JP2013105883A - Photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element which passivates a surface of crystalline silicon.SOLUTION: A photoelectric conversion element 10 includes: a crystal silicon substrate 1; an amorphous film 2; electrodes 3, 6, and a passivation film 5. The crystal silicon substrate 1 has an irregularity structure, including a recessed part 1c protruding in the incident direction of solar light, on one surface. The crystal silicon substrate 1 includes diffusion regions 1a, 1b at the incident side of the solar light. The amorphous film 2 is formed by an amorphous phase so as to contact with the irregularity structure of the crystal silicon substrate 1 which includes the recessed part 1c. The electrode 3 is formed so as to contact with the diffusion region 1b of the crystal silicon substrate 1. The passivation film 5 is formed so as to contact with a rear surface of the crystal silicon substrate 1. The electrode 6 is formed so as to contact with the rear surface of the crystal silicon substrate 1 and the passivation film 5.

Description

  The present invention relates to a photoelectric conversion element.

  Back-contact solar cells are designed to improve the conversion efficiency by increasing the amount of received light by eliminating the shadow caused by the electrodes on the light receiving surface side by forming the pn junction and the electrode on the back surface side that were conventionally on the light receiving surface side. It is.

  As a back contact solar cell, a solar cell in which an ip junction and an in junction are formed on the back surface of a crystalline semiconductor material is known (Patent Document 1).

  The ip junction is made of i-type amorphous silicon and p-type amorphous silicon. The in junction is made of i-type amorphous silicon and n-type amorphous silicon. The p-type amorphous silicon, i-type amorphous silicon, and n-type amorphous silicon are formed by a plasma CVD (Chemical Vapor Deposition) method.

JP 2010-80887 A

  However, when amorphous silicon is formed as a passivation film on the surface of the single crystal silicon by the plasma CVD method, if the surface of the single crystal silicon is textured, the surface of the single crystal silicon is composed of the (111) plane. Is epitaxially grown and it is difficult to passivate the single crystal silicon.

  Accordingly, the present invention has been made to solve such a problem, and provides a photoelectric conversion element capable of passivating the surface of crystalline silicon.

  According to the embodiment of the present invention, the photoelectric conversion element includes a crystalline silicon substrate, a first amorphous film, and a p / n junction. The crystalline silicon substrate has a first conductivity type, and an uneven structure including a hemispherical concave portion protruding in the sunlight incident direction is formed on one surface. The first amorphous film is formed in contact with the concavo-convex structure including the hemispherical concave portion of the crystalline silicon substrate and is made of an amorphous phase. The p / n junction is formed on one surface side of the crystalline silicon substrate or the other surface side of the crystalline silicon substrate.

  According to the embodiment of the present invention, the photoelectric conversion element includes a single crystal silicon substrate and first to fourth amorphous films.

  The single crystal silicon substrate has a first conductivity type, and a concavo-convex structure including a hemispherical concave portion protruding in the incident direction of sunlight is formed on one surface. The first amorphous film is formed in contact with the concavo-convex structure including the hemispherical concave portion of the single crystal silicon substrate and is made of an amorphous phase. The second amorphous film is formed in contact with the other surface of the single crystal silicon substrate and is made of a non-doped amorphous phase. The third amorphous film is disposed in contact with the second amorphous film, has a second conductivity type opposite to the first conductivity type, and is made of an amorphous phase. The fourth amorphous film is disposed adjacent to and in contact with the second amorphous film, has the first conductivity type, and is made of an amorphous phase. .

  Furthermore, according to an embodiment of the present invention, the photoelectric conversion element includes a crystalline silicon substrate and first and second amorphous films. The crystalline silicon substrate has a first conductivity type, and an uneven structure including a hemispherical concave portion protruding in the sunlight incident direction is formed on one surface. The first amorphous film is formed in contact with the concavo-convex structure including the hemispherical concave portion of the crystalline silicon substrate, and is made of a non-doped and amorphous phase. The second amorphous film is formed in contact with the first amorphous film, has a second conductivity type opposite to the first conductivity type, and is made of an amorphous phase.

  In the photoelectric conversion element according to the embodiment of the present invention, the crystalline silicon substrate has a concavo-convex structure including a hemispherical recess protruding in the incident direction of sunlight on one surface. Then, when a thin film is deposited on the concavo-convex structure including the hemispherical concave portion of the crystalline silicon substrate, the concavo-convex structure has a plane orientation other than (111), so the thin film does not epitaxially grow and is made of an amorphous phase. . As a result, the first amorphous film made of the amorphous phase is formed in contact with the concavo-convex structure including the hemispherical concave portion of the crystalline silicon substrate.

  Therefore, the surface of the crystalline silicon substrate can be passivated.

  In the photoelectric conversion element according to the embodiment of the present invention, the single crystal silicon substrate has a concavo-convex structure including a hemispherical recess protruding in the sunlight incident direction on one surface. Then, when a thin film is deposited on the concavo-convex structure including the hemispherical concave portion of the single crystal silicon substrate, the concavo-convex structure has a plane orientation other than (111). Become. As a result, the first amorphous film made of the amorphous phase is formed in contact with the concavo-convex structure including the hemispherical concave portion. Further, a pin junction is formed by the single crystal silicon substrate and the second to fourth amorphous films on the side opposite to the surface where the concave portion of the single crystal silicon substrate is formed.

  Therefore, in the back contact photoelectric conversion element, the surface of the single crystal silicon substrate can be passivated by the first amorphous film.

  Furthermore, in the photoelectric conversion element according to the embodiment of the present invention, the crystalline silicon substrate has a concavo-convex structure including a hemispherical concave portion protruding in the sunlight incident direction on one surface. Then, when a thin film is deposited on the concavo-convex structure including the hemispherical concave portion of the crystalline silicon substrate, the concavo-convex structure has a plane orientation other than (111), so the thin film does not epitaxially grow and is made of an amorphous phase. . As a result, the first amorphous film made of the amorphous phase is formed in contact with the concavo-convex structure including the hemispherical concave portion of the crystalline silicon substrate. The second amorphous film is formed in contact with the first amorphous film.

  Therefore, in the photoelectric conversion element in which the pin junction is formed on the sunlight incident side, the surface of the single crystal silicon substrate can be passivated by the first amorphous film.

It is sectional drawing which shows the structure of the photoelectric conversion element by Embodiment 1 of this invention. 3 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 1. FIG. FIG. 3 is a first process diagram showing a method for manufacturing the photoelectric conversion element shown in FIG. 2. FIG. 3 is a second process diagram showing a method for manufacturing the photoelectric conversion element shown in FIG. 2. 6 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 2. FIG. 6 is a cross-sectional view illustrating a configuration of a photoelectric conversion element according to Embodiment 2. FIG. 6 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 3. FIG. FIG. 8 is a first process diagram illustrating a method for manufacturing the photoelectric conversion element illustrated in FIG. 7. FIG. 8 is a second process diagram illustrating a method for manufacturing the photoelectric conversion element illustrated in FIG. 7. 6 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 4. FIG. 7 is a cross-sectional view illustrating a configuration of a photoelectric conversion element according to Embodiment 3. FIG. 10 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 5. FIG. It is a 1st process drawing which shows the manufacturing method of the photoelectric conversion element shown in FIG. FIG. 13 is a second process diagram illustrating a method for manufacturing the photoelectric conversion element illustrated in FIG. 12. 10 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 6. FIG. 6 is a cross-sectional view illustrating a configuration of a photoelectric conversion element according to Embodiment 4. FIG. 10 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 7. FIG. FIG. 18 is a first process diagram illustrating a method for manufacturing the photoelectric conversion element illustrated in FIG. 17. FIG. 18 is a second process diagram illustrating a method for manufacturing the photoelectric conversion element illustrated in FIG. 17. FIG. 18 is a third process diagram illustrating a method for manufacturing the photoelectric conversion element illustrated in FIG. 17. 10 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 8. FIG.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  In this specification, the “amorphous phase” refers to a state in which silicon (Si) atoms and the like are randomly arranged. Moreover, although amorphous silicon is described as “a-Si”, this notation actually means that hydrogen (H) atoms are included. The same applies to amorphous silicon carbide (a-SiC), amorphous silicon nitride (a-SiN), amorphous silicon carbon nitride (a-SiCN), amorphous silicon germanium (a-SiGe), and amorphous germanium (a-Ge). Means that an H atom is contained. Furthermore, the “crystalline silicon substrate” refers to a single crystal silicon substrate or a polycrystalline silicon substrate.

[Embodiment 1]
1 is a cross-sectional view showing a configuration of a photoelectric conversion element according to Embodiment 1 of the present invention. Referring to FIG. 1, a photoelectric conversion element 10 according to Embodiment 1 of the present invention includes a crystalline silicon substrate 1, an amorphous film 2, electrodes 3 and 6, and a passivation film 5.

  The crystalline silicon substrate 1 is composed of an n-type single crystal silicon substrate or a p-type single crystal silicon substrate. The crystalline silicon substrate 1 is composed of an n-type polycrystalline silicon substrate or a p-type polycrystalline silicon substrate.

  Each of the n-type single crystal silicon substrate and the p-type single crystal silicon substrate has, for example, a (100) plane orientation and a specific resistance of 0.1 to 1.0 Ω · cm. Each of the n-type single crystal silicon substrate and the p-type single crystal silicon substrate has a thickness of 100 to 300 μm, for example, and preferably has a thickness of 100 to 200 μm. The same applies to the n-type polycrystalline silicon substrate or the p-type polycrystalline silicon substrate except for the plane orientation.

Crystalline silicon substrate 1 includes diffusion regions 1a and 1b on one surface side thereof. Each of diffusion regions 1a and 1b has a conductivity type opposite to that of crystalline silicon substrate 1, and has a depth of, for example, 200 nm. Moreover, the dopant concentration of the diffusion region 1b is higher than the dopant concentration of the diffusion region 1a. For example, the diffusion region 1a has a dopant concentration of 1 × 10 ¹⁹ cm ⁻³ and the diffusion region 1b has a dopant concentration of 1 × 10 ²⁰ cm ⁻³ .

  Further, the crystalline silicon substrate 1 has a concavo-convex structure including a hemispherical concave portion 1c protruding in the incident direction of sunlight on one surface. This uneven structure is a so-called “honeycomb texture”. And the recessed part 1c has a width | variety of several micrometers in the in-plane direction of the crystalline silicon substrate 1, for example.

  The amorphous film 2 is made of an amorphous phase and is formed in contact with the concavo-convex structure including the concave portion 1 c of the crystalline silicon substrate 1. The amorphous film 2 is made of an n-type amorphous film or an i-type amorphous film when the crystalline silicon substrate 1 has an n-type conductivity type. The amorphous film 2 is made of a p-type amorphous film or an i-type amorphous film when the crystalline silicon substrate 1 has a p-type conductivity type. The amorphous film 2 has a thickness of 10 nm, for example.

  The electrode 3 is formed in contact with the diffusion region 1 b of the crystalline silicon substrate 1. The electrode 3 is made of, for example, silver (Ag).

  The passivation film 5 is formed in contact with the other surface of the crystalline silicon substrate 1 (= the surface opposite to the surface where the recess 1c is formed). The passivation film 5 is made of a silicon oxide film and has a thickness of 10 to 100 nm, for example.

  The electrode 6 is formed in contact with the crystalline silicon substrate 1 and the passivation film 5. The electrode 6 is made of, for example, aluminum (Al).

  Since one surface of the crystalline silicon substrate 1 has a concavo-convex structure including the hemispherical concave portion 1c protruding in the incident direction of sunlight as described above, the surface of the crystalline silicon substrate 1 is (111 ) And a different plane orientation.

  As a result, even if the thin film is deposited on the surface of the crystalline silicon substrate 1 (= the surface on which the concave portion 1 c is formed), the thin film does not grow epitaxially, and the amorphous film 2 made of an amorphous phase is formed on the crystalline silicon substrate 1. Are formed on the surface (= surface on which the concave portion 1c is formed).

  Therefore, the surface of the crystalline silicon substrate 1 can be passivated.

  Hereinafter, examples of the photoelectric conversion element 10 will be described.

Example 1
FIG. 2 is a cross-sectional view illustrating a configuration of the photoelectric conversion element according to the first embodiment. Referring to FIG. 2, photoelectric conversion element 10 </ b> A includes an n-type single crystal silicon substrate 11, an n-type amorphous film 12, electrodes 13 and 16, and a passivation film 15.

The n-type single crystal silicon substrate 11 has a (100) plane orientation and a specific resistance of 0.1 to 1.0 Ω · cm. The thickness of the n-type single crystal silicon substrate 11 is, for example, 200 μm. An uneven structure (honeycomb texture) including a recess 11 c is formed on one surface of the n-type single crystal silicon substrate 11. The n-type single crystal silicon substrate 11 has diffusion regions 11a and 11b on one surface side. Each of diffusion regions 11a and 11b has a p-type conductivity, and includes, for example, boron (B) as a dopant. The B concentration of the diffusion region 11a is, for example, 1 × 10 ¹⁹ cm ⁻³ , and the B concentration of the diffusion region 11b is, for example, 1 × 10 ²⁰ cm ⁻³ .

The n-type amorphous film 12 is formed in contact with the concave-convex structure including the concave portion 1 c of the n-type single crystal silicon substrate 11. The n-type amorphous film 12 is made of n-type a-Si. The film thickness of the n-type amorphous film 12 is, for example, 10 nm, and the phosphorus (P) concentration in the n-type amorphous film 12 is, for example, 1 × 10 ¹⁷ cm ⁻³ to 1 × 10 ^19. It is in the range of cm ⁻³ .

  The electrode 13 is formed in contact with the diffusion region 11 b of the n-type single crystal silicon substrate 11. The electrode 13 is made of Ag.

Passivation film 15 is formed in contact with the other surface of n-type single crystal silicon substrate 11 (the surface opposite to the surface where recess 11c is formed). Then, the passivation film 15 is made of, for example, a silicon dioxide (SiO _2), having a 10~100nm thickness.

