WO2009131115A1 - Solar cell manufacturing method, solar cell manufacturing device, and solar cell - Google Patents

Abstract

Disclosed is a solar cell manufacturing method in which an anti-reflection film (22) containing a conductive dopant different than that of a silicon substrate (1) which has p-type or n-type conductivity is formed on the silicon substrate (1), the anti-reflection film (22) is heat treated, and the dopant contained in the anti-reflection film (22) is diffused into the silicon substrate (1).

Description

SOLAR CELL MANUFACTURING METHOD, SOLAR CELL MANUFACTURING DEVICE, AND SOLAR CELL

The present invention relates to a solar cell manufacturing method, a solar cell manufacturing apparatus, and a solar cell.
More specifically, by forming a laminated structure consisting of a diffusion layer and an antireflection film on a silicon substrate using a film formation process, cell characteristics are improved, and manufacturing time is reduced and the number of processes is reduced. , And a solar cell manufacturing method, a solar cell manufacturing apparatus, and a solar cell capable of reducing manufacturing costs.
This application claims priority based on Japanese Patent Application No. 2008-115976 for which it applied on April 25, 2008, and uses the content here.

Conventionally, as a silicon solar cell, a single crystal silicon solar cell using single crystal silicon, a polysilicon solar cell using a polysilicon layer, an amorphous silicon solar cell using amorphous silicon, and the like are known.
In a single crystal silicon solar cell, a diffusion layer, an antireflection film, and a surface electrode are sequentially formed on the surface side of a p-type single crystal silicon substrate, and a BSF layer and a back electrode are sequentially formed on the back surface side of the silicon substrate. Has a structured.
The diffusion layer is a layer in which phosphorus (P), which is an n-type dopant, is diffused in a silicon single crystal.
The antireflection film contains silicon nitride (Si ₃ N ₄ ).

A texture structure for preventing reflection is formed on the surface of the single crystal silicon substrate by texture etching.
The diffusion layer is obtained by diffusing phosphorus (P) on the surface of the silicon substrate, and as a method for diffusing phosphorus (P), a gas diffusion method, a coating diffusion method, or the like is used ( Patent Documents 1 and 2).
Since impurities remain on the surface of the diffusion layer, the surface of the diffusion layer is cleaned using hydrofluoric acid or the like in order to remove the impurities.
For this reason, in the manufacturing process of the solar cell, it is necessary to take out the substrate from the apparatus used in the diffusion step, clean it once, and carry the cleaned substrate into a vacuum device for forming an antireflection film. there were.

As a method for forming the surface electrode, a so-called fire-through process is used (Patent Documents 3 to 5).
In this process, the silver paste applied on the antireflection film is baked so that a predetermined pattern is formed, the formed silver electrode breaks through the antireflection film, and the silver electrode and the diffusion layer are in contact with each other. Yes.

JP-A-6-29562 JP 2004-247364 A JP-A-5-259488 Japanese Patent Laid-Open No. 10-233518 JP 2000-323735 A

By the way, in the conventional method for manufacturing a silicon solar cell, after the impurities on the surface of the diffusion layer are cleaned using hydrofluoric acid or the like, an antireflection film is formed on the diffusion layer. Defects and the like due to impurities occur at the interface with the antireflection film.
As a result, there is a problem that it is difficult to further improve the cell characteristics.
In addition, when manufacturing this silicon solar cell, a dedicated device is prepared for each process in order to perform a process of forming an antireflection film on the diffusion layer after the process of cleaning impurities on the surface of the diffusion layer. There was a problem that it was necessary.
Further, since the apparatus is changed for each process, there is a problem that the lead time of the manufacturing process becomes long, and it is difficult to reduce the manufacturing time and the number of processes.
As described above, in the conventional manufacturing method, it is very difficult to reduce the manufacturing time, the number of processes, and the manufacturing cost.

The present invention has been made to solve the above-described problems, and can improve the cell characteristics, and it is not necessary to prepare a dedicated device for each process, thereby shortening the manufacturing time and the number of processes. In addition, the manufacturing cost can be reduced, and it is not necessary to previously form a diffusion layer on the substrate, and the formation of the antireflection film including the dopant reduces the manufacturing time and the number of processes. A solar cell manufacturing method, a solar cell manufacturing apparatus, and a solar cell capable of reducing manufacturing time and the number of processes by simultaneously performing dopant diffusion and surface electrode fire-through The purpose is to provide.
Or it aims at providing the manufacturing method of a solar cell, the manufacturing apparatus of a solar cell, and a solar cell in which the washing | cleaning process in air | atmosphere becomes unnecessary after a diffusion process.

As a result of intensive studies on silicon-based solar cells, the present inventors formed an antireflection film containing a dopant on a silicon substrate, and then heat-treated the antireflection film. It has been found that the dopant contained in the antireflection film can be diffused into the silicon substrate to form a diffusion layer, and that there is no risk of impurities occurring at the interface between the diffusion layer and the antireflection film. The present inventors have found that the film formation and heat treatment can be performed using one film formation process, and the present invention has been completed.

