WO2017051635A1 - Semiconductor substrate, photoelectric conversion element, method for manufacturing semiconductor substrate, and method for manufacturing photoelectric conversion element - Google Patents

Abstract

This semiconductor substrate is provided with, in the surface thereof, a plurality of protruding sections (11) and recessed sections (12) among the protruding sections (11). Each of the protruding sections (11) is provided with sloped surfaces (11c). Each of the recessed sections (12) is provided with the bottom of a bent surface. The angle of the sloped surfaces (11c) of the protruding sections (11) is larger than 49.5° but equal to or smaller than 55.2°. The curvature radius of the bent surface of each of the recessed sections (12) is larger than 13 nm.

Description

Semiconductor substrate, photoelectric conversion element, semiconductor substrate manufacturing method, and photoelectric conversion element manufacturing method

This application claims the benefit of priority to Japanese Patent Application No. 2015-186521 filed on Sep. 24, 2015, and the contents of which are incorporated herein by reference. .

The present invention relates to a semiconductor substrate, a method for manufacturing a semiconductor substrate, and a method for manufacturing a photoelectric conversion element.

In recent years, expectations for solar cells that directly convert solar energy into electrical energy have increased rapidly, especially from the viewpoint of global environmental problems. There are various types of solar cells, such as those using compound semiconductors or organic materials, but the mainstream is currently using silicon crystals.

Currently, the most manufactured and sold solar cells have a structure in which electrodes are formed on a light receiving surface that is a surface on which sunlight is incident and a back surface that is opposite to the light receiving surface, respectively.

However, when an electrode is formed on the light receiving surface, sunlight is reflected and absorbed by the electrode, so that the amount of incident sunlight is reduced by the area of the electrode. For this reason, development of solar cells in which electrodes are formed only on the back surface is also underway.

For example, Japanese Patent No. 3271990 (Patent Document 1) discloses a crystalline silicon substrate having a large number of pyramidal irregularities formed on the surface by anisotropic etching, and a chemical vapor deposition method on the irregularities. A photovoltaic element comprising: an amorphous or microcrystalline silicon layer provided by the step; and a valley portion of a pyramidal uneven portion provided on a surface of a substrate is formed in a round shape. (For example, claim 1 of Patent Document 1).

Japanese Patent No. 3271990

However, in the photovoltaic element described in Patent Document 1, high characteristics may not be obtained.

In addition, when a film is formed on the concavo-convex portion of the photovoltaic element described in Patent Document 1, the film formed on the concavo-convex portion may crack and the characteristics may deteriorate.

The embodiment disclosed herein includes a plurality of convex portions and a concave portion between the convex portions on the surface, the convex portion includes an inclined surface, the concave portion includes a curved bottom, and the angle of the inclined surface is 49.5. It is a semiconductor substrate that is larger than 5 ° and smaller than or equal to 55.2 ° and has a curved radius of curvature larger than 13 nm.

The embodiment disclosed herein includes the above-described semiconductor substrate, and a first conductivity type amorphous semiconductor film and a second conductivity type amorphous semiconductor film on a second surface opposite to the surface of the semiconductor substrate, A photoelectric conversion element comprising a first electrode on the first conductive type amorphous semiconductor film and a second electrode on the second conductive type amorphous semiconductor film.

The embodiment disclosed herein includes the semiconductor substrate, the first conductivity type region and the second conductivity type region on the second surface opposite to the surface of the semiconductor substrate, and the first conductivity type region on the first conductivity type region. It is a photoelectric conversion element provided with 1 electrode and the 2nd electrode on a 2nd conductivity type area | region.

The embodiment disclosed herein includes the semiconductor substrate, the first conductivity type region on the surface of the semiconductor substrate, the second conductivity type region on the second surface opposite to the surface of the semiconductor substrate, and the first It is a photoelectric conversion element provided with the 1st electrode on a conductivity type area | region, and the 2nd electrode on a 2nd conductivity type area | region.

Embodiment disclosed here is a photoelectric conversion element provided with said semiconductor substrate.
The embodiment disclosed herein includes a step of forming a plurality of convex portions and concave portions between the convex portions on the surface of the semiconductor substrate, a step of performing acid etching of the surface on which the convex portions and the concave portions are formed, Performing a round etching of the surface after the acid etching, and in the step of performing the round etching, the angle of the inclined surface of the convex portion is set to be larger than 49.5 ° and not more than 55.2 °, and the curved surface of the bottom of the concave portion This is a method for manufacturing a semiconductor substrate in which the radius of curvature is larger than 13 nm.

The embodiment disclosed herein includes a step of forming a semiconductor substrate having a plurality of convex portions and concave portions between the convex portions on the surface by the above-described method of manufacturing a semiconductor substrate, and a side opposite to the surface of the semiconductor substrate Forming a first conductive type amorphous semiconductor film and a second conductive type amorphous semiconductor film on the second surface, and forming a first electrode on the first conductive type amorphous semiconductor film And a step of forming a second electrode on the second conductivity type amorphous semiconductor film.

The embodiment disclosed herein includes a step of forming a semiconductor substrate having a plurality of convex portions and concave portions between the convex portions on the surface by the above-described method of manufacturing a semiconductor substrate, and a side opposite to the surface of the semiconductor substrate Forming a first conductivity type region and a second conductivity type region on the second surface, forming a first electrode on the first conductivity type region, and forming a second electrode on the second conductivity type region. A process for forming the photoelectric conversion element.

The embodiment disclosed herein includes a step of forming a semiconductor substrate having a plurality of convex portions and concave portions between the convex portions on the surface by the method for manufacturing a semiconductor substrate, and a first conductive material on the surface of the semiconductor substrate. A step of forming a mold region, a step of forming a second conductivity type region on a second surface opposite to the surface of the semiconductor substrate, a step of forming a first electrode on the first conductivity type region, And a step of forming a second electrode on the two-conductivity type region.

According to the embodiment disclosed herein, a photoelectric conversion element having high characteristics can be manufactured.

