Semiconductor device

Abstract

To provide a semiconductor device that has a transistor with excellent electrical characteristics, and a semiconductor device that has a high aperture ratio and has a capacitive element which increases charge capacity.SOLUTION: A semiconductor device has a transistor 102 and a capacitive element 105 on an insulation surface, where the transistor has a gate electrode 13, an oxide semiconductor film 19a overlapping the gate electrode, a nitride insulating film 15 and an oxide insulating film 17 which function as a gate insulating film between the gate electrode and the oxide semiconductor film, conductive films 21a, 21b which function as a pair of electrodes contacting the oxide semiconductor film, an oxide insulating film 25 contacting the oxide semiconductor film, a metal oxide film 27 on the oxide insulating film, a nitride insulating film 29, and a conductive film 31 which is formed on an opening 41 of the nitride insulating film and functions as a pixel electrode contacting the conductive film 21b. The capacitive element has a film 19b having conductivity on the oxide insulating film 17, the film having conductivity and a metal oxide film 27 provided between the conductive film 31 and the conductive film.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an article, a method, or a manufacturing method. The invention relates to the 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 also relates to a capacitor element having a film containing such 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 formed using a semiconductor thin film formed on a substrate. The technology for constructing transistors 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 usable semiconductor thin films, but other materials and Oxide semiconductors have been attracting attention as a solution.

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

[0005] In oxide semiconductors, the penetration of impurities such as hydrogen can cause shallow electrical doping. It has been pointed out that a toner level is formed and electrons are generated as carriers. 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 the hydrogen blocking property, is oxidized. The entire surface of the substrate is then coated with a conductive material to cover the channel region of the semiconductor film, the source electrode, and the drain electrode. By providing the insulating film over the entire length, entry of hydrogen into the oxide semiconductor film can be suppressed, and leakage current can be prevented. This is suppressed (see Patent Document 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-165528 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-138934 [Patent Document 3] Japanese Patent Application Laid-Open No. 2010-16163 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 containing This is because the oxide semiconductor film is prone to oxygen deficiency and tends to have a normally-on characteristic. This is because the loss generates charges, which reduces the resistance. If the device has a high power consumption, malfunctions may occur more easily when the device is in operation, or power consumption may increase when the device is not in operation. In addition, the transistors may deteriorate over time or undergo stress testing. There is a problem in that the amount of fluctuation 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 aluminum oxide can be deposited by sputtering using an aluminum oxide target. When a film is formed, arcing occurs, generating fine particles. The inclusion of fine particles in the deposited film causes a decrease in yield.

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

[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, or 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 containing a material that can be an oxide semiconductor, typically indium and M (M is Al, Ga, Y, Zr, La, Ce, or Nd), and a film having transparency. 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 capacitor.

[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 that functions as a gate insulating film. a metal oxide film on the oxide insulating film, and a first insulating film formed in the 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 nitride, yttrium oxide, yttrium oxynitride, hafnium oxide, yttrium oxynitride It is formed of hafnium, titanium oxide, tantalum oxide, or tantalum oxynitride. The metal oxide film may be separated.

[0014] The oxide semiconductor film and the conductive film may be an In-Ga oxide, an 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 a surface temperature of 100°C to 700°C or 100°C to 500°C The amount of oxygen released in terms of oxygen atoms is 1.0 × 10 18 atoms / cm 3 That's all . [Effects of the Invention]

[0017] According to one embodiment of the present invention, a semiconductor device including a transistor with excellent electrical characteristics is provided. Alternatively, according to one embodiment of the present invention, it is possible to achieve a high aperture ratio and an increased charge capacity. It is possible to provide a semiconductor device having a capacitor element that can be used for the purpose of the present invention. According to one embodiment of the present invention, semiconductor devices can be manufactured with high yield. In this manner, semiconductor devices can be manufactured with high productivity. [Brief explanation of the drawings]

[0018] [Figure 1] 1A and 1B are a block diagram and a circuit diagram illustrating one embodiment of a semiconductor device. [Figure 2] FIG. 1 is a top view illustrating one embodiment of a semiconductor device. [Figure 3] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 4] 1A to 1C are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. [Figure 5] 1A to 1C are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. [Figure 6] 1A to 1C are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. [Figure 7] 1A to 1C are cross-sectional views illustrating one embodiment 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 embodiment of a method for manufacturing a semiconductor device. [Figure 10] 1A to 1C are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. [Figure 11] 1A to 1C are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. [Figure 12] FIG. 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 embodiment 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] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 17] 1A to 1C are cross-sectional views illustrating one embodiment of a method for manufacturing a semiconductor device. [Figure 18] FIG. 10 is a diagram illustrating the transmittance of a sample. [Figure 19] FIG. 10 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. 10 is a diagram illustrating the sheet resistance of a sample. [Figure 22] FIG. 10 is a diagram illustrating the sheet resistance of a sample. [Figure 23] FIG. 2 is a diagram illustrating the structure of a sample. [Figure 24] 10A and 10B are diagrams illustrating the concentration of hydrogen contained in an oxide semiconductor film. [Figure 25] FIG. 10 is a diagram illustrating Vg-Id characteristics. [Figure 26] FIG. 10 is a diagram illustrating the relationship between the channel length and the 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] FIG. 1 is a cross-sectional view illustrating one embodiment of a semiconductor device. [Figure 30] FIG. 1 is a top view illustrating one embodiment of a semiconductor device. [Figure 31] FIG. 10 is a diagram illustrating the temperature dependence of resistivity. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following description, and the embodiments and methods thereof may be modified without departing from the spirit and scope of the present invention. It will be readily apparent to those skilled in the art that various modifications may be made to the design 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 embodiments and examples described below, the same parts or parts having similar functions In the case of parts, the same symbols or the same hatch patterns are used in common among different drawings, and the repetition The explanation of repetition will be omitted.

[0020] In each figure described in this specification, the size of each component, the thickness of the film, or the area is The figures may be exaggerated for clarity and are not necessarily limited to that scale. stomach.

[0021] In addition, terms such as first, second, and third used in this specification are used interchangeably to avoid confusion of components. It is not intended to limit the number of items. The terms "second" or "third" can be used interchangeably to explain the present invention.

[0022] The functions of the "source" and "drain" are also different when the direction of the current changes 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 refers to the potential difference between two points, and potential refers to the electrostatic field at a certain point. This refers to the electrostatic energy (electrical potential energy) of a unit charge in a particle. However, in general, the potential difference between the 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, the term "potential" may be read as "voltage." , voltage may be read as potential.

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

[0025] (Embodiment 1) In this embodiment, a semiconductor device according to 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. 1A includes a pixel portion 10 1, a scanning line driving circuit 104, and a signal line driving circuit 106 are arranged parallel or approximately parallel to each other. m scanning lines 107, the potentials of which are controlled by a scanning line driving circuit 104; The individual electrodes are arranged parallel or approximately parallel to each other, and the potential is controlled by a signal line driving circuit 106. and n signal lines 109. Furthermore, the pixel section 101 has multiple The pixel 103 is arranged parallel or approximately 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 rows or substantially parallel to each other. The circuit 106 may be collectively referred to as a drive circuit section.

[0027] Each scanning line 107 is connected 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 any one of the columns among the pixels 103 arranged in m rows and n columns. 3. Both m and n are integers equal to or greater than 1. is m pixels 103 arranged in any one of the columns among the pixels 103 arranged in m rows and n columns. 3. The capacitance lines 115 are arranged parallel to the scanning lines 107. When the pixels 103 are arranged in m rows and n columns, one of the pixels 103 is arranged in 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 set appropriately according to the specifications of the pixel 103. The orientation 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. In addition, one of the pair of electrodes of the liquid crystal element 121 for each pixel 103 in each row may be applied. may be given different potentials.

[0031] The liquid crystal element 121 controls the transmission or non-transmission of light by the optical modulation action of the liquid crystal. The optical modulation effect of the liquid crystal 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 diagonal direction or an electric field in a diagonal 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, and the like.

[0032] The display device having the liquid crystal element 121 can be driven in various modes, such as TN mode and 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 (Side-to-Side 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 following. The liquid crystal that exhibits the blue phase has a response speed of 1 msec or less. 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. 1B, the source electrode and the drain electrode of the transistor 102 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 electrodes of the scan line 1. 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 the 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 retained by turning off the transistor 102. By repeating this process for each row, an image can be displayed.

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

[0039] One of the source electrode and the drain electrode of the transistor 133 is supplied with a data signal. The gate electrode of the transistor 133 is electrically connected to the signal line 109. The signal 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 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 functions 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 transistor 133 is connected to the other of the source electrode and drain electrode of the capacitor 132. It is electrically connected to one electrode of the element 105 .

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

[0043] One of the source and drain electrodes of the transistor 135 is given 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 the gate signal is applied. are electrically connected.

[0044] The transistor 135 has a function of adjusting the 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 capacitor 105 is electrically connected to the other of the source electrode and the drain electrode of the transistor 133. The other of the pair of electrodes is connected to the other of the source electrode and 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 105 It functions as a storage capacitor to store the

[0047] One of the pair of electrodes of the light emitting element 131 is connected to the source electrode and 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 wiring 141 functions as a gate.

[0048] The light emitting element 131 may be, for example, an organic electroluminescence element (also known as 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] Note that 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. The power supply potential VDD is applied to the wiring 141, and the low power supply potential VSS is applied to the wiring 142.

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

[0051] The pixel 103 to which the data has been written is retained 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 at a brightness corresponding to the amount of current flowing. You can display images.