That is, in the method for manufacturing a solar cell according to the first aspect of the present invention, an antireflection film containing a dopant having a conductivity type different from that of the silicon substrate is formed on a silicon substrate having a p-type or n-type conductivity (antireflection). A film forming step), and heat-treating the antireflection film to diffuse the dopant contained in the antireflection film into the silicon substrate (heat treatment step).

In the method for manufacturing a solar cell according to the first aspect of the present invention, after forming the antireflection film (the antireflection film forming step), a surface electrode is formed on the antireflection film (surface electrode forming step), When diffusing the dopant contained in the antireflection film into the silicon substrate (heat treatment step), by heating the silicon substrate on which the antireflection film and the surface electrode are formed, the surface electrode and the surface electrode are heated. It is preferable to conduct the silicon substrate and diffuse the dopant into the silicon substrate.

In the method for manufacturing a solar cell according to the first aspect of the present invention, a back electrode containing aluminum is formed on the back surface of the silicon substrate (back electrode forming step), and the antireflection film is formed (antireflection film forming step). ), When an antireflection film containing an n-type dopant is formed on the surface of the silicon substrate having a p-type conductivity, and the dopant contained in the antireflection film is diffused into the silicon substrate (heat treatment step) ), By heating the silicon substrate on which the antireflection film and the back electrode are formed, the dopant is diffused into the silicon substrate, and a part of the aluminum is diffused into the silicon substrate. Is preferred.

In the method for manufacturing a solar cell according to the first aspect of the present invention, when the dopant contained in the antireflection film is diffused into the silicon substrate (heat treatment step), the maximum heating temperature is 600 ° C. or more and It is preferably 1200 ° C. or lower, and the heating time is preferably 1 minute or longer and 120 minutes or shorter.

In the method for manufacturing a solar cell according to the first aspect of the present invention, before forming the antireflection film, the silicon substrate is exposed to plasma in a vacuum (plasma treatment step), and the silicon substrate is exposed to the plasma. Then, it is preferable to form the antireflection film while keeping the silicon substrate in a vacuum.

In the method for manufacturing a solar cell according to the first aspect of the present invention, the antireflection film is formed by a plasma CVD method, and the same plasma CVD apparatus is used to expose the silicon substrate to plasma in a vacuum (plasma treatment). Step), the antireflection film is preferably formed by the plasma CVD method (antireflection film forming step).

The solar cell manufacturing apparatus according to the second aspect of the present invention includes a film forming apparatus for forming an antireflection film containing the dopant on the substrate while introducing a gas containing the dopant, and an electrode on the substrate. An electrode forming apparatus to be formed; and a heating apparatus that heats the substrate and diffuses the dopant into the substrate.

In the solar cell manufacturing apparatus according to the second aspect of the present invention, it is preferable that the film forming apparatus includes a plasma generation unit that performs plasma processing on the substrate.

The solar cell manufacturing apparatus according to the second aspect of the present invention preferably includes a substrate transport mechanism for transporting the substrate in the order of the film forming device, the electrode forming device, and the heating device.

Moreover, the solar cell of the third aspect of the present invention includes a silicon substrate having a p-type or n-type conductivity, a diffusion layer stacked on the silicon substrate, and containing a dopant having a conductivity type different from that of the silicon substrate, An antireflective film on the diffusion layer and containing the dopant.

In the solar cell of the third aspect of the present invention, the dopant concentration of the diffusion layer is preferably lower than the dopant concentration of the antireflection film.

According to the method for manufacturing a solar cell of the present invention, since the above steps are included, the antireflection film is heat-treated by the heat treatment step, and at the same time, a diffusion layer is formed in a region near the interface with the antireflection film in the silicon substrate. be able to.
Further, the diffusion process and the antireflection film forming process can be performed using a film forming process.
Therefore, the step of forming the diffusion layer in advance on the substrate is not necessary, the manufacturing time can be reduced and the number of steps can be reduced, and the manufacturing cost can be reduced.

In addition, since the film formation process is used, it is not necessary to prepare a dedicated device for each process, the manufacturing time and the number of processes can be reduced, and the manufacturing cost can be reduced.
Further, even in the case where texture is formed by dry etching, it can be carried out using a continuous vacuum apparatus together with the formation of an antireflection film containing a dopant and heat treatment.
Therefore, the exhaust time can be shortened compared to the conventional method, for example, the method of repeatedly performing the vacuum-atmosphere including the cleaning of the air atmosphere in the middle, and the entire manufacturing time and the number of processes can be reduced. .

In addition, since the main processing can be performed in a vacuum, the substrate can be kept clean.
Furthermore, even when formation of the back surface BSF injection layer by sputtering, formation of the back surface electrode by sputtering, or the like is necessary, these steps can be performed consistently in a vacuum.
In addition, when the surface electrode forming step for forming the surface electrode on the antireflection film is provided after the antireflection film forming step, the diffusion of the dopant and the fire-through of the surface electrode can be performed at the same time, thereby reducing the manufacturing time. In addition, the number of processes can be reduced.

