CN107527960B

CN107527960B - Method for manufacturing HBC type crystal solar cell

Info

Publication number: CN107527960B
Application number: CN201710468365.0A
Authority: CN
Inventors: 松崎淳介; 高桥明久; 齐藤一也; 浅利伸; 大園修司; 铃木英夫; 山口昇
Original assignee: Ulvac Inc
Current assignee: Ulvac Inc
Priority date: 2016-06-22
Filing date: 2017-06-20
Publication date: 2022-04-26
Anticipated expiration: 2037-06-20
Also published as: JP2017228661A; CN107527960A; JP6742168B2

Abstract

The present invention relates to a method for manufacturing an HBC-type crystal solar cell and an HBC-type crystal solar cell. The manufacturing method uses a substrate composed of crystalline silicon of a first conductivity type, and includes, in order: a step of forming an i-type amorphous Si layer α and an i-type amorphous Si layer β independently or simultaneously; a step of forming a photoresist; forming a site a having the same conductivity type as the first conductivity type and a site B having a different conductivity type from the first conductivity type at positions separated from each other by a photoresist so as to be internally present in the amorphous Si layer β and to be partially exposed on the outer surface side of the amorphous Si layer β by an ion implantation method using a mask; annealing the ion-implanted amorphous Si layer β; forming a conductive member so as to cover the portion a and the portion B on the outer surface side of the amorphous Si layer β and the photoresist; and removing the photoresist covered with the conductive member.

Description

Method for manufacturing HBC type crystal solar cell

Technical Field

The present invention relates to a method for manufacturing an HBC-type crystal solar cell, which can simplify the manufacturing process and can stably obtain an ion-implanted region and an electrode shape having a clear outline in a plan view, and an HBC-type crystal solar cell.

Background

Conventionally, it has been known that a back contact solar cell can obtain high power generation efficiency in a solar cell using crystalline silicon as a substrate (hereinafter, also referred to as a crystalline solar cell). Among them, the power generation efficiency of a heterojunction type back contact type (HBC type) crystal solar cell is identified as the highest in the world, and it has attracted attention from various aspects.

In such an HBC-type crystalline solar cell, the portion composed of the n-type amorphous Si layer and the portion composed of the p-type amorphous Si layer are respectively locally disposed on the back surface (surface on the opposite side of the light incident surface) of the silicon substrate with the i-type amorphous Si layer interposed therebetween, and are spaced apart from each other. In order to obtain such a structure, it is known to manufacture an HBC type crystal solar cell through the process shown in fig. 25 (for example, the prior art of patent document 1).

Fig. 25 is a schematic cross-sectional view showing an example of a manufacturing method of a conventional HBC-type crystal solar cell. That is, in fig. 25 (a), an i-type amorphous Si layer 1002 and an n-type amorphous Si layer 1003 are formed on a single surface of a silicon substrate 1001.

In fig. 25 (b), a photoresist 1004 having a desired pattern is formed on the n-type amorphous Si layer 1003.

In fig. 25 (c), the i-type amorphous Si layer 1002 and the n-type amorphous Si layer 1003 are etched using a photoresist 1004.

In fig. 25 (d), after etching, the photoresist 1004 is stripped.

In fig. 25 (e), an etch stopper 1005 is formed. The etching stopper layer 1005 is masked, and the etching stopper layer 1005 on the partition portion where the n-type amorphous Si layer 1003 is not formed is etched. Further, the i-type amorphous Si layer 1006 and the p-type amorphous Si layer 1007 are formed over the entire region.

In fig. 25 (f), a photoresist 1008 is formed on the partition portion.

In (g) of fig. 25, the i-type amorphous Si layer 1006 and the p-type amorphous Si layer 1007 are etched using the photoresist 1008.

In fig. 25 (h), after etching, the photoresist 1008 is stripped.

In fig. 25 (i), the etching stopper layer 1005 is peeled off.

In fig. 25 (j), an i-type amorphous Si layer 1009 is formed at a partition between the i-type amorphous Si layers 1002 and at a partition between the n-type amorphous Si layer 1003 and the p-type amorphous Si layer 1007.

That is, in the conventional method for manufacturing the HBC-type crystalline solar cell, a specific pattern region including the n-type amorphous Si layer 1003 and the p-type amorphous Si layer 1007 can be formed by performing the above-described plurality of steps [ fig. 25 ]. For this reason, photolithography, etching, and the like have to be performed a plurality of times. However, when patterning is performed by such a method, as shown in fig. 25, the number of steps increases, which leads to an increase in the cost of the production line, and further, it is difficult to achieve cost reduction of the solar cell.

