WO1992018990A1

WO1992018990A1 - Method for manufacturing transparent conductive film

Info

Publication number: WO1992018990A1
Application number: PCT/JP1992/000455
Authority: WO
Inventors: Tokio Nakada
Original assignee: Tokio Nakada
Priority date: 1991-04-10
Filing date: 1992-04-10
Publication date: 1992-10-29
Also published as: JP3325268B2

Abstract

A film forming method capable of forming a transparent conductive film whose surface has a texture structure by a sputtering method. By using a target (40) of an oxide, which has at least the composition of the objective film as its component, and by sputtering the target in a gas atmosphere containing OH, a transparent conductive film is formed on a base (50).

Description

--書明方法方法製造製造製造製造

【Technical field】

The present invention relates to a method for manufacturing a transparent conductive film having a surface texture structure, and more particularly to a method for manufacturing a transparent conductive film suitable for a configuration of a photoelectric conversion device by sputtering.

[Background Art]

And a transparent conductive film, conventionally, S n 0 ₂ system, _{_{(eg, I n 2 O 3: S}} n O 2 (1 0 wt%), ITO) I n 2 0 3 system and the like are known . Recently, low-cost ZnO-based thin films have attracted attention as a transparent conductive film replacing these thin films.

Although it is a matter of course that the requirements for using a transparent conductive film in a photoelectric conversion device are low resistance and high transmittance, the film surface is also incident due to the light confinement effect. It is important to have a surface texture structure that allows effective use of light and to have high transmittance in the near-infrared region. Also, it is desired that the resistive resistance be as low as possible (<10 Ω / port).

By the way, a transparent conductive film having a surface texture structure is conventionally known by a chemical vapor deposition (CVD) method.

That is, for the S n 〇 _{2, "M. Mizuhashi et al:} ... Jpn J. Appl phys 27 (11) (1988) 2053 - 2061" to, H ₂ _{0 / S n C l 4,} CH 3 OH / H z O, and as a raw material HFZS n C and 0 ₂ / S i H _4, Ri by the CVD method, S n 0 _2: Example for formation of the F Is described. Also,: the "H. IIDA et al. IEEE Electron Device Lett EDL 4 No.5 (1983) 157", using the same raw material and the above documents, by optimizing the substrate temperature, CVD method Nyo Li S n 0 ₂ Is described.

In addition, for the Z n 0 ·· B,: to "A. Yamada et al Tech nical Digest of the International PVSEC- 5, Kyoto, Jap an (1990) 1033", Jechirujinku: the H ₂ 0 as a raw material, dopant An example is described in which B is used as a substrate and a film is formed by MOCVD.

Meanwhile, the S n 0 ₂ is resistant problem of poor to hydrogen plasma. On the other hand, ZnO has good resistance to hydrogen plasma. Therefore, the Amorufu § scan S i film, when forming on S n 0 ₂ by the plasma CVD method is considered to be Koti ring of Z n O film on S n 0 _2.

However, when a transparent conductive film is produced by the above-mentioned MOCVD method, there is a problem that a large amount of toxic gas is often used as a main raw material.

On the other hand, there is a sputtering method as a method for producing a transparent conductive film that does not use a toxic gas as a main raw material. However, conventionally, a transparent conductive film having a surface texture structure has not been obtained by the sputtering method.

In addition, the transparent conductive ZnO: B film obtained by the MOCVD method described above has a problem that the change with time is large. For example, This film is 200 in air. If left for 10 hours in the state of C, the resistance value changes to about twice the initial value. In the case of solar batteries, environmental resistance is a major issue, and this is also an issue to be solved.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a method for manufacturing a transparent conductive film capable of forming a transparent conductive film having a surface texture structure by a sputtering method.

According to one embodiment of the present invention, in order to achieve the above object, in a method for producing a transparent conductive film on a substrate by sputtering, at least a part of the composition of a target film is used as a component. A method for producing a transparent conductive film is provided, wherein the target is sputtered in a gas atmosphere containing OH to form a transparent conductive film.

