JP3453329B2 - Transparent conductive film and method for manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent conductive film and a method for manufacturing the same, and more particularly to a transparent conductive film made of indium oxide / tin oxide composite oxide (ITO) for solar cells and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, for example, a transparent conductive film has been used as an electrode of an amorphous silicon (hereinafter referred to as a-Si) solar cell which is a type IV semiconductor. FIG. 1 shows an example of such an a-Si solar cell, in which a transparent conductive film 2 made of tin oxide (hereinafter referred to as SnO ₂ ) is used as a surface transparent electrode on a glass substrate 1, and a- Si layer 3 and indium oxide on the a-Si layer 3 as a back transparent electrode
A transparent conductive film 4 made of a tin oxide composite oxide (hereinafter referred to as ITO) is laminated, an aluminum electrode film 5 is further laminated thereon, and an aluminum electrode 6 as a collector electrode is separately provided on the transparent conductive film 2. Substrate 1, transparent conductive film 2
Photoelectromotive force is generated by the light 7 incident on the a-Si layer 3 through. The transparent conductive film 2 is formed by a known thermochemical vapor deposition method, has a thickness of about 1 μm, and has irregularities of 0.1 μm or less on its surface. These irregularities greatly contribute to increase in photovoltaic power, that is, improvement in power generation efficiency.

One of the reasons for this is that the light incident from the glass substrate 1 side is less likely to be reflected by the irregularities at the interface between the transparent conductive film 2 and the a-Si layer 3, and is effectively taken into the a-Si layer 3. Secondly, the light reflected at the interface between the transparent conductive film 4 and the aluminum electrode film is the transparent conductive film 2, a−
Although it is returned to the interface of the Si layer 3, the incident angle at that time becomes large, so that the ratio of being totally reflected and not going outside increases. Here, similarly to the lower transparent conductive film 2, if the upper transparent conductive film 4 has irregularities on its surface, the proportion of total reflection that does not go outside increases, which leads to further improvement in power generation efficiency.

[0004]

There is a vacuum vapor deposition method or the like as a method for manufacturing the transparent conductive film 4 made of ITO and having irregularities on the surface. In the vacuum vapor deposition method, the transparent conductive film 4 having a structure having irregularities on the surface is used. Can be manufactured, but it is necessary to heat the substrate to 350 ° C. or higher. When the transparent conductive film 4 is formed on the a-Si layer 3 at a temperature of 350 ° C. or higher, a-
There is a problem that power generation efficiency is significantly reduced due to crystallization of the Si layer 3 and diffusion of doped impurities.
A transparent conductive film made of ITO having a low resistance and having an uneven structure on the surface at a substrate temperature of about 150 ° C. or lower at which crystallization of the i layer 3 and diffusion of doped impurities do not occur A manufacturing method has been demanded.

The present invention has been made in order to solve the above-mentioned problems, and is a transparent conductive film made of ITO having high transmittance and low resistance without causing thermal damage to the IV group semiconductor power generation layer, and It is an object to provide a manufacturing method thereof.

[0006]

A transparent conductive film according to the present invention is a transparent conductive film laminated on a group IV semiconductor power generation layer and does not cause thermal damage to the group IV semiconductor power generation layer.
In the temperature range of 50 ° C or lower, 50 to 99.99% by volume of
Gon gas, 50-0.01 vol% steam, 1 vol% or less
Indium oxide in the presence of a mixed gas containing oxygen gas below
The sputtered particles of the um-tin oxide composite oxide are the group IV semiconductors described above.
A film thickness of 50 on the group IV semiconductor power generation layer by acting on the body power generation layer.
Triangular crystal grains are formed in the range of ~ 1000 nm.
It is characterized by having a large number of uneven interfaces . Well
Moreover, the transparent conductive film according to the present invention is formed on the Group IV semiconductor power generation layer.
Which is a transparent conductive film laminated on the
5 in the temperature range of 150 ° C or less that does not cause thermal damage to the layer
0-99.99 volume% oxygen gas, 50-0.01 volume
% In the presence of mixed gas containing 100% steam
The vapor of the complex oxide of tin oxide and tin oxide is applied to the Group IV semiconductor power generation layer.
The thickness of the group IV semiconductor power generation layer is 50 to 1000
The film is formed in the range of nm and many hemispherical crystal grains are lined up.
Characterized by having an uneven interface formed by
And

