JP2014007284A - Method for manufacturing solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively obtain a solar cell having a point contact cell structure and excellent in power generation performance in a simple step.SOLUTION: A method for manufacturing a solar cell includes: a first step of selectively implanting oxygen ions into one surface side of a semiconductor substrate of a first conductivity type in a predetermined pattern; a second step of forming an oxide film having the predetermined pattern in a surface layer on the one surface side of the semiconductor substrate by oxidizing a part into which the oxygen ions were implanted by performing first annealing for the semiconductor substrate; a third step of selectively implanting impurity ions of the first conductivity type into at least a part of a closed region which is surrounded by the predetermined pattern and in which the oxygen film is not formed on the one surface side of the semiconductor substrate; and a fourth step of forming a semiconductor layer of the first conductivity type in which an impurity of the first conductivity type is diffused at a higher concentration than other regions of the semiconductor substrate in the closed region in the surface layer on the one surface side of the semiconductor substrate by performing second annealing for the semiconductor substrate.

Description

  The present invention relates to a method for manufacturing a solar battery cell, and more particularly to a method for manufacturing a solar battery cell having a point contact cell structure in which a semiconductor layer is partially provided on a back surface side opposite to a light receiving surface.

  Research on the point contact cell structure of solar cells goes back more than 20 years ago, and at that time, photoelectric conversion efficiency of 24% was already realized using p-type single crystal silicon (for example, see Non-Patent Document 1). . However, in the manufacturing process, for example, when forming the p + layer on the back surface side, which is the maximum point of the point contact cell structure, using an n-type substrate, an oxidation that is a passivation film of a portion forming the p + layer It is necessary to remove and pattern the film as desired. However, the patterning of the oxide film is generally performed by patterning using a resist from the time to the present time, and the process becomes complicated, the cost is high, and this structure is practically realized industrially. Was difficult.

  Therefore, in order to industrialize the point contact cell structure, an attempt was made to form an electrode on the back side by printing and baking aluminum paste from above the insulating film and not patterning the insulating film. (For example, refer nonpatent literature 2).

A. Wang, J. Zhao, M.A.Green “24% efficient silicon solar cells”, Appl. Phys. Lett, vol.57 (6), 6 August 1990, pp.602-604 G. Beaucarne, “LOCAL CONTACT STRUCTURES FOR INDUSTRIAL PERC-TYPE SOLAR CELLS”, 20th European Photovoltaic Solar Energy Conference, 6-10 June Barcelona Spain 2005, pp.942-945

  However, the technology of Non-Patent Document 2 can realize a configuration similar to that of Non-Patent Document 1, but does not involve the power generation performance of the original ideal solar cell that can be realized by the point contact cell structure on the back surface. It was.

  The present invention has been made in view of the above, and manufacture of a solar battery cell having a point contact cell structure and capable of producing a solar battery having excellent power generation performance at a low cost by a simple process. The purpose is to obtain a method.

  In order to solve the above-described problems and achieve the object, a method for manufacturing a solar battery cell according to the present invention is a method in which oxygen ions are selectively implanted in a predetermined pattern on one surface side of a first conductivity type semiconductor substrate. And oxidizing the portion where one side of the semiconductor substrate is implanted with the oxygen ions to oxidize the surface of the one side of the semiconductor substrate with the predetermined pattern. A second step of forming a film, and a first conductivity type selectively in at least a part of a closed region surrounded by the predetermined pattern in a region where the oxide film is not formed on one surface side of the semiconductor substrate A third step of implanting impurity ions of the first and second annealings of the semiconductor substrate, and impurities of the first conductivity type are added to the closed region in the surface layer on one surface side of the semiconductor substrate. And a fourth step of forming a first conductivity type semiconductor layer that is diffused in higher concentration than region.

  According to the present invention, there is an effect that a solar battery cell having a point contact cell structure and excellent in power generation performance can be manufactured at a low cost by a simple process.

