JP4767110B2 - Solar cell and method for manufacturing solar cell - Google Patents

Description

  The present invention relates to a solar cell in which high solar cell characteristics are obtained by selectively forming a passivation film according to the type of impurity diffusion layer, and a method for manufacturing the solar cell.

In recent years, development of clean energy has been demanded due to the problem of depletion of energy resources and global environmental problems such as increase of CO _{2 in} the atmosphere. In particular, solar power generation using solar cells has been developed as a new energy source. It has been put to practical use and is on the path of development.

  Conventionally, a solar cell forms a pn junction by diffusing an impurity having a conductivity type opposite to that of a silicon substrate, for example, on a light receiving surface of a monocrystalline or polycrystalline silicon substrate, Products manufactured by forming electrodes on the back surface on the opposite side (hereinafter also simply referred to as the back surface) are mainly used. It is also common to increase the output by the back surface field effect by diffusing impurities of the same conductivity type as the silicon substrate at a high concentration on the back surface of the silicon substrate. In addition, attempts have been made to further increase the output by forming electrodes on the back surface of the silicon substrate using a passivation film and point contacts. Such attempts include a PERL (Passive Emitter Rear Locally Diffused) cell structure as shown in FIG. 6, a floating junction cell as shown in FIG.

  The PERL cell in FIG. 6 has an n electrode 607 on the light receiving surface side of a p-type silicon substrate 601, and an n + layer 605 and an antireflection film 609 made of a silicon nitride film are formed on the surface of the light receiving surface. The silicon nitride film also serves as a passivation film for the light receiving surface. A p + layer 606 is formed on the back surface of the silicon substrate 601, and a first passivation film 603 made of a silicon oxide film is formed on the surface of the silicon substrate 601 other than the surface in contact with the p + layer 606. The p + layer 606 and the p electrode 608 are directly connected.

  In the floating junction cell of FIG. 7, an n-electrode 707 is formed on the light-receiving surface side of a p-type silicon substrate 701, and a p-electrode 708 is formed on the back surface side. An antireflection film 709 made of an n + layer 705 and a silicon nitride film is formed on the light receiving surface. The silicon nitride film also serves as a passivation film for the light receiving surface. Further, an n + layer 705 and a p + layer 706 are formed on the back surface, and the p + layer 706 and the p electrode 708 are directly connected. A first passivation film 703 made of a silicon oxide film is formed on the surface of the silicon substrate 701 other than the surface in contact with the p + layer 706.

  In addition, a so-called back junction solar cell has been developed in which no electrode is formed on the light receiving surface of the silicon substrate and a pn junction is formed on the back surface of the silicon substrate. Since the back junction solar cell generally does not have an electrode on the light receiving surface, there is no shadow loss due to the electrode, and a higher output is obtained compared to the above solar cell having electrodes on the light receiving surface and the back surface of the silicon substrate. Can be expected (Patent Document 1). Back junction solar cells are used in applications such as solar cars and concentrating solar cells by utilizing such characteristics.

In recent years, research focusing on the relationship between the fixed charges of the impurity diffusion layer and the dielectric film has been conducted. In general, it has been reported that a silicon nitride film having a positive fixed charge has a high passivation property for an n-type layer, and an aluminum oxide film having a negative fixed charge has a high passivation property for a p-type diffusion layer (non-patent document). 1).
U.S. Pat. No. 4,927,770 “SURFACE PASSIVATION OF SILICON BY MEANS OF NEGATIVE CHARGE DIELECTRICS”, 19th European Photovoltaic Solar Energy Conference, 7-11 June 2004, Parce.

  In conventional solar cells, there are few examples of using different passivation films for the impurity diffusion layers. Although there are attempts to use different types of passivation films on the light-receiving surface side and the back surface side as shown in FIGS. 6 and 7, the passivation film is merely selectively used according to the classification of the light-receiving surface side and the back surface side. Accordingly, an object of the present invention is to form an optimum passivation film on the first conductivity type impurity diffusion layer or the second conductivity type impurity diffusion layer on the silicon substrate surface, thereby reducing the surface recombination rate and It is to increase the conversion efficiency.

The present invention, on the first surface of the silicon substrate, a solar cell p ⁺ layer and the n ⁺ layer is formed, on the p ⁺ layer, silicon oxide and / or aluminum oxide is formed as the first passivation film At least one layer of the film containing, on the n ⁺ layer, at least one layer of the film containing silicon nitride, which is formed as a second passivation film, a solar cell in which it respectively has been made form.

Further, the present invention is pre-Symbol refractive index of silicon nitride is formed as the second passivation film is preferably from 1.9 to 3.6, a surface opposite to the incident side of sunlight of the silicon substrate It is preferable to have a pn junction.

The manufacturing method of the present invention includes a step of forming a p ⁺ layer and an n ⁺ layer on one surface of a silicon substrate, and an oxidation formed as a first passivation film on one surface of the silicon substrate including the p ⁺ layer. Forming a film of at least one layer containing silicon and / or aluminum oxide ; a patterning step of leaving a first passivation film in accordance with the shape of the p ⁺ layer; and a first surface of the silicon substrate including the n ⁺ layer. forming a film of at least one layer containing silicon nitride, which is formed as a second passivation film, p ⁺ layer and the n ⁺ layer, the step of patterning the passivation film for forming an electrode on each, p ⁺ layer and the n ⁺ layer The present invention also relates to a method for manufacturing a solar cell including a step of forming electrodes on each of them.

Further, the manufacturing method of the present invention includes a step of forming a p ⁺ layer and an n ⁺ layer on one surface of a silicon substrate, and a nitridation formed as a second passivation film on the one surface of the silicon substrate including the n ⁺ layer. Forming a film including at least one layer including silicon; patterning process for leaving a second passivation film in accordance with the shape of the n ⁺ layer; forming a first passivation film on one surface of the silicon substrate including the p ⁺ layer ; Forming at least one layer containing silicon oxide and / or aluminum oxide , p ⁺ layer and n ⁺ layer, passivation film patterning step for forming electrodes on each, p ⁺ layer and n ⁺ layer And a step of forming electrodes on each of them.

  In the manufacturing method of the present invention, it is preferable that the patterning step is performed using an etching paste.

The manufacturing method of the present invention is a method for manufacturing a solar cell in which a p ⁺ layer and an n ⁺ layer are formed on one surface of a silicon substrate, and is a first method for forming an n ⁺ layer on one surface of a silicon substrate. A step of forming a two diffusion mask, a step of patterning the second diffusion mask to form an n ⁺ layer, a step of removing the second diffusion mask, and a p ⁺ layer on one surface of the silicon substrate. Forming at least one layer containing silicon nitride formed as the first diffusion mask and second passivation film, and patterning the first diffusion mask and second passivation film to form a p ⁺ layer If, forming at least one layer of the film containing silicon oxide and / or aluminum oxide is formed as the first passivation film on the p ⁺ layer, the p ⁺ layer and the n ⁺ layer, the electrodes each The method of manufacturing a solar cell comprising a step of forming.

