JP2003124133A - Gas-separated catalyst cvd system, photoelectric conversion device manufactured by using the system, and method of manufacturing the device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a catalyst CVD system that can uniformly form an Si- based thin film in a high quality and large area at a high speed, and to provide a photoelectric conversion device manufactured by using the CVD system and a method of manufacturing the conversion device. SOLUTION: The catalyst CVD system forms the Si-based thin film on a substrate by blowing out a hydrogen gas and an Si-based gas from a shower plate having a plurality of gas blowing-out holes. The introducing route of the hydrogen gas is separated from that of the Si-based gas until the route passes through the shower plate. In addition, a thermal catalyzer connected to a DC power source and having an active hydrogen density adjusting function and a heat radiation reducing structure is installed to the hydrogen gas introducing route on the upstream side of the shower plate. Moreover, the distance between the adjacent two gas blowing-out holes of the shower plate is made shorter than that between the shower plate and substrate.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gas separation type catalyst CV.
The present invention relates to a D device, a photoelectric conversion device manufactured by using the D device, and a manufacturing method thereof, and in particular, a Si-based thin film in a photoelectric conversion device represented by a thin-film Si-based solar cell can be uniformly formed at high speed and in a large area. The present invention relates to a gas separation type catalytic CVD device, a photoelectric conversion device manufactured using the same, and a manufacturing method thereof.

[0002]

Prior Art and Problems to be Solved by the Invention Si
High-speed, high-quality film formation of a system-based thin film is essential for cost reduction of a thin-film Si-based solar cell. As a method for forming a Si-based thin film at a low temperature, plasma CVD is roughly classified.
There are a (PECVD) method and a catalytic CVD (Cat-CVD) method (HW-CVD method (hot wire CVD method) has the same principle). However, because the former uses plasma, it is inevitable that charged particles such as ions and electrons will damage the film-forming surface, and film quality can be improved with higher frequencies, but at the same time it is technically necessary to increase the area. Since it becomes very difficult, the latter, which is plasma-free and does not have a principle restriction on increasing the area, has recently attracted attention (H. Matsumura, Jpn. J. Appl. Phys. 37 (199).
8) 3175-3187, REI Schropp et al, Technicaldig
est of 11th PVSEC (1999) p. 929-930).

By the way, catalytic CVD with SiH ₄ + H ₂ system
The film forming principle of the method is considered as follows. Reaction on the surface of catalyst (radical formation reaction) SiH ₄ → Si + 4H ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ a H ₂ → 2H ・ ・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ B Reaction in gas phase SiH ₄ + H → SiH ₃ + H ₂・ ・ ・ ・ A SiH ₄ + Si → Si ₂ H ₄ or 2SiH ₂・ ・ ・ ・ ・ b H ₂ + Si → SiH ₂・ ・ ・ ・・ ・ ・ ・ ・ ・ ・ ・ C Reaction on film forming surface (surface DB generation, deposition) Si-H (s) + H → Si- (s) + H ₂ ↑ _{SiH (s) + SiH 3 →} Si- (s) + SiH 4 ↑ ···· b Si- (s) + SiH 3 → Si-SiH 3 (s) ······· c where catalytic CVD Then, as shown in equations a and b In addition, since H (atomic hydrogen) is very efficiently produced in a large amount, a large amount of SiH ₃ which is the main deposition species is produced by the formula a, and as a result, high-speed film formation can be realized relatively easily. . The presence of a large amount of H also facilitates crystallization under high-speed film forming conditions.

However, S obtained by the catalytic CVD method
At present, the film quality of the i film, particularly the film quality of the crystalline Si film is not always sufficient, and there is a problem that it is inferior to that of the PECVD method.

In order to solve such a problem, for example, Japanese Patent No. 2692326 discloses a catalytic CVD method in which a radiation blocking member through which a gas can pass is installed between a catalyst body and a substrate. According to this, the problem of heat radiation, which is one of the conventional problems of the catalytic CVD method, can be solved, but improvement of the film quality cannot be achieved by this alone.