1-1 is principal part sectional drawing for demonstrating the structure of the photovoltaic cell concerning Embodiment 1 of this invention. 1-2 is a figure for demonstrating the structure of the photovoltaic cell concerning Embodiment 1 of this invention, and is the top view seen from the photovoltaic cell light-receiving surface side. 1-3 is a figure for demonstrating the structure of the photovoltaic cell concerning Embodiment 1 of this invention, and is the bottom view which looked at the photovoltaic cell from the surface (back surface) on the opposite side to a light-receiving surface. . FIGS. 2-1 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. FIGS. 2-2 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. FIGS. 2-3 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. FIGS. 2-4 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. FIGS. 2-5 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. FIGS. 2-6 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 2-7 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 2-8 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. FIG. 3 is a flowchart for explaining the procedure of the solar cell manufacturing method according to the first embodiment of the present invention. FIG. 4A is a schematic diagram for explaining the oxygen ion implantation method according to the first embodiment of the present invention. FIG. 4-2 is a schematic diagram for explaining the oxygen ion implantation method according to the first embodiment of the present invention. FIG. 4-3 is a schematic diagram for explaining the oxygen ion implantation method according to the first embodiment of the present invention. FIG. 5A is a schematic diagram illustrating an arrangement state of an oxygen implantation mask in the first ion implantation step. FIG. 5B is a schematic diagram illustrating an arrangement state of the oxygen implantation mask in the second ion implantation step. FIG. 6 is a schematic diagram showing the configuration of a boron implantation mask. FIG. 7 is a flowchart for explaining the procedure of a conventional solar cell manufacturing method for forming a point contact cell structure by patterning using a resist. 8-1 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 2 of this invention, and shows the process of forming a texture structure in the light-receiving surface side of a p-type silicon substrate. FIG. 8-2 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 2 of this invention, and shows the process of forming a texture structure in the light-receiving surface side of a p-type silicon substrate. FIG. 8-3 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 2 of this invention, and shows the process of forming a texture structure in the light-receiving surface side of a p-type silicon substrate. FIG. 8-4 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 2 of this invention, and shows the process of forming a texture structure in the light-receiving surface side of a p-type silicon substrate. FIG. FIGS. 9-1 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 3 of this invention. FIGS. 9-2 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 3 of this invention. 9-3 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 3 of this invention. 9-4 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 3 of this invention. FIGS. 9-5 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 3 of this invention. FIGS. FIGS. 9-6 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 3 of this invention. FIGS. 10-1 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 4 of this invention. 10-2 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 4 of this invention. 10-3 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 4 of this invention. 10-4 is principal part sectional drawing for demonstrating the manufacturing method of the photovoltaic cell concerning Embodiment 4 of this invention.

  Embodiments of a method for manufacturing a solar battery cell according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited to the following description, In the range which does not deviate from the summary of this invention, it can change suitably. In the drawings shown below, the scale of each member may be different from the actual scale for easy understanding. The same applies between the drawings. Further, even a plan view may be hatched to make the drawing easy to see.

Embodiment 1 FIG.
1-1 is principal part sectional drawing for demonstrating the structure of the photovoltaic cell concerning Embodiment 1 of this invention. 1-2 is a figure for demonstrating the structure of the photovoltaic cell concerning Embodiment 1, and is the top view seen from the photovoltaic cell light-receiving surface side. 1-3 is a figure for demonstrating the structure of the photovoltaic cell concerning Embodiment 1, and is the bottom view which looked at the photovoltaic cell from the surface (back surface) on the opposite side to a light-receiving surface. The solar battery cell according to the first embodiment has a point contact cell structure on the back surface side.

  In the solar cell according to the present embodiment, an impurity diffusion layer (n-type impurity diffusion layer) 4 is formed by phosphorous diffusion on the light-receiving surface side of the semiconductor substrate 1 made of p-type silicon (Si) and silicon. An antireflection film 5 made of a nitride film is formed.

  As the semiconductor substrate 1, for example, a p-type single crystal or polycrystalline silicon substrate to which gallium or boron is added can be used. The semiconductor substrate 1 is not limited to this, and an n-type silicon substrate may be used. The antireflection film 5 may be a silicon oxide film.

  An n-type impurity diffusion layer electrode 6 (hereinafter referred to as an n-layer electrode 6) made of an electrode material containing silver and glass penetrates the antireflection film 5 on the light receiving surface side of the semiconductor substrate 1. It is electrically connected to the n-type impurity diffusion layer 4 and provided in a comb shape. As the n-layer electrode 6, a plurality of long and narrow grid electrodes 6 a are provided in the in-plane direction of the light receiving surface of the semiconductor substrate 1, and the bus electrode 6 b electrically connected to the grid electrode 6 a is provided on the light receiving surface of the semiconductor substrate 1. It is provided so as to be substantially orthogonal to the grid electrode 6a in the in-plane direction, and is electrically connected to the n-type impurity diffusion layer 4 at the bottom surface.