The manufacturing method of the present invention is a method for manufacturing a solar cell in which a p ⁺ layer and an n ⁺ layer are formed on one surface of a silicon substrate, and is a first method for forming a p ⁺ layer on one surface of a silicon substrate. A step of forming a diffusion mask, a step of patterning the first diffusion mask to form a p ⁺ layer, a step of removing the first diffusion mask, and an n ⁺ layer on one surface of the silicon substrate. Forming a film of at least one layer containing silicon oxide and / or aluminum oxide formed as the second diffusion mask and first passivation film , patterning the second diffusion mask and first passivation film , and n ⁺ forming a layer, and forming a film of at least one layer containing silicon nitride is formed as the second passivation film on the n ⁺ layer, p ⁺ layer and the n ⁺ layer, the electrodes each It is a manufacturing method of a solar cell and a step of forming.

In the manufacturing method of the present invention, the first diffusion mask and second passivation film is preferably a single layer film of silicon nitride or a laminated film containing silicon nitride, and the second diffusion mask and first passivation film is It is preferably a single layer film of silicon oxide and / or aluminum oxide, or a laminated film containing silicon oxide and / or aluminum oxide.

  According to the present invention, by forming an optimum passivation film on the first conductivity type impurity diffusion layer or the second conductivity type impurity diffusion layer on the surface of the silicon substrate, the surface recombination speed can be reduced, and the solar cell having high conversion efficiency. A battery can be provided.

<Solar cell>
The solar cell of the present invention will be described based on FIG.

  FIG. 1 shows a back junction solar cell as an embodiment of the solar cell according to the present invention. FIG.1 (b) is the front view which looked at the solar cell from the opposite surface (henceforth the back surface) of the light-receiving surface. A p-electrode 108 and an n-electrode 107 serving as main electrodes having a large current collecting function are formed at both ends, and in addition, a thin p-electrode 108 and an n-electrode 107 are formed so as to penetrate each other. It is also possible to provide the alignment mark 102 on the back surface. This may be provided in order to print accurately when applying and patterning a paste in the manufacturing process described later. 1A is a cross-sectional view of FIG. 1B cut in the II direction. A p electrode 108 and an n electrode 107 are provided on the back surface of the solar cell, and a p + layer 106, which is a high-concentration p-type doped layer formed by doping boron or the like as an impurity in the silicon substrate, and an impurity in the silicon substrate, respectively. The n + layer 105 which is a high-concentration n-type doped layer formed by doping phosphorus or the like is connected. In this figure, the silicon substrate 101 is an n-type silicon substrate, but a p-type silicon substrate may be used.

In the present invention, a region where the majority carriers are holes in the silicon substrate, such as the p + layer 106, is referred to as a first conductivity type impurity diffusion layer. On the other hand, a region where majority carriers are electrons in the silicon substrate, such as the n + layer 105 and the n-type silicon substrate 101, is referred to as a second conductivity type impurity diffusion layer. When a p-type silicon substrate is used for the solar cell, the silicon substrate can be used as the first conductivity type impurity layer.

  In FIG. 1A, the exposed surfaces of the p + layer 106 and the n + layer 105 other than the surfaces connected to the p electrode 108 and the n electrode 107 are in contact with the first passivation film 103 and the second passivation film 104, respectively. Yes. The second passivation film 104 is also formed on the exposed portion of the undoped n-type silicon substrate 101. That is, the solar cell of the present invention has the first passivation film 103 on the first conductivity type impurity diffusion layer on one surface of the silicon substrate and the second passivation film on the second conductivity type impurity diffusion layer on one surface of the silicon substrate. 104. Further, an antireflection film 109 that also serves as a second passivation film is formed on the light receiving surface side.

  Moreover, the solar cell of the present invention is preferably a so-called back junction solar cell in which a pn junction is formed on the back surface of the silicon substrate shown in FIG. In the solar cell of the present invention, the passivation film formed on the surface is distinguished depending on the type of the conductive impurity diffusion layer, so that the problem can be solved. However, the present invention is not limited to the back junction solar cell.

≪Passivation film≫
In the solar cell of the present invention, the chemical composition of the first passivation film and the second passivation film are different. The first passivation film is formed in accordance with the shape of the surface in contact with the first conductivity type impurity diffusion layer on the outer surface of the silicon substrate. The first passivation film is preferably a film containing silicon oxide or aluminum oxide. The first passivation film may be a single-layer film made of one chemical composition, or may be a laminated film made of many chemical composition films including films such as silicon oxide and aluminum oxide. In the case of a laminated film, it is preferable that silicon oxide or aluminum oxide is in contact with the first conductivity type impurity diffusion layer. Although the thickness of the first passivation film depends on the film quality, it is preferably 10 to 200 nm in consideration of workability in the subsequent process. Further, it may be formed by a CVD method, or may be formed by a coating agent or paste printing.

  The second passivation film is formed in accordance with the shape of the surface in contact with the second conductivity type impurity diffusion layer on the outer surface of the silicon substrate. The second passivation film is preferably a film containing, for example, silicon nitride. The second passivation film may be a single layer film made of one chemical composition, or may be a laminated film made up of a number of films including a film such as silicon nitride. In the case of a laminated film, silicon nitride is preferably in contact with the second conductivity type impurity diffusion layer. Further, when silicon nitride is used for the second passivation film, it is preferable to use a material having a refractive index of 1.9 to 3.6. In the case where silicon nitride is used as the antireflection film on the light receiving surface side that also serves as the second passivation film, it is preferable to use a refractive index of about 2 with good light transmission. At this time, since the second passivation film also functions as an antireflection film, the film thickness is preferably 70 to 80 nm. On the other hand, when used on the back surface, it is preferable to use a film adjusted to have a refractive index of 2.6 to 3.6 so that the light permeability is poor but the passivation property is high.

  Based on each of FIG. 2 and FIG. 3 which show sectional drawing of the solar cell of this invention, the form of the other solar cell of this invention is demonstrated hereafter.

FIG. 2 shows another embodiment of the solar battery according to the present invention, which has a double-sided junction cell structure. The silicon substrate 201 may be p-type or n-type, but in this example, the silicon substrate 201 is p-type. An n electrode 207 is provided on the light receiving surface side, and an n + layer 205b and an antireflection film 209 are formed on the surface of the light receiving surface. An n + layer 205 a and a p + layer 206 are formed on the back surface, and a second passivation film 204 is formed immediately below the n + layer 205 of the silicon substrate 201. A first passivation film 203 is formed immediately below the exposed surface of the silicon substrate 201 and the p + layer 206 except for the portion where the second passivation film 204 is formed. As described above, in the conventional solar cell, an attempt is made to prevent the surface recombination by making the chemical composition of the passivation film different between the surface on the light receiving surface side and the surface on the back surface side. However, in the solar cell of this embodiment, the n-electrode 207 and the p-electrode 208 are also formed on the back surface so that a pn junction is formed on the back surface, and the passivation is formed on the back surface depending on the type of the impurity diffusion layer. Different types of membranes are distinguished.

