JP6026356B2 - Deposition equipment - Google Patents

Description

  The present invention relates to a film forming apparatus using a chemical bath deposition method, and more particularly to a film forming apparatus capable of suppressing the generation of bubble streaks and forming a film having excellent film thickness uniformity.

  Conventionally, a film is formed by a chemical bath deposition method (CBD method: Chemical Bath Deposition). The chemical bath deposition method (hereinafter also referred to as CBD method) is a method of depositing a film on a substrate immersed in a reaction solution. The precipitation reaction is allowed to proceed by adjusting the temperature of the reaction solution, the solute concentration, pH, etc., and controlling the degree of supersaturation. In addition, it is known that the solute concentration or pH changes every moment when a colloid is generated by a side reaction during the reaction, particularly when a gaseous component such as ammonia is dissolved.

  As a film forming apparatus using the CBD method, in Patent Document 1, a first piston is inserted into a first opening and a second piston is inserted into a second opening having a smaller opening area than the first opening. A cylinder in which a liquid is sealed between the first piston and the second piston, a film formation tank mounted on the first piston, and a film formation tank. A supply system mechanism for supplying the film solution into the film formation tank, a circulation system mechanism provided in conjunction with the film formation tank for circulating the film formation solution in the film formation tank, There is disclosed a film forming apparatus that is provided so as to be separable from the film tank and includes a discharge system mechanism that discharges the film forming solution from the film forming tank.

In Patent Document 1, since the supply system mechanism and the discharge system mechanism can be separated from the film formation tank, interference from the outside can be prevented when the film formation solution is introduced, and weight measurement can be performed accurately. Further, since the circulation system mechanism is provided so as to be interlocked with the film formation tank, the weight of the film formation solution can be directly measured and managed with high accuracy even during film formation.
Patent Document 1 describes that a rectifying plate for rectifying the film forming solution is provided inside the film forming tank. Further, it is described that the circulation system mechanism circulates the film forming solution by flowing the film forming solution overflowing from the upper part of the film forming tank into the bottom of the film forming tank. Further, Patent Document 1 discloses that a film forming solution is supplied from above to a film forming tank through a supply pipe.

JP 2012-134216 A Japanese Patent No. 4050841

The film forming apparatus disclosed in Patent Document 1 has a problem in that bubble streaks occur in the formed film.
In addition, when a film forming solution is supplied to the film forming tank from above, it is difficult to ensure uniformity of the film forming solution with respect to the substrate, and the film thickness is formed when a large number of substrates are formed in one batch. There is a problem that variations occur.

  Here, in the conventional wet etching processing apparatus described in Patent Document 2, an etching solution supply nozzle 2 is attached to the bottom of a bottomed box-shaped processing tank 1 whose upper side is open, while the upper edge. An overflow rod 3 is provided around the processing object 4 so that the processing object 4 is immersed in the processing tank 1 filled with the etching solution 6 while being placed on the processing object installation mechanism 5. . The overflow tank 3 is connected to the etching liquid supply nozzle 2 via the circulation pump 7 and the filter 8. The etching liquid 6 overflowing from the processing tank 1 is collected by the overflow tank 3 and then supplied to the etching liquid. It is discharged again from the nozzle 2 into the treatment tank 1 and recirculated. In the wet etching processing apparatus disclosed in Patent Document 2, since the uniformity of etching cannot be obtained, the uniformity of the film thickness cannot be obtained even when used in a film forming apparatus.

  An object of the present invention is to provide a film forming apparatus capable of solving the problems based on the above-described prior art, suppressing the generation of bubble streaks, and forming a film having excellent film thickness uniformity.

  In order to achieve the above object, the present invention provides a film forming apparatus for forming a film on a film forming material using a chemical bath deposition method, in which a reaction solution is stored and the film forming material is converted into a reaction solution. A reaction tank for immersing and forming a film on the material to be deposited, a supply pipe provided at the bottom of the reaction tank for supplying the reaction solution into the reaction tank, a supply unit for supplying the reaction solution, and a supply It is provided at the other end of the tube, and has a bubble removing portion for removing bubbles from the reaction solution, and the supply tube is formed with a hole for supplying the reaction solution into the reaction vessel. A film forming apparatus is provided.

It is preferable to have a circulation unit that supplies the reaction solution that has passed through the bubble removal unit to the supply pipe again. For example, a plurality of deposition materials are vertically installed in the reaction tank.
Further, it is preferable that a current plate is provided between the supply pipe and the film forming material in the reaction tank. Furthermore, it is preferable that the opening rate per unit length of the hole of the supply pipe is lower on the opposite side to the bubble removal part side and higher on the bubble removal part side.

  According to the film forming apparatus of the present invention, a film having no bubble streaks and excellent film thickness uniformity can be obtained.

(A) is a schematic diagram which shows the film-forming apparatus of embodiment of this invention, (b) is a typical perspective view which shows the arrangement | positioning state of the film-forming material. (A) is typical sectional drawing which shows arrangement | positioning of the supply pipe | tube of the film-forming apparatus shown to Fig.1 (a), (b) is the hole of the supply pipe | tube of the film-forming apparatus shown to Fig.1 (a). It is a schematic diagram which shows arrangement | positioning, (c) is a typical perspective view which shows the bubble removal part used for the film-forming apparatus of embodiment of this invention. (A) is a typical perspective view which shows the 1st example of the film-forming apparatus for a comparison, (b) is a schematic perspective view which shows the 2nd example of the film-forming apparatus for a comparison. . (A) is a drawing substitute photograph showing a film formed by using the film forming apparatus of the embodiment of the present invention, and (b) is a film forming apparatus of the second example shown in FIG. 3 (b). 2 is a drawing-substituting photograph showing a film formed using a film. It is typical sectional drawing which shows an example of the photoelectric conversion element formed using the film-forming apparatus of embodiment of this invention. (A), (b) is for demonstrating the formation method of the buffer layer using the film-forming apparatus of embodiment of this invention, (a) is a model which shows the state before formation of a buffer layer. It is a typical sectional view, and (b) is a typical sectional view showing a state after formation of a buffer layer. It is typical sectional drawing which shows an example of the solar cell formed using the film-forming apparatus of embodiment of this invention. (A) And (b) is typical sectional drawing which shows the formation process of the buffer layer using the film-forming apparatus of embodiment of this invention in order of a process.