  On the other hand, on the surface layer of the back surface of the semiconductor substrate 1, a passivation oxide film 2 which is a back surface passivation film made of a silicon oxide film is provided over the entire surface. A p + layer (p-type semiconductor layer) 3 in which a p-type impurity element is diffused at a higher concentration than other regions in the semiconductor substrate 1 is formed on the surface layer on the back surface of the semiconductor substrate 1. The p + layer 3 is a so-called BSF (Back Surface Field) layer. The p + layer 3 is a dot-shaped region surrounded by the passivation oxide film 2 in the back surface of the semiconductor substrate 1, and a plurality of p + layers 3 are arranged in a lattice pattern in the back surface of the semiconductor substrate 1.

  On the p + layer 3, a p + layer electrode (point contact electrode) 7 (hereinafter referred to as a p + layer electrode 7), which is an aluminum electrode made of an electrode material containing aluminum, glass or the like, is provided. . In FIG. 1-3, the p + layer electrode 7 is seen through.

  Next, a method for manufacturing the solar cell according to the present embodiment will be described with reference to FIGS. 2-1 to 2-8 and FIG. FIGS. 2-1 to 2-8 are cross-sectional views of relevant parts for explaining the method of manufacturing the solar battery cell according to the first embodiment. FIG. 3 is a flowchart for explaining the procedure of the method for manufacturing the solar battery cell according to the first embodiment.

  First, a p-type silicon substrate (hereinafter referred to as a p-type silicon substrate 1) is prepared as the semiconductor substrate 1 (FIG. 2-1), and the p-type silicon substrate 1 is sodium hydroxide or water at about 80 ° C. to 100 ° C. The damaged layer formed at the time of slicing is removed by etching using an alkaline aqueous solution such as potassium oxide or an acid solution such as a mixed solution of hydrofluoric acid and nitric acid at room temperature.

Next, oxygen (O ₂ ) is selectively ion-implanted into the region excluding the dot-like region that will later form the p + layer 3 on the back side of the p-type silicon substrate 1 (FIG. 2-2, step S10). . Oxygen ion implantation is performed by covering the dot-like region where the p + layer 3 is formed on the back surface side of the p-type silicon substrate 1 with an oxygen implantation mask.

  4A to 4C are schematic diagrams for explaining the oxygen ion implantation method according to the first embodiment. FIG. 4A shows a state in which the dot-like region where the p + layer 3 will be formed later is covered with the oxygen implantation mask 11 on the back surface side of the p-type silicon substrate 1. The oxygen implantation mask 11 includes a plurality of point-like mask portions 11a that cover a dot-like region where the p + layer 3 will be formed later, and a connection portion 11b that connects adjacent point-like mask portions 11a. Is done.

  When oxygen is ion-implanted into the back surface side of the p-type silicon substrate 1 using the oxygen implantation mask 11, as shown in FIG. An ion non-implanted region is formed. The oxygen ion non-implanted regions are a region 1a covered with the point-shaped mask portion 11a when oxygen ions are implanted on the back side of the p-type silicon substrate 1, and a region 1b covered with the connection portion 11b when oxygen ions are implanted. . FIG. 4B is a schematic diagram illustrating the oxygen ion implantation region 2a and the oxygen ion non-implantation region when oxygen ions are implanted into the back surface side of the p-type silicon substrate 1 using the oxygen implantation mask 11.

  The design range of the dimension of the point contact portion (p + layer 3) of the point contact cell structure is, for example, a point contact portion (p + layer 3) having a diameter of 30 μm to 100 μm and arranged in a lattice shape The interval between the portions (p + layer 3) is set to 250 to 500 μm.

  Here, for example, when the width of the connecting portion 11b in the oxygen implantation mask 11 is 30 μm, the region where oxygen cannot be implanted on the back surface side of the p-type silicon substrate 1 is 10% of the back surface side of the p-type silicon substrate 1. In addition, since the passivation oxide film 2 cannot be formed in the region 1b covered with the connection portion 11b at the time of oxygen ion implantation, the passivation effect is impaired.

