JP2013110187A - Photoelectric conversion element and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element capable of improving conversion efficiency.SOLUTION: A photoelectric conversion element 10 comprises a crystal silicon substrate 1, a light incident layer 3, electrodes 4, 6, and a passivation film 5. An uneven structure is not formed on a light receiving face 1a of the crystal silicon substrate 1. Also, the crystal silicon substrate 1 includes a diffusion region 2 having a conductivity type opposite to the crystal silicon substrate 1 in contact with the light receiving face 1a. The diffusion region 2 includes a diffusion region 2a, and a diffusion region 2b having a dopant concentration higher than that of the diffusion region 2a. The light incident layer 3 is arranged on the light receiving face 1a of the crystal silicon substrate 1, and has an uneven structure including a recess part 3a projecting in an incident direction of sunlight. The electrode 4 penetrates through the light incident layer 3, and is arranged in contact with the diffusion region 2b. The passivation film 5 is arranged in contact with a rear face of the crystal silicon substrate 1. The electrode 6 is arranged in contact with the rear face of the crystal silicon substrate 1 and the passivation film 5.

Description

  The present invention relates to a photoelectric conversion element and a manufacturing method thereof.

  Conventionally, a solar cell in which a concavo-convex structure is formed on a light receiving surface of a silicon substrate is known (Patent Document 1).

This solar cell includes a silicon substrate, an n-type diffusion layer, a p ⁺ -type diffusion layer, a passivation film, an insulating film, and first and second electrodes. The n-type diffusion layer is formed on the light receiving surface of the silicon substrate. The passivation film is disposed so as to cover the n-type diffusion layer. The first electrode penetrates the passivation film and is connected to the n ⁺⁺ type diffusion layer in the n type diffusion layer.

The insulating film is formed in contact with the back surface opposite to the light receiving surface of the silicon substrate. The p ⁺ type diffusion layer is formed on a part of the back surface opposite to the light receiving surface of the silicon substrate. The second electrode penetrates the insulating film and is connected to the p ⁺ type diffusion layer.

JP 2011-142210 A

  However, in the conventional solar cell, since the concavo-convex structure is formed on the light receiving surface side of the silicon substrate, insufficient cleaning of the light receiving surface of the silicon substrate occurs in the manufacturing process of the solar cell, and a uniform diffusion layer is formed. This is difficult, and the recombination of carriers increases as the area of the interface between the silicon substrate and the passivation film increases. As a result, there exists a problem that the characteristic of a solar cell falls.

  Therefore, according to the embodiment of the present invention, a photoelectric conversion element capable of improving the conversion efficiency is provided.

  Moreover, according to this Embodiment, the manufacturing method of the photoelectric conversion element which can improve conversion efficiency is provided.

  According to the embodiment of the present invention, the photoelectric conversion element includes a semiconductor substrate, a light incident layer, and a bonding portion. The semiconductor substrate is made of crystalline silicon in which the uneven structure is not formed on the light receiving surface. The light incident layer is formed on the light receiving surface of the semiconductor substrate, and has a concavo-convex structure having a hemispherical cross-sectional shape in which the surface on the light incident side protrudes in the incident direction of sunlight. The bonding portion is disposed on the light receiving surface side of the semiconductor substrate or on the side opposite to the light receiving surface.

  According to the embodiment of the present invention, a method for manufacturing a photoelectric conversion element includes a first method of forming a light incident layer on a light receiving surface of a semiconductor substrate made of crystalline silicon on which a light receiving surface is not formed with an uneven structure. A second step of forming a concavo-convex structure having a hemispherical cross-sectional shape protruding in the incident direction of sunlight on the surface of the light incident layer on the light incident side, opposite to the light receiving surface side or the light receiving surface of the semiconductor substrate And a third step of forming a joint on the side.

  In the photoelectric conversion element according to the embodiment of the present invention, the light incident layer is formed on the light receiving surface of the semiconductor substrate, and the light incident side surface of the light incident layer protrudes in the sunlight incident direction. The concavo-convex structure has a cross-sectional shape. And the uneven structure is not formed in the light-receiving surface of a semiconductor substrate. As a result, the light receiving surface of the semiconductor substrate is sufficiently cleaned in the manufacturing process of the photoelectric conversion element. In addition, the area of the interface between the light incident layer and the semiconductor substrate is smaller than when the light receiving surface of the semiconductor substrate is made uneven, and carrier recombination at the interface between the light incident layer and the light receiving surface of the semiconductor substrate is suppressed. . Furthermore, when the junction is disposed on the light receiving surface side of the semiconductor substrate, a diffusion region or a semiconductor thin film for forming the junction is formed uniformly.

  Therefore, the conversion efficiency of the photoelectric conversion element can be improved.

  In addition, the method for manufacturing a photoelectric conversion element according to the embodiment of the present invention includes a step of forming a light incident layer on a light receiving surface of a semiconductor substrate on which the uneven structure is not formed on the light receiving surface, and a light incident side of the light incident layer. Forming a concavo-convex structure having a hemispherical cross-sectional shape protruding in the incident direction of sunlight on the surface of the semiconductor substrate, and a step of forming a bonding portion on the light receiving surface side of the semiconductor substrate or on the side opposite to the light receiving surface. As a result, the light receiving surface of the semiconductor substrate is sufficiently cleaned in the manufacturing process of the photoelectric conversion element. In addition, the area of the interface between the light incident layer and the semiconductor substrate is smaller than when the light receiving surface of the semiconductor substrate is made uneven, and carrier recombination at the interface between the light incident layer and the light receiving surface of the semiconductor substrate is suppressed. . Furthermore, when the junction is disposed on the light receiving surface side of the semiconductor substrate, a diffusion region or a semiconductor thin film for forming the junction is formed uniformly.

  Therefore, the conversion efficiency of the photoelectric conversion element can be improved.

It is sectional drawing which shows the structure of the photoelectric conversion element by Embodiment 1 of this invention. It is sectional drawing which shows the specific example of the light-incidence layer shown in FIG. It is a top view of the light-incidence layer shown in FIG. 3 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 1. FIG. It is a 1st process drawing which shows the manufacturing method of the photoelectric conversion element shown in FIG. It is a 2nd process drawing which shows the manufacturing method of the photoelectric conversion element shown in FIG. It is a 2nd process drawing which shows the manufacturing method of the photoelectric conversion element shown in FIG. 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. It is a 1st process drawing which shows the manufacturing method of the photoelectric conversion element shown in FIG. It is a 2nd process drawing which shows the manufacturing method of the photoelectric conversion element shown in FIG. FIG. 11 is a third process diagram illustrating a method for manufacturing the photoelectric conversion element illustrated in FIG. 10. It is a 4th process drawing which shows the manufacturing method of the photoelectric conversion element shown in FIG. 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. 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. 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. 23 is a first process diagram showing a method of manufacturing the photoelectric conversion element shown in FIG. 22. FIG. 23 is a second process diagram illustrating a method of manufacturing the photoelectric conversion element illustrated in FIG. 22. FIG. 23 is a third process diagram illustrating a method for manufacturing the photoelectric conversion element illustrated in FIG. 22. FIG. 23 is a fourth process diagram illustrating the method for manufacturing the photoelectric conversion element illustrated in FIG. 22. 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. Amorphous silicon carbide (a-SiC), amorphous silicon oxide (a-SiO), amorphous silicon nitride (a-SiN), amorphous silicon carbon nitride (a-SiCN), amorphous silicon germanium (a-SiGe) and amorphous germanium Similarly, (a-Ge) means that an H atom is contained. Furthermore, “crystalline silicon” refers to single crystal silicon or polycrystalline silicon.

[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, a light incident layer 3, electrodes 4 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.

The crystalline silicon substrate 1 has no uneven structure on the light receiving surface 1a. The crystalline silicon substrate 1 includes a diffusion region 2 in contact with the light receiving surface 1a. The diffusion region 2 has a conductivity type opposite to that of the crystalline silicon substrate 1 and has a depth of, for example, 200 nm. The diffusion region 2 includes diffusion regions 2a and 2b. The dopant concentration of the diffusion region 2b is higher than the dopant concentration of the diffusion region 2a. For example, the diffusion region 2a has a dopant concentration of 1 × 10 ¹⁹ cm ⁻³ and the diffusion region 2b has a dopant concentration of 1 × 10 ²⁰ cm ⁻³ .

  The light incident layer 3 is disposed in contact with the light receiving surface 1a of the crystalline silicon substrate 1 and has a thickness of, for example, several μm. Moreover, in the light incident layer 3, the uneven structure containing the hemispherical recessed part 3a protruded in the incident direction of sunlight is formed in the light incident side surface. This uneven structure is a so-called “honeycomb texture”. And the recessed part 3a has a width | variety of several micrometers in the in-plane direction of the crystalline silicon substrate 1, for example.

  The electrode 4 penetrates the light incident layer 3 and is formed in contact with the diffusion region 2 b of the crystalline silicon substrate 1. The electrode 4 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 light receiving surface 1a). The passivation film 5 is made of silicon dioxide (SiO ₂ ) 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).

  FIG. 2 is a cross-sectional view showing a specific example of the light incident layer 3 shown in FIG. With reference to FIG. 2, the light incident layer 3 includes any one of the light incident layers 31 to 33.

With reference to FIG. 2A, the light incident layer 31 is formed of a passivation film 311. The passivation film 311 is made of, for example, SiO ₂ and has a film thickness of, for example, several μm. And the passivation film 311 has the recessed part 311a which has the same shape and the same size as the recessed part 3a on the surface by the side of light incidence.

With reference to FIG. 2B, the light incident layer 32 is made of an antireflection film 321. The antireflection film 321 is made of, for example, silicon nitride (Si ₃ N ₄ ) or SiO ₂ and has a thickness of, for example, several μm. The antireflection film 321 has a concave portion 321a having the same shape and size as the concave portion 3a on the surface on the light incident side.

Referring to FIG. 2C, the light incident layer 33 includes a passivation film 331 and an antireflection film 332. The passivation film 331 is made of, for example, SiO ₂ and has a thickness of 1 μm to ₂ μm, for example. The antireflection film 332 is made of, for example, Si ₃ N ₄ or SiO ₂ and has a film thickness of, for example, 1 μm to ₂ μm. In this case, the thickness of the passivation film 331 may be the same as or different from the thickness of the antireflection film 332. The antireflection film 332 has a concave portion 332a having the same shape and size as the concave portion 3a on the surface on the light incident side. In the light incident layer 33, a passivation film 331 is formed in contact with the light receiving surface 1 a of the crystalline silicon substrate 1.

  In the light incident layer 33, a recess may be formed so as to reach the passivation film 331. In this case, both the passivation film 331 and the antireflection film 332 are uneven.

  FIG. 3 is a plan view of the light incident layer 3 shown in FIG. With reference to (a) of FIG. 3, the recessed part 3a is formed between the line 3b and the line 3b. The line 3b has a circular or arc shape. Accordingly, the recesses 3a are arranged concentrically.

  Referring to FIG. 3B, the recess 3a is formed between the line 3c and the line 3c. The line 3 c has a straight shape and is arranged along two sides of a quadrangle that is a planar shape of the light incident layer 3. Accordingly, the recesses 3a are arranged in a stripe shape.

  In FIG. 3B, the line 3c is arranged along the vertical direction on the paper surface of FIG. 3, but in the first embodiment, the line 3c is not limited to this, and the line 3c is shown in FIG. You may arrange | position along the horizontal direction in the paper surface.

  In addition, the line 3c is arranged in parallel to two sides of the quadrangle that is the planar shape of the light incident layer 3. However, in Embodiment 1, the line 3c is not limited to this, and the line 3c may be a square side and an arbitrary side. You may arrange | position along the direction which makes an angle.

  Referring to FIG. 3C, the recess 3a is formed in a region surrounded by two lines 3c and two lines 3d. Each of the lines 3c and 3d has a linear shape, the line 3c is arranged along two sides of a quadrangle that is a planar shape of the light incident layer 3, and the line 3d is a plane of the light incident layer 3. It is arranged along the other two sides of the quadrangular shape. Therefore, the recess 3a is arranged in a mesh shape.

  Each of the lines 3c and 3d is arranged in parallel with two sides of a quadrangle that is a planar shape of the light incident layer 3. However, in the first embodiment, each of the lines 3c and 3d is not limited thereto. May be arranged along a direction that forms an arbitrary angle with the square side.

  Thus, the recessed part 3a is arrange | positioned in the pattern of concentric form, stripe form, and mesh form.

  As described above, since the uneven structure is not formed on the light receiving surface 1a of the crystalline silicon substrate 1, the diffusion region 2 is formed uniformly. Further, when the light incident layer 3 includes a passivation film, the area of the interface between the passivation film and the crystalline silicon substrate 1 is smaller than when the light receiving surface 1a of the crystalline silicon substrate 1 is made uneven, so that the carrier (electron and electron) Recombination of holes) is suppressed. Furthermore, the light receiving surface of the crystalline silicon substrate 1 can be sufficiently cleaned during the manufacturing process of the photoelectric conversion element 10.

  Therefore, the conversion efficiency of the photoelectric conversion element 10 can be improved.

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

Example 1
FIG. 4 is a cross-sectional view showing the configuration of the photoelectric conversion element in Example 1. Referring to FIG. 4, photoelectric conversion element 10 </ b> A includes an n-type single crystal silicon substrate 11, a light incident layer 13, electrodes 14 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.

  The n-type single crystal silicon substrate 11 has no uneven structure on the light receiving surface 11a. The n-type single crystal silicon substrate 11 includes a p-type diffusion region 12 in contact with the light receiving surface 11a. The p-type diffusion region 12 has a p-type conductivity type which is the opposite conductivity type to the n-type single crystal silicon substrate 11, and includes, for example, boron (B) as a dopant. The depth of the p-type diffusion region 12 is, for example, 200 nm.