When the film is formed by using the sputtering method, 150 ° C. which does not cause thermal damage to the IV group semiconductor power generation layer.
In the following temperature range, argon gas is 50 to 99.99% by volume, water vapor is 50 to 0.01% by volume, and oxygen gas is 0 to 1%.
Indium oxide in the presence of mixed gas containing each volume%
Sputtered particles of um-tin oxide composite oxide were generated from group IV semiconductors.
It acts on the electric layer. If the amount of water vapor added is less than 0.01% by volume, no unevenness will appear on the surface of the formed transparent conductive film, so the lower limit of the amount of water vapor added is 0.01% by volume. On the other hand, when the amount of water vapor added exceeds 50% by volume, the resistivity of the film increases (for example, the resistivity exceeds 1 × 10 ⁻³ Ω · cm), resulting in a film with poor electrical performance. The value is 50% by volume.

When the film is formed by the vacuum vapor deposition method, the group IV
Temperature below 150 ° C that does not cause thermal damage to the semiconductor power generation layer
In degrees zone, an oxygen gas 50 to 99.99% by volume, the coexistence of a gas mixture containing, respectively water vapor 50 to 0.01 vol%
Under the indium oxide-tin oxide composite oxide vapor group IV and half
It acts on the conductor power generation layer . The reason for limiting the numerical value of the amount of added steam is the same as above.

The transparent conductive film formed by the sputtering method has a large number of triangular crystal grains arranged as shown in FIG. 3 (a).
It has an uneven interface. Meanwhile, vacuum steaming
The transparent conductive film formed by the deposition method has unevenness formed by arranging a large number of hemispherical crystal grains shown in FIG.
It has a shaped interface.

The film thickness of the transparent conductive film is in the range of 50 to 1000 nm .

The method for producing a transparent conductive film according to the present invention is
In a method for producing a transparent conductive film laminated on a group IV semiconductor power generation layer, (a) a step of loading a substrate having a group IV semiconductor power generation layer into a vacuum container; A step of adjusting the temperature of the substrate to a temperature range of 150 ° C. or lower that does not cause damage; (c) 50 to 99.
99% by volume argon gas and 50-0.01% by volume water
A mixed gas containing steam and 1% by volume or less of oxygen gas
Introduced and used as film material Indium oxide / tin oxide composite oxide
Discharge by applying high frequency between the target and the substrate
Generated in the target surface in the presence of the mixed gas.
From indium oxide / tin oxide composite oxide sputtered particles
The sputtered particles are ejected and deposited on the Group IV semiconductor power generation layer to form a concavo-convex shape in which a large number of triangular crystal grains are arranged .
Indium oxide / tin oxide composite oxide film with interface
A step of forming a laminate in a film thickness range of 50 to 1000 nm ,
It is characterized by including. In addition, the transparent according to the present invention
The method of manufacturing the conductive film is such that the conductive film is laminated on the group IV semiconductor power generation layer.
In the method of manufacturing a transparent conductive film according to
A step of loading a substrate having an electric layer into a vacuum container,
(B) Does not cause thermal damage to the group IV semiconductor power generation layer 150
A step of adjusting the temperature of the substrate to a temperature range of ℃ or less, before (c)
In a vacuum container, 50 to 0.01% by volume of water vapor and 50 to
A mixed gas containing 99.99% by volume of oxygen gas is introduced.
Indium oxide / tin oxide composite oxide used as film material
Is heated with an evaporation source to evaporate to generate steam,
A discharge is generated in the area sandwiched between the source and the substrate, and the mixture
Indium oxide / tin oxide composite oxide in the presence of gas
Steam, water vapor, oxygen gas is turned into plasma, and in the plasma
Of active species of the above-mentioned group IV semiconductor power generation layer on the hemisphere
Oxide having an uneven interface with a large number of crystal grains
A film of indium-tin oxide composite oxide with a film thickness of 50 to 1000
and a step of forming a laminate in the range of nm.
To collect.