Patent document 1: japanese patent laid-open No. 2012-243797

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for manufacturing an HBC-type crystal solar cell and an HBC-type crystal solar cell, which can significantly reduce the number of steps in manufacturing and can stably obtain an ion implantation region and an electrode shape having a clear outline in a plan view.

A method for manufacturing an HBC type crystal solar cell according to a first aspect of the present invention uses a substrate made of crystalline silicon of a first conductivity type, and includes, in order: a step of forming an i-type amorphous Si layer α and an i-type amorphous Si layer β separately or simultaneously, the i-type amorphous Si layer α covering one surface of the substrate on which light is incident, and the i-type amorphous Si layer β covering the other surface located on the opposite side of the one surface; forming a photoresist so as to cover a region, in which an impurity is not introduced in a subsequent step, of an outer surface of the amorphous Si layer β; forming a site a having the same conductivity type as the first conductivity type and a site B having a different conductivity type from the first conductivity type at positions separated from each other by the photoresist (due to the presence of the photoresist) so as to be internally present in the amorphous Si layer β and to be partially exposed on the outer surface side of the amorphous Si layer β by an ion implantation method using a mask; annealing the ion-implanted amorphous Si layer β; forming a conductive member so as to cover the portion a, the portion B and the photoresist on the outer surface side of the amorphous Si layer β; and removing the photoresist covered with the conductive member.

In the method for manufacturing an HBC-type crystal solar cell according to the first aspect of the present invention, a mask having an opening shape such that a portion of the photoresist defining the outer shape of a portion a or a portion B into which ions are implanted can be seen when the portion a or the portion B is viewed in plan view through the opening of the mask may be used.

In the method for manufacturing an HBC type crystal solar cell according to the first aspect of the present invention, the method may further include, before the step of forming the photoresist: forming an n-type amorphous Si layer so as to cover the i-type amorphous Si layer α; and forming a SiN layer so as to cover the n-type amorphous Si layer.

In the method for manufacturing an HBC-type crystalline solar cell according to the first aspect of the present invention, the method may further include a step of forming an n-type amorphous Si layer so as to cover the i-type amorphous Si layer α before the step of forming the photoresist, and a step of forming an SiN layer so as to cover the n-type amorphous Si layer after the step of forming the conductive member.

In the method for manufacturing an HBC-type crystal solar cell according to the first aspect of the present invention, the step of forming the conductive member may be followed by a step of forming an SiN layer so as to cover the i-type amorphous Si layer α.

An HBC type crystal solar cell according to a second aspect of the present invention includes at least: a substrate made of a first conductivity type crystalline silicon exhibiting a photoelectric conversion function; an i-type amorphous Si layer α disposed so as to cover a surface of the substrate on which light is incident; and an i-type amorphous Si layer β disposed so as to cover the other surface located on the opposite side of the one surface of the substrate, wherein a site a having the same conductivity type as the first conductivity type and a site B having a different conductivity type from the first conductivity type are disposed so as to be separated from each other so as to be present inside the amorphous Si layer β and to be partially exposed on the outer surface side of the amorphous Si layer β, and electrodes made of a conductive member are disposed so as to cover the exposed outer surfaces of the site a and the site B individually.

A method for manufacturing an HBC type crystal solar cell according to a first aspect of the present invention is a method for manufacturing an HBC type crystal solar cell using a substrate made of crystalline silicon of a first conductivity type, the method including the steps of: forming i-type amorphous Si layers α and β covering one surface and the other surface of the substrate, respectively; a step of forming a photoresist on a region where no impurity is introduced in a subsequent step, among the outer surface of β; forming a site a having the same conductivity type as the first conductivity type and a site B having a different conductivity type from the first conductivity type at positions separated by the photoresist by an ion implantation method using a mask so that the sites a and B are present inside the β and a part of the sites B is exposed on the outer surface side of the β; a step of performing annealing treatment; forming a conductive member so as to cover the portion a, the portion B, and the photoresist; and a step of removing the photoresist covered with the conductive member, thereby producing an HBC-type crystal solar cell having the above-described structure.

