Semiconductor Device

Abstract

To provide a semiconductor device including a transistor with excellent electric characteristics, and including a capacitor element having a high opening ratio and increasing the charge capacity.SOLUTION: A semiconductor device includes a transistor 102 and a capacitor element 105 on an insulating surface. The transistor includes a gate electrode (conductive film 13), an oxide semiconductor film 19a overlapping with the gate electrode, a gate insulating film (a nitride insulating film 15 and an oxide insulating film 17) between the gate electrode and the oxide semiconductor film, conductive films 21a, 21b functioning as a pair of electrodes in contact with the oxide semiconductor film, oxide insulating films 23, 25 in contact with the oxide semiconductor film, a metal oxide film 27 on the oxide insulating film, and a conductive film 31 formed in an opening part of the metal oxide film and functioning as a pixel electrode in contact with the conductive film 21b. The capacitor element includes a film 19b with conductivity on the oxide insulating film 17, a conductive film 31, and a metal oxide film 27 provided between the film 19b with conductivity and the conductive film 31.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an article, a method, or a manufacturing method. The present invention relates to a method, manufacture, or composition of matter. One embodiment of the present invention is a semiconductor device, a display device, a light-emitting device, a power storage device, and a driving method thereof. In particular, one embodiment of the present invention relates to a semiconductor device that can be an oxide semiconductor, The present invention relates to a capacitor element having a film containing a material as an electrode and a manufacturing method thereof. One embodiment of the present invention is a semiconductor device including a transistor having an oxide semiconductor film and a manufacturing method thereof. Regarding the law. [Background technology]

[0002] A transistor (thin film transistor (TFT)) is made by using a semiconductor thin film formed on a substrate. The technology of constructing a transistor is attracting attention. It is widely used in electronic devices such as image display devices (display devices). Silicon-based semiconductor materials are widely known as semiconductor thin films that can be used, but other materials and Oxide semiconductors have been attracting attention as a new type of semiconductor.

[0003] For example, indium (In), gallium (Ga) and nickel are used as the active layer of a transistor. A transistor using an oxide semiconductor containing lead (Zn) has been disclosed (see Patent Document 1). ).

[0004] In addition, the oxide semiconductor film used in the active layer of the transistor has a stacked structure. A technique for improving rear mobility has been disclosed (see Patent Document 2).

[0005] In oxide semiconductors, impurities such as hydrogen can cause shallow doping. It has been pointed out that a toner level is formed and electrons that act as carriers are generated. As a result, A transistor using an oxide semiconductor has a negative shift in threshold voltage and is normally on. This results in a leakage current when no voltage is applied to the gate (i.e., in the off state). Therefore, the aluminum oxide film, which has hydrogen blocking properties, is used as an oxide film. The entire surface of the substrate is then coated with a semiconductor layer so as to cover the channel region, the source electrode, and the drain electrode. By providing the insulating film over the entire length of the oxide semiconductor film, entry of hydrogen into the oxide semiconductor film can be suppressed, and leakage current can be prevented. (See Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2006-165528 A [Patent Document 2] JP 2011-138934 A [Patent Document 3] JP 2010-16163 A Summary of the Invention [Problem to be solved by the invention]

[0007] Defects contained in an oxide semiconductor film include oxygen vacancies. The threshold voltage of a transistor using an oxide semiconductor film is shifted in the negative direction. This is because the oxide semiconductor film is easily oxygen deficient. This is because the loss in the transistor generates charges, resulting in a lower resistance. If the device has a large number of EEPROMs, malfunctions may occur easily during operation, or power consumption may increase when the device is not in operation. In addition, the deterioration of transistors due to aging and stress testing can cause various problems. There is a problem in that the variation in electrical characteristics, typically the threshold voltage, increases.

[0008] On the other hand, aluminum oxide films are generally formed by sputtering or atomic layer deposition (ALD). The film can be formed by atomic layer deposition (ALD). However, the sputtering method using an aluminum oxide target produces aluminum oxide. When a film is formed, arcing occurs, generating fine particles. The inclusion of fine particles in the deposited film leads to a decrease in yield.

[0009] In addition, the method for forming an aluminum oxide film by atomic layer deposition is based on trimethylaluminum Since TMA and water vapor are introduced alternately into the processing chamber, the deposition time is longer and the throughput is This is one of the reasons for the decline in

[0010] In view of the above, one embodiment of the present invention provides a semiconductor device including a transistor with excellent electrical characteristics. Alternatively, the present invention has a capacitance element that has a high aperture ratio and is capable of increasing the charge capacity. To provide a semiconductor device, and to provide a method for manufacturing a semiconductor device with high yield. Alternatively, a method for manufacturing a semiconductor device with high productivity is provided. A novel method and a novel semiconductor device are provided. [Means for solving the problem]

[0011] One embodiment of the present invention is a film including a material that can be an oxide semiconductor, typically an indium and M (M is Al, Ga, Y, Zr, La, Ce, or Nd), and a film having a translucency. between a conductive film having a material that can be an oxide semiconductor and a light-transmitting conductive film and a metal oxide film provided on the first insulating film.

[0012] Another embodiment of the present invention is a semiconductor device including a transistor and a capacitor over an insulating surface. The transistor includes a gate electrode, an oxide semiconductor film overlapping the gate electrode, and a gate insulating film. a gate insulating film between the gate electrode and the oxide semiconductor film; and a pair of electrodes in contact with the oxide semiconductor film. and a first conductive film which functions as a gate insulating film and a second ... a metal oxide film on the oxide insulating film; and a first insulating film formed in an opening of the metal oxide film. and a second conductive film which functions as a pixel electrode and is in contact with the conductive film. A conductive film on the gate insulating film, a second conductive film, and a conductive film and a second conductive film. and a metal oxide film provided between the films.

[0013] The metal oxide film may be aluminum oxide, aluminum oxynitride, gallium oxide, or oxide. Gallium oxide, yttrium oxide, yttrium oxynitride, hafnium oxide, oxynitride It is formed of hafnium, titanium oxide, tantalum oxide, or tantalum oxynitride. The metal oxide membrane may be separate.

[0014] The oxide semiconductor film and the conductive film are made of In-Ga oxide, In-Zn oxide, or is formed of In-M-Zn oxide (M is Al, Ga, Y, Zr, La, Ce, or Nd) The conductive film contains a metal element contained in the oxide semiconductor film.

[0015] The oxide semiconductor film and the conductive film have a multilayer structure including a first film and a second film. The first film may have a different atomic ratio of metal elements from the second film.

[0016] The oxide insulating film contains more oxygen than the oxygen that satisfies the stoichiometric composition. The oxide insulating film containing more oxygen than the stoichiometric composition has a TDS( In the Thermal Desorption Spectroscopy (TDS) analysis, Heat treatment with surface temperatures between 100°C and 700°C or between 100°C and 500°C The amount of oxygen released, calculated as the number of oxygen atoms, is 1.0 × 10 18 atoms / cm 3 That's all. . Effect of the Invention

[0017] According to one embodiment of the present invention, a semiconductor device including a transistor with excellent electrical characteristics is provided. According to one embodiment of the present invention, the aperture ratio can be increased and the charge capacity can be increased. It is possible to provide a semiconductor device having a capacitance element capable of According to one embodiment of the present invention, a semiconductor device can be manufactured with high yield. In this manner, a semiconductor device can be manufactured with high productivity. [Brief description of the drawings]

[0018] [Figure 1] 1A and 1B are a block diagram and a circuit diagram illustrating one embodiment of a semiconductor device. [Diagram 2] FIG. 1 is a top view illustrating one embodiment of a semiconductor device. [Diagram 3] 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 4] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a semiconductor device. [Diagram 5] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a semiconductor device. [Figure 6] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a semiconductor device. [Figure 7] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a semiconductor device. [Figure 8] FIG. 1 is a top 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] 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 13] FIG. 1 illustrates a band structure of a transistor. [Figure 14] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a semiconductor device. [Figure 15] 1A to 1C are top views illustrating one embodiment of a method for manufacturing a semiconductor device. [Figure 16] 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 17] 1A to 1C are cross-sectional views illustrating one mode of a method for manufacturing a semiconductor device. [Figure 18] FIG. 1 is a diagram illustrating the transmittance of a sample. [Figure 19] FIG. 1 is a diagram illustrating the sheet resistance of a sample. [Figure 20] FIG. 2 is a diagram illustrating the structure of a sample. [Figure 21] FIG. 1 is a diagram illustrating the sheet resistance of a sample. [Figure 22] FIG. 1 is a diagram illustrating the sheet resistance of a sample. [Diagram 23] FIG. 2 is a diagram illustrating the structure of a sample. [Figure 24] 13A and 13B are diagrams illustrating the concentration of hydrogen contained in an oxide semiconductor film. [Diagram 25] FIG. 1 is a diagram illustrating Vg-Id characteristics. [Figure 26] FIG. 2 is a diagram illustrating the relationship between channel length and threshold voltage. [Figure 27] 1A to 1C are diagrams illustrating external views of electronic devices according to an embodiment. [Figure 28] FIG. 2 is a diagram illustrating a display module. [Figure 29] 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Diagram 30] FIG. 1 is a top view illustrating one embodiment of a semiconductor device. [Diagram 31] FIG. 4 is a diagram illustrating the temperature dependence of resistivity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] In this specification, when an etching process is performed after a photolithography process, The mask formed in the photolithography process is removed.

[0025] (Embodiment 1) 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.

[0026] FIG. 1A 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 103 is arranged parallel or substantially parallel to the signal line 109. The capacitance lines 115 are arranged along the scanning lines 107. 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.

[0027] Each scanning line 107 corresponds to one of the pixels 103 arranged in m rows and n columns in the pixel section 101. The signal lines 109 are electrically connected to the n pixels 103 arranged in any one row. is m pixels 103 arranged in m rows and n columns, and m pixels 103 arranged in any one of the columns. 3. m and n are both integers of 1 or more. is m pixels 103 arranged in m rows and n columns, and m pixels 103 arranged in any one of the columns. 3. The capacitance lines 115 are arranged parallel to each other along the scanning lines 107. In the case where the pixels 103 are arranged in m rows and n columns, any one of the pixels 103 may be arranged in a matrix of m rows and n columns. The pixel electrodes 103 are electrically connected to n pixels 103 arranged in a row.

[0028] 1B and 1C can be used for the pixel 103 of the display device shown in FIG. 1A. 2 shows an example of a circuit configuration.

[0029] The pixel 103 shown in FIG. 1B includes a liquid crystal element 121, a transistor 102, and a capacitor element 105 and has.

[0030] The potential of one of the pair of electrodes of the liquid crystal element 121 is appropriately set according to the specifications of the pixel 103. The alignment state of the liquid crystal element 121 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 121 of each pixel 103. A potential may be applied to one of the pair of electrodes of the liquid crystal element 121 for each row of the pixels 103. may be given different potentials.

[0031] The liquid crystal element 121 controls the transmission or non-transmission of light by the optical modulation effect of the liquid crystal. The optical modulation effect of liquid crystals is achieved by the electric field applied to the liquid crystal (horizontal electric field, vertical electric field). The liquid crystal element 121 is controlled by an electric field in a direction or an electric field in an oblique direction. These include nematic liquid crystals, cholesteric liquid crystals, smectic liquid crystals, and thermotropic liquid crystals. , lyotropic liquid crystal, ferroelectric liquid crystal, antiferroelectric liquid crystal, etc.

[0032] The display device having the liquid crystal element 121 can be driven in, for example, a TN mode or a VA mode. ASM (Axially Symmetric Aligned Micro-ce) ll) mode, OCB (Optically Compensated Birefringence ngence) mode, MVA mode, PVA (Patterned Vertical Alignment mode, IPS mode, FFS mode, or TBA (Tran You can also use the sverse bend alignment mode. However, the present invention is not limited to this, and various liquid crystal elements and driving methods thereof can be used.

[0033] 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.

[0034] In the configuration of the pixel 103 shown in FIG. One of the drain electrodes is electrically connected to the signal line 109, and the other is connected to a pair of the liquid crystal element 121. The gate electrode of the transistor 102 is electrically connected to the other of the scan lines 1 and 2. 07. The transistor 102 is turned on or off. This has the function of controlling the writing of data of the data signal.

[0035] In the configuration of the pixel 103 shown in FIG. 1B, one of a pair of electrodes of the capacitor 105 is The other end is electrically connected to a pair of electrodes of the liquid crystal element 121. The potential value of the capacitance line 115 depends on the specifications of the pixel 103. The capacitance element 105 serves as a storage capacitor for storing written data. It has all the functions.

[0036] For example, in a display device having the pixel 103 shown in FIG. 1B, the scanning line driver circuit 104 The pixels 103 in each row are selected in sequence, and the transistors 102 are turned on to output the data signal. Write the data.

[0037] The pixel 103 to which the data has been written is held by turning off the transistor 102. By performing this process row by row, an image can be displayed.

[0038] In addition, the pixel 103 shown in FIG. 1C includes a transistor 1 for switching a display element. 33, a transistor 102 for controlling driving of the pixel, a transistor 135, and a capacitance element 105 and a light-emitting element 131.

[0039] A data signal is applied to one of the source electrode and the drain electrode of the transistor 133. The gate electrode of the transistor 133 is electrically connected to the signal line 109. The pixel is electrically connected to a scanning line 107 to which a scanning signal is applied.

[0040] The transistor 133 is turned on or off to transmit the data of the data signal. It has the function of controlling the writing of data.

[0041] One of the source electrode and the drain electrode of the transistor 102 serves as an anode line. The source electrode and the drain electrode of the transistor 102 are electrically connected to the wiring 137. The other end is electrically connected to one electrode of the light-emitting element 131. The gate electrode of the second transistor is connected to the other of the source electrode and drain electrode of the transistor 133 and the capacitor It is electrically connected to one electrode of the element 105 .

[0042] The transistor 102 is turned on or off to produce a light emitting element 131. It has the function of controlling the flow of current.

[0043] One of the source and drain electrodes of the transistor 135 is provided with a data reference potential. The other of the source electrode and the drain electrode of the transistor 135 is connected to a wiring 139. , which is electrically connected to one electrode of the light-emitting element 131 and the other electrode of the capacitor 105. Furthermore, the gate electrode of the transistor 135 is connected to the scanning line 107 to which a gate signal is applied. are electrically connected.

[0044] The transistor 135 has a function of adjusting a current flowing through the light-emitting element 131. For example, When the internal resistance of the light emitting element 131 increases due to deterioration of the light emitting element 131, the transistor The current flowing through the wiring 139 to which one of the source electrode and the drain electrode of the transistor 135 is connected is By monitoring, the current flowing through the light emitting element 131 can be corrected. The potential applied to 39 can be, for example, 0V.

[0045] One of a pair of electrodes of the capacitor 105 is connected to the gate electrode of the transistor 102 and the The other of the source electrode and the drain electrode of the transistor 133 is electrically connected to the capacitor element 105. The other of the pair of electrodes is the other of the source electrode and the drain electrode of the transistor 135, It is electrically connected to one electrode of the light emitting element 131 .

[0046] In the configuration of the pixel 103 shown in FIG. 1C, the capacitor element 105 It has a function as a storage capacitor for storing the

[0047] One of the pair of electrodes of the light emitting element 131 is a source electrode and a drain electrode of the transistor 135. The other electrode, the other electrode of the capacitor 105, and the source electrode and the drain electrode of the transistor 102 The other of the pair of electrodes of the light emitting element 131 is electrically connected to the cathode. The transistor 141 is electrically connected to a wiring 141 which functions as a gate.

[0048] The light-emitting element 131 may be, for example, an organic electroluminescence element (also called an organic EL element). However, the light emitting element 131 is not limited to this. Alternatively, an inorganic EL element made of an inorganic material may be used.

[0049] A high power supply potential VDD is applied to one of the wiring 137 and the wiring 141, and a In the configuration shown in FIG. 1C, a high voltage is applied to the wiring 137. A power supply potential VDD is applied to the line 141, and a low power supply potential VSS is applied to the line 142.

[0050] In a display device having the pixel 103 shown in FIG. 1C, the image of each row is generated by a scanning line driving circuit 104. The elements 103 are selected in sequence, the transistors 133 are turned on, and data of the data signal is written. Enter.

[0051] The pixel 103 to which the data has been written is held by turning off the transistor 133. Furthermore, since the transistor 133 is connected to the capacitor 105, The data stored in the memory can be held for a long time. The amount of current flowing between the source electrode and the drain electrode of the transistor 102 is controlled, and the light-emitting element The element 131 emits light with a luminance according to the amount of current flowing through it. Images can be displayed.

[0052] Next, a specific configuration of the element substrate included in the display device will be described. A specific example of a liquid crystal display device using a liquid crystal element 103 will be described. A top view of the pixel 103 shown in (B) is shown in FIG.

[0053] In addition, in FIG. 1B and FIG. 1C, a liquid crystal element 121 and a light emitting element 131 are used as display elements. However, one aspect of the embodiment of the present invention is not limited to this. For example, EL (electroluminescence) elements (organic and and inorganic EL elements, organic EL elements, inorganic EL elements), LEDs (white LEDs, red LEDs ED, green LED, blue LED, etc.), transistors (transistors that emit light according to the current ), electron emission element, liquid crystal element, electronic ink, electrophoretic element, grating light valve GLV, plasma display (PDP), MEMS (microelectromechanical systems) Digital Micromirror Device (DMD), DMS (Digital Micro Shutter), MIRASOL (trademark), IMOD (Interference Modulation (energy modulation) element, electrowetting element, piezoelectric ceramic disk Play, carbon nanotubes, etc., electro-magnetic effects, contrast, brightness, reflection There are display media that change their reflectance and transmittance. An example of a display device using electron-emitting devices is an EL display. For this purpose, a field emission display (FED) or SED type flat panel display is used. i(SED:Surface-conduction Electron-emitte) An example of a display device using liquid crystal elements is a liquid crystal display. Spray (transmissive LCD, semi-transmissive LCD, reflective LCD) LCDs are used for displaying electronic ink or other electronic devices. An example of a display device using an electrophoretic element is electronic paper.

[0054] In FIG. 2, the conductive film 13 functioning as the scanning line is oriented in a direction substantially perpendicular to the signal line (left in the figure). The conductive film 21a, which functions as a signal line, is disposed so as to extend in a direction substantially parallel to the scanning line. The conductive film functions as a capacitance line. The conductor 21c extends in a direction parallel to the signal line. The conductive film 13 is electrically connected to the scanning line driving circuit 104 (see FIG. 1(A)). The conductive film 21a functioning as a signal line and the conductive film 21c functioning as a capacitance line are The sensor 102 is electrically connected to an operating circuit 106 (see FIG. 1(A)).

[0055] The transistor 102 is provided in a region where the scanning line and the signal line intersect. The gate electrode 102 includes a conductive film 13 that functions as a gate electrode, a gate insulating film (not shown in FIG. 2), and a gate insulating film 13b. ), an oxide semiconductor film 19a in which a channel region is formed on the gate insulating film, The conductive film 13 is made of conductive films 21a and 21b which function as electrodes. The region overlapping with the oxide semiconductor film 19a is the gate of the transistor 102. The conductive film 21a also functions as a signal line. The region overlapping with 19a functions as a source electrode or a drain electrode of the transistor 102. In addition, in FIG. 2, the end portion of the scan line is formed in the oxide semiconductor film 19a in the top view. Therefore, the scanning lines are located on the outer side of the edge of the screen, blocking the light from the backlight or other light source. As a result, the oxide semiconductor film 19a included in the transistor is illuminated with light. Therefore, the transistor is not irradiated with the semiconductor laser, and the fluctuation of the electrical characteristics of the transistor can be suppressed.

[0056] The conductive film 21b has a light-transmitting property and functions as a pixel electrode in the opening 41. It is electrically connected to the conductive film 31 .

[0057] The capacitor 105 is connected to a conductive film 21c that functions as a capacitor line. The element 105 includes a conductive film 19b formed on the gate insulating film and a transistor 1 a dielectric film provided on the insulating film 02, a light-transmitting conductive film 31 functioning as a pixel electrode, The dielectric film is a metal oxide film that is transparent and has low oxygen permeability. The conductive film 19b formed on the gate insulating film has light transmitting properties. The capacitor 105 has a light-transmitting property.

[0058] Since the capacitor 105 has a light-transmitting property, the capacitor 105 is large in the pixel 103. Therefore, the aperture ratio can be increased, typically by 55%. It is possible to increase the charge capacity to 60% or more, preferably 60% or more. For example, a semiconductor device with high resolution, such as a liquid crystal display device, can be obtained. In this case, the area of ​​the pixel is small, and the area of ​​the capacitance element is also small. In a semiconductor device with a low capacitance, the charge capacity stored in the capacitance element is small. Since the capacitor 105 described in the embodiment has a light-transmitting property, the capacitor can be provided in a pixel. As a result, it is possible to increase the aperture ratio while obtaining a sufficient charge capacity in each pixel. The pixel density is 200ppi or more, 300ppi or more, or even 500ppi or more. The present invention can be suitably used for high-resolution semiconductor devices.