[0012]

Either a sputtering method or a vacuum evaporation method
However , if the amount of water vapor added is less than 0.01% by volume, the uneven shape will not appear at the interface of the formed transparent conductive film.
The lower limit of the amount of steam added is 0.01% by volume. on the other hand,
If the amount of steam added exceeds 50% by volume, the resistivity of the film will be 1 ×.
The upper limit of the amount of water vapor added is set to 50% by volume because the film exceeds 10 -3 Ω · cm and has poor electrical performance.

[0014]

Various preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 2 is a schematic structural view showing an apparatus used for manufacturing a transparent conductive film according to the first embodiment of the present invention. In the first embodiment, the ITO transparent conductive film is formed on the glass substrate by using the sputtering device 10. The sputtering apparatus 10 includes a vacuum container 11 that is evacuated by a vacuum exhaust device (not shown). The sputter source 12 is composed of a target 13 made of ITO, a magnetic field generating magnet 14, a target holder electrode 15 having a water cooling function, a shield 16, and an insulator 17 having a vacuum sealing function. A high frequency power source 19 is connected to the target holder electrode 15 via a matching unit 18.

A heater 21 is provided on the opposite side of the target 13.
The substrate holder electrode 22 having the above is installed, and the substrate 20 is attached and held on the lower surface thereof. A gas inlet 25a of a gas supply pipe 25 communicating with a gas flow rate control device (not shown) is arranged near the target 13.

In the above-described apparatus, first, the substrate 20 made of non-alkali glass or the like is ultrasonically cleaned with an organic solvent (for example, acetone) and then attached to the substrate holder electrode 22 in the vacuum container 11 and 2 × 10 ^−. Pre-exhaust below ⁶ Torr. Further, the substrate 21 is heated to about 150 ° C. by the heater 21.

Further, a gas inlet 25 is provided in the vacuum container 11.
The process gas is introduced via a. This process gas is obtained by adding 10 volume% of steam (H ₂ O) to 90 volume% of argon gas (Ar). The amount of gas exhausted by the vacuum pump and the amount of gas introduced by the gas supply device are controlled to adjust the internal pressure of the vacuum container 11 to 5 × 10 ⁻³ Torr.

Next, the high frequency power source 1 is passed through the matching device 18.
9. When high frequency power is applied to the target holder electrode 15 from 9, a discharge is generated between the electrodes 15 and 22, the argon ions generated by the discharge collide with the surface of the target 13, and the sputtered particles are directed toward the substrate 20. Jump out. Thereby, the ITO sputtered particles are deposited on the substrate 20 and the ITO film 24 is formed. The obtained ITO film 2
No. 4 has a film thickness of 50 to 1000 nm (0.05 to 1 μm)
And the resistivity was 5 × 10 ⁻⁴ Ω · cm. This resistivity value is substantially the same as that formed by the conventional method.

FIG. 3A is a photomicrograph of the transparent conductive film according to the first embodiment of the present invention formed as described above, observed and photographed with a scanning electron microscope (SEM). Thus, it was found that a large number of triangular crystal grains were formed and the surface of the transparent conductive film had an uneven shape.
On the other hand, FIG. 3B is a microscope in which a transparent conductive film formed by introducing only 100% by volume of argon gas without water vapor through the gas introduction port 25a (other conditions are the same) was observed and photographed by SEM. It is a photograph. As described above, the surface of the conventional film is smooth and does not have an uneven shape. From a comparison of the two, when water vapor is added to the process gas to form a film, the surface of the transparent conductive film becomes uneven, and the proportion of incident light that is totally reflected and does not go outside increases. Was found to improve.