According to the solar cell manufacturing apparatus of the present invention, since it has the above-described apparatus, the film formation of the antireflection film containing the dopant, the heat treatment of the antireflection film, the diffusion of the dopant into the silicon substrate, and the electrode formation are performed in a series. It can carry out using the following apparatus group.
Further, it is possible to shorten the manufacturing time, the number of processes, and the manufacturing cost.

Further, even when there is a texture forming process by dry etching, these processes can be performed using a continuous vacuum apparatus.
Therefore, the exhaust time can be shortened compared with the conventional apparatus, and the overall manufacturing time and the number of processes can be reduced.
Further, since the main processing can be performed in a vacuum using a series of devices, the substrate can be kept clean.
Furthermore, even when a back surface BSF injection layer forming process by sputtering, a back electrode forming process by sputtering, or the like is required, these processes can be performed consistently in a vacuum using a series of devices. it can.

It is sectional drawing which shows the solar cell of one Embodiment of this invention. It is a schematic diagram which shows the manufacturing apparatus of the solar cell of one Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the solar cell of one Embodiment of this invention.

A solar cell manufacturing method, a solar cell manufacturing apparatus, and a best mode for carrying out the solar cell of the present invention will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

FIG. 1 is a sectional view showing a solar cell according to an embodiment of the present invention. In FIG. 1, reference numeral 1 is a silicon substrate, reference numeral 2 is a diffusion layer, reference numeral 3 is an antireflection film, reference numeral 4 is a BSF layer, reference numeral Reference numeral 5 denotes a first back electrode, reference numeral 6 denotes a second back electrode, and reference numeral 7 denotes a front electrode.
As the silicon substrate 1, a p-type single crystal silicon substrate obtained by diffusing p-type dopants such as boron (B), gallium (Ga), aluminum (Al), and indium (In) in single crystal silicon, a single crystal Any one of n-type single crystal silicon substrates in which n-type dopants such as phosphorus (P), arsenic (As), and antimony (Sb) are diffused in silicon is appropriately selected according to the application. Used.
On the surface of the silicon substrate 1, a textured structure (not shown) having minute irregularities is formed by texture etching.

In the solar cell, the power generation efficiency can be increased by using the silicon substrate 1 on which the texture is formed.
As the silicon substrate 1, a substrate on which a texture is formed may be prepared, or a texture may be formed by dry etching the substrate in the present embodiment.
As the silicon substrate 1, a polycrystalline silicon substrate is preferably used in addition to the single crystal silicon substrate described above, and can be appropriately selected and used according to the application.

When the silicon substrate 1 is a p-type silicon substrate, a thin thickness obtained by diffusing n-type dopants such as phosphorus (P), arsenic (As), and antimony (Sb) near the surface of the silicon substrate 1 This layer is the diffusion layer 2.
When the silicon substrate 1 is an n-type silicon substrate, p-type dopants such as boron (B), gallium (Ga), aluminum (Al), and indium (In) are diffused near the surface of the silicon substrate 1. The thin layer obtained by this is the diffusion layer 2.

In the case of using a multilayer film in which a high refractive index film and a low refractive index film are laminated as the antireflection film 3, examples of materials constituting these films include a refractive index of 1.0 to 4. 0 silicon nitride (SiN _x ), titanium oxide (TiO ₂ ), niobium oxide (Nb ₂ O ₅ ), magnesium fluoride (MgF ₂ ), magnesium oxide (MgO), silicon oxide (SiO ₂ ), etc. are preferably used. It is done.
When the antireflection film 3 is a single layer, for example, a film made of a transparent material such as silicon nitride (SiN _x ) formed on the diffusion layer 2 by a CVD method is used.
When the silicon substrate 1 is a p-type silicon substrate, this film contains n-type dopants such as phosphorus (P), arsenic (As), and antimony (Sb).
When the silicon substrate 1 is an n-type silicon substrate, this film contains a p-type dopant such as boron (B), gallium (Ga), or aluminum (Al).
In the case of performing the fire-through process, silicon nitride (SiN _x ) and titanium oxide (TiO ₂ ) are preferably used as this film.

The diffusion layer 2 is a region obtained by diffusing the dopant contained in the antireflection film 3 on the surface of the silicon substrate 1 by heat-treating the antireflection film 3.
The dopant concentration of the diffusion layer 2 is determined so that a pn junction necessary for the solar cell is generated.
For example, since the dopant concentration of the diffusion layer 2 is determined by the diffusion amount from the antireflection film 3, it is often lower than the dopant concentration of the antireflection film 3 after diffusion.
Usually, the dopant concentration of the antireflection film 3 to be formed is set higher than the dopant concentration required for the diffusion layer 2.
However, the present invention is not limited to this, and the dopant concentration in the antireflection film 3 and the diffusion layer may be reversed after diffusion depending on the equilibrium state of diffusion between the silicon and the antireflection film 3.

The BSF layer 4 is a thin layer formed by diffusing elements constituting the back electrode or the like of the silicon substrate 1 into the silicon substrate by heat treatment.
For example, the BSF layer 4 is formed by forming a back surface electrode containing aluminum on the back surface of a p-type silicon substrate, and diffusing aluminum into the silicon substrate by heat treatment.
The 1st back electrode 5, the 2nd back electrode 6, and the surface electrode 7 are metal electrodes obtained by baking the paste containing conductive metals, such as silver and aluminum.
The second back surface electrode 6 is formed on the back surface of the silicon substrate 1 so as to have a belt-like pattern, and is provided so as to cross the central portion of the back surface.
The first back electrode 5 is provided on both sides of the second back electrode 6 and is formed on the back surface of the recon substrate 1 so as to have a rectangular pattern.

