JP2007103572A - Method of forming embedded electrode of solar battery, and manufacturing method of solar battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming an embedded electrode of a solar battery capable of preventing a yield from dropping, the service life of the solar battery from shortening, and its performance from degrading, saving a substrate material, and thinning the solar battery. <P>SOLUTION: An etching mask layer 102 is formed on the surface of a p-type silicon substrate 101 and patterned by laser to form an aperture 104. The silicon substrate 101 is etched through the aperture 104 by means of an acid or alkaline solution to form a groove 105. An n<SP>++</SP>diffusion layer 107 is formed on an internal side face of the groove 105 using the etching mask layer 102 as a diffusion mask. The mask layer 102 is removed, and an n<SP>+</SP>diffusion layer 108 is formed on the surface of the silicon substrate 101. An SiNx film 109 serving as a passivation film and an anti-reflective film for incident light is formed on the n<SP>++</SP>diffusion layer 107 and the n<SP>+</SP>diffusion layer 108. Ag paste is filled in the groove 105 by printing, thereby forming the embedded electrode 114. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for forming an embedded electrode of a solar cell and a method for manufacturing the solar cell, which can prevent the shortening of the lifetime and the decrease in performance while improving the conversion efficiency of the solar cell.

  In order to increase the efficiency of the solar cell, it is necessary to reduce the ratio of the area of the electrode to the light receiving area. In order to satisfy this requirement, a buried electrode is used. Solar cells using embedded electrodes can increase the contact area between the substrate and the electrode without increasing the area occupied by the electrode by embedding the electrode in the substrate, thus reducing the series resistance. And FF (fill factor) can be improved. Further, by using the embedded electrode, it is possible to reduce the occupied area of the electrode without increasing the series resistance. Therefore, it is possible to achieve both reduction of the occupied area of the electrode and improvement of the short-circuit current density.

  As a method for manufacturing this type of solar cell, there is a method conventionally including the steps shown in the schematic cross-sectional views of FIGS. 9 and 10 (see Japanese Patent Application Laid-Open No. 05-326989 (Patent Document 1)).

  In this solar cell manufacturing method, first, a single crystal or polycrystalline P-type silicon substrate 501 (FIG. 10A) is removed in order to remove a damaged layer near the surface when slicing from an ingot. The surface portion is etched with an acidic or alkaline solution until the outline shown by the broken line in FIG. 10A is obtained (FIG. 10B). At this time, a texture structure is formed on the light receiving surface in order to improve the absorption efficiency of incident light. In FIGS. 9 and 10, the texture is not shown in order to avoid complication.

Next, heating is performed in a quartz tube furnace at 850 ° C. for 20 minutes to perform thermal diffusion of POCl ₃ , thereby forming an N + diffusion layer 502 on the surface that becomes the light receiving surface of the silicon substrate 501 (FIG. 9 ( c)).

Subsequently, a passivation film 503 made of SiO _{2 is} formed on the N + diffusion layer 502 by a dry oxidation method for surface stabilization (FIG. 9D).

This on the passivation film 503, a TiO ₂ film 504 atmospheric pressure CVD (chemical vapor deposition) method by laminating a first antireflection film (FIG. 9 (e)).

  Next, an Al paste is printed on the back surface of the silicon substrate 501 and baked to form a P + diffusion layer 506 and a back electrode 507 (FIG. 10F).

Next, a coating solution (PSG solution) containing phosphorus impurities is applied to the surface of the TiO ₂ film 504 and dried to form a PSG film 509 (FIG. 10G). The components of the PSG solution are 80 cc of ethyl alcohol C ₂ H ₅ OH, 5 grams of phosphorus pentoxide P ₂ O ₅ , 1 cc of ethyl silicate Si (OC ₂ H ₅ ) ₄ and 8 cc of CH ₃ COOH acetate. It has been made.

  Next, a polyimide film 510 (thickness: 25 μm) is attached to the surface of the PSG film 509 (FIG. 10H).