  The electrode 16 is formed in contact with the n-type single crystal silicon substrate 11 and the passivation film 15. The electrode 16 is made of Al.

  3 and 4 are first and second process diagrams showing a method of manufacturing the photoelectric conversion element 10A shown in FIG. 2, respectively.

  The n-type single crystal silicon substrate 11 having the (100) plane orientation is ultrasonically cleaned with ethanol or the like and degreased. Then, a silicon nitride (SiN) film is formed on one surface of the n-type single crystal silicon substrate 11, and the formed SiN film is patterned by photolithography and etching to produce a mask 20 (step of FIG. 3). (See (a)). The mask 20 has a small hole 21 having a diameter of about 2 to 3 μm, for example.

After the step (a), the n-type single crystal silicon substrate 11 is isotropically etched through the mask 20 using a mixed acid of hydrofluoric acid (HF) and nitric acid (HNO ₃ ), and the mask 20 is removed. Thereby, a concavo-convex structure (honeycomb texture) including the concave portion 11c is formed on one surface side of the n-type single crystal silicon substrate 1 (see step (b) in FIG. 3).

  A BSG (Boron Silicate Glass) film 22 containing boron (B), which is a p-type dopant, is applied to the surface of the n-type single crystal silicon substrate 11 (= the surface on which the recesses 11c are formed) by APCVD (Atmospheric Pressure Chemical Vapor Deposition). ) Method (see step (c) in FIG. 3).

  Thereafter, the BSG film 22 / n-type single crystal silicon substrate 11 is heat-treated at a temperature of 800 ° C. for 1 hour in a nitrogen gas atmosphere. Then, after the heat treatment, the BSG film 22 is removed. As a result, a diffusion region 23 is formed on the surface side of the n-type single crystal silicon substrate 11 (see step (d) in FIG. 3).

  Subsequently, a BSG film is formed by the APCVD method so as to cover the diffusion region 23, a resist is applied to the entire surface of the formed BSG film, and the applied resist is patterned by photolithography to produce a resist pattern. . Then, the BSG film is etched using the produced resist pattern as a mask to form the BSG film 24 (see step (e) in FIG. 3).

  Then, the BSG film 24 / n-type single crystal silicon substrate 11 is heat-treated at a temperature of 950 ° C. for 50 minutes in a nitrogen gas atmosphere. Then, after the heat treatment, the BSG film 24 is removed. As a result, diffusion regions 11a and 11b are formed on the surface side of n-type single crystal silicon substrate 11 (see step (f) in FIG. 4). Since the diffusion region 11b is formed by two heat treatments of the BSG film, the B concentration is higher than that of the diffusion region 11a, and the depth of the diffusion region 11b is deeper than that of the diffusion region 11a.

After the step (f), the n-type single crystal silicon substrate 11 is heat-treated in an oxygen atmosphere at a temperature of 1000 ° C. to form a passivation film 15 made of SiO _{2 on} the back surface of the n-type single crystal silicon substrate 11 (= recess 11c is formed). (Refer to step (g) in FIG. 4). Note that SiO ₂ is also formed on the surface where the recess 11c is formed, but this SiO ₂ is removed by HF.

Then, an n-type amorphous film 12 made of n-type a-Si is formed on the surface of the n-type single crystal silicon substrate 11 by a plasma CVD method (see step (h) in FIG. 4). In this case, the conditions for forming n-type a-Si are that the flow rate of silane (SiH ₄ ) gas is 20 sccm, the flow rate of hydrogen (H ₂ ) gas is 150 sccm, and the flow rate of phosphine (PH ₃ ) gas is 100 sccm. The RF power at 13.56 MHz is 16 to 80 mW / cm ² and the reaction pressure is 13.3 Pa to 665 Pa. The PH ₃ gas is diluted with H ₂ gas, and its concentration is 0.2%.

  After the step (h), contact holes 25 and 26 are respectively formed in the n-type amorphous film 12 and the passivation film 16 by photolithography and etching (see step (i) in FIG. 4).

  Then, the electrode 13 is formed on the n-type amorphous film 12 side, and the electrode 16 is formed on the passivation film 15 side. Thus, the photoelectric conversion element 10A is completed (see step (j) in FIG. 4).

  In the step (h), when the n-type amorphous film 12 made of n-type a-Si is deposited on the n-type single crystal silicon substrate 11, the surface of the n-type single crystal silicon substrate 11 (= recess 11c is formed). Since the concavo-convex structure (honeycomb texture) including the concave portions 11c is formed on the surface, the surface of the n-type single crystal silicon substrate 11 has a plane orientation other than (111). As a result, even if the thin film is deposited on the surface of the n-type single crystal silicon substrate 11 (= the surface where the recess 11c is formed), the thin film does not grow epitaxially. Therefore, the n-type amorphous film 12 made of n-type a-Si can be formed on the surface of the n-type single crystal silicon substrate 11 (= the surface on which the recess 11c is formed).

  In the photoelectric conversion element 10A, sunlight is irradiated to the photoelectric conversion element 10A from the n-type amorphous film 12 side. The reflection of sunlight is suppressed by the honeycomb texture and enters the n-type single crystal silicon substrate 11 through the n-type amorphous film 12.

  Then, holes and electrons are photoexcited in the n-type single crystal silicon substrate 11. The photoexcited holes are formed by the diffusion regions 11a and 11b and the bulk region of the n-type single crystal silicon substrate 11 (= the region other than the diffusion regions 11a and 11b of the n-type single crystal silicon substrate 11). It moves by diffusion in the direction of the / n junction, and reaches the diffusion regions 11a and 11b by an internal electric field by the p / n junction. The holes that have reached the diffusion region 11a are suppressed from being recombined at the interface between the diffusion region 11a and the n-type amorphous film 12, and reach the diffusion region 11b by diffusion. Thus, the n-type amorphous film 12 functions as a passivation film for the surface of the n-type single crystal silicon substrate 11. The holes reach the electrode 13 from the diffusion region 11b.

  On the other hand, the photoexcited electrons move to the back side of the n-type single crystal silicon substrate 11 by diffusion. Then, electrons that have reached the interface between the n-type single crystal silicon substrate 11 and the passivation film 15 are suppressed from recombination and reach the electrode 16 by diffusion. The electrons that have reached the electrode 16 reach the electrode 13 from the electrode 16 via a load and recombine with the holes.

  Thus, since the photoelectric conversion element 10A includes the n-type single crystal silicon substrate 11 whose surface orientation on the light incident side is other than (111), the n-type amorphous film 12 made of an amorphous phase is provided. It is formed in contact with the surface of n-type single crystal silicon substrate 11 (= surface on which recess 11c is formed). As a result, of the photogenerated holes and electrons, recombination of holes that are minority carriers is suppressed by the n-type amorphous film 12.

  Therefore, the surface of the n-type single crystal silicon 11 can be passivated.

  In the above description, the n-type amorphous film 12 is n-type a-Si. However, in the photoelectric conversion element 10A, the n-type amorphous film 12 is not limited to this. It may be made of any one of SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN.

The n-type a-SiGe is formed by plasma CVD using SiH ₄ gas, germane (GeH ₄ ) gas, H ₂ gas, and PH ₃ gas as material gases. The n-type a-SiN is formed by plasma CVD using SiH ₄ gas, ammonia (NH ₃ ) gas, H ₂ gas, and PH ₃ gas as material gases. The n-type a-SiC is formed by plasma CVD using SiH ₄ gas, methane (CH ₄ ) gas, H ₂ gas, and PH ₃ gas as material gases. The n-type a-SiCN is formed by plasma CVD using SiH ₄ gas, CH ₄ gas, NH ₃ gas, H ₂ gas, and PH ₃ gas as material gases.

  Even when the n-type amorphous film 12 is made of any of n-type a-SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN, the n-type amorphous film 12 is amorphous. Since it consists of a mass phase, the surface of the n-type single crystal silicon substrate 11 can be passivated.

  Further, the photoelectric conversion element 10 </ b> A may include an i-type amorphous film instead of the n-type amorphous film 12. In this case, the i-type amorphous film may be made of any of i-type a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN.

i-type a-Si is formed by a plasma CVD method using SiH ₄ gas and H ₂ gas as material gases. i-type a-SiGe is formed by plasma CVD using SiH ₄ gas, GeH ₄ gas and H ₂ gas as material gases. i-type a-SiN is formed by plasma CVD using SiH ₄ gas, NH ₃ gas, and H ₂ gas as material gases. i-type a-SiC is formed by plasma CVD using SiH ₄ gas, CH ₄ gas, and H ₂ gas as material gases. i-type a-SiCN is formed by plasma CVD using SiH ₄ gas, CH ₄ gas, NH ₃ gas, and H ₂ gas as material gases.

  Furthermore, the photoelectric conversion element 10 </ b> A may include an n-type polycrystalline silicon substrate instead of the n-type single crystal silicon substrate 11. The n-type polycrystalline silicon substrate has a specific resistance of 0.1 to 1.0 Ω · cm, for example, a thickness of 200 μm. Then, the surface of the n-type polycrystalline silicon substrate is honeycomb-textured by dry etching using the mask 20 shown in step (a) of FIG.

  Even when the photoelectric conversion element 10A includes an n-type polycrystalline silicon substrate, the n-type amorphous film 12 made of an amorphous phase is deposited on the n-type single crystal silicon substrate, and the n-type amorphous The film 12 is made of the various materials described above. Further, when the photoelectric conversion element 10A includes an n-type polycrystalline silicon substrate, the photoelectric conversion element 10A may include an i-type amorphous film instead of the n-type amorphous film 12, and i The type amorphous film is made of the various materials described above.

  The photoelectric conversion element 10A may further include an antireflection film in contact with the n-type amorphous film 12. In this case, the antireflection film is made of, for example, a silicon nitride film and has a thickness of 10 to 100 nm.

(Example 2)
FIG. 5 is a cross-sectional view illustrating a configuration of the photoelectric conversion element according to the second embodiment. Referring to FIG. 5, photoelectric conversion element 10 </ b> B includes a p-type single crystal silicon substrate 31, a p-type amorphous film 32, electrodes 33 and 36, and a passivation film 35.

The p-type single crystal silicon substrate 31 has a (100) plane orientation and a specific resistance of 0.1 to 1.0 Ω · cm. The thickness of the p-type single crystal silicon substrate 31 is, for example, 200 μm. An uneven structure (honeycomb texture) including a recess 31 c is formed on one surface of the p-type single crystal silicon substrate 31. The p-type single crystal silicon substrate 31 has diffusion regions 31a and 31b on one surface side. Each of the diffusion regions 31a and 31b has an n-type conductivity, and includes, for example, P as a dopant. The P concentration in the diffusion region 31a is, for example, 1 × 10 ¹⁹ cm ⁻³ , and the P concentration in the diffusion region 11b is, for example, 1 × 10 ²⁰ cm ⁻³ .

The p-type amorphous film 32 is formed in contact with the concavo-convex structure including the concave portion 31 c of the p-type single crystal silicon substrate 31. The p-type amorphous film 32 is made of p-type a-Si. The thickness of the p-type amorphous film 32 is, for example, 10 nm, and the B concentration in the p-type amorphous film 32 is, for example, 1 × 10 ¹⁷ cm ⁻³ to 1 × 10 ¹⁹ cm ^−3. Range.

  Electrode 33 is formed in contact with diffusion region 31 b of p-type single crystal silicon substrate 31. The electrode 33 is made of Ag.

Passivation film 35 is formed in contact with the other surface of p-type single crystal silicon substrate 31 (the surface opposite to the surface where recess 31c is formed). The passivation film 35 is made of, for example, SiO ₂ and has a thickness of 10 to 100 nm.

  The electrode 36 is formed in contact with the p-type single crystal silicon substrate 31 and the passivation film 35. The electrode 36 is made of Al.

  The photoelectric conversion element 10B is manufactured according to the steps (a) to (j) shown in FIGS. In this case, in steps (a) and (b), a concavo-convex structure (honeycomb texture) including the concave portion 31 c is formed on one surface of the p-type single crystal silicon substrate 31.

  In addition, in the steps (c) to (f), the diffusion regions 31a and 31b are formed. The dopant source of P is a PSG (Phosphorus Silicate Glass) film.

  Further, in step (g), a passivation film 35 is formed on the back surface of the p-type single crystal silicon substrate 31. In step (h), the p-type amorphous film 32 is formed on one surface of the p-type single crystal silicon substrate 31. It is formed on (the surface on which the recess 31c is formed).

  Furthermore, electrodes 33 and 36 are formed in steps (i) and (j).

  In the step (h), when the p-type amorphous film 32 made of p-type a-Si is deposited on the p-type single crystal silicon substrate 31, the surface of the p-type single crystal silicon substrate 31 (= the recess 31c is formed). Since the concavo-convex structure (honeycomb texture) including the concave portion 31c is formed on the surface), the surface of the p-type single crystal silicon substrate 31 has a plane orientation other than (111). As a result, even if the thin film is deposited on the surface of the p-type single crystal silicon substrate 31 (= the surface where the recess 31c is formed), the thin film does not grow epitaxially. Therefore, the p-type amorphous film 32 made of p-type a-Si can be formed on the surface of the p-type single crystal silicon substrate 31 (= the surface on which the recess 31c is formed).

  In the photoelectric conversion element 10B, sunlight is irradiated to the photoelectric conversion element 10B from the p-type amorphous film 32 side. The reflection of sunlight is suppressed by the honeycomb texture and enters the p-type single crystal silicon substrate 31 through the p-type amorphous film 32.

  Then, holes and electrons are photoexcited in the p-type single crystal silicon substrate 31. The photoexcited electrons are formed by the diffusion regions 31a and 31b and the bulk region of the p-type single crystal silicon substrate 31 (= the region other than the diffusion regions 31a and 31b of the p-type single crystal silicon substrate 31). It moves by diffusion in the direction of the n-junction, and reaches the diffusion regions 31a and 31b by an internal electric field by the p / n junction. The electrons that have reached the diffusion region 31a are suppressed from being recombined at the interface between the diffusion region 31a and the p-type amorphous film 32, and reach the diffusion region 31b by diffusion. Thus, the p-type amorphous film 32 functions as a passivation film for the surface of the p-type single crystal silicon substrate 31. The electrons reach the electrode 33 from the diffusion region 31b.

