JP2015211117A - Method of manufacturing solar cell and solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method of manufacturing a solar cell in which a low resistance region of high impurity concentration, and a high resistance region of low impurity concentration are formed on a semiconductor substrate by a single heat treatment.SOLUTION: A method of manufacturing a solar cell including a step of forming a suppression film 12 for suppressing diffusion on the surface of an n-type single crystal silicon substrate 1, and a step of thinning a partial region of the suppression film 12. The method further includes a step of diffusing impurities on the surface of the suppression film 12 into the n-type single crystal silicon substrate 1, by performing heat treatment thereof, and differentiating the amount of impurities diffused into the n-type single crystal silicon substrate 1 depending on the thickness of the suppression film 12.

Description

  The present invention relates to a solar cell manufacturing method and a solar cell.

  In a conventional solar cell, an impurity diffusion layer formed on a light incident surface (hereinafter referred to as a light receiving surface) or a region under the electrode opposite to the light receiving surface (hereinafter referred to as a back surface) and a region other than under the electrode. There is a technique of changing the impurity concentration and forming an optimum diffusion layer in each region. In particular, for solar cells with high photoelectric conversion efficiency, the choice is to form a low-resistance diffusion layer in which a large amount of impurities are diffused in a region in contact with the electrode and to form a low-concentration high-resistance layer in a region other than the electrode A technique called an emitter structure is often used. The selective emitter structure is a structure in which an emitter region having a surface impurity concentration higher than the surrounding is selectively formed in a region connected to an electrode in a diffusion layer formed on the surface of a semiconductor substrate. The selective emitter structure can increase the surface impurity concentration of the emitter region in contact with the electrode while maintaining the impurity concentration of the junction at an appropriate concentration, and the ohmic contact resistance between the semiconductor substrate and the electrode can be increased. Reduce and improve fill factor. Further, in the emitter region, since the impurity is diffused at a high concentration, the electric field effect in the region connected to the electrode is increased, carrier recombination can be suppressed, and the open circuit voltage is improved.

  As a manufacturing method, a method is disclosed in which a layer that inhibits diffusion is formed on the surface of a semiconductor substrate, and a high-concentration layer is formed in the opening of the inhibition layer, and a low-concentration diffusion layer is formed after removal of the inhibition layer (for example, a patent). Reference 1). Also disclosed is a method in which a high-concentration diffusion layer is once formed on the surface of a semiconductor substrate, a part of the region is shaved to remove the high-concentration layer on the surface, and an internal low-concentration portion is exposed (for example, Patent Documents). 2).

JP 2012-54457 A Special table 2013-509695

  However, according to the technique disclosed in Patent Document 1, it is necessary to form a low-resistance impurity diffusion layer, remove the mask film, and perform a high-resistance diffusion process again. For this reason, it is necessary to perform the heat treatment twice, and the process becomes complicated, and deterioration of the substrate quality due to heat cannot be avoided.

  Alternatively, according to the technique disclosed in Patent Document 2, the heat treatment is performed only once, but it is necessary to apply an etching paste to the surface for etching the semiconductor substrate. For this reason, a process for cleaning contamination on the substrate surface is newly required. Furthermore, since the high resistance region is formed by cutting the low resistance portion of the semiconductor substrate surface, there is a problem that the uneven shape for reducing the reflectance previously formed on the substrate surface is changed.

  The present invention has been made in view of the above, and obtains a method for manufacturing a solar cell in which a low resistance region having a high impurity concentration and a high resistance region having a low impurity concentration are formed on a semiconductor substrate by a single heat treatment. For the purpose.

  In particular, an object of the present invention is to obtain a method for manufacturing a solar cell having a low resistance region constituting a contact region for electrode formation in a high resistance region having a low impurity concentration.

  In order to solve the above-described problems and achieve the object, the present invention forms a second conductive type diffusion layer on the first main surface of the first conductive type semiconductor substrate having the first and second main surfaces. And a step of forming the first current collecting electrode on a part of the first main surface and a step of forming the second current collecting electrode on the second main surface. The step of forming the diffusion layer of the second conductivity type is to form a suppression film that suppresses impurity diffusion so that it is thinner than the peripheral region in the region where the first current collecting electrode on the first main surface is formed. A step of forming a solid phase diffusion source on the suppression film, and a heat treatment to perform impurity diffusion from the solid phase diffusion source on the first main surface, a second conductivity type diffusion layer, and a first current collector Forming a second conductivity type high-concentration diffusion region selectively formed in a region where an electrode is to be formed.

  According to the present invention, since the thickness of the suppression film formed on the surface of the semiconductor substrate differs from region to region, there is a difference in the time taken for impurities to pass through the suppression film and reach the semiconductor substrate during heat treatment. Therefore, the depth of impurity penetration can be changed for each region of the semiconductor substrate by one heat treatment, and an impurity diffusion layer having a different impurity diffusion amount for each region can be formed.

FIG. 1 is a diagram schematically illustrating a solar cell formed by using the method for manufacturing a solar cell according to the first embodiment, where (a) is a plan view and (b) is an A-A diagram of (a). It is sectional drawing. FIGS. 2A and 2B are views for explaining the concept of the method for manufacturing the solar cell. 3A to 3E are manufacturing process diagrams of the solar cell. 4A to 4C are manufacturing process diagrams of the solar cell. FIGS. 5A to 5C are manufacturing process diagrams of the solar cell. FIG. 6: is sectional drawing of the solar cell which shows the state in the middle of the process of the manufacturing method of the solar cell concerning Embodiment 2 of this invention. 7A to 7C are process cross-sectional views illustrating a part of the manufacturing process of the solar cell according to the third embodiment of the present invention. 8A to 8C are process cross-sectional views illustrating a part of the manufacturing process of the solar cell according to the fourth embodiment of the present invention. 9A to 9C are process cross-sectional views illustrating a part of the manufacturing process of the solar cell according to the fifth embodiment of the present invention. 10A to 10C are process cross-sectional views illustrating a part of the manufacturing process of the solar cell according to the sixth embodiment of the present invention. FIG. 11: is a figure which shows typically the solar cell formed using the manufacturing method of the solar cell concerning Embodiment 7, (a) is a top view, (b) is AA of (a). It is sectional drawing. FIG. 12 is a view for explaining the concept of the solar cell manufacturing method. 13A to 13E are manufacturing process diagrams of the solar cell. 14A to 14C are manufacturing process diagrams of the solar cell. FIGS. 15A and 15B are manufacturing process diagrams of the solar cell. FIG. 16: is a figure which shows typically the solar cell formed using the manufacturing method of the solar cell concerning Embodiment 8, (a) is a top view, (b) is AA of (a). It is sectional drawing. FIG. 17 is a view for explaining the concept of the solar cell manufacturing method. FIG. 18 is a view showing a state during the production of the solar cell. FIG. 19 is a graph showing the thickness of the suppression film used in the embodiment and the change in sheet resistance after impurity diffusion. FIG. 20 is a graph showing the thickness of a solid phase diffusion source (BSG) used as a suppression film used in the embodiment and the maximum peak concentration of impurities after impurity diffusion.