[0059] 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.

[0060] Next, a cross-sectional view taken along the dashed line AB and CD in FIG. 2 is shown in FIG. The transistor 102 is a channel etch type transistor. The channel length direction of the transistor 102, the transistor 102 and the conductor that functions as a pixel electrode 1 is a cross-sectional view of the connection portion of the conductive film 31 and the capacitance element 105. The cross-sectional view at CD is 1 is a cross-sectional view of a transistor 102 in a channel width direction.

[0061] The transistor 102 shown in FIG. 3 is a transistor having a single gate structure. The gate electrode 13 is formed on the substrate 11. A nitride insulating film 15 is formed on the conductive film 13 that functions as a gate electrode. 5, and the nitride insulating film 15 and the oxide insulating film 17 are formed on the 1, an oxide semiconductor film 19a overlapping with the conductive film 13 functioning as a gate electrode; The conductive film 19a is in contact with the conductive film 21a and the conductive film 21b functioning as a pair of electrodes. The oxide insulating film 17, the oxide semiconductor film 19a, and the conductive film 21a functioning as a pair of electrodes An oxide insulating film 23 is formed on the oxide insulating film 21b, and an oxide insulating film 2 5 is formed. The nitride insulating film 15, the oxide insulating film 17, the oxide insulating film 23, and the oxide insulating film 5 are formed. A metal oxide film 27 is formed on the film 25 and the conductive film 21b. A nitride insulating film 29 is formed on the conductive film 21a, which functions as a pair of electrodes. On the other hand, a conductive film 31 connected to the conductive film 21b is formed on the nitride insulating film 29. The conductive film 31 functions as a pixel electrode.

[0062] The capacitor 105 shown in FIG. 3 is formed on the oxide insulating film 17. film 19b, a metal oxide film 27, a nitride insulating film 29, and a conductive film functioning as a pixel electrode. 31 and

[0063] The oxide insulating films 23 and 25 are separated over the transistor 102 in this embodiment. The separated oxide insulating films 23 and 25 overlap with the oxide semiconductor film 19a. In addition, a metal oxide film 27 covers the transistor 102 and the separated oxide insulating films 23 and 25. At the same time, it is provided as a dielectric for the capacitance element 105 .

[0064] The metal oxide film 27 is an oxide film that has light transmitting properties and low oxygen permeability. It is preferable to use a high dielectric material for the metal oxide film 27. Representative examples of the oxides include aluminum oxide, aluminum oxynitride, gallium oxide, and gallium oxynitride. Yttrium oxide, yttrium oxynitride, hafnium oxide, hafnium oxynitride Examples of metal oxide films include metal oxide films formed of titanium oxide, titanium oxide, tantalum oxide, tantalum oxynitride, and the like. The metal oxide film is an insulating film or a semiconductor film.

[0065] The thickness of the metal oxide film 27 is 0.5 nm or more and 50 nm or less, and the average thickness is 2 nm or more and 10 nm or less. The thickness of the metal oxide film 27 is set to 0.5 nm or more, preferably 2 nm or more. This prevents oxygen from moving from the oxide semiconductor film 19a and the oxide insulating films 23 and 25 to the outside. On the other hand, the thickness of the metal oxide film 27 is set to 50 nm or less, preferably 10 nm or less. By setting the thickness m or less, the metal oxide film 27 has high insulating properties. This is because it can be obtained by a method of oxidizing a metal film. This will be discussed later.

[0066] The nitride insulating film 29 may be an insulating film having low water permeability. It is possible to use an insulating film with low hydrogen and water permeability. It is preferable to use a high dielectric material as the nitride insulating film 29. The nitride insulating film 29 is preferably a silicon nitride film or a silicon nitride oxide film. Examples of the nitride insulating film include an aluminum nitride film and an aluminum nitride oxide film.

[0067] The thickness of the nitride insulating film 29 is 50 nm or more and 300 nm or less, preferably 100 nm or more. It is less than 200 nm.

[0068] The oxide semiconductor film 19a is typically an In-Ga oxide film, an In-Zn oxide film, or an I nM-Zn oxide film (M is Al, Ga, Y, Zr, La, Ce, or Nd) It is formed of an oxide film.

[0069] In addition, the oxide insulating film 23 or the oxide insulating film 25 provided over the oxide semiconductor film 19a In order to provide a semiconductor device that is a semiconductor substrate, an oxide insulating film containing more oxygen than the oxygen that satisfies the stoichiometric composition is provided. The oxide insulating film containing more oxygen than the oxygen content satisfying the stoichiometric composition is preferably A portion of the oxygen is released by oxidation. The insulating film is a material whose surface temperature is between 100°C and 700°C or less according to TDS analysis. The amount of oxygen released in terms of oxygen atoms during heat treatment at 500°C or higher is 1.0 x 1 0 18 atoms / cm 3More than 3.0×10 20 atoms / cm 3 That's it The insulating film is an oxide insulating film.

[0070] A transistor using an oxide semiconductor film having oxygen vacancies has a threshold voltage This is because the oxide semiconductor This is because oxygen vacancies in the body membrane generate electric charges, resulting in a low resistance. If the transistor has a normally-on characteristic, malfunctions are likely to occur during operation, or Various problems occur, such as high power consumption during operation. This leads to a problem of an increase in the amount of variation in the electrical characteristics of the transistor, typically the threshold voltage. There is.

[0071] However, in the transistor 102 described in this embodiment, The oxide insulating film 23 or the oxide insulating film 25 to be provided is an oxide having a stoichiometric composition. The insulating film can be formed using an oxide insulating film containing more oxygen than silicon. A metal oxide film 27 is provided on the semiconductor film 19a, the oxide insulating film 23, and the oxide insulating film 25. A nitride insulating film 29 is provided on the metal oxide film 27. As a result, the oxide insulating film Oxygen contained in the film 23 or the oxide insulating film 25 efficiently moves to the oxide semiconductor film 19a. In addition, oxygen vacancies in the oxide semiconductor film 19a can be reduced. This can reduce the transfer of water and further hydrogen from the oxide semiconductor film 19a to the oxide semiconductor film 19a. As a result, the transistor has normally-off characteristics. The experiment has demonstrated that it is possible to reduce the amount of variation in the electrical characteristics of a transistor, typically the threshold voltage. can.

[0072] In the capacitor 105, the conductive film 19b is a semiconductor film having a conductivity of 100 to 1000 . This film is formed at the same time, and oxygen vacancies are formed due to plasma damage, etc., making it conductive. Alternatively, the conductive film 19b has the same conductivity as the oxide semiconductor film 19a. It is a film formed at the time of deposition, and its conductivity is enhanced by the inclusion of impurities. Alternatively, the conductive film 19b is a film formed simultaneously with the oxide semiconductor film 19a, In addition to containing impurities, oxygen vacancies are formed due to plasma damage, etc., resulting in high conductivity. It is a membrane that has been

[0073] In the transistor 102, an oxide semiconductor film 19a and a metal oxide film 27 are formed between the oxide semiconductor film 19a and the metal oxide film 27. The insulating films 23 and 25 are formed on the capacitor element 105, but the insulating film 19b is electrically conductive. There is no oxide insulating film 23 or 25 between the metal oxide films 27. The dielectric of 05 is a metal oxide film 27 and a nitride insulating film 29. It is possible to increase the charge capacity of the capacitor 105. In the capacitor 105, a metal oxide film 27 and a nitride insulating film, which are high dielectric materials, are used as dielectrics. By using the insulating film 29, the charge capacity of the capacitor element 105 can be increased.

[0074] The element substrate of the semiconductor device described in this embodiment is The conductive film that functions as a pixel electrode is formed as a capacitor. The other electrode of the element is used. Since the step of forming a film is not required, the manufacturing process can be reduced. As a result, the area occupied by the capacitor element is increased, The aperture ratio of the pixel can be increased.

[0075] The structure of the transistor 102 will be described in detail below.

[0076] 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. In addition, silicon, silicon carbide, etc. may be used. A single crystal semiconductor substrate, a polycrystalline semiconductor substrate, a compound of silicon germanium, etc. It is also possible to use a semiconductor substrate, an SOI substrate, etc., on which a semiconductor element is formed. The substrate 11 may be a glass substrate. When used, 6th generation (1500mm x 1850mm), 7th generation (1870mm x 22 00mm), 8th generation (2200mm x 2400mm), 9th generation (2400mm x 28 By using large area substrates such as 1000mm and 10th generation (2950mm x 3400mm), Therefore, a large display device can be manufactured.

[0077] In addition, a flexible substrate is used as the substrate 11, and the transistor 102 is directly formed on the flexible substrate. Alternatively, a peeling layer may be provided between the substrate 11 and the transistor 102. The release layer is used to separate the semiconductor device from the substrate 11 after a part or whole of the semiconductor device is completed thereon. In this case, the transistor 102 is heat-resistant. It can be transferred to weaker or more flexible substrates.

[0078] The conductive film 13 functioning as the gate electrode is made of aluminum, chromium, copper, tantalum, titanium, etc. A metal element selected from the group consisting of tungsten, molybdenum, and tungsten, or a metal element selected from the group consisting of the above-mentioned metal elements. The metal elements may be alloys of the above metal elements or alloys of the above metal elements. In addition, one or more metal elements selected from manganese and zirconium may be used. The conductive film 13 functioning as the gate electrode may have a single-layer structure or a laminated structure of two or more layers. For example, a single layer structure of an aluminum film containing silicon, an aluminum film on a titanium film, A two-layer structure in which a titanium film is laminated on a titanium nitride film, a two-layer structure in which a titanium film is laminated on a titanium nitride film, Two-layer structure in which a tungsten film is laminated on a tantalum film, a tantalum nitride film or a tungsten nitride film Two-layer structure with tungsten film on top of titanium film, two-layer structure with copper film on top of titanium film, A titanium film is formed on the titanium film, and an aluminum film is laminated on the titanium film. There are also aluminum, titanium, tantalum, tungsten, molybdenum, etc. A film of elements selected from the group consisting of chromium, neodymium, and scandium, or a combination of multiple elements. A gold film or a nitride film may also be used.

[0079] The conductive film 13 functioning as a gate electrode is made of indium tin oxide or tungsten oxide. Indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, titanium oxide Indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, indium zinc oxide A conductive material having light transmitting properties, such as indium tin oxide doped with silicon oxide, is used. In addition, the conductive material having light transmitting properties and the metal element may be laminated. It is also possible.

[0080] The nitride insulating film 15 may be made of the same material as the nitride insulating film 29, as appropriate.

[0081] The thickness of the nitride insulating film 15 is 5 nm or more and 100 nm or less, and more preferably 20 nm or more. It is preferable to set it to 80 nm or less.

[0082] The oxide insulating film 17 is made of, for example, silicon oxide, silicon oxynitride, aluminum oxide, or oxide. Hafnium oxide, gallium oxide, Ga-Zn-based metal oxide, etc. may be used. or in a single layer.

[0083] The oxide insulating film 17 is made of hafnium silicate (HfSiO x ), 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.

[0084] The thickness of the oxide insulating film 17 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.

[0085] The nitride insulating film 15 and the oxide insulating film 17 function as gate insulating films. Only one of the insulating film 15 and the oxide insulating film 17 is covered with the conductive film 13 which functions as a gate electrode. and the oxide semiconductor film 19a to function as a gate insulating film.

[0086] The oxide semiconductor film 19a is typically made of In-Ga oxide, In-Zn oxide, In- Formed using M-Zn oxide (M is Al, Ga, Y, Zr, La, Ce, or Nd) do.

[0087] When the oxide semiconductor film 19a is an In-M-Zn oxide film, the sum of In and M is When the atomic percentage of In is 100 atomic %, the atomic ratio of In and M is preferably 25 atomic %. % and M is less than 75 atomic %, and more preferably In is 34 atomic % or less. tomic%, and M is less than 66 atomic%.

[0088] The oxide semiconductor film 19a has an energy gap of 2 eV or more, preferably 2.5 eV or more. In this way, the oxide semiconductor having a wide energy gap is By using a conductor, the off-state current of the transistor 102 can be reduced.

[0089] The thickness of the oxide semiconductor film 19a is 3 nm to 200 nm, preferably 3 nm to 100 nm. 00 nm or less, and more preferably 3 nm or more and 50 nm or less.

[0090] The oxide semiconductor film 19a is an In-M-Zn oxide film (wherein M is Al, Ga, Y, Zr, La, In the case of In-M-Zn oxide films, the sputtering method used to deposit In-M-Zn oxide films is The atomic ratio of the metal elements in the annealing 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 :1:1, In:M:Zn=1:1:1.2, and In:M:Zn=3:1:2 are preferred. The atomic ratio of the oxide semiconductor film 19a to be formed may be calculated by subtracting the above-mentioned sputtering time from the atomic ratio of the oxide semiconductor film 19a. The atomic ratio of metal elements contained in the target varies by ±40%. .

[0091] As the oxide semiconductor film 19a, an oxide semiconductor film with low carrier density is used. For example, The oxide semiconductor film 19a has a carrier density of 1×10 17 pieces / cm 3 Below, preferably 1 ×10 15 pieces / cm 3 Less than 1×10, more preferably 13 pieces / cm 3 The following is more preferred: 1×10 11 pieces / cm 3 The following oxide semiconductor film is used.

[0092] In addition, the semiconductor characteristics and electrical characteristics (field effect) of the required transistors are not limited to these. It is sufficient to use a material with an appropriate composition according to the required properties (e.g., the resultant mobility, threshold voltage, etc.). In order to obtain semiconductor characteristics of a transistor, the carrier density and impurity of the oxide semiconductor film 19a are controlled. The concentration of metals, defect density, atomic ratio of metal elements to oxygen, interatomic distance, density, etc. are appropriately adjusted. It is preferable.

[0093] Note that the oxide semiconductor film 19a is an oxide semiconductor having a low impurity concentration and a low density of defect states. By using a conductive film, it is possible to fabricate a transistor with even better electrical characteristics. Here, it is preferable that the impurity concentration is low and the defect level density is low (there is little oxygen vacancy). High purity authentic or substantially high purity authentic. High purity authentic or substantially high purity authentic Since the oxide semiconductor has few carrier generation sources, the carrier density can be reduced. Therefore, a transistor in which a channel region is formed in the oxide semiconductor film can be formed. In this case, the threshold voltage becomes negative (also called normally-on). In addition, a highly-purified intrinsic or substantially highly-purified intrinsic oxide semiconductor film has a low defect level. Because of the low density, the trap level density may also be low. The oxide semiconductor film, which is essentially highly pure and intrinsic, has a significantly small off-state current and a channel width of 1×1 0 6 Even if the device has a channel length L of 10 μm, the voltage between the source and drain electrodes is In the drain voltage range of 1V to 10V, the off-state current is Below the measurement limit of the analyzer, i.e. 1×10 -13 You can get a characteristic of A or less. Therefore, the transistor in which the channel region is formed in the oxide semiconductor film has poor electrical characteristics. In some cases, the transistor can have small fluctuations and high reliability. Charges trapped in the trap level take a long time to disappear, just like fixed charges. Therefore, the channel is generated in the oxide semiconductor film having a high density of trap states. The electrical characteristics of the transistor in which the hole region is formed may become unstable. can be hydrogen, nitrogen, an alkali metal, or an alkaline earth metal.

[0094] Hydrogen contained in the oxide semiconductor film reacts with oxygen that is bonded to metal atoms to form water. Oxygen vacancies are formed in the lattice from which oxygen has been removed (or in the portion from which oxygen has been removed). When hydrogen enters the gap, electrons, which act as carriers, can be generated. When it bonds with oxygen, which bonds with metal atoms, it can generate electrons, which act as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen has normally-on characteristics. It is easy to become.

[0095] Therefore, in the oxide semiconductor film 19a, oxygen vacancies and hydrogen are reduced as much as possible. Specifically, it is preferable that the oxide semiconductor film 19a is By SIMS (Secondary Ion Mass Spectrometry) The resulting hydrogen concentration is 5×10 19 atoms / cm 3 Less than or equal to 1×10 1 9 atoms / cm 3 Below, 5 x 10 18 atoms / cm 3 Less than or equal to 1×10 18 atoms / cm 3 Less than or equal to 5×10 17 atoms / cm 3 Below, More preferably, 1×10 16 atoms / cm 3 The following applies.

[0096] The oxide semiconductor film 19a contains silicon or carbon, which is one of the Group 14 elements. As a result, oxygen vacancies increase in the oxide semiconductor film 19a, causing the oxide semiconductor film 19a to become n-type. The concentrations of silicon and carbon in the nitride semiconductor film 19a (obtained by secondary ion mass spectrometry) The concentration of 18 atoms / cm 3 Less than or equal to 2×10 17 atoms / cm 3 The following applies.

[0097] In addition, in the oxide semiconductor film 19a, an alkali metal ion concentration obtained by secondary ion mass spectrometry is The concentration of metal or alkaline earth metal is 1×10 18 atoms / cm 3 The following is preferably is 2 × 10 16 atoms / cm 3 The following are the alkali metals and alkaline earth metals: When a compound is bonded to an oxide semiconductor, carriers may be generated, increasing the off-state current of a transistor. For this reason, the alkali metal or alkali metal in the oxide semiconductor film 19a may become large. It is preferable to reduce the concentration of alkaline earth metals.

[0098] In addition, when the oxide semiconductor film 19a contains nitrogen, electrons that serve as carriers are generated, and The carrier density increases and it becomes easier to make the material n-type. Therefore, the transistor having the oxide semiconductor film tends to be normally on. In this case, it is preferable that the nitrogen content is reduced as much as possible. For example, in the case of secondary ion mass spectrometry, The nitrogen concentration obtained is 5×10 18 atoms / cm 3 It is preferable to do the following: .

[0099] The oxide semiconductor film 19a may have a non-single crystal structure. For example, CAAC-OS (C Axis Aligned-Crystalline Oxide Semiconductor), polycrystalline structure, microcrystalline structure (described later), Among non-single crystal structures, the amorphous structure has the highest defect level density, C AAC-OS has the lowest defect state density.

[0100] The oxide semiconductor film 19a may have, for example, an amorphous structure. For example, the atomic arrangement is disordered and has no crystalline components.

[0101] Note that the oxide semiconductor film 19a may have an amorphous structure, a microcrystalline structure, a polycrystalline structure, or a A mixed film having two or more of the following regions may be used: a region of a CAAC-OS structure, a region of a single crystal structure, and a region of a crystalline structure. The mixed film may have, for example, an amorphous structure region, a microcrystalline structure region, a polycrystalline structure region, a CA In some cases, the crystal structure may have two or more regions, either an AC-OS region or a single crystal structure region. In addition, the mixed film may have, for example, an amorphous structure region, a microcrystalline structure region, a polycrystalline structure region, a CA When the material has a laminated structure of two or more regions of either an AC-OS region or a single crystal structure region There is.

[0102] The conductive film 19b is an oxide semiconductor film formed at the same time as the oxide semiconductor film 19a. Therefore, the conductive film 19b is formed by processing the oxide semiconductor film 19a. The film contains the same metal element. In other words, it contains a material that can become an oxide semiconductor. In addition, the oxide semiconductor film 19a has a crystal structure similar to or different from that of the oxide semiconductor film 19a. However, the oxide semiconductor film formed at the same time as the oxide semiconductor film 19a contains impurities or The oxide semiconductor film has oxygen vacancies, and thus the film 19b has conductivity. The impurity that can be used is hydrogen. Instead of hydrogen, boron, phosphorus, It may contain tin, antimony, rare gas elements, alkali metals, alkaline earth metals, etc. stomach.

[0103] Therefore, both the oxide semiconductor film 19a and the conductive film 19b are formed in the oxide insulating film 1. 7, but has a different impurity concentration. For example, the oxide semiconductor film 19a has a high impurity concentration. The hydrogen concentration is 5×1019 atoms / cm 3 Less than 5 x 10 18 ato ms / cm 3 Less than or equal to 1×10 18 atoms / cm 3 Less than or equal to 5, more preferably ×10 17 atoms / cm 3 Less than 1×10, more preferably 16 atoms / cm 3 The hydrogen concentration in the conductive film 19b is 8×10 19 atoms / cm 3 More than 1×10 20 atoms / cm 3 More preferably, 5×10 20 atoms / cm 3 In addition, the conductivity of the oxide semiconductor film 19a is higher than that of the oxide semiconductor film 19b. The hydrogen concentration in the film 19b is twice as high, preferably 10 times or more.