3 is a schematic cross-sectional view of the heterojunction back contact cell of Embodiment 1. FIG. 3 is a schematic enlarged perspective view of an example of a convex portion of a light receiving surface of a semiconductor substrate of the heterojunction back contact cell of Embodiment 1. FIG. 3 is a schematic enlarged cross-sectional view of an example of a convex portion of a light receiving surface of a semiconductor substrate of a heterojunction back contact cell according to Embodiment 1. FIG. 3 is a schematic enlarged cross-sectional view of an example of a recess of a light receiving surface of a semiconductor substrate of a heterojunction back contact cell according to Embodiment 1. FIG. 6 is a schematic cross-sectional view illustrating a part of the manufacturing process of the example of the method for manufacturing the heterojunction back contact cell of Embodiment 1. FIG. 6 is a schematic cross-sectional view illustrating a part of the manufacturing process of the example of the method for manufacturing the heterojunction back contact cell of Embodiment 1. FIG. 6 is a schematic cross-sectional view illustrating a part of the manufacturing process of the example of the method for manufacturing the heterojunction back contact cell of Embodiment 1. FIG. 6 is a schematic cross-sectional view illustrating a part of the manufacturing process of the example of the method for manufacturing the heterojunction back contact cell of Embodiment 1. FIG. 6 is a schematic cross-sectional view illustrating a part of the manufacturing process of the example of the method for manufacturing the heterojunction back contact cell of Embodiment 1. FIG. 6 is a schematic cross-sectional view illustrating a part of the manufacturing process of the example of the method for manufacturing the heterojunction back contact cell of Embodiment 1. FIG. 6 is a schematic cross-sectional view illustrating a part of the manufacturing process of the example of the method for manufacturing the heterojunction back contact cell of Embodiment 1. FIG. 6 is a schematic cross-sectional view illustrating a part of the manufacturing process of the example of the method for manufacturing the heterojunction back contact cell of Embodiment 1. FIG. 6 is a schematic cross-sectional view illustrating a part of the manufacturing process of the example of the method for manufacturing the heterojunction back contact cell of Embodiment 1. FIG. 6 is a schematic cross-sectional view illustrating a part of the manufacturing process of the example of the method for manufacturing the heterojunction back contact cell of Embodiment 1. FIG. 6 is a schematic cross-sectional view illustrating a part of the manufacturing process of the example of the method for manufacturing the heterojunction back contact cell of Embodiment 1. FIG. 6 is a schematic cross-sectional view illustrating a part of the manufacturing process of the example of the method for manufacturing the heterojunction back contact cell of Embodiment 1. FIG. 6 is a schematic cross-sectional view of a heterojunction back contact cell of Embodiment 2. FIG. 6 is a schematic cross-sectional view of a heterojunction back contact cell according to Embodiment 3. FIG. 6 is a schematic cross-sectional view of a back electrode type solar battery cell according to Embodiment 4. FIG. 10 is a schematic cross-sectional view illustrating a part of the manufacturing process of an example of the manufacturing method of the back electrode type solar battery cell of Embodiment 4. FIG. 10 is a schematic cross-sectional view illustrating a part of the manufacturing process of an example of the manufacturing method of the back electrode type solar battery cell of Embodiment 4. FIG. 10 is a schematic cross-sectional view illustrating a part of the manufacturing process of an example of the manufacturing method of the back electrode type solar battery cell of Embodiment 4. FIG. 10 is a schematic cross-sectional view illustrating a part of the manufacturing process of an example of the manufacturing method of the back electrode type solar battery cell of Embodiment 4. FIG. 10 is a schematic cross-sectional view illustrating a part of the manufacturing process of an example of the manufacturing method of the back electrode type solar battery cell of Embodiment 4. FIG. 10 is a schematic cross-sectional view illustrating a part of the manufacturing process of an example of the manufacturing method of the back electrode type solar battery cell of Embodiment 4. FIG. 10 is a schematic cross-sectional view illustrating a part of the manufacturing process of an example of the manufacturing method of the back electrode type solar battery cell of Embodiment 4. FIG. 10 is a schematic cross-sectional view illustrating a part of the manufacturing process of an example of the manufacturing method of the back electrode type solar battery cell of Embodiment 4. FIG. 10 is a schematic cross-sectional view illustrating a part of the manufacturing process of an example of the manufacturing method of the back electrode type solar battery cell of Embodiment 4. FIG. 6 is a schematic cross-sectional view of a double-sided electrode type solar battery cell of Embodiment 5. FIG. FIG. 6 is a result of investigating the relationship between the wavelength of light incident on the substrates of Experimental Examples 1 to 4 and the reflectance. FIG. FIG. 6 is a diagram showing an average value of angles α of inclined surfaces of convex portions on the surface of substrates in Experimental Examples 1 to 4. FIG. 7 shows the relative values of the reverse saturation current densities of Experimental Example 2 and 5-7, where the reverse saturation current density of the heterojunction back contact cell of Experimental Example 1 is 1. FIG. 4 is a schematic enlarged cross-sectional view of a substrate of Experimental Example 1. FIG. 10 is a schematic enlarged cross-sectional view of a substrate of Experimental Example 5. FIG. 10 is a schematic enlarged cross-sectional view of a substrate of Experimental Example 8. FIG. It is a typical expanded sectional view of the board | substrate of Experimental example 9. FIG. It is a measurement result of the curvature radius of the curved surface of the bottom of the recessed part of the surface of the board | substrate of Experimental example 1, 5, 8 and 9. FIG.

Hereinafter, embodiments will be described. In the drawings used to describe the embodiments, the same reference numerals represent the same or corresponding parts.

[Embodiment 1]
FIG. 1 is a schematic cross-sectional view of the heterojunction back contact cell of Embodiment 1 which is an example of the photoelectric conversion element of the embodiment. The heterojunction back contact cell of Embodiment 1 includes a semiconductor substrate 1, a plurality of convex portions 11 provided on a light receiving surface that is a first surface of the semiconductor substrate 1, and concave portions 12 between the convex portions 11. And an amorphous silicon film 9 a on the convex portion 11 and the concave portion 12. As the amorphous silicon film 9a, for example, an i-type amorphous silicon film, an n-type amorphous silicon film, or an i-type amorphous silicon film and an n-type amorphous silicon film from the light receiving surface side are used. Can be used.

Further, the heterojunction back contact cell of Embodiment 1 includes the first i-type amorphous semiconductor film 2 and the second i-type amorphous semiconductor film 2 on the back surface 1a which is the second surface opposite to the first surface of the semiconductor substrate 1. 2 i-type amorphous semiconductor film 4, first conductivity-type amorphous semiconductor film 3 on first i-type amorphous semiconductor film 2, and second i-type amorphous semiconductor film 4 A second conductive type amorphous semiconductor film 5, a first electrode 6 on the first conductive type amorphous semiconductor film 3, and a second electrode 7 on the second conductive type amorphous semiconductor film 5 are provided. Yes.

In the first embodiment, the semiconductor substrate 1 is an n-type single crystal silicon substrate, and the first i-type amorphous semiconductor film 2 and the second i-type amorphous semiconductor film 4 are respectively i-type amorphous. A case where the first conductive type amorphous semiconductor film 3 is a p-type amorphous silicon film and the second conductive type amorphous semiconductor film 5 is an n-type amorphous silicon film will be described. However, it goes without saying that the present invention is not limited to this.

In the present embodiment, “i-type” is not only a completely intrinsic state but also a sufficiently low concentration (n-type impurity concentration is less than 1 × 10 ¹⁵ / cm ³ and p-type impurity concentration is 1 × (Less than 10 ¹⁵ / cm ³ ) is meant to include n-type or p-type impurities. In the present embodiment, “n-type” means a state where the n-type impurity concentration is 1 × 10 ¹⁵ / cm ³ or more, and “p-type” means that the p-type impurity concentration is 1 × 10 ¹⁵ / cm ^3. It means a state of cm ³ or more. The n-type impurity concentration and the p-type impurity concentration can be measured by, for example, secondary ion mass spectrometry (SIMS).

In this embodiment, “amorphous silicon” includes not only amorphous silicon in which the dangling bonds of silicon atoms are not terminated with hydrogen, but also dangling of silicon atoms such as hydrogenated amorphous silicon. It also includes those whose hands are terminated with hydrogen or the like.