  Below, the manufacturing method of the solar cell concerning this invention and embodiment of a solar cell are described in detail based on drawing. In addition, this invention is not limited by this embodiment, In the range which does not deviate from the summary, it can change suitably. In the drawings shown below, the scale of each layer or each member may be different from the actual for easy understanding, and the same applies to the drawings. Further, even a plan view may be hatched to make the drawing easy to see.

Embodiment 1 FIG.
FIG. 1 is a diagram schematically showing a first embodiment of a solar cell according to the present invention, in which (a) is a plan view and (b) is an AA cross-sectional view of (a). 2 (a) and 2 (b) are diagrams for explaining the concept of the solar cell manufacturing method, FIGS. 3 (a) to (e), FIGS. 4 (a) to (c), and FIG. 5 (a). ) To (c) are production process diagrams of the solar cell. In this embodiment mode, a diffusion type solar cell (hereinafter may be referred to as a solar cell) which is an example of a crystalline solar cell and a manufacturing method thereof will be described.

The solar cell 10 according to the first embodiment includes an n-type single crystal silicon substrate 1 serving as a first conductivity type semiconductor substrate having a first main surface serving as a light receiving surface 1A and a second main surface serving as a back surface 1B. A p-type diffusion layer 2 as a second conductivity type diffusion region and a high-concentration p-type diffusion region 2D as a contact region are formed. An n-type diffusion layer 3 is formed on the back surface 1B side. Further, on the light receiving surface 1A and the back surface 1B, a light receiving surface electrode 7 including a bus electrode 7B and a grid electrode 7G and a back surface electrode 8 are formed. Further, on the light receiving surface 1A and the back surface 1B, a silicon oxide (SiO ₂ ) film as the passivation films 5a and 5b and a silicon nitride (SiN film) as the antireflection films 6a and 6b are formed.

The p-type diffusion layer 2 as the second conductivity type diffusion region and the high-concentration p-type diffusion region 2D as the contact region are as shown in FIGS. 2 (a) and 2 (b). Then, a suppression film 12 such as a silicon oxide (SiO ₂ ) film that suppresses impurity diffusion is formed, and the suppression film 12 is formed to be divided into a thin region 12a and a thick region 12b. Then, a boron silicate glass (BSG) layer containing boron as a solid phase diffusion source 14 serving as an impurity diffusion source for forming the second conductivity type semiconductor layer is formed on the suppression film 12. The solid-phase diffusion source 14b formed in the thin region 12a is formed with a shorter distance to the n-type single crystal silicon substrate 1 than the solid-phase diffusion source 14a formed in the thick region 12b of the suppression film 12 (FIG. 2). (A)). In addition to the silicon oxide film, the suppression film 12 may be a film that does not affect the semiconductor substrate due to diffusion of unnecessary substances during heat treatment, such as a silicon nitride film (SiN). . On the other hand, there is a method of forming the suppression film 12 with a printing paste, but this is not preferable because the above-described unnecessary impurities may enter the substrate during the heat treatment.

  After that, a heat treatment is applied to the semiconductor substrate in which the n-type single crystal silicon substrate 1, the suppression film 12, and the solid phase diffusion source 14 are integrated, and the second conductivity type layer 4 is formed from the solid phase diffusion source 14. Impurities reach the light receiving surface 1A of the n-type single crystal silicon substrate 1, and the p-type diffusion layer 2 as the second conductivity type layer and the high concentration p-type diffusion region 2D are formed on the light receiving surface 1A of the n-type single crystal silicon substrate 1. Is formed. The second conductivity type layer 4 includes a p-type diffusion layer 2 as a high-resistance second conductivity type layer containing a low amount of impurities immediately below the region 12b where the suppression film 12 is thick, and a region immediately below the region 12a where the suppression film 12 is thin. It is formed by being divided into a high-concentration p-type diffusion region 2D as a low-resistance second conductive type layer containing a large amount of impurities.

  Note that a fine concavo-convex structure called a texture is usually formed on the light receiving surface 1A of the n-type single crystal silicon substrate 1 which is a first conductivity type semiconductor substrate (not shown) to reduce light reflection (not shown). ). A layer structure such as the second conductivity type layer 4 is formed on the texture. Further, the texture is formed on the back surface 1B as well as the light receiving surface 1A.

  As the first conductivity type semiconductor substrate according to the present embodiment, for example, a single crystal or polycrystalline silicon substrate that is an n-type containing a small amount of phosphorus or the like can be used. In this case, as described above, for example, a boron silicate glass (BSG) layer containing boron can be used for the solid phase diffusion source 14. For formation of the BSG layer, for example, low pressure CVD or normal pressure CVD can be used.

  The light-receiving surface and the back surface of the first conductivity type semiconductor substrate preferably have a texture in order to reduce reflectivity. However, a flat structure or a structure in which an uneven structure and a flat structure are combined according to the application. It may be used.

  An impurity layer of the first conductivity type may be formed on the back surface of the first conductivity type semiconductor substrate, but since it is not directly related to the present invention, any structure may be used and the present invention is limited. is not.

  Further, as the first conductivity type semiconductor substrate, for example, a p-type single crystal or a polycrystal containing a small amount of boron can be used instead of the n-type, and a phosphorus silicate glass containing phosphorus as a solid phase diffusion source. (PSG) can also be used.

  3 (a) to 3 (e), 4 (a) to 4 (c), and 5 (a) to 5 (c) are diagrams illustrating a manufacturing process of the solar cell manufacturing method according to the first embodiment. . In the first embodiment, an n-type single crystal silicon substrate 1 that has been subjected to appropriate pretreatment, for example, removal of a damaged layer after slicing and formation of a texture is used (FIG. 3A).

  For example, a silicon oxide film having a thickness of 5 nm to less than 60 nm is formed on the light-receiving surface 1A of the n-type single crystal silicon substrate 1 as the suppression film 12 that suppresses impurity diffusion (FIG. 3B). Preferably, as will be described later, as shown in FIG. 19, since the impurity does not reach the first conductivity type semiconductor substrate and does not change from the first conductivity type until the thickness of the suppression film reaches 60 nm, the thickness is set to 5 nm to 40 nm. Is desirable. A silicon oxide film is used as the suppression film 12 in FIG. Although it is possible to use a suppression film of 5 nm or less, it is not preferable because the suppression effect decreases. The suppression film 12 is formed uniformly.

  An etching paste 11 capable of reducing the thickness of the suppression film 12 is printed on the uniformly formed suppression film 12 (FIG. 3C).