Hereinafter, a film forming apparatus of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
FIG. 1A is a schematic view showing a film forming apparatus according to an embodiment of the present invention, and FIG. 1B is a schematic perspective view showing an arrangement state of film forming materials. 2A is a schematic cross-sectional view showing the arrangement of the supply pipe of the film forming apparatus shown in FIG. 1A, and FIG. 2B is the schematic view of the supply pipe of the film forming apparatus shown in FIG. It is a schematic diagram which shows arrangement | positioning of a hole, (c) is a typical perspective view which shows the bubble extraction part used for the film-forming apparatus of embodiment of this invention.

A film forming measure 10 shown in FIG. 1A forms a film on the film forming material S using a chemical bath deposition method. The film forming material S is, for example, a plate-like substrate, but is not particularly limited. For example, the film-forming material S may be semi-finished products such as semiconductor elements, photoelectric conversion elements, and solar cells.
Here, the chemical bath deposition method is a general formula [M (L) i] m + ⇔Mn ++ iL (wherein M: metal element, L: ligand, m, n, i: positive number). The film is formed by depositing a film on the film-forming material S at an appropriate speed in a stable environment by setting the supersaturation condition by the equilibrium represented by

  A film forming apparatus 10 illustrated in FIG. 1A includes a reaction tank 12, an outer tank 14, a supply pipe 16, a bubble removal unit 18, a heater 20, and a pump 22. The supply pipe 16, the bubble vent 18, the heater 20, and the pump 22 are connected by a pipe 26, whereby the reaction solution 13 supplied to the reaction tank 12 is supplied to the supply pipe 16, and It can be circulated. Moreover, the piping 26 and the piping 28 provided in the outer tank 14 are connected. Thereby, the reaction solution 13 collected in the outer tank 14 can also be circulated and reused.

In the reaction tank 12, a reaction solution 13 for forming a film on the film forming material S is stored in the inside 12 a, and the film forming material S is immersed in the reaction solution 13 to form a predetermined film on the film forming material S. This is for forming a film. The reaction tank 12 is open at the top 12b. As shown in FIG. 1B, a plurality of film forming materials S are vertically installed in the reaction tank 12 with a predetermined interval. The film forming material S is not limited to a plurality, and may be one.
The reaction tank 12 is not particularly limited, and known reaction tanks and containers used for the chemical bath deposition method can be appropriately used.
As the reaction solution 13, a solution having a component corresponding to a film to be formed is used. When the photoelectric conversion layer is formed by CIGS, the reaction solution used for forming the buffer layer will be described in detail later.

The outer tank 14 stores the reaction solution 13 overflowed from the upper part 12 b of the reaction tank 12, and is provided so as to surround the outer edge of the reaction tank 12. A pipe 28 for taking out the reaction solution 13 accumulated in the outer tank 14 to the outside is provided at the bottom of the outer tank 14. This pipe 28 is connected to the pipe 26 as described above. The reaction solution 13 collected in the outer tank 14 is supplied to the supply pipe 16 via the pipe 26 via the heater 20 and the pump 22. Thereby, the overflowed reaction solution 13 can be utilized again.
It is preferable to have a lid that closes the upper part 12 b of the reaction tank 12 and the opening of the outer tank 14.

The supply pipe 16 supplies the reaction solution 13 to the reaction tank 12. The supply pipe 16 is provided in the lower part 12 c of the reaction tank 12 so as to penetrate the reaction tank 12, and supplies the reaction solution 13 from the lower side of the reaction tank 12 to the inside 12 a.
The supply pipe 16 has a pipe 26 connected to one end thereof. The side to which this pipe 26 is connected is called the supply side or the upstream side. In addition, the supply pipe 16 is connected to the bubble removal part 18 at the other end. The side to which the bubble removal unit 18 is connected is referred to as the bubble removal unit 18 side or the downstream side. The reaction solution 13 is supplied to the supply pipe 16 from the supply side toward the bubble removal unit 18.

A plurality of holes 16a are formed in the supply pipe 16 (see FIG. 2A), and the holes 16a are arranged toward the bottom 12d of the reaction tank 12 (see FIG. 2A). By directing the hole 16a to the bottom 12d, the reaction solution 13 can be supplied without disturbing the flow.
As shown in FIG. 2B, the supply pipe 16 preferably has an opening rate per unit length of the hole 16a that is lower on the supply side of the reaction solution and higher on the bubble removal unit 18 side. Thereby, the reaction solution 13 can be more uniformly supplied to the film forming material S in the longitudinal direction of the supply pipe 16, and the film thickness uniformity can be improved.
The aperture ratio per unit length can be changed, for example, by changing the pitch of the holes 16a. Further, for example, the average interval between the holes 16a on the upstream side from the center of the supply pipe 16 may be double the average interval between the holes 16a on the downstream side.
The position, number, density, and the like of the holes 16a of the supply pipe 16 are not particularly limited, and are appropriately set depending on the size of the film forming apparatus, the film forming target, the film forming conditions, and the like. .