[0104] In addition, the oxide semiconductor film formed at the same time as the oxide semiconductor film 19a is exposed to plasma. The oxide semiconductor film can be damaged by the above-mentioned reaction, and oxygen vacancies can be formed. For example, When a film is formed on an oxide semiconductor film by plasma CVD or sputtering, the oxide The oxide semiconductor film is exposed to plasma, and oxygen vacancies are generated. In the etching treatment for forming the oxide insulating film 25, the oxide semiconductor film is etched into the plasma. When the oxide semiconductor film is exposed to the oxygen, oxygen vacancies are generated. Alternatively, the oxide semiconductor film becomes a mixture of oxygen and hydrogen. Exposure to plasma of mixed gas, hydrogen, rare gas, ammonia, etc. generates oxygen vacancies. As a result, the conductivity of the oxide semiconductor film becomes high and becomes a conductive film 19b.

[0105] That is, the conductive film 19b can be said to be a highly conductive oxide semiconductor film. The conductive film 19b can also be considered to be a highly conductive metal oxide film.

[0106] In addition, when a silicon nitride film is used as the nitride insulating film 29, the silicon nitride film is hydrogenated. Therefore, hydrogen in the nitride insulating film 29 is formed simultaneously with the oxide semiconductor film 19a. When hydrogen diffuses into the oxide semiconductor film, it bonds with oxygen in the oxide semiconductor film and becomes a carrier The oxygen vacancies in the oxide semiconductor film are filled with electrons in the silicon nitride film. When hydrogen enters the oxide semiconductor, electrons are generated as carriers. The film becomes more conductive, becoming conductive film 19b.

[0107] When hydrogen is added to an oxide semiconductor with oxygen vacancies, hydrogen enters the oxygen vacancy sites. A donor level is formed near the conduction band. As a result, the oxide semiconductor has high electrical conductivity. The oxide semiconductor that has been made conductive can be called an oxide conductor. That is, the conductive film 19b can be said to be formed of an oxide conductive film. In addition, an oxide semiconductor has a large energy gap and therefore transmits visible light. On the other hand, an oxide conductor is an oxide semiconductor that has a donor level near the conduction band. Therefore, the effect of absorption due to the donor level is small, and the absorption of visible light is as strong as that of an oxide semiconductor. It has translucency.

[0108] The conductive film 19b has a lower resistivity than the oxide semiconductor film 19a. The resistivity of the oxide semiconductor film 19b is 1×10 -8 more than 1x10 -1 It is preferable that the ratio is less than 1×10 -3 Ωcm or more 1×10 4 Less than Ωcm , and more preferably, the resistivity is 1×10 -3 Ωcm or more 1×10 -1 Less than Ωcm good.

[0109] The conductive films 21a and 21b functioning as a pair of electrodes are made of aluminum, titanium, chromium, Nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, or tungsten A single metal made of stainless steel or an alloy containing stainless steel as the main component is used in a single-layer structure or a multi-layer structure. For example, a single layer structure of aluminum film containing silicon, aluminum on titanium film, Two-layer structure with a tungsten film on top of an aluminum film; two-layer structure with a copper film on top of a tungsten film; A two-layer structure in which a copper film is laminated on a magnesium-aluminum alloy film, and a copper film is laminated on a titanium film Two-layer structure with copper film on tungsten film, two-layer structure with titanium film or titanium nitride film A titanium film or titanium nitride film is laminated with an aluminum film or a copper film. a three-layer structure in which a titanium film or a titanium nitride film is formed on the first layer; Molybdenum nitride film and aluminum layer on the molybdenum film or molybdenum nitride film A molybdenum film or a molybdenum nitride film is then formed on the copper film. There are three-layer structures. Transparent conductive materials containing indium oxide, tin oxide, or zinc oxide are used. It may be used.

[0110] The oxide insulating film 23 or the oxide insulating film 25 contains oxygen having a stoichiometric composition. It is preferable to use an oxide insulating film containing a lot of oxygen. Then, an oxide insulating film that transmits oxygen is formed. An oxide insulating film containing more oxygen than the oxygen that satisfies the condition is formed.

[0111] The oxide insulating film 23 is an oxide insulating film that transmits oxygen. The oxygen desorbed from the oxide insulating film 25 provided on the oxide insulating film 23 is absorbed through the oxide insulating film 23. The oxide insulating film 23 can be transferred to the oxide semiconductor film 19a. The oxide insulating film 25 may also serve as a film for reducing damage to the oxide semiconductor film 19a when the oxide insulating film 25 is formed. It works.

[0112] 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. In the present specification, a silicon oxynitride film is a film having a higher oxygen content than nitrogen as a composition. A silicon nitride oxide film is a film that contains more nitrogen than oxygen. Refers to a large membrane.

[0113] In addition, the number of defects at the interface between the oxide insulating film 23 and the oxide semiconductor film 19a is small. is preferable. Typically, the ESR measurement shows that the oxide semiconductor film 19a has a defect-derived g The spin density of the signal that appears with a value between 1.89 and 1.96 is 1×10 17 spins / c m 3 It is preferably below the lower detection limit.

[0114] Note that in the oxide insulating film 23, all of the oxygen that has entered the oxide insulating film 23 from the outside is In some cases, the oxide insulating film 23 may move to the outside. In some cases, part of the oxygen remains in the oxide insulating film 23. As oxygen enters the oxide insulating film 23, the oxygen contained in the oxide insulating film 23 flows out of the oxide insulating film 23. The movement of oxygen may cause the movement of oxygen in the oxide insulating film 23 in some cases.

[0115] An oxide insulating film 25 is formed so as to be in contact with the oxide insulating film 23. The oxide insulating film 25 is 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 formed by heating. Heat causes some of the oxygen to be released. Acids that contain more oxygen than is required for the stoichiometric composition The oxide insulating film is a material whose surface temperature is between 100°C and 700°C or between 10 The amount of oxygen released in terms of oxygen atoms during heat treatment at 0°C to 500°C is 1.0 x 10 18 atoms / cm 3 More than 3.0×10 20 atoms / cm 3 End The oxide insulating film is

[0116] The oxide insulating film 25 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.

[0117] In addition, the oxide insulating film in which the oxide insulating film 23 and the oxide insulating film 25 are stacked has a defect amount The oxide insulating film with few defects is measured at ESR of 100K or less. In the obtained spectrum, the first signal, g A second signal with a g value between 2.001 and 2.003, and a second signal with a g value between 1.964 and 1.9 A third signal of 66 or less is observed. Also, the g value is between 2.037 and 2.039. Up to 1.964 to 1.966 spin density is 1×10 18 spins / cm 3 is less than 1×10 17 spins / cm 3 More than 1×10 18 spins / cm 3 In the ESR spectrum below 100K, the g value is 2.037 or less. The first signal is below 2.039, the second signal is above 2.001 and below 2.003. The third signal with a g value between 1.964 and 1.966 is nitrogen oxide (NO x (x is 0 to 2, preferably 1 to 2) corresponds to a signal caused by nitrogen oxides. Representative examples include nitrogen monoxide and nitrogen dioxide. That is, the g value is 2.037 or more. The lower the spin density, the greater the oxide density. It can be said that the content of nitrogen oxides in the insulating film is small.

[0118] In this embodiment, a plurality of oxide insulating films are provided between the oxide semiconductor film 19a and the metal oxide film 27. Although the oxide insulating film 23 and the oxide insulating film 25 are provided, only one of the oxide insulating film 23 and the oxide insulating film 25 may be provided. stomach.

[0119] Since the metal oxide film 27 is provided on the oxide insulating film 25, As a result, oxygen contained in the oxide insulating film 25 is efficiently The amount of oxygen vacancies in the oxide semiconductor film is reduced by the oxygen vacancies in the oxide semiconductor film. This can be done.

[0120] An oxide semiconductor film 19a and an oxide insulating film 29 are formed on the inner side of the nitride insulating film 15 and the nitride insulating film 29. The insulating films 23 and 25 are provided to prevent water from entering the oxide semiconductor film 19a from the outside. Furthermore, hydrogen migration can be reduced.

[0121] The conductive film 31 is a light-transmitting conductive film. Indium oxide film containing tungsten oxide, indium zinc oxide film containing tungsten oxide, Indium oxide film containing titanium oxide, indium tin oxide film containing titanium oxide, Indium tin oxide (ITO) film, indium zinc oxide film, silicon oxide film Examples of such a thin film include an indium tin oxide film.

[0122] The conductive film 31 may be formed in a comb shape or a shape having slits 31b. A cross-sectional view of the case is shown in FIG. 29. By making the conductive film 31 in this layout, The liquid crystal can be driven in PS mode or FFS mode. A top view of the conductive film 31 with the lit 31b is shown in FIG. Depending on the situation, the LCD can also be driven in VA mode.

[0123] Next, a method for manufacturing the transistor 102 and the capacitor 105 shown in FIG. This will be explained with reference to FIG.

[0124] As shown in FIG. 4A, a conductive film 12 that will become a conductive film 13 is formed on a substrate 11. The film is formed by a sputtering method, a CVD method, a vapor deposition method or the like.

[0125] In this embodiment, a glass substrate is used as the substrate 11. The conductive film 12 is a 100 mm thick film. A tungsten film with a thickness of nm is formed by sputtering.

[0126] Next, a mask is formed on the conductive film 12 by a photolithography process using a first photomask. Next, a part of the conductive film 12 is etched using the mask, as shown in FIG. As shown in FIG. 1, a conductive film 13 that functions as a gate electrode is formed. After that, the mask is removed. Remove.

[0127] The conductive film 13 functioning as the gate electrode may be formed by electrolytic plating instead of the above-mentioned method. The conductive layer may be formed by a method such as a printing method or an ink jet method.

[0128] Here, the tungsten film is etched by dry etching to form a gate electrode. Then, a conductive film 13 that functions as a conductive film is formed.

[0129] Next, as shown in FIG. 4(C), a nitride insulating film is formed on the conductive film 13 which functions as a gate electrode. Then, the insulating film 15 and the oxide insulating film 16 that will later become the oxide insulating film 17 are formed. On the insulating film 16, an oxide semiconductor film 19a and an oxide semiconductor film 19b having electrical conductivity are formed. A film 18 is formed.

[0130] The nitride insulating film 15 and the oxide insulating film 16 are formed by sputtering, CVD, deposition, or the like. Form.

[0131] Here, we used the plasma CVD method with silane, nitrogen, and ammonia as raw material gases. As the nitride insulating film 15, a silicon nitride film having a thickness of 300 nm is formed.

[0132] The oxide insulating film 16 may be 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.

[0133] When a gallium oxide film is formed as the oxide insulating film 16, MOCVD (Metal O Formed using the organic chemical vapor deposition (OCVD) method It is possible.

[0134] Here, we used the plasma CVD method with silane and dinitrogen monoxide as raw material gases to oxidize As the insulating film 16, a silicon oxynitride film having a thickness of 50 nm is formed.

[0135] The oxide semiconductor film 18 can be formed by a sputtering method, a coating method, a pulsed laser deposition method, a laser deposition method, or the like. It can be formed by using an ablation method or the like.

[0136] When an oxide semiconductor film is formed by a sputtering method, a power source for generating plasma The device may be an RF power supply device, an AC power supply device, a DC power supply device, or the like, as appropriate.

[0137] 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 because it is easy to form a CAAC-OS, which will be described later.

[0138] The target may be appropriately selected depending on the composition of the oxide semiconductor film to be formed. .

[0139] 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.

[0140] Here, an In-Ga-Zn oxide (hereinafter referred to as IGZO) target (In:G A 3 mm thick oxide semiconductor film was formed by sputtering using a ZnO film (a:Zn=1:1:1). A 5 nm thick In-Ga-Zn oxide film is formed.

[0141] Next, a photolithography process using a second photomask is performed on the oxide semiconductor film 18. After a mask is formed by etching, part of the oxide semiconductor film is etched using the mask. As a result, element-isolated oxide semiconductor films 19a and 19c are formed as shown in FIG. After that, the mask is removed.

[0142] Here, a mask is formed over the oxide semiconductor film, and the oxide semiconductor film is etched by a wet etching method. By selectively etching a portion of the conductor film 18, oxide semiconductor films 19a and 19c are formed. Complete.

[0143] Next, as shown in FIG. 5(A), conductive film 2 which will later become conductive films 21a, 21b, and 21c is formed. Form 0.

[0144] The conductive film 20 is formed by a sputtering method, a CVD method, a vapor deposition method, or the like.

[0145] Here, a tungsten film with a thickness of 50 nm and a copper film with a thickness of 300 nm are sputtered in this order. The layers are laminated by a coating method.

[0146] Next, a mask is formed on the conductive film 20 by a photolithography process using a third photomask. Next, the conductive film 20 is etched using the mask to form a mask as shown in FIG. In this way, the conductive films 21a and 21b function as a pair of electrodes, and the conductive film 21b functions as a capacitance line. The film 21c is then formed, and the mask is then removed.

[0147] Here, a mask is formed on the copper film by a photolithography process. The tungsten film and the copper film are etched using a quartz crystal to form the conductive films 21a, 21b, and 21c. The copper film is then etched using a wet etching method. 6 of The tungsten film is etched by the dry etching method used. In the process, fluorides are formed on the surface of the copper film. The fluorides remove copper elements from the copper film. As a result, the copper concentration in the oxide semiconductor film 19a can be reduced.

[0148] Next, as shown in FIG. 5C, the oxide semiconductor films 19a and 19c and the conductive film 21a, On 21b and 21c, an oxide insulating film 22 which will later become an oxide insulating film 23 and an oxide insulating film 24 which will later become an oxide insulating film 25 are formed. An oxide insulating film 24 that will become an insulating film 25 is formed.

[0149] After the oxide insulating film 22 is formed, the oxide insulating film 2 is continuously removed without being exposed to the air. After the oxide insulating film 22 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 22 and the oxide insulating film 24 in the In addition, the impurity concentration in the oxide insulating film 24 can be reduced. The amount of oxygen vacancies in the oxide semiconductor film 19a can be reduced. It can be reduced.

[0150] The oxide insulating film 22 is placed in a vacuum-evacuated processing chamber of a plasma CVD apparatus. The substrate is maintained at a temperature of 280° C. or higher and 400° C. or lower, and a source gas is introduced into the processing chamber. The pressure in the chamber is set to 20 Pa or more and 250 Pa or less, and more preferably 100 Pa or more and 250 Pa or less. Under the conditions below, a silicon oxide film is formed by supplying high frequency power to an electrode provided in the processing chamber. Alternatively, a silicon oxynitride film can be formed.

[0151] As the source gas for the oxide insulating film 22, 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.

[0152] By using the above conditions, an oxide insulating film that transmits oxygen is formed as the oxide insulating film 22. In addition, by providing the oxide insulating film 22, the oxide insulating film to be formed later can be formed. In the formation step of 25, damage to the oxide semiconductor film 19a can be reduced.

[0153] The oxide insulating film 22 is placed in a processing chamber of a plasma CVD apparatus that has been evacuated to a vacuum. The substrate is maintained at a temperature of 280° C. or higher and 400° C. or lower, and a source gas is introduced into the processing chamber. The pressure in the treatment chamber is set to 100 Pa or more and 250 Pa or less, and high-frequency power is applied to the electrode installed in the treatment chamber. Depending on the conditions for supplying the silicon oxide film or the silicon oxynitride film, a silicon oxide film or a silicon oxynitride film can be formed. do.

[0154] Under the film formation conditions, by setting the substrate temperature to the above temperature, the bonding strength between silicon and oxygen As a result, the oxide insulating film 22 is oxygen-permeable, dense, and hard. Oxide insulating film, typically etched using 0.5% by weight hydrofluoric acid at 25°C. A silicon oxide film or an oxide film having a dipping speed of 10 nm / min or less, preferably 8 nm / min or less. A silicon nitride film can be formed.

[0155] In addition, since the oxide insulating film 22 is formed while heating, the oxide semiconductor Hydrogen, water, and the like contained in the oxide semiconductor film 19a can be desorbed. The hydrogen contained in the oxide film combines with oxygen radicals generated in the plasma to form water. In the deposition process of step 2, the substrate is heated, and oxygen and hydrogen are combined to form Water is desorbed from the oxide semiconductor film. By forming the oxide semiconductor film 19a, the amount of water and hydrogen contained in the oxide semiconductor film 19a can be reduced. can be done.

[0156] In addition, since heating is performed in the process of forming the oxide insulating film 22, the oxide semiconductor film 19a The heating time in the exposed state is short, and oxygen is removed from the oxide semiconductor film by the heat treatment. That is, the amount of oxygen vacancies in the oxide semiconductor film can be reduced. It is possible.

[0157] Here, the oxide insulating film 22 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 is transmitted can be formed.

[0158] 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 2 Under the following conditions of high frequency power supply, silicon oxide film or oxide A silicon nitride film is formed.

[0159] 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.

[0160] 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 oxidation of the source gas proceeds, the oxygen content in the oxide insulating film 24 becomes lower than the stoichiometric ratio. On the other hand, in the film formed at the above substrate temperature, the bonds between silicon and oxygen Because the combined force is weak, some of the oxygen in the film is released by the heat treatment in the subsequent process. An acid that contains more oxygen than satisfies the stoichiometric composition and loses some of the oxygen when heated. In addition, an oxide insulating film 22 can be formed on the oxide semiconductor film 19a. Therefore, in the step of forming the oxide insulating film 24, the oxide insulating film 22 This serves as a protective film for the oxide semiconductor film 19a. The oxide insulating film 24 can be formed by using high-frequency power with high power density while reducing the can.

[0161] 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 It is.

[0162] In addition, when forming the conductive films 21a and 21b that function as a pair of electrodes, The oxide semiconductor film 19a is damaged by the etching, and the back surface of the oxide semiconductor film 19a is A channel (the oxide semiconductor film 19a facing the conductive film 13 functioning as a gate electrode) However, oxygen vacancies occur on the surface opposite to the surface on which the oxide insulating film 24 is stoichiometrically structured. By using an oxide insulating film containing more oxygen than the oxygen that satisfies the composition requirement, This makes it possible to repair the oxygen vacancies that have occurred on the back channel side. Since the defects contained in the semiconductor film 19a can be reduced, the reliability of the transistor 102 can be improved. It is possible to improve the performance.

[0163] Next, a photolithography process using a fourth photomask is performed on the oxide insulating film 24. Next, the oxide insulating film 22 and the oxide insulating film 24 are formed using the mask. 5(D), the oxide insulating film 23 and the oxide insulating film 24 are left. 25 is formed. After this, the mask is removed.

[0164] In this step, the oxide insulating film 22 and the oxide insulating film 2 As a result, the oxide semiconductor film 19c is Since the oxide semiconductor film 19c is exposed to plasma during the etching process, oxygen vacancies in the oxide semiconductor film 19c may increase. It is possible.

[0165] As shown in the cross-sectional view of AB, the oxide semiconductor film 19a The oxide insulating film 23 and the oxide insulating film 25 are arranged so that their ends are located outside the CD As shown in the cross-sectional view of FIG. 1, an oxide semiconductor film 19a is formed on the outer side of the oxide semiconductor film 19a in the channel width direction. The oxide insulating film 22 and the oxide insulating film 25 are arranged so that the ends of the insulating film 23 and the oxide insulating film 25 are located. As a result, the oxide insulating film 23 and the oxide insulating film 24 are separated. In addition, the oxide insulating film 22 and the oxide insulating film 24 can be formed. During the etching, a part of the oxide insulating film 16 is also etched, and an oxide insulating film 17 is formed. As a result, the nitride insulating film 15 is exposed.

[0166] Next, a heat treatment is performed. The temperature of the heat treatment is typically 150° C. or higher and 400° C. or lower. The temperature is preferably 300°C or higher and 400°C or lower, and more preferably 320°C or higher and 370°C or lower.

[0167] The heat treatment can be performed using an electric furnace, an RTA device, or the like. Therefore, heat treatment can be performed at a temperature above the distortion point of the substrate for a short period of time. The processing time can be reduced.

[0168] Heat treatment is carried out in a vacuum of nitrogen, oxygen, or ultra-dry air (water content of 20 ppm or less, preferably 1 ppm). pm or less, preferably 10 ppb or less air), or rare gases (argon, helium, etc.) In addition, the above-mentioned nitrogen, oxygen, ultra-dry air, or rare gas may be mixed with hydrogen, water, or the like. It is preferable that the above is not included.

[0169] By this heat treatment, part of oxygen contained in the oxide insulating film 25 is oxidized to the oxide semiconductor film 19a Thus, the amount of oxygen vacancies in the oxide semiconductor film 19a can be reduced.

