Manufacturing method for solar cell and solar cell

Abstract

To provide a manufacturing method for a solar cell whose performance can be improved.SOLUTION: A manufacturing method for a solar cell 1 includes: a) a first substrate cleaning step; b) a step of forming a first semiconductor layer material film and a lift off layer material film; c) a step of etching the material film and forming first semiconductor layers 23, 25 and a lift off layer, in which an end part of the lift off layer in a third region 9 of a first region 7 is modified by side etching into a modification part; d) a second substrate cleaning step, in which an oxidation solution includes ozone, an oxide film removing solution includes hydrofluoric acid and hydrochloric acid, and the modification part includes chlorine Cl; e) a step of forming a second semiconductor layer material film; f) a step of forming second semiconductor layers 33, 35 using a lift off method, in which the modification part in the third region 9 remains; and g) a step of forming a first electrode layer 27 and a second electrode layer 37 so as to separate at an insulating layer 43, which is the modification part in the third region 9.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a back electrode type (back contact type) solar cell, and to a back electrode type solar cell. [Background technology]

[0002] Patent Document 1 discloses a back electrode type solar cell. Such a back electrode type solar cell includes a semiconductor substrate that functions as a photoelectric conversion layer, a first semiconductor layer including a first conductive type semiconductor layer and a first electrode layer that are stacked in order on a portion of the back surface side of the semiconductor substrate, and a second semiconductor layer including a second conductive type semiconductor layer and a second electrode layer that are stacked in order on another portion of the back surface side of the semiconductor substrate.

[0003] In general, an etching method using photolithography technology is used in the patterning of the first semiconductor layer (first patterning) and the patterning of the second semiconductor layer (second patterning). However, the etching method using photolithography technology requires processes such as applying photoresist by spin coating, drying the photoresist, exposing the photoresist, developing the photoresist, etching the semiconductor layer using the photoresist as a mask, and removing the photoresist, making the process complicated.

[0004] In this regard, Patent Document 1 describes a technique for simplifying the patterning process by using a lift-off method that uses a lift-off layer (sacrificial layer) in the second patterning.

[0005] Also, before the deposition of the first semiconductor layer prior to the first patterning, the deposition surface (surface) of the semiconductor substrate may be cleaned. Also, before the deposition of the second semiconductor layer prior to the second patterning, the deposition surface (surface) of the semiconductor substrate may be cleaned. In cleaning the surfaces of these semiconductor substrates, a known technique is to form an oxide film on the surface of the semiconductor substrate using an oxidizing solution such as ozone water, and then remove the oxide film on the surface of the semiconductor substrate using an acidic solution (oxide film removal solution) such as hydrofluoric acid. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2014-75526 A Summary of the Invention [Problem to be solved by the invention]

[0007] In a back electrode type solar cell, improved insulation between the first electrode layer and the second electrode layer formed on the back side of the semiconductor substrate contributes to improved performance.

[0008] An object of the present invention is to provide a method for manufacturing a solar cell that enables performance improvement, and a solar cell. [Means for solving the problem]

[0009] Here, the inventors of the present application have found that, in cleaning the semiconductor substrate before the deposition of the second semiconductor layer before the second patterning by the lift-off method, by using an acidic solution such as hydrofluoric acid HF containing hydrochloric acid HCl as a cleaning solution (oxide film removal solution), the hydrochloric acid HCl corrodes the altered portion of the end of the lift-off layer altered by side etching in the first patterning, leaving chlorine Cl, and the etching rate of the altered portion of the lift-off layer containing chlorine Cl can be reduced. As a result, the inventors of the present application have found that, in the second patterning by the lift-off method, the altered portion of the lift-off layer remains, and the remaining altered portion of the lift-off layer functions as an insulating layer between the first electrode layer and the second electrode layer, thereby improving the insulation between the first electrode layer and the second electrode layer. As a result, the performance of the solar cell can be improved.

[0010] The inventors of the present application also discovered that, as described above, hydrochloric acid HCl corrodes the insulating layer, which is the altered portion of the lift-off layer, and therefore metal ions are removed from the insulating layer, metal contamination is suppressed, and chlorine Cl remains, further improving the insulation between the first electrode layer and the second electrode layer, thereby improving the performance of the solar cell.