  A rectifying plate 24 is provided between the supply pipe 16 and the film forming material S. The rectifying plate 24 is provided in the interior 12 a of the reaction vessel 12 without a gap. The rectifying plate 24 is formed with a plurality of holes 24a. The hole 24a is circular, for example. The flow of the reaction solution 13 can be homogenized by the current plate 24, and the reaction solution 13 can be supplied more uniformly to the film forming material S. Note that the rectifying plate 24 is not necessarily provided.

The bubble removal part 18 is for suppressing generation | occurrence | production of the bubble in the reaction tank 12 inside 12a. For example, as shown in FIG. 1A and FIG. 2C, the bubble vent 18 is connected to the supply pipe 16 and the pipe 26, and the pipe 26 is connected to a lower position. In addition, a return pipe 19 is connected to the upper part of the bubble removing section 18, and the return pipe 19 is directed to the outer tub 14 with an opening at the end thereof. The return pipe 19 is provided with a valve 29a. In addition, a valve 29 b is provided in the pipe 26 of the bubble vent 18.
The reaction solution 13 supplied to the supply pipe 16 contains bubbles generated by entraining air during the transfer or heating to a predetermined temperature. When the reaction solution 13 moves from the supply side to the bubble removal unit 18 side, since there is a flow, bubbles are not easily generated in the interior 12 a of the reaction tank 12. When the reaction solution 13 is supplied from the supply pipe 16 to the bubble removal unit 18, the reaction solution 13 accumulates, and bubbles float on the surface. The reaction solution 13 flows to the pipe 26 side in the Fl direction, but since the bubbles are gas and light, they move back to the Fa pipe 19 side in the Fa direction. Thereby, bubbles are removed from the reaction solution 13. The reaction solution 13 partially moves along with the bubbles to the return pipe 19, but the reaction solution 13 is returned to the outer tank 14. By adjusting the opening / closing degree of the valve 29a, the bubbles can be efficiently moved to the return pipe 19 and removed. Further, for example, the opening / closing rate of the valve 29b is adjusted according to the amount of foam in the foam removal unit 18. Thereby, the reaction solution 13 without bubbles can be sent to the reaction tank 12. In addition, the structure of the bubble removal part 18 is not specifically limited to the structure shown to Fig.1 (a) and FIG.2 (c).

  The heater 20 heats the reaction solution 13 to a predetermined temperature. The heater 20 is connected to the bubble removal unit 18 via a pipe 26. The configuration of the heater 20 is not particularly limited, and various known heaters used in the CBD method can be used.

  The pump 22 functions as a supply unit that supplies the reaction solution 13 to the supply pipe 16 and also functions as a circulation unit that circulates the reaction solution 13 and supplies the reaction solution 13 to the supply pipe 16 again. The configuration of the pump 22 is not particularly limited as long as the reaction solution 13 can be transferred, and a known one can be appropriately used.

Next, the reaction solution 13 will be described in detail. An appropriate reaction solution 13 is used according to the film to be formed. Specifically, the reaction solution 13 will be described using an example of a photoelectric conversion element and a buffer layer of a solar cell, which will be described in detail later. The buffer layer is made of a compound containing sulfide, for example.
As the reaction solution 13, for example, a solution containing a predetermined metal ion, thiourea, or thioacetamide is used. For example, as the reaction solution 13, a solution described in the following literature can be used. The literature includes MA Contreras, et. Al., Thin Solid Films, 403, 204, (2002) when the given metal is zinc, and C. Hubert, et al. When the given metal is cadmium. , Phys. Stat. Sol. 205, 2335, (2008), D. Hariskos, et al., Sol. Energ. Mat. Sol. C, 41, 345, (1996) ).
The example described below is a preferred composition of the reaction solution 13. In the following, the case where the predetermined metal is zinc will be described, but the same applies to the case of cadmium, indium, and tin.

  The Zn source preferably contains at least one selected from the group consisting of zinc sulfate, zinc acetate, zinc nitrate, zinc citrate, and hydrates thereof. The concentration is not particularly limited and is preferably 0.001 to 0.5M. It is preferable to contain thiourea as the S source. The concentration of thiourea is not particularly limited and is preferably 0.01 to 1.0M.

The reaction solution 13 preferably contains an ammonium salt such as NH ₄ OH that functions as a pH adjuster or the like. The ammonium salt is also a component that functions as a complexing agent or the like. The concentration of the ammonium salt is preferably 0.001 to 10.0M. Thereby, pH can be adjusted and the solubility or supersaturation degree of a metal ion can be adjusted. When the concentration of the ammonium salt is in the range of 0.001 to 10.0M, the reaction rate is high and the film can be formed at a practical production rate.

  Furthermore, 1M or more of alkali metal ions may be included. Here, the alkali metal source preferably contains trisodium citrate, tripotassium citrate, trilithium citrate and / or a hydrate thereof. Sodium is taken into the buffer layer when trisodium citrate is used, potassium is used when tripotassium citrate is used, and lithium is used when trilithium citrate is used.

  The trisodium citrate, tripotassium citrate, and trilithium citrate also serve as a component that functions as a complexing agent. For example, in JP-A-2002-343987, citric acid in a reaction solution is used. It is described that the concentration of trisodium is preferably 0.001 to 0.25M.