The p-type diffusion region 12 is composed of p-type diffusion regions 12a and 12b. The B concentration in the p-type diffusion region 12b is higher than the B concentration in the p-type diffusion region 12a. For example, the p-type diffusion region 12a has a B concentration of 1 × 10 ¹⁹ cm ⁻³ and the p-type diffusion region 12b has a B concentration of 1 × 10 ²⁰ cm ⁻³ .

  The light incident layer 13 is disposed in contact with the light receiving surface 11a of the n-type single crystal silicon substrate 11, and has a thickness of, for example, several μm. In addition, the light incident layer 13 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 13a protruding in the sunlight incident direction on the light incident side surface. And the recessed part 13a has a width | variety of several micrometers in the in-plane direction of the n-type single crystal silicon substrate 11, for example. Furthermore, the light incident layer 13 is made of any of the light incident layers 31 to 33 (see FIG. 2) described above.

  The electrode 14 penetrates the light incident layer 13 and is formed in contact with the p-type diffusion region 12 b of the n-type single crystal silicon substrate 11. The electrode 14 is made of Ag, for example.

The passivation film 15 is formed in contact with the back surface of the n-type single crystal silicon substrate 11 (= the surface opposite to the light receiving surface 11a). The passivation film 15 is made of SiO ₂ and has a thickness of 10 to 100 nm, for example.

  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, for example, Al.

  5 to 7 are first to third process diagrams showing a method of manufacturing the photoelectric conversion element 10A shown in FIG.

  When the production of the photoelectric conversion element 10A is started, a silicon ingot is sliced to produce an n-type single crystal silicon substrate, and the produced n-type single crystal silicon substrate is etched with a mixed solution of hydrofluoric acid and nitric acid, Remove the damage layer caused by slicing. Thereby, an n-type single crystal silicon substrate 11 is prepared (see step (a) in FIG. 5).

Then, a passivation film 21 made of SiO ₂ is formed on the back surface (surface opposite to the light receiving surface 11a) of the n-type single crystal silicon substrate 11 by an APCVD (Atmospheric Pressure Chemical Vapor Deposition) method (step (b) in FIG. 5). )reference).

  Thereafter, a polyboron film (PBF) is applied to the light-receiving surface 11 a of the n-type single crystal silicon substrate 11 and heated in a quartz furnace to diffuse B into the n-type single crystal silicon substrate 11. In this case, the diffusion temperature is, for example, 910 ° C., and the diffusion time is, for example, 30 minutes. As a result, a p-type diffusion region 22 is formed on the light-receiving surface 11a side of the n-type single crystal silicon substrate 11 (see step (c) in FIG. 5).

  Subsequently, a silicon oxide film 23 is formed on the light receiving surface 11a of the n-type single crystal silicon substrate 11 by the APCVD method (see step (d) in FIG. 5).

  Then, a part of the silicon oxide film 23 is removed using an etching paste to form a silicon oxide film 24 (see step (e) in FIG. 5).

  Thereafter, a polyboron film (PBF) is applied to the opening of the silicon oxide film 24 and heated in a quartz furnace to diffuse B into the p-type diffusion region 22 of the n-type single crystal silicon substrate 11. In this case, the diffusion temperature is, for example, 910 ° C., and the diffusion time is, for example, 30 minutes. As a result, a p-type diffusion region 12 is formed on the light-receiving surface 11a side of the n-type single crystal silicon substrate 11 (see step (f) in FIG. 5).

Then, the silicon oxide film 24 is removed using hydrofluoric acid (see step (g) in FIG. 6). Subsequently, a passivation film 25 made of SiO ₂ is formed on the light receiving surface 11a of the n-type single crystal silicon substrate 11 by the APCVD method (see step (h) in FIG. 6). Thereafter, an antireflection film 26 made of SiO ₂ is deposited on the passivation film 25 by the APCVD method (see step (i) in FIG. 6). In this case, the film thickness of the antireflection film 26 is, for example, 5 μm.

As described above, by removing the silicon oxide film 24 with hydrofluoric acid in the step (g) before forming the passivation film 25 in the step (h), the light receiving surface 11a of the n-type single crystal silicon substrate 11 becomes a hydrogen atom ( H) and a passivation film 25 made of SiO ₂ is formed by the APCVD method in step (h), whereby the interface between the passivation film 25 (= SiO ₂ ) and the light receiving surface 11a of the n-type single crystal silicon substrate 11 is formed. The level density decreases to 10 ¹⁰ cm ^−2, and recombination of carriers (electrons and holes) at the interface between the passivation film 25 (= SiO ₂ ) and the light receiving surface 11 a of the n-type single crystal silicon substrate 11 is suppressed. Is done.

  Subsequently, the antireflection film 26 is irradiated with laser light to roughen the surface of the antireflection film 26 and form an antireflection film 27 having a recess 27a on the surface (see step (j) in FIG. 6). In this case, laser light of Nd: YAG laser or Nd: YVO laser is used as the laser light. This laser beam has a wavelength of 532 nm, an oscillation frequency of 5 kHz, and a power of 0.1 to 0.5 W. Then, the laser beam is scanned to form a recess 27a having any one of the patterns (a) to (c) in FIG. When the concave portion 27a having a mesh pattern shown in FIG. 3C is formed, laser light is irradiated at intervals of 5 μm in the vertical and horizontal directions, or laser light is scanned in a lattice pattern at a constant interval (5 μm pitch). To do.

  After the step (j), the n-type single crystal silicon substrate 11 is immersed in hydrofluoric acid, and the residue is removed and the antireflection film 27 is etched. Thereby, the antireflection film 28 is formed. The passivation film 25 and the antireflection film 28 constitute the light incident layer 13 described above, and the light incident layer 13 has a concave portion 13a having a size of 3 to 5 μm on the light incident side surface (step of FIG. 6). (See (k)).

  Then, through holes 29 and 30 are formed in the light incident layer 13 and the passivation film 16 by photolithography and etching, respectively (see step (l) in FIG. 7).

  Thereafter, an Ag paste is printed in the through hole 29 and sintered to form the electrode 14. Moreover, Al is vapor-deposited on the back surface of the n-type single crystal silicon substrate 11 to form the electrode 16. Thus, the photoelectric conversion element 10A is completed (see step (m) in FIG. 7).

  When the light incident layer 13 is composed of only a passivation film or only an antireflection film, the passivation film or antireflection film having a film thickness of about 5 μm is the p-type diffusion of the n-type single crystal silicon substrate 11 in the step (h). The antireflection film 26 is not formed in the step (i), which is deposited on the region 12. Then, in steps (j) and (k), the passivation film or the antireflection film is etched by the above-described method, and the light incident film 13 having the recess 13a is formed.

  In the photoelectric conversion element 10A, sunlight is applied to the photoelectric conversion element 10A from the light incident layer 13 side. The reflection of sunlight is suppressed by the honeycomb texture and enters the n-type single crystal silicon substrate 11 through the light incident layer 13.

  Then, holes and electrons are photoexcited in the n-type single crystal silicon substrate 11. The photoexcited holes are caused by the p-type diffusion regions 12a and 12b and the bulk region of the n-type single crystal silicon substrate 11 (= the region other than the p-type diffusion regions 12a and 12b of the n-type single crystal silicon substrate 11). It moves by diffusion in the direction of the formed p / n junction, and reaches the p-type diffusion regions 12a and 12b by an internal electric field by the p / n junction. The holes that have reached the p-type diffusion region 12a are suppressed from being recombined at the interface between the p-type diffusion region 12a and the light incident layer 13, and reach the p-type diffusion region 12b by diffusion. Thus, the light incident layer 13 functions as a passivation film for the surface of the n-type single crystal silicon substrate 11. The holes reach the electrode 14 from the p-type diffusion region 12b.

  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 14 from the electrode 16 via a load and recombine with the holes.

  As described above, the photoelectric conversion element 10 </ b> A is manufactured using the n-type single crystal silicon substrate 11 in which the uneven structure is not formed on the surface. As a result, the p-type diffusion region 12 is formed uniformly. Further, in the manufacturing process of the photoelectric conversion element 10A, the light receiving surface 11a of the n-type single crystal silicon substrate 11 is sufficiently cleaned. Furthermore, the area of the interface between the passivation film 25 of the light incident layer 13 and the n-type single crystal silicon substrate 11 is reduced, and recombination of carriers (electrons and holes) is suppressed.

  Therefore, the conversion efficiency of the photoelectric conversion element 10A can be improved.

  Note that 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, and has a thickness of 200 μm, for example.

Further, in the photoelectric conversion element 10A, a high-concentration diffusion region containing P for BSF (Back Surface Filed) at a high concentration (about 1 × 10 ²⁰ cm ⁻³ ) is in contact with the electrode 16 with n-type single crystal silicon. You may form in a part of board | substrate 11. FIG.

(Example 2)
FIG. 8 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 2. Referring to FIG. 8, photoelectric conversion element 10 </ b> B includes p-type single crystal silicon substrate 51, light incident layer 53, electrodes 54 and 56, and passivation film 55.

  The p-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 p-type single crystal silicon substrate 51 is, for example, 200 μm. The p-type single crystal silicon substrate 51 has an n-type diffusion region 52 in contact with the light receiving surface 51a. The n-type diffusion region 52 has an n-type conductivity type which is the opposite conductivity type to the p-type single crystal silicon substrate 51, and includes, for example, phosphorus (P) as a dopant. The depth of the n-type diffusion region 52 is, for example, 200 nm.

The n-type diffusion region 52 includes n-type diffusion regions 52a and 52b. The P concentration of n type diffusion region 52b is higher than the P concentration of n type diffusion region 52a. For example, the n-type diffusion region 52a has a P concentration of 1 × 10 ¹⁹ cm ⁻³ and the n-type diffusion region 52b has a P concentration of 1 × 10 ²⁰ cm ⁻³ .

  The light incident layer 53 is disposed in contact with the light receiving surface 51a of the p-type single crystal silicon substrate 51, and has a thickness of, for example, several μm. The light incident layer 53 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 53a protruding in the sunlight incident direction on the light incident side surface. And the recessed part 53a has a width | variety of several micrometers in the in-plane direction of the p-type single crystal silicon substrate 51, for example. Furthermore, the light incident layer 53 includes any of the light incident layers 31 to 33 (see FIG. 2) described above.

  The electrode 54 penetrates the light incident layer 53 and is formed in contact with the n-type diffusion region 52 b of the p-type single crystal silicon substrate 51. The electrode 54 is made of Ag, for example.

The passivation film 55 is formed in contact with the back surface of the p-type single crystal silicon substrate 51 (= the surface opposite to the light receiving surface 51a). Then, a passivation film 55 is made of SiO _2, for example, has a 10~100nm thickness.

  Electrode 56 is formed in contact with p-type single crystal silicon substrate 51 and passivation film 55. The electrode 56 is made of, for example, Al.

The photoelectric conversion element 10B is manufactured according to the steps (a) to (m) shown in FIGS. In this case, n-type diffusion regions 52a and 52b are formed in steps (c) to (f). Then, phosphorus oxychloride (POCl ₃ ) is used as a diffusion source of P, and the p-type single crystal silicon substrate 51 is heated in a quartz furnace in an atmosphere of POCl ₃ to enter the p-type single crystal silicon substrate 51. Is diffused to form an n-type diffusion region 52. At this time, the diffusion temperature is, for example, 890 ° C., and the diffusion time is, for example, 20 minutes.

  In steps (h) to (k), a light incident layer made of any one of a passivation film, an antireflection film, and a passivation film / antireflection film is formed.

  In the photoelectric conversion element 10B, sunlight is applied to the photoelectric conversion element 10B from the light incident layer 53 side. The reflection of sunlight is suppressed by the honeycomb texture and is incident on the p-type single crystal silicon substrate 51 through the light incident layer 53.

  Then, holes and electrons are photoexcited in the p-type single crystal silicon substrate 51. The photoexcited electrons are formed by the n-type diffusion regions 52a and 52b and the bulk region of the p-type single crystal silicon substrate 51 (= the region other than the n-type diffusion regions 52a and 52b of the p-type single crystal silicon substrate 51). It moves by diffusion in the direction of the p / n junction, and reaches the n-type diffusion regions 52a and 52b by an internal electric field by the p / n junction. The electrons that have reached the n-type diffusion region 52a are suppressed from recombination at the interface between the n-type diffusion region 52a and the light incident layer 53, and reach the n-type diffusion region 52b by diffusion. Thus, the light incident layer 53 functions as a passivation film for the surface of the p-type single crystal silicon substrate 51. Then, the electrons reach the electrode 54 from the n-type diffusion region 52b.

  On the other hand, the photoexcited holes move to the back side of the p-type single crystal silicon substrate 51 by diffusion. The holes that have reached the interface between the p-type single crystal silicon substrate 51 and the passivation film 55 are suppressed from recombination and reach the electrode 56 by diffusion. Then, the electrons reach the electrode 56 from the electrode 54 through the load and recombine with the holes.

  Thus, the photoelectric conversion element 10B is manufactured using the p-type single crystal silicon substrate 51 in which the uneven structure is not formed on the surface. As a result, the n-type diffusion region 52 is formed uniformly. Further, in the manufacturing process of the photoelectric conversion element 10B, the light receiving surface 51a of the p-type single crystal silicon substrate 51 is sufficiently cleaned. Furthermore, the area of the interface between the passivation film of the light incident layer 53 and the p-type single crystal silicon substrate 51 is reduced, and recombination of carriers (electrons and holes) is suppressed.

  Therefore, the conversion efficiency of the photoelectric conversion element 10B can be improved.

  The photoelectric conversion element 10B may include a p-type polycrystalline silicon substrate instead of the p-type single crystal silicon substrate 51. 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.