The silicon substrate 501 subjected to the above steps is fixed to an XY stage of a short wavelength laser device. Then, in a hydrogen gas atmosphere of 200 Torr, XeCl excimer laser light (λ = 308 nm) having an irradiation line width of 20 μm is irradiated to the electrode formation position on the surface side of the silicon substrate 501 in a predetermined pattern at room temperature. The XeCl excimer laser beam has a pulse width of 50 nsec or less, a pulse speed of 100 Hz, and an irradiation energy of 3.0 J / cm ² . By this XeCl excimer laser light irradiation, a groove 512 reaching the silicon substrate 501 from the uppermost polyimide film 510 is formed. Further, an N ++ diffusion layer 514 is formed on the inner surface of the groove 512 and on the peripheral portion of the inner surface formed on the silicon substrate 501.

  Next, Ag paste is filled in the groove 512 by printing. At this time, the Ag paste is formed over a wider range than the opening of the groove 512 in the polyimide film 510 in a plan view so as to protrude from the surface of the uppermost polyimide film 510. (FIG. 10 (j)).

Next, the polyimide film 510 is removed together with the excess Ag paste existing above the polyimide film 510. Then, the embedded electrode 9 on the light receiving surface is formed by baking the Ag paste remaining in the groove 512 at 700 ° C. During this firing, the PSG film 509 remaining on the light receiving surface other than the electrode forming portion is densified to have a refractive index of 1.45, and a TiO ₂ film 504 (refractive index) as a first antireflection film. 2.2) and functions as a two-layer antireflection film (FIG. 10 (k)).

  Another conventional solar cell manufacturing method includes the steps shown in the schematic cross-sectional views of FIGS.

  In this solar cell manufacturing method, first, a single crystal or polycrystalline P-type silicon substrate 601 (FIG. 11A) is etched with an acidic or alkaline solution to remove a damaged layer near the surface. (FIG. 11B).

  Next, a groove 612 is formed in the electrode forming portion on the surface which becomes the light receiving surface of the silicon substrate 601 using a dicing apparatus generally used for cutting an IC chip (FIG. 11C).

  On the surface of the silicon substrate 601 and the inner surface of the groove 612, an N ++ diffusion layer 602, which is a deep bonding layer having a surface carrier concentration higher than that of a normal N + diffusion layer, is formed (FIG. 11D).

  Next, the groove 612 is filled with chemical-resistant wax 613 by screen printing. The wax 612 is disposed so as to protrude from the surface of the N ++ diffusion layer 602 and over a wider range than the opening of the groove 612 in plan view (FIG. 11E).

  Thereafter, etching is performed with an acidic or alkaline solution to remove the N ++ diffusion layer 602 other than in the groove 612 and to form fine irregularities on the surface of the silicon substrate 601 in order to reduce the reflectance of the light receiving surface. Thus, a texture structure is formed (FIG. 11 (f)). In FIGS. 11 and 12, the texture is not shown in order to avoid complication.

  Next, the wax 613 protruding from the groove 612 and the surface of the silicon substrate 601 is removed (FIG. 12G).

  Next, an N + diffusion layer 622 is formed on the surface of the silicon substrate 601 (FIG. 12H).

Next, a passivation film 603 of SiO ₂ is formed on the surface of the N + diffusion layer 622 by a dry oxidation method for stabilization (FIG. 12I).

Next, as a first antireflection film, a TiO ₂ film 604 is laminated by an atmospheric pressure CVD method (FIG. 12 (j)).

  Next, an Al paste is printed on the back surface of the silicon substrate 601 and baked to form a P + diffusion layer 606 serving as a BSF (Back Surface Field) layer and a back electrode 607 (FIG. 12 (k)). )).

  Next, an Ag paste is printed in the groove 612 by screen printing and baked to form the embedded electrode 616 on the light receiving surface (FIG. 12L).

Finally, an MgF ₂ film 604 serving as a _second antireflection film is formed on the surface by vapor deposition to complete the solar cell (FIG. 12 (m)).