The pH of the reaction solution 13 before the start of the reaction is, for example, 9.0 to 12.5.
When the pH of the reaction solution 13 before the start of the reaction is less than 9.0, the decomposition reaction of the component (S) such as thiourea does not proceed or even proceeds so slowly that the precipitation reaction does not proceed. The decomposition reaction of thiourea is as follows. The decomposition reaction of thiourea is described in Journal of the Electrochemical Society, 141, 205-210 (1994), Journal of Crystal Growth 299, 136-141 (2007) and the like.
_{SC (NH 2) 2 + OH} - ⇔SH - + CH 2 N 2 + H 2 O
SH ⁻ + OH ⁻ ⇔S ² + + H ₂ O
If the pH of the reaction solution 13 before the start of the reaction is more than 12.5, the effect that the component (N) that also functions as a complexing agent or the like makes a stable solution increases, and the precipitation reaction does not proceed or proceeds. Will be very slow.

  The pH after completion of the reaction of the reaction solution 13 is not particularly limited. The pH of the reaction solution 13 after the reaction is preferably 7.5 to 12.5. If the pH of the reaction solution 13 after the completion of the reaction is less than 7.5, it means that the reaction does not proceed, which is meaningless when considering efficient production. In addition, if there is such a pH drop in a system containing ammonia that has a buffering effect, it is highly possible that ammonia has volatilized excessively in the heating process, and it is considered that manufacturing improvements are necessary. It is done. When the pH of the reaction solution 13 after the reaction is over 12.5, the decomposition of thiourea is promoted, but since most of the zinc ions are stabilized as ammonium complexes, the progress of the precipitation reaction may be extremely slow. . The pH after completion of the reaction of the reaction solution 13 is more preferably 9.5 to 10.5.

In addition, a substrate containing a metal that can easily be dissolved in an alkaline solvent, such as a metal that can form a complex ion with a hydroxide ion, for example, an Al base material mainly composed of Al that can be applied as a flexible substrate. An anodized substrate having an anodized film mainly composed of Al ₂ O ₃ formed on at least one surface side, and an Al material mainly composed of Al on at least one surface side of an Fe material mainly composed of Fe Anodized substrate in which an anodized film mainly composed of Al ₂ O ₃ is formed on at least one surface side of the laminated clad material, and Al is mainly disposed on at least one surface side of the Fe material mainly composed of Fe. Even when an anodized substrate such as an anodized substrate in which an anodized film containing Al ₂ O ₃ as a main component is formed on at least one surface side of a base material on which an Al film as a component is formed is used. , May cause damage to the film-forming material S No, it is possible to form a high uniformity buffer layer.

  The reaction temperature is, for example, 60 to 98 ° C. When the reaction temperature is less than 60 ° C., the reaction rate becomes slow, and the film does not grow. Even when the film is grown, it is difficult to obtain a desired thickness, for example, 50 nm or more at a practical reaction rate. When the reaction temperature exceeds 98 ° C., it is difficult to maintain the uniformity of the reaction temperature, resulting in film thickness unevenness due to temperature unevenness. Furthermore, when the reaction is carried out in an open system, a change in concentration due to evaporation of the solvent or the like occurs, making it difficult to maintain stable film deposition conditions. The reaction temperature is preferably 70 to 90 ° C.

  The reaction time is not particularly limited. Although the reaction time depends on the reaction temperature, for example, a film having a sufficient thickness for satisfactorily covering the base can be formed in 10 to 90 minutes.

In the film forming apparatus 10, the film forming material S is disposed in the reaction tank 12, and then the reaction solution 13 that has been heated to a predetermined temperature by the heater 20 according to the film forming conditions is supplied via the supply pipe 16 by the pump 22. Then, the reaction vessel 12 is supplied from the bottom, and the reaction vessel 12 is filled with the reaction solution 13. Thereafter, the reaction solution 13 is supplied from the lower part into the reaction tank 14 through the supply pipe 16 according to the film forming conditions for a predetermined time. At this time, since the hole 16a of the supply pipe 16 faces the bottom 12d, the reaction solution 13 is supplied to the film forming material S without disturbing the flow. Further, since the current plate 24 is provided, the reaction solution 13 is uniformly supplied to the film forming material S. The reaction solution 13 that has passed through the supply pipe 16 is removed from the reaction solution 13 at the bubble removal unit 18. Thereby, generation | occurrence | production of the bubble in the reaction tank 12 can be suppressed, generation | occurrence | production of a bubble streak can be suppressed in a film | membrane, and a film | membrane with high film thickness uniformity can be formed into a film. For this reason, even if the film thickness is as thin as several tens of nm and a high film thickness accuracy is required, the film can be formed with a predetermined film thickness accuracy.
In the film forming apparatus 10, even when a plurality of film forming materials S are collected and a film is formed on each of the film forming materials S, bubble streaks are not generated in each film forming material S and the film thickness uniformity is maintained. A high film can be formed. In addition, the film forming material S may be disposed after the inside 12 a of the reaction tank 12 is filled with the reaction solution 13.

The reaction solution 13 from which bubbles have been removed by the bubble removal unit 18 is sent to the heater 20 via the pipe 26 and is used again for film formation. The foam removed by the foam removal unit 18 is supplied to the outer tank 14 through a return pipe 19 together with a part of the reaction solution 13. On the other hand, the reaction solution 13 supplied to the reaction tank 12 overflows from the upper part 12 b of the reaction tank 12 to the outer tank 14 when the volume of the reaction tank 12 is exceeded. The reaction solution 13 accumulated in the outer tub 14 is supplied again to the supply pipe 16 via the pipe 28 via the pipe 26, the heater 20, and the pump 22, and is used again for film formation. Thus, by using the reaction solution 13 again, the amount of the reaction solution 13 required for film formation can be reduced.
Note that the film forming material S may be disposed after the inside 12 a of the reaction tank 12 is filled with the reaction solution 13.

