present invention, in a semiconductor device including an oxide semiconductor film, In another embodiment of the present invention, a semiconductor device using an oxide semiconductor film can be manufactured by using the oxide semiconductor film. In a semiconductor device or the like, impurities in an oxide semiconductor film can be reduced. According to one embodiment of the present invention, in a semiconductor device including an oxide semiconductor film, electrical characteristics can be improved. According to one embodiment of the present invention, a semiconductor device including an oxide semiconductor film can be This can improve reliability. [Brief description of the drawings]

[0016] [Figure 1] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a transistor. [Diagram 2] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a transistor. [Diagram 3] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a transistor. [Figure 4] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a transistor. [Diagram 5] 1A and 1B are a top view and a cross-sectional view illustrating one embodiment of a transistor. [Figure 6] 1A and 1B are a block diagram and a circuit diagram illustrating one embodiment of a semiconductor device. [Figure 7] FIG. 1 is a top view illustrating one embodiment of a semiconductor device. [Figure 8] 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 9] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a semiconductor device. [Figure 10] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a semiconductor device. [Figure 11] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a semiconductor device. [Figure 12] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a semiconductor device. [Figure 13] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a semiconductor device. [Figure 14] FIG. 2 is a diagram showing a nanobeam electron diffraction pattern of an oxide semiconductor film. [Figure 15] FIG. 1 is a cross-sectional view illustrating one embodiment of a transistor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following description, and the embodiments and aspects of the present invention may be modified without departing from the spirit and scope of the present invention. It will be readily understood by those skilled in the art that various modifications may be made to the embodiments and details of the present invention. However, the present invention should not be construed as being limited to the description of the following embodiments and examples. In the following embodiments and examples, the same parts or parts having similar functions are In the case of parts, the same reference numerals or the same hatch patterns are used in common among different drawings, and the repetition The explanation of the repetition will be omitted.

[0018] In each figure described in this specification, the size, thickness, or area of ​​each component is indicated by the following formula: The figures may be exaggerated for clarity and are not necessarily limited to scale. stomach.

[0019] In addition, the terms "first," "second," "third," etc., used in this specification are used interchangeably to avoid confusion of components. The number is added for convenience and is not intended to be a numerical limit. The terms can be replaced with "second" or "third" as appropriate for explanation.

[0020] The function of the "source" and "drain" is to change the direction of the current during circuit operation. For this reason, in this specification, the terms "sauce" and "dressing" are used interchangeably. The terms "in" and "in" may be used interchangeably.

[0021] Voltage is the potential difference between two points, and potential is the electrostatic field at a certain point. This refers to the electrostatic energy (electrical potential energy) possessed by a unit charge in a particle. Generally, the potential difference between a potential at a certain point and a reference potential (for example, ground potential) This is simply called potential or voltage, and potential and voltage are often used synonymously. Therefore, in this specification, unless otherwise specified, potential may be read as voltage. In this specification, voltage may be read as potential.

[0022] In this specification, when an etching process is performed after a photolithography process, The mask formed in the photolithography process is removed.

[0023] (Embodiment 1) In this embodiment, a semiconductor device according to one embodiment of the present invention and a manufacturing method thereof will be described with reference to drawings. Please refer to the following for explanation.

[0024] 1A to 1C are a top view and a cross-sectional view of a transistor 50 included in a semiconductor device. The transistor 50 shown in FIG. 1 is a channel-etched transistor. FIG. 1(A) is a top view of a transistor 50, and FIG. 1(B) is a top view of a transistor 50 along the dashed line A- in FIG. FIG. 1(C) is a cross-sectional view taken along dashed line CD in FIG. 1(A). In FIG. 1A, for clarity, a substrate 11, a gate insulating film 13, an oxide insulating film 23, The oxide insulating film 24, the nitride insulating film 25, etc. are omitted.

[0025] The transistor 50 shown in FIG. 1B and FIG. 1C has a gate An electrode 12, a gate insulating film 13 formed on the substrate 11 and the gate electrode 12, and a gate insulating film A semiconductor film 14 overlapping the gate electrode 12 via an insulating film 13 and a pair of electrodes in contact with the semiconductor film 14 The electrode 21 and the electrode 22 are the same as those in the first embodiment.

[0026] The pair of electrodes 21 and 22 function as a source electrode and a drain electrode. In the first and second electrodes 21 and 22, the electrode 21 has at least a first protective film 21b and a conductive film 21a. The electrode 22 includes at least a first protective film 22b and a conductive film 22a. Each of the conductive films 21b and 22b contacts the semiconductor film 14. On top of this, second protective films 20a and 20b are formed.

[0027] The first protective films 21b and 22b are formed by disposing the metal elements constituting the conductive films 21a and 22a in a semiconductor film. The first protective films 21b and 22b have a function of preventing diffusion of the metal into the metal layer 14. Titanium, tantalum, molybdenum, or titanium nitride, tantalum nitride, molybdenum nitride, or molybdenum nitride It is formed by appropriately using a material such as a fluorine atom.

[0028] The conductive films 21a and 22a are made of a low resistance material such as copper, aluminum, gold, silver, or molybdenum. The element or alloy, or the compound having this as the main component, is formed into a single layer structure or a laminate structure. For example, a single layer structure of an aluminum film containing silicon, a silicon-containing aluminum film on a silicon substrate, A two-layer structure in which a tantalum film is laminated, a copper film, a silver film, and a copper-magnesium-aluminum alloy film are laminated on the copper film. Or a two-layer structure with gold film laminated, aluminum film, copper film, silver film, or titanium film on gold film Or a two-layer structure forming a titanium nitride film, a molybdenum film or a molybdenum nitride film and Aluminum, copper, silver, or gold films are layered on top of the molybdenum or molybdenum nitride film. A three-layer structure in which a film is laminated and then a molybdenum film or molybdenum nitride film is formed on top of the laminate. There is.

[0029] The pair of electrodes 21 and 22 also function as wiring, so Conductive films are formed using low resistance materials such as copper, aluminum, gold, silver, and molybdenum. Therefore, a semiconductor device in which wiring delay is suppressed can be manufactured using a large-area substrate. Therefore, a semiconductor device with reduced power consumption can be manufactured.

[0030] Second protective films 20a and 20b are formed on the pair of electrodes 21 and 22. The insulating film 13, the semiconductor film 14, the pair of electrodes 21 and 22, the second protective films 20a and 20b An insulating film 26 is formed thereon.

[0031] The second protective films 20a, 20b form the first protective films and / or the conductive films 21a, 22a. In the processing step for forming the second protective film, the second protective film functions as an etching protective film. 20a and 20b are conductive films 21a and 22a exposed to plasma, typically oxygen plasma. The second protective films 20a and 20b have a function of preventing the conductive films 21a and 22a from being damaged. For these reasons, the second protective film 20a and the second protective film 20b have a function of preventing the diffusion of the metal elements constituting the second protective film 20a. 0b is made of a material having etching resistance when etching the conductive films 21a and 22a. The second protective films 20a and 20b are formed using a material having plasma resistance. The second protective films 20a and 20b are made of the same metal as the conductive films 21a and 22a. It is formed using a material that prevents diffusion of metal elements.

[0032] The second protective films 20a and 20b are made of silicon nitride, silicon oxynitride, or aluminum nitride. The insulating film is formed by appropriately using an aluminum nitride oxide or the like. In this specification, the silicon nitride oxide film and the aluminum nitride oxide film are films that contain more nitrogen than oxygen. This refers to films with a high content of elements (atomic ratio), such as silicon oxynitride films and aluminum oxynitride films. This refers to a film that contains more oxygen than nitrogen (atomic ratio).

[0033] Alternatively, the second protective films 20a and 20b may be made of indium tin oxide (hereinafter also referred to as ITO). ), indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide Lead oxide, indium oxide with titanium oxide, indium tin oxide with titanium oxide, Conductive materials with light-transmitting properties such as indium zinc oxide and indium tin oxide containing silicon oxide It is formed using a film.

[0034] Alternatively, the second protective films 20a and 20b may be formed on the semiconductor film 14 or the oxide film 15, which will be described later. An oxide semiconductor or oxide containing In, Ga, or Zn that can be used is appropriately used. and form it.

[0035] In the pair of electrodes 21 and 22, the electrode 21 includes at least a conductive film 21a and a first The electrode 22 has at least a conductive film 22a and a first protective film 22b. The second protective films 20a and 20b are formed using a conductive film having light-transmitting properties. In this case, the second protective films 20a and 20b function as parts of the electrodes 21 and 22, respectively. do.

[0036] In the cross-sectional view shown in FIG. 1B, the side surfaces of the second protective films 20a and 20b are opposite to the conductive film 21. That is, the upper surfaces of the conductive films 21a and 22a are located outside the side surfaces of the second protective film 21a and 22a. The second protective films 20a, 20b are covered with the conductive films 21a, 22a. Therefore, the second protective films 20a and 20b are used as a mask to When the first protective film 21b, 22b is formed, the side surfaces of the conductive films 21a, 22a are exposed to plasma. It will be less likely to be done.

[0037] The second protective films 20a and 20b, the conductive films 21a and 22a, and the first protective films 21b and 22 A mask formed of an organic resin (typically formed of a resist) used to form b The mask is then decomposed in the gas phase using oxygen plasma, a process called ashing. Alternatively, the mask can be removed by ashing using a stripping solution. In order to make it easier, after ashing, a mask made of organic resin is removed using a remover. can be removed.

[0038] In addition, an oxide insulating film is formed as a protective film on the conductive films 21a and 22a by sputtering or CV. When the conductive films 21a and 22a are formed by the D method or the like, the conductive films 21a and 22a are exposed to oxygen plasma.

[0039] However, when the conductive films 21a and 22a are exposed to oxygen plasma, the conductive films are The metal element reacts with oxygen to produce a metal oxide. The conductive films 21a and 21b have a high conductivity, which causes a problem of diffusion into the semiconductor film 14. When the second protective films 20a and 20b as shown in FIG. 1(B) are provided on the second insulating film 2a, The protective films 20a and 20b act as masks, and the sides of the conductive films 21a and 22a are exposed to oxygen plasma. As a result, metal oxides are generated by reaction between the metal elements that make up the conductive film and oxygen. This makes it difficult for the conductive film to be formed, and reduces the migration of metal elements constituting the conductive film to the semiconductor film 14. It is possible.

[0040] That is, it is possible to reduce the impurity concentration of the semiconductor film 14. Therefore, it is possible to reduce the variation in the electrical characteristics of the transistor 50 having the same.

[0041] Other configuration details of transistor 50 are described below.

[0042] There is no particular restriction on the material of the substrate 11, but it should be at least strong enough to withstand the subsequent heat treatment. It is necessary to have heat resistance. For example, glass substrate, ceramic substrate, quartz substrate, surface treatment substrate, etc. A fiber substrate or the like may be used as the substrate 11. Also, a single material such as silicon or silicon carbide may be used. Crystalline semiconductor substrates, polycrystalline semiconductor substrates, compound semiconductor substrates such as silicon germanium, SO It is also possible to use a semiconductor substrate such as an I-substrate, and a semiconductor element is provided on the substrate. In addition, when a glass substrate is used as the substrate 11, Generation (1500mm x 1850mm), 7th generation (1870mm x 2200mm), 8th Generation (2200mm x 2400mm), 9th generation (2400mm x 2800mm), 1st By using large area substrates such as 2950mm x 3400mm, large display devices can be produced. can be produced.

[0043] In addition, a flexible substrate is used as the substrate 11, and the transistor 50 is directly formed on the flexible substrate. Alternatively, a release layer may be provided between the substrate 11 and the transistor 50. The layer is separated from the substrate 11 after a semiconductor device is partially or completely completed thereon, and then the layer is removed. In this case, the transistor 50 is placed on a substrate having poor heat resistance. It can also be transferred to a plate or flexible substrate.

[0044] The gate electrode 12 is formed by stacking a protective film 12a and a conductive film 12b. The second protective film 21b and the second protective film 22b may be formed by appropriately using the same material as the first protective film 21b and the second protective film 22b. The conductive film 12b can be formed by appropriately using the same material as the conductive films 21a and 22a. By providing the protective film 12a, the adhesion between the substrate 11 and the conductive film 12b can be improved. do.

[0045] The conductive film 12b is made of indium tin oxide or 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, indium oxide containing silicon oxide A light-transmitting conductive material such as indium tin oxide can also be used. A laminated structure of a conductive material having optical properties and the above metal element may also be used.

[0046] In this embodiment, the gate electrode 12 is provided with the protective film 12a, but the gate electrode 12 may be provided with only the conductive film 12b. The gate electrode 12 may be formed by

[0047] The gate insulating film 13 is made of, for example, silicon oxide, silicon oxynitride, silicon nitride oxide, or nitrogen. Silicon oxide, aluminum oxide, aluminum oxynitride, aluminum nitride, aluminum oxide nitride Aluminum, hafnium oxide, gallium oxide, Ga-Zn metal oxide, etc. It is preferable that the insulating layer 100 is provided as a laminate or a single layer.

[0048] In the gate insulating film 13, the film in contact with the gate electrode 12 is made of silicon nitride, Forming a nitride insulating film such as silicon oxynitride, aluminum nitride, or aluminum oxynitride This prevents diffusion of metal elements constituting the conductive film 12b included in the gate electrode 12. This is preferable because it is possible to

[0049] The gate insulating film 13 is made of hafnium silicate (HfSiOx ), nitrogen is added Hafnium Silicate (HfSi x O y N z ), nitrogen-doped hafnium aluminium minate (HfAl x O y N z ), hafnium oxide, yttrium oxide and other high- The use of k-materials can reduce the gate leakage of transistors.

[0050] The thickness of the gate insulating film 13 is 5 nm or more and 400 nm or less, and more preferably 10 nm or more. It is preferably 300 nm or less, and more preferably 50 nm or more and 250 nm or less.

[0051] The semiconductor film 14 is a semiconductor such as silicon, germanium, gallium arsenide, or gallium nitride. The semiconductor film 14 may have a single crystal structure or a non-single crystal structure. The non-single crystal structure can be, for example, a polycrystalline structure, a microcrystalline structure, or an amorphous structure. Includes structure.

[0052] The semiconductor film 14 is made of a semiconductor such as silicon, germanium, gallium arsenide, or gallium nitride. When a semiconductor element is used, the thickness of the semiconductor film 14 is 20 nm or more and 500 nm or less, preferably The thickness is set to 50 nm or more and 200 nm or less, and more preferably 70 nm or more and 150 nm or less.

[0053] The semiconductor film 14 may be made of an oxide semiconductor containing In, Ga, or Zn. The oxide semiconductor containing In, Ga, or Zn is typically an In-Ga oxide. In-Zn oxide, In-M-Zn oxide (M is Ti, Ga, Y, Zr, La, Ce, Nd, or Hf).