  On the other hand, the photoexcited holes move to the back side of the p-type single crystal silicon substrate 31 by diffusion. The holes reaching the interface between the p-type single crystal silicon substrate 31 and the passivation film 35 are suppressed from recombination and reach the electrode 36 by diffusion. Then, the electrons reach the electrode 36 from the electrode 33 through the load and recombine with the holes.

  Thus, since the photoelectric conversion element 10B includes the p-type single crystal silicon substrate 31 whose surface orientation on the light incident side is other than (111), the p-type amorphous film 32 made of an amorphous phase is provided. It is formed in contact with the surface of the p-type single crystal silicon substrate 31 (= surface on which the recess 31c is formed). As a result, of the photogenerated holes and electrons, recombination of electrons that are minority carriers is suppressed by the p-type amorphous film 32.

  Therefore, the surface of the p-type single crystal silicon 31 can be passivated.

  In the above description, the p-type amorphous film 32 is p-type a-Si. However, in the photoelectric conversion element 10B, the p-type amorphous film 32 is not limited to this. It may consist of any one of SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN.

The p-type a-SiGe is formed by plasma CVD using SiH ₄ gas, GeH ₄ gas, H ₂ gas and diborane (B ₂ H ₆ ) gas as material gases. The p-type a-SiN is formed by plasma CVD using SiH ₄ gas, NH ₃ gas, H ₂ gas, and B ₂ H ₆ gas as material gases. The p-type a-SiC is formed by plasma CVD using SiH ₄ gas, CH ₄ gas, H ₂ gas, and B ₂ H ₆ gas as material gases. The p-type a-SiCN is formed by plasma CVD using SiH ₄ gas, CH ₄ gas, NH ₃ gas, H ₂ gas, and B ₂ H ₆ gas as material gases.

  Even when the p-type amorphous film 32 is made of any of p-type a-SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN, the p-type amorphous film 32 is amorphous. Since it consists of a mass phase, the surface of the p-type single crystal silicon substrate 31 can be passivated.

  In addition, the photoelectric conversion element 10B may include an i-type amorphous film instead of the p-type amorphous film 32. In this case, the i-type amorphous film may be made of any of i-type a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN.

  i-type a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, i-type a-SiCN are formed by the plasma CVD method using the above-described material gases.

  Furthermore, the photoelectric conversion element 10 </ b> B may include a p-type polycrystalline silicon substrate instead of the p-type single crystal silicon substrate 31. The p-type polycrystalline silicon substrate has a specific resistance of 0.1 to 1.0 Ω · cm, and has a thickness of 200 μm, for example. Then, the surface of the p-type polycrystalline silicon substrate is honeycomb-textured by dry etching using the mask 20 shown in step (a) of FIG.

  Even when the photoelectric conversion element 10B includes a p-type polycrystalline silicon substrate, the p-type amorphous film 32 is made of the various materials described above. Further, when the photoelectric conversion element 10B includes a p-type polycrystalline silicon substrate, the photoelectric conversion element 10B may include an i-type amorphous film instead of the p-type amorphous film 32. The type amorphous film is made of the various materials described above.

  Further, the photoelectric conversion element 10B may further include an antireflection film in contact with the p-type amorphous film 32. In this case, the antireflection film is made of, for example, a silicon nitride film and has a thickness of 10 to 100 nm.

  As described above, according to the first embodiment, the photoelectric conversion element 10 having the p / n junction on the light incident side has a plane orientation other than (111) on the surface of the crystalline silicon substrate 1 on the light incident side. A crystalline silicon substrate 1 having an uneven structure including a recess 1c is provided. As a result, the amorphous film 2 is composed of an amorphous phase, not a crystalline phase. Therefore, the crystalline silicon substrate 1 can be passivated.

  In the photoelectric conversion element 10, minority carriers are easily recombined by an internal electric field present at the interface between the amorphous film 2 and the diffusion region 1 a, and easily reach the electrode 3. Therefore, the conversion efficiency of the photoelectric conversion element 10 can be improved.

[Embodiment 2]
FIG. 6 is a cross-sectional view showing the configuration of the photoelectric conversion element according to the second embodiment. Referring to FIG. 6, the photoelectric conversion element 100 according to the second embodiment includes a single crystal silicon substrate 41, an amorphous film 42, an oxide film 43, and electrodes 441 to 44n.

  Single crystal silicon substrate 41 is formed of an n-type single crystal silicon substrate or a p-type single crystal silicon substrate.

  Each of the n-type single crystal silicon substrate and the p-type single crystal silicon substrate has, for example, a (100) plane orientation and a specific resistance of 0.1 to 1.0 Ω · cm. Each of the n-type single crystal silicon substrate and the p-type single crystal silicon substrate has a thickness of 100 to 300 μm, for example, and preferably has a thickness of 100 to 200 μm.

  The single crystal silicon substrate 41 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 41c protruding in the incident direction of sunlight on one surface. The recess 41 c has a width of, for example, several μm in the in-plane direction of the single crystal silicon substrate 41.

  Single crystal silicon substrate 41 includes diffusion regions 411 to 41n on the other surface side. The diffusion regions 411, 413, ..., 41n-2, 41n have an n-type conductivity when the single-crystal silicon substrate 41 has an n-type conductivity, and the single-crystal silicon substrate 41 has a p-type. When it has a conductivity type, it has a p-type conductivity type. Diffusion regions 412, 414,..., 41 n-1 have p-type conductivity when single-crystal silicon substrate 41 has n-type conductivity, and single-crystal silicon substrate 41 has p-type conductivity. The n-type conductivity type.

  As described above, the diffusion regions 411, 413,..., 41n-2, 41n have the same conductivity type as that of the single crystal silicon substrate 41, and the diffusion regions 412, 414,. Has a conductivity type opposite to that of the single crystal silicon substrate 41.

  The diffusion regions 411, 413, ..., 41n-2, 41n and the diffusion regions 412, 414, ..., 41n-1 are alternately arranged in the in-plane direction of the single crystal silicon substrate 41.

The dopant concentration in each of the diffusion regions 411, 413,..., 41n-2, 41n is, for example, 1 × 10 ¹⁹ cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ , and the diffusion regions 412, 414,. The dopant concentration in each of 41n-1 is, for example, 1 × 10 ¹⁹ cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ .

  In addition, the diffusion regions 411, 413, ..., 41n-2, 41n and the diffusion regions 412, 414, ..., 41n-1 have a depth of 200 nm to 400 nm, for example.

  The amorphous film 42 is made of an amorphous phase and is formed in contact with the concavo-convex structure including the concave portion 41 c of the single crystal silicon substrate 41. The amorphous film 42 is made of an n-type amorphous film or an i-type amorphous film when the single crystal silicon substrate 41 has an n-type conductivity type. Further, the amorphous film 42 is made of a p-type amorphous film or an i-type amorphous film when the single crystal silicon substrate 41 has a p-type conductivity type. The amorphous film 42 has a thickness of 10 nm, for example.

Oxide film 43 is provided in contact with the back surface of single crystal silicon substrate 41 (the surface opposite to the surface on which recess 41c is formed). Then, oxide film 43 is made of, for example, SiO _2, its thickness is, for example, 10 nm to 100 nm.

  Each of the electrodes 441 to 44n is made of Ag, for example. The electrodes 441, 443,..., 44n-2, 44n are formed so as to be in contact with the diffusion regions 411, 413, ..., 41n-2, 41n through the oxide film 43, respectively. In addition, the electrodes 442, 444,..., 44n-1 are formed so as to be in contact with the diffusion regions 412, 414,.

  The diffusion regions 411, 413, ..., 41n-2, 41n and the diffusion regions 412, 414, ..., 41n-1 have the same length in the direction perpendicular to the paper surface of FIG. Further, the area occupancy ratio, which is the ratio of the entire area of the diffusion regions 412, 414,..., 41 n−1 to the area of the single crystal silicon substrate 41, is 60 to 93%. .., 41n-2, 41n, the area occupancy ratio, which is the ratio of the total area of the single crystal silicon substrate 41, is 5 to 20%.

  As described above, the area occupancy of the diffusion regions 412, 414,..., 41 n-1 is larger than the area occupancy of the diffusion regions 411, 413,. This is because the electrons and holes photoexcited in the silicon substrate 41 are easily separated by the pn junction, and the contribution ratio of the photoexcited electrons and holes to power generation is increased.

  As described above, since the concavo-convex structure including the hemispherical concave portion 41c protruding in the sunlight incident direction is formed on one surface of the single crystal silicon substrate 41, the surface of the single crystal silicon substrate 41 is It has a plane orientation different from the plane orientation of (111).

  As a result, even if the thin film is deposited on the surface of the single crystal silicon substrate 41 (the surface on which the concave portion 41c is formed), the thin film does not grow epitaxially, and the amorphous film 42 made of an amorphous phase is formed on the single crystal silicon substrate. 41 is formed on the surface.

  Therefore, the surface of the single crystal silicon substrate 41 can be passivated.

  Hereinafter, examples of the photoelectric conversion element 100 will be described.

(Example 3)
FIG. 7 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 3. Referring to FIG. 7, photoelectric conversion element 100A includes an n-type single crystal silicon substrate 51, an n-type amorphous film 52, an oxide film 53, and electrodes 541 to 54n.

  The n-type single crystal silicon substrate 51 has a (100) plane orientation and a specific resistance of 0.1 to 1.0 Ω · cm. The thickness of the n-type single crystal silicon substrate 51 is, for example, 200 μm.

  In addition, the n-type single crystal silicon substrate 51 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 51c protruding in the incident direction of sunlight on one surface. Recess 51 c has a width of several μm in the in-plane direction of n-type single crystal silicon substrate 51.

  Further, the n-type single crystal silicon substrate 51 has n-type diffusion regions 511, 513,..., 51-2, 51n and p-type diffusion regions 512, 514,. Include on the side. , 51-2, 51 n and p-type diffusion regions 512, 514,..., 51 n-1 are alternately arranged in the in-plane direction of the n-type single crystal silicon substrate 51. Is done.

The P concentration in each of the n-type diffusion regions 511, 513,..., 51-2, 51n is, for example, 5 × 10 ¹⁹ cm ⁻³ . In addition, the B concentration in each of the p-type diffusion regions 512, 514,..., 51n−1 is, for example, 8 × 10 ¹⁹ cm ⁻³ . As a result, the n-type diffusion regions 511, 513, ..., 51-2, 51n and the p-type diffusion regions 512, 514, ..., 51n-1 have a specific resistance of about 2 × 10 ^-3 Ω · cm. Have

  The depths of the n-type diffusion regions 511, 513,..., 51-2, 5n are, for example, 200 nm, and the depths of the p-type diffusion regions 512, 514,. 200 nm.

The n-type amorphous film 52 is made of an amorphous phase and is formed in contact with the concavo-convex structure including the concave portion 51 c of the n-type single crystal silicon substrate 51. The n-type amorphous film 52 is made of, for example, n-type a-Si and has a thickness of 10 nm. The P concentration in the n-type amorphous film 52 is, for example, 1 × 10 ¹⁷ cm ⁻³ to 1 × 10 ¹⁹ cm ⁻³ .

Oxide film 53 is formed in contact with the back surface of n-type single crystal silicon substrate 51 (the surface opposite to the surface where recess 51c is formed). Then, oxide film 53 is made of, for example, SiO _2, its thickness is, for example, 10 nm to 100 nm.

  Each of the electrodes 541 to 54n is made of Ag, for example. Electrodes 541, 543,..., 54n-2, 54n are formed so as to be in contact with n-type diffusion regions 511, 513,. In addition, the electrodes 542, 544,..., 54n-1 are formed so as to be in contact with the p-type diffusion regions 512, 514,.

  The n-type diffusion regions 511, 513, ..., 51n-2, 51n and the p-type diffusion regions 512, 514, ..., 51n-1 have the same length in the direction perpendicular to the paper surface of FIG. And the area occupation rate which is the ratio for which the whole area of p type diffused region 512,514, ..., 51n-1 occupies for the area of the n type single crystal silicon substrate 51 is 60 to 93%, and is n type. The area occupancy ratio, which is the ratio of the entire area of diffusion regions 511, 513,..., 51n-2, 51n to the area of n-type single crystal silicon substrate 51, is 5 to 20%.

  The reason why the area occupancy of the p-type diffusion regions 512, 514,..., 51n-1 and the n-type diffusion regions 511, 513,. In the conversion element 100, the area occupation ratios of the diffusion regions 412, 414,..., 41 n-1 and the diffusion regions 411, 413,. For the same reason.

  8 and 9 are first and second process diagrams showing a method of manufacturing the photoelectric conversion element 100A shown in FIG. 7, respectively.

  When the manufacture of the photoelectric conversion element 100A is started, the concavo-convex structure (= honeycomb texture) including the concave portions 51c is formed on one of the n-type single crystal silicon substrates 51 in accordance with the same steps (a) and (b) of FIG. It is formed on the surface (see steps (a) and (b) in FIG. 8). In this case, a mask 20 having a small hole 21 having a diameter of 2 to 3 μm is used.

  After the step (b), a PSG film is formed on the back surface of the n-type single crystal silicon substrate 51 (the surface opposite to the surface where the recess 51c is formed) by the APCVD method. Then, the formed PSG film is patterned by photolithography and etching to form a PSG film 55 (see step (c) in FIG. 8).

  Thereafter, the PSG film 55 / n-type single crystal silicon substrate 51 is heat-treated in a nitrogen atmosphere at a temperature of 800 ° C. for 1 hour to remove the PSG film 55. Thus, n-type diffusion regions 511, 513,..., 51n-2, 51n are formed (see step (d) in FIG. 8).

  Subsequently, a BSG film is formed on the back surface of the n-type single crystal silicon substrate 51 (the surface opposite to the surface on which the recess 51c is formed) by the APCVD method. Then, the formed BSG film is patterned by photolithography and etching to form a BSG film 56 (see step (e) in FIG. 8).

