JP5320376B2 - Method for producing polycrystalline silicon solar cell panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cheap polycrystalline silicon solar cell panel by forming a polycrystalline silicon film on which a pn junction was formed in a small number of steps and in a short time. <P>SOLUTION: A manufacturing method of a polycrystalline silicon solar cell panel includes: a step of forming an amorphous silicon film on a substrate surface in sputtering using a target composed of a silicon doped into an n-type or p-type; a step of plasma-doping a surface layer of the amorphous silicon film in a p-type or n-type dopant; and a step of melting and recrystallizing the plasma-doped amorphous silicon film by scanning the plasma on the amorphous silicon film. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a polycrystalline silicon solar cell panel and a method for manufacturing the same.

  Crystalline silicon solar cells can be broadly classified into single crystal silicon solar cells and polycrystalline silicon solar cells. In general, a crystalline silicon solar cell has a thickness of about 200 μm by cutting an n-type or p-type doped silicon ingot 30 with a wire 31 or using a dicing technique, as shown in FIG. The sliced ingot is used as a silicon plate that becomes the main body of the solar cell (see Patent Document 1).

  The silicon ingot may be a single crystal silicon ingot produced by the Czochralski method or the like, or a polycrystalline silicon ingot solidified using a molten silicon mold called a cast method. The size of a general silicon ingot is 300 mm in diameter if it is single crystal silicon, and is almost the same size although the shape is different in polycrystalline silicon. Therefore, it is difficult to obtain a large-area silicon plate or silicon film from a silicon ingot.

  On the other hand, as a method for producing a polycrystalline silicon film for a polycrystalline solar cell, a method is known in which silicon particles deposited on a support substrate are melted to be polycrystallized (see Patent Document 2). FIG. 2 shows a polycrystalline silicon film forming apparatus. Silicon particles 42 (20 nm or less) generated by applying an arc discharge 41 to the silicon anode 40 are deposited on the support substrate 45 through the transport tube 44 on the argon gas 43; the silicon particles 42 deposited on the support substrate 45 are High temperature plasma 46 is irradiated and melted; annealing is performed with a halogen lamp 47 to form a polycrystalline silicon plate; in a separation chamber 48, the support substrate 45 and the polycrystalline silicon plate 49 are separated.

  Furthermore, a method of polycrystallizing an amorphous silicon film formed on a glass substrate by a catalytic chemical vapor deposition (Cat-CVD) method with a high energy beam (flash lamp) has been studied (Patent Document 3, non-patent document). Reference 1). More specifically, after forming Cr as an electrode on a 20 mm quartz substrate, an amorphous silicon film of 3 μm is formed by Cat-CVD, and heat treatment is performed with a flash lamp (processing time: 5 ms), the amorphous silicon film is polycrystallized.

JP 2000-263545 A JP-A-6-268242 JP 2008-53407 A

Proceedings of the 54th Japan Society of Applied Physics Academic Lecture "In-plane uniform crystallization of amorphous silicon thin film by flash lamp annealing"

  As described above, various techniques for producing a crystalline silicon film or a crystalline silicon plate for producing a crystalline silicon solar cell have been studied. As a first means for reducing the manufacturing cost of the crystalline silicon solar cell, it is possible to reduce the manufacturing cost of the polycrystalline silicon film or the polycrystalline silicon plate.

  As described in Patent Document 2, it may be possible to generate high-purity silicon particles by applying an arc to the silicon anode, but it is difficult to control the size of the silicon powder. Therefore, the characteristics of a solar cell having a polycrystalline silicon film obtained therefrom are difficult to improve. Moreover, in order to deposit silicon powder uniformly and uniformly on the substrate surface, the manufacturing equipment becomes complicated.

  In addition, a method of polycrystallizing an amorphous silicon film produced by the Cat-CVD method as described in Patent Document 3 described above is also effective, but the Cat-CVD method has a problem that the amorphous silicon film formation rate is slow. is there. Moreover, in the Cat-CVD method, a dangerous gas such as monosilane gas must be used, and the exhaust equipment becomes complicated.