[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 FIGS. 1B and 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, an EL (electroluminescence) element (organic and and inorganic EL elements, organic EL elements, inorganic EL elements), LEDs (white LEDs, red LEDs ED, green LED, blue LED, etc.), transistor (transistor that emits light according to the current electron emission element, liquid crystal element, electronic ink, electrophoretic element, grating light valve GLV (global low voltage), plasma display (PDP), MEMS (microelectromechanical systems) Digital Micromirror Device (DMD), DMS (Digital Micro Shutter), MIRASOL (registered trademark), IMOD (Interference Modulation (light modulation) element, electrowetting element, piezoelectric ceramic disc By electro-magnetic effects, such as carbon nanotubes, contrast, brightness, and reflection Some display devices have display media that change reflectance, transmittance, etc. 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 a liquid crystal element is a liquid crystal display. Spray (transmissive LCD, semi-transmissive LCD, reflective LCD) LCDs (e.g., LCDs with electronic ink, LCDs with direct viewing, LCDs with projection) are also available. An example of a display device using electrophoretic elements is electronic paper.

[0054] In FIG. 2, the conductive film 13 functioning as a scanning line is oriented in a direction substantially perpendicular to the signal line (left in the drawing). The conductive film 21a that functions as a signal line is disposed so as to extend in the direction of the scanning line. The conductive film functions as a capacitance line. The conductive lines 21c are provided so as to extend in a direction parallel to the signal lines. 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 power supply 104 is electrically connected to the power supply 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 14 that functions as a gate electrode. ), an oxide semiconductor film 19a in which a channel region is formed on the gate insulating film, a pair of The conductive film 13 is made up 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. 2, the end of the scan line is formed in the oxide semiconductor film 19a in the top view. Therefore, the scanning lines are positioned outside the edge of the screen, blocking the light from the backlight or other light sources. As a result, when light is irradiated onto the oxide semiconductor film 19a included in the transistor, Therefore, the change in 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 element 105 is connected to the 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] In this way, since the capacitor 105 has light-transmitting properties, the capacitor 105 is large in the pixel 103. Therefore, the aperture ratio can be increased, typically 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 becomes smaller, and the area of ​​the capacitance element also becomes smaller. In a semiconductor device with a low capacitance, the charge capacity stored in the capacitance element is small. Since the capacitor 105 described in this embodiment has a light-transmitting property, the capacitor can be provided in a pixel. This makes it possible to obtain a sufficient charge capacity in each pixel while increasing the aperture ratio. pixel density is 200ppi or more, 300ppi or more, and even 500ppi or more The present invention can be suitably used for high-resolution semiconductor devices.

[0059] Furthermore, according to one embodiment of the present invention, the aperture ratio can be increased even in a high-resolution display device. This allows for efficient use of light from light sources such as backlights, and reduces the power consumption of the display device. The force can be reduced.

[0060] Next, a cross-sectional view taken along the dashed lines AB and CD in FIG. 2 is shown in FIG. The transistor 102 is a channel-etched 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, and the cross-sectional view at CD is a cross-sectional view of the transistor. 1 is a cross-sectional view of a transistor 102 in the channel width direction.

[0061] The transistor 102 shown in FIG. 3 is a transistor with a single gate structure. The gate electrode 13 is formed on the substrate 11. The nitride insulating film 15 is formed on the conductive film 13 that functions as a gate electrode. 5, and the oxide insulating film 17 formed on the nitride insulating film 15 and the oxide insulating film 17 , an oxide semiconductor film 19a overlapping with the conductive film 13 functioning as a gate electrode, and an oxide semiconductor The conductive film 19a is in contact with the conductive film 21a and the conductive film 21b, which function 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 22 is formed on the oxide insulating film 23. 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 described 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. The capacitor 105 is also provided as a dielectric material for the capacitor element 105 .

[0064] The metal oxide film 27 is an oxide film that is light-transmitting and has low oxygen permeability. It is preferable to use a high dielectric material for the metal oxide film 27. Representative examples include aluminum oxide, aluminum oxynitride, gallium oxide, and gallium oxynitride. Sodium, yttrium oxide, yttrium oxynitride, hafnium oxide, hafnium oxynitride Examples of metal oxide films include those made of titanium, 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 to m or less, the metal oxide film 27 has high insulating properties. This is because it can be obtained by oxidizing a metal film. This will be discussed later.

[0066] The nitride insulating film 29 can be an insulating film with 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. , an aluminum nitride film, an aluminum nitride oxide film, and the like.

[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 an oxide insulating film containing more oxygen than the oxygen required for the stoichiometric composition; The oxide insulating film containing more oxygen than that satisfying the stoichiometric composition is preferably Oxidation containing more oxygen than the stoichiometric composition The surface temperature of the insulating film is 100°C or higher and 700°C or lower in TDS analysis. The amount of oxygen released in terms of oxygen atoms during heat treatment at temperatures between 500°C and 1.0×1 0 18 atoms / cm 3or more, preferably 3.0 × 10 20 atoms / cm 3 That's all It is an oxide insulating film.

[0070] A transistor using an oxide semiconductor film containing oxygen vacancies has a threshold voltage This is because oxide semiconductors tend to have a normally-on characteristic. This is because oxygen vacancies in the film cause charges to be generated, resulting in a low resistance. If the transistor has normally-on characteristics, malfunctions may occur easily during operation or This can cause various problems, such as increased power consumption over time. This leads to a problem of an increase in the amount of fluctuation 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. The metal oxide film 27 is then covered with a nitride insulating film 29. 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 hydrogen from the oxide semiconductor film 19a to the oxide semiconductor film 19a. As a result, the transistor has normally-off characteristics. Experiments have shown that it is possible to reduce the amount of variation in the electrical characteristics of transistors, typically the threshold voltage. can.

[0072] In the capacitor 105, the conductive film 19b is formed between the oxide semiconductor film 19a and the oxide semiconductor film 19b. The film is formed at the same time, and oxygen deficiency occurs due to plasma damage, etc., resulting in a conductive Alternatively, the conductive film 19b may have 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, It also contains impurities and oxygen deficiencies 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 is formed between the oxide semiconductor film 19a and the metal oxide film 27. The capacitor element 105 has the insulating films 23 and 25, but the conductive film 19b and There are no oxide insulating films 23 and 25 between the metal oxide films 27. The dielectric of 05 is a metal oxide film 27 and a nitride insulating film 29. This allows the charge capacity of the capacitor 105 to be increased. In the capacitor 105, a metal oxide film 27 and a nitride insulating film 28, 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 a substrate for forming an oxide semiconductor film of a transistor. The conductive film that functions as a pixel electrode is formed on the insulating film. The other electrode of the element is used. Since the process 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, and 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 strong enough to withstand the subsequent heat treatment. It must be heat resistant. For example, glass substrates, ceramic substrates, quartz substrates, and surface treatment substrates are A fiber substrate or the like may be used as the substrate 11. Also, silicon, silicon carbide, or the like may be used. Single crystal semiconductor substrates, polycrystalline semiconductor substrates, and compounds such as silicon germanium It is also possible to apply a semiconductor substrate, an SOI substrate, etc., and a semiconductor element is formed on these substrates. 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 10th generation (2950mm x 3400mm) 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 all of the semiconductor device is completed thereon. The transistor 102 can be transferred to another substrate. 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, or the like. 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 layer can be formed by using an alloy of the above metal elements or an alloy combining 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 aluminum film containing silicon, or aluminum on titanium film Two-layer structure with titanium film laminated on titanium nitride film, two-layer structure with titanium film laminated on titanium nitride film, Two-layer structure with tungsten film stacked on tantalum film, tantalum nitride film or 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 silicon, chromium, neodymium, and scandium, or a composite 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, tungsten oxide, or the like. 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, a laminate structure of the above-mentioned light-transmitting conductive material and the above-mentioned metal element can be used. It is also possible.

[0080] The nitride insulating film 15 can 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 recommended 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 a single layer.

[0083] The oxide insulating film 17 is made of hafnium silicate (HfSiO x ), nitrogen added Hafnium silicate (HfSi x O y N z ), nitrogen-doped hafnium aluminium Laminate (HfAl x O y N z ), hafnium oxide, yttrium oxide, etc. The use of k-materials can reduce 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 preferable to set the thickness to 300 nm or less, and more preferably to set the thickness to 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 an In-Ga oxide, an In-Zn oxide, an In- M-Zn oxide (M is Al, Ga, Y, Zr, La, Ce, or Nd) is used. 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 percentage of M is preferably 25 atomic %. more preferably In is greater than 34 atomic % and M is less than 75 atomic %; atomic% 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 or more and 200 nm or less, preferably 3 nm or more and 100 nm or less. 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 (M is Al, Ga, Y, Zr, La, In the case of In-Mn-Zn oxide films, the sputtering method used to deposit In-Mn-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, In:M:Zn=3:1:2 are preferred. The atomic ratio of the oxide semiconductor film 19a to be formed may be adjusted by adding the above-mentioned sputtering error. 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 x10 15 pieces / cm 3 or less, more preferably 1 × 10 13 pieces / cm 3 The following is more preferred: 1×10 11 pieces / cm 3 The following oxide semiconductor film is used.

[0092] However, the semiconductor characteristics and electrical characteristics (field effect) of the required transistors are not limited to these. It is sufficient to use an appropriate composition depending on the required properties (e.g., the mobility, threshold voltage, etc.). In order to obtain semiconductor characteristics of the transistor, the carrier density and impurity of the oxide semiconductor film 19a are controlled. The material concentration, defect density, atomic ratio of metal elements to oxygen, interatomic distance, density, etc. are set appropriately. 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 oxide semiconductors have 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. The threshold voltage tends to be 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 range of drain voltage from 1V to 10V, the off-state current is Below the measurement limit of the analyzer, i.e., 1×10 -13 You can get the trait of A or below. Therefore, a transistor in which a channel region is formed in the oxide semiconductor film has good electrical characteristics. The transistor may 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 desorbed (or in the part from which oxygen has been desorbed). When hydrogen enters the gap, electrons, which act as carriers, are generated. When bonded to oxygen, which bonds to metal atoms, electrons, which act as carriers, may be generated. 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 to measure the oxide semiconductor film 19a by secondary ion mass spectrometry ( SIMS (Secondary Ion Mass Spectrometry) The resulting hydrogen concentration is 5 x 10 19 atoms / cm 3 Less than 1×10, more preferably 1 9 atoms / cm 3 Below, 5 x 10 18 atoms / cm 3 Less than 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) concentration) is 2 x 10 18 atoms / cm 3 Less than or equal to 2 x 10 17 atoms / cm 3 The following applies.