The surface electrode 7 is formed on the surface of the silicon substrate 1. The front surface electrode 7 has a configuration in which a plurality (for example, 50) of strip-shaped electrode pieces formed along the longitudinal direction of the second back surface electrode 6 are arranged.
The surface electrode 7 is connected to the diffusion layer 2 by a fire-through process.
The heat treatment step for forming the diffusion layer 2, the heat treatment step for forming the BSF layer 4, and the step for heat treating the surface electrode 7 by a fire-through process can be performed individually. On the other hand, if any two processes or all processes are performed simultaneously, the process can be shortened and the apparatus can be reduced.

Next, the manufacturing method of the solar cell of this embodiment is demonstrated based on drawing.
FIG. 2 is a schematic diagram showing the solar cell manufacturing apparatus of the present embodiment. In FIG. 2, reference numeral 11 denotes a film forming apparatus for forming an antireflection film containing a dopant while introducing a gas containing the dopant onto the substrate. Reference numeral 12 denotes an electrode forming apparatus for forming electrodes on a substrate. Reference numeral 13 denotes a heating device that heats the substrate and diffuses the dopant into the substrate.
The film forming apparatus 11 includes a plasma generation unit 14 that exposes the substrate to plasma. In the film forming apparatus 11, the electrode forming apparatus 12, and the heating apparatus 13, a substrate transport mechanism 15 that transports the substrate is provided so as to pass through these apparatuses.

The inside of the film forming apparatus 11 is maintained in a vacuum state, and the film forming apparatus 11 is used in a state where the inside is set to a predetermined pressure.
The insides of the electrode forming device 12 and the heating device 13 are maintained at atmospheric pressure, and the electrode forming device 12 and the heating device 13 are used under this atmospheric pressure.
For this reason, a load lock chamber (not shown) may be provided between the film forming apparatus 11 and the electrode forming apparatus 12.
Further, an etching apparatus (not shown) for performing dry etching of texture may be provided on the upstream side of the film forming apparatus 11 in the substrate transfer path.
In this case, the substrate is transported between the film forming apparatus 11 and the etching apparatus while maintaining a vacuum.

Next, a method for manufacturing the solar cell of the present embodiment using this manufacturing apparatus will be described with reference to FIG.
As shown in FIG. 3A, the surface of the p-type or n-type conductive silicon substrate 21 is exposed to plasma and cleaned (plasma treatment).
The p-type or n-type conductive silicon substrate 21 is selected from a single crystal silicon substrate or a polysilicon substrate according to the application. Also, a p-type or n-type conductive silicon substrate having a texture structure (not shown) formed on the surface of the silicon substrate 21 is selected.
Specifically, a silicon substrate is placed in a plasma CVD apparatus for forming an antireflection film, the inside of the plasma CVD apparatus is decompressed, and plasma is generated while introducing argon into the plasma CVD apparatus. As a result, the substrate is exposed to plasma, and the substrate is cleaned.
Regarding such plasma processing, a plasma processing may be performed by installing a dedicated plasma generation apparatus in the apparatus shown in FIG.
Before the cleaning, a dry etching process may be performed in a vacuum in order to form a texture structure on the surface of the substrate.
Further, in the case where the silicon layer is formed on the substrate while the vacuum atmosphere is maintained after dry etching, it is possible to save the trouble of taking it out into the atmosphere and cleaning it.

Next, as shown in FIG. 3B, an antireflection film 22 containing a dopant having a conductivity type different from that of the silicon substrate 21 is formed on the surface of the silicon substrate 21.
The antireflection film 22 is formed while heating the silicon substrate 21.
For example, when the silicon substrate 21 is a p-type silicon substrate, an antireflection film containing an n-type dopant such as phosphorus (P), arsenic (As), or antimony (Sb) is formed.
When the silicon substrate 21 is an n-type silicon substrate, an antireflection film containing a p-type dopant such as boron (B), gallium (Ga), or aluminum (Al) is formed.

Here, when a p-type silicon substrate is employed as the silicon substrate 21 and an antireflection film made of silicon nitride (SiN _x ) containing phosphorus (P) is deposited on the silicon substrate by a CVD method, SiH ₄ Gas, NH ₃ gas, PH ₃ gas diluted with H ₂ , and N ₂ gas as a carrier gas are introduced into the film forming apparatus 11 and film formation is performed by plasma CVD.
The resistance value of this silicon nitride (SiN _x ) is reduced by 10% or more by doping phosphorus (P) as compared to the case where it is not doped.

Next, as shown in FIG. 3C, a silver surface electrode 7 having a predetermined shape is formed on the antireflection film 22 by a screen printing method.
Next, the first back electrode 5 and the second back electrode 6 having a predetermined shape are formed on the back surface of the silicon substrate 21 by screen printing (FIG. 3D).
Aluminum is suitable for the material of the first back electrode 5 and silver is suitable for the material of the second back electrode 6.

