JPH10233520A - Method and device for manufacturing thin-film solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and device for manufacturing a thin-film solar cell wherein a thin-film solar cell of high photoelectric conversion efficiency is manufactured at high operation rate. SOLUTION: A plurality of film-forming chambers comprising a reaction chamber 22 where film-forming reaction is performed and a heater chamber 32 provided with a heater 31 are provided. While, in the film-forming camber, a film substrate 1 of long size is step-transported, a thin-film which constitutes a thin-film solar cell is formed on a substrate 1, and the openings of a reaction chamber 22 and heater chamber 32 are sealed up with the substrate in between in film-forming. Here, the opening of the heater chamber 32 is covered with a shielding member 3p. By introducing hydrogen gas or material gas of film into the heater chamber 32, temperature control for the substrate 1 is performed. A material gas introduction opening 23, valves 41 and 42, and a vacuum pump 51 are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for manufacturing a thin-film solar cell in which a photoelectric conversion layer mainly composed of a photoelectric conversion material such as amorphous silicon is formed on a flexible substrate.

[0002]

2. Description of the Related Art In recent years, a thin-film solar cell using an a-Si-based material such as amorphous silicon (hereinafter referred to as a-Si) or an a-Si alloy, which is a typical thin-film photoelectric conversion device, has attracted attention. A thin-film solar cell has a thin-film solar cell element (or cell) in which at least three thin films of a first electrode layer, a photoelectric conversion layer, and a second electrode layer are stacked on a substrate. In thin-film solar cells, cost reduction by mass production is the biggest issue, and a significant increase in production per unit time is desired.

Usually, the mass productivity of a-Si thin film solar cells is limited by the process of forming an a-Si thin film. When a rigid substrate such as glass is used, it is necessary to mount the substrate on a tray having a relatively large heat capacity and form a film with a load-lock type manufacturing apparatus. It is difficult to greatly improve mass productivity due to heating of the tray and 3) reciprocation between the atmosphere and vacuum in the load lock chamber. In order to improve mass productivity, several thin-film solar cell manufacturing apparatuses using a flexible plastic film or a stainless steel film as a substrate have been proposed. One of them is Y.Ichika
"IEEE 1st World Conference on Photovolt"
aic Energy Conversion "(1994), pp. 441-444.

FIG. 5 is a schematic sectional view of an apparatus for manufacturing a thin film solar cell of the stepping roll type. The manufacturing apparatus is composed of a plurality of film forming chambers, and the substrate 1 sent from the feed roll 11 forms a thin film through a plurality of film forming chambers R, is laminated, and is wound up by a winding roll 12. Even when only a-Si is formed, three p-layers, i-layers, and n-layers are required. Above the substrate 1 in each of the film forming chambers is a vertically movable heater chamber 32 containing a heater 31, and below is a reaction chamber 22 for forming a thin film. The opening of the heater chamber 32 and the opening of the reaction chamber 22 are overlapped via an O-ring. Reaction chamber 2
2 is an electrode 2 for sputtering or plasma CVD.
1 is provided, and the electrode 21 is connected to the power supply W. When the heater chamber 32 is raised and opened, the substrate can be transferred. When the heater chamber 32 is lowered and the film forming chamber R is closed, the film forming chamber is independent of other film forming chambers. It is in an airtight state where the pressure can be controlled, and film formation is possible. Deposition chamber closed →
Multi-layers can be sequentially stacked without any mutual diffusion of gas during film formation as a single step sequence consisting of gas introduction → pressure control → film formation → gas exhaust → film formation chamber opening → substrate transfer. It is.

For example, when forming an a-Si thin film solar cell,
Usually, the heater temperature is 150-300 ° C. If the film forming chamber is directly sealed with such a high temperature heater, 1) the sealing O-ring such as fluoro rubber is damaged.
2) There is a problem that the heater itself is deformed by the interaction between heat and force. As a countermeasure, the film forming chamber has the following structure. FIG. 6 is a schematic sectional view of a film forming chamber of a conventional apparatus for manufacturing a thin film solar cell of a stepping roll system. The lower part of the film forming chamber than the substrate 1 is the reaction chamber 22 and the upper part is the heater chamber 32. The reaction chamber 22 has a gas inlet 23 into which a source gas (a mixed gas of hydrogen gas and silane gas in the case of a-Si, and an atmospheric gas in the case of sputtering) and an RF having a large number of holes for blowing the source gas. Electrode 2
The gas pressure is controlled by a valve 41 and a vacuum pump 51.
Is controlled by An O-ring 24 is placed on the periphery of the opening of the reaction chamber 22, and when the heater chamber 32 is lowered, the film formation chamber is sealed with the periphery of the opening and the substrate 1 interposed therebetween. The heater chamber 32 surrounds the heater 31, and a cooling pipe 33 surrounds the heater 31.
Is attached.