In Japanese Patent Laid-Open No. 11-54441, a raw material gas is supplied into a container in which a thermal catalyst is placed, the inside of the container is isolated from the substrate, and the gas is blown out from a gas outlet by a differential pressure. Although a catalytic CVD apparatus for supplying to a substrate is disclosed, this also solves the problem of heat radiation, which has been one of the conventional problems of the catalytic CVD method, but cannot improve the film quality by itself. there were. Further, since gas is not separated and introduced, for example, when SiH ₄ is used as the source gas, most of the film deposition occurs in the container in which the thermal catalyst is placed, and the surface of the substrate installed outside the container However, there is a problem that the film forming speed of the film is extremely reduced.

The present invention has been made on the basis of such a background, and a gas separation catalyst C capable of uniformly forming a Si-based thin film at a high speed and with a high quality and in a large area.
An object is to provide a VD device, a photoelectric conversion device manufactured using the VD device, and a manufacturing method thereof.

[0008]

To achieve the above object, in a gas separation type catalytic CVD apparatus according to a first aspect, hydrogen gas and Si-based gas are jetted from a shower plate having a plurality of gas jet holes. A catalytic CVD apparatus for forming a film on a film formation substrate, wherein the introduction path of the hydrogen gas is separated from the introduction path of the Si-based gas until it passes through the shower plate, and A thermal catalyst connected to a heating power source is disposed on the upstream side of the hydrogen gas introduction path.

In the gas separation type catalytic CVD apparatus, it is desirable that the hydrogen gas and the Si-based gas be mixed while passing through the shower plate.

In the above gas separation type catalytic CVD apparatus, it is desirable that at least one of the hydrogen gas introduction path and the Si-based gas introduction path be selected so that the doping gas can be introduced.

Further, in the above gas separation type catalytic CVD apparatus, it is desirable to provide a plurality of the thermal catalysts so that they can be heated independently.

Further, in the gas separation type catalytic CVD apparatus, heating of the thermal catalyst is intermittently or periodically performed by intermittently or periodically supplying electric power to the thermal catalyst. desirable.

In the gas separation type catalytic CVD apparatus, it is desirable that the distance between the thermal catalyst and the shower plate be variable.

In the gas separation type catalytic CVD apparatus, it is desirable that the diameter of the hydrogen gas ejection hole and the diameter of the Si gas ejection hole are different.

Further, in the above gas separation type catalytic CVD apparatus, it is desirable that the total number of hydrogen gas ejection holes and the total number of Si gas ejection holes be different.

Further, in the above gas separation type catalytic CVD apparatus, a hydrogen gas introduction path without a thermal catalyst is additionally provided in the gas introduction path, and the hydrogen gas in a path without the thermal catalyst is provided. It is desirable that the flow rate and the hydrogen gas flow rate of the path in which the thermal catalyst is arranged can be controlled independently.

Further, in the gas separation type catalytic CVD apparatus, it is desirable to dispose a radiation blocking member between the thermal catalyst and the hydrogen gas ejection hole.

Further, in the above gas separation type catalytic CVD apparatus, the distance between two adjacent gas ejection holes of the shower plate is preferably equal to or less than the distance between the shower plate and the film formation substrate. .

According to a twelfth aspect of the photoelectric conversion device, the S formed by using the gas separation type catalytic CVD device as described above.
It is characterized by having an i-based thin film.

Further, in the above photoelectric conversion device, it is desirable that the Si-based thin film is a crystalline Si film.

Further, in the above photoelectric conversion device, it is desirable that the Si-based thin film is a crystalline Si film and the volume fraction of the crystal component is 60% or more and 95% or less.

In the method of manufacturing a photoelectric conversion device according to the fifteenth aspect, it is desirable that the temperature of the thermal catalyst when the Si-based thin film is formed be 1000 ° C. or more and 2000 ° C. or less.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a gas separation type catalytic CVD apparatus 1c which ejects gas from a flat shower plate 1b to form a film.

