JPH01189815A - Manufacture of transparent conductive film - Google Patents

Abstract

PURPOSE:To enhance light transmittance even at a low temperature and reduce resistivity by spraying a heated base plate with spray liquid having a specific composition so as to form a transparent conductive film by the effect of thermal decomposition reaction. CONSTITUTION:Spray liquid 12 is prepared with aqueous solution or alcoholic solution including raw material for forming a transparent conductive film (for example, stannic chloride) and ammonium halide (for example, ammonium fluoride) or hydrogen halide. A base plate 2a (for example, glass applied with SiO2 as an undercoat) is mounted on a hot plate 11 so as to be heated (up to 400 deg.C). And next, a compressor 16 is operated so that a spray device 14 sprays the base plate 2a with the spray liquid, thereby the transparent conductive film (fluorine doped stannic oxide thin film) 2b is formed on the base plate 2a by the effect of thermal decomposition reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) The present invention relates to a method for producing a transparent conductive film, and particularly to a method for producing a transparent conductive film using a spray pyrolysis method.

′ of ゛bi. In recent years, there has been an increasing need to form thin films of metal oxides such as tin oxide and indium oxide on substrates such as glass in semiconductor devices, liquid crystal display devices, and other applications.

As shown in FIG. 3, for example, an amorphous silicon solar cell 1 is formed by laminating an α-3T film 4 and a back metal 6 on a substrate 2 with a transparent electrode. Therefore, the manufacturing process is as follows: (1) A transparent conductive film with a thickness of about 0.2 to 1.0 gm is placed on the glass substrate 2a. 12b to form a transparent electrode-attached substrate 2, (2) a step of forming amorphous silicon MLα-3ifi4 on the transparent electrode-attached substrate 2 by plasma CVD method, (3) Spar 2 evening method. Or use vacuum evaporation method A! l to 0
, a step of forming a back metal 6 on the α-3i film 4 to a thickness of about 21 Lm.

Consists of.

In the transparent electrode forming step (1), it has conventionally been common to form, for example, a tin oxide (S nO2) film on the glass substrate 2a by a chemical vapor deposition (CVD) method or a spray pyrolysis method. Ta.

The chemical vapor deposition (CVD) method is a reaction at normal pressure, and a continuous process using a conveyor furnace is possible, making it easy to mass produce and uniformly forming a film over a large area. However, like the sputtering method, it has the problem that it is difficult to form a textured structure.

On the other hand, since the spray pyrolysis method described in L is a process under normal pressure like the CVD method, it is possible to produce in large quantities, and it is also possible to easily form a textured structure. When fabricated, etc., CVD
It has been found that higher conversion efficiency can be achieved by using a substrate manufactured by this method than by the conventional method.

However, according to research experiments conducted by the present inventors, a halogen-doped transparent conductive film formed by the conventional spray pyrolysis method has a transmittance of 80% or more and a specific resistance of 3 X l O- at high temperatures of 500°C or higher. A film with a thickness of about 1 Ωcm can be formed, but the light transmittance is as low as about 60% at temperatures below 400°C, and the specific resistance is as large as 5 x l O-100 m, so 40
It has been found that the production cost of an amorphous solar cell substrate having sufficient conversion efficiency can be reduced by increasing the light transmittance and decreasing the specific resistance at a low temperature of 0° C. or lower.

Furthermore, the conventional spray pyrolysis method has a slow film deposition rate, and improvements in productivity have been desired.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a transparent conductive film using a spray pyrolysis method that can form a transparent conductive film with high light transmittance and low specific resistance at low temperatures.

Another object of the present invention is to provide a method for producing a transparent conductive film by spray pyrolysis, which has a high deposition rate and improved productivity.

The above objects are achieved by the present invention. In summary, the present invention involves spraying a spray solution prepared by adding an oxidizing agent to a water or alcohol solution of a raw material for forming a transparent conductive film and ammonium halide or hydrogen halide onto a heated substrate, and causing a thermal decomposition reaction. This is a method for producing a transparent conductive film, characterized in that a transparent conductive film is formed on the substrate. The raw material for forming the transparent conductive film is tin, indium or zinc, and the oxidizing agent is hydrogen peroxide (HzOz) or an oxoacid such as nitrous acid (HNOl), nitric acid (HNOl), etc.
3), permanganic acid (8Mn04), chromic acid (Hz
Cr04), perchloric acid (HCl2), chloric acid (HC
03), chlorous acid (HClOz), hypochlorous acid ()i
Cl 2 O) and its salts are preferably used. Particularly preferred are hydrogen peroxide, permanganic acid, or perchloric acid, which have a strong oxidizing effect.