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

[0098] Furthermore, when nitrogen is contained in the oxide semiconductor film 19a, electrons serving as carriers are generated, and As a result, the carrier density increases and it becomes easier to make the semiconductor n-type. Therefore, the transistor having the oxide semiconductor film tends to be normally on. In this case, it is preferable that nitrogen 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. For example, CAAC-OS (C Axis Aligned-Crystalline Oxide Semiconductor), polycrystalline structure, microcrystalline structure (described later), or 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 does not have crystalline components.

[0101] Note that the oxide semiconductor film 19a may have an amorphous structure, a microcrystalline structure, or a polycrystalline structure. The film may be a mixed film having two or more of the following: a CAAC-OS region, a CAAC-OS region, and a single crystal structure region. The mixed film may have, for example, an amorphous structure region, a microcrystalline structure region, a polycrystalline structure region, a CA It may have two or more regions, either an AC-OS region or a single crystal structure region. The mixed film may have, for example, an amorphous structure region, a microcrystalline structure region, a polycrystalline structure region, a CA When the layer structure has two or more types of regions, either AC-OS region or 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. It is a film containing the same metal element. That is, 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 19b has an electrically conductive property due to the oxygen vacancy. The impurity that can be used is hydrogen. However, 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. Therefore, the impurity concentration of the conductive film 19b is high. The hydrogen concentration is 5×1019 atoms / cm 3 Less than 5 x 10 18 ato ms / cm 3 Less than 1 × 10 18 atoms / cm 3 Less than or equal to 5, more preferably x10 17 atoms / cm 3 or less, more preferably 1 × 10 16 atoms / cm 3 The hydrogen concentration contained in the conductive film 19b is 8×10 19 atoms / cm 3 or more, preferably 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 simultaneously with the oxide semiconductor film 19a is exposed to plasma. The oxide semiconductor film can be damaged by the oxygen vacancies. 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 exposed to the oxygen, oxygen vacancies are generated. Alternatively, the oxide semiconductor film is a mixture of oxygen and hydrogen. When exposed to plasma of a mixed gas, hydrogen, rare gas, ammonia, etc., oxygen vacancies are generated. As a result, the oxide semiconductor film becomes highly conductive 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 said to be a highly conductive metal oxide film.

[0106] Furthermore, 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 forms carriers. 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 and becomes 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 conductivity. The oxide semiconductor that has become a conductor 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, oxide semiconductors have a large energy gap and are therefore transparent to visible light. On the other hand, oxide conductors are oxide semiconductors that have donor levels near the conduction band. Therefore, the influence of absorption by 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 preferably 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 If it is 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 tung A single metal consisting of stainless steel or an alloy with this as the main component is used in a single layer structure or a laminated structure. For example, a single layer structure of aluminum film containing silicon, aluminum film on titanium film, Two-layer structure with aluminum film laminated on tungsten film, two-layer structure with aluminum film laminated on tungsten film, copper- Two-layer structure with copper film laminated on magnesium-aluminum alloy film, and copper film laminated on titanium film Two-layer structure with a copper film on a tungsten film, two-layer structure with a titanium film or titanium nitride film A titanium film or titanium nitride film is laminated with an aluminum film or copper film. a three-layer structure in which a titanium film or titanium nitride film is formed thereon; a molybdenum film or 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 top of the copper film. There are three-layer structures, etc. 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 large amount 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 is permeable to oxygen. The oxide insulating film 23 is formed on the substrate 3. ... The oxide insulating film 23 can be transferred to the oxide semiconductor film 19a. The oxide insulating film 25 is also used 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, silicon oxynitride film, or the like having a thickness of 50 nm or less can be used. In the specification, a silicon oxynitride film is a film having a higher oxygen content than nitrogen content. 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, and typically, it is found by ESR measurement that the oxide semiconductor film 19a has a defect-derived g The spin density of the signal appearing at a value between 1.89 and 1.96 is 1×10 17 spins / c m 3 It is preferably below the lower limit of detection.

[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 is migrated to the outside. In some cases, part of the oxygen remains in the oxide insulating film 23. Oxygen enters the oxide insulating film 23, and the oxygen contained in the oxide insulating film 23 flows out of the oxide insulating film 23. The movement may cause oxygen to move in the oxide insulating film 23.

[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 required for the stoichiometric composition. The oxide insulating film containing more oxygen than the oxygen that satisfies the stoichiometric composition is formed by heating. Heat causes some of the oxygen to be released. Acids containing more oxygen than the stoichiometric composition In TDS analysis, the surface temperature of the oxide insulating film is 100°C or higher and 700°C or lower, or 10 The amount of oxygen released in terms of oxygen atoms during heat treatment at 0°C to 500°C is 1.0x 10 18 atoms / cm 3 or more, preferably 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 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, having a g value of 2.037 or more and 2.039 or less A second signal with a value between 2.001 and 2.003, and 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. The 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 more. The first signal is above 2.039 and below, and 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 (where x is 0 or more and 2 or less, preferably 1 or more and 2 or less) corresponds to a signal caused by nitrogen oxides. Typical examples include nitrogen monoxide and nitrogen dioxide. That is, the g value is 2.037 or more. The lower the spin density, which is 0.39 or less or 1.964 or more and 1.966 or less, the more the oxide It can be said that the content of nitrogen oxides contained in the insulating film is low.

[0118] Here, 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 over the oxide insulating film 25, the metal oxide film 27 is As a result, oxygen contained in the oxide insulating film 25 is efficiently transferred to the outside. The oxygen vacancies in the oxide semiconductor film 19a are reduced by the oxygen vacancies in the oxide semiconductor film 19a. This can be done.

[0120] An oxide semiconductor film 19a and an oxide insulating film 29 are formed inside the nitride insulating film 15 and the nitride insulating film 29. Therefore, water, even water from the outside, is prevented from reaching the oxide semiconductor film 19a. 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, acid Indium oxide film containing titanium oxide, indium tin oxide film containing titanium oxide, Indium tin oxide (hereinafter referred to as ITO) film, indium zinc oxide film, silicon oxide added Examples include an indium tin oxide film.

[0122] The conductive film 31 may be formed in a comb-like shape or a shape having slits 31b. 29 shows a cross-sectional view of the case where the conductive film 31 is laid out in this manner. The liquid crystal can be driven in PS mode or FFS mode. 30 shows a top view of the case where the lit 31b is provided. 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. 3 will be described with reference to FIGS. This will be explained using FIG.

[0124] As shown in FIG. 4(A), 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] Here, 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, and the mask is formed as shown in FIG. ) 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 ink 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. 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 that functions as a gate electrode. Then, an insulating film 15 is formed on the insulating film 16, which will later become an oxide insulating film 17. On the insulating film 16, an oxide semiconductor film 19a and an oxide semiconductor film 19b are formed. A film 18 is formed.

[0130] The nitride insulating film 15 and the oxide insulating film 16 are formed by sputtering, CVD, vapor 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 source gases. Representative examples of silicon-containing deposition gases 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 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 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 is used. The device may be an RF power supply device, an AC power supply device, a DC power supply device, or the like.

[0137] The sputtering gas is a rare gas (typically argon), oxygen gas, or a mixture of rare gas and oxygen. In the case of a mixed gas of rare gas and oxygen, the ratio of oxygen to rare gas is Increasing the gas ratio is preferable because it facilitates the formation of 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, a chamber It is necessary not only to evacuate the inside of the chamber to a high vacuum, but also to highly purify the sputtering gas. The oxygen gas and argon gas used have a dew point of -40°C or less, preferably -80°C or less. Gas that has been highly purified to -100°C or below, and more preferably -120°C or below 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 3000-membrane oxide semiconductor film was deposited by sputtering using a SiO2 / ZnO film (SiO2: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 forming a mask, 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. 4(D). After this, the mask is removed.

[0142] Here, a mask is formed over the oxide semiconductor film, and the oxide semiconductor is removed by wet etching. 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 the 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 21a functions as a capacitance line. The film 21c is formed, and then the mask is 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 etchant to form the conductive films 21a, 21b, and 21c. The copper film is then etched using wet etching. The tungsten film is etched by the dry etching method used. In this process, fluorides are formed on the surface of the copper film. This reduces the diffusion of copper, thereby reducing the copper concentration in the oxide semiconductor film 19a.

[0148] Next, as shown in FIG. 5C, oxide semiconductor films 19a and 19c, a 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 22 is continuously formed without being exposed to the atmosphere. 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 of 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 made of a silicon dioxide film 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 raw material gas is introduced into the processing chamber. The pressure in the air is set to 20 Pa or more and 250 Pa or less, more preferably 100 Pa or more and 250 Pa or less. Under the conditions below, high frequency power is supplied to an electrode provided in the processing chamber, and a silicon oxide film is formed. Alternatively, a silicon oxynitride film can be formed.

[0151] As the source gas of the oxide insulating film 22, a deposition gas containing silicon and an oxidizing gas are used. Representative examples of silicon-containing deposition gases 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, it is possible to prevent the oxide insulating film 22 from being formed later. In the forming step of 25, damage to the oxide semiconductor film 19a can be reduced.