In this case, if the amount of water vapor added is less than 0.01% by volume, no irregularities will appear on the surface of the formed transparent conductive film, so the lower limit of the amount of water vapor added is 0.01% by volume. On the other hand, if the amount of added water vapor exceeds 50% by volume, the resistivity of the film will exceed 1 × 10 ⁻³ Ω · cm, resulting in a film with poor electrical performance. Therefore, the upper limit of the amount of added water vapor is 50.
Volume%

The transmittance is further improved by adding oxygen at the same time as adding water vapor. However, if oxygen is added in an amount of 1% by volume or more, the resistivity of the film decreases, which is not preferable.

FIG. 4 is a graph showing a comparison of short-circuit currents of the solar cell including the transparent conductive film according to the first embodiment and the conventional transparent conductive film. The structure of the solar cell was as shown in FIG. As a comparative example, assuming that the short-circuit current of the solar cell using the transparent conductive film to which water vapor is not added is 1, the short-circuit current Isc of the solar cell using the transparent conductive film manufactured in this study is significantly increased to 1.50. Therefore, it was found that it has a large photoelectric conversion efficiency.

(Second Embodiment) FIG. 5 is a schematic structural view showing an apparatus used for manufacturing a transparent conductive film according to a second embodiment of the present invention. In the second embodiment, the vacuum vapor deposition device 3
0 is used to form an ITO transparent conductive film on a glass substrate. The vacuum vapor deposition device 30 includes a vacuum container 31 that is evacuated by a vacuum exhaust device (not shown). An evaporation material 33 made of ITO is installed in the evaporation source 32. Here, the evaporation source 32 may be of any heating method such as an electron beam heating method, a resistance heating method, or a laser heating method. The gas supply pipe 38 is introduced through the side wall of the vacuum container 31, and the gas introduction port 38 a is opened in the vacuum container 31. The gas supply pipe 38 communicates with a gas flow rate control device (not shown) including a process gas supply source.

A high frequency coil 34 for generating a discharge is fixed above the evaporation source 32 through an insulator 35 having a vacuum sealing function. The high frequency coil 34 has a matching device 36
A high frequency power supply 37 is connected via. Further, a substrate holder electrode 39 having a heater 40 is provided above the high frequency coil 34. A substrate 41 is attached and held on the lower surface of the substrate holder electrode 39.

In the above-mentioned apparatus, first, the substrate 41 made of non-alkali glass or the like is ultrasonically cleaned with an organic solvent (for example, acetone) and then attached to the substrate holder electrode 39 so that the substrate 41 is preliminarily kept at 2 × 10 ⁻⁶ Torr or less. Exhaust. Heater 4
The substrate 41 is heated to about 150 ° C. by 0.

Further, a gas inlet 38 is provided in the vacuum container 31.
The process gas is introduced via a. This process gas is obtained by adding 10 volume% of steam (H ₂ O) to 90 volume% of oxygen gas (O ₂ ). By controlling the exhaust amount by the vacuum pump and the gas introduction amount by the gas supply device,
The internal pressure of the vacuum container 31 is adjusted to 8 × 10 ⁻⁴ Torr.

Next, the evaporation material 33 composed of ITO is heated and evaporated by the evaporation source 32, and at the same time, a high frequency power is applied from the high frequency power supply 37 to the coil 34 through the matching device 36 to generate the discharge plasma 43. The film-forming components are generated and deposited on the substrate 41. Thereby, the ITO film 42 as a transparent conductive film is formed on the substrate 41. The obtained ITO film 42 has a film thickness of 50 to 1000 nm (0.05
~ 1 μm) and its resistivity is 6 × 10 ^-4 Ω ・
It was cm. This resistivity value is substantially the same as that formed by the conventional method.

FIG. 6 (a) is a photomicrograph of the transparent conductive film according to the second embodiment of the present invention formed as described above, observed and photographed with a scanning electron microscope (SEM). As described above, it was found that a large number of hemispherical crystal grains were formed and the surface of the transparent conductive film had an uneven shape.
On the other hand, FIG. 6B is a microscope in which the transparent conductive film formed by introducing only 100% by volume of oxygen gas without water vapor through the gas introduction port 38a (other conditions are the same) was observed and photographed by SEM. It is a photograph. As described above, the surface of the conventional film is smooth and does not have an uneven shape. From a comparison of the two, when water vapor is added to the process gas to form a film, the surface of the transparent conductive film becomes uneven, and the proportion of incident light that is totally reflected and does not go outside increases. Was found to improve.

