JP2012099661A - Method of manufacturing oxide semiconductor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stacked structure of a metal oxide thin film that can improve crystallinity of ZnO, can reduce the thickness of a ZnO thin film by the improvement, and can achieve sufficient electron field-effect mobility and high transmissivity.SOLUTION: A stacked structure is composed of a first thin film, which is an amorphous film containing oxide of a metal element M1 of one or both of In and Sn, and a second thin film that is stacked on and in contact with the first thin film and contains at least ZnO.

Description

  The present invention relates to a laminated structure of a thin film containing a metal oxide, a thin film transistor and a thin film solar cell using the same.

  Field effect transistors are widely used as unit electronic elements, high frequency signal amplifying elements, liquid crystal driving elements and the like of semiconductor memory integrated circuits, and are the most widely used electronic devices at present.

  Among them, with the remarkable development of display devices in recent years, not only in liquid crystal display devices (LCD) but also in various display devices such as electroluminescence display devices (EL) and field emission displays (FED), they are used as display elements. Thin film transistors (TFTs) are frequently used as switching elements that drive a display device by applying a driving voltage.

In Patent Document 1 regarding an electrode structure of a ZnO thin film, the crystallinity of ZnO is improved by forming zinc oxide (ZnO) on an oxide thin film having a cubic structure such as polycrystalline In ₂ O ₃ on a substrate. It is disclosed that it is possible.
However, the preferred film thickness of In ₂ O ₃ that improves the crystallinity of ZnO is unknown, and therefore it was unknown how much a cubic structure is necessary.

In Patent Document 2 relating to a photovoltaic element, an oxide of indium and zinc (In ₂ O ₃ : ZnO = 90: 10 mass ratio) with a reduced film thickness instead of ZnO doped with Al or Ga (hereinafter referred to as IZO). IZO is a registered trademark of Idemitsu Kosan Co., Ltd.) as a transparent electrode for CIGS solar cells. However, In is very expensive compared to Zn, and there is a problem that it is difficult to obtain cost merit only by reducing the film thickness.

In order to crystallize a thin film containing ZnO, it was necessary to set the film thickness to a certain level or more.
For this reason, when a thin film containing ZnO is used for the channel layer of a bottom gate type TFT, a region having insufficient crystallinity occurs in a portion adjacent to the gate insulating film, and sufficient field effect transfer is achieved even when a voltage is applied. Could not get the degree.
In addition, when a thin film containing ZnO is used for a thin film solar cell such as a-Si or CIGS, it is difficult to ensure high transmittance because the film thickness is increased.

JP-A-9-255491 JP 2010-098263 A

It is an object of the present invention to improve the crystallinity of a thin film containing ZnO, thereby reducing the thickness of the ZnO thin film, and achieving a sufficient field effect mobility and high transmittance. It is to provide a laminated structure of physical thin films.
Another object of the present invention is to provide a thin film transistor having excellent TFT characteristics using the above laminated structure as a channel layer.
Furthermore, the objective of this invention is using the said laminated structure for an upper electrode, and is providing the thin film solar cell which has the outstanding electromotive force.

  In order to achieve the above object, the inventors have intensively studied. As a result, if an amorphous thin oxide film made of a specific metal oxide is used as an underlayer, it is made of ZnO or ZnO doped with Al or Ga. Since the crystallinity of the thin film can be greatly improved, it has been found that the ZnO layer can be thinned, and that the transmittance can be improved thereby, and the present invention has been completed.