  Therefore, in the present invention, it has been studied to obtain a polycrystalline silicon film of a polycrystalline silicon solar cell by polycrystallizing an amorphous silicon film formed by sputtering using doped silicon as a target.

  In order to further reduce the manufacturing cost of the polycrystalline silicon solar cell, it is important to reduce the number of steps in the manufacturing flow. The manufacturing flow of a conventional polycrystalline silicon solar cell includes at least 1) forming an amorphous silicon film, 2) polycrystallizing the amorphous silicon film to form a polycrystalline silicon film, and 3) using the polycrystalline silicon film as a dopant. And 4) activating the doped dopant.

  The present invention simplifies the manufacturing flow by performing the crystallization of the amorphous silicon film and the activation of the doped dopant in a single process in the manufacturing flow of the conventional polycrystalline solar cell. It aims at reducing the manufacturing cost of a crystalline solar cell.

  That is, the method for manufacturing a polycrystalline silicon solar cell panel according to the present invention includes a step of sputtering an amorphous silicon film using doped silicon as a target, and doping while polycrystallizing the amorphous silicon film by plasma irradiation. Activating the doped dopant. Thereby, a polycrystalline silicon film in which a pn junction is formed can be obtained in a small number of steps and in a short time; therefore, a polycrystalline silicon solar cell panel that can be manufactured at low cost can be provided.

That is, this invention relates to the manufacturing method and polycrystalline solar cell panel of a polycrystalline solar cell panel shown below.
[1] A step of sputtering an amorphous silicon film on a substrate surface using a target made of silicon doped in n-type,
Plasma doping the surface layer of the amorphous silicon film with a p-type dopant;
A step shall be the said scanning in plasma doped amorphous silicon film plasma amorphous silicon film and melted, and polycrystallized allowed to Tayui crystal silicon film,
Masking a portion of the polycrystalline silicon film and partially etching the polycrystalline silicon film to a thickness capable of removing the p-type dopant;
Removing the mask, and placing electrodes in the partially etched region of the polycrystalline silicon film and the masked and unetched region, respectively;
A method for producing a polycrystalline silicon solar cell panel.
[2] A step of sputtering an amorphous silicon film on the surface of the substrate using a target made of silicon doped in p-type,
Plasma doping the surface layer of the amorphous silicon film with an n-type dopant;
A step shall be the said scanning in plasma doped amorphous silicon film plasma to melt the amorphous silicon film Tayui crystal silicon film,
Masking a portion of the polycrystalline silicon film and partially etching the polycrystalline silicon film to a thickness capable of removing the n-type dopant;
Removing the mask, and placing electrodes in the partially etched region of the polycrystalline silicon film and the masked and unetched region, respectively;
A method for producing a polycrystalline silicon solar cell panel.

[3] The manufacturing method according to [1] or [2], wherein the substrate includes one of glass and quartz.
[4] The manufacturing method according to [1] or [2], wherein the substrate is a conductor.

[5] The manufacturing method according to [1] or [2], wherein the plasma to be scanned is atmospheric pressure plasma.
[6] The manufacturing method according to [1] or [2], wherein the scanning speed is 100 mm / second or more and 2000 mm / second or less.

  According to the present invention, since a polycrystalline silicon film having a pn junction can be formed in a small number of steps and in a short time, an inexpensive polycrystalline solar cell panel is provided.

It is a figure which shows the state which cut | disconnects a silicon ingot with a wire. It is a figure which shows the outline of the manufacturing apparatus of the conventional polycrystalline silicon plate. It is a figure which shows the flow which forms the polycrystalline silicon film in which the pn junction was formed in the board | substrate. It is a figure which shows the flow which manufactures a back contact type solar cell panel. It is a figure which shows the flow which manufactures a double-sided contact-type solar cell panel. It is the schematic of the atmospheric pressure plasma apparatus used in order to make an amorphous silicon film into a silicon polycrystalline film.

  The polycrystalline silicon solar cell panel of the present invention includes a step of forming an n-type or p-type doped amorphous silicon film, a step of doping a surface layer of the amorphous silicon film with a p-type dopant or an n-type dopant, And polycrystallizing the amorphous silicon film doped with the dopant to form a polycrystalline silicon film. The polycrystalline silicon film thus obtained is used as a silicon film of a polycrystalline silicon solar cell.