  FIG. 3 shows an embodiment of the solar battery according to the present invention, which is a schematic structure of a floating junction cell. In this example, the silicon substrate 301 is p-type, and an n electrode 307 is formed on the light receiving surface side and a p electrode 308 is formed on the back surface side. An n + layer 305b and an antireflection film 309 are formed on the light receiving surface. Further, on the back surface, a low concentration n + layer 305a and a p + layer 306 as a back surface electric field (BSF) are formed in order to improve passivation properties, and the p + layer 306 and the p electrode 308 are directly connected. A first passivation film 303 is formed immediately below the exposed surface of the p + layer 306 and the silicon substrate 301, and a second passivation film 304 is formed immediately below the n + layer 305a.

<Method for manufacturing solar cell>
≪Production method 1≫
Hereinafter, the manufacturing method of the solar cell of this invention is demonstrated based on FIG. 4 (a) to 4 (k) show one n + layer and one p + layer formed on the back surface of the silicon substrate for convenience of explanation. In the present invention, the first diffusion mask is formed by patterning the first conductivity type impurity diffusion layer on one surface of the silicon substrate, and the second diffusion mask is the second conductivity type impurity on one surface of the silicon substrate. It is used for patterning the diffusion layer. The first etching paste is a paste for etching the first diffusion mask, and the second etching paste is a paste for etching the second diffusion mask.

  First, as shown in FIG. 4A, an n-type silicon substrate 401 is prepared. Here, for example, polycrystalline silicon or single crystal silicon can be used for the silicon substrate 401. The size and shape of the silicon substrate 401 are not particularly limited. For example, the thickness can be a rectangular shape with a thickness of 100 μm to 300 μm and a side of 100 mm to 200 mm.

  In addition, it is preferable to use a silicon substrate 401 from which, for example, the slice damage caused by slicing is removed, and the surface of the silicon substrate 401 is mixed with an aqueous solution of hydrogen fluoride and nitric acid or an alkali such as sodium hydroxide. Etching with aqueous solution.

Next, as shown in FIG. 4B, a texture mask 413 made of a silicon oxide film or the like is formed on the back surface of the n-type silicon substrate 401, and a texture structure 410 is formed on the light receiving surface of the silicon substrate 401. The texture structure 410 of the light-receiving surface is formed by etching using, for example, a solution obtained by adding isopropyl alcohol to an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide to a temperature of 70 ° C. or higher and 80 ° C. or lower. Can do. By forming the texture mask 413 on the back surface of the silicon substrate 401, the texture structure 410 can be formed only on the light receiving surface, and the back surface can be flat. Here, the texture mask 413 can be formed by, for example, steam oxidation, atmospheric pressure CVD, or SiOG (spin-on-glass) printing / firing. Although the thickness of the texture mask 413 is not specifically limited, For example, it can be set as the thickness of 300 nm or more and 800 nm or less.

  As the texture mask 413, a silicon nitride film or a stacked body of a silicon oxide film and a silicon nitride film can be used in addition to the silicon oxide film. Here, the texture mask 413 made of a silicon nitride film can be formed by, for example, a plasma CVD method or an atmospheric pressure CVD method, and the thickness is not particularly limited, but can be, for example, 60 nm or more and 100 nm or less.

  The texture mask 413 is temporarily removed after the texture structure 410 is formed. Note that the texture mask 413 can be used as it is as the first diffusion mask without being removed.

  Next, in FIG. 4C, first, a first diffusion mask 411 made of a silicon oxide film or the like is formed on the entire light receiving surface and back surface of the silicon substrate 401. The first diffusion mask 411 made of a silicon oxide film can be formed by, for example, steam oxidation, atmospheric pressure CVD, or SiOG (spin-on-glass) printing / firing. The thickness of the first diffusion mask 411 made of the silicon oxide film is not particularly limited, but can be, for example, a thickness of 100 nm to 300 nm.

  Then, the first etching paste is printed in a desired pattern only on the first diffusion mask 411 on the back surface of the silicon substrate 401 by, for example, a screen printing method. The first etching paste includes phosphoric acid or ammonium hydrogen fluoride as an etching component, water, an organic solvent, and a thickener as components other than the etching component, and is adjusted to a viscosity suitable for screen printing. it can. By etching the silicon substrate 401 after printing the first etching paste at 100 to 400 ° C., only the portion of the first diffusion mask 411 formed on the back surface of the silicon substrate 401 on which the first etching paste is printed is etched. Can be removed. In addition, the method of heat processing is not specifically limited, For example, it can carry out by heating using a hot plate, a belt furnace, or oven.

After the heat treatment, the first etching paste after the heat treatment is removed by immersing the silicon substrate 401 in water and applying ultrasonic waves to perform ultrasonic cleaning. As a result, a part of the back surface of the silicon substrate 401 is exposed and a window 414 is formed. In addition to ultrasonic water washing, the back surface of the silicon substrate 401 is generally known as SC-1 cleaning (RCA Standard).
Clean-1), SC-2 cleaning (RCA Standard Clean-2), cleaning with a mixed solution of sulfuric acid and hydrogen peroxide, and cleaning using a thin hydrogen fluoride aqueous solution or a cleaning solution containing a surfactant.

  As the first diffusion mask 411, a silicon nitride film or a stacked body of a silicon oxide film and a silicon nitride film can be used in addition to the silicon oxide film. The first diffusion mask made of the silicon nitride film can be formed by, for example, a plasma CVD method or an atmospheric pressure CVD method, and the thickness is not particularly limited, but can be, for example, 40 nm or more and 80 nm or less.

  Next, in FIG. 4D, boron or the like, which is a p-type impurity as the first conductivity type impurity, is vapor-phase diffused in the silicon substrate 401, so that the window 414 portion in FIG. A p + layer 406 is formed as a first conductivity type impurity diffusion layer. Thereafter, the first diffusion mask 411 of the silicon substrate 401 and BSG (boron silicate glass) formed by diffusing boron are all removed using an aqueous hydrogen fluoride solution or the like. Note that the p + layer 406 may be formed by applying a solvent containing boron to the window 414 in FIG.

  Next, in FIG. 4E, a second diffusion mask 412 made of silicon oxide or the like is formed on the entire light receiving surface and back surface of the silicon substrate 401. Then, the second etching paste is printed in a desired pattern only on the first diffusion mask 412 on the back surface of the silicon substrate 401. The second etching paste can have the same composition as the first etching paste described above, or may have a different composition. The portion where the second etching paste is printed out of the portion where the second diffusion mask 412 is formed on the back surface of the silicon substrate 401 by heat-treating the silicon substrate 401 after printing the second etching paste at 100 to 400 ° C. Can be removed by etching. After the heat treatment, a treatment is performed in the same manner as the method described above with reference to FIG.

  Needless to say, as the second diffusion mask 412, it is possible to use a silicon nitride film or a stacked body made of a silicon oxide film and a silicon nitride film in addition to the silicon oxide film.