In the present invention, the target transparent conductive film is, for example, Zn0,

Zn0: X (X is one of Al, Si, B, F, and CI)

At least one),

S n O ₂

S n 0 ₂ Y (Y is at least one of F and C 1)

I n ₂ O

I n ₂₀ 0 3: Z (Z is at least one of S n 0 ₂ and S n

1)

Is mentioned. OH in the gas atmosphere containing OH is generated by decomposing a compound having an OH group. As the compound having an OH group, for example, at least one of water and alcohol can be used. These can be used alone or as a mixture with an inert gas such as Ar.

In addition, a compound gas containing an unblendable substance to be doped can be mixed into the sputtering gas.

As a target for forming a film of the target substance described above, a target composed of the same substance as the target substance can be used. In addition, reactive sputtering is performed by introducing metals such as n, Sn, and InSn, which are mixed or not mixed with unbleached substances, and introducing oxygen in addition to other gases. You can also do

Further, the present invention uses an oxide-based target having at least the composition of a target film as a component, and performs sputtering in a gas atmosphere containing OH to form an oxide on a substrate. A system transparent conductive film may be formed.

According to another aspect of the present invention, there is provided a method of manufacturing an oxide-based transparent conductive film on a substrate by sputtering, wherein the oxide-based transparent conductive film has at least a target film composition as a component. A method for producing a transparent conductive film is provided, wherein sputtering is performed using a target and a gas containing B ₂ _Hε .

As the gas containing B ₂ Hs, for example, a gas obtained by diluting B ₂ Hs with Ar is used.

In this case, as the target, for example, ZnO is used. It is.

When a transparent conductive film is formed according to the present invention, a texture structure is formed on the surface of the film. This generation mechanism is not always clear, but can be considered as follows.

That is, in the case of sputtering, OH such as from H ₂ 0 in the plasma, there is the active species, such as H, 0, is considered to have influenced your Keru growth mode to film formation initial.

OH in the atmosphere is generated by decomposing compounds having OH groups. For example, water and alcohol. In other words, for example, when steam is mixed with Ar and supplied, it is decomposed in plasma and OH is generated. Further, 〇 H in the atmosphere, for example, and H which is generated by decomposing a gas containing hydrogen such as B ₂ H _e, is made fresh from 0 Metropolitan separated from the oxide-based target.

In the present invention, since the film is formed by sputtering, not only is toxic gas not used as a raw material, but also it is easy to form a large-area transparent conductive film.

When the surface texture structure thus formed is observed with a scanning electron microscope (SEM), it can be seen that many pyramid-shaped protrusions such as quadrangular pyramids are formed. When light is incident on a film having such a texture structure on the surface, much light returns to the incident side due to reflection and refraction on the slope of the pyramid. When a photoelectric conversion element such as a solar cell is formed, the incident light is effectively taken into the element, improving the light utilization rate. I do.

As described above, according to the present invention, a transparent conductive film having a surface texture structure can be formed by sputtering.

[Single description of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a DC magnetron sputtering apparatus preferably used for producing a transparent conductive film of the present invention.

Figure 2 shows the wavelength dependence of the total transmittance Td, turbidity M (= Td-T / Td; T is the normal incidence transmittance), and diffuse reflectance R of the sample thin film of Example 1. Graph showing results.

FIG. 3 is a graph showing the wavelength dependence of the total transmittance T d, turbidity M and diffuse reflectance R of the sample of Example 2.

FIG. 4 is a graph showing the wavelength dependence of the total transmittance Td, turbidity M, and diffuse reflectance R of the sample of Example 3 (3-a, 3-b, 3-c).

FIG. 5 is a graph showing the wavelength dependence of the total transmittance T d, turbidity, and diffuse reflectance R of the sample of Example 4.

Figure 6 is a graph showing the substrate temperature dependence of resistivity, mobility, and carrier concentration for the sample of Example 3 (3-a, 3-b, 3-c).

7A is a photograph showing the observation result of the sample of Comparative Example 4 by SEM, and FIG. 7B is a photograph showing the observation result of the sample surface of Example 5 by SEM.

FIG. 8 shows the results for the samples of Examples 5 to 7 and Comparative Examples 4 and 5. A graph showing the wavelength dependence of the total transmittance Td.