  In order to activate the etching paste 11, for example, a heat treatment at 100 ° C. to 400 ° C. for 1 to 30 minutes is applied to the n-type single crystal silicon substrate 1 to cause the etching paste 11 to erode the suppression film 12 (FIG. 3D). .

  The amount of erosion of the etching paste 11 can be controlled by the treatment temperature and time, and a treatment that achieves the desired suppression film thickness is applied. Thereafter, the etching paste 11 is immersed in an alkaline solution, for example, an aqueous solution of sodium hydroxide of 0.5 to 10% by weight to remove the etching paste 11 (FIG. 3E).

  In the region 12 a of the suppression film 12 that has been eroded by the etching paste 11, the suppression film 12 is thin, and a recess 13 having a thin suppression film 12 is formed, for example, with a remaining thickness of 5 nm to 30 nm of the suppression film 12. The remaining thickness of the suppression film 12 can be controlled by the amount of erosion of the etching paste 11, and can be mainly controlled by the activation temperature and the heat treatment time of the etching paste 11 described above. A solid phase diffusion source 14 containing an impurity capable of forming a second conductivity type layer when diffused into the first conductivity type semiconductor substrate on the upper part of the suppression film 12 in which the recess 13 is formed, for example, containing boron A silicon oxide film (BSG film) is formed (FIG. 4A). The solid phase diffusion source 14 may be a single BSG film as described above, but may be a stack of BSG and an oxide film as long as it can diffuse impurities into the semiconductor substrate.

  The solid phase diffusion source 14 may be formed in a concavo-convex shape in accordance with the concavo-convex shape of the suppression film 12 or may be formed so that the upper portion of the solid phase diffusion source 14 is flat as shown in FIG. Good. In the present embodiment, for ease of understanding, the upper part of the solid phase diffusion source 14 is illustrated to be flat. The thick region 12b of the suppression film 12 has a long distance between the n-type single crystal silicon substrate 1 and the solid phase diffusion source 14, and the thin region 12a of the suppression film 12 has the n type single crystal silicon substrate 1 and the solid phase diffusion source 14. The distance to is short. Subsequently, heat treatment is applied to the n-type single crystal silicon substrate 1 at, for example, 900 ° C. to 1100 ° C. for 10 minutes to 120 minutes.

4 (b) to 4 (c) and FIG. 5 (a), the n-type single crystal silicon substrate 1, the suppression film 12, the solid phase diffusion source 14, and the solid phase diffusion source 14 diffused from the heat treatment. It also shows how the formed impurity layer changes. In the region 12a where the suppression film 12 between the solid phase diffusion source 14 and the n-type single crystal silicon substrate 1 is thin, impurities are diffused into the n-type single crystal silicon substrate 1 from the beginning of the heat treatment to form an impurity layer 2d ₂ (FIG. 4). (B)). The impurity layer 2d ₂ of n-type single-crystalline silicon substrate 1 is a semiconductor substrate of a first conductivity type is shown the function of the second conductivity type layer. On the other hand, in the region 12 b where the suppression film 12 is thick between the solid phase diffusion source 14 and the n-type single crystal silicon substrate 1, an impurity layer 2 d ₁ in which impurities are diffused is formed in the suppression film 12.

As described above, the n-type single crystal silicon substrate 1 in the initial stage of the heat treatment is formed with the second conductivity type layer formed by diffusing impurities and the region where the impurities are not diffused. When the heat treatment is further continued, the impurity layer 2d ₂ diffuses deeper into the n-type single crystal silicon substrate 1 (FIG. 4C). Even at this stage, the impurity layer 2d _{1 in} the thick region 12b of the suppression film 12 does not reach the light receiving surface 1A of the n-type single crystal silicon substrate 1 and does not form the second conductivity type layer. In other words, the light-receiving surface 1A of the n-type single crystal silicon substrate 1 is divided into two regions, a high-concentration p-type diffusion region 2D that is a deep second conductivity type layer and a region where the light-receiving surface 1A of the n-type single crystal silicon substrate 1 is exposed. Two regions are formed. Subsequently, in the final stage of the heat treatment, the impurity layer in the thick region 12b of the suppression film 12 reaches the light receiving surface 1A of the n-type single crystal silicon substrate 1, and the p-type diffusion layer 2 is formed (FIG. 5A). )). Therefore, on the light-receiving surface 1A of the n-type single crystal silicon substrate 1 after the heat treatment, the p-type diffusion layer 2 which is the second conductivity type layer in which a small amount of impurities are diffused and the impurities are diffused deeply and the amount of impurities is increased. There are many high-concentration p-type diffusion regions 2D that are second conductivity type layers. A broken line AA ′ in the drawing indicates a portion that is an interface between the n-type single crystal silicon substrate 1 and the suppression film 12 for easy understanding.

After completion of the heat treatment, phosphorus is diffused into the back surface 1B of the n-type single crystal silicon substrate 1 which is the first conductivity type semiconductor substrate using, for example, POCl ₃ gas, and the n-type diffusion which is the diffusion layer of the first conductivity type layer. Layer 3 is formed (FIG. 5B). Subsequently, the solid phase diffusion source 14 and the suppression film 12 are removed by immersing in, for example, a hydrofluoric acid aqueous solution of 1 to 10 vol%. At the same time, the oxide film layer containing phosphorus formed on the back surface 1B side can also be removed. After removal of the solid phase diffusion source 14 and the suppression film 12, only the n-type single crystal silicon substrate 1 remains, and the light receiving surface 1A of the n-type single crystal silicon substrate 1 is a shallow second conductivity type layer with a small amount of impurities. A type diffusion layer 2 and a high-concentration p-type diffusion region 2D, which is a deep second conductivity type layer with a large amount of impurities, are formed (FIG. 5C). The p-type diffusion layer 2 functions as a high-resistance conductive layer, and the high-concentration p-type diffusion region 2D and the n-type diffusion layer 3 as the first conductivity type layer on the back surface 1B function as a low-resistance conductive layer. On the other hand, it is preferable to dispose the first conductivity type layer on the back surface 1B, but it may not be formed, and the first embodiment is not limited.

  According to this embodiment, since the shape of the solar cell substrate surface is not deformed after the impurity diffusion step, the reflectance can be maintained at a low level. In addition, since a plurality of impurity diffusion layers can be formed by only one heat treatment, a low carrier resistance, a long carrier lifetime due to suppression of carrier deactivation due to impurities, and a low thermal history result in low substrate quality. Deterioration can be suppressed, and a solar cell having a longer carrier lifetime and excellent photoelectric conversion efficiency can be produced.

  Further, since the high-concentration p-type diffusion region 2D is formed up to a region deeper than the p-type diffusion layer 2, even when the surface is eroded due to alloying at the time of forming the light-receiving surface electrode, etc. Since the low resistance region remains, the contact resistance can be reliably reduced.

  The method for creating the thick region 12b and the thin region 12a of the suppression film 12 is not limited to the method of the first embodiment, and other methods can be used. This point will be described later.