In the present invention, when producing a transparent conductive film made of halogen-doped tin oxide, indium oxide, zinc oxide, etc., the oxidizing agent as described above is added to the spray solution to increase the oxidation degree of the film and reduce the dopant concentration. It has been discovered that the transmittance of a transparent conductive film can be increased. It has also been found that by adding an oxidizing agent to the spray solution in this manner, the carrier concentration in the transparent conductive film decreases, but the mobility increases and the specific resistance decreases.

More specifically, the transparent conductive film obtained by the conventional spray pyrolysis method has a transmittance of about 60% and a resistivity of at least 5×10 when the film-forming temperature is about 400°C and the thickness is 4000 mm. According to the present invention, the thickness is 7 Ωcm or more at the same processing time and the same film forming temperature.
The thickness can be increased to 300 mm, and the transmittance can be 80% or more, and the specific resistance can be 4.0 x 10' Ωcm or less.

Furthermore, as can be understood from the above explanation, the deposition rate is greatly increased to more than 1Os/S compared to the conventional 6.0 people/S. It is thought that the reason why the deposition rate is increased in this way is that the oxidation reaction of the oxidizing agent added to the spray solution contributes to the acceleration of the deposition rate.

Moreover, the substrates conventionally provided in the spray pyrolysis method are 500
Although it was necessary to maintain the substrate temperature between 300 and 600 degrees Celsius, in the present invention, an extremely good conductive film could be formed by maintaining the substrate temperature between 300 and 400 degrees Celsius. Achieving a thermal decomposition reaction by lowering the substrate temperature has the advantage of reducing the production cost of a substrate with a transparent conductive electrode and suppressing the diffusion of alkali metals into a transparent conductive film when soda lime glass is used. This is also believed to be due to the oxidation reaction of the oxidizing agent added to the spray solution.

Although the present invention can be implemented in various devices, typical examples will be explained with reference to the drawings.

FIG. 1 shows a pneumatic spray device 10. In this embodiment, a hot plate 1 heated by a heater etc.
1 is provided, and a substrate 2a such as a glass plate is placed on the hot plate 11. The glass plate 2
According to the present invention, a is 500°C when no oxidizing agent is added.
Compared to the high temperature of ~650℃, it is hot play) 1
1 at 300°C to 450°C, preferably 350 to 400°C
It is heated to a low temperature such as °C.

On the other hand, a spray liquid 12 containing a transparent conductive material such as tin, indium, or zinc is deposited on the substrate 2a.
is fed from the tank 13 to the nozzle 15 of the spray 5at4. The spray device 14 includes a compressor 16.
compressed air is supplied from the nozzle 15, and the spray liquid 1 is
Control means 17 controls the pressure and flow rate of the compressed air from the compressor 16, which sprays 2 onto the substrate 2a.
The particle size and flow rate of the spray are appropriately selected by controlling the . Generally, spray equipment W114 includes kelp L/
Compressed air of approximately 0.5 kg/crn''G is supplied from the 11 sir 16, and a spray liquid atomizer having a spray particle diameter of 10 to 10,001 m is supplied from the nozzle 15 with a hole diameter of 0.5 mm at a flow rate of 0.1 It is repeatedly sprayed onto the substrate 2a at predetermined time intervals at ~1.0ml/sec.

FIG. 2 illustrates another device for carrying out the present invention.9 The device 20 of this embodiment is an ultrasonic injection device.0 In this embodiment, the same device as described in connection with FIG. A hot plate (21) heated by a heater or the like is provided on the hot plate (21).

For example, a substrate 2a such as a glass plate is placed.

The glass plate 2a is similarly heated at 300 mm on the hot plate 21.
In this embodiment, the hot plate 21 and the substrate 2a are placed in a closed container 22.

Appropriate exhaust holes (not shown) and the like are formed in the closed container 22.