According to the present invention, the following laminated structure, thin film transistor, and thin film solar cell are provided.
1. A first thin film which is an amorphous film containing an oxide of one or both of the metal elements M1 and In and Sn, and contains at least ZnO laminated in contact with the first thin film A laminated structure consisting of a second thin film.
2. 2. The laminated structure according to 1, wherein the first thin film further contains an oxide of one or more metal elements M2 selected from the group consisting of Zn, Al, and Ga.
3. 3. The laminated structure according to 1 or 2, wherein the first and second thin films are laminated and then heat-treated in an oxygen atmosphere.
4). The laminated structure according to any one of 1 to 3, wherein the thickness of the first thin film is 3 to 50 nm.
5. The laminated structure according to any one of 1 to 4, wherein the second thin film has a thickness of 20 to 200 nm.
6). The laminated structure according to any one of 2 to 5, wherein the combination of the metal elements M1 and M2 is selected from the following combinations.
(M1; M2) = (In; Ga), (In; Zn), (In; Ga and Zn) and (In and Sn; Zn)
7). The laminated structure according to any one of 1 to 6, wherein the second thin film further contains one or both of Al and Ga.
8). A thin film transistor having a channel layer on a gate insulating film,
The channel layer comprises:
A first thin film containing an oxide of one or both of metal elements M1 and In and Sn, and a second thin film containing at least ZnO and laminated on the first thin film. A thin film transistor having a laminated structure.
9. 9. The thin film transistor according to 8, wherein the first thin film further contains an oxide of one or more metal elements M2 selected from the group consisting of Zn, Al, and Ga.
10. The thin film transistor according to 8 or 9, wherein the first thin film has a thickness of 5 to 50 nm.
11. The thin film transistor according to any one of 8 to 10, wherein the second thin film has a thickness of 30 to 100 nm.
12 The thin film transistor according to any one of 9 to 11, wherein the combination of the metal elements M1 and M2 is selected from the following combinations.
(M1; M2) = (In; Ga), (In; Zn), (In; Ga and Zn) and (In and Sn; Zn)
13. The thin film transistor according to any one of 8 to 12, wherein the second thin film further contains one or both of Al and Ga oxides.
14 On the back electrode, a light absorption layer, an interface layer and an upper electrode are thin film solar cells provided in this order,
A first thin film containing an oxide of one or both of the metal elements M1 and In and Sn, and a first thin film containing at least ZnO laminated in contact with the first thin film. A thin film solar cell comprising a laminated structure comprising two thin films.
15. 15. The thin film solar cell according to 14, wherein the first thin film further contains an oxide of one or more metal elements M2 selected from the group consisting of Zn, Al, and Ga.
16. The thin film solar cell according to 14 or 15, wherein the thickness of the first thin film is 3 to 30 nm.
17. The thin film solar cell according to any one of 14 to 16, wherein the upper electrode has a thickness of 100 to 1000 nm.
18. The thin film solar cell according to any one of 15 to 18, wherein the combination of the metal elements M1 and M2 is selected from the following combinations.
(M1; M2) = (In; Ga), (In; Zn), (In; Ga and Zn) and (In and Sn; Zn)
19. The thin film solar cell according to any one of 14 to 18, wherein the second thin film further contains one or both of Al and Ga oxides.

  According to the present invention, the crystallinity of ZnO can be improved by laminating a thin film containing at least ZnO on a specific oxide thin film. When the stacked structure is used for a channel layer of a bottom gate TFT, the contact resistance with the gate electrode can be reduced, and the TFT characteristics can be greatly improved. Moreover, when the said laminated structure is used for a thin film solar cell, short circuit current density (Isc)> 20mA is achieved in a thin film thickness, tact time can be shortened, and higher transmittance can be achieved.

2 is an X-ray diffraction (XRD) chart before annealing of the laminated structure produced in Example 1 and Comparative Example 1. FIG. It is a XRD chart after annealing of the laminated structure produced in Example 1 and Comparative Example 1. 10 is a chart showing transfer characteristics of thin film transistors manufactured in Example 15 and Comparative Example 3. 10 is a chart showing field effect mobility of the thin film transistors manufactured in Example 15 and Comparative Example 3.

(1) Laminated structure The laminated structure of the present invention is formed on the first thin film, which is an amorphous film containing an oxide of one or both of In and Sn, and the first thin film. It is characterized by comprising a second thin film containing at least ZnO laminated in contact therewith.
Furthermore, in the laminated structure of the present invention, the first thin film may further contain an oxide of one or more metal elements M2 selected from the group consisting of Zn, Al, and Ga.

  By providing the second thin film on the amorphous first thin film containing the oxides of the metal elements M1 and M2, the influence of the film stress of the first thin film on the second thin film can be reduced. This can improve the crystallinity of the second thin film and reduce the occurrence of cracks. Lattice defects based on cracks become carrier traps, and it is possible to prevent the field effect mobility from being lowered and the S value of the TFT from being deteriorated. This is presumably because the thin film containing the oxides of the metal elements M1 and M2 has ionic bonding properties suitable for promoting crystal growth of the second thin film containing at least ZnO.