Although a vacuum pump 1d is provided in the exhaust system, it is desirable to use a dry vacuum pump such as a turbo molecular pump in order to suppress impurities from being mixed into the film from the exhaust system. The ultimate vacuum is preferably at least 1E ^-3 Pa or less and more preferably 1E ^-4 Pa or less. The pressure during film formation is in the range of about 10 to 1000 Pa.

The source gases are SiH ₄ , Si ₂ H ₆ , and Si.
Si-based gas 1e such as F ₄ , Si ₂ F ₆ and SiH ₂ Cl ₂ is used, and hydrogen gas 1f is used as a dilution gas. When doping, B ₂ H ₆ or the like is used as the p-type doping gas,
PH ₃ or the like is used as the n-type doping gas.

At least S is formed in the hydrogen gas introduction passage 1g.
The i-type gas introduction path 1h is separated until it passes through the shower plate 1b, and the hydrogen gas introduction path is connected to a DC power supply 1i which is a heating power supply upstream of the shower plate 1b. 1j is provided.
For the thermal catalyst 1j, a refractory metal material such as tungsten or tantalum is used, and a direct current is passed through the metal material to generate heat and raise the temperature. The temperature of the thermal catalyst is 1000-200.
It can be set as needed in the range of 0 ° C. The shape of the thermal catalyst may be linear or planar.

The temperature of the substrate 1k is set to a temperature condition of 100 to 400 ° C. by the substrate heater 1L, preferably 150.
-350 degreeC. In this apparatus, since the thermal catalyst 1j is installed at a position apart from the region where the film is formed with the shower plate 1b interposed therebetween, the heat radiation to the film formation surface is suppressed to a low level, and the substrate temperature is easily controlled. can do.

Here, the distance between two adjacent hydrogen gas ejection holes 1m of the shower plate 1b and the distance between two adjacent Si gas ejection holes 1n are the same as those of the shower plate 1b and the substrate 1k. The distance is less than or equal to. If this distance is exceeded, variations in film thickness and film quality cannot be ignored. Specifically, it becomes difficult to control the film thickness at about ± 15% or less, resulting in non-uniform power generation characteristics and reduced efficiency. Further, with respect to the film quality, for example, the crystallization rate cannot be controlled at about ± 20% or less, which also leads to a decrease in efficiency.

If the uniformity of the film thickness and the film quality is insufficient as described above, the hydrogen gas and the Si-based gas may be mixed while passing through the shower plate 1b. For example, if the introduction paths are fused within the thickness of the shower plate,
Hydrogen gas and Si-based gas can be mixed while passing through the shower plate 1b.

Next, when a doping gas (not shown) such as B ₂ H ₆ or PH ₃ is mixed and introduced, the introduction path of the gas is a hydrogen gas introduction path provided with a thermal catalyst. At least one of 1f and Si-based gas introduction path 1h in which a thermal catalyst is not disposed can be selected as necessary. If you choose the latter, the normal PECVD
The same doping characteristics as in the method can be expected, but the former may be selected especially when it is necessary to increase the activity of the doping element. However, in the former case, there is a loss component that is excited and decomposed when it comes into contact with the thermal catalyst to form a film in the introduction path pipe, so the introduction amount of the doping gas is adjusted accordingly.

The greatest feature of the gas separation type catalytic CVD method of the present invention is that the Si-based gas as the source gas and the hydrogen gas are introduced separately and only the hydrogen gas is activated by the thermal catalyst. It is in. This significantly improves the film quality, which has been a problem in the past. High-speed film formation is also achieved.

That is, the conventional gas non-separation type catalyst CV
In the D method, a large amount of originally undesired Si (atomic silicon) originating from the formula a is produced, so that the film quality is deteriorated when the film is formed. Also, this Si is expressed by the formula b
And the formula c promotes the production of SiH ₂ or Si ₂ H ₄ , and the film formation of these molecules also causes the deterioration of the film quality. Furthermore, these SiH ₂ and Si ₂ H
₄ promotes the formation of higher order silane by the polymerization reaction with SiH ₄ , but even if the ratio of this adsorbed on the surface of the film formation increases, the film quality deteriorates.