  According to the method for manufacturing a solar cell according to the first embodiment, a high resistance second conductivity type layer and a low resistance second conductivity type are formed on the light receiving surface of the first conductivity type semiconductor substrate by one heat treatment. The layer can be formed, the low-resistance second conductivity type layer and the electrode can be brought into contact with each other, and the first conductivity type semiconductor substrate is not deteriorated due to the multiple heat treatments. Long solar cells can be manufactured. In addition, when forming the second conductive type layer having high resistance and the second conductive type layer having low resistance, the light receiving surface of the semiconductor substrate of the first conductive type is covered with the suppression film. A high-purity solar cell can be manufactured without contact of a contamination source such as a paste with the surface. Further, since the second conductivity type layer can be formed without cutting the light receiving surface, the initial light receiving surface shape, for example, texture can be maintained, and a solar cell maintaining a low reflectance can be manufactured. That is, according to the method for manufacturing a solar cell according to the first embodiment, it has excellent characteristics such as long carrier lifetime, low reflectance, and no deterioration of substrate quality due to contamination, and has high photoelectric conversion efficiency. A solar cell can be manufactured.

  FIG.1 (b) shows sectional drawing of the solar cell manufactured using the manufacturing method of the solar cell of this Embodiment 1. FIG. A p-type diffusion layer 2 which is a second conductivity type layer containing a small amount of impurities on the light-receiving surface 1A side of the n-type single crystal silicon substrate 1 which is a first conductivity type semiconductor substrate, and a low resistance second conductivity containing a large amount of impurities. A high-concentration p-type diffusion region 2D, which is a mold layer, is formed. A passivation film 5a is formed on the light receiving surface 1A, and an antireflection film 6a is formed on the passivation film 5a. Since the p-type diffusion layer, which is an impurity diffusion layer, is formed by general thermal diffusion, the concentration distribution in the depth direction of the p-type diffusion layer takes a standard attenuation shape. The depth of the second conductivity type layer is preferably about 500 nm to 2 μm in order to add a field effect in order to suppress recombination of minority carriers at the interface between the light receiving surface electrode and the first conductivity type semiconductor substrate. When the depth is less than 500 nm, the impurity concentration increases and recombination increases in order to maintain the same conductivity. When the depth is deeper than 2 μm, the total amount of impurities increases even at a low concentration. Recombination increases and the characteristics of the solar cell deteriorate. The light-receiving surface electrode is formed so as to be in contact with the low resistance second conductivity type layer. The structure on the back surface 1B side only needs to have a function as a solar cell. For example, as shown in FIG. 1B, a passivation film 5b, an antireflection film 6b, and a back electrode 8 are formed.

  In the method of manufacturing the solar cell of the first embodiment, the p-type diffusion layer 2 which is the above-described second conductivity type layer and the high-concentration p-type having a higher concentration than the second conductivity type diffusion layer 2 are formed on the light receiving surface 1A. Although the diffusion region 2D is described as being formed, it may be formed on the back surface of the first conductivity type semiconductor substrate. Further, for example, the second conductivity type layer is the light receiving surface, and the first conductivity type layer is the back surface. In addition, diffusion layers having different concentrations may be formed on both sides.

  The first conductivity type layer can be formed by using, for example, phosphorus silicate glass (PSG), which is a silicon oxide film containing phosphorus, as a solid phase diffusion source. For example, a silicon oxide film or a silicon nitride film can be used as the suppression film at that time. The heat treatment method may be performed separately for the light receiving surface and the back surface, or both surfaces may be heat treated simultaneously. The area of the region where the suppression film is thin may be arbitrary, and the shape may be any shape such as a line shape, a broken line shape, or a dot shape.

Embodiment 2. FIG.
Since the manufacturing method of the solar cell 10 according to the second embodiment is the same as the manufacturing method of the solar cell shown in the first embodiment except for the structure of the suppression film 12, the details are as referring to the first embodiment. Is omitted.

  FIG. 6 is a cross-sectional view of a solar cell being manufactured by the method for manufacturing a solar cell according to the second embodiment. In the method for manufacturing a solar cell according to the second embodiment, the suppression film 12 is formed so as to have an opening reaching the surface of the n-type single crystal silicon substrate 1, and the solid-phase diffusion source 14 is formed of n-type single crystal silicon. A heat treatment is performed in a state where the substrate 1 is in contact with the surface of the substrate 1, and impurity diffusion is performed. In the present embodiment, after the suppression film 12 is uniformly formed, an opening 15 is formed by printing a part of the suppression film 12, for example, by a heat treatment for 10 to 30 minutes at a temperature of 200 to 400 ° C. or laser irradiation. Then, it wash | cleans using alkaline solution, for example, 0.5-10 weight% of sodium hydroxide aqueous solution, and the mixed solution of a sulfuric acid and hydrogen peroxide. Thereafter, the solid phase diffusion source 14 is formed in a region where the suppression film 12 is not subjected to an opening process and a region formed by opening the suppression film 12.

  According to the method for manufacturing a solar cell according to the second embodiment, since the solid phase diffusion source 14 is formed in the opening 15 of the suppression film 12, the impurity diffuses into the n-type single crystal silicon substrate 1 immediately after the heat treatment, Similar to the solar cell of the first embodiment, a high-concentration p-type diffusion region 2D which is a low-resistance second conductive type layer is formed. In addition, since the impurity diffuses in the region where the suppression film 12 remains as in the first embodiment, a high resistance second conductivity type layer is formed at the end of the heat treatment.

  Therefore, a high-concentration p-type diffusion region 2D that is a low-resistance second conductivity type layer in which impurities are diffused deeper than in the first embodiment, and a p-type diffusion layer 2 that is a high-resistance second conductivity type layer; Can be formed by a single heat treatment, so that deterioration of the substrate quality can be suppressed and a solar cell with a long carrier lifetime can be realized. That is, according to the method for manufacturing a solar cell according to the second embodiment, a solar cell with a high photoelectric conversion efficiency is provided, which includes a low-resistance second conductivity type layer having a long carrier lifetime and impurities diffused deeper. Realized.

  The step of forming the suppression film includes a step of removing and opening the suppression film to expose the surface of the first conductivity type semiconductor substrate. Therefore, the solar cell manufactured by this manufacturing method can diffuse more impurities into the solar cell substrate in the region where the suppression film is opened, can form a lower resistance impurity diffusion layer, and manufactures a low resistance solar cell. it can.

Embodiment 3 FIG.
In the first and second embodiments, the thin region 12a and the thick region 12b of the suppression film 12 are formed, and the solid phase diffusion source 14 is formed on the upper layer, thereby controlling the diffusion depth and concentration profile. Thus, the high concentration region and the low concentration region were formed by one heat treatment. In the present embodiment, a modified example of the method for forming the pattern of the suppression film 12 will be described. In the first and second embodiments, the suppression film 12 is etched using an etching paste. However, in this embodiment, a pattern of the resin component (resist) R1 is formed, and the suppression film 12 in that portion is thin. It is a method of forming or not forming.