  In the present invention, being amorphous means that a peak indicating a crystal structure cannot be confirmed when X-ray diffraction (XRD) is measured.

  As a result, when the stacked structure is used for the channel layer of a bottom gate type TFT, the crystallinity near the interface with the gate insulating film is improved, thereby increasing the field effect mobility and greatly improving the TFT characteristics. be able to. Moreover, when the laminated structure is used for a thin film solar cell, a short-circuit current density (Isc)> 20 mA can be achieved at a thin film thickness, the tact time can be shortened, and a higher transmittance can be achieved.

  The laminated structure of the present invention is preferably one in which the first and second thin films are laminated and then subjected to heat treatment (annealing) in an oxygen atmosphere. The conditions for the heat treatment are preferably 0.5 to 2 hours at a temperature of 200 to 400 ° C. in an oxygen atmosphere such as air. By performing the heat treatment in this manner, the crystallinity of the second thin film can be further improved. Comparing FIGS. 1 and 2, it can be seen that the crystallinity of the second thin film changes with the orientation of ZnO in the C-axis direction as an index before and after annealing.

  The first thin film contains an oxide of at least one of In and Sn, which are metal elements M1, and optionally contains one or more oxides selected from the group consisting of Zn, Al, and Ga, which are metal elements M2. Do it. That is, the first thin film may be made of only an oxide of In or Sn, or may be made of an oxide of In and Sn, or one of In and Sn and Zn, It may be composed of one or more oxides of Al and Ga, or may be composed of an oxide of In and Sn and one or more oxides of Zn, Al, and Ga. The metal element M1 is preferably only In or In and Sn.

When both In and Sn are contained as the metal element M1, the ratio of In ₂ O ₃ and SnO ₂ is preferably 90:10 to 99.9: 0.1 in terms of mass ratio, and 95: 5 to 99 .8: 0.2 is more preferable.

  When the metal element M2 is contained, the ratio of the total amount of the oxide of the metal element M1 and the total amount of the oxide of the metal element M2 is preferably 20:80 to 95: 5, and 30:70 More preferably, it is -90: 10.

The following combinations (M1; M2) of the metal elements M1 and M2 constituting the first thin film are preferable.
(M1; M2) = (In; Ga), (In; Zn), (In; Ga and Zn) and (In and Sn; Zn)

  Although the film thickness of a 1st thin film can be suitably set with the use of laminated structure, since the crystallinity of a 1st thin film can be reduced as it is 3-50 nm, it is preferable. In addition, if the thickness of the first thin film is 3 to 50 nm, more preferably 5 to 50 nm, a reduction in tact time can be expected. A more preferable thickness of the first thin film is 7 to 20 nm.

  Although the film thickness of a 2nd thin film can also be suitably set with the use of laminated structure, it is preferable that it is 20-200 nm, and it is more preferable that it is 30-150 nm. When the thickness of the second thin film containing ZnO is 20 to 200 nm, the crystallinity of ZnO can be sufficiently increased.

  The second thin film may further contain one or both oxides of Al and Ga. By containing an oxide of Al or Ga, conductivity can be imparted to the second thin film.

  The ratio of the oxide of Al and / or Ga in the second thin film is preferably 0.2 to 5% by mass when the total amount of the second thin film is 100% by mass, More preferably, it is -3 mass%. If the ratio of the oxide of Al and / or Ga is less than 0.2% by mass, the conductivity may not be imparted, and if it exceeds 5% by mass, the conductivity may be lowered.

The laminated structure of the present invention can be manufactured by a known method. For example, it can be manufactured as follows.
A first thin film material is deposited on a supporting substrate such as a glass plate by a known method such as sputtering, and a second thin film material is further formed thereon by sputtering or the like. A film is formed by a known method so as to have a predetermined film thickness.
When a plurality of metal oxides are used for the first and second thin films, an oxide sputtering target having a desired composition ratio may be used.
Further, as described above, the crystallinity of the second thin film can be further enhanced by performing heat treatment in an oxygen atmosphere such as air after the second thin film is formed.