On the other hand, according to the gas separation type catalytic CVD method of this method,
Then, only the hydrogen gas is activated by the thermal catalyst,
Since the reaction of a is eliminated in principle, the production of Si
It can be eliminated, and as a result, expression b and
And SiH according to formula c₂And Si₂H_FourAlmost no generation of
Can be combed and, as a result, higher silanes
The film quality can be significantly reduced because the generation of
Can be improved. The reaction of formula a is
-SiH occurs on the downstream side including the plate, so SiH ₃The efficiency
Can be guided to the substrate, and high-speed film formation can be achieved.

At this time, the active hydrogen density is a very important physical quantity for the film quality and the film forming rate of the film to be obtained. The method for controlling the density is as follows.

The first method is a method of controlling the temperature of the thermal catalyst, and the density of active hydrogen can be increased or decreased in proportion to the temperature of the thermal catalyst. The temperature of the thermal catalyst is 1000
It can be set in the range of ℃ to 2000 ℃. However, 1200
If the temperature is lower than 0 ° C, the effect of adding the thermal catalyst cannot be obtained remarkably, and if the temperature is higher than 1900 ° C, problems such as degassing of impurities from the catalyst and peripheral members and evaporation of the material of the catalyst itself occur. It is preferably set in the range of 1200 ° C to 1900 ° C.

At this time, when tungsten is used as the material of the thermal catalyst, the temperature of the thermal catalyst is preferably 1600 ° C. or higher. The reason is that the thermal catalyst 1j is disposed only in the hydrogen gas passage in the structure of the apparatus, and when it contacts only the hydrogen gas, the lower limit value of the temperature of the thermal catalyst is not limited, but in reality, It cannot be completely avoided that the components of the Si-based gas 1e reversely diffuse and penetrate into the shower plate 1b from the hydrogen gas ejection holes 1m to some extent and come into contact with the thermal catalyst 1j to react therewith. Then, tungsten reacts with Si to form a silicide, and the thermal catalyst 1j is slightly altered. Of course, even if a silicide is formed, it can be used as it is depending on the degree, but when the replacement frequency of the catalyst becomes frequent, it is desirable to avoid the formation of the silicide by raising the temperature of the catalyst to 1600 ° C. or higher. . In addition,
When tantalum is used as the material of the thermal catalyst, there is no lower limit of temperature conditions. However, regardless of which material is used, when the temperature of the thermal catalyst becomes 1400 ° C or less, it is slightly diffused and diffused into the Si-based gas. Since it becomes a mode in which the deposited Si is deposited on the surface of the thermal catalyst, when it is used at a temperature of 1400 ° C. or lower to some extent, the temperature of the thermal catalyst is sufficiently raised and the deposited Si while flowing hydrogen gas if necessary. Evaporate and remove. By this treatment, the thermal catalyst 1j can be repeatedly used.

The second method for controlling the density of active hydrogen is
It controls the surface area of the thermal catalyst. This makes it possible to control the density of active hydrogen while maintaining the temperature above a certain temperature without lowering the temperature of the thermal catalyst. For example, when a linear one is used as the thermal catalyst 1j, the surface area of the thermal catalyst can be controlled by selecting the line length and the wire diameter. In practice, it is difficult to change the wire length or wire diameter of the thermal catalyst 1j during use of the apparatus, and in this case, a plurality of independently heatable thermal catalysts are provided (not shown). ), The density of active hydrogen can be changed stepwise if the number of thermal catalysts to be heated is determined.

The third method for controlling the density of active hydrogen is
This is a method of heating the thermal catalyst 1j intermittently or periodically. Specifically, the thermocatalyst 1 can be provided by a mechanism for intermittently applying a DC voltage from the DC power supply 1i in a pulsed manner, or by supplying the power with a low-frequency AC power supply (not shown).
The heating of j can be done periodically. As a result, the reaction time between the hydrogen gas and the thermal catalyst 1j per unit time can be continuously controlled, so that the density of active hydrogen can be continuously controlled.