However, in the above conventional solar cell manufacturing method, when forming the embedded electrode, the silicon substrates 501 and 601 and the stacked body thereon are removed to form the grooves 512 and 612 using a laser or a dicing apparatus. Therefore, the silicon substrates 501 and 601 and the laminated body are easily damaged. Therefore, there is a problem that the yield is reduced. In addition, when grooves are formed using a laser or a dicing apparatus, there is a problem that stress accumulation and fine scratches occur in the silicon substrates 501 and 601 and the laminate, leading to shortening of the life of the solar cell and deterioration of performance. is there. Further, since it is necessary to use relatively thick silicon substrates 501 and 601 in order to prevent breakage when forming a groove by a laser or a dicing apparatus, there is a problem that it is difficult to save the substrate material and make the solar cell thinner. .
JP-A-5-326989

  Therefore, the problem of the present invention is that the embedded electrode of the solar cell that can prevent the yield reduction, the shortening of the life of the solar cell and the performance, and the reduction of the substrate material and the thinning of the solar cell can be achieved. It is providing the formation method of this, and the manufacturing method of a solar cell.

In order to solve the above problems, a method for forming a buried electrode of a solar cell of the present invention includes:
Forming an etching mask layer on the surface of the semiconductor substrate;
Patterning the etching mask layer;
Forming a groove by etching in a portion of the semiconductor substrate corresponding to a portion removed by patterning of the etching mask layer;
And a step of embedding a conductor in the groove of the semiconductor substrate.

  According to the above configuration, a groove is formed on the surface of the semiconductor substrate by etching, and a conductor is embedded in the groove to form a buried electrode. Therefore, since the stress and scratches generated in the semiconductor substrate can be reduced as compared with the conventional case where grooves are formed in the substrate with a laser or a dicing apparatus, it is possible to prevent the life of the solar cell from being shortened and the performance from being deteriorated. In addition, it is possible to prevent the semiconductor substrate from being damaged during the formation of the groove, and to improve the manufacturing yield of the solar cell. In addition, since a thinner semiconductor substrate than the conventional one can be used, it is possible to reduce the material used and reduce the thickness of the solar cell.

  The surface of the semiconductor substrate refers to a surface that becomes a light receiving surface when the solar cell is completed.

  In one embodiment of the method for forming a buried electrode of a solar cell, the etching mask layer is formed of silicon oxide or silicon nitride.

  According to the embodiment, the etching mask layer can be easily formed.

  In one embodiment of the method for forming a buried electrode of a solar cell, the step of patterning the etching mask layer is performed using a laser or an etching paste.

  According to the embodiment, the etching mask layer can be patterned with a small number of steps.

In one embodiment of the method for forming a buried electrode of a solar cell, the etching mask layer is formed of silicon oxide,
A groove is formed in the semiconductor substrate by etching using an aqueous potassium hydroxide solution or an aqueous sodium hydroxide solution.

  According to the embodiment, the groove can be formed in the semiconductor substrate with a predetermined shape and depth with good control.

In one embodiment of the method for forming a buried electrode of a solar cell, the etching mask layer is formed of silicon nitride,
Grooves are formed in the semiconductor substrate by etching using an aqueous potassium hydroxide solution, an aqueous sodium hydroxide solution, or a mixed solution of hydrofluoric acid and nitric acid.

  According to the embodiment, the groove can be formed in the semiconductor substrate with a predetermined shape and depth with good control.

  In one embodiment of the method for forming an embedded electrode of a solar cell, the step of embedding a conductor in the groove of the semiconductor substrate is performed by screen printing of an Ag paste.

  According to the embodiment, the Ag paste can be efficiently embedded in the groove of the semiconductor substrate by screen printing.

  In one embodiment of the method for forming a buried electrode of a solar cell, after the step of forming a groove in the semiconductor substrate portion, diffusion is performed using the etching mask layer as a diffusion mask, and the inner surface of the groove is formed. Forming an impurity diffusion layer;

According to the above embodiment,
By using the etching mask layer used for forming the groove in the semiconductor substrate also as a diffusion mask, the impurity diffusion layer can be formed on the inner surface of the groove with a small number of steps. Therefore, it is possible to reduce labor and cost in forming the embedded electrode of the solar cell.

  A method for manufacturing a solar cell according to the present invention includes a method for forming an embedded electrode of the solar cell.

  According to the above configuration, since the embedded electrode of the solar cell can be formed on the semiconductor substrate thinner than the conventional one with a high yield, a thin solar electrode can be manufactured with a high yield.