FIG. 2 shows a schematic enlarged perspective view of an example of the convex portion 11 of the light receiving surface of the semiconductor substrate 1 of the heterojunction back contact cell of the first embodiment. In the present embodiment, a case where a texture structure is provided on the light receiving surface of the semiconductor substrate 1 will be described, but the present invention is not limited to this. In addition, when the texture structure is provided in the light-receiving surface of the semiconductor substrate 1, the convex part 11 of the light-receiving surface of the semiconductor substrate 1 may have a quadrangular pyramid shape.

In the present embodiment, the convex portion 11 includes a quadrangular bottom surface 11d substantially parallel to the back surface 1a of the semiconductor substrate 1, and four triangular inclined surfaces 11c provided on the bottom surface 11d so as to incline to the bottom surface 11d. And have. One inclined surface 11c is adjacent to and in contact with one inclined surface 11c on each side thereof. The convex portion 11 has four lines 11e where two adjacent inclined surfaces 11c are in contact with each other, and a vertex 11f which is an intersection of these four lines 11e.

FIG. 3 shows a schematic enlarged cross-sectional view of an example of the convex portion 11 of the light receiving surface of the semiconductor substrate of the heterojunction back contact cell of the first embodiment. In the present embodiment, the angle of the inclined surface 11c of the convex portion 11 is defined as an angle α formed by the line 11e and the bottom surface 11d of the convex portion 11, for example, as shown in FIG.

FIG. 4 shows a schematic enlarged cross-sectional view of an example of the recess 12 on the light receiving surface of the semiconductor substrate of the heterojunction back contact cell of the first embodiment. In the present embodiment, the radius of curvature of the curved surface at the bottom of the recess 12 is defined as the radius r of the virtual circle 11g having the line 11e of the projection 11 located on both sides of the recess 12 as a tangent.

In the present embodiment, the angle of the inclined surface 11c of the convex portion 11 is greater than 49.5 ° and not greater than 55.2 °. When the angle of the inclined surface 11c of the convex portion 11 is larger than 49.5 ° and not larger than 55.2 °, the light incident on the light receiving surface of the semiconductor substrate 1 can be sufficiently taken into the semiconductor substrate 1. Therefore, high characteristics can be obtained.

Further, in the present embodiment, the angle of the inclined surface 11c of the convex portion 11 is preferably 50 ° or more, and more preferably 52.9 ° or more. In this case, since more light incident on the light receiving surface of the semiconductor substrate 1 can be taken into the semiconductor substrate 1, higher characteristics can be obtained.

Moreover, in this embodiment, it is preferable that the angle of the inclined surface 11c of the convex part 11 is 53.5 degrees or less. When the angle of the inclined surface 11c of the convex portion 11 is 53.5 ° or less, more light incident on the light receiving surface of the semiconductor substrate 1 can be taken into the semiconductor substrate 1, and thus higher characteristics can be obtained. Can be obtained.

In this embodiment, the curvature radius of the curved surface at the bottom of the recess 12 is set to be larger than 13 nm. When the curvature radius of the curved surface at the bottom of the recess 12 is larger than 13 nm, it is possible to reduce the occurrence of cracks in the film on the recess 12, and therefore cracks are formed in the film on the recess 12. The resulting deterioration in characteristics can be suppressed. In this embodiment, the deterioration of the characteristics due to the formation of cracks in the film includes, for example, the deterioration of the characteristics due to the decrease in reflectivity and the deterioration of the characteristics due to the decrease in the passivation property of the film. Can be mentioned.

In the present embodiment, the radius of curvature of the curved surface at the bottom of the recess 12 is preferably 80 nm or less. In this case, since it is possible to further reduce the occurrence of cracks in the film on the recess 12, it is possible to further suppress deterioration in characteristics due to the formation of cracks in the film on the recess 12. .

In the present embodiment, the radius of curvature of the curved surface at the bottom of the recess 12 is preferably 65 nm or less. In this case, since it is possible to further reduce the occurrence of cracks in the film on the recess 12, it is possible to further suppress deterioration in characteristics due to the formation of cracks in the film on the recess 12. .

As described above, in the present embodiment, the film on the convex portion 11 and the concave portion 12 is set by setting the angle of the inclined surface 11c of the convex portion 11 and the radius of curvature of the curved surface at the bottom of the concave portion 12 as described above. By suppressing the occurrence of cracks in the semiconductor substrate 1 and improving the reflectance and passivation properties, it is possible to obtain high characteristics by incorporating a large amount of light into the semiconductor substrate 1.

In addition, in this embodiment, the average value of the angle of the inclined surface 11c of the convex part 11 should just satisfy | fill the above-mentioned angle. However, from the viewpoint of obtaining high characteristics, it is preferable that the number of the inclined surfaces 11c of the convex portion 11 satisfying the above-mentioned angle is larger than the number of the inclined surfaces 11c of the convex portion 11 not satisfying the above-described angle. .

In this embodiment, it is only necessary that at least one of the curvature radii of the curved surface at the bottom of the recess 12 satisfies the above-described curvature radius. However, from the viewpoint of obtaining high characteristics, the number of curvature radii of the bottom curved surface of the recess 12 that satisfies the above-described curvature radius is the number of curvature radii of the bottom curved surface of the recess 12 that does not satisfy the above-described curvature radius. More is preferable.

<Method for manufacturing heterojunction back contact cell>
Hereinafter, an example of a method for manufacturing the heterojunction back contact cell of Embodiment 1 will be described with reference to schematic cross-sectional views of FIGS.

First, as shown in FIG. 5, a semiconductor substrate 1 is prepared. Next, as shown in FIG. 6, a plurality of convex portions 11 and concave portions 12 between the convex portions 11 are formed on the light receiving surface of the semiconductor substrate 1. The method of forming the convex portions 11 and the concave portions 12 on the light receiving surface of the semiconductor substrate 1 is not particularly limited, but can be formed by, for example, texture etching the light receiving surface of the semiconductor substrate 1.

The texture etching of the light receiving surface of the semiconductor substrate 1 can be performed, for example, by alkali etching the light receiving surface of the semiconductor substrate 1. Alkali etching is performed using, for example, an alkaline solution containing at least one of a sodium hydroxide aqueous solution and a potassium hydroxide aqueous solution.

After the convex portions 11 and the concave portions 12 are formed on the light receiving surface of the semiconductor substrate 1, acid etching of the light receiving surface of the semiconductor substrate 1 is performed. The acid etching of the light receiving surface of the semiconductor substrate 1 is performed using, for example, a hydrogen fluoride aqueous solution on the light receiving surface of the semiconductor substrate 1.

After acid etching of the light receiving surface of the semiconductor substrate 1, round etching of the light receiving surface of the semiconductor substrate 1 is performed. The round etching of the light receiving surface of the semiconductor substrate 1 is performed using, for example, a mixed acid containing hydrofluoric acid, nitric acid, and water on the light receiving surface of the semiconductor substrate 1. In the round etching of the light receiving surface of the semiconductor substrate 1, the angle of the inclined surface 11c of the convex portion 11 is the above-mentioned angle (greater than 49.5 °, 55.2 ° or less, preferably 50 ° or more, more preferably 52.9). And the curvature radius of the curved surface at the bottom of the recess 12 satisfies the above-mentioned curvature radius (greater than 13 nm, preferably less than 80 nm, more preferably less than 65 nm). Done.