  Then, the BSG film 56 / n-type single crystal silicon substrate 51 is heat-treated in a nitrogen atmosphere at a temperature of 800 ° C. for 1 hour, and the BSG film 56 is removed. Thereby, p-type diffusion regions 512, 514,..., 51n-1 are formed (see step (f) in FIG. 9).

  Thereafter, the n-type single crystal silicon substrate 51 is oxidized in an oxygen gas atmosphere at a temperature of 975 ° C. for 10 minutes, and the oxide film 53 is opposite to the back surface of the n-type single crystal silicon substrate 51 (the surface opposite to the surface on which the recess 51c is formed). (Refer to step (g) in FIG. 9). In this case, an oxide film is also formed on one surface of the n-type single crystal silicon substrate 51 (the surface on which the recess 51c is formed), but this oxide film is removed by HF.

Then, an n-type amorphous film 52 made of n-type a-Si is formed on one surface of the n-type single crystal silicon substrate 51 (surface on which the recess 51c is formed) by a plasma CVD method (step of FIG. h)). In this case, the conditions for forming n-type a-Si are as follows: the flow rate of SiH ₄ gas is 20 sccm, the flow rate of H ₂ gas is 150 sccm, the flow rate of PH ₃ gas is 100 sccm, and the RF power of 13.56 MHz Is 16 to 80 mW / cm ² , and the reaction pressure is 13.3 Pa to 665 Pa. The PH ₃ gas is diluted with H ₂ gas, and its concentration is 0.2%.

  After step (h), contact is made by photolithography and etching so as to reach n-type diffusion regions 511, 513,..., 51n-2, 51n and p-type diffusion regions 512, 514,. Holes are formed in the oxide film 53, and electrodes 541 to 54n are formed. Thereby, the photoelectric conversion element 100A is completed (see step (i) in FIG. 9).

  In the step (h), when the n-type amorphous film 52 made of n-type a-Si is deposited on the n-type single crystal silicon substrate 51, the surface of the n-type single crystal silicon substrate 51 (= the recess 51c is formed). Since the concavo-convex structure (honeycomb texture) including the concave portion 51c is formed on the surface), the surface of the n-type single crystal silicon substrate 51 has a plane orientation other than (111). As a result, even if the thin film is deposited on the surface of the n-type single crystal silicon substrate 51 (= the surface where the recess 51c is formed), the thin film does not grow epitaxially. Therefore, the n-type amorphous film 52 made of n-type a-Si can be formed on the surface of the n-type single crystal silicon substrate 51 (= surface on which the recess 51c is formed).

  In the photoelectric conversion element 100A, sunlight is irradiated to the photoelectric conversion element 100A from the n-type amorphous film 52 side. The reflection of sunlight is suppressed by the honeycomb texture and enters the n-type single crystal silicon substrate 51 through the n-type amorphous film 52.

  Then, holes and electrons are photoexcited in the n-type single crystal silicon substrate 51. Then, the holes photoexcited in the vicinity of the interface between the n-type single crystal silicon substrate 51 and the n-type amorphous film 52 enter the interface between the n-type single crystal silicon substrate 51 and the n-type amorphous film 52 by diffusion. To reach.

The n-type single crystal silicon substrate 51 has an optical band gap of about 1.1 eV and an activation energy of 0.14 to 0.19 eV. The n-type amorphous film 52 (n-type a-Si) has an optical band gap of about 1.84 eV and an activation energy of 0.2 eV. Therefore, the valence band edge of the n-type amorphous film 52 (n-type a-Si) is energetically higher by 0.68 to 0.73 eV than the valence band edge of the n-type single crystal silicon substrate 51. . That is, the interface between the n-type single crystal silicon substrate 51 and the n-type amorphous film 52, the height for holes is present barrier _{B h} is 0.68～0.73EV.

As a result, holes reaching the interface between the n-type single crystal silicon substrate 51 and the n-type amorphous film 52 of this barrier B _h to n-type amorphous film 52 (n-type a-Si) in The movement is blocked, and recombination is suppressed by the passivation effect of the n-type amorphous film 52 (n-type a-Si) on the surface of the n-type single crystal silicon substrate 51, so that the back surface of the n-type single crystal silicon substrate 51. Spread to the side. Then, the holes reach the p-type diffusion regions 512, 514,..., 51n-1, and the electrodes 542, 544,. 54n-1.

  On the other hand, the photoexcited electrons reach the n-type diffusion regions 511, 513,..., 51n-2, 51n by diffusion, and are electroded from the n-type diffusion regions 511, 513,. 541, 543, ..., 54n-2, 54n.

  Then, the electrons reach the electrodes 542, 544,..., 54n-1 from the electrodes 541, 543,..., 54n-2, 54n via the load, and recombine with the holes.

  As described above, the photoelectric conversion element 100 </ b> A is a back contact photoelectric conversion element in which electrons and holes are extracted from the back side of the n-type single crystal silicon substrate 51. Further, since the photoelectric conversion element 100A includes the n-type single crystal silicon substrate 51 whose surface orientation on the light incident side is other than (111), the n-type amorphous film 52 made of an amorphous phase is an n-type. It is formed in contact with the surface of the single crystal silicon substrate 51 (= surface on which the recess 51c is formed). As a result, of the photogenerated holes and electrons, recombination of holes that are minority carriers is suppressed by the n-type amorphous film 52.

  Accordingly, in the back contact photoelectric conversion element 100A, the surface of the n-type single crystal silicon substrate 51 can be passivated.

  In the above description, the n-type amorphous film 52 is described as n-type a-Si. However, in the photoelectric conversion element 100A, the n-type amorphous film 52 is not limited to this. It may be made of any one of SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN. The n-type a-SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN are formed by the plasma CVD method using the above-described material gas.

  Even when the n-type amorphous film 52 is made of any of n-type a-SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN, the n-type amorphous film 52 is amorphous. Since it consists of a mass phase, the surface of the n-type single crystal silicon substrate 51 can be passivated.

  In addition, the photoelectric conversion element 100A may include an i-type amorphous film instead of the n-type amorphous film 52. In this case, the i-type amorphous film may be made of any of i-type a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN. The i-type a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN are formed by the plasma CVD method using the material gas described above.

  Further, the photoelectric conversion element 100A may further include an antireflection film in contact with the n-type amorphous film 52. In this case, the antireflection film is made of, for example, a silicon nitride film and has a thickness of 10 to 100 nm.

Example 4
FIG. 10 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 4. Referring to FIG. 10, photoelectric conversion element 100B includes a p-type single crystal silicon substrate 61, a p-type amorphous film 62, an oxide film 63, and electrodes 641 to 64n.

  The p-type single crystal silicon substrate 61 has a (100) plane orientation and a specific resistance of 0.1 to 1.0 Ω · cm. The thickness of the p-type single crystal silicon substrate 61 is, for example, 200 μm.

  The p-type single crystal silicon substrate 61 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 61c protruding in the sunlight incident direction on one surface. Recess 61 c has a width of several μm in the in-plane direction of n-type single crystal silicon substrate 61.

  Further, the p-type single crystal silicon substrate 61 has p-type diffusion regions 611, 613,..., 61-2, 61n and n-type diffusion regions 612, 614,. Include on the side. The p-type diffusion regions 611, 613, ..., 61-2, 61n and the n-type diffusion regions 612, 614, ..., 61n-1 are alternately arranged in the in-plane direction of the p-type single crystal silicon substrate 61. Is done.

The B concentration in each of the p-type diffusion regions 611, 613,..., 61-2, 61n is, for example, 8 × 10 ¹⁹ cm ⁻³ . Further, the P concentration in each of the n-type diffusion regions 612, 614,..., 61n−1 is, for example, 5 × 10 ¹⁹ cm ⁻³ . As a result, the p-type diffusion regions 611, 613, ..., 61-2, 61n and the n-type diffusion regions 612, 614, ..., 61n-1 have a specific resistance of about 2 × 10 ^-3 Ω · cm. Have

  The depths of the p-type diffusion regions 611, 613,..., 61-2, 61n are, for example, 200 nm, and the depths of the n-type diffusion regions 612, 614,. 200 nm.

The p-type amorphous film 62 is made of an amorphous phase, and is formed in contact with the concavo-convex structure including the concave portion 61 c of the p-type single crystal silicon substrate 61. The p-type amorphous film 62 is made of, for example, p-type a-Si and has a thickness of 10 nm. The B concentration in the p-type amorphous film 62 is, for example, 1 × 10 ¹⁷ to 1 × 10 ¹⁹ cm ⁻³ .

Oxide film 63 is provided in contact with the back surface of p-type single crystal silicon substrate 61 (the surface opposite to the surface where recess 61c is formed). Then, oxide film 63 is made of, for example, SiO _2, its thickness is, for example, 10 nm to 100 nm.

  Each of the electrodes 641 to 64n is made of Ag, for example. The electrodes 641, 643,..., 64n-2, 64n are formed so as to be in contact with the p-type diffusion regions 611, 613,. Further, the electrodes 642, 644,..., 64n-1 are formed so as to be in contact with the n-type diffusion regions 612, 614,.

  The p-type diffusion regions 611, 613, ..., 61-2, 61n and the n-type diffusion regions 612, 614, ..., 61n-1 have the same length in the direction perpendicular to the paper surface of FIG. And the area occupation rate which is the ratio which the whole area of n type diffused region 612,614, ..., 61n-1 occupies for the area of the p type single crystal silicon substrate 61 is 60 to 93%, and is p type. The area occupancy ratio, which is the ratio of the entire area of diffusion regions 611, 613,..., 61-2, 61n to the area of p-type single crystal silicon substrate 61, is 5 to 20%.

  The reason why the area occupation ratios of the n-type diffusion regions 612, 614,..., 61n-1 and the p-type diffusion regions 611, 613,. In the conversion element 100, the area occupation ratios of the diffusion regions 412, 414,..., 41 n-1 and the diffusion regions 411, 413, ..., 41 n-2, 41 n are set to 60 to 93% and 5 to 20%, respectively. For the same reason.

  The photoelectric conversion element 100B is manufactured according to the steps (a) to (i) shown in FIGS. In this case, a concavo-convex structure (honeycomb texture) having a concave portion 61 c is formed on one surface of the p-type single crystal silicon substrate 61 in steps (a) and (b) of FIG.

  Further, in steps (c) and (d) of FIG. 8, p-type diffusion regions 611, 613,..., 61n are formed, and in steps (e) of FIG. Mold diffusion regions 612, 614, ..., 61n-1 are formed.

  Further, in step (g) of FIG. 9, an oxide film 63 is formed. In step (h) of FIG. 9, a p-type amorphous film 62 is formed. In step (i) of FIG. 64n is formed.

  In the step (h), when the p-type amorphous film 62 made of p-type a-Si is deposited on the p-type single crystal silicon substrate 61, the surface of the p-type single crystal silicon substrate 61 (= the recess 61c is formed). Since the concavo-convex structure (honeycomb texture) including the concave portions 61c is formed on the surface), the surface of the p-type single crystal silicon substrate 61 has a plane orientation other than (111). As a result, even if the thin film is deposited on the surface of the p-type single crystal silicon substrate 61 (= the surface where the recess 61c is formed), the thin film does not grow epitaxially. Therefore, the p-type amorphous film 62 made of p-type a-Si can be formed on the surface of the p-type single crystal silicon substrate 61 (= the surface on which the recess 61c is formed).

  In the photoelectric conversion element 100B, sunlight is applied to the photoelectric conversion element 100B from the p-type amorphous film 62 side. The reflection of sunlight is suppressed by the honeycomb texture and enters the p-type single crystal silicon substrate 61 through the p-type amorphous film 62.

  Then, holes and electrons are photoexcited in the p-type single crystal silicon substrate 61. Then, the photoexcited electrons near the interface between the p-type single crystal silicon substrate 61 and the p-type amorphous film 62 reach the interface between the p-type single crystal silicon substrate 61 and the p-type amorphous film 62 by diffusion. To do.

The p-type single crystal silicon substrate 61 has an optical band gap of about 1.1 eV and an activation energy of 0.14 to 0.19 eV. The p-type amorphous film 62 (p-type a-Si) has an optical band gap of about 1.84 eV and an activation energy of 0.3 eV. Accordingly, the conduction band edge of the p-type amorphous film 62 (p-type a-Si) is energetically higher than the conduction band edge of the p-type single crystal silicon substrate 61 by 0.58 to 0.63 eV. That is, the interface between the p-type single crystal silicon substrate 61 and the p-type amorphous film 62, the height is present a barrier _{B e} is 0.58~0.63eV to electrons.

Movement resulting, to the p-type electron reaching the interface between the single crystal silicon substrate 61 and the p-type amorphous film 62, p-type amorphous film 62 (p-type a-Si) in this barrier B _e Is inhibited, and recombination is suppressed by the passivation effect of the p-type amorphous film 62 (p-type a-Si) on the surface of the p-type single crystal silicon substrate 61, and the back side of the p-type single crystal silicon substrate 61 Spreading to is promoted. Then, the electrons reach the n-type diffusion regions 612, 614,..., 61n-1, and the electrodes 642, 644,. -1.

  On the other hand, the photoexcited holes reach the p-type diffusion regions 611, 613,..., 61n-2, 61n by diffusion, and from the p-type diffusion regions 611, 613,. , 64n-2, 64n.

  Then, the electrons reach the electrodes 641, 643,..., 64n-2, 64n from the electrodes 642, 644,.

  As described above, the photoelectric conversion element 100 </ b> B is a back contact photoelectric conversion element in which electrons and holes are extracted from the back side of the p-type single crystal silicon substrate 61. Further, since the photoelectric conversion element 100B includes the p-type single crystal silicon substrate 61 whose surface orientation on the light incident side is other than (111), the p-type amorphous film 62 made of an amorphous phase is a p-type. It is formed in contact with the surface of the single crystal silicon substrate 61 (= surface on which the recess 61c is formed). As a result, recombination of electrons that are minority carriers among the photogenerated holes and electrons is suppressed by the p-type amorphous film 62.