  Next, in FIG. 4F, the silicon substrate 401 is diffused in a vapor phase with phosphorus or the like as an n-type impurity as the second conductivity type impurity. An n + layer 405 is formed as a second conductivity type impurity diffusion layer. Thereafter, the second diffusion mask 412 on the light-receiving surface and the back surface of the silicon substrate 401 and PSG (phosphorus silicate glass) formed by diffusing phosphorus are all removed using a hydrogen fluoride aqueous solution or the like. Note that the n + layer 405 may be formed by applying a solvent containing phosphorus to the window 415 in FIG. 4E on the back surface of the silicon substrate 401 and then heating.

  Next, as shown in FIG. 4G, dry oxidation (thermal oxidation) is performed on the silicon substrate 401 to form a first passivation film 403 made of a silicon oxide film on the entire back surface of the silicon substrate 401. At this time, the silicon oxide film 403a is also formed on the entire light receiving surface. Here, the first passivation film 403 made of a silicon oxide film can be formed by, for example, steam oxidation, atmospheric pressure CVD, or the like in addition to dry oxidation. In addition to the silicon oxide film, an aluminum oxide film having a negative fixed charge can be formed as the first passivation film 403 by an evaporation method or the like. Note that the first passivation film 403 may be a laminated film made of a silicon oxide film, an aluminum oxide film, or the like.

  Next, as shown in FIG. 4H, in this embodiment, since the n-type silicon substrate 401 is used, the first passivation film 403 on the back surface of the silicon substrate 401 other than the surface on which the p + layer 406 is formed. Is removed by etching using an etching paste. The etching paste used at this time may be the same as the etching paste described above. By this operation, the first passivation film 403 is formed only on the p + layer 406 on the back surface.

  Next, as shown in FIG. 4I, a second passivation film 404 is formed on the surface of the silicon substrate 401 from which the first passivation film 403 has been removed. Specifically, a silicon nitride film is formed as a second passivation film 404 on the surface of the n-type silicon substrate 401 and the n + layer 405 by depositing silicon nitride by a plasma CVD method. Although the second passivation film 404 is also formed on the first passivation film 403 in the present embodiment, the second passivation film 404 may have a thickness equivalent to that of the first passivation film 403. In that case, it is possible to form the second passivation film separately by covering the first conductivity type impurity diffusion layer with a metal mask or the like. Further, as the silicon nitride film used as the second passivation film to be formed, a film adjusted between refractive indexes 2.6 to 3.6 having higher passivation properties can be used when used on the back surface side.

Here, since the silicon nitride film has positive fixed electrification, it is known that the silicon nitride film is suitable as the second passivation film 404. On the other hand, the silicon nitride film does not have a large passivation effect on the first conductivity type impurity diffusion layer. Therefore, the maximum effect can be obtained by selectively forming a silicon oxide film having a high passivation effect on the first conductivity type impurity diffusion layer as the first passivation film 403.

  Next, in FIG. 4J, all of the silicon oxide film 403a on the light receiving surface of the silicon substrate 401 is once removed using a hydrogen fluoride aqueous solution or the like, and nitrided with a refractive index of 1.9 to 2.1 on the light receiving surface. An antireflection film 409 made of a silicon film or the like is formed. At the same time, a part of the first passivation film 403 and the second passivation film 404 is removed to form a contact hole 416 and a contact hole 417, and a part of the n + layer 405 and the p + layer 406 are exposed. The contact hole 416 and the contact hole 417 can be created by the following method. First, after an etching paste is printed on the second passivation film 404, the silicon substrate 401 is subjected to a heat treatment at 100 to 400 ° C. After the heat treatment, the silicon substrate 401 is immersed in water, and an ultrasonic wave is applied to perform ultrasonic treatment. By performing sonic cleaning, the etching paste after the heat treatment is removed. In this case, in addition to ultrasonic cleaning, the back surface of the silicon substrate 401 is generally known as SC-1, SC-2 cleaning, cleaning with a mixed solution of sulfuric acid and hydrogen peroxide, thin hydrogen fluoride aqueous solution or surface activity. Cleaning can also be performed using a cleaning liquid containing an agent.

  Finally, as shown in FIG. 4 (k), an n electrode 407 is formed on the n + layer 405 by printing a silver paste in each of the contact hole 416 and the contact hole 417 and then baking at 500 to 700 ° C. A p-electrode 408 is formed on the p + layer 406. Thereby, a back junction solar cell is completed.

  Note that the silicon substrate 401 may be p-type. When the silicon substrate 401 is n-type, a pn junction is formed on the back surface by the p + layer 406 on the back surface of the silicon substrate 401 and the n-type silicon substrate 401, and when the silicon substrate 401 is p-type, the silicon substrate A pn junction is formed on the back surface by the n + layer 405 and the p-type silicon substrate 401 on the back surface of 401. Further, the order of forming the first passivation film and the second passivation film is not limited.

  Further, in order to increase printing accuracy, it is preferable to form two circular alignment marks on the back surface of the silicon substrate 401 with a laser marker as shown in FIG. The alignment mark is preferably placed at a place other than the place where the n + layer 405 and the p + layer 406 are formed so as not to deteriorate the performance of the back junction solar cell.

≪Production method 2≫
Hereinafter, another method for manufacturing the solar cell of the present invention will be described with reference to FIG. In FIGS. 5A to 5I, only one n + layer and one p + layer are formed on the back surface of the silicon substrate for convenience of explanation, but a plurality of layers are actually formed.

  First, as shown in FIG. 5A, an n-type silicon substrate 501 is prepared. Here, as the silicon substrate 501, for example, polycrystalline silicon or single crystal silicon can be used, and the same one as used in the manufacturing method 1 can also be used. Further, the silicon substrate 501 may be p-type. Note that the slice damage caused by slicing the silicon substrate 501 is removed by the same method as the manufacturing method 1.

Next, as shown in FIG. 5B, a texture mask 513 made of a silicon oxide film or the like is formed on the back surface of the silicon substrate 501, and a texture structure 510 is formed on the light receiving surface of the silicon substrate 501. The texture structure 510 of the light-receiving surface is formed by etching using, for example, a solution obtained by adding isopropyl alcohol to an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide to a temperature of 70 ° C. or higher and 80 ° C. or lower. Can do. By forming the texture mask 513 on the back surface of the silicon substrate 501, the texture structure 510 can be formed only on the light receiving surface, and the back surface can be flat. Here, the texture mask 513 can be formed by, for example, steam oxidation, atmospheric pressure CVD, or SiOG (spin-on-glass) printing / firing. The thickness of the texture mask 513 made of the silicon oxide film is not particularly limited, but can be, for example, a thickness of 300 nm to 800 nm.

  In addition to the silicon oxide film, the texture mask 513 can be a silicon nitride film or a stacked body of a silicon oxide film and a silicon nitride film. Here, the texture mask 513 made of a silicon nitride film can be formed by, for example, a plasma CVD method or an atmospheric pressure CVD method, and the thickness is not particularly limited, but can be, for example, 60 nm or more and 100 nm or less.

  The texture mask 513 is temporarily removed after the texture structure 510 is formed. Note that it is also possible to use it as the second diffusion mask without removing it.