A fourth method for controlling the density of active hydrogen is
The distance between the thermal catalyst 1j and the shower plate 1b is variable. Since the active hydrogen has a life, the density of the active hydrogen released from the shower plate 1b can be reduced by increasing this distance, and can be increased by shortening it.

A fifth method for controlling the density of active hydrogen is
The diameter of the hydrogen gas ejection hole 1m and the diameter of the Si-based gas ejection hole 1n can be designed and adjusted separately, and the total number of hydrogen gas ejection holes 1m and the total number of Si-based gas ejection holes 1n can be adjusted. Are designed and adjusted separately. Hydrogen gas spouting hole 1
Reducing the diameter of m or reducing the total number of holes can reduce the density of active hydrogen, and increasing the diameter of the hydrogen gas ejection holes 1 m or increasing the total number of holes can increase the density of active hydrogen.

The sixth method for controlling the density of active hydrogen is
A hydrogen gas introduction path (not shown) without a thermal catalyst is added to the gas introduction path to independently control the flow rate of hydrogen gas passing through the heat catalyst and the flow rate of hydrogen gas not passing through the heat catalyst. It can be so. As a result, the active hydrogen gas and the inactive hydrogen gas can be mixed at an arbitrary gas flow rate ratio, so that the density of the active hydrogen after being released from the shower plate 1b can be continuously controlled.

Next, as a factor that greatly affects the quality of the formed film, there is a problem of thermal radiation from the thermal catalyst 1j, which has often been a problem in the conventional catalytic CVD method.
In the gas separation type catalytic CVD method of the present invention, since the shower plate 1b exists between the thermal catalyst 1j and the substrate 1k, this thermal radiation can be greatly reduced. Normally, the shower plate 1b alone has a sufficient effect of blocking thermal radiation, but if the effect of thermal radiation is still not negligible,
A member that blocks thermal radiation may be installed between the shower plate 1b and the thermal catalyst 1j so that thermal radiation from the thermal catalyst 1j is not directly emitted downstream from the shower plate 1b. As a member that blocks this heat radiation, for example, a metal plate or the like can be used. It is desirable that this plate is provided with a shower-like gas passage hole that is arranged so as not to overlap with the gas ejection holes of the shower plate and blocks heat radiation but allows gas to pass therethrough. This makes it possible to form a high-quality film that is hardly affected by heat radiation.

Here, crystalline Si such that the volume fraction of the crystal component in the Si-based thin film is 60% or more and 95% or less.
When the film is used for a solar cell, a low cost and high efficiency thin film crystalline Si solar cell can be manufactured by the high-speed and high-quality film forming characteristics of the gas separation type catalytic CVD method described above. However, when the volume fraction of the crystal component is less than 65%, the short-circuit current density is reduced and the efficiency is significantly reduced due to the reduction of the spectral sensitivity characteristic particularly for long-wavelength light. Further, when the volume fraction of the crystal component exceeds 90%, the amorphous component, which is indispensable for inactivating the crystal grain boundaries, is insufficient, and the open-circuit voltage characteristic tends to deteriorate and the efficiency tends to decrease. It will be noticeable. Therefore, the volume fraction of the crystal component is desirably 65% or more and 90% or less.

As described above, according to the present invention, since the Si-based gas and the hydrogen gas are separately introduced and only the hydrogen gas is activated by the thermal catalyst, the Si-based thin film can be formed at high speed and with high quality. It will be possible. Further, by using this method, it is possible to manufacture a low-cost and highly efficient thin film Si solar cell.

[0045]

As described above, in the gas separation type catalytic CVD apparatus according to the first aspect, the hydrogen gas introduction path and the Si-based gas introduction path are separated until they pass through the shower plate. A thermal catalyst connected to a heating power source is provided on the upstream side of the shower plate in the introduction path of, and also has a function of adjusting the active hydrogen density,
In addition, since it has a structure that reduces heat radiation, and the distance between two adjacent gas ejection holes of the shower plate is set to be equal to or less than the distance between the shower plate and the film formation substrate, the Si-based thin film can be processed at high speed. It is possible to form a film with high quality and even over a large area.