As an example of conditions for suitably performing such round etching, for example, a mixed acid containing hydrofluoric acid (HF), nitric acid (HNO ₃ ), and water (H ₂ O) at 30 ° C. to 60 ° C. is used for 30 seconds. The conditions for performing etching for ˜90 seconds can be mentioned, but not limited thereto. From the viewpoint of suitably performing round etching, the ratio of the volume of nitric acid to the volume of hydrofluoric acid in the mixed acid is preferably 70 or more and 100 or less, and the ratio of the volume of water to the volume of hydrofluoric acid is 35 or more. It is preferable that it is 50 or less. In this embodiment, hydrofluoric acid means a hydrogen fluoride aqueous solution having a hydrogen fluoride concentration of 50% by mass, and nitric acid means a nitric acid aqueous solution having a nitric acid concentration of 60% by mass.

Next, as shown in FIG. 7, an amorphous silicon film 9 a is formed so as to be in contact with the entire light receiving surface of the semiconductor substrate 1. The formation method of the amorphous silicon film 9a is not particularly limited, but for example, a plasma CVD (Chemical Vapor Deposition) method can be used.

Next, as shown in FIG. 8, a first i-type amorphous semiconductor film 2 is formed so as to be in contact with the entire back surface 1a of the semiconductor substrate 1, and subsequently, as shown in FIG. A type amorphous semiconductor film 3 is formed. A method for forming the first i-type amorphous semiconductor film 2 and the first conductive type amorphous semiconductor film 3 is not particularly limited, and for example, a plasma CVD method can be used.

Next, as shown in FIG. 10, the first i-type amorphous semiconductor film 2 and the first conductivity-type amorphous semiconductor film 3 are formed on the first conductivity-type amorphous semiconductor film 3 in the thickness direction. An etching mask 31 having an opening at a location to be etched is formed.

Next, as shown in FIG. 11, by using the etching mask 31 as a mask, the first i-type amorphous semiconductor film 2 and the first conductive amorphous semiconductor film 3 are etched in the thickness direction, A part of the back surface 1a of the semiconductor substrate 1 is exposed. Thereafter, as shown in FIG. 12, the etching mask 31 is removed.

Next, as illustrated in FIG. 13, the second surface is formed so as to cover the exposed surface of the back surface 1 a of the semiconductor substrate 1 and the first i-type amorphous semiconductor film 2 and the first conductive amorphous semiconductor film 3. An i-type amorphous semiconductor film 4 is formed, and subsequently, a second conductive type amorphous semiconductor film 5 is formed as shown in FIG. A method for forming the second i-type amorphous semiconductor film 4 and the second conductive type amorphous semiconductor film 5 is not particularly limited, and for example, a plasma CVD method can be used.

Next, as shown in FIG. 15, an etching mask 32 is formed only on the portion where the second i-type amorphous semiconductor film 4 and the second conductive amorphous semiconductor film 5 are left on the back surface 1 a of the semiconductor substrate 1. Form.

Next, as shown in FIG. 16, by using the etching mask 32 as a mask, the second i-type amorphous semiconductor film 4 and the second conductive amorphous semiconductor film 5 are etched in the thickness direction, A part of the first conductive type amorphous semiconductor film 3 is exposed.

Thereafter, the etching mask 32 is removed, and the first electrode 6 is formed on the first conductive type amorphous semiconductor film 3 and the second conductive type amorphous semiconductor film 5 is formed on the second conductive type amorphous semiconductor film 5 as shown in FIG. By forming the two electrodes 7, the heterojunction back contact cell of Embodiment 1 can be obtained.

[Embodiment 2]
FIG. 17 is a schematic cross-sectional view of the heterojunction back contact cell of Embodiment 2, which is another example of the photoelectric conversion element of the embodiment. The heterojunction back contact cell according to the second embodiment is characterized in that a silicon nitride (SiN) film 9 b is provided as a film on the convex portion 11 and the concave portion 12 of the light receiving surface of the semiconductor substrate 1. As the semiconductor substrate 1, for example, an n-type single crystal silicon substrate similar to that of the first embodiment is used.

In addition to the SiN film 9b, as the film on the light receiving surface of the semiconductor substrate 1 on the light receiving surface 11 and the concave portion 12, SiC _x N _y O _z F _v H _w (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) , 0 ≦ z ≦ 1, 0 ≦ v ≦ 1, 0 ≦ w ≦ 1, (x + y + z + v + w)> 0), a film represented by the formula, amorphous silicon, etc. It may be a composite film with an amorphous semiconductor film. The formation method of these films is not particularly limited, but can be formed by, for example, a plasma CVD method. In the above formula, Si represents silicon, C represents carbon, N represents nitrogen, O represents oxygen, F represents fluorine, and H represents hydrogen. In the above formula, x represents the atomic ratio of carbon, y represents the atomic ratio of nitrogen, z represents the atomic ratio of oxygen, v represents the atomic ratio of fluorine, and w represents hydrogen. Shows the atomic ratio.

Since the description other than the above in the second embodiment is the same as that in the first embodiment, the description thereof will not be repeated.

[Embodiment 3]
FIG. 18 is a schematic cross-sectional view of a heterojunction back contact cell of Embodiment 3, which is another example of the photoelectric conversion element of the embodiment. The heterojunction back contact cell of Embodiment 3 is characterized in that a silicon carbide (SiC) film 9 c is provided as a film on the convex portion 11 and the concave portion 12 of the light receiving surface of the semiconductor substrate 1. As the semiconductor substrate 1, for example, an n-type single crystal silicon substrate similar to that of the first embodiment is used.

Since the description other than the above in the third embodiment is the same as that in the first and second embodiments, the description thereof will not be repeated.

[Embodiment 4]
In FIG. 19, the typical sectional drawing of the back surface electrode type photovoltaic cell of Embodiment 4 which is another example of the photoelectric conversion element of Embodiment is shown. As shown in FIG. 19, the back electrode type solar cell of Embodiment 4 includes a semiconductor substrate 1, a first conductivity type region 63 provided at a distance from the back surface 1 a of the semiconductor substrate 1, and a second conductivity. And a mold region 65. The first electrode 6 is provided on the first conductivity type region 63, and the second electrode 7 is provided on the second conductivity type region 65. As the semiconductor substrate 1, for example, an n-type single crystal silicon substrate similar to that of the first embodiment is used.

Further, on the convex portion 11 and the concave portion 12 of the light receiving surface of the semiconductor substrate 1, SiC _x N _y O _z F _v H _w (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ v ≦ 1, 0 ≦ w ≦ 1, (x + y + z + v + w)> 0) is provided, and the back surface 1a of the semiconductor substrate 1 is also provided with a dielectric such as a silicon oxide film or a silicon nitride film. A body membrane 67 is provided.

Hereinafter, an example of a method for manufacturing the back electrode type solar battery cell of Embodiment 4 will be described with reference to schematic cross-sectional views of FIGS.