  Accordingly, in the back contact photoelectric conversion element 100B, the surface of the p-type single crystal silicon substrate 61 can be passivated.

  In the above description, the p-type amorphous film 62 is p-type a-Si. However, in the photoelectric conversion element 100B, the p-type amorphous film 62 is not limited to this. It may consist of any one of SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN. Then, p-type a-SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN are formed by the plasma CVD method using the above-described material gas.

  Even when the p-type amorphous film 62 is made of any of p-type a-SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN, the p-type amorphous film 62 is amorphous. Since it consists of a mass phase, the surface of the p-type single crystal silicon substrate 61 can be passivated.

  In addition, the photoelectric conversion element 100B may include an i-type amorphous film instead of the p-type amorphous film 62. In this case, the i-type amorphous film may be made of any of i-type a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN. The i-type a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN are formed by the plasma CVD method using the material gas described above.

  Further, the photoelectric conversion element 100B may further include an antireflection film in contact with the p-type amorphous film 62. In this case, the antireflection film is made of, for example, a silicon nitride film and has a thickness of 10 to 100 nm.

[Embodiment 3]
FIG. 11 is a cross-sectional view showing the configuration of the photoelectric conversion element 200 according to the third embodiment. Referring to FIG. 11, photoelectric conversion element 200 according to Embodiment 3 includes crystalline silicon substrate 71, i-type amorphous film 72, amorphous film 73, transparent conductive film 74, and electrodes 75 and 77. And a passivation film 76.

  The crystalline silicon substrate 71 is made of an n-type single crystal silicon substrate or a p-type single crystal silicon substrate. The crystalline silicon substrate 71 is made of an n-type polycrystalline silicon substrate or a p-type polycrystalline silicon substrate.

  Each of the n-type single crystal silicon substrate and the p-type single crystal silicon substrate has, for example, a (100) plane orientation and a specific resistance of 0.1 to 1.0 Ω · cm. Each of the n-type single crystal silicon substrate and the p-type single crystal silicon substrate has a thickness of 100 to 300 μm, for example, and preferably has a thickness of 100 to 200 μm. The same applies to the n-type polycrystalline silicon substrate or the p-type polycrystalline silicon substrate except for the plane orientation.

  In addition, the crystalline silicon substrate 71 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 71 c protruding in the incident direction of sunlight on one surface. The recess 71 c has a width of, for example, several μm in the in-plane direction of the crystalline silicon substrate 71.

  The i-type amorphous film 72 is made of an amorphous phase and is formed in contact with the concavo-convex structure including the concave portion 71 c of the crystalline silicon substrate 71. The i-type amorphous film 72 has a thickness of 10 nm, for example.

  The amorphous film 73 is a p-type amorphous film when the crystalline silicon substrate 71 has n-type conductivity. The amorphous film 73 is an n-type amorphous film when the crystalline silicon substrate 71 has a p-type conductivity. The amorphous film 73 is formed in contact with the i-type amorphous film 72 and has a thickness of 10 nm, for example.

The transparent conductive film 74 is formed in contact with the amorphous film 73. The transparent conductive film 74 is made of any of ITO (Indium Tin Oxide), SnO ₂ and ZnO.

  The electrode 75 is formed in contact with the transparent conductive film 74. The electrode 75 is made of Ag, for example.

  The passivation film 76 is formed in contact with the other surface of the crystalline silicon substrate 71 (= the surface opposite to the surface where the recess 71 c is formed). The passivation film 76 is made of a silicon oxide film and has a thickness of 10 to 100 nm, for example.

  The electrode 77 is formed in contact with the crystalline silicon substrate 71 and the passivation film 76. The electrode 77 is made of, for example, Al.

  In the photoelectric conversion element 200, sunlight is incident from the transparent conductive film 74 side. The photoelectric conversion element 200 has a structure in which an i-type amorphous film 72 and an amorphous film 73 (made of an n-type amorphous film or a p-type amorphous film) are sequentially stacked on a crystalline silicon substrate 71. Become. As a result, in the photoelectric conversion element 200, a pin junction that separates photoexcited electrons and holes from each other is provided on the incident side of sunlight.

  As described above, since the concavo-convex structure including the hemispherical concave portion 71c protruding in the sunlight incident direction is formed on one surface of the crystalline silicon substrate 71, the surface of the crystalline silicon substrate 71 is (111 ) And a different plane orientation.

  As a result, even if the thin film is deposited on the surface of the crystalline silicon substrate 71 = the surface on which the recess 71c is formed), the thin film does not grow epitaxially, and the i-type amorphous film 72 made of an amorphous phase is formed on the crystalline silicon substrate. 71 is formed on the surface.

  Therefore, the surface of the crystalline silicon substrate 71 can be passivated.

  Hereinafter, examples of the photoelectric conversion element 200 will be described.

(Example 5)
FIG. 12 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 5. Referring to FIG. 12, photoelectric conversion element 200A includes an n-type single crystal silicon substrate 81, an i-type amorphous film 82, a p-type amorphous film 83, a transparent conductive film 84, and electrodes 85 and 87. And a passivation film 86.

  N-type single crystal silicon substrate 81 has a (100) plane orientation and a specific resistance of 0.1 to 1.0 Ω · cm. The n-type single crystal silicon substrate 81 has a thickness of 200 μm, for example.

  In addition, the n-type single crystal silicon substrate 81 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 81c protruding in the sunlight incident direction on one surface. The recess 81c has a width of, for example, several μm in the in-plane direction of the n-type single crystal silicon substrate 81.

  The i-type amorphous film 82 is made of an amorphous phase, and is formed in contact with the concavo-convex structure including the concave portion 81 c of the n-type single crystal silicon substrate 81. The i-type amorphous film 82 is made of, for example, i-type a-Si and has a thickness of 10 nm.

  The p-type amorphous film 83 is made of an amorphous phase and is formed in contact with the i-type amorphous film 82. The p-type amorphous film 83 is made of, for example, p-type a-Si and has a thickness of 10 nm.

The transparent conductive film 84 is formed in contact with the p-type amorphous film 83. The transparent conductive film 84 is made of any one of ITO, SnO ₂ , and ZnO.

  The electrode 85 is formed in a comb shape in contact with the transparent conductive film 84. The electrode 85 is made of Ag, for example.

Passivation film 86 is formed in contact with the other surface of n-type single crystal silicon substrate 81 (= the surface opposite to the surface where recess 81 c is formed). The passivation film 86 is made of SiO ₂ and has a thickness of 10 to 100 nm, for example.

  Electrode 87 is formed in contact with n-type single crystal silicon substrate 81 and passivation film 86. The electrode 87 is made of, for example, Al.

  13 and 14 are first and second process diagrams showing a method of manufacturing the photoelectric conversion element 200A shown in FIG. 12, respectively.

  When the manufacture of the photoelectric conversion element 200A is started, the concavo-convex structure (honeycomb texture) including the concave portion 81c is formed on one surface of the n-type single crystal silicon substrate 81 in accordance with the same steps (a) and (b) of FIG. (See steps (a) and (b) of FIG. 13). In this case, the mask 20 having the small holes 21 is used.

After the step (b), the n-type single crystal silicon substrate 81 is oxidized in an oxygen gas atmosphere at a temperature of 975 ° C. for 10 minutes, and a passivation film 86 made of SiO ₂ is formed on the back surface of the n-type single crystal silicon substrate 81 ( It is formed on the surface opposite to the surface where the recess 81c is formed (see step (c) in FIG. 13).

In the step (c), an oxide film (SiO ₂ ) is also formed on one surface of the n-type single crystal silicon substrate 81 (the surface where the recess 81c is formed). Therefore, the oxide film formed on one surface of the n-type single crystal silicon substrate 81 is removed by HF, and one surface of the n-type single crystal silicon substrate 81 is terminated with hydrogen.

  Then, an i-type amorphous film 82 made of i-type a-Si and a p-type amorphous film 83 made of p-type a-Si are sequentially stacked on one surface of an n-type single crystal silicon substrate 81 by plasma CVD. (See step (d) in FIG. 13).

In this case, the formation conditions of i-type a-Si are as follows: the flow rate of SiH ₄ gas is 10 sccm, the flow rate of H ₂ gas is 100 sccm, and the RF power of 13.56 MHz is 16 to 80 mW / cm ^2. The pressure is 13.3 Pa to 665 Pa. The p-type a-Si is formed under the conditions that the flow rate of SiH ₄ gas is ₂ sccm, the flow rate of H ₂ gas is 42 sccm, the flow rate of B ₂ H ₆ gas is 12 sccm, and the RF power of 13.56 MHz. Is 16 to 80 mW / cm ² , and the reaction pressure is 13.3 Pa to 665 Pa. _{Incidentally,} B 2 _{H 6} gas is diluted with _{H 2} gas, its concentration is 0.1%.

  After the step (d), a transparent conductive film 84 is formed in contact with the p-type amorphous film 83 by sputtering (see step (e) in FIG. 13).

  Then, the electrode 85 is formed in contact with the transparent conductive film 84 (see step (f) in FIG. 14). Thereafter, a contact hole is formed in the passivation film 86 by photolithography and etching, and an electrode 87 is formed. Thus, the photoelectric conversion element 200A is completed (see step (g) in FIG. 14).

  In the step (d), when the i-type amorphous film 82 made of i-type a-Si is formed on one surface of the n-type single crystal silicon substrate 81 (surface on which the recess 81c is formed), Since the crystalline silicon substrate 81 includes a concavo-convex structure (honeycomb texture) including a concave portion 81 c on one surface thereof, the surface of the n-type single crystal silicon substrate 81 has a plane orientation other than (111). As a result, even if the thin film is deposited on the surface of the n-type single crystal silicon substrate 81 (= the surface where the recess 81c is formed), the thin film does not grow epitaxially. Therefore, the i-type amorphous film 82 made of i-type a-Si can be formed on the surface of the n-type single crystal silicon substrate 81 (= surface on which the recess 81c is formed).

  In the photoelectric conversion element 200A, sunlight is irradiated to the photoelectric conversion element 200A from the transparent conductive film 84 side. The reflection of sunlight is suppressed by the honeycomb texture and enters the n-type single crystal silicon substrate 81 through the transparent conductive film 84, the p-type amorphous film 83 and the i-type amorphous film 82.

  Then, holes and electrons are photoexcited in n-type single crystal silicon substrate 81. Then, the photoexcited holes move by diffusion toward the interface between the i-type amorphous film 82 and the n-type single crystal silicon substrate 81, and the i-type amorphous film 82 and the n-type single crystal silicon substrate 81. To reach the interface.

  Since i-type amorphous film 82 is made of an amorphous phase as described above, the surface of n-type single crystal silicon substrate 81 is passivated. As a result, recombination of holes is suppressed at the interface between the i-type amorphous film 82 and the n-type single crystal silicon substrate 81, and the p-type amorphous film 83, the i-type amorphous film 82, and the n-type The p-type amorphous film 83 is reached by the internal electric field of the pin junction formed by the single crystal silicon substrate 81, and reaches the electrode 85 through the transparent conductive film 84.

  On the other hand, the photoexcited electrons move to the back side of the n-type single crystal silicon substrate 81 by diffusion. Then, electrons that reach the interface between the n-type single crystal silicon substrate 81 and the passivation film 86 are suppressed from recombination and reach the electrode 87 by diffusion. The electrons that have reached the electrode 87 reach the electrode 85 from the electrode 87 via a load and recombine with the holes.

  Thus, since the photoelectric conversion element 200A includes the n-type single crystal silicon substrate 81 whose surface orientation on the light incident side is other than (111), the i-type amorphous film 82 made of an amorphous phase is provided. It is formed in contact with the surface of n-type single crystal silicon substrate 81 (= surface on which recess 81 c is formed). As a result, of the photogenerated holes and electrons, recombination of holes that are minority carriers is suppressed by the i-type amorphous film 82 and reaches the p-type amorphous film 83 by the internal electric field of the pin junction. It becomes easy to do.

  Therefore, the surface of the n-type single crystal silicon substrate 81 can be passivated.

  In the above description, the i-type amorphous film 82 is i-type a-Si. However, in the photoelectric conversion element 200A, the i-type amorphous film 82 is not limited to this. It may consist of any one of SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN. The i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN are formed by the plasma CVD method using the above-described material gas.

  Even when the i-type amorphous film 82 is made of any one of i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN, the i-type amorphous film 82 is amorphous. Since it consists of a mass phase, the surface of the n-type single crystal silicon substrate 81 can be passivated.

  In the above description, the p-type amorphous film 83 is p-type a-Si. However, in the photoelectric conversion element 200A, the p-type amorphous film 83 is not limited to this. It may consist of any of a-SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN. Then, p-type a-SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN are formed by the plasma CVD method using the above-described material gas.

  Furthermore, the photoelectric conversion element 200 </ b> A may include an n-type polycrystalline silicon substrate instead of the n-type single crystal silicon substrate 81. The n-type polycrystalline silicon substrate has a specific resistance of 0.1 to 1.0 Ω · cm, and has a thickness of 200 μm, for example. Then, the surface of the n-type polycrystalline silicon substrate is honeycomb-textured by dry etching using the mask 20 shown in step (a) of FIG.

  Even when the photoelectric conversion element 200A includes an n-type polycrystalline silicon substrate, the i-type amorphous film 82 and the p-type amorphous film 83 are made of the various materials described above. Even if the i-type amorphous film 82 is formed in contact with the n-type polycrystalline silicon substrate, the i-type amorphous film 82 has an amorphous phase and can passivate the surface of the n-type polycrystalline silicon substrate.

(Example 6)
FIG. 15 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 6. Referring to FIG. 15, photoelectric conversion element 200B includes a p-type single crystal silicon substrate 91, an i-type amorphous film 92, an n-type amorphous film 93, a transparent conductive film 94, and electrodes 95 and 97. And a passivation film 96.

  The p-type single crystal silicon substrate 91 has a (100) plane orientation and a specific resistance of 0.1 to 1.0 Ω · cm. The p-type single crystal silicon substrate 91 has a thickness of 200 μm, for example.

