Semiconductor device

Abstract

To provide a semiconductor device capable of reducing oxygen deficiency in a metal oxide, and of stabilizing electrical characteristics.SOLUTION: A semiconductor device comprises: a gate electrode; a gate insulating film provided on the gate electrode; a first metal oxide film provided on the gate insulating film; a source electrode and a drain electrode provided so as to be contacted with the first metal oxide film; and a passivation film provided on the source electrode and the drain electrode. The passivation film is configured by sequentially laminating a first insulating film, a second metal oxide film, and a second insulating film.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a semiconductor device using an oxide semiconductor.

[0002] In this specification, a semiconductor device is a device that can function by utilizing semiconductor characteristics. In this specification, a transistor refers to a semiconductor device, and an electric device including the transistor Optical devices, semiconductor circuits, and electronic devices are all included in the category of semiconductor devices. [Background technology]

[0003] It is used in many flat panel displays, such as liquid crystal displays and light-emitting displays. The transistors used are made of amorphous silicon and single crystal silicon formed on a glass substrate. The silicon semiconductor is made of silicon semiconductor such as polycrystalline silicon or polysilicon. Transistors that use silicon semiconductors are also used in integrated circuits (ICs).

[0004] A technology that uses metal oxides that exhibit semiconducting properties in transistors instead of the silicon semiconductors mentioned above. In this specification, metal oxides that exhibit semiconducting properties are referred to as "oxide semiconductors." For example, Zn-O oxides or In-Ga-Z A transistor is manufactured using an nO-based oxide, and the transistor is used as a switch for pixels of a display device. Techniques for use in etching elements and the like have been disclosed (see Patent Documents 1 and 2). ).

[0005] By the way, it has been pointed out that hydrogen is a carrier source in oxide semiconductors. Therefore, it is necessary to take measures to prevent hydrogen from being mixed in during the formation of the oxide semiconductor. This is also the case. In addition to the oxide semiconductor, by reducing the hydrogen in the gate insulating film in contact with the oxide semiconductor, fluctuations in the threshold voltage are reduced (see Patent Document 3). (See Patent Document 3).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] Furthermore, in a metal oxide, carriers can be supplied not only by hydrogen but also by oxygen vacancies in the metal oxide. A part of the oxygen vacancies in the metal oxide acts as a donor and generates electrons, which are carriers, in the metal oxide. If there are many oxygen vacancies in the metal oxide including the channel formation region of the transistor, electrons are generated in the channel formation region, which becomes a factor causing the threshold voltage of the transistor to fluctuate in the negative direction. Furthermore, in a metal oxide, carriers can be supplied not only by hydrogen but also by oxygen vacancies in the metal oxide. A part of the oxygen vacancies in the metal oxide acts as a donor and generates electrons, which are carriers, in the metal oxide. If there are many oxygen vacancies in the metal oxide including the channel formation region of the transistor, electrons are generated in the channel formation region, which becomes a factor causing the threshold voltage of the transistor to fluctuate in the negative direction. Also, the threshold voltage of the transistor is affected by the insulating film provided in contact with the metal oxide film including the channel formation region. For example, when negative fixed charges such as oxygen ions of unbonded oxygen are included in the insulating film, the threshold voltage of the transistor can be shifted in the positive direction. However, if oxygen desorbs from the insulating film and is released to the outside, the negative fixed charges decrease, and the threshold voltage of the transistor may fluctuate in the negative direction. Also, the threshold voltage of the transistor is affected by the insulating film provided in contact with the metal oxide film including the channel formation region. For example, when negative fixed charges such as oxygen ions of unbonded oxygen are included in the insulating film, the threshold voltage of the transistor can be shifted in the positive direction. However, if oxygen desorbs from the insulating film and is released to the outside, the negative fixed charges decrease, and the threshold voltage of the transistor may fluctuate in the negative direction. Also, the threshold voltage of the transistor is affected by the insulating film provided in contact with the metal oxide film including the channel formation region. For example, when negative fixed charges such as oxygen ions of unbonded oxygen are included in the insulating film, the threshold voltage of the transistor can be shifted in the positive direction. However, if oxygen desorbs from the insulating film and is released to the outside, the negative fixed charges decrease, and the threshold voltage of the transistor may fluctuate in the negative direction.

[0008] Also, the threshold voltage of the transistor is affected by the insulating film provided in contact with the metal oxide film including the channel formation region. For example, when negative fixed charges such as oxygen ions of unbonded oxygen are included in the insulating film, the threshold voltage of the transistor can be shifted in the positive direction. However, if oxygen desorbs from the insulating film and is released to the outside, the negative fixed charges decrease, and the threshold voltage of the transistor may fluctuate in the negative direction. Also, the threshold voltage of the transistor is affected by the insulating film provided in contact with the metal oxide film including the channel formation region. For example, when negative fixed charges such as oxygen ions of unbonded oxygen are included in the insulating film, the threshold voltage of the transistor can be shifted in the positive direction. However, if oxygen desorbs from the insulating film and is released to the outside, the negative fixed charges decrease, and the threshold voltage of the transistor may fluctuate in the negative direction. Also, the threshold voltage of the transistor is affected by the insulating film provided in contact with the metal oxide film including the channel formation region. For example, when negative fixed charges such as oxygen ions of unbonded oxygen are included in the insulating film, the threshold voltage of the transistor can be shifted in the positive direction. However, if oxygen desorbs from the insulating film and is released to the outside, the negative fixed charges decrease, and the threshold voltage of the transistor may fluctuate in the negative direction. Also, the threshold voltage of the transistor is affected by the insulating film provided in contact with the metal oxide film including the channel formation region. For example, when negative fixed charges such as oxygen ions of unbonded oxygen are included in the insulating film, the threshold voltage of the transistor can be shifted in the positive direction. However, if oxygen desorbs from the insulating film and is released to the outside, the negative fixed charges decrease, and the threshold voltage of the transistor may fluctuate in the negative direction. Also, the threshold voltage of the transistor is affected by the insulating film provided in contact with the metal oxide film including the channel formation region. For example, when negative fixed charges such as oxygen ions of unbonded oxygen are included in the insulating film, the threshold voltage of the transistor can be shifted in the positive direction. However, if oxygen desorbs from the insulating film and is released to the outside, the negative fixed charges decrease, and the threshold voltage of the transistor may fluctuate in the negative direction. Also, the threshold voltage of the transistor is affected by the insulating film provided in contact with the metal oxide film including the channel formation region. For example, when negative fixed charges such as oxygen ions of unbonded oxygen are included in the insulating film, the threshold voltage of the transistor can be shifted in the positive direction. However, if oxygen desorbs from the insulating film and is released to the outside, the negative fixed charges decrease, and the threshold voltage of the transistor may fluctuate in the negative direction.

[0009] Therefore, one aspect of the present invention is to reduce oxygen vacancies in a metal oxide including a channel formation region, and prevent oxygen contained in an insulating film in contact with the metal oxide from being released to the outside, and thus an object is to provide a semiconductor device having good electrical characteristics and stable electrical characteristics. This is one of the objectives.

Means for Solving the Problems

[0010] In a transistor using a metal oxide, in order to reduce oxygen vacancies in the metal oxide, supplying oxygen into the metal oxide can be mentioned. Therefore, in one aspect of the present invention, an insulating film from which oxygen is desorbed by heat treatment is provided in contact with a metal oxide film including a channel formation region. As a result, oxygen desorbed during heat treatment is supplied into the metal oxide, and oxygen vacancies can be reduced.

[0011] In addition, an insulating film (also referred to as a first insulating film) from which oxygen is desorbed by heat treatment may not be able to supply oxygen to the metal oxide sufficiently because oxygen desorbed during heat treatment diffuses outward. Therefore, in one aspect of the present invention, a metal oxide film (also referred to as a second metal oxide film) different from the metal oxide film including a channel formation region (also referred to as a first metal oxide film) is provided in contact with the insulating film from which oxygen is desorbed by heat treatment. Since the second metal oxide film can prevent oxygen permeation, by providing the second metal oxide film, outward diffusion of oxygen desorbed during heat treatment can be prevented. Therefore, oxygen can be sufficiently supplied to the first metal oxide film, and furthermore, oxygen contained in the insulating film can be prevented from being desorbed to the outside. (also referred to as a second metal oxide film) is provided. Since the second metal oxide film can prevent oxygen permeation, by providing the second metal oxide film, outward diffusion of oxygen desorbed during heat treatment can be prevented. Therefore, oxygen can be sufficiently supplied to the first metal oxide film, and furthermore, oxygen contained in the insulating film can be prevented from being desorbed to the outside. This can be prevented.

[0012] In addition, oxygen deficiency may occur in the second metal oxide film for preventing oxygen permeation. However, in one aspect of the present invention, since the second metal oxide film is provided by being sandwiched between insulating films (the first insulating film and the second insulating film) from which oxygen desorbs by heat treatment, the oxygen deficiency of the second metal oxide film can be sufficiently compensated.

[0013] One aspect of the present invention includes a gate electrode, a gate insulating film provided on the gate electrode, a first metal oxide film provided on the gate insulating film, a source electrode and a drain electrode provided in contact with the first metal oxide film, and a passivation film provided on the source electrode and the drain electrode. The passivation film is a semiconductor device in which a first insulating film, a second metal oxide film, and a second insulating film are sequentially laminated.

[0014] Another aspect of the present invention includes a gate electrode, a gate insulating film provided on the gate electrode, a first metal oxide film provided on the gate insulating film, a source electrode and a drain electrode provided in contact with the first metal oxide film, and a passivation film provided on the source electrode and the drain electrode. The gate insulating film is a semiconductor device in which a second insulating film, a second metal oxide film, and a first insulating film are sequentially laminated.

[0015] In each of the above configurations, the semiconductor device is such that the first insulating film is thicker than the second insulating film.

[0016] In another aspect of the present invention, the semiconductor device includes an underlying insulating film, a first metal oxide film provided on the underlying insulating film, and a source electrode and a drain provided in contact with the first metal oxide film. An electrode, a first metal oxide film, a source electrode, and a gate insulation provided on the drain electrode A film, a gate electrode provided on the first metal oxide film via the gate insulation film, and having The base insulation film is formed by laminating a first insulation film, a second metal oxide film, and a second insulation film in this order Yes.

[0017] In another aspect of the present invention, the semiconductor device includes a base insulation film and a base insulation film provided on the base insulation film A first metal oxide film, a source electrode and a drain provided in contact with the first metal oxide film An electrode, a gate insulation provided on the first metal oxide film, the source electrode, and the drain electrode A film, and a gate electrode provided on the first metal oxide film via the gate insulation film, and having The gate insulation film is formed by laminating a second insulation film, a second metal oxide film, and a first insulation film in this order Yes.

[0018] In each of the above configurations, it is preferable that the first insulation film is thinner than the second insulation film.

[0019] Further, in each of the above configurations, the first metal oxide film is a semiconductor thicker than the second metal oxide film Device. Note that if the metal oxide film is about 5 nm, oxygen permeation can be prevented Further, since the metal oxide film has a high relative dielectric constant, when using a metal oxide film outside the metal oxide film including the channel formation region, if the film thickness is too thick, the parasitic capacitance may increase There is. Therefore, the film thickness of the second metal oxide film is preferably 5 nm or more and 15 nm or less preferably. Preferably.

[0020] In each of the above configurations, it is preferable to use an insulating film in which oxygen is desorbed by heat treatment for the first insulating film and the second insulating film film.

[0021] In each of the above configurations, the first metal oxide film and the second metal oxide film preferably contain two or more elements selected from In, Ga, Sn and Zn. Also, in each of the above configurations the elements contained in the first metal oxide film and the elements contained in the second metal oxide film may be the same or different. For example, as the first metal oxide film and the second metal oxide film, an In-Ga-Zn-O-based material may be used, or as the first metal oxide film, an In-Ga-Zn-O-based material may be used, and as the second metal oxide film, an In- Ga-Zn-O-N-based material may be used.

[0022] Also, depending on the amount of hydrogen or oxygen deficiency, the metal oxide film can be a conductor, a semiconductor, or an insulator. For example, the resistivity of the metal oxide film changes depending on the amount of hydrogen or oxygen deficiency contained in the metal oxide film.

[0023] When heat treatment is performed using insulating films that do not desorb oxygen by heat treatment on both sides of the insulating film sandwiching the metal oxide film, the metal oxide film becomes electrically conductive. Also, when heat treatment is performed using insulating films that desorb oxygen by heat treatment on both sides of the insulating film sandwiching the metal oxide film, the metal oxide film becomes electrically insulating. In terms of the resistivity of the metal oxide film, when the resistivity is 10 [Ω·cm] or less it becomes a conductor, and when the resistivity is 1×10 [Ω·cm] or more it becomes an insulator. 8 In addition, in order for the first metal oxide film to be a semiconductor, since it only needs to have a value between the resistivity that becomes a conductor and the resistivity that becomes an insulator, the first metal oxide film may be formed so that its resistivity exceeds 10 [Ω·cm] and is less than 1×10

[0024] 8 [Ω·cm].

[0025] The first metal oxide film and the second metal oxide film may be amorphous or crystalline. For example, the first metal oxide film may be non-single crystalline. When viewed perpendicular to the ab plane of the crystal, the atomic arrangement is triangular, hexagonal, equilateral triangular, or equilateral hexagonal. When viewed from a direction perpendicular to the c-axis, the metal atoms are in a layered form, or the metal atoms and oxygen atoms are in a layered form. It is preferable that the metal oxide contains a phase in which the metals are arranged in a layered form. CAAC-OS film: C Axis Aligned Crystallin We will call it e Oxide Semiconductor.

[0026] By using a CAAC-OS film as the first metal oxide film, the This suppresses the fluctuation of the electrical characteristics of transistors caused by the application of heat, bias, etc., and The reliability of the device can be improved. Effect of the Invention

[0027] According to one embodiment of the present invention, oxygen vacancies in a metal oxide are reduced, and a metal oxide that is in contact with the metal oxide is By preventing the oxygen contained in the insulating film from being released to the outside, good electrical properties and In addition, it is possible to provide a semiconductor device having stable electrical characteristics. [Brief description of the drawings]

[0028]

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MODE FOR CARRYING OUT THE INVENTION

[0029] Embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be easily understood by those skilled in the art that the form and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments shown below. In the configuration of the present invention described below, the same reference numerals are commonly used for the same parts or parts having the same function among different drawings, and the repeated description thereof will be omitted. It is not limited to the following description, and it will be easily understood by those skilled in the art that the form and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments shown below. Among those skilled in the art, it will be easily understood that the form and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments shown below. It is not limited to the description of the embodiments shown below. In the configuration of the present invention described below, the same reference numerals are commonly used for the same parts or parts having the same function among different drawings, and the repeated description thereof will be omitted. In the configuration of the present invention described below, the same reference numerals are commonly used for the same parts or parts having the same function among different drawings, and the repeated description thereof will be omitted. In the configuration of the present invention described below, the same reference numerals are commonly used for the same parts or parts having the same function among different drawings, and the repeated description thereof will be omitted.

[0030] In each of the figures described in this specification, the size, film thickness, or area of each component may be exaggerated for clarity. Therefore, it is not necessarily limited to that scale.

[0031] Also, terms such as first, second, and third used in this specification and the like are attached to avoid confusion of components and are not numerically limiting. Therefore, for example, "first" can be appropriately replaced with "second" or "third" and described.