  As shown in FIG. 7A, after forming a thin suppression film 12A on the light receiving surface 1A side of the n-type single crystal silicon substrate 1, a resin component (resist) R1 is printed in an arbitrary region using a printing paste or the like. To do.

  Subsequently, as shown in FIG. 7B, a thin suppression film 12B is formed again. At this time, the second suppression film is not formed on the resin component R1, and is formed as a thin region 12a.

  Finally, as shown in FIG. 7C, the resin component R1 is removed using a solution that does not affect the suppression film 12, such as an alkaline solution.

  In this way, the suppression films 12 having different thicknesses having the thick regions 12b and the thin regions 12a are formed. However, according to this method, since the formation is performed without an etching process, the deterioration of the substrate surface or Contamination can be avoided.

  Thereafter, for example, as in FIG. 4A of the first embodiment, the solid-phase diffusion source 14 is formed and heat treatment is performed, whereby the same solar cell can be obtained. In addition, even when the thin suppression film 12B is formed on the resin component R1 in the process of FIG. 7B, when the resin component R1 is removed, it is similarly removed by lift-off.

  As described above, the step of forming the suppression film includes the first film formation step of forming the suppression film and the substance that becomes the protective film after the first film formation step is placed on the suppression film and then suppressed. A film is further formed to provide a second film forming step of forming a protective film region and a suppression film having a different thickness in a region other than the protective film. According to this method, since the thickness of the thin region of the suppression film can be arbitrarily controlled by forming the suppression film for the first time, impurities formed on the first conductivity type semiconductor substrate, which is a solar cell substrate immediately below the suppression film A uniform diffusion layer can be formed in the diffusion layer.

Embodiment 4 FIG.
In the present embodiment, a modified example of the method for forming the pattern of the suppression film 12 will be described. In the third embodiment, a method is used in which a pattern of the resin component (resist) R1 is formed and the suppression film 12 in that portion is formed thin or not formed. In the present embodiment, As shown in FIGS. 8A to 8C, a metal mask M made of stainless steel is placed in place of the pattern of the resin component (resist) R1.

  As shown in FIG. 8A, similar to the method of the third embodiment, after forming a thin suppression film 12A on the light receiving surface 1A side of the n-type single crystal silicon substrate 1, this metal mask M is placed. .

  Subsequently, as shown in FIG. 8B, a thin suppression film 12B is formed again. At this time, the second suppression film is not formed on the metal mask M, and is formed as a thin region 12a. On the other hand, in a region where the metal mask M does not exist, a thin suppression film 12B is laminated on the thin suppression film 12A to form a thick region 12b.

  Finally, as shown in FIG. 8C, the metal mask M is removed.

  In this way, the suppression films 12 having different thicknesses are formed. According to this method, the suppression film 12 can be formed without undergoing a resin component peeling step using a solution such as an alkaline solution, and no solution is required. However, the damage on the substrate surface can be further reduced because it only has to be physically removed.

  Thereafter, similar to FIG. 4A of the first embodiment, for example, the solid-phase diffusion source 14 is formed and heat treatment is performed, whereby the same solar cell 10 can be obtained.

  Instead of the metal mask, for example, a silicon or carbon mask plate similar to that of the semiconductor substrate may be placed on the suppression film, and the second suppression film may be formed. Since the second suppression film is not formed in the mask placement area, a thin area is formed in the mask area, and a thick suppression film is formed in the areas other than the mask, which is the sum of the first and second times. In addition, it is possible to install a mask from the first film formation. A thick suppression film is formed in areas other than the mask area, and only a thin film is formed in the area directly under the mask due to the wraparound of the film forming components.

Embodiment 5 FIG.
In the present embodiment, a modified example of the method for forming the pattern of the suppression film 12 will be described. In the fourth embodiment, the thin portion of the suppression film is formed using the stainless steel metal mask M. However, in the present embodiment, as shown in FIGS. A mask plate MP made of silicon, carbon, stainless steel or the like is placed away from the suppression film formation surface of the n-type single crystal silicon substrate 1 during film formation.

  As shown in FIG. 9A, first, a mask plate MP is set on the light receiving surface 1A side of the n-type single crystal silicon substrate 1 apart from the suppression film formation surface of the n-type single crystal silicon substrate 1.

  Subsequently, as shown in FIG. 9B, the suppression film 12 is formed. At this time, a suppression film is hardly formed in a region where the mask plate MP is present, and is formed as a thin region 12D, while a suppression film 12 having a normal film thickness is formed in a region where the mask plate MP is not present.

  Finally, as shown in FIG. 9C, the mask plate MP is removed.

  In this way, the suppression films 12 having different thicknesses are formed. According to this method, the suppression film 12 can be formed in a single film forming process, and is subjected to a resin component peeling process using a solution such as an alkaline solution. It can be formed without any need for a peeling solution and can be physically removed, so that the damage on the substrate surface can be further reduced.

  Thereafter, for example, as in FIG. 4A of the first embodiment, the solid-phase diffusion source 14 is formed and heat treatment is performed, whereby the same solar cell can be obtained.

  In addition, by forming the suppression film once, a thick suppression film 12b is formed in a region without the mask of the mask plate MP, and a thin suppression film 12a due to a sneak component is formed in a region immediately below the mask plate MP. It is formed. According to this method, the suppression film can be provided with a difference in film thickness by forming the suppression film once, and it is preferable that unnecessary substances do not touch the semiconductor substrate such as the n-type single crystal silicon substrate 1.

  The thin suppression film 12a in the region immediately below the mask is formed such that a thicker film is formed closer to the opening of the mask, and a thinner film is formed closer to the central part shielded by the mask away from the opening. With the tilted suppression film thickness, the suppression film in a region narrower than the shielding mask width can be selectively formed thin, and impurities can be diffused concentrated in the thinnest region. Therefore, the area where the impurities on the light receiving surface 1A are diffused at a high concentration can be reduced. Furthermore, since the center of the shielded region has a high concentration and changes to a low concentration as it approaches the periphery of the shielded portion, an increase in the amount of impurities is suppressed even if the periphery that is the changed region is designed to be large. . Therefore, a large extra area for alignment required when forming the electrode can be secured. In other words, even if the total amount of impurities is the same, by using this embodiment, the extra region can be enlarged, and the margin for stepping off due to misalignment during electrode formation can be improved. Therefore, it is possible to prevent the electrode from coming into contact with the low-concentration diffusion layer, and to suppress a decrease in open circuit voltage.