First, as shown in FIG. 20, a diffusion mask 62 is provided on each of the light receiving surface and the back surface 1a of the semiconductor substrate 1, and an opening 61a is provided in a part of the diffusion suppression mask 62 on the back surface 1a of the semiconductor substrate 1. . In addition, the formation method of the opening part 61a is not specifically limited, For example, methods, such as photolithography, can be used.

Next, as shown in FIG. 21, the back surface 1 a of the semiconductor substrate 1 exposed from the opening 61 a of the diffusion suppression mask 62 of the first main surface 1 b of the semiconductor substrate 1 by flowing an n-type impurity-containing gas 64. An n-type impurity is diffused to form a first conductivity type region 63 which is an n-type impurity diffusion region. As the n-type impurity-containing gas 64, for example, POCl ₃ containing phosphorus which is an n-type impurity can be used. The n-type impurity diffusion region may be a region having an n-type impurity concentration higher than that of the semiconductor substrate 1.

Next, after once removing all of the diffusion suppression mask 62 on the light receiving surface and the back surface 1a of the semiconductor substrate 1, the diffusion suppression mask 62 is provided again on the entire surface of the light receiving surface and the back surface 1a of the semiconductor substrate 1, and FIG. As shown, an opening 61 b is provided in a part of the diffusion suppression mask 62 on the back surface 1 a of the semiconductor substrate 1.

Next, as shown in FIG. 23, by flowing a p-type impurity-containing gas 66, p-type is applied to the back surface 1 a of the semiconductor substrate 1 exposed from the opening 61 b of the diffusion suppression mask 62 on the back surface 1 a of the semiconductor substrate 1. Impurities are diffused to form a second conductivity type region 65 which is a p-type impurity diffusion region.

Next, as shown in FIG. 24, all the diffusion suppression masks 62 on the light receiving surface and the back surface 1a of the semiconductor substrate 1 are removed. Next, as shown in FIG. 25, a dielectric film 67 is formed on the entire back surface 1 a of the semiconductor substrate 1.

Next, as shown in FIG. 26, the light receiving surface of the semiconductor substrate 1 is subjected to texture etching, acid etching, and round etching in this order on the light receiving surface of the semiconductor substrate 1 in the same manner as in the first to third embodiments. A plurality of convex portions 11 and concave portions 12 between the convex portions 11 are formed on the surface. Here, in the round etching, the angle of the inclined surface 11c of the convex portion 11 is the above-mentioned angle (greater than 49.5 °, 55.2 ° or less, preferably 50 ° or more, more preferably 52.9 ° or more, preferably Is 53.5 ° or less), and the curvature radius of the curved surface at the bottom of the recess 12 is such that the above-mentioned curvature radius (greater than 13 nm, preferably 80 nm or less, more preferably 65 nm or less) is satisfied.

Next, as shown in FIG. 27, a dielectric film 9d is formed on the convex portion 11 and the concave portion 12 of the light receiving surface of the semiconductor substrate 1. Next, as shown in FIG. 28, contact holes 70 and 71 are formed by removing a part of the dielectric film 67 on the back surface 1 a of the semiconductor substrate 1. In addition, the formation method of the contact holes 70 and 71 is not specifically limited, For example, methods, such as photolithography, can be used.

Next, as shown in FIG. 19, the first electrode 6 is formed on the first conductivity type region 63 through the contact hole 70, and the second electrode 7 is formed on the second conductivity type region 65 through the contact hole 71. . Thereby, the back electrode type solar cell of Embodiment 4 can be obtained.

In the above description, an n-type impurity diffusion region is formed as the first conductivity type region 63 and a p-type impurity diffusion region is formed as the second conductivity type region 65. However, a p-type impurity diffusion is used as the first conductivity type region 63. A region may be formed, and an n-type impurity diffusion region may be formed as the second conductivity type region 65.

Since the description other than the above in the fourth embodiment is the same as that in the first to third embodiments, the description thereof will not be repeated.

[Embodiment 5]
FIG. 29 is a schematic cross-sectional view of a double-sided electrode type solar battery cell of Embodiment 5, which is another example of the photoelectric conversion element of the embodiment. As shown in FIG. 29, a double-sided electrode solar cell of Embodiment 5 includes a semiconductor substrate 1 made of a single crystal silicon substrate such as an n-type single crystal silicon substrate similar to that of Embodiment 1, and the semiconductor substrate 1 A first conductivity type region 63 on the back surface 1 a serving as the back surface and a second conductivity type region 65 on the light receiving surface of the semiconductor substrate 1 are provided. A first electrode 7 is provided on the first conductivity type region 63, and a second electrode 8 is provided on the second conductivity type region 65.

The double-sided electrode type solar battery cell of Embodiment 5 can be manufactured as follows, for example. First, similarly to the first to fourth embodiments, by performing texture etching, acid etching, and round etching in this order on the light receiving surface of the semiconductor substrate 1, a plurality of protrusions 11 are formed on the light receiving surface of the semiconductor substrate 1. And the concave portion 12 between the convex portions 11. Here, in the round etching, the angle of the inclined surface 11c of the convex portion 11 is the above-mentioned angle (greater than 49.5 °, 55.2 ° or less, preferably 50 ° or more, more preferably 52.9 ° or more, preferably Is 53.5 ° or less), and the curvature radius of the curved surface at the bottom of the recess 12 is such that the above-mentioned curvature radius (greater than 13 nm, preferably 80 nm or less, more preferably 65 nm or less) is satisfied.

Next, the first conductivity type region 63 is formed on the back surface 1 a of the semiconductor substrate 1, and the second conductivity type region 65 is formed on the light receiving surface of the semiconductor substrate 1. Thereafter, a dielectric film 9 d is formed on the second conductivity type region 65. By undergoing the above steps, the double-sided electrode solar cell of Embodiment 5 can be obtained.

Since the description other than the above in the fifth embodiment is the same as in the first to fourth embodiments, the description thereof will not be repeated.

<Preparation of the substrate of Experimental Example 1>
First, an n-type silicon single crystal ingot was cut with a wire saw to cut out an n-type silicon single crystal substrate. Next, texture etching is performed on the surface of the n-type silicon single crystal substrate by alkaline etching using an aqueous sodium hydroxide solution, and a plurality of quadrangular pyramidal convex portions and convex portions are formed on the surface of the n-type silicon single crystal substrate. A recess was formed between them. Then, the board | substrate of Experimental example 1 was obtained by performing the acid etching using the hydrogen fluoride aqueous solution about the surface of the n-type silicon single crystal substrate in which the convex part and the recessed part were formed by texture etching.

<Preparation of the substrate of Experimental Example 2>
The surface of the substrate after the acid etching in Experimental Example 1 was further mixed with about 42 ° C. mixed acid (hydrofluoric acid (hydrogen fluoride aqueous solution having a hydrogen fluoride concentration of 50% by mass)) containing nitric acid and water: nitric acid Round etching was performed by dipping in a volume of (a nitric acid aqueous solution having a nitric acid concentration of 60 mass%): volume of water = 1: 100: 50) for 180 seconds to obtain a substrate of Experimental Example 2.