  In addition, the p-type single crystal silicon substrate 91 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 91c protruding in the sunlight incident direction on one surface. And the recessed part 91c has a width | variety of several micrometers in the in-plane direction of the p-type single crystal silicon substrate 91, for example.

  The i-type amorphous film 92 is made of an amorphous phase, and is formed in contact with the concavo-convex structure including the concave portion 91 c of the p-type single crystal silicon substrate 91. The i-type amorphous film 92 is made of, for example, i-type a-Si and has a thickness of 10 nm.

  The n-type amorphous film 93 is made of an amorphous phase and is formed in contact with the i-type amorphous film 92. The n-type amorphous film 93 is made of, for example, n-type a-Si and has a thickness of 10 nm.

The transparent conductive film 94 is formed in contact with the n-type amorphous film 93. The transparent conductive film 94 is made of any one of ITO, SnO ₂ , and ZnO.

  The electrode 95 is formed in a comb shape in contact with the transparent conductive film 94. The electrode 95 is made of Ag, for example.

The passivation film 96 is formed in contact with the other surface of the p-type single crystal silicon substrate 91 (= the surface opposite to the surface where the recess 91c is formed). The passivation film 96 is made of SiO ₂ and has a thickness of 10 to 100 nm, for example.

  Electrode 97 is formed in contact with p-type single crystal silicon substrate 91 and passivation film 96. The electrode 97 is made of, for example, Al.

  The photoelectric conversion element 200B is manufactured according to steps (a) to (g) shown in FIGS. 13 and 14.

  In this case, in steps (a) and (b) of FIG. 13, a concavo-convex structure (honeycomb texture) including a concave portion 91 c is formed on one surface of the p-type single crystal silicon substrate 91.

  Further, in step (c) of FIG. 13, passivation film 96 is formed on the back surface of p-type single crystal silicon substrate 91 (the surface opposite to the surface on which recess 91 c is formed).

  Further, in step (d) of FIG. 13, the i-type amorphous film 92 (i-type a-Si) and the n-type amorphous film 93 (n-type a-Si) are formed on one side of the p-type single crystal silicon substrate 91. Are sequentially laminated on the surface (the surface on which the recess 91c is formed).

  Further, in step (e) of FIG. 13, a transparent conductive film 94 is formed in contact with the n-type amorphous film 93.

  Further, in step (f) of FIG. 14, the electrode 95 is formed in contact with the transparent conductive film 94, and in step (g) of FIG. 14, the electrode 97 is in contact with the p-type single crystal silicon substrate 91 and the passivation film 96. It is formed.

  In the step (d), when the i-type amorphous film 92 made of i-type a-Si is formed on one surface of the p-type single crystal silicon substrate 91, the p-type single crystal silicon substrate 91 Since the surface has a concavo-convex structure (honeycomb texture) including the concave portion 91c, the surface of the p-type single crystal silicon substrate 91 has a plane orientation other than (111). As a result, even if the thin film is deposited on the surface of the p-type single crystal silicon substrate 91 (= the surface where the recess 91c is formed), the thin film does not grow epitaxially. Accordingly, the i-type amorphous film 92 made of an amorphous phase can be formed on the surface of the p-type single crystal silicon substrate 91 (= the surface on which the recess 91c is formed).

  In the photoelectric conversion element 200B, sunlight is irradiated to the photoelectric conversion element 200B from the transparent conductive film 94 side. The reflection of sunlight is suppressed by the honeycomb texture and enters the p-type single crystal silicon substrate 91 through the transparent conductive film 94, the n-type amorphous film 93 and the i-type amorphous film 92.

  Then, holes and electrons are photoexcited in the p-type single crystal silicon substrate 91. Then, the photoexcited electrons move by diffusion toward the interface between the i-type amorphous film 92 and the p-type single crystal silicon substrate 91, and the i-type amorphous film 92 and the p-type single crystal silicon substrate 91 To reach the interface.

  Since i-type amorphous film 92 is made of an amorphous phase as described above, the surface of p-type single crystal silicon substrate 91 is passivated. As a result, recombination of holes is suppressed at the interface between the i-type amorphous film 92 and the p-type single crystal silicon substrate 91, and the n-type amorphous film 93, the i-type amorphous film 92, and the p-type The n-type amorphous film 93 is reached by an internal electric field of a pin junction formed by the single crystal silicon substrate 91, and reaches the electrode 95 through the transparent conductive film 94.

  On the other hand, the photoexcited holes move to the back side of the p-type single crystal silicon substrate 91 by diffusion. Then, the holes reaching the interface between the p-type single crystal silicon substrate 91 and the passivation film 96 are suppressed from recombination and reach the electrode 97 by diffusion. The electrons that have reached the electrode 95 reach the electrode 97 from the electrode 95 via a load and recombine with the holes.

  Thus, since the photoelectric conversion element 200B includes the p-type single crystal silicon substrate 91 whose surface orientation on the light incident side is other than (111), the i-type amorphous film 92 made of an amorphous phase is provided. It is formed in contact with the surface of the p-type single crystal silicon substrate 91 (= the surface where the recess 91c is formed). As a result, among the photogenerated holes and electrons, electrons which are minority carriers are suppressed from recombination by the i-type amorphous film 92 and reach the n-type amorphous film 93 by the internal electric field of the pin junction. It becomes easy to do.

  Therefore, the surface of the p-type single crystal silicon substrate 91 can be passivated.

  In the above description, the i-type amorphous film 92 is i-type a-Si. However, in the photoelectric conversion element 200B, the i-type amorphous film 92 is not limited to this. It may consist of any one of SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN. The i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN are formed by the plasma CVD method using the above-described material gas.

  Even when the i-type amorphous film 92 is made of any one of i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN, the i-type amorphous film 92 is amorphous. Since it consists of a solid phase, the surface of the p-type single crystal silicon substrate 91 can be passivated.

  In the above description, the n-type amorphous film 93 is n-type a-Si. However, in the photoelectric conversion element 200B, the n-type amorphous film 93 is not limited to this. It may consist of any of a-SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN. The n-type a-SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN are formed by the plasma CVD method using the above-described material gas.

  Furthermore, the photoelectric conversion element 200 </ b> B may include a p-type polycrystalline silicon substrate instead of the p-type single crystal silicon substrate 91. The p-type polycrystalline silicon substrate has a specific resistance of 0.1 to 1.0 Ω · cm, and has a thickness of 200 μm, for example. Then, the surface of the p-type polycrystalline silicon substrate is honeycomb-textured by dry etching using the mask 20 shown in step (a) of FIG.

  Even when the photoelectric conversion element 200B includes a p-type polycrystalline silicon substrate, the i-type amorphous film 92 and the n-type amorphous film 93 are made of the various materials described above. Even if the i-type amorphous film 92 is formed in contact with the p-type polycrystalline silicon substrate, the i-type amorphous film 92 has an amorphous phase and can passivate the surface of the p-type polycrystalline silicon substrate.

[Embodiment 4]
FIG. 16 is a cross-sectional view illustrating a configuration of the photoelectric conversion element according to the fourth embodiment. Referring to FIG. 16, the photoelectric conversion element 300 according to the fourth embodiment includes a single crystal silicon substrate 101, an amorphous film 102, i-type amorphous films 111 to 11n, and amorphous films 121 to 12m. 131-13m-1 and electrodes 141-14n.

  The single crystal silicon substrate 101 has, for example, a (100) plane orientation and a specific resistance of 0.1 to 1.0 Ω · cm. The single crystal silicon substrate 101 has a thickness of 100 to 300 μm, for example, and preferably has a thickness of 100 to 200 μm.

  Further, the single crystal silicon substrate 101 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 101c protruding in the incident direction of sunlight on one surface. The recess 101 c has a width of several μm in the in-plane direction of the single crystal silicon substrate 101.

  The amorphous film 102 is provided in contact with the concavo-convex structure (honeycomb texture) including the concave portion 101 c of the single crystal silicon substrate 101. The amorphous film 102 has an n-type or i-type conductivity type when the single crystal silicon substrate 101 has an n-type conductivity type, and has a p-type conductivity type when the single crystal silicon substrate 101 has a p-type conductivity type. , P-type or i-type conductivity type.

  Each of i-type amorphous films 111 to 11n is provided in contact with the back surface of single-crystal silicon substrate 101 (the surface opposite to the surface where recess 101c is formed). Each of the i-type amorphous films 111 to 11n is made of, for example, i-type a-Si and has a film thickness of, for example, 10 nm.

  The amorphous films 121 to 12m have an n-type conductivity when the single crystal silicon substrate 101 has an n-type conductivity type, and have a p-type when the single crystal silicon substrate 101 has a p-type conductivity type. Have the conductivity type. As described above, the amorphous films 121 to 12 m have the same conductivity type as that of the single crystal silicon substrate 101.

  The amorphous films 121 to 12m are provided in contact with the i-type amorphous films 111, 113, ..., 11n-2, 11n, respectively.

  When the single crystal silicon substrate 101 has an n-type conductivity type, the amorphous films 131 to 13m-1 have a p-type conductivity type, and when the single crystal silicon substrate 101 has a p-type conductivity type, n-type conductivity. Thus, the amorphous films 131 to 13m have a conductivity type opposite to that of the single crystal silicon substrate 101.

  The amorphous films 131 to 13m-1 are provided in contact with the i-type amorphous films 112, 114, ..., 11n-1, respectively.

  The electrodes 141, 143, ..., 14n-2, 14n are provided in contact with the amorphous films 121 to 12m, respectively. The electrodes 142, 144,..., 14n-1 are provided in contact with the amorphous films 131 to 13m-1, respectively. And each of the electrodes 141-14n consists of Ag, for example.

  The i-type amorphous films 111 to 11n, the amorphous films 121 to 12m, and the amorphous films 131 to 13m-1 have the same length in the direction perpendicular to the paper surface of FIG. Further, the amorphous films 121 to 12m have the same width as the widths of the i-type amorphous films 111, 113,..., 11n-2, 11n, respectively, in the in-plane direction of the single crystal silicon substrate 101. . Further, the amorphous films 131 to 13m-1 have the same width as that of the i-type amorphous films 112, 114, ..., 11n-1 in the in-plane direction of the single crystal silicon substrate 101, respectively. . The area occupancy ratio, which is the ratio of the entire area of the amorphous films 131 to 13m−1 to the area of the single crystal silicon substrate 101, is 60 to 93%, and the entire area of the amorphous films 121 to 12m is The area occupation ratio, which is the ratio of the area to the area of the single crystal silicon substrate 101, is 5 to 20%.

  As described above, the area occupancy of the amorphous films 131 to 13m-1 is larger than the area occupancy of the amorphous films 121 to 12m because the electrons and holes photoexcited in the single crystal silicon substrate 101 are used. This is because it is easy to be separated by the pin junction, and the contribution ratio of photoexcited electrons and holes to power generation is increased.

  Since one surface of the single crystal silicon substrate 101 has a concavo-convex structure including a hemispherical recess 101 c protruding in the sunlight incident direction as described above, the surface of the single crystal silicon substrate 101 is It has a plane orientation different from the plane orientation of (111).

  As a result, even if a thin film is deposited on the surface of the single crystal silicon substrate 101, the thin film does not grow epitaxially, and an amorphous film 102 made of an amorphous phase is formed on the surface of the single crystal silicon substrate 101.

  Therefore, the surface of the single crystal silicon substrate 101 can be passivated.

  Hereinafter, examples of the photoelectric conversion element 300 will be described.

(Example 7)
FIG. 17 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 7. Referring to FIG. 17, photoelectric conversion element 300A includes an n-type single crystal silicon substrate 201, n-type amorphous films 202, 221 to 22m, i-type amorphous films 211 to 21n, and a p-type amorphous film. It includes a membrane 231 to 23m-1 and electrodes 241 to 24n.

  The n-type single crystal silicon substrate 201 has a (100) plane orientation and a specific resistance of 0.1 to 1.0 Ω · cm. The n-type single crystal silicon substrate 201 has a thickness of 200 μm, for example.

  In addition, the n-type single crystal silicon substrate 201 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 201c protruding in the incident direction of sunlight on one surface. And the recessed part 201c has a width | variety of several micrometers in the in-plane direction of the n-type single crystal silicon substrate 201, for example.

  The n-type amorphous film 202 is formed in contact with the concavo-convex structure including the concave portion 201 c of the n-type single crystal silicon substrate 201. The n-type amorphous film 202 is made of, for example, n-type a-Si and has a thickness of 10 nm.

  The i-type amorphous films 211 to 21n are provided in contact with the back surface of the n-type single crystal silicon substrate 201 (the surface opposite to the surface where the recesses 201c are formed). Each of the i-type amorphous films 211 to 21n is made of, for example, i-type a-Si and has a film thickness of, for example, 10 nm.

  The n-type amorphous films 221 to 22m are provided in contact with the i-type amorphous films 211, 213, ..., 21n-2, 21n, respectively.

  The p-type amorphous films 231 to 23m−1 are provided in contact with the i-type amorphous films 212, 214,.

  The electrodes 241, 243,..., 24n-2, 24n are provided in contact with the n-type amorphous films 221 to 22m, respectively. The electrodes 242, 244,..., 24n-1 are provided in contact with the p-type amorphous films 231 to 23m-1, respectively. Each of the electrodes 241 to 24n is made of Ag, for example.

  The i-type amorphous films 211 to 21n, the n-type amorphous films 221 to 22m, and the p-type amorphous films 231 to 23m-1 have the same length in the direction perpendicular to the paper surface of FIG. In addition, the n-type amorphous films 221 to 22m have the widths of the i-type amorphous films 211, 213,..., 21n-2, 21n in the in-plane direction of the n-type single crystal silicon substrate 201, respectively. Have the same width. Further, the p-type amorphous films 231 to 23m−1 are respectively formed in the in-plane direction of the n-type single crystal silicon substrate 201 with the widths of the i-type amorphous films 212, 214,. Have the same width. The area occupation ratio, which is the ratio of the entire area of the p-type amorphous films 231 to 23m−1 to the area of the n-type single crystal silicon substrate 201, is 60 to 93%. The area occupation ratio, which is the ratio of the entire area of 221 to 22 m to the area of the n-type single crystal silicon substrate 201, is 5 to 20%.