  As described above, in the method for forming the embedded electrode of the solar cell of the present invention, a groove is formed by etching on the surface of the semiconductor substrate, and the conductor is embedded in the groove to form the embedded electrode. Compared to the conventional method of forming grooves in a substrate with a laser or a dicing apparatus, the stress and scratches generated in the semiconductor substrate can be reduced, and the lifetime of the solar cell and the deterioration in performance can be prevented. Further, it is possible to prevent the semiconductor substrate from being damaged during the formation of the groove, and to improve the manufacturing yield of the solar cell. In addition, since a thinner semiconductor substrate than the conventional one can be used, it is possible to save the material used and to reduce the thickness of the solar cell.

  Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

(First embodiment)
1 and 2 are schematic cross-sectional views showing the steps performed in the method for manufacturing a solar cell as the first embodiment of the present invention, and in particular, the schematic cross-sections showing in detail the steps performed in the method for forming a buried electrode. FIG.

  First, etching is performed on the entire surface of a single crystal or polycrystalline P-type silicon substrate 101 (FIG. 1A) with an acidic or alkaline solution. As a result, damage generated in the vicinity of the cut surface when the P-type silicon substrate 101 is sliced from the ingot is removed, and the absorption efficiency of incident light on the surface serving as the light receiving surface (the upper surface in FIGS. 1 and 2). A texture structure for improving the above is formed (FIG. 1B). In FIGS. 1 and 2, the texture is not shown in order to avoid complication.

  Next, an SiOx film is deposited on the front and back surfaces of the silicon substrate 101 by an atmospheric pressure CVD (chemical vapor deposition) method or an SiNx film is deposited by a P (plasma) -CVD method, and an etching mask is used. A layer 102 is formed (FIG. 1C). Note that the etching mask layer 102 on the back surface of the silicon substrate 101 is not necessarily required, and is arranged according to the thickness of the substrate 101 and the depth of a groove to be formed later.

  Next, an opening 104 having a pattern corresponding to the groove pattern to be formed is formed in the etching mask layer 102 on the surface of the silicon substrate 101 by using a laser (FIG. 1D).

  Next, the silicon substrate 101 is etched using an acidic or alkaline solution to form a groove 105 continuous with the opening 104 of the etching mask layer (FIG. 1E). Here, when the etching mask layer 102 is formed of a SiOx film, alkali etching is performed using a potassium hydroxide aqueous solution, a sodium hydroxide aqueous solution, or the like. When the etching mask layer 102 is formed of a SiNx film, an alkali etch using a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution or an acid etch using a mixed solution of hydrofluoric acid and nitric acid is performed. . When forming the groove 105 in the silicon substrate 101, the etching reduces the thickness of the etching mask layer 102 on the front surface side of the silicon substrate 101 and removes the etching mask layer 102 on the back surface side of the silicon substrate 101. .

Next, the etching mask layer 102 using as a diffusion mask, by vapor phase diffusion or the like using POCl _3, to form the N ++ diffusion layer 107 on the inner surface of the groove 105 of the silicon substrate.

Next, the etching mask layer 102 on the surface of the silicon substrate 101 is removed with hydrofluoric acid (FIG. 2F), and a vapor phase using POCl ₃ is formed on the surface of the silicon substrate 101 from which the etching mask layer 102 has been removed. An N + diffusion layer 108 is formed by diffusion or the like (FIG. 2G).

  Next, a SiNx film 109 functioning as a passivation film for stabilizing the light receiving surface and an antireflection film for incident light is formed on the N ++ diffusion layer 107 and the N + diffusion layer 108 by the P-CVD method (FIG. 2 (h)).

  Next, an Al paste is printed on the back surface of the silicon substrate 101 and baked to form the P + diffusion layer 111 and the back electrode 112 (FIG. 2 (i)).

  Finally, an Ag paste is embedded in the groove 105 on the surface of the silicon substrate 101 by printing and baked to form the embedded electrode 114. When the Ag paste is baked, the SiNx film 109 on the inner surface of the groove 105 is dissolved in Ag, so that the buried electrode 114 is electrically connected to the N ++ diffusion layer 107. Further, the protruding electrode 115 having a predetermined pattern is formed on the surface of the back electrode 112 (the lower surface in FIG. 2 (j)) to complete the solar cell.