Next, the silicon substrate 21 on which the antireflection film 22, the surface electrode 7, the first back electrode 5, and the second back electrode 6 are formed is heat-treated (FIG. 3E).
The conditions for this heat treatment are that the atmosphere is a reducing atmosphere or an inert atmosphere, the temperature is 600 ° C. or more and 1200 ° C. or less, and the time is 1 minute or more and 120 minutes or less.
By this heat treatment, the dopant contained in the antireflection film 22 diffuses into the silicon substrate 21.
Thereby, the diffusion layer 2 is formed on the upper part (front side) of the silicon substrate 21.

Further, the aluminum contained in the first back electrode 5 is diffused into the silicon substrate 21 by this heat treatment, and the BSF layer 4 is formed under the silicon substrate 21 (back surface side).
Further, the surface electrode 7 penetrates the antireflection film 22 by fire-through and is connected to the silicon substrate 21.
The antireflection film 22 becomes the antireflection film 3 having a reduced dopant concentration by heat treatment.
The solar cell of this embodiment can be obtained by the above.

According to the solar cell of the present embodiment, the diffusion layer 2 including the n-type (or p-type) dopant and the n-type (or p-type) dopant on the p-type (or n-type) silicon substrate 1. Since the antireflection film 3 is laminated, there is no possibility that defects due to impurities occur at the interface between the diffusion layer 2 and the antireflection film 3, and the cell characteristics can be further improved.

According to the solar cell manufacturing method of the present embodiment, the antireflection film 22 containing a dopant having a conductivity type different from that of the silicon substrate 21 is formed on the surface of the silicon substrate 21, and then the antireflection film 22 is formed. The formed silicon substrate 21 is subjected to a heat treatment to diffuse the dopant contained in the antireflection film 22 into the silicon substrate 21. Accordingly, the diffusion step and the antireflection film formation step can be performed using the film formation process without cleaning the diffusion layer.

In addition, since a film forming process such as a CVD method is used, it is not necessary to prepare a dedicated apparatus for each process, and the manufacturing time and the number of processes can be reduced, and the manufacturing cost can be reduced. .
In this embodiment, the heat treatment is performed after the antireflection film 22, the front electrode 7, the first back electrode 5, and the second back electrode 6 are formed. However, after the antireflection film is formed, after the front electrode is formed, the back surface is formed. Each may be performed after the electrodes are formed, or any one of them may be performed collectively.
If the heat treatment is performed collectively as described above, the heat treatment step and the accompanying cooling period can be shortened, so that the step can be greatly shortened.
Moreover, the apparatus which performs heat processing can be reduced.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1
An antireflection film made of silicon nitride (SiN _x ) containing phosphorus (P) is formed on a p-type single crystal silicon substrate having a texture structure on the surface by texture etching and having a thickness of 220 μm and a square of 156 mm by CVD. A film was formed.
The film forming conditions are as follows: substrate temperature: 300 ° C., SiH ₄ gas flow rate: 100 sccm, NH ₃ gas flow rate: 80 sccm, H ₂ diluted 1 vol% PH ₃ gas flow rate: 1500 sccm, carrier gas N ₂ gas flow rate : 1000 sccm, power: 1000 W.
The thickness of the obtained antireflection film was 70 nm.

Next, a silver paste was applied in a thickness of 20 μm to the region where the second back electrode was formed on the back surface of the silicon substrate by screen printing, and then dried at 150 ° C. for 10 minutes.
Next, an aluminum paste with a thickness of 20 μm was applied to the region of the back surface of the silicon substrate where the first back electrode was formed by screen printing, and then dried at 150 ° C. for 10 minutes.
Furthermore, a silver paste was applied in a thickness of 20 μm by screen printing on the surface of the silicon substrate where the surface electrode was formed, and then dried at 150 ° C. for 10 minutes.

Next, this silicon substrate was heat-treated at 750 ° C. for 30 minutes.
As a result, the dopant contained in the antireflection film diffused into the silicon substrate, and an n-type diffusion layer was formed in the silicon substrate.
In addition, aluminum of the first back electrode diffused into the silicon substrate, and a BSF layer having a depth of about 10 μm was formed on the back surface of the silicon substrate.
Furthermore, the surface electrode broke through the antireflection film containing phosphorus (P) -doped silicon nitride (SiN _x ) and became conductive with the diffusion layer.
The solar cell obtained in this way had a light conversion efficiency equivalent to that of a solar cell having a diffusion layer formed by a conventional method.

(Example 2)
Antireflection made of silicon nitride (SiN _x ) containing boron (B) by PE-CVD method on an n-type single crystal silicon substrate with a thickness of 220μm and 156mm square with a texture structure formed by texture etching A film was formed.
The film formation conditions are as follows: substrate temperature: 300 ° C., SiH ₄ gas flow rate: 100 sccm, NH ₃ gas flow rate: 80 sccm, H ₂ diluted 0.5 vol% B ₂ H ₆ gas flow rate: 1500 sccm, carrier gas. The flow rate of N ₂ gas was 1000 sccm, and the power was 1000 W.
The thickness of the obtained antireflection film was 70 nm.