[0054] The oxide semiconductor is In-M-Zn oxide (M is Ti, Ga, Y, Zr, La, Ce, N In the case of In-M-Zn oxide, the sputtering temperature is The atomic ratio of the metal elements in the target preferably satisfies In≧M and Zn≧M. The atomic ratio of the metal elements in such a sputtering target is In:M:Zn=1:1: The atomic ratio of the oxide semiconductor film to be formed is preferably In:M:Zn=3:1:2. The ratios are calculated by taking the number of atoms of the metal elements contained in the sputtering target as the error. This includes a ratio variation of plus or minus 30%.

[0055] When the oxide semiconductor is an In-M-Zn oxide, the sum of In and M is 100 atoms. When the atomic ratio of In and M is ic%, the atomic ratio of In is preferably 25 atomic % or more. , M is less than 75 atomic %, more preferably In is 34 atomic % or more, and M is Less than 66 atomic%.

[0056] The oxide semiconductor has an energy gap of 2 eV or more, preferably 2.5 eV or more. The energy gap is preferably 3 eV or more. By using this for the conductor film 14, the off-state current of the transistor 50 can be reduced.

[0057] The oxide semiconductor may have a single crystal structure or a non-single crystal structure as appropriate. For example, CAAC-OS (C Axis Aligned Crystallography) ine oxide semiconductor), polycrystalline structure, microcrystalline structure (described later) Among non-single crystal structures, the amorphous structure has the highest defect level density. Among them, CAAC-OS has the lowest density of defect states.

[0058] When an oxide semiconductor is used as the semiconductor film 14, the thickness of the semiconductor film 14 is 3 nm or more. 00 nm or less, preferably 3 nm or more and 100 nm or less, and more preferably 3 nm or more and 50 nm or less.

[0059] As the oxide semiconductor, an oxide semiconductor having a low impurity concentration and a low density of defect states is used. This makes it possible to manufacture a transistor having even better electrical characteristics. Here, high purity refers to low impurity concentration and low defect level density (low oxygen vacancies). It is called authentic or substantially authentic with high purity.

[0060] A highly pure intrinsic or substantially highly pure intrinsic oxide semiconductor has a small carrier generation source. Therefore, the carrier density can be reduced. The transistor in which the channel region is formed in the semiconductor film 14 has a negative threshold voltage. In some cases, the electrical characteristics are unlikely to be such that the device is normally on.

[0061] The carrier density of oxide semiconductors is 1×10 17 pieces / cm 3 Less than or equal to 1×10 1 5 pieces / cm 3 Less than 1×10, more preferably 13 pieces / cm 3 Less than or equal to 1× 10 11 pieces / cm 3 It is preferable that:

[0062] In addition, a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor has a low density of defect states. Therefore, the trap level density may be low.

[0063] In addition, a transistor having a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor has a significantly smaller off-state current and a channel width of 1×10 6 μm and the channel length L is 10 μm. Even for elements, the voltage between the source and drain electrodes (drain voltage) is 1V to 10V In the range of 1, the off-state current is below the measurement limit of the semiconductor parameter analyzer, that is, 1 ×10 -13 It is possible to obtain a characteristic of A or less.

[0064] Therefore, the electrical characteristics of a transistor in which a channel region is formed in an oxide semiconductor are not easily changed. In some cases, the trap quasi-electron trapping in an oxide semiconductor can be used to form a small and highly reliable transistor. Charges trapped at the site take a long time to dissipate and behave as if they were fixed charges. Therefore, a channel region is formed in an oxide semiconductor with a high density of trap states. The electrical characteristics of the transistors formed may become unstable. Examples include nitrogen, an alkali metal, or an alkaline earth metal.

[0065] The hydrogen contained in the oxide semiconductor reacts with the oxygen that is bonded to the metal atom to form water, and the acid Oxygen vacancies are formed in the lattice from which the atoms have been removed (or in the area from which the oxygen has been removed). When hydrogen enters, electrons, which act as carriers, may be generated. Also, some of the hydrogen may be converted to gold. By bonding with oxygen, which bonds with a metal atom, electrons that act as carriers can be generated. Therefore, a transistor using an oxide semiconductor containing hydrogen has normally-on characteristics. Easy to use.

[0066] For this reason, it is preferable that the amount of hydrogen in the oxide semiconductor is reduced as much as possible. In oxide semiconductors, secondary ion mass spectrometry (SIMS) The hydrogen concentration obtained by mass spectrometry was calculated as 5×10 19 atoms / cm 3 Less than or equal to 1×10 19 atoms / cm 3 Below, 5×1 0 18 atoms / cm 3 Less than or equal to 1×10 18 atoms / cm 3 More details below. Preferably 5 x 10 17 atoms / cm 3 Less than 1×10, more preferably 16 ato ms / cm 3 The following applies.

[0067] When an oxide semiconductor contains silicon or carbon, which is one of the group 14 elements, oxygen The number of defects increases, and the oxide semiconductor becomes n-type. Degrees, 2×10 18 atoms / cm 3 Less than or equal to 2 x 10 17 atoms / c m 3 The following applies.

[0068] In addition, in the oxide semiconductor, an alkali metal or is the concentration of alkaline earth metals, 1×10 18 atoms / cm 3 Below, preferably 2 x 1 0 16 atoms / cm 3 Alkali metals and alkaline earth metals are oxide semiconductors. When it bonds with a conductor, it can generate carriers, which increases the off-state current of the transistor. For this reason, the concentration of alkali metal or alkaline earth metal in the oxide semiconductor It is preferable to reduce

[0069] In addition, when nitrogen is contained in an oxide semiconductor, electrons that act as carriers are generated, and the carrier density is increased. As a result, transistors using oxide semiconductors containing nitrogen are Therefore, in the oxide semiconductor, the nitrogen It is preferable that the amount of the ionized water is as small as possible. For example, the amount of the ionized water obtained by secondary ion mass spectrometry is preferably as small as possible. The nitrogen concentration is 5×10 18 atoms / cm 3 It is preferable to do the following:

[0070] In addition, the concentration of copper, aluminum, gold, silver, or molybdenum in the semiconductor film 14 is , 1×10 18 atoms / cm 3 The following are the copper and aluminum in the semiconductor film 14. By setting the concentration of gold, silver, or molybdenum to the above concentration, the electrical characteristics of the transistor can be improved. In addition, the reliability of the transistor can be improved.

[0071] The first protective films 21b and 22b may be made of a single metal such as titanium, tantalum, or molybdenum. When a conductive material that easily bonds with oxygen, such as an oxide or alloy, is used, the oxide contained in the oxide semiconductor The element is bonded to the conductive material contained in the first protective films 21b and 22b, forming an oxide semiconductor. In the semiconductor film 14, an oxygen vacancy region is formed. A part of the constituent elements of the conductive material forming the first protective films 21b and 22b is mixed into the semiconductor film 14. As a result, in the semiconductor film 14 made of an oxide semiconductor, A low resistance region is formed in the vicinity of the region in contact with the protective films 21b and 22b of the first insulating film 1. , contacting the first protective films 21b and 22b, and the gate insulating film 13 and the first protective film 21b, The low resistance region is formed between the first and second gate electrodes 22b and 22c. The low resistance region is formed of an oxide semiconductor because of its high conductivity. It is possible to reduce the contact resistance between the semiconductor film 14 and the first protective films 21b and 22b, The on-state current of the transistor can be increased.

[0072] The insulating film 26 can be an oxide insulating film or a nitride insulating film as appropriate.

[0073] Here, when an oxide semiconductor is used as the semiconductor film 14, an oxide semiconductor is used as the insulating film 26. The oxide insulating film 23 and the oxide insulating film 24 capable of reducing oxygen vacancies in a semiconductor The nitride insulating film 25 can prevent impurities from the semiconductor film 14 from migrating from the semiconductor film 14. The oxide insulating film 23, the oxide insulating film 24, and the nitride insulating film 25 are described in detail below. This article explains:

[0074] The oxide insulating film 23 is an oxygen-permeable oxide insulating film. This serves as a film for reducing damage to the semiconductor film 14 when forming the oxide insulating film 24 to be formed later. It also works.

[0075] The oxide insulating film 23 has a thickness of 5 nm to 150 nm, preferably 5 nm or more. A silicon oxide film, a silicon oxynitride film, or the like having a thickness of 50 nm or less can be used.

[0076] In addition, it is preferable that the oxide insulating film 23 has a small amount of defects. Therefore, the spin of the signal at g=2.001 originating from the silicon dangling bond Density is 3×1017 spins / cm 3 This is because the oxide insulation If the film 23 contains a large number of defects, oxygen will be bonded to the defects, and the oxide insulating film 2 This is because the amount of oxygen permeating through 3 decreases.

[0077] In addition, it is preferable that the number of defects at the interface between the oxide insulating film 23 and the semiconductor film 14 is small. Typically, the ESR measurement shows that the g value is 1.93, which is due to defects in the semiconductor film 14. The spin density of the signal is 1×10 17 spins / cm 3 Below the detection limit, It is preferable that

[0078] Note that in the oxide insulating film 23, all of the oxygen that has entered the oxide insulating film 23 from the outside is Some oxygen does not move outside the oxide insulating film 23 and remains in the oxide insulating film 23. As oxygen enters the oxide insulating film 23, the oxygen contained in the oxide insulating film 23 In some cases, oxygen may move in the oxide insulating film 23 due to the movement of oxygen to the outside.

[0079] When an oxide insulating film that transmits oxygen is formed as the oxide insulating film 23, the oxide insulating film 23 The oxide insulating film 23 is formed on the semiconductor substrate 10. ... It can be moved to the membrane 14.

[0080] An oxide insulating film 24 is formed so as to be in contact with the oxide insulating film 23. 4 is formed using an oxide insulating film containing more oxygen than the oxygen that satisfies the stoichiometric composition. The oxide insulating film containing more oxygen than the stoichiometric composition is heated to remove the oxygen. A part of the element is released. The oxide insulating film contains more oxygen than the oxygen that satisfies the stoichiometric composition. In TDS analysis, the amount of oxygen released was 1.0 x 10 18 atoms / cm 3 More than 3.0×10 20 atoms / cm 3 The oxide insulating film It is.

[0081] The oxide insulating film 24 has a thickness of 30 nm to 500 nm, preferably 50 nm. A silicon oxide film, a silicon oxynitride film, or the like having a thickness of 400 nm or more and 400 nm or less can be used.

[0082] In addition, it is preferable that the oxide insulating film 24 has a small amount of defects. Therefore, the spin of the signal at g=2.001 originating from the silicon dangling bond Density is 1.5×10 18 spins / cm 3 Less than or even 1×10 18 spins / cm 3 Note that the oxide insulating film 24 has a thickness smaller than that of the oxide insulating film 23. Since the insulating film 23 is located away from the semiconductor film 14, the insulating film 23 may have a higher defect density than the oxide insulating film 23.

[0083] Further, oxygen, hydrogen, water, an alkali metal, an alkaline earth metal, etc. are deposited on the oxide insulating film 24. By providing the nitride insulating film 25 having the blocking effect, oxygen from the semiconductor film 14 is prevented from being generated. It is possible to prevent the diffusion of nitrogen to the outside and the intrusion of hydrogen, water, etc. into the semiconductor film 14 from the outside. Examples of the oxide insulating film include silicon nitride, silicon oxynitride, aluminum nitride, and aluminum oxynitride. In addition, oxygen, hydrogen, water, alkali metals, alkaline earth metals, etc. Instead of a nitride insulating film that has a blocking effect, a silicon oxide film that has a blocking effect against oxygen, hydrogen, water, etc. An oxide insulating film having a blocking effect against oxygen, hydrogen, water, and the like may be provided. The insulating film may be aluminum oxide, aluminum oxynitride, gallium oxide, or oxynitride. Gallium, yttrium oxide, yttrium oxynitride, hafnium oxide, hafnium oxynitride Examples include Um.

[0084] Next, a method for manufacturing the transistor 50 shown in FIG. 1 will be described with reference to FIGS. do.

[0085] As shown in FIG. 2A, a gate electrode 12 is formed on a substrate 11. A gate insulating film 13 is formed.

[0086] Here, a glass substrate is used as the substrate 11.

[0087] The method of forming the gate electrode 12 will be described below. First, the sputtering method, the CVD method, and the evaporation method are used. A protective film and a conductive film are formed by a deposition method or the like, and a photolithography process is performed on the conductive film. Next, the mask is used to form a protective film and a conductive film. A part of the gate electrode 12 is formed by etching the protective film 12a and the conductive film 12b. After this, the mask is removed.

[0088] The gate electrode 12 may be formed by electrolytic plating, printing, ink jet printing, or the like instead of the above-mentioned method. It may be formed by a jet method or the like.

[0089] Here, a titanium film with a thickness of 35 nm and a copper film with a thickness of 200 nm are deposited by sputtering. Next, a mask is formed by a photolithography process, and the mask is used to Then, a part of the copper film is dry etched, and a part of the titanium film is dry etched to form a titanium A protective film 12a made of a silicon film and a conductive film 12b are then formed.

[0090] The gate insulating film 13 is formed by a sputtering method, a CVD method, a vapor deposition method or the like.

[0091] The gate insulating film 13 is a silicon oxide film, a silicon oxynitride film, or a silicon nitride oxide film. When forming a silicon film, a deposition gas containing silicon and an oxidizing gas are used as the source gas. Representative examples of deposition gases containing silicon include silane, disilane, Examples of oxidizing gases include trisilane, fluorinated silane, etc. Examples of oxidizing gases include oxygen, ozone, and nitrous oxide. , nitrogen dioxide, etc.

[0092] In addition, when a gallium oxide film is formed as the gate insulating film 13, MOCVD (Metal Organic Chemical Vapor Deposition (OCVD) method It can be formed by:

[0093] Next, as shown in FIG. 2(B), a semiconductor film 14 is formed on the gate insulating film 13.

[0094] A method for forming the semiconductor film 14 will be described below. Next, a semiconductor film that will become 14 is formed on the semiconductor film by a photolithography process. After forming the mask, a part of the semiconductor film is etched using the mask, so that the semiconductor film is formed as shown in FIG. A semiconductor film with element isolation is formed as shown in Fig. 1. After that, the mask is removed.

[0095] The semiconductor film that becomes the semiconductor film 14 can be formed by sputtering, coating, pulsed laser deposition, The film can be formed by using a laser ablation method, a CVD method, or the like.

[0096] In the case where an oxide semiconductor film is formed as the semiconductor film 14, a plasma is formed by a sputtering method. The power supply for generating the radiator can be an RF power supply, an AC power supply, a DC power supply, etc. It can be used.

[0097] The sputtering gas is a rare gas (typically argon), oxygen gas, or a mixture of a rare gas and oxygen. A mixed gas is used as appropriate. In the case of a mixed gas of rare gas and oxygen, the ratio of oxygen to rare gas is It is preferable to increase the gas ratio.

[0098] The target may be appropriately selected depending on the composition of the oxide semiconductor film to be formed. .