(2) Thin Film Transistor The thin film transistor of the present invention is a thin film transistor having a channel layer on a gate insulating film, wherein the channel layer contains an oxide of one or both of metal elements M1 and In and Sn. It is characterized by comprising a laminated structure comprising one thin film and a second thin film containing at least ZnO, which is laminated in contact with the first thin film.
In the thin film transistor of the present invention, the first thin film may further contain an oxide of one or more metal elements M2 selected from the group consisting of Zn, Al, and Ga.

  When the above laminated structure is used for the channel layer of a bottom-gate TFT, the crystallinity of the second thin film containing ZnO is improved, so that it is possible to suppress grain boundary scattering and greatly improve TFT characteristics. can do. In addition, by using a film containing ZnO containing reduction resistance as a channel layer, a nitride film having better passivation than an oxide film can be directly stacked, and a reduction in manufacturing cost can be expected.

  The film thickness of the first thin film in the channel layer of the thin film transistor of the present invention is preferably 5 to 50 nm, and more preferably 7 to 20 nm. If the thickness of the first thin film is less than 5 nm, the effect of improving the crystallinity of the second thin film may be insufficient. If the thickness exceeds 50 nm, the channel thickness of the thin film transistor becomes thicker. There is a possibility that the effect of improving mobility cannot be obtained.

  The film thickness of the second thin film in the channel layer of the thin film transistor of the present invention is preferably 30 to 100 nm, and more preferably 40 to 80 nm. If the thickness of the second thin film is less than 30 nm, the channel thickness of the thin film transistor becomes thinner, so that the effect of improving the field effect mobility may not be obtained. If the thickness of the second thin film exceeds 100 nm, the field effect mobility varies. May be incurred.

  The preferred combination of the metal elements M1 and M2 in the first thin film in the channel layer of the thin film transistor of the present invention, the ratio of each oxide, and the component added to the second thin film are the same as in the above-described laminated structure of the present invention. .

  The thin film transistor of the present invention can be manufactured using a known bottom gate thin film transistor manufacturing method, except that the stacked structure of the present invention is used as a channel layer.

(3) Thin Film Solar Cell The thin film solar cell of the present invention is a thin film solar cell in which a light absorption layer, an interface layer, and an upper electrode are provided in this order on a back electrode, and the upper electrode is composed of In and Sn. A laminated structure comprising a first thin film containing an oxide of one or both of the metal elements M1 and a second thin film containing at least ZnO provided in contact with the first thin film It is characterized by that.
In the thin film solar cell of the present invention, the first thin film may further contain an oxide of one or more metal elements M2 selected from the group consisting of Zn, Al, and Ga.

  The thin film solar cell of the present invention can achieve the short-circuit current density (Isc)> 20 mA even when the upper electrode is thin, by using the above laminated structure as the upper electrode. Higher transmittance can be achieved.

  The film thickness of the first thin film in the upper electrode of the thin film solar cell of the present invention is preferably 3 to 30 nm, and more preferably 7 to 20 nm. If the first film thickness is less than 3 nm, the effect of improving the crystallinity of the second thin film may be insufficient, and if it exceeds 30 nm, a large amount of expensive indium is used. Not right.

  Although the film thickness of the upper electrode of the thin film solar cell of this invention can be suitably set according to the performance calculated | required, it is preferable that it is 100-1000 nm, and it is more preferable that it is 200-500 nm. If the film thickness of the upper electrode is less than 100 nm, the conductivity may be insufficient, and if it exceeds 1000 nm, the short-circuit current density of the solar cell may be reduced due to absorption.

  The preferred combination of the metal elements M1 and M2 in the first thin film in the upper electrode of the thin film solar cell of the present invention, the ratio of each oxide, and the component added to the second thin film are the same as in the above laminated structure of the present invention. It is.

  The thin film solar cell of this invention can be manufactured using a well-known method except using the laminated structure of the said invention as an upper electrode.