Further, in the photoelectric conversion element 10B, a part of the p-type single crystal silicon substrate 51 includes a high concentration diffusion region containing B B at a high concentration (about 1 × 10 ²⁰ cm ⁻³ ) so as to be in contact with the electrode 56. You may form in.

  The other description of the photoelectric conversion element 10B is the same as the description of the photoelectric conversion element 10A.

  As described above, according to the first embodiment, the photoelectric conversion element 10 in which the p / n junction exists on the light incident side does not have the uneven structure on the light receiving surface 1a of the crystalline silicon substrate 1, and A light incident layer 3 having a concavo-convex structure including a recess 1a on the surface is provided. The p / n junction is a homojunction. As a result, as described above, the diffusion region 2 is uniformly formed, and in the process of manufacturing the photoelectric conversion element 10, the light receiving surface 1a of the crystalline silicon substrate 1 is sufficiently cleaned, and the light incident layer 3 forms a passivation film. If included, the area of the interface between the passivation film and the crystalline silicon substrate 1 is reduced, and recombination of carriers (electrons and holes) is suppressed.

  Therefore, the conversion efficiency of the photoelectric conversion element 10 can be improved.

  In the above description, it has been described that the recesses 12a and 52a are formed using laser light and chemicals. However, the first embodiment is not limited thereto, and the recesses 12a and 52a are formed using only laser light. May be.

[Embodiment 2]
FIG. 9 is a cross-sectional view illustrating a configuration of the photoelectric conversion element according to the second embodiment. Referring to FIG. 9, the photoelectric conversion element 100 according to the second embodiment includes a single crystal silicon substrate 61, a light incident layer 63, an oxide film 64, and electrodes 651 to 65n.

  Single crystal silicon substrate 61 is formed of an n-type single crystal silicon substrate or a p-type single crystal silicon substrate. The single crystal silicon substrate 61 has no uneven structure on the light receiving surface 61a.

  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.

  Single crystal silicon substrate 61 includes diffusion regions 611 to 61n on the side opposite to light receiving surface 61a. The diffusion regions 611, 613, ..., 61n-2, 61n have an n-type conductivity type when the single-crystal silicon substrate 61 has an n-type conductivity type, and the single-crystal silicon substrate 61 has a p-type conductivity. When it has a conductivity type, it has a p-type conductivity type. The diffusion regions 612, 614,..., 61n-1 have a p-type conductivity when the single crystal silicon substrate 61 has an n-type conductivity type, and the single crystal silicon substrate 61 has a p-type conductivity type. The n-type conductivity type.

  Thus, diffusion regions 611, 613,..., 61n-2, 61n have the same conductivity type as that of single crystal silicon substrate 61, and diffusion regions 612, 614,. Has a conductivity type opposite to that of the single crystal silicon substrate 61.

  The diffusion regions 611, 613, ..., 61n-2, 61n and the diffusion regions 612, 614, ..., 61n-1 are alternately arranged in the in-plane direction of the single crystal silicon substrate 61.

The dopant concentration in each of the diffusion regions 611, 613,..., 61n-2, 61n is, for example, 1 × 10 ¹⁹ cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ , and the diffusion regions 612, 614,. The dopant concentration in each of 61n-1 is, for example, 1 × 10 ¹⁹ cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ .

  In addition, the depths of the diffusion regions 611, 613, ..., 61n-2, 61n and the diffusion regions 612, 614, ..., 61n-1 are, for example, 200 nm to 400 nm.

  The light incident layer 63 is disposed in contact with the light receiving surface 61a of the single crystal silicon substrate 61, and has a thickness of, for example, several μm. In addition, the light incident layer 63 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 63a protruding in the incident direction of sunlight on the surface on the light incident side. And the recessed part 63a has a width | variety of several micrometers in the in-plane direction of the single crystal silicon substrate 61, for example. Moreover, the recessed part 63a has the plane pattern shown in either of (a)-(c) of FIG. Furthermore, the light incident layer 63 is made of any of the light incident layers 31 to 33 (see FIG. 2) described above.

Oxide film 64 is provided in contact with the back surface of single crystal silicon substrate 61 (the surface opposite to light receiving surface 61a). Then, oxide film 64 is made of, for example, SiO _2, its thickness is, for example, 10 nm to 100 nm.

  Each of the electrodes 651 to 65n is made of Ag, for example. Electrodes 651, 653,..., 65n-2, 65n are formed so as to be in contact with the diffusion regions 611, 613,. Further, the electrodes 652, 654,..., 65n-1 are formed so as to be in contact with the diffusion regions 612, 614,.

  The diffusion regions 611, 613, ..., 61n-2, 61n and the diffusion regions 612, 614, ..., 61n-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 612, 614,..., 61n−1 to the area of the single crystal silicon substrate 61, is 60 to 93%, and the diffusion regions 611, 613, ..., 61n-2, 61n, the area occupancy ratio, which is the ratio of the entire area of the single crystal silicon substrate 61 to the area of the single crystal silicon substrate 61, is 5 to 20%.

  As described above, the area occupancy of the diffusion regions 612, 614,..., 61n-1 is larger than the area occupancy of the diffusion regions 611, 613,. This is because the electrons and holes photoexcited in the silicon substrate 61 are easily separated by the p / n junction, and the contribution ratio of the photoexcited electrons and holes to power generation is increased.

  Thus, the photoelectric conversion element 100 has a structure in which a p / n junction made of a homojunction is disposed on the back surface side of the single crystal silicon substrate 61.

  In the photoelectric conversion element 100, when sunlight is irradiated from the light incident layer 63 side to the photoelectric conversion element 100, electrons and holes are photoexcited in the single crystal silicon substrate 61.

  Even if the photoexcited electrons and holes diffuse to the light incident layer 63 side, they are difficult to recombine due to the passivation effect of the single crystal silicon substrate 61 by the light incident layer 63 and diffuse to the diffusion regions 611 to 61n side.

  Then, the electrons and holes diffused toward the diffusion regions 611 to 61n are separated by an internal electric field by the diffusion regions 612, 614,..., 61n−1 / single crystal silicon substrate 61 (= p / n junction), .., 61n-1 or the diffusion regions 611, 613,..., 61n through the holes 652, 654,. , 65n, and the electrons reach the electrodes 651, 653, ..., 65n through the diffusion regions 611, 613, ..., 61n or the diffusion regions 612, 614, ..., 61n-1. Alternatively, the electrodes 652, 654,.

  Electrons that have reached the electrodes 651, 653,..., 65n or the electrodes 652, 654,..., 65n-1 and the electrodes 651, 653,. , 65n-1 or the electrodes 651, 653,..., 65n through the load connected to −1 and recombine with holes.

  As described above, the photoelectric conversion element 100 is a back-contact type photoelectric device that extracts electrons and holes photoexcited in the single crystal silicon substrate 61 from the back surface (= the surface opposite to the light receiving surface 61a) of the single crystal silicon substrate 61. It is a conversion element.

  As described above, since the concavo-convex structure is not formed on the light receiving surface 61 a of the single crystal silicon substrate 61, the area of the interface between the light incident layer 63 and the single crystal silicon substrate 61 is the light reception of the single crystal silicon substrate 61. It becomes smaller than the case where the surface 61a is uneven | corrugated. As a result, recombination of carriers (electrons and holes) is suppressed. Further, the light receiving surface of the single crystal silicon substrate 61 can be sufficiently cleaned during the manufacturing process of the photoelectric conversion element 100.

  Therefore, the conversion efficiency of the photoelectric conversion element 100 can be improved.

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

(Example 3)
FIG. 10 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 3. Referring to FIG. 10, photoelectric conversion element 100A includes an n-type single crystal silicon substrate 71, a light incident layer 73, an oxide film 74, and electrodes 751 to 75n.

  The n-type single crystal silicon substrate 71 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 71 is, for example, 200 μm.

  Further, the n-type single crystal silicon substrate 71 has no uneven structure on the light receiving surface 71a. The n-type single crystal silicon substrate 71 has an n-type diffusion region 710 on the light receiving surface 71a side. The n-type diffusion region 710 includes P as a dopant and functions as a surface electric field layer (FSF).

  Further, the n-type single crystal silicon substrate 71 includes n-type diffusion regions 711, 713,..., 71-2, 71n and p-type diffusion regions 712, 714,. It is included on the reverse side opposite. , 71-2, 71 n and p-type diffusion regions 712, 714,..., 71 n-1 are alternately arranged in the in-plane direction of the n-type single crystal silicon substrate 71. Is done.

The P concentration in each of the n-type diffusion regions 711, 713,..., 71-2, 71n is, for example, 5 × 10 ¹⁹ cm ⁻³ . Further, the B concentration in each of the p-type diffusion regions 712, 714,..., 71n-1 is, for example, 8 × 10 ¹⁹ cm ⁻³ .

  The depths of the n-type diffusion regions 711, 713,..., 71-2, 7n are, for example, 200 nm, and the depths of the p-type diffusion regions 712, 714,. 200 nm.

  The light incident layer 73 is disposed in contact with the light receiving surface 71a of the n-type single crystal silicon substrate 71 and has a thickness of, for example, several μm. The light incident layer 73 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 73a protruding in the sunlight incident direction on the light incident side surface. And the recessed part 73a has a width | variety of several micrometers in the in-plane direction of the n-type single crystal silicon substrate 71, for example. Moreover, the recessed part 73a has the plane pattern shown in either of (a)-(c) of FIG. Further, the light incident layer 73 is made of any of the light incident layers 31 to 33 (see FIG. 2) described above.

  Each of the electrodes 751 to 75n is made of Ag, for example. The electrodes 751, 753,..., 75n-2, 75n are formed so as to be in contact with the n-type diffusion regions 711, 713,. In addition, the electrodes 752, 754,..., 75n-1 are formed so as to be in contact with the p-type diffusion regions 712, 714,.

  , 71n-2, 71n and p-type diffusion regions 712, 714,..., 71n-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 p type diffusion region 712,714, ..., 71n-1 occupies for the area of the n type single crystal silicon substrate 71 is 60 to 93%, and is n type. The area occupancy ratio, which is the ratio of the total area of diffusion regions 711, 713,..., 71n-2, 71n to the area of n-type single crystal silicon substrate 71, is 5 to 20%.

  The reason why the area occupancy of the p-type diffusion regions 712, 714,..., 71n-1 and the n-type diffusion regions 711, 713,. In the conversion element 100, the area occupancy ratios of the diffusion regions 612, 614, ..., 61n-1 and the diffusion regions 611, 613, ..., 61n-2, 61n are set to 60 to 93% and 5 to 20%, respectively. For the same reason.

  11 to 14 are first to fourth process diagrams showing a method of manufacturing the photoelectric conversion element 100A shown in FIG.

  When the production of the photoelectric conversion element 100A is started, a silicon ingot is sliced to produce an n-type single crystal silicon substrate, and the produced n-type single crystal silicon substrate is etched with a mixed solution of hydrofluoric acid and nitric acid, Remove the damage layer caused by slicing. Thus, an n-type single crystal silicon substrate 71 is prepared (see step (a) in FIG. 11).

  Then, the n-type single crystal silicon substrate 71 is thermally oxidized in an atmosphere of oxygen or water vapor to form silicon oxide films 81 and 82 on the light receiving surface 71a and the back surface of the n-type single crystal silicon substrate 71, respectively (step of FIG. 11). (See (b)). In this case, the temperature of thermal oxidation is, for example, 950 ° C., and the oxidation time is, for example, 10 minutes.

  Thereafter, a part of the silicon oxide film 82 is removed using an etching paste, and a silicon oxide film 83 is formed on the back surface of the n-type single crystal silicon substrate 71 (see step (c) in FIG. 11). Thereby, an opening for diffusing P is formed.

Subsequently, the n-type single crystal silicon substrate 71 is heated in a quartz furnace in an atmosphere of phosphorus oxychloride (POCl ₃ ) to diffuse P into the n-type single crystal silicon substrate 71 from the opening of the silicon oxide film 83. , 71n-2, 71n are formed (see step (d) in FIG. 11). In this case, the diffusion temperature is, for example, 890 ° C., and the diffusion time is, for example, 20 minutes.

  Then, the silicon oxide films 81 and 83 are removed with hydrofluoric acid (see step (e) in FIG. 11).

  Thereafter, the n-type single crystal silicon substrate 71 is thermally oxidized in an atmosphere of oxygen or water vapor to form silicon oxide films 84 and 85 on the light receiving surface 71a and the back surface of the n-type single crystal silicon substrate 71, respectively (step of FIG. 12). (Refer to (f)). In this case, the temperature of thermal oxidation is, for example, 950 ° C., and the oxidation time is, for example, 10 minutes. The film thickness of the silicon oxide film 85 on the n-type diffusion regions 711, 713,..., 71n-2, 71n is a region other than the n-type diffusion regions 711, 713,. Thicker than above.

  Then, etch back is performed using hydrofluoric acid. At this time, only the n-type diffusion regions 711, 713,..., 71n-2, 71n leave the silicon oxide film, and silicon in regions other than the n-type diffusion regions 711, 713,. The oxide film and the silicon oxide film 84 on the light receiving surface 71a of the n-type single crystal silicon substrate 71 are removed. As a result, a silicon oxide film 86 is formed in contact with the n-type diffusion regions 711, 713,..., 71n-2, 71n (see step (g) in FIG. 12).

Subsequently, a protective film 87 made of SiO ₂ is formed on the light receiving surface 71a of the n-type single crystal silicon substrate 71 by the APCVD method (see step (h) in FIG. 12).