  FIG. 3 shows a flow for forming a polycrystalline silicon film in which a pn junction is formed among the flows for manufacturing the solar cell panel of the present invention.

  In step 1, a substrate 1 is prepared. The substrate 1 may be an insulating transparent substrate such as glass or quartz, or may be a conductive substrate such as metal or ITO. When the substrate 1 is an insulating transparent substrate, it can be a back contact solar cell; when the substrate 1 is a conductive substrate, it is a solar cell having a front electrode and a back electrode. be able to.

  In step 2, the texture 2 is formed on the surface of the substrate 1. The texture 2 is formed on the surface of the substrate 1 on which the silicon film is formed. If the substrate 1 is a glass substrate, the texture 2 may be formed by treating the surface of the glass substrate with a chemical solution containing hydrogen fluoride to form an uneven shape. If the substrate 1 is a glass substrate, the texture 2 may be formed using plasma mixed with fluorine gas.

  In step 3, an amorphous silicon film 3 is sputter-deposited on the surface of the substrate 1 where the texture 2 is formed using a sputtering apparatus. Sputter deposition is performed using a silicon target as a material, and the silicon target is doped p-type or n-type. The method of doping the silicon target is not limited. For example, doping with p or p may be performed with boron or a boron compound, and doping with n or a gas or compound containing phosphorus or arsine may be used. Good.

It is preferable that the dopant concentration in the silicon target is usually in the range of 10 × 10 ¹⁴ / cm ² to 10 × 10 ¹⁸ / cm ² .

  If a p-type doped silicon target is used as a material, a p-type amorphous silicon film 3 is formed by sputtering; if an n-type doped silicon target is used as a material, an n-type amorphous silicon film 3 is formed by sputtering. Is done.

  The silicon target may be doped either p-type or n-type. However, it is generally difficult to perform plasma doping with an n-type dopant (step 4 described later). This is because a general n-type dopant is a highly toxic substance such as phosphorus or arsine. Therefore, it is preferable to form an n-type amorphous silicon film 3 from an n-type doped silicon target and plasma-dope it with a p-type dopant.

  For sputter deposition, a silicon target doped n-type or p-type may be mounted in the chamber of the sputter deposition apparatus and power may be supplied. For example, as film forming conditions, the pressure in the chamber is 0.5 Pa, the power of the DC power source is 1 kW, and the electrode interval is 100 mm.

  The thickness of the amorphous silicon film 3 formed by sputtering on the textured surface of the substrate 1 is not particularly limited, but is preferably in the range of 10 μm to 100 μm, for example, about 50 μm.

  In step 4, the surface layer of the amorphous silicon film 3 formed by sputtering is doped with a dopant to form a doping layer 4. When the amorphous silicon film 3 is an n-type amorphous silicon film, a p-type doping layer 4 is formed by doping with a p-type dopant. On the other hand, when the amorphous silicon film 3 is a p-type amorphous silicon film, an n-type doping layer 4 is formed by doping with an n-type dopant.

Examples of p-type dopants include boron or boron compounds. Examples of the boron compound include diborane (B ₂ H ₆ ). Examples of n-type dopants include gases and compounds containing phosphorus or arsenic.

  Doping with a dopant can be performed using plasma. Doping using plasma refers to a technique in which a dopant gas is introduced into a vacuum apparatus, the dopant is ionized by plasma generated using high frequency, and the ionized dopant is introduced into the surface layer of the amorphous silicon film 3. .

For example, when B ₂ H ₆ gas is used as the p-type dopant, B ₂ H ₆ gas (0.5% He dilution) and Ar gas are allowed to flow through the chamber of the vacuum apparatus; a high frequency of 13.56 MHz is used. Boron is ionized by the generated plasma; ionized boron is introduced into the surface layer of the (n-type) silicon sputtered film 3 and is p-type doped. The pressure in the vacuum apparatus during doping may be appropriately adjusted, but may be set to about 0.5 Pa. The flow rate of B ₂ H ₆ gas may be set to 100 sccm, and the flow rate of Ar gas may be set to 100 sccm. The time required for doping can be between 30 seconds and 60 seconds.