[0032] The functions of "source" and "drain" may be interchanged when the direction of current changes in the circuit operation. For this reason, in this specification and the like, the terms "source" and "drain" are assumed to be interchangeable.

[0033] (Embodiment 1) In this embodiment, a semiconductor device according to an aspect of the present invention and a method for manufacturing the same will be described with reference to FIGS. 1 to 3.

[0034] <Example of the configuration of the semiconductor device> FIG. 1 shows a plan view and a cross-sectional view of a transistor 200 as an example of a semiconductor device according to an aspect of the present invention. Here, FIG. 1(A) is a plan view, and FIGS. 1(B) and 1(C) are cross-sectional views taken along the A1-A2 cross-section and the B1-B2 cross-section in FIG. 1(A), respectively. Note that in FIG. 1(A), some of the components of the transistor 200 (for example, the gate insulating film 104, etc.) are omitted to avoid complexity.

[0035] The transistor 200 shown in FIG. 1 has a gate electrode 102 and a gate electrode 1 on a substrate 100. A gate insulating film 104 provided on 02, and a metal oxide film 106a provided on the gate insulating film 104, and a source electrode or a drain electrode 108a, 108b provided in contact with the metal oxide film 106a. The metal oxide film 106a is also referred to as an oxide semiconductor since it exhibits semiconductor characteristics.

[0036] Further, the transistor 200 shown in FIG. 1 is a transistor having a bottom gate structure, and the source electrode or drain electrodes 108a, 108b are top contact structures in contact with the upper surface of the metal oxide film 106a. Note that the source electrode or drain electrodes 108a, 108b may be bottom contact structures in contact with the lower surface of the metal oxide film 106a.

[0037] The region where the metal oxide film 106a and the gate electrode 102 overlap functions as a channel formation region.

[0038] The metal oxide film 106a is a metal oxide containing two or more elements selected from In, Ga, Sn, and Zn. The metal oxide preferably has a band gap of 2 eV or more and less than 6 eV, more preferably 2.5 eV or more and 5.5 eV or less, and even more preferably 3 eV or more and 5 eV or less. By using a metal oxide having a wide band gap in this way, the off-current of the transistor 2 00 can be reduced.

[0039] A passivation film 110 is provided on the metal oxide film 106a, the source electrode or drain electrodes 108a, 108b. The passivation film 110 is provided so as to be in contact with the metal oxide film 106a. In the transistor 200 shown in FIG. 1, the p ​​​​​​The passivation film 110 has an insulating film 112, a metal oxide film 114, and an insulating film 116. Here, the insulating films 112 and 116 are insulating films from which oxygen desorbs by heat treatment. are used.

[0040] In this specification and the like, "oxygen desorbs by heat treatment" means that, by TDS (Thermal Desorption Spectroscopy) analysis, the desorption amount (or release amount) of oxygen converted to oxygen atoms is 1.0×10 18 cm -3 or more, preferably or 3.0×10 20 cm -3 or more. Also, "oxygen does not desorb by heat treatment" means that, by TDS analysis, the desorption amount (or release amount) of oxygen converted to oxygen atoms is 1. 0×10 0×10 18 cm -3 less than.

[0041] Hereinafter, a method for quantifying the oxygen release amount by converting it to oxygen atoms by TDS analysis will be described.

[0042] The desorption amount of gas when performing TDS analysis is proportional to the integrated value of the ionic strength. Therefore, the desorption amount of gas can be calculated from the ratio of the integrated value of the measured ionic strength to the reference value of the standard sample. The reference value of the standard sample is the ratio of the atomic density to the integrated value of the ionic strength corresponding to the atom in a sample containing atoms of a predetermined density. is.

[0043] For example, from the TDS analysis results of a silicon wafer containing hydrogen of a predetermined density as a standard sample, and the TDS analysis results of the insulating film, the desorption amount (N O2 ) of oxygen molecules in the insulating film is obtained by Equation 1 It is possible. Here, it is assumed that all of the gas detected at mass number 32 obtained by TDS analysis is derived from oxygen molecules. Although there is CH3OH with a mass number of 32, it is considered to have a low possibility of existence and is not considered here. Also, regarding oxygen molecules containing oxygen atoms with a mass number of 17 and oxygen atoms with a mass number of 18, which are isotopes of oxygen atoms, they are not considered because their abundance ratios in nature are extremely small. There is CH3OH with a mass number of 32, but it is considered to have a low possibility of existence and is not considered here. In addition, regarding oxygen molecules containing oxygen atoms with a mass number of 17 and oxygen atoms with a mass number of 18, which are isotopes of oxygen atoms, since their abundance ratios in nature are extremely small, they are not considered.

[0044] N O2 =N H2 / S H2 ×S O2 ×α (Formula 1)

[0045] N H2 is the value obtained by converting the hydrogen molecules desorbed from the standard sample into density. S H2 is the integrated value of the ionic strength when the standard sample is analyzed by TDS. Here, the reference value of the standard sample is set as N H2 / S H2 . S O2 is the integrated value of the ionic strength when the insulating film is analyzed by TDS and α is a coefficient that affects the ionic strength in TDS analysis. Regarding the details of Formula 1 , reference can be made to Japanese Patent Laid-Open No. 6-275697. The above numerical values of the desorption amount of oxygen are measured values obtained using a temperature-programmed desorption analyzer EMD-WA1000S / W manufactured by Denshi Kagaku Co., Ltd. with a silicon wafer containing 1×10 cm 16 of hydrogen atoms as the standard sample -3 . .

[0046] Also, in TDS analysis, a part of oxygen is detected as oxygen atoms. The ratio of oxygen molecules to oxygen atoms can be calculated from the ionization rate of oxygen molecules. Note that the above-mentioned α is for oxygen molecules . Since it includes the ionization rate of the child, by evaluating the amount of oxygen molecule desorption, the amount of oxygen atom desorption can also be estimated. can be estimated.

[0047] Note that N O2 is the amount of oxygen molecule desorption. In the insulating film, the desorption amount of oxygen in terms of oxygen atoms is twice the desorption amount of oxygen molecules. The desorption amount of oxygen is twice the desorption amount of oxygen molecules.

[0048] As an example of a film from which oxygen desorbs by heat treatment, there is silicon oxide (SiOx (x > 2)) with excess oxygen. Silicon oxide with excess oxygen (SiOx (x> 2)) contains more oxygen atoms per unit volume than twice the number of silicon atoms. The number of silicon atoms and oxygen atoms per unit volume are values measured by the Rutherford backscattering method. number of atoms and the number of oxygen atoms per unit volume are values measured by the Rutherford backscattering method. The number of silicon atoms and oxygen atoms per unit volume are values measured by the Rutherford backscattering method.

[0049] The metal oxide film 106a is provided between the gate insulating film 104 and the insulating film 112. The insulating film 112 is an insulating film from which oxygen desorbs by heat treatment, and the gate insulating film 104 is an insulating film from which oxygen does not desorb by heat treatment. By performing heat treatment, oxygen desorbs from the insulating film 112 and is supplied to the metal oxide film 106a.

[0050] In addition, the insulating film from which oxygen desorbs by heat treatment contains a large amount of negative fixed charges such as oxygen ions of unbonded oxygen. By providing an insulating film from which oxygen desorbs by heat treatment in contact with the metal oxide film including the channel formation region, the threshold voltage of the transistor can be positively shifted and is therefore preferable. and is therefore preferable. and is therefore preferable.

[0051] However, during heat treatment, the oxygen desorbing from the insulating film diffuses outward, so the metal oxide There may be cases where oxygen cannot be sufficiently supplied to the film 106a. Furthermore, when oxygen diffuses outward the negative fixed charges in the insulating film decrease. As the negative fixed charges decrease there is a risk that the threshold voltage of the transistor will shift negatively.

[0052] Therefore, in one aspect of the present invention, in contact with the insulating film 112, a metal oxide film 114 different from the metal oxide film 106a is provided. Since the metal oxide film can prevent the permeation of oxygen it is possible to prevent oxygen contained in the insulating film 112 from desorbing and diffusing outward during heat treatment.

[0053] In addition, oxygen deficiency may occur in the metal oxide film 114. In one aspect of the present invention, the metal oxide film 114 is provided by sandwiching it with insulating films (insulating film 112 and insulating film 11 6) from which oxygen desorbs by heat treatment.

[0054] Even if the metal oxide film is an extremely thin film with a film thickness of about 5 nm, it can prevent the permeation of oxygen. In addition, since the relative dielectric constant of the metal oxide film is high (for example, 15), when using a metal oxide film other than the metal oxide film including the channel formation region if the film thickness exceeds 15 nm, there is a risk that the parasitic capacitance will increase. Therefore, the film thickness of the metal oxide film 114 is preferably 5 nm or more and 15 nm or less. Also, by making the metal oxide film 114 an extremely thin film as described above, it is possible to prevent a significant increase in parasitic capacitance compared to the case where the metal oxide film 114 is not used in part of the passivation film.

[0055] The metal oxide film 114 provided to prevent the outward diffusion of oxygen desorbs oxygen by heat treatment By being sandwiched between the insulating film 112 and the insulating film 116, oxygen desorbs from the insulating film 1 12 and the insulating film 116 during heat treatment, is supplied to the metal oxide film 114, and is compensated for oxygen deficiency to be insulated (show insulation). Thus, even when the metal oxide film 114 is used as a part of the passivation film 110, it is not necessary to affect the electrical characteristics of the transistor 200.

[0056] In addition, in order to efficiently supply oxygen to the metal oxide film 106a, the film thickness of the insulating film 112 in contact with the metal oxide film 106a is preferably thicker than the film thickness of the insulating film 116 in contact with the metal oxide film 114. The film thicknesses of the insulating film 112 and the insulating film 116 may be appropriately set according to the film thickness of the passivation film 110.

[0057] By using a film from which oxygen desorbs by heat treatment as the insulating film 112, oxygen is supplied from the insulating film 112 to the metal oxide film 106a, and the interface level between the insulating film 112 and the metal oxide film 106a can be reduced. Therefore, it is possible to suppress charges and the like that may be generated due to the operation of the transistor 200 from being trapped at the interface between the insulating film 112 and the metal oxide film 106a, and the transistor 200 can be made into a transistor with little deterioration in electrical characteristics.

[0058] In addition, by providing the metal oxide film 114 in contact with the insulating film 112, outward diffusion of oxygen can be prevented, so that oxygen deficiency in the metal oxide film 106a including the channel formation region can be sufficiently compensated. Thereby, it is possible to suppress the threshold voltage of the transistor from shifting negatively. Also, the negative fixed charges in the insulating film 112 are reduced. This can prevent the following. As a result, it is possible to suppress the negative shift of the threshold voltage of the transistor as the negative fixed charge decreases.

[0059] Also, the hydrogen concentration of the metal oxide film 106a and the metal oxide film 114 is 1×10 20 at oms / cm 3 or less, preferably 1×10 19 atoms / cm 3 or less, more preferably 1×10 18 atoms / cm 3 or less. In the channel formation region made of the metal oxide film 106a, since the hydrogen concentration is reduced, the variation in the threshold voltage is small before and after light irradiation and before and after the BT (thermal bias) stress test, so that it has stable electrical characteristics and can be made into a highly reliable transistor. Also, the hydrogen concentration of the metal oxide film 114 used as an insulator rather than a semiconductor is preferably a lower concentration .

[0060] The metal oxide film 114 is a metal oxide containing two or more elements selected from In, Ga, Sn, and Zn, similar to the metal oxide film 106a. Here, the elements contained in the metal oxide film 114 and the elements contained in the metal oxide film 106a may be the same or different . For example, as the metal oxide film 106a and the metal oxide film 114, an In-Ga -Zn-O-based material may be used, or as the metal oxide film 106a, an In-Ga-Zn -O-based material may be used, and as the metal oxide film 114, an In-Ga-Zn-O-N-based material may be used.

[0061] 〈Application Examples of Semiconductor Devices〉 ​​​​​Figures 2(A) to 2(C) show cross-sections of transistors having a configuration different from that of transistor 200. The structure is shown.

[0062] The transistor 210 shown in Fig. 2(A) has a gate electrode 102 on a substrate 100, a gate insulating film 120 provided on the gate electrode 102, a metal oxide film 106a provided on the gate insulating film 120, and source electrodes or drain electrodes 108a and 108b provided in contact with the metal oxide film 106a. The difference between transistor 200 and transistor 210 is that a metal oxide film for preventing outward diffusion of oxygen is provided in a part of the gate insulating film 120. That is, the gate insulating film 120 has a three-layer structure of an insulating film 122, a metal oxide film 124, and an insulating film 126. Also, an insulating film 118 is provided as a passivation film on the metal oxide film 106a and the source electrodes or drain electrodes 108a and 108b. Here, the insulating films 122 and 126 are insulating films from which oxygen desorbs by heat treatment. Also, the insulating film 118 is an insulating film from which oxygen does not desorb by heat treatment. In contact with the metal oxide film 106a, there are source electrodes or drain electrodes 108a, 108b. It has them.

[0063] The difference between transistor 200 and transistor 210 is that a metal oxide film for preventing outward diffusion of oxygen is provided in a part of the gate insulating film 120. That is, the point is that a metal oxide film for preventing outward diffusion of oxygen is provided in a part of the gate insulating film 120. That is, the gate insulating film 120 has a three-layer structure of an insulating film 122, a metal oxide film 124, and an insulating film 126. Also, an insulating film 118 is provided as a passivation film on the metal oxide film 106a and the source electrodes or drain electrodes 108a and 108b. Here, the insulating films 122 and 126 are insulating films from which oxygen desorbs by heat treatment. Also, the insulating film 118 is an insulating film from which oxygen does not desorb by heat treatment. The gate insulating film 120 has a three-layer structure of an insulating film 122, a metal oxide film 124, and an insulating film 126. It is so. Also, an insulating film 118 is provided as a passivation film on the metal oxide film 106a and the source electrodes or drain electrodes 108a, 108b. Here, the insulating films 122 and 126 are insulating films from which oxygen desorbs by heat treatment. Also, the insulating film 118 is an insulating film from which oxygen does not desorb by heat treatment. Also, for the metal oxide film 106a to efficiently supply oxygen, it is preferable that the insulating film 122 in contact with the metal oxide film 106a is thicker than the insulating film 126 in contact with the metal oxide film 124. The film thicknesses of the insulating film 122 and the insulating film 126 may be appropriately set according to the film thickness of the gate insulating film 120. Also, if the metal oxide film 124 is at least 5 nm or more, oxygen permeation can be prevented, so it may be appropriately set according to the film thickness of the gate insulating film 120. Also, for the metal oxide film 106a to efficiently supply oxygen, it is preferable that the insulating film 122 in contact with the metal oxide film 106a is thicker than the insulating film 126 in contact with the metal oxide film 124. The film thicknesses of the insulating film 122 and the insulating film 126 may be appropriately set according to the film thickness of the gate insulating film 120. Also, if the metal oxide film 124 is at least 5 nm or more, oxygen permeation can be prevented, so it may be appropriately set according to the film thickness of the gate insulating film 120.

[0064] Also, for the metal oxide film 106a to efficiently supply oxygen, it is preferable that the insulating film 122 in contact with the metal oxide film 106a is thicker than the insulating film 126 in contact with the metal oxide film 124. The insulating film 122 in contact with the metal oxide film 106a is preferably thicker than the insulating film 126 in contact with the metal oxide film 124. The film thicknesses of the insulating film 122 and the insulating film 126 may be appropriately set according to the film thickness of the gate insulating film 120. Also, if the metal oxide film 124 is at least 5 nm or more, oxygen permeation can be prevented, so it may be appropriately set according to the film thickness of the gate insulating film 120. Also, if the metal oxide film 124 is at least 5 nm or more, oxygen permeation can be prevented, so it may be appropriately set according to the film thickness of the gate insulating film 120. That's fine.