  Then, a polyboron film (PBF) is applied to the back surface of the n-type single crystal silicon substrate 71 and heated in a quartz furnace to diffuse boron into the n-type single crystal silicon substrate 71. In this case, the diffusion temperature is, for example, 910 ° C., and the diffusion time is, for example, 30 minutes. As a result, p-type diffusion regions 712, 714,..., 71n-1 are formed on the back side of the n-type single crystal silicon substrate 71 (see step (i) in FIG. 12).

  Thereafter, the silicon oxide films 86 and 87 are removed with hydrofluoric acid (see step (j) in FIG. 12).

Subsequently, a protective film 88 made of SiO ₂ is formed on the back surface of the n-type single crystal silicon substrate 71 by the APCVD method (see step (k) in FIG. 13).

Then, the n-type single crystal silicon substrate 71 is put in a quartz furnace in an atmosphere of phosphorus oxychloride (POCl ₃ ) and heated, and the light-receiving surface 71a of the n-type single crystal silicon substrate 71 enters the n-type single crystal silicon substrate 71. Is diffused to form a diffusion region 710 (see step (l) in FIG. 13). In this case, the heating temperature is, for example, 725 ° C., and the heating time is, for example, 30 minutes. A PSG (Phosphorus Silicate Glass) film 89 is formed on the diffusion region 710.

Thereafter, the PSG film 89 and the protective film 88 (= SiO ₂ ) are removed with hydrofluoric acid (see step (m) in FIG. 13).

Then, a passivation film 90 made of SiO ₂ by APCVD method on the back surface of the n-type single crystal silicon substrate 71, a passivation film 91 made of SiO ₂ on the light receiving surface 71a of the n-type single crystal silicon substrate 71 by dry oxidation (See step (n) in FIG. 13). In this case, the temperature of dry oxidation is, for example, 850 ° C., and the oxidation time is, for example, 240 minutes.

Thereafter, an antireflection film 92 made of SiO ₂ is formed on the passivation film 91 by the APCVD method (see step (o) in FIG. 13). In this case, the film thickness of the antireflection film 92 is, for example, 5 μm.

  Subsequently, the antireflection film 92 is irradiated with laser light to roughen the surface of the antireflection film 92 and form an antireflection film 93 having a recess 93a on the surface (see step (p) in FIG. 14). In this case, laser light of Nd: YAG laser or Nd: YVO laser is used as the laser light. This laser beam has a wavelength of 532 nm, an oscillation frequency of 5 kHz, and a power of 0.1 to 0.5 W. Then, a laser beam is scanned to form a recess 93a having a planar pattern of any one of (a) to (c) of FIG. When the concave portion 93a having a mesh-like plane pattern shown in FIG. 3C is formed, the laser light is irradiated with laser light at intervals of 5 μm in the vertical and horizontal directions, or the laser light is emitted at regular intervals (5 μm pitch). Scan in a grid pattern.

  After the step (p), the n-type single crystal silicon substrate 71 is immersed in hydrofluoric acid, and the residue is removed and the antireflection film 93 is etched. Thereby, the antireflection film 94 is formed. The passivation film 91 and the antireflection film 94 constitute the light incident layer 73 described above, and the light incident layer 73 has a concave portion 73a having a size of 3 to 5 μm on the light incident side surface (step of FIG. 14). (See (q)).

And corresponding to n-type diffusion regions 711, 713,..., 71n-2, 71n and p-type diffusion regions 712, 714,..., 71n-1 formed on the back surface of the n-type single crystal silicon substrate 71. A part of the passivation film 90 (= SiO ₂ ) to be removed is removed with an etching paste to form an opening (see step (r) in FIG. 14).

  Thereafter, a metal paste is printed on the back surface of the n-type single crystal silicon substrate 71 and baked. As a result, the electrodes 751 to 75n connected to the n-type diffusion regions 711, 713,..., 71n-2, 71n and the p-type diffusion regions 712, 714,. It is formed. Thereby, the photoelectric conversion element 100A is completed (see step (s) in FIG. 14).

  In the case where the light incident layer 73 is made of only the passivation film or only the antireflection film, the passivation film or antireflection film having a thickness of about 5 μm is the diffusion region 710 of the n-type single crystal silicon substrate 71 in the step (n). The antireflection film 92 is not formed in the step (o). Then, in the steps (p) and (q), the passivation film or the antireflection film is etched by the method described above, and the light incident film 73 having the recess 73a is formed.

  In the photoelectric conversion element 100 </ b> A, when sunlight is irradiated from the light incident layer 73 side to the photoelectric conversion element 100 </ b> A, electrons and holes are photoexcited in the n-type single crystal silicon substrate 71.

  Even if the photoexcited electrons and holes diffuse to the light incident layer 73 side, they are regenerated by the passivation effect on the n-type single crystal silicon substrate 71 by the light incident layer 73 and the surface field effect (FSF) by the n-type diffusion region 710. .., 71n-2, 71n, and p-type diffusion regions 712, 714,..., 71n-1 side.

  The n-type diffusion regions 711, 713,..., 71n-2, 71n and the p-type diffusion regions 712, 714,. , 714,..., 71n-1 / n type single crystal silicon substrate 71 (= p / n junction), and the holes are separated by p-type diffusion regions 712, 714,. , 75n-1 through the electrode 1, and the electrons pass through the n-type diffusion regions 711, 713, ..., 71n-2, 71n to the electrodes 751, 753,. ., 75n-2, 75n is reached.

  Electrons reaching the electrodes 751, 753,..., 75n-2, 75n are between the electrodes 751, 753,..., 75n-2, 75n and the electrodes 752, 754,. Reach the electrodes 752, 754,..., 75n-1 through the load connected to the, and recombine with holes.

  As described above, the photoelectric conversion element 100A takes out electrons and holes photoexcited in the n-type single crystal silicon substrate 71 from the back surface (= the surface opposite to the light receiving surface 71a) of the n-type single crystal silicon substrate 71. It is a contact type photoelectric conversion element.

  As described above, since the uneven structure is not formed on the light receiving surface 71a of the n-type single crystal silicon substrate 71, the n-type diffusion region 710 is uniformly formed. Further, the area of the interface between the passivation film 91 of the light incident layer 73 and the n-type single crystal silicon substrate 71 is smaller than when the light receiving surface 71 a of the n-type single crystal silicon substrate 71 is made uneven. As a result, recombination of carriers (electrons and holes) is suppressed. Furthermore, the light receiving surface 71a of the n-type single crystal silicon substrate 71 can be sufficiently cleaned during the manufacturing process of the photoelectric conversion element 100A.

  Therefore, the conversion efficiency of the photoelectric conversion element 100A can be improved.

Example 4
FIG. 15 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 4. Referring to FIG. 15, photoelectric conversion element 100B includes a p-type single crystal silicon substrate 101, a light incident layer 103, an oxide film 104, and electrodes 1051 to 105n.

  The p-type single crystal silicon substrate 101 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 101 is, for example, 200 μm.

  Further, the p-type single crystal silicon substrate 101 has no uneven structure on the light receiving surface 101a. The p-type single crystal silicon substrate 101 has a p-type diffusion region 102 on the light receiving surface 101a side. The p-type diffusion region 102 includes B as a dopant and functions as a surface electric field layer (FSF).

  Further, the p-type single crystal silicon substrate 101 includes p-type diffusion regions 1011, 1013,..., 101 n-2, 101 n and n-type diffusion regions 1012, 1014,. It is included on the reverse side opposite. , 101n-2, 101n and n-type diffusion regions 1012, 1014,..., 101n-1 are alternately arranged in the in-plane direction of the p-type single crystal silicon substrate 101. Is done.

The B concentration in each of the p-type diffusion regions 1011, 1013,..., 101n-2, 101n is, for example, 5 × 10 ¹⁹ cm ⁻³ . In addition, the P concentration in each of the n-type diffusion regions 1012, 1014,..., 101 n−1 is, for example, 8 × 10 ¹⁹ cm ⁻³ .

  The depth of the p-type diffusion regions 1011, 1013,..., 101n-2, 101n is, for example, 200 nm, and the depth of the n-type diffusion regions 1012, 1014,. 200 nm.

  The light incident layer 103 is disposed in contact with the light receiving surface 101a of the p-type single crystal silicon substrate 101, and has a thickness of, for example, several μm. The light incident layer 103 has a concavo-convex structure (honeycomb texture) including a hemispherical concave portion 103a protruding in the sunlight incident direction on the light incident side surface. The recess 103 a has a width of, for example, several μm in the in-plane direction of the p-type single crystal silicon substrate 101. Moreover, the recessed part 103a has the plane pattern shown in either of (a)-(c) of FIG. Further, the light incident layer 103 is formed of any of the light incident layers 31 to 33 (see FIG. 2) described above.

  Each of the electrodes 1051 to 105n is made of Ag, for example. The electrodes 1051, 1053,..., 105n-2, 105n are formed so as to be in contact with the p-type diffusion regions 1011, 1013,. In addition, the electrodes 1052, 1054,..., 105n-1 are formed so as to be in contact with the n-type diffusion regions 1012, 1014,.

  .., 101n-2, 101n and n-type diffusion regions 1012, 1014,..., 101n-1 have the same length in the direction perpendicular to the paper surface of FIG. Further, the area occupation ratio, which is the ratio of the entire area of the n-type diffusion regions 1012, 1014,..., 101 n−1 to the area of the p-type single crystal silicon substrate 101, is 60 to 93%. The area occupancy ratio, which is the ratio of the total area of diffusion regions 1011, 1013,..., 101 n-2, 101 n to the area of p-type single crystal silicon substrate 101, is 5 to 20%.

  The reason why the area occupancy of the n-type diffusion regions 1012, 1014,..., 101n−1 and the p-type diffusion regions 1011, 1013,. In the conversion element 100, the area occupancy ratios of the diffusion regions 612, 614, ..., 61n-1 and the diffusion regions 611, 613, ..., 61n-2, 61n 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 (s) shown in FIGS. In this case, in the step (b) in FIG. 11 to the step (j) in FIG. 12, the p-type diffusion regions 1011, 1013,..., 101n-2, 101n and the n-type diffusion regions 1012, 1014,. 101n-1 is formed.

  Further, in step (l) of FIG. 13, the p-type diffusion region 102 is formed.

  Further, in the step (n) in FIG. 13 to the step (q) in FIG. 14, a concavo-convex structure (honeycomb texture) having a concave portion 103 a is formed on the light incident side surface of the light incident layer 103.

  In the photoelectric conversion element 100 </ b> B, when sunlight is applied to the photoelectric conversion element 100 </ b> B from the light incident layer 103 side, electrons and holes are photoexcited in the p-type single crystal silicon substrate 101.

  Even if the photoexcited electrons and holes diffuse to the light incident layer 103 side, they are regenerated by the passivation effect on the p-type single crystal silicon substrate 101 by the light incident layer 103 and the surface field effect (FSF) by the p-type diffusion region 102. .., 101n-2, 101n and n-type diffusion regions 1012, 1014,..., 101n-1 side.

  , 101n-2, 101n and the n-type diffusion regions 1012, 1014,..., 101n-1 side are diffused into the n-type diffusion region 1012. , 1014,..., 101n−1 / p type single crystal silicon substrate 101 (= p / n junction), and the holes are separated by p-type diffusion regions 1011, 1013,. , 105n-2, 105n through 2101n, and electrons reach the electrodes 1012, 1014 through n-type diffusion regions 1012, 1014,. ..., 105n-1 is reached.

  Electrons reaching the electrodes 1012, 1014,..., 105n-1 are connected between the electrodes 1011, 1013,..., 105n-2, 105n and the electrodes 1012, 1014,. Reach the electrodes 1011, 1013,..., 105 n-2, 105 n through the applied load and recombine with holes.

  As described above, the photoelectric conversion element 100B takes out electrons and holes photoexcited in the p-type single crystal silicon substrate 101 from the back surface (= the surface opposite to the light receiving surface 101a) of the p-type single crystal silicon substrate 101. It is a contact type photoelectric conversion element.

  As described above, since the uneven structure is not formed on the light receiving surface 101a of the p-type single crystal silicon substrate 101, the p-type diffusion region 102 is formed uniformly. Further, the area of the interface between the passivation film of the light incident layer 103 and the p-type single crystal silicon substrate 101 is smaller than when the light receiving surface 101a of the p-type single crystal silicon substrate 101 is made uneven. As a result, recombination of carriers (electrons and holes) is suppressed. Furthermore, the light receiving surface 101a of the p-type single crystal silicon substrate 101 can be sufficiently cleaned during the manufacturing process of the photoelectric conversion element 100B.

  Therefore, the conversion efficiency of the photoelectric conversion element 100B can be improved.

  The other description of the photoelectric conversion element 100B is the same as the description of the photoelectric conversion element 100A.

  Other explanations in the second embodiment are the same as those in the first embodiment.

[Embodiment 3]
FIG. 16 is a cross-sectional view illustrating a configuration of the photoelectric conversion element according to the third embodiment. Referring to FIG. 16, the photoelectric conversion element 200 according to the third embodiment includes a crystalline silicon substrate 111, an amorphous film 112, a light incident layer 113, electrodes 114 and 116, and a passivation film 115.

  The crystalline silicon substrate 111 is the same as the crystalline silicon substrate 1 described above except that it does not include the diffusion region 2.

  The amorphous film 112 is disposed on the crystalline silicon substrate 111 in contact with the light receiving surface 111 a of the crystalline silicon substrate 111.

  When the crystalline silicon substrate 111 has n-type conductivity, the amorphous film 112 is made of i-type amorphous film / p-type amorphous film or p-type amorphous film. When the amorphous film 112 is composed of an i-type amorphous film / p-type amorphous film, the i-type amorphous film is disposed in contact with the light-receiving surface 111a of the crystalline silicon substrate 111, and the p-type amorphous film The film is disposed in contact with the light incident layer 113. When the amorphous film 112 is a p-type amorphous film, the p-type amorphous film is in contact with the crystalline silicon substrate 111 and the light incident layer 113 and between the crystalline silicon substrate 111 and the light incident layer 113. Placed in.