[0011] Therefore, the method for manufacturing a solar cell according to the present invention is a method for manufacturing a back electrode type solar cell including a semiconductor substrate, a first semiconductor layer including a first conductive type semiconductor layer disposed in a first region which is a part of the back surface side of the semiconductor substrate, a second semiconductor layer including a second conductive type semiconductor layer disposed in a second region which is another part of the back surface side of the semiconductor substrate, a first electrode layer corresponding to the first semiconductor layer, and a second electrode layer corresponding to the second semiconductor layer, the method including: a) a first substrate cleaning step of cleaning the back surface side of the semiconductor substrate using a first cleaning solution; b) a first semiconductor layer material film formation step of forming a material film of a first semiconductor layer and a material film of a lift-off layer on the entire surface of the back surface side of the semiconductor substrate; The method includes a first semiconductor layer forming step of forming the first semiconductor layer and the lift-off layer in the first region by etching the material film of the first semiconductor layer and the material film of the lift-off layer in the first region, d) a second substrate cleaning step of cleaning the back surface side of the semiconductor substrate in the second region using a second cleaning solution, e) a second semiconductor layer material film forming step of forming a material film of the second semiconductor layer on the entire back surface side of the semiconductor substrate, f) a second semiconductor layer forming step of forming the second semiconductor layer in the second region by etching and removing the lift-off layer using a lift-off method, and g) an electrode layer forming step of forming the first electrode layer in the first region and the second electrode layer in the second region. The first substrate cleaning step includes a1) a first oxidation step of forming a first oxide film on the back surface side of the semiconductor substrate using a first oxidation solution as the first cleaning solution, and a2) a first oxide film removal step of removing the first oxide film using a first oxide film removal solution as the first cleaning solution. The second substrate cleaning step includes: d1) a second oxidation step of forming a second oxide film on the back surface side of the semiconductor substrate by using a second oxidation solution as the second cleaning solution; and d2) a second oxide film removal step of removing the second oxide film by using a second oxide film removal solution as the second cleaning solution. In the first semiconductor layer forming step, an end of the lift-off layer in a third region, which is a part of the first region on the second region side, is altered by side etching to become an altered portion.In the second substrate cleaning step, the second oxidizing solution contains ozone, the second oxide film removal solution contains hydrofluoric acid and hydrochloric acid, and the altered portion contains chlorine with reduced metal ions. In the second semiconductor layer forming step, the altered portion of the lift-off layer in the third region remains. In the electrode layer forming step, the first electrode layer and the second electrode layer are formed so as to be separated by an insulating layer that is the altered portion of the lift-off layer in the third region.

[0012] The solar cell of the present invention is a back electrode type solar cell comprising a semiconductor substrate, a first semiconductor layer including a first conductive type semiconductor layer arranged in a first region which is a part of the back surface side of the semiconductor substrate, a second semiconductor layer including a second conductive type semiconductor layer arranged in a second region which is another part of the back surface side of the semiconductor substrate, a first electrode layer corresponding to the first semiconductor layer, and a second electrode layer corresponding to the second semiconductor layer, and an insulating layer containing chlorine Cl is arranged in a third region which is between the first electrode layer and the second electrode layer and is a part of the first region on the second region side. Effect of the Invention

[0013] According to the present invention, the performance of a solar cell can be improved. [Brief description of the drawings]

[0014] [Figure 1] FIG. 2 is a diagram showing the solar cell according to the embodiment as viewed from the back surface side. [Diagram 2] 2 is a cross-sectional view of the solar cell shown in FIG. 1 taken along line II-II. [Figure 3A] 3A to 3C are diagrams illustrating a first semiconductor layer material film forming step and a lift-off layer forming step in the method for manufacturing a solar cell according to the present embodiment. [Figure 3B] 3A to 3C are diagrams illustrating a resist formation step in the method for manufacturing a solar cell according to the present embodiment. [Figure 3C] 5A to 5C are diagrams illustrating a first semiconductor layer forming step in the method for manufacturing a solar cell according to the embodiment. [Figure 3D]5A to 5C are diagrams illustrating a resist removal step in the method for manufacturing a solar cell according to the present embodiment. [Figure 3E] 4A to 4C are diagrams illustrating a second semiconductor layer material film forming step in the method for manufacturing a solar cell according to the embodiment. [Figure 3F] 5A to 5C are diagrams illustrating a second semiconductor layer forming step in the method for manufacturing a solar cell according to the embodiment. [Figure 3G] 3A to 3C are diagrams illustrating an electrode layer forming step in the manufacturing method of the solar cell according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals. For convenience, hatching and reference numerals may be omitted, in which case other drawings shall be referred to.

[0016] (Solar Cell) Fig. 1 is a view of the solar cell according to this embodiment as seen from the back surface side, and Fig. 2 is a cross-sectional view of the solar cell along line II-II in Fig. 1. The solar cell 1 shown in Fig. 1 and Fig. 2 is a back electrode type (also called a back contact type or back junction type) heterojunction solar cell.