[0065] The transistor 220 shown in Fig. 2(B) includes a gate electrode 102 on a substrate 100, a gate insulating film 120 provided on the gate electrode 102, a metal oxide film 106a provided on the gate insulating film 120, and source electrodes or drain electrodes 108a, 108b provided in contact with the metal oxide film 106a. Further, a passivation film 110 is provided on the metal oxide film 106a, the source electrodes or drain electrodes 108a, 108b.

[0066] Regarding the gate insulating film 120 and the passivation film 110 in the transistor 220, since the descriptions of the transistors 200 and 210 can be referred to, detailed explanation is omitted.

[0067] Also, in the transistors 200, 210, and 220, the top contact structure where the source electrodes or drain electrodes 108a, 108b are in contact with the upper surface of the metal oxide film 106a has been described. In a transistor according to an aspect of the present invention, a bottom contact structure where the source electrodes or drain electrodes 108a, 108b are in contact with the lower surface of the metal oxide film 106a can also be adopted. An example of the bottom contact structure is shown in Fig. 2(C).

[0068] The transistor 230 shown in Fig. 2(C) includes a gate electrode 102 on a substrate 100, a gate insulating film 104 provided on the gate electrode 102, source electrodes or drain electrodes 108a, 108b provided on the gate insulating film 104, and a metal oxide film 106a provided in contact with the source electrodes or drain electrodes 108a, 108b. On the 106a, a passivation film 110 is provided in the same manner as the transistor 200. It is.

[0069] The passivation film 110 is provided so as to cover the entire metal oxide film 106a. Therefore, oxygen can be efficiently supplied to the metal oxide film 106a.

[0070] In addition, in the case of a transistor having a bottom contact structure, a metal oxide film for preventing outward diffusion of oxygen may be provided on a part of the gate insulating film, or a part of the gate insulating film and a part of the passivation film. A metal oxide film for preventing outward diffusion of oxygen may be provided. For preventing outward diffusion of oxygen, a metal oxide film may be provided on a part of the gate insulating film, or a metal oxide film for preventing outward diffusion of oxygen may be provided on a part of the gate insulating film and a part of the passivation film. As described above, in one aspect of the present invention, in order to reduce oxygen deficiency in the metal oxide film (the first metal oxide film) including the channel formation region, oxygen is removed by heat treatment in contact with the first metal oxide film. An insulating film (the first insulating film) is provided. Further, in contact with the insulating film (the first insulating film) from which oxygen is desorbed by heat treatment, a metal oxide film (the second metal oxide film) different from the first metal oxide film is provided. Further, the second metal oxide film is provided sandwiched between insulating films (the first insulating film and the second insulating film) from which oxygen is desorbed by heat treatment.

[0071] As described above, in one aspect of the present invention, in order to reduce oxygen deficiency in the metal oxide film (the first metal oxide film) including the channel formation region, oxygen is removed by heat treatment in contact with the first metal oxide film. An insulating film (the first insulating film) is provided. Further, in contact with the insulating film (the first insulating film) from which oxygen is desorbed by heat treatment, a metal oxide film (the second metal oxide film) different from the first metal oxide film is provided. Further, the second metal oxide film is provided sandwiched between insulating films (the first insulating film and the second insulating film) from which oxygen is desorbed by heat treatment. By providing the insulating film (the first insulating film) in contact with the first metal oxide film, oxygen is desorbed by heat treatment. Also, oxygen is desorbed by heat treatment. An insulating film (the first insulating film) in contact with a metal oxide film (the second metal oxide film) different from the first metal oxide film is provided. By providing the insulating film (the first insulating film) in contact with the first metal oxide film, oxygen is desorbed by heat treatment. An insulating film (the first insulating film) in contact with a metal oxide film (the second metal oxide film) different from the first metal oxide film is provided. Further, the second metal oxide film is provided sandwiched between insulating films (the first insulating film and the second insulating film) from which oxygen is desorbed by heat treatment.

[0072] By sandwiching the insulating film 112 (or the insulating film 122) from which oxygen is desorbed by heating between the metal oxide film 106 a and the metal oxide film 114 (or the metal oxide film 124), the oxygen desorbed from the insulating film 112 (or the insulating film 122) during heat treatment can be prevented from being released to the outside. And the oxygen deficiency of the metal oxide film 106a can be sufficiently compensated. Also, It is possible to prevent a decrease in the negative fixed charge contained in the insulating film 112 (or the insulating film 122). And prevent a decrease in the negative fixed charge contained in the insulating film 112 (or the insulating film 122). This can be achieved. That is, according to one aspect of the present invention, the oxygen deficiency in the metal oxide film 106a is reduced, and oxygen contained in the insulating film 112 (or insulating film 122) in contact with the metal oxide film 106a is prevented from being released to the outside, thereby providing a semiconductor device with good electrical characteristics and stable electrical characteristics.

[0073] <Method for manufacturing a semiconductor device> Next, as an example of a method for manufacturing a semiconductor device according to one aspect of the present invention, a method for manufacturing the transistor 200 will be described with reference to FIG. 3.

[0074] First, after forming a conductive film applicable to the gate electrode on the substrate 100, a resist mask is formed on the conductive film by a photolithography process, and the conductive film is etched into a desired shape using the resist mask to form the gate electrode 102. Then, a gate insulating film 104 is formed on the gate electrode 102 (see FIG. 3(A)). As the substrate 100, a substrate having an insulating surface can be used. For example, substrates such as glass substrates,

[0075] ceramic substrates, quartz substrates, and sapphire substrates can be used. Also, as long as it has an insulating surface, single-crystal semiconductor substrates such as silicon and silicon carbide, polycrystalline semiconductor substrates, compound semiconductor substrates such as silicon germanium, and SOI substrates can also be applied, and semiconductor elements may be provided on these substrates. There is no major limitation on the substrates that can be used for the substrate 100, but it is necessary to have heat resistance to withstand subsequent heat treatment (see FIG. 3(A)). In the present embodiment, a glass substrate is used as the substrate 100. possible, and semiconductor elements may be provided on these substrates. There is no major limitation on the substrates that can be used for the substrate 100, but it is necessary to have heat resistance to withstand subsequent heat treatment This can be achieved. That is, according to one aspect of the present invention, the oxygen deficiency in the metal oxide film 106a This can be achieved. That is, according to one aspect of the present invention, the oxygen deficiency in the metal oxide film 106a

[0076] Further, a flexible substrate can also be used as the substrate 100. When using a flexible substrate as the substrate 100, transistors may be directly fabricated on the flexible substrate, or transistors 200 may be fabricated on another fabrication substrate and then peeled off and transferred. In addition, in order to peel off and transfer from the fabrication substrate to the flexible substrate, a release layer and an insulating film are provided on the fabrication substrate, and transistors 200 are fabricated thereon. When using a flexible substrate, transistors may be directly fabricated on the flexible substrate, or transistors 200 may be fabricated on another fabrication substrate and then peeled off and transferred. After that, it may be peeled off and transferred to the flexible substrate. In addition, in order to peel off and transfer from the fabrication substrate to the flexible substrate, a release layer and an insulating film are provided on the fabrication substrate, and transistors 200 are fabricated thereon. That's all.

[0077] As the conductive material applicable to the gate electrode 102, a single metal composed of aluminum, titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, or tungsten, or an alloy having this as a main component can be used. In addition, the conductive film applicable to the gate electrode 102 is formed in a single-layer structure or a laminated structure using the above-described conductive material. For example, there are a single-layer structure of an aluminum film containing silicon, a two-layer structure in which a titanium film is laminated on an aluminum film, a two-layer structure in which a titanium film is laminated on a tungsten film, a two-layer structure in which a copper film is laminated on a copper-magnesium-aluminum alloy film, a three-layer structure in which a titanium film and an aluminum film are laminated on the titanium film, and a titanium film is further formed thereon, etc. In addition, a transparent conductive material containing indium oxide and indium oxide containing tin oxide or zinc oxide may be used. The conductive film applicable to the gate electrode 102 is formed by a sputtering method, a plasma CVD method, etc., with a film thickness of 50 nm or more and 300 nm or less. After that, a resist mask is formed on the conductive film by a photolithography process, and the conductive film is etched into a desired shape using the resist mask to form the gate electrode 102. Note that the resist mask There are structures such as a three-layer structure in which a titanium film is overlapped with an aluminum film on the titanium film and a titanium film is further formed thereon. In addition, a transparent conductive material containing indium oxide and indium oxide containing tin oxide or zinc oxide may be used. That's all.

[0078] The conductive film applicable to the gate electrode 102 is formed by a sputtering method, a plasma CVD method, etc., with a film thickness of 50 nm or more and 300 nm or less. After that, a resist mask is formed on the conductive film by a photolithography process, and the conductive film is etched into a desired shape using the resist mask to form the gate electrode 102. After that, a resist mask is formed on the conductive film by a photolithography process, and the conductive film is etched into a desired shape using the resist mask to form the gate electrode 102. By using the resist mask, the conductive film is etched into a desired shape to form the gate electrode 102. Note that the resist mask As such, in addition to the photolithography process, an inkjet method, a printing method, etc. can be appropriately used. Also, as the etching process, dry etching, wet etching, or a combination of dry etching and wet etching can be performed. In this embodiment state, as the conductive film, tungsten is formed with a film thickness of 150 nm by a sputtering method.

[0079] As the gate insulating film 104, any oxide insulating film such as silicon oxide, gallium oxide, or aluminum oxide, or a nitride insulating film such as silicon nitride or aluminum nitride , or an insulating film selected from silicon oxynitride, aluminum oxynitride, or silicon nitride oxide, etc. can be used. In addition to the above materials, high-k materials such as hafnium oxide, yttrium oxide, hafnium silicate (HfSi O (x > 0, y > 0)), hafnium silicate with nitrogen added (HfSiO x O y (x > 0, y > 0)), hafnium aluminate (HfAl (x > 0, y > 0)), etc. can be used. Note that the gate insulating film 104 may be formed in a single-layer structure of the high-k material or x N y in a laminated structure with an insulating film made of the above materials. ート(HfAl x O y (x > 0, y > 0)), etc. can be used. The gate insulating film 104 may be formed with a film thickness of 5 nm or more and 300 nm or less by a sputtering method, a plasma CVD method, etc. By using the above high-k material as the gate insulating film 104, the thickness of the electrical (e.g., in terms of a silicon oxide film) gate insulating film can be changed.

[0080] The gate insulating film 104 is formed by a sputtering method, a plasma CVD method, etc. with a film thickness of 5 nm or more and 300 nm or less. By using the above high-k material as the gate insulating film 104, the thickness of the electrical (e.g., in terms of a silicon oxide film) gate insulating film can be changed. ​Since the physical gate insulating film can be thickened without being depleted, the gate leakage current can be reduced. It can be reduced.

[0081] In this embodiment, as the gate insulating film 104, a silicon oxynitride film is formed by plasma CVD method. The silicon oxide film formed by plasma CVD method is a film in which oxygen does not desorb by heat treatment. It is a film from which oxygen does not desorb.

[0082] Next, a metal oxide film 106 is formed on the gate insulating film 104 (see Fig. 3(B)).

[0083] As the material of the metal oxide film 106, a metal oxide material containing two or more selected from In, Ga, Zn and Sn can be used. For example, a quaternary metal oxide such as In-Sn-Ga-Zn-O system material, or a ternary metal oxide such as In-Ga-Zn-O system material, In-Sn-Zn-O system material, In-Al-Zn-O system material, Sn-Ga-Zn-O system material, Al-Ga-Zn-O system material, Sn-Al-Zn-O system material, or a binary metal oxide such as In-Zn-O system material, Sn-Zn-O system material, Al-Zn-O system material, Zn-Mg-O system material, Sn-Mg-O system material, In-Mg-O system material, In-Ga-O system material, In-O system material, Sn-O system material, Zn-O system material, etc. can be used. Here, for example, the In-Ga-Zn-O system material means an oxide having indium (In), gallium (Ga), and zinc (Zn), and its composition ratio is not particularly limited. Also, it may contain elements other than In, Ga, and Zn. At this time, it is preferable to make oxygen excessive with respect to the stoichiometric ratio of the metal oxide film. To make oxygen excessive is preferable. For example, the In-Ga-Zn-O system material means an oxide having indium (In), gallium (Ga), and zinc (Zn), and its composition ratio is not particularly limited. Also, it may contain elements other than In, Ga, and Zn. At this time, it is preferable to make oxygen excessive with respect to the stoichiometric ratio of the metal oxide film. is not particularly limited. Also, it may contain elements other than In, Ga, and Zn. At this time, it is preferable to make oxygen excessive with respect to the stoichiometric ratio of the metal oxide film. is preferable. This can suppress the generation of carriers due to oxygen deficiency in the metal oxide film.

[0084] When using an In-Ga-Zn-O-based material as the material of the metal oxide film 106, as an example of the target, there is one having a composition ratio of In2O3:Ga2O3:ZnO = 1:1:1 [mole ratio]. Further, a target having a composition ratio of In2O3:Ga2O3:ZnO = 1:1:2 [mole ratio], a target having a composition ratio of In2O3:Ga2O3:ZnO = 1:1:4 [mole ratio], or a target having a composition ratio of In2O3:Ga2O3:ZnO = 2: 1:8 [mole ratio] can also be used. When using an In-Zn-O-based material as the material of the metal oxide film 106, in terms of atomic ratio, In:Zn = 0.5 or more and 50 or less:1, preferably In:Zn = 1 or more and 20 or less:

[0085] 1, more preferably In:Zn = 3 or more and 30 or less:2. By setting the atomic ratio of Zn within the above-mentioned range, the field-effect mobility of the transistor 200 can be improved. Here, when the atomic ratio of the compound is In:Zn:O = X:Y:Z, it is preferable that Z > 1.5X + Y. 1, more preferably In:Zn = 3 or more and 30 or less:2. By setting the atomic ratio of Zn within the above-mentioned range, the field-effect mobility of the transistor 200 can be improved. Here, when the atomic ratio of the compound is In:Zn:O = X:Y:Z, it is preferable that Z > 1.5X + Y. Here, when the atomic ratio of the compound is In:Zn:O = X:Y:Z, it is preferable that Z > 1.5X + Y.

[0086] As the metal oxide film 106, a material represented by the chemical formula InMO3(ZnO) m (m > 0) may be used. Here, M represents one or more metal elements selected from Ga, Al, Mn, and Co. For example, as M, Ga, Ga and Al, Ga and Mn, or G a and Co, etc. may be used. a and Co, etc. may be used.

[0087] The metal oxide film 106 can be formed by sputtering, molecular beam epitaxy, atomic layer deposition, or​ It can be formed by pulsed laser deposition. Also, the thickness of the metal oxide film 106 is , 5 nm or more and 100 nm or less, preferably 10 nm or more and 30 nm or less. Note that the metal oxide film is a semiconductor immediately after film formation.