  Next, in FIG. 5C, a second diffusion mask 512 made of a silicon oxide film or the like is formed on the entire light receiving surface and back surface of the silicon substrate 501. The second diffusion mask 512 made of a silicon oxide film can be formed by, for example, steam oxidation, atmospheric pressure CVD, or SiOG (spin-on-glass) printing / firing. The thickness of the second diffusion mask 512 made of the silicon oxide film is not particularly limited, and can be, for example, a thickness of 100 nm to 300 nm.

  Then, the second etching paste is printed in a desired pattern only on the second diffusion mask 512 on the back surface of the silicon substrate 501 by a screen printing method or the like. The second etching paste contains phosphoric acid or ammonium hydrogen fluoride as an etching component, and contains water, an organic solvent, and a thickener in addition to the etching component, and is adjusted to a viscosity suitable for screen printing. By heat-treating the silicon substrate 501 after printing the second etching paste at 100 to 400 ° C., the portion of the second diffusion mask 512 on the back surface of the silicon substrate 501 on which the second etching paste is printed can be etched and removed. In addition, the method of heat processing is not specifically limited, For example, it can carry out by heating using a hot plate, a belt furnace, or oven.

  Then, after the heat treatment, the second etching paste after the heat treatment is removed by immersing the silicon substrate 501 in water and applying ultrasonic waves to perform ultrasonic cleaning. Thereby, the window 515 is formed. In addition to ultrasonic cleaning, the back surface of the silicon substrate 501 includes generally known SC-1, SC-2 cleaning, cleaning with a mixed solution of sulfuric acid and hydrogen peroxide, a thin hydrogen fluoride aqueous solution or a surfactant. It can also be cleaned using a cleaning solution.

  As the second diffusion mask 512, a silicon nitride film or a stacked body of a silicon oxide film and a silicon nitride film can be used in addition to the silicon oxide film. The second diffusion mask made of the silicon nitride film can be formed by, for example, a plasma CVD method or an atmospheric pressure CVD method, and the thickness is not particularly limited, but can be, for example, 40 nm or more and 80 nm or less.

  Next, in FIG. 5D, the silicon substrate 501 is subjected to vapor phase diffusion of phosphorus or the like as an n-type impurity as a second conductivity type impurity, so that the window 515 portion of FIG. An n + layer 505 is formed. Thereafter, the second diffusion mask 512 on the light-receiving surface and the back surface of the silicon substrate 501 and PSG (phosphorus silicate glass) formed by diffusing phosphorus are all removed using a hydrogen fluoride aqueous solution or the like. Note that the n + layer 505 may be formed by applying a solvent containing phosphorus to the window 515 in FIG.

  Next, in FIG. 5E, first, a first diffusion mask 511 made of a silicon nitride film is formed on the entire back surface of the silicon substrate 501. The first diffusion mask 511 on the back surface side can be formed by, for example, a plasma CVD method or an atmospheric pressure CVD method, and the thickness of the silicon nitride film is not particularly limited, but may be, for example, 40 nm or more and 100 nm or less. it can.

  Here, a silicon oxide film is formed on the light receiving surface of the silicon substrate 501. The silicon oxide film on the light-receiving surface side can be formed by, for example, steam oxidation, atmospheric pressure CVD, or SiOG (spin-on-glass) printing / firing, and the thickness is not particularly limited. For example, the thickness is 100 nm to 300 nm. can do.

  Then, a first etching paste containing an etching component that can be etched in a desired pattern is printed on the first diffusion mask 511 on the back surface. Here, the first etching paste is printed, for example, by a screen printing method or the like, and is printed on a portion corresponding to the formation location of the p + layer 506. After printing, etching is performed by the method described above to form the window 514.

  Next, in FIG. 5F, a p + layer 506 is formed in the window 514 portion on the surface of the silicon substrate 501 by vapor-phase diffusing boron or the like as a first conductivity type impurity into the silicon substrate 501. To do. Then, the silicon oxide film on the light receiving surface of the silicon substrate 501 and BSG (boron silicate glass) formed by diffusing boron are all removed using a hydrogen fluoride aqueous solution or the like. Note that the p + layer 506 may be formed by applying a solvent containing boron to the window 514 on the back surface of the silicon substrate 501 and then heating.

  Next, in FIG. 5G, the first passivation film 503 is formed on the p + layer 506 by performing dry oxidation (thermal oxidation). Then, an antireflection film 509 made of a silicon nitride film is formed on the light receiving surface. The silicon nitride film used as the first diffusion mask 511 can be a film adjusted between a refractive index of 2.6 and 3.6 with higher passivation properties when used on the back surface side. The first diffusion mask 511 functions as a second passivation film.

  The first passivation film 503 can be formed by, for example, steam oxidation, atmospheric pressure CVD, or the like, in addition to dry oxidation. Further, in addition to the silicon oxide film, aluminum oxide having a negative fixed charge can be formed as the first passivation film by an evaporation method or the like.

  Next, in FIG. 5H, a part of the first passivation film 503 and the first diffusion mask 511 is removed to form a contact hole 516 and a contact hole 517. Here, the contact hole 516 and the contact hole 517 are formed by the following method. First, after the etching paste is printed, the silicon substrate 501 is subjected to heat treatment, and the portion on which the etching paste is printed can be removed. After the heat treatment, the etching paste after the heat treatment is removed by immersing the silicon substrate 501 in water and applying ultrasonic waves to perform ultrasonic cleaning. Also here, in addition to ultrasonic cleaning, the back surface of the silicon substrate 501 is generally known SC-1, SC-2 cleaning, cleaning with a mixed solution of sulfuric acid and hydrogen peroxide, thin hydrogen fluoride aqueous solution or surface activity. Cleaning can also be performed using a cleaning liquid containing an agent.

Finally, in FIG. 5I, a silver paste is printed on each of the contact hole 516 and the contact hole 517 and then baked to form an n electrode 507 on the n + layer 505 and a p electrode 508 on the p + layer 506. Form. Thereby, a back junction solar cell is completed.

Note that the film formation order of the first diffusion mask and the second diffusion mask is not limited.
As mentioned above, although this invention was demonstrated giving an example about embodiment of the manufacturing method of the solar cell of this invention, this invention is not limited to these.

  For example, an acid resistant resist is used in place of the etching paste, an opening is formed only on the second conductivity type impurity diffusion layer with an HF solution, and the resist is lifted off after the silicon nitride film is formed. It is possible to form a silicon nitride film only on the layer. Further, in this step, the description is made using an etching paste for simplification of the process, but all the steps using the etching paste can be replaced with a photolithography process.

  Moreover, although the back junction solar cell was demonstrated as an example, this invention is a 1st conductivity type impurity diffusion layer (on the cell single side | surface, such as a double junction cell as shown in FIG. 2, and a floating junction cell as shown in FIG. The present invention can be applied to all solar cells in which the p layer and the p + layer) and the second conductivity type impurity diffusion layer (n layer and n + layer) coexist.