[0017] Solar cell 1 includes a semiconductor substrate 11 with two main surfaces, and the main surface of semiconductor substrate 11 has a first region 7 and a second region 8. In the following, the main surface of semiconductor substrate 11 that receives light is referred to as the light-receiving surface, and the main surface of semiconductor substrate 11 opposite the light-receiving surface is referred to as the back surface.

[0018] The first region 7 has a so-called comb shape and includes a plurality of finger portions 7f corresponding to the teeth of the comb and busbar portions 7b corresponding to supports for the teeth of the comb. The busbar portions 7b extend in a first direction (X direction) along one side of the semiconductor substrate 11, and the finger portions 7f extend from the busbar portions 7b in a second direction (Y direction) intersecting the first direction.

[0019] Similarly, the second region 8 has a so-called comb shape and has a plurality of finger portions 8f corresponding to the teeth of the comb and a busbar portion 8b corresponding to a support portion of the teeth of the comb. The busbar portion 8b extends in a first direction along one side portion of the semiconductor substrate 11 opposite the other side portion, and the finger portions 8f extend in a second direction from the busbar portion 8b.

[0020] The finger portions 7f and 8f are strip-shaped extending in the second direction and are alternately provided in the first direction. The first region 7 and the second region 8 may be formed in a stripe pattern.

[0021] As shown in FIG. 2, the solar cell 1 includes a passivation layer 13 and an optical adjustment layer 15, which are formed (deposited, stacked) in this order on the light-receiving surface side of the semiconductor substrate 11. The solar cell 1 also includes a passivation layer 23, a p-type (first conductive type) semiconductor layer 25, and a first electrode layer 27, which are formed (deposited, stacked) in this order on a portion (mainly, the first region 7) of the back surface side of the semiconductor substrate 11. The solar cell 1 also includes a passivation layer 33, an n-type (second conductive type) semiconductor layer 35, and a second electrode layer 37, which are formed (deposited, stacked) in this order on another portion (mainly, the second region 8) of the back surface side of the semiconductor substrate 11. The passivation layer 23 and the p-type (first conductive type) semiconductor layer 25 constitute the first semiconductor layer, and the passivation layer 33 and the n-type (second conductive type) semiconductor layer 35 constitute the second semiconductor layer.

[0022] The semiconductor substrate 11 is formed of a crystalline silicon material such as single crystal silicon or polycrystalline silicon. The semiconductor substrate 11 is, for example, an n-type semiconductor substrate in which a crystalline silicon material is doped with an n-type dopant. The semiconductor substrate 11 may be, for example, a p-type semiconductor substrate in which a crystalline silicon material is doped with a p-type dopant. An example of the n-type dopant is phosphorus (P). An example of the p-type dopant is boron (B). The semiconductor substrate 11 functions as a photoelectric conversion substrate that absorbs incident light from the light-receiving surface side and generates photocarriers (electrons and holes).

[0023] By using crystalline silicon as the material for the semiconductor substrate 11, the dark current is relatively small, and a relatively high output (stable output regardless of illuminance) can be obtained even when the intensity of incident light is low.

[0024] Semiconductor substrate 11 may have a pyramidal fine uneven structure called a texture structure on the light-receiving surface side, which reduces the reflection of incident light on the light-receiving surface and improves the light trapping effect in semiconductor substrate 11.

[0025] Furthermore, the semiconductor substrate 11 may have a pyramidal fine uneven structure, called a texture structure, on the back surface side thereof, which increases the efficiency of collection of light that is not absorbed by the semiconductor substrate 11 and passes through it.

[0026] The passivation layer 13 is formed on the light-receiving surface side of the semiconductor substrate 11. The passivation layer 23 is formed in a first region 7 on the back surface side of the semiconductor substrate 11. The passivation layer 33 is formed in a second region 8 on the back surface side of the semiconductor substrate 11. The passivation layers 13, 23, and 33 are formed of, for example, an intrinsic (i-type) amorphous silicon material. The passivation layers 13, 23, and 33 suppress recombination of carriers generated in the semiconductor substrate 11 and increase the carrier collection efficiency.

[0027] The optical adjustment layer 15 is formed on the passivation layer 13 on the light-receiving surface side of the semiconductor substrate 11. The optical adjustment layer 15 functions as an anti-reflection layer that prevents or suppresses reflection of incident light, and improves the efficiency of light incidence on the semiconductor substrate 11. The optical adjustment layer 15 also functions as a protective layer that protects the light-receiving surface side of the semiconductor substrate 11 and the passivation layer 13. The optical adjustment layer 15 is formed of an insulating material, for example, silicon oxide (SiO), silicon nitride (SiN), or a composite thereof such as silicon oxynitride (SiON).