  Therefore, in the present embodiment, such a problem is solved by the following method. First, the oxygen implantation mask 11 is disposed on the back side of the p-type silicon substrate 1 at the arrangement position (first arrangement position) as shown in FIG. 4A (first ion implantation step). ). FIGS. 5A and 5B are schematic views showing the arrangement state of the oxygen implantation mask 11 in the ion implantation step. 5A shows the arrangement state of the point-shaped mask portion 11a and the connection portion 11b in the first ion implantation step in a wider range than FIG. 4-1. 4A and 5B, the oxygen implantation mask 11 is disposed on the back surface side of the p-type silicon substrate 1 at the arrangement position (first arrangement position) where the connecting portion 11 b extends in the horizontal direction of the drawing. Yes.

  Then, for example, in the middle of the oxygen ion implantation processing time, the oxygen ion implantation is temporarily stopped, and the oxygen implantation mask 11 is rotated 90 degrees as shown in FIG. 4-3 to the arrangement position (second arrangement position). It arrange | positions on the back surface side of the p-type silicon substrate 1, and implements oxygen ion implantation again (2nd ion implantation process). FIG. 4C is a schematic diagram illustrating a state where the oxygen implantation mask 11 is rotated 90 degrees and disposed again on the back side of the p-type silicon substrate 1. In FIG. 5B, the arrangement state of the point-shaped mask portion 11a and the connection portion 11b in the second ion implantation process is shown in a wider range than that in FIG. In FIGS. 4-3 and 5-2, the oxygen implantation mask 11 is disposed on the back surface side of the p-type silicon substrate 1 at the arrangement position (second arrangement position) where the connecting portion 11b extends in the vertical direction of the drawing. Yes. At the second arrangement position, the point-like mask portion 11a covers (overlaps) the arrangement position of the point-like mask portion 11a at the first arrangement position, and the position of the connecting portion 11b is different from the first arrangement position.

  By performing such a first ion implantation step and a second ion implantation step, oxygen ions are implanted into the region 1b covered with the connection portion 11b in the first ion implantation step. It is possible to inject oxygen into the entire back side of the p-type silicon substrate 1 except for the portion (point 1a covered with the point-like mask portion 11a) of the point contact that becomes the p + layer 3. Become. Thereby, the generation of the oxygen ion non-implanted region due to the connection portion 11 is prevented, and the loss of the passivation effect due to the generation of the non-formation region of the passivation oxide film 2 due to the connection portion 11 is prevented.

  As the oxygen implantation mask 11, for example, a mask formed by coating a photoresist on the surface of a metal plate such as SUS can be used. By using the mask configured as described above as the oxygen implantation mask 11, it is possible to maintain the rigidity as the mask by the metal plate and prevent the diffusion of the metal element to the substrate by the photoresist coating. Can be placed directly on the substrate or installed in the vicinity, thereby improving the accuracy.

  Next, the p-type silicon substrate 1 is annealed to oxidize (thermally oxidize) the oxygen ion-implanted portion on the back side of the p-type silicon substrate 1 to remove the dot-shaped region that becomes the p + layer 3. A passivation oxide film 2 having a predetermined pattern is formed on the surface layer on the back side of the p-type silicon substrate 1 (FIG. 2-3, step S20).

  Next, boron (B) is selectively applied to a dot-shaped region (region 1a covered with the point-shaped mask portion 11a at the time of oxygen ion implantation) on the back surface side of the p-type silicon substrate 1 where the passivation oxide film 2 is not formed. ) Is ion-implanted (FIG. 2-4, step S30). For example, boron ion implantation is performed in a region where the passivation oxide film 2 is not formed on the back surface side of the p-type silicon substrate 1 as shown in FIG. 6 (region 1a covered with the point mask portion 11a at the time of oxygen ion implantation). Is performed using a boron implantation mask 21 having an opening 22 at a position corresponding to. FIG. 6 is a schematic diagram showing the configuration of the boron implantation mask 21.

  As the boron implantation mask 21, for example, a mask formed by coating a photoresist on the surface of a metal plate such as SUS can be used. By using the mask configured in this manner as the boron implantation mask 21, it is possible to maintain the rigidity as a mask by the metal plate and prevent the diffusion of the metal element to the substrate by the photoresist coating. Can be placed directly on the substrate or installed in the vicinity, thereby improving the accuracy. A stencil mask can be used as the boron implantation mask 21.