[0099] In order to obtain a highly pure intrinsic or substantially highly pure intrinsic oxide semiconductor film, Not only is it necessary to evacuate the inside of the chamber to a high vacuum, but it is also necessary to highly purify the sputtering gas. The oxygen gas and argon gas used should have a dew point of -40°C or less, preferably -80°C or less. Gas that has been highly purified to -100℃ or less, more preferably -120℃ or less By using the above, it is possible to prevent moisture and the like from being taken into the oxide semiconductor film as much as possible. do.

[0100] Here, an In-Ga-Zn oxide target (In:Ga:Zn=1:1:1) was used. A 35-nm-thick In-Ga-Zn oxide film was deposited as an oxide semiconductor film by sputtering. Next, a mask is formed over the oxide semiconductor film, and a part of the oxide semiconductor film is By selectively etching, the semiconductor film 14 is formed.

[0101] After that, a first heat treatment may be performed. In this case, hydrogen, water, and the like contained in the semiconductor film 14 are eliminated by the first heat treatment, and the semiconductor film 14 is oxidized. The hydrogen concentration and water concentration in the semiconductor film can be reduced. Typically, the temperature is 300° C. or higher and 400° C. or lower, and preferably 320° C. or higher and 370° C. or lower. .

[0102] The first heat treatment can be performed using an electric furnace, an RTA device, or the like. This allows the heat treatment to be performed at a temperature equal to or higher than the distortion point of the substrate for a short period of time. The heat treatment time can be shortened.

[0103] The first heat treatment is carried out in a nitrogen, oxygen, or ultra-dry air (water content of 20 ppm or less, preferably air at less than 1 ppm, preferably less than 10 ppb), or rare gases (argon, helium The above-mentioned nitrogen, oxygen, ultra-dry air, or rare gas may be added to the water atmosphere. It is preferable that the material does not contain hydrogen, water, etc. Also, after heat treatment in a nitrogen or rare gas atmosphere, Alternatively, the semiconductor film 14 may be heated in an oxygen or ultra-dry air atmosphere. Hydrogen, water, etc. can be desorbed, and oxygen can be supplied into the semiconductor film 14. As a result, the amount of oxygen vacancies contained in the semiconductor film 14 can be reduced.

[0104] Next, as shown in FIG. 2C, a film 17a to be a first protective film, a conductive film 17b, and Next, a mask 1 is placed on the film 18 that will be the second protective film. Form 9a, 19b.

[0105] The film 17a serving as the first protective film, the conductive film 17b, and the film 18 serving as the second protective film are made of a spatula. It is formed by using a tarpaulin deposition method, a CVD method, a deposition method, or the like.

[0106] Here, a titanium film having a thickness of 35 nm is formed by sputtering as the film 17a which becomes the first protective film. The conductive film 17b is formed by sputtering a copper film having a thickness of 200 nm. The second protective film 18 is formed by a plasma CVD method. A silicon nitride film with a thickness of 200 nm is formed. A mask is then formed by a photolithography process. Form 19a, 19b.

[0107] Next, as shown in FIG. 2(D), a film to be a second protective film is formed using masks 19a and 19b. A pair of second protective films 20a and 20b are formed by etching a part of the second protective film 18. The protective film 18 is etched by dry etching, wet etching, or the like. The second protective films 20a and 20b can be used as a hard mask in a later process. Since the distance between the second protective films 20a and 20b is the channel length of the transistor, The film 18 serving as the second protective film is formed by dry etching, which allows anisotropic etching. is preferred.

[0108] Next, as shown in FIG. 3(A), the masks 19a and 19b are removed. After the masks 19a and 19b are removed by a cleaning process to make them easier to remove, a remover is used to remove the masks 19a and 19b. a, 19b are removed.

[0109] In the process of removing the masks 19a and 19b, the conductive film 17b is exposed. The semiconductor film 14 is covered with the film 17a, which is the first protective film, and is not exposed. The metal elements constituting the film 17 b do not migrate to the semiconductor film 14 .

[0110] Next, as shown in FIG. 3B, the conductive film 17b is covered with second protective films 20a and 20b. A pair of conductive films 21a and 22a are formed by etching a part of the first protective film. The film 17a to be the conductive film is not etched, and the conductive film 17b is selectively etched. As a result, the semiconductor film 14 is not exposed in the etching process, and the conductive film 17 During etching of the conductive film 17b, the metal elements constituting the conductive film 17b do not migrate to the semiconductor film 14. In addition, the conductive film 17b is etched by wet etching to form an isotropic conductive film. In order to etch the film 17b, the side surface is positioned inside the side surfaces of the second protective films 20a and 20b. Conductive films 21a and 22a are formed so as to be disposed at the positions of the first protective film 17a. As a condition for selectively etching the conductive film 17b without etching, the etchant is nitric acid. , perchloric acid, a mixture of phosphoric acid, acetic acid, and nitric acid (aluminum mixed acid solution), etc. can be used appropriately. .

[0111] Here, hydrogen peroxide, ammonium acetate, malonic acid, and ethylenediamine are used as etchants. Wet with a mixture of aminetetraacetic acid and 5-amino-1H-tetrazole monohydrate The conductive film 17b is selectively etched using an etching method.

[0112] Next, as shown in FIG. 3(C), second protective films 20a and 20b are used to cover the first protective film. The film 17a is partially etched to form a pair of first protective films 21b and 22b. The film 17a serving as the first protective film is etched by dry etching, wet etching, etc. can be used appropriately.

[0113] Here, the first protective film is formed by dry etching using chlorine as an etching gas. The film 17a is then etched.

[0114] The side surfaces of the second protective films 20a and 20b are located outside the side surfaces of the conductive films 21a and 22a. That is, the upper surfaces of the conductive films 21a and 22a are covered with the second protective films 20a and 20b, and The second protective films 20a and 20b protrude outward from the conductive films 21a and 22a. Therefore, when a part of the film 17a that becomes the first protective film is etched, the conductive films 21a and 22a are As a result, even if the semiconductor film 14 is exposed, the semiconductor Therefore, the migration of metal elements constituting the conductive films 21a and 22a to the body film 14 can be reduced.

[0115] As a result, the impurity concentration in the semiconductor film 14 can be reduced.

[0116] Next, as shown in FIG. 3D, the semiconductor film 14, the pair of electrodes 21 and 22, and the pair of second electrodes 23 and 24 are An insulating film 26 is formed on the protective films 20a and 20b.

[0117] The insulating film 26 can be formed by appropriately using a sputtering method, a CVD method, or the like.

[0118] Here, in the case where the semiconductor film 14 is an oxide semiconductor film, in order to reduce oxygen vacancies in the oxide semiconductor film, A method for forming the insulating film 26 that can be formed using this method will be described below.

[0119] On the semiconductor film 14, the pair of electrodes 21 and 22, and the pair of second protective films 20a and 20b, The oxide insulating film 23 is formed. Next, the oxide insulating film 24 is formed on the oxide insulating film 23. .

[0120] After the oxide insulating film 23 is formed, the oxide insulating film 2 is successively removed without being exposed to the air. After the oxide insulating film 23 is formed, the source gas The oxide insulating film 24 is continuously formed by adjusting one or more of the flow rate, pressure, high frequency power, and substrate temperature. By forming the oxide insulating film 23 and the oxide insulating film 24 in In addition, the impurity concentration in the oxide insulating film 24 can be reduced. The amount of oxygen vacancies in the semiconductor film 14 can be reduced. do.

[0121] The oxide insulating film 23 is made of a silicon oxide film placed in a vacuum-evacuated processing chamber of a plasma CVD apparatus. The substrate is kept at a temperature of 180° C. to 400° C., preferably 200° C. to 370° C. A raw material gas is introduced into the processing chamber to set the pressure in the processing chamber to 20 Pa or more and 250 Pa or less. More preferably, the pressure is set to 100 Pa or more and 250 Pa or less, and a high frequency is applied to the electrode provided in the processing chamber. Depending on the conditions of supplying the microwave power, the oxide insulating film 23 may be a silicon oxide film or a silicon oxynitride film. A silicon film can be formed.

[0122] As the source gas for the oxide insulating film 23, a deposition gas containing silicon and an oxidizing gas are used. Representative examples of deposition gases containing silicon include silane, disilane, Examples of oxidizing gases include trisilane, fluorinated silane, etc. Examples of oxidizing gases include oxygen, ozone, and nitrous oxide. , nitrogen dioxide, etc.

[0123] By using the above conditions, an oxide insulating film that transmits oxygen is formed as the oxide insulating film 23. In addition, by providing the oxide insulating film 23, the oxide insulating film In the process of forming 24, damage to the semiconductor film 14 can be reduced.

[0124] The oxide insulating film 23 is placed in a vacuum evacuated processing chamber of a plasma CVD apparatus. The substrate is heated at 200° C. or higher and 400° C. or lower, more preferably at 220° C. or higher and 370° C. or lower. Preferably, the temperature is 300° C. or higher and 400° C. or lower, and more preferably, the temperature is 320° C. or higher and 370° C. or lower. The pressure in the processing chamber is maintained at 100 Pa or more and 250 Pa or less by introducing a raw material gas into the processing chamber. The oxide insulating film is formed by supplying high frequency power to an electrode provided in a processing chamber under the following conditions. As the film 23, a silicon oxide film or a silicon oxynitride film can be formed.

[0125] In the film formation conditions, the substrate temperature is set to 300° C. or higher and 400° C. or lower, and more preferably 32 By setting the temperature to 0°C or higher and 370°C or lower, the bonding strength between silicon and oxygen becomes stronger. As a result, The oxide insulating film 23 is typically an oxide insulating film that is oxygen-permeable, dense, and hard. The etching rate in 0.5% by weight hydrofluoric acid at 25°C is 10 nm / min or less. Preferably, a silicon oxide film or a silicon oxynitride film is formed at a rate of 8 nm / min or less. This can be done.

[0126] In addition, in this process, the oxide insulating film 23 is formed while heating. In this manner, hydrogen, water, and the like contained in the semiconductor film 14 can be desorbed. The hydrogen contained in the film combines with oxygen radicals generated in the plasma to form water. During the deposition process of 23, the substrate is heated, and oxygen and hydrogen are combined to form The water is desorbed from the oxide semiconductor film. By forming the oxide semiconductor film, the amount of water and hydrogen contained in the oxide semiconductor film can be reduced. .

[0127] Furthermore, by setting the pressure in the treatment chamber to 100 Pa or more and 250 Pa or less, the oxide insulating film The water content in the 23 is reduced, which reduces the variation in the electrical characteristics of the transistor 50. In addition, the pressure in the processing chamber can be reduced by 100 ps. By setting the pressure to 00 Pa or more and 250 Pa or less, when the oxide insulating film 23 is formed, It is possible to reduce damage to the semiconductor film 14, and the amount of oxygen vacancies contained in the semiconductor film 14 can be reduced. In particular, the oxide insulating film 23 or the oxide insulating film 24 to be formed later can be reduced. By increasing the film formation temperature, typically to a temperature higher than 220° C., the In addition, some of the oxygen in the semiconductor is easily removed, forming oxygen vacancies. In order to increase the thickness of the oxide insulating film 24, the film forming conditions are used to reduce the number of defects in the oxide insulating film 24 to be formed later. As a result, the amount of oxygen desorption can be reduced by reducing the oxygen vacancies in the semiconductor film 14. However, it may be difficult to maintain the pressure in the processing chamber at 100 Pa or more and 250 Pa or less. In addition, damage to the semiconductor film 14 during the formation of the oxide insulating film 23 is reduced, so that the oxide insulating film 23 can be easily formed. Even if the amount of oxygen desorbed from the insulating film 24 is small, the oxygen vacancies in the semiconductor film 14 can be reduced. It is Noh.

[0128] In addition, by increasing the amount of oxidizing gas to 100 times or more the amount of deposition gas containing silicon, The hydrogen content in the oxide insulating film 23 can be reduced. Since the amount of hydrogen mixed into the film 14 can be reduced, the threshold voltage of the transistor is shifted negatively. This can suppress the

[0129] In addition, the deposition rate of the oxide insulating film 23 is set to 60 nm / min or more and 200 nm / min or less. Therefore, it is possible to form the oxide insulating film 23 while suppressing the oxidation of the conductive films 21a and 22a. As a result, the oxide insulating film 23 can be formed while improving the stability of the conductive films 21a and 22a. It is possible.

[0130] Here, the oxide insulating film 23 is made of silane at a flow rate of 30 sccm and 4000 sccm. The source gas was nitrous oxide with a flow rate of 1.0 cm, the pressure in the processing chamber was 200 Pa, and the substrate temperature was 220°C. A 27.12MHz high-frequency power source was used to supply 150W of high-frequency power to the parallel plate electrodes. A silicon oxynitride film with a thickness of 50 nm is formed by the plasma CVD method under the following conditions. In this manner, a silicon oxynitride film through which oxygen can pass can be formed. In this embodiment, the oxide insulating film 23 is formed using a high frequency power source of 27.12 MHz. However, the present invention is not limited to this, and may be implemented, for example, by using a high frequency power source of 13.56 MHz. An oxide insulating film 23 may be formed.

[0131] The oxide insulating film 24 is placed in a vacuum-evacuated processing chamber of a plasma CVD apparatus. The substrate is kept at a temperature of 180° C. or higher and 280° C. or lower, more preferably 200° C. or higher and 240° C. or lower. The raw material gas is introduced into the processing chamber to set the pressure in the processing chamber at 100 Pa or more and 250 Pa or less. More preferably, the pressure is set to 100 Pa or more and 200 Pa or less. .17W / cm 2 More than 0.5W / cm 2 Less than or equal to 0.25 W / cm 2 End 0.35W / cm 2Under the following conditions of high frequency power supply, silicon oxide film or oxide A silicon nitride film is formed.

[0132] As the source gas of the oxide insulating film 24, a deposition gas containing silicon and an oxidizing gas are used. Representative examples of deposition gases containing silicon include silane, disilane, Examples of oxidizing gases include trisilane, fluorinated silane, etc. Examples of oxidizing gases include oxygen, ozone, and nitrous oxide. , nitrogen dioxide, etc.

[0133] The oxide insulating film 24 is formed under the conditions of high frequency irradiation with the above power density in a processing chamber at the above pressure. Supplying microwave power increases the efficiency of decomposing the source gas in the plasma, and oxygen radicals are increased. As the source gas is added, the oxidation of the source gas proceeds, so that the oxygen content in the oxide insulating film 24 becomes stoichiometric. On the other hand, in the film formed at the substrate temperature, the composition of silicon and oxygen is Since the bonding strength is weak, some of the oxygen in the film is released by the heat treatment in the subsequent process. It contains more oxygen than the stoichiometric composition, and some of the oxygen is released by heating. In addition, an oxide insulating film 23 can be formed on the semiconductor film 14. Therefore, in the process of forming the oxide insulating film 24, the oxide insulating film 23 is semi-insulated. This serves as a protective film for the conductive film 14. As a result, damage to the semiconductor film 14 is reduced, and the The oxide insulating film 24 can be formed by using high-frequency power with a high power density.