FIG. 9 is a graph showing the dependence of resistivity, mobility, and carrier concentration on the doping amount of B ₂ H ₆ for each of the samples of Examples 5 to 7 and Comparative Example 4.

10A is a photograph showing the observation result of the sample of Comparative Example 6 by SEM, and FIG. 10B is a photograph showing the observation result of the sample surface of Example 9 by SEM.

FIG. 11 is a graph showing the dependence of resistivity, mobility, and carrier concentration on the doping amount of B ₂ H ₆ for each of the samples of Examples 8 to 13 and Comparative Example 6.

【Example】

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following examples, film formation is performed using the DC magnetron sputtering apparatus shown in FIG. The DC magnetron sputtering device shown in FIG. 1 has a vacuum chamber 1 that is evacuated by an exhaust system 2 having an exhaust device (not shown), and a gas chamber for introducing gas into the vacuum chamber 1. The system includes a gas introduction system 3, a target electrode 4, a substrate electrode 5, and a power supply device (not shown).

The gas introduction system 3 is connected to an Ar gas supply source (not shown) to regulate the introduction amount of Ar gas and a flow control valve 31 for controlling the introduction amount of the mixture of the impurity doping gas and the texture structure forming gas. It is provided with a flow control valve 32 for adjusting the flow rate, a flow control valve 33 for adjusting the introduction amount of the mixed gas, and a gas inlet 34 to which the gas introduction system 3 is connected. The target gas May be introduced in advance. For example, as shown in the examples below, B ₂ previously diluted with Ar

It is possible to use H _e.

Target electrode 4 is connected to target 40 and this target

A water-cooled electrode 41 for holding 40 and applying a voltage thereto, and a magnetron magnet arranged in the water-cooled electrode 41

4 2 and a target shield 43.

The substrate electrode 5 includes a plate 51 on which the substrate 50 is placed, a plate holder 52 for holding the plate 51, and a heater 53 for heating the substrate 50. As the substrate, glass, quartz or the like is used. In the present embodiment, the distance between the substrate 50 and the target 40 is 35 πιπι in Examples 1 to 4 and Comparative Examples 1 and 2. Further, in Example 5 and later, and in Comparative Example 4 and later, 5 Omm is set.

For example, a disk having a diameter of 10 cm is used as the target 40. Is a substance, Z n O (9 9 9 wt.) Or Z n O: sintered body of A 1 (2 wt% A 1 2 0 3) is used. Is a the introduced gas, and A r, and H ₃ B 0 ₃ or B ₂ 0 ₃ for doping, is used and H ₂ 0 or CH ₃ 0H for textured product. Further, a mixed gas of A r and beta ₂ Eta _epsilon is Ru is used.

Next, specific examples of the present invention will be described in detail. Production of ZnO thin film>

(Example 1)

Use 99.9% ZnO as a target and Data Gas pressure (the working gas ^{pressure) 5 X 1 0 _ 3 Torr} , under the conditions of a substrate temperature of 4 0 0, the spatter gas and H ₂ 0, by performing 1 hour spatter, on a glass substrate 1 A thin ZnO film was formed with a thickness of 5 Km.

(Comparative Example 1)

Sputtering was carried out under the same conditions as in Example 1 except that the sputtering gas was Ar, and a ZnO thin film having a thickness of 1.5 m was formed on a glass substrate.

(Comparative Example 2)

Spatter gas _{A r + H 2 (1:} 1) and the other was is performed spatter under the same conditions as the actual施例1, Z n O with a thickness of 1 5 m on a glass substrate. A thin film was formed.

(Comparative Example 3)

Spatter gas _{A r + 0 2 (1:} 1) and the other was is performed spatter under the same conditions as the actual施例1, Z n O with a thickness of 1 5 m on a glass substrate. A thin film was formed.

When the surface of each ZnO thin film manufactured as described above was observed by SEM, the length of one side of the bottom surface of the sample of Example 1 was about 0.5 m. Many pyramid-shaped protrusions having a height of about 0.5 ^ m were formed, confirming that a surface texture structure was generated. On the other hand, in Comparative Examples 1, 2, and 3, all had slight surface irregularities and no texture structure was formed.