[0088] Also, the metal oxide film 106 may be amorphous or may have crystallinity. For example, the metal oxide film 106 is non-single crystal. Specifically, when viewed from a direction perpendicular to the ab plane of the non-single crystal, it has an atomic arrangement of triangle, hexagon, equilateral triangle, or regular hexagon, and when viewed from a direction perpendicular to the c axis, it contains a phase in which metal atoms are arranged in layers or a phase in which metal atoms and oxygen atoms are arranged in layers. In this specification, the metal oxide film is referred to as a CAAC-OS film. Also, by using a CAAC-OS film as the film including the channel formation region of the transistor 200, fluctuations in the electrical characteristics of the transistor 200

[0089] caused by irradiation with visible light or ultraviolet light and application of heat, bias, etc. can be suppressed, and the reliability of the semiconductor device can be improved. There are, for example, the following two methods for making the metal oxide film 106

[0090] into a CAAC-OS film. One method is a method of forming the metal oxide film 106 while heating the Note that, when forming the metal oxide film 106, by increasing the temperature at which the substrate 100 is heated, a CAAC-OS film in which the proportion of the crystalline portion is larger than that of the amorphous portion can be obtained. .

[0091] Also, when the formation of the metal oxide film 106 is performed in two steps, while maintaining the substrate 100 at a substrate temperature of 100 °C or higher and 450°C or lower, a first layer of metal oxide film is formed on the gate insulating film 104, and a heat treatment is performed at 550°C or higher and lower than the strain point of the substrate in an atmosphere of nitrogen, oxygen, a noble gas, or dry air. By this heat treatment, a crystal region (including tabular crystals) is formed in a region including the surface of the first layer of metal oxide film. Then, the second layer of metal oxide film is formed thicker than the first layer of metal oxide film. Thereafter, a heat treatment is performed again at 550°C or higher and lower than the strain point of the substrate, and the first layer of metal oxide film in which a crystal region (including tabular crystals) is formed in the region including the surface is used as a seed for crystal growth, and crystal growth is performed upward to crystallize the entire second layer of metal oxide film. Note that the first layer of oxide semiconductor film is preferably formed to have a thickness of 1 nm or more and 10 nm or less. When forming the metal oxide film 106 using the sputtering method, it is preferable to reduce the hydrogen concentration contained in the metal oxide film 106 as much as possible. To reduce the hydrogen concentration, high-purity noble gas (typically argon), oxygen, in which impurities such as hydrogen, water, compounds containing hydroxyl groups, or hydrides are removed, and a mixed gas of noble gas and oxygen are appropriately used as the atmosphere gas supplied into the processing chamber of the sputtering apparatus. Further, the exhaust of the processing chamber may be performed by combining a cryopump having a high exhaust capacity for water and a sputter ion pump having a high exhaust capacity for hydrogen.

[0092]

[0093] ​​​​​​​​​​ By doing as described above, it is possible to form the metal oxide film 106 with reduced hydrogen contamination. Even when using the above sputtering apparatus, the metal oxide film 106 is formed to contain a certain amount of nitrogen. For example, the nitrogen concentration of the metal oxide film 106 measured by secondary ion mass spectrometry (SIMS: Secondary Ion Mass Spectrometry) is less than 5×10 cm 18 cm -3 −3.

[0094] When forming or after forming the metal oxide film 106, charges may be generated due to oxygen deficiency in the metal oxide film 106. Generally, in a metal oxide film, a part of the oxygen deficiency becomes a donor and generates electrons as carriers. That is, also in the transistor 200, a part of the oxygen deficiency in the metal oxide film 106 becomes a donor, and electrons as carriers are generated, causing the threshold voltage of the transistor 200 to fluctuate in the negative direction. Thus, in the metal oxide film 106, the generation of these electrons is prominent in the oxygen deficiency occurring near the interface between the metal oxide film 106 and the gate insulating film 104. Therefore, after forming the metal oxide film 106, a first heat treatment is performed. The first heat treatment is performed to release hydrogen (compounds containing water and hydroxyl groups) from the metal oxide film. That is, the first heat treatment desorbs hydrogen, which is an unstable carrier source, from the metal oxide film 106, thereby suppressing the threshold voltage of the transistor 200 from fluctuating in the negative direction. Furthermore, the reliability of the transistor 200 can be improved. The first heat treatment is performed to release hydrogen (compounds containing water and hydroxyl groups) from the metal oxide film. That is, the first heat treatment desorbs hydrogen, which is an unstable carrier source, from the metal oxide film 106, thereby suppressing the threshold voltage of the transistor 200 from fluctuating in the negative direction. Furthermore, the reliability of the transistor 200 can be improved. The first heat treatment is performed to release hydrogen (compounds containing water and hydroxyl groups) from the metal oxide film. That is, the first heat treatment desorbs hydrogen, which is an unstable carrier source, from the metal oxide film 106, thereby suppressing the threshold voltage of the transistor 200 from fluctuating in the negative direction. Furthermore, the reliability of the transistor 200 can be improved.

[0095] Therefore, after forming the metal oxide film 106, a first heat treatment is performed.

[0096] The first heat treatment is performed to release hydrogen (compounds containing water and hydroxyl groups) from the metal oxide film. That is, the first heat treatment desorbs hydrogen, which is an unstable carrier source, from the metal oxide film 106, thereby suppressing the threshold voltage of the transistor 200 from fluctuating in the negative direction. Furthermore, the reliability of the transistor 200 can be improved. The first heat treatment is performed to release hydrogen (compounds containing water and hydroxyl groups) from the metal oxide film. That is, the first heat treatment desorbs hydrogen, which is an unstable carrier source, from the metal oxide film 106, thereby suppressing the threshold voltage of the transistor 200 from fluctuating in the negative direction. Furthermore, the reliability of the transistor 200 can be improved. The first heat treatment is performed to release hydrogen (compounds containing water and hydroxyl groups) from the metal oxide film. That is, the first heat treatment desorbs hydrogen, which is an unstable carrier source, from the metal oxide film 106, thereby suppressing the threshold voltage of the transistor 200 from fluctuating in the negative direction. Furthermore, the reliability of the transistor 200 can be improved. The first heat treatment is performed to release hydrogen (compounds containing water and hydroxyl groups) from the metal oxide film. That is, the first heat treatment desorbs hydrogen, which is an unstable carrier source, from the metal oxide film 106, thereby suppressing the threshold voltage of the transistor 200 from fluctuating in the negative direction. Furthermore, the reliability of the transistor 200 can be improved. The first heat treatment is performed to release hydrogen (compounds containing water and hydroxyl groups) from the metal oxide film. That is, the first heat treatment desorbs hydrogen, which is an unstable carrier source, from the metal oxide film 106, thereby suppressing the threshold voltage of the transistor 200 from fluctuating in the negative direction. Furthermore, the reliability of the transistor 200 can be improved.

[0097] The temperature of the first heat treatment is, for example, 150°C or higher and lower than the substrate distortion point temperature, preferably 250°C or higher and 450°C or lower, more preferably 300°C or higher and 450°C or lower, and is carried out in an oxidative atmosphere or an inert atmosphere. Here, the oxidative atmosphere refers to an atmosphere containing 10 ppm or more of an oxidative gas such as oxygen, ozone, or nitrogen oxide. Further, the inert atmosphere refers to an atmosphere in which the aforementioned oxidative gas is less than 10 ppm and is filled with nitrogen or a noble gas. The treatment time is 3 minutes to 24 hours. Heat treatment exceeding 24 hours is not preferable because it causes a decrease in productivity . There is no special limitation on the heating device used for the first heat treatment, and it may be equipped with a device for heating the object to be treated by heat conduction or heat radiation from a heating element such as a resistance heating element. For example, an electric furnace or an RTA (Rapid Thermal Anneal) device such as an LRTA (Lamp Rapid Thermal Anneal) device or a GRTA

[0098] (Gas Rapid Thermal Anneal) device can be used. The LRTA device is a device that heats the object to be treated by radiation of light (electromagnetic waves) emitted from a lamp such as a halogen lamp, metal halide lamp, xenon arc lamp, carbon arc lamp, high-pressure sodium lamp, or high-pressure mercury lamp. The GRTA device is a device that performs heat treatment using high-temperature gas . Next, a resist mask is formed on the metal oxide film 106 by a photolithography process, and using the resist mask, the metal oxide film 106 is etched into a desired shape to form an island-shaped metal oxide film 106a (see Fig. 3(C)). Note that the resist mask is a phot .

[0099] Next, a resist mask is formed on the metal oxide film 106 by a photolithography process, and using the resist mask, the metal oxide film 106 is etched into a desired shape to form an island-shaped metal oxide film 106a (see Fig. 3(C)). Note that the resist mask is a phot​ In addition to the lithography process, inkjet methods, printing methods, etc. can be appropriately used. The etching is preferably performed such that the end of the metal oxide film 106a has a tapered shape. By making the end of the island-shaped metal oxide film 106a have a tapered shape, in the production of the transistor 200 after this step, the coating property of the film to be formed can be improved, and breakage of the film can be prevented. The tapered shape can be formed by etching while retracting the resist mask.

[0100] For the etching process, dry etching or wet etching may be used, or these may be combined. As the etching solution used for wet etching, a solution obtained by mixing phosphoric acid, acetic acid, and nitric acid, ammonia perhydrate (31 wt% hydrogen peroxide solution: 28 wt% ammonia water: water = 5:2:2 (volume ratio)), etc. can be used. Further, ITO-07 N (manufactured by Kanto Chemical Co., Inc.) may be used.

[0101] As the etching gas used for dry etching, a gas containing chlorine (chlorine-based gas, for example, chlorine (Cl2), boron trichloride (BCl3), silicon tetrachloride (SiCl4), carbon tetrachloride (CCl4), etc.) is preferable. Further, a gas containing fluorine (fluorine-based gas, for example, carbon tetrafluoride (CF4), sulfur hexafluoride (SF6), nitrogen trifluoride (NF3), trifluoromethane (C HF3), etc.), hydrogen bromide (HBr), oxygen (O2), a gas obtained by adding a noble gas such as helium (He) or argon (Ar) to these gases, etc. can be used.

[0102] As dry etching, parallel plate type RIE (Reactive Ion Etchi ng) method and ICP (Inductively Coupled Plasma) A combined plasma etching method can be used. Etching conditions (power applied to the coil-type electrode, power applied to the substrate-side electrode, The temperature of the electrode on the substrate side, etc. are adjusted appropriately.

[0103] Next, a conductive film applicable to a source electrode and a drain electrode is formed on the metal oxide film 106a. Then, a resist mask is formed on the conductive film by a photolithography process. The conductive film is etched into a desired shape using a mask, and a source electrode or a drain electrode 1 is formed. The source electrode or drain electrode 108a and 108b are formed (see FIG. 3(D)). The conductive material applicable to the gate electrode 102 may be the same as that applicable to the gate electrode 108b. The following conductive materials can be used.

[0104] In this embodiment, the source and drain electrodes 108a and 108b are formed by sputtering. By the etching method, a titanium film with a thickness of 50 nm, an aluminum film with a thickness of 100 nm, and a After forming a titanium film having a thickness of 100 nm, a photolithography process and an etching process are performed. It is formed.

[0105] Next, pads are formed on the metal oxide film 106a and the source and drain electrodes 108a and 108b. In the present embodiment, a passivation film 110 is formed (see FIG. 3(E)). As the insulating film 110, an insulating film 112, a metal oxide film 114, and an insulating film 116 are formed in this order. .

[0106] The insulating film 112 and the insulating film 116 are made of silicon oxide, gallium oxide, or aluminum oxide. An insulating film selected from among um, silicon oxynitride, aluminum oxynitride, etc. can be used. Note that the film formation method of the insulating film 112 and the insulating film 116 may be the same as that of the gate insulating film 104. That is, the same film formation method may be applied.

[0107] Since the metal oxide film 114 can use the same materials and film formation method as the metal oxide film 106, detailed description thereof will be omitted. That is, detailed description will be omitted.

[0108] The film thickness of the passivation film 110 may be 50 nm or more and 1000 nm or less, preferably 100 nm or more and 300 nm or less.

[0109] In this embodiment, as the insulating film 112, a silicon oxide film with a film thickness of 200 nm is formed by sputtering, and as the metal oxide film 114, a metal oxide film of the In-Ga-Zn-O system with a film thickness of 5n m is formed by sputtering, and as the insulating film 116, a silicon oxide film with a film thickness of 50 nm is formed by sputtering. That is, a silicon oxide film with a film thickness of 50 nm is formed by sputtering as the insulating film 116.

[0110] Note that when forming the insulating films 112 and 116 using the sputtering method, as long as possible, it is preferable to reduce the hydrogen concentration contained in the insulating films 112 and 116. For reducing the hydrogen concentration, as the atmosphere gas supplied into the processing chamber of the sputtering apparatus, a high-purity rare gas (typically argon) from which impurities such as hydrogen, water, and compounds containing hydroxyl groups are removed, oxygen, and a mixed gas of the rare gas and oxygen are appropriately used. Further, the exhaust gas of the processing chamber may be a combination of a cryopump with a high exhaust capacity for water and a sputter ion pump with a high exhaust capacity for hydrogen. That is, a high-purity rare gas (typically argon) from which impurities such as hydrogen, water, and compounds containing hydroxyl groups are removed, oxygen, and a mixed gas of the rare gas and oxygen are appropriately used as the atmosphere gas supplied into the processing chamber of the sputtering apparatus. Further, the exhaust gas of the processing chamber may be a combination of a cryopump with a high exhaust capacity for water and a sputter ion pump with a high exhaust capacity for hydrogen. That is, the exhaust gas of the processing chamber may be a combination of a cryopump with a high exhaust capacity for water and a sputter ion pump with a high exhaust capacity for hydrogen. That is, it may be used in combination.

[0111] During the first heat treatment, hydrogen is released from the metal oxide film 106a, and oxygen may desorb from the upper surface of the metal oxide film 1 06a to the outside. As a result, oxygen vacancies may occur in the metal oxide film 106a. In order to compensate for the newly generated oxygen vacancies, it is preferable to perform a second heat treatment after forming the passivation film 110.

[0112] Since the conditions and apparatus for the second heat treatment may be appropriately used for the conditions and apparatus of the first heat treatment, detailed description is omitted.

[0113] By performing the second heat treatment, oxygen desorbs from the insulating film 112 and is supplied to the metal oxide film 106a. Also, since a metal oxide film 114 for preventing outward diffusion of oxygen is provided on the insulating film 112, outward diffusion of oxygen contained in the insulating film 112 can be prevented during the second heat treatment, and oxygen can be efficiently supplied to the metal oxide film 106a. Moreover, since the metal oxide film 114 has its oxygen vacancies compensated by being supplied with oxygen from the insulating film 112 and the insulating film 116, its resistance increases and it becomes an insulator (showing insulation properties). Thus, even when the metal oxide film 114 is used as part of the passivation film 110, it does not affect the electrical characteristics of the transistor 200.

[0114] By performing the first heat treatment and the second heat treatment, the hydrogen concentration in the metal oxide film 106a and the metal oxide film 114 is reduced, and they become highly purified metal oxides. Also, the hydrogen concentration of the metal oxide film 106a and the metal oxide film 114 is 1×10 20 atoms / cm 3 or less, preferably 1×10 19atoms / cm 3 More preferably, it is 1×10 18 atoms / cm 3 or less. Further, the metal oxide used as an insulator instead of a semiconductor The hydrogen concentration of the film 114 is preferably a lower concentration. Note that the hydrogen concentrations in the metal oxide film 106 a and the metal oxide film 114 are measured by SIMS analysis.