Embodiment 6 FIG.
In the present embodiment, a modified example of the method for forming the pattern of the suppression film 12 will be described. In the fifth embodiment, the mask plate MP is disposed away from the substrate surface and the thin portion of the suppression film is formed. However, in this embodiment, the thickness of the film can be controlled by controlling the substrate temperature during the film formation. This is a method for forming a thin region. As shown in FIGS. 10A to 10C, a susceptor P provided with a void PV is prepared when a substrate is installed during the formation of a suppression film using low pressure CVD or normal pressure CVD. Since the substrate temperature in the region located in the gap PV is lower than the others, the reaction in the region is limited, the suppression film 12 formed is thinned, and a thin region 12D is generated. When a cooling gas is allowed to flow through the gap PV, only a thinner film is likely to be formed.

  As shown in FIG. 10A, first, a susceptor P having a gap PV provided on the back surface 1B side of the n-type single crystal silicon substrate 1 is installed.

  Subsequently, as shown in FIG. 10B, the suppression film 12 is formed. At this time, the suppression film 12 is difficult to be formed in a region having the void PV, and is formed as a thin region 12D, while the suppression film 12 having a normal film thickness is formed in a region without the void PV.

  Finally, as shown in FIG. 10C, the susceptor P is removed.

  In this way, the suppression films 12 having different thicknesses are formed. According to this method, the suppression film 12 can be formed in a single film forming process, and is subjected to a resin component peeling process using a solution such as an alkaline solution. It can be formed without. And since the jig | tool should be mounted | worn by the back surface 1B side instead of the light-receiving surface 1A side, the damage of the board | substrate surface can be reduced further.

  Thereafter, for example, as in FIG. 4A of the first embodiment, the solid-phase diffusion source 14 is formed and heat treatment is performed, whereby the same solar cell can be obtained.

  As described above, when the suppression film is formed by the low pressure CVD or the normal pressure CVD, the susceptor P having the gap PV on the back surface is prepared when the first conductivity type semiconductor substrate is installed. Since the substrate temperature of the n-type single crystal silicon substrate 1 which is the first conductivity type semiconductor substrate in the region located in the gap PV is lower than the others, the reaction in the region is limited and a suppression film is formed. Thinning results in a thin area 12D.

  After passing through the solar cell manufacturing steps of the above-described third to sixth embodiments, a passivation film is formed on the light receiving surface and the back surface using a general solar cell manufacturing step, and further on the passivation film on the light receiving surface. An antireflection film is formed on the surface. As the passivation film, a silicon oxide film, a silicon nitride film, an aluminum oxide film, or the like can be used. For example, a silicon oxide film or a silicon nitride film can be used as the antireflection film. Subsequently, electrodes are formed on the light receiving surface and the back surface. The electrode can be formed by printing and baking a paste containing, for example, silver or aluminum. Since the present invention is not limited to the passivation film, the antireflection film, and the electrode, materials and processes other than those described above may be used. As for the electrode formation position, it is preferable that the electrode is formed on a low-resistance second conductive type layer in which a large amount of impurities are diffused, and alignment based on the outer shape of the first conductive type semiconductor substrate or some reference in advance. By providing the first conductive type semiconductor substrate, an electrode can be formed on the high-concentration second conductive type layer.

Embodiment 7 FIG.
Since the manufacturing method of the solar cell concerning Embodiment 7 is the same as the manufacturing method of the solar cell of Embodiment 1 except for the suppression film, the details are omitted as referring to Embodiment 1. FIG. 11 is a diagram schematically showing a seventh embodiment of the solar cell according to the present invention, in which (a) is a plan view and (b) is an AA sectional view of (a). FIG. 12 is a diagram for explaining the concept of the solar cell manufacturing method, FIGS. 13 (a) to (e), FIGS. 14 (a) to (c), FIGS. 15 (a) and 15 (b), It is a manufacturing process figure of the solar cell. In this embodiment mode, a diffusion type solar cell (hereinafter may be referred to as a solar cell) which is an example of a crystalline solar cell and a manufacturing method thereof will be described.

In the manufacturing method of the solar cell 10 according to the seventh embodiment, the suppression film 22 is formed on the light receiving surface 1A of the n-type single crystal silicon substrate 1 as the first conductivity type semiconductor substrate. It differs from the manufacturing method of the solar cell of Embodiments 1-6 that it consists of sources. A solid phase diffusion source such as BSG is used for the suppression film 22. The suppression film 22 is cut and thinned by heat-treating an arbitrary region, for example, at 100 ° C. to 400 ° C. for 1 to 30 minutes using, for example, an etching paste. Another solid phase diffusion source 24 is formed. Here, as the suppression film 22, a solid phase diffusion source of p-type impurities having a low boron concentration, for example, an impurity concentration of 10 ¹⁸ to 10 ²⁰ , is used, while as the solid phase diffusion source 24, a high boron concentration is used. A solid phase diffusion source having a concentration of, for example, 10 ²¹ or more is used. As a result of intensive studies, even if a solid phase diffusion source is used for the suppression film 22, the influence from the solid phase diffusion source 24 formed on the suppression film 22 can be controlled by changing the thickness of the suppression film. The inventors have found that diffusion layers having different impurity concentrations can be formed. By using a solid phase diffusion source for the suppression film 22, it is possible to have both a function as a suppression film and a function as a diffusion source. FIG. 19 is a graph showing the thickness of the suppression film used in the embodiment and the change in sheet resistance after impurity diffusion. FIG. 20 is a graph showing the peak concentration of impurities when another solid phase diffusion source is formed on the BSG film and the impurities are diffused through the BSG. The vertical axis represents the maximum impurity concentration, and the measurement was performed for a solid phase diffusion source having a thickness of 30 nm. As can be seen from this result, diffusion layers having different impurity concentrations can be formed by changing the thickness of the solid phase diffusion source. In addition to the BSG film described above, an oxide film containing an impurity that functions as an acceptor, such as gallium or indium, can also be used as the suppression film 22.

  In the solar cell of the first embodiment, the high-concentration p-type diffusion region 2D is formed to reach a region deeper than the p-type diffusion layer 2, but in the solar cell of the present embodiment, the high-concentration p The type diffusion region 2D is characterized in that it is selectively formed in the vicinity of the surface of the p-type diffusion layer 2. Others are the same as those of the solar cell according to the first embodiment, and the description thereof is omitted here. In addition, the same code | symbol was attached | subjected to the same site | part.

  In manufacturing, as shown in the conceptual diagram of FIG. 12, the solid-phase diffusion source is formed on the light-receiving surface 1A of the n-type single crystal silicon substrate 1 which is the first conductivity type semiconductor substrate, and a part of the region is thinly formed. A substrate in which the suppression film 22 and the solid phase diffusion source 24 formed at a concentration higher than that of the suppression film 22 are integrated is formed, and heat treatment is applied to the substrate.

  First, as shown in FIG. 13 (a), in the solar cell manufacturing method of the seventh embodiment, as described in the first embodiment, an appropriate pretreatment, for example, removal of a damaged layer after slicing is performed. Or an n-type single crystal silicon substrate 1 having a texture formed thereon.