Figure 2 shows the total transmittance T d and turbidity M of the sample thin film of Example 1. (= Td-T / Td; T is the transmittance at normal incidence) and the measurement results of the wavelength dependence of the diffuse reflectance R are shown. As shown in FIG. 2, (shown by a solid line in this figure) sample was deposited by introducing Eta ₂ 0 is compared with the sample of Comparative Example was sputtered using A r 1 (indicated by a broken line in this figure) Thus, it can be seen that the turbidity is promoted as the turbidity M increases. This turbidity corresponds to diffuse reflection in accordance with the surface unevenness, and its magnitude can serve as one index for determining whether or not it has a texture structure.

ぐ Ζ Ο 製作: Β Thin film fabrication 1>

(Example 2)

Using a target of 99.9% of 鈍 ηΟ as the target, the sputtering gas was changed to boric acid solution under the conditions of a sputtering gas pressure (operating gas pressure) of 5 X 10 ^_3 Torr and a substrate temperature of 400. H ₃ B 0 ₃ + H ₂ 0) solution gas and Ar are mixed in a one-to-one ratio and sputtered for 1 hour to form a film having a thickness of about 1.5 μm on a glass substrate. Then, a ZII0: B thin film was formed.

(Example 3)

A sputtering gas, a solution gas and Alpha iota »and mixed gas in a one-to-one borate methyl alcohol _{_{(H 3 B 0 3 + CH}} a OH), the substrate temperature, room temperature (Example 3 - a) , At 300 ° C. (Example 3—b) and at 400 ° C. (Example 3—c), the sputtering was performed under the same conditions as in Example 2 above, A Zn0 ·· B thin film was formed with a thickness of 1.5 m.

(Example 4)

The sputtering gas, solution gas boric acid + H ₂ 0 + CH ₃ OH and A Sputtering was performed under the same conditions as in Example 2 except that r and were mixed in a one-to-one ratio, and a ZnO: B thin film was formed on a glass substrate to a thickness of about 1.5 jam. Was formed.

<Zn0: Evaluation of B thin film 1>

When the surface of each of the ZnO: B thin films fabricated as described above was observed by SEM, it was observed that a texture structure was formed in each of the samples. In particular, the surface texture of the sample of Example 2 was remarkable.

3 to 5 show the wavelength dependence of the total transmittance T d, turbidity M and diffuse reflectance R for each of the samples of Examples 2 to 4. FIG. 6 shows the substrate temperature dependence of resistivity, mobility, and carrier concentration for the sample of Example 3.

As shown in FIGS. 3 to 5, the turbidity indicating the degree of white turbidity was highest when a mixed solution of boric acid water and alcohol was used, and reached 70% or more at 600 nm. In addition, as shown in Fig. 4, the turbidity increased with the substrate temperature. The transmittance in the near-infrared region decreases with decreasing substrate temperature, suggesting that the lower the temperature, the higher the boron concentration doped in the film.

This is also reflected in the electrical characteristics shown in FIG. 6, where the lower the temperature, the lower the resistivity and the higher the carrier concentration.

<Zn0: Production of B thin film 2>

(Example 5)

Using a target of 99.9% Zn n as the target, -2

Tag gas pressure (operating gas pressure) 2 X 10 Torr, substrate temperature 2000, sputtering gas used to dilute 积₂ Η ₆ with Ar 得₂ Η _Ε concentration 1 Sputtering was performed for 1 hour using a gas of 0.0 vol% to form a Zn0: B thin film with a thickness of about 2 ιιί on a glass substrate.

(Example 6)

The sputtering gas, B ₂ except that the H _e was B ₂ H _e concentration 0. 8 vol% gas obtained by diluting with A r is performed Supadzuta the same conditions as in Example 5, a glass substrate A ZnO: B thin film having a thickness of about 2 m was formed thereon.

(Example 7)

The sputtering gas, in addition to the beta ₂ Eta _epsilon was beta ₂ Eta _epsilon concentration 0 · 5 vol% of gas obtained by diluting with A r is performed sputtering under the same conditions as those in Example 5, a glass substrate A Zn0: B thin film was formed on the upper surface with a thickness of about 2 m.