Therefore, according to the manufacturing method of the first aspect of the present invention, the number of steps in manufacturing can be significantly reduced as compared with the conventional manufacturing method. Further, when the portion a or the portion B is formed by an ion implantation method using a mask, since a photoresist exists between the portion a and the portion B, an ion implantation region having a clear profile in a plan view can be stably obtained. Further, when the photoresist is removed, the conductive member in a region covering the photoresist (a region overlapping the photoresist) is also removed together with the photoresist. Therefore, according to the present invention, the electrodes separately covering the site a and the site B are obtained naturally without performing patterning processing on the conductive member.

Therefore, the first aspect of the present invention provides a method for manufacturing an HBC type crystal solar cell, which can significantly reduce the number of steps in manufacturing, and can stably obtain an ion implantation region having a clear profile in a plan view and an electrode that does not require patterning. Therefore, the present invention contributes to the construction of a low-cost production line for an HBC type crystal solar cell.

An HBC type crystal solar cell according to a second aspect of the present invention includes i type amorphous Si layers α and β covering one surface and the other surface of a substrate made of crystalline silicon of a first conductivity type. The i-type amorphous Si layer α is disposed on the front surface (light incident surface) of the substrate, and the i-type amorphous Si layer β is disposed on the back surface (surface opposite to the light incident surface, that is, the other surface) of the substrate. Further, a site a having the same conductivity type as the first conductivity type and a site B having a different conductivity type from the first conductivity type are arranged so as to be separated from each other so that the site a is internally present in the β and a part of the site B is exposed on the outer surface side of the β. This structure can be formed by performing ion implantation processing for forming the site a and the site B in the amorphous Si layer β. Therefore, in this structure, even after the formation of the site a and the site B, the outer surface of the amorphous Si layer β can maintain a flat distribution, and therefore, the electrode formed in the subsequent step and made of a conductive member can maintain flatness. This can stabilize the removal of the photoresist, which is performed to leave the electrodes so as to overlap the portions a and B, respectively.

Therefore, the second aspect of the present invention contributes to providing an HBC type crystal solar cell capable of significantly reducing the number of steps in a production line.

Drawings

Fig. 1 is a schematic cross-sectional view showing a first embodiment of the HBC-type crystal solar cell according to the present invention.

Fig. 2 is a schematic cross-sectional view showing a manufacturing process of the HBC type crystal solar cell shown in fig. 1.

Fig. 3 is a schematic cross-sectional view illustrating a subsequent process to the process shown in fig. 2.

Fig. 4 is a schematic cross-sectional view showing a subsequent process to the process shown in fig. 3.

Fig. 5 is a schematic cross-sectional view showing a subsequent process to the process shown in fig. 4.

Fig. 6 is a flowchart showing a manufacturing process of the HBC type crystal solar cell of the conventional example (fig. 25).

Fig. 7 is a flowchart showing a manufacturing process of the HBC type crystal solar cell of the present invention (fig. 1).

Fig. 8 is a graph showing the relationship between the ion energy and the stop range of boron (B).

Fig. 9 is a graph showing a concentration distribution of phosphorus (P) observed in the depth direction of the substrate by changing the ion energy of phosphorus (P).

Fig. 10 is a schematic cross-sectional view of a film formation apparatus used for forming an amorphous Si film or the like.

Fig. 11 is a schematic cross-sectional view of an ion implantation apparatus.

Fig. 12 is a schematic cross-sectional view of an annealing apparatus.

Fig. 13 is a schematic cross-sectional view showing a second embodiment of the HBC-type crystal solar cell according to the present invention.

Fig. 14 is a schematic cross-sectional view showing a manufacturing process of the HBC type crystal solar cell shown in fig. 13.

Fig. 15 is a schematic cross-sectional view showing a process subsequent to the process shown in fig. 14.

Fig. 16 is a schematic cross-sectional view showing a subsequent process to the process shown in fig. 15.

Fig. 17 is a schematic cross-sectional view showing a process subsequent to the process shown in fig. 16.

Fig. 18 is a flowchart showing a manufacturing process of the HBC type crystal solar cell of the present invention (fig. 13).

Fig. 19 is a schematic cross-sectional view showing a third embodiment of the HBC-type crystal solar cell according to the present invention.

Fig. 20 is a schematic cross-sectional view showing a manufacturing process of the HBC-type crystal solar cell shown in fig. 19.

Fig. 21 is a schematic cross-sectional view showing a process subsequent to the process shown in fig. 20.

Fig. 22 is a schematic cross-sectional view showing a process subsequent to the process shown in fig. 21.

Fig. 23 is a schematic cross-sectional view showing a process subsequent to the process shown in fig. 22.

Fig. 24 is a flowchart showing a manufacturing process of the HBC type crystal solar cell of the present invention (fig. 19).