[Example]
<Correlation between the refractive index of the second passivation film and the lifetime of the n-type silicon substrate>
Silicon nitride films having various refractive indexes are formed on an n-type silicon substrate having a specific resistance of 2.8 Ωcm by 75 nm, and the relationship between the refractive index of the silicon nitride film and the minority carrier lifetime of the silicon substrate, that is, the lifetime (τ). The correlation was examined. As this silicon substrate, a wafer cut out from an adjacent location of the same silicon ingot is used, and it is considered that the bulk lifetime of the wafer shows a similar value. Therefore, the higher the lifetime value, the smaller the surface recombination rate of minority carriers. As the silicon substrate, one having a thickness of 200 μm in which slice damage was previously etched with a mixed acid of hydrogen fluoride aqueous solution and nitric acid was used. The silicon nitride film was formed by plasma CVD, and its refractive index was controlled by adjusting the flow ratio of SiH ₄ / NH ₃ . The lifetime (τ) was measured by a μ-PCD method (microwave photoconductive decay method) using a 904 nm semiconductor laser. Note that the μ-PCD method is a method in which a microwave is applied to a silicon substrate and the lifetime is measured from a change in reflectance with time. The results are shown in FIG. The horizontal axis represents the refractive index of the silicon nitride film, and the vertical axis represents the lifetime (τ) of the n-type silicon substrate.

  It was shown that the lifetime is greatly improved from the refractive index of the silicon nitride film of 2.6. And it was shown that the increase of the lifetime value with respect to the refractive index becomes moderate at a refractive index of 3.6. Further, in this study, a silicon nitride film having a refractive index of 3.6 or higher has a high silicon ratio, and thus a stable silicon nitride film cannot be formed. From the above, it is shown that the lifetime of the n-type silicon substrate becomes high by forming the n-type silicon substrate surface with the silicon nitride film whose refractive index is controlled to 2.6 to 3.6. It was. From this, it was suggested that the silicon nitride film having a refractive index controlled to 2.6 to 3.6 can be used as the second passivation film of the present invention that can reduce the surface recombination rate.

<Examination of type of passivation film and surface recombination velocity>
Various passivation films were formed on the first conductivity type impurity diffusion layer and the second conductivity type impurity diffusion layer, and the surface recombination velocity (S (cm / s)) in each conductivity type impurity diffusion layer was calculated.

  First, five n-type silicon substrates having a side of 125 mm and a thickness of 200 μm were prepared in which slice damage was etched in advance with a mixed acid of hydrofluoric acid and nitric acid. Then, the following processes (1) to (5) were performed.

  (1) An n-type silicon substrate was dry-oxidized at 900 ° C. for 120 minutes in an oxygen atmosphere to form a silicon oxide film having a thickness of 40 nm on the surface.

  (2) A silicon nitride film having a refractive index of 3.3 having a thickness of 75 nm was formed on the surface of an n-type silicon substrate by plasma CVD.

(3) A vapor-phase diffusion using BBr ₃ is performed on an n-type silicon substrate in an atmosphere of 1000 ° C. to form a p + layer on the surface, and the same method as the above (1) is formed on the formed p + layer. A silicon oxide film having a thickness of 45 nm was formed.

  (4) A silicon nitride film having a refractive index of 3.3 and a thickness of 75 nm was formed on the n-type silicon substrate formed in the above (3) on which a p + layer was formed.

  (5) An aluminum oxide film having a thickness of 100 nm was formed on the n-type silicon substrate in (3) above by forming a p + layer by vapor deposition.

  Table 1 shows the results of calculating the surface recombination velocity (S) on the surface of each of the five types of silicon substrates by a known method from the values measured by the μ-PCD method described above.

  As shown in Table 1, the surface recombination velocity when the silicon oxide film and the aluminum oxide film are formed on the first conductivity type impurity diffusion layer is about 1 when the silicon nitride film having a refractive index of 3.3 is formed. / 4 or so. Further, the surface recombination rate when the silicon nitride film having a refractive index of 3.3 is formed on the second conductivity type impurity diffusion layer is about 1 / 2.5 when the silicon oxide film and the aluminum oxide film are formed. It was shown that there is. From the above, it was shown that surface recombination can be effectively suppressed by using a silicon oxide film and an aluminum oxide film as the first passivation film and a silicon nitride film as the second passivation film.

Example 1
An embodiment of the present invention will be described with reference to FIG. 4 using a back junction solar cell as an example.

  As shown in FIG. 4A, the slice damage layer of the n-type silicon wafer having a side of 125 mm and a thickness of about 200 μm was removed using a mixed acid of hydrofluoric acid and nitric acid to form an n-type silicon substrate 401.

Subsequently, as shown in FIG. 4B, the texture structure 410 is formed by etching the light-receiving surface of the silicon substrate 401 using an etching solution heated to 80 ° C. with a small amount of isopropyl alcohol added to an aqueous sodium hydroxide solution. did. At this time, a texture mask 413 made of a silicon oxide film was formed on the back surface side by a normal pressure CVD method before the texture etching process, so that the texture structure 410 was formed only on the light receiving surface side. Although not shown, the alignment marks used in the subsequent printing process are the first conductivity type impurity diffusion layer and the second
A laser marker was previously formed at a position not overlapping with the conductive impurity diffusion layer. Then, the texture mask 413 was once removed by HF processing.

  Subsequently, in FIG. 4C, a first diffusion mask 411 having a thickness of 250 nm was formed on the entire surface by atmospheric pressure CVD on both the light receiving surface side and the back surface side. Only the first diffusion mask 411 on the back surface of the silicon substrate 401 was printed with a first etching paste mainly composed of phosphoric acid in a desired shape according to the alignment mark. Thereafter, the silicon substrate 401 was heated to 320 ° C. and washed with water to form a window 414 for p + diffusion in the first diffusion mask 411.

Next, in FIG. 4D, first, vapor phase diffusion using BBr ₃ is performed in an atmosphere of 1000 ° C. for 60 minutes, so that boron as a first conductivity type impurity is formed on the back surface exposed by the window 414 of the silicon substrate 401. Was diffused to form a p + layer 406 on the exposed portion of the back surface of the silicon substrate 401. Thereafter, the first diffusion mask on the light receiving surface and the back surface of the silicon substrate 401 and BSG (boron silicate glass) formed by diffusing boron were all removed using an aqueous hydrogen fluoride solution.

  Subsequently, in FIG. 4E, a second diffusion mask 412 made of a 250 nm silicon oxide film is formed on both sides of the silicon substrate 401 by the atmospheric pressure CVD method in the same manner as before, and a second main component containing phosphoric acid as a main component. The etching paste was aligned with the alignment mark, printed in the shape of the n + layer 405, heated, and washed with water, thereby forming a window 415 for performing n + diffusion on the second diffusion mask 412.

Then, as shown in FIG. 4 (f), by performing vapor phase diffusion using POCl _{3 in} an atmosphere of 900 ° C. for 30 minutes, the back surface exposed by the window 415 of the silicon substrate 401 is exposed to phosphorus which is a second conductivity type impurity. Was diffused to form an n + layer 405 on the exposed portion of the back surface of the silicon substrate 401. Thereafter, the second diffusion mask on the light receiving surface and the back surface of the silicon substrate 401 and PSG (phosphorus silicate glass) formed by diffusing phosphorus were all removed using a hydrogen fluoride aqueous solution.