  Next, phosphorus (P) is ion-implanted into the entire surface on the light receiving surface side of the p-type silicon substrate 1 (FIG. 2-5, step S40). Then, annealing is performed on the p-type silicon substrate 1 to form a p + layer 3 in a region where boron is ion-implanted on the back surface side of the p-type silicon substrate 1, and also on the light-receiving surface side of the p-type silicon substrate 1. An n-type impurity diffusion layer 4 is formed on the entire surface (FIG. 2-6, step S50). As a result, a PN junction is formed on the light receiving surface side of the p-type silicon substrate 1.

  Next, in order to improve photoelectric conversion efficiency, a silicon nitride film is formed as an antireflection film 5 on the light receiving surface side of the p-type silicon substrate 1 on which the n-type impurity diffusion layer 4 is formed (FIG. 2-7, step S60). ). For the formation of the antireflection film 5, for example, a plasma CVD method is used, and a silicon nitride film is formed as the antireflection film 5 using a mixed gas of silane and ammonia. A silicon oxide film may be formed as the antireflection film 5.

  Next, a back surface aluminum electrode material paste that is an electrode material of the p + layer electrode 7 and contains aluminum, glass, or the like is applied onto the p + layer 3 on the back surface side of the p-type silicon substrate 1 by screen printing and dried. Further, on the antireflection film 5 on the light-receiving surface side of the p-type silicon substrate 1, a light-receiving surface electrode material paste containing silver, glass or the like as the electrode material of the n-layer electrode 6 is selected as the shape of the n-layer electrode 6 Specifically, it is applied by screen printing and dried (step S70).

  Thereafter, firing is performed in the air at a temperature of, for example, 750 ° C. to 900 ° C. (FIG. 2-8, step S80). As a result, the p + layer electrode 7 is formed on the p + layer 3 on the back surface side of the p type silicon substrate 1, and the n layer electrode 6 is formed on the light receiving surface side of the p type silicon substrate 1. In addition, silver in the n-layer electrode 6 penetrates the antireflection film 5 and the n-type impurity diffusion layer 4 and the n-layer electrode 6 are electrically connected.

  As described above, the solar battery cell according to the first embodiment having the point contact cell structure shown in FIGS. Note that the order of application of the paste as the electrode material may be switched between the light receiving surface side and the back surface side.

  For comparison, a conventional method for manufacturing a point contact cell structure in which a point contact cell structure is formed by patterning using a resist will be described. FIG. 7 is a flowchart for explaining the procedure of a conventional solar cell manufacturing method for forming a point contact cell structure by patterning using a resist.

  First, an oxide film is formed on the entire surface of the p-type silicon substrate (step S110), and a resist is formed on the entire back surface of the p-type silicon substrate by a printing method (step S120). Then, using the resist as a mask, the oxide films on the light receiving surface side and the end surface of the p-type silicon substrate are removed by etching (step S130). Thereafter, the resist is removed (step S140).

Next, a PN junction is formed by forming an impurity diffusion layer (n-type impurity diffusion layer) by diffusing phosphorus oxychloride (POCl ₃ ), phosphoric acid or the like on the surface of the p-type silicon substrate by a vapor phase diffusion method. (Step S150). Then, after protecting the light-receiving surface side with a resist, acid-resistant resin or the like, the p-type silicon substrate is immersed in a hydrofluoric acid solution, whereby an impurity diffusion layer (n-type impurity diffusion) between the end surface and the back surface side of the p-type silicon substrate is obtained. Layer).

  Next, an oxide film is formed on the entire surface of the p-type silicon substrate (step S160). Next, a resist is formed on the oxide film on the back surface of the p-type silicon substrate by a printing method with a predetermined pattern having an opening corresponding to the p + layer formation region (step S170). Then, using the resist as a mask, the oxide film exposed from the opening of the resist is removed by etching to form an opening in the oxide film, and the back surface of the p-type silicon substrate is exposed (step S180). Thereafter, the resist is removed (step S190).

  Then, after protecting the opening other than the oxide film opening on the back surface of the p-type silicon substrate with a resist or the like, boron is diffused into the surface layer of the p-type silicon substrate exposed from the opening of the oxide film by a vapor phase diffusion method to form p + A layer is formed (step S200). Thus, a solar battery cell having a point contact cell structure is produced. As described above, in the conventional method for manufacturing a solar cell in which the point contact cell structure is formed by patterning using a resist, the process is long, complicated, and expensive.

