JPS61225713A - Transparent electroconductive film and making thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a transparent conductive film that is corrosion resistant and is optimal as a substrate for solar cells.

"Prior Art" In general, transparent conductive films that are transparent and conductive in the visible light region are used as transparent electrodes in new display systems such as liquid crystal displays and EL displays, and as transparent electrodes in amorphous silicon solar cells. It is used by forming a film on a transparent glass substrate to prevent photomask charging. Indium oxide and tin oxide are mainly used as materials for these transparent conductive films. In particular, indium oxide is capable of lowering the resistance, and by adding tin oxide, it is currently possible to obtain a resistance of about 1O-4Ω, which is comparable to that of C.

"Problems to be Solved by the Invention" As described above, transparent conductive films, especially indium oxide films, have excellent conductivity properties, but when considering acid resistance or reduction resistance, they are extremely weak films. 0 for example 100
When a film formed by vapor-depositing indium oxide with a thickness of 500 to 1000 people on a glass plate is immersed in hydrochloric acid with a concentration of 500% to 1000%.
In some cases, it dissolves away in 1 to 3 seconds and is completely useless. Indium oxide is an oxygen-deficient transparent conductive film and has an acceptor conductivity type. Among them, the bond between indium and oxygen is strong, so when ion bombardment is performed in a high-temperature atmosphere containing hydrogen or in plasma, the oxygen becomes Mg1L, and metallic iodium precipitates, resulting in devitrification. This becomes a big problem when using this indium oxide film as a semiconductor film for solar cells. This is because the amorphous silicon film currently used as a semiconductor film for solar cells is mainly produced by a plasma CVD method using hydrogen plasma. One possible solution to this problem is to form another layer as a blocking layer on top of the indium oxide film, but using oxides such as TiO2 or 5i02 will impede electrical conductivity. Although it has been proposed to use a tin oxide film having properties as this blocking layer (Japanese Unexamined Patent Publication No. 58-218704), it is not sufficient in terms of plasma reactivity resistance.

The present invention has been made to solve the above problems, and in the first invention, the surface of a transparent conductive film containing indium oxide or tin oxide as a main component. The present invention provides a transparent conductive film with improved corrosion resistance, characterized in that a protective film made of at least one or two or more of nitrides, carbides, and borides is formed on the film, and more specifically, indium oxide, indium oxide, and borides. Or a multi-component film made of at least one nitride of titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, niobium nitride, tantalum nitride, and chromium nitride, or a combination of two or more of these, on a transparent conductive film of tin oxide. A transparent conductive film overcoated with nitride is provided, and at least one of zirconium carbide, hafnium carbide, tantalum carbide, chromium carbide, silicon carbide, vanadium carbide, titanium carbide, and tungsten carbide is provided on the transparent conductive film. The present invention also provides a transparent conductive film overcoated with a multi-component carbide composed of one carbide or a combination of two or more of these carbides, and further includes zirconium boride, octunium boride, vanadium boride,
At least one of niobium boride, tantalum boride, and titanium boride
The present invention provides a transparent conductive film overcoated with a multi-element boride composed of two or more borides or a combination of two or more of these borides. Also, one or more nitrides, carbides 2
A transparent conductive film in combination with boride is also provided.

Further, in the second invention, nitride, carbide,
In a method for manufacturing a transparent conductive film that forms a protective film consisting of at least one or two or more borides, the protective film is coated with nitrogen, which is a constituent component, on the surface of a transparent conductive film whose main component is indium oxide or tin oxide. , at least one of carbon and boron
At least a portion of the surface of the transparent conductive film is nitrided, carbonized, or borated by emitting ions, and then the surface is protected with at least one or two or more of nitrides, carbides, and borides. The present invention provides a method for producing a transparent conductive film with improved corrosion resistance, which is characterized by forming a film.

The present invention will be explained in more detail below.

FIG. 1 is a drawing showing an embodiment of a transparent conductive film according to the present invention, where l is a substrate, 2 is a transparent conductive film whose main component is indium oxide or tin oxide, 3 is a protective film, and 4 is a Indicates an alkali barrier membrane.