  As described above, according to the method for forming the embedded electrode of the solar cell and the method for manufacturing the solar cell of this embodiment, the surface electrode 112 as the embedded electrode is formed on the light receiving surface side surface of the silicon substrate 101. The groove 105 is formed by etching without using a conventional laser or dicing apparatus. Therefore, it is possible to prevent damage to the substrate and laminate as in the conventional case, and it is possible to prevent the yield from decreasing. Moreover, the fine damage | wound in a board | substrate can be prevented and the shortening of the lifetime of a solar cell and a performance fall can be prevented. In addition, since a relatively thin silicon substrate 101 can be used, the substrate material can be saved and the solar cell can be thinned.

(Second Embodiment)
3 and 4 are schematic cross-sectional views showing the steps performed in the method for manufacturing a solar cell as the second embodiment of the present invention, and in particular, the schematic cross-sections showing in detail the steps performed in the method for forming an embedded electrode. FIG.

  First, as in the first embodiment, the entire surface of a single crystal or polycrystalline P-type silicon substrate 201 (FIG. 3A) is etched with an acidic or alkaline solution to remove damage to the silicon substrate 201. At the same time, a texture is formed on the surface (upper surface in FIGS. 3 and 4) to be the light receiving surface (FIG. 3B). In FIGS. 3 and 4, the texture is not shown in order to avoid complication.

  Next, an SiOx film is deposited on the front and back surfaces of the silicon substrate 201 by an atmospheric pressure CVD method or an SiNx film is deposited by a P-CVD method to form an etching mask layer 202 (FIG. 3C). )). Note that the etching mask layer 202 on the back surface of the silicon substrate 201 is not necessarily required, and is arranged according to the thickness of the substrate 201 and the depth of a groove to be formed later.

  Next, an etching paste 203 having a pattern corresponding to the groove pattern to be formed is disposed on the surface of the etching mask layer 202 by screen printing. (FIG. 3 (d)).

  Subsequently, the etching mask layer 202 on which the etching paste 203 is disposed is heated and washed to form an opening 204 in the etching mask layer 202 (FIG. 3E).

  Next, the silicon substrate 201 is etched using an acidic or alkaline solution to form a groove 205 continuous with the opening 204 of the etching mask layer (FIG. 3F). Here, when the etching mask layer 202 is formed of a SiOx film, alkali etching is performed using a potassium hydroxide aqueous solution, a sodium hydroxide aqueous solution, or the like. Further, when the etching mask layer 202 is formed of a SiNx film, an alkali etch using a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution or an acid etch using a mixed solution of hydrofluoric acid and nitric acid is performed. . When forming the groove 205 in the silicon substrate 201, the etching reduces the thickness of the etching mask layer 202 on the front surface side of the silicon substrate 201 and removes the etching mask layer 202 on the back surface side of the silicon substrate 201. .

Next, using the etching mask layer 202 as a diffusion mask, an N ++ diffusion layer 207 is formed on the inner surface of the groove 205 of the silicon substrate by vapor phase diffusion using POCl ₃ or the like.

Next, the etching mask layer 202 on the surface of the silicon substrate 201 is removed with hydrofluoric acid (FIG. 4G), and a vapor phase using POCl ₃ is formed on the surface of the silicon substrate 201 from which the etching mask layer 202 has been removed. An N + diffusion layer 208 is formed by diffusion or the like (FIG. 4H).

  Next, a SiNx film 209 that functions as a passivation film for stabilizing the light receiving surface and an antireflection film for incident light is formed on the N ++ diffusion layer 207 and the N + diffusion layer 208 by the P-CVD method (FIG. 4 (i)).

  Next, an Al paste is printed on the back surface of the silicon substrate 201 and baked to form a P + diffusion layer 211 and a back electrode 212 (FIG. 4J).