[0170] When the oxide insulating film 23 and the oxide insulating film 25 contain water, hydrogen, or the like, the nitride insulating film When heat treatment is performed after the insulating film 29 is formed, the oxide insulating film 23 and the oxide insulating film 25 are Water, hydrogen, and the like contained in the oxide semiconductor film 19a move to the oxide semiconductor film 19a, and defects are generated in the oxide semiconductor film 19a. However, the oxide insulating film 23 and the oxide insulating film 25 are heated. The water, hydrogen, and the like contained in the semiconductor device can be eliminated, and the electrical characteristics of the transistor 102 can be improved. This reduces the variation and suppresses the fluctuation of the threshold voltage.

[0171] The oxide insulating film 24 is formed on the oxide insulating film 22 while being heated. The oxygen is transferred to the oxide semiconductor film 19a, and oxygen vacancies in the oxide semiconductor film 19a are reduced. Therefore, the heat treatment may not be performed.

[0172] The heat treatment forms the oxide insulating film 22 and the oxide insulating film 24 shown in FIG. Alternatively, the oxide insulating film 23 and the oxide insulating film 25 shown in FIG. In the case of the heat treatment after the formation, oxygen does not move to the oxide semiconductor film 19c. Since the oxide semiconductor film 19c is exposed, oxygen is released from the oxide semiconductor film 19c. As a result, the conductivity of the conductive film 19b to be formed later is improved. This is preferable because it is possible to increase the

[0173] Here, the heat treatment is performed in a mixed gas atmosphere of nitrogen and oxygen at 350° C. for 1 hour.

[0174] Next, as shown in FIG. 6(A), the nitride insulating film 15, the oxide semiconductor film 19c, and the oxide insulating film 19b are An insulating film 17, an oxide insulating film 23, an oxide insulating film 25, and a conductive film 21 functioning as a pair of electrodes. A metal film 26 is formed on the conductive films 21a, 21b and 21c.

[0175] The metal film 26 is a metal oxide that has a light transmitting property and a low oxygen permeability when oxidized. It is preferable to use a metal film or a metal nitride film as the film. Representative examples of the metal film include aluminum and Gallium, yttrium, hafnium, titanium, tantalum, tantalum nitride, etc. are used. The metal film 26 is formed by sputtering, vapor deposition or the like.

[0176] The thickness of the metal film 26 is 0.5 nm to 50 nm, and the average thickness is 2 nm to 10 nm. By making the metal film 26 have the above thickness, it is possible to prevent the metal film 26 from being damaged during the subsequent oxygen introduction process. In this process, the entire metal film 26 can be oxidized. Oxygen can be introduced into one or more of the film 23 and the oxide insulating film 25 .

[0177] Next, oxygen O * is introduced to oxidize the metal film 26, resulting in the structure shown in FIG. As shown in the figure, a metal oxide film 26a is formed. For example, aluminum is used as the metal film 26. When this is used, an aluminum oxide film is formed as the metal oxide film 26a. In this case, nitrogen may be introduced together with oxygen to form a metal oxide nitride film.

[0178] The method of introducing oxygen into the metal film 26 includes ion implantation, ion doping, and plasma. In addition, oxygen is introduced by treating the entire surface of the substrate 11 at once. Alternatively, for example, a linear ion beam may be used. In this case, the substrate 11 or the ion beam is moved (scanned) relatively to remove the metal. Oxygen can be introduced to the entire surface of the film 26. The oxygen introduction process is performed while heating. It is also possible.

[0179] Representative examples of oxygen introduced into the metal film 26 include oxygen radicals, ozone, and oxygen atoms. Oxygen can also be produced by gases that contain oxygen. Representative examples of gases that contain oxygen include oxygen gas, nitrous oxide gas, nitrogen dioxide gas, and ozone. Gases containing oxygen include hydrogen gas, water vapor, and mixed gases of oxygen and hydrogen. An inert gas such as nitrogen or a rare gas may be introduced.

[0180] When oxygen is introduced by ion implantation, the dose of oxygen is 1×10 13 ions / cm 2 5×10 or more 16 ions / cm 2 It is preferable that such a dough be as follows: By adjusting the amount of the shift, the oxide insulating film 23 or the oxide insulating film 25 can contain more oxygen. It is possible to increase the amount.

[0181] In addition, when oxygen is introduced in the plasma treatment, the oxygen in the oxygen plasma is introduced into the metal film 26. The introduction of oxygen in plasma processing is done by plasma CVD equipment and dry etching equipment. In addition, when using a plasma processing apparatus, It is preferred to apply a bias to the support or electrode on which the plate 11 is mounted. Oxygen having energy, typically oxygen molecular ions, oxygen atomic ions, etc., are introduced to the substrate 11 side. This allows the amount of oxygen introduced into the metal film 26 to be increased. .

[0182] In addition, when oxygen is introduced in plasma processing, the oxygen is excited by microwaves to form a high-density oxygen plasma. The generation of the turbulence promotes the oxidation of the metal film 26, forming a dense metal oxide film 26a. At the same time, the amount of oxygen introduced into one or more of the oxide insulating film 23 and the oxide insulating film 25 is increased. In addition, when oxygen is excited by microwaves to generate high-density oxygen plasma, The introduction of oxygen is performed on the oxide semiconductor film 19a, the oxide semiconductor film 19c, the oxide insulating film 23, and the oxide semiconductor film 19b. A temperature at which oxygen is not released from the oxide insulating film 25 is typically 250° C. or lower, preferably 2 It is preferable to carry out the reaction at a temperature of 00°C or lower.

[0183] In addition, the throughput can be improved by introducing oxygen into the metal film 26 in the plasma treatment. It is possible.

[0184] By introducing oxygen into the metal film 26 formed on the substrate 11, a metal oxide film 26a is formed. Therefore, it is possible to prevent the generation of particles in the process of forming the metal oxide film 26a. It is possible to increase the yield. After the film is formed, oxygen is introduced into the metal film to form a metal oxide film, making it suitable for mass production. As the capacity of semiconductor devices increases, it becomes possible to manufacture semiconductor devices using large-area substrates.

[0185] After this, a heat treatment may be performed. The heat treatment can be used to convert the metal oxide film 26a into a metal oxide film. This makes it possible to strengthen the bond between the electrons and oxygen, and in the subsequent heat treatment, the oxide insulation This can suppress oxygen desorption from the film 22 and the oxide insulating film 24. The temperature is 300°C or higher and 500°C or lower, preferably 400°C or higher and 450°C or lower.

[0186] Next, as shown in FIG. 6(B), a layer that will later become a nitride insulating film 29 is formed on the metal oxide film 26a. A nitride insulating film 28 is formed.

[0187] The nitride insulating film 28 is formed by a sputtering method, a CVD method, or the like.

[0188] The oxide semiconductor film 19c becomes the conductive film 19b. 28, when a silicon nitride film is formed by the plasma CVD method, The hydrogen contained in the oxide semiconductor film 19c diffuses into the oxide semiconductor film 19b, forming a film 19b having higher conductivity. It is possible.

[0189] 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 The nitride insulating film 28 was formed by the plasma CVD method, in which 1000 MW of high frequency power was supplied to parallel plate electrodes. The plasma CVD device has an electrode area of ​​50 nm. 6000cm 2 This is a parallel plate type plasma CVD device, and the power supplied is This is converted to power per unit (power density) of 1.7 x 10 -1 W / cm 2 It is.

[0190] Next, a heat treatment may be performed. The temperature of the heat treatment is typically 150° C. or higher and 40° C. or lower. 0°C or lower, preferably 300°C or higher and 400°C or lower, preferably 320°C or higher and 370°C or lower Note that in this heat treatment, a metal film is formed over the oxide insulating film 23 and the oxide insulating film 25. Since the oxide film 27 is provided, the oxide insulating film 23 or the oxide insulating film 25 The oxygen in the oxide semiconductor film 19a is efficiently transferred to the oxide semiconductor film 19a, and oxygen vacancies in the oxide semiconductor film 19a are eliminated. As a result, the negative shift of the threshold voltage can be reduced. In addition, the amount of variation in the threshold voltage can be reduced.

[0191] In addition, in the case where hydrogen is contained in the nitride insulating film 28, the nitride insulating film The hydrogen contained in 28 moves to the conductive film 19b, and the conductive film 19b This is preferable because it further enhances the stability.

[0192] Next, a fifth photomask is used to form a photoresist film on the nitride insulating film 28. After forming a mask, the metal oxide film 26a and the nitride insulating film 28 are formed using the mask. 6(C), the metal oxide film 27 and the A nitride insulating film 29 is formed.

[0193] Next, as shown in FIG. 7A, a conductive film 21b and a nitride insulating film 29 are formed on the conductive film 21b. A conductive film 30 that will become 31 is formed.

[0194] The conductive film 30 is formed by a sputtering method, a CVD method, a vapor deposition method, or the like.

[0195] Next, a mask is formed on the conductive film 30 by a photolithography process using a sixth photomask. Next, a part of the conductive film 30 is etched using the mask, as shown in FIG. ) the conductive film 31 is formed, and then the mask is removed.

[0196] Through the above steps, the transistor 102 and the capacitor 105 are manufactured. It is possible.

[0197] In this embodiment, after a metal film is formed, oxygen is introduced into the metal film to form a metal oxide film. This allows the formation of a metal oxide film while preventing the generation of particles. Therefore, semiconductor devices can be manufactured with high yield.

[0198] In addition, the transistor described in the embodiment has a structure in which more oxygen than oxygen that satisfies the stoichiometric composition is contained. Since a metal oxide film with low oxygen permeability is formed on an oxide insulating film containing silicon, the oxide insulating film It is possible to prevent the oxygen contained in the film from diffusing to the outside. As a result, the oxide insulation The oxygen contained in the insulating film is efficiently transferred to the oxide semiconductor film, and the oxygen contained in the oxide semiconductor film is The amount of elemental deficiency can be reduced.

[0199] In addition, an oxide semiconductor film is included inside the plurality of nitride insulating films. The nitride insulating film prevents the transfer of water, hydrogen, and the like to the oxide semiconductor film. The amount of water, hydrogen, etc. contained in the nitride semiconductor film can be reduced.

[0200] As described above, a transistor having normally-off characteristics can be manufactured. In addition, the electrical characteristics of transistors, typically the threshold voltage, change over time or due to stress testing. It is possible to manufacture a transistor in which the amount of voltage fluctuation is reduced.

[0201] In addition, the element substrate of the semiconductor device described in this embodiment is a semiconductor substrate including an oxide semiconductor film of a transistor. At the same time, one electrode of the capacitor element is formed. The other electrode of the capacitor is used. Since a step of forming a conductive film on the pair of electrodes is not required, the manufacturing steps can be reduced. As a result, the area occupied by the capacitor element is increased. At the same time, the aperture ratio of the pixel can be increased.

[0202] As described above, a semiconductor device including an oxide semiconductor film has improved electrical characteristics. can be obtained.

[0203] <Variation 1> Here, a modification of the metal oxide film 27 shown in the first embodiment will be described with reference to FIG. do.

[0204] FIG. 8 is a top view of a pixel 103, in which the structure of a transistor 102 is indicated by a dashed line, and a metal oxide The oxide film 27 is shown by hatching.

[0205] As shown in FIG. 8A, the metal oxide film 27 can be formed on the entire surface of the pixel 103. As a result, oxygen contained in the oxide insulating film 23 or the oxide insulating film 25 moves to the outside. As a result, oxygen vacancies in the oxide semiconductor film 19a can be reduced. It is possible.

[0206] Alternatively, as shown in FIG. 8B, in the pixel 103, the separated metal oxide film 27 In the step shown in FIG. 6(A), the thickness of the metal film 26 is thinned. By reducing the thickness of the metal oxide film, it is possible to form the separated metal oxide films 27a and 27b. After forming a metal oxide film on the entire surface of the pixel 103, a part of the metal oxide film is removed, Separate metal oxide films 27a, 27b can be formed.

[0207] The separated metal oxide film may have a small thickness, such as a metal oxide film 27b shown in FIG. 8(B). At least, it is preferable that the oxide insulating film be provided over the transistor 102. It is possible to prevent oxygen contained in the oxide insulating film 23 or the oxide insulating film 25 from moving to the outside. As a result, oxygen vacancies in the oxide semiconductor film 19a can be reduced.

[0208] The separated metal oxide film is a metal oxide film 27a shown in FIG. It is preferable that the capacitor elements 105 are formed on the entire surface of the region. It is possible to reduce the variation in the charge capacity of the semiconductor device.

[0209] Here, the metal oxide film 27 has been described using a top view of the pixel 103. It is also possible to form metal oxide films of similar shape on the road.

[0210] <Variation 2> A modification of the semiconductor device shown in the first embodiment is shown in FIG.

[0211] The semiconductor device shown in FIG. 9 is different from the semiconductor device shown in FIG. The order of forming the nitride insulating film 15, the oxide insulating film 17, A conductive film 19b, conductive films 21a and 21b functioning as a pair of electrodes, and a conductive film 21 c, a nitride insulating film 29 is formed over the oxide insulating film 23 and the oxide insulating film 25, and the nitride insulating film 29 is A metal oxide film 27 is formed on the insulating film 29. A conductive film 3 serving as a pixel electrode is also formed on the insulating film 29. 1 is formed on the metal oxide film 27.

[0212] In the semiconductor device shown in FIG. 9, the conductive film 19b included in the capacitance element 105 is , and contacts the nitride insulating film 29. Also, between the conductive film 19b and the metal oxide film 27 2, the nitride insulating film 29 is formed. In the oxygen introduction step, the amount of oxygen introduced into the conductive film 19b can be reduced. As a result, the conductivity of the conductive film 19b can be further increased.

[0213] In addition, in the oxygen introduction step performed in the step of forming the metal oxide film 27, a pair of The conductive films 21a, 21b, and 21c functioning as electrodes are covered with a nitride insulating film 29. Therefore, the conductive films 21a, 21b and 21c functioning as a pair of electrodes are As a result, the conductive films 21a and 21b functioning as a pair of electrodes can be prevented from being oxidized. b and the conductive film 21c can be prevented from increasing in resistance.

[0214] As a result, in a semiconductor device formed using a large area substrate, it is possible to reduce wiring delay. It is possible.

[0215] <Variation 3> A modification of the semiconductor device shown in the first embodiment is shown in FIG.

[0216] The semiconductor device shown in FIG. 10 is different from the semiconductor device shown in FIG. The difference is that it is not formed over the entire surface of plate 11, but only over transistor 102.

[0217] In this semiconductor device, after the oxide insulating film 24 is formed as shown in FIG. 6(A) is formed. Next, oxygen is introduced into the metal film 26 to form a metal An oxide film 26 a is formed on the oxide insulating film 24 .

[0218] Next, a mask is formed on the metal oxide film by a photolithography process, and the mask is The oxide insulating film 22, the oxide insulating film 24, and the metal oxide film 26a are etched using a As a result, the oxide insulating film 23, the oxide insulating film 25, and the metal oxide insulating film 26 are formed as shown in FIG. A nitride film 27 can be formed.

[0219] After that, the nitride insulating film 29 and the conductive film 31 are formed.

[0220] In the semiconductor device shown in FIG. 10, a metal oxide film 27 is formed on a transistor 102. Therefore, oxygen vacancies in the oxide semiconductor film 19a can be reduced. As a result, oxygen contained in the oxide insulating film is efficiently transferred to the oxide semiconductor film, and the oxide semiconductor The amount of oxygen vacancies in the film can be reduced.

[0221] <Variation 4> A modification of the semiconductor device shown in the first embodiment is shown in FIG.

[0222] The semiconductor device shown in FIG. 11 is different from the semiconductor device shown in FIG. Note that the oxide insulating film 25 has a stoichiometric composition. It is described that the insulating film is formed of an oxide insulating film containing more oxygen than oxygen.

[0223] In this semiconductor device, as shown in FIG. 5C, an oxide insulating film 22 is formed, and then an oxide A mask is formed on the oxide insulating film 22 by a photolithography process. The oxide insulating film 22 is etched using the etching agent, to obtain the oxide insulating film 22 shown in FIG. Next, the metal oxide film 23 is formed through the steps shown in FIG. 7, a nitride insulating film 29 and a conductive film 31 are formed.

[0224] In the semiconductor device shown in FIG. 11, an oxygen layer having a stoichiometric composition is formed on the oxide insulating film 23. However, the oxide insulating film containing more oxygen than the metal oxide film 27 is not formed. In the step of forming the metal film 26, oxygen is introduced into the metal film 26. In addition, oxygen can be introduced into the oxide insulating film 23. The oxygen introduced into the oxide semiconductor film 19a is moved to the oxide semiconductor film 19a. In addition, the oxide semiconductor film 19a can reduce oxygen vacancies. In this modification, however, an oxide semiconductor film 19a is provided on the oxide semiconductor film 19a. Since the oxide insulating film 23 is formed, the defect level at the interface can be reduced. As a result, it is possible to reduce the variation in the threshold voltage of the transistor.

[0225] <Variation 5> A modification of the semiconductor device shown in the first embodiment is shown in FIG.

[0226] Here, the number of defects in the oxide semiconductor film is further reduced compared to the semiconductor device shown in FIG. A semiconductor device having a transistor capable of implementing the present invention will be described with reference to the drawings. The transistor described in the embodiment has a multi-layer structure in which an oxide semiconductor film is formed, as compared with the semiconductor device shown in FIG. The difference is that a multilayer film having a number of layers is provided.

[0227] 12 is a cross-sectional view of an element substrate of a semiconductor device. -B is a cross-sectional view between B and C.

[0228] The transistor 102a illustrated in FIG. 12A includes the nitride insulating film 15 and the oxide insulating film 17. A multilayer film 37a overlaps the conductive film 13 that functions as a gate electrode through the intermediation of the multilayer film 37a. The nitride insulating film has a pair of conductive films 21a and 21b that function as electrodes in contact with the nitride insulating film. The oxide insulating film 17, the multilayer film 37a, and the conductive film 21 functioning as a pair of electrodes On the a and b, an oxide insulating film 23, an oxide insulating film 25, a metal oxide film 27, and a nitride A material insulating film 29 is formed.

[0229] The capacitor element 105b shown in FIG. 12A includes a multilayer film 37 formed on an oxide insulating film 17. b, the metal oxide film 27 in contact with the multilayer film 37b, and the nitride insulating film 27 in contact with the metal oxide film 27. The multilayer film 37b has a nitride insulating film 29 and a conductive film 31 in contact with the nitride insulating film 29. The conductive film 21c functions as a wiring.

[0230] In the transistor 102b described in this embodiment, the multilayer film 37a is an oxide semiconductor film. The multilayer film 37a has a two-layer structure. A part of the oxide semiconductor film 19a functions as a channel region. The oxide insulating film 23 is formed so as to contact the 9a. In other words, the oxide semiconductor film 19a and the oxide insulating film 25 are formed. An oxide semiconductor film 39a is provided between the first and second electrodes 3 and 3.

[0231] The oxide semiconductor film 39a is composed of one or more elements that constitute the oxide semiconductor film 19a. Therefore, the interface between the oxide semiconductor film 19a and the oxide semiconductor film 39a is Therefore, the movement of carriers is not hindered at the interface. This increases the field effect mobility of the transistor.

[0232] The oxide semiconductor film 39a is typically an In-Ga oxide film, an In-Zn oxide film, or an I nM-Zn oxide film (M is Al, Ga, Y, Zr, La, Ce, or Nd), In addition, the energy of the bottom of the conduction band is closer to the vacuum level than that of the oxide semiconductor film 19a. is the energy of the bottom of the conduction band of the oxide semiconductor film 39a and the conduction The difference in energy from the lower end of the band is 0.05 eV or more, 0.07 eV or more, or 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 electron affinity of the oxide semiconductor film 39a and the oxide semiconductor film 19a The difference between the electron affinity of is 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 Below.

[0233] The oxide semiconductor film 39a contains In, and thus the carrier mobility (electron mobility) is increased. This is preferable.

[0234] The oxide semiconductor film 39a is formed by doping Al, Ga, Y, Zr, La, Ce, or Nd with In. A higher atomic ratio may have the following effects: (1) Oxide semiconductor (2) Enlarging the energy gap of the oxide semiconductor film 39a. (3) The diffusion of impurities from the outside is reduced. (4) The oxide semiconductor film 19a (5) Al, Ga, Y, Zr, La, Ce, or Nd Since is a metal element that has a strong bond with oxygen, oxygen deficiency is unlikely to occur.

[0235] When the oxide semiconductor film 39a is an In-M-Zn oxide film, the sum of In and M is 10 When the atomic percentage of In is 0 atomic %, the atomic ratio of In to M is preferably 50 atomic %. % or less, M is 50 atomic % or more, and more preferably, In is 25 atomic % or less. c% or less, and M is 75 atomic% or more.