  The reason why the area occupation ratio is set in this way is as described above.

  18 to 20 are first to third process diagrams showing a method of manufacturing the photoelectric conversion element 300A shown in FIG.

  When the manufacture of the photoelectric conversion element 300A is started, the concavo-convex structure (honeycomb texture) including the concave portion 201c is formed on one surface of the n-type single crystal silicon substrate 201 by the same steps as steps (a) and (b) of FIG. (See steps (a) and (b) in FIG. 18). In this case, the mask 20 having the small holes 21 is used.

Then, the i-type a-Si film 220 and the n-type a-Si film 230 are sequentially stacked on the other surface of the n-type single crystal silicon substrate 201 (the surface opposite to the surface where the recesses 201c are formed) by the plasma CVD method. (See step (c) in FIG. 18). In this case, each of the i-type a-Si film 220 and the n-type a-Si film 230 has a thickness of 10 nm. The i-type a-Si film 220 is formed under the conditions that the flow rate of SiH ₄ gas is 10 sccm, the flow rate of H ₂ gas is 100 sccm, and the RF power of 13.56 MHz is 16 to 80 mW / cm ² . The reaction pressure is 13.3 Pa to 665 Pa. The n-type a-Si film 230 is formed under the conditions of SiH ₄ gas flow rate of 20 sccm, H ₂ gas flow rate of 150 sccm, PH ₃ gas flow rate of 100 sccm, and 13.56 MHz RF power. Is 16 to 80 mW / cm ² , and the reaction pressure is 13.3 Pa to 665 Pa. The PH ₃ gas is diluted with H ₂ gas, and its concentration is 0.2%.

  After the step (c), an n-type amorphous film 202 (n-type a-Si) is formed on one surface of the n-type single crystal silicon substrate 201 (surface on which the recesses 201c are formed) by a plasma CVD method. (See step (d) in FIG. 18). In this case, the formation condition of the n-type amorphous film 202 is the same as the formation condition of the n-type a-Si film 230.

  After the step (d), a resist is applied to the entire surface of the n-type a-Si film 230, and the applied resist is patterned by photolithography to form a resist pattern 240 (see step (e) in FIG. 18). .

  Then, the n-type a-Si film 230 is etched using the resist pattern 240 as a mask. As a result, n-type amorphous films 221 to 22m are formed (see step (f) in FIG. 19).

Thereafter, the p-type a-Si film 250 is formed on the other surface of the n-type single crystal silicon substrate 201 (the surface opposite to the surface where the recesses 201c are formed) by plasma CVD (step (g) in FIG. 19). reference). In this case, the p-type a-Si film 260 is formed on the resist pattern 240. Further, the formation conditions of the p-type a-Si films 250 and 260 are that the flow rate of SiH ₄ gas is ₂ sccm, the flow rate of H ₂ gas is 42 sccm, the flow rate of B ₂ H ₆ gas is 12 sccm, and The 56 MHz RF power is 16 to 80 mW / cm ² , and the reaction pressure is 13.3 Pa to 665 Pa. _{Incidentally,} B 2 _{H 6} gas is diluted with _{H 2} gas, its concentration is 0.1%.

  Then, the resist pattern 240 is removed. In this case, the p-type a-Si film 260 is removed by lift-off (see step (h) in FIG. 19).

  Subsequently, a resist is applied to the entire surfaces of the n-type amorphous films 221 to 22m and the p-type a-Si film 250, and the applied resist is patterned by photolithography to form a resist pattern 270 (FIG. 19). Step (i)).

  Then, the i-type a-Si film 220 and the p-type a-Si film 250 are etched using the resist pattern 270 as a mask, and the resist pattern 270 is removed. As a result, i-type amorphous films 211 to 21n and p-type amorphous films 231 to 23m-1 are formed (see step (j) in FIG. 20).

  Thereafter, a resist is applied to the entire surface of the n-type amorphous films 221 to 22m and the p-type amorphous films 231 to 23m-1, and the applied resist is patterned by photolithography to form a resist pattern 280 ( Step (k) in FIG. 20).

  Then, Ag is formed on the n-type amorphous films 221 to 22m and the p-type amorphous films 231 to 23m-1 by vapor deposition or sputtering using the resist pattern 280 as a mask, and the resist pattern 280 is removed. Thus, the electrodes 241 to 24n are formed, and the photoelectric conversion element 300A is completed (see step (l) in FIG. 20).

  In the step (d) of FIG. 18, when the n-type amorphous film 202 made of n-type a-Si is deposited on the n-type single crystal silicon substrate 201, Since the concavo-convex structure (honeycomb texture) including the recesses 201c is formed, the surface of the n-type single crystal silicon substrate 201 has a plane orientation other than (111). As a result, even if the thin film is deposited on the surface of the n-type single crystal silicon substrate 201 (= the surface where the recess 201c is formed), the thin film does not grow epitaxially. Therefore, the n-type amorphous film 202 made of n-type a-Si can be formed on the surface of the n-type single crystal silicon substrate 201 (= the surface on which the recesses 201c are formed).

  In the photoelectric conversion element 300A, sunlight is irradiated to the photoelectric conversion element 300A from the n-type amorphous film 202 side. The reflection of sunlight is suppressed by the honeycomb texture and enters the n-type single crystal silicon substrate 201 through the n-type amorphous film 202.

  Then, holes and electrons are photoexcited in the n-type single crystal silicon substrate 201. Then, the holes photoexcited in the vicinity of the interface between the n-type single crystal silicon substrate 201 and the n-type amorphous film 202 enter the interface between the n-type single crystal silicon substrate 201 and the n-type amorphous film 202 by diffusion. To reach.

The n-type single crystal silicon substrate 201 has an optical band gap of about 1.1 eV and an activation energy of 0.14 to 0.19 eV. The n-type amorphous film 202 (n-type a-Si) has an optical band gap of about 1.84 eV and an activation energy of 0.2 eV. Therefore, the interface between the n-type single crystal silicon substrate 51 and the n-type amorphous film 52, as described above, the height is 0.68~0.73eV barrier _{B h} for holes is present To do.

As a result, holes reaching the interface between the n-type single crystal silicon substrate 201 and the n-type amorphous film 202 of this barrier _{B h} to n-type amorphous film 202 (n-type a-Si) in The back surface of the n-type single crystal silicon substrate 201 is restrained from being recombined by the passivation effect of the n-type amorphous film 202 (n-type a-Si) on the surface of the n-type single crystal silicon substrate 201. Spread to the side. Then, the holes reach the vicinity of the i-type amorphous films 212, 214,..., 21n-1, and the p-type amorphous films 231 to 23m-1 and the i-type amorphous films 212, 214. ,..., 21n-1 and the n-type single-crystal silicon substrate 201, i-type amorphous films 212, 214,. , 24n-1 through the films 231 to 23m-1.

  On the other hand, the photoexcited electrons reach the vicinity of the i-type amorphous films 211, 213,..., 21n-2, 21n by diffusion, and the i-type amorphous films 211, 213,. .., 24n-2, 24n through −2, 21n and n-type amorphous films 221-22m.

  Then, the electrons reach the electrodes 242, 244, ..., 24n-1 from the electrodes 241, 243, ..., 24n-2, 24n via the load, and recombine with the holes.

  Thus, the photoelectric conversion element 300 </ b> A is a back contact photoelectric conversion element in which electrons and holes are extracted from the back side of the n-type single crystal silicon substrate 201. In addition, since the photoelectric conversion element 200A includes the n-type single crystal silicon substrate 201 whose surface orientation on the light incident side is other than (111), the n-type amorphous film 202 made of an amorphous phase is an n-type. It is formed in contact with the surface of the single crystal silicon substrate 201 (= the surface where the recesses 201c are formed). As a result, recombination of holes that are minority carriers among the photogenerated holes and electrons is suppressed by the n-type amorphous film 202.

  Therefore, in the back contact photoelectric conversion element 300A, the surface of the n-type single crystal silicon substrate 201 can be passivated.

  In the above description, the n-type amorphous film 202 is n-type a-Si. However, in the photoelectric conversion element 300A, the n-type amorphous film 202 is not limited to this. It may be made of any one of SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN. The n-type a-SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN are formed by the plasma CVD method using the above-described material gas.

  Even when the n-type amorphous film 202 is made of any of n-type a-SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN, the n-type amorphous film 202 is amorphous. Since it consists of a mass phase, the surface of the n-type single crystal silicon substrate 201 can be passivated.

  In addition, the photoelectric conversion element 300A may include an i-type amorphous film instead of the n-type amorphous film 202. In this case, the i-type amorphous film may be made of any of i-type a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN. The i-type a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN are formed by the plasma CVD method using the material gas described above.

  Further, the i-type amorphous films 211 to 21n have been described as i-type a-Si. However, in the photoelectric conversion element 300A, the i-type amorphous films 211 to 21n are not limited to the i-type amorphous films 211 to 21n. It may consist of any of a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN. The i-type a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN are formed by the plasma CVD method using the material gas described above.

  Furthermore, although the n-type amorphous films 221 to 22m have been described as n-type a-Si, in the photoelectric conversion element 300A, the n-type amorphous films 221 to 22m are not limited to the n-type a-Si. It may consist of any of a-SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN. The n-type a-SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN are formed by the plasma CVD method using the above-described material gas.

  Further, the p-type amorphous films 231 to 23m-1 have been described as p-type a-Si. However, the photoelectric conversion element 300A is not limited thereto, and the p-type amorphous films 231 to 23m-1 are not limited thereto. May consist of any of p-type a-SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN. Then, p-type a-SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN are formed by the plasma CVD method using the above-described material gas.

  Furthermore, the photoelectric conversion element 300A may further include an antireflection film in contact with the n-type amorphous film 202. In this case, the antireflection film is made of, for example, a silicon nitride film and has a thickness of 10 to 100 nm.

(Example 8)
FIG. 21 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 8. Referring to FIG. 21, a photoelectric conversion element 300B includes a p-type single crystal silicon substrate 301, a p-type amorphous film 302, i-type amorphous films 311 to 31n, and p-type amorphous films 321 to 321. 32m, n-type amorphous films 331 to 33m-1, and electrodes 341 to 34n.

  The p-type single crystal silicon substrate 301 has a (100) plane orientation and a specific resistance of 0.1 to 1.0 Ω · cm. The p-type single crystal silicon substrate 301 has a thickness of 200 μm, for example.

  In addition, the p-type single crystal silicon substrate 301 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 301 c protruding in the incident direction of sunlight on one surface. The recess 301c has a width of, for example, several μm in the in-plane direction of the p-type single crystal silicon substrate 301.

  The p-type amorphous film 302 is formed in contact with the concavo-convex structure including the concave portion 301 c of the p-type single crystal silicon substrate 301. The p-type amorphous film 302 is made of, for example, p-type a-Si and has a thickness of 10 nm.

  The i-type amorphous films 311 to 31n are provided in contact with the back surface of the p-type single crystal silicon substrate 301 (the surface opposite to the surface where the recesses 301c are formed). Each of the i-type amorphous films 311 to 31n is made of i-type a-Si, for example, and has a film thickness of 10 nm, for example.

  The p-type amorphous films 321 to 32m are provided in contact with the i-type amorphous films 311, 313,..., 31n-2, 31n, respectively.

  The n-type amorphous films 331 to 33m−1 are provided in contact with the i-type amorphous films 312, 314,.

  The electrodes 341, 343,..., 34n-2, 34n are provided in contact with the p-type amorphous films 321 to 32m, respectively. The electrodes 342, 344,..., 34n-1 are provided in contact with the n-type amorphous films 331 to 33m-1, respectively. And each of the electrodes 341-34n consists of Ag, for example.

  The i-type amorphous films 311 to 31n, the p-type amorphous films 321 to 32m, and the n-type amorphous films 331 to 33m-1 have the same length in the direction perpendicular to the paper surface of FIG. In addition, the p-type amorphous films 321 to 32m have the widths of the i-type amorphous films 311, 313,..., 31n-2, 31n in the in-plane direction of the p-type single crystal silicon substrate 301, respectively. Have the same width. Further, the n-type amorphous films 331 to 33m−1 are respectively formed in the in-plane direction of the p-type single crystal silicon substrate 301 with the widths of the i-type amorphous films 312, 314,. Have the same width. The area occupation ratio, which is the ratio of the total area of the n-type amorphous films 331 to 33m−1 to the area of the p-type single crystal silicon substrate 301, is 60 to 93%. The area occupation ratio, which is the ratio of the entire area of 321 to 32 m to the area of the p-type single crystal silicon substrate 301, is 5 to 20%.

  The reason why the area occupation ratio is set in this way is as described above.

  The photoelectric conversion element 300B is manufactured according to the steps (a) to (l) shown in FIGS.

  In this case, in steps (a) and (b) of FIG. 18, an uneven portion (honeycomb texture) including the recess 301 c is formed on one surface of the p-type single crystal silicon substrate 301.

  In step (d) shown in FIG. 18, a p-type amorphous film 302 is formed by plasma CVD.

  Further, in step (c) to step (j) shown in FIG. 18, i-type amorphous films 311 to 31n, p-type amorphous films 321 to 32m, and n-type amorphous films 331 to 33m are formed. It is formed.

  Further, in steps (k) and (l) of FIG. 20, electrodes 341 to 34n are formed.

  In the step (d) of FIG. 18, when a p-type amorphous film 302 made of p-type a-Si is deposited on the p-type single crystal silicon substrate 301, one surface of the p-type single crystal silicon substrate 301 is formed on one surface. Since the concavo-convex structure (honeycomb texture) including the concave portion 301c is formed, the surface of the p-type single crystal silicon substrate 301 has a plane orientation other than (111). As a result, even if the thin film is deposited on the surface of the p-type single crystal silicon substrate 301 (= the surface where the recess 301c is formed), the thin film does not grow epitaxially. Accordingly, the p-type amorphous film 302 made of p-type a-Si can be formed on the surface of the p-type single crystal silicon substrate 301 (= the surface on which the concave portion 301c is formed).