  Finally, an Ag paste is embedded in the groove 205 on the surface of the silicon substrate 201 by printing and baked to form the embedded electrode 214. When the Ag paste is baked, the SiNx film 209 on the inner surface of the groove 205 is dissolved in Ag, so that the buried electrode 214 is electrically connected to the N ++ diffusion layer 207. Further, the protruding electrode 215 having a predetermined pattern is formed on the surface of the back electrode 212 (the lower surface in FIG. 4K), thereby completing the solar cell.

  According to the present embodiment, since the resist pattern used when forming the groove 205 in the silicon substrate 201 by etching is patterned using the etching paste 203, the resist pattern can be easily formed. Therefore, the groove 205 can be formed by a simple process by etching. As a result, the embedded electrode 214 can be easily formed in the groove 205. Since the groove 205 can be easily formed by etching, the damage to the substrate can be reduced as compared with the conventional case where the groove is formed by a laser or a dicing apparatus, and the production yield and the performance of the solar cell can be improved. . Further, since a relatively thin silicon substrate 201 can be used, the substrate material can be saved and the solar cell can be made thinner.

(Third embodiment)
5 and 6 are schematic cross-sectional views showing the steps performed in the method for manufacturing a solar cell as the third embodiment of the present invention, and in particular, the schematic cross-sections showing in detail the steps performed in the method for forming a buried electrode. FIG.

  First, as in the first embodiment, the entire surface of the single-crystal or polycrystalline P-type silicon substrate 301 (FIG. 5A) is etched with an acidic or alkaline solution to remove damage to the silicon substrate 301. At the same time, a texture is formed on the surface (upper surface in FIGS. 5 and 6) to be the light receiving surface (FIG. 5B). In FIGS. 5 and 6, the texture is not shown in order to avoid complication.

  Next, an SiOx film is deposited on the front and back surfaces of the silicon substrate 301 by an atmospheric pressure CVD method or an SiNx film is deposited by a P-CVD method to form an etching mask layer 302 (FIG. 5C )). Note that the etching mask layer 302 on the back surface of the silicon substrate 301 is not necessarily required, and is disposed according to the thickness of the substrate 301 and the depth of a groove to be formed later.

  Next, an opening 304 having a pattern corresponding to the groove pattern to be formed is formed in the etching mask layer 302 on the surface of the silicon substrate 301 by using a laser (FIG. 5D).

  Next, the silicon substrate 301 is etched using an acidic or alkaline solution to form a groove 305 continuous with the opening 304 of the etching mask layer. Here, when the etching mask layer 302 is formed of a SiOx film, alkali etching is performed using a potassium hydroxide aqueous solution, a sodium hydroxide aqueous solution, or the like. When the etching mask layer 302 is formed of a SiNx film, an alkali etch using a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution or an acid etch using a mixed solution of hydrofluoric acid and nitric acid is performed. . When forming the groove 305 in the silicon substrate 301, the etching reduces the thickness of the etching mask layer 302 on the front surface side of the silicon substrate 301 and removes the etching mask layer 302 on the back surface side of the silicon substrate 301. .

Next, the etching mask layer 302 on the surface of the silicon substrate 301 is removed with hydrofluoric acid, and (FIG. 5E) the surface of the silicon substrate 301 and the inner surface of the groove 305 are formed by vapor phase diffusion using POCl _3. Then, an N + diffusion layer 308 is formed (FIG. 6F).

  Next, a passivation film for stabilizing the light receiving surface and SiNx 309 functioning as an antireflection film for light incident on the light receiving surface are formed by the P-CVD method (FIG. 6G).

  Next, an Al paste is printed on the back surface of the silicon substrate 301 and baked to form a P + diffusion layer 311 and a back electrode 312 (FIG. 6H).

  Finally, an Ag paste is embedded in the groove 305 on the surface of the silicon substrate 301 by printing and baked to form the embedded electrode 314. When the Ag paste is baked, the SiNx film 309 on the inner surface of the groove 305 is dissolved in Ag, so that the embedded electrode 314 is electrically connected to the silicon substrate 301. Further, the protruding electrode 315 having a predetermined pattern is formed on the surface of the back electrode 312 (the lower surface in FIG. 6I), thereby completing the solar cell.