  For example, a silicon oxide film having a thickness of 5 nm to less than 60 nm is formed on the light receiving surface 1A of the n-type single crystal silicon substrate 1 as a suppression film 22 that suppresses impurity diffusion (FIG. 13B). The suppression film 22 is formed uniformly.

  An etching paste 11S that can reduce the thickness of the suppression film 22 is printed on the uniformly formed suppression film 22 (FIG. 13C).

  In order to activate the etching paste 11S, for example, a heat treatment at 100 to 400 ° C. for 1 to 30 minutes is applied to the n-type single crystal silicon substrate 1 to cause the etching paste 11S to erode the suppression film 22 (FIG. 13D). . Thereafter, the etching paste 11S is immersed in an alkaline solution, for example, an aqueous solution of sodium hydroxide of 0.5 to 10% by weight to remove the etching paste 11S (FIG. 13E).

  The suppression film 22 in the portion eroded by the etching paste 11S is thin, and the suppression film 22 is thin, and the recess 13 is formed so that the remaining thickness of the suppression film 22 is, for example, 5 nm to 30 nm. The lower layer of the recess 13 is a thin region 22a. Again, the remaining thickness of the suppression film 22 can be controlled by the amount of erosion of the etching paste 11S, and can be mainly controlled by the activation temperature and the heat treatment time of the etching paste 11S. A solid phase diffusion source 24 containing an impurity capable of forming a second conductivity type layer when diffused to the first conductivity type semiconductor substrate above the thin region 22a of the suppression film in which the recess 13 is formed, for example, A silicon oxide film (BSG film) containing boron is formed (FIG. 14A).

  Again, the solid phase diffusion source 24 may be formed in a concavo-convex shape in accordance with the concavo-convex shape of the suppression film 22, and is formed so that the upper portion of the solid phase diffusion source 24 is flat as shown in FIG. May be. In the present embodiment, for ease of understanding, the upper part of the solid phase diffusion source 24 is illustrated to be flat. The thick region 22b of the suppression film 22 has a long distance between the first conductive type semiconductor substrate and the solid phase diffusion source 24, and the thin region 22a of the suppression film 22 has the first conductive type semiconductor substrate and the solid phase diffusion source 24. The distance to is short. Subsequently, a heat treatment of, for example, 900 ° C. to 1100 ° C. and 10 minutes to 120 minutes is applied to the first conductivity type semiconductor substrate.

FIG. 14B shows an initial state of the heat treatment, and a low-concentration second conductivity type layer 2d ₁ is formed on the entire light-receiving surface 1A of the n-type single crystal silicon substrate 1. On the other hand, high-concentration impurity diffusion has begun in the thin suppression film 22a in which the suppression film 22 made of a solid phase diffusion source is thin, and a high-concentration impurity diffusion layer 2d ₂ is formed in the suppression film 22. When further heat treatment is applied, the state shown in FIG. 14C is obtained, and the low-concentration second conductivity type layer 2d ₁ is formed deeper. Impurities from the solid phase diffusion source 24 diffuse in the thin suppression film 22 a and reach the surface of the n-type single crystal silicon substrate 1.

FIG. 15A shows a state in which heat treatment is further performed. The low-concentration second conductivity type layer 2d ₁ is formed deeper and becomes the p-type diffusion layer 2 as the second conductivity type layer. Further, high-concentration impurities are diffused into the n-type single crystal silicon substrate 1 which is the first conductive type semiconductor substrate, and a high-concentration p-type diffusion region 2D which is a high-concentration second conductive type layer is also formed.

  Thereafter, the back surface is processed in the same manner as in the first embodiment, and the shape shown in FIG. As shown in FIG. 15B, according to the manufacturing method of the seventh embodiment, the second conductivity type having a low impurity concentration on the light receiving surface of the n-type single crystal silicon substrate 1 which is the first conductivity type semiconductor substrate. A p-type diffusion layer 2 which is a layer is formed, and a high-concentration p-type diffusion region 2D which is a second conductivity type layer having a high impurity concentration is formed in a part of the region. Although illustrated in FIG. 15B, the n-type diffusion layer 3 that is the first-type conductive layer may or may not be formed on the back surface.

  In this way, the solar cell obtained by the manufacturing process shown in Embodiment 7 can be manufactured as a solar cell by obtaining a general passivation film, an antireflection film, and an electrode. FIG.11 (b) is sectional drawing which shows an example of the solar cell manufactured through the manufacturing method of this Embodiment 7. FIG. A p-type diffusion layer 2 that is a low-concentration and deep second-conductivity type layer is formed on the light-receiving surface 1A of the n-type single crystal silicon substrate 1 that is a first-conductivity-type semiconductor substrate, and a high-concentration and shallow region in a part of the region. A high-concentration p-type diffusion region 2D that is the second conductivity type layer is formed. A passivation film 5a is formed on the p-type diffusion layer 2 and the high-concentration p-type diffusion region 2D, which are the second conductivity type layers, and an antireflection film 6a is formed on the passivation film 5a. The light-receiving surface electrode 7 is formed so as to be in contact with the high-concentration p-type diffusion region 2D, which is a second conductivity type layer having a low resistance property because impurities exist at a high concentration. On the back surface, an n-type diffusion layer 3, which is a first conductivity type layer, a passivation film 5b, an antireflection film 6b, and a back electrode 8 are formed.

  In the solar cell that has undergone the solar cell manufacturing method according to the seventh embodiment, in addition to the effects shown in the first embodiment, the high-concentration p-type diffusion region 2D that is the second conductivity type layer has a low concentration and is shallow. Since it is formed inside the n-type single crystal silicon substrate 1 which is the lower part of the p-type diffusion layer 2 which is the second conductivity type layer and a high-concentration diffusion layer is not formed deeply, carrier deactivation is prevented. And a solar cell with a longer carrier lifetime can be realized. Furthermore, a low-concentration and deep diffusion layer is formed on the entire surface including the region of the high-concentration p-type diffusion region 2D, and the influence from the outermost surface of the substrate can be reduced, so that the saturation current density of the second conductivity type layer is reduced. And the deactivation of the carrier can be further suppressed. In addition, since the high-concentration p-type diffusion region 2D containing impurities at a high concentration is formed on the outermost surface of the light-receiving surface, the contact resistance with the light-receiving surface electrode 7 is low as in the solar cell shown in the first embodiment. Can be maintained. That is, according to the method for manufacturing a solar cell according to the seventh embodiment, a solar cell exhibiting high photoelectric conversion efficiency having low contact resistance and a longer carrier lifetime can be realized.