[0153] 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 raw material gas is introduced into the processing chamber. The pressure in the processing 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 processing chamber. Depending on the conditions for supplying the silicon dioxide, 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 becomes oxygen-permeable, dense, and hard. Oxide insulating film, typically etched using 0.5 wt % hydrofluoric acid at 25°C A silicon oxide film or an oxide film having a grading rate 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 The hydrogen, water, etc. contained in the oxide semiconductor film 19a can be desorbed. The hydrogen contained in the oxide insulating film 2 combines with oxygen radicals generated in the plasma to form water. Since the substrate is heated during the film formation process in step 2, the The 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 desorption from the oxide semiconductor film by the heat treatment is prevented. 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 formed by using silane at a flow rate of 30 sccm and silane at a flow rate of 4000 sccm. The source gas was dinitrogen monoxide (NO) of 2.0 cm, the pressure in the processing chamber was 200 Pa, and the substrate temperature was 220°C. A 27.12MHz high-frequency power supply 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 way, a silicon oxynitride film that is permeable to oxygen can be formed.

[0158] The oxide insulating film 24 is made of a silicon dioxide film placed in a vacuum-evacuated processing chamber of a plasma CVD apparatus. The substrate is kept at 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 100 Pa or more and 200 Pa or less, and .17W / cm 2 More than 0.5W / cm 2 or less, more preferably 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 a source gas for the oxide insulating film 24, a deposition gas containing silicon and an oxidizing gas are used. Representative examples of silicon-containing deposition gases 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 a high frequency of the above power density in a processing chamber under the above pressure. By supplying wave power, the decomposition efficiency of the source gas in the plasma increases, and oxygen radicals increase. As the amount of oxygen added increases, the oxidation of the source gas progresses, and 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 substrate temperature above, the bond 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 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 As a result, the oxide semiconductor film 19a is protected from damage. The oxide insulating film 24 can be formed using high frequency power with high power density while reducing the can.

[0161] Here, the oxide insulating film 24 is formed by silane at a flow rate of 200 sccm and silane at a flow rate of 4000 s ccm of dinitrogen monoxide was used as the source gas, 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 type plasma CVD The power supplied is converted to power per unit area (power density) of 0.25W. / cm 2 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 The channel (oxide semiconductor film 19a) faces the conductive film 13 that functions as a gate electrode. However, the oxide insulating film 24 has a stoichiometric composition. By using an oxide insulating film containing more oxygen than the oxygen that satisfies the composition requirement, This allows the oxygen vacancies occurring on the back channel side to be repaired. Since defects contained in the semiconductor film 19a can be reduced, the reliability of the transistor 102 can be improved. It can 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 removed. 25 is formed, and then 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 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 formed 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 placed so that the ends of the insulating film 23 and the oxide insulating film 25 are positioned. As a result, the separated oxide insulating film 23 and the oxide insulating film 24 are The oxide insulating film 22 and the oxide insulating film 24 can be formed. During the etching, part of the oxide insulating film 16 is also etched, forming an oxide insulating film 17. 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, more preferably 320°C or higher and 370°C or lower.

[0167] The heat treatment can be carried out 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 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.) 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 By moving oxygen to the oxide semiconductor film 19a, 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 Water, hydrogen, and the like contained in the oxide semiconductor film 19a move to the oxide semiconductor film 19a, and defects are formed 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 layer can be eliminated, and the electrical characteristics of the transistor 102 can be improved. This reduces variations and suppresses fluctuations in threshold voltage.

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

[0172] The heat treatment also 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. The heat treatment after the formation of the oxide semiconductor film 19c prevents oxygen from moving 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, 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 19d 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 film 21a, 21b, and the conductive film 21c.

[0175] The metal film 26 is a metal oxide that is oxidized to have light transmittance and low oxygen permeability. It is preferable to use a metal film or a metal nitride film as the film, and typically aluminum, 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 or more and 50 nm or less, and the average film thickness is 2 nm or more and 10 nm or less. 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 formation of a 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 etching. 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 the metal. Oxygen can be introduced into the entire surface of the film 26. The oxygen introduction process is carried out while heating. It is also possible.

[0179] Typical examples of oxygen introduced into the metal film 26 include oxygen radicals, ozone, and oxygen atoms. Oxygen can also be generated from oxygen-containing gases. Representative examples of gases containing oxygen include oxygen gas, nitrous oxide gas, nitrogen dioxide gas, and ozone. Examples of gases that contain oxygen include carbon dioxide, 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 5x10 or more 16 ions / cm 2 It is preferable that such a dose be as follows: By adjusting the amount of the offset, 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 performed using plasma CVD equipment and dry etching equipment. In addition, when using a plasma treatment apparatus, Preferably, a bias is applied to the support or electrode on which plate 11 is mounted. Energetic oxygen, 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 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. When oxygen is excited by microwaves to generate high-density oxygen plasma, The introduction of oxygen is performed by 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, 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, by introducing oxygen into the metal film 26 in the plasma treatment, the throughput can be improved. 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 forming the film, oxygen is introduced into the metal film to form a metal oxide film, which is 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. By the heat treatment, the metal oxide film 26a is decomposed into the metal oxide film 26b. 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 film that will later become a nitride insulating film 29 is formed on the metal oxide film 26a. Then, 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 plasma CVD, 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 HCl at a flow rate of 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 substrate temperature was set at 350°C under 100 Pa, and a 27.12 MHz high frequency power supply was used for 1000 The nitride insulating film 28 was formed by plasma CVD using a 1000W high-frequency power supply to parallel plate electrodes. The plasma CVD device is used to form a silicon nitride film with a thickness of 50 nm. 6000cm 2 It is a parallel plate type plasma CVD device, and the supplied power is This translates to 1.7 x 10 power per unit (power density). -1 W / cm 2 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 on 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. Furthermore, the amount of variation in threshold voltage can be reduced.

[0191] In addition, in the case where the nitride insulating film 28 contains hydrogen, 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 efficiency.

[0192] Next, a photolithography process is performed on the nitride insulating film 28 using a fifth photomask. 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 metal oxide film 28 having the opening 41 are formed. A nitride insulating film 29 is formed.

[0193] Next, as shown in FIG. 7A, a conductive film 21b is formed on the conductive film 21b and the nitride insulating film 29. 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, and the mask is formed 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 forming a metal film, oxygen is introduced into the metal film to form a metal oxide film. This allows the formation of a metal oxide film while preventing particle generation. Therefore, semiconductor devices can be manufactured with high yield.

[0198] In addition, the transistor described in the embodiment contains more oxygen than the oxygen that satisfies the stoichiometric composition. Since a metal oxide film with low oxygen permeability is formed on an oxide insulating film containing silicon, It is possible to prevent the oxygen contained in the film from diffusing to the outside. 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 oxide semiconductor film can be reduced.

[0200] From the above, a normally-off transistor can be manufactured. In addition, the electrical characteristics of transistors, typically the threshold voltage, change over time or due to stress testing. Therefore, a transistor with reduced voltage fluctuation can be manufactured.

[0201] In addition, the element substrate of the semiconductor device described in this embodiment has an oxide semiconductor film and a At the same time, one electrode of the capacitor element is formed. is used as the other electrode of the capacitor element. Since a step of forming a conductive film on the pair of electrodes is not required, the manufacturing process can be reduced. As a result, the area occupied by the capacitor element can be 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 the pixel 103, in which the structure of the transistor 102 is indicated by a dashed line, and the metal oxide The oxide film 27 is shown by hatching.

[0205] As shown in FIG. 8(A), 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 may be reduced. By reducing the thickness, it is possible to form 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 and 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). It is preferable that the oxide insulating film be provided over the transistor 102 at least. Therefore, oxygen contained in the oxide insulating film 23 or the oxide insulating film 25 can be prevented 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. 8(B). It is preferable that the capacitor element 105 is formed on the entire surface of the region where the capacitor element 105 is to be formed. It is possible to reduce the variation in charge capacity.

[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 roads.

[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 has a metal oxide film 27 and a nitride film 28, which are different from the semiconductor device shown in FIG. The order of forming the nitride insulating film 15, the oxide insulating film 17, and the oxide insulating film 29 is different. The conductive film 19b, the conductive films 21a and 21b functioning as a pair of electrodes, and the conductive film 21 c, the 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 formed over the oxide insulating film 23 and the oxide insulating film 25. 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 capacitor element 105 , contacts the nitride insulating film 29. In addition, 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 increase in the resistance value of the conductive film 21c can be suppressed.

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

[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. 3 in that the metal oxide film 27 is a base material. The difference is that it is not formed on the entire surface of the plate 11, but is formed only on the transistor 102.

[0217] In this semiconductor device, after forming the oxide insulating film 24 in FIG. 5(C), 6(A) is formed. Next, oxygen is introduced into the metal film 26, and the 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 then the mask is The oxide insulating film 22, the oxide insulating film 24, and the metal oxide film 26a are etched using a By this, 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, a nitride insulating film 29 and a 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 contained 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. 3 in that the oxide insulating film 25 is formed. Here, the oxide insulating film 25 has a stoichiometric composition. The insulating film is formed of an oxide insulating film containing more oxygen than the insulating film containing oxygen.

[0223] In this semiconductor device, as shown in FIG. 5(C), an oxide insulating film 22 is formed, and then an oxide insulating film 23 is formed. A mask is formed on the oxide insulating film 22 by a photolithography process. The oxide insulating film 22 is etched using the etching solution, thereby forming the oxide insulating film 22 as shown in FIG. Next, the metal oxide film 23 is formed by the steps shown in FIG. 6(A) and subsequent steps. 7. A nitride insulating film 29 and a conductive film 31 are formed.

[0224] In the semiconductor device shown in FIG. 11, an oxygen film 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, in the step of introducing oxygen 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, 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 fluctuation 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 performing this transformation will be described with reference to the drawings. The transistor described in the example has a structure in which an oxide semiconductor film is formed multiple times, compared to the semiconductor device shown in FIG. The difference is that a multilayer film having several layers is provided.