Fig. 25 is a schematic cross-sectional view showing a conventional manufacturing process of an HBC-type crystal solar cell.

Description of the symbols

BM conductive part

PR photoresist

100 HBC type crystal solar cell

101 substrate

101a one side

101b another side

102 i type amorphous Si layer (. beta.)

103 part A

104 part B

112 i type amorphous Si layer (. alpha.)

113 n type amorphous Si layer

114 anti-reflection layer

Detailed Description

A first embodiment of a heterojunction-type back-contact (HBC-type) crystal solar cell according to the present invention will be described below with reference to the accompanying drawings.

< first embodiment >

(general concept and Process A)

(HBC type crystal solar cell)

Fig. 1 is a diagram illustrating the structure of an HBC-type crystal solar cell 100I (100) according to a first embodiment of the present invention.

The solar cell 100I (100) of the first embodiment is a case where "n" (described later)⁺Site and p⁺The site "is formed by ion implantation in the vicinity of the back surface inside the i-type amorphous Si layer formed so as to cover the back surface (the opposite side to the light incident surface: the lower surface in fig. 1) of the substrate.

In the present embodiment, n is formed⁺Site and p⁺The ion implantation method is used as a site, but as long as impurity atoms are introduced into the amorphous Si layer in an ion state, the method is not limited to the ion implantation method, and impurity introduction may be performed by using a plasma doping method or the like. However, in the following description, an ion implantation method is used as a typical example of the impurity introduction method, and the details are described.

The HBC type crystal solar cell 100I according to the first embodiment includes at least: a substrate 101 made of crystalline silicon of a first conductivity type (e.g., n-type semiconductor) exhibiting a photoelectric conversion function; an i-type amorphous Si layer (α)112 disposed so as to cover one surface 101a on which light (indicated by an arrow) is incident on the substrate 101; and an i-type amorphous Si layer (β)102 disposed so as to cover the other surface 101b located on the opposite side of the one surface 101 a.

In the HBC-type crystal solar cell 100I, an n-type amorphous Si Layer 113 and an Anti-Reflection Layer (AR Layer)114 are stacked in this order on the one surface 101a side of the substrate 101 so as to cover the I-type amorphous Si Layer (α). As the antireflection layer 114, for example, an insulating nitride film, a silicon nitride film, a titanium oxide film, an aluminum oxide film, or the like is preferably used.

In the HBC type crystal solar cell 100I, the conductivity type is the same as the first conductivity type (for example, n)⁺Type) and a site (B)104 having a conductivity type different from the first conductivity type are arranged so as to be separated from each other in such a manner that the interior thereof exists in the amorphous Si layer (β)102 and a part thereof is exposed on the outer surface side of the amorphous Si layer (β) 102. In fig. 1, a portion (C) represents a partition portion between a portion (a)103 and a portion (B) 104.

That is, in the HBC-type crystal solar cell 100I according to the first embodiment, each of the portion (a)103 and the portion (B)104 is a local region formed by implanting a desired element into the surface layer portion of the substrate 101.

In fig. 1, symbol d1 is the thickness of the amorphous Si layer (β)102, and symbol d2 represents the depth of the site (a)103 and the site (B) 104. An example of the thickness d1 of the amorphous Si layer (β)102 is about 200 nm. The site (a)103 and the site (B)104 are formed by an ion implantation method described later.

According to this method, the amorphous Si layer (β)102 can be formed only by performing ion implantation treatment for forming the site (a)103 and the site (B)104, respectively. Therefore, in this structure, the outer surface of the amorphous Si layer (β)102 maintains a flat profile even after the formation of the site (a)103 and the site (B) 104. Therefore, the electrode BM made of a conductive material formed on the portion (a)103 and the portion (B)104 in the subsequent step can maintain flatness. Further, the photoresist removal is performed so as to leave the electrode BM in the portions overlapping with the portion a and the portion B, respectively, and to be stabilized.

(method for producing HBC type Crystal solar cell)

A method for manufacturing the HBC type crystal solar cell 100I (100) according to the first embodiment shown in fig. 1 will be described. Fig. 2 to 5 are schematic cross-sectional views showing steps of manufacturing the HBC type crystal solar cell shown in fig. 1. Fig. 7 is a flowchart showing a manufacturing process of the HBC type crystal solar cell shown in fig. 1. Hereinafter, "amorphous Si" is abbreviated as "a-Si".