[0236] In addition, the oxide semiconductor film 19a and the oxide semiconductor film 39a are In-M-Zn oxide films ( In the case where M is Al, Ga, Y, Zr, La, Ce, or Nd, the oxide semiconductor film 19a In comparison, M (Al, Ga, Y, Zr, La, Ce, or Nd) is large, and typically, the above-mentioned elements contained in the oxide semiconductor film 19a The atomic ratio is 1.5 times or more, preferably 2 times or more, and more preferably 3 times or more higher than that of the molecule. It is a numerical ratio.

[0237] In addition, the oxide semiconductor film 19a and the oxide semiconductor film 39a are In-M-Zn oxide films ( In the case where M is Al, Ga, Y, Zr, La, Ce, or Nd, the oxide semiconductor film 39a In:M:Zn=x 1 :y 1 :z 1 [Atomic ratio], the oxide semiconductor film 19a is In:M: Zn=x 2 :y 2 :z 2 [Atomic ratio], y 1 / x 1 y 2 / x 2 Larger than Preferably, y 1 / x 1 y 2 / x 2 More preferably, y 1 / x 1 y 2 / x 2 More preferably, y 1 / x 1 y 2 / x 2 More than three times larger than

[0238] The oxide semiconductor film 19a is an In-M-Zn oxide film (wherein M is Al, Ga, Y, Zr, La , Ce, or Nd), the target used to form the oxide semiconductor film 19a In this case, the atomic ratio of metal elements is In:M:Zn=x 1 :y 1 :z 1 So, 、 x 1 / y 1 is 1 / 3 or more and 6 or less, and further 1 or more and 6 or less, and z 1 / y 1 1 / 3 or more 6 It is more preferable that z is 1 or more and 6 or less. 1 / y 1 between 1 and 6 This makes it easier to form a CAAC-OS film as the oxide semiconductor film 19a. Representative examples of atomic ratios of metal elements in the get are In:M:Zn=1:1:1, In:M :Zn=1:1:1.2, In:M:Zn=3:1:2, etc.

[0239] The oxide semiconductor film 39a is an In-M-Zn oxide film (wherein M is Al, Ga, Y, Zr, La , Ce, or Nd), the target used for forming the oxide semiconductor film 39a In this case, the atomic ratio of metal elements is In:M:Zn=x 2 :y 2 :z 2 So, 、 x 2 / y 2 <x 1 / y 1 Where z 2 / y 2 is between 1 / 3 and 6, or between 1 and 6. It is preferable that z 2 / y 2 By setting the value of The ratio of the number of atoms of the target metal elements makes it easier to form a CAAC-OS film. Examples of the table are In:M:Zn=1:3:2, In:M:Zn=1:3:4, In:M: Examples include Zn=1:3:6, In:M:Zn=1:3:8, etc.

[0240] Note that the atomic ratios of the oxide semiconductor film 19a and the oxide semiconductor film 39a are each subject to error. The atomic ratios listed above may vary by ±40%.

[0241] The oxide semiconductor film 39a is a film that is used as an oxide semiconductor when forming the oxide insulating film 25 to be formed later. It also functions as a membrane for reducing damage to the body membrane 19a.

[0242] The thickness of the oxide semiconductor film 39a is 3 nm to 100 nm, preferably 3 nm to 50 nm. Let it be 0 nm.

[0243] Similarly to the oxide semiconductor film 19a, the oxide semiconductor film 39a has a non-single crystal structure, for example. The non-single crystal structure may be, for example, a CAAC-OS, a polycrystalline structure, or a microcrystalline structure, which will be described later. It may have a crystalline structure or an amorphous structure.

[0244] The oxide semiconductor film 39a may have an amorphous structure, for example. For example, the atomic arrangement is disordered and has no crystalline components.

[0245] Note that the oxide semiconductor film 19a and the oxide semiconductor film 39a each have an amorphous structure. The regions are microcrystalline, polycrystalline, CAAC-OS, and single crystal. The mixed film may have two or more of the above-mentioned regions. region, microcrystalline region, polycrystalline region, CAAC-OS region, and single crystal region. In some cases, the mixed film has a single layer structure having two or more regions. The regions are: microcrystalline structure, polycrystalline structure, CAAC-OS, single crystal structure. In some cases, the laminated structure may include two or more of the above-mentioned structural regions.

[0246] The oxide semiconductor film 19a and the oxide semiconductor film 39a are not simply laminated. A continuous junction (here, the energy of the bottom of the conduction band changes continuously between the layers) is used. In other words, trap centers and recombination centers are formed at the interfaces of each film. The layer structure is designed so that there are no impurities that would create such defect levels. When impurities are present between the oxide semiconductor film 19a and the oxide semiconductor film 39a, the energy The continuity of the Gate band is lost, and carriers are trapped or recombined at the interface, causing dissipation. It will be destroyed.

[0247] To form continuous junctions, a multi-chamber deposition system equipped with a load lock chamber is required. Each film is laminated in succession using a sputtering device without exposing it to the air. Each chamber in the sputtering apparatus is required for the oxide semiconductor film. In order to remove impurities such as water as much as possible, an adsorption type vacuum pump such as a cryopump is used. High vacuum pump (5×10 -7 Pa~1×10 -4 It is preferable to use a temperature of up to about 10 Pa. Alternatively, a turbo molecular pump and cold trap can be combined to separate the chamber from the exhaust system. It is preferable to prevent the backflow of gases into the bar, especially gases containing carbon or hydrogen. stomach.

[0248] Note that, instead of the multilayer film 37a, a transistor 102c shown in FIG. It may have a multi-layer film 38a.

[0249] In place of the multilayer film 37b, a multilayer film such as a capacitive element 105c shown in FIG. 12(B) is used. It may have a membrane 38b.

[0250] The multilayer film 38a includes an oxide semiconductor film 49a, an oxide semiconductor film 19a, and an oxide semiconductor film The multilayer film 38b includes a conductive film 49b, a conductive film 19b, and a conductive film 39b. That is, the multilayer films 38a and 38b have a three-layer structure. In the multilayer film 38a, the oxide semiconductor film 19a functions as a channel region.

[0251] The oxide insulating film 17 and the oxide semiconductor film 49a are in contact with each other. An oxide semiconductor film 49a is provided between the oxide semiconductor film 19a and the oxide semiconductor film 49b.

[0252] The multilayer film 38a and the oxide insulating film 23 are in contact with each other. The oxide semiconductor film 19a is in contact with the oxide insulating film 23. That is, between the oxide semiconductor film 19a and the oxide insulating film 23, An oxide semiconductor film 39a is provided.

[0253] The oxide semiconductor film 49a is formed using a material and a method similar to those of the oxide semiconductor film 39a. It is possible.

[0254] The oxide semiconductor film 49a is preferably thinner than the oxide semiconductor film 19a. The thickness of the semiconductor film 49a is set to 1 nm or more and 5 nm or less, preferably 1 nm or more and 3 nm or less. This makes it possible to reduce the amount of variation in the threshold voltage of the transistor.

[0255] In the transistor described in this embodiment, Therefore, the oxide semiconductor film 39a and the oxide Even if a trap level is formed between the insulating films 23 due to impurities and defects, the trap There is a gap between the top level and the oxide semiconductor film 19a. Electrons flowing through 9a are less likely to be captured by the trap level, which increases the on-current of the transistor. It is possible to increase the field effect mobility and the trap level. When an electron is captured by the transistor, the electron becomes a negative fixed charge. However, the oxide semiconductor film 19a and the trapping current are not uniform. Since there is a gap between the trap level and the electron capture at the trap level, it is possible to reduce the capture of electrons at the trap level. This makes it possible to reduce the variation in threshold voltage.

[0256] In addition, the oxide semiconductor film 39a can block impurities from the outside. The amount of impurities moving from the outside to the oxide semiconductor film 19a can be reduced. The oxide semiconductor film 39a is less likely to form oxygen vacancies. It is possible to reduce the impurity concentration and oxygen vacancy amount in a.

[0257] In addition, an oxide semiconductor film 49a is provided between the oxide insulating film 17 and the oxide semiconductor film 19a. The oxide semiconductor film 39 is disposed between the oxide semiconductor film 19a and the oxide insulating film 23. Since the oxide semiconductor film 49a is provided near the interface between the oxide semiconductor film 49a and the oxide semiconductor film 19a, the silicon and carbon concentrations in the oxide semiconductor film 19a, Alternatively, silicon or carbon in the vicinity of the interface between the oxide semiconductor film 39a and the oxide semiconductor film 19a The concentration of can be reduced.

[0258] The transistor 102c having such a structure includes a multilayer film 3 including an oxide semiconductor film 32. The extremely low number of defects in 8a makes it possible to improve the electrical characteristics of transistors Typically, it is possible to increase the on-current and improve the field effect mobility. Threshold voltage in the BT stress test and the light BT stress test, which are examples of stress tests The fluctuation is small and the reliability is high.

[0259] <Band structure of transistor> Next, the multilayer film 37a provided in the transistor 102b shown in FIG. Regarding the band structure of the multilayer film 38a provided in the transistor 102c shown in FIG. 2(B), This will be explained using FIG.

[0260] Here, for example, the oxide semiconductor film 19a has an energy gap of 3.15 eV. The oxide semiconductor film 39a is made of In-Ga-Zn oxide having an energy gap of The energy gap is 3.5 eV. Measured using a psometer (HORIBA JOBIN YVON UT-300) It is possible.

[0261] Vacuum levels and valence band top energies of the oxide semiconductor film 19a and the oxide semiconductor film 39a The ionization potentials of these two electrons are 8 eV and 8.2 eV, respectively. The energy difference between the vacuum level and the top of the valence band is measured by ultraviolet photoelectron spectroscopy (UPS). Raviolet Photoelectron Spectroscopy (P Measurements can be performed using a HI VersaProbe.

[0262] Therefore, the vacuum level and the conduction band minimum of the oxide semiconductor film 19a and the oxide semiconductor film 39a The energy difference (also called electron affinity) between these two electrons is 4.85 eV and 4.7 eV, respectively. I did.

[0263] FIG. 13A shows a schematic diagram of a part of the band structure of the multilayer film 37a. A case where a silicon oxide film is provided in contact with the multilayer film 37a will be described. ) indicates the energy of the bottom of the conduction band of the silicon oxide film, and EcS1 indicates the energy of the oxide EcS2 represents the energy of the bottom of the conduction band of the semiconductor film 19a, and EcS3 represents the energy of the bottom of the conduction band of the oxide semiconductor film 39a. EcI2 indicates the energy of the conduction band edge of the silicon oxide film. In addition, EcI1 corresponds to the oxide insulating film 17 in FIG. 12(A), and EcI2 corresponds to 12A, which corresponds to the oxide insulating film 23.

[0264] As shown in FIG. 13A, in the oxide semiconductor film 19a and the oxide semiconductor film 39a, The energy at the bottom of the conduction band changes smoothly without any barrier. In other words, it changes continuously. This is because the oxide semiconductor film 39a is the same as the oxide semiconductor film 19a. The oxide semiconductor film 19a and the oxide semiconductor film 39a contain a common element, and oxygen is mixed between the oxide semiconductor film 19a and the oxide semiconductor film 39a. This can be said to be because a mixed layer is formed by the movement of the

[0265] As shown in FIG. 13A, the oxide semiconductor film 19a of the multilayer film 37a serves as a well. In the transistor using the layer film 37a, a channel region is formed in the oxide semiconductor film 19a. It can be seen that the energy of the conduction band minimum of the multilayer film 37a changes continuously. Therefore, the oxide semiconductor film 19a and the oxide semiconductor film 39a are continuously joined. I can say.

[0266] As shown in FIG. 13A, the boundary between the oxide semiconductor film 39a and the oxide insulating film 23 Although trap levels due to impurities or defects may be formed near the surface, the oxide semiconductor The film 39a is provided to separate the oxide semiconductor film 19a from the trap levels. However, if the energy difference between EcS1 and EcS2 is small, Electrons in the film 19a may exceed the energy difference and reach the trap level. When electrons are captured in the gate level, a negative charge is generated at the oxide insulating film interface, causing a transistor The threshold voltage of the capacitor is shifted in the positive direction. When the energy difference is set to 0.1 eV or more, preferably 0.15 eV or more, a transistor This is advantageous because it reduces fluctuations in the threshold voltage of the capacitor and results in stable electrical characteristics.

[0267] FIG. 13(B) shows a schematic diagram of a part of the band structure of the multilayer film 37a, and FIG. In this example, a silicon oxide film is placed in contact with the multilayer film 37a. In addition, EcI1 shown in FIG. 13(B) is the conductivity of the silicon oxide film. EcS1 is the energy of the conduction band minimum of the oxide semiconductor film 19a. EcI2 indicates the energy of the bottom of the conduction band of the silicon oxide film. corresponds to the oxide insulating film 17 in FIG. 12(A), and EcI2 corresponds to the oxide insulating film 17 in FIG. In this case, it corresponds to the oxide insulating film 23 .

[0268] In the transistor shown in FIG. 12A, a conductive film 21a serving as a pair of electrodes, During the formation of 21b, the upper part of the multilayer film 37a, i.e., the oxide semiconductor film 39a, is etched. On the other hand, the upper surface of the oxide semiconductor film 19a may be A mixed layer of the oxide semiconductor film 19a and the oxide semiconductor film 39a may be formed.

[0269] For example, the oxide semiconductor film 19a is made of In, Ga, and Zn in an atomic ratio of 1:1:1. -Ga-Zn oxide, or In-Ga- with In:Ga:Zn=3:1:2 [atomic ratio] The oxide semiconductor film is formed by using Zn oxide as a sputtering target. The semiconductor film 39a is an In-Ga-Zn oxide film having an atomic ratio of In:Ga:Zn=1:3:2. In-Ga-Zn oxide with an atomic ratio of In:Ga:Zn=1:3:4, or In In-Ga-Zn oxide with an atomic ratio of Ga:Zn=1:3:6 was sputtered. In the case where the oxide semiconductor film is formed using the oxide semiconductor film 19a as a get, the oxide semiconductor film 19b is thicker than the oxide semiconductor film 19a. Since the semiconductor film 39a contains a large amount of Ga, the upper surface of the oxide semiconductor film 19a is covered with GaOx A layer or a mixed layer containing more Ga than the oxide semiconductor film 19a can be formed.

[0270] Therefore, even when the oxide semiconductor film 39a is etched, the E The energy of the bottom of the conduction band on the cI2 side becomes higher, and the band structure shown in Figure 13(B) appears. This may be the case.

[0271] When the band structure shown in FIG. 13(B) is obtained, when observing the cross section of the channel region, In some cases, the multilayer film 37a appears to be composed of only the oxide semiconductor film 19a. However, in reality, the oxide semiconductor film 19a has more Ga than the oxide semiconductor film 19a. Since a mixed layer containing a large amount of uranium is formed, the mixed layer can be regarded as the 1.5th layer. The mixed layer can be obtained by, for example, EDX analysis or the like, by determining the elements contained in the multilayer film 37a. When the element is measured, the composition above the oxide semiconductor film 19a can be analyzed to confirm the result. For example, the composition of the upper portion of the oxide semiconductor film 19a is different from the composition of the oxide semiconductor film 19a. This can be confirmed by the fact that the Ga content is higher than that of the other alloys.

[0272] FIG. 13C shows a schematic diagram of a part of the band structure of the multilayer film 38a. A case where a silicon oxide film is provided in contact with the multilayer film 38a will be described. ) indicates the energy of the bottom of the conduction band of the silicon oxide film, and EcS1 indicates the energy of the oxide EcS2 represents the energy of the bottom of the conduction band of the semiconductor film 19a, and EcS3 represents the energy of the bottom of the conduction band of the oxide semiconductor film 39a. EcS3 is the energy of the conduction band minimum of the oxide semiconductor film 49a. EcI2 indicates the energy of the bottom of the conduction band of the silicon oxide film. corresponds to the oxide insulating film 17 in FIG. 12B, and EcI2 corresponds to the oxide insulating film 17 in FIG. In this case, it corresponds to the oxide insulating film 23 .

[0273] As shown in FIG. 13C, the oxide semiconductor film 49a, the oxide semiconductor film 19a, and the oxide In the compound semiconductor film 39a, the energy of the conduction band minimum changes smoothly without any barrier. In other words, it can be said that the change is continuous. The oxide semiconductor film 39a and the oxide semiconductor film 39b contain the same elements as the oxide semiconductor film 19a. between the oxide semiconductor film 19a and the oxide semiconductor film 39a, This can be attributed to the formation of a mixed layer due to the mutual movement of elements.

[0274] As shown in FIG. 13C, the oxide semiconductor film 19a of the multilayer film 38a serves as a well. In the transistor using the layer film 38a, a channel region is formed in the oxide semiconductor film 19a. It can be seen that the energy of the conduction band minimum of the multilayer film 38a changes continuously. Therefore, the oxide semiconductor film 49a, the oxide semiconductor film 19a, and the oxide semiconductor film 39a It can also be said that the two are continuously joined.

[0275] Note that the oxide insulating film 17, the oxide semiconductor film 19a, and the oxide insulating film 23 are stacked in this order. In this case, the oxide semiconductor film 19a is formed in the vicinity of the interface between the oxide semiconductor film 19a and the oxide insulating film 23, and the oxide semiconductor film 1 In the vicinity of the interface between 9a and the oxide insulating film 17, a trap level due to impurities or defects is formed. However, as shown in FIG. 13C, the oxide semiconductor film 39a and the oxide semiconductor film By providing the oxide semiconductor film 19a, the trap level can be separated from the oxide semiconductor film 19a. However, the energy difference between EcS1 and EcS2, and the energy difference between EcS1 and EcS3 When the energy difference between the oxide semiconductor film 19a and the oxide semiconductor film 19b is small, the electrons in the oxide semiconductor film 19a exceed the energy difference and When electrons are captured in the trap level, the oxide insulating film Negative charges are generated at the interface, and the threshold voltage of the transistor shifts in the positive direction. Therefore, the energy difference between EcS1 and EcS2 and the energy difference between EcS1 and EcS3 are When the energy difference is set to 0.1 eV or more, preferably 0.15 eV or more, the transistor This is preferable because it reduces the fluctuation of the threshold voltage and provides stable electrical characteristics.

[0276] Note that the structures and methods described in this embodiment may be different from the structures and methods described in other embodiments. They can be used in appropriate combination.

[0277] <Variation 6> A modification of the semiconductor device shown in the first embodiment is shown in FIG.

[0278] The semiconductor device shown in FIG. 14 is different from the semiconductor device shown in FIG. The difference is that it has not been created.

[0279] In such a semiconductor device, after forming the metal oxide film 26a in FIG. 6(B), A mask is formed on the metal oxide film 26a by a photolithography process. The metal oxide film 26a is etched using a mask to form an opening 41. Through steps 7(A) and thereafter, a conductive film 31 is formed.

[0280] In the semiconductor device shown in FIG. 14, the nitride insulating film 29 is not formed. Then, etching is performed to form the oxide insulating film 23 and the oxide insulating film 25 shown in FIG. During the etching process, the oxide semiconductor film 19c is damaged and oxygen vacancies are formed. As a result, the oxide semiconductor film 19c becomes the conductive film 19b.

[0281] As a result, the oxide semiconductor film of the transistor is formed on the oxide semiconductor film, which is one of the electrodes of the capacitor. A film having electrical conductivity can be formed.

[0282] <Variation 7> The conductive film 21 functioning as a pair of electrodes is provided in the transistor shown in Embodiment 1. a, 21b: tungsten, titanium, aluminum, copper, molybdenum, chromium, Alternatively, a conductive material that easily bonds with oxygen, such as tantalum or an alloy, can be used. As a result, the conductive film 21 functions as a pair of electrodes together with the oxygen contained in the oxide semiconductor film 19a. The conductive materials contained in 21a and 21b are bonded to each other, forming oxygen vacancy regions in the oxide semiconductor film 19a. In addition, a conductive film 21a serving as a pair of electrodes is formed in the oxide semiconductor film 19a. In some cases, some of the constituent elements of the conductive material forming 21b may be mixed in. In the compound semiconductor film 19a, the conductive films 21a and 21b functioning as a pair of electrodes are in contact with each other. A low resistance region is formed near the region. The low resistance region is a conductive film functioning as a pair of electrodes. A conductive film 21 is in contact with the oxide insulating film 17 and functions as a pair of electrodes. The low resistance region is formed between the oxide semiconductor film 19a and 21b because of its high conductivity. It is possible to reduce the contact resistance between the conductive film 21a and the conductive film 21b which function as a pair of electrodes. Therefore, the on-state current of the transistor can be increased.