[0028] The p-type (first conductivity type) semiconductor layer 25 is formed on the passivation layer 23, i.e., in the first region 7 on the back surface side of the semiconductor substrate 11. The p-type semiconductor layer 25 is formed of, for example, an amorphous silicon material. The p-type semiconductor layer 25 is, for example, a p-type semiconductor layer in which an amorphous silicon material is doped with a p-type dopant (for example, the above-mentioned boron (B)).

[0029] The n-type (second conductivity type) semiconductor layer 35 is formed on the passivation layer 33, i.e., in the second region 8 on the back surface side of the semiconductor substrate 11. The n-type semiconductor layer 35 is formed of, for example, an amorphous silicon material. The n-type semiconductor layer 35 is, for example, an n-type semiconductor layer in which an amorphous silicon material is doped with an n-type dopant (for example, the above-mentioned phosphorus (P)).

[0030] The p-type semiconductor layer 25 and the passivation layer 23 (first semiconductor layer), and the n-type semiconductor layer 35 and the passivation layer 33 (second semiconductor layer) form strips extending in the second direction (Y direction) and are arranged alternately in the first direction (X direction).

[0031] The first electrode layer 27 corresponds to the p-type semiconductor layer 25 (first semiconductor layer), specifically, is formed on the p-type semiconductor layer 25 in a first region 7 on the back surface side of the semiconductor substrate 11. The second electrode layer 37 corresponds to the n-type semiconductor layer 35 (second semiconductor layer), specifically, is formed on the n-type semiconductor layer 35 in a second region 8 on the back surface side of the semiconductor substrate 11. Each of the first electrode layer 27 and the second electrode layer 37 may be composed of a metal electrode layer, or may be composed of a transparent electrode layer and a metal electrode layer.

[0032] The transparent electrode layer is formed of a transparent conductive material, such as ITO (Indium Tin Oxide: a composite oxide of indium oxide and tin oxide). The metal electrode layer is formed of a conductive paste material containing, for example, a particulate metal material such as silver, copper, or aluminum, an insulating resin material, and a solvent.

[0033] The first electrode layer 27 and the second electrode layer 37 are in the form of strips extending in the second direction (Y direction) and are arranged alternately in the first direction (X direction). The first electrode layer 27 and the second electrode layer 37 are separated from each other.

[0034] The first electrode layer 27 covers the p-type semiconductor layer 25 except for a third region 9 which is a part of the first region 7 on the second region 8 side. On the other hand, the second electrode layer 37 covers the entire n-type semiconductor layer 35 in the second region 8.

[0035] An insulating layer 43 formed by a lift-off method in a semiconductor layer formation step described later is disposed in a third region 9, which is a part of the first region 7 on the second region 8 side of the p-type semiconductor layer 25 (first semiconductor layer). The insulating layer 43 is disposed between the first electrode layer 27 and the second electrode layer 37.

[0036] The insulating layer 43 includes a material such as silicon oxide (SiO), silicon nitride (SiN), silicon carbide (SiC), or a compound thereof such as silicon oxynitride (SiON), silicon oxycarbide (SiOC), silicon carbonate nitride (SiCN), or silicon oxycarbonitride (SiOCN). The insulating layer 43 contains chlorine Cl, and metal ions are reduced in the insulating layer 43 due to hydrochloric acid HCl in a substrate cleaning process described later.

[0037] In addition, a portion of the second semiconductor layer on the semiconductor substrate 11 side, for example, the n-type semiconductor layer 35 and a portion of the passivation layer 33 on the semiconductor substrate 11 side, of the passivation layer 33, contain chlorine Cl due to hydrochloric acid HCl in the substrate cleaning process described below.

[0038] On the other hand, a portion of the first semiconductor layer on the semiconductor substrate 11 side, for example, the p-type semiconductor layer 25 and a portion of the passivation layer 23 on the semiconductor substrate 11 side, does not contain chlorine Cl.

[0039] The end faces of the first semiconductor layer, i.e., the p-type semiconductor layer 25 and the passivation layer 23, on the second region 8 side and the end face of the insulating layer 43 on the second region 8 side are aligned in the order of the crystal grain boundaries of the insulating layer 43, and are continuous without any steps in the stacking direction of these layers (the direction intersecting the XY plane).

[0040] In addition, the end faces of the second semiconductor layer, i.e., the n-type semiconductor layer 35 and the passivation layer 33, on the first region 7 side and the end face of the second electrode layer 37 on the first region 7 side are aligned in the order of the crystal grain boundaries of the second electrode layer 37, and are continuous without any steps in the stacking direction of these layers (the direction intersecting the XY plane).