Hereinafter, differences between the conventional example and the first embodiment will be described by using fig. 6 and 25 showing the conventional example as appropriate.

The respective steps for manufacturing the HBC type crystal solar cell 100 according to the first embodiment will be described in detail. First, in the texturing step, the substrate 101 is subjected to a wet etching process using, for example, potassium hydroxide (KOH) or sodium hydroxide (NaOH) as an etchant. Then, organic matter and metal contaminants remaining on the treated substrate 101 are removed using nitric fluoride acid. Accordingly, the one surface 101a and the other surface 101b of the substrate 101 are processed to have a textured shape [ first step: fig. 2 (a) ].

The i-type a-Si film (α)112 and the i-type a-Si film (β)102 are formed on the one surface 101a and the other surface 101b of the substrate 101 processed into the above-described textured shape by CVD under predetermined conditions [ second step: fig. 2 (b) ].

Next, an n-type a-Si film 113 and a silicon nitride (SiN) film 114 (anti-reflection layer) are sequentially formed on the i-type a-Si film 112 disposed on the one surface 101a of the substrate 101 by a CVD method under predetermined conditions [ third step: fig. 2 (c) ].

The film formation in the second step and the third step is performed using, for example, a manufacturing apparatus (hereinafter, also referred to as a CVD apparatus) 700, and the manufacturing apparatus 700 performs the film formation by the CVD method shown in fig. 10.

In the CVD apparatus 700 shown in fig. 10, the process chambers are arranged in series. A tray (not shown) on which a substrate 101 made of crystalline silicon is mounted is sequentially passed through each processing chamber, thereby forming an i-type a-Si film 112, an i-type a-Si film 102, an n-type a-Si film 113, and a silicon nitride (SiN) film 114 on the substrate 101.

The CVD apparatus 700 includes: a loading chamber (L)751, a heating chamber (H)752, a film formation inlet chamber (EN)753, a first film formation chamber (S1)754, a second film formation chamber (S2)755, a third film formation chamber (S3)756, a fourth film formation chamber (S4)757, a film formation outlet chamber (EX)758, a transport chamber (T)759, and a take-out chamber (UL) 760.

The substrate 101 mounted on a tray (not shown) loaded from the loading chamber (L)751 has textures formed on both the front and back surfaces thereof. The substrate 101 can move only in the forward direction from the loading chamber (L)751 to the unloading chamber (UL)760 in a state of being mounted on a tray (not shown). That is, in the manufacturing apparatus 700 shown in fig. 10, the substrate 101 mounted on the tray (not shown) does not need to be returned in the reverse direction [ the direction from the take-out chamber (UL)760 to the loading chamber (L)751 ]. Therefore, the manufacturing apparatus 700 shown in fig. 10 is excellent in mass productivity.

After the atmosphere is set to a desired reduced pressure, the substrate 101 carried into the loading chamber 751 is moved from the loading chamber 751 to the heating chamber 752, and heat treatment is performed by the heater 752H at the point a. The substrate 101 having reached the desired temperature is moved to the film formation inlet chamber (EN)753, and the atmosphere in the film formation inlet chamber 753 in which the substrate 101 is housed is adjusted in accordance with the atmospheric conditions at the time of forming the i-type a-Si film 112 in the first film formation chamber 754 in the next step. The film formation inlet chamber 753 has a heater 753H, and the temperature of the substrate 101 is adjusted so as to be a temperature preferable for producing the i-type a-Si film α (112).

Next, the temperature-adjusted substrate 101 is moved to the first film forming chamber 754 and passed through the spot C, thereby forming the i-type a-Si film α (112) only on one surface side of the substrate 101 by the CVD method. This makes it possible to obtain a state in which the a-Si film α (112) is formed on one surface (101a) of the substrate 101. Here, the cathode 754C2 is connected to a power source 754E2, and a desired film-forming gas is introduced from a gas supply unit 754G during film formation.

Next, the substrate 101 on which the i-type a-Si film α (112) is formed is moved to the second film formation chamber 755 and passes through the point D, so that the i-type a-Si film (β)102 is formed only on the other surface side of the substrate 101 by the CVD method. Thus, the i-type a-Si film (β)102 is formed on the other surface (101b) of the substrate 101. This state is the HBC type crystal solar cell 100B having the structure shown in fig. 2 (B). Here, the cathode 755C1 is connected to a power supply 755E1, and a desired film-forming gas is introduced from the gas supply unit 755G during film formation.