[Production of laminated structure]
Example 1
Eagle 2000 (manufactured by Corning) is used as an alkali-free glass, and IZO (made by Idemitsu Kosan Co., Ltd., registered trademark, In ₂ O ₃ : ZnO = 95: 5 mass ratio), which is the material of the first thin film, is obtained by RF sputtering. A 10 nm film was formed. Next, 40 nm of ZnO which is the material of the second thin film was formed by RF sputtering. The film forming conditions were as follows.
Deposition condition of the first thin film (IZO film) Target-substrate distance 88mm
Substrate temperature Room temperature Gas flow rate Ar = 10sccm
Deposition pressure 0.5Pa
Sputter power 2.3 W / cm2
Deposition condition of second thin film (ZnO film) Target-substrate distance 88mm
Substrate temperature 150 ° C
Gas flow rate Ar = 10 sccm, O ₂ = 10 sccm
Deposition pressure 1Pa
Sputter power 2.3 W / cm ²

The IZO / ZnO thin film laminated structure thus obtained was annealed in air at 350 ° C. for 1 hour. FIG. 1 shows the X-ray diffraction (XRD) result of the thin film before annealing, and FIG. 2 shows the XRD result of the thin film after annealing.
The crystallinity of the second thin film was evaluated based on the orientation of ZnO in the C-axis direction. Specifically, the crystallinity was evaluated using a value obtained by dividing the peak intensity of ZnO (0002) by the film thickness as a relative index. A larger index value indicates higher crystallinity. The results are shown in Table 1.

Examples 2-14
Each laminated structure was fabricated in the same manner as in Example 1 except that the film thickness and composition of the first and second thin films were changed to those shown in Table 1. Further, XRD was measured in the same manner as in Example 1 to evaluate crystallinity. The results are shown in Table 1.

Comparative Example 1
Eagle 2000 was used as non-alkali glass, and ZnO was deposited to 40 nm by RF sputtering, and then annealed in air at 350 ° C. for 1 hour. FIG. 1 shows the XRD result of the thin film before annealing, and FIG. 2 shows the XRD result of the thin film after annealing. Further, the crystallinity of the obtained ZnO film was evaluated in the same manner as in Example 1. The results are shown in Table 1.

  From the results of Table 1, high crystallinity is obtained even when the thickness of the second thin film containing ZnO is reduced by forming the first thin film as the underlayer of the second thin film containing ZnO. You can see that

  From the results of FIGS. 1 and 2, the ZnO film formed on the IZO film in Example 1 as an underlayer is superior in crystallinity to the ZnO single film having the same film thickness in Comparative Example 1. Recognize.

Example 15
[Production of Thin Film Transistor]
A thin film transistor was fabricated with the following materials and conditions.
-Gate electrode Eagle 2000 was used as non-alkali glass, and Cr was formed by sputtering. Next, a photoresist was applied, exposed, developed, and etched, and finally the resist was peeled to form a gate electrode.
· An insulating film above the substrate was set in a CVD apparatus, film formation was carried out in the SiO _2. SiO ₂ was formed by plasma chemical vapor deposition (PCVD) using SiH ₄ + N ₂ O + N ₂ gas, and the film thickness was set to 50 nm.
Channel deposition The substrate with an insulating film thus obtained was set in a sputtering apparatus, and an oxide thin film laminated structure made of IZO / ZnO was produced in the same manner as in Example 1.

Etch stopper The substrate was set in a CVD apparatus, and a SiN _x film was formed. SiN _x was formed by plasma enhanced chemical vapor deposition (PCVD) using SiH ₄ + NH ₃ + N ₂ gas, and the film thickness was set to 100 nm.
-Patterning of channel and etch stopper Photoresist was applied to the substrate, exposed, developed, and dry etched, and finally the resist was peeled off to obtain a channel layer.
Protective film further set the substrate in a CVD apparatus, film formation was carried out in the SiN _x. SiN _x was formed by plasma enhanced chemical vapor deposition (PCVD) using SiH ₄ + NH ₃ + N ₂ gas, and the film thickness was set to 100 nm.
Next, a photoresist was applied to the substrate, and exposure, development, and dry etching were performed. Finally, the resist was peeled off to form contact holes for source, drain, and gate electrodes.

-Source and drain electrodes After sputter-depositing ITO on the substrate, a photoresist was applied, exposed, developed, and etched, and finally the resist was removed to form source and drain electrodes.

Using the thin film transistor thus obtained, the magnitude of the drain current (I _d ) accompanying the change in the gate voltage (V _g ) was measured to evaluate the transfer characteristics. The results are shown in FIG.
Further, the magnitude of the field effect mobility accompanying the change of the gate voltage (Vg) was calculated. The results are shown in FIG.