[0115] By the first heat treatment and the second heat treatment, the hydrogen concentration is sufficiently reduced and purified, and sufficient oxygen is supplied to reduce the defect levels in the energy gap caused by oxygen vacancies Using the metal oxide film 106a, the off-current of the transistor 200 can be reduced Specifically, the off-current at room temperature (25°C) (here, the value per unit channel width ( 1 μm)) is 100 zA (1 zA (zeptoampere) is 1×10 -21 A) or less, desirably 10 zA or less.

[0116] Also, alkali metals such as lithium (Li) and sodium (Na) are impurities for the metal oxide film 10 6a and the metal oxide film 114, so it is preferable to reduce their contents The concentration of alkali metals contained in the metal oxide film 106a and the metal oxide film 114 is 2×10 16 cm -3 or less, preferably 1×10 15 cm -3 or less is preferable . Further, since alkaline earth metals are also impurities, it is preferable to reduce their contents .

[0117] Also, the metal oxide film can be a conductor or a semiconductor depending on the amounts of hydrogen and oxygen vacancies or may be an insulator. For example, the resistivity of the metal oxide film depends on the amounts of hydrogen and oxygen deficiencies contained in the metal oxide film.

[0118] By using insulating films that do not desorb oxygen by heat treatment on both sides of the insulating film sandwiching the metal oxide film, heat treatment (e.g., 350 °C) is performed, and the resistivity of the metal oxide film becomes 10 [Ω·cm] or less, so that the metal oxide film becomes a conductor. Also, when heat treatment (e.g., 350 °C) is performed using insulating films that desorb oxygen by heat treatment on both sides of the insulating film sandwiching the metal oxide film, the resistivity becomes 1 × 10 [Ω·cm] or more, so that the metal oxide film becomes an insulator (showing insulating properties 8 ). Therefore, in order to make the metal oxide film 114 an insulator, it may be formed so that the resistivity becomes 1 × 10 8 Ω·cm] or more.

[0119] Also, in order to make the metal oxide film 106a a semiconductor, since it may take a value between the resistivity that becomes a conductor and the resistivity that becomes an insulator, the metal oxide film 106a may be formed so that the resistivity exceeds 10 [Ω·cm and is less than 1 × 10 [Ω·cm]. 8

[0120] The transistor 200 can be fabricated by the above steps (see Fig. 3(E)).

[0121] By providing an insulating film that desorbs oxygen by heat treatment in contact with a metal oxide film (oxide semiconductor) including a channel formation region, and providing a metal oxide film for preventing outward diffusion of oxygen in contact with the insulating film, outward diffusion of oxygen from the insulating film can be suppressed, and oxygen can be efficiently supplied to the metal oxide film including the channel formation region. Thereby, oxygen can be efficiently supplied to the metal oxide film including the channel formation region. oxide film including the channel formation region. Thereby, oxygen can be efficiently supplied to the metal oxide film including the channel formation region. ​​Since it is possible to reduce the oxygen deficiency in the metal oxide film, it is possible to suppress the generation of electrons as carriers and suppress the fluctuation of the threshold voltage of the transistor in the negative direction. Even for the metal oxide film for preventing outward diffusion of oxygen, the oxygen deficiency can be reduced and insulation can be achieved by sandwiching it with an insulating film from which oxygen is desorbed by heat treatment and performing the heat treatment.

[0122] Also, the metal oxide film for preventing outward diffusion of oxygen is sandwiched between insulating films from which oxygen is desorbed by heat treatment, and by performing heat treatment, it is possible to reduce the oxygen deficiency and achieve insulation even for the metal oxide film for preventing outward diffusion of oxygen.

[0123] <Method for manufacturing an application example of a semiconductor device> When manufacturing the transistor 210 shown in FIG. 2(A), it may be manufactured as follows.

[0124] After forming the gate electrode 102 on the substrate 100, the gate insulating film 120 is formed. The gate insulating film 120 is formed in the order of the insulating film 126, the metal oxide film 124, and the insulating film 122. The materials and film formation methods of the insulating film 126 and the insulating film 122 are the same as those of the insulating film 116 and the insulating film 112. Also, the materials and film formation methods of the metal oxide film 124 are the same as those of the metal oxide film 114.

[0125]

[0126] Next, after forming the gate insulating film 120, it is preferable to perform the first heat treatment. Here, since the metal oxide film 124 is sandwiched between the insulating film 126 and the insulating film 122 from which oxygen is desorbed by heat treatment, the metal oxide film 124 becomes an insulator (shows insulating properties). Then, a metal oxide film is formed on the gate insulating film 120, and by performing a photolithography process and an etching process on the metal oxide film, the metal oxide film 106a is formed.

[0127] ​​​​​​​​​Next, after forming a conductive film on the metal oxide film 106a, a photolithography process and an etching process are performed on the conductive film to form the source electrode or drain electrodes 108a and 108b.

[0128] Next, an insulating film 118 is formed on the metal oxide film 106a, the source electrode or drain electrodes 108a and 108b. The insulating film 118 is the same as the material and film formation method of the insulating film 112. After that, a second heat treatment may be performed.

[0129] Thus, the transistor 210 can be manufactured.

[0130] When manufacturing the transistor 220 shown in FIG. 2(B), it may be manufactured as follows.

[0131] After forming the gate electrode 102 on the substrate 100, the gate insulating film 120 is formed.

[0132] Next, after forming a metal oxide film on the gate insulating film 120, a photolithography process and an etching process are performed on the metal oxide film to form the metal oxide film 106a. After that, a first heat treatment is performed. As a result, the oxygen desorbed from the insulating film 126 is supplied to the metal oxide film 124, and the oxygen desorbed from the insulating film 122 is supplied to the metal oxide films 124 and 106a. Also, hydrogen, water, etc. contained in the metal oxide film 106a can be reduced.

[0133] Next, on the metal oxide film 106a, the source electrode or drain electrodes 108a and 108b, and the passivation film 110 are formed. After that, a second heat treatment is performed.

[0134] Thus, the transistor 220 can be manufactured.

[0135] This embodiment can be implemented in appropriate combination with the configurations described in other embodiments. That is.

[0136] (Embodiment 2) In this embodiment, a transistor having a structure different from that of the transistor shown in the previous embodiment will be described. will be described.

[0137] FIG. 4 shows a plan view and a cross-sectional view of a transistor 400 as an example of a semiconductor device according to an aspect of the present invention. Here, FIG. 4(A) is a plan view, and FIGS. 4(B) and 4(C) are cross-sectional views taken along the A1-A2 cross-section and the B1-B2 cross-section in FIG. 4(A), respectively. In FIG. 4(A), in order to avoid complication, some of the components of the transistor 400 (for example, the gate insulating film 304, etc.) are omitted. and FIG. 4(C) are cross-sectional views related to the B1-B2 cross-section in FIG. 4(A), respectively. In FIG. 4(A), in order to avoid complication, some of the components of the transistor 400 (for example, the gate insulating film 304, etc.) are omitted. and FIG. 4(C) are cross-sectional views related to the B1-B2 cross-section in FIG. 4(A), respectively. In FIG. 4(A), in order to avoid complication, some of the components of the transistor 400 (for example, the gate insulating film 304, etc.) are omitted. In FIG. 4(A), in order to avoid complication, some of the components of the transistor 400 (for example, the gate insulating film 304, etc.) are omitted. For example, the gate insulating film 304, etc.) are omitted.

[0138] The transistor 400 shown in FIG. 4(A) includes a metal oxide film 306a on a substrate 300 via an underlying insulating film 310, source electrodes or drain electrodes 308a and 308b provided in contact with the metal oxide film 306a, a gate insulating film 304 provided on the metal oxide film 306a and the source electrodes or drain electrodes 308a and 308b, and a gate electrode 302 provided so as to overlap the metal oxide film 306a on the gate insulating film 304. source electrodes or drain electrodes 308a and 308b provided in contact with the metal oxide film 306a, a gate insulating film 304 provided on the metal oxide film 306a and the source electrodes or drain electrodes 308a and 308b, and a gate electrode 302 provided so as to overlap the metal oxide film 306a on the gate insulating film 304. source electrodes or drain electrodes 308a and 308b, and a gate electrode 302 provided so as to overlap the metal oxide film 306a on the gate insulating film 304. source electrodes or drain electrodes 308a and 308b, and a gate electrode 302 provided so as to overlap the metal oxide film 306a on the gate insulating film 304. gate insulating film 304, and a gate electrode 302 provided so as to overlap the metal oxide film 306a on the gate insulating film 304.

[0139] Note that the substrate 300 may be the same as the substrate 100. Also, the metal oxide film 306a may be formed of the same material and in the same manner as the metal oxide film 106a. Further, the source electrodes or drain electrodes 308a and 308b may be the same as the source electrodes or drain electrodes. source electrodes or drain electrodes 308a and 308b may be the same as the source electrodes or drain electrodes. source electrodes or drain electrodes 308a and 308b may be the same as the source electrodes or drain electrodes. What is formed by the same material and the same method as the rain electrodes 108a and 108b may be used. Also, for the gate insulating film 304, what is formed by the same material and the same method as the gate insulating film 104 may be used. Also, for the gate electrode 302, what is formed by the same material and the same method as the gate electrode 102 may be used.

[0140] Also, the transistor 400 shown in FIG. 4 is a top-gate structure transistor, and the source electrode or drain electrodes 308a and 308b are top contact structures in contact with the upper surface of the metal oxide film 306a. Note that the source electrode or drain electrodes 308a and 308b may be bottom contact structures in contact with the lower surface of the metal oxide film 306a.

[0141] The region where the metal oxide film 306a and the gate electrode 302 overlap functions as a channel formation region.

[0142] Also, a base insulating film 310 is provided on the substrate 300. The base insulating film 310 is provided so as to be in contact with the metal oxide film 306a. In the transistor 400 shown in FIG. 4, the base insulating film 310 includes an insulating film 312, a metal oxide film 314, and an insulating film 316. Here, the insulating film 312 and the insulating film 316 are insulating films from which oxygen desorbs by heat treatment. Note that for the gate insulating film 304, an insulating film from which oxygen does not desorb by heat treatment is used.

[0143] The metal oxide film 306a is provided between the gate insulating film 304 and the insulating film 312. The insulating film 312 is an insulating film from which oxygen desorbs by heat treatment. Heat treatment is performed. As a result, oxygen is desorbed from the insulating film 312 and supplied to the metal oxide film 306a.

[0144] In addition, in one aspect of the present invention, a metal oxide film 314 for preventing outward diffusion of oxygen is provided in contact with the insulating film 312 from which oxygen is desorbed by heat treatment. Thereby, it is possible to prevent oxygen contained in the insulating film 312 from desorbing and diffusing outward during heat treatment.

[0145] Furthermore, in one aspect of the present invention, the metal oxide film 314 provided to prevent outward diffusion of oxygen is sandwiched between the insulating film 312 and the insulating film 316 from which oxygen is desorbed by heat treatment. As a result, during heat treatment, oxygen is also desorbed from the insulating film 316 and supplied to the metal oxide film 314. Since the metal oxide film 314 is supplied with oxygen from the insulating film 312 and the insulating film 316, oxygen deficiency is compensated and it becomes an insulator (shows insulating properties).

[0146] Thus, even when the metal oxide film 314 is used as a part of the underlying insulating film 310, it is not necessary to affect the electrical characteristics of the transistor 400.

[0146] In addition, in order to efficiently supply oxygen to the metal oxide film 306a, the insulating film 312 in contact with the metal oxide film 306a is preferably thicker than the insulating film 316 in contact with the metal oxide film 314.

[0147] The film thicknesses of the insulating film 312 and the insulating film 316 may be appropriately set according to the film thickness of the underlying insulating film 310.

[0147] The insulating film 312 may be formed of the same material and in the same manner as the insulating film 112. In addition, the metal oxide film 314 may be formed of the same material and in the same manner as the metal oxide film 114. In addition, the insulating film 316 may be the same as the insulating film 116.The same materials formed by the same method may be used.

[0148] By using a film from which oxygen desorbs by heat treatment as the insulating film 312, oxygen is supplied from the insulating film 312 to the metal oxide film 306a, and the interface level between the insulating film 312 and the metal oxide film 306a can be reduced. Therefore, it is possible to suppress charges and the like that may be generated due to the operation of the transistor 400 from being trapped at the interface between the insulating film 312 and the metal oxide film 306a, and the transistor 400 can be made into a transistor with less deterioration in electrical characteristics.

[0149] The metal oxide film 314 is, like the metal oxide film 306a, a metal oxide containing two or more elements selected from In, Ga, Sn, and Zn. Here, the elements contained in the metal oxide film 314 and the elements contained in the metal oxide film 306a may be the same or different. For example, as the metal oxide film 306a and the metal oxide film 314, an In—Ga—Zn—O-based material may be used, or as the metal oxide film 306a, an In—Ga—Zn—O-based material may be used, and as the metal oxide film 314, an In—Ga—Zn—O—N-based material may be used.

[0150] <Examples of Application of Semiconductor Device> FIGS. 5(A) to 5(C) show the cross-sectional structures of transistors having configurations different from that of the transistor 400.

[0151] The transistor 410 shown in FIG. 5(A) has, on the substrate 300, an insulating film 318 provided as an underlying insulating film, a metal oxide film 306a on the insulating film 318, source electrodes or drain electrodes 308a and 308b provided in contact with the metal oxide film 306a, and the metal oxide film 306a, A gate insulating film 320 provided on the source or drain electrodes 308a and 308b; A metal oxide film 306a is provided on the gate insulating film 320 so as to overlap with the channel forming region of the metal oxide film 306a. and a gate electrode 302 .

[0152] The difference between the transistor 400 and the transistor 410 is that the gate insulating film 320 has a The metal oxide film is provided to prevent the outward diffusion of oxygen. The insulating film 320 has a three-layer structure consisting of an insulating film 322, a metal oxide film 324, and an insulating film 326. In addition, an insulating film 318 is provided as a base insulating film. , 322 and the insulating film 318 are made of an insulating film from which oxygen is released by heat treatment.

[0153] In order to efficiently supply oxygen to the metal oxide film 306a, The insulating film 322 in contact with the metal oxide film 324 is preferably thicker than the insulating film 326 in contact with the metal oxide film 324. The thicknesses of the insulating films 322 and 326 are appropriately set depending on the thickness of the gate insulating film 320. In addition, if the metal oxide film 324 is at least 5 nm thick, oxygen can pass through it. This can be prevented by setting the thickness appropriately according to the thickness of the gate insulating film 320.

[0154] The transistor 420 shown in FIG. 5B is a transistor including a gold layer and a base insulating film 310 disposed on the substrate 300. A metal oxide film 306a and a source electrode or a drain electrode provided in contact with the metal oxide film 306a. The source and drain electrodes 308a and 308b, the metal oxide film 306a, and the source and drain electrodes 30 A gate insulating film 320 is provided on the gate electrodes 8a and 308b. A metal oxide film is provided on the gate insulating film 320. A gate electrode 302 is provided so as to overlap a channel forming region of the semiconductor film 306a. Do it.

[0155] In the transistor 420, for the base insulating film 310 and the gate insulating film 320, reference can be made to the descriptions of the transistor 400 and the transistor 410, and thus detailed description is omitted. Also, in the transistors 400, 410, and 420, the source electrode or drain electrodes 308a, 308b are in contact with the upper surface of the metal oxide film 306a, and the top contact structure has been described. In the transistor according to one aspect of the present invention, the source electrode or drain electrodes 308a, 308b can also adopt a bottom contact structure in contact with the lower surface of the metal oxide film 306a. An example of the bottom contact structure is shown in FIG. 5(C). Omit the detailed description.