[0006] The film substrate 1 is connected to the SCAF-structured thin-film solar cell (an electrode of different polarity of the thin-film solar cell and an individual electrode on the opposite side of the substrate are electrically connected to each other on the inner wall surface of the hole formed in the substrate. SCAF stands for Series-Connection through Appertur.
es formed on Film.
(Disclosed in Japanese Patent Application Laid-Open No. 24 (1999)), the source gas passing through the hole and remaining in the heater chamber 32 diffuses into the reaction chamber 32 and becomes a contamination source. There's a problem. In order to avoid this, a flexible pipe 34 is connected to the vacuum pump 5 to prevent gas from flowing from the heater chamber 22 to the reaction chamber 32 as a bypass line.

[0007]

In a stepping roll type manufacturing apparatus, the inside of a film forming chamber must be exposed to the atmosphere when the roll is attached or detached. At this time, the moisture adsorbed on the inner wall of the film formation chamber is released at the time of film formation, and causes impurities (oxygen) to degrade device characteristics. As a countermeasure,
The inside of the reaction chamber is designed to be as hot as possible so that moisture can be removed in a short time after evacuation.
Pre-deposition was performed immediately after the roll was mounted to form an a-Si coating on the inner wall of the film forming apparatus, thereby suppressing the release of moisture from the inner wall of the apparatus. On the other hand, the heater chamber was cooled to 100 ° C. or less to prevent thermal damage to the O-ring.
That is, the wall of the heater chamber is a cold wall, so that the a-Si film does not adhere during the film formation. Therefore, moisture will be released from the inner wall of the heater for a long time, and when a film is formed on a substrate with a hole such as a SCAF thin film solar cell, the diffusion of the moisture through the hole is a characteristic of the thin film solar cell. Was causing the decrease.

In view of the above problems, it is an object of the present invention to reduce the amount of water released from the film forming chamber wall, to reduce the number of steps (the number of times of film formation) until the photoelectric conversion efficiency is stabilized, and to increase the photoelectric conversion efficiency. An object of the present invention is to provide an apparatus and a method for manufacturing a thin-film solar cell capable of manufacturing a thin-film solar cell at a high operation rate.

[0009]

Means for Solving the Problems In order to achieve the above object, there are provided a plurality of film forming chambers including a reaction chamber in which a film forming reaction is performed and a heater chamber having a heater. While step-transporting a film substrate, a thin film constituting a thin-film solar cell is formed on the substrate, and the openings of the reaction chamber and the heater chamber are sealed with the substrate therebetween during film formation. In the manufacturing apparatus, the opening of the heater chamber is covered with a shielding member.

The shielding member is preferably a thin plate or foil made of a metal material, or a thin plate or film made of a heat-resistant polymer material. The metal material is preferably aluminum or stainless steel. The heat-resistant polymer material is preferably polyimide or aramid. The thickness of the shielding member is preferably 0.01 to 2 mm.

The surface of the shielding member on the film forming chamber side is preferably subjected to an unevenness treatment. The unevenness treatment is preferably sand blasting. The shielding member may be in close contact with the heater. The shielding member is installed in parallel with the heater, the heater chamber is provided with a gas inlet and a gas outlet connected to a vacuum pump via a valve, and the pressure in the heater chamber is It is desirable that the pressure can be controlled independently of the pressure in the reaction chamber.

Preferably, the distance is 0.5 to 10 mm. The shielding member is preferably provided with a high reflectance coating made of aluminum, silver, gold, or the like. It is preferable that a high transmittance thin film made of silicon dioxide or silicon nitride is further formed on the high reflectance coating.

In the method of manufacturing a solar cell using the above-described apparatus for manufacturing a thin film solar cell, after the film forming chamber is opened to the atmosphere, a thin film unique to the film forming chamber is provided on the surface of the shielding member for each film forming chamber. After the film formation, a thin film forming a solar cell is formed. In the method for manufacturing a solar cell using the above-described apparatus for manufacturing a thin film solar cell, the gas introduced into the heater chamber is a hydrogen gas or a source gas used for film formation.

In the method of manufacturing a solar cell using the above-described apparatus for manufacturing a thin-film solar cell, the substrate temperature is adjusted by controlling the pressure in the heater chamber. The pressure in the heater chamber is preferably 0.1 to 100 Pa.
According to the present invention, since the above-described shielding member shields the reaction chamber from the heater chamber, the conventional release of moisture from the heater chamber wall is blocked, and the decrease in photoelectric conversion efficiency due to moisture is prevented. It can be expected that it will not occur. Also, a substrate having a hole such as a SCAF solar cell can be mounted in the same manner as a substrate having no hole.