Transparent IJ1 mainly composed of indium oxide in the present invention
As a conductive film, tin has a ratio of 0.5 to 3 relative to indium oxide.
It is a tin-doped indium oxide conductive film that contains 0% by weight, preferably about 5 to 10% by weight, and is imparted with electrical conductivity.Also, as a transparent conductive film whose main component is tin oxide, the tin-doped indium oxide is 0.1 to 5% by weight, preferably 0.3 to 5% by weight
A fluorine-doped tin oxide conductive film having 2% by weight and imparted with TL conductivity, or having antimony in an amount of 0.1 to 30% by weight, preferably 0.3 to 5% by weight, based on the tin oxide. , an antimony-doped tin oxide conductive film that has been given conductivity.

Such a tin-topped indium oxide conductive film can be manufactured by a sputtering method, a vacuum evaporation method, etc., and a fluorine-doped tin oxide conductive film can be manufactured by a CVD method (Chemical
The antimony-doped tin oxide conductive film can be manufactured by a CVD method, a sputtering method, a vacuum deposition method, a solution spray method, etc. be able to. The thickness of such a transparent conductive film is determined depending on the resistance value, optical properties, etc. to be obtained;
The range is about 2μ.

When obtaining a transparent conductive film with a lower resistance value.

An indium oxide-based conductive film is most suitable, and a film formed by reactive vapor deposition or reactive sputtering is preferred.

The substrate 1 forming the transparent conductive film 2 described above is selected from the viewpoints of transparency, optical properties, durability, and poetic characteristics of 'rH.
Alkali-containing glass plates, low alkali-containing glass plates, or alkali-free glass plates such as soda-lime silicate glass plates, aluminosilicate glass plates, borosilicate glass plates, rhidium aluminosilicate glass plates, quartz glass plates, etc. are most preferred, but if Depending on the case, a transparent plastic plate or a transparent plastic film may also be used.

In addition, with alkali-containing glass plates such as soda lime silicate glass plates, or glass plates with low alkali content, the alkaline components on the surface of the glass plates dissolve and cause haze (cloudiness) on the transparent conductive film formed thereon. 5i02 on the transparent conductive film forming side of the -F glass plate to prevent
, Al2O3.

It is preferable to form an alkali barrier film 4 mainly composed of an oxide such as Z'r(b).

In the present invention, at least one of nitrides, carbides, and borides is used to improve the corrosion resistance, especially plasma resistance, of a transparent conductive film containing Pf# indium or tin oxide as a main component.
A protective film consisting of one or more types is formed. Particularly preferably, the protective film is made of at least one or more of nitrides, carbides, and borides of metal elements of Groups A and H, metal elements of Group V B, or metal elements of Group B. Specifically, from a multi-component nitride composed of at least one nitride or a combination of two or more of titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, niobium nitride, tantalum nitride, and chromium nitride. Naruho 1aII! , or zirconium carbide, hafnium carbide, tantalum carbide, chromium carbide.

AS, which is composed of at least one carbide of silicon carbide, vanadium carbide, titanium carbide, and tungsten carbide, or a multi-component carbide composed of a combination of two or more of these, or zirconium boride, hafnium boride, and boron. A protective film made of at least one boride selected from vanadium chloride, niobium boride, tantalum boride, and titanium boride, or a multi-element boride composed of a combination of two or more of these, or the above-mentioned nitride or multi-element nitride. ill!
etc. are used.