[0134] In addition, in the deposition conditions of the oxide insulating film 24, the deposition gas containing silicon is By increasing the flow rate of the reactive gas, it is possible to reduce the number of defects in the oxide insulating film 24. Typically, ESR measurements reveal that the g value is 2.0 due to the dangling bonds of silicon. The spin density of the signal appearing in 01 is 6×10 17 spins / cm 3 Less than 3x, preferably 10 17 spins / cm 3 Less than or equal to 1.5×10 17 spins / cm 3 below As a result, the signal quality of the transistor is improved. It can increase reliability.

[0135] Here, the oxide insulating film 24 is made of silane at a flow rate of 200 sccm and SiO at a flow rate of 4000 s. The source gas was nitrous oxide (N2O) at 1.0 ccm, the pressure in the processing chamber was 200 Pa, and the substrate temperature was 220° C. A 27.12MHz high-frequency power source was used to apply 1500W of high-frequency power to the parallel plate electrodes. A silicon oxynitride film with a thickness of 400 nm is formed by the supplied plasma CVD method. The plasma CVD device has an electrode area of ​​6000 cm 2 Parallel plate plasma CVD The power supplied to the device is converted to power per unit area (power density) of 0.25W. / cm 2 In this embodiment, a high frequency power source of 27.12 MHz is used. However, the present invention is not limited to this method, and may be applied to, for example, The oxide insulating film 24 may be formed using a high frequency power source of 0.56 MHz.

[0136] Next, a heat treatment may be performed. The temperature of the heat treatment is typically 150° C. or higher and 30 The heating temperature is set to 0° C. or lower, preferably 200° C. or higher and 250° C. or lower. can be carried out in the same manner.

[0137] By this heat treatment, part of oxygen contained in the oxide insulating film 24 is moved to the semiconductor film 14. As a result, the oxygen vacancies in the semiconductor film 14 can be reduced. The amount of oxygen vacancies contained in 14 can be reduced.

[0138] In the case where the oxide insulating film 23 and the oxide insulating film 24 contain water, hydrogen, or the like, A nitride insulating film 25 having a blocking function is then formed and heat treatment is performed, whereby the Water, hydrogen, and the like contained in the oxide insulating film 23 and the oxide insulating film 24 move to the semiconductor film 14, However, the heating causes defects in the oxide insulating film 23. In addition, water, hydrogen, and the like contained in the oxide insulating film 24 can be eliminated. This can reduce the variation in the electrical characteristics of the capacitor 50 and suppress the fluctuation in the threshold voltage. Cut.

[0139] In addition, by forming the oxide insulating film 24 on the oxide insulating film 23 while heating, a semiconductor It is possible to move oxygen to the semiconductor film 14 and reduce oxygen vacancies in the semiconductor film 14. Therefore, the heat treatment may not be required.

[0140] The heat treatment temperature is 150° C. or higher and 300° C. or lower, preferably 200° C. or higher and 250° C. or lower. By setting the following, the diffusion of copper, aluminum, gold, silver, molybdenum, etc., and oxide semiconductors can be achieved. Contamination of the membrane can be suppressed.

[0141] Here, heat treatment is performed in a nitrogen and oxygen atmosphere at 220° C. for 1 hour.

[0142] In addition, when forming the pair of electrodes 21 and 22, the semiconductor film 1 is etched by etching the conductive film. 4 is damaged, and the back channel of the semiconductor film 14 (the gate electrode However, oxygen vacancies occur on the surface facing the electrode 12 and the surface opposite the electrode 12. By using an oxide insulating film containing more oxygen than the oxygen that satisfies the stoichiometric composition, The oxygen vacancies on the back channel side can be repaired by the heat treatment. As a result, defects in the semiconductor film 14 can be reduced, and the signal quality of the transistor 50 can be improved. The reliability can be improved.

[0143] Next, the nitride insulating film 25 is formed by sputtering, CVD or the like.

[0144] When the nitride insulating film 25 is formed by the plasma CVD method, The substrate placed in the evacuated processing chamber is heated to 300° C. or higher and 400° C. or lower, more preferably A temperature of 320° C. or higher and 370° C. or lower is preferable because a dense nitride insulating film can be formed. stomach.

[0145] When a silicon nitride film is formed as the nitride insulating film 25 by the plasma CVD method, the silicon It is preferable to use a deposition gas containing carbon, nitrogen, and ammonia as the source gas. By using a small amount of ammonia as a feed gas compared to nitrogen, the ammonia in the plasma The silicon-containing deposition gas dissociates and generates active species. This breaks the silicon-hydrogen bond and the nitrogen triple bond. Promoted bonding, fewer silicon and hydrogen bonds, fewer defects, and dense silicon nitride On the other hand, the amount of ammonia relative to nitrogen in the source gas is high. If the temperature is too low, the decomposition of the silicon-containing deposition gas and nitrogen will not proceed, and silicon and hydrogen bonds will form. As a result, defects are increased and a rough silicon nitride film is formed. For these reasons, the flow rate ratio of nitrogen to ammonia in the raw gas is preferably 5 to 50. It is preferable to set the value to 10 or more and 50 or less.

[0146] Here, silane at a flow rate of 50 sccm and 5000 The source gases were nitrogen at a flow rate of 100 sccm and ammonia at a flow rate of 100 sccm. The pressure in the processing chamber was The pressure was set at 100 Pa, the substrate temperature was set at 350°C, and a 27.12 MHz high frequency power source was used for 1000 A 50 nm thick nitride film was formed by plasma CVD using a 1000 MHz high frequency power supply to parallel plate electrodes. A silicon film is formed. The plasma CVD device has an electrode area of ​​6000 cm. 2 It is flat This is a horizontal and flat type plasma CVD device, and the supplied power is expressed as power per unit area (power density ) is converted to 1.7 × 10 -1 W / cm 2 It is.

[0147] Through the above steps, a film consisting of the oxide insulating film 23, the oxide insulating film 24, and the nitride insulating film 25 is formed. An insulating film 26 can be formed by the above process.

[0148] Next, a heat treatment may be performed. The temperature of the heat treatment is typically 150° C. or higher and 30 The temperature is 0° C. or lower, preferably 200° C. or higher and 250° C. or lower.

[0149] Through the above steps, the transistor 50 can be manufactured.

[0150] In this embodiment, the gate electrode 12 is provided between the substrate 11 and the semiconductor film 14. Although the explanation was given using a bottom-gate transistor, as shown in FIG. The film 26 functions as a gate insulating film, and a gate electrode 28 is formed on the insulating film 26. That is, a first protective layer is formed on the semiconductor film 14. A pair of electrodes 21 and 22 are formed of a film and a conductive film. The semiconductor film 14, the pair of electrodes 21 and 22, and the second protective film 20a and 20b are provided. An insulating film 26 that functions as a gate insulating film is provided on the films 20a and 20b. A transistor having a gate electrode 28 can be formed. As shown in FIG. 1, the gate electrode 12 is disposed between the substrate 11 and the semiconductor film 14, and the gate electrode 12 is disposed on the insulating film 26. The transistor 54 may have a dual gate structure having a gate electrode 28.

[0151] In this embodiment, in a transistor, a pair of electrodes is formed by a first protective film and a conductive film. A second protective layer having a side surface on the conductive film and located outside the conductive film. The upper surface of the conductive film is covered with a second protective film, and the side surface of the second protective film is Since the conductive film is located outside the conductive film, plasma, for example oxygen plasma, is applied to the conductive film. As a result, the area exposed to the plasma is reduced. Since the generation of compounds is reduced, the metal elements that make up the conductive film are less likely to migrate to the semiconductor film. become.

[0152] In addition, when the conductive film constituting the pair of electrodes is processed, the semiconductor film is By being covered with the film that serves as the first protective film, the metal elements that make up the conductive film serve as the first protective film. The electrons are blocked by the film, making it difficult for them to move into the semiconductor film.

[0153] As a result, the components of the wiring and electrodes, copper, aluminum, gold, silver, molybdenum, The diffusion of impurities such as fluorine into the semiconductor film can be suppressed. The concentration of can be reduced.

[0154] As a result, a semiconductor device having improved electrical characteristics can be obtained. A semiconductor device can be obtained.

[0155] (Embodiment 2) In this embodiment, a method for forming a pair of electrodes different from that in the first embodiment is described with reference to FIG. This will be explained with reference to FIG.

[0156] As in the first embodiment, after the process of FIG. 2, a gate electrode is formed on a substrate 11 as shown in FIG. 2(D). A gate electrode 12, a gate insulating film 13, a semiconductor film 14, a film 17a serving as a first protective film, and a conductive film 17b, masks 19a and 19b, and a pair of second protective films 20a and 20b are formed.

[0157] Next, as shown in FIG. 4(A), a part of the conductive film 17b is removed using masks 19a and 19b. The conductive film 21a is etched to form a pair of conductive films 21a and 22a. Similarly, the film 17a to be the first protective film is not etched, and the conductive film 17b is selectively etched. As a result, the semiconductor film 14 is not exposed in the etching process. Therefore, when the conductive film 17b is etched, the metal elements constituting the conductive film 17b are etched into the semiconductor film. 14. Also, the conductive film 17b is etched by using a wet etching method. In this way, the conductive film 17b is isotropically etched, and the second protective films 20a and 20b are The conductive films 21a and 22a can be formed so that their side surfaces are located inside the surface.

[0158] Next, in order to remove copper remaining on the film 17a which will become the first protective film, As a result, as shown in FIG. In this etching process, the conductive films 21a and 2 The conditions under which the first protective film 17a can be selectively etched without etching the second protective film 2a are set. As such conditions, the etchant may be hydrofluoric acid, hydrochloric acid, phosphoric acid, etc. In addition, SF can be used as an etching gas. 6、 Fluorides such as CF4, C l2, chlorides such as BCl3, or mixtures of fluorides and chlorides such as SF6 and BCl3 The film 17c serving as the first protective film can be used as a protective film for the semiconductor film 14. In order to function as a first protective film, a film 17c is formed so as to cover the semiconductor film 14. Therefore, in the etching process, the film 17a which is to be the first protective film is preferably It is sufficient to etch a few nm, typically 1 nm to 5 nm.

[0159] Next, as shown in FIG. 4(C), the masks 19a and 19b are removed. After the masks 19a and 19b are removed by a cleaning process to make them easier to remove, a remover is used to remove the masks 19a and 19b. a, 19b are removed.

[0160] In the process of removing the masks 19a and 19b, the semiconductor film 14 is treated as a first protective film. Since the conductive film 21a and the conductive film 22a are covered with the film 17c and are not exposed, The metal element does not migrate to the semiconductor film 14 .

[0161] Before forming the film 17c which will become the first protective film, the masks 19a and 19b are removed. In this case, the second protective films 20a and 20b are used as a mask to form a film to be the first protective film. Etch 17a.

[0162] Next, as shown in FIG. 4(D), second protective films 20a and 20b are used to cover the first protective film and the The film 17c is partially etched to form a pair of first protective films 21b and 22b.

[0163] Here, the first protective layer is formed by dry etching using chlorine as an etching gas. The film 17c to be formed is etched.

[0164] The side surfaces of the second protective films 20a and 20b are located outside the side surfaces of the conductive films 21a and 22a. That is, the upper surfaces of the conductive films 21a and 22a are covered with the second protective films 20a and 20b, and The second protective films 20a and 20b protrude outward from the conductive films 21a and 22a. Therefore, when a part of the film 17c that becomes the first protective film is etched, the conductive films 21a and 22a are As a result, even if the semiconductor film 14 is exposed, the semiconductor Therefore, the migration of metal elements constituting the conductive films 21a and 22a to the body film 14 can be reduced.

[0165] As a result, the impurity concentration in the semiconductor film 14 can be reduced.

[0166] Next, as in the first embodiment, as shown in FIG. 3(D), the semiconductor film 14 and the pair of electrodes 21 , 22 and the pair of second protective films 20a, 20b, an insulating film 26 is formed on the first protective film 20a, 20b.

[0167] Through the above steps, a transistor can be manufactured.

[0168] In this embodiment, in the transistor, a pair of electrodes includes at least a first protective film and and a conductive film, and a second protective layer is provided on the conductive film and has a side surface located outside the conductive film. The upper surface of the conductive film is covered with a second protective film, and the side surface of the second protective film is Since the conductive film is located outside the conductive film, plasma, for example oxygen plasma, is applied to the conductive film. As a result, the area exposed to the plasma is reduced. Since the generation of compounds is reduced, the metal elements that make up the conductive film are less likely to migrate to the semiconductor film. become.

[0169] In addition, in the film that becomes the first protective film and the conductive film that constitute the pair of electrodes, the conductive film is processed. When the semiconductor film is formed, the first protective film is formed on the semiconductor film, so that the gold constituting the conductive film is not easily damaged. The metal elements are blocked by the film that serves as the first protective film, making it difficult for them to migrate into the semiconductor film.

[0170] As a result, the components of the wiring and electrodes, copper, aluminum, gold, silver, molybdenum, The diffusion of impurities such as fluorine into the semiconductor film can be suppressed. The concentration of can be reduced.

[0171] As a result, a semiconductor device having improved electrical characteristics can be obtained. A semiconductor device can be obtained.

[0172] (Embodiment 3) In this embodiment, when an oxide semiconductor film is used as the semiconductor film, FIG. 1 shows a semiconductor device having a transistor capable of further reducing the amount of defects in the semiconductor film. The transistor described in this embodiment has the following features in comparison with the first embodiment: The present invention is characterized in that the multilayer film includes an oxide semiconductor film and an oxide film in contact with the oxide semiconductor film. different.

[0173] FIG. 5A shows a top view and a cross-sectional view of a transistor 60 included in the semiconductor device. 5(B) is a cross-sectional view of the transistor 60 taken along dashed line AB in FIG. 5(A). 5(C) is a cross-sectional view taken along dashed line CD in FIG. 5(A). In (A), for clarity, the substrate 11 and some of the components of the transistor 60 (e.g., the gate The gate insulating film 13, the oxide insulating film 23, the oxide insulating film 24, the nitride insulating film 25, etc. are omitted. is doing.

[0174] The transistor 60 shown in FIG. 5A to FIG. 5C is a gate insulating film 13. The multilayer film 16 overlaps the base electrode 12, and a pair of electrodes 21 and 22 contact the multilayer film 16. In addition, an oxide insulating film is formed on the gate insulating film 13, the multilayer film 16, and the pair of electrodes 21 and 22. An insulating film 26 consisting of an insulating film 23, an oxide insulating film 24, and a nitride insulating film 25 is formed. do.

[0175] The gate electrode 12 is formed by stacking a protective film 12a and a conductive film 12b. In the electrodes 21 and 22, the electrode 21 has a first protective film 21b in contact with the multilayer film 16 and a conductive film The electrode 22 has at least a first protective film 22b in contact with the multilayer film 16 and a conductive The conductive film 21a has at least a second protective film 22a. 20a and 20b are formed.