Next, a silicon layer doped with phosphorus (P) having a thickness of 0.5 μm is formed on the back surface of the silicon substrate by DC magnetron sputtering, and silver paste is applied to the back surface by a screen printing method to a thickness of 20 μm. And then dried at 150 ° C. for 10 minutes.
Next, a silver paste was applied in a thickness of 20 μm to the region where the surface electrode on the surface of the silicon substrate was formed by screen printing, and then dried at 150 ° C. for 10 minutes.

Next, this silicon substrate was heat-treated at 750 ° C. for 30 minutes.
As a result, the dopant contained in the antireflection film diffused into the silicon substrate, and a p-type diffusion layer was formed in the silicon substrate.
Furthermore, the surface electrode penetrated the antireflection film made of boron (B) -doped silicon nitride (SiN _x ) and contacted the diffusion layer.
The solar cell obtained in this way had a light conversion efficiency equivalent to that of a solar cell having a diffusion layer formed by a conventional method.

(Example 3)
Antireflection made of silicon nitride (SiN _x ) containing phosphorus (P) by a catalytic-CVD method on a p-type single crystal silicon substrate with a thickness of 220 μm and a 156 mm square with a texture structure formed by texture etching A film was formed.
The film formation conditions were as follows: substrate temperature: 300 ° C., SiH ₄ gas flow rate: 100 sccm, NH ₃ gas flow rate: 80 sccm, 1 vol% PH ₃ gas flow rate of H ₂ dilution: 1500 sccm, carrier gas N ₂ gas The flow rate was 1000 sccm and the power was 1000 W.
The thickness of the obtained antireflection film was 70 nm.

Next, a silver paste was applied in a thickness of 20 μm to the region where the second back electrode was formed on the back surface of the silicon substrate by screen printing, and then dried at 150 ° C. for 10 minutes.
Next, an aluminum paste with a thickness of 20 μm was applied to the region of the back surface of the silicon substrate where the first back electrode was formed by screen printing, and then dried at 150 ° C. for 10 minutes.
Furthermore, a silver paste was applied in a thickness of 20 μm by screen printing on the surface of the silicon substrate where the surface electrode was formed, and then dried at 150 ° C. for 10 minutes.

Next, this silicon substrate was heat-treated at 750 ° C. for 30 minutes.
As a result, the dopant contained in the antireflection film diffused into the silicon substrate, and an n-type diffusion layer was formed in the silicon substrate.
In addition, aluminum of the first back electrode diffused into the silicon substrate, and a BSF layer having a depth of about 10 μm was formed on the back surface of the silicon substrate.
Furthermore, the surface electrode broke through the antireflection film containing phosphorus (P) -doped silicon nitride (SiN _x ) and became conductive with the diffusion layer.
The solar cell obtained in this way had a light conversion efficiency equivalent to that of a solar cell having a diffusion layer formed by a conventional method.

Example 4
A DC magnetron sputtering method using silicon (Si) containing phosphorus (P) as a target on a p-type single crystal silicon substrate having a thickness of 220 μm and a 156 mm square with a texture structure formed by texture etching. An antireflection film made of silicon nitride (SiN _x ) containing (P) was formed.
The film formation conditions were: substrate temperature: 100 ° C., Ar gas flow rate: 50 sccm, NH ₃ gas flow rate: 50 sccm, and sputtering power: 3 W / cm ² .
The thickness of the obtained antireflection film was 70 nm.

Next, a silver paste was applied in a thickness of 20 μm to the region where the second back electrode was formed on the back surface of the silicon substrate by screen printing, and then dried at 150 ° C. for 10 minutes.
Next, an aluminum paste with a thickness of 20 μm was applied to the region of the back surface of the silicon substrate where the first back electrode was formed by screen printing, and then dried at 150 ° C. for 10 minutes.
Furthermore, a silver paste was applied in a thickness of 20 μm by screen printing on the surface of the silicon substrate where the surface electrode was formed, and then dried at 150 ° C. for 10 minutes.

Next, this silicon substrate was heat-treated at 750 ° C. for 30 minutes.
As a result, the dopant contained in the antireflection film diffused into the silicon substrate, and an n-type diffusion layer was formed in the silicon substrate.
In addition, aluminum of the first back electrode diffused into the silicon substrate, and a BSF layer having a depth of about 10 μm was formed on the back surface of the silicon substrate.
Furthermore, the surface electrode broke through the antireflection film containing phosphorus (P) -doped silicon nitride (SiN _x ) and became conductive with the diffusion layer.
The solar cell obtained in this way had a light conversion efficiency equivalent to that of a solar cell having a diffusion layer formed by a conventional method.

(Example 5)
Anti-reflection made of silicon nitride (SiN _x ) containing phosphorus (P) by PE-CVD method on a p-type single crystal silicon substrate with a thickness of 220μm and 156mm square with texture structure formed by texture etching A film was formed.
The film formation conditions were as follows: substrate temperature: 300 ° C., SiH ₄ gas flow rate: 100 sccm, NH ₃ gas flow rate: 80 sccm, 1 vol% PH ₃ gas flow rate of H ₂ dilution: 1500 sccm, carrier gas N ₂ gas The flow rate was 1000 sccm and the power was 1000 W.
The thickness of the obtained antireflection film was 70 nm.