These nitrides, carbides, and borides are in a state in which they simultaneously exhibit delocalization of outer shell electrons, which is a characteristic of the metallic state, and at least partial covalent bonding. Due to the latter function, it has wear resistance equal to or higher than that of oxides. Furthermore, since many of these non-oxide compounds have a large heat of formation, they are thought to have better chemical reaction resistance than oxides. In particular, regarding plasma reactivity resistance, it is thought that since these nitrides, carbides, and borides do not contain oxygen, they are difficult to change in response to reducing plasma containing H2, etc. This means that when these nitrides, carbides, and borides are used as an overcoat on a transparent conductive film when producing amorphous silicon for . In addition, since these nitrides, carbides, and borides have delocalized outer shell electrons as mentioned above, these act as conduction electrons and have a bulk value of 19-4 to 1.
This fact means that even if a film of these nitrides, carbides, or borides is overcoated on a transparent conductive film, its sheet resistance as a substrate for solar cells is low. This fact is advantageous compared to overcoating with oxides, etc., which have no conductivity at all; in other words, overcoating with nitrides, carbides, and borides It has excellent properties in terms of plasma reactivity resistance and resistance value. However, many of these nitrides, carbides, and borides have absorption in the visible region, and these films tend to be costly, so single films of these compounds are not used as transparent conductive films. The thickness of these nitride, carbide, and boride films, which are rarely used as nitrides, has properties close to those of bulk materials, considering that they improve the plasma reactivity resistance of the underlying transparent conductive film. If you can create a film with a transparent conductive film, there is no need to make it that thick.Although these films are absorbent, by making the film thinner, it is possible to increase the transmittance of the entire overcoated transparent conductive film to 85% or more. It is also possible to do so. The film thickness suitable for this purpose is:
As a nitride, the thickness is 100 Å or less, preferably 20 to 50 Å.
In the case of carbides, borides, etc., their absorption is larger than that of nitrides, so the number is preferably 40 Å or less, preferably 15 to 40.

The method for creating films of these nitrides, carbides, and borides does not need to be limited to specific methods such as vapor deposition and sputtering, but the film thickness shown above has effective plasma reactivity resistance. In order to achieve this, it is necessary to fabricate a film with properties as close to those of the bulk as possible, and for this purpose, sputtering, ion plating, plasma CVD
It is desirable to use a plasma-assisted film fabrication method such as the method, and it is believed that a dense 11 film close to the bulk material also serves as an effective diffusion barrier. Furthermore, if the underlying transparent conductive film is also produced by the CVD method, and the nitride, carbide, and boride films are also produced by the plasma CVD method, online production up to amorphous silicon is possible. Furthermore, if a film of these nitrides, carbides, or borides is directly formed on an oxide film such as indium oxide or tin oxide, a mixture layer of nitride and oxide is likely to be formed at the interface, and If the thickness of the mixture layer becomes too large.

In some cases, these layers come to the surface. Therefore, if the surface of the transparent conductive film is hit with nitrogen ions, carbon ions, boron ions, etc. in advance, it becomes easier to form a nitride, carbide, or boride layer thereon. Furthermore, if an ion gun with uniform energy is used for this treatment, the thickness of the interface layer can be adjusted to some extent easily.

Since the transparent conductive film of the present invention has high plasma reactivity resistance,
Each insertion/removal hole can be formed on such a transparent conductive film by a plasma CVD method. Therefore, such a transparent conductive film is most suitable as a transparent electrode for an amorphous solar cell.

In manufacturing an amorphous solar cell, for example, a P-type amorphous Si film, an i-type amorphous Si film, and an n-type amorphous 5illQ are sequentially formed on the transparent conductive film of the present invention formed on a glass substrate by plasma CVD. Manufactured by

"Example" The present invention will be explained in detail below.

Example 1 A metallic indium target containing 10at$ (atomic ratio %) of tin and a pure metallic zirconium sputtering target were placed on the cathode in the vacuum chamber of a sputtering device, respectively, and the surface was polished by ceria polishing and water washing. The washed 1.1 layer thick soda lime silicate glass substrate was placed in a vacuum chamber and heated with an oil diffusion pump at 5.OX 1O-
Evacuate to 5 Tart or less. Also, raise the substrate temperature to about 370℃.
Fill with mixed gas of B and set the vacuum level to 2.2 x 10-”
Torr, apply a DC voltage of 500V to the tin-indium alloy target, and perform press sputtering for 10 minutes. After press sputtering, open the shutter and sputter for 5 minutes.
The atmosphere in the vacuum chamber was completely replaced with a mixed gas of Ar':N2-95:5 without breaking the zero-order vacuum in which the I n203 conductive film containing tX was obtained, and the degree of vacuum was reduced to 5. OXl0-3T
After adjusting to art, ion bombardment was applied to the substrate surface by applying a DC voltage of 500 to 800 V to the electrode, followed by applying a DC voltage of 900 V to the zirconium target for 1
After press sputtering for 0 minutes, sputtering was performed for 4 seconds. The thickness of the overcoated zirconium nitride protective film was approximately 30 mm. The thus obtained transparent conductive film had a specific resistance of 2.5 Xl0-4Ω-0 and a transmittance of 80%, which was almost the same as that without overcoating.