Here, FIG. 3A is a schematic perspective view showing a first example of a film forming apparatus for comparison, and FIG. 3B shows a second example of the film forming apparatus for comparison. It is a model perspective view. The same components as those in the film forming apparatus 10 shown in FIG. 1A are denoted by the same reference numerals, and detailed description thereof is omitted.
The film forming apparatus 100 shown in FIG. 3 (a) is the same as the film forming apparatus 10 shown in FIG. 1 (a) except that the bubble vent 18 is not provided on the downstream side of the supply pipe 16. Since it is the same structure as the membrane apparatus 10, the detailed description is abbreviate | omitted.
Further, the film forming apparatus 102 shown in FIG. 3B is different from the film forming apparatus 10 shown in FIG. 1A in that the bubble vent 18 is not provided on the downstream side of the supply pipe 16. Since the configuration is the same as that of the film forming apparatus 10 except that the reaction solution 13 is supplied from both sides of the tube 16, detailed description thereof is omitted.

In the film forming apparatus 100 in which the bubble removal unit 18 is not provided on the downstream side illustrated in FIG. 3A, bubbles B are generated on the downstream side. In the film forming apparatus 102 that supplies the reaction solution 13 from both sides shown in FIG. As a result, it was confirmed that when the film was formed by the film forming apparatus 102 shown in FIG. 3B, bubble streaks α were formed on the film as shown in FIG. 4B. Although not shown, even when a film is formed by the film forming apparatus 100 shown in FIG.
On the other hand, as shown in FIG. 4A, it has been confirmed that the film forming apparatus 10 can form a film having high film thickness uniformity without generating bubble streaks.

Next, a specific example of film formation using the film formation apparatus 10 will be described.
For example, the film forming apparatus 10 can form the buffer layer 38 of the photoelectric conversion element 30 illustrated in FIG. 5. Prior to the description of the formation of the buffer layer 38, first, the photoelectric conversion element 30 shown in FIG. 5 will be described.
The photoelectric conversion element 30 shown in FIG. 5 is formed on the back surface electrode 34 formed on the surface 32 a of the substrate 32, the photoelectric conversion layer 36 formed on the surface 34 a of the back electrode 34, and the surface 36 a of the photoelectric conversion layer 36. And a transparent electrode 40 formed on the buffer layer 38, and an upper electrode 42 formed on the back electrode 34 and the transparent electrode 40.

Examples of the substrate 32 include glass substrates such as non-alkali glass and quartz glass, ceramic substrates made of alumina, a metal substrate made of stainless steel, titanium foil, silicon, and the like, and a polymer made of polyimide or the like. A substrate can be used.
When the insulating layer is not formed, the substrate 32 is composed of a single member having insulating properties.
The substrate 32 preferably has a metal plate from the viewpoint of heat resistance and lightness. When an anodic oxide film is used for the insulating layer, at least one metal plate of aluminum, iron, zirconium, titanium, magnesium, copper, niobium and tantalum or a metal plate made of an alloy of the above metal is used. It is preferable.

The substrate 32 is not limited to a single layer structure, and may be a laminated substrate. In this case, a clad material in which an aluminum plate or an aluminum alloy plate is laminated and integrated on one side or both sides of a metal plate that is not aluminum can be used. This clad material is more preferable from the viewpoint of easy formation of an anodized film and high durability. In the case of a clad material integrated on both sides of an aluminum plate or an aluminum alloy plate on both sides of the metal plate, the warp of the substrate due to the difference in thermal expansion coefficient between the aluminum or aluminum alloy and the anodized film made of Al ₂ O ₃ , Further, peeling of the anodized film can be suppressed.
In addition, the clad material which laminated | stacked the aluminum plate on the single side | surface of a metal plate is described as Al / metal, and the clad material which laminated | stacked the aluminum plate on both surfaces of the metal plate is described as Al / metal / Al. Various material names are included in the metal. As the metal plate, for example, a stainless plate, a steel plate, a titanium plate or the like is used.

  The back electrode 34 is made of, for example, Mo, Cr, or W and a combination thereof. The back electrode 34 may have a single layer structure or a laminated structure such as a two-layer structure. The back electrode 34 is preferably composed of Mo. The film thickness of the back electrode 34 is preferably about 200 to 1000 nm.

  Since the photoelectric conversion layer 36 can obtain high photoelectric conversion efficiency, for example, a chalcogen compound semiconductor, a compound semiconductor having a chalcopyrite structure, and a compound semiconductor having a defect stannite structure are used. The film thickness of the photoelectric conversion layer 36 is preferably 1.0 to 3.0 μm, and particularly preferably 1.5 to 2.0 μm.

As a chalcogen compound (compound containing S, Se, Te), a II-VI compound: ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, etc., an I-III-VI _II group compound: CuInSe ₂ , CuGaSe ₂ , Cu (In, Ga) Se ₂ , CuInS ₂ , CuGaSe ₂ , Cu (In, Ga) (S, Se) _2, etc., I-III ₃ -VI Group ₅ compounds: Culn ₃ Se ₅ , CuGa ₃ Se ₅ , Cu ( In, Ga) ₃ Se _{5 and the} like can be preferably exemplified.

The compound semiconductor having a chalcopyrite structure and defects stannite structure, I-III-VI _{2 compound: CuInSe 2, CuGaSe 2, Cu} (In, Ga) Se 2, CuInS 2, CuGaSe 2, Cu (In, Ga ) (S, Se) _{2 and the} like, and I-III ₃ -VI Group ₅ compounds: CuIn ₃ Se ₅ , CuGa ₃ Se ₅ , Cu (In, Ga) ₃ Se _{5 and the} like can be preferably exemplified. The above (In, Ga) and (S, Se) are respectively (In _1-x Ga _x ) and (S _1-y Se _y ) (where x = 0 to 1, y = 0 to 1). Show.
Moreover, the photoelectric converting layer 36 can also be comprised with a CZTS type compound, for example. An example of the CZTS compound is Cu ₂ ZnSnS ₄ .