Next, this silicon substrate with an antireflection film was subjected to laser annealing using a YAG laser emitting a second harmonic with an output of 100 W, and the dopant contained in the antireflection film was diffused into the silicon substrate.
The laser annealing conditions were energy density: 300 mJ / cm ² and irradiation time: 30 minutes.
As a result, a thin n-type diffusion layer was formed in the silicon substrate and in the vicinity of the interface with the antireflection film.

Next, a silver paste was applied in a thickness of 20 μm to the region where the second back electrode was formed on the back surface of the silicon substrate by screen printing, and then dried at 150 ° C. for 10 minutes.
Next, an aluminum paste with a thickness of 20 μm was applied to the region of the back surface of the silicon substrate where the first back electrode was formed by screen printing, and then dried at 150 ° C. for 10 minutes.
Further, a silver paste was applied in a thickness of 20 μm by a screen printing method on a region where the surface electrode on the surface of the silicon substrate was formed, and then dried at 150 ° C. for 10 minutes.
Thereby, the 1st back electrode, the 2nd back electrode, and the surface electrode were formed.

Next, this silicon substrate was heat-treated at 750 ° C. for 3 seconds.
As a result, a BSF layer having a depth of about 10 μm was formed on the back surface of the silicon substrate.
At the same time, the surface electrode broke through the antireflection film containing phosphorus (P) -doped silicon nitride (SiN _x ) and became conductive with the diffusion layer.
The solar cell obtained in this way had a light conversion efficiency equivalent to that of a solar cell having a diffusion layer formed by a conventional method.

(Example 6)
An antireflection film made of silicon nitride (SiN _x ) containing phosphorus (P) is formed on a p-type polysilicon substrate having a thickness of 200 μm and a 156 mm square with a texture structure formed by texture etching, by plasma CVD. A film was formed.
The film formation conditions were as follows: substrate temperature: 300 ° C., SiH ₄ gas flow rate: 100 sccm, NH ₃ gas flow rate: 80 sccm, 1 vol% PH ₃ gas flow rate of H ₂ dilution: 1500 sccm, carrier gas N ₂ gas The flow rate was 1000 sccm and the power was 1000 W.
The thickness of the obtained antireflection film was 70 nm.

Next, a silver paste was applied in a thickness of 20 μm to the region where the second back electrode was formed on the back surface of the silicon substrate by screen printing, and then dried at 150 ° C. for 10 minutes.
Next, an aluminum paste with a thickness of 20 μm was applied to the region of the back surface of the silicon substrate where the first back electrode was formed by screen printing, and then dried at 150 ° C. for 10 minutes.
Furthermore, a silver paste was applied in a thickness of 20 μm by screen printing on the surface of the silicon substrate where the surface electrode was formed, and then dried at 150 ° C. for 10 minutes.

Next, this silicon substrate was heat-treated at 750 ° C. for 3 seconds.
As a result, the dopant contained in the antireflection film diffused into the silicon substrate, and a p-type diffusion layer was formed in the silicon substrate.
A BSF layer having a depth of about 10 μm was formed on the back surface of the silicon substrate.
Furthermore, the surface electrode broke through the antireflection film containing phosphorus (P) -doped silicon nitride (SiN _x ) and became conductive with the diffusion layer.
The solar cell thus obtained has a light conversion efficiency equivalent to that of a solar cell in which a diffusion layer is formed by a conventional method using a polysilicon substrate.

(Comparative example)
A paint containing phosphorus (P) is applied to the surface of a p-type single crystal silicon substrate having a thickness of 220 μm and a 156 mm square with a texture structure formed by texture etching, and then heat-treated at 900 ° C. for 10 minutes. An n-type diffusion layer having a thickness of about 0.5 μm was formed near the surface of the silicon substrate.

Next, this diffusion layer was washed with hydrofluoric acid and further washed with ultrapure water. Next, an antireflection film made of silicon nitride (SiN _x ) was formed on the diffusion layer by CVD.
The film forming conditions were: substrate temperature: 300 ° C., SiH ₄ gas flow rate: 30 sccm, NH ₃ gas flow rate: 30 sccm, carrier gas N ₂ gas flow rate: 600 sccm, and power: 300 W.
The thickness of the obtained antireflection film was 70 nm.

Next, a silver paste was applied in a thickness of 20 μm to the region where the second back electrode was formed on the back surface of the silicon substrate by screen printing, and then dried at 150 ° C. for 10 minutes.
Next, an aluminum paste with a thickness of 20 μm was applied to the region of the back surface of the silicon substrate where the first back electrode was formed by screen printing, and then dried at 150 ° C. for 10 minutes.
Furthermore, a silver paste was applied in a thickness of 20 μm by screen printing on the surface of the silicon substrate where the surface electrode was formed, and then dried at 150 ° C. for 10 minutes.
Thereby, the 1st back electrode, the 2nd back electrode, and the surface electrode were formed.