In addition, the temperature of the shield member is controlled by controlling the pressure of the heater chamber, and the temperature of the shield member is controlled over substantially the entire surface of the shield member, regardless of whether the shield member is in close contact with or away from the heater. Since the heating can be performed to the same extent as that described above, the release of moisture from the shielding member after the roll is attached is only in the initial stage and does not last for a long time. Therefore, although the operation rate of the manufacturing apparatus is characterized by being high, it can be expected.

Further, when the shield member and the heater are separated, the infrared reflectance of the shield member is increased, and the temperature control of the shield member is broadly controlled by the pressure of the gas having a large heat capacity, mainly hydrogen gas, in the heater chamber. It can be performed quickly, and an improvement in the operation rate of the manufacturing apparatus can be expected. In addition, the surface of the shielding member is roughened, and the peeling of the formed thin film does not occur,
The yield of solar cells can be expected to be high.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION

Example 1 FIG. 1 is a schematic cross-sectional view of a film forming chamber of an apparatus for manufacturing a thin-film solar cell according to an example of the present invention. Most of the configuration is the same as that of the conventional film forming chamber (FIG. 5), and thus only the differences will be described. There are two changes from the conventional structure. 1 is that the inside of the heater chamber 32 is the reaction chamber 22.
Is that the shielding member 3p is attached so as to be independent of
Reference numeral 2 denotes a point where a valve 42 independent of the valve 41 on the reaction chamber side is inserted into the flexible pipe 8 serving as a bypass line.

As the shielding member 3p, an aluminum foil, a stainless steel foil, or a heat-resistant polymer film such as polyimide or aramid can be used. It is effective to form a metal film, a SiO ₂ film, or the like on these films in order to prevent gas release. In order to keep the temperature of the shielding member 3p in the vicinity of the periphery 32a of the heater chamber at 150 ° C. or less, the thickness of the shielding member 3p needs to be 2 mm or less. Shielding member 3
When the thickness of p is 2 mm or less, the heat conduction in the lateral direction from the heater is sufficiently small, and the temperature rise near the peripheral portion 32a of the shielding member 3p can be suppressed. Although there is no lower limit of the thickness in terms of such a thermal effect, it is necessary to withstand many repetitions of contact with the substrate, and in terms of mechanical strength or abrasion, it is 0.0%.
1 mm is the lower limit.

When a film is formed on a perforated substrate such as a SCAF-structured solar cell, the surface of the shielding member is passed through a-
As a result, the Si film is formed in a dot-like manner, and in some cases, the film is peeled off, which may cause pinholes in the solar cell. In order to prevent film peeling, it is effective to apply sandblasting to the surface of the shielding member 3p to make the surface uneven.

Hereinafter, a procedure of a-Si film formation in the film forming apparatus of this embodiment will be briefly described. First, the heater chamber 32 is lowered, the film forming chamber is sealed, the valve 42 is opened, and the heater chamber 3 is opened.
2 and a source gas is introduced. Pressure control valve 41
After the pressure in the reaction chamber 22 is stabilized by controlling
2 is closed, power is supplied to the RF electrode 21, and an a-Si film is formed on the substrate 1. After a predetermined film thickness is formed, the RF power supply and the introduction of the source gas are stopped, and after the valve 42 is opened, the pressure control valve 41 is fully opened to evacuate. During film formation, the heater chamber and the reaction chamber are completely separated by the shielding member 3p and the valve 42, and the heater 31 is sufficiently heated over substantially the entire surface of the shielding member 3p itself, so that gas emission can be suppressed. In advance to the shielding member 3p
Pre-deposition of the a-Si coating can further suppress outgassing. In this embodiment, the source gas is introduced to the heater side for the film formation, because the temperature of the shielding member is almost raised to the heater temperature by the heat conduction of the gas. When the space on the heater side is in a vacuum state, the temperature difference between the heater and the shielding member is several tens of degrees Celsius, depending on conditions.
-100 ° C, and the accuracy of the temperature control of the shielding member is reduced.