In addition, the field-effect mobility and off-current (I _off ) of the obtained thin film transistor were measured by the following method. The results are shown in Table 2.
-Field effect mobility Field effect mobility was evaluated by Hall effect measurement.
The Hall measuring device and the measurement conditions are as follows.
Hall measuring device manufactured by Toyo Technica: Resi Test 8310
Measurement conditions Measurement temperature: Room temperature (25 ° C)
Measurement magnetic field: 0.45T
Measurement current: 10 ⁻¹² to 10 ⁻⁴ A
Measurement mode: AC magnetic field hall measurement

・ I _off (off current)
The drain current (I _d ) when the gate voltage (V _g ) = − 5 V was _defined as the off-current (I _off ).
The off-current is usually 5 × 10 ⁻⁹ A or less, preferably 1 × 10 ⁻⁹ A or less, more preferably 5 × 10 ⁻¹⁰ A or less, and particularly preferably 1 × 10 ⁻¹⁰ A or less. When the off-state current is 5 × 10 ⁻⁹ A or less, the leakage current is small and it can be used as a thin film transistor for a display.

Examples 16-27
A thin film transistor was manufactured in the same manner as in Example 15 except that the channel film formation was performed using the materials shown in Table 2, and the field effect mobility and I _off (off current) were measured in the same manner as in Example 1. The results are shown in Table 2.

Comparative Example 3
A transistor using only ZnO as a channel layer was fabricated in the same manner as in Example 15 except that channel film formation was performed in the same manner as in Comparative Example 1. Similarly to Example 15, transfer characteristics, field effect mobility, and I _{The off} (off current) was measured. The results are shown in FIG. Further, the magnitude of the field effect mobility accompanying the change of the gate voltage (V _g ) was calculated. The results are shown in FIG.

As is clear from FIG. 3, the drain current value (I _d ) of Example 15 at the gate voltage (V _g ) = 0.1 V was improved by almost one digit compared with the drain current value of Comparative Example 3.
Further, as apparent from FIG. 4, the field effect mobility of Comparative Example 3 at the gate voltage (V _g ) = 25 V is 13 cm ² / Vs, whereas the field effect mobility of Example 15 is 53 cm ² / V. It can be seen that the ZnO film formed on the IZO film in Example 15 using the IZO film in Example 15 as a base layer exhibits significantly higher field effect mobility than the ZnO single film having the same film thickness in Comparative Example 3.

From the results in Table 2, it can be seen that the thin film transistors manufactured in Examples 15 to 27 have high field-effect mobility, very low off-state current (I _off ), and excellent TFT characteristics.

  As described above, the thin film transistor of the present invention using the laminated structure of the first thin film made of a specific metal oxide and the second thin film containing ZnO as the channel layer has excellent TFT characteristics. It can be used as a driving element for a liquid crystal display device or the like.

Example 28
[Preparation of CIGS thin film solar cell]
A CIGS thin film solar cell was produced under the following materials and conditions. -Glass substrate Soda lime glass was used.
-Back electrode layer A Mo film was formed to a thickness of 500 nm by direct current sputtering.
-Light absorption layer Cu, In, Ga, and Se were formed into a film so as to have a thickness of 5000 nm using a pass-through sputtering apparatus.
Buffer layer A 200 nm InS film was formed by CBD (position on chemical bath) method.
-N-type semiconductor layer A ZnO film was formed by sputtering to a thickness of 500 nm.
-Transparent electrode layer 1 (first thin film)
A film of In ₂ O ₃ having a thickness of 10 nm was formed by sputtering.
-Transparent electrode layer 2 (second thin film)
AZO (ZnO: Al ₂ O ₃ = 99: 1 mass ratio) was formed to a thickness of 200 nm by a sputtering method. At this time, the substrate temperature was set to 150 ° C.

In the obtained CIGS thin film solar cell, the thickness of the transparent electrode layer (total thickness of the first and second thin films) that achieves a short-circuit current density (Isc)> 20 mA, and the average transmission of AZO at a thickness of 400 to 1200 nm The rate was determined by the following method. The results are shown in Table 3.
-Film thickness of transparent electrode layer 2 that achieves short-circuit current density (Isc)> 20 mA Only AZO was deposited on glass and measured using a contact-type film thickness meter (DEKTAK, manufactured by ULVAC).
-Average transmittance | permeability Only AZO was formed into a film on glass, the transmittance | permeability of the wavelength range 400-1200 nm was measured, and the average value was computed.