[0156] In addition, in the transistors 400, 410, and 420, the source electrode or drain electrodes 308a, 308b are in contact with the upper surface of the metal oxide film 306a, and the top contact structure has been described. In the transistor according to one aspect of the present invention, the source electrode or drain electrodes 308a, 308b can also adopt a bottom contact structure in contact with the lower surface of the metal oxide film 306a. An example of the bottom contact structure is shown in FIG. 5(C). The source electrode or drain electrodes 308a, 308b are in contact with the upper surface of the metal oxide film 306a, and the top contact structure has been described. In the transistor according to one aspect of the present invention, the source electrode or drain electrodes 308a, 308b can also adopt a bottom contact structure in contact with the lower surface of the metal oxide film 306a. An example of the bottom contact structure is shown in FIG. 5(C). The source electrode or drain electrodes 308a, 308b are in contact with the upper surface of the metal oxide film 306a, and the top contact structure has been described. In the transistor according to one aspect of the present invention, the source electrode or drain electrodes 308a, 308b can also adopt a bottom contact structure in contact with the lower surface of the metal oxide film 306a. An example of the bottom contact structure is shown in FIG. 5(C). The source electrode or drain electrodes 308a, 308b are in contact with the upper surface of the metal oxide film 306a, and the top contact structure has been described. In the transistor according to one aspect of the present invention, the source electrode or drain electrodes 308a, 308b can also adopt a bottom contact structure in contact with the lower surface of the metal oxide film 306a. An example of the bottom contact structure is shown in FIG. 5(C). The source electrode or drain electrodes 308a, 308b are in contact with the upper surface of the metal oxide film 306a, and the top contact structure has been described. In the transistor according to one aspect of the present invention, the source electrode or drain electrodes 308a, 308b can also adopt a bottom contact structure in contact with the lower surface of the metal oxide film 306a. An example of the bottom contact structure is shown in FIG. 5(C). Shown in FIG. 5(C).

[0157] The transistor 430 shown in FIG. 5(C) has a base insulating film 310 provided on the substrate 300, source electrodes or drain electrodes 308a, 308b provided on the base insulating film 310, a metal oxide film 306a provided in contact with the source electrodes or drain electrodes 308a, 308b, a gate insulating film 304 provided on the source electrodes or drain electrodes 308a, 308b and the metal oxide film 306a, and a gate electrode 302 provided so as to overlap the channel formation region of the metal oxide film 306a. The transistor 430 shown in FIG. 5(C) has a base insulating film 310 provided on the substrate 300, source electrodes or drain electrodes 308a, 308b provided on the base insulating film 310, a metal oxide film 306a provided in contact with the source electrodes or drain electrodes 308a, 308b, a gate insulating film 304 provided on the source electrodes or drain electrodes 308a, 308b and the metal oxide film 306a, and a gate electrode 302 provided so as to overlap the channel formation region of the metal oxide film 306a. The transistor 430 shown in FIG. 5(C) has a base insulating film 310 provided on the substrate 300, source electrodes or drain electrodes 308a, 308b provided on the base insulating film 310, a metal oxide film 306a provided in contact with the source electrodes or drain electrodes 308a, 308b, a gate insulating film 304 provided on the source electrodes or drain electrodes 308a, 308b and the metal oxide film 306a, and a gate electrode 302 provided so as to overlap the channel formation region of the metal oxide film 306a. The transistor 430 shown in FIG. 5(C) has a base insulating film 310 provided on the substrate 300, source electrodes or drain electrodes 308a, 308b provided on the base insulating film 310, a metal oxide film 306a provided in contact with the source electrodes or drain electrodes 308a, 308b, a gate insulating film 304 provided on the source electrodes or drain electrodes 308a, 308b and the metal oxide film 306a, and a gate electrode 302 provided so as to overlap the channel formation region of the metal oxide film 306a. The transistor 430 shown in FIG. 5(C) has a base insulating film 310 provided on the substrate 300, source electrodes or drain electrodes 308a, 308b provided on the base insulating film 310, a metal oxide film 306a provided in contact with the source electrodes or drain electrodes 308a, 308b, a gate insulating film 304 provided on the source electrodes or drain electrodes 308a, 308b and the metal oxide film 306a, and a gate electrode 302 provided so as to overlap the channel formation region of the metal oxide film 306a. The transistor 430 shown in FIG. 5(C) has a base insulating film 310 provided on the substrate 300, source electrodes or drain electrodes 308a, 308b provided on the base insulating film 310, a metal oxide film 306a provided in contact with the source electrodes or drain electrodes 308a, 308b, a gate insulating film 304 provided on the source electrodes or drain electrodes 308a, 308b and the metal oxide film 306a, and a gate electrode 302 provided so as to overlap the channel formation region of the metal oxide film 306a.

[0158] As described above, the transistor according to one aspect of the present invention can take various forms. Can take.

[0159] Also, the configurations, methods, etc. shown in this embodiment are suitable for the configurations, methods, etc. shown in other embodiments. They can be used in combination as appropriate.

[0160] (Embodiment 3) In this embodiment, a semiconductor device using the transistor shown in the previous embodiment, its manufacturing method, and examples of circuit configurations and operations will be described with reference to FIGS. 6 to 8. Also , in this embodiment, an example of a semiconductor device having a configuration corresponding to a so-called DRAM (Dynamic Random Access Memory) will be described. In the circuit diagram , in order to indicate that it is a transistor using an oxide semiconductor, the symbol of OS may be attached together.

[0161] <Cross-sectional structure of the semiconductor device> First, an example of the cross-sectional structure of the semiconductor device will be described with reference to FIG. 6(A). FIG. 6 (A) shows a semiconductor device having a transistor 400 and a capacitor element 402.

[0162] The transistor 400 in FIG. 6(A) is applied with the transistor which is one aspect of the present invention . The transistor 400 has a metal oxide film 306a, source electrodes or drain electrodes 308a and 308b, a gate insulating film 304 , and a gate electrode 302a on a substrate 300 via an underlying insulating film 310. The underlying insulating film 310 has an insulating film 312, a metal oxide film 314, and an insulating film 316.

[0163] The capacitor element 402 in FIG. 6(A) has a gate insulating film 304, a source electrode or drain electrode 308a, and an electrode 302b. The source electrode or drain electrode 308a functions as one electrode of the capacitor element 402, and the electrode 302b functions as the other electrode of the capacitor element 402. ​​​​

[0164] An insulating film 330 is provided so as to cover the transistor 400 and the capacitive element 402. A source electrode or a drain electrode 308b and a wiring 332 are connected through an opening provided in the insulating film 330.

[0165] <Basic Circuit> Next, the basic circuit configuration and operation of the semiconductor device shown in Fig. 6(A) will be described with reference to Fig. 6(B). In the semiconductor device shown in Fig. 6(B), a first wiring (1st Line) is electrically connected to a source electrode or a drain electrode of the transistor 400, a second wiring (2nd Line) is electrically connected to a gate electrode of the transistor 400, one electrode of the capacitive element 402 is electrically connected to a drain electrode or a source electrode of the transistor 400, and a third wiring (3rd Line) is electrically connected to the other electrode of the capacitive element 402. (B).

[0166] Here, for example, a transistor using an oxide semiconductor is applied to the transistor 400. A transistor using an oxide semiconductor has a feature that its off-current is extremely small. Therefore, by turning off the transistor 400, the potential applied to the capacitive element 402 can be held for an extremely long time.

[0167] In the semiconductor device shown in Fig. 6(B), by taking advantage of the feature that the potential applied to the capacitive element 402 can be held, information can be written, held, and read as follows.

[0168] Next, writing and holding of information will be described. For simplicity here, the Assume that the potential is fixed. First, set the potential of the second wiring to the potential at which the transistor 400 becomes on, and turn on the transistor 400. As a result, the potential of the first wiring is applied to one of the electrodes of the capacitor element 402. That is, a predetermined charge is applied to the capacitor element 402 (writing). Then, by setting the potential of the second wiring to the potential at which the transistor 400 becomes off and turning off the transistor 400, the charge applied to the capacitor element 402 is retained (holding). Since the transistor 400 has an extremely small off-current as described above, it can retain the charge for a long time. Next, the reading of information will be described. In a state where a predetermined potential (constant potential) is applied to the first wiring, when the potential of the second wiring is set to the potential at which the transistor 400 becomes on, the first wiring takes a different potential according to the amount of charge held in the capacitor element 402. Therefore, the information held can be read by detecting the potential of the first wiring. Next, the rewriting of information will be described. The rewriting of information is performed in the same manner as the above-described writing and holding of information. That is, the potential of the second wiring is set to the potential at which the transistor 400 becomes on, and the transistor 400 is turned on. As a result, the potential of the first wiring (the potential related to the new information) is applied to one of the electrodes of the capacitor element 402. Then, by setting the potential of the second wiring to the potential at which the transistor 400 becomes off and turning off the transistor 400, the capacitor element 402 is brought into a state where a charge related to the new information is applied.

[0169]

[0170]

[0171] ​​​​​​​​​​​​​​​Thus, the semiconductor device according to one aspect of the present invention can directly rewrite information by writing information again. Therefore, high-speed operation of the semiconductor device is realized.

[0172] Note that the above description is for the case of using an n-type transistor (n-channel transistor) having electrons as carriers. Needless to say, a p-type transistor having holes as majority carriers can be used instead of the n-type transistor.

[0173] FIG. 7 shows an example of a circuit diagram of a semiconductor device having (m×n) memory cells 450. The configuration of the memory cell 450 in FIG. 7 is the same as that in FIG. 6. That is, the first wiring in FIG. 6 corresponds to the bit line BL in FIG. 7, the second wiring in FIG. 6 corresponds to the word line WL in FIG. 7, and the third wiring in FIG. 6 corresponds to the source line SL in FIG. 7 (see FIG. 7).

[0174] The semiconductor device shown in FIG. 7 includes n bit lines BL, m word lines WL, a memory cell array in which memory cells 450 are arranged in a matrix of m (rows) × n (columns), a first drive circuit 461 connected to the n bit lines BL, and a second drive circuit 462 connected to the m word lines WL.

[0175] The memory cell 450 is composed of a transistor 400 and a capacitor element 402. The gate electrode of the transistor 400 is connected to the word line WL. One of the source electrode or the drain electrode of the transistor 400 is connected to the bit line BL, and the other of the source electrode or the drain electrode of the transistor 400 is connected to one of the electrodes of the capacitor element 402. It is connected to the square. The other electrode of the capacitive element 402 is connected to the source line SL, and a certain potential is applied. The transistor 400 is applied with the transistor shown in the previous embodiment.

[0176] A semiconductor device according to an aspect of the present invention is a transistor using an oxide semiconductor in a channel formation region. Therefore, it has a feature that the off-current is smaller than that of a transistor using single-crystalline silicon in the channel formation region. For this reason, when the transistor is applied to the semiconductor device shown in FIG. 7 recognized as a so-called DRAM, it is possible to obtain a memory with an extremely long refresh period.

[0177] <Method for manufacturing a semiconductor device> Next, a method for manufacturing the semiconductor device shown in FIG. 6 will be described with reference to FIG.

[0178] First, an insulating film 312, a metal oxide film 3 14, and an insulating film 316 are sequentially formed on the substrate 300 as a base insulating film 310 (see FIG. 8(A)). Note that since the substrate 300 can be made of the same material as the substrate 10 0, a detailed description thereof is omitted. Also, the insulating film 312 and the insulating film 316 can refer to the descriptions of the insulating film 112 and the insulating film 116, respectively.

[0179] Next, a metal oxide film 306a is formed on the base insulating film 310 (see FIG. 8(B)). The metal oxide film 306a can refer to the description of the metal oxide film 106a.

[0180] Next, after forming source electrodes or drain electrodes 308a and 308b in contact with the metal oxide film 306a, on the metal oxide film 306a, the source electrodes or drain electrodes 308a and 308b ​​​​​​ A gate insulating film 304 is formed. Then, on the gate insulating film 304, a gate electrode 302a is formed in a region overlapping with the channel formation region of the metal oxide film 306a, and an electrode 302b is formed in a region overlapping with the source electrode or drain electrode 308a (see Fig. 8(C)). The source electrode or drain electrodes 308a and 308b can refer to the description of the source electrode or drain electrodes 108a and 108b.

[0181] Next, an insulating film 330 that functions as an interlayer insulating film is formed so as to cover the gate insulating film 304, the gate electrode 302a, and the electrode 302b. Then, an opening is formed in the insulating film 330 and the gate insulating film 304, and a wiring 332 is formed on the insulating film 330 to electrically connect the source electrode or drain electrode 308b and the wiring 332.

[0182] As the insulating film 330 that functions as an interlayer insulating film, an inorganic material (such as silicon oxide, silicon nitride, silicon oxynitride, etc.), a photosensitive or non-photosensitive organic material (such as polyimide, acrylic, polyamide, polyimide amide, resist, or benzocyclobutene), a material in which a skeletal structure is formed by the bond between silicon (Si) and oxygen (O) and the substituent contains at least hydrogen, or a material having at least one of fluorine, an alkyl group, or an aromatic hydrocarbon in the substituent, so-called siloxane, and their laminated structures can be used.

[0183] Also, the wiring 332 is formed by forming a conductive film using a sputtering method, a plasma CVD method, etc., and then performing a photolithography process and an etching process on the conductive film. As the material of the conductive film, aluminum, chromium, copper, tantalum, titanium, molybdenum, etc. It is possible to use an element selected from tungsten, an alloy containing the above-described element as a component, or the like. Any one of manganese, magnesium, zirconium, beryllium, neodymium, scandium, or a material obtained by combining a plurality of these may be used. Details are the same as those of the gate electrode 102 and the like.

[0184] Through the above steps, a semiconductor device having the transistor 400 and the capacitive element 402 can be fabricated (see Fig. 8(D)).

[0185] As described above, the configurations, methods, etc. shown in the present embodiment can be used in appropriate combination with the configurations, methods, etc. shown in other embodiments.

[0186] (Embodiment 4) The semiconductor device according to an aspect of the present invention can be applied to various electronic devices (including gaming machines). Examples of the electronic device include, for example, a television device (also referred to as a TV or a television receiver), a monitor for a computer, a camera such as a digital camera and a digital video camera, a digital photo frame, a mobile phone (also referred to as a mobile phone or a mobile phone device), a portable game machine, a portable information terminal, an audio playback device, and a large game machine such as a pachinko machine. Examples of the electronic device equipped with the semiconductor device described in the above embodiment will be described. Fig. 9(A) shows a notebook personal computer, which is composed of a main body 3001, a housing 3002, a display unit 3003, a keyboard 3004, and the like. The semiconductor devices shown in Embodiments 1 and 2 can be applied to the display unit 3003. Also, as shown in Embodiment 3,

[0187] 2, the semiconductor device can be applied to the display unit 3003. The semiconductor device can be applied to the memory circuit included inside the housing 3002. In practice Since the semiconductor devices according to Embodiments 1 to 3 have fluctuations in electrical characteristics suppressed, they can be made into a highly reliable notebook personal computer.