  As described above, in the method for manufacturing the solar battery cell according to the first embodiment, the passivation oxide film 2 and the p + layer 3 are formed using ion implantation. Thereby, in the manufacturing method of the photovoltaic cell according to the first embodiment, the passivation oxide film 2 and the p + layer 3 can be formed with high quality in a simple and short process without going through a patterning process using a resist, and the process is simplified. And cost reduction can be achieved.

  Moreover, in the manufacturing method of the photovoltaic cell according to the first embodiment, since the n-type impurity diffusion layer 4 is formed using ion implantation, the n-type impurity diffusion layer formed by the conventional air-layer diffusion method is used. A high-quality n-type impurity diffusion layer having excellent uniformity of n-type impurity diffusion can be formed. Thereby, it is possible to improve the photoelectric conversion efficiency. For example, it is possible to cope with the thinning of the n-type impurity diffusion layer for improving the photoelectric conversion efficiency.

  Therefore, according to the solar cell manufacturing method according to the first embodiment described above, the point contact cell structure is formed by applying the ion implantation process, thereby increasing the complexity and cost of the conventional patterning process. Thus, it is possible to prevent the deterioration of the power generation performance due to the simplification process. Thus, a high photoelectric conversion efficiency solar cell having a point contact cell structure can be manufactured at low cost by a simple process without going through a patterning process using a resist.

Embodiment 2. FIG.
In the first embodiment, the case where the texture structure which is the light confinement structure is not formed has been described. In the second embodiment, a case will be described in which minute irregularities are formed on the light receiving surface side of the p-type silicon substrate 1 as a texture structure. The micro unevenness increases the area for absorbing light from the outside on the light receiving surface, suppresses the reflectance on the light receiving surface, and has a structure for confining light. In addition, the manufacturing method of the photovoltaic cell concerning Embodiment 2 is the same as the manufacturing method of the photovoltaic cell concerning Embodiment 1 except the formation process of the texture structure shown below.

  FIGS. 8-1 to FIGS. 8-4 are principal part sectional views for explaining a method for manufacturing a solar battery cell according to the second embodiment, in which a texture structure is formed on the light receiving surface side of the p-type silicon substrate 1. It is a figure which shows a process. In the case of the point contact cell structure, in order to maximize the effect of the passivation structure on the back surface of the semiconductor substrate 1, the back surface side of the semiconductor substrate 1 is preferably a flat surface. A texture structure is formed on the light receiving surface side of the silicon substrate 1.

  First, the p-type silicon substrate 1 is prepared (FIG. 8-1), and the damaged layer formed at the time of slicing is removed. Next, the p-type silicon substrate 1 is oxidized to form a mask oxide film 31 on the entire surface of the p-type silicon substrate 1 (FIG. 8-2). Next, only the mask oxide film 31 on the light receiving surface side of the p-type silicon substrate 1 is removed by, for example, RIE (Reactive Ion Etching) (FIG. 8C).

  Then, for example, by etching the p-type silicon substrate 1 using an alkaline aqueous solution such as sodium hydroxide having a concentration of 1 wt% to several wt%, a texture structure is formed on the surface of the p-type silicon substrate 1 on the light receiving surface side. The minute irregularities 32 are formed. By forming such a texture structure on the light-receiving surface side of the p-type silicon substrate 1, multiple reflections of light are generated on the surface of the solar cell, effectively reducing the reflectance and improving the photoelectric conversion efficiency. Can be made. Thereafter, by removing the mask oxide film 31, the p-type silicon substrate 1 having a texture structure formed on the light receiving surface side is obtained (FIG. 8-4).

  Thereafter, a solar cell with high photoelectric conversion efficiency having a point contact cell structure can be manufactured in the same manner as in the first embodiment.

  As described above, according to the method for manufacturing a solar battery cell according to the second embodiment, a solar battery cell having a point contact cell structure that is more excellent in photoelectric conversion efficiency without undergoing a patterning process using a resist. It can be manufactured inexpensively by a simple process.

Embodiment 3 FIG.
In Embodiment 3, a method for manufacturing a solar battery cell having a back contact type point contact cell structure will be described. FIGS. 9-1 to FIGS. 9-6 are principal part sectional views for explaining a method for manufacturing a solar battery cell according to the third embodiment. In addition, each process shown below is performed by the process similar to the case of Embodiment 1. FIG.

  First, the steps described with reference to FIGS. 2-1 to 2-3 in the first embodiment are performed, and the passivation oxide film 2 having a predetermined pattern excluding the dot-like region is formed on the p-type silicon substrate 1. It forms in the surface layer of the back side (FIGS. 9-1).