Next, the substrate 101 on which the i-type a-Si film α (112) and the i-type a-Si film (β)102 are formed is moved to the third film forming chamber 756 and passes at the point E. Accordingly, the n-type a-Si film 113 is formed only on the i-type a-Si film α (112) on one surface side of the substrate 101 by the CVD method. This makes it possible to obtain a state in which the n-type a-Si film 113 is formed on the i-type a-Si film α (112) on the one surface (101a) side of the substrate 101. Here, the cathode 756C2 is connected to a power supply 756E2, and a desired film-forming gas is introduced from the gas supply unit 756G during film formation.

Next, the substrate 101 having the i-type a-Si film α (112) and the n-type a-Si film 113 formed on one surface side is moved to the fourth film forming chamber 757 and passes through at the point F. Accordingly, a silicon nitride (SiN) film 114 is formed only on the n-type a-Si film 113 on one surface side of the substrate 101 by the CVD method. This makes it possible to obtain a state in which the n-type a-Si film 113 and the SiN film 114 are sequentially laminated on the i-type a-Si film α (112) on the one surface (101a) side of the substrate 101. This state is the HBC type crystal solar cell 100C having the structure shown in fig. 2 (C). Here, the cathode 757C2 is connected to a power supply 757E2, and a desired film-forming gas is introduced from a gas supply unit 757G at the time of film formation.

When the i-type a-Si film (α)112, the i-type a-Si film (β)102, the n-type a-Si film 113, and the SiN film 114 are formed in the first film forming chamber 754 to the fourth film forming chamber 757, the temperature of the substrate may be controlled to be a temperature preferable for producing each thin film by using the temperature control units 754TC1, 755TC2, 756TC1, and 757TC1 provided in each film forming chamber.

As shown in fig. 2 (c), the substrate 101 having the i-type a-Si film (α)112, the n-type a-Si film 113, and the SiN film 114 formed on one surface side and the i-type a-Si film (β)102 formed on the other surface side is moved to the film formation outlet chamber (EX)758, then moved to the take-out chamber (UL)760 through the transfer chamber (T)759, and the interior of the take-out chamber is set to the atmospheric pressure, whereby the substrate is carried out to the outside of the sputtering apparatus.

Thereafter, a desired photoresist PR is applied to the i-type a-Si film 102 disposed on the other surface 101b of the substrate 101, followed by patterning. Accordingly, a photoresist PR having a predetermined opening in a region where ion implantation is performed in a later step is formed on the i-type a-Si film 102 [ fourth step: fig. 2 (d) ]. Further, a known material can be used as the photoresist material, but an organic-inorganic hybrid photoresist material such as a Spin-On-Glass (SOG) material is preferable because it has higher resistance to ion implantation than a completely organic photoresist material such as PMMA. Further, after forming a photoresist using a known photoresist material, an ultra-thin metal film of several nm (for example, 1 to 5nm) may be formed and given a function as a photoresist.

Next, p-type ions such as boron (B) ions are locally implanted into the i-type a-The vicinity of the outer surface 102b of the Si film 102 [ fifth step: FIG. 3 (a)]Thereby forming p⁺Site (a)103[ fifth step: of FIG. 3 (c)]。

At this time, as shown in fig. 3 (b), a mask M1 is used which has an opening shape such that, when the portion a in which ions are implanted through the opening of the mask is viewed in plan, a portion of the photoresist PR defining the outer shape of the portion a can be seen.

In fig. 3 (b), a symbol M1e is defined as a position when the edge of the mask M1 is projected onto the photoresist PR, and a symbol pse is defined as a position of an edge defining an opening of the photoresist PR. At this time, the mask M1 was designed so that the difference between M1e and the pri (Δ M1A, Δ M1B) at each end of the mask M was greater than zero. In the present invention, by using the photoresist PR in addition to the mask M1, the outline of the region a can be defined more clearly than when only the mask M1 is used. Thus, according to the invention, for p⁺The portion (a)103 can be formed in a shape having a clear shape up to the outer edge thereof.

Next, n-type ions such as phosphorus (P) ions are locally implanted near the outer surface 102b of the i-type a-Si film 102 and at P through a mask M2⁺Between the sites (A)103 and not with p⁺The position where the portion (a)103 overlaps [ sixth step: FIG. 4 (a)]. Accordingly, n is formed⁺Site (B)104[ sixth step: of FIG. 4 (c)]。

At this time, as shown in fig. 4 (B), a mask M2 is used which has an opening shape such that, when the region B in which ions are implanted through the opening of the mask is viewed in plan, a region of the photoresist PR defining the outer shape of the region B can be seen.