[0283] In addition, the conductive films 21a and 21b functioning as a pair of electrodes are formed of a conductive material that is easily bonded to oxygen. The conductive material is a material that does not easily bond with oxygen, such as titanium nitride, tantalum nitride, or ruthenium. By forming such a layered structure, a conductive material that functions as a pair of electrodes can be formed. At the interface between the conductive films 21a and 21b and the oxide insulating film 23, a conductive layer functioning as a pair of electrodes is formed. The conductive films 21a and 21b can be prevented from being oxidized, and the conductive films 21a and 21b function as a pair of electrodes. It is possible to suppress the increase in resistance of 1a and 21b.

[0284] Note that the structures and methods described in this embodiment may be different from the structures and methods described in other embodiments. They can be used in appropriate combination.

[0285] <Variation 8> In the method for manufacturing a transistor described in this embodiment, After the conductive films 21a and 21b are formed, the oxide semiconductor film 19a is formed by a plasma annealing process in an oxidizing atmosphere. The oxide semiconductor film 19a can be supplied with oxygen by exposing it to an oxidizing atmosphere. The atmosphere may be oxygen, ozone, nitrous oxide, nitrogen dioxide, etc. In this process, the oxide semiconductor is irradiated with plasma generated without applying a bias to the substrate 11 side. As a result, the oxide semiconductor film 19a is not damaged, In addition, oxygen can be supplied, and the amount of oxygen vacancies in the oxide semiconductor film 19a can be reduced. In addition, the oxide semiconductor film 19a can be reduced by etching. Impurities such as halogens, such as fluorine and chlorine, can be removed. It is preferable to perform the plasma treatment while heating at 300°C or higher. The hydrogen contained in the semiconductor film 19a is bonded to water. Water is released from the oxide semiconductor film 19a. The content of oxygen and water can be reduced.

[0286] Note that the structures and methods described in this embodiment may be different from the structures and methods described in other embodiments. They can be used in appropriate combination.

[0287] (Embodiment 2) In this embodiment mode, a semiconductor device different from that in Embodiment Mode 1 and a manufacturing method thereof will be described with reference to drawings. In this embodiment, an oxide film is formed between different gate electrodes in a transistor. The transistor has a dual gate structure, that is, a nitride semiconductor film is provided. This embodiment differs from embodiment 1. Note that a description of the configuration that overlaps with embodiment 1 will be omitted.

[0288] A specific configuration of the element substrate included in the display device will be described. Here, the pixel 103 A specific example of a liquid crystal display device using a liquid crystal element will be described. A top view of the pixel 103 shown in FIG.

[0289] In the top view of the pixel 103 shown in FIG. 15, a conductive film 13 functioning as a gate electrode, an acid The oxide semiconductor film 19a, the conductive films 21a and 21b, and the oxide insulating film 25 are each partially or The difference from the first embodiment is that the second embodiment has a conductive film 31a which functions as a gate electrode and completely overlaps the first embodiment. The conductive film 31a functioning as a gate electrode is formed in the opening 41a. The conductive film 13 functions as a conductive film.

[0290] Next, a cross-sectional view taken along dashed lines AB and CD in FIG. 15 is shown in FIG. The transistor 102a is a channel etch type transistor. -B is the channel length direction of the transistor 102a, and 1 is a cross-sectional view of a connection portion of a conductive film 31 that functions as a capacitor element 105a, and FIG. The cross-sectional view shows the channel width direction of the transistor 102a and the conductive layer functioning as a gate electrode. 1 is a cross-sectional view of a connection portion between a film 13 and a conductive film 31a functioning as a gate electrode.

[0291] The transistor 102a shown in FIG. 16 is a transistor having a dual gate structure. The conductive film 13 functions as a gate electrode and is provided on the plate 11. The nitride insulating film 15 is formed on the conductive film 13 which functions as a gate electrode. The oxide insulating film 17 formed on the film 15 and the nitride insulating film 15 and the oxide insulating film 17 are interposed therebetween. The oxide semiconductor film 19a overlaps with the conductive film 13 functioning as a gate electrode. The conductive film 19a is in contact with conductive films 21a and 21b, which function as a pair of electrodes. In addition, the oxide insulating film 17, the oxide semiconductor film 19a, and the conductive film 2 functioning as a pair of electrodes An oxide insulating film 23 is formed on the layers 1a and 21b, and an oxide insulating film is formed on the oxide insulating film 23. The nitride insulating film 15, the oxide insulating film 23, the oxide insulating film 25, and the conductive film 25 are formed. A metal oxide film 27 is formed on 21b, and a nitride insulating film 29 is formed on the metal oxide film 27. In addition, one of the conductive films 21a and 21b functioning as a pair of electrodes is a conductive film. The conductive film 31 connected to the conductive film 21b and the conductive film 31a functioning as a gate electrode are made of nitride. It is formed on the insulating film 29. The conductive film 31 functions as a pixel electrode.

[0292] As shown in the cross-sectional view of CD, the nitride insulating film 15, the metal oxide film 27, and the nitride In the opening 41a provided in the insulating film 29, the conductive film 31 which functions as a gate electrode is a is connected to the conductive film 13 that functions as a gate electrode. The conductive film 13 functioning as the gate electrode and the conductive film 31a functioning as the gate electrode have the same potential.

[0293] Therefore, by applying the same voltage to each gate electrode of the transistor 102a, the initial characteristic -Reduction of performance variations, suppression of degradation during GBT stress test and performance at different drain voltages In addition, the oxide semiconductor film 19a can suppress the fluctuation in the on-state current rising voltage. Since the area through which the carriers flow is larger in the film thickness direction, the amount of carrier movement is As a result, the on-state current of the transistor 102a increases and the field effect transition The mobility is high, typically with a field effect mobility of 20 cm 2 / V s or more.

[0294] The oxide insulating films 23 and 25 are separated over the transistor 102a in this embodiment. The separated oxide insulating films 23 and 25 overlap with the oxide semiconductor film 19a. In addition, in a cross-sectional view in the channel width direction, an oxide insulating film 23 is formed on the outer side of the oxide semiconductor film 19a. and an end of the oxide insulating film 25. In the channel width direction shown in FIG. The conductive film 31a functioning as a gate electrode is formed through the oxide insulating film 23 and the oxide insulating film 25. The oxide semiconductor film 19a is formed on the first insulating film 19c.

[0295] At the edge of the oxide semiconductor film that is processed by etching or the like, the oxide semiconductor film is damaged during the processing. Defects are formed and the material is contaminated by impurities, so stresses such as electric fields When a material is provided with a potential, it is easily activated, which makes it more likely to become n-type (low resistance). Therefore, the end of the oxide semiconductor film 19a overlapping with the conductive film 13 functioning as a gate electrode The n-type end is a conductive layer that functions as a pair of electrodes. If the n-type region is provided between the films 21a and 21b, the n-type region becomes a carrier path. However, as shown in the cross section of CD, the channel In the width direction, the conductive film 31a functioning as the gate electrode is disposed between the oxide insulating films 23 and 25. The conductive layer functions as a gate electrode by facing the side surface of the oxide semiconductor film 19a through the conductive layer. The side surface of the oxide semiconductor film 19a or the side surface and its vicinity are affected by the electric field of the film 31a. As a result, the generation of a parasitic channel in the region containing the gate insulating film is suppressed. This results in a transistor with excellent electrical characteristics, with a steep rise in drain current.

[0296] In addition, the oxide insulating film 23 or the oxide insulating film 25 provided over the oxide semiconductor film 19a is formed of an oxide insulating film containing more oxygen than the oxygen that satisfies the stoichiometric composition. is preferred.

[0297] By providing the metal oxide film 27 having low oxygen permeability over the oxide insulating films 23 and 25, The oxygen contained in the oxide insulating film 23 or the oxide insulating film 25 is prevented from diffusing to the outside. Therefore, oxygen vacancies in the oxide semiconductor film 19a can be reduced. be.

[0298] In addition, an oxide semiconductor film 19a is included inside the nitride insulating film 15 and the nitride insulating film 29. Therefore, the movement of water, hydrogen, etc. from the outside to the oxide semiconductor film 19a is suppressed by the nitride insulating film. 15 and the nitride insulating film 29. As a result, the oxide semiconductor film 19a The content of water, hydrogen, etc. can be reduced.

[0299] As a result, the transistor 102a becomes a transistor having normally-off characteristics. In addition, the electrical characteristics of transistors, typically threshold voltages, can be changed over time or by stress testing. The amount of voltage fluctuation can be reduced.

[0300] In the capacitor 105a, the conductive film 19b is an oxide semiconductor film 19a. The film is formed at the same time as the plasma damage, etc., and oxygen vacancies are formed, resulting in a conductive Alternatively, the conductive film 19b is a film having improved conductivity. The film is formed at the same time, and contains impurities to enhance its electrical conductivity. Alternatively, the conductive film 19b is a film formed simultaneously with the oxide semiconductor film 19a. In addition, it contains impurities and oxygen vacancies are formed due to plasma damage, etc., resulting in high conductivity. It is a coated membrane.

[0301] In the capacitance element 105a, the metal oxide film 27, which is a high dielectric material, is used as a dielectric. In addition, the use of the nitride insulating film 29 can increase the charge capacity of the capacitor element 105a. It is possible.

[0302] The element substrate of the semiconductor device described in this embodiment is The conductive film that functions as a pixel electrode is formed as a capacitor. The other electrode of the element is used. Since the step of forming a film is not required, the manufacturing process can be reduced. As a result, the area occupied by the capacitor element is increased, The aperture ratio of the pixel can be increased.

[0303] The following describes the details of the configuration of the transistor 102a. Descriptions of components with the same reference numerals will be omitted.

[0304] The conductive film 31a functioning as the gate electrode is made of the same material as the conductive film 31 shown in the first embodiment. Fees can be used as appropriate.

[0305] Next, a method for manufacturing the transistor 102a and the capacitor 105a shown in FIG. The following description will be given with reference to FIGS. 4 to 6 and 17. FIG.

[0306] As in the first embodiment, a gate electrode and a gate electrode are formed on a substrate 11 through the steps shown in FIG. 4 to FIG. 6(B). The conductive film 13, the nitride insulating film 15, the oxide insulating film 16, and the oxide semiconductor film 19a function as , a conductive film 19b, conductive films 21a and 21b functioning as a pair of electrodes, and an oxide insulating film. The insulating film 22, the oxide insulating film 24, the metal oxide film 26a, and the nitride insulating film 28 are formed. In this process, photolithography is performed using the first to fourth photomasks. A lithography process is carried out.

[0307] Next, a fifth photomask is used to form a photoresist film on the nitride insulating film 28. After forming a mask, the nitride insulating film 15, the metal oxide film 26a, and 17A, the nitride insulating film 28 is partially etched to form an opening 41 and The nitride insulating film 15 having the opening 41a, the metal oxide film 27, and the nitride insulating film 29 are Form.

[0308] Next, as shown in FIG. 17(B), the conductive film 13 and the conductive film 21 which function as the gate electrode are b and on the nitride insulating film 29, a conductive film 30 which will later become conductive films 31 and 31a is formed.

[0309] Next, a mask is formed on the conductive film 30 by a photolithography process using a sixth photomask. Next, a part of the conductive film 30 is etched using the mask, and the mask is formed as shown in FIG. As shown in FIG. 1C, a conductive film 31 functioning as a pixel electrode and a conductive film 32 functioning as a gate electrode are The conductive film 31a is formed, and then the mask is removed.

[0310] Through the above steps, the transistor 102a and the capacitor 105a are manufactured. It is possible.

[0311] The transistor described in this embodiment has a gate electrode functioning in the channel width direction. The conductive film 31a is in contact with the side surface of the oxide semiconductor film 19a via the oxide insulating films 23 and 25. By facing each other, the oxide semiconductor layer 31a is formed by the effect of the electric field of the conductive film 31a functioning as a gate electrode. The occurrence of a parasitic channel on the side surface of the conductive film 19a or on the region including the side surface and its vicinity As a result, the drain current rises sharply at the threshold voltage, and the electrical characteristics are improved. This results in a transistor with excellent performance.

[0312] In addition, the transistor described in this embodiment contains more oxygen than the oxygen that satisfies the stoichiometric composition. By providing a metal oxide film with low oxygen permeability over the oxide insulating film containing oxygen, It is possible to prevent the oxygen contained in the insulating film from diffusing to the outside. The oxygen contained in the insulating film is efficiently transferred to the oxide semiconductor film, and the This can reduce the amount of oxygen vacancies.

[0313] In addition, an oxide semiconductor film is included inside the plurality of nitride insulating films. The nitride insulating film prevents the transfer of water, hydrogen, and the like to the oxide semiconductor film. The amount of water, hydrogen, etc. contained in the nitride semiconductor film can be reduced.

[0314] As described above, a transistor having normally-off characteristics can be manufactured. In addition, the electrical characteristics of transistors, typically the threshold voltage, change over time or due to stress testing. It is possible to manufacture a transistor in which the amount of voltage fluctuation is reduced.

[0315] In addition, the element substrate of the semiconductor device described in this embodiment is a semiconductor substrate including an oxide semiconductor film of a transistor. At the same time, one electrode of the capacitor element is formed. The other electrode of the capacitor is used. Since a step of forming a conductive film on the pair of electrodes is not required, the manufacturing steps can be reduced. As a result, the area occupied by the capacitor element is increased. At the same time, the aperture ratio of the pixel can be increased.

[0316] As described above, a semiconductor device including an oxide semiconductor film has improved electrical characteristics. can be obtained.

[0317] Note that the structures and methods described in this embodiment may be different from the structures and methods described in other embodiments. Also, it can be used in appropriate combination with modified examples.

[0318] (Embodiment 3) In this embodiment, a transistor included in the semiconductor device described in the above embodiment is In one embodiment, the present invention can be applied to an oxide semiconductor film and a conductive film which is an electrode of a capacitor. Note that the conductive film is also called a highly conductive oxide semiconductor film. In order to clarify the above, an oxide semiconductor film will be first described as a typical example.

[0319] The oxide semiconductor film is an oxide semiconductor having a single crystal structure (hereinafter referred to as a single crystal oxide semiconductor). , a polycrystalline oxide semiconductor (hereinafter referred to as a polycrystalline oxide semiconductor), oxide semiconductors having an amorphous structure (hereinafter referred to as microcrystalline oxide semiconductors) and amorphous oxide semiconductors having an amorphous structure (hereinafter referred to as The oxide semiconductor film may be formed of one or more of the following: Alternatively, the oxide semiconductor film may be an amorphous oxide semiconductor film. The semiconductor layer may be made of an oxide semiconductor having a conductor and crystal grains. The CAAC-OS, a polycrystalline oxide semiconductor, and a microcrystalline oxide semiconductor will be described.

[0320] <caac-os> The CAAC-OS film is one of the oxide semiconductor films having multiple crystal parts. The crystals in the AC-OS film have a c-axis orientation. The area of ​​the crystals in the C-OS film is 2500 nm 2 More preferably, 5 μm or more 2 Below More preferably, 1000 μm or more 2 In addition, in the cross-sectional TEM image, By having a ratio of 50% or more, preferably 80% or more, and more preferably 95% or more, The resulting thin film has properties close to those of a crystal.

[0321] 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.

[0322] 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 the convexity and is aligned parallel to the surface on which the CAAC-OS film is formed or the top surface. In this specification, "parallel" means that two straight lines are arranged at an angle of -10° or more and 10° or less. Therefore, it includes the case where the angle is between -5° and 5°. " refers to a state in which two straight lines are arranged at an angle of 80° or more and 100° or less. This also includes cases where the angle is between 85° and 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] X-ray diffraction (XRD) of CAAC-OS film The structure of the CAAC-OS film was analyzed using the out-of-plane method. In the analysis, a peak may appear at a diffraction angle (2θ) of around 31°. This peak is I Since it is assigned to the (00x) plane (x is an integer) of the nGaZn oxide crystal, The crystals of the OS film have a c-axis orientation, and the c-axis is oriented in a direction approximately perpendicular to the surface on which the film is formed or the upper surface. It can be confirmed that there is.

[0327] 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°. This is attributed to the (110) plane of the InGaZn oxide crystal. In the case of a crystalline oxide semiconductor film, 2θ is fixed at about 56°, and the normal vector of the sample surface is aligned along the axis (φ When the sample is rotated around the (φ) axis while analyzing (φ scan), the results show that the bonds are equivalent to the (110) plane. In contrast, in the case of the CAAC-OS film, 2 Even when θ is fixed at around 56° and φ is scanned, no clear peak appears.

[0328] 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.

[0329] The crystals are 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 along the surface on which the CAAC-OS film is formed or along the surface on which the CAAC-OS film is formed. The orientation of the CAAC-OS film is parallel to the normal vector of the top surface. When the shape of the CAAC-OS film is changed by etching, the c-axis of the crystal is aligned with the surface on which the CAAC-OS film is formed. Or it may not be parallel to the normal vector of the upper surface.

[0330] In addition, the crystallinity in the CAAC-OS film does not have to be uniform. When the crystalline part of the film is formed by crystal growth from the vicinity of the top surface of the CAAC-OS film, The area near the surface may have a higher crystallinity than the area near the surface on which it is formed. When impurities are added to the AC-OS film, the crystallinity of the region to which the impurities are added changes, resulting in a partial In some cases, regions of differing crystallinity may be formed.

[0331] In addition, in the out-of-plane analysis of the CAAC-OS film, 2θ was 31°. In addition to the peaks around 2θ of 36°, a peak may also appear around 2θ of 36°. The peaks near the c-axis are due to the presence of crystals that do not have the c-axis orientation in the CAAC-OS film. The CAAC-OS film shows a peak at 2θ of about 31° and a peak at 2θ of about 36°. It is preferable that there is no peak in the vicinity.

[0332] 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.

[0333] 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.

[0334] 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.

[0335] 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.

[0336] <Microcrystalline oxide semiconductor> 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.

[0337] 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 peaks indicating the diameters larger than those of the crystals in the nc-OS film (e.g. When electron beam diffraction (also called selected area electron beam diffraction) is performed using an electron beam with a diameter of 50 nm or more, On the other hand, for the nc-OS film, the diffraction pattern is crystalline. The probe diameter is close to the size of the crystal part or smaller than the crystal part (for example, 1 nm to 30 nm). When electron beam diffraction using a sagittal beam (also called nanobeam electron diffraction), spots are observed. In addition, when nanobeam electron diffraction was performed on the nc-OS film, the In addition, nanobeads were observed in the nc-OS film. When electron diffraction is performed, multiple spots may be observed within a ring-shaped region.

[0338] The nc-OS film is an oxide semiconductor film that has 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.

[0339] <Oxide Semiconductor Film and Oxide Conductor Film> Next, the resistivity of an oxide semiconductor film and a conductive film will be described. For convenience, a film having electrical conductivity will be described as an oxide conductor film.

[0340] Here, an oxide semiconductor film such as the oxide semiconductor film 19a shown in FIG. 2 used in a transistor is A film formed of a semiconductor (hereinafter referred to as an oxide semiconductor film (OS)) and an electrode of a capacitor element The conductive film 19b shown in FIG. 2 is formed of an oxide conductor. The temperature dependence of resistivity of each film (hereinafter referred to as oxide conductor film (OC)) This will be described with reference to FIG. 31. In FIG. 31, the horizontal axis indicates the measured temperature, and the vertical axis indicates the resistance. The measurement results for the oxide semiconductor film (OS) are indicated by circles, and the measurement results for the oxide conductor film (O The measurement results of C) are indicated by square marks.

[0341] The sample including the oxide semiconductor film (OS) was formed on a glass substrate with an atomic ratio of In:Ga A sputtering method was used to deposit a thick ZnO film using a sputtering target with a ratio of 1:1:1.2. An In-Ga-Zn oxide film having a thickness of 35 nm was formed, and the atomic ratio of the film was In:Ga:Zn=1:4. A 20 nm thick In- A Ga-Zn oxide film was formed, and then heat-treated in a nitrogen atmosphere at 450°C. The silicon oxynitride film is then formed by plasma CVD. It was produced by forming

[0342] The sample containing the oxide conductor (OC) was prepared by depositing an In:Ga atomic ratio on a glass substrate. A sputtering method was used with a sputtering target of Zn=1:1:1 to deposit a 10 ... After forming a 00 nm In-Ga-Zn oxide film and heat-treating it in a nitrogen atmosphere at 450 °C, The silicon nitride was then deposited by plasma CVD. It was prepared by forming a con film.