[0227] 12 shows a cross-sectional view of an element substrate included in a semiconductor device. -B, a cross-sectional view between CD.

[0228] The transistor 102a shown in FIG. 12A includes the nitride insulating film 15 and the oxide insulating film 17. a multilayer film 37a overlapping the conductive film 13 functioning as a gate electrode via a gate electrode; The nitride insulating film 21a has a pair of conductive films 21a and 21b that function as electrodes in contact with the nitride insulating film 21a. The film 15, 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 film 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 be in contact with the insulating film 9a. The oxide insulating film 25 is formed as shown in FIG. 3, an oxide semiconductor film 39a is provided.

[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 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 band of the oxide semiconductor film 19a. 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 more Below.

[0233] The oxide semiconductor film 39a contains In, which increases carrier mobility (electron mobility). 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 is a metal element that has a strong bond with oxygen, so 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 and M is 0 atomic %, the atomic percentage of In is preferably 50 atomic %. % or less, M is 50 atomic % or more, and more preferably In is 25 atomic % or more. 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 ( When 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 in atomic ratio, 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 ( When M is Al, Ga, Y, Zr, La, Ce, or Nd, the oxide semiconductor film 39a In:M:Zn=x1:y1:z1 [atomic ratio], and the oxide semiconductor film 19a was In:M: If the atomic ratio of Zn is x2:y2:z2, then y1 / x1 is greater than y2 / x2. Preferably, y1 / x1 is 1.5 times or more greater than y2 / x2. 1 / x1 is more than twice as large as y2 / x2, and more preferably, y1 / x1 is greater than y2 / x2. is more than three times larger than

[0238] The oxide semiconductor film 19a is an In-M-Zn oxide film (M is Al, Ga, Y, Zr, La , Ce, or Nd), the target used to form the oxide semiconductor film 19a In the above, if the atomic ratio of metal elements is In:M:Zn=x1:y1:z1, 、 x1 / y 1 is 1 / 3 or more and 6 or less, further 1 or more and 6 or less, and z1 / y1 is 1 / 3 or more and 6 or less. It is more preferable that z1 / y1 is 1 or more and 6 or less. This makes it easier to form a CAAC-OS film as the oxide semiconductor film 19a. As representative examples of the atomic ratio of the metal elements in the getter, In:M:Zn = 1:1:1, In:M :Zn = 1:1:1.2, In:M:Zn = 3:1:2, etc. are available.

[0239] When the oxide semiconductor film 39a is an In-M-Zn oxide film (M is Al, Ga, Y, Zr, La , Ce, or Nd), in the target used to form the oxide semiconductor film 39a , if the atomic ratio of the metal elements is In:M:Zn = x2:y2:z2, then 、 x2 / y 2 < x1 / y1, and z2 / y2 is preferably 1 / 3 or more and 6 or less, more preferably 1 or more and 6 or less. By setting z2 / y2 to 1 or more and 6 or less, it becomes easier to form a CAAC-OS film as the oxide semiconductor film 39 a. Representative examples of the atomic ratio of the metal elements in the target include In:M:Zn = 1:3:2, In:M:Zn = 1:3:4, In:M: 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 each include fluctuations of plus or minus 40% of the above atomic ratios with an error.

[0241] The oxide semiconductor film 39a also functions as a damage relaxation film for the oxide semiconductor film 19a when forming the oxide insulating film 25 formed later.

[0242] The thickness of the oxide semiconductor film 39a is 3 nm or more and 100 nm or less, preferably 3 nm or more and 5 0 nm.

[0243] Also, like the oxide semiconductor film 19a, the oxide semiconductor film 39a has, for example, a non-single crystal structure ​​​The non-single crystal structure may be, for example, a CAAC-OS structure, 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, for example, an amorphous structure. For example, the atomic arrangement is disordered and does not have crystalline components.

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

[0246] The oxide semiconductor film 19a and the oxide semiconductor film 39a are not simply formed by laminating the respective films. The structure is a continuous junction (here, the energy of the bottom of the conduction band changes continuously between each film). In other words, trap centers and recombination centers are formed at the interfaces of each film. The layer structure is such that there are no impurities that form defect levels. When impurities are present between the oxide semiconductor film 19a and the oxide semiconductor film 39a, the energy The continuity of the energy 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 being exposed to the atmosphere. Each chamber in the sputtering device 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 pumping (5×10 -7 Pa~1×10 -4 It is preferable to Alternatively, a turbomolecular pump and a cold trap can be combined to separate the chamber from the exhaust system. It is preferable to prevent the backflow of gases, especially gases containing carbon or hydrogen, into the bar. stomach.

[0248] Instead of the multilayer film 37a, a transistor 102c shown in FIG. 12(B) may be used. It may have a multilayer film 38a.

[0249] In place of the multilayer film 37b, a multilayer film such as a capacitor element 105c shown in FIG. 12(B) may be 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 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 and the oxide insulating film 23 contact each other. 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] The transistor described in this embodiment has a structure in which a semiconductor layer is formed between the oxide semiconductor film 19a and the oxide insulating film 23. The oxide semiconductor film 39a is provided on the oxide semiconductor film 39b. 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 also to increase the trap level. When an electron is captured by the transistor, the electron becomes a fixed negative charge. However, the oxide semiconductor film 19a and the trapping transistor are not uniformly connected. Since there is a gap between the trap level and the electron trap, it is possible to reduce the capture of electrons at the trap level. This allows the variation in threshold voltage to be reduced.

[0256] In addition, the oxide semiconductor film 39a can block impurities from the outside. The amount of impurities that move 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 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 formed between the oxide semiconductor film 19a and the oxide insulating film 23. a 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, or 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 defect count 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. The 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] <Transistor band structure> Next, the multilayer film 37a provided in the transistor 102b shown in FIG. 12A and the multilayer film 37b 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, which has an energy gap of The energy gap is 3.5 eV. Measurement is performed using a psometer (HORIBA JOBIN YVON UT-300) It is possible.

[0261] The vacuum level and the energy at the top of the valence band of the oxide semiconductor film 19a and the oxide semiconductor film 39a The ionization potentials (also called ionization potentials) 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 Measurement 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. It was.

[0263] FIG. 13(A) 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 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 minimum of the silicon oxide film. In addition, EcI1 corresponds to the oxide insulating film 17 in FIG. 12(A), and EcI2 corresponds to , which corresponds to the oxide insulating film 23 in FIG.

[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 means that 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 when the water moves to the

[0265] As shown in FIG. 13A, the oxide semiconductor film 19a of the multilayer film 37a serves as a well, and In a 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 changes continuously in the multilayer film 37a. 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 and defects can 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, the oxide semiconductor Electrons in the film 19a may exceed the energy difference and reach the trap level. When electrons are trapped in the 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, the transistor This is advantageous because it reduces fluctuations in the threshold voltage of the capacitor and provides 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. 13(A) shows a schematic diagram of the band structure of the multilayer film 37a. ) is a modified example of the band structure shown in FIG. 1. In this example, a silicon oxide film is placed in contact with the multilayer film 37a. The case where the silicon oxide film is provided will be described. EcS1 represents 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 illustrated in FIG. 12A, a conductive film 21a serving as a pair of electrodes, When forming the multilayer film 37a, the oxide semiconductor film 39a is etched. On the other hand, the upper surface of the oxide semiconductor film 19a may be damaged during the formation of the oxide semiconductor film 39a. 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 In:Ga:Zn=1:1:1. -Ga-Zn oxide, or In-Ga- with an atomic ratio of In:Ga:Zn=3:1:2 This is an oxide semiconductor film formed using Zn oxide as a sputtering target. The semiconductor film 39a is an In-Ga-Zn oxide film with 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 Since the semiconductor film 39a contains a large amount of Ga, 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 EcS1 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 occur.

[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 a larger amount of Ga than the oxide semiconductor film 19a. Since a mixed layer containing a large amount of ammonium nitrate is formed, this mixed layer can be regarded as the 1.5th layer. The mixed layer can be analyzed by, for example, EDX analysis to determine the elements contained in the multilayer film 37a. When the element is measured, it can be confirmed by analyzing the composition above the oxide semiconductor film 19a. For example, the composition above the oxide semiconductor film 19a can be This can be confirmed by the fact that the Ga content is higher than that of the other alloys.

[0272] FIG. 13(C) 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 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 represents 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. 12(B), 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 semiconductor film 49b are In the compound semiconductor film 39a, the energy at the bottom of the conduction band changes smoothly without any barrier. In other words, it can be said that the temperature changes continuously. The oxide semiconductor film 39a and the oxide semiconductor film 19a contain the same elements. 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, and In a 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 changes continuously in the multilayer film 38a. 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 19b is formed in the vicinity of the interface between the oxide semiconductor film 19a and the oxide insulating film 23. In the vicinity of the interface between 9a and the oxide insulating film 17, trap levels due to impurities and defects are formed. However, as shown in FIG. 13(C), 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 is small, electrons in the oxide semiconductor film 19a exceed the energy difference and When electrons are captured in the trap level, the oxide insulating film A negative charge is 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 fluctuations in 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. 3 in that the nitride insulating film 29 is formed. The difference is that it has not been done.

[0279] In this semiconductor device, after the metal oxide film 26a is formed as shown 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 the steps from 7(A) onwards, the conductive film 31 is formed.

[0280] In the semiconductor device shown in FIG. 14, the nitride insulating film 29 is not formed. Then, etching for forming 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 and the electrode of the capacitor A conductive film 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, or Alternatively, a conductive material that easily bonds with oxygen, such as tantalum itself 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, and oxygen vacancy regions are formed 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 in the vicinity of the region. The low resistance region is a conductive film that functions as a pair of electrodes. The 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. 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. This makes it possible to increase the on-state current of the transistor.