[0188] FIG. 9(B) shows a personal digital assistant (PDA). The main body 3021 is provided with a display unit 3023, an external interface 3025, operation buttons 3024, etc. Also, there is a stylus 3022 as an accessory for operation. The semiconductor devices shown in Embodiments 1 and 2 can be applied to the display unit 3023. Further, the semiconductor device shown in Embodiment 3 can be applied to the memory circuit included inside the main body 3021. Since the semiconductor devices according to Embodiments 1 to 3 have fluctuations in electrical characteristics suppressed, they can be made into a highly reliable personal digital assistant (PDA). )

[0189] FIG. 9(C) shows an example of an electronic book. For example, the electronic book is composed of two housings, a housing 2701 and a housing 2703. The housing 2701 and the housing 2703 are integrated by a shaft portion 2711, and can perform an opening and closing operation with the shaft portion 2711 as an axis. With such a configuration, it becomes possible to perform an operation like a paper book.

[0190] A display unit 2705 is incorporated in the housing 2701, and a display unit 2707 is incorporated in the housing 2703. The display unit 2705 and the display unit 2707 may be configured to display a continuous screen, or may be configured to display different screens. With a configuration of displaying different screens, for example, a text is displayed on the right display unit (display unit 2705 in FIG. 9(C)), and the left display ​​​​​​​​​​​​An image can be displayed on a display unit (display unit 2707 in FIG. 9(C)). The semiconductor devices shown in Embodiments 1 and 2 can be applied to display unit 2705 and display unit 2707. Also, the semiconductor device shown in Embodiment 3 can be applied to the memory circuit contained inside housings 2701 and 2703. Since the semiconductor devices according to Embodiments 1 to 3 have fluctuations in electrical characteristics suppressed, they can be made into highly reliable electronic books.

[0191] Also, FIG. 9(C) shows an example in which the housing 2701 is provided with an operation unit and the like. For example, in the housing 2701, a power supply 2721, operation keys 2723, a speaker 2725, etc. are provided. With the operation keys 2723, pages can be turned. Note that a configuration may be adopted in which a keyboard, a pointing device, etc. are provided on the same surface as the display unit of the housing. Also, on the back surface or side surface of the housing, external connection terminals (earphone terminals, USB terminals, etc.), a recording medium insertion part, etc. may be provided. Furthermore, the electronic book may be configured to have a function as an electronic dictionary.

[0192] Also, the electronic book may be configured to be able to wirelessly transmit and receive information. With wireless, it is also possible to configure the electronic book to purchase and download desired book data, etc. from an electronic book server.

[0193] FIG. 9(D) shows a mobile phone, which is composed of two housings, housing 2800 and housing 2801. On housing 2801, there are a display panel 2802, a speaker 2803, a microphone 2804, a pointing device 2806, a camera lens 2807, an external connection terminal 2 808, etc. Also, on housing 2800, there is a solar cell for charging the mobile phone ​ It is provided with a 2810 and an external memory slot 2811. Also, the antenna is built into the housing 280 1. The semiconductor devices shown in Embodiments 1 and 2 can be applied to the display panel 2802 . Also, the semiconductor device shown in Embodiment 3 can be applied to the memory circuit included inside the housings 2800 and 280 1. Since the semiconductor devices according to Embodiments 1 to 3 have fluctuations in electrical characteristics suppressed, a highly reliable mobile phone can be made .

[0194] Also, the display panel 2802 is provided with a touch panel, and a plurality of operation keys 2805 being video-displayed in FIG. 9(D) are indicated by dotted lines . Note that a booster circuit for boosting the voltage output by the solar cell 2810 to the voltage required for each circuit is also mounted .

[0195] The display direction of the display panel 2802 changes appropriately according to the usage form. Also, since a camera lens 2807 is provided on the same surface as the display panel 2802, a video phone is possible . The speaker 2803 and the microphone 2804 are not limited to voice calls, and video phone calls, recording, playback, etc. are possible . Further, the housing 2800 and the housing 2801 can be slid and changed from the unfolded state as shown in FIG. 9(D) to an overlapping state, enabling miniaturization suitable for portability .

[0196] The external connection terminal 2808 can be connected to various cables such as an AC adapter and a USB cable , enabling charging and data communication with a personal computer, etc. Also, by inserting a recording medium into the external memory slot 2811, it is possible to handle larger amounts of data storage and transfer . .

[0197] In addition to the above functions, those equipped with an infrared communication function, a television receiving function, etc. are also acceptable.

[0198] FIG. 9(E) shows a digital video camera, which is composed of a main body 3051, a display unit (A) 3057, an eyepiece part 3053, an operation switch 3054, a display unit (B) 3055, a battery 3056, etc. The semiconductor devices shown in Embodiments 1 and 2 can be applied to the display unit (A) 3057 and the display unit (B) 3055. Also, the semiconductor device shown in Embodiment 3 can be applied to the memory circuit included inside the main body 3051. Since the semiconductor devices according to Embodiments 1 to 3 have fluctuations in electrical characteristics suppressed, they can be made into a highly reliable digital video camera.

[0199] FIG. 9(F) shows an example of a television device. The television device 9600 has a display unit 9603 incorporated in a housing 9601. The display unit 9603 can display images. Also, here, a configuration in which the housing 9601 is supported by a stand 9605 is shown. The semiconductor devices shown in Embodiments 1 and 2 can be applied to the display unit 9603 and the semiconductor device shown in Embodiment 3 can be applied to the memory circuit included inside the housing 9601. Since the semiconductor devices according to Embodiments 1 to 3 have fluctuations in electrical characteristics suppressed, they can be made into a highly reliable television device. The television device 9600 can be operated by an operation switch provided in the housing 9601 or a separate remote

[0200] control unit. Also, the remote control unit can be used to send signals from the remote control unit to the television device 9600. to the television device 9600. It may be configured to include a display unit that displays the information to be output.

[0201] Note that the television device 9600 is configured to include a receiver, a modem, etc. The receiver can receive more general television broadcasts, and can be connected to a communication network via a modem, either wired or wirelessly, so as to perform one-way (from sender to receiver) or two-way (between sender and receiver, or between receivers, etc.) information communication.

[0202] This embodiment can be implemented in appropriate combination with the configurations described in other embodiments. Yes.

Example

[0203] In this example, a MOS (Metal Oxide Semiconductor) substrate was fabricated, and breakdown voltage measurement and C-V (Capacitance-Voltage) measurement were performed. The results will be described with reference to FIGS. 10 to 15.

[0204] First, the method for fabricating the sample used in this example will be described.

[0205] As Sample A, on a silicon substrate, as a first insulating film, a silicon oxide film with a film thickness of 50 nm was formed by sputtering. Next, on the silicon oxide film, as a metal oxide film by sputtering, an In-Ga-Zn-O-N-based metal oxide film with a film thickness of 10 nm was formed. Next, on the In-Ga-Zn-O-N-based metal oxide film, as a second insulating film by sputtering, a silicon oxide film with a film thickness of 50 nm was formed.

[0206] Sample B uses an In-Ga-Zn-O-N-based metal oxide as the metal oxide film in Sample A. Instead of the biofilm, a metal oxide film of In-Ga-Zn-O system with a film thickness of 10 nm was formed by sputtering method. For other configurations and manufacturing methods, they are the same as those of Sample A.

[0207] As Sample C, on a silicon substrate, as the first insulating film, a silicon oxynitride film with a film thickness of 50 nm was formed by plasma CVD method. Next, on the silicon oxynitride film, a metal oxide film of In-Ga-Zn-O system with a film thickness of 10 nm was formed by sputtering ring method. Then, on the metal oxide film of In-Ga-Zn-O system, as the second insulating film, a silicon oxynitride film with a film thickness of 50 nm was formed by plasma C VD method.

[0208] Sample D replaced the silicon oxide film (the first insulating film and the second insulating film) in Sample A with a silicon oxynitride film with a film thickness of 50 nm formed by plasma CVD method. For other configurations and manufacturing methods, they are the same as those of Sample A.

[0209] As Sample E, on a silicon substrate, a silicon oxide film with a film thickness of 100 nm was formed by sputtering method.

[0210] Next, heat treatment was performed on Samples A to E. As the heat treatment conditions, it was carried out at a temperature of 300 °C for 1 hour in a nitrogen atmosphere.

[0211] Next, for each of Samples A to E, on the second insulating film, an electrode (electrode area 0.785 mm 2 ) made of an aluminum-titanium alloy film with a film thickness of 400 nm was formed by sputtering method.

[0212] Finally, Samples A to E were subjected to heat treatment at a temperature of 250 °C for 1 hour in a nitrogen atmosphere. I did.

[0213] The structures of the MOS substrates of samples A to E obtained as described above are shown in Table 1.

[0214] [Table 1]

[0215] Next, the current-voltage (IV) characteristics of samples A to E were measured. Measurements were taken at 13 points each.

[0216] The results of the withstand voltage measurement are shown in Figs. 10 to 12. Fig. 10(A) shows the results for sample A, and Fig. 1 11(B) shows the results for sample B, FIG. 11(A) shows the results for sample C, and FIG. 11(B) shows the results for sample B. 10 to 12, the horizontal axis indicates the voltage Vcc of sample D, and FIG. 12 indicates the voltage Vcc of sample E. The vertical axis indicates voltage, and the vertical axis indicates current.

[0217] In the sample C shown in FIG. 11(A) and the sample D shown in FIG. 11(B), the current rise In contrast, sample A shown in FIG. 10(A) and sample B shown in FIG. In sample B shown in (B), the current rise is slower than in samples C and D. In addition, sample E shown in FIG. 12 has the same breakdown voltage as samples A and B. It was found that it had pressure resistance.

[0218] Next, CV measurements were performed on samples A to E. Four measurements were performed on each sample. went.

[0219] The results of the CV measurements are shown in Figs. 13 to 15. Fig. 13(A) shows the results for sample A. FIG. 13(B) shows the results for sample B, FIG. 14(A) shows the results for sample C, and FIG. FIG. 13 shows the results for sample D, and FIG. 15 shows the results for sample E. In FIGS. indicates voltage, and the vertical axis indicates capacitance value.

[0220] For sample C shown in Fig. 14(A) and sample D shown in Fig. 14(B), CV curves were obtained. As can be seen from the results in Figure 11, the results were not satisfactory for samples C and D. This is thought to be because the insulation film in the In contrast, sample A shown in FIG. 13(A), sample B shown in FIG. 13(B), and sample C shown in FIG. In the case of sample E, a good CV curve was obtained.

[0221] Furthermore, the CV curves of samples A and B are positively polarized compared to the CV curve of sample E. This is because the negative shift in the α-H bands in samples A and B is greater than that in sample E. This is because there is a large amount of fixed charge, and such an insulating film is called a transistor channel type. By forming the metal oxide film including the metal oxide film having the insulating layer, the threshold voltage of the transistor can be reduced. It was suggested that it is possible to shift the

[0222] Samples C and D are made of an insulating film sandwiching a metal oxide film, and a nitriding agent formed by plasma CVD. Silicon oxide nitride film is used. In the case of the metal oxide film, oxygen is not released by the heat treatment. Therefore, oxygen is supplied from the insulating film to the metal oxide film. It is considered that the metal oxide film could not be insulated. In the conventional semiconductor device, silicon oxide films are used as insulating films sandwiching metal oxide films. The silicon oxide film formed by the sputtering method loses oxygen when heat treated, It is considered that oxygen was sufficiently supplied to the metal oxide film and the metal oxide film could be insulated. This is considered to have improved the breakdown voltages of Sample A and Sample B.

[0223] From the above results, when a metal oxide film is provided between insulating films from which oxygen desorbs by heat treatment, it was shown that the metal oxide film functions as an insulating film.

Example

[0224] In this example, in a structure in which a metal oxide film is formed on an insulating film that releases oxygen by heat treatment by TDS analysis, the amount of oxygen that permeates through the metal oxide film from the insulating film and diffuses outward will be described for the results of the investigation. will be described for the results of the investigation.

[0225] First, Samples F to I used in this example will be described.

[0226] As Sample F, a silicon oxide film with a thickness of 100 nm was formed on a glass substrate by sputtering. Next, an In-Ga-Zn-O-based metal oxide film with a thickness of 5 nm was formed on the silicon oxide film by sputtering. Next, an In-Ga-Zn-O-based metal oxide film with a thickness of 5 nm was formed on the silicon oxide film by sputtering.

[0227] As Sample G, a silicon oxide film with a thickness of 100 nm was formed on a glass substrate by sputtering. Next, an In-Ga-Zn-O-based metal oxide film with a thickness of 10 nm was formed on the silicon oxide film by sputtering. Next, an In-Ga-Zn-O-based metal oxide film with a thickness of 10 nm was formed on the silicon oxide film by sputtering.

[0228] As Sample H, a silicon oxide film with a thickness of 100 nm was formed on a glass substrate by sputtering. Next, an In-Ga-Zn-O-based metal oxide film with a thickness of 15 nm was formed on the silicon oxide film by sputtering. Next, an In-Ga-Zn-O-based metal oxide film with a thickness of 15 nm was formed on the silicon oxide film by sputtering.

[0229] As Sample I, a silicon oxide film with a film thickness of 100 nm was formed on a glass substrate by sputtering. film was formed.

[0230] Next, TDS analysis was performed on Samples F to I. In this example, the numerical value of the amount of oxygen desorbed was measured using a temperature-programmed desorption analyzer EMD-WA1000S / W manufactured by Denshi Kagaku Co., Ltd. was used.

[0231] Fig. 16 shows the TDS analysis results of Samples F to I.

[0232] As shown in Fig. 16, for Sample I on which only the silicon oxide film was formed, the peak became high around 200 °C. On the other hand, for Samples F to H on which the metal oxide film was formed on the silicon oxide film, almost no peak was detected. For Samples F to H on which the metal oxide film was formed on the silicon oxide film, almost no peak was detected. For Samples F to H on which the metal oxide film was formed on the silicon oxide film, almost no peak was detected.

[0233] From the results of Fig. 16, it was found that the oxygen contained in the silicon oxide film was not released to the outside due to the formation of the metal oxide film on the silicon oxide film. Also, it was shown that if the metal oxide film was formed to a thickness of at least 5 nm, the oxygen contained in the silicon oxide film was not released to the outside. From the above results, it was proved that the metal oxide film can prevent oxygen permeation. From the results of Fig. 16, it was found that the oxygen contained in the silicon oxide film was not released to the outside due to the formation of the metal oxide film on the silicon oxide film. Also, it was shown that if the metal oxide film was formed to a thickness of at least 5 nm, the oxygen contained in the silicon oxide film was not released to the outside. From the above results, it was proved that the metal oxide film can prevent oxygen permeation. From the results of Fig. 16, it was found that the oxygen contained in the silicon oxide film was not released to the outside due to the formation of the metal oxide film on the silicon oxide film. Also, it was shown that if the metal oxide film was formed to a thickness of at least 5 nm, the oxygen contained in the silicon oxide film was not released to the outside. From the above results, it was proved that the metal oxide film can prevent oxygen permeation. From the above results, it was proved that the metal oxide film can prevent oxygen permeation. From the above results, it was proved that the metal oxide film can prevent oxygen permeation.

Example

[0234] In this example, the results of the investigation of the resistivity of the metal oxide film will be described with reference to Fig. 17. will be described.

[0235] First, the samples used in this example will be described with reference to Fig. 17.

[0236] (Condition 1) On both sides of the insulating film sandwiching the metal oxide film 506, an insulating film that does not desorb oxygen by heat treatment was used. The case where this is done is designated as Condition 1.