[0343] As can be seen from FIG. 31, the temperature dependence of resistivity in the oxide conductor film (OC) is The temperature dependence of resistivity is smaller than that of oxide semiconductor films (OS). Typically, it is 80K or higher. The change in resistivity of the oxide conductor film (OC) at 290K or less is less than ±20%. Alternatively, the rate of change in resistivity from 150K to 250K is less than ±10%. That is, an oxide conductor is a degenerate semiconductor, and the conduction band edge and the Fermi level are coincident or approximately coincident. For this reason, the oxide conductor film is used as the electric field of resistor elements, wiring, and capacitor elements. The electrode can be used for a pixel electrode, a common electrode, etc.

[0344] Note that the structures and methods described in this embodiment may be different from the structures and methods described in other embodiments. Also, it can be used in appropriate combination with modified examples.

[0345] (Embodiment 4) In this embodiment, a structural example of an electronic device to which a semiconductor device of one embodiment of the present invention is applied will be described. In addition, in this embodiment, a display module to which the semiconductor device of one embodiment of the present invention is applied will be described. The rule will be described with reference to FIG.

[0346] The display module 8000 shown in FIG. 28 includes an upper cover 8001 and a lower cover 8002. Between them, touch panel 8004 connected to FPC8003, A display panel 8006, a backlight unit 8007, a frame 8009, a printed circuit board The backlight unit 8007, the battery 8011, and the LCD panel 8012 are also included. The telly 8011, the touch panel 8004, etc. may not be provided.

[0347] The semiconductor device of one embodiment of the present invention can be used for the display panel 8006, for example.

[0348] The upper cover 8001 and the lower cover 8002 are connected to the touch panel 8004 and the display panel The shape and dimensions can be changed as appropriate to match the size of 8006.

[0349] The touch panel 8004 is a resistive or capacitive touch panel. The display panel 8006 can be used by overlapping it with the opposing substrate (sealing substrate). It is also possible to provide a touch panel function to the display panel. It is also possible to provide an optical sensor in each pixel of the 8006 to make it into an optical touch panel. Alternatively, a touch sensor electrode is provided in each pixel of the display panel 8006, and a capacitive touch sensor is provided. It may also be a panel.

[0350] The backlight unit 8007 includes a light source 8008. Alternatively, the light diffusing plate may be provided at the end of the light receiving unit 8007.

[0351] The frame 8009 protects the display panel 8006 and also supports the movement of the printed circuit board 8010. It also functions as an electromagnetic shield to block electromagnetic waves generated by the operation of the frame. The frame 8009 may also function as a heat sink.

[0352] The printed circuit board 8010 includes a power supply circuit, a signal circuit for outputting a video signal, and a clock signal. The power supply circuit is provided with a signal processing circuit. Alternatively, the power source may be a battery 8011 provided separately. 1 can be omitted if commercial power is used.

[0353] The display module 8000 also includes components such as a polarizing plate, a retardation plate, and a prism sheet. Additional ones may be provided.

[0354] FIG. 27 is an external view of an electronic device including a semiconductor device of one embodiment of the present invention.

[0355] The electronic device may be, for example, a television device (television or television receiver) (also called "computer monitors"), digital cameras, digital video cameras, etc. digital photo frames, mobile phones (also called mobile phones or mobile phone devices), These include large game machines such as small game machines, portable information terminals, audio playback devices, and pachinko machines. can be.

[0356] FIG. 27A shows a portable information terminal, which includes a main body 1001, a housing 1002, a display unit 1003, and a The display unit 1003b is a touch panel. By touching the keyboard button 1004 displayed on the display unit 1003b, Of course, the display unit 1003a can be configured as a touch panel. The transistor described in the above embodiment may be used as a switching element in a liquid crystal panel. By fabricating a display panel or an organic light-emitting panel and applying it to the display units 1003a and 1003b, It is possible to provide a highly reliable portable information terminal.

[0357] The portable information terminal shown in FIG. 27(A) displays various information (still images, videos, text images, etc.). Functions that display calendars, dates, or times on the display, functions that display Ability to manipulate or edit displayed information, processed by various software (programs) In addition, the rear and side of the housing may be provided with terminals for external connection. It may also be configured to include a connector (such as an earphone jack or USB port) and a recording medium insertion section.

[0358] The portable information terminal shown in FIG. 27(A) is configured to be capable of wirelessly transmitting and receiving information. The desired book data can be purchased and downloaded wirelessly from an electronic book server. It is also possible to configure the device to perform this function.

[0359] FIG. 27B shows a portable music player. The main body 1021 has a display unit 1023 and an earphone. The device has a fixing part 1022 for mounting to an external device, a speaker, an operation button 1024, and an external memory slot. The transistors described in the above embodiment are switched By preparing a liquid crystal panel or an organic light-emitting panel as an element and applying it to the display unit 1023, This makes it a more reliable portable music player.

[0360] Furthermore, the portable music player shown in FIG. 27(B) is equipped with an antenna, a microphone function, and a wireless function. If you carry it with you and connect it to your mobile phone, you can enjoy wireless hands-free driving while driving a car. Conversation in Lee is also possible.

[0361] FIG. 27C shows a mobile phone, which is composed of two housings, a housing 1030 and a housing 1031. The housing 1031 includes a display panel 1032, a speaker 1033, a microphone, and the like. 1034, pointing device 1036, camera lens 1037, external connection terminal The housing 1030 also includes a solar cell 1038 for charging the mobile phone. 040, an external memory slot 1041, etc. Also, the antenna is attached to the housing 1031 The transistor described in the above embodiment is provided in the display panel 1032. By applying this, a highly reliable mobile phone can be obtained.

[0362] The display panel 1032 is equipped with a touch panel, and in FIG. The operation keys 1035 are indicated by dotted lines. It also implements a boost circuit to boost the voltage supplied to each circuit to the voltage required.

[0363] The display direction of the display panel 1032 changes appropriately depending on the usage mode. The camera lens 1037 is located on the same surface as the lens 1032, so video calls are possible. The speaker 1033 and the microphone 1034 are not limited to voice calls, but can also be used for video calls, Recording and playback are possible. Furthermore, the housing 1030 and the housing 1031 can be slid to each other. As shown in 27(C), the device can be folded from the unfolded state to the overlapped state, making it suitable for carrying. This makes it possible to miniaturize the device.

[0364] The external connection terminal 1038 can be connected to various cables such as AC adapters and USB cables. It is possible to charge the battery and to communicate data with a personal computer, etc. By inserting a recording medium into the external memory slot 1041, it is possible to store and transfer a larger amount of data. Cut.

[0365] In addition to the above functions, it also has infrared communication function, TV reception function, etc. Good too.

[0366] FIG. 27D shows an example of a television device. The television device 1050 is A display unit 1053 is built into the housing 1051. The display unit 1053 displays an image. In addition, the CPU is built into the stand 1055 that supports the housing 1051. The transistor described in the above embodiment is provided in the display portion 1053 and the CPU. By applying this, a highly reliable television device 1050 can be obtained.

[0367] The television device 1050 can be operated using an operation switch provided on the housing 1051 or a separate remote control. The remote control can be operated by a remote controller. A display unit for displaying information output from the machine may be provided.

[0368] The television device 1050 includes a receiver, a modem, and the like. This allows reception of general television broadcasts, and can also be used for wired or wireless reception via a modem. By connecting to a network, communication can be one-way (sender to receiver) or two-way It is also possible to communicate information in both directions (between sender and receiver, or between receivers). .

[0369] The television device 1050 also includes an external connection terminal 1054 and a storage medium playback / recording unit 1055. 052, and an external memory slot. The external connection terminal 1054 is a It can be connected to any type of cable, enabling data communication with a personal computer, etc. In the storage medium playback and recording unit 1052, a disk-shaped recording medium is inserted and It is possible to read the stored data and write it to the recording medium. Images and videos stored in the external memory 1056 inserted in the reslot It is also possible to display it on the display unit 1053.

[0370] In addition, when the off-leak current of the transistor described in the above embodiment is extremely small, By applying this transistor to the external memory 1056 and the CPU, power consumption can be reduced sufficiently. This results in a highly reliable television apparatus 1050 with reduced power consumption.

[0371] This embodiment may be implemented in appropriate combination with other embodiment modes described in this specification. This can be done. EXAMPLES

[0372] In this embodiment, the resistivity of a metal film and a metal oxide film formed by introducing oxygen into the metal film is The results of the measurements will be explained below.

[0373] <Sample A1> The method for preparing sample A1 is explained below. First, a metal film was formed on a glass substrate. A 5 nm thick aluminum film was formed as a metal film by sputtering.

[0374] Next, oxygen was introduced into the metal film to form a metal oxide film. The metal film formed of the aluminum film is exposed to oxygen plasma generated in the apparatus, and the metal film was oxidized to form an aluminum oxide film as the metal oxide film.

[0375] Next, a pair of electrodes was formed on the metal oxide film. A pair of electrodes was formed by a 100 nm thick aluminum film using a stripping method. The distance between the pair of electrodes is 1000 μm, and the length over which the pair of electrodes faces is 70900 μm. It was m.

[0376] Through the above steps, sample A1 was produced.

[0377] <Sample A2> As a comparative example, a metal oxide film was not formed as in the sample A1, and a pair of electrodes was formed on the metal film. The sample with the pole formed was designated as sample A2.

[0378] Next, the electrical conductivity, resistivity, and resistance of Sample A1 and Sample A2 are shown in Table 1.

[0379] [Table 1]

[0380] As shown in Table 1, by introducing oxygen into a metal film, a highly insulating metal oxide film can be formed. I found out that... EXAMPLES

[0381] In this embodiment, the relationship between the presence or absence of a metal oxide film and the transmittance of a capacitor element is shown in FIG. 8 will be used to explain.

[0382] <Sample B1> A method for manufacturing the sample B1 will be described. First, an oxide semiconductor film was formed over a glass substrate. Here, we used In-Ga-Zn oxide with an atomic ratio of In:Ga:Zn=1:1:1. The sputtering target was oxygen and the sputtering gas was 35 nm thick. An In-Ga-Zn oxide film was formed.

[0383] Next, a metal film was formed over the oxide semiconductor film. An aluminum film having a thickness of 5 nm was formed as the metal film.

[0384] Next, oxygen was introduced into the metal film to form a metal oxide film. The metal film formed of the aluminum film is exposed to oxygen plasma generated in the apparatus, and the metal film was oxidized to form an aluminum oxide film as the metal oxide film.

[0385] Next, a nitride insulating film was formed on the metal oxide film by plasma CVD. A silicon nitride film having a thickness of 100 nm was formed as a nitride insulating film.

[0386] Next, a light-transmitting conductive film was formed on the nitride insulating film. A 100 nm thick indium oxide-tin oxide compound (ITO-SiO 2 ) conductivity The film was formed as a light-transmitting conductive film.

[0387] Through the above steps, sample B1 was fabricated.

[0388] <Sample B2> A method for manufacturing Sample B2 will be described. After forming a metal film in Sample B1, an acid was added to the metal film. A sample in which a nitride insulating film and a light-transmitting conductive film were laminated without introducing oxygen was designated as sample B2. In the sample B2, the aluminum film formed as the metal film was It is extremely thin, with a thickness of only 5 nm, and therefore has light-transmitting properties.

[0389] Next, the transmittance of Sample B1 and Sample B2 was measured using a spectrophotometer. The transmittance of sample B2 is shown in FIG.

[0390] In FIG. 18, the solid line indicates the transmittance of sample B1, and the dashed line indicates the transmittance of sample B2. From 18, the transmittance of sample B1 and sample B2 are almost the same, so it is possible to introduce oxygen into the metal film. It can be seen that the metal oxide film formed by the above process has light transmitting properties. Even if the metal oxide film is provided, the transmittance of the capacitor element can be maintained. EXAMPLES

[0391] In this example, the resistance of an oxide semiconductor film will be described with reference to FIGS. In this embodiment, an oxide semiconductor is used in each step of forming a transistor and a capacitor. The resistance of the film was measured.

[0392] A manufacturing method and a structure of a sample having an oxide semiconductor film are described with reference to FIGS. 19 and 20. FIG. 19(A) shows a part of the process for fabricating each sample, and FIG. 20A shows a top view of each sample, and FIG. 20B shows the sheet resistance of each sample. 20(E) through 20(E) are cross-sectional views taken along dashed line A1-A2 in FIG. Next, samples C1, C2, and C5, which are comparative examples, and a capacitive element according to one embodiment of the present invention will be described. Samples C3 and C4 each having an oxide semiconductor film that can be used for a semiconductor device were fabricated.

[0393] <Sample C1> A method for preparing sample C1 will be described below.

[0394] A gate electrode (not shown) is formed on a glass substrate 1901 in an area where a transistor is to be formed. Here, a tungsten film with a thickness of 100 nm was formed as the gate electrode. Formed.

[0395] Next, a plasma CV film is formed on the glass substrate 1901 and the gate electrode as an insulating film 1903. A silicon nitride film having a thickness of 400 nm was formed by method D.

[0396] Next, on the insulating film 1903, an insulating film 1904 is formed by a plasma CVD method. A silicon oxynitride film having a thickness of nm was formed.

[0397] Next, on the insulating film 1904, an In-Ga layer having an atomic ratio of In:Ga:Zn=1:1:1 is formed. -Zn oxide was used as a sputtering target, and a 35 mm thick film was formed by sputtering. After that, a mask was formed by photolithography. An oxide semiconductor film 1905 was formed by etching using a fluorine-containing oxide film.

[0398] Next, heat treatment was performed at 450°C for 1 hour in a nitrogen atmosphere, followed by a nitrogen and oxygen mixed gas. Heat treatment was performed at 450°C for 1 hour in an atmosphere (nitrogen = 80%, oxygen = 20%).

[0399] Next, a thick insulating film 1903 and an oxide semiconductor film 1905 are formed by a sputtering method. A 50 nm thick tungsten film, a 400 nm thick aluminum film, and a 100 nm thick tungsten film were After laminating the titanium films in order, they are etched using a mask formed by a photolithography process. A conductive film 1907 and a conductive film 1909 were formed by performing a plating treatment.

[0400] Next, the insulating film 1904, the oxide semiconductor film 1905, the conductive film 1907, and the conductive film 190 An insulating film that will later become the insulating film 1910 was formed on the substrate 9. Silicon oxynitride film (1st SiON) with a thickness of 50 nm and silicon oxynitride film (2nd SiON) with a thickness of 400 nm were formed by the D method. A silicon oxynitride film (2nd SiON) was formed (Step S1 in FIG. 19(A)). .

[0401] Next, heat treatment is performed at 350°C for 1 hour in a mixed gas atmosphere of nitrogen and oxygen. (Step S2 in FIG. 19(A)).

[0402] Next, an insulating film that will later become insulating film 1911 is formed on the insulating film that will later become insulating film 1910. The insulating film was a silicon nitride film with a thickness of 50 nm formed by plasma CVD. (Step S6 in FIG. 19(A)).

[0403] Next, a photolithography process is performed on the insulating film that will later become the insulating film 1910. After providing a mask, etching is performed to form an insulating film having openings 1913 and 1915. 1910 and an insulating film 1911 were formed.

[0404] Sample C1 was fabricated by the above steps. A cross-sectional view of Sample C1 is shown in FIG. In C1, the oxide semiconductor film 1905 is a silicon oxynitride film formed as an insulating film 1910. It comes into contact with the com membrane.

[0405] <Sample C2> A method for fabricating the sample C2 will be described. After step S2 of the sample C1, the insulating film 191 After a mask formed by photolithography is placed on the insulating film that will become 0, etching is performed. A sealing process was performed to form an opening 1914 (Step S4 in FIG. 19(A)).

[0406] Next, an insulating film that will later become the insulating film 1911 is formed. A silicon nitride film having a thickness of 50 nm was formed by method D (step S6 in FIG. 19(A)).

[0407] Next, a photolithography process is performed on the insulating film that will later become the insulating film 1910. After providing a mask, etching is performed to form an insulating film having openings 1913 and 1915. 1910 and an insulating film 1911 were formed.

[0408] Sample C2 was fabricated by the above steps. A cross-sectional view of sample C2 is shown in FIG. In C2, the oxide semiconductor film 1905 is a silicon nitride film formed as an insulating film 1911. in contact with the membrane.

[0409] <Sample C3> A method for fabricating sample C3 will be described. After step S2 of sample C1, the insulating film 191 A metal film is formed on the insulating film, which is 0, and oxygen is introduced into the metal film to form a metal oxide film. was formed (Step 3 in FIG. 19(A)).

[0410] Here, a 5 nm thick aluminum film is formed as the metal film by sputtering. In addition, oxygen was introduced into the aluminum film by exposing the aluminum film to oxygen plasma. An aluminum oxide film was formed as the metal oxide film.

[0411] Next, a mask formed by a photolithography process is provided on the metal oxide film, and then, An etching process was performed to form an opening 1914 (Step S4 in FIG. 19(A)).

[0412] Next, an insulating film that will later become the insulating film 1911 is formed. A silicon nitride film having a thickness of 50 nm was formed by method D (step S6 in FIG. 19(A)).

[0413] Next, a photolithography process is performed on the insulating film that will later become the insulating film 1911. After providing a mask, etching is performed to form an insulating film having openings 1913 and 1915. A film 1910, an insulating film 1911, and a metal oxide film 1912 were formed.

[0414] Sample C3 was fabricated by the above steps. A cross-sectional view of sample C3 is shown in FIG. In C3, the oxide semiconductor film 1905 is a silicon nitride film formed as an insulating film 1911. in contact with the membrane.

[0415] <Sample C4> A method for fabricating sample C4 will be described. After step S2 of sample C1, the insulating film 191 After a mask formed by photolithography is placed on the insulating film that will become 0, etching is performed. A sealing process was performed to form an opening 1914 (Step S4 in FIG. 19(A)).

[0416] Next, the oxide semiconductor film 1905, the conductive film 1907, the conductive film 1909, and the opening 191 A metal film is formed on the insulating film having 4, and oxygen is introduced into the metal film to form a metal oxide A film was formed (Step S5 in FIG. 19(A)).

[0417] Here, a 5 nm thick aluminum film is formed as the metal film by sputtering. In addition, oxygen was introduced into the aluminum film by exposing the aluminum film to oxygen plasma. An aluminum oxide film was formed as the metal oxide film.

[0418] Next, an insulating film that will later become the insulating film 1911 is formed. A silicon nitride film having a thickness of 50 nm was formed by method D (step S6 in FIG. 19(A)).

[0419] Next, a photolithography process is performed on the insulating film that will later become the insulating film 1911. After providing a mask, etching is performed to form an insulating film having openings 1913 and 1915. A film 1910, an insulating film 1911, and a metal oxide film 1912 were formed.

[0420] Sample C4 was fabricated by the above steps. A cross-sectional view of sample C4 is shown in FIG. In C4, the oxide semiconductor film 1905 is an oxide film formed as a metal oxide film 1912. It comes into contact with the aluminum film.

[0421] <Sample C5> The method for preparing sample C5 is as follows. A 100 mm thick film was deposited on a glass substrate by sputtering. nm indium oxide-tin oxide compound (ITO-SiO 2 A conductive film of The composition of the sputtering target used for the conductive film was In 2 O 3 :SnO 2 :SiO 2 After that, the mixture was heated at 250°C for 1 hour in a nitrogen atmosphere. Processing was carried out.

[0422] Next, indium oxide-tin oxide compound (ITO-SiO 2 ) on the conductive film of sample C1 A conductive film 1907 and a conductive film 1909 were formed in the same manner as in sample C4.

[0423] Sample C5 was fabricated by the above steps.

[0424] In the samples C1 to C5, the conductive film 1907 and the conductive film 1909 are spaced apart by 1 The conductive film 1907 and the conductive film 1909 face each other in the oxide semiconductor film 1905. The length of the sample was set to 1 mm, and the number of transistors in each sample was set to 20.

[0425] Next, the oxide semiconductor films in Samples C1 to C4 and the oxide semiconductor films in Sample C5 were Indium-tin oxide compound (ITO-SiO 2 ) Conductive film, each sheet resistance was measured In the samples C1 to C5, the conductive film 1907 was set to the ground potential, and the conductive A voltage of 1 V was applied to the film 1909.

[0426] The measurement results are shown in FIG. It can be seen that the sheet resistance of the oxide is reduced compared to that of the sample C1. When a film formed on a semiconductor film is etched, the film is exposed to plasma, and the oxide semiconductor It can be seen that the oxide semiconductor film is damaged and the sheet resistance of the oxide semiconductor film is reduced. Sample C4 has the same sheet resistance as sample C2. Even if an aluminum oxide film is provided between the films, hydrogen contained in the silicon nitride film does not form an oxide semiconductor. It can be seen that the metal oxide migrates to the oxide semiconductor film and the sheet resistance of the oxide semiconductor film is reduced.