When films were formed on these transparent conductive film substrates using an ordinary plasma CVD apparatus for producing p-type amorphous silicon, a film without any overcoat could only be obtained with a thickness of about 0.5 to IW. While devitrification was observed in the above cases, devitrification was not observed even at 1.5 to 2 W in the case where the zirconium nitride protective film of this example was overcoated.

Example 2 A titanium nitride target was set in place of the metallic zirconium target in Example 1, and a transparent conductive film of indium oxide containing 10 atl of tin (film thickness of approximately 4200 mm) was prepared in the same manner as in Example 1. The atmosphere inside was completely replaced with pure argon gas without breaking the zero-order vacuum obtained, and the degree of vacuum was reduced to 4. After adjusting to OX 1O-3 Torr, 2.8KV RF main voltage was applied to the titanium nitride target.
After press sputtering for 0 minutes, sputtering was performed for 3 seconds to form a titanium nitride film. The thickness of this protective film made of titanium nitride was about 30 mm. The transparent conductive film thus obtained has a specific resistance of 2.8X 10-4Ω・Cat and a transmittance of 7.
It was about 5 to 8 oz. When an amorphous silicon film was formed on this transparent conductive film in the same manner as in Example 1, the degree of devitrification at an OW of 1.5 to 2 was smaller than that in the case without any over-21. Ta.

Example 3 A zirconium boride target was set in place of the metal zirconium target in Example 1, and a transparent conductive film of indium oxide (film thickness approximately 4,200 mm) containing 10 at$ of tin was first prepared in the same manner as in Example 1. Completely replace the atmosphere inside with pure argon gas without breaking the zero-order vacuum, and reduce the degree of vacuum to 4. After adjusting to OX 101Torr,
2. For zirconium boride targets. After applying a constant RF voltage of OKV and press sputtering for 10 minutes, sputtering was performed for 3 seconds to form a zirconium boride film. The thickness of this protective film made of zirconium boride was approximately 30 mm. The transparent conductive film thus obtained has a specific resistance of 2.8×1
It was 0-4Ω·c+s, and the transmittance was about 75 to 80%. When an amorphous silicon film was formed on this transparent conductive film in the same manner as in Example 1, the result was 15 to 2
．． The degree of devitrification in OW was less than without any overcoat.

Example 4 A chromium carbide target was set in place of the metal zirconium target in Example 1, and a transparent conductive II (film thickness of about 4200 mm After completely replacing the atmosphere in the vacuum chamber with pure argon gas without breaking the zero-order vacuum, and adjusting the degree of vacuum to 4.0 x 10 Torr, a chromium carbide target of 2. After applying a constant RF voltage of OKV and press sputtering for 10 minutes, sputtering was performed for 3 seconds to form a chromium carbide. This protective film made of chromium carbide had a weight of about 40%. The transparent conductive film thus obtained had a specific resistance of 3.4×10 −3 Ω·cm and a transmittance of about 75 to 80%. When an amorphous silicon film was formed on this transparent conductive film in the same manner as in Example 1, the results were 1.5 to 2. The degree of devitrification in the OW was less than without any over-two-tone.