  The method for forming the photoelectric conversion layer 36 is not particularly limited. For example, the CI (G) S-based photoelectric conversion layer 36 containing Cu, In, (Ga), S can be formed by a known method such as a selenization method or a multi-source deposition method.

  Specifically, the buffer layer 38 is made of CdS, ZnS, Zn (S, O) and / or Zn (S, O, OH), SnS, Sn (S, O) and / or Sn (S, O, OH). ), InS, In (S, O) and / or In (S, O, OH), etc., and a metal sulfide containing at least one metal element selected from the group consisting of Cd, Zn, Sn, In It is preferable.

The thickness of the buffer layer 38 is preferably 10 nm to 2 μm, and more preferably 15 to 200 nm. If the buffer layer 38 is thinner than 10 nm, the photoelectric conversion layer 36 may be damaged when the transparent electrode 40 formed after the buffer layer 38 is formed. On the other hand, if the buffer layer 38 is too thick, the amount of light incident on the photoelectric conversion layer 36 may be reduced.
Further, if the buffer layer 38 has a film thickness unevenness, when the film thickness is small, the photoelectric conversion layer 36 may be damaged or not. On the other hand, when the film thickness is large, the amount of light to the photoelectric conversion layer 36 varies. For this reason, it is preferable that the buffer layer 38 has high film thickness uniformity.

  The transparent electrode 40 captures light into the photoelectric conversion layer 36 and functions as an electrode through which a current generated in the photoelectric conversion layer 36 flows, paired with the back electrode 40. Although the transparent electrode 40 can be comprised by a well-known composition, it is preferable to comprise by n-ZnO, such as ZnO: Al. The film thickness of the transparent electrode 40 is, for example, 50 nm to 2 μm.

The upper electrode 42 is an electrode for taking out the current generated in the photoelectric conversion layer 36 from the transparent electrode 40 when the photoelectric conversion element 30 is a cell. For this reason, the upper electrode 42 may not be provided.
The upper electrode 42 is made of aluminum, for example. The upper electrode 42 is formed by, for example, a sputtering method, a vapor deposition method, a CVD method, or the like. The upper electrode 42 is also referred to as a grid electrode.

Next, a method for forming the buffer layer 38 of the photoelectric conversion element 30 using the film forming apparatus 10 will be described.
6A and 6B are diagrams for explaining a method for forming a buffer layer using the film forming apparatus according to the embodiment of the present invention. FIG. 6A shows a state before the buffer layer is formed. It is a typical sectional view shown, and (b) is a typical sectional view showing the state after formation of a buffer layer.
First, as shown in FIG. 6A, a substrate having a back electrode 34 formed on the surface 32a of the substrate 32 and a photoelectric conversion layer 36 made of CIGS formed on the back electrode 34 is prepared. . The film forming material 44 is in this state. A buffer layer 38 is formed on the surface 36 a of the photoelectric conversion layer 36 of the film forming material 44.
In addition, since the back surface electrode 34 and the photoelectric conversion layer 36 of the film formation material 44 can be formed by a known method, the detailed description of the manufacturing method is omitted.

In the formation of the buffer layer 38, the reaction solution 13 that is used for forming the above-described photoelectric conversion element and the buffer layer of the solar cell is used.
A film forming material 44 is placed in the reaction tank 12 of the film forming apparatus 10. Then, the reaction solution 13 brought to a predetermined temperature by the heater 20 in accordance with the film formation conditions is supplied from the lower part into the reaction tank 12 through the supply pipe 16 by the pump 22, and the reaction tank 12 is filled with the reaction solution 13. Fulfill. Thereafter, the reaction solution 13 is supplied from the lower part into the reaction tank 14 through the supply pipe 16 according to the film forming conditions for a predetermined time. Thereby, the buffer layer 38 is formed on the surface 36a of the photoelectric conversion layer 36 as shown in FIG. Note that a mask is preferably provided on the surface 34 a of the back electrode 34. Alternatively, the film forming material 44 may be disposed after the inside 12 a of the reaction tank 12 is filled with the reaction solution 13.
In the formation of the buffer layer 38, the reaction solution 13 that has passed through the supply pipe 16 is removed from the reaction solution 13 by the bubble removal unit 18, and bubbles are prevented from being generated in the reaction tank 12. Generation of bubble streaks can be suppressed. Thereby, the buffer layer 38 without a bubble streak is obtained.

In the supply pipe 16, the reaction solution 13 and bubbles are mixed. However, since the bubbles are pushed more easily by the flow than the reaction solution 13, the bubbles move together with some of the reaction solutions 13 to the bubble removal unit 18, and only the reaction solution 13 not containing bubbles enters the reaction tank 12. Sent.
The reaction solution 13 that has passed through the bubble vent 18 is sent to the heater 20 via the pipe 26 and the valve 29b, and is used again for film formation. The foam removed by the foam removal unit 18 is supplied to the outer tank 14 through a return pipe 19 together with a part of the reaction solution 13. On the other hand, the reaction solution 13 supplied to the reaction tank 12 overflows from the upper part 12 b of the reaction tank 12 to the outer tank 14 when the volume of the reaction tank 12 is exceeded. The reaction solution 13 collected in the outer tank 14 is sent to the supply pipe 16 via the pipe 28 and is used again for film formation. Thus, by using the reaction solution 13 again, the amount of the reaction solution 13 required for forming the buffer layer 38 can be reduced.