In this case, if the amount of water vapor added is less than 0.01% by volume, no irregularities will appear on the surface of the formed transparent conductive film, so the lower limit of the amount of water vapor added is 0.01% by volume. On the other hand, if the amount of added water vapor exceeds 50% by volume, the resistivity of the film will exceed 1 × 10 ⁻³ Ω · cm, resulting in a film with poor electrical performance. Therefore, the upper limit of the amount of added water vapor is 50.
Volume%

FIG. 7 is a graph showing a comparison of short-circuit currents of the solar cell including the transparent conductive film according to the second embodiment and the conventional transparent conductive film. The structure of the solar cell was as shown in FIG. As a comparative example, assuming that the short-circuit current of the solar cell using the transparent conductive film to which water vapor is not added is 1, the short-circuit current Isc of the solar cell using the transparent conductive film produced in this study is significantly increased to 1.45. Therefore, it was found that it has a large photoelectric conversion efficiency.

[0032]

As described above, according to the present invention, the spatter is
It is possible to form a transparent conductive film having a concavo-convex structure at the interface at a substrate temperature of 150 ° C. or less by using either the vacuum deposition method or the vacuum deposition method, and to obtain the group IV semiconductor power generation layer without causing thermal damage. The obtained transparent conductive film has high transmittance and low resistance. A large short circuit current Isc is obtained in the solar cell using such a transparent conductive film of the present invention, and the photoelectric conversion efficiency is remarkably improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of the structure of a group IV semiconductor solar cell.

FIG. 2 is a schematic configuration diagram showing a sputtering apparatus used for manufacturing the transparent conductive film according to the first embodiment of the present invention.

3A is a micrograph showing a transparent conductive film according to the first embodiment of the present invention, and FIG. 3B is a micrograph showing a conventional transparent conductive film.

FIG. 4 is a graph showing a comparison of short-circuit currents of a solar cell including the transparent conductive film of the first embodiment and a solar cell including a conventional transparent conductive film.

FIG. 5 is a schematic configuration diagram showing a vacuum vapor deposition apparatus used for manufacturing a transparent conductive film according to a second embodiment of the present invention.

6A is a micrograph showing a transparent conductive film according to a second embodiment of the present invention, and FIG. 6B is a micrograph showing a conventional transparent conductive film.

FIG. 7 is a graph showing a comparison between short-circuit currents of a solar cell including the transparent conductive film of the second embodiment and a solar cell including a conventional transparent conductive film.

[Explanation of symbols]

1 ... substrate, 2 ... SnO ₂ transparent conductive film, 3 ... IV group semiconductor power layer (a-Si layer), 4 ... ITO transparent conductive film, 5 ... aluminum electrode film, 6 ... aluminum electrode (collecting electrode),
10 ... Sputtering apparatus, 11 ... Vacuum container, 12 ... Sputter source, 13 ... Target, 14 ... Magnet, 15 ... Target holder electrode, 16 ... Shield, 17 ... Insulator, 1
8 ... Matching device, 19 ... High frequency power supply, 20 ... Substrate, 21 ... Heater, 22 ... Substrate holder electrode, 23 ... Insulator, 24 ... I
TO transparent conductive film, 25 ... Gas supply pipe, 25a ... Gas introduction port, 26 ... Exhaust port, 30 ... Vacuum deposition apparatus, 31 ... Vacuum container, 32 ... Evaporation source, 33 ... Evaporation material, 34 ... High frequency coil, 35 ... Insulator, 36 ... Matching device, 37 ... High frequency power supply,
38 ... Gas supply pipe, 38a ... Gas introduction port, 39 ... Substrate holder electrode, 40 ... Heater, 41 ... Substrate, 42 ... ITO transparent conductive film, 43 ... Plasma, 46 ... Exhaust port.