[0041] (Method of manufacturing solar cell according to the present embodiment) Hereinafter, with reference to Figs. 3A to 3G, a method for manufacturing the solar cell 1 of the present embodiment shown in Figs. 1 and 2 will be described. Fig. 3A is a diagram showing a first semiconductor layer material film forming step and a lift-off layer forming step in the method for manufacturing a solar cell according to the present embodiment, and Fig. 3B is a diagram showing a resist forming step in the method for manufacturing a solar cell according to the present embodiment. Fig. 3C is a diagram showing a first semiconductor layer forming step in the method for manufacturing a solar cell according to the present embodiment, and Fig. 3D is a diagram showing a resist removing step in the method for manufacturing a solar cell according to the present embodiment. Fig. 3E is a diagram showing a second semiconductor layer material film forming step in the method for manufacturing a solar cell according to the present embodiment, and Fig. 3F is a diagram showing a second semiconductor layer forming step in the method for manufacturing a solar cell according to the present embodiment. Fig. 3G is a diagram showing an electrode layer forming step in the method for manufacturing a solar cell according to the present embodiment.

[0042] First, both sides of the semiconductor substrate 11 are cleaned using a first cleaning solution (first substrate cleaning step). Specifically, a first oxide film is formed on both sides of the semiconductor substrate 11 using a first oxidizing solution as the first cleaning solution (first oxidation step), and then the first oxide film is removed using a first oxide film removal solution as the first cleaning solution (first oxide film removal step). The first oxidizing solution contains ozone O3. The first oxide film removal solution contains hydrofluoric acid HF but does not contain hydrochloric acid HCl. This prevents chlorine Cl from adhering to the back side of the semiconductor substrate 11.

[0043] Next, as shown in FIG. 3A, a passivation layer material film 23Z and a p-type (first conductivity type) semiconductor layer material film 25Z (first semiconductor layer material film) are formed (deposited, stacked) in sequence on the entire back surface side of the semiconductor substrate 11, for example, using a CVD method (first semiconductor layer material film formation process).

[0044] At this time, as described above, in the first substrate cleaning step, the first cleaning solution (first oxide film removal solution) does not contain hydrochloric acid (HCl), and chlorine Cl does not adhere to the back surface side of the semiconductor substrate 11, so that the first semiconductor layer material film, for example, the passivation layer material film 23Z and a portion of the passivation layer material film 23Z on the semiconductor substrate 11 side of the p-type (first conductivity type) semiconductor layer material film 25Z do not contain chlorine Cl.

[0045] Further, for example, by using a CVD method, a passivation layer 13 is formed (deposited, laminated) on the entire surface of the light-receiving surface side of the semiconductor substrate 11. The order of forming the passivation layer material film 23Z and the p-type semiconductor layer material film 25Z, and the passivation layer 13, is not limited. The passivation layer 13 on the light-receiving surface side may be formed in a subsequent second semiconductor layer material film forming process.

[0046] Next, for example, by using a CVD method, a lift-off layer (sacrificial layer) 41 is formed (deposited, laminated) on the entire back surface of the semiconductor substrate 11, specifically, on the entire surface of the p-type semiconductor layer material film 25Z. The lift-off layer 41 is made of a material such as silicon oxide (SiO), silicon nitride (SiN), silicon carbide (SiC), or a compound thereof such as silicon oxynitride (SiON), silicon oxycarbide (SiOC), silicon carbonate nitride (SiCN), or silicon oxycarbonitride (SiOCN).

[0047] Next, as shown in Figures 3B to 3D, a resist 90 is used to remove the lift-off layer 41, the p-type semiconductor layer material film 25Z, and the passivation layer material film 23Z (first semiconductor layer material film) in the second region 8 on the back surface side of the semiconductor substrate 11, thereby forming a patterned passivation layer 23 and the p-type semiconductor layer 25 (first semiconductor layer), and the lift-off layer 41 in the first region 7.

[0048] 3B, on the back surface side of the semiconductor substrate 11, a resist 90 is formed on the p-type semiconductor layer material film 25Z and the lift-off layer 41 in the first region 7 by using a photolithography method, a printing method, or the like (resist forming step). Also, on the entire light-receiving surface side of the semiconductor substrate 11, a resist 90 is formed by using a photolithography method, a printing method, or the like (resist forming step).

[0049] 3C, the lift-off layer 41, the p-type semiconductor layer material film 25Z, and the passivation layer material film 23Z in the second region 8 are etched on the back surface side of the semiconductor substrate 11 using the resist 90 as a mask, thereby forming the patterned lift-off layer 41, the p-type semiconductor layer 25, and the passivation layer 23 in the first region 7 (first semiconductor layer formation step). As an etching solution for the lift-off layer 41, the p-type semiconductor layer 25, and the passivation layer 23, an acidic solution such as hydrofluoric acid is used.