Moreover, the above-mentioned film-forming apparatus 10 can form the buffer layer 38 of the solar cell 50 shown, for example in FIG. Prior to the description of the formation of the buffer layer 38, the solar cell 50 shown in FIG. 7 shown in FIG. 7 will be described first.
A solar cell 50 shown in FIG. 7 is obtained by integrating the photoelectric conversion elements 30 shown in FIG. In the solar cell 50, the same components as those of the photoelectric conversion element 30 shown in FIG.

  In the solar cell 50, the back electrode 34, the photoelectric conversion layer 36, the buffer layer 38, and the transparent electrode 40 are laminated, and the first groove P 1 that penetrates only the back electrode 34, the photoelectric conversion layer 36, and the buffer layer. And a third groove P3 that penetrates the photoelectric conversion layer 36, the buffer layer 38, and the transparent electrode 40 is formed.

In the solar cell 50, it is separated into a plurality of photoelectric conversion elements 52 by the first groove portion P1 to the third groove portion P3. By filling the second open groove 62 with the transparent electrode 40, a structure in which the transparent electrode 40 of a certain photoelectric conversion element 52 is connected in series to the back electrode 34 of the adjacent photoelectric conversion element 52 is obtained. Electrically connected in series so that the voltage generated in each photoelectric conversion element 52 is added. At this time, the effective portion of the photoelectric conversion function is the region 54.
The solar cell 50 is configured such that electrons flow in the direction D shown in FIG. 7, the back electrode 34 is a positive electrode, and the transparent electrode 40 is a negative electrode.
FIG. 7 illustrates the repeated series connection structure of the photoelectric conversion elements 52 in an easy-to-understand manner. The connection of the minus lead electrode may be the transparent electrode 40 as illustrated, or the second open groove P2 may be connected. The back electrode 34 located below may be used.

A method for forming the buffer layer 38 of the solar cell 50 using the film forming apparatus 10 will be described.
FIGS. 8A and 8B are schematic cross-sectional views showing the buffer layer forming process using the film forming apparatus of the embodiment of the present invention in the order of steps.
First, as shown in FIG. 8A, a back electrode 34 is formed on a substrate 32, the back electrode 34 is separated by a first groove portion P1, and a photoelectric sensor composed of CIGS on the back electrode 34 is formed. A layer in which the conversion layer 36 is formed is prepared. The film forming material 56 is in this state. A buffer layer 38 is formed on the surface 36 a of the photoelectric conversion layer 36 of the film forming material 56.
As the film forming material 56, for example, an anodized substrate in which the above-described anodized film containing Al ₂ O ₃ as a main component is formed on the substrate 32 is used. Since the back electrode 34 and the photoelectric conversion layer 36 of the film forming material 56 can be formed by a known method, a detailed description of the manufacturing method is omitted.

In the formation of the buffer layer 38 of the solar cell 50, the reaction solution 13 used for the formation of the above-described photoelectric conversion element and the buffer layer of the solar cell is used.
The method of forming the buffer layer 38 of the solar cell 50 is the same as that of the photoelectric conversion element 30 described above except that the configuration of the film forming material 56 is different from the method of forming the buffer layer 38 of the photoelectric conversion element 30 described above. This is the same as the method for forming the buffer layer 38. For this reason, the detailed description is abbreviate | omitted. Note that a mask is preferably provided on the surface 34 a of the back electrode 34.
Even in this case, the buffer layer 38 is formed on the surface 36a of the photoelectric conversion layer 36 as shown in FIG. The buffer layer 38 has no bubble streaks and is excellent in film thickness uniformity.
Furthermore, by using the reaction solution 13 again, the buffer layer 38 can be formed with a small amount of the reaction solution 13.

  The present invention is basically configured as described above. Although the film forming apparatus of the present invention has been described in detail above, the present invention is not limited to the above-described embodiments, and various improvements or modifications may be made without departing from the spirit of the present invention. is there.

In this example, the film forming apparatus of Examples 1 to 3 and Comparative Examples 1 and 2 shown below was used to form a film having a thickness of 40 nm on the film forming material using the reaction solution shown below. The obtained film was evaluated for film thickness unevenness and bubble streaks. As film formation conditions, the temperature of the reaction solution was 90 ° C., and the flow rate of the reaction solution was 8 L / min.
Moreover, in the film-forming apparatuses of Examples 1 to 3 and Comparative Examples 1 and 2, the size of the reaction tank was common, and the size was 40 cm × 10 cm × 50 cm. In this reaction tank, 18 SUS (stainless steel) substrates (thickness: 100 μm) having a size of 30 cm square were placed in parallel as a film forming material to form a film. As will be described later, the evaluation of the film thickness unevenness is performed using a deviation from the average value of all 18 substrates.

The following was used for the reaction solution.
In the reaction solution, an aqueous solution (I) of zinc sulfate aqueous solution (0.18 [M]), an aqueous solution (II) of thiourea aqueous solution (thiourea 0.30 [M]), and an aqueous solution (III) of trisodium citrate Aqueous solution (0.18 [M]) and aqueous ammonia (0.3 [M]) were prepared as aqueous solution (IV), respectively. Next, among these aqueous solutions, aqueous solution (I), aqueous solution (II), and aqueous solution (III) are mixed in the same volume, and zinc sulfate 0.06 [M], thiourea 0.10 [M], A mixed solution of trisodium acid 0.06 [M] was completed, and this mixed solution and 0.3 [M] aqueous ammonia were mixed in equal volumes to obtain a reaction solution.
When mixing the aqueous solutions (I) to (IV), the aqueous solution (IV) was added last. In order to obtain a transparent reaction solution, it is important to add the aqueous solution (IV) last. The reaction solution is zinc sulfate 0.03 [M], thiourea 0.05 [M], trisodium citrate 0.03 [M] and ammonia 0.15 [M]. The pH of the reaction solution was 10.3.