  On the other hand, the amorphous film 112 is made of an i-type amorphous film / n-type amorphous film or an n-type amorphous film when the crystalline silicon substrate 111 has a p-type conductivity type. When the amorphous film 112 is composed of an i-type amorphous film / n-type amorphous film, the i-type amorphous film is disposed in contact with the light-receiving surface 111a of the crystalline silicon substrate 111, and is n-type amorphous. The film is disposed in contact with the light incident layer 113. When the amorphous film 112 is an n-type amorphous film, the n-type amorphous film is in contact with the crystalline silicon substrate 111 and the light incident layer 113 and between the crystalline silicon substrate 111 and the light incident layer 113. Placed in.

The light incident layer 113 is disposed in contact with the amorphous film 112 and has a thickness of, for example, several μm. The light incident layer 113 is made of an antireflection film such as ITO (Indium Tin Oxide), SnO _2, and Zno. Further, the light incident layer 113 has a concavo-convex structure including a hemispherical concave portion 113a protruding in the incident direction of sunlight on the surface on the light incident side. The recess 113a has a width of, for example, several μm in the in-plane direction of the crystalline silicon substrate 111. Moreover, the planar shape of the recessed part 113a consists of either of the planar shapes shown to (a)-(c) of FIG.

  The electrode 114 is formed in contact with the light incident layer 113. The electrode 114 is made of Ag, for example.

The passivation film 115 is formed in contact with the back surface of the crystalline silicon substrate 111 (= the surface opposite to the light receiving surface 111a). Then, a passivation film 115 is made of SiO _2, for example, has a 10~100nm thickness.

  The electrode 116 is formed in contact with the back surface of the crystalline silicon substrate 111 and the passivation film 115. The electrode 116 is made of, for example, Al.

  Thus, the photoelectric conversion element 200 has a structure in which a p / n junction (or pin junction) made of a heterojunction is disposed on the light receiving surface side of the crystalline silicon substrate 111.

  As described above, the photoelectric conversion element 200 is manufactured using the crystalline silicon substrate 111 in which the uneven structure is not formed on the light receiving surface 111a. As a result, the amorphous film 112 is formed uniformly. Further, in the manufacturing process of the photoelectric conversion element 200, the light receiving surface 111a of the crystalline silicon substrate 111 is sufficiently cleaned. Furthermore, the area of the interface between the amorphous film 112 and the crystalline silicon substrate 111 is reduced, and recombination of carriers (electrons and holes) is suppressed.

  Therefore, the conversion efficiency of the photoelectric conversion element 200 can be improved.

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

(Example 5)
FIG. 17 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 5. Referring to FIG. 17, photoelectric conversion element 200 </ b> A includes an n-type single crystal silicon substrate 121, an amorphous film 122, a light incident layer 123, electrodes 124 and 126, and a passivation film 125. The amorphous film 122 includes an i-type amorphous film 1221 and a p-type amorphous film 1222.

  The n-type single crystal silicon substrate 121 is the same as the n-type single crystal silicon substrate 11 described above except that it does not include the diffusion region 12.

  The i-type amorphous film 1221 is disposed on the n-type single crystal silicon substrate 121 in contact with the light receiving surface 121 a of the n-type single crystal silicon substrate 121. The i-type amorphous film 1221 is made of, for example, i-type a-Si, and has a film thickness of, for example, 10 nm.

The p-type amorphous film 1222 is disposed on the i-type amorphous film 1221 in contact with the i-type amorphous film 1221. The p-type amorphous film 1222 is made of, for example, p-type a-Si, and has a film thickness of, for example, 10 nm. The p-type amorphous film 1222 includes, for example, B as a dopant, and the B concentration is, for example, 1 × 10 ¹⁹ cm ⁻³ .

  The light incident layer 123 is disposed on the p-type amorphous film 1222 in contact with the p-type amorphous film 1222. The light incident layer 123 is made of the same material as the light incident layer 113 and has a thickness of several μm. The light incident layer 123 has a concavo-convex structure including a concave portion 123a on the surface on the light incident side. Recess 123a has a hemispherical cross-sectional shape protruding in the incident direction of sunlight, and has a size of several μm in the in-plane direction of n-type single crystal silicon substrate 121. Moreover, the planar shape of the recessed part 123a consists of either the planar shape shown to (a)-(c) of FIG.

  The electrode 124 is disposed in contact with the light incident layer 123. The electrode 124 is made of Ag, for example.

Passivation film 125 is disposed in contact with the back surface of n-type single crystal silicon substrate 121 (the surface opposite to light receiving surface 121a). The passivation film 125 is made of, for example, SiO ₂ .

  Electrode 126 is disposed in contact with the back surface of n-type single crystal silicon substrate 121 and passivation film 125. The electrode 126 is made of, for example, Al.

  18 and 19 are first and second process diagrams showing a method for manufacturing the photoelectric conversion element 200A shown in FIG. 17, respectively.

  When the production of the photoelectric conversion element 200A is started, a silicon ingot is sliced to produce an n-type single crystal silicon substrate, and the produced n-type single crystal silicon substrate is etched with a mixed solution of hydrofluoric acid and nitric acid, Remove the damage layer caused by slicing. Thus, an n-type single crystal silicon substrate 121 is prepared (see step (a) in FIG. 18).

  Then, an i-type amorphous film 1221 made of i-type a-Si is deposited on the light-receiving surface 121a of the n-type single crystal silicon substrate 121 by plasma CVD (Chemical Vapor Deposition) (step (b) in FIG. 18). reference).

In this case, silane (SiH ₄ ) gas and hydrogen (H ₂ ) gas are used as material gases, and the flow rate of SiH ₄ gas is, for example, 10 sccm, and the flow rate of H ₂ gas is, for example, 100 sccm. Moreover, the reaction pressure when depositing i-type a-Si is, for example, in the range of 13.3 Pa to 665 Pa, and the RF power is, for example, in the range of 16 to 80 mW / cm ² .

  After the step (b), a p-type amorphous film 1222 made of p-type a-Si is deposited on the i-type amorphous film 1221 by plasma CVD (see step (c) in FIG. 18).

In this case, SiH ₄ gas, H ₂ gas, and diborane (B ₂ H ₆ ) gas diluted with hydrogen are used as the material gas, and the flow rate of SiH ₄ gas is ₂ sccm, for example, and the flow rate of H ₂ gas Is, for example, 42 sccm, and the flow rate of the B ₂ H ₆ gas is, for example, 12 sccm. The reaction pressure when depositing p-type a-Si is, for example, in the range of 13.3 Pa to 665 Pa, and the RF power is, for example, in the range of 16 to 80 mW / cm ² . The concentration of B ₂ H ₆ gas diluted with hydrogen is 0.1%.

After the step (c), a passivation film 127 made of SiO ₂ is deposited on the back surface of the n-type single crystal silicon substrate 121 by the APCVD method (see step (d) in FIG. 18).

  Then, a light incident layer 128 made of ITO is deposited on the p-type amorphous film 1222 by sputtering (see step (e) in FIG. 18). In this case, the film thickness of the light incident layer 128 is, for example, 5 μm.

  After the step (e), the surface of the light incident layer 128 is roughened by a laser beam by the same method as in the step (p) of FIG. 14, and the light incident layer 129 having the concave portion 129a on the surface is formed (step of FIG. f)). In this case, laser light of Nd: YAG laser or Nd: YVO laser is used as the laser light. This laser beam has a wavelength of 532 nm, an oscillation frequency of 5 kHz, and a power of 0.1 to 0.5 W. Then, a laser beam is scanned to form a recess 129a having a pattern of any one of (a) to (c) of FIG. When the concave portion 129a having a mesh pattern shown in FIG. 3C is formed, the laser light is irradiated with laser light at intervals of 5 μm in the vertical and horizontal directions, or the laser light is latticed at a constant interval (5 μm pitch). To scan.

  After the step (f), the n-type single crystal silicon substrate 121 is immersed in hydrofluoric acid, and the residue is removed and the light incident layer 129 is etched. Thereby, the light incident layer 123 is formed. And the light-incidence layer 123 has the recessed part 123a whose size is 3-5 micrometers on the surface by the side of light incidence (refer process (g) of FIG. 19).

  Thereafter, a part of the passivation film 127 is removed with an etching paste (see step (h) in FIG. 19). As a result, a passivation film 125 is formed.

  Then, the electrode 124 is formed over the light incident layer 123, and the electrode 126 is formed so as to be in contact with the back surface of the n-type single crystal silicon substrate 121 and the passivation film 125. Thus, the photoelectric conversion element 200A is completed (see step (i) in FIG. 19).

  In the photoelectric conversion element 200 </ b> A, when sunlight is irradiated from the light incident layer 123 side to the photoelectric conversion element 200 </ b> A, electrons and holes are photoexcited in the n-type single crystal silicon substrate 121.

  The photoexcited electrons and holes are separated by a pin junction by the n-type single crystal silicon substrate 121 / amorphous film 122 (i-type a-Si / p-type a-Si), and the holes are i-type amorphous. The light incident layer 123 (= ITO) is reached via the material film 1221 and the p-type amorphous film 1222, and the light incident layer 123 (= ITO) reaches the electrode 124.

  On the other hand, the electrons move to the back side of the n-type single crystal silicon substrate 121 by diffusion and reach the electrode 126.

  The electrons that have reached the electrode 126 reach the electrode 124 through a load connected between the electrode 124 and the electrode 126 and recombine with the holes.

  As described above, since the uneven structure is not formed on the light receiving surface 121a of the n-type single crystal silicon substrate 121, the amorphous film 122 is formed uniformly. Further, the area of the interface between the amorphous film 122 and the n-type single crystal silicon substrate 121 is smaller than when the light receiving surface 121a of the n-type single crystal silicon substrate 121 is made uneven. The i-type amorphous film 1221 functions as a passivation film for the light-receiving surface 121 a of the n-type single crystal silicon substrate 121. As a result, hole recombination is suppressed. Further, the light receiving surface of the n-type single crystal silicon substrate 121 can be sufficiently cleaned during the manufacturing process of the photoelectric conversion element 200A.

  Therefore, the conversion efficiency of the photoelectric conversion element 200A can be improved.

  Note that the photoelectric conversion element 200A may include an n-type polycrystalline silicon substrate instead of the n-type single crystal silicon substrate 121. 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.

In photoelectric conversion element 200 </ b> A, a high concentration diffusion region containing P for BSF at a high concentration (about 1 × 10 ²⁰ cm ⁻³ ) is formed in part of n-type single crystal silicon substrate 121 so as to be in contact with electrode 126. You may form in.

  Furthermore, the i-type amorphous film 1221 is not limited to i-type a-Si, but is made of i-type a-SiC, i-type a-SiO, i-type a-SiN, i-type a-SiCN, and i-type a-SiGe. It may consist of either.

  Further, the p-type amorphous film 1222 is not limited to p-type a-Si, but p-type a-SiC, p-type a-SiO, p-type a-SiN, p-type a-SiCN, p-type a-SiGe, It may consist of either p-type a-Ge.

In this case, p-type a-SiC is formed by plasma CVD using SiH ₄ gas, methane (CH ₄ ) gas, B ₂ H ₆ gas, and H ₂ gas as material gases. The p-type a-SiO is formed by plasma CVD using SiH ₄ gas, oxygen (O ₂ ) gas, B ₂ H ₆ gas, and H ₂ gas as material gases. The p-type a-SiN is formed by plasma CVD using SiH ₄ gas, ammonia (NH ₃ ) gas, B ₂ H ₆ gas, and H ₂ gas as material gases. The p-type a-SiCN is formed by plasma CVD using SiH ₄ gas, CH ₄ gas, NH ₃ gas, B ₂ H ₆ gas and H ₂ gas as material gases. The p-type a-SiGe is formed by plasma CVD using SiH ₄ gas, germane (GeH ₄ ) gas, B ₂ H ₆ gas, and H ₂ gas as material gases. The p-type a-Ge is formed by a plasma CVD method using GeH ₄ gas, B ₂ H ₆ gas, and H ₂ gas as material gases.

Further, 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-SiO is formed by plasma CVD using SiH ₄ gas, O ₂ 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-SiCN is formed by plasma CVD using SiH ₄ gas, CH ₄ gas, NH ₃ 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.

  Note that i-type a-Ge is also assumed as the i-type amorphous film 1221, but i-type a-Ge has an optical band gap smaller than that of the n-type single crystal silicon substrate 121. When Ge is used as the i-type amorphous film 1221, it is difficult to improve the open circuit voltage Voc. This is because in the photoelectric conversion element 200A, the optical band gap of the i-type amorphous film 1221 in the amorphous film 122 dominantly determines the open circuit voltage Voc.

  Therefore, i-type a-SiC, i-type a-SiO, i-type a-SiN, i-type a-SiCN, and i-type a-Si having an optical band gap larger than that of the n-type single crystal silicon substrate 121. , I-type a-SiGe is used as the i-type amorphous film 1221.

  Furthermore, in the photoelectric conversion element 200 </ b> A, the amorphous film 122 may be composed only of the p-type amorphous film 1222. In this case, the p-type amorphous film 1222 (= p-type a-Si or the like) is in contact with the light-receiving surface 121a of the n-type single crystal silicon substrate 121 and the light incident layer 123, and the light-receiving surface of the n-type single crystal silicon substrate 121. It is disposed between 121 a and the light incident layer 123. The p-type amorphous film 1222 (= p-type a-Si or the like) functions as a passivation film for the light-receiving surface 121a of the n-type single crystal silicon substrate 121. Therefore, in the photoelectric conversion element 200 </ b> A, the above-described effects can be obtained even when the amorphous film 122 is composed of only the p-type amorphous film 1222.