On the other hand, a spray liquid 23 containing a transparent conductive forming material to be formed into a film on the substrate 2a is fed from the tank 24 to the ultrasonic spraying device 25 via the feeding pump 26. The ultrasonic injection device 25 is ultrasonically vibrated by the ultrasonic vibration generating means 100. Further, entrained gas (carrier gas) is supplied into the airtight container 22 from a compressor 27 via a flow meter 28.
1 Normally compressed air is supplied.

Generally, the ultrasonic jetting device 25 includes the ultrasonic vibration generating means 10.
0 output lO~soow, frequency 20~100KH
It is vibrated by the ultrasonic waves of z, and the spray liquid 2 is released from the tank 24.
According to this example, the spray liquid has a particle size of about 0.1 to 1
Mist droplets with approximately uniform particle size are obtained within a range of 0.4 m. Further, in this embodiment, compressed air of, for example, about 0.5 kg/crn''G is jetted onto the heating substrate 2a from the compressor 27 at a rate of about 21/min (standard condition).a The fine particles of the spray liquid 23 atomized by the sonic spray device!125 are directly heated to the substrate 2a.
Although it is possible to spray onto the substrate 2b, as described above, it is more uniform to spray the fine particles of the spray liquid atomized by the ultrasonic spray bag W25 onto the substrate 2b together with a carrier gas such as air. film formation is achieved.

As the ultrasonic jetting device 25 used in the present invention, for example, the one described in Japanese Patent Application No. 77572/1984, or any other device well known to those skilled in the art can be used.

In each of the above examples, the spray liquid contains tin(II) fluoride (SnFz) mixed as a raw material for forming a transparent conductive film.
), tin 7y (ff) (SmF3), tin chloride (
■) (SnC exchange), tin chloride (IT) (Sncu+
), tin(II) bromide (S nBrz), tin bromide (IT) (S nB r4 ), tin iodide (
II) (SnIz), tin iodide (17) (SnI
4), tin nitrate (Iff) (S n (NO3) now), indium (III) fluoride (I n Fl
), indium (I) chloride (I ncjL), indium (III) chloride (I nc13), indium (m) bromide (InBr3), indium iodide (Il
l) (In13), indium nitrate (m) (I n
(NO x ) and ammonium fluoride or hydrogen fluoride in an aqueous solution or alcohol droplets, and hydrogen peroxide (Hz 02) as an oxidizing agent, or, for example, nitrous acid (HNOz), nitric acid (HNO, ), permanganic acid. (HMnO+), chromic acid (Hz Cro+), chloric acid (HCJ103), hypochlorous acid (HC10), and other oxoacids and their salts are preferably added. At this time, the amount of tin chloride (Sn0 4) used as a raw material for forming a transparent conductive film is 0.01-1.00 mol/ml, ammonium fluoride is 0.01-1.000 mol/ml, and the oxidizing agent is is 1-100% by volume, preferably 3-100%
8% added.

Next, an example will be described in which the method according to the present invention is applied to the production of a tin oxide film substrate used in a semiconductor device.

Example 1 A transparent conductive film was manufactured using a manufacturing apparatus having the configuration shown in FIG. As the substrate 2a, a 10 cm square ordinary glass with a 5 iOz undercoat on the surface was used, and it was placed on a hot plate 11 and heated to a surface temperature of 400°C.

The spray solution contains tin chloride (SnC) in ethanol.
5H2O) at 0.1 mol/1. Ammonium fluoride (N
H4F) to 0.1 mol/liter, hydrogen peroxide solution ()iz
An aqueous solution containing about 5% by volume of O (concentration: about 35%) was prepared.

Next, the compressor 16 is operated to supply compressed air of approximately 0.5 kg/cm''q to the spray device 14, and the sprayed particle size is 10 to 1 from the nozzle 15 with a hole diameter of 0.5 mm.
000An spray liquid atomizer with a flow rate of 0.3m
It was sprayed onto the substrate 2al- at a rate of 100 min/sec.

This spraying cycle was repeated 10 times in which the spraying was continued for about 10 seconds and then stopped for 10 seconds.

substrate? Fu, L-doped tin oxide thin fi2b on a is about 8
It was formed with a thickness of 0.000 mm. The transmittance of the thin film is 400
It is about 80% in the visible range of ~800 nm, and the specific resistance is about 3
The length was 10 cm.