  Further, in order to dope the surface layer of the n-type amorphous silicon film 3 with the p-type dopant, solid boron may be used as the p-type dopant. When solid boron is used, the solid boron is placed in a vacuum chamber and Ar gas is flowed (the flow rate of Ar gas is 100 SCCM); the solid boron is ionized by plasma generated using high frequency; Boron is introduced into the surface layer of the n-type amorphous silicon film 3 to perform p-type doping. The pressure in the vacuum apparatus during doping may be appropriately adjusted, but may be set to about 10 Pa. The time required for doping can be 30 to 60 seconds.

The dose of ionized boron to the n-type amorphous silicon film 3 may be adjusted so that a pn junction required in the solar cell can be formed, but it is 10 × 10 ¹⁶ / cm ² to 10 × 10. It has been found experimentally that a range of ¹⁸ / cm ² is preferred. This is to increase the photoelectric conversion efficiency of the obtained solar cell.

  In step 5, the amorphous silicon film 3 including the doping layer 4 is irradiated with plasma and melted, and immediately after that, it is cooled and polycrystallized, so that the amorphous silicon film 3 is made into the polycrystalline silicon film 5.

  The plasma irradiated to the amorphous silicon film 3 is preferably atmospheric pressure plasma. Atmospheric pressure plasma is plasma irradiated in an atmospheric pressure environment. Irradiation with atmospheric pressure plasma can be performed using an atmospheric pressure plasma apparatus. An outline of an atmospheric pressure plasma apparatus that can be used here is shown in FIG. An atmospheric pressure plasma apparatus 50 shown in FIG. 5 includes a cathode 20 and an anode 21. A plasma injection port 22 is provided in the anode 21. When a DC voltage is applied between the cathode 20 and the anode 21, arc discharge is generated, so that plasma 23 is ejected from the plasma injection port 22 by flowing an inert gas (nitrogen gas or the like). Such an atmospheric pressure plasma apparatus is described in, for example, Japanese Patent Application Laid-Open No. 2008-53632.

  The substrate 1 (see step 4 in FIG. 3) on which the amorphous silicon film 3 including the doping layer 4 is formed is mounted on a stage (not shown) that can move in the XYZ axes of the atmospheric pressure plasma apparatus 50. Heat treatment is performed by scanning the atmospheric pressure plasma source from one end to the other end of the surface of the amorphous silicon film 3. The amorphous silicon film 3 (including the doping layer 4 as the surface layer) in the region irradiated with the plasma 23 is melted.

  By appropriately controlling the temperature of the atmospheric pressure plasma 23 on the surface of the amorphous silicon film 3, the melting condition of the amorphous silicon film 3 including the doping layer 4 is adjusted. The temperature of the atmospheric pressure plasma 23 on the surface of the amorphous silicon film 3 can be arbitrarily controlled by the power of the atmospheric pressure power source, the interval between the injection port 22 and the amorphous silicon film 3, and the like.

The temperature of the atmospheric pressure plasma is generally 1 × 10 ⁴ ° C. or higher, but it is preferable to adjust the temperature at the tip of the plasma injection port 22 to be about 2 × 10 ³ ° C. The plasma injection port 22 can be arranged at a distance of about 5 mm from the amorphous silicon film 3. The input power is 20 kw, the plasma 23 is extruded with an inert gas, and is injected onto the amorphous silicon film 3. It is preferable that the plasma 23 from the injection port 22 is irradiated to a 40 mm diameter region on the substrate surface.

The scanning speed is preferably 1 × 10 ² mm / second to 2 × 10 ³ mm / second, for example, about 1 × 10 ³ mm / second. If the scanning speed is 100 mm or less, the underlying glass substrate 1 may melt and adversely affect the resulting polycrystalline silicon film 5. If the scanning speed is 2000 mm or more, only the surface layer of the amorphous silicon film 3 is melted, and the whole cannot be melted. In addition, the apparatus system becomes complicated to scan at a speed of 2000 mm / second or more.