<Preparation of the substrate of Experimental Example 3>
About the surface of the substrate after acid etching in Experimental Example 1, the volume of a mixed acid (hydrofluoric acid (hydrogen fluoride aqueous solution having a hydrogen fluoride concentration of 50 mass%)) of about 42 ° C. further containing hydrofluoric acid, nitric acid, and water: nitric acid Round etching was performed by dipping in a volume of (a nitric acid aqueous solution having a nitric acid concentration of 60% by mass): volume of water = 1: 70: 35 for 180 seconds to obtain a substrate of Experimental Example 3.

<Preparation of the substrate of Experimental Example 4>
About the surface of the substrate after acid etching in Experimental Example 1, the volume of a mixed acid (hydrofluoric acid (hydrogen fluoride aqueous solution having a hydrogen fluoride concentration of 50 mass%)) of about 42 ° C. further containing hydrofluoric acid, nitric acid, and water: nitric acid Round etching was performed by dipping in a volume of (a nitric acid aqueous solution having a nitric acid concentration of 60 mass%): volume of water = 1: 50: 25) for 180 seconds to obtain a substrate of Experimental Example 4.

<Measurement of reflectivity of substrate surface of Experimental Examples 1 to 4>
The relationship between the wavelength of light incident on the substrates of Experimental Examples 1 to 4 fabricated as described above and the reflectance was investigated. The result is shown in FIG. In FIG. 30, the horizontal axis indicates the wavelength [nm] of the light incident on the substrates of Experimental Examples 1 to 4, and the vertical axis indicates the reflectance [% of incident light having the respective wavelengths of the substrates of Experimental Examples 1 to 4]. %].

As shown in FIG. 30, the substrate of Experimental Example 1 had the highest reflectance with respect to incident light. Further, the substrate of Experimental Example 3 had the lowest reflectance, and the reflectance increased in the order of Experimental Example 4 and Experimental Example 2.

<Measurement of the angle of the inclined surface of the convex portion of the substrates of Experimental Examples 1 and 5 to 7>
Next, a cross section along a line in which two adjacent inclined surfaces of the quadrangular pyramid shape of the substrates of Experimental Examples 1 to 4 contact each other was formed, and an SEM photograph of the cross section was taken. Then, from the SEM photographs of the cross sections of the substrates of Experimental Examples 1 to 4, the angle α of the inclined surfaces of the convex portions of the substrates of Experimental Examples 1 to 4 was measured, and the convex portions of the substrates of Experimental Examples 1 to 4 were measured. The average value of the angle α of the inclined surfaces was calculated. The result is shown in FIG. In FIG. 31, the horizontal axis indicates the substrates of Experimental Examples 1 to 4, and the vertical axis indicates the average value of the angle α [°] of the inclined surface of the convex portion of each of the substrates of Experimental Examples 1 and 5 to 7. Is shown.

From the results shown in FIG. 31, the average value of the angle α of the inclined surface of the convex portion of the substrate of Experimental Example 1 is 49.5 °, and the average value of the angle α of the inclined surface of the convex portion of the substrate of Experimental Example 2 is It was confirmed to be 52.9 °. Moreover, the average value of the angle α of the inclined surface of the convex portion of the substrate of Experimental Example 3 is 55.2 °, and the average value of the angle α of the inclined surface of the convex portion of the substrate of Experimental Example 4 is 54.3 °. It was confirmed that there was.

<Summary>
From the results shown in FIGS. 30 and 31, from the viewpoint of reducing the reflectance on the surface of the substrate and taking light into the substrate, the angle α of the inclined surface of the convex portion of the substrate is more than 49.5 °. It was confirmed that it was 55.2 ° or less, preferably 52.9 ° or more and 55.2 ° or less.

<Preparation of Substrates for Experimental Examples 5-7>
The surface of the substrate after the acid etching in Experimental Example 1 was further mixed with about 42 ° C. mixed acid (hydrofluoric acid (hydrogen fluoride aqueous solution having a hydrogen fluoride concentration of 50% by mass)) containing nitric acid and water: nitric acid Round etching was performed by dipping in a volume of (a nitric acid aqueous solution having a nitric acid concentration of 60 mass%): volume of water = 1: 70: 35) for 30 seconds to obtain a substrate of Experimental Example 5.

Further, the surface of the substrate after the acid etching in Experimental Example 1 was further mixed with about 42 ° C. mixed acid (hydrofluoric acid (hydrogen fluoride aqueous solution having a hydrogen fluoride concentration of 50 mass%)) containing hydrofluoric acid, nitric acid, and water. : Round etching was carried out by dipping in nitric acid (volume of nitric acid aqueous solution having a nitric acid concentration of 60% by mass: volume of water = 1:70:35) for 15 seconds to obtain a substrate of Experimental Example 6.

Furthermore, the surface of the substrate after acid etching in Experimental Example 1 is further mixed with about 42 ° C. mixed acid (hydrofluoric acid (hydrogen fluoride aqueous solution having a hydrogen fluoride concentration of 50 mass%)) containing hydrofluoric acid, nitric acid, and water. : Round etching was performed by immersing in nitric acid (volume of nitric acid aqueous solution having a nitric acid concentration of 60% by mass: volume of water = 1: 100: 50) for 270 seconds to obtain a substrate of Experimental Example 7.

<Measurement of Reverse Saturation Current Density of Cells of Experimental Examples 1, 2, and 5-7>
Using the substrates of Experimental Examples 1, 2, and 5 to 7 manufactured as described above, the heterojunction back contact cells (Substrate) of Experimental Examples 1, 2, and 5 to 7 having the structure shown in FIG. The film on the light receiving surface was made of SiN film). Then, the reverse saturation current density [fA / cm ² ] was measured for each of the heterojunction back contact cells of Experimental Examples 1, 2, and 5 to 7. The result is shown in FIG. In FIG. 32, the horizontal axis represents the heterojunction back contact cell of each of Experimental Examples 1, 2, and 5 to 7, and the vertical axis represents the reverse saturation current density of the heterojunction back contact cell of Experimental Example 1. 2 shows the relative values of the reverse saturation current densities of the heterojunction back contact cells of Experimental Examples 2 and 5 to 7 when 1.

From the results shown in FIG. 32, the heterojunction back contact cells of Experimental Examples 2 and 5 to 7 fabricated using the substrates of Experimental Examples 2 and 5 to 7 that were subjected to round etching were subjected to round etching. It was confirmed that the reverse saturation current density can be reduced as compared with the heterojunction back contact cell of Experimental Example 1 manufactured using the substrate of Experimental Example 1 that was not used.

<Measurement of curvature radius of curved surface of bottom of recess of substrate of Experimental Examples 1, 5, 8 and 9>
Substrates of Experimental Examples 8 and 9 were prepared in the same manner as Experimental Example 5 except that the round etching time of the substrate of Experimental Example 5 was changed to 60 seconds and 90 seconds, respectively.

Then, a cross section was formed along a line in which two adjacent pyramid-shaped inclined surfaces of the substrates of Experimental Examples 1, 5, 8 and 9 obtained as described above were in contact with each other. FIG. 33 shows a schematic enlarged cross-sectional view of the substrate of Experimental Example 1, and FIG. 34 shows a schematic enlarged cross-sectional view of the cross section of the substrate of Experimental Example 5. FIG. 35 shows a schematic enlarged cross-sectional view of the substrate of Experimental Example 8, and FIG. 36 shows a schematic enlarged cross-sectional view of the substrate of Experimental Example 9.