[0176] In the transistor 60 shown in this embodiment, the multilayer film 16 is a semiconductor film 14 and an oxide film 15. In other words, the multilayer film 16 has a two-layer structure. The multilayer film 16 functions as a channel region. An oxide insulating film 23 is formed in contact with the multilayer film 16. The oxide insulating film 24 is formed so as to be in contact with the oxide insulating film 23. That is, An oxide film 15 is provided between the semiconductor film 14 and the oxide insulating film 23 .

[0177] When an oxide semiconductor is used as the semiconductor film 14, the oxide film 15 constitutes an oxide semiconductor. The oxide film 15 is an oxide film composed of one or more elements having the same structure as the semiconductor film 1. Since the oxide film 15 is made of one or more of the elements constituting the semiconductor film 14, Therefore, the movement of carriers is not hindered at the interface. This increases the field effect mobility of the transistor.

[0178] The oxide film 15 is typically made of In-Ga oxide, In-Zn oxide, In-M-Zn oxide (M is Ti, Ga, Y, Zr, La, Ce, Nd or Hf) and The energy of the lower end of the conduction band is closer to the vacuum level than that of the oxide film 14. The difference between the energy of the bottom of the conduction band of the semiconductor film 14 and the energy of the bottom of the conduction band of the semiconductor film 14 is 0 0.05 eV or more, 0.07 eV or more, 0.1 eV or more, or 0.15 eV or more and 2 eV or less, 1 eV or less, 0.5 eV or less, or 0.4 eV or less. That is, the oxide film The difference between the electron affinity of the semiconductor film 14 and the electron affinity of the semiconductor film 15 is 0.05 eV or more and 0.07 eV or more, 0.1 eV or more, or 0.15 eV or more and 2 eV or less, 1 eV or less, 0 .5 eV or less, or 0.4 eV or less.

[0179] The oxide film 15 is preferably made of In, since the carrier mobility (electron mobility) is increased by the In content. I wish.

[0180] As the oxide film 15, Ti, Ga, Y, Zr, La, Ce, Nd or Hf is added to the oxide film 15 more than In. A high atomic ratio may have the following effects: (1) The oxide film 15 has a high atomic ratio. (2) To increase the energy gap. (3) To decrease the electron affinity of the oxide film 15. (4) It has higher insulating properties than the semiconductor film 14. (5) ) Ti, Ga, Y, Zr, La, Ce, Nd and Hf are metal elements that have strong bonding strength with oxygen. Therefore, Ti, Ga, Y, Zr, La, Ce, Nd or Hf has a higher atomic number than In. By having this ratio, oxygen deficiency is less likely to occur.

[0181] The oxide film 15 is an In-M-Zn oxide film (wherein M is Ti, Ga, Y, Zr, La, Ce, In the case of Nd or Hf, sputtering is used to deposit In-M-Zn oxide. The atomic ratio of the metal elements in the target preferably satisfies M>In and Zn>M. The atomic ratio of metal elements in such a sputtering target is In:Ga:Zn=1: 3:4, In:Ga:Zn=1:3:5, In:Ga:Zn=1:3:6, In:Ga: Zn=1:3:7, In:Ga:Zn=1:3:8, In:Ga:Zn=1:3:9, I n:Ga:Zn=1:3:10, In:Ga:Zn=1:6:7, In:Ga:Zn=1 :6:8, In:Ga:Zn=1:6:9, In:Ga:Zn=1:6:10 are preferred .

[0182] When the oxide film 15 is an In-M-Zn oxide film, the sum of In and M is 100 atom. When expressed as mic%, the atomic ratio of In and M is preferably 50 atomic % In. less than 50 atomic %, M is 50 atomic % or more, and more preferably In is less than 25 atomic %. , M is 75 atomic% or more.

[0183] The semiconductor film 14 and the oxide film 15 are In-M-Zn oxide films (M is Ti, Ga , Y, Zr, La, Ce, Nd or Hf), the oxide film is Atomic ratio of M (Ti, Ga, Y, Zr, La, Ce, Nd, or Hf) contained in 15 is large, typically 1.5 times or more larger than the above atoms contained in the semiconductor film 14. The atomic ratio is preferably at least two times, and more preferably at least three times higher.

[0184] The semiconductor film 14 and the oxide film 15 are In-M-Zn oxide films (M is Ti, Ga , Y, Zr, La, Ce, Nd or Hf), the oxide film 15 is In:M:Zn=x 1:y1:z1 [atomic ratio], and the semiconductor film 14 is In:M:Zn=x2:y2:z2 [atomic ratio]. If the ratio is y1 / x1, then y1 / x1 is greater than y2 / x2, and preferably y1 / x1 is greater than y2 More preferably, y1 / x1 is 2 times greater than y2 / x2. More preferably, y1 / x1 is greater than y2 / x2 by a factor of three or more. In the semiconductor film 14, when y2 is equal to or larger than x2, a transistor using the semiconductor film 14 can be manufactured. This is preferable because it can give stable electrical characteristics to the transistor. However, y2 must be at least three times larger than x2. In this case, the field effect mobility of a transistor using the semiconductor film 14 is reduced. , y2 is preferably less than three times x2.

[0185] The semiconductor film 14 may be formed by the same process as that of the semiconductor film shown in the first embodiment. can be done.

[0186] The oxide film 15 has an atomic ratio of In:M:Zn=1:3:(3.05 or more, 10 or a sputtering target with an atomic ratio of In:M:Zn=1:6:( A sputtering target having a refractive index of 6.05 or more and 10 or less can be used. The M / In contained in the semiconductor film 14 formed using such a sputtering target The atomic ratio of Zn / In is smaller than that of the target. In the Ga-Zn oxide film, the atomic ratio of Zn to M (Zn / M) is 0.5 or more. do.

[0187] By using such a sputtering target, CAAC-O It is possible to form a film of In-Ga-Zn oxide, which is S.

[0188] The oxide film 15 is formed to prevent damage to the semiconductor film 14 when the oxide insulating film 24 is formed later. As a result, the amount of oxygen vacancies in the semiconductor film 14 is reduced. Furthermore, by forming the oxide film 15, the oxide film formed on the semiconductor film 14 can be The insulating film, for example, an oxide insulating film, is prevented from being mixed with the semiconductor film 14. can.

[0189] The thickness of the oxide film 15 is 3 nm or more and 100 nm or less, preferably 3 nm or more and 50 nm or less. Below.

[0190] Similarly to the semiconductor film 14, the oxide film 15 may be formed to have a single crystal structure or a non-single crystal structure. The non-single crystal structure can be, for example, CAAC-OS (C Axis Al igned Crystalline Oxide Semiconductor), This includes a crystalline structure, a microcrystalline structure (described below), or an amorphous structure.

[0191] The semiconductor film 14 and the oxide film 15 are respectively an amorphous structure region and a microcrystalline structure region. A mixture of two or more of the following: a polycrystalline region, a CAAC-OS region, and a single crystal region. The mixed film may be, for example, a region having an amorphous structure, a region having a microcrystalline structure, a region having a polycrystalline structure, or the like. The structure has two or more regions, either a region of CAAC-OS structure or a region of single crystal structure. In addition, the mixed film may have a single layer structure, for example, an amorphous structure region, a microcrystalline structure region, and Two or more of the following regions are included: a region of a polycrystalline structure, a region of a CAAC-OS structure, and a region of a single crystal structure In some cases, the semiconductor film 14 and the oxide film 15 are stacked in this order. Alternatively, the semiconductor film 14 may have a stacked structure of a crystal structure and a CAAC-OS structure. The oxide film 15 may be a laminated structure of CAAC-OS and CAAC-OS. .

[0192] When the semiconductor film 14 and the oxide film 15 are both CAAC-OS, It is preferable that the oxide film 15 has high crystallinity at the interface with the CA. In the case of AC-OS, the blocking of the conductive films 21a and 22a included in the pair of electrodes 21 and 22 Since the conductive film 21a and the conductive film 22a have a bonding effect, the metal elements constituting the conductive film 21a and the conductive film 22a migrate to the semiconductor film 14. It is possible to suppress the above.

[0193] In the multilayer film 16, the gate electrode 12 is overlapped and the pair of electrodes 21 and 22 are disposed between the gate electrode 12 and the pair of electrodes 21 and 22. The region between the two is called the channel formation region. The region where the gas mainly flows is called a channel region. The semiconductor film 14 is a channel region. His name is Nell-cho.

[0194] Here, the oxide film 15 is provided between the semiconductor film 14 and the oxide insulating film 23. Therefore, a transistor caused by impurities and defects occurs between the oxide film 15 and the oxide insulating film 23. Even if a trap level is formed, there is a gap between the trap level and the semiconductor film 14. As a result, electrons flowing through the semiconductor film 14 are less likely to be captured by the trap level, and the on-state of the transistor is improved. It is possible to increase the on-state current and improve the field effect mobility. Furthermore, when an electron is captured by a trap level, the electron becomes a negative fixed charge. As a result, the threshold voltage of the transistor varies. Since there is a gap between the ion and the trap level, the capture of electrons at the trap level is reduced. This makes it possible to reduce the variation in threshold voltage.

[0195] In addition, the oxide film 15 can block impurities from the outside. It is possible to reduce the amount of impurities that move to the semiconductor film 14. In addition, the oxide film 15 is Therefore, the impurity concentration and oxygen vacancies in the semiconductor film 14 are low. It is possible to reduce the amount.

[0196] The semiconductor film 14 and the oxide film 15 are not simply laminated but are continuously joined ( In this case, a structure is formed in which the energy at the bottom of the conduction band changes continuously between the layers. In other words, defect levels such as trap centers and recombination centers are created at the interfaces of each film. The laminated structure is one in which no impurities that would form a semiconductor film are present. If impurities are present between the oxide film 15 and the semiconductor layer 4, the continuity of the energy band is lost. At the interface, the carriers are trapped or recombine and disappear.

[0197] To form continuous junctions, a multi-chamber deposition system equipped with a load lock chamber is required. It is necessary to use a suitable device to laminate the films in succession without exposing them to the atmosphere.

[0198] The multilayer film 16 is formed between the gate insulating film 13 and the semiconductor film 14 in the same manner as the oxide film 15. Alternatively, an oxide film may be formed.

[0199] In the transistor described in this embodiment, an oxide insulating film 23 is formed between the semiconductor film 14 and the oxide insulating film 23. Since the semiconductor film 15 is provided, the concentration of silicon or carbon in the semiconductor film 14 or the concentration of the semiconductor The concentration of silicon and carbon in the vicinity of the interface between the conductor film 14 and the oxide film 15 can be reduced. can.

[0200] The transistor 60 having such a structure is a multilayer film 16 including a semiconductor film 14. Since there are very few defects, it is possible to improve the electrical characteristics of transistors. In terms of the efficiency, it is possible to increase the on-current and improve the field effect mobility. For example, the variation in threshold voltage in the BT stress test and the optical BT stress test is small. and highly reliable.

[0201] Note that the configurations and methods described in this embodiment may be applied to other embodiments and examples. The present invention can be used in appropriate combination with the above-mentioned configurations and methods.

[0202] (Embodiment 4) In this embodiment, a semiconductor device which is one embodiment of the present invention will be described with reference to drawings. Note that in this embodiment, a semiconductor device which is one embodiment of the present invention will be described using a display device as an example. In this embodiment, an oxide semiconductor film is used as the semiconductor film.

[0203] FIG. 6A shows an example of a semiconductor device. The semiconductor device shown in FIG. 1, a scanning line driving circuit 104, and a signal line driving circuit 106 are arranged in parallel or approximately in parallel. m scanning lines 107 are provided and the potentials of which are controlled by a scanning line driving circuit 104, The individual electrodes are arranged in parallel or approximately in parallel, and the potential is controlled by a signal line driver circuit 106. The pixel section 101 has n signal lines 109. The pixel array 301 includes a number of pixels 301. The pixels 301 are arranged parallel or approximately parallel to each other along the scanning line 107. The capacitance lines 115 are arranged along the signal lines 109. The scanning line driving circuit 104 and the signal line driving circuit 105 may be arranged in a row or substantially in parallel. The circuit 106 may be collectively referred to as a drive circuit section.

[0204] Each scanning line 107 corresponds to one of the pixels 301 arranged in m rows and n columns in the pixel section 101. The signal lines 109 are electrically connected to the n pixels 301 arranged in any one row. is m pixels 301 arranged in m rows and n columns, and m pixels 301 arranged in any one of the columns. 1. m and n are both integers of 1 or more. is n pixels 301 arranged in any one of the rows among the pixels 301 arranged in m rows and n columns. 1. Capacitor lines 115 are arranged parallel to each other along the signal line 109. In the case where the pixels 301 are arranged in m rows and n columns, any one of the pixels 301 may be arranged in a matrix of m rows and n columns. The pixel array 301 is electrically connected to m pixels 301 arranged in a column.

[0205] 6B and 6C show a pixel 301 of the display device shown in FIG. The figure shows a circuit configuration that can be used.

[0206] The pixel 301 shown in FIG. 6B includes a liquid crystal element 132, a transistor 131_1, and a capacitor. The element 133_1 and the element 133_2 are also included.

[0207] The potential of one of the pair of electrodes of the liquid crystal element 132 is appropriately set according to the specifications of the pixel 301. The alignment state of the liquid crystal element 132 is set by the written data. A common potential (common potential) is applied to one of a pair of electrodes of the liquid crystal element 132 in each pixel 301. In addition, one of the pair of electrodes of the liquid crystal element 132 for each row of pixels 301 may be applied. may be given different potentials.

[0208] For example, the display device including the liquid crystal element 132 can be driven in a TN mode, an STN mode, or the like. Mode, VA mode, ASM (Axially Symmetric Aligned M icro-cell mode, OCB (Optically Compensated Birefringence mode, FLC (Ferroelectric Liquid id Crystal) mode, AFLC (AntiFerroelectric Li quid Crystal) mode, MVA mode, PVA (Patterned Ve Vertical Alignment) mode, IPS mode, FFS mode, or TB A (Transverse Bend Alignment) mode may be used. In addition to the above-mentioned driving method, the display device can be driven by ECB (Electro cally Controlled Birefringence) mode, PDLC( Polymer Dispersed Liquid Crystal) mode, PNL C (Polymer Network Liquid Crystal) mode, guest However, the liquid crystal element and its driving method are not limited to these. A variety of different ones can be used.

[0209] Also, a liquid crystal composition containing a liquid crystal exhibiting a blue phase and a chiral agent. The liquid crystal element may be configured by the liquid crystal that exhibits the blue phase. Since it is short and optically isotropic, alignment treatment is not required and viewing angle dependency is small.

[0210] In the pixel 301 in the mth row and the nth column, One of the electrodes is electrically connected to the signal line DL_n, and the other is a pair of electrodes of the liquid crystal element 132. The gate electrode of the transistor 131_1 is electrically connected to the other of the scan lines G L_m. The transistor 131_1 is in an on state or an off state. By this, the write control circuit 100 has a function of controlling the writing of data of the data signal.