In fig. 4 (b), a symbol M2e is defined as a position when the edge of the mask M2 is projected onto the photoresist PR, and a symbol pse is defined as a position of an edge defining an opening of the photoresist PR. At this time, the mask M2 was designed so that the difference between M2e and the pri (Δ M2A, Δ M2B) at each end of the mask M was greater than zero. In the present invention, light is used in combination with the mask M2The resist PR can define the outline of the portion B more clearly than when only the mask M2 is used. Thus, according to the invention, for n⁺The portion (B)104 can be formed in a shape having a definite shape up to the outer edge thereof.

Accordingly, the HBC crystal solar cell 100G is formed ((c) of fig. 4)]Of the same conductivity type as the first conductivity type of the substrate (e.g., n)⁺Type) region (a)103 and a region (B)104 having a conductivity type different from the first conductivity type are arranged so as to be separated from each other so that the region is present inside the i-type a-Si layer 102 and a part of the region is exposed on the outer surface side of the a-Si layer 102. At this stage, a photoresist PR is present on a portion (C) of the i-type a-Si layer 102 where a partition of the portion (a) and the portion (B) is formed.

Next, after the annealing treatment [ seventh step ], the conductive member BM functioning as an electrode is formed so as to cover the portion a, the portion B, and the photoresist. The annealing treatment will be described in detail later.

The conductive member BM is formed by a sputtering method under predetermined conditions [ eighth step: fig. 5 (a) ]. Accordingly, the conductive member BM formed in the portion a or the portion B is disconnected from the conductive member BM formed in the photoresist.

Since the conductive member BM is used as an electrode, a material having high conductivity (low resistance) is preferable, and examples thereof include Ag, Al, Cu, Ti, and the like. The conductive member BM may be a laminated film having two or more layers other than the single layer film. As a representative example thereof, a laminated film of a transparent conductive film (ITO or the like) and a metal film (Ag or the like) may be cited.

Finally, the photoresist is peeled off from the outer surface of the a-Si layer 102 by irradiating, for example, UV light [ ninth process: fig. 5 (b) ]. At this time, the conductive member BM on the photoresist is also removed together. Accordingly, the outer surface of the a-Si layer 102 remains only in the portion formed on the site a or the site B in the conductive member BM. Therefore, the conductive member BM along the site a or the site B is formed and can be used as an electrode. This step is a process called "peeling (リフトオフ)".

By sequentially including the above steps, the HBC type crystal solar cell 100I (100) having the structure shown in fig. 1 can be produced.

Here, as shown in fig. 2 (b), the i-type a-Si film (β)102 is originally formed as a single film in the thickness direction and in-plane direction. Therefore, even if p is formed near the outer surface 102b of the i-type a-Si film 102 in the third and fourth steps performed after the passage⁺Sites (A)103 and n⁺In the case of the portion (B)104, the portion (C) as the spacer, that is, the region where no ion is implanted, also exists as a single film in the thickness direction.

Further, the i-type a-Si film 102 as a single film is formed so as not to reach the other surface 101b of the substrate⁺Sites (A)103 and n⁺The region (B)104 is such that the i-type a-Si film 102 present in contact with the other surface 101B of the substrate is present as a single film continuous in the in-plane direction of the substrate.

Thus, in the HBC type crystal solar cell 100I (100) of the present embodiment (fig. 1), the I-type a-Si film 102 is formed except for p⁺Sites (A)103 and n⁺The region other than the region (B)104 is present as a "single film" (here, the "single film" means that no interface is present inside the i-type a-Si layer 102), and thus the i-type a-Si film 102 maintains its function as a passivation film.

In contrast, in the conventional structure shown in fig. 25 (j), in order to form the n-type a-Si layer 1003 and the p-type a-Si layer 1007, the i-type a-Si layer 1002 formed between these layers and the silicon substrate 1001 is temporarily formed with partitions in the surface direction of the substrate by etching (in the state of fig. 25 (c) and (g)). Finally, as shown in fig. 25 (j), the i-type a-Si layer 1009 is formed on the partition portion and filled with the partition portion. Therefore, in the i-type a-Si layer in fig. 25 (j), an interface (the dotted line between 1002 and 1009 in fig. 25 (j) corresponds to the interface) exists in the in-plane direction of the substrate. Due to the presence of such an interface, the film is discontinuous in the in-plane direction of the substrate, and there is a possibility that the i-type a-Si layer cannot function effectively as a passivation film.