  Next, boron (B) is selectively ion-implanted into a part of the dot-shaped region where the passivation oxide film 2 is not formed on the back side of the p-type silicon substrate 1 (FIG. 9-2). .

  Next, selective to another part of the dot-like region where the passivation oxide film 2 is not formed on the back side of the p-type silicon substrate 1 (region where boron (B) is not ion-implanted). Phosphorus (P) is ion-implanted (FIG. 9-3).

  Then, annealing is performed on the p-type silicon substrate 1 to form a p + layer 3 in a region where boron is ion-implanted on the back surface side of the p-type silicon substrate 1, and phosphorus on the back surface side of the p-type silicon substrate 1. An n-type impurity diffusion layer 4 is formed in the region where ions are implanted (FIG. 9-4). Thereby, a PN junction is formed on the back side of the p-type silicon substrate 1.

  Next, in order to improve the photoelectric conversion efficiency, a silicon nitride film is formed as the antireflection film 5 on the light receiving surface side of the p-type silicon substrate 1 (FIG. 9-5).

  Next, a back surface aluminum electrode material paste that is an electrode material of the p + layer electrode 7 and contains aluminum, glass, or the like is applied onto the p + layer 3 on the back surface side of the p-type silicon substrate 1 by screen printing and dried. Further, a light receiving surface electrode material paste, which is an electrode material for the n-layer electrode 6 and contains silver, glass, or the like, is applied onto the n-type impurity diffusion layer 4 on the back surface side of the p-type silicon substrate 1 by a screen printing method and dried. Let Thereafter, firing is performed in the air at a temperature of 750 ° C. to 900 ° C., for example. Thereby, on the back side of the p-type silicon substrate 1, the p + layer electrode 7 is formed on the p + layer 3, and the n-layer electrode 6 is formed on the n-type impurity diffusion layer 4 (FIGS. 9-6).

  As described above, according to the method for manufacturing a solar cell according to the third embodiment, the back contact type having a point contact cell structure having excellent photoelectric conversion efficiency without undergoing a patterning process using a resist. A solar battery cell can be manufactured inexpensively by a simple process.

Embodiment 4 FIG.
In the fourth embodiment, a manufacturing method of a solar battery cell having a texture structure which is a light confinement structure and a back contact type point contact cell structure will be described. 10-1 to 10-4 are cross-sectional views of relevant parts for explaining the method of manufacturing the solar battery cell according to the fourth embodiment. In addition, each process shown below is performed by the process similar to the case of Embodiment 1- Embodiment 3. FIG.

  The step described with reference to FIG. 9-1 in the third embodiment is performed to form the passivation oxide film 2 having a predetermined pattern excluding the dot-like region on the surface layer on the back surface side of the p-type silicon substrate 1. . Thereafter, by changing the conditions for oxygen ion implantation, an oxide film 41 having a thickness smaller than that of the passivation oxide film 2 is formed only in the region where the p + layer 3 is to be formed in the dot-shaped region (FIG. 10-1). ).

  Next, etching is performed on the p-type silicon substrate 1 using the passivation oxide film 2 and the oxide film 41 as a mask, so that dots on the light-receiving surface side of the p-type silicon substrate 1 and on the back surface side of the p-type silicon substrate 1 are obtained. In the region where the n-type impurity diffusion layer 4 is to be formed, the fine irregularities 32 are formed as a texture structure (FIG. 10-2).

  Next, the oxide film 41 is removed by immersing the p-type silicon substrate 1 in a dilute hydrogen fluoride (HF) aqueous solution, for example (FIG. 10-3). At this time, the oxide film 41 is removed under the condition that the passivation oxide film 2 remains.

  And the area | region where boron was ion-implanted among the dot-shaped area | regions in the back surface side of the p-type silicon substrate 1 by implementing the process demonstrated using FIGS. 9-2-FIG. 9-4 in Embodiment 3. FIG. Then, the p + layer 3 is formed, and the n-type impurity diffusion layer 4 is formed in a region where phosphorus is ion-implanted in the dot-like region on the back side of the p-type silicon substrate 1 (FIG. 10-4). The n-type impurity diffusion layer 4 is formed in a dot-like region where the minute irregularities 32 are formed on the back side of the p-type silicon substrate 1.

  Thereafter, a high photoelectric conversion efficiency solar cell having a texture structure and a point contact cell structure can be manufactured in the same manner as in the third embodiment.