[0283] The conductive films 21a and 21b, which function as a pair of electrodes, are made 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. A laminated structure may be used. By using such a laminated 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 film is formed which functions as a pair of electrodes. 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 prevent the resistance of 1a and 21b from increasing.

[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 Embodiment 1, After forming the conductive films 21a and 21b, the oxide semiconductor film 19a is formed by plating 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. Furthermore, the etching treatment can reduce the amount of oxide remaining on the surface of the oxide semiconductor film 19a. 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 compound semiconductor film 19a is bonded to form 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, in other words, a structure in which a nitride semiconductor film is provided. This differs from embodiment 1. Note that explanations of configurations that overlap with embodiment 1 will be omitted.

[0288] 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 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, the conductive film 13 functioning as a gate electrode, the acid The oxide semiconductor film 19a, the conductive films 21a and 21b, and the oxide insulating film 25 are each partially or completely covered with the conductive films 21a and 21b. The difference from the first embodiment is that the second embodiment has a conductive film 31a that functions as a gate electrode and overlaps the entire surface. 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 the dashed lines AB and CD in FIG. 15 is shown in FIG. The transistor 102a is a channel-etched transistor. -B is the channel length direction of the transistor 102a, and 1 is a cross-sectional view of the connection portion of the conductive film 31 that functions as a capacitor element 105a, and 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 the film 13 and the conductive film 31a that functions as a gate electrode.

[0291] The transistor 102a shown in FIG. 16 is a transistor with a dual gate structure. The substrate 11 has a conductive film 13 that functions as a gate electrode. and a nitride insulating film 15 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 interposed therebetween The oxide semiconductor film 19a overlaps with the conductive film 13 functioning as a gate electrode, and the oxide semiconductor film 19b 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 serving as a pair of electrodes An oxide insulating film 23 is formed on the layers 1a and 21b, and an oxide insulating film 24 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 the metal oxide film 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 that function as a pair of electrodes, The conductive film 31 connected to the conductive film 21b and the conductive film 31a functioning as the 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 section 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 formed. a is connected to the conductive film 13 that functions as a gate electrode. The conductive film 13 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 in GBT stress tests and at different drain voltages It is possible to suppress fluctuations in the on-state current rising voltage. In this case, the area in which carriers flow is larger in the film thickness direction, and the amount of carrier movement is As a result, the on-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 from each other over the transistor 102a shown in this embodiment. The separated oxide insulating films 23 and 25 overlap with the oxide semiconductor film 19a. In addition, in the cross-sectional view in the channel width direction, an oxide insulating film 23 is formed on the outside of the oxide semiconductor film 19a. and the end of the oxide insulating film 25 are located. In addition, 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 insulating film 19c.

[0295] At the edge of the oxide semiconductor film processed by etching or the like, damage caused by the processing Defects are formed and the material is contaminated by impurities, so stresses such as electric fields When a potential is applied, it is easily activated, which makes it more likely to become n-type (low resistance). Therefore, the edge of the oxide semiconductor film 19a overlapping with the conductive film 13 functioning as a gate electrode The n-type end portion 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 the CD, the channel In the width direction, the conductive film 31a functioning as the gate electrode is sandwiched between the oxide insulating films 23 and 25. The conductive film 19a faces the side surface of the oxide semiconductor film 19a through the conductive film 19a, and functions as a gate electrode. The side surface of the oxide semiconductor film 19a or the side surface and its vicinity is 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 with 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] Further, 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 prevented 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 the transistor, typically the threshold voltage, 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 formed of the oxide semiconductor film 19a. The film is formed at the same time as the plasma damage, etc., and oxygen deficiency occurs, resulting in conductive Alternatively, the conductive film 19b is a film having improved conductivity. The film is formed at the same time and contains impurities, thereby increasing the conductivity of the film. Alternatively, the conductive film 19b is a film formed simultaneously with the oxide semiconductor film 19a. It contains impurities and oxygen deficiencies are formed due to plasma damage, etc., resulting in high conductivity. It is a coated membrane.

[0301] In addition, in the capacitor element 105a, a metal oxide film 27 made of a high dielectric material is used as a dielectric. By using the nitride insulating film 29, the charge capacity of the capacitor element 105a can be increased. It is possible.

[0302] The element substrate of the semiconductor device described in this embodiment is a substrate for forming an oxide semiconductor film of a transistor. The conductive film that functions as a pixel electrode is formed on the insulating film. The other electrode of the element is used. Since the process 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, and The aperture ratio of the pixel can be increased.

[0303] The following describes the details of the configuration of the transistor 102a. The description of the 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. Materials can be used as appropriate.

[0305] Next, a method for manufacturing the transistor 102a and the capacitor 105a shown in FIGS. This will be explained with reference to FIGS. 4 to 6 and 17.

[0306] As in the first embodiment, a gate electrode and a gate electrode are formed on a substrate 11 through the steps shown in FIGS. 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 photolithography process is performed on the nitride insulating film 28 using a fifth photomask. After forming a mask, the nitride insulating film 15, the metal oxide film 26a, and 17(A), 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 formed. Form.

[0308] Next, as shown in FIG. 17(B), the conductive film 13 and the conductive film 21 which function as gate electrodes are b and 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 which functions as a pixel electrode and a conductive film 32 which functions as a gate electrode are formed. 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 connected to the side surface of the oxide semiconductor film 19a via the oxide insulating films 23 and 25. By facing each other, the oxide semiconductor is formed by the influence of the electric field of the conductive film 31a which functions 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 electrical characteristics are improved, where the rise in drain current at the threshold voltage is steep. This results in a transistor with excellent performance.

[0312] In addition, the transistor described in this embodiment contains oxygen in an amount greater than that which satisfies the stoichiometric composition. By providing a metal oxide film with low oxygen permeability over an 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 oxide semiconductor film can be reduced.

[0314] From the above, a normally-off transistor can be manufactured. In addition, the electrical characteristics of transistors, typically the threshold voltage, change over time or due to stress testing. Therefore, a transistor with reduced voltage fluctuation can be manufactured.

[0315] In addition, the element substrate of the semiconductor device described in this embodiment has an oxide semiconductor film and a At the same time, one electrode of the capacitor element is formed. is used as the other electrode of the capacitor element. Since a step of forming a conductive film on the pair of electrodes is not required, the manufacturing process can be reduced. As a result, the area occupied by the capacitor element can be 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. It can also 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 that is an electrode of a capacitor can be used. Note that the conductive film is also called a highly conductive oxide semiconductor film. To understand 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), a microcrystalline oxide semiconductor oxide semiconductors (hereinafter referred to as microcrystalline oxide semiconductors) and amorphous oxide semiconductors (hereinafter referred to as amorphous oxide semiconductors) 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 oxide semiconductor may be made of a conductor and a crystal grain. CAAC-OS, polycrystalline oxide semiconductor, and microcrystalline oxide semiconductor will be described.

[0320] <caac-os> The CAAC-OS film is one of oxide semiconductor films having multiple crystal parts. The crystals contained in the AC-OS film have a c-axis orientation. The area of ​​the crystal part contained 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, the crystal By having 50% or more, preferably 80% or more, and more preferably 95% or more of the above-mentioned portion, 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 under a tron ​​microscope, clear boundaries between the crystalline parts are 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 observed, it can be confirmed that metal atoms are arranged in layers in the crystalline part. Each layer of the CAAC-OS film is formed on a surface (also called a surface to be formed) or on a concave surface of 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 includes angles between 85° and 95°.

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

[0324] When electron diffraction is performed on the CAAC-OS film, spots (bright spots) indicating orientation are 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 this is the case.

[0326] X-ray diffraction (XRD) of the 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 due to the Since it is attributed 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, the in-p X-rays incident on the CAAC-OS film are perpendicular to the c-axis. In the Lane analysis, a peak may appear around 2θ of 56°. The crystal structure of InGaZn oxide is composed of (110) plane. In the case of a crystalline oxide semiconductor film, 2θ is fixed at around 56°, and the normal vector of the sample surface is aligned with the axis (φ When the analysis (φ scan) is performed while rotating the sample around the (110) axis, the bonds equivalent to the (110) plane are observed. In contrast, in the case of the CAAC-OS film, 2 peaks are observed. Even when θ is fixed at around 56° and φ is scanned, no clear peak appears.

[0328] From the above, it can be concluded 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 a plane parallel to the ab plane of the crystal.

[0329] The crystals are formed when the CAAC-OS film is formed or when a crystallization process such as a heat treatment is performed. As described above, the c-axis of the crystal is aligned with the surface on which the CAAC-OS film is formed or 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 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] Furthermore, the crystallinity of the CAAC-OS film may not 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 to be formed. When impurities are added to the AC-OS film, the crystallinity of the region where the impurities are added changes, and the 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 around 36°, a peak may also appear. The peaks around the center of the CAAC-OS film indicate that the CAAC-OS film contains crystalline parts that do not have the c-axis orientation. The CAAC-OS film exhibits a peak at 2θ of around 31° and a peak at 2θ of around 36°. It is preferable that no peaks are present nearby.

[0332] The CAAC-OS film is an oxide semiconductor film with a low concentration of impurities. The oxide semiconductor film is made of an element other than the main component, such as silicon or a transition metal element. The elements such as ZnO, which have stronger bonding strength with oxygen than the metal elements constituting the oxide semiconductor film, By removing oxygen from the oxide semiconductor film, the atomic arrangement of the oxide semiconductor film is disrupted, and the crystallinity is reduced. In addition, heavy metals such as iron and nickel, argon, and carbon dioxide are Because the diameter (or molecular radius) is large, when the molecule is contained inside the oxide semiconductor film, The impurities contained in the oxide semiconductor film are likely to disturb the atomic arrangement of the oxide semiconductor film, which may result in a decrease in crystallinity. The pure material may act as a carrier trap or a carrier generation source.