The effect of this embodiment on the characteristics of the SCAF solar cell will be described. FIG. 2 is a graph showing the dependence of the photoelectric conversion efficiency of the SCAF-structure solar cell manufactured by the apparatus for manufacturing a thin-film solar cell according to the present invention on the number of deposition steps. The size of the SCAF solar cell is 40cm x 80cm. For comparison, FIG. 2 additionally shows the case of a SCAF-structured solar cell formed by a conventional film forming chamber. The symbol “■” indicates the case where pre-deposition was performed using the shielding member, the symbol “白” indicates the case where pre-deposition was not performed using the shielding member, and the symbol “□” indicates the case where no conventional shielding member was used.

From FIG. 2, the shielding member and the pre-deposition,
It can be seen that the rise time of the conversion efficiency is shorter in the order of only the shielding member and the absence of the shielding member, and the conversion efficiency at the time of stabilization is higher. That is, according to the present invention,
The mass productivity of the thin-film solar cell was improved, and the characteristics of the thin-film solar cell were also improved. Embodiment 2 In this embodiment, the shield member and the heater are separated from each other, and the temperature of the surface of the shield member, that is, the substrate temperature is controlled by the gas pressure in the heater chamber. FIG. 3 is a schematic sectional view of a film forming chamber of a thin-film solar cell manufacturing apparatus according to another embodiment of the present invention. Since the heat capacity of a normal cast aluminum heater is large, it is very difficult to rapidly raise and lower the temperature. On the other hand, since the heat capacity of the shielding member and the substrate is very small, rapid temperature rise and fall in several seconds to several minutes are possible.

The heater chamber 32 was provided with a gas line provided with a gas inlet 35, a pressure control valve 43, and a vacuum pump 52 of a different system from the reaction chamber 22. With this configuration, the gas pressure in the heater chamber 32 can be changed independently of the reaction chamber 22. In order to increase the temperature change of the shielding member when the gas pressure in the heater chamber 32 is changed, 1) a distance (referred to as a heat gap) is provided between the shielding member and the heater, and the temperature rise due to heat conduction is reduced. avoid,
2) It is necessary to avoid the temperature rise due to heat radiation from the heater by making the surface of the shielding member on the heater side high reflectivity.

The above-mentioned heat gap is suitably about 0.5 to 10 mm. If it is less than 0.5 mm, the heat gap (distance) becomes non-uniform, and the temperature of the shielding member tends to be non-uniform. If it is more than 10 mm, convection occurs irregularly and the temperature and its distribution become unstable. It is important to keep the in-plane thermal gap uniform by tensioning the shielding member by the spacer 3b fixed to the periphery of the heater.

Examples of the high-reflectance shielding member include polyimide, aramid, and the like formed by depositing or sputtering a high-reflectivity metal thin film of aluminum, silver, or gold on a heat-resistant film of aluminum foil, polyimide, or aramid. The heat-resistant film was effective. Further, when a high transmittance material such as silicon dioxide or silicon nitride is formed on the above metal surface as a protective film, and a multilayer is formed, a high reflectance can be maintained for a long time.

FIG. 4 is a graph showing the dependence of the substrate temperature on the pressure in the heater chamber in the apparatus for manufacturing a thin film solar cell according to the present invention. The thickness of the silver thin film formed on the surface as a shielding member
Using a 50μm polyimide film, the thermal gap is 3mm
And The substrate used was a 50 μm thick polyimide film. The gas introduced into the heater chamber and the reaction chamber was hydrogen gas having a large heat capacity. The pressure in the reaction chamber was 50 Pa. The heater temperature was 280 ° C.

FIG. 4 shows that the pressure on the heater side is 0.1 Pa to 100 Pa.
It can be seen that the substrate temperature can be controlled in a range of about 100 ° C. by changing the range.

[0028]

According to the present invention, a plurality of film forming chambers each including a reaction chamber in which a film forming reaction is performed and a heater chamber having a heater are provided, and the film forming chamber is transported while a long film substrate is transported step by step. A thin film forming a thin film solar cell is formed on the substrate, and the reaction chamber and the opening of the heater chamber are sealed with the substrate interposed therebetween during film formation. Since the opening of the heater chamber is covered by a shielding member, the conventional discharge of moisture from the heater chamber wall is blocked, the photoelectric conversion efficiency does not decrease due to the moisture, and the production can be performed at a high yield. The burden on solar cell manufacturing equipment is high. In addition, a substrate having a hole such as a SCAF solar cell can be mounted similarly to a substrate having no hole.

In addition, even when the shielding member is thin and is in close contact with or away from the heater, in this case, the temperature of the shielding member is controlled by controlling the pressure of the heater chamber, and the heating temperature of the shielding member itself is almost all over. Since the heating can be performed to the same extent as that described above, the release of moisture from the shielding member after the roll is attached is only in the initial stage and does not last for a long time. Therefore, the operation rate of the manufacturing apparatus is high.