[0237] First, on a glass substrate 500, as an insulating film 502, a silicon oxynitride film with a film thickness of 10 0 nm was formed by plasma CVD method.

[0238] Next, a tungsten film with a film thickness of 100 nm was formed by sputtering method. After that, photolithography process and etching process were performed on the tungsten film to form electrodes 504a, 5 04b.

[0239] Next, as a metal oxide film 506, an In-Ga-Zn-O-based metal oxide film was formed by sputtering method. The film formation conditions of the metal oxide film were as follows: using a target with a composition ratio of In:Ga:Zn = 1:1 :1, Ar / O2 = 30 / 15 sccm, pressure 0.4 Pa, power supply 0. 5 kW, substrate temperature 200 °C, and film thickness 30 nm. After that, the metal oxide film 506 was heat-treated in a nitrogen atmosphere at 450 °C for 1 hour.

[0240] Next, as an insulating film 508, a silicon oxynitride film with a film thickness of 100 nm was formed by plasma CVD method.

[0241] Next, openings were formed so that electrodes 504a and electrode 504b were exposed by performing photolithography process and etching process on the insulating film 508 and the metal oxide film 506.

[0242] Finally, the sample was heat-treated in a nitrogen atmosphere at 350 °C for 1 hour.

[0243] (Condition 2) The case where insulating films from which oxygen desorbs by heat treatment are used for both of the insulating films sandwiching the metal oxide film 506 is designated as Condition 2. ​

[0244] First, on the glass substrate 500, as the insulating film 502, a silicon oxide film with a film thickness of 10 0 nm was formed by sputtering.

[0245] Next, a tungsten film with a film thickness of 100 nm was formed by sputtering. After that, a photolithography process and an etching process were performed on the tungsten film to form electrodes 504a and 5 04b.

[0246] Next, as the metal oxide film 506, an In-Ga-Zn-O-based metal oxide film was formed by sputtering. The film formation conditions of the metal oxide film were as follows: using a target with a composition ratio of In:Ga:Zn = 1:1 :1, Ar / O2 = 30 / 15 sccm, pressure 0.4 Pa, power supply 0. 5 kW, substrate temperature 200 °C, and film thickness 30 nm. After that, the metal oxide film 506 was heat-treated in a nitrogen atmosphere at 450 °C for 1 hour.

[0247] Next, as the insulating film 508, a silicon oxide film with a film thickness of 100 nm was formed by sputtering .

[0248] Next, an opening was formed by performing a photolithography process and an etching process on the insulating film 508 and the metal oxide film 506 so that the electrodes 504a and the electrode 504b were exposed.

[0249] Finally, the sample was heat-treated in a nitrogen atmosphere at 350 °C for 1 hour.

[0250] (Condition 3) When an insulating film from which oxygen desorbs by heat treatment is used for the insulating film 502 and an insulating film from which oxygen does not desorb by heat treatment is used for the insulating film 508, this is defined as Condition 3.

[0251] First, on a glass substrate 500, as an insulating film 502, a silicon oxide film with a film thickness of 10 0 nm was formed by sputtering.

[0252] Next, a tungsten film with a film thickness of 100 nm was formed by sputtering. After that, a photolithography process and an etching process were performed on the tungsten film to form electrodes 504a and 5 04b.

[0253] Next, as a metal oxide film 506, an In-Ga-Zn-O-based metal oxide film was formed by sputtering. The film formation conditions of the metal oxide film were as follows: using a target with a composition ratio of In:Ga:Zn = 1:1 :1, Ar / O2 = 30 / 15 sccm, pressure 0.4 Pa, power supply 0. 5 kW, substrate temperature 200 °C, and film thickness 30 nm. After that, the metal oxide film 506 was heat-treated in a nitrogen atmosphere at 450 °C for 1 hour.

[0254] Next, as an insulating film 508, a silicon oxynitride film with a film thickness of 100 nm was formed by plasma CVD.

[0255] Next, openings were formed by performing a photolithography process and an etching process on the insulating film 508 and the metal oxide film 506 so that the electrodes 504a and the electrode 504b were exposed.

[0256] Finally, the sample was heat-treated in a nitrogen atmosphere at 350 °C for 1 hour.

[0257] (Condition 4) When an insulating film from which oxygen does not desorb by heat treatment was used for the insulating film 502 and an insulating film from which oxygen desorbs by heat treatment was used for the insulating film 508, this was designated as Condition 4.

[0258] First, on a glass substrate 500, as an insulating film 502, a silicon oxynitride film with a film thickness of 10 0 nm was formed by plasma CVD method.

[0259] Next, a tungsten film with a film thickness of 100 nm was formed by sputtering method. Then, photolithography process and etching process were performed on the tungsten film to form electrodes 504a and 5 04b.

[0260] Next, as a metal oxide film 506, an In-Ga-Zn-O-based metal oxide film was formed by sputtering method. The film formation conditions of the metal oxide film were that a target with a composition ratio of In:Ga:Zn = 1:1 :1 was used, Ar / O2 = 30 / 15 sccm, pressure 0.4 Pa, power supply 0. 5 kW, substrate temperature 200 °C, and film thickness 30 nm. Then, the metal oxide film 506 was heat-treated in a nitrogen atmosphere at 450 °C for 1 hour.

[0261] Next, as an insulating film 508, a silicon oxide film with a film thickness of 100 nm was formed by sputtering method on it.

[0262] Next, by performing photolithography process and etching process on the insulating film 508 and the metal oxide film 506, openings were formed so that the electrodes 504a and the electrode 504b were exposed.

[0263] Finally, the sample was heat-treated in a nitrogen atmosphere at 350 °C for 1 hour.

[0264] Next, for each of the samples described in Conditions 1 to 4, the conductivity σ was measured at four points . Regarding the results of obtaining the resistivity ρ from the measured conductivity σ, the average value of the four points was calculated and is shown in Table 2.

[0265]

Table 2

[0266] As shown in Table 2, the resistivity ρ of the metal oxide film under Condition 1 was found to be 1.4×10 ―2 [Ω· cm]. Also, the resistivity ρ of the metal oxide film under Condition 2 was found to be 7.4 ×10 9 [Ω·cm]. Also, the resistivity ρ of the metal oxide film under Condition 3 was found to be 8.6×10 [Ω·cm]. Also, the resistivity ρ of the metal 3 oxide film under Condition 4 was found to be 8.5×10 [Ω·cm]. 6

[0267] From the results of Condition 1, it was found that the resistance of the metal oxide film 506 decreased by heat treatment after film formation remained unchanged even when heat treatment was performed after the formation of the insulating film 508 and remained low. As a result, it was found that the metal oxide film 506 has the characteristics of a conductor.

[0268] Also, from the results of Condition 2, it was found that the resistance of the metal oxide film 506 decreased by heat treatment after film formation increased by performing heat treatment after the formation of the insulating film 508. This is presumably because the oxygen deficiency generated in the metal oxide film is compensated by the oxygen supply from the insulating film 502 and the insulating film 508. As a result, it was found that the metal oxide film 506 becomes an insulator (shows insulating properties).

[0269] Also, from the results of Condition 3 and Condition 4, the resistance of the metal oxide film 506 becomes higher than that of Condition 1 and lower than that of Condition 2 by heat treatment after the formation of the insulating film 508. As a result, the metal acid ​​​​​​​The oxide film 506 was found to be a semiconductor.

[0270] From the above results, it was shown that the resistance of the metal oxide film can be adjusted by the type of the insulating film in contact with the metal oxide film (or the amount of oxygen desorbed from the insulating film).

Explanation of symbols

[0271] 100 Substrate 102 Gate electrode 104 Gate insulating film 106 Metal oxide film 106a Metal oxide film 108a Source electrode or drain electrode 108b Source electrode or drain electrode 110 Passivation film 112 Insulating film 114 Metal oxide film 116 Insulating film 118 Insulating film 120 Gate insulating film 122 Insulating film 124 Metal oxide film 126 Insulating film 200 Transistor 210 Transistor 220 Transistor 230 Transistor 300 Substrate 302 Gate electrode 304 Gate insulating film 306a Metal oxide film 308a Source electrode or drain electrode 308b Source electrode or drain electrode 310 Underlying insulating film 312 Insulating film 314 Metal oxide film 316 Insulating film 318 Insulating film 320 Gate insulating film 322 Insulating film 324 Metal oxide film 326 Insulating film 330 Insulating film 332 Wiring 400 Transistor 402 Capacitive element 410 Transistor 420 Transistor 430 Transistor 450 Memory cell 461 Drive circuit 462 Drive circuit 500 Glass substrate 502 Insulating film 504a Electrode 504b Electrode 506 Metal oxide film 508 Insulating film 2701 Housing 2703 Housing 2705 Display unit 2707 Display unit 2711 Shaft portion 2721 Power supply 2723 Operation key 2725 Speaker 2800 Housing 2801 Housing 2802 Display panel 2803 Speaker 2804 Microphone 2805 Operation key 2806 Pointing device 2807 Camera lens 2808 External connection terminal 2810 Solar cell 2811 External memory slot 3001 Main body 3002 Housing 3003 Display unit 3004 Keyboard 3021 Main body 3022 Stylus 3023 Display unit 3024 Operation button 3025 External interface 302a Gate electrode 302b electrode 3051 body 3053 eyepiece 3054 operation switch 3055 display unit (B) 3056 battery 3057 display unit (A) 9600 television device 9601 housing 9603 display unit 9605 stand

Claims

1. a first conductive film having a function as a gate electrode of a transistor; a first insulating film having a region disposed above the first conductive film; a first metal oxide film having a region disposed above the first insulating film and having a channel formation region of the transistor; a second conductive film having a region in contact with each of the side surface and the upper surface of the first metal oxide film and having a function as one of a source electrode or a drain electrode of the transistor; a third conductive film having a region in contact with each of the side surface and the upper surface of the first metal oxide film and having a function as the other of the source electrode or the drain electrode of the transistor; a second insulating film having a region disposed above the second conductive film, a region disposed above the third conductive film, a region disposed above the first metal oxide film, and containing silicon oxide; a second metal oxide film having a region disposed above the second insulating film; a third insulating film having a region disposed above the second metal oxide film; and having the second insulating film has a region thicker than the third insulating film; the second insulating film has a region in contact with the first metal oxide film in a region between the second conductive film and the third conductive film; the first metal oxide film has two or more elements selected from indium, gallium, tin, and zinc; the second metal oxide film has two or more elements selected from indium, gallium, tin, and zinc; the second metal oxide film has an overlap with the channel formation region of the first metal oxide film; the second metal oxide film is not in contact with the second conductive film and is not in contact with the third conductive film; a semiconductor device, wherein a periphery of a region of the first metal oxide film that has an overlap with the first conductive film and does not have an overlap with the second conductive film and the third conductive film has an overlap with the second metal oxide film.

2. a first conductive film having a function as a gate electrode of a transistor; a first insulating film having a region disposed above the first conductive film; a first metal oxide film having a region disposed above the first insulating film and having a channel formation region of the transistor; It has a region in contact with each of the side surface and the upper surface of the first metal oxide film, and has a second conductive film that functions as one of the source electrode or the drain electrode of the transistor. It has a region in contact with each of the side surface and the upper surface of the first metal oxide film, and has a third conductive film that functions as the other of the source electrode or the drain electrode of the transistor. It has a region disposed above the second conductive film, a region disposed above the third conductive film, and a region disposed above the first metal oxide film, and has a second insulating film containing silicon oxide. It has a second metal oxide film having a region disposed above the second insulating film. It has a third insulating film having a region disposed above the second metal oxide film. The second insulating film has a region thicker than the third insulating film. The second insulating film has a region in contact with the first metal oxide film in a region between the second conductive film and the third conductive film. The first metal oxide film has two or more elements selected from indium, gallium, tin, and zinc. The second metal oxide film has two or more elements selected from indium, gallium, tin, and zinc. When viewed from a direction perpendicular to the c-axis, the first metal oxide film includes a phase in which metal atoms are arranged in layers or a phase in which metal atoms and oxygen atoms are arranged in layers. The second metal oxide film has an overlap with the channel formation region of the first metal oxide film. The second metal oxide film is not in contact with the second conductive film and is not in contact with the third conductive film. A semiconductor device in which a periphery of a region of the first metal oxide film that has an overlap with the first conductive film and does not have an overlap with the second conductive film and the third conductive film has an overlap with the second metal oxide film.

3. It has a first conductive film that functions as a gate electrode of a transistor. It has a first insulating film having a region disposed above the first conductive film. It has a region disposed above the first insulating film and has a first metal oxide film having a channel formation region of the transistor. It has a region in contact with each of the side surface and the upper surface of the first metal oxide film, and has a second conductive film that functions as one of the source electrode or the drain electrode of the transistor. A third conductive film having regions in contact with the side surface and the upper surface of the first metal oxide film respectively, and having a function as the other of the source electrode or the drain electrode of the transistor; A second insulating film having a region disposed above the second conductive film, having a region disposed above the third conductive film, having a region disposed above the first metal oxide film, and containing silicon oxide; A second metal oxide film having a region disposed above the second insulating film; A third insulating film having a region disposed above the second metal oxide film; The second conductive film and the third conductive film contain metal oxides; The second insulating film has a region thicker than the third insulating film; The second insulating film has a region in contact with the first metal oxide film in a region between the second conductive film and the third conductive film; The first metal oxide film contains two or more elements selected from indium, gallium, tin, and zinc; The second metal oxide film contains two or more elements selected from indium, gallium, tin, and zinc; The second metal oxide film overlaps with a channel formation region of the first metal oxide film; The second metal oxide film does not contact the second conductive film and does not contact the third conductive film; A semiconductor device, wherein a periphery of a region of the first metal oxide film that overlaps with the first conductive film and does not overlap with the second conductive film and the third conductive film overlaps with the second metal oxide film.

4. A first conductive film having a function as a gate electrode of a transistor; A first insulating film having a region disposed above the first conductive film; A first metal oxide film having a region disposed above the first insulating film and having a channel formation region of the transistor; A second conductive film having regions in contact with the side surface and the upper surface of the first metal oxide film respectively, and having a function as one of the source electrode or the drain electrode of the transistor; A third conductive film having regions in contact with the side surface and the upper surface of the first metal oxide film respectively, and having a function as the other of the source electrode or the drain electrode of the transistor; A second insulating film having a region disposed above the second conductive film, having a region disposed above the third conductive film, having a region disposed above the first metal oxide film, and containing silicon oxide; A second metal oxide film having a region disposed above the second insulating film; A third insulating film having a region disposed above the second metal oxide film; and The second conductive film and the third conductive film contain a metal oxide; The second insulating film has a region thicker than the third insulating film; The second insulating film has a region in contact with the first metal oxide film in a region between the second conductive film and the third conductive film; The first metal oxide film contains two or more elements selected from indium, gallium, tin, and zinc; The second metal oxide film contains two or more elements selected from indium, gallium, tin, and zinc; The first metal oxide film includes a phase in which metal atoms are arranged in layers or a phase in which metal atoms and oxygen atoms are arranged in layers when viewed from a direction perpendicular to the c-axis; The second metal oxide film overlaps with a channel formation region of the first metal oxide film; The second metal oxide film is not in contact with the second conductive film and is not in contact with the third conductive film; A semiconductor device, wherein a periphery of a region of the first metal oxide film that overlaps with the first conductive film and does not overlap with the second conductive film and the third conductive film overlaps with the second metal oxide film.

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