  According to the above method, prior to the formation of the solid phase diffusion source, a step of forming a lower layer solid phase diffusion source having a concentration different from that of the solid phase diffusion source in the opening is included. That is, a step of using a film containing an impurity to be diffused into a suppression film that suppresses impurity diffusion, a step of removing and opening the suppression film in an arbitrary region, and two layers having different concentrations on the suppression film and the opening A step of forming a solid phase diffusion source, a step of diffusing impurities from the solid phase diffusion source in the opening by heat treatment to form an impurity diffusion layer on the solar cell substrate, and a solid phase diffusion through the suppression film by heat treatment Diffusing impurities from the source into the solar cell substrate.

  According to this manufacturing method, a deep diffusion layer can be uniformly formed on the solar cell substrate, and a two-phase solid phase diffusion source for newly forming a film is formed in the opened region. A deep diffusion layer and a shallow diffusion layer with different concentrations from the deep diffusion layer can be formed, and three types of diffusion layers with different concentrations can be formed at the same time on the solar cell substrate. Since an optimal diffusion layer can be formed, a solar cell that can further suppress carrier recombination and has low contact resistance and excellent photoelectric conversion efficiency is realized.

Embodiment 8 FIG.
The manufacturing method of the solar cell according to the eighth embodiment is the same as the manufacturing method of the solar cell of the first to seventh embodiments except for the suppression film and the solid phase diffusion source, and therefore, refer to the first to seventh embodiments. The details are omitted.

  FIG. 16 is a diagram schematically showing an eighth embodiment of the solar cell 10 according to the present invention, in which (a) is a plan view and (b) is an AA cross-sectional view of (a). 17 and 18 are diagrams for explaining the concept of the solar cell manufacturing method. In this embodiment mode, a diffusion type solar cell (hereinafter may be referred to as a solar cell) which is an example of a crystalline solar cell and a manufacturing method thereof will be described.

  In the present embodiment, suppression including impurities that can be changed to the second conductivity type when diffused into the n-type single crystal silicon substrate 1 on the light receiving surface 1A of the n-type single crystal silicon substrate 1 as the first conductivity type semiconductor substrate. A film 22, for example, BSG is formed with a thickness of 60 nm or more, and a part of the suppression film 22 is opened. In the opened region, a solid phase diffusion source 22S, for example, BSG is formed with a thickness of 1 to 40 nm, and another solid phase diffusion source 24 is formed on the solid phase diffusion source 22S.

  The n-type single crystal silicon substrate 1 as the first conductivity type semiconductor substrate that has undergone the process shown in FIG. 17 is heat-treated to diffuse the impurities to form the p-type diffusion layer 2 that is the second conductivity type diffusion layer. FIG. 18 is a cross-sectional view before forming the solar cell electrode and the like formed by the solar cell manufacturing method according to the eighth embodiment. A p-type diffusion layer 2 is formed in the region where the suppression film 22b is formed on the light receiving surface 1A, and a deep low-concentration p-type diffusion layer 2S is formed in the region where the suppression film 22 is opened. A high concentration p-type diffusion region 2D is formed in the vicinity of the light receiving surface 1A of the low concentration p-type diffusion layer 2S.

  Since the impurity concentration of the low-concentration p-type diffusion layer 2S located immediately below the light-receiving surface electrode can be formed lower than the impurity concentration of the second conductivity type layer that needs to move carriers on the light-receiving surface, It is possible to further reduce the deactivation of the carrier immediately below. In addition, the high-concentration p-type diffusion region 2D that needs to be formed at a high concentration for contact with the light-receiving surface electrode can be formed shallowly, and the deactivation of carriers can be suppressed by the high-concentration impurities. Therefore, the p-type diffusion layer 2 that is the second conductivity type layer, the low-concentration p-type diffusion layer 2S that is the low-concentration second conductivity type layer, and the high-concentration p-type diffusion region 2D are suitable for the respective regions. Thus, recombination of carriers can be further suppressed, and the contact resistance with the light receiving surface electrode can be suppressed to a low level. Therefore, the solar cell manufactured using the method for manufacturing a solar cell according to the eighth embodiment realizes a solar cell with a long carrier lifetime and low contact resistance and excellent photoelectric conversion efficiency.

  1 n-type single crystal silicon substrate, 2 p-type diffusion layer, 2D high-concentration p-type diffusion region, 2S low-concentration p-type diffusion layer, 3 n-type diffusion layer, 4 second conductivity type layer, 5a, 5b passivation film, 6a , 6b Antireflection film, 7 Light-receiving surface electrode, 7B Bus electrode, 7G Grid electrode, 8 Back electrode, 12, 22 Suppression film, 14, 24 Solid phase diffusion source, 11, 11S Etching paste.

Claims (8)

Forming a second conductive type diffusion layer on the first main surface of a first conductive type semiconductor substrate having first and second main surfaces;
Forming a first current collecting electrode on a part of the first main surface;
Forming a second current collecting electrode on the second main surface,
The step of forming the second conductivity type diffusion layer includes:
Forming a suppression film for suppressing impurity diffusion so as to be thinner than a peripheral region in a region where the first current collecting electrode is formed on the first main surface;
Forming a solid phase diffusion source on the suppression film;
By heat treatment, impurities are diffused from the solid phase diffusion source to the first main surface, and a second conductivity is selectively formed in a region where a second conductivity type diffusion layer and the first current collecting electrode are formed. And a step of simultaneously forming a high concentration diffusion region of the mold. The step of forming the suppression film includes
The method for manufacturing a solar cell according to claim 1, further comprising a step of removing the suppression film to open and exposing the surface of the semiconductor substrate of the first conductivity type. The step of forming the suppression film includes
The manufacturing method of the solar cell of Claim 1 including the process of forming into a suppression film | membrane containing the impurity diffused in the suppression film | membrane which suppresses impurity diffusion. The step of forming the suppression film includes
Thinning a partial region of the suppression film after forming the suppression film;
The method for producing a solar cell according to claim 1, further comprising: forming the solid phase diffusion source on a suppression film. The step of forming the suppression film includes
A first film forming step of forming the suppression film;
After the first film formation step, a substance that becomes a protective film is placed on the suppression film, and then the suppression film is further formed to form a suppression film having a different thickness in the protective film region and the region other than the protective film. The manufacturing method of the solar cell of any one of Claim 1, 3, 4 provided with the 2nd film-forming process to form. Prior to the formation of the solid phase diffusion source,
The method for manufacturing a solar cell according to claim 3, comprising a step of forming a lower layer solid phase diffusion source having a concentration different from that of the solid phase diffusion source in the opening.   The solar cell manufactured using the manufacturing method of the solar cell of any one of Claim 1 to 6. A first conductivity type semiconductor substrate having first and second main surfaces;
A second conductivity type diffusion layer formed on the first main surface of the semiconductor substrate;
Selectively formed on a part of the first main surface, continuously formed in a high-concentration diffusion region having a higher impurity concentration than the diffusion layer of the second conductivity type, and a lower layer of the high-concentration diffusion region; The solar cell according to claim 7, further comprising a low concentration diffusion region having an impurity concentration lower than that of the second conductivity type diffusion layer.

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