(Example 6)
FIG. 20 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 6. Referring to FIG. 20, photoelectric conversion element 200 </ b> B includes a p-type single crystal silicon substrate 131, an amorphous film 132, a light incident layer 133, electrodes 134 and 136, and a passivation film 135. The amorphous film 132 includes an i-type amorphous film 1321 and an n-type amorphous film 1322.

  The p-type single crystal silicon substrate 131 is the same as the above-described p-type single crystal silicon substrate 51 except that the p-type diffusion region 52 is not included.

  The i-type amorphous film 1321 is disposed on the p-type single crystal silicon substrate 131 in contact with the light receiving surface 131 a of the p-type single crystal silicon substrate 131. The i-type amorphous film 1321 is made of, for example, i-type a-Si, and has a film thickness of, for example, 10 nm.

The n-type amorphous film 1322 is disposed on the i-type amorphous film 1321 in contact with the i-type amorphous film 1321. The n-type amorphous film 1322 is made of, for example, n-type a-Si and has a film thickness of, for example, 10 nm. The n-type amorphous film 1322 includes, for example, P as a dopant, and the P concentration is, for example, 1 × 10 ¹⁹ cm ⁻³ .

  The light incident layer 133 is disposed on the n-type amorphous film 1322 in contact with the n-type amorphous film 1322. The light incident layer 133 is made of the same material as the light incident layer 113 and has a thickness of several μm. The light incident layer 133 has a concavo-convex structure including a concave portion 133a on the surface on the light incident side. Recess 133a has a hemispherical cross-sectional shape protruding in the incident direction of sunlight, and has a size of several μm in the in-plane direction of p-type single crystal silicon substrate 131. Moreover, the planar shape of the recessed part 133a consists of either of the planar shapes shown to (a)-(c) of FIG.

  The electrode 134 is disposed in contact with the light incident layer 133. The electrode 134 is made of Ag, for example.

Passivation film 135 is disposed in contact with the back surface of p-type single crystal silicon substrate 131 (the surface opposite to light receiving surface 131a). The passivation film 135 is made of, for example, SiO ₂ .

  Electrode 136 is disposed in contact with the back surface of p-type single crystal silicon substrate 131 and passivation film 135. The electrode 136 is made of, for example, Al.

  The photoelectric conversion element 200B is manufactured according to the steps (a) to (i) shown in FIGS.

  In this case, the i-type amorphous film 1321 made of i-type a-Si is formed by plasma CVD using the same material gas and the same conditions as the i-type amorphous film 1221 made of i-type a-Si. .

The n-type amorphous film 1322 made of n-type a-Si is formed by plasma CVD using 20 sccm of SiH ₄ gas, 150 sccm of H ₂ gas, and 50 sccm of phosphine (PH ₃ ) gas diluted with hydrogen. Formed by law. The reaction pressure when forming n-type a-Si is in the range of 13.3 Pa to 665 Pa, and the RF power is in the range of 16 to 80 mW / cm ² .

  In the photoelectric conversion element 200 </ b> B, when sunlight is irradiated from the light incident layer 133 side to the photoelectric conversion element 200 </ b> B, electrons and holes are photoexcited in the p-type single crystal silicon substrate 131.

  The photoexcited electrons and holes are separated by a pin junction by the p-type single crystal silicon substrate 131 / amorphous film 132 (i-type a-Si / n-type a-Si), and the electrons are i-type amorphous. It reaches the light incident layer 133 (= ITO) through the film 1321 and the n-type amorphous film 1322 and reaches the electrode 134 from the light incident layer 133 (= ITO).

  On the other hand, the holes move to the back side of the p-type single crystal silicon substrate 131 by diffusion and reach the electrode 136.

  The electrons that have reached the electrode 134 reach the electrode 136 via a load connected between the electrode 134 and the electrode 136 and recombine with the holes.

  As described above, since the uneven structure is not formed on the light receiving surface 131a of the p-type single crystal silicon substrate 131, the amorphous film 132 is uniformly formed. Further, the area of the interface between the amorphous film 132 and the p-type single crystal silicon substrate 131 is smaller than when the light receiving surface 131a of the p-type single crystal silicon substrate 131 is made uneven. The i-type amorphous film 1321 functions as a passivation film for the light-receiving surface 131a of the p-type single crystal silicon substrate 131. As a result, recombination of electrons is suppressed. Furthermore, the light receiving surface of the p-type single crystal silicon substrate 131 can be sufficiently cleaned during the manufacturing process of the photoelectric conversion element 200B.

  Therefore, the conversion efficiency of the photoelectric conversion element 200B can be improved.

  Note that the photoelectric conversion element 200B may include a p-type polycrystalline silicon substrate instead of the p-type single crystal silicon substrate 131. 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.

Further, in the photoelectric conversion element 200 </ b> B, a high-concentration diffusion region containing B for BSF at a high concentration (about 1 × 10 ²⁰ cm ⁻³ ) so as to be in contact with the electrode 136 is part of the p-type single crystal silicon substrate 131. You may form in.

  Further, the i-type amorphous film 1321 is not limited to i-type a-Si, but may be i-type a-SiC, i-type a-SiO, i-type a-SiN, i-type a-SiCN, i-type a-SiGe. It may consist of either.

  Further, the n-type amorphous film 1322 is not limited to n-type a-Si, but n-type a-SiC, n-type a-SiO, n-type a-SiN, n-type a-SiCN, n-type a-SiGe, It may consist of any of n-type a-Ge.

In this case, n-type a-SiC is formed by plasma CVD using SiH ₄ gas, CH ₄ gas, PH ₃ gas, and H ₂ gas as material gases. The n-type a-SiO is formed by a plasma CVD method using SiH ₄ gas, O ₂ gas, PH ₃ gas, and H ₂ gas as material gases. The n-type a-SiN is formed by plasma CVD using SiH ₄ gas, NH ₃ gas, PH ₃ gas, and H ₂ gas as material gases. The n-type a-SiCN is formed by plasma CVD using SiH ₄ gas, CH ₄ gas, NH ₃ gas, PH ₃ gas, and H ₂ gas as material gases. The n-type a-SiGe is formed by plasma CVD using SiH ₄ gas, GeH ₄ gas, PH ₃ gas, and H ₂ gas as material gases. The n-type a-Ge is formed by a plasma CVD method using GeH ₄ gas, PH ₃ gas, and H ₂ gas as material gases.

  Furthermore, i-type a-SiC or the like is formed by plasma CVD using each of the gases described above.

  The reason why i-type a-Ge is excluded as the i-type amorphous film 1321 is the same as the reason why i-type a-Ge is excluded as the i-type amorphous film 1221.

  Furthermore, in the photoelectric conversion element 200 </ b> B, the amorphous film 132 may be composed only of the n-type amorphous film 1322. In this case, the n-type amorphous film 1322 (= n-type a-Si or the like) is in contact with the light-receiving surface 131a of the p-type single crystal silicon substrate 1321 and the light incident layer 133, and the light-receiving surface of the p-type single crystal silicon substrate 131. It is disposed between 131a and the light incident layer 133. The n-type amorphous film 1322 (= n-type a-Si or the like) functions as a passivation film for the light-receiving surface 131a of the p-type single crystal silicon substrate 131. Therefore, in the photoelectric conversion element 200 </ b> B, the above-described effects can be obtained even when the amorphous film 132 is composed only of the p-type amorphous film 1322.

  The other description about the photoelectric conversion element 200B is the same as the description of the photoelectric conversion element 200A.

  Other explanations in the third embodiment are the same as those in the first embodiment.

[Embodiment 4]
FIG. 21 is a cross-sectional view showing the configuration of the photoelectric conversion element according to the fourth embodiment. Referring to FIG. 21, a photoelectric conversion element 300 according to Embodiment 4 includes a single crystal silicon substrate 141, a light incident layer 142, i-type amorphous films 151 to 15n, amorphous films 161 to 16m, 171-17m-1 and electrodes 181-18n.

  The single crystal silicon substrate 141 is the same as the single crystal silicon substrate 61 described above.

  The light incident layer 142 is disposed on the single crystal silicon substrate 141 in contact with the light receiving surface 141 a of the single crystal silicon substrate 141. The light incident layer 142 is made of any of the light incident layers 31 to 33 shown in FIG. 2, and has a hemispherical concave portion 142a protruding in the sunlight incident direction on the light incident side. Recess 142 a has a size of several μm in the in-plane direction of single crystal silicon substrate 141. And the planar shape of the recessed part 142a consists of either the planar shape shown to (a)-(c) of FIG.

  Each of i-type amorphous films 151 to 15n is provided in contact with the back surface (surface opposite to light receiving surface 141a) of single crystal silicon substrate 141. Each of the i-type amorphous films 151 to 15n is made of, for example, i-type a-Si and has a film thickness of, for example, 10 nm.

  The amorphous films 161 to 16m have an n-type conductivity when the single crystal silicon substrate 141 has an n-type conductivity type, and have a p-type when the single crystal silicon substrate 141 has a p-type conductivity type. Have the conductivity type. As described above, the amorphous films 161 to 16 m have the same conductivity type as that of the single crystal silicon substrate 141.

  The amorphous films 161 to 16m are provided in contact with the i-type amorphous films 151, 153, ..., 15n-2, 15n, respectively.

  When the single crystal silicon substrate 141 has an n-type conductivity type, the amorphous films 171 to 17m-1 have a p-type conductivity type, and when the single crystal silicon substrate 141 has a p-type conductivity type, n-type conductivity. Thus, the amorphous films 171 to 17m have a conductivity type opposite to that of the single crystal silicon substrate 141.

  The amorphous films 171 to 17m−1 are provided in contact with the i-type amorphous films 152, 154,.

  The electrodes 181, 183,..., 18n-2, 18n are provided in contact with the amorphous films 161 to 16m, respectively. The electrodes 182, 184,..., 18n-1 are provided in contact with the amorphous films 171 to 17m-1, respectively. Each of the electrodes 181 to 18n is made of Ag, for example.

  The i-type amorphous films 151 to 15n, the amorphous films 161 to 16m, and the amorphous films 171 to 17m-1 have the same length in the direction perpendicular to the paper surface of FIG. Further, the amorphous films 161 to 16m have the same width as the widths of the i-type amorphous films 151, 153,..., 15n-2, 15n in the in-plane direction of the single crystal silicon substrate 141, respectively. . Further, the amorphous films 171 to 17m-1 have the same width as the widths of the i-type amorphous films 152, 154, ..., 15n-1 in the in-plane direction of the single crystal silicon substrate 141, respectively. . The area occupancy ratio, which is the ratio of the entire area of the amorphous films 171 to 17m-1 to the area of the single crystal silicon substrate 141, is 60 to 93%, and the entire area of the amorphous films 161 to 16m is The area occupation ratio, which is the ratio of the area to the area of the single crystal silicon substrate 141, is 5 to 20%.

  As described above, the area occupancy of the amorphous films 171 to 17m-1 is larger than the area occupancy of the amorphous films 161 to 16m because electrons and holes photoexcited in the single crystal silicon substrate 141 are used. Is made easier to separate by a pin junction, and the contribution ratio of photoexcited electrons and holes to power generation is increased.

  As described above, since an uneven structure is not formed on the light receiving surface 141a of the single crystal silicon substrate 141, the area of the interface between the passivation film of the light incident layer 142 and the single crystal silicon substrate 141 is as follows. It becomes smaller than the case where the light receiving surface 141a of 141 is made uneven. As a result, recombination of carriers (electrons and holes) is suppressed. In addition, during the manufacturing process of the photoelectric conversion element 300, the light receiving surface 141a of the single crystal silicon substrate 141 can be sufficiently cleaned.

  Therefore, the conversion efficiency of the photoelectric conversion element 300 can be improved.

  Note that the photoelectric conversion element 300 may not include the i-type amorphous films 151 to 15n. In this case, the amorphous films 161 to 16m and the amorphous films 171 to 17m-1 are formed in contact with the back surface of the single crystal silicon substrate 141. Therefore, the photoelectric conversion element 300 has a structure in which a p / n junction made of a heterojunction is disposed on the back side of the single crystal silicon substrate 141.

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

(Example 7)
FIG. 22 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 7. Referring to FIG. 22, in photoelectric conversion element 300 </ b> A, single crystal silicon substrate 141 of photoelectric conversion element 300 shown in FIG. 21 is replaced with n-type single crystal silicon substrate 201, and amorphous films 161-16 m are replaced with n-type amorphous. The amorphous films 171 to 17m-1 are replaced with the p-type amorphous films 221 to 22m-1 in place of the material films 211 to 21m, and the others are the same as the photoelectric conversion element 300.

  The n-type single crystal silicon substrate 201 is the same as the n-type single crystal silicon substrate 121 described above.

  The n-type amorphous films 211 to 21m are arranged in contact with the i-type amorphous films 151, 153, ..., 15n-2, 15n, respectively. Each of the n-type amorphous films 211 to 21m is made of, for example, n-type a-Si, and has a film thickness of, for example, 10 nm.

  The p-type amorphous films 221 to 22m−1 are disposed in contact with the i-type amorphous films 152, 154,. Each of the p-type amorphous films 221 to 22m-1 is made of, for example, p-type a-Si and has a film thickness of, for example, 10 nm.

  In the photoelectric conversion element 300 </ b> A, the light incident layer 142 is disposed in contact with the light receiving surface 201 a of the n-type single crystal silicon substrate 201. The i-type amorphous films 151 to 15n are arranged in contact with the back surface (= the surface opposite to the light receiving surface 201a) of the n-type single crystal silicon substrate 201. Further, the electrodes 181, 183,..., 18 n-2, 18 n are disposed in contact with the n-type amorphous films 211 to 21 m, respectively, and the electrodes 182, 184,. The p-type amorphous films 221 to 22m−1 are disposed in contact with each other.