Next, this silicon substrate was heat-treated at 750 ° C. for 3 seconds.
As a result, a BSF layer having a depth of about 10 μm was formed on the back surface of the silicon substrate.
At the same time, the surface electrode broke through the antireflection film made of silicon nitride (SiN _x ) and became conductive with the diffusion layer.
The solar cell thus obtained had a photoelectric conversion efficiency of 12 to 17%.
However, when the cleaning is insufficient or when the substrate is not kept in a clean state after the cleaning, the photoelectric conversion efficiency may be lowered and the quality may vary.

From the above results, it was found that the solar cells of Examples 1 to 6 can obtain the same output and photoelectric conversion efficiency as compared with the solar cell of the comparative example.
Further, in the solar cells of Examples 1 to 6, since the antireflection film and the diffusion layer can be formed by a film forming process, a cleaning process is not required as in the comparative example, and the manufacturing time is shortened and the number of processes is reduced. Reductions and manufacturing costs have become possible.

As described above in detail, the present invention improves the cell characteristics of the solar battery, eliminates the need for preparing a dedicated device for each process, and reduces the manufacturing time, the number of processes, and the manufacturing cost. The present invention is useful for a solar cell manufacturing method, a solar cell manufacturing apparatus, and a solar cell.

DESCRIPTION OF SYMBOLS 1 Silicon substrate 2 Diffusion layer 3 Antireflection film 4 BSF layer 5 1st back surface electrode 6 2nd back surface electrode 7 Surface electrode 11 Film-forming apparatus 12 Electrode forming apparatus 13 Heating apparatus 14 Plasma generating part 15 Substrate conveyance mechanism 21 Silicon substrate 22 Reflection Prevention film

Claims (11)

A solar cell manufacturing method comprising:
An antireflection film containing a dopant having a conductivity type different from that of the silicon substrate is formed on a silicon substrate having a conductivity type of p-type or n-type,
A method of manufacturing a solar cell, comprising: heat treating the antireflection film to diffuse a dopant contained in the antireflection film into the silicon substrate. It is a manufacturing method of the solar cell of Claim 1, Comprising:
After forming the antireflection film, a surface electrode is formed on the antireflection film,
When diffusing the dopant contained in the antireflection film into the silicon substrate, the surface electrode and the silicon substrate are heated by heating the silicon substrate on which the antireflection film and the surface electrode are formed. A method for producing a solar cell, comprising conducting and diffusing the dopant into the silicon substrate. It is a manufacturing method of the solar cell of Claim 1 or Claim 2,
Forming a back electrode containing aluminum on the back surface of the silicon substrate;
When forming the antireflection film, an antireflection film containing an n-type dopant is formed on the surface of the silicon substrate having a p-type conductivity,
When diffusing the dopant contained in the antireflection film into the silicon substrate, the dopant is diffused into the silicon substrate by heating the silicon substrate on which the antireflection film and the back electrode are formed. And a part of the aluminum is diffused into the silicon substrate. It is a manufacturing method of the solar cell as described in any one of Claims 1-3,
When diffusing the dopant contained in the antireflection film into the silicon substrate, the maximum heating temperature is 600 ° C. or more and 1200 ° C. or less, and the heating time is 1 minute or more and 120 minutes or less, A method for manufacturing a solar cell. It is a manufacturing method of the solar cell according to any one of claims 1 to 4,
Before forming the antireflection film, the silicon substrate is exposed to plasma in a vacuum,
A method for manufacturing a solar cell, comprising: forming the antireflection film in a state where the silicon substrate is held in a vacuum after the silicon substrate is exposed to the plasma. It is a manufacturing method of the solar cell of Claim 5, Comprising:
The antireflection film is formed by a plasma CVD method,
A method for manufacturing a solar cell, comprising using the same plasma CVD apparatus, exposing the silicon substrate to plasma in a vacuum, and forming the antireflection film by the plasma CVD method. A solar cell manufacturing apparatus,
A film forming apparatus for forming an antireflection film containing the dopant on the substrate while introducing a gas containing the dopant;
An electrode forming apparatus for forming an electrode on the substrate;
A heating device for heating the substrate to diffuse the dopant into the substrate;
An apparatus for manufacturing a solar cell, comprising: The solar cell manufacturing apparatus according to claim 7,
The apparatus for manufacturing a solar cell, wherein the film forming apparatus includes a plasma generating unit that performs plasma processing on the substrate. The solar cell manufacturing apparatus according to claim 7 or 8,
An apparatus for manufacturing a solar cell, comprising: a substrate transport mechanism that transports the substrate in the order of the film forming device, the electrode forming device, and the heating device. A solar cell,
A silicon substrate whose conductivity type is p-type or n-type;
A diffusion layer stacked on the silicon substrate and including a dopant of a conductivity type different from that of the silicon substrate;
An antireflective coating on the diffusion layer and containing the dopant;
A solar cell comprising: The solar cell according to claim 10,
The solar cell according to claim 1, wherein a dopant concentration of the diffusion layer is lower than a dopant concentration of the antireflection film.

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