  Thereafter, as shown in FIG. 4G, the silicon oxide film as the first passivation film 403 was formed on the back surface of the silicon substrate 401 by holding in an oxygen atmosphere at 900 ° C. for 120 minutes. At the same time, a silicon oxide film was formed on the light receiving surface.

  Next, as shown in FIG. 4H, the first passivation film 403 on the back surface of the n + layer 405 and the n-type silicon substrate 401, which is formed on the silicon substrate 401 and the n + layer 405, is removed. did. This could be removed by printing, heating, and washing with an etching paste mainly composed of phosphoric acid.

  Then, as shown in FIG. 4I, a second passivation film 404 made of a silicon nitride film was formed by a plasma CVD method on a portion where the first passivation film 403 was not formed. Since the second passivation film 404 is formed on the back surface side, the second passivation film 404 is not a normally used film having a high refractive index of about 2 but has a low refractive index so that the passivation property is high although the light transmission is low. A film adjusted to 3 was used.

  Subsequently, as shown in FIG. 4J, the silicon oxide film on the light receiving surface side is removed by HF treatment, and an antireflection film 409 made of a silicon nitride film having a refractive index of 2 is formed on the light receiving surface side by plasma CVD. Filmed. Then, a paste mainly composed of phosphoric acid was similarly printed, heated and washed on the n + layer 405 and the p + layer 406 to provide contact holes 416 and 417 as electrode contact openings. .

  Finally, as shown in FIG. 4K, a silver paste was printed and baked in the contact hole 416 and the contact hole 417 to form an n-electrode 407 and a p-electrode 408, and a solar cell was manufactured.

(Example 2)
The same operation as in FIG. 4F in Example 1 was performed. Thereafter, a second passivation film made of a silicon nitride film having a refractive index of 3 was formed on the silicon substrate by plasma CVD, and an antireflection film made of a silicon nitride film having a refractive index of 2 was formed on the light receiving surface side. An etching paste mainly composed of phosphoric acid is printed in the shape of the p + layer, heated, and washed with water to provide an opening as an exposed portion of the p + layer in the second passivation film, and then an aluminum oxide film is formed by vapor deposition. A first passivation film made of an aluminum oxide film was formed on the layer exposed portion. Then, contact holes were formed on the n + layer and the p + layer in the same manner as in Example 1, and a silver paste was printed and baked to form an n electrode and a p electrode, thereby producing a solar cell.

(Example 3)
The Example of this invention is disclosed based on FIG. 5 by taking a back junction solar cell as an example.

  As shown in FIG. 5A, the slice damage layer of the n-type silicon wafer having a side of 125 mm and a thickness of about 200 μm was removed using a mixed acid of hydrofluoric acid and nitric acid to form an n-type silicon substrate 501.

  Subsequently, as shown in FIG. 5B, the texture structure 510 is formed by etching the light receiving surface of the silicon substrate 501 using an etching solution heated to 80 ° C. with a small amount of isopropyl alcohol added to an aqueous sodium hydroxide solution. did. At this time, a texture mask 513 made of a silicon oxide film was formed on the back surface side by the atmospheric pressure CVD method before the texture etching process, so that only the light receiving surface side was made the texture structure 510. Thereafter, although not shown, an alignment mark used in a subsequent printing process was previously formed with a laser marker at a position where it did not overlap the first conductivity type impurity diffusion layer and the second conductivity type impurity diffusion layer. Then, the texture mask 513 was once removed by HF processing.

  Subsequently, in FIG. 5C, a second diffusion mask 512 made of silicon oxide having a thickness of 250 nm was formed on the entire back surface and light receiving surface of the silicon substrate 501 by atmospheric pressure CVD. Subsequently, the second etching paste containing phosphoric acid as a main component was aligned with the alignment mark and printed in a desired shape only on the second diffusion mask 512 on the back surface. Thereafter, the silicon substrate 501 was heated to 320 ° C. and washed with water, whereby a window 515 for performing n + diffusion was formed in the second diffusion mask 512.

In FIG. 5D, the second conductivity type impurity phosphorus is diffused on the back surface exposed by the window 515 of the silicon substrate 501 by performing vapor phase diffusion using POCl _{3 in} an atmosphere of 900 ° C. for 50 minutes. Then, an n + layer 505 that is a second conductivity type impurity diffusion layer was formed on the exposed portion of the back surface of the silicon substrate 501. Thereafter, the second diffusion mask 512 on the light-receiving surface and the back surface of each silicon substrate 501 and PSG (phosphorus silicate glass) formed by diffusing phosphorus were all removed using an aqueous hydrogen fluoride solution.

  Thereafter, in FIG. 5E, a first diffusion mask 511 made of a silicon nitride film having a refractive index of 3 was formed on the back surface and the light receiving surface of the silicon substrate 501 by plasma CVD. A silicon oxide film as a protective film having a thickness of 250 nm was formed on the light receiving surface side by an atmospheric pressure CVD method. Subsequently, a first etching paste mainly composed of phosphoric acid was printed, heated, and washed in the shape of the p + layer 506 to form a window for p + diffusion in the first diffusion mask 511.

Then, in FIG. 5 (f), boron which is the first conductivity type impurity is formed on the back surface exposed by the window 514 of each silicon substrate 501 by performing vapor phase diffusion using BBr _{3 in} an atmosphere of 1000 ° C. for 60 minutes. Was diffused to form a p + layer 506 on the exposed portion of the back surface of the silicon substrate 501. Thereafter, BSG (boron silicate glass) formed by diffusing boron and the silicon oxide film on the light receiving surface were all removed using an aqueous hydrogen fluoride solution.

  Next, as shown in FIG. 5G, a first passivation film 503 made of a 200 nm silicon oxide film was formed on the p + layer 506 by atmospheric pressure CVD. Subsequently, an antireflection film 509 made of a silicon nitride film having a refractive index of 2 was formed on the light receiving surface side by plasma CVD.

  Thereafter, as shown in FIG. 5 (h), a paste mainly composed of phosphoric acid is similarly printed, heated and washed on the n + layer 505 and the p + layer 506, thereby forming contact holes as electrode contact openings. 516 and a contact hole 517 were provided.

  Finally, as shown in FIG. 5I, a silver paste was printed and fired in each of the contact hole 516 and the contact hole 517 to form an n-electrode 507 and a p-electrode 508, and a solar cell was manufactured.

Example 4
The same procedure as in FIG. 5F in Example 3 was performed.

  Subsequently, an antireflection film made of a silicon nitride film having a refractive index of 2 was formed on the light receiving surface side by plasma CVD. Thereafter, an aluminum oxide film was formed by vapor deposition to form a first passivation film on the p + layer exposed portion. Then, contact holes were provided on the n + layer and the p + layer in the same manner as in Example 3, and silver paste was printed and baked to form an n electrode and a p electrode.