[0050] At this time, as described above, in the first semiconductor layer material film formation process, the first semiconductor layer material film, for example, the passivation layer material film 23Z and the p-type (first conductivity type) semiconductor layer material film 25Z, a portion of the passivation layer material film 23Z on the semiconductor substrate 11 side does not contain chlorine Cl, and therefore the first semiconductor layer, for example, the passivation layer 23 and the p-type (first conductivity type) semiconductor layer 25, a portion of the passivation layer 23 on the semiconductor substrate 11 side does not contain chlorine Cl.

[0051] At this time, due to the side etching, the acid solution, which is the etching solution, corrodes the end of lift-off layer 41 in third region 9, which is a part of first region 7 on the second region 8 side, and the end of lift-off layer 41 is altered. The end of lift-off layer 41 in third region 9 that has been altered in this way is referred to as altered portion 43. Specifically, altered portion 43 of lift-off layer 41 in third region 9 is in a half-etched state.

[0052] 3D, resist 90 on the back surface side and the light-receiving surface side is removed (resist removal step). An example of an etching solution for resist 90 is an alkaline solution such as an aqueous solution of potassium hydroxide.

[0053] Next, both sides of the semiconductor substrate 11 are cleaned using a second cleaning solution (second substrate cleaning step). Specifically, a second oxide film is formed on both sides of the semiconductor substrate 11 using a second oxidizing solution as the second cleaning solution (second oxidation step), and then the second oxide film is removed using a second oxide film removal solution as the second cleaning solution (second oxide film removal step). The second oxidizing solution contains ozone O3. The second oxide film removal solution contains hydrofluoric acid HF and hydrochloric acid HCl. As a result, chlorine Cl adheres to the back side of the semiconductor substrate 11 in the second region 8 and the back side of the lift-off layer 41 in the first region 7. In addition, metal ions are reduced on the back side of the semiconductor substrate 11 in the second region 8 and the back side of the lift-off layer 41 in the first region 7, and metal contamination is suppressed.

[0054] Furthermore, hydrochloric acid HCl corrodes the altered portions 43 at the ends of the lift-off layer 41, leaving behind chlorine Cl. As a result, the etching rate of the altered portions 43 at the ends of the lift-off layer 41 becomes slower than the etching rate of the portions other than the ends of the lift-off layer 41. Furthermore, metal ions are reduced in the altered portions 43 at the ends of the lift-off layer 41, suppressing metal contamination.

[0055] Next, as shown in FIG. 3E, a passivation layer material film 33Z and an n-type (second conductivity type) semiconductor layer material film 35Z (second semiconductor layer material film) are sequentially formed (deposited, stacked) on the entire back surface of the semiconductor substrate 11, specifically on the lift-off layer 41 in the first region 7 and in the second region 8, using, for example, a CVD method (second semiconductor layer material film formation process).

[0056] At this time, as described above, in the second substrate cleaning step, the second cleaning solution (second oxide film removal solution) contains hydrochloric acid HCl, and chlorine Cl adheres to the back surface side of the semiconductor substrate 11 in the second region 8 and the back surface side of the lift-off layer 41 in the first region 7, so that the second semiconductor layer material film, for example, the passivation layer material film 33Z and a portion of the passivation layer material film 33Z on the semiconductor substrate 11 side of the n-type (second conductivity type) semiconductor layer material film 35Z, contain chlorine Cl.

[0057] Next, as shown in FIG. 3F, a lift-off method using a lift-off layer (sacrificial layer) is used to remove the passivation layer material film 33Z and the n-type semiconductor layer material film 35Z (second semiconductor layer material film) in the first region 7 on the back surface side of the semiconductor substrate 11, thereby forming a patterned passivation layer 33 and an n-type semiconductor layer 35 (second semiconductor layer) in the second region 8 (second semiconductor layer formation process).

[0058] Specifically, by removing the lift-off layer 41, the passivation layer material film 33Z and the n-type semiconductor layer material film 35Z on the lift-off layer 41 are removed, and the passivation layer 33 and the n-type semiconductor layer 35 are formed in the second region 8. As a removal solution for the lift-off layer 41, an acidic solution such as hydrofluoric acid is used, for example.

[0059] At this time, as described above, in the second semiconductor layer material film formation process, the second semiconductor layer material film, for example, the passivation layer material film 33Z and the n-type (second conductivity type) semiconductor layer material film 35Z, a portion of the passivation layer material film 33Z on the semiconductor substrate 11 side contains chlorine Cl, so that the second semiconductor layer, for example, the passivation layer 33 and the n-type (second conductivity type) semiconductor layer 35, a portion of the passivation layer 33 on the semiconductor substrate 11 side contains chlorine Cl.

[0060] At this time, the altered portion 43 of the lift-off layer 41 remains in the third region 9 where the etching rate is slow.