(Comparative Example 4)

Sputtering was performed under the same conditions as in Example 5 except that the sputtering gas was changed to Ar 100%, to form a Zn 2 thin film with a thickness of about 2 m on a glass substrate. (Comparative Example 5)

As a target,飩度9 9 9 percent Ζ η Ο:. Α 1 used _{(2 wt% A 1 2 0} 3), the sputtering gas pressure (the working gas pressure) 2 X one 2

Sputtering was performed for 1 hour using Ar 100% gas as the sputter gas under the conditions of 10 Torr and a substrate temperature of 200. --A ZnO: Al thin film was formed on a glass substrate with a thickness of about 2 tm.

Evaluation of ZnO: B thin film 2>

When the surface of each of the ZnO: B thin films manufactured as described above was observed by SEM, it was confirmed that the texture structure was formed in each of the samples of Examples 5, 6, and 7. Was observed. Fig. 7 (A) shows a photograph of the observation result of the sample of Comparative Example 4, and Fig. 7 (B) shows a photograph of the observation result of the sample of Example 5. In FIG. 7 (B), the surface has a pyramid-shaped irregularity peculiar to the texture structure.

FIG. 8 shows the wavelength dependence of the total transmittance T d for the samples of Examples 5 to 7 and Comparative Examples 4 and 5. FIG. 9 shows the dependence of resistivity, mobility, and carrier concentration on the doping amount of Β ₂ Η ₆ for each of the samples of Examples 5 to 7 and Comparative Example 4.

As shown in FIG. 8, the B ₂ H ₆ -doped sample (b, c, d) in the near infrared region was smaller than the ZnO: A1 thin film of Comparative Example 5 in the near-infrared region. The transmittance is 髙ぃ. Comparing d and e in the figure, ZnO: B (d) has a high mobility and a low carrier concentration even at almost the same resistivity. For this reason, ZnO: B (d) can reduce free electron absorption and correspondingly increase the transmittance.

Also, different Z n O of B-doped amount: If you compare the B thin film, the more high concentration of beta ₂ Eta _epsilon, it can be seen that reduces the permeability over rate in the near infrared region. On the other hand, Remind as in FIG. 9, the mobility, career concentration is increased as the concentration of beta ₂ Eta _epsilon is high And, resistivity, it can be seen that the concentration of B ₂ H _e is higher the more dark to small.

By the way, in the case of a transparent conductive film, it is desirable that the resistivity be as low as possible and that the transmittance be in the range of 300 nm to 130 O nm in practical use such as a solar cell. Example 5, 6, 7 of Z _n 0: each sample thin film B satisfies substantially the condition. In particular, as described above, the sample thin film of ZnO: B of Example 5 has a remarkable texture structure, can expect an effect of confining incident light, and is preferable as a transparent conductive film.

<Zn0: Production of B thin film 3>

(Examples 8 to 13)

As a target, using a Z n O of Dondo 9 9.9%, a spa Ttagasu pressure (the working gas pressure) 2 X 1 0- Torr, as a spatter gas, beta ₂ Eta _epsilon at A r using diluted B ₂ H _s concentration 1 obtained. 0 vol% of a gas, in each of the following substrate temperature, perform the 1 hour spatter, Z n a thickness of approximately 2 m on a glass substrate 〇 : B thin film was formed.

Example 8: 150

Example 9: 200. C

Example 10: 250. C

Example 11: 300. C

Example 12: 350 ° C

Example 13: 0 ° C

(Comparative Example 6)

New paper Sputtering was carried out under the same conditions as in Example 8 except that the substrate temperature was set to 100 ° C (sputtered without heating) to form a Zn film with a thickness of about 2 m on the glass substrate. O: B thin film was formed.

When the surface of each of the ZnO: B thin films manufactured as described above was observed by SEM, it was observed that a texture structure was formed in any of the samples of Examples 9 to 13. Was. It was also observed that a texture structure was formed for the sample of Example 8 although it was not so remarkable as compared with the samples of Example 9 and thereafter. FIG. 10 (B) shows a photograph of the observation result of the sample of Example 9. The figure has a surface structure exhibiting pyramid-shaped irregularities peculiar to the texture structure. The surface structure was almost the same for each sample from 200 ° C to 400 ° C. Moreover, it can have sample Nitsu of Comparative Example 6, not using B ₂ H _e, as compared to that shown in FIG. 7 (A), slight but although irregularities of the surface were observed. FIG. 10 (A) shows a photograph of the observation result of Comparative Example 6.