Then, from the cross-sections of the substrates of Experimental Examples 1, 5, 8, and 9, the curvature radii of the curved surfaces of the bottoms of the recesses on the surface of each of the substrates of Experimental Examples 1, 5, 8, and 9 were measured. The result is shown in FIG. Note that the horizontal axis of FIG. 37 represents the round etching time [seconds] of each of the substrates of Experimental Examples 1, 5, 8, and 9, and the vertical axis represents each of the substrates of Experimental Examples 1, 5, 8, and 9. The curvature radius [nm] of the curved surface of the bottom of the recess on the surface of the substrate is shown.

37, it was confirmed that the curvature radius of the curved surface at the bottom of the concave portion of the substrate of Experimental Example 1 was 13 nm, and the curvature radius of the curved surface at the bottom of the concave portion of the substrate of Experimental Example 5 was 45 nm. Further, it was confirmed that the radius of curvature of the curved surface of the bottom of the concave portion of the substrate of Experimental Example 8 was 68 nm, and the radius of curvature of the curved surface of the bottom of the concave portion of the substrate of Experimental Example 9 was 73 nm.

<Summary>
From the results shown in FIGS. 32 and 37, from the viewpoint of reducing the occurrence of cracks formed in the film on the concave portion on the surface of the substrate and reducing the reverse saturation current density, the curved surface at the bottom of the concave portion of the substrate is used. It was confirmed that the radius of curvature is preferably larger than 13 nm.

[Appendix]
(1) The embodiment disclosed herein includes a plurality of convex portions and concave portions between the convex portions on the surface, the convex portions include an inclined surface, the concave portion includes a curved bottom, and the angle of the inclined surface. Is a semiconductor substrate having a curvature radius of the curved surface larger than 13 nm. In this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(2) In the semiconductor substrate of the embodiment disclosed herein, the angle is preferably 50 ° or more, and more preferably 52.9 ° or more. In this case, a photoelectric conversion element with higher characteristics can be obtained.

(3) In the semiconductor substrate of the embodiment disclosed herein, the angle is preferably 53.5 ° or less. In this case, a photoelectric conversion element with higher characteristics can be obtained.

(4) In the semiconductor substrate of the embodiment disclosed herein, the radius of curvature is preferably 80 nm or more. In this case, a photoelectric conversion element with higher characteristics can be obtained.

(5) In the semiconductor substrate according to the embodiment disclosed herein, the radius of curvature is preferably 65 nm or less. In this case, it is possible to obtain a photoelectric conversion element having higher characteristics.

(6) In the semiconductor substrate of the embodiment disclosed herein, the convex portion may have a quadrangular pyramid shape. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(7) The semiconductor substrate of the embodiment disclosed herein may include a film on the recess. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(8) In the semiconductor substrate of the embodiment disclosed herein, the film is made of SiC _x N _y O _z F _v H _w (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ v). ≦ 1, 0 ≦ w ≦ 1, (x + y + z + v + w)> 0) may be included. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(9) In the semiconductor substrate of the embodiment disclosed herein, the film may include an amorphous semiconductor film. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(10) In the semiconductor substrate of the embodiment disclosed herein, the amorphous semiconductor film may include amorphous silicon. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(11) The semiconductor substrate of the embodiment disclosed herein may have an n-type or p-type conductivity type. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(12) The semiconductor substrate of the embodiment disclosed herein may be an n-type single crystal silicon substrate.

(13) The semiconductor substrate of the embodiment disclosed herein may include the above-described semiconductor substrate.

(14) In the embodiment disclosed herein, the semiconductor substrate, the first conductive type amorphous semiconductor film and the second conductive type amorphous semiconductor on the second surface opposite to the surface of the semiconductor substrate are provided. A photoelectric conversion element includes a semiconductor film, a first electrode on a first conductive amorphous semiconductor film, and a second electrode on a second conductive amorphous semiconductor film. In this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(15) The photoelectric conversion element of the embodiment disclosed herein may further include a first i-type amorphous semiconductor film between the first conductive type amorphous semiconductor film and the second surface. Good. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(16) The photoelectric conversion element of the embodiment disclosed herein may further include a second i-type amorphous semiconductor film between the second conductive type amorphous semiconductor film and the second surface. Good. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(17) The embodiment disclosed herein includes the semiconductor substrate, the first conductivity type region and the second conductivity type region on the second surface opposite to the surface of the semiconductor substrate, and the first conductivity type region. A photoelectric conversion element comprising the upper first electrode and the second electrode on the second conductivity type region. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(18) An embodiment disclosed herein includes the above-described semiconductor substrate, a first conductivity type region on a surface of the semiconductor substrate, and a second conductivity type region on a second surface opposite to the surface of the semiconductor substrate. A photoelectric conversion element including a first electrode on the first conductivity type region and a second electrode on the second conductivity type region. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(19) The embodiment disclosed herein includes a step of forming a plurality of convex portions and concave portions between the convex portions on the surface of the semiconductor substrate, and a step of performing acid etching on the surface where the convex portions and the concave portions are formed. And a step of performing round etching of the surface after acid etching, and in the step of performing round etching, the angle of the inclined surface of the convex portion is set to be larger than 49.5 ° and not larger than 55.2 °, and the bottom of the concave portion This is a method for manufacturing a semiconductor substrate, wherein the radius of curvature of the curved surface is larger than 13 nm. In this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(20) In the method of manufacturing a semiconductor substrate according to the embodiment disclosed herein, the angle is preferably 50 ° or more, and more preferably 52.9 ° or more. In this case, a photoelectric conversion element with higher characteristics can be obtained.

(21) In the method of manufacturing a semiconductor substrate according to the embodiment disclosed herein, the angle is preferably 53.5 ° or less. In this case, a photoelectric conversion element with higher characteristics can be obtained.

(22) In the method of manufacturing a semiconductor substrate according to the embodiment disclosed herein, it is preferable that the radius of curvature is 80 nm or less. In this case, a photoelectric conversion element with higher characteristics can be obtained.

(23) In the method of manufacturing a semiconductor substrate according to the embodiment disclosed herein, it is preferable that the radius of curvature is 65 nm or less. In this case, it is possible to obtain a photoelectric conversion element having higher characteristics.