  According to the present embodiment, in the process shown in FIG. 6F, the N + diffusion layer 308 is formed in the surface of the silicon substrate 1 and in the groove 305 by a single vapor phase diffusion process. Less. Therefore, the embedded electrode 314 can be formed in the groove 305 with a small number of steps. Since the groove 305 can be easily formed by etching, damage to the substrate can be reduced as compared with the conventional case where the groove is formed by a laser or a dicing apparatus, and the manufacturing yield and the performance of the solar cell can be improved. . In addition, since a relatively thin silicon substrate 301 can be used, the substrate material can be saved and the solar cell can be thinned.

(Fourth embodiment)
7 and 8 are schematic cross-sectional views showing the steps performed in the method for manufacturing a solar cell as the fourth embodiment of the present invention, and in particular, the schematic cross-sections showing in detail the steps performed in the method for forming the buried electrode. FIG.

  First, as in the first embodiment, the entire surface of the single-crystal or polycrystalline P-type silicon substrate 401 (FIG. 7A) is etched with an acidic or alkaline solution to remove damage to the silicon substrate 401. At the same time, a texture is formed on the surface (upper surface in FIGS. 7 and 8) to be the light receiving surface (FIG. 7B). 7 and 8, the texture is not shown in order to avoid complication.

  Next, SiOx films or SiNx films are deposited on both the front and back surfaces of the silicon substrate 401 to form an etching mask layer 402 (FIG. 7C). When the etching mask layer 402 is a SiOx film, deposition is performed by atmospheric pressure CVD, and when the etching mask layer 402 is a SiNx film, deposition is performed by P-CVD. Note that the etching mask layer 402 on the back surface of the silicon substrate 401 is not always necessary, and is arranged according to the thickness of the substrate 401 and the depth of a groove to be formed later.

  Next, an etching paste 403 having a pattern corresponding to the groove pattern to be formed is disposed on the surface of the etching mask layer 402 by screen printing. (FIG. 7D).

  Subsequently, the etching mask layer 402 on which the etching paste 403 is disposed is heated and washed to form openings 404 in the etching mask layer 402 (FIG. 7E).

  Next, the silicon substrate 401 is etched using an acidic or alkaline solution to form a groove 405 that continues to the opening 404 of the etching mask layer (FIG. 8F). Here, when the etching mask layer 402 is formed of a SiOx film, alkali etching is performed using a potassium hydroxide aqueous solution, a sodium hydroxide aqueous solution, or the like. When the etching mask layer 402 is formed of a SiNx film, an alkali etch using a potassium hydroxide aqueous solution or a sodium hydroxide aqueous solution or an acid etch using a mixed solution of hydrofluoric acid and nitric acid is performed. . When the groove 405 is formed in the silicon substrate 401, the etching reduces the thickness of the etching mask layer 402 on the front surface side of the silicon substrate 401 and removes the etching mask layer 402 on the back surface side of the silicon substrate 401. .

Next, the etching mask layer 402 on the surface of the silicon substrate 401 is removed with hydrofluoric acid, and an N + diffusion layer 408 is formed on the surface of the silicon substrate 401 and the inner surface of the groove 405 by vapor phase diffusion using POCl ₃ or the like. It forms (FIG.8 (g)).

  Next, a passivation film for stabilizing the light receiving surface and SiNx 409 functioning as an antireflection film for light incident on the light receiving surface are formed by P-CVD (FIG. 8H).

  Next, an Al paste is printed on the back surface of the silicon substrate 401 and baked to form a P + diffusion layer 411 and a back electrode 412 (FIG. 8I).

  Finally, an Ag paste is embedded in the groove 405 on the surface of the silicon substrate 401 by printing and baked to form the embedded electrode 414. When the Ag paste is baked, the SiNx film 409 on the inner surface of the groove 405 is dissolved in Ag, so that the embedded electrode 414 is electrically connected to the silicon substrate 401. In addition, a protruding electrode 415 having a predetermined pattern is formed on the surface of the back electrode 412 (the lower surface in FIG. 8J) to complete the solar cell.