Example 5 A metal indium target containing 10 at$ of tin and a pure zirconium boride sputtering target were each set on the cathode in the vacuum chamber of a sputtering device. A silica-alkali Bayer film material soda lime silicate glass substrate (thickness: 1..1+u+) whose surface has been cleaned by ceria polishing and water washing is placed in a vacuum chamber, and 5. Evacuate to OX 1 (15 orr or less. Also, raise the substrate temperature to about 370°C. Next, fill the vacuum chamber with a mixed gas of Ar: 02 = 82:38, and increase the degree of vacuum to 2.2 x 10- 'Torr, apply a DC voltage of 500V to the tin-indium alloy target, and perform press sputtering for 10 minutes. After press sputtering, open the shutter and sputter for 5 minutes, and the film thickness is 42.
An I n203 conductive film containing 10atX of transparent tin was obtained.
Completely replace the gas with a mixed gas of r:N2=85:15, and reduce the degree of vacuum to 5. After adjusting to OX 1O-3Torr, 500~8
A DC voltage of 0.00V was applied to apply ion bombardment to the substrate surface, and then a DC voltage of 800V was applied to the zirconium boride target for press sputtering for 10 minutes, followed by snogging for 4 seconds. The thickness of the overcoated Wi-retaining film made of boronitride zirconium was about 30 mm.

The transparent conductive film thus obtained has a specific resistance of 2.5×1
0"4ΩΦC intestine, the transmittance was 80%, and there was almost no difference from that without O/(- coating.

When a film was formed on these transparent conductive film substrates using a normal P-type amorphous silicon production plasma CVD apparatus, the film without any oat coating had a power consumption of 0.5 to tW.
A film could only be obtained at a certain temperature, and devitrification was observed at higher temperatures.
No devitrification was observed in the coated membrane even at 1.5 to 2 W.

Example 6 A metallic tin target containing 1 oat$ of antimony and a pure metallic titanium target were each set on a cathode in a vacuum chamber. A saw lime silicate glass substrate with a thickness of 1.1 m, whose surface was cleaned by ceria polishing and water washing, was placed in a vacuum chamber, and an oil diffusion pump was used for 5. OX 1O-5
Exhaust to below Torr. Also, raise the substrate temperature to about 370°C. Next, the vacuum chamber was filled with Ar: 02=55:
Fill with 45% mixed gas and set the vacuum level to 8. OX to 3
Torr was set, a DC voltage of 500 V was applied to the antimony-tin alloy target, and Ll press sputtering was performed for 10 minutes.

After press sputtering, the shutter was opened and sputtering was performed for 5 minutes, and a transparent conductive film with a thickness of 2,700 mm was obtained.
Next, without breaking the vacuum, change the atmosphere in the vacuum chamber to Ar:M2=8
Completely replace the gas with a 0:20 mixed gas and reduce the degree of vacuum to 2.5.
After adjusting to X 1O-3Torr, D of 500-600v
Ion bombardment was applied to the substrate surface by applying pressure, followed by press sputtering for 10 minutes by applying a DC voltage of 900 V to the titanium target, followed by sputtering for 4 seconds. The thickness of the titanium protective film is thought to be about 30 people.The transparent conductive film thus obtained has a specific resistance of 6.3 Xl0-3Ω・c
m, transmittance was 70%, which was almost the same as that without overcoating. On these transparent conductive film substrates, ordinary p-type amorphous silicon production plasma CV is applied.
When a film was formed using the apparatus of D, a film without any overcoat could only be obtained at about 0.5 to 1W, and devitrification was observed above that, whereas the nitrided film of this example No devitrification was observed in the titanium overneated film even at 1.5 to 2 W.