  In the photoelectric conversion element 300B, sunlight is irradiated to the photoelectric conversion element 300B from the p-type amorphous film 302 side. The reflection of sunlight is suppressed by the honeycomb texture and is incident on the p-type single crystal silicon substrate 301 through the p-type amorphous film 302.

  Then, holes and electrons are photoexcited in the p-type single crystal silicon substrate 301. Then, the photoexcited electrons near the interface between the p-type single crystal silicon substrate 301 and the p-type amorphous film 302 reach the interface between the p-type single crystal silicon substrate 301 and the p-type amorphous film 302 by diffusion. To do.

The p-type single crystal silicon substrate 301 has an optical band gap of about 1.1 eV and an activation energy of 0.14 to 0.19 eV. The p-type amorphous film 302 (p-type a-Si) has an optical band gap of about 1.84 eV and an activation energy of 0.3 eV. Therefore, the interface between the p-type single crystal silicon substrate 301 and the p-type amorphous film 302, as described above, the height is present a barrier _{B e} is 0.58~0.63eV the electronic .

Movement resulting, to the p-type electron reaching the interface between the single crystal silicon substrate 301 and the p-type amorphous film 302, p-type amorphous film 302 (p-type a-Si) in this barrier _{B e} Is prevented, and recombination is suppressed by the passivation effect of the p-type amorphous film 302 (p-type a-Si) on the surface of the p-type single crystal silicon substrate 301, and the back side of the p-type single crystal silicon substrate 301. Spreading to is promoted. Then, the electrons reach the vicinity of the i-type amorphous films 312, 314, ..., 31n-1, and the n-type amorphous films 331 to 33m-1 and the i-type amorphous films 312, 314, .., 31n-1 and the p-type single crystal silicon substrate 301, i-type amorphous films 312, 314,. , 34n-1 through 331 to 33m-1.

  On the other hand, the photoexcited holes reach the vicinity of the i-type amorphous films 311, 313,..., 31n-2, 31n by diffusion, and the i-type amorphous films 311, 313,. The electrodes 341, 343,..., 34n-2, 34n are reached through 31n-2, 31n and p-type amorphous films 321-32m.

  Then, the electrons reach the electrode electrodes 341, 343,..., 34n-2, 34n from the electrodes 342, 344,..., 34n-1 via the load, and recombine with the holes.

  As described above, the photoelectric conversion element 300 </ b> B is a back contact photoelectric conversion element in which electrons and holes are extracted from the back side of the p-type single crystal silicon substrate 301. Further, since the photoelectric conversion element 300B includes the p-type single crystal silicon substrate 301 whose surface orientation on the light incident side is other than (111), the p-type amorphous film 302 made of an amorphous phase is a p-type. It is formed in contact with the surface of the single crystal silicon substrate 301 (= the surface where the recess 301 c is formed). As a result, recombination of electrons that are minority carriers among the photogenerated holes and electrons is suppressed by the p-type amorphous film 302.

  Accordingly, in the back contact photoelectric conversion element 300B, the surface of the p-type single crystal silicon substrate 301 can be passivated.

  In the above description, the p-type amorphous film 302 is p-type a-Si. However, in the photoelectric conversion element 300B, the p-type amorphous film 302 is not limited to this. It may consist of any one of SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN. Then, p-type a-SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN are formed by the plasma CVD method using the above-described material gas.

  Even when the p-type amorphous film 302 is made of any of p-type a-SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN, the p-type amorphous film 302 is amorphous. Since it is made of a solid phase, the surface of the p-type single crystal silicon substrate 301 can be passivated.

  In addition, the photoelectric conversion element 300B may include an i-type amorphous film instead of the p-type amorphous film 302. In this case, the i-type amorphous film may be made of any of i-type a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN. The i-type a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN are formed by the plasma CVD method using the material gas described above.

  Further, the i-type amorphous films 311 to 31n have been described as i-type a-Si. However, in the photoelectric conversion element 300B, the i-type amorphous films 311 to 31n are not limited to this. It may consist of any of a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN. The i-type a-Si, i-type a-SiGe, i-type a-SiN, i-type a-SiC, and i-type a-SiCN are formed by the plasma CVD method using the material gas described above.

  Further, the p-type amorphous films 321 to 32m have been described as p-type a-Si. However, in the photoelectric conversion element 300B, the p-type amorphous films 321 to 32m are not limited to the p-type a-Si. It may consist of any of a-SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN. Then, p-type a-SiGe, p-type a-SiN, p-type a-SiC, and p-type a-SiCN are formed by the plasma CVD method using the above-described material gas.

  Further, the n-type amorphous films 331 to 33m-1 have been described as n-type a-Si. However, in the photoelectric conversion element 300B, the n-type amorphous films 331 to 33m-1 are not limited thereto. May consist of any of n-type a-SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN. The n-type a-SiGe, n-type a-SiN, n-type a-SiC, and n-type a-SiCN are formed by the plasma CVD method using the above-described material gas.

  Further, the photoelectric conversion element 300B may further include an antireflection film in contact with the p-type amorphous film 302. In this case, the antireflection film is made of, for example, a silicon nitride film and has a thickness of 10 to 100 nm.

  The photoelectric conversion element 10 described above is a photoelectric conversion element having a p / n junction on the light incident side of the crystalline silicon substrate 1, and the photoelectric conversion element 100 is formed on the opposite side of the single crystal silicon substrate 41 from the light incident side. It is a photoelectric conversion element having an n junction.

  Therefore, the photoelectric conversion element according to the embodiment of the present invention has a first conductivity type, and a crystalline silicon substrate having a concavo-convex structure including a hemispherical recess protruding in the sunlight incident direction formed on one surface And a first amorphous film formed in contact with the concavo-convex structure including the hemispherical concave portion of the crystalline silicon substrate and made of an amorphous phase, and one surface side of the crystalline silicon substrate or the other of the crystalline silicon substrate. What is necessary is just to provide the p / n junction part formed in the surface side.

  When manufacturing a photoelectric conversion element having such a structure, when a thin film is deposited on a concavo-convex structure including a hemispherical concave portion of a crystalline silicon substrate, the thin film does not epitaxially grow and consists of an amorphous phase. As a result, the first amorphous film made of the amorphous phase is formed in contact with the concavo-convex structure including the hemispherical concave portion of the crystalline silicon substrate. Therefore, since the surface of the crystalline silicon substrate can be passivated, the photoelectric conversion element according to the embodiment of the present invention only needs to have the above-described configuration.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to a photoelectric conversion element.

  1,71 Crystal silicon substrate, 1a, 1b, 11a, 11b, 31a, 31b, 411-41n Diffusion region, 1c, 11c, 31c, 41c, 51c, 61c Recess, 2, 73, 102, 121-12m, 131- 13m-1 amorphous film, 3, 6, 13, 16, 36, 75, 77, 85, 87, 95, 97, 141-14n, 241-24n, 341-34n, 441-44n electrodes, 5, 15 35, 76, 86, 96 Passivation film 10, 10A, 10B, 100, 100A, 100B, 200, 200A, 200B, 300, 300A, 300B Photoelectric conversion element 11, 51, 81, 201 n-type single crystal silicon Substrate, 12, 52, 93, 221-2m, 331-33m-1 n-type amorphous film, 20 mask, 21 small hole, 31, 61 , 91, 301 p-type single crystal silicon substrate, 32, 62, 231-23m-1, 302, 321-32m p-type amorphous film, 41, 101 single crystal silicon substrate, 42 amorphous film, 43, 53 63, oxide film, 72, 82, 92, 111-11n, 211-21n, 311-31n i-type amorphous film, 74, 84, 94 transparent conductive film, 83, 202 p-type amorphous film, 511, , 51n-2, 51n, 612, 614, ..., 61n-1 n-type diffusion region, 512, 514, ..., 51n-1, 611, 613, ..., 61n- 2,61n p-type diffusion region.

Claims (16)

A crystalline silicon substrate having a first conductivity type and having a concavo-convex structure including a hemispherical concave portion protruding in the incident direction of sunlight formed on one surface;
A first amorphous film formed in contact with the concavo-convex structure including the hemispherical concave portion of the crystalline silicon substrate and made of an amorphous phase;
A photoelectric conversion element comprising: a p / n junction formed on the one surface side of the crystalline silicon substrate or the other surface side of the crystalline silicon substrate. The p / n junction is
A bulk region of the crystalline silicon substrate;
2. The photoelectric conversion according to claim 1, further comprising: a diffusion region provided in contact with the bulk region on the one surface side of the crystalline silicon substrate and having a second conductivity type opposite to the first conductivity type. element.   The photoelectric conversion element according to claim 2, wherein the crystalline silicon substrate is a single crystal silicon substrate.   The photoelectric conversion element according to claim 2, wherein the crystalline silicon substrate is a polycrystalline silicon substrate. The crystalline silicon substrate is a single crystal silicon substrate,
The p / n junction is
A bulk region of the single crystal silicon substrate;
A first diffusion region provided in contact with the bulk region on the other surface side of the single crystal silicon substrate and having a second conductivity type opposite to the first conductivity type;
In the in-plane direction of the single crystal silicon substrate, adjacent to the first diffusion region, in contact with the bulk region, provided on the other surface side of the single crystal silicon substrate, and having the first conductivity type The photoelectric conversion element according to claim 1, comprising two diffusion regions. The first conductivity type is n-type,
The photoelectric conversion element according to claim 2, wherein the second conductivity type is p-type. The first conductivity type is p-type,
The photoelectric conversion element according to any one of claims 2 to 5, wherein the second conductivity type is an n-type. A single crystal silicon substrate having a first conductivity type and having a concavo-convex structure including a hemispherical concave portion protruding in the incident direction of sunlight on one surface;
A first amorphous film formed in contact with the concavo-convex structure including the hemispherical concave portion of the single crystal silicon substrate and made of an amorphous phase;
A second amorphous film formed in contact with the other surface of the single crystal silicon substrate and made of a non-doped amorphous phase;
A third amorphous film that is disposed in contact with the second amorphous film and has a second conductivity type opposite to the first conductivity type and is made of an amorphous phase;
A fourth amorphous layer adjacent to the third amorphous film and in contact with the second amorphous film, having the first conductivity type and comprising an amorphous phase; A photoelectric conversion element comprising a film. The first conductivity type is n-type,
The photoelectric conversion element according to claim 8, wherein the second conductivity type is a p-type. The first amorphous film includes n-type amorphous silicon germanium, n-type amorphous silicon, n-type amorphous silicon nitride, n-type amorphous silicon carbide, n-type amorphous silicon carbon nitride, i-type amorphous silicon germanium, and i-type. It consists of any one of amorphous silicon, i-type amorphous silicon nitride, i-type amorphous silicon carbide and i-type amorphous silicon carbon nitride,
The second amorphous film is made of any of i-type amorphous silicon germanium, i-type amorphous silicon, i-type amorphous silicon nitride, i-type amorphous silicon carbide, and i-type amorphous silicon carbon nitride,
The third amorphous film is composed of any one of p-type amorphous silicon germanium, p-type amorphous silicon, p-type amorphous silicon nitride, p-type amorphous silicon carbide, and p-type amorphous silicon carbon nitride,
The fourth amorphous film is made of any one of n-type amorphous silicon germanium, n-type amorphous silicon, n-type amorphous silicon nitride, n-type amorphous silicon carbide, and n-type amorphous silicon carbon nitride. The photoelectric conversion element as described in 2. The first conductivity type is p-type,
The photoelectric conversion element according to claim 8, wherein the second conductivity type is an n-type. The first amorphous film includes p-type amorphous silicon germanium, p-type amorphous silicon, p-type amorphous silicon nitride, p-type amorphous silicon carbide, p-type amorphous silicon carbon nitride, i-type amorphous silicon germanium, and i-type. It consists of any one of amorphous silicon, i-type amorphous silicon nitride, i-type amorphous silicon carbide and i-type amorphous silicon carbon nitride,
The second amorphous film is made of any of i-type amorphous silicon germanium, i-type amorphous silicon, i-type amorphous silicon nitride, i-type amorphous silicon carbide, and i-type amorphous silicon carbon nitride,
The third amorphous film is made of any of n-type amorphous silicon germanium, n-type amorphous silicon, n-type amorphous silicon nitride, n-type amorphous silicon carbide, and n-type amorphous silicon carbon nitride,
The fourth amorphous film is made of any one of p-type amorphous silicon germanium, p-type amorphous silicon, p-type amorphous silicon nitride, p-type amorphous silicon carbide, and p-type amorphous silicon carbon nitride. The photoelectric conversion element as described in 2. A crystalline silicon substrate having a first conductivity type and having a concavo-convex structure including a hemispherical concave portion protruding in the incident direction of sunlight formed on one surface;
A first amorphous film that is formed in contact with the concavo-convex structure including the hemispherical concave portion of the crystalline silicon substrate, and is made of a non-doped amorphous phase;
A second amorphous film formed in contact with the first amorphous film, having a second conductivity type opposite to the first conductivity type, and comprising an amorphous phase; A photoelectric conversion element comprising:   The first amorphous film is made of any one of i-type amorphous silicon germanium, i-type amorphous silicon, i-type amorphous silicon nitride, i-type amorphous silicon carbide, and i-type amorphous silicon carbon nitride. The photoelectric conversion element as described in 2. The crystalline silicon substrate comprises an n-type single crystal silicon substrate or an n-type polycrystalline silicon substrate,
The second amorphous film is made of any one of p-type amorphous silicon germanium, p-type amorphous silicon, p-type amorphous silicon nitride, p-type amorphous silicon carbide, and p-type amorphous silicon carbon nitride. Or the photoelectric conversion element of Claim 14. The crystalline silicon substrate comprises a p-type single crystal silicon substrate or a p-type polycrystalline silicon substrate,
The second amorphous film is made of any of n-type amorphous silicon germanium, n-type amorphous silicon, n-type amorphous silicon nitride, n-type amorphous silicon carbide, and n-type amorphous silicon carbon nitride. Or the photoelectric conversion element of Claim 14.

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