(Comparative example)
The same operation as in FIG. 4F in Example 1 was performed. Then, a passivation film made of a silicon nitride film was formed on the entire back surface by plasma CVD. At this time, the passivation film was a silicon nitride film prepared to have a refractive index of 2 which is normally used. A contact hole was provided as an electrode contact opening on the n + layer and the p + layer in the same manner as in Example 1, and a silver paste was printed and baked to form an n electrode and a p electrode, thereby producing a solar cell.

  FIG. 8 shows a schematic cross-sectional view of the solar cell manufactured in this comparative example. This solar cell is a so-called back junction solar cell in which a pn junction is formed on the back surface. In a solar cell using an n-type silicon substrate 801, an n + layer 805 and a p + layer 806 are formed on the back surface, and are connected to an n electrode 807 and a p electrode 808, respectively. The portions other than the portion connected to the n-electrode 807 and the p-electrode 808 on the back surface are covered with a passivation film 818, and the light-receiving surface side is covered with an antireflection film 809.

<Performance study>
Here, the standard irradiation conditions (AM 1.5G, 100 mW / cm ² , 25 ° C.) of the solar cell produced in Examples 1 to 4 and the solar cell produced in the comparative example are as follows. Shown in the table.

Where jsc: short circuit current density
Voc: Open circuit voltage
F. F: Curve factor
η: Conversion efficiency From the above results, it was found that the solar cell of the present invention has higher conversion efficiency than the back junction solar cell manufactured in the comparative example.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

(A) is typical sectional drawing of the back junction type solar cell by this invention, (b) is a typical top view of a back surface. It is typical sectional drawing of an example (double-sided junction cell) of the solar cell by this invention. It is typical sectional drawing of an example (floating junction cell) of the solar cell by this invention. It is typical sectional drawing which shows an example of the manufacturing process of the manufacturing method of the back junction type solar cell of this invention. It is typical sectional drawing which shows an example of the manufacturing process of the manufacturing method of the back junction type solar cell of this invention. It is typical sectional drawing of an example (PERL cell) of the conventional solar cell. It is typical sectional drawing of another example (floating junction cell) of the conventional solar cell. It is typical sectional drawing of the conventional back junction type solar cell produced by the comparative example. It is the figure which showed correlation with the refractive index of the silicon nitride film as a 2nd passivation film, and the lifetime of an n-type silicon substrate.

Explanation of symbols

101, 201, 301, 401, 501, 601, 701, 801 Silicon substrate, 102 alignment mark, 103, 203, 303, 403, 503 first passivation film, 104, 204, 304, 404, 504 second passivation film, 105, 205a, 205b, 305a, 305b, 405, 505, 605, 705, 805 n + layer, 106, 206, 306, 406, 506, 606, 706, 806 p + layer, 107, 207, 307, 407, 507, 607, 707, 807 n-electrode, 108, 208, 308, 408, 508, 608, 708, 808 p-electrode, 109, 209, 309, 409, 509, 609, 709, 809 antireflection film, 403a silicon oxide film, 410, 510 texture structure, 41 , 511 first diffusion mask, 412,512 second diffusion mask, 413,513 texture mask, 414,415,514,515 windows, 416,417,516,517 contact hole, 818 a passivation film.

Claims (10)

The first surface of the silicon substrate, a solar cell p ⁺ layer and the n ⁺ layer is formed, on the p ⁺ layer, containing at least silicon oxide and / or aluminum oxide is formed as the first passivation film 1 film layer, on the n ⁺ layer, a solar cell at least one layer of the film containing silicon nitride, which is formed as a second passivation film, characterized in that it made their respective shapes. The refractive index of silicon nitride is formed as the second passivation film solar cell according to claim 1, characterized in that a 1.9 to 3.6. 3. The solar cell according to claim 1, wherein the silicon substrate has a pn junction on a surface opposite to a sunlight incident side of the silicon substrate. Forming a p ⁺ layer and an n ⁺ layer on one surface of a silicon substrate;
Forming at least one layer film including silicon oxide and / or aluminum oxide formed as a first passivation film on one surface of the silicon substrate including the p ⁺ layer;
In accordance with the shape of the p ⁺ layer, a patterning step for leaving the first passivation film,
Forming at least one film including silicon nitride formed as a second passivation film on one surface of a silicon substrate including the n ⁺ layer;
a passivation film patterning step for forming electrodes on each of the p ⁺ layer and the n ⁺ layer;
forming electrodes on each of the p ⁺ layer and the n ⁺ layer;
The manufacturing method of the solar cell characterized by including. Forming a p ⁺ layer and an n ⁺ layer on one surface of a silicon substrate;
Forming at least one film including silicon nitride formed as a second passivation film on one surface of a silicon substrate including the n ⁺ layer;
In accordance with the shape of the n ⁺ layer, a patterning step for leaving the second passivation film,
Forming at least one layer film including silicon oxide and / or aluminum oxide formed as a first passivation film on one surface of the silicon substrate including the p ⁺ layer;
a passivation film patterning step for forming electrodes on each of the p ⁺ layer and the n ⁺ layer;
forming electrodes on each of the p ⁺ layer and the n ⁺ layer;
The manufacturing method of the solar cell characterized by including. The patterning step, producing a solar cell according to claim 4 or 5, characterized in that is carried out using an etching paste. A method for manufacturing a solar cell in which a p ⁺ layer and an n ⁺ layer are formed on one surface of a silicon substrate,
Forming a second diffusion mask for forming an n ⁺ layer on one surface of the silicon substrate;
Patterning the second diffusion mask to form an n ⁺ layer;
Removing the second diffusion mask;
Forming at least one film including silicon nitride formed as a first diffusion mask and second passivation film for forming a p ⁺ layer on one surface of a silicon substrate;
Patterning the first diffusion mask and second passivation film to form a p ⁺ layer;
Forming a film of at least one layer containing silicon oxide and / or aluminum oxide formed as a first passivation film;
forming electrodes on each of the p ⁺ layer and the n ⁺ layer;
The manufacturing method of the solar cell characterized by including. A method for manufacturing a solar cell in which a p ⁺ layer and an n ⁺ layer are formed on one surface of a silicon substrate,
Forming a first diffusion mask for forming a p ⁺ layer on one surface of a silicon substrate;
Patterning the first diffusion mask to form a p ⁺ layer;
Removing the first diffusion mask;
Forming at least one film including silicon oxide and / or aluminum oxide formed as a second diffusion mask and first passivation film for forming an n ⁺ layer on one surface of a silicon substrate;
Patterning the second diffusion mask and first passivation film to form an n ⁺ layer;
Forming at least one film containing silicon nitride formed as a second passivation film;
forming electrodes on each of the p ⁺ layer and the n ⁺ layer;
The manufacturing method of the solar cell characterized by including. 8. The method for manufacturing a solar cell according to claim 7 , wherein the first diffusion mask and second passivation film is a single layer film of silicon nitride or a laminated film containing silicon nitride. 9. The solar cell according to claim 8 , wherein the second diffusion mask and first passivation film is a single layer film of silicon oxide or / and aluminum oxide, or a laminated film containing silicon oxide or / and aluminum oxide. Manufacturing method.

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