Example 7 S formed by CVD method as alkali barrier film
A silica-alkali barrier film material soda-lime-silicate glass substrate (plate thickness 2.0 mm) with an iO,+ film (film thickness 800 mm) on the surface was thoroughly cleaned, and the glass substrate was then placed in a CVD device. I put it in. After heating the glass substrate to 500°C, tetramethyltin vapor (1,1×10=mol/min), oxygen (0,5Q/min) and bromotrifluoromethane (0,1(2/min)) were added to the surface of the glass substrate. About 3,000 people/minute were sprayed with nitrogen gas (2Q/minute) containing
1 minute. Next, the glass substrate with the transparent conductive film was placed in a vacuum chamber of a sputtering apparatus in which a titanium nitride sputtering target was set. and set the vacuum chamber at 1, OX 10 bTor.
After evacuation to r, a mixed gas of Ar:N2-95:5 was introduced, and the degree of vacuum was adjusted to 2.5 x 1O-3 Torr, and a voltage of 500 to 100 OV was applied to apply ion bombardment to the surface of the glass substrate. Next, 2. onto the titanium nitride target. After applying an RF main voltage of OKV and press sputtering for 10 minutes, sputtering was performed for 3 seconds. The thickness of the overcoated titanium nitride film was approximately 30 mm. The transparent conductive film thus obtained has a specific resistance of 8.5 Xl0-4Ω・c
m, transmittance was 70%, which was almost unchanged from that without overcoating.

When films were formed on these transparent conductive film substrates using an ordinary plasma CVD apparatus for manufacturing p-type amorphous silicon, films without any overcoat could only be obtained at a power consumption of about 0.5 to tW. In contrast to the above, devitrification was observed in the film overcoated with titanium nitride devitrification on the wood flow side, even at 1.5 to 2 W, no devitrification was observed.

"Effects of the Invention" As described above, according to the present invention, it is possible to significantly improve the plasma reactivity resistance of a transparent TRT conductive film, especially an indium oxide film, in a reducing atmosphere. ,!!It is very advantageous to use this film composition as a substrate for a solar cell with 1ffi.

Furthermore, since the nitride/carbide/boride film according to the present invention is a very hard film, it is possible to use this film as a protective layer for so-called uneven structure films for solar cells. can.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1.2 shows a cross-sectional view for explaining the transparent conductive film according to the present invention. l:2! body, 2: transparent conductive film, 3: protective film. 4: Alkaline barrier film]!

Claims (8)

[Claims] (1) Corrosion resistance characterized by forming a protective film made of at least one or more of nitrides, carbides, and borides on the surface of a transparent conductive film whose main component is indium oxide or tin oxide. improved transparent conductive film. (2) The protective film is made of at least one nitride of titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, niobium nitride, tantalum nitride, and chromium nitride, or a multi-component nitride composed of a combination of two or more of these nitrides. The transparent conductive film according to claim 1, characterized in that: (3) The thickness of the protective film made of nitride or multi-component nitride is 1
The transparent conductive film according to claim 2, characterized in that it has a thickness of 0 to 100 Å, preferably 20 to 50 Å. (4) The protective film is made of zirconium carbide, hafnium carbide, tantalum carbide, chromium carbide, silicon carbide, vanadium carbide,
The transparent conductive film according to claim 1, characterized in that it is made of a carbide of at least one of titanium carbide and tungsten carbide, or a multi-component carbide composed of a combination of two or more thereof. (5) The thickness of the protective film made of carbide or multi-component carbide is 1
The transparent conductive film according to claim 4, characterized in that it has a thickness of 0 to 100 Å, preferably 15 to 40 Å. (6) Multi-component boron in which the protective film is composed of at least one boride selected from zirconium boride, hafnium boride, vanadium boride, niobium boride, tantalum boride, and titanium boride, or a combination of two or more of these borides. The transparent conductive film according to claim 1, characterized in that it is made of a compound. (7) The thickness of the protective film made of boride or multi-boride is 1
The transparent conductive film according to claim 6, characterized in that it has a thickness of 0 to 100 Å, preferably 15 to 40 Å. (8) In a method for producing a transparent conductive film, which forms a protective film made of at least one or more of nitrides, carbides, and borides on the surface of a transparent conductive film whose main component is indium oxide or tin oxide. , indium oxide, or tin oxide as a main component, at least one of nitrogen, carbon, and boron ions, which are constituent components of the protective film, is emitted onto the surface of at least one of the transparent conductive films. Part nitrided,
A method for producing a transparent conductive film with improved corrosion resistance, characterized by carbonizing or borating, and then forming a protective film made of at least one or two or more of nitrides, carbides, and borides on the surface. .