Comparative Example 1 A transparent conductive film was produced in the same manner as in Example 1, using the same spray liquid as in Example 1 except that it did not contain any hydrogen peroxide solution.

Fluorine-doped tin oxide thin film 112 produced in this way
b had a thickness of only about 5000 mm, the transmittance of the thin film was about 60% in the visible range from 400 to 800 nm, and the resistivity was about 5 x 10' Ωcm.

Example 2 A transparent conductive film was manufactured using a manufacturing apparatus having the configuration shown in FIG. As the substrate 2a, a 10 cm square ordinary glass with a 5 iOz undercoat on the surface was used, and it was placed on a hot plate 11 and heated to a surface temperature of 400°C.

The same spray solution as in Example 1 was prepared. The spray liquid is transferred to the ultrasonic spray device 25 by the pump 26 at a rate of approximately 2 mu/m.
It was supplied at a flow rate of in. The ultrasonic generating means 100 was operated to atomize the spray liquid using ultrasonic waves with an output of 100 W and a frequency of 28 Kl (z) to obtain a spray having a substantially uniform particle size of lβm.Furthermore, the compressor 27 was operated. about 0
．． Compressed air of 5 kg/CG was jetted onto the heating substrate 2a at a rate of about 2 JL/m1n (standard state). This spraying was continued for about 12 minutes.

A fluorine-doped tin oxide thin film 2b is formed on the substrate 2a with a thickness of approximately 750 mm.
It was formed with a thickness of 0. The transmittance of the thin film is 400-8
It is about 80% in the visible range of 00 nm, and the specific resistance is about 4
It was 10-3 Ωcm.

FIG. 4 shows the X-ray diffraction pattern of the transparent conductive film produced in this example.

Comparative Example 2 A transparent conductive film was produced in the same manner as in Example 2, using the same spray liquid as in Example 2 except that it did not contain any hydrogen peroxide solution.

Fluorine-doped tin oxide thin film 2b produced in this way
had a thickness of only about 4000 nm, the transmittance of the thin film was about 63% in the visible range from 400 to 800 nm, and the resistivity was about 6 x 10-3 ΩCm.

The X-ray diffraction pattern of the transparent conductive film produced in this comparative example is shown in Figure 5. Comparative examination of Figures 4 and 5 reveals that the addition of an oxidizing agent reduces the amount of fluorine that replaces oxygen in the film. It can be seen that the donor is dominated by oxygen vacancies.

Left "LD" Ll As explained above, according to the method for producing a transparent conductive film according to the present invention, a transparent conductive film with high light transmittance and low specific resistance can be formed at a low temperature of 400° C. or lower, and further, It has the advantage of fast deposition rate and improved productivity.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic cross-sectional views illustrating an embodiment of an apparatus for carrying out the method for producing a transparent conductive film according to the present invention. FIG. 3 is a cross-sectional view of an amorphous silicon solar cell. FIG. 4 is an xm diffraction pattern of an s film formed by the method for producing a transparent conductive film according to the present invention. FIG. 5 is an X-ray diffraction pattern of a thin film formed by a conventional transparent conductive film manufacturing method. 2a: Substrate 2b: Transparent conductive film 11.21: Hot plate 12.23 Varnish spray liquid 14 Varnish spray device 16: Compressor 25: Ultrasonic spray device 100: Ultrasonic vibration generating means -2 Fig. 4

Claims (1)

[Scope of Claims] 1) A spray solution prepared by adding an oxidizing agent to an aqueous or alcoholic solution containing a raw material for forming a transparent conductive film and ammonium halide or hydrogen halide is sprayed onto a heated substrate, and then heated. A method for producing a transparent conductive film, which comprises forming a transparent conductive film on the substrate by a decomposition reaction. 2) The manufacturing method according to claim 1, wherein the raw material for forming the transparent conductive film is a halide, nitrate, or carbonate of tin, indium, or zinc. 3) The production method according to claim 1 or 2, wherein the oxidizing agent is hydrogen peroxide (H_2O_2) or an oxoacid or a salt thereof.