  When the amorphous silicon film 3 including the doping layer 4 is melted by irradiation with atmospheric pressure plasma and then rapidly cooled, the amorphous silicon film 3 becomes a polycrystalline silicon film 5 having a small crystal grain size. At this time, it is preferable to cool as rapidly as possible so that the crystal grain size of the polycrystal becomes 0.05 μm or less.

  Further, a trace amount of hydrogen gas may be mixed with the inert gas that extrudes the atmospheric pressure plasma 23. By mixing a small amount of hydrogen, the oxide film formed on the surface of the amorphous silicon film 3 can be removed, and the polycrystalline silicon film 5 with few crystal defects can be obtained.

  As described above, according to the present invention, the amorphous silicon film 3 including the doping layer 4 formed on the surface of the substrate 1 is melted with atmospheric pressure plasma and then cooled to be polycrystallized. On the other hand, it is difficult to melt the bulk silicon disposed on the surface of the substrate 1 as in the past with atmospheric pressure plasma, and it is necessary to melt with high temperature plasma in a vacuum environment. Compared with the case of using high-temperature plasma in a vacuum environment, the atmospheric pressure plasma can rapidly melt and polycrystallize the amorphous silicon film 3 having a large area.

  Furthermore, the present invention is characterized in that the amorphous silicon film 3 is polycrystallized after the doping layer 4 is formed by doping the surface layer of the amorphous silicon film 3 with a dopant. Thereby, in the polycrystallization step, the dopant contained in the doping layer 4 can also be activated, and the polycrystalline silicon film 5 in which the pn junction is formed is obtained. On the other hand, conventionally, an amorphous silicon film has been polycrystallized and then doped with a dopant. Therefore, apart from the polycrystallization step, a treatment (annealing) step for activating the dopant after doping to form a pn junction is required.

  The inventor has found that the dopant contained in the surface layer of the amorphous silicon film 3 can be activated by performing the polycrystallization step by atmospheric pressure plasma.

  Hereinafter, a flow for obtaining a solar cell using the polycrystalline silicon film 5 formed on the substrate 1 will be described with reference to FIGS. 4A and 4B.

Back contact solar cell (Fig. 4A)
First, when the substrate 1 is a transparent insulating substrate (such as a glass substrate), a back contact solar cell can be manufactured. A back contact type solar cell refers to a solar cell that does not have an electrode disposed on a light receiving surface and has both an anode and a cathode on a surface opposite to the light receiving surface.

  4A, a part of the surface of the polycrystalline silicon film 5 obtained in step 5 is partially etched. The partial etching can be performed using, for example, the mask 7. The mask 7 can be formed using a resist used in a semiconductor process. That is, a resist is applied to the surface of the polycrystalline silicon film 5 by various methods such as a spin method, a spray method, a screen printing method, and an ink jet method; and a mask 7 is formed by patterning as necessary (Step A). ).

  By etching the polycrystalline silicon film 5, the surface layer of the polycrystalline silicon film 5 not covered with the mask 7 is removed to expose the exposed surface 6 (step B). Etching of the polycrystalline silicon film 5 may be performed by wet etching using, for example, a solution containing hydrogen fluoride and nitric acid as an etchant, but is not particularly limited. The thickness of the surface layer to be removed (etching depth d) may be set to a thickness that can remove the region where the dopant doped in Step 4 is diffused. Thereby, the doped type of the surface of the polycrystalline silicon film 5 and the doped type of the exposed surface 6 can be made different.

  The etching depth d should be set as appropriate. When a boron-containing gas of p-type dopant is used as the dopant, the etching depth d is usually 500 mm or more in consideration of the dopant diffusion region in view of the characteristics as a solar cell. The upper limit of the etching depth is about 10 μm. More specifically, it is about 1000 mm.

  After removing the surface layer of the polycrystalline silicon film 5 by partial etching, the mask 7 is removed (step C).

  Next, an insulating film (not shown) that covers the edge of the substrate 1 may be formed. Thereby, it is possible to prevent the deterioration of the electrical characteristics at the end portion. The insulating film may be a silicon nitride film or the like, and is formed by a sputtering method.