[0061] Next, as shown in FIG. 3G, optical adjustment layer 15 is formed over the entire light-receiving surface side of semiconductor substrate 11, that is, on passivation layer 13, by using, for example, a CVD method.

[0062] Next, a first electrode layer 27 and a second electrode layer 37 are formed on the back surface side of the semiconductor substrate 11 (electrode layer forming step). Specifically, the first electrode layer 27 is formed on the p-type semiconductor layer 25 in the first region 7, and the second electrode layer 37 is formed on the n-type semiconductor layer 35 in the second region 8. At this time, the first electrode layer 27 and the second electrode layer 37 are formed so as to be separated by an insulating layer, which is the altered portion 43 of the lift-off layer 41 in the third region 9.

[0063] Through the above steps, the back electrode type solar cell 1 of this embodiment shown in Figs. 1 and 2 is obtained.

[0064] As described above, according to the manufacturing method of the solar cell 1 of the present embodiment, in the cleaning of the semiconductor substrate 11 before the formation of the second semiconductor layers 33, 35 (second substrate cleaning step) before the second patterning by the lift-off method, hydrochloric acid HCl is contained in an acidic solution such as hydrofluoric acid HF as a cleaning solution (oxide film removal solution). As a result, the hydrochloric acid HCl corrodes the altered portion 43 at the end of the lift-off layer 41 that has been altered by side etching in the first patterning, leaving chlorine Cl, and the etching rate of the altered portion 43 of the lift-off layer 41 containing chlorine Cl can be reduced. As a result, in the second patterning by the lift-off method, the altered portion 43 of the lift-off layer 41 remains, and the remaining altered portion 43 of the lift-off layer functions as an insulating layer between the first electrode layer 27 and the second electrode layer 37, and the insulation between the first electrode layer 27 and the second electrode layer 37 can be improved. As a result, the performance of the solar cell 1 can be improved.

[0065] As described above, hydrochloric acid HCl corrodes insulating layer 43, which is the altered portion of lift-off layer 41, and therefore metal ions are removed from insulating layer 43, suppressing metal contamination and leaving chlorine Cl, thereby further improving the insulation between first electrode layer 27 and second electrode layer 37. As a result, the performance of solar cell 1 can be improved.

[0066] Incidentally, in cleaning the semiconductor substrate 11 before the formation of the first semiconductor layers 23, 25 and before the first patterning (first substrate cleaning process), if an acidic solution such as hydrofluoric acid HF contains hydrochloric acid HCl as a cleaning solution (oxide film removal solution), metal contamination on the surface of the semiconductor substrate 11 can be suppressed, but chlorine Cl will remain on the surface of the semiconductor substrate 11, causing a chlorine-doped n-layer between the semiconductor substrate 11 and the p-type semiconductor layer 35, resulting in a decrease in performance of the solar cell 1.

[0067] In this regard, according to the manufacturing method of the solar cell 1 of this embodiment, in cleaning the semiconductor substrate before the formation of the first semiconductor layers 23, 25 before the first patterning (first substrate cleaning step), the cleaning solution (oxide film removal solution) does not contain hydrochloric acid HCl in an acidic solution such as hydrofluoric acid HF. This prevents chlorine Cl from remaining on the surface of the semiconductor substrate 11 and prevents a chlorine-doped n-layer from being generated between the semiconductor substrate 11 and the p-type semiconductor layer 35, thereby improving the performance of the solar cell 1.

[0068] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various changes and modifications are possible. For example, in the above-mentioned embodiments, the first conductive type semiconductor layer is a p-type semiconductor layer, and the second conductive type semiconductor layer is an n-type semiconductor layer, but the first conductive type semiconductor layer may be an n-type semiconductor layer, and the second conductive type semiconductor layer may be a p-type semiconductor layer. [Explanation of symbols]

[0069] 1. Solar Cell 7 First area 7b, 8b Busbar section 7f,8f Finger section 8 Second area 9 Third area 11 Semiconductor substrate 13 Passivation Layer 15 Optical adjustment layer 23 Passivation layer (first semiconductor layer) 23Z Passivation layer material film (first semiconductor layer material film) 25 p-type semiconductor layer (first conductive type semiconductor layer) (first semiconductor layer) 25Z p-type semiconductor layer material film (first semiconductor layer material film) 27 First electrode layer 33 Passivation layer (second semiconductor layer) 33Z Passivation layer material film (second semiconductor layer material film) 35 n-type semiconductor layer (second conductive type semiconductor layer) (second semiconductor layer) 35Z n-type semiconductor layer material film (second semiconductor layer material film) 37 Second electrode layer 41 Lift-off layer 43 Deformed part (insulating layer) 90 Resist