Example 29
A CIGS thin film solar cell was produced in the same manner as in Example 28 except that ZnO: Ga ₂ O ₃ (99: 1 mass ratio) was used as the transparent electrode layer 2, and performance evaluation was performed in the same manner as in Example 28. The results are shown in Table 3.

Comparative Example 4
A CIGS thin film solar cell was produced in the same manner as in Example 28 except that the transparent electrode layer 1 was not produced, and performance evaluation was performed. The results are shown in Table 3.

  From the results in Table 3, it can be seen that the thin film solar cells produced in Examples 28 and 29 can suppress the film thickness of the transparent electrode layer that achieves Isc> 20 mA, thereby obtaining a high transmittance.

According to the present invention, a good interface between a gate insulating film and a semiconductor thin film can be obtained, and a thin film transistor with high performance and mass productivity can be provided.
The thin film transistor of the present invention has excellent TFT performance and is useful as a driving element for liquid crystal display devices and the like.
Since the thin film solar cell of this invention can make the film thickness of a transparent electrode layer small, it is useful as a high performance solar cell which has a high transmittance | permeability.

Claims (19)

A first thin film which is an amorphous film containing an oxide of one or both of the metal elements M1 and In and Sn, and contains at least ZnO laminated in contact with the first thin film A laminated structure consisting of a second thin film.   The multilayer structure according to claim 1, wherein the first thin film further contains an oxide of one or more metal elements M2 selected from the group consisting of Zn, Al, and Ga.   The laminated structure according to claim 1, wherein the first and second thin films are laminated and then heat-treated in an oxygen atmosphere.   The laminated structure according to claim 1, wherein the first thin film has a thickness of 3 to 50 nm.   The laminated structure according to claim 1, wherein the second thin film has a thickness of 20 to 200 nm. The laminated structure according to any one of claims 2 to 5, wherein a combination of the metal elements M1 and M2 is selected from the following combinations.
(M1; M2) = (In; Ga), (In; Zn), (In; Ga and Zn) and (In and Sn; Zn)   The laminated structure according to any one of claims 1 to 6, wherein the second thin film further contains one or both of Al and Ga oxides. A thin film transistor having a channel layer on a gate insulating film,
The channel layer comprises:
A first thin film containing an oxide of one or both of metal elements M1 and In and Sn, and a second thin film containing at least ZnO and laminated on the first thin film. A thin film transistor having a laminated structure.   The thin film transistor according to claim 8, wherein the first thin film further contains an oxide of one or more metal elements M2 selected from the group consisting of Zn, Al, and Ga.   The thin film transistor according to claim 8 or 9, wherein the thickness of the first thin film is 5 to 50 nm.   The thin film transistor according to claim 8, wherein the second thin film has a thickness of 30 to 100 nm. The thin film transistor according to any one of claims 9 to 11, wherein a combination of the metal elements M1 and M2 is selected from the following combinations.
(M1; M2) = (In; Ga), (In; Zn), (In; Ga and Zn) and (In and Sn; Zn)   The thin film transistor according to any one of claims 8 to 12, wherein the second thin film further contains one or both of Al and Ga oxides. On the back electrode, a light absorption layer, an interface layer and an upper electrode are thin film solar cells provided in this order,
A first thin film containing an oxide of one or both of the metal elements M1 and In and Sn, and a first thin film containing at least ZnO laminated in contact with the first thin film. A thin film solar cell comprising a laminated structure comprising two thin films.   The thin film solar cell according to claim 14, wherein the first thin film further contains an oxide of one or more metal elements M2 selected from the group consisting of Zn, Al, and Ga.   The thin film solar cell according to claim 14 or 15, wherein the first thin film has a thickness of 3 to 30 nm.   The thin film solar cell according to any one of claims 14 to 16, wherein the film thickness of the upper electrode is 100 to 1000 nm. The thin film solar cell according to any one of claims 15 to 18, wherein a combination of the metal elements M1 and M2 is selected from the following combinations.
(M1; M2) = (In; Ga), (In; Zn), (In; Ga and Zn) and (In and Sn; Zn) The thin film solar cell according to any one of claims 14 to 18, wherein the second thin film further contains one or both of Al and Ga oxides.

Images