  Thereafter, as shown in Step D, one electrode 8 and the other electrode 9 are arranged. One electrode 8 is disposed on the surface of the polycrystalline silicon film 5 that remains without being etched away. The other electrode 9 is disposed on the exposed surface 6 exposed by partial etching. Examples of the electrode material include Ag, Cu, a solder material, and the like, but are not particularly limited as long as it is a conductor.

  In this way, a back contact solar cell can be obtained. That is, sunlight is taken into the polycrystalline silicon film 5 through the substrate 1 and electricity is taken out through the electrodes 8 and 9.

In this way, a solar cell comparable to that of a commercially available crystalline solar cell was obtained. For example, a solar cell having an open circuit voltage of 0.5 V (10 cm ² conversion) could be obtained.

Double-sided contact solar cell (Figure 4B)
On the other hand, when the substrate 1 is a conductor, a double-sided contact solar cell can be obtained. The double-sided contact solar cell is a solar cell having one electrode (front surface electrode) on the light receiving surface and the other electrode on the back surface, and the substrate 1 as a conductor acts as the other electrode.

  In step E in FIG. 4B, the antireflection layer 11 is formed on the surface of the polycrystalline silicon film 5 obtained in step 5. The antireflection layer 11 is made of silicon oxide or the like, but the material is not particularly limited. Part of the surface of the polycrystalline silicon film 5 is exposed as the exposed surfaces 12 a and 12 b without being covered with the antireflection layer 11.

  Next, as shown in Step F, the surface electrodes 13a and 13b (electrical wiring) are disposed on the exposed surfaces 12a and 12b. Examples of the surface electrode material include Ag, Cu, solder material, and the like, but are not particularly limited as long as it is a conductor.

  In this way, a double-sided contact solar cell can be obtained. That is, sunlight is taken into the crystalline silicon film 5 through the antireflection layer 11, and electricity is taken out through the surface electrodes 13a and 13b and the substrate 1 acting as the back electrode.

  As described above, according to the present invention, a solar cell panel having a large area can be provided inexpensively and efficiently.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Texture 3 Amorphous silicon film 4 Doping layer 5 Polycrystalline silicon film 6 Exposed surface 7 Mask 8 One electrode 9 The other electrode 11 Antireflection layer 12a Exposed surface 12b Exposed surface 13a, 13b Surface electrode 20 Cathode 21 Anode 22 Plasma Injection port 23 Plasma 30 Ingot 31 Wire 40 Silicon anode 41 Arc discharge 42 Silicon particle 43 Argon gas 44 Transport tube 45 Support substrate 46 High temperature plasma 47 Halogen lamp 48 Separation chamber 49 Polycrystalline silicon plate 50 Atmospheric pressure plasma apparatus

Claims (6)

using an n-type doped silicon target to sputter an amorphous silicon film on the substrate surface;
Plasma doping the surface layer of the amorphous silicon film with a p-type dopant;
A step you said plasma doped amorphous silicon film by scanning the plasma to melt the amorphous silicon film and Tayui crystal silicon film,
Masking a portion of the polycrystalline silicon film and partially etching the polycrystalline silicon film to a thickness capable of removing the p-type dopant;
Removing the mask, and placing electrodes in the partially etched region of the polycrystalline silicon film and the masked and unetched region, respectively;
A method for producing a polycrystalline silicon solar cell panel. a step of sputtering an amorphous silicon film on the surface of the substrate using a p-type doped silicon target;
Plasma doping the surface layer of the amorphous silicon film with an n-type dopant;
A step you said plasma doped amorphous silicon film by scanning the plasma to melt the amorphous silicon film and Tayui crystal silicon film,
Masking a portion of the polycrystalline silicon film and partially etching the polycrystalline silicon film to a thickness capable of removing the n-type dopant;
Removing the mask, and placing electrodes in the partially etched region of the polycrystalline silicon film and the masked and unetched region, respectively;
A method for producing a polycrystalline silicon solar cell panel.   The manufacturing method of Claim 1 or 2 with which the said board | substrate contains either glass and quartz.   The manufacturing method according to claim 1, wherein the substrate is a conductor.   The manufacturing method according to claim 1, wherein the plasma to be scanned is atmospheric pressure plasma.   The manufacturing method according to claim 1, wherein the scanning speed is 100 mm / second or more and 2000 mm / second or less.

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