According to the photoelectric conversion device of the twelfth aspect, the gas separation type catalytic CVD device as described above is used to perform S conversion.
Since the i-based thin film is formed, high-quality and large-area film formation can be performed at high speed, and thus the manufacturing cost can be significantly reduced.

Further, according to the manufacturing method of the photoelectric conversion device of the fifteenth aspect, since the temperature of the thermal catalyst when forming the Si-based thin film is set to 1000 ° C. or more and 2000 ° C. or less,
The hydrogen gas can be effectively activated, and high-speed and high-quality Si-based film formation can be realized. Further, the Si-based film can be easily crystallized.

[Brief description of drawings]

FIG. 1 shows a device according to the invention.

[Explanation of symbols]

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kenji Fukui             6 at 1166 Haseno, Jamizo-cho, Yokaichi-shi, Shiga               Kyocera Corporation Shiga Yokaichi Factory F-term (reference) 4K030 AA06 AA17 BA29 EA05 FA17                       JA05 JA10 KA25 KA41                 5F045 AA03 AB03 AC01 AD05 AD06                       AD07 AE17 AE19 AE21 BB02                       BB08 BB16 CA13 DC65 DP03                       EE07 EF05                 5F051 AA05 CA08 CA14 CA21

Claims (15)

[Claims] 1. A catalytic CVD apparatus for ejecting hydrogen gas and Si-based gas from a shower plate having a plurality of gas ejection holes to form a film on a film formation substrate, wherein the introduction path of the hydrogen gas is It is separated from the Si-based gas introduction path until it passes through the shower plate, and a thermal catalyst connected to a heating power source is disposed in the hydrogen gas introduction path upstream of the shower plate. A gas separation type catalytic CVD apparatus characterized in that 2. The gas separation type catalytic CVD apparatus according to claim 1, wherein the hydrogen gas and the Si-based gas are mixed while passing through the shower plate. 3. The gas separation type according to claim 1, wherein at least one of the hydrogen gas introduction path and the Si-based gas introduction path is selected so that the doping gas can be introduced. Catalytic CVD apparatus. 4. The gas separation type catalytic CVD apparatus according to claim 1, wherein a plurality of the thermal catalysts are provided so that they can be independently heated. 5. The gas separation type catalytic CVD apparatus according to claim 1, wherein the thermal catalyst is heated intermittently or periodically. 6. The gas separation type catalytic CVD apparatus according to claim 1, wherein the distance between the thermal catalyst and the shower plate can be changed. 7. The gas separation type catalytic CVD apparatus according to claim 1, wherein a diameter of the hydrogen gas ejection hole and a diameter of the Si-based gas ejection hole are different from each other. 8. The gas separation type catalytic CVD apparatus according to claim 1, wherein the total number of the hydrogen gas ejection holes and the total number of the Si-based gas ejection holes are different. 9. A hydrogen gas introduction path is additionally provided in the gas introduction path in which a thermal catalyst is not provided, and the flow rate of hydrogen gas in the path in which the thermal catalyst is not provided and the thermal catalyst are provided. 2. The gas separation type catalytic CVD apparatus according to claim 1, wherein the flow rate of hydrogen gas in the above-mentioned path can be controlled independently. 10. A radiation blocking member is provided between the thermal catalyst and the hydrogen gas ejection hole.
The gas separation type catalytic CVD apparatus described in 1. 11. The gas separation type catalytic CVD apparatus, wherein a distance between two adjacent gas ejection holes of the shower plate is equal to or less than a distance between the shower plate and the film formation substrate. 12. A photoelectric conversion device having a Si-based thin film formed by using the gas separation type catalytic CVD device according to claim 1. 13. The photoelectric conversion device according to claim 12, wherein the Si-based thin film is a crystalline Si film. 14. The photoelectric conversion according to claim 12, wherein the Si-based thin film is a crystalline Si film, and the volume fraction of its crystal component is 60% or more and 95% or less. apparatus. 15. The method for manufacturing a photoelectric conversion device according to claim 12, wherein the temperature of the thermal catalyst is 1000 ° C. or more and 2000 ° C. or less when the Si-based thin film is formed.