(24) The semiconductor substrate manufacturing method of the embodiment disclosed herein may further include a step of forming a film on the recess. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(25) In the method of manufacturing a semiconductor substrate according to the embodiment disclosed herein, the film is made of SiC _x N _y O _z F _v H _w (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ v ≦ 1, 0 ≦ w ≦ 1, (x + y + z + v + w)> 0) may be included. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(26) In the semiconductor substrate manufacturing method of the embodiment disclosed herein, the film may include an amorphous semiconductor film. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(27) In the semiconductor substrate manufacturing method of the embodiment disclosed herein, the amorphous semiconductor film may contain amorphous silicon. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(28) In the method of manufacturing a semiconductor substrate according to the embodiment disclosed herein, the semiconductor substrate may have an n-type or p-type conductivity type. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(29) In the method of manufacturing a semiconductor substrate according to the embodiment disclosed herein, the semiconductor substrate includes silicon, and the step of forming the convex portion and the concave portion may include a step of alkali etching the surface of the semiconductor substrate. Good. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(30) In the method for manufacturing a semiconductor substrate of the embodiment disclosed herein, the alkali etching step may be performed using an alkaline solution containing at least one of a sodium hydroxide aqueous solution and a potassium hydroxide aqueous solution. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(31) In the method of manufacturing a semiconductor substrate according to the embodiment disclosed herein, the step of performing acid etching may be performed using a hydrogen fluoride aqueous solution. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(32) In the semiconductor substrate manufacturing method of the embodiment disclosed herein, the step of performing round etching is preferably performed using a mixed acid containing hydrofluoric acid, nitric acid, and water. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(33) In the method for manufacturing a semiconductor substrate according to the embodiment disclosed herein, the ratio of the volume of nitric acid to the volume of hydrofluoric acid is preferably 70 or more and 100 or less. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(34) In the method for manufacturing a semiconductor substrate according to the embodiment disclosed herein, the ratio of the volume of water to the volume of hydrofluoric acid is preferably 35 or more and 50 or less. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(35) The embodiment disclosed herein includes a step of forming a semiconductor substrate having a plurality of convex portions and concave portions between the convex portions on the surface by the method for manufacturing a semiconductor substrate, and a surface of the semiconductor substrate. Forming a first conductive type amorphous semiconductor film and a second conductive type amorphous semiconductor film on the second surface on the opposite side, and forming a first electrode on the first conductive type amorphous semiconductor film A method for manufacturing a photoelectric conversion element includes a step of forming and a step of forming a second electrode on a second conductivity type amorphous semiconductor film. In this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(36) The method for manufacturing a photoelectric conversion element according to the embodiment disclosed herein further includes a step of forming a first i-type amorphous semiconductor film on the second surface, and the first conductivity-type amorphous The semiconductor film may be formed on the first i-type amorphous semiconductor film. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(37) The method of manufacturing a photoelectric conversion element according to the embodiment disclosed herein further includes a step of forming a second i-type amorphous semiconductor film on the second surface, and the second conductivity-type amorphous The semiconductor film may be formed on the second i-type amorphous semiconductor film. Also in this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(38) The embodiment disclosed herein includes a step of forming a semiconductor substrate having a plurality of convex portions and concave portions between the convex portions on the surface by the method for manufacturing a semiconductor substrate, and a surface of the semiconductor substrate. Forming a first conductivity type region and a second conductivity type region on the second surface on the opposite side, forming a first electrode on the first conductivity type region, and forming a first electrode on the second conductivity type region. And a process of forming two electrodes. In this case, it is possible to obtain a photoelectric conversion element having high characteristics.

(39) An embodiment disclosed herein includes a step of forming a semiconductor substrate having a plurality of convex portions and concave portions between the convex portions on the surface by the method for manufacturing a semiconductor substrate, and Forming a first conductivity type region; forming a second conductivity type region on a second surface opposite to the surface of the semiconductor substrate; and forming a first electrode on the first conductivity type region. And a step of forming a second electrode on the second conductivity type region. In this case, it is possible to obtain a photoelectric conversion element having high characteristics.

Although the embodiments and examples of the present invention have been described as described above, it is also planned from the beginning to appropriately combine the configurations of the above-described embodiments and examples.

The embodiments and examples disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

The embodiments disclosed herein can be used for semiconductor substrates such as silicon substrates and their manufacture, and photoelectric conversion elements such as solar cells and their manufacture.

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate, 1a back surface, 1st i-type amorphous semiconductor film, 3rd 1st conductivity type amorphous semiconductor film, 4th 2nd i-type amorphous semiconductor film, 5nd 2nd conductivity type amorphous Semiconductor film, 6 first electrode, 7 second electrode, 9a amorphous silicon film, 9b SiN film, 9c silicon carbide (SiC) film, 9d dielectric film, 11 convex portion, 11c inclined surface, 11d bottom surface, 11e line , 11f apex, 12 recesses, 31, 32 etching mask, 61a, 61b opening, 62 diffusion suppression mask, 63 first conductivity type region, 64 n-type impurity containing gas, 65 second conductivity type region, 66 p-type impurity containing Gas, 67 dielectric film, 70, 71 contact holes.

Claims (10)

Provided on the surface with a plurality of convex portions and concave portions between the convex portions,
The convex portion includes an inclined surface, and the concave portion includes a curved bottom,
The angle of the inclined surface is greater than 49.5 ° and less than or equal to 55.2 °,
A semiconductor substrate having a radius of curvature of the curved surface larger than 13 nm. The semiconductor substrate according to claim 1, wherein the convex portion has a quadrangular pyramid shape. 3. The semiconductor substrate according to claim 1, wherein a film is provided on the recess. The semiconductor substrate according to any one of claims 1 to 3, wherein the semiconductor substrate is an n-type single crystal silicon substrate. A photoelectric conversion element comprising the semiconductor substrate according to any one of claims 1 to 4. Forming a plurality of convex portions and concave portions between the convex portions on the surface of the semiconductor substrate;
Performing acid etching of the surface on which the convex portions and the concave portions are formed;
Performing a round etching of the surface after the acid etching,
In the step of performing the round etching, the angle of the inclined surface of the convex portion is set to be larger than 49.5 ° and 55.2 ° or smaller, and the curvature radius of the curved surface at the bottom of the concave portion is set to be larger than 13 nm. Production method. The method for manufacturing a semiconductor substrate according to claim 6, wherein the step of performing the round etching is performed using a mixed acid containing hydrofluoric acid, nitric acid, and water. Forming a semiconductor substrate having a plurality of convex portions and concave portions between the convex portions on the surface by the method of manufacturing a semiconductor substrate according to claim 6 or 7;
Forming a first conductive amorphous semiconductor film and a second conductive amorphous semiconductor film on a second surface opposite to the surface of the semiconductor substrate;
Forming a first electrode on the first conductive type amorphous semiconductor film;
Forming a second electrode on the second conductive type amorphous semiconductor film. A method for manufacturing a photoelectric conversion element. Forming a semiconductor substrate having a plurality of convex portions and concave portions between the convex portions on the surface by the method of manufacturing a semiconductor substrate according to claim 6 or 7;
Forming a first conductivity type region and a second conductivity type region on a second surface opposite to the surface of the semiconductor substrate;
Forming a first electrode on the first conductivity type region;
Forming a second electrode on the second conductivity type region. A method for manufacturing a photoelectric conversion element. Forming a semiconductor substrate having a plurality of convex portions and concave portions between the convex portions on the surface by the method of manufacturing a semiconductor substrate according to claim 6 or 7;
Forming a first conductivity type region on the surface of the semiconductor substrate;
Forming a second conductivity type region on a second surface opposite to the surface of the semiconductor substrate;
Forming a first electrode on the first conductivity type region;
Forming a second electrode on the second conductivity type region. A method for manufacturing a photoelectric conversion element.

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