[0211] One of a pair of electrodes of the capacitor 133_1 is connected to a wiring to which a potential is supplied (hereinafter, a capacitor line CL ) and the other is electrically connected to the other of the pair of electrodes of the liquid crystal element 132. The value of the potential of the capacitance line CL is appropriately set according to the specifications of the pixel 301. The child 133_1 has a function as a storage capacity for storing written data.

[0212] For example, in a display device having the pixel 301 shown in FIG. 6B, the scanning line driver circuit 104 The pixels 301 in each row are selected in sequence, and the transistors 131_1 are turned on to output data signals. Write data.

[0213] The pixel 301 to which the data has been written is turned off by turning off the transistor 131_1. By repeating this process row by row, an image can be displayed.

[0214] In addition, the pixel 301 shown in FIG. 6C includes a transistor 131_2 and a capacitor 133_ 2, a transistor 134, and a light-emitting element 135.

[0215] One of the source electrode and the drain electrode of the transistor 131_2 is supplied with a data signal. Further, the transistor The gate electrode of 131_2 is a wiring to which a gate signal is applied (hereinafter, referred to as a scanning line GL_m). ) is electrically connected to

[0216] The transistor 131_2 is turned on or off to output the data signal. It has a function to control writing of data.

[0217] One of a pair of electrodes of the capacitor 133_2 is connected to a wiring to which a potential is applied (hereinafter, a potential supply line VL_a), and the other is electrically connected to the source electrode of the transistor 131_2 and The gate electrode is electrically connected to the other of the drain electrodes.

[0218] The capacitor 133_2 has a function as a storage capacitor for storing written data. .

[0219] One of the source electrode and the drain electrode of the transistor 134 is connected to the potential supply line VL_a. Furthermore, the gate electrode of the transistor 134 is electrically connected to the gate of the transistor 131_ The second source electrode and the second drain electrode are electrically connected to each other.

[0220] One of the anode and the cathode of the light-emitting element 135 is electrically connected to the potential supply line VL_b. The other of the two is electrically connected to the other of the source electrode and drain electrode of the transistor 134. will be done.

[0221] The light-emitting element 135 may be, for example, an organic electroluminescence element (also called an organic EL element). However, the light emitting element 135 is not limited to this. Alternatively, an inorganic EL element made of an inorganic material may be used.

[0222] A high power supply potential VDD is applied to one of the potential supply lines VL_a and VL_b. and the other is supplied with a low power supply potential VSS.

[0223] In a display device having the pixel 301 shown in FIG. 6C, the image of each row is generated by the scanning line driving circuit 104. The elements 301 are sequentially selected, the transistor 131_2 is turned on, and the data of the data signal is Write.

[0224] The pixel 301 to which the data has been written is turned off by turning off the transistor 131_2. Furthermore, the state of the transistor 134 is changed according to the potential of the written data signal. The amount of current flowing between the source electrode and the drain electrode is controlled, and the light emitting element 135 The light is emitted with a brightness that corresponds to the flow rate. By performing this process row by row, an image can be displayed.

[0225] Next, a specific example of a liquid crystal display device using liquid crystal elements in the pixels 301 will be described. Here, a top view of the pixel 301 shown in FIG. 6(B) is shown in FIG. 7. The counter electrode, the liquid crystal element, and the first protective films 314d and 314e are omitted.

[0226] In FIG. 7, the conductive film 304c functioning as the scanning line is oriented in a direction substantially perpendicular to the signal line ( The conductive film 313d, which functions as a signal line, is provided so as to extend in the center (left and right direction). The capacitor extends in a direction substantially perpendicular to the line (vertical direction in the figure). The conductive film 313f is provided so as to extend in a direction parallel to the signal lines. The conductive film 304c is electrically connected to the scanning line driver circuit 104 (see FIG. 6A). The conductive film 313d functions as a signal line, and the conductive film 31 3f is electrically connected to the signal line driver circuit 106 (see FIG. 6(A)).

[0227] The transistor 103 is provided in a region where the scanning line and the signal line intersect. The gate electrode 304c functions as a conductive film, and the gate insulating film 304b functions as a gate electrode. A semiconductor film 308b in which a channel region is formed on the gate insulating film, The conductive films 313d and 313e function as a source electrode and a drain electrode. The conductive film 304c also functions as a scan line, and a region overlapping with the semiconductor film 308b is a transistor. The conductive film 313d functions as a gate electrode of the transistor 103. The conductive film 313d also functions as a signal line. The region overlapping with the semiconductor film 308b is the source electrode or drain electrode of the transistor 103. In FIG. 7, the scanning lines function as semiconductor electrodes. Therefore, the scanning line is not incident from a light source such as a backlight. As a result, the semiconductor film 308 included in the transistor functions as a light shielding film that blocks light from the Since the region b is not irradiated with light, fluctuations in the electrical characteristics of the transistor can be suppressed.

[0228] In addition, the conductive film 313e has a light-transmitting property that functions as a pixel electrode in the opening 362c. The conductive film 320b is electrically connected to the conductive film 320b.

[0229] The capacitor 105 is connected to a conductive film 313f that functions as a capacitor line in an opening 362. The capacitance element 105 is formed by a conductive film 3 formed on the gate insulating film. 08c, a dielectric film formed of a nitride insulating film provided on the transistor 103, and The gate insulating film is made of a conductive film 320b having a light-transmitting property and functions as a base electrode. The conductive film 308c formed thereon has a light-transmitting property. It has photochemical properties.

[0230] In this way, since the capacitor 105 has a light-transmitting property, the capacitor 105 is large and can be placed in the pixel 301. Therefore, it is possible to form the aperture ratio in a large area, preferably 50% or more. or 55% or more, preferably 60% or more, and the charge capacity can be increased. For example, a semiconductor device with high resolution, such as a liquid crystal display, can be obtained. In a display device, the area of ​​a pixel is reduced, and the area of ​​a capacitance element is also reduced. In a semiconductor device with high resolution, the charge capacity stored in the capacitive element is small. However, since the capacitor 105 shown in this embodiment has a light-transmitting property, the capacitor By providing the element, it is possible to obtain a sufficient charge capacity in each pixel while increasing the aperture ratio. Typically, high resolution displays have a pixel density of 200 ppi or more, or even 300 ppi or more. The present invention can be suitably used for semiconductor devices having a large number of semiconductor devices.

[0231] In addition, the pixel 301 shown in FIG. 7 has a side that is parallel to the conductive film 313d that functions as a signal line. In comparison, the side parallel to the conductive film 304c functioning as the scanning line is longer than the side The conductive film 313f functioning as a line is parallel to the conductive film 313d functioning as a signal line. As a result, the area of ​​the conductive film 313f in the pixel 301 is reduced. This allows the aperture ratio to be increased. Since the conductive film 313f is in direct contact with the conductive film 308c without using a connection electrode, This can greatly increase the aperture ratio.

[0232] In addition, according to one embodiment of the present invention, the aperture ratio can be increased even in a high-resolution display device. This allows the light from light sources such as backlights to be used efficiently, and reduces the power consumption of the display device. The force can be reduced.

[0233] Next, a cross-sectional view taken along dashed line CD in FIG. 7 is shown in FIG. 8. In FIG. 8, A driver circuit portion (a top view is omitted) including a scanning line driver circuit 104 and a signal line driver circuit 106. ) is shown in a cross-sectional view of FIG. AB. In this embodiment, a vertical electric field type liquid crystal display device is He explains.

[0234] The liquid crystal display device shown in this embodiment has a liquid crystal display device between a pair of substrates (a substrate 302 and a substrate 342). The element 322 is sandwiched.

[0235] The liquid crystal element 322 is connected to a light-transmitting conductive film 320b above the substrate 302 to control the alignment. A liquid crystal layer 321 and a conductive film 350 are formed on the liquid crystal layer 321. Note that the light-transmitting conductive film 320b is used as one electrode of the liquid crystal element 322. The conductive film 350 functions as the other electrode of the liquid crystal element 322 .

[0236] Thus, a liquid crystal display device is a device that has liquid crystal elements. The liquid crystal display device includes a driving circuit for driving a plurality of pixels. A control circuit, a power supply circuit, a signal generating circuit, a backlight module, etc., are arranged in It is also called a liquid crystal module.

[0237] In the driver circuit portion, a conductive film 304a functions as a gate electrode, and a gate insulating film A functional insulating film 305 and an insulating film 306, a semiconductor film 308a in which a channel region is formed, The conductive films 313a and 313b functioning as a source electrode and a drain electrode, and the first protective film The transistor 102 is formed by the semiconductor film 308a and the semiconductor film 308b. The insulating film is provided on the conductive film 313a. The second protective film 312a is provided on the conductive film 313b. The second protective films 312a and 312b are formed of a conductive film having a light-transmitting property. When the second protective films 312a and 312b are formed, they function as a source electrode and a drain electrode. Also constitutes the transistor 102.

[0238] In the pixel portion, a conductive film 304c functions as a gate electrode, and a gate insulating film The insulating film 305 and the insulating film 306 are formed on the gate insulating film. a semiconductor film 308b serving as a source electrode and a drain electrode; The transistor 103 is composed of the first protective film 314d and the first protective film 314e. The conductive film 308b is provided on the gate insulating film. The second protective films 312d and 312g are provided on the first protective films 312d and 312g. The second protective film 312d and the insulating film 318 are provided as protective films. When the second protective film 312g is formed of a conductive film having light-transmitting properties, the second protective film 312d and the second protective film 312g are The transistor 103 functions as a source electrode and a drain electrode.

[0239] In addition, the conductive film 320b having a light-transmitting property and functioning as a pixel electrode is formed on the second protective film 312. g, the insulating film 316 and the insulating film 318 are connected to the conductive film 313e in the openings formed therein. To be continued.

[0240] Also, a conductive film 308c functioning as one electrode and a dielectric film The insulating film 318 and the light-transmitting conductive film 320b functioning as the other electrode form a capacitor. 105. The conductive film 308c is provided on the gate insulating film.

[0241] In the driving circuit section, the conductive film 304a and the conductive film 304c are formed at the same time. 4b and the conductive film 314 formed simultaneously with the conductive films 313a, 313b, 313d, and 313e. The light-transmitting conductive film 323c is formed at the same time as the light-transmitting conductive film 320b. Connected with 0a.

[0242] The conductive film 304b and the light-transmitting conductive film 320a are formed by insulating films 305, 306, The connection is made through an opening provided in the insulating film 316 and the insulating film 318. The light-transmitting conductive film 320a is a second protective film 312f, an insulating film 316, and The connection is made through an opening provided in the insulating film 318 .

[0243] Here, the components of the display device shown in FIG. 8 will be described below.

[0244] Conductive films 304a, 304b, and 304c are formed on the substrate 302. The conductive film 04a functions as a gate electrode of a transistor in the driver circuit portion. 304c is formed in the pixel portion 101 and functions as a gate electrode of a transistor in the pixel portion. The conductive film 304b is formed in the scanning line driver circuit 104 and is connected to the conductive film 313c. do.

[0245] For the substrate 302, the material of the substrate 11 shown in Embodiment 1 can be used as appropriate.

[0246] The conductive films 304a, 304b, and 304c may be the same as those of the gate electrode 12 shown in the first embodiment. Materials and manufacturing methods can be used as appropriate.

[0247] An insulating film 305, an insulating film 306, and an insulating film 307 are formed on the substrate 302 and the conductive films 304a, 304c, and 304b. The insulating film 305 and the insulating film 306 are formed on the transistor of the driving circuit section. The insulating film functions as a gate insulating film and a gate insulating film of a transistor in the pixel portion 101 .

[0248] The insulating film 305 may be the nitride insulating film described in the gate insulating film 13 of the first embodiment. The insulating film 306 is preferably formed using the gate insulating film shown in Embodiment 1. It is preferable to form the insulating film by using the oxide insulating film described above with respect to the insulating film 13 .

[0249] On the insulating film 306, semiconductor films 308a and 308b and a conductive film 308c are formed. The semiconductor film 308a is formed in a position overlapping with the conductive film 304a. The semiconductor film 308b functions as a channel region of the transistor in the conductive film 3 It is formed in a position overlapping with 04c and functions as a channel region of the transistor in the pixel area. The conductive film 308c functions as one electrode of the capacitor 105.

[0250] The semiconductor films 308a and 308b and the conductive film 308c are the same as those shown in Embodiment 1. The material and manufacturing method of the semiconductor film 14 can be appropriately used.

[0251] The conductive film 308c contains the same metal element as the semiconductor films 308a and 308b. The film is characterized by containing impurities, such as hydrogen. In addition, boron, phosphorus, tin, antimony, rare gas elements, and aluminium are used as impurities instead of hydrogen. It may contain alkali metals, alkaline earth metals, etc.

[0252] The semiconductor films 308a and 308b and the conductive film 308c are formed on the gate insulating film. Specifically, the semiconductor films 308a and 308b are formed in a different impurity concentration. In addition, the conductive film 308c has a high impurity concentration. The hydrogen concentration in 8b is 5×10 19 atoms / cm 3 Less than or equal to 5×10 18 atoms / cm 3 Less than or equal to 1×10 18 atoms / cm 3 The following is better Preferably 5 x 10 17 atoms / cm 3 Less than 1×10, more preferably 16 atom s / cm 3 The hydrogen concentration in the conductive film 308c is 8×10 19 atoms / cm 3 More than 1×10 20 atoms / cm 3 More than this, more preferable 5×10 20 atoms / cm 3 The above is the case. In addition, the semiconductor films 308a and 308b In comparison, the hydrogen concentration in the conductive film 308c is twice as high, preferably 10 times higher. It is.

[0253] In addition, the conductive film 308c has a lower resistivity than the semiconductor films 308a and 308b. The resistivity of the conductive film 308c is 1×10 -8 more than 1x10 -1 times or less, typically 1×10 -3 Less than Ωcm top 1×10 4 Ωcm, and more preferably a resistivity of 1×10 -3 Ωcm or more 1×10 -1 It is preferable that the resistivity is less than Ωcm.

[0254] The semiconductor films 308a and 308b are formed at the interfaces with the insulating films 306 and 316. Since the semiconductor film 308 is in contact with a film made of a material capable of improving the surface characteristics, a and 308b function as semiconductors, and a transistor having the semiconductor films 308a and 308b is formed. The capacitor has excellent electrical properties.

[0255] On the other hand, the conductive film 308c is insulated in the opening 362 (see FIG. 11(A)). The insulating film 318 is in contact with the insulating film 318. The insulating film 318 is resistant to impurities from the outside, such as water, alkali metals, The film is made of a material that prevents alkaline earth metals and the like from diffusing into the semiconductor film, and further Therefore, the hydrogen of the insulating film 318 is formed simultaneously with the semiconductor films 308a and 308b. When hydrogen diffuses into the semiconductor film, it combines with oxygen in the semiconductor film and becomes a carrier. Electrons are generated. Also, the insulating film 318 is formed by the plasma CVD method or the sputtering method. When the semiconductor film 308d is formed, the semiconductor film 308d is exposed to plasma, and oxygen vacancies are generated. When hydrogen contained in the insulating film 318 enters the gap, electrons, which act as carriers, are generated. As a result, the semiconductor film becomes highly conductive, becoming a conductive film 308c. The film 308c having a high conductivity can be said to be an oxide semiconductor film having a high conductivity. The film 308c can be considered to be a highly conductive metal oxide film.