  According to this embodiment, since the resist pattern used when forming the groove 405 in the silicon substrate 401 by etching is patterned using the etching paste 403, the resist pattern can be easily formed. Therefore, the groove 405 can be formed by a simple process by etching. As a result, the embedded electrode 414 can be easily formed in the groove 405. Since the groove 405 can be easily formed by etching, damage to the substrate can be reduced as compared with the conventional case where the groove is formed by a laser or a dicing apparatus, and the manufacturing yield and the performance of the solar cell can be improved. . In addition, since a relatively thin silicon substrate 401 can be used, the substrate material can be saved and the solar cell can be thinned.

It is sectional drawing which shows the process in the manufacturing method of the solar cell of 1st Embodiment. FIG. 2 is a cross-sectional view illustrating steps in the method for manufacturing the solar cell according to the first embodiment, following FIG. 1. It is sectional drawing which shows the process in the manufacturing method of the solar cell of 2nd Embodiment. FIG. 4 is a cross-sectional view illustrating steps in the method for manufacturing the solar cell according to the second embodiment, following FIG. 3. It is sectional drawing which shows the process in the manufacturing method of the solar cell of 3rd Embodiment. FIG. 6 is a cross-sectional view illustrating steps in the method for manufacturing the solar cell according to the third embodiment, following FIG. 5. It is sectional drawing which shows the process in the manufacturing method of the solar cell of 4th Embodiment. FIG. 8 is a cross-sectional view illustrating steps in the method for manufacturing the solar cell according to the fourth embodiment, following FIG. 7. It is sectional drawing which shows the process in the manufacturing method of the conventional solar cell. FIG. 10 is a cross-sectional view illustrating steps in a conventional solar cell manufacturing method following FIG. 9. It is sectional drawing which shows the process in the manufacturing method of the conventional solar cell. Following FIG. 11, it is sectional drawing which shows the process in the manufacturing method of the conventional solar cell.

Explanation of symbols

101, 201, 301, 401 P-type silicon substrate 102, 202, 302, 402 Etching mask layer 104, 204, 304, 404 Etching mask layer opening 105, 205, 305, 405 P-type silicon substrate groove 107, 207 N ++ Diffusion layer 108, 208, 308, 408 N + diffusion layer 109, 209, 309, 409 SiNx film 1111, 211, 311, 411 P + diffusion layer 112, 212, 312, 412 Back electrode 114, 214, 314, 414 Embedded electrode 115, 215, 315, 415 Protruding electrode 403 Etching paste

Claims (8)

Forming an etching mask layer on the surface of the semiconductor substrate;
Patterning the etching mask layer;
Forming a groove by etching in a portion of the semiconductor substrate corresponding to a portion removed by patterning of the etching mask layer;
And a step of embedding a conductor in the groove of the semiconductor substrate. In the formation method of the embedded electrode of the solar cell of Claim 1,
The method for forming a buried electrode of a solar cell, wherein the etching mask layer is formed of silicon oxide or silicon nitride. In the formation method of the embedded electrode of the solar cell of Claim 1,
The step of patterning the etching mask layer is performed using a laser or an etching paste. In the formation method of the embedded electrode of the solar cell of Claim 1,
The etching mask layer is formed of silicon oxide,
A method for forming a buried electrode of a solar cell, wherein a groove is formed in the semiconductor substrate by etching using an aqueous potassium hydroxide solution or an aqueous sodium hydroxide solution. In the formation method of the embedded electrode of the solar cell of Claim 1,
The etching mask layer is formed of silicon nitride,
A method for forming an embedded electrode of a solar cell, comprising forming a groove in the semiconductor substrate by etching using a potassium hydroxide aqueous solution, a sodium hydroxide aqueous solution, or a mixed solution of hydrofluoric acid and nitric acid. In the formation method of the embedded electrode of the solar cell of Claim 1,
The method for forming an embedded electrode of a solar cell, wherein the step of embedding a conductor in the groove of the semiconductor substrate is performed by screen printing of an Ag paste. In the formation method of the embedded electrode of the solar cell of Claim 1,
A step of forming an impurity diffusion layer on an inner surface of the groove by performing diffusion using the etching mask layer as a diffusion mask after the step of forming a groove in the semiconductor substrate portion; A method for forming an embedded electrode of a battery.   A method for manufacturing a solar cell, comprising the method for forming an embedded electrode of a solar cell according to claim 1.

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