1 1, with the respective samples of Example 8-1 3 Oyopi Comparative Example 6 shows the resistivity, mobility, the doping amount dependency of B ₂ H _e of calibration Li A concentration. As shown in the figure, a material having a low resistivity is obtained in a wide temperature range from 150 ° to 300 °. In addition, even if the substrate temperature is low, low resistivity is obtained. Then, as described above, 200. In the range of C to 400 ° C, the surface structure exhibits pyramid-shaped irregularities peculiar to the texture structure. Is obtained.

This means that a transparent conductive film having a desired surface structure can be obtained even when film formation is performed at a relatively low temperature of about 200 ° C. Moreover, there is an advantage that the substrate temperature does not need to be strictly controlled, and the film forming process is facilitated.

Evaluation of the whole example>

According to the embodiments described above, H ₂ 0 or alcohol, or by using these mixed solution gas as the sputtering gas, rather by efficiency, texturing of the film can be realized. Further, as shown in Examples 2 to 4, by doping with boron, a low-resistance film having a high total transmittance could be obtained.

In addition, by using a sputtering gas obtained by diluting B ₂ H _S with Ar using a Zn0 target, a film having a low resistivity and a texture structure can be formed at a relatively low temperature in a film forming process. Thus, a film can be formed.

In addition, the following items were examined in order to evaluate the environmental resistance of the sample of 上述 η 上述: Β obtained by each of the above-described examples.

① ZnQ: Rate of change in sheet resistance after the sample of B was left in the air for 200 and 10 hours.

The initial sheet resistance value 4 Ω changed to 4.4 Ω. Therefore, the change was reduced by about 10%.

(2) The rate of change in sheet resistance after boiling the ZnO: B sample in boiling water (100 ° C) for 2 hours.

In this case, as in ①, the change was reduced by about 10%. Therefore, if there is almost no change in the normal temperature range Conceivable. Therefore, under normal conditions of use, there is little change over time.

Thus, the transparent conductive film produced by the present invention has a low resistivity, a high transmittance, and is textured, so that it can be used as a window material for a solar cell or an optical sensor. By using this, improvement of photoelectric conversion efficiency is expected. In addition, since the device has good environmental resistance, it is possible to reduce the time-dependent change of a device used outdoors such as a solar cell, and to prolong its life.

Claims

The scope of the claims

1. In the method of manufacturing a transparent conductive film on a substrate by sputtering,

Manufacturing a transparent conductive film by sputtering a target having at least a part of the composition of a target film as a component in a gas atmosphere containing OH to form a transparent conductive film. Method,

2. In Claim 1, the target transparent conductive film is:

Z n 0,

Zn0: X (X is one of Al, Si, B, F and CI)

At least one),

S n 0

S n 0 Y (Y is at least one of F and C I),

I n 2 O a

I n ₂ O: Z (Z is at least one of S n 0 ₂ and S n

1)

A method for producing a transparent conductive film.

3. The method for producing a transparent conductive film according to claim 2, wherein the O H in the gas atmosphere containing O H is generated by decomposing a compound having an O H group.

4. The method for producing a transparent conductive film according to claim 3, wherein the compound having an OH group is at least one of water and alcohol.

5. In claim 1, the OH in the gas atmosphere containing 0H is formed by decomposing a gaseous compound having an OH group. A method for producing a transparent conductive film,

6. In the method of manufacturing an oxide-based transparent conductive film on a substrate by sputtering,

Also an oxide-based target having the composition of the film of interest as a component least for a, and the transparent conductive film by using a gas containing B ₂ H _S, characterized that you to scan package data Manufacturing method.

7. The method of claim 6, B ₂ gas containing H ₆ is, beta ₂ Eta _epsilon a method for producing a transparent conductive film is a gas diluted A r.