[0256] However, one aspect of the embodiment of the present invention is not limited to this, and the conductive film 308c In some cases, it is possible that the insulating film 318 is not in contact with the insulating film 318 .

[0257] In addition, one aspect of the embodiment of the present invention is not limited to this, and the conductive film 308c is In some cases, the semiconductor film 308a or 308b may be formed in a separate process. In that case, the conductive film 308c is different from the semiconductor films 308a and 308b. For example, the conductive film 308c may be made of indium tin oxide. , indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide Indium oxide with titanium oxide, indium tin oxide with titanium oxide, indium Indium tin oxide, indium zinc oxide, indium tin oxide containing silicon oxide, etc. It may be formed by

[0258] The semiconductor device described in this embodiment includes a semiconductor film of a transistor and a capacitor. In addition, a light-transmitting conductive film that functions as a pixel electrode is formed. For this reason, a conductive film is newly formed in order to form a capacitor element. Since the step of forming a transparent electrode is not required, the manufacturing steps of the semiconductor device can be reduced. Since the capacitor element has optical properties, the capacitor element has optical transparency. As a result, the area occupied by the capacitor element is increased. While maintaining the brightness, the aperture ratio of the pixel can be increased.

[0259] The second protective films 312a, 312b, 312d, 312f, and 312g are the same as those in the first embodiment. The materials and manufacturing methods for the second protective films 20a and 20b shown below can be used appropriately.

[0260] The conductive films 313a, 313b, 313c, 313d, and 313e are the same as those shown in the first embodiment. The conductive films 21a and 22a constituting the pair of electrodes 21 and 22 are made of an appropriate material and are produced by an appropriate method. This can be done.

[0261] The first protective films 314a, 314b, 314c, 314d, and 314e are the same as those in the first embodiment. The materials and manufacturing methods for the first protective films 21b and 22b shown below can be used appropriately.

[0262] An insulating film 306, semiconductor films 308a and 308b, a conductive film 308c, a second protective film Films 312a, 312b, 312d, 312f, 312g, conductive films 313a, 313b, 3 13c, 313d, 313e, and the first protective films 314a, 314b, 314c, 314 An insulating film 316 and an insulating film 318 are formed on the layers 314d and 314e. The insulating film 316 is As with the insulating film 306, the interface characteristics with the semiconductor films 308a and 308b can be improved. It is preferable to use a material capable of forming the insulating film having at least the same properties as the oxide insulating film 24 in Embodiment 1. As shown in the embodiment 1, the same material and manufacturing method can be used as appropriate. Alternatively, the nitride insulating film 23 and the oxide insulating film 24 may be laminated.

[0263] The insulating film 318, like the insulating film 305, is resistant to external impurities such as water and alkaline metals. It is preferable to use a material that prevents metals, alkaline earth metals, etc. from diffusing into the semiconductor film. Silicon nitride, silicon oxynitride, aluminum nitride, aluminum oxynitride, and other nitrided insulating materials The thickness of the insulating film 318 is 30 nm or more and 200 nm or less. The insulating film 318 is preferably formed by sputtering, C The film can be formed by appropriately using a VD method or the like.

[0264] In addition, conductive films 320a and 320b having light-transmitting properties are formed on the insulating film 318. The light-transmitting conductive film 320a is conductive in the opening 364a (see FIG. 12A). The conductive film 304b is electrically connected to the conductive film 304b, and the conductive film 304b is electrically connected to the conductive film 304b at the opening 364b (see FIG. 12(A)). That is, the conductive film 304b and the conductive film 313c are electrically connected to each other. The conductive film 320b having light-transmitting properties functions as a connection electrode. 3A). In FIG. 3A, the conductive film 313e is electrically connected to the conductive film 313e, and functions as a pixel electrode of the pixel. The light-transmitting conductive film 320b is used as one of a pair of electrodes of a capacitor. It can function.

[0265] In order to form a connection structure in which the conductive film 304b and the conductive film 313c are in direct contact with each other, the conductive film 3 Before forming 13c, a patterning process is performed to form openings in the insulating film 305 and the insulating film 306. It is necessary to perform photolithography and form a mask, but the connection structure of FIG. However, as shown in FIG. 8, the conductive film 320a having light transmitting property is used to make the conductive The conductive film 304b and the conductive film 313c are connected to each other. There is no need to create a direct connection, and one photomask can be reduced. That is, the number of manufacturing steps of the semiconductor device can be reduced.

[0266] The light-transmitting conductive films 320a and 320b are made of indium oxide containing tungsten oxide. Indium Zinc Oxide with Tungsten Oxide, Indium Zinc Oxide with Titanium Oxide Oxide, indium tin oxide with titanium oxide, ITO, indium zinc oxide, silicon oxide A conductive material having optical transparency, such as indium tin oxide containing silicon, can be used. .

[0267] In addition, a film having color (hereinafter, referred to as a color film 346) is formed on the substrate 342. The colored film 346 functions as a color filter. A light-shielding film 344 is formed on the substrate 342 and is adjacent to the light-shielding film 344. The colored film 346 does not necessarily have to be provided. For example, In some cases, such as when the device is black and white, the color film 346 may not be provided.

[0268] The colored film 346 may be any colored film that transmits light in a specific wavelength range. For example, A red (R) color filter that transmits light in the red wavelength range, and a green (G) color filter that transmits light in the green wavelength range. A green (G) color filter transmits light in the blue wavelength range, and a blue (B) color filter transmits light in the blue wavelength range. A filter or the like can be used.

[0269] The light-shielding film 344 may be made of a metal or other material as long as it has a function of blocking light in a specific wavelength range. Alternatively, an organic insulating film containing a black pigment or the like can be used.

[0270] In addition, an insulating film 348 is formed on the colored film 346. The insulating film 348 is planarized. The function of the colored film 346 is to prevent impurities contained therein from diffusing toward the liquid crystal element. It has the function of controlling

[0271] In addition, a conductive film 350 is formed on the insulating film 348. The conductive film 350 is The liquid crystal element has a function as the other of the pair of electrodes. An insulating film having a function as an alignment film is formed on the films 320a and 320b and the conductive film 350. It may be formed separately.

[0272] In addition, the liquid crystal layer 3 is provided between the conductive films 320a and 320b having light transmitting properties and the conductive film 350. The liquid crystal layer 321 is formed on the substrate 3 using a sealing material (not shown). The sealing material is used to prevent moisture from entering the device. In order to suppress oxidation, it is preferable to have a structure in which the inorganic material is in contact with the inorganic material.

[0273] In addition, a liquid crystal layer 321 is provided between the conductive films 320a and 320b having light-transmitting properties and the conductive film 350. A spacer may be provided to maintain the thickness (also called the cell gap) of the pixel.

[0274] A method for manufacturing an element portion provided on a substrate 302 shown in the semiconductor device shown in FIG. 9 to 12.

[0275] First, prepare a substrate 302. Here, a glass substrate is used as the substrate 302.

[0276] Next, a conductive film is formed on the substrate 302, and the conductive film is processed into a desired region. The conductive films 304a, 304b, and 304c are formed. The formation of c is performed by forming a mask by a first patterning in a desired region, and then covering the mask. It can be formed by etching the uncut areas (see FIG. 9(A)).

[0277] The conductive films 304a, 304b, and 304c are typically formed by deposition or CVD. The insulating film can be formed by a method such as sputtering or spin coating.

[0278] Next, an insulating film 305 is formed on the substrate 302 and the conductive films 304a, 304b, and 304c. Then, an insulating film 306 is formed on the insulating film 305 (see FIG. 9A).

[0279] The insulating film 305 and the insulating film 306 are formed by a sputtering method, a CVD method, or the like. When the insulating film 305 and the insulating film 306 are successively formed in a vacuum, impurities are easily removed. This is preferable because it suppresses the inclusion of

[0280] Next, a semiconductor film 307 is formed over the insulating film 306 (see FIG. 9B).

[0281] The semiconductor film 307 can be formed by sputtering, coating, pulsed laser deposition, laser ablation, etc. The film can be formed by using a diffusion method or the like.

[0282] Next, the semiconductor film 307 is processed into desired regions to form island-shaped semiconductor films 308a and 30 The semiconductor films 308a, 308b, and 308d are formed. A mask is formed by a second patterning in a desired area, and the area not covered by the mask is The etching can be performed by dry etching. Dry etching, wet etching, or a combination of both can be used ( See Figure 9(C).

[0283] Next, a first heat treatment may be performed. The same conditions as those for the heat treatment are used. The first heat treatment is performed to form the semiconductor films 308a and 308b. The crystallinity of the oxide semiconductor used for the insulating films 305 and 306 and the semiconductor Impurities such as hydrogen and water can be removed from the conductive films 308a, 308b, and 308d. Note that a first heating step may be performed before etching the semiconductor film 307.

[0284] Next, a first protective film is formed on the insulating film 306 and the semiconductor films 308a, 308b, and 308d. A film 309 serving as a protective film, a conductive film 310, and a film 311 serving as a second protective film are formed in this order (FIG. 1 0(A)).

[0285] The first protective film 309 and the conductive film 310 are formed by, for example, a sputtering method. The film 311 that becomes the second protective film can be formed using, for example, C The insulating film can be formed by a VD method, a sputtering method, or the like.

[0286] Next, the film 311 to be the second protective film is processed into a desired region to form the second protective film 31 2a, 312b, 312c, 312d, and 312e are formed. The formation of 312a, 312b, 312c, 312d, and 312e provides a third patterning in the desired area. forming a mask by etching the area not covered by the mask, After that, the mask is removed (see FIG. 10(B)).

[0287] Next, the conductive film 310 and the film 309 to be the first protective film are processed into desired regions. As a result, the conductive films 313a, 313b, 313c, 313d, and 313e and the first protective film 314a, 314b, 314c, 314d, and 314e are formed. The protective films 312a, 312b, 312c, 312d, and 312e function as masks, By etching the area not covered by the mask, the conductive films 313a, 313b, and 313c are 13c, 313d, 313e, and the first protective films 314a, 314b, 314c, 314 d, 314e can be formed (see FIG. 10(C)).

[0288] Next, the insulating film 306, the semiconductor films 308a, 308b, and 308d, and the second protective film 312a , 312b, 312c, 312d, 312e, conductive film 313a, 313b, 313c, 3 13d, 313e, on the first protective films 314a, 314b, 314c, 314d, 314e An insulating film 315 is formed to cover the above (see FIG. 11A).

[0289] The insulating film 315 can be formed using the same oxide insulating film 23 and the oxide insulating film 24 as those described in Embodiment 1. A lamination can be formed using similar conditions.

[0290] Next, the insulating film 315 is processed into a desired region to form an insulating film 316 and an opening 362. The insulating film 316 and the opening 362 are formed in a desired region by forming a fourth pattern. A mask is formed by etching, and the area not covered by the mask is etched. It can be formed by the above (see FIG. 11(B)).

[0291] The opening 362 is formed so that the surface of the semiconductor film 308d is exposed. The method for forming 62 may be, for example, a dry etching method. The method for forming the opening 362 is not limited to this, and may be a wet etching method or a dry etching method. A combination of dry etching and wet etching may also be used.

[0292] After that, a second heat treatment may be performed. The oxygen vacancies in the semiconductor films 308a and 308b are eliminated by transferring the oxygen As a result, oxygen vacancies in the semiconductor films 308a and 308b can be reduced. The amount can be reduced.

[0293] Next, an insulating film 317 is formed on the insulating film 316 and the semiconductor film 308d (FIG. 11(C) reference).

[0294] The insulating film 317 is made of a material that is free of impurities from the outside, such as oxygen, hydrogen, water, alkali metals, It is preferable to use a material that prevents the alkaline earth metal or the like from diffusing into the semiconductor film, and further preferably contains hydrogen, and is typically an inorganic insulating material containing nitrogen, such as a nitride insulating film. The insulating film 317 can be formed by, for example, a CVD method, a sputtering method, etc. It can be formed using:

[0295] When the insulating film 317 is formed by using a CVD method, a sputtering method, or the like, the semiconductor film 30 The insulating film 318d is exposed to plasma, and oxygen vacancies are generated in the semiconductor film 308d. 7 is a semiconductor film impurity such as water, alkali metal, alkaline earth metal, etc. The film is made of a material that prevents the diffusion of hydrogen into the atmosphere, and it also contains hydrogen. When hydrogen in the film 317 diffuses into the semiconductor film 308d, the hydrogen becomes an oxide in the semiconductor film 308d. The hydrogen in the insulating film 317 combines with the electron vacancy to generate an electron carrier. When the hydrogen diffuses into the semiconductor film 308d, the hydrogen bonds with oxygen in the semiconductor film 308d, forming carriers. As a result, the semiconductor film 308d becomes highly conductive, and the conductivity This results in a film 308c having the structure.

[0296] In addition, the insulating film 317 is preferably formed at a high temperature in order to enhance blocking properties. For example, the substrate temperature is 100° C. or higher and lower than the distortion point of the substrate, and more preferably 300° C. or higher and 40 It is preferable to form the film by heating at a temperature of 0°C or less. Oxygen is released from the films 308a and 308b, and the carrier concentration increases. Therefore, the temperature is set so that such a phenomenon does not occur.

[0297] Before the insulating film 317 is formed, the semiconductor film 308d is treated with a plasma containing a rare gas and hydrogen. By exposing the semiconductor film 308d to oxygen, oxygen vacancies are formed in the semiconductor film 308d. As a result, the electrons that are carriers in the semiconductor film 308d are It is possible to further increase the molecular weight, and the conductivity of the conductive film 308c can be further increased. It can be done.

[0298] Next, insulating films 305, 306, 316, 317 and second protective films 312c, 312e are formed. By processing the desired area, openings 364a, 364b, and 364c are formed. The insulating film 317 etched in the step is used as the insulating film 318, and the second The first and second protective films 312c and 312e are referred to as second protective films 312f and 312g, respectively. 318, and openings 364a, 364b, and 364c are formed in the desired areas by a fifth patterning. and then etching the area not covered by the mask. (See FIG. 12A). Note that the second protective films 312c and 312e are light-transmitting. In the case where the second protective films 312c and 312e are formed of a conductive film having a high conductivity, It is not necessary to etch.

[0299] The opening 364a is formed so that the surface of the conductive film 304b is exposed. The opening 364b is formed so as to expose the conductive film 313c. The conductive film 313e is formed so as to be exposed.

[0300] The openings 364a, 364b, and 364c can be formed, for example, by dry etching. However, the method for forming the openings 364a, 364b, and 364c may be different. The etching method is not limited to this, and may be a wet etching method or a dry etching method. A formation method in which wet etching is combined may also be used.