For film thickness unevenness, the film thickness of each substrate was measured, and the average value was obtained. The deviation of the measured value of the film thickness of each substrate from this average value was determined.
For the evaluation of the film thickness unevenness, A is the one where the maximum deviation from the average value of the measured film thickness is ± 10% or less, and the maximum deviation from the average value of the measured film thickness exceeds ± 10% and is ± 15. The difference between the average value of the measured film thickness is C, and the maximum deviation from the average value of the measured film thickness is ±. What was 20% or more was set to D.

  About foam streaks, the presence or absence of foam streaks was visually evaluated for each substrate. For the evaluation of the bubble streak, the case where the bubble streak cannot be visually recognized is A, the foam streak can be visually recognized, and the foam streak portion has a thickness increase of less than 7.5% than the other average value. C was defined as B, in which bubble streaks could be visually recognized, and the bubble streaks had a thickness increase of 7.5% or more than other average values.

Hereinafter, the film forming apparatuses of Examples 1 to 3 and Comparative Examples 1 and 2 will be described.
In the present embodiment, the following supply pipe type A and supply pipe type B were used for the supply pipe 16. In the supply pipe type A, the average interval of the supply holes 16a on the upstream side (pipe 26 side) from the center of the supply pipe 16 is half the average interval of the holes 16a on the downstream side (foaming portion 18 side). The supply pipe type B is formed with holes 16a for supplying liquid at regular intervals.
Example 1 is different from the film forming apparatus 10 shown in FIG. 1A in that the supply pipe type A is used for the supply pipe 16, and other configurations are the same as those of the film forming apparatus 10 shown in FIG. Since it is the same structure, detailed description is abbreviate | omitted.
Example 2 is different from the film forming apparatus 10 shown in FIG. 1A in that the supply pipe type B is used for the supply pipe 16, and other configurations are the same as those of the film forming apparatus 10 shown in FIG. Since it is the same structure, detailed description is abbreviate | omitted.
Example 3 is different from the film forming apparatus 10 shown in FIG. 1A in that the supply pipe type B is used for the supply pipe 16 and the rectifying plate 24 is not provided. ), The detailed configuration is omitted.

The comparative example 1 is different from the film forming apparatus 10 shown in FIG. 1A in that the supply pipe type A is used for the supply pipe 16 and the bubble vent 18 is provided on the upstream side instead of the downstream side of the supply pipe 16. The other configuration is the same as that of the film forming apparatus 10 shown in FIG.
In Comparative Example 2, in the film forming apparatus 10 shown in FIG. 1A, the supply pipe type A is used for the supply pipe 16, the rectifying plate 24 is not provided, and the bubble vent 18 is connected to the supply pipe 16. However, the configuration other than that is the same as that of the film forming apparatus 10 shown in FIG.

As shown in Table 1, in Example 1, the bubble removal part is provided on the downstream side of the supply pipe, the rectifying plate is provided, and the average interval of the supply holes 16a on the upstream side from the center of the supply pipe 16 is set. The film thickness was doubled, and high evaluation was obtained for film thickness unevenness and bubble streaks.
In Example 2, the bubble removal part is provided on the downstream side of the supply pipe, the rectifying plate is provided, and the holes 16a of the supply pipe 16 are formed at equal intervals, and high evaluation is obtained for film thickness unevenness and bubble streaks. I was able to.
In Example 3, the bubble removal part was provided on the downstream side of the supply pipe, and the holes 16a of the supply pipe 16 were formed at equal intervals, and high evaluation was obtained for the bubble streaks.

In Comparative Example 1, the bubble removal part is provided on the upstream side of the supply pipe, and the current plate is provided. In Comparative Example 1, the degree of bubble streaks was large.
In Comparative Example 2, the bubble removal part is provided on the upstream side of the supply pipe, and the current plate is provided. In Comparative Example 2, the degree of film thickness unevenness is large, and the degree of bubble streaks is also large.

DESCRIPTION OF SYMBOLS 10 Film-forming apparatus 12 Reaction tank 14 Outer tank 16 Supply pipe 18 Bubble extraction part 20 Heater 22 Pump 24 Current plate 26, 28 Piping 30 Photoelectric conversion element 32 Substrate 34 Back surface electrode 36 Photoelectric conversion layer 38 Buffer layer 40 Transparent electrode 42 Upper electrode 44, 56, S Film-forming material 50 Solar cell α Bubble streak

Claims (5)

A film forming apparatus for forming a film on a film forming material using a chemical bath deposition method,
A reaction tank in which a reaction solution is stored, and the film forming material is immersed in the reaction solution to form the film on the film forming material;
A supply pipe that is provided at a lower portion of the reaction tank and supplies the reaction solution into the reaction tank;
A supply unit that is provided at one end of the supply pipe and supplies the reaction solution;
Provided at the other end of the supply pipe, and has a bubble removal part for removing bubbles from the reaction solution,
The supply pipe has a plurality of holes for supplying the reaction solution into the reaction tank, and the holes are arranged toward the bottom of the reaction tank. apparatus.   The film forming apparatus according to claim 1, further comprising a circulation unit that supplies the reaction solution that has passed through the bubble removal unit to the supply pipe again.   The film forming apparatus according to claim 1, wherein a plurality of the film forming materials are vertically installed in the reaction tank.   The film forming apparatus according to claim 1, wherein a rectifying plate is provided between the supply pipe and the film forming material in the reaction tank.   The film forming apparatus according to claim 1, wherein the hole of the supply pipe has an opening ratio per unit length that is lower on the opposite side to the bubble removal unit side and higher on the bubble removal unit side. .