Claims

1. A method for manufacturing a back electrode type solar cell comprising: a semiconductor substrate; a first semiconductor layer including a first conductive type semiconductor layer disposed in a first region that is a part of a back surface side of the semiconductor substrate; a second semiconductor layer including a second conductive type semiconductor layer disposed in a second region that is another part of the back surface side of the semiconductor substrate; a first electrode layer corresponding to the first semiconductor layer; and a second electrode layer corresponding to the second semiconductor layer, a first substrate cleaning step of cleaning the back surface side of the semiconductor substrate using a first cleaning solution; a first semiconductor layer material film formation step of forming a first semiconductor layer material film and a lift-off layer material film on the entire back surface side of the semiconductor substrate; a first semiconductor layer forming step of forming the first semiconductor layer and the lift-off layer in the first region by etching the material film of the first semiconductor layer and the material film of the lift-off layer in the second region using a resist; a second substrate cleaning step of cleaning the back surface side of the semiconductor substrate in the second region using a second cleaning solution; a second semiconductor layer material film forming step of forming a second semiconductor layer material film on the entire back surface side of the semiconductor substrate; a second semiconductor layer forming step of forming the second semiconductor layer in the second region by etching and removing the lift-off layer using a lift-off method; an electrode layer forming step of forming the first electrode layer in the first region and forming the second electrode layer in the second region; Including, The first substrate cleaning step includes: a first oxidation step of forming a first oxide film on the back surface side of the semiconductor substrate using a first oxidation solution as the first cleaning solution; a first oxide film removing step of removing the first oxide film by using a first oxide film removing solution as the first cleaning solution; Including, The second substrate cleaning step includes: a second oxidation step of forming a second oxide film on the back surface side of the semiconductor substrate using a second oxidizing solution as the second cleaning solution; a second oxide film removing step of removing the second oxide film by using a second oxide film removing solution as the second cleaning solution; Including, In the first semiconductor layer forming step, an end portion of the lift-off layer in a third region, which is a part of the first region on the second region side, is altered by side etching to become an altered portion, In the second substrate cleaning step, the second oxidizing solution contains ozone, the second oxide film removing solution contains hydrofluoric acid and hydrochloric acid, and the altered portion contains chlorine with reduced metal ions; In the second semiconductor layer forming step, an altered portion of the lift-off layer in the third region remains, In the electrode layer forming step, the first electrode layer and the second electrode layer are formed so as to be separated by an insulating layer which is a modified portion of the lift-off layer in the third region. How solar cells are manufactured.

2. The first semiconductor layer includes a p-type semiconductor layer as the first conductive type semiconductor layer, and the second semiconductor layer includes an n-type semiconductor layer as the second conductive type semiconductor layer, In the first substrate cleaning step, the first oxidizing solution contains ozone, the first oxide film removing solution contains hydrofluoric acid but does not contain hydrochloric acid, and chlorine Cl does not adhere to the back surface side of the semiconductor substrate, In the first semiconductor layer material film forming step, a portion of the second semiconductor layer material film on the semiconductor substrate side does not contain chlorine, In the first semiconductor layer forming step, a portion of the second semiconductor layer on the semiconductor substrate side does not contain chlorine, In the second substrate cleaning step, chlorine adheres to the back surface side of the semiconductor substrate in the second region, In the second semiconductor layer material film forming step, a portion of the material film of the second semiconductor layer in the second region on the semiconductor substrate side contains chlorine, In the second semiconductor layer forming step, a portion of the second semiconductor layer on the semiconductor substrate side contains chlorine. The method for producing the solar cell according to claim 1 .

3. A back electrode type solar cell comprising: a semiconductor substrate; a first semiconductor layer including a first conductive type semiconductor layer disposed in a first region that is a part of a back surface side of the semiconductor substrate; a second semiconductor layer including a second conductive type semiconductor layer disposed in a second region that is another part of the back surface side of the semiconductor substrate; a first electrode layer corresponding to the first semiconductor layer; and a second electrode layer corresponding to the second semiconductor layer, an insulating layer containing chlorine Cl is disposed in a third region between the first electrode layer and the second electrode layer and which is a part of the first region on the second region side; Solar cell.

4. The first semiconductor layer includes a p-type semiconductor layer as the first conductive type semiconductor layer, and the second semiconductor layer includes an n-type semiconductor layer as the second conductive type semiconductor layer, a portion of the first semiconductor layer on the semiconductor substrate side does not contain chlorine; A portion of the second semiconductor layer on the semiconductor substrate side contains chlorine. The solar cell according to claim 3 .

5. The solar cell according to claim 3 , wherein the insulating layer includes any one of SiO, SiN, SiC, SiCN, SiON, SiOC, and SiOCN.

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