[0333] The CAAC-OS film is an oxide semiconductor film with a low density of defect states. Oxygen vacancies in semiconductor films can 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 number of carrier generation sources, the carrier density can be reduced. The transistor using the oxide semiconductor film has electrical characteristics (noise) such that the threshold voltage is negative. It is also called "marine.") It is rare for it to become pure or substantially pure. An intrinsic oxide semiconductor film has few carrier traps. Transistors using this film have little fluctuation in electrical characteristics and are highly reliable. Note that it takes time for the 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 is fixed. Therefore, a transistor using an oxide semiconductor film with a high density of defect states has unstable electrical characteristics. This may be the case.

[0335] In addition, the electrical characteristics of transistors using CAAC-OS films are improved by irradiation with visible light or ultraviolet light. There is little gender variation.

[0336] <Microcrystalline oxide semiconductor> In the microcrystalline oxide semiconductor film, crystal parts can be clearly seen in the TEM image. 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 nm or less, or 1 nm to 3 nm. The oxide semiconductor film having nc-OS (nanocrystalline O The nc-OS film is called an oxide semiconductor film. In EM observation images, the 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 analytical 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 device, the crystal plane is analyzed using the out-of-plane method. In addition, the peaks indicating the crystal grains with a diameter larger than that of the crystalline part (e.g., When electron beam diffraction (also called selected area electron beam diffraction) is performed using an electron beam of 50 nm or more, On the other hand, for the nc-OS film, the 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) is performed, spots are observed. Furthermore, when nanobeam electron diffraction is performed on the nc-OS film, circular patterns (ripples) are observed. In addition, nanobeams on the nc-OS film may be observed. When electron diffraction is performed, multiple spots may be observed within the ring-shaped region.

[0338] The nc-OS film is an oxide semiconductor film with higher order than an amorphous oxide semiconductor film. Therefore, the nc-OS film has a lower density of defect states than the amorphous oxide semiconductor film. In the nc-OS film, there is no regularity in the crystal orientation 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, the conductive film will be described as an oxide conductor film.

[0340] Here, when an oxide semiconductor film such as the oxide semiconductor film 19a used in a transistor as shown in FIG. 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 in each film (hereinafter referred to as oxide conductor film (OC)) This will be explained with reference to Figure 31. In Figure 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 a circle, 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 Zn=1:1:1.2 sputtering target. An In-Ga-Zn oxide film with a thickness of 35 nm was formed, and the atomic ratio was In:Ga:Zn=1:4. :5 sputtering target was used to deposit a 20 nm thick In- A Ga-Zn oxide film was formed, and after heat treatment in a nitrogen atmosphere at 450°C, and heat treatment in a mixed gas atmosphere of silicon and oxygen, and then a silicon oxynitride film is formed by plasma CVD. was formed and produced.

[0342] The sample containing the oxide conductor (OC) film was formed on a glass substrate with an atomic ratio of In:Ga. Zn=1:1:1 sputtering target was used 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 film was then heated at 450°C in a mixed gas atmosphere of nitrogen and oxygen, and then deposited by plasma CVD. It was prepared by forming a com 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 resistivity change rate of the oxide conductor film (OC) at 290K or less is less than ±20% Alternatively, the rate of change in resistivity between 150K and 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. Therefore, it is considered that the oxide conductor film is used for the resistance element, wiring, and capacitance element. It can be used for electrodes, pixel electrodes, common electrodes, etc.

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

[0345] (Fourth embodiment) In this embodiment, structural examples of electronic devices 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 using a semiconductor device according to one embodiment of the present invention will be described. The module 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 and A display panel 8006, a backlight unit 8007, a frame 8009, a printed circuit board The backlight unit 8007, the battery 8011, and the 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 needed to fit the size of the 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 create 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. It may be provided at the end of the light source unit 8007 and may be configured to use a light diffusion plate.

[0351] The frame 8009 has a function of protecting the display panel 8006 and also a function of preventing 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 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] Examples of electronic devices include television sets (televisions or television receivers) (also called "computer monitors"), cameras such as digital cameras and digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), Examples include large game machines such as small game machines, mobile information terminals, sound reproduction devices, and pachinko machines. can be.

[0356] FIG. 27(A) shows a portable information terminal, which includes a main body 1001, a housing 1002, a display unit 1003, and a display unit 1004. The display unit 1003a, 1003b, etc. 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 parts 1003a and 1003b, This makes it possible to provide a highly reliable portable information terminal.

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

[0358] The portable information terminal shown in FIG. 27(A) is configured to be capable of transmitting and receiving information wirelessly. You can also purchase and download desired book data from an electronic book server wirelessly. It is also possible to configure it so that it is downloaded.

[0359] FIG. 27(B) shows a portable music player, and the main body 1021 has a display unit 1023 and earphones. a fixing part 1022 for attaching to a speaker, an operation button 1024, an external memory slot, The transistor shown in the above embodiment is a switching transistor. By manufacturing 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 and connect it to your mobile phone, you can enjoy wireless hands-free driving while driving a car. Conversations in Lee are 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 is provided with a display panel 1032, a speaker 1033, a microphone, and the like. Phone 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. The antenna is mounted on the housing 1031 The transistor described in the above embodiment is incorporated in the display panel 1032. By applying this, a highly reliable mobile phone can be obtained.

[0362] The display panel 1032 is also equipped with a touch panel, and the image displayed on the display panel 1032 is shown in FIG. The multiple operation keys 1035 are indicated by dotted lines. A boost circuit is also implemented to boost the voltage received to the voltage required for each circuit.

[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 microphone 1034 are not limited to voice calls, but also to video calls, Recording and playback are possible. Furthermore, the housing 1030 and the housing 1031 can be slid apart. As shown in 27(C), it 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. 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 functions, TV reception functions, etc. Good too.

[0366] FIG. 27(D) 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 incorporated in the display portion 1053 and the CPU. By applying this, television device 1050 can be made highly reliable.

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

[0368] The television device 1050 is configured to include a receiver, a modem, and the like. It is possible to receive general television broadcasts, and also to receive wired or wireless signals via a modem. By connecting to a communication network, it can be one-way (sender to receiver) or two-way It is also possible to communicate information in both directions (between a sender and a 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 for connecting a USB cable or the like. It can be connected to any type of cable, enabling data communication with a personal computer, etc. In the storage medium playback / 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 or CPU, power consumption can be reduced sufficiently. This can result in a highly reliable television device 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. [Example]

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

[0373] <Sample A1> The method for fabricating sample A1 will be explained. 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 galvanic deposition method. The distance between the pair of electrodes is 1000 μm, and the length of the pair of electrodes facing each other is 70900 μm. It was m.

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

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

[0378] Next, Table 1 shows the conductivity, resistivity, and resistance of Sample A1 and Sample A2.

[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... [Example]

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

[0382] <Sample B1> A method for manufacturing 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 a thickness of 35 nm was obtained. 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 a 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. Conductive indium oxide-tin oxide compound (ITO-SiO2) with a thickness of 100 nm was fabricated by the The film was formed as a light-transmitting conductive film.

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

[0388] <Sample B2> The manufacturing method of Sample B2 will be described. After forming the metal film in Sample B1, the metal film was treated with an acid. A sample in which a nitride insulating film and a light-transmitting conductive film were stacked 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 just 5 nm, and therefore has translucency.

[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. 18, the transmittance of sample B1 and sample B2 is 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 this method has light-transmitting properties. Even if a metal oxide film is provided, the transmittance of the capacitor element can be maintained. [Example]

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

[0392] The manufacturing method and structure of a sample having an oxide semiconductor film are shown in FIGS. 19 and 20. 19(A) shows a part of the steps in the fabrication method for each sample, and ) shows the sheet resistance of each sample. Figure 20(A) is a top view of each sample, and Figure 20(B) 20(E) through 20(E) are cross-sectional views taken along the dashed line A1-A2 in FIG. Next, samples C1, C2, and C5, which are comparative examples, and a capacitor 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> The method for preparing sample C1 will be described below.

[0394] On the glass substrate 1901, a gate electrode (not shown) is formed in the region 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 with a thickness of 400 nm was formed by the D method.

[0396] Next, on the insulating film 1903, an insulating film 1904 is formed by plasma CVD to a thickness of 50 A silicon oxynitride film with a thickness of nm was formed.

[0397] Next, on the insulating film 1904, In-Ga with In:Ga:Zn=1:1:1 (atomic ratio) was 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 silicon dioxide film.

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

[0399] Next, a thick film was formed on the insulating film 1903 and the oxide semiconductor film 1905 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, etching is performed using a mask formed by photolithography. A conductive film 1907 and a conductive film 1909 were formed by performing a coating treatment.

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

[0401] Next, heat treatment is carried out 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 deposited on the insulating film that will later become insulating film 1910. The insulating film was formed by forming a silicon nitride film with a thickness of 50 nm using the plasma CVD method. This was accomplished (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 Figure 20(B). In C1, the oxide semiconductor film 1905 is formed by a silicon oxynitride film as an insulating film 1910. It comes into contact with the corn membrane.

[0405] <Sample C2> The method for fabricating sample C2 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)).

[0406] Next, an insulating film was formed that would later become the insulating film 1911. A silicon nitride film having a thickness of 50 nm was formed by the D method (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 Figure 20(C). In C2, the oxide semiconductor film 1905 is formed by a silicon nitride film formed as an insulating film 1911. in contact with the membrane.

[0409] <Sample C3> The 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 becomes 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. Furthermore, oxygen was introduced into the aluminum film by exposing the aluminum film to oxygen plasma. An aluminum oxide film was formed as a 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 was formed that would later become the insulating film 1911. A silicon nitride film having a thickness of 50 nm was formed by the D method (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. 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 Figure 20(D). In C3, the oxide semiconductor film 1905 is formed by a silicon nitride film formed as an insulating film 1911. in contact with the membrane.