  As described above, according to the method for manufacturing a solar cell according to the fourth embodiment, a solar cell having a point contact cell structure having a higher photoelectric conversion efficiency without going through a resist patterning process. It can be manufactured inexpensively by a simple process.

  Moreover, the solar cell module excellent in photoelectric conversion efficiency is realizable by forming several photovoltaic cells which have the structure demonstrated in said embodiment, and electrically connecting adjacent photovoltaic cells. In this case, for example, one n-layer electrode 6 and the other p + layer electrode 7 of adjacent solar cells may be electrically connected.

  As described above, the method for manufacturing a solar battery cell according to the present invention is useful when a solar battery having a point contact cell structure is manufactured at low cost by a simple process.

1 Semiconductor substrate (p-type silicon substrate)
DESCRIPTION OF SYMBOLS 1a Area | region covered by the point-shaped mask part at the time of oxygen ion implantation 1b Area | region covered by the connection part at the time of oxygen ion implantation 2 Passivation oxide film 2a Oxygen ion implantation area | region 3 p + layer (p-type semiconductor layer)
4 n-type impurity diffusion layer 5 antireflection film 6 n-type impurity diffusion layer electrode (n-layer electrode)
6a Grid electrode 6b Bus electrode 7 P + layer electrode (p + layer electrode)
DESCRIPTION OF SYMBOLS 11 Oxygen implantation mask 11a Point-shaped mask part 11b Connection part 21 Boron implantation mask 22 Opening 31 Mask oxide film 32 Micro unevenness 41 Oxide film

Claims (8)

A first step of selectively implanting oxygen ions in a predetermined pattern on one surface side of a first conductivity type semiconductor substrate;
First annealing is performed on the semiconductor substrate to oxidize a portion where the oxygen ions are implanted on one surface side of the semiconductor substrate to form an oxide film having the predetermined pattern on a surface layer on the one surface side of the semiconductor substrate. A second step;
A third step of selectively implanting first conductivity type impurity ions into at least a part of a closed region surrounded by the predetermined pattern in a region where the oxide film is not formed on the one surface side of the semiconductor substrate; When,
First annealing is performed on the semiconductor substrate, and a first conductivity type impurity is diffused at a higher concentration in the closed region of the surface layer on one surface side of the semiconductor substrate than in other regions of the semiconductor substrate. A fourth step of forming a type semiconductor layer;
The manufacturing method of the photovoltaic cell characterized by including. The first step includes
A mask having a predetermined pattern and having a plurality of mask portions and a connecting portion for connecting adjacent mask portions to each other is arranged at a first arrangement position on one surface side of the semiconductor substrate, and the oxygen ions are implanted. A first ion implantation step;
A first ion implantation step of implanting the oxygen ions by arranging the mask at a first arrangement position on one side of the semiconductor substrate;
The mask portion covers the arrangement position of the mask portion at the first arrangement position, and the mask is arranged at a second arrangement position where the position of the connection portion is different from the first arrangement position, and the oxygen ions are implanted. A second ion implantation step to be performed;
The manufacturing method of the photovoltaic cell of Claim 1 characterized by the above-mentioned. The mask has a photoresist formed on the surface of a metal plate,
The manufacturing method of the photovoltaic cell of Claim 1 or 2 characterized by these. The mask is a stencil mask;
The manufacturing method of the photovoltaic cell of Claim 1 or 2 characterized by these. The semiconductor substrate is a p-type silicon substrate doped with gallium;
The manufacturing method of the photovoltaic cell as described in any one of Claims 1-4 characterized by these. The semiconductor substrate is an n-type silicon substrate;
The manufacturing method of the photovoltaic cell as described in any one of Claims 1-4 characterized by these. Forming a second impurity diffusion layer in which impurities of the second conductivity type are diffused on the other surface side of the semiconductor substrate;
The manufacturing method of the photovoltaic cell as described in any one of Claims 1-6 characterized by these. Implanting second conductivity type impurity ions into a closed region surrounded by the predetermined pattern in a region where the oxide film is not formed on one side of the semiconductor substrate;
Performing a third anneal on the semiconductor substrate to form a third conductivity type semiconductor layer in which a second conductivity type impurity is diffused in a surface layer of the semiconductor substrate in the closed region;
Having
The manufacturing method of the photovoltaic cell as described in any one of Claims 1-6 characterized by these.

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