[0427] The oxide semiconductor films included in Samples C2 to C4 are the same as those included in Sample C5. Indium-tin oxide compound (ITO-SiO 2 ) has a sheet resistance one order of magnitude lower than that of conventional conductive films. To a high degree, indium oxide-tin oxide compounds (ITO-SiO 2 ) conductive film In addition, it can be used as an electrode.

[0428] <Temperature dependence> Next, the temperature dependence of the sheet resistance of samples C2 to C4 was measured. The substrate temperatures are set to 25°C, 60°C, 100°C, 120°C, and 150°C. The sheet resistance was measured. The measurement results are shown in FIG. 21. In FIG. 21, the horizontal axis 1 / T (measurement temperature) and the vertical axis indicates the sheet resistance. The black markers indicate the measurement results of sample C2, the black markers indicate the measurement results of sample C3, and the circle markers indicate the measurement results of sample C4. The measurement results for sample C4 are shown.

[0429] From FIG. 21, it can be seen that the sheet resistance of the oxide semiconductor film does not change even if the measurement temperature is increased. That is, the oxide semiconductor films included in Samples C2 to C4 can be regarded as degenerate semiconductors. The oxide semiconductor films included in Samples C2 to C4 have a sheet resistance value that does not change even when the temperature is changed. Since the change in capacitance is small, the electrode can be used as a capacitor element.

[0430] <High temperature and humidity storage test> Next, the change in sheet resistance when samples C2 to C4 are stored at high temperature and high humidity will be Here, samples C2 to C4 were measured in an atmosphere with a temperature of 60° C. and a humidity of 95%. After storing for 330 hours, the sheet resistance of each sample was measured. The measurement results are shown in FIG. In FIG. 22, the horizontal axis indicates the test time, and the vertical axis indicates the sheet resistance. In the figure, the triangle marker indicates the measurement results of sample C2, and the cross marker indicates the measurement results of sample C3. The circle markers indicate the measurement results for sample C4.

[0431] From FIG. 22, it can be seen that the sheet resistance values ​​of samples C2 to C4 are low. It can be seen that the amount of time variation in the sheet resistance value is small for samples C2 to C4. The oxide semiconductor films included in Samples C2 to C4 had low sheet resistance in a high-temperature and high-humidity environment. Since the resistance fluctuation is small, it can be used as an electrode for a capacitance element. EXAMPLES

[0432] In this embodiment, a metal film is formed over an oxide semiconductor film, and oxygen is introduced into the metal film. Steps of forming a metal oxide film and hydrogen concentrations in an oxide semiconductor film in each step The evaluation results will be explained.

[0433] <Sample D1> A method for manufacturing the sample D1 will be described. The sample D1 is a glass substrate as shown in FIG. An oxide semiconductor film 803 is formed over a metal film 805. It was created by creating

[0434] Here, the oxide semiconductor film 803 is formed by using a compound having an atomic ratio of In:Ga:Zn=1:1:1. The In-Ga-Zn oxide was used as a sputtering target and the sputtering method was A 100 nm thick In-Ga-Zn oxide film was formed.

[0435] The metal film 805 is an aluminum film having a thickness of 5 nm formed by sputtering. Formed.

[0436] <Sample D2> A method for manufacturing the sample D2 will be described. As shown in FIG. 23B, the sample D2 is a glass substrate. An oxide semiconductor film 813 was formed over the oxide semiconductor film 811, and a metal film was formed over the oxide semiconductor film 813. Then, oxygen is introduced into the metal film to form a metal oxide film 815.

[0437] Here, the oxide semiconductor film 813 is the same as the oxide semiconductor film 803 in Sample D1. An IGZO film with a thickness of 100 nm was formed. By exposing the metal film formed of an aluminum film to the plasma, an oxide film 815 is formed. An aluminum oxide film was formed.

[0438] <Sample D3> A method for fabricating Sample D3 will be described. As shown in Fig. 23(C), Sample D3 was fabricated by forming an oxide semiconductor film 823 on a glass substrate 821, forming a metal oxide film 8 25 on the oxide semiconductor film 823, and forming a nitride insulating film 827 on the metal oxide film 825. was fabricated.

[0439] Here, the oxide semiconductor film 823 was formed as an IGZO film with a thickness of 100 nm, similar to the oxide semiconductor film 803 shown in Sample D1. The metal oxide film 825 was formed as a metal film and then oxygen was introduced into the metal film to form an aluminum oxide film. The nitride insulating film 827 was formed as a silicon nitride film with a thickness of 100 nm by plasma CVD method.

[0440] <Sample D4> A method for fabricating Sample D4 will be described. As shown in Fig. 23(D), Sample D4 was fabricated by forming an oxide semiconductor film 833 on a glass substrate 831, and forming a nitride insulating film 83 5 on the oxide semiconductor film 833.

[0441] Here, the oxide semiconductor film 833 was formed as an IGZO film with a thickness of 100 nm, similar to the oxide semiconductor film 803 shown in Sample D1. Also, the nitride insulating film 835 was formed as a silicon nitride film with a thickness of 100 nm, similar to the nitride insulating film 827 shown in Sample D3.

[0442] <SIMS analysis> SIMS analysis was performed on Samples D1 to D4. In each sample, the concentration of hydrogen in the oxide semiconductor film was measured from the substrate side to the oxide semiconductor film. The measurement results of Sample D1 are shown in Fig. 24(A 24(B), the measurement results of sample D2 are shown in FIG. 24(B), and the measurement results of sample D3 are shown in FIG. ) and the measurement result of sample D4 is shown in FIG. 24(D).

[0443] In FIG. 24, the horizontal axis indicates the distance in the depth direction, and the vertical axis indicates the hydrogen concentration. In FIG. 24, the glass substrate is indicated as glass, the oxide semiconductor film is indicated as IGZO, The metal film is indicated as Al, the metal oxide film is indicated as AlOx, and the nitride insulating film is indicated as SiN.

[0444] 24A and 24B, the oxide semiconductor film of Sample D2 has a higher conductivity than that of Sample D1. This is because the hydrogen concentration in the plasma processing device increases when oxygen is introduced into the metal film. This is because the contained hydrogen is introduced into the oxide semiconductor film simultaneously with oxygen.

[0445] 24B and 24C, the oxide semiconductor film of Sample D3 has a higher conductivity than that of Sample D2. This indicates that hydrogen contained in the nitride insulating film is oxidized to the metal oxide film. It can be seen that the oxygen ions are transferred to the oxide semiconductor film through the

[0446] 24C and 24D, the oxide semiconductor film of Sample D3 is different from the oxide semiconductor film of Sample D4. This is because the hydrogen concentration is high when oxygen is introduced into the metal film. This is because hydrogen and oxygen are introduced into the oxide semiconductor film at the same time.

[0447] From the above, when oxygen is introduced into a metal film formed on an oxide semiconductor film, At the same time, hydrogen was introduced into the oxide semiconductor film. Even if a metal oxide film is formed between the nitride insulating film, hydrogen contained in the nitride insulating film is absorbed into the oxide semiconductor. was found to migrate into the membrane. EXAMPLES

[0448] In this example, a transistor was fabricated and its Vg-Id characteristics and reliability were evaluated. The results will be explained below.

[0449] <Sample E1> In the sample E1, a transistor corresponding to the transistor 102a shown in FIG. 16 of the first embodiment is used. The method for producing sample E1 will be described.

[0450] First, a glass substrate is used as the substrate 11, and a conductive film serving as a gate electrode is formed on the substrate 11. A film 13 was formed.

[0451] As the conductive film 13, a tungsten film having a thickness of 200 nm is formed by a sputtering method. A mask is formed on the tungsten film by a photolithography process, and the mask is used to It was formed by etching a part of the tungsten film.

[0452] Next, a nitride insulating film 15 is formed on the conductive film 13 which functions as a gate electrode. An oxide insulating film 17 was formed on the insulating film 15 .

[0453] As the nitride insulating film 15, a silicon nitride film having a thickness of 400 nm is formed, and as the oxide insulating film 1 As the film 7, a silicon oxynitride film was formed to a thickness of 50 nm.

[0454] The silicon nitride film includes a first silicon nitride film, a second silicon nitride film, and a third silicon nitride film. The silicon nitride film was laminated in three layers.

[0455] The first silicon nitride film was prepared by using silane at a flow rate of 200 sccm and 2000 sccm The plasma CVD equipment was used with nitrogen at a flow rate of 100 sccm and ammonia gas at a flow rate of 100 sccm as raw material gases. The pressure in the treatment chamber was controlled to 100 Pa, and a high-frequency current of 27.12 MHz was applied. The source was used to supply 2000 W of power and the thickness was formed to be 50 nm.

[0456] For the second silicon nitride film, silane at a flow rate of 200 sccm, The plasma CVD equipment was operated using nitrogen at a flow rate of 2000 sccm and ammonia gas at a flow rate of 2000 sccm as raw material gases. The pressure in the processing chamber is controlled to 100 Pa, and a high frequency of 27.12 MHz is applied. A power of 2000 W was supplied using a power supply, and the film was formed to a thickness of 300 nm.

[0457] The third silicon nitride film was prepared by using silane at a flow rate of 200 sccm and 5000 sccm. The nitrogen gas was supplied to the processing chamber of the plasma CVD equipment at a flow rate of 1 The temperature was controlled at 0.00 Pa, and 2000 W of power was supplied using a 27.12 MHz high-frequency power supply. The first silicon nitride film and the second silicon nitride film were formed to a thickness of 50 nm. The substrate temperature was set to 350° C. when the silicon nitride film and the third silicon nitride film were formed.

[0458] The silicon oxynitride film was prepared by using silane at a flow rate of 20 sccm and a Nitrous oxide was supplied as a raw material gas to the processing chamber of the plasma CVD device, and the pressure in the processing chamber was set at 4 The pressure was controlled at 0 Pa, and 100 W of power was supplied using a 27.12 MHz high-frequency power source. The silicon oxynitride film was formed at a substrate temperature of 350° C. did.

[0459] Next, a conductive layer serving as a gate electrode is formed through the nitride insulating film 15 and the oxide insulating film 17. An oxide semiconductor film 19a was formed so as to overlap the film 13.

[0460] Here, an oxide semiconductor film having a thickness of 35 nm is formed over the oxide insulating film 17 by a sputtering method. After the formation of the oxide semiconductor film, a mask is formed over the oxide semiconductor film by a photolithography process. A part of the oxide semiconductor film is etched using a mask to form an oxide semiconductor film 19a. Ta.

[0461] The oxide semiconductor film 19a is an In-Ga-Zn oxide film having an atomic ratio of In:Ga:Zn=1:1:1. Zn oxide was used as the sputtering target and 50% oxygen was used as the sputtering gas. into the processing chamber of the sputtering device, and the pressure in the processing chamber is controlled to 0.6 Pa. The oxide semiconductor film was formed by supplying a direct current of 2.5 kW. The temperature was set to 170°C.

[0462] Next, a heat treatment was performed. Here, the heat treatment was performed for 1 hour in a nitrogen atmosphere at 480°C. Then, the heat treatment was carried out for 1 hour in a mixed gas atmosphere of nitrogen and oxygen at 480°C.

[0463] Next, conductive films 21a and 21b that function as a pair of electrodes in contact with the oxide insulating film 17 are formed. Successful.

[0464] First, a conductive film was formed over the oxide insulating film 17 and the oxide semiconductor film 19a. As a result, an aluminum film having a thickness of 400 nm is formed on a tungsten film having a thickness of 50 nm. A titanium film having a thickness of 100 nm was formed on the aluminum film. A mask is formed on the conductive film by a process, and a part of the conductive film is etched using the mask. Then, conductive films 21a and 21b functioning as a pair of electrodes were formed.

[0465] Next, the substrate is moved to a reduced pressure processing chamber, heated to 220° C., and then placed in the processing chamber. A high-frequency power of 150 W was supplied to the upper electrode using a 27.12 MHz high-frequency power source. The oxide insulating film 17 was exposed to oxygen plasma generated in a dinitrogen oxide atmosphere.

[0466] Next, an oxide insulating film is formed over the oxide insulating film 17 and the conductive films 21a and 21b, and then, A part of the oxide insulating film is etched to form an oxide insulating film 23 and an oxide insulating film 25. Successful.

[0467] Here, the oxide insulating film 23 and the oxide insulating film 25 were formed.

[0468] The oxide insulating film 23 is made of silane at a flow rate of 30 sccm and one Nitrous oxide was used as the source gas, the pressure in the processing chamber was 40 Pa, the substrate temperature was 220°C, and A 50 nm thick oxide film was formed by plasma CVD using a 1000 MHz high-frequency power supply to parallel plate electrodes. A silicon nitride film was formed.

[0469] The oxide insulating film 25 is made of silane at a flow rate of 160 sccm and silane at a flow rate of 4000 sccm. Nitrous oxide was used as the source gas, the pressure in the processing chamber was 200 Pa, and the substrate temperature was 220°C. A 400 nm thick film was fabricated using the plasma CVD method, in which 500 W of high-frequency power was supplied to parallel plate electrodes. Under these conditions, the amount of oxygen in the stoichiometric composition was less than that of the silicon oxynitride film. The silicon oxynitride film contains a large amount of oxygen and some of the oxygen is released by heating. This can be done.

[0470] Next, heat treatment is performed to remove water, nitrogen, hydrogen, and the like from the oxide insulating film 23 and the oxide insulating film 25. At the same time, part of oxygen contained in the oxide insulating film 25 is supplied to the oxide semiconductor film. Here, the heat treatment was performed at 350°C for 1 hour in a mixed gas atmosphere of nitrogen and oxygen. .

[0471] Next, a metal film is formed on the oxide insulating film 25, and then oxygen is introduced into the metal film to form a metal oxide film. A membrane was formed.

[0472] Here, an aluminum film is deposited on oxygen plasma generated in a sputtering device. The metal film formed was exposed and oxidized to form a 5 nm thick aluminum oxide film. A minium film was formed.

[0473] Next, a nitride insulating film 29 having a thickness of 100 nm was formed on the metal oxide film. The film was prepared by mixing silane at a flow rate of 50 sccm, nitrogen at a flow rate of 5000 sccm, and The source gas was ammonia gas of 100 m, the pressure in the processing chamber was 100 Pa, and the substrate temperature was 350°C. The film was formed by the plasma CVD method in which 1000 W of high frequency power was supplied to parallel plate electrodes. .

[0474] Next, the nitride insulating film 15, the oxide insulating film 23, the oxide insulating film 25, the metal oxide film 27, An opening is formed in a part of the nitride insulating film 29, reaching the conductive film 13 which functions as a gate electrode. Formed.

[0475] Next, a conductive film 31a that functions as a gate electrode was formed on the nitride insulating film 29. The conductive film 31a functioning as a gate electrode is electrically connected to the conductive film 13 functioning as a gate electrode. The configuration is such that it can be connected.

[0476] Here, the conductive film 31a functioning as the gate electrode is formed by sputtering to a thick An indium oxide - tin oxide compound (ITO - SiO 2 ) containing 100 nm of silicon oxide was formed into a conductive film. The composition of the sputtering target used for the conductive film was In 2 O 3 :SnO 2 :SiO 2 = 85:10:5 [wt%]. Thereafter, heat treatment was performed at 250 °C for 1 hour in a nitrogen atmosphere.

[0477] Through the above steps, transistors included in sample E1 were fabricated.

[0478] In this example, transistors with a channel width of 2 μm and channel lengths of 1 μm, 1.25 μm, 1.5 μm, 2 μm, 4 μm, and 6 μm were fabricated respectively.

[0479] <Sample E2> As a comparative example, in the transistor 102a shown in FIG. 16, a transistor having no metal oxide film 27 and a conductive film 31a functioning as a gate electrode was fabricated. The sample containing the transistor was designated as sample E2. <Sample E3>

[0480] <Sample E3> As a comparative example, in the transistor 102a shown in FIG. 16, a transistor having no metal oxide film 27 was fabricated. The sample containing the transistor was designated as sample E3.

[0481] <Vg - Id Characteristics> Next, the Vg - Id characteristics of the transistors of samples E1 to E3 were measured. Here, the substrate temperature was set at 25 °C, the potential difference between the source and drain (hereinafter also referred to as drain voltage, Vd) was set at 1 V and 10 V, and the potential difference between the source and gate electrodes (hereinafter also referred to as gate voltage, Vg) was The current flowing between the source and drain when the voltage (hereafter referred to as the The change in the gate current (Vg) versus the drain current (Id) was measured.

[0482] FIG. 25A shows a transistor having a channel length of 1 μm in the sample E1. The Vg-Id characteristics of a transistor are shown in Fig. 25(B). Figure 25(C) shows the Vg-Id characteristics of a transistor with a channel length of 6 μm. 25, the horizontal axis represents the gate voltage Vg, and the first vertical axis represents the drain The vertical axis represents the current Id, and the second vertical axis represents the field effect mobility. Here, the field effect mobility is In order to show values ​​in the saturation region, the field-effect mobility calculated at Vd=10 V is shown.

[0483] As shown in Figure 25, a transistor with excellent Vg-Id characteristics can be fabricated in sample E1. I realized that this was what had happened.

[0484] <Relationship between channel length and threshold voltage> The relationship between the channel length L and the threshold voltage Vth of the transistors in the samples E1 to E3 FIG. 26 shows the relationship between the transistors included in the samples E1 to E3. , the threshold voltage Vth for each channel length L is plotted. The vertical axis indicates the actual channel length of the transistor, and the vertical axis indicates the threshold voltage of the transistor.

[0485] In the transistors included in sample E1, the measured channel length was 0.64 μm to 6 The threshold voltage fluctuates little up to 0.5 μm. On the other hand, the metal oxide film 27 As the measured channel length becomes shorter, the samples E2 and E3, which do not have the In the actual measurement, when the channel length was less than 2 μm, the threshold voltage shifted in the negative direction. This shows that the metal oxide film 2 on the transistor is By forming the metal oxide film 27 on the oxide semiconductor film, In addition, oxygen can be introduced into the oxide insulating film formed on the oxide semiconductor film. As a result, the oxide semiconductor film has a small channel length. Even for transistors, it is possible to reduce the variation in threshold voltage, and It is possible to fabricate a transistor of this type.

Claims

1. an oxide semiconductor film having a channel formation region of a transistor; a first conductive film having a region in contact with a top surface of the oxide semiconductor film and functioning as one of a source electrode and a drain electrode of the transistor; a second conductive film having a region in contact with a top surface of the oxide semiconductor film and functioning as the other of the source electrode and the drain electrode of the transistor; a first insulating film having a region in contact with an upper surface of the oxide semiconductor film, a region in contact with an upper surface of the first conductive film, and a region in contact with an upper surface of the second conductive film; a second insulating film having a region in contact with an upper surface of the first insulating film; a third insulating film having a region in contact with the first insulating film and a region in contact with the second insulating film; a third conductive film having a region functioning as a pixel electrode; a fourth conductive film having a region overlapping the third conductive film via the third insulating film; a fifth conductive film having a region in contact with the fourth conductive film without passing through an opening; the third insulating film has a region in contact with the third conductive film and a region in contact with the fourth conductive film; the third insulating film has a region overlapping the channel formation region via the first insulating film and the second insulating film; the third conductive film has a region in contact with the first conductive film through an opening formed in the third insulating film; the second conductive film has a region extending in a first direction in a plan view, the fifth conductive film has a region extending along the first direction in a plan view, the fifth conductive film has the same material as the source electrode or the drain electrode; The third conductive film does not have a region overlapping with the fifth conductive film.

2. an oxide semiconductor film having a channel formation region of a transistor; a first conductive film having a region in contact with a top surface of the oxide semiconductor film and functioning as one of a source electrode and a drain electrode of the transistor; a second conductive film having a region in contact with a top surface of the oxide semiconductor film and functioning as the other of the source electrode and the drain electrode of the transistor; a first insulating film having a region in contact with an upper surface of the oxide semiconductor film, a region in contact with an upper surface of the first conductive film, and a region in contact with an upper surface of the second conductive film; a second insulating film having a region in contact with an upper surface of the first insulating film; a third insulating film having a region in contact with the first insulating film and a region in contact with the second insulating film; a third conductive film having a region functioning as a pixel electrode; a fourth conductive film having a region overlapping the third conductive film via the third insulating film; a fifth conductive film having a region in contact with the fourth conductive film without passing through an opening; the third insulating film has a region in contact with the third conductive film, a region in contact with the fourth conductive film, and a region in contact with the fifth conductive film; the third insulating film has a region overlapping the channel formation region via the first insulating film and the second insulating film; the third conductive film has a region in contact with the first conductive film through an opening formed in the third insulating film; the second conductive film has a region extending in a first direction in a plan view, the fifth conductive film has a region extending along the first direction in a plan view, the fifth conductive film has the same material as the source electrode or the drain electrode; The third conductive film does not have a region overlapping with the fifth conductive film.

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