Front page continuation (72) Inventor Akemi Takano 5-717-1, Fukahori-cho, Nagasaki-shi, Nagasaki Mitsubishi Heavy Industries, Ltd. Nagasaki Laboratory (56) Reference JP-A-56-9906 (JP, A) JP-A-SHO 56-9905 (JP, A) Japanese Patent Laid-Open No. 4-242017 (JP, A) Akira Kanehara, Thin film <The function and application>, Japan, Japan Standards Association, April 20, 1991, 1st edition , P. 104- 106 (58) Fields investigated (Int.Cl. ⁷ , DB name) C23C 14/00-14/58 H01B 5/14 H01B 13/00 H01L 31/04

Claims (4)

(57) [Claims] 1. A transparent conductive film laminated on a group IV semiconductor power generation layer, which is 50 to 99.99 in a temperature range of 150 ° C. or lower that does not cause thermal damage to the group IV semiconductor power generation layer.
% Argon gas, 50-0.01 volume% steam,
In the presence of a mixed gas containing 1% by volume or less of oxygen gas
In front of sputtered particles of indium oxide / tin oxide composite oxide
On the group IV semiconductor power generation layer by acting on the group IV semiconductor power generation layer
Film with a thickness of 50 to 1000 nm is formed in a triangular shape
1. A transparent conductive film having an uneven interface in which a large number of crystal grains are lined up . 2. A transparent layer formed on a Group IV semiconductor power generation layer.
A conductive film that causes thermal damage to the Group IV semiconductor power generation layer.
50-99.99 bodies in the temperature range of 150 ° C or less
% Product oxygen gas, 50-0.01 volume% water vapor
Indium oxide / tin oxide composite acid in the presence of mixed gas
Of the group IV semiconductor power generation layer by reacting the vapor of the compound with the group IV semiconductor power generation layer.
Film formation on the semiconductor power generation layer in a film thickness range of 50 to 1000 nm
Formed by arranging a large number of hemispherical crystal grains
Transparent conductive material having an uneven interface
film. 3. A transparent layer formed on a Group IV semiconductor power generation layer.
In the method of manufacturing a conductive film, (a) a substrate having a group IV semiconductor power generation layer is carried into a vacuum container.
A step of entering, 150 which does not adversely thermal damage (b) IV group semiconductor power layer
A step of adjusting the temperature of the substrate to a temperature range of ℃ or less, and (c) 50 to 99.99 volume% of Al in the vacuum container.
Gon gas, 50-0.01 vol% steam and 1 vol% or less
Introduce a mixed gas containing oxygen gas below and
Indium oxide / tin oxide composite oxide target and before
A high frequency is applied to the substrate to generate a discharge,
Indium oxide from the target surface in the presence of mixed gas
・ Sputter particles of tin oxide composite oxide
Depositing putter particles on the group IV semiconductor power generation layer,
Oxidation having a rough interface with a large number of square crystal grains
Indium-tin oxide composite oxide film with a thickness of 50-100
A method of manufacturing a transparent conductive film, comprising a step of forming a laminate in a range of 0 nm . 4. A transparent layer formed on a Group IV semiconductor power generation layer.
In the method of manufacturing a conductive film, (a) a substrate having a group IV semiconductor power generation layer is carried into a vacuum container.
A step of entering, 150 which does not adversely thermal damage (b) IV group semiconductor power layer
A step of adjusting the temperature of the substrate to a temperature range of ℃ or less, and (c) 50 to 0.01% by volume of water vapor in the vacuum container.
And 50 to 99.99% by volume oxygen gas
A gas is introduced to mix indium oxide and tin oxide, which are film materials.
Heating the compound oxide with an evaporation source to evaporate to produce steam,
A discharge is generated in a region sandwiched between the evaporation source and the substrate,
In the presence of the mixed gas, the indium oxide / tin oxide composite
Compound oxide vapor, water vapor, and oxygen gas are turned into plasma and
Active species in plasma were deposited on the Group IV semiconductor power generation layer.
Have a rough interface with many hemispherical crystal grains.
Film of indium oxide / tin oxide composite oxide
And a step of forming a layer in a range of 1000 nm .