  The i-type amorphous films 151 to 15n, the n-type amorphous films 211 to 21m, and the p-type amorphous films 221 to 22m-1 have the same length in the direction perpendicular to the paper surface of FIG. In addition, the n-type amorphous films 211 to 21m have the widths of the i-type amorphous films 151, 153,..., 15n-2, 15n 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 221 to 22m−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 152, 154,. Have the same width. The area occupation ratio, which is the ratio of the entire area of the p-type amorphous films 221 to 22m-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 total area of 211 to 21 m to the area of the n-type single crystal silicon substrate 201, is 5 to 20%.

  As described above, the area occupation ratio of the p-type amorphous films 221 to 22m-1 is larger than the area occupation ratio of the n-type amorphous films 211 to 21m in the n-type single crystal silicon substrate 201. This is because the generated electrons and holes are easily separated by a pin junction, and the contribution ratio of photoexcited electrons and holes to power generation is increased.

  23 to 26 are first to fourth process diagrams showing a method of manufacturing the photoelectric conversion element 300A shown in FIG.

  When production of the photoelectric conversion element 300A is started, a silicon ingot is sliced to produce an n-type single crystal silicon substrate, and the produced n-type single crystal silicon substrate is etched with a mixed solution of hydrofluoric acid and nitric acid, Remove the damage layer caused by slicing. Thus, an n-type single crystal silicon substrate 201 is prepared (see step (a) in FIG. 23).

Then, the i-type a-Si film 220 and the n-type a-Si film 230 are sequentially stacked on the back surface (surface opposite to the light receiving surface 201a) of the n-type single crystal silicon substrate 201 by plasma CVD (FIG. 23). Steps (b) and (c)). 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, for example. 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), 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 (d) in FIG. 23). .

  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 231 to 23m are formed (see step (e) in FIG. 23).

Thereafter, the resist pattern 240 / n-type amorphous film 231 to 23m / n-type single crystal silicon substrate 201 is washed with hydrofluoric acid, and the p-type a-Si film 250 is removed from the back surface (light-receiving surface) of the n-type single crystal silicon substrate 201. On the surface opposite to 201a) by plasma CVD (see step (f) in FIG. 24). 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.

  Then, the resist pattern 240 is removed. In this case, the p-type a-Si film 260 is removed by lift-off (see step (g) in FIG. 24).

  Subsequently, a resist is applied to the entire surfaces of the n-type amorphous films 231 to 23m and the p-type a-Si film 250, and the applied resist is patterned by photolithography to form a resist pattern 270 (FIG. 24). Step (h)). In this case, the resist pattern 270 on the n-type amorphous films 231 to 23m has the same width as the n-type amorphous film 231 to 23m, and the resist pattern 270 on the p-type a-Si film 250 is p It has a narrower width than the type a-Si film 250.

  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 151 to 15n, n-type amorphous films 211 to 21m, and p-type amorphous films 221 to 22m-1 are formed (see step (i) in FIG. 24).

Thereafter, a passivation film 271 made of SiO ₂ is deposited on the light receiving surface 201a of the n-type single crystal silicon substrate 201 by the APCVD method (see step (j) in FIG. 25). Subsequently, an antireflection film 272 made of SiO ₂ is deposited on the passivation film 271 by the APCVD method (see step (k) in FIG. 25).

  After the step (k), the surface of the antireflection film 272 is roughened by the laser beam by the same method as in the step (p) of FIG. 14, and the antireflection film 273 having the concave portion 273a is formed on the surface (step of FIG. l)). In this case, laser light of Nd: YAG laser or Nd: YVO laser is used as the laser light. This laser beam has a wavelength of 532 nm, an oscillation frequency of 5 kHz, and a power of 0.1 to 0.5 W. Then, the laser beam is scanned to form the recess 273a having any one of the patterns shown in FIGS. When the concave portion 273a having a mesh pattern shown in FIG. 3C is formed, the laser light is irradiated with laser light at intervals of 5 μm in the vertical and horizontal directions, or the laser light is latticed at a constant interval (5 μm pitch). To scan.

  After the step (l), the n-type single crystal silicon substrate 201 is immersed in hydrofluoric acid, and the residue is removed and the antireflection film 273 is etched. Thereby, the antireflection film 274 is formed. The passivation film 271 and the antireflection film 274 constitute a light incident layer 142, and the light incident layer 142 has a concave portion 142a having a size of 3 to 5 μm on the surface on the light incident side (step (m in FIG. 25 (m )reference).

  Then, electrodes 181, 183,..., 18 n-2, 18 n are formed on n-type amorphous films 211 to 21 m, respectively, and electrodes 182, 184,. It is formed on the membrane 221 to 22m-1. Thus, the photoelectric conversion element 300A is completed (see step (n) in FIG. 26).

  In the photoelectric conversion element 300 </ b> A, when sunlight is irradiated from the light incident layer 142 side to the photoelectric conversion element 300 </ b> A, electrons and holes are photoexcited in the n-type single crystal silicon substrate 201.

  Even if the photoexcited electrons and holes are diffused to the light incident layer 142 side, they are difficult to recombine due to the passivation effect of the n-type single crystal silicon substrate 201 by the passivation film 271 of the light incident layer 142, and the n-type amorphous Diffusion to the films 211 to 21m and the p-type amorphous films 221 to 22m-1 side.

  Then, the electrons and holes diffused toward the n-type amorphous films 211 to 21m and the p-type amorphous films 221 to 22m-1 are the n-type single crystal silicon substrate 201 / i-type amorphous films 152 and 154. ,..., 15n−1 / p-type amorphous films 221 to 22m−1 (= pin junctions) are separated by an internal electric field, and the holes are i-type amorphous films 152, 154,. 15n-1 and the p-type amorphous films 221 to 22m-1 reach the electrodes 182, 184,..., 18n-1, and the electrons are i-type amorphous films 151, 153,. , 15n-2, 15n-1 and the n-type amorphous films 211 to 21m-1 reach the electrodes 181, 183, ..., 18n-2, 18n.

  Electrons reaching the electrodes 181, 183, ..., 18n-2, 18n are between the electrodes 181, 183, ..., 18n-2, 18n and the electrodes 182, 184, ..., 18n-1. Reach the electrodes 182, 184,..., 18n-1 through the load connected to, and recombine with holes.

  Thus, the photoelectric conversion element 300A takes out the electrons and holes photoexcited in the n-type single crystal silicon substrate 201 from the back surface (= the surface opposite to the light receiving surface 201a) of the n-type single crystal silicon substrate 201. It is a contact type photoelectric conversion element.

  In the photoelectric conversion element 300 </ b> A, since the uneven structure is not formed on the light receiving surface 201 a of the n-type single crystal silicon substrate 201, the interface between the passivation film of the light incident layer 142 and the n-type single crystal silicon substrate 201. Is smaller than the case where the light receiving surface 201a of the n-type single crystal silicon substrate 201 is made uneven. As a result, recombination of carriers (electrons and holes) is suppressed. In addition, the light receiving surface 201a of the n-type single crystal silicon substrate 201 can be sufficiently cleaned during the manufacturing process of the photoelectric conversion element 300A.

  Therefore, the conversion efficiency of the photoelectric conversion element 300A can be improved.

  Each of the i-type amorphous films 151 to 15n is not limited to i-type a-Si, but i-type a-SiC, i-type a-SiO, i-type a-SiN, i-type a-SiCN, and i-type. It may consist of either a-SiGe.

  The n-type amorphous films 211 to 21m are not limited to n-type a-Si, but are n-type a-SiC, n-type a-SiO, n-type a-SiN, n-type a-SiCN, and n-type a-. It may consist of either SiGe or n-type a-Ge.

  Further, the p-type amorphous films 221 to 22m-1 are not limited to p-type a-Si, but p-type a-SiC, p-type a-SiO, p-type a-SiN, p-type a-SiCN, and p-type. It may consist of either a-SiGe or p-type a-Ge.

  And i-type a-SiC etc., n-type a-SiC etc. and p-type a-SiC etc. are formed by plasma CVD method using the gas mentioned above.

  Furthermore, the photoelectric conversion element 300A may not include the i-type amorphous films 151 to 15n. In this case, the n-type amorphous films 211 to 21m (= n-type a-Si and the like) and the p-type amorphous films 221 to 22m-1 (= p-type a-Si and the like) are n-type single crystal silicon substrates. It is arranged in contact with the back surface of 201. The n-type amorphous films 211 to 21m (= n-type a-Si and the like) and the p-type amorphous films 221 to 22m-1 (= p-type a-Si and the like) are formed on the n-type single crystal silicon substrate 201. It functions as a passivation film with respect to the back surface. Therefore, in the photoelectric conversion element 300A, the above-described effects can be obtained even when the i-type amorphous films 151 to 15n are not provided.

  Furthermore, the photoelectric conversion element 300A may not include the i-type amorphous films 151, 153, ..., 15n-2, 15n. In this case, the n-type amorphous films 211 to 21m (= n-type a-Si or the like) are disposed in contact with the back surface of the n-type single crystal silicon substrate 201. The n-type amorphous films 211 to 21m (= n-type a-Si, etc.) and the i-type amorphous films 152, 154,..., 15n-1 are formed on the back surface of the n-type single crystal silicon substrate 201. On the other hand, it functions as a passivation film. Therefore, in the photoelectric conversion element 300A, the above-described effects can be obtained even when the i-type amorphous films 151, 153,..., 15n-2, 15n are not provided.

  Furthermore, the photoelectric conversion element 300A may not include the i-type amorphous films 152, 154,. In this case, the p-type amorphous films 221 to 22m−1 (= p-type a-Si or the like) are arranged in contact with the back surface of the n-type single crystal silicon substrate 201. The p-type amorphous films 221 to 22m-1 (= p-type a-Si, etc.) and the i-type amorphous films 151, 153,..., 15n-2, 15n are n-type single crystal silicon substrates. The back surface of 201 functions as a passivation film. Therefore, in the photoelectric conversion element 300A, the above-described effects can be obtained even when the i-type amorphous films 152, 154,.

(Example 8)
FIG. 27 is a cross-sectional view illustrating a configuration of a photoelectric conversion element in Example 8. Referring to FIG. 27, in photoelectric conversion element 300B, n-type amorphous films 211 to 21m are replaced by replacing n-type single crystal silicon substrate 201 of photoelectric conversion element 300A shown in FIG. 22 with p-type single crystal silicon substrate 301. Instead of the p-type amorphous films 311 to 31m, the p-type amorphous films 221 to 22m-1 are replaced with n-type amorphous films 321 to 32m-1, and the others are the same as the photoelectric conversion element 300A. The same.

  The p-type single crystal silicon substrate 301 is the same as the p-type single crystal silicon substrate 131 described above.

  The p-type amorphous films 311 to 31m are disposed in contact with the i-type amorphous films 151, 153, ..., 15n-2, 15n, respectively. Each of the p-type amorphous films 311 to 31m is made of, for example, p-type a-Si, and has a film thickness of, for example, 10 nm.

  The n-type amorphous films 321 to 32m−1 are disposed in contact with the i-type amorphous films 152, 154,. Each of the n-type amorphous films 321 to 32m−1 is made of, for example, n-type a-Si, and has a film thickness of, for example, 10 nm.

  In the photoelectric conversion element 300 </ b> B, the light incident layer 142 is disposed in contact with the light receiving surface 301 a of the p-type single crystal silicon substrate 301. The i-type amorphous films 151 to 15n are disposed in contact with the back surface of the p-type single crystal silicon substrate 301 (= the surface opposite to the light receiving surface 301a). Further, the electrodes 181, 183,..., 18n-2, 18n are disposed in contact with the p-type amorphous films 311 to 31m, respectively, and the electrodes 182, 184,. The n-type amorphous films 321 to 32m−1 are disposed in contact with each other.

  The i-type amorphous films 151 to 15n, the p-type amorphous films 311 to 31m, and the n-type amorphous films 321 to 32m-1 have the same length in the direction perpendicular to the paper surface of FIG. In addition, the p-type amorphous films 311 to 31m have the widths of the i-type amorphous films 151, 153,..., 15n-2, 15n 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 321 to 32m−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 152, 154,. Have the same width. The area occupation ratio, which is the ratio of the entire area of the n-type amorphous films 321 to 32m−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 311 to 31 m to the area of the p-type single crystal silicon substrate 301, is 5 to 20%.

  As described above, the area occupancy of the n-type amorphous films 321 to 32m-1 is larger than the area occupancy of the p-type amorphous films 311 to 31m by photoexcitation in the p-type single crystal silicon substrate 301. This is because the generated electrons and holes are easily separated by a pin junction, and the contribution ratio of photoexcited electrons and holes to power generation is increased.

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

  In the photoelectric conversion element 300 </ b> B, when sunlight is applied to the photoelectric conversion element 300 </ b> B from the light incident layer 142 side, electrons and holes are photoexcited in the p-type single crystal silicon substrate 301.

  Even if the photoexcited electrons and holes diffuse to the light incident layer 142 side, they are difficult to recombine due to the passivation effect of the p-type single crystal silicon substrate 301 by the passivation film of the light incident layer 142, and the p-type amorphous film It diffuses toward 311 to 31m and the n-type amorphous films 321 to 32m-1.

  Then, the electrons and holes diffused toward the p-type amorphous films 311 to 31m and the n-type amorphous films 321 to 32m-1 become the p-type single crystal silicon substrate 301 / i-type amorphous films 152 and 154. ,..., 15n−1 / n-type amorphous films 321 to 32m−1 (= pin junctions) are separated by an internal electric field, and electrons are i-type amorphous films 152, 154,. -1 and n-type amorphous films 321 to 32m-1 to reach the electrodes 182, 184,..., 18n-1, and the holes are i-type amorphous films 151, 153,. , 15n-2, 15n-1 and the p-type amorphous films 311 to 31m-1 reach the electrodes 181, 183, ..., 18n-2, 18n.