[0301] Next, a conductive film 31 is formed on the insulating film 318 so as to cover the openings 364a, 364b, and 364c. 9 is formed (see FIG. 12(B)).

[0302] The conductive film 319 can be formed by, for example, a sputtering method.

[0303] Next, the conductive film 319 is processed into a desired region to form a light-transmitting conductive film 320a, The light-transmitting conductive films 320a and 320b are formed. A mask is formed on the region by a sixth patterning, and the region not covered by the mask is It can be formed by etching (see FIG. 12(C)).

[0304] Through the above steps, a pixel portion having a transistor and a driver circuit portion are formed on the substrate 302. In the manufacturing process shown in this embodiment, the first to sixth patterns This means that transistors and capacitors can be formed simultaneously using six masks. Cut.

[0305] In this embodiment, hydrogen contained in the insulating film 318 is diffused into the semiconductor film 308d. The conductivity of the semiconductor film 308d was increased by masking the semiconductor films 308a and 308b. The semiconductor film 308d is doped with impurities, typically hydrogen, boron, phosphorus, tin, antimony, rare earth metal, etc. Gas elements, alkali metals, alkaline earth metals, etc. are added to make the semiconductor film 308d conductive. The semiconductor film 308d may be doped with hydrogen, boron, phosphorus, tin, antimony, or a rare gas element. The methods of adding the elements include ion doping and ion implantation. As a method for adding an alkali metal, an alkaline earth metal, or the like to the film 308d, For example, the semiconductor film 308d may be exposed to a solution containing the metal oxide.

[0306] Next, the structure formed on the substrate 342 provided opposite the substrate 302 will be described below. Provide an explanation.

[0307] First, a substrate 342 is prepared. The substrate 342 is made of the same material as that of the substrate 302. Next, a light-shielding film 344 and a colored film 346 are formed on the substrate 342 (FIG. 13( See A).

[0308] The light-shielding film 344 and the colored film 346 are formed of various materials by a printing method, an ink-jet method, They are formed at desired positions by an etching method using photolithography technology.

[0309] Next, an insulating film 348 is formed on the light-shielding film 344 and the colored film 346 (see FIG. 13(B)). see).

[0310] The insulating film 348 is an organic insulating film such as acrylic resin, epoxy resin, polyimide, etc. By forming the insulating film 348, for example, the colored film 346 It is possible to prevent impurities contained therein from diffusing to the liquid crystal layer 321 side. However, the insulating film 348 is not necessarily required, and a structure in which the insulating film 348 is not formed may be used. good.

[0311] Next, a conductive film 350 is formed over the insulating film 348 (see FIG. 13C). As the conductive film 319, the material shown in FIG.

[0312] Through the above steps, the structure formed on the substrate 342 can be formed.

[0313] Next, the insulating film 31 formed on the substrate 302 and the substrate 342, more specifically, on the substrate 302, 8, the conductive films 320a and 320b having light transmitting properties and the conductive film 35 formed on the substrate 342 0, an alignment film 323 and an alignment film 352 are formed. The film can be formed by using a rubbing method, a photo-alignment method, or the like. A liquid crystal layer 321 is formed between the substrate 342 and the liquid crystal layer 321. or by bonding the substrate 302 and the substrate 342 together and then using the capillary phenomenon. An injection method for injecting liquid crystal can be used.

[0314] Through the above steps, the display device shown in FIG. 8 can be manufactured.

[0315] Note that this embodiment mode can be appropriately combined with other embodiment modes shown in this specification. do.

[0316] (Embodiment 5) In this embodiment, a transistor included in the semiconductor device described in the above embodiment is In the following, one embodiment that can be applied to the semiconductor film 14 and the oxide film 15 will be described. Here, an oxide semiconductor is used as the semiconductor film 14. However, an oxide film can also have a similar structure.

[0317] Oxide semiconductor films are roughly classified into non-single-crystal oxide semiconductor films and single-crystal oxide semiconductor films. The non-single-crystal oxide semiconductor film is called CAAC-OS (C Axis Aligned Crystal-Oxide Semiconductor Film). (stalline oxide semiconductor) film, polycrystalline oxide semiconductor The term CAAC-O refers to a film, a microcrystalline oxide semiconductor film, an amorphous oxide semiconductor film, etc. The S film and the microcrystalline oxide semiconductor film will be described.

[0318] First, we will explain the CAAC-OS film.

[0319] The CAAC-OS film is one of the oxide semiconductor films that has multiple crystal parts. The crystal part is small enough to fit inside a cube with one side less than 100 nm. The crystal parts contained in the OS film are cubes with one side less than 10 nm, 5 nm, or 3 nm. The CAAC-OS film has a smaller size than the microcrystalline oxide semiconductor film. It is characterized by a low density of defect states.

[0320] The CAAC-OS film was observed under a transmission electron microscope (TEM). When observed using a quartz crystal microscope, clear boundaries between the crystals were observed. It is not possible to confirm the grain boundary. It can be said that the AAC-OS film is less susceptible to the decrease in electron mobility caused by grain boundaries.

[0321] The CAAC-OS film was observed by TEM from a direction roughly parallel to the sample surface (cross-sectional TEM observation). When the metal atoms are observed, it can be confirmed that they are arranged in layers in the crystal part. Each layer of the CAAC-OS film is formed on a surface on which the film is to be formed (also called a surface on which the film is to be formed) or on a concave surface on the upper surface. The shape reflects a convexity, and is aligned parallel to the surface on which the CAAC-OS film is formed or the upper surface.

[0322] In this case, "parallel" means that the angle between the two lines is between -10° and 10°. Therefore, it includes the case where the angle is between -5° and 5°. Also, "vertical" means , refers to a state in which two straight lines are arranged at an angle of 80° or more and 100° or less. This includes cases where the angle is greater than 5° and less than 95°.

[0323] On the other hand, the CAAC-OS film was observed by TEM from a direction roughly perpendicular to the sample surface (plane T EM observation reveals that metal atoms are arranged in triangular or hexagonal shapes in the crystals. However, no regularity was observed in the arrangement of metal atoms between different crystal regions. do not have.

[0324] When electron beam diffraction was performed on the CAAC-OS film, spots (bright spots) indicating orientation were observed. is observed.

[0325] Cross-sectional and planar TEM observations revealed that the crystals in the CAAC-OS film had an orientation. It can be seen that...

[0326] Figure 14(A) shows a sample in which a CAAC-OS with a thickness of 100 nm was thinned to 50 nm. The results of nanobeam electron diffraction from the surface side of the sample are shown below. The diameter of the electron beam is 1 nm (written as φ1 nm), 10 nm (written as φ10 nm), 20 nm (written as φ20 nm) In either case, the diameter was set to 30 nm (φ30 nm). The smaller the diameter of the electron beam, the higher the orientation. It was found that...

[0327] X-ray diffraction (XRD) of CAAC-OS film When the structure was analyzed using the device, for example, CAAC-OS with InGaZnO4 crystals was In the out-of-plane analysis of the film, the diffraction angle (2θ) peaked at around 31°. This peak is attributed to the (009) plane of the InGaZnO4 crystal. Therefore, the crystals of the CAAC-OS film have a c-axis orientation, and the c-axis faces the surface on which the film is formed or the upper surface. It can be seen that it is oriented in a roughly vertical direction.

[0328] On the other hand, in-p X-rays are incident on the CAAC-OS film from a direction approximately perpendicular to the c-axis. In the lane method, a peak may appear at 2θ around 56°. is attributed to the (110) plane of the InGaZnO4 crystal. In the case of a nitride semiconductor film, 2θ is fixed at around 56°, and the normal vector of the sample surface is the axis (φ axis). When the sample is rotated and analyzed (φ scan), a crystal plane equivalent to the (110) plane is detected. In contrast, in the case of the CAAC-OS film, six peaks are observed, which are assigned to Even when φ is fixed at around 56° and scanned, no clear peak appears.

[0329] From the above, it is considered that the orientation of the a-axis and b-axis is uniform between different crystal regions in the CAAC-OS film. Although it is irregular, it has a c-axis orientation, and the c-axis is parallel to the normal vector of the surface on which it is formed or the upper surface. Therefore, the layered structure confirmed by the cross-sectional TEM observation mentioned above is consistent with the Each layer of arranged metal atoms is in a plane parallel to the ab plane of the crystal.

[0330] The crystalline part is formed when the CAAC-OS film is formed or after a crystallization process such as a heat treatment. As described above, the c-axis of the crystal is aligned to the surface on which the CAAC-OS film is to be formed. For example, in the CAAC-OS film, When the shape is changed by etching, the c-axis of the crystal is aligned with the CAAC-OS film. It may not be parallel to the face or top surface normal vector.

[0331] In the CAAC-OS film, the distribution of c-axis oriented crystal parts does not need to be uniform. For example, the crystals in the CAAC-OS film grow from the top surface of the CAAC-OS film. When the crystal is formed by the above method, the region near the top surface has more c-axis oriented crystals than the region near the surface on which the crystal is formed. In addition, the CAAC-OS film containing impurities may have a high ratio of impurities. The doped region may change in quality, forming regions with partially different crystal portions.

[0332] In addition, the out-of-plane crystal structure of the CAAC-OS film with InGaZnO4 crystals In the analysis by the method, in addition to the peak at 2θ near 31°, a peak also appeared at 2θ near 36°. The peak at 2θ of around 36° may be due to the c-axis orientation in some parts of the CAAC-OS film. The CAAC-OS film contains crystals that do not have the 2θ value of about 31°. It is preferable that the spectrum shows a peak at 2θ of about 36° and does not show a peak at 2θ of about 36°.

[0333] The CAAC-OS film is an oxide semiconductor film with a low concentration of impurities. The oxide semiconductor film is preferably made of silicon or a transition metal element other than the main component of the oxide semiconductor film. The elements that bond to oxygen stronger than the metal elements that form the oxide semiconductor film, such as Zn, By removing oxygen from the oxide semiconductor film, the atomic arrangement of the oxide semiconductor film is disturbed, and the crystallinity is reduced. In addition, heavy metals such as iron and nickel, argon, and carbon dioxide are Since the diameter (or molecular radius) of the ions is large, when the ions are contained inside the oxide semiconductor film, the oxide semiconductor film The impurities contained in the oxide semiconductor film are disturbed, which causes a decrease in crystallinity. Pure materials may act as carrier traps or carrier generation sources.

[0334] The CAAC-OS film is an oxide semiconductor film with a low density of defect states. Oxygen vacancies in semiconductor films act as carrier traps and trap hydrogen. This can become a carrier generation source.

[0335] The low impurity concentration and low defect level density (low oxygen vacancies) are called high purity intrinsic or The term "high-purity intrinsic" refers to a substantially high-purity intrinsic oxide semiconductor. Since the film has a small carrier generation source, the carrier density can be reduced. The transistor using the oxide semiconductor film has electrical characteristics (noise) in which the threshold voltage is negative. It is also called "marine". It is rare for it to become "high purity genuine" or "substantially high purity". The intrinsic oxide semiconductor film has few carrier traps. Transistors using the film have little fluctuation in electrical characteristics and are highly reliable. Note that it takes a certain time for charges trapped in the carrier traps in the oxide semiconductor film to be released. The time is long and the charge may behave as if it were a fixed charge. In addition, a transistor using an oxide semiconductor film having a high density of defect states has unstable electrical characteristics. There may be cases where this occurs.

[0336] In addition, the electrical characteristics of transistors using CAAC-OS films are improved by irradiation with visible light or ultraviolet light. Gender variation is small.

[0337] Next, a microcrystalline oxide semiconductor film will be described.

[0338] In the TEM image of the microcrystalline oxide semiconductor film, crystal parts can be clearly seen. The crystal parts contained in the microcrystalline oxide semiconductor film may have a size of 1 nm or more and 100 nm or more. In particular, the size of the particles is between 1 nm and 10 nm. Nanocrystals (nc) are microcrystals with a diameter of 1 to 3 nm or less. The oxide semiconductor film having nc-OS (nanocrystalline O The nc-OS film is called a T In EM images, grain boundaries may not be clearly visible.

[0339] The nc-OS film is a microscopic region (e.g., a region of 1 nm to 10 nm, especially a region of 1 nm or less). The nc-OS film has a periodic atomic arrangement in the region of 3 nm or less. There is no regularity in the crystal orientation between the crystal parts, and therefore no orientation is observed throughout the film. Therefore, the nc-OS film cannot be distinguished from an amorphous oxide semiconductor film depending on the analysis method. For example, XRD, which uses X-rays with a diameter larger than that of the crystal part, is used for nc-OS films. When structural analysis is performed using the out-of-plane method, the crystal planes are In addition, the nc-OS film has a larger diameter (e.g., 50 When electron beam diffraction (also called selected area electron beam diffraction) is performed using an electron beam of 1 nm or more, On the other hand, the diffraction pattern of the nc-OS film is similar to that of the crystalline part. Use an electron beam with a diameter close to the size of the crystal or smaller than the crystal part (for example, 1 nm to 30 nm). When electron beam diffraction (also called nanobeam electron beam diffraction) is performed, spots are observed. When nanobeam electron diffraction was performed on the nc-OS film, bright spots were observed in a circular (ring-like) pattern. In addition, nanobeam electron diffraction (NAD) analysis of the nc-OS film revealed that the NC-OS film had a high degree of diffraction. When this is done, multiple spots may be observed within the ring-shaped area.

[0340] Figure 14 shows the nanobeam electron diffraction patterns of the sample with the nc-OS film at different measurement points. In this example, the sample was cut in a direction perpendicular to the surface on which the nc-OS film was formed. The specimen is sliced ​​to a thickness of 10 nm or less. The sagittal beam is incident from a direction perpendicular to the cut surface of the sample. When nanobeam electron diffraction is performed on a sample, a diffraction pattern showing the crystal planes is obtained. It was found that no orientation to a specific crystal plane was observed.

[0341] The nc-OS film is an oxide semiconductor film with higher order than an amorphous oxide semiconductor film. Therefore, the nc-OS film has a lower density of defect states than the amorphous oxide semiconductor film. In the nc-OS film, the crystal orientation is not regular between different crystal parts. The OS film has a higher density of defect states than the CAAC-OS film.

[0342] The oxide semiconductor film may be, for example, an amorphous oxide semiconductor film, a microcrystalline oxide semiconductor film, or a C The AAC-OS film may be a laminate film having two or more kinds of AAC-OS films.

Claims

[Claim 1] A semiconductor film; a pair of first protective films in contact with the semiconductor film; a pair of conductive films each having copper, aluminum, gold, silver, or molybdenum and in contact with the pair of first protective films; a pair of second protective films in contact with the pair of conductive films on the opposite side to the pair of first protective films; a gate insulating film in contact with the semiconductor film; a gate electrode overlapping the semiconductor film via the gate insulating film; In a cross-sectional view, the side surfaces of the pair of second protective films are located outside the pair of conductive films.

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