[0415] <Sample C4> The 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. Furthermore, oxygen was introduced into the aluminum film by exposing the aluminum film to oxygen plasma. An aluminum oxide film was formed as a metal oxide film.

[0418] Next, an insulating film was formed that would later become the insulating film 1911. A silicon nitride film having a thickness of 50 nm was formed by the D method (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. 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 Figure 20(E). In C4, the oxide semiconductor film 1905 is formed by the oxide aluminum 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. A conductive film of indium oxide-tin oxide compound (ITO-SiO2) was formed. The composition of the sputtering target used for the conductive film was In2O3:SnO2:SiO 2 = 85:10:5 [wt %]. After that, it was heated at 250 °C for 1 hour in a nitrogen atmosphere. Processing was carried out.

[0422] Next, specimen C1 was deposited on a conductive film of indium oxide-tin oxide compound (ITO-SiO2). As in sample C4, a conductive film 1907 and a conductive film 1909 were formed.

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

[0424] In 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 included in Samples C1 to C4 and the oxide semiconductor films included in Sample C5 were Conductive film of indium-tin oxide compound (ITO-SiO2) and measuring the sheet resistance of each In the samples C1 to C5, the conductive film 1907 was set to the ground potential, and the conductive 1 V was applied to the film 1909.

[0426] The measurement results are shown in FIG. 19B. It can be seen that the sheet resistance of sample C1 is reduced compared to 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 damage occurs in the semiconductor film, reducing the sheet resistance of the oxide semiconductor film. Sample C4 has the same sheet resistance as sample C2, and therefore the oxide semiconductor film and silicon nitride film 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 oxide semiconductor film is migrated 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 in Sample C5. Compared to conductive films made of indium-tin oxide (ITO-SiO2), the sheet resistance is one order of magnitude lower. High degree of conductivity, similar to that of indium oxide-tin oxide (ITO-SiO2) conductive films 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 Figure 21. In Figure 21, the horizontal axis represents 1 / T (measurement temperature), and the vertical axis represents 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 material C4 are shown.

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

[0430] <High temperature and humidity storage test> Next, we will examine the change in sheet resistance when samples C2 to C4 are stored at high temperature and humidity. Here, samples C2 to C4 were measured in an atmosphere of 60°C temperature and 95% humidity. After storing for 330 hours, the sheet resistance of each sample was measured. The measurement results are shown in Figure 22. 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 is small for samples C2 to C4. The oxide semiconductor films included in Samples C2 to C4 exhibited a sheet resistance of 1000 MPa in a high-temperature, high-humidity environment. Since the resistance fluctuation is small, it can be used as an electrode for a capacitance element. [Example]

[0432] In this example, 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 below.

[0433] <Sample D1> A method for fabricating sample D1 will be described. Sample D1 is fabricated on a glass substrate as shown in FIG. An oxide semiconductor film 803 is formed on a substrate 801, and a metal film 805 is formed on the oxide semiconductor film 803. It was created by creating

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

[0435] As the metal film 805, a 5 nm thick aluminum film was formed by sputtering. Formed.

[0436] <Sample D2> A method for fabricating sample D2 will be described. Sample D2 is fabricated on a glass substrate as shown in FIG. 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 was introduced into the metal film to form a metal oxide film 815.

[0437] Here, the oxide semiconductor film 813 has the following characteristics, similar to the oxide semiconductor film 803 shown in Sample D1: An IGZO film with a thickness of 100 nm was formed. By exposing the metal film formed of aluminum to the plasma, the metal oxide film 815 is formed. An aluminum nitride film was formed.

[0438] <Sample D3> The manufacturing method of Sample D3 will be described. As shown in FIG. 23(C), Sample D3 is 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. Thus, it is 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> The manufacturing method of Sample D4 will be described. As shown in FIG. 23(D), Sample D4 is 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. The measurement results of Sample D1 are shown in FIG. 24(A ), the measurement results of Sample D2 are shown in FIG. 24(B), the measurement results of Sample D3 are shown in FIG. 24(C ), and the measurement results of Sample D4 are 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 represented as glass, and the oxide semiconductor film is represented as IGZO. The metal film is denoted as Al, the metal oxide film is denoted as AlOx, and the nitride insulating film is denoted as SiN.

[0444] 24A and 24B show that 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 equipment increases when oxygen is introduced into the metal film. This is because the contained hydrogen is introduced into the oxide semiconductor film together with oxygen.

[0445] 24B and 24C, the oxide semiconductor film of Sample D3 is thinner than that of Sample D2. This indicates that the hydrogen contained in the nitride insulating film is absorbed into the metal oxide film. It can be seen that the oxygen atoms are transferred to the oxide semiconductor film through the

[0446] 24C and 24D, the oxide semiconductor film of Sample D3 is thinner than that 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 was found to migrate to the membrane. [Example]

[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 was 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 11 is formed on the substrate 11 to function as a gate electrode. 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 that 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. As the film 7, a silicon oxynitride film having a thickness of 50 nm was formed.

[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 to form a three-layer structure.

[0455] The first silicon nitride film was formed using silane at a flow rate of 200 sccm and silane at a flow rate of 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 processing chamber is controlled to 100 Pa, and a high frequency current of 27.12 MHz is applied. The source was used to supply a power of 2000 W and the thickness was formed to be 50 nm.

[0456] For the second silicon nitride film, silane at a flow rate of 200 sccm and 2000 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 supply was used to supply 2000 W of power, and the film was formed to a thickness of 300 nm.

[0457] The third silicon nitride film was formed using silane at a flow rate of 200 sccm and silane at a flow rate of 5000 sccm. cm of nitrogen was supplied as a source gas to the processing chamber of the plasma CVD equipment, and the pressure in the processing chamber was kept at 1 The pressure was controlled to 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 silane at a flow rate of 3000 sccm. Nitrous oxide was supplied as a raw material gas to the processing chamber of the plasma CVD equipment, and the pressure in the processing chamber was set at 4 The pressure was controlled to 0 Pa, and 100 W of power was supplied using a 27.12 MHz high frequency power supply. The substrate temperature during the silicon oxynitride film formation was 350°C. did.

[0459] Next, a conductive film which functions 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 on the oxide insulating film 17 by a sputtering method. After the formation, 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 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 power of 2.5 kW. The temperature was set to 170°C.

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

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

[0465] Next, the substrate is moved to a depressurized processing chamber, heated at 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 supply. 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 The oxide insulating film is partially 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 silane at a flow rate of 2000 sccm. Nitrous oxide was used as the source gas, the pressure in the processing chamber was 40 Pa, the substrate temperature was 220°C, and The plasma CVD method was used to apply 1000 W of high frequency power to parallel plate electrodes, and a 50 nm thick oxide film was formed. 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 400nm thick film was fabricated using the plasma CVD method, in which 500W of high frequency power was supplied to parallel plate electrodes. Under these conditions, a silicon oxynitride film with a stoichiometric composition was formed. A silicon oxynitride film containing a large amount of oxygen is formed, and part 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. and supplying part of oxygen contained in the oxide insulating film 25 to the oxide semiconductor film. Here, the heat treatment was carried out 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 film was formed.

[0472] Here, an aluminum film is deposited in 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 aluminum 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 using a mixture of silane at a flow rate of 50 sccm, nitrogen at a flow rate of 5000 sccm, and 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 that 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 to connect.

[0476] Here, the conductive film 31a functioning as the gate electrode is formed by sputtering. Indium oxide-tin oxide compound (ITO-SiO2) containing silicon oxide with a thickness of 100 nm ) A conductive film was formed. The composition of the sputtering target used for the conductive film was In 2O3:SnO2:SiO2 = 85:10:5 [wt%]. After that, in a nitrogen atmosphere , heat treatment was performed at 250 °C for 1 hour.

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

[0478] In this example, the channel width was 2 μm, and transistors with 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 including the transistor was designated as Sample E2.

[0480] As a comparative example, in the transistor 102a shown in FIG. 16, a transistor having no metal oxide film 27 was fabricated. The sample including the transistor was designated as Sample E3. <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 25 °C, the potential difference between the source and drain (hereinafter also referred to as drain voltage, Vd) was set to 1 V and 10 V, and the potential difference between the source and gate electrodes (hereinafter also referred to as gate voltage, Vg) was varied from -15 V to 15 V. The change characteristics of the current flowing between the source and drain (hereinafter also referred to as drain current, Id), that is, the Vg-Id characteristics were measured.

[0482] ​​​​​ FIG. 25(A) shows the structure of a transistor included in sample E1 with a channel length of 1 μm. The Vg-Id characteristics of the transistor are shown in Figure 25(B), where the channel length is 2 μm. 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. In order to show the value in the saturated region, the field-effect mobility calculated at Vd=10 V is shown.

[0483] As can be seen from Figure 25, a transistor with excellent Vg-Id characteristics can be fabricated using sample E1. I realized that this was happening.

[0484] <Relationship between channel length and threshold voltage> The relationship between the channel length L and the threshold voltage Vth of the transistors in 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 ranged from 0.64 μm to 6 On the other hand, the threshold voltage fluctuates little up to 0.5 μm. In the samples E2 and E3 where no channel was provided, the measured channel length became shorter. 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 is formed on the transistor as shown in sample E1. By forming the metal oxide film 27, the metal oxide film 27 is formed on the oxide semiconductor film. Oxygen can be introduced into the oxide insulating film formed on the oxide semiconductor film. As a result, the transistor with a short channel length can be formed. Even for transistors, it is possible to reduce the fluctuation of the threshold voltage, and It is possible to fabricate a transistor of this type.

Claims

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

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

Images