  Electrons reaching the electrodes 182, 184, ..., 18n-1 are connected between the electrodes 181, 183, ..., 18n-2, 18n and the electrodes 182, 184, ..., 18n-1. Reach the electrodes 181, 183,..., 18 n-2, 18 n through the applied load and recombine with holes.

  As described above, the photoelectric conversion element 300B takes out electrons and holes photoexcited in the p-type single crystal silicon substrate 301 from the back surface (= the surface opposite to the light receiving surface 301a) of the p-type single crystal silicon substrate 301. It is a contact type photoelectric conversion element.

  In the photoelectric conversion element 300 </ b> B, since the uneven structure is not formed on the light receiving surface 301 a of the p-type single crystal silicon substrate 301, the interface between the passivation film of the light incident layer 142 and the p-type single crystal silicon substrate 301. Is smaller than when the light receiving surface 301a of the p-type single crystal silicon substrate 301 is made uneven. As a result, recombination of carriers (electrons and holes) is suppressed. Further, the light receiving surface 301a of the p-type single crystal silicon substrate 301 can be sufficiently cleaned during the manufacturing process of the photoelectric conversion element 300B.

  Therefore, the conversion efficiency of the photoelectric conversion element 300B can be improved.

  The p-type amorphous films 311 to 31m are not limited to p-type a-Si, but p-type a-SiC, p-type a-SiO, p-type a-SiN, p-type a-SiCN, and p-type a-. It may consist of either SiGe or p-type a-Ge.

  The n-type amorphous films 321 to 32m-1 are not limited to n-type a-Si, but are n-type a-SiC, n-type a-SiO, n-type a-SiN, n-type a-SiCN, and n-type. It may consist of either a-SiGe or n-type a-Ge.

  And n-type a-SiC etc. and p-type a-SiC etc. are formed by plasma CVD method using the gas mentioned above.

  Further, the photoelectric conversion element 300B may not include the i-type amorphous films 151 to 15n. In this case, the p-type amorphous films 311 to 31m (= p-type a-Si or the like) and the n-type amorphous films 321 to 32m-1 (= n-type a-Si or the like) are formed on the p-type single crystal silicon substrate. It arrange | positions in contact with the back surface of 301. FIG. The p-type amorphous films 311 to 31m (= p-type a-Si and the like) and the n-type amorphous films 321 to 32m-1 (= n-type a-Si and the like) are formed on the p-type single crystal silicon substrate 301. It functions as a passivation film with respect to the back surface. Therefore, in the photoelectric conversion element 300B, the above-described effects can be obtained even when the i-type amorphous films 151 to 15n are not provided.

  Furthermore, the photoelectric conversion element 300B may not include the i-type amorphous films 151, 153, ..., 15n-2, 15n. In this case, the p-type amorphous films 311 to 31 m (= p-type a-Si or the like) are disposed in contact with the back surface of the p-type single crystal silicon substrate 301. The p-type amorphous films 311 to 31m (= p-type a-Si, etc.) and the i-type amorphous films 152, 154,..., 15n-1 are formed on the back surface of the p-type single crystal silicon substrate 301. On the other hand, it functions as a passivation film. Therefore, in the photoelectric conversion element 300B, the above-described effects can be obtained even when the i-type amorphous films 151, 153,..., 15n-2, 15n are not provided.

  Furthermore, the photoelectric conversion element 300B may not include the i-type amorphous films 152, 154,. In this case, the n-type amorphous films 321 to 32m−1 (= n-type a-Si or the like) are disposed in contact with the back surface of the p-type single crystal silicon substrate 301. The n-type amorphous films 321 to 32m-1 (= n-type a-Si, etc.) and the i-type amorphous films 151, 153,..., 15n-2, 15n are p-type single crystal silicon substrates. It functions as a passivation film for the back surface of 301. Therefore, in the photoelectric conversion element 300B, the above-described effect can be obtained even when the i-type amorphous films 152, 154,.

  The other description of the photoelectric conversion element 300B is the same as the description of the photoelectric conversion element 300A.

  Other explanations in the fourth embodiment are the same as those in the first embodiment.

  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 p / n on the side opposite to the light incident side of the single crystal silicon substrate 61. The photoelectric conversion element having an n junction, the photoelectric conversion element 200 is a photoelectric conversion element having a p / n junction on the light incident side of the crystalline silicon substrate 111, and the photoelectric conversion element 300 is a light of the single crystal silicon substrate 141. It is a photoelectric conversion element having a p / n junction on the side opposite to the incident side.

  Therefore, the photoelectric conversion element according to the embodiment of the present invention is formed on a light receiving surface of a semiconductor substrate made of crystalline silicon on which a light receiving surface is not provided with a concavo-convex structure, and a light incident side surface is sunlight. It is only necessary to include a light incident layer having a concavo-convex structure having a hemispherical cross-sectional shape protruding in the incident direction, and a joint disposed on the light receiving surface side of the semiconductor substrate or on the opposite side of the light receiving surface.

  In the photoelectric conversion element having such a configuration, since the uneven structure is not formed on the light receiving surface of the semiconductor substrate, the area of the interface between the light incident layer and the semiconductor substrate is when the light receiving surface of the semiconductor substrate is made uneven. Smaller than. As a result, recombination of carriers (electrons and holes) is suppressed. In addition, the light receiving surface of the semiconductor substrate can be sufficiently cleaned during the manufacturing process of the photoelectric conversion element. Therefore, since the conversion efficiency of the photoelectric conversion element can be improved, the photoelectric conversion element according to the embodiment of the present invention only needs to have the above-described configuration.

  Moreover, the manufacturing method of the photoelectric conversion element by embodiment of this invention should just be a method of manufacturing the photoelectric conversion element which has the structure mentioned above. Therefore, the manufacturing method of the photoelectric conversion element according to the embodiment of the present invention includes a first step of forming a light incident layer on a light receiving surface of a semiconductor substrate made of crystalline silicon on which the uneven structure is not formed on the light receiving surface, A second step of forming a concavo-convex structure having a hemispherical cross-sectional shape protruding in the incident direction of sunlight on the light incident side surface of the light incident layer, and bonding to the light receiving surface side of the semiconductor substrate or the side opposite to the light receiving surface And a third step of forming the part.

  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 and a manufacturing method thereof.

  1,111 crystal silicon substrate, 1a, 11a, 51a, 61a, 71a, 101a, 111a, 141a, 201a, 301a light receiving surface, 2, 2a, 2b, 12, 12a, 12b, 52, 52a, 52b, 161b to 16m , 171-17m-1, 611-61n Diffusion region, 3, 13, 31-33, 53, 63, 73, 113, 133, 142 Light incident layer, 3a, 13a, 53a, 63a, 73a, 103a, 113a, 123a, 133a, 142a, 311a, 321a, 332a Recess, 4, 6, 14, 16, 54, 56, 114, 116, 124, 126, 134, 136, 181-18n, 651-65n, 751-75n, 1051 ~ 105n electrode, 5, 15, 55, 115, 125, 135 passivation film, 10, 10 , 10B, 100, 100A, 100B, 200, 200A, 200B, 300, 300A, 300B photoelectric conversion element, 11, 71, 121, 201 n-type single crystal silicon substrate, 51, 101, 131, 301 p-type single crystal silicon Substrate, 61 Single crystal silicon substrate, 64, 74 Oxide film, 112, 122, 132 Amorphous film, 102, 221-22m-1, 311-31m, 712, 714, ..., 71n-1, 1012 , 101n-1 p-type diffusion region, 151-15n, 1221, 1321 i-type amorphous film, 211-21m, 321-32m-1, 710, 711, 713, ..., 71n- 2, 71n, 1011, 1013, ..., 101n-2, 101n n-type diffusion region, 1222 p-type amorphous film, 1322 n-type AkiraTadashimaku.

Claims (19)

A semiconductor substrate made of crystalline silicon in which the uneven structure is not formed on the light receiving surface;
A light incident layer that is formed on the light receiving surface of the semiconductor substrate and has a concavo-convex structure having a hemispherical cross-sectional shape in which the light incident side surface protrudes in the incident direction of sunlight;
A photoelectric conversion element provided with the junction part arrange | positioned at the light-receiving surface side of the said semiconductor substrate, or the said light-receiving surface opposite side.   The photoelectric conversion element according to claim 1, wherein the light incident layer is formed of a passivation film that is formed in contact with a light receiving surface of the semiconductor substrate and has a surface on the light incident side that has the uneven structure. The light incident layer is
A passivation film formed in contact with the light receiving surface of the semiconductor substrate;
An antireflection film formed in contact with the passivation film,
The photoelectric conversion element according to claim 1, wherein a surface on the light incident side of the antireflection film or a surface on the light incident side of the passivation film and the antireflection film has the uneven structure.   The photoelectric conversion element according to claim 1, wherein the light incident layer is formed of an antireflection film that is formed on a light receiving surface of the semiconductor substrate and has a light incident side surface having the uneven structure. The joint is
A diffusion region disposed in the semiconductor substrate in contact with the light receiving surface of the semiconductor substrate and having a first conductivity type;
4. The photoelectric conversion element according to claim 2, further comprising a bulk region disposed in contact with the diffusion region in the semiconductor substrate and having a second conductivity type opposite to the first conductivity type. 5. The joint is
An amorphous film disposed between the light receiving surface of the semiconductor substrate and the light incident layer and having a first conductivity type;
The photoelectric conversion element according to claim 4, including the semiconductor substrate having a second conductivity type opposite to the first conductivity type.   The photoelectric conversion element according to claim 5, wherein the semiconductor substrate is made of polycrystalline silicon or single crystal silicon. The semiconductor substrate is made of single crystal silicon,
The joint is
A first diffusion region disposed in the semiconductor substrate in contact with a surface opposite to the light receiving surface of the semiconductor substrate and having a first conductivity type;
The first conductive layer is disposed in the semiconductor substrate in contact with the surface opposite to the light receiving surface of the semiconductor substrate and adjacent to the first diffusion region in an in-plane direction of the semiconductor substrate. A second diffusion region having a second conductivity type opposite to the mold;
4. The photoelectric conversion element according to claim 2, further comprising: a bulk region disposed in the semiconductor substrate in contact with the first and second diffusion regions and having the second conductivity type. 5. The semiconductor substrate is made of single crystal silicon,
The joint is
A first amorphous film disposed on the opposite side of the light receiving surface of the semiconductor substrate and having a first conductivity type;
A second substrate opposite to the first conductivity type is disposed on the opposite side of the light receiving surface of the semiconductor substrate and adjacent to the first amorphous film in an in-plane direction of the semiconductor substrate. A second amorphous film having a conductivity type;
The photoelectric conversion element according to claim 2, comprising the semiconductor substrate having the second conductivity type. The first conductivity type is p-type,
The photoelectric conversion element according to claim 5, wherein the second conductivity type is an n-type. The first conductivity type is n-type,
The photoelectric conversion element according to claim 5, wherein the second conductivity type is p-type. A first step of forming a light incident layer on a light receiving surface of a semiconductor substrate made of crystalline silicon on which the uneven structure is not formed on the light receiving surface;
A second step of forming a concavo-convex structure having a hemispherical cross-sectional shape protruding in the sunlight incident direction on the light incident side surface of the light incident layer;
And a third step of forming a bonding portion on the light receiving surface side of the semiconductor substrate or on the side opposite to the light receiving surface.   The method for manufacturing a photoelectric conversion element according to claim 12, wherein in the first step, a passivation film is formed in contact with the light receiving surface of the semiconductor substrate. The first step includes
Forming a passivation film in contact with the light receiving surface of the semiconductor substrate;
Forming an antireflection film in contact with the passivation film,
The method for manufacturing a photoelectric conversion element according to claim 12, wherein in the second step, the light incident side surface of the antireflection film or the surface of the passivation film and the light incident side of the antireflection film is roughened.   The method for manufacturing a photoelectric conversion element according to claim 12, wherein an antireflection film is formed on a light receiving surface of the semiconductor substrate in the first step. In the third step, a diffusion region having a first conductivity type is formed in the semiconductor substrate having a second conductivity type opposite to the first conductivity type in contact with the light receiving surface of the semiconductor substrate. ,
The method for manufacturing a photoelectric conversion element according to claim 13 or 14, wherein the first and second steps are performed after the third step. In the third step, an amorphous film having a second conductivity type opposite to the first conductivity type is deposited on the light receiving surface of the semiconductor substrate having the first conductivity type;
The method for manufacturing a photoelectric conversion element according to claim 15, wherein the first and second steps are performed after the third step. The semiconductor substrate is made of single crystal silicon,
The third step includes
A first diffusion region having a second conductivity type opposite to the first conductivity type is formed in the semiconductor substrate in contact with a surface opposite to the light receiving surface of the semiconductor substrate having the first conductivity type. And a process of
The second diffusion region having the first conductivity type is in contact with the surface opposite to the light receiving surface of the semiconductor substrate and adjacent to the first diffusion region in the in-plane direction of the semiconductor substrate. The method for producing a photoelectric conversion element according to claim 13, comprising a step of forming in a semiconductor substrate. The semiconductor substrate is made of single crystal silicon,
The third step includes
Depositing a first amorphous film having a second conductivity type opposite to the first conductivity type on the opposite side of the light receiving surface of the semiconductor substrate having the first conductivity type;
Depositing a second amorphous film having the first conductivity type on the opposite side of the light receiving surface of the semiconductor substrate adjacent to the first amorphous film in an in-plane direction of the semiconductor substrate; The manufacturing method of the photoelectric conversion element of Claim 13 or Claim 14 containing these.

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