Further, when the shield member and the heater are separated, the infrared reflectance of the shield member is increased, and the temperature control of the shield member is broadly controlled by the pressure of the gas having a large heat capacity, mainly hydrogen gas, in the heater chamber. It can be done quickly and the operating rate of the manufacturing equipment is improved. Further, the surface of the shielding member is roughened, and the formed thin film does not peel off, and the yield of the solar cell is increased.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a film forming chamber of a thin film solar cell manufacturing apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing the dependence of the photoelectric conversion efficiency of a SCAF solar cell manufactured by the thin film solar cell manufacturing apparatus according to the present invention on the number of deposition steps.

FIG. 3 is a schematic cross-sectional view of a film forming chamber of a thin-film solar cell manufacturing apparatus according to another embodiment of the present invention.

FIG. 4 is a graph showing the dependence of the substrate temperature on the pressure in the heater chamber in the apparatus for manufacturing a thin film solar cell according to the present invention.

FIG. 5 is a schematic sectional view of an apparatus for manufacturing a thin-film solar cell using a stepping roll method.

FIG. 6 is a schematic cross-sectional view of a film forming chamber of a conventional stepping roll type thin film solar cell manufacturing apparatus.

[Explanation of symbols]

 Reference Signs List 1 substrate 11 feed roll 12 take-up roll 21 RF electrode 22 reaction chamber 23 gas inlet 24 O-ring 31 heater 32 heater chamber 32a heater chamber rim 33 cooling pipe 34 pipe 35 gas inlet 3p shielding member 3b spacer 41 valve 42 valve 51 Pump 52 Pump R Deposition chamber E Power supply

Claims (16)

[Claims] An apparatus has a plurality of deposition chambers each comprising a reaction chamber in which a deposition reaction is performed and a heater chamber having a heater, and a thin film is formed on the substrate while step-transporting a long film substrate through the deposition chamber. An apparatus for manufacturing a thin film solar cell, in which a thin film constituting a solar cell is formed and an opening of the reaction chamber and the opening of the heater chamber are hermetically sealed with the substrate therebetween during the film formation, wherein the opening of the heater chamber is a shielding member. An apparatus for manufacturing a thin-film solar cell, comprising: 2. The apparatus according to claim 1, wherein the shielding member is a thin plate or foil made of a metal material, or a thin plate or film made of a heat-resistant polymer material. 3. The apparatus according to claim 2, wherein the metal material is aluminum or stainless steel. 4. The apparatus according to claim 2, wherein the heat-resistant polymer material is polyimide or aramid. 5. The shielding member has a thickness of 0.01 to 2 mm.
The apparatus for manufacturing a thin-film solar cell according to any one of claims 1 to 4, wherein 6. The apparatus for manufacturing a thin-film solar cell according to claim 1, wherein the surface of the shielding member on the side of the film forming chamber is subjected to an unevenness treatment. 7. The apparatus according to claim 6, wherein the concavo-convex treatment is sand blasting. 8. The apparatus according to claim 1, wherein the shielding member is in close contact with the heater. 9. The heater is provided in parallel with the heater, and the heater chamber is provided with a gas inlet and a gas outlet connected to a vacuum pump via a valve. 8. The apparatus according to claim 1, wherein the pressure in the chamber can be controlled independently of the pressure in the reaction chamber. 10. The apparatus according to claim 9, wherein the distance is 0.5 to 10 mm. 11. An apparatus according to claim 9, wherein said shielding member is provided with a high reflectance coating made of aluminum, silver, gold or the like. 12. The apparatus according to claim 11, wherein a high transmittance thin film made of silicon dioxide or silicon nitride is further formed on the high reflectance coating. 13. A method for manufacturing a thin-film solar cell using the apparatus for manufacturing a thin-film solar cell according to claim 1, wherein after the film-forming chamber is opened to the atmosphere, the film-forming chamber is provided on the surface of the shielding member. Forming a thin film unique to a film forming chamber, and then forming a thin film constituting the thin film solar cell. 14. A method for manufacturing a thin film solar cell using the apparatus for manufacturing a thin film solar cell according to claim 1, wherein the gas introduced into the heater chamber is a hydrogen gas or a raw material gas used for film formation. A method for producing a thin-film solar cell, comprising: 15. A method for manufacturing a thin film solar cell using the apparatus for manufacturing a thin film solar cell according to claim 9, wherein a substrate temperature is adjusted by controlling a pressure in the heater chamber. Of manufacturing a thin film solar cell. 16. The pressure in the heater chamber is 0.1 to 100P.
The method according to claim 15, wherein a.