Fig. 8 is a graph showing the relationship between Ion Energy (Ion Energy) and Stopping Range (Stopping Range) of boron (B).

The stop range is an index indicating how far the implanted ions can enter the film in the depth direction of the film.

As can be seen from the graph, the ion energy and stop range are in a proportional relationship in which the ion implantation depth increases if the ion energy increases.

Therefore, by selecting a predetermined ion energy, the stop position can be changed to a specific depth when boron (B) ion implantation is performed on the i-type a-Si layer 102. By utilizing this relationship, p shown in fig. 1 can be formed with good reproducibility⁺A site (A) 103.

In an example, by selecting 3keV as the ion energy, p with a depth of about 15nm can be obtained⁺A site (A) 103. At this time, if the thickness d1 of the i-type a-Si layer 102 shown in FIG. 1 is set to 200nm, the thickness of the remaining boron (B) ions without being implanted is the value shown by (d1-d2) in FIG. 1. The portion of the i-type a-Si layer 102 having the thickness of d1-d2 exists as a single film in the in-plane direction of the substrate.

As the ion energy at the time of ion implantation, p is formed according to the formation of p as in the above-mentioned example⁺Sites (A)103 and n⁺The thickness d1 of the i-type a-Si layer 102 in the region (B)104, the thickness (d1-d2) of the portion of the i-type a-Si layer 102 required as a passivation film, and the p⁺Sites (A)103 and n⁺The thickness d2 required for the portion (B)104 is selected to have an appropriate value. However, when the ion energy is increased, the surface of the i-type a-Si layer 102 to be processed becomes rough, and the flatness cannot be maintained.

Therefore, when the i-type a-Si layer 102 is processed, it is preferable that the ion energy [ keV ] is 20 or less, and further, when considering the film thickness of the i-type a-Si layer 102 (that is, the relationship between the thickness of the i-type a-Si layer and the thickness that is desired to remain as a passivation film), it is preferable that the thickness is 5 or less. When the ion energy [ keV ] is 5 or less, the process is performed at a lower energy, and thus the flatness of the surface of the i-type a-Si layer 102 can be maintained.

Further, it was confirmed that the relationship between the ion energy and the stop range of boron (B) described above is also established for phosphorus (P). Therefore, by utilizing this relationship, n shown in fig. 1 can be formed with good reproducibility⁺And (B) 104. Further, with respect to phosphorus (P), n is formed⁺The ion energy [ keV ] is the same as that of boron (B) in terms of the conditions such as the film thickness of the i-type a-Si layer 102 to be the site (B)104 and the like and in the sense of ensuring the surface flatness of the i-type a-Si layer 102]By selecting 20 or less, and further selecting 5 or less, the same effect as in the case of boron (B) can be obtained.

From this graph, the ion energy [ keV ] at the time of ion implantation was confirmed]When the concentration of phosphorus is changed to 3, 6 and 15, [ atoma/cm ]³]Is 10⁺¹⁸In the depth direction of the substrate [ nm ]]Is about 30, 43, 78. Thus, n can be formed in the depth direction so as to have a predetermined phosphorus concentration at each depth position⁺And (B) 104.

It was confirmed that the same relationship as the above-described concentration distribution of phosphorus (P) observed in the depth direction of the substrate for phosphorus (P) is also established for boron (B). Therefore, by utilizing this relationship, p shown in fig. 1 can be formed in the depth direction so as to have a predetermined boron concentration⁺A site (A) 103.

The ion implantation in the first step and the second step is performed by using, for example, an ion implantation apparatus 1200 shown in fig. 11.

Fig. 11 is a cross-sectional view of an ion implantation apparatus 1200 used in the p-type ion implantation step (fifth step) and the n-type ion implantation step (sixth step) in the present invention. The ion implantation apparatus 1200 includes: a vacuum tank 1201; an ICP discharge-based plasma generation unit using a permanent magnet 1205, an RF introduction coil 1206, and an RF introduction window (quartz) 1212; and a vacuum exhaust unit (not shown).

The inside of the vacuum vessel 1201 is divided into a plasma generation chamber and a plasma processing chamber by

electrodes

1208, 1209 having a plurality of openings (for example, in a grid pattern). A substrate support table 1204 for supporting a substrate 1203 to be processed (corresponding to the substrate 101 after the texture forming step) is disposed in the plasma processing chamber. The electrode 1208 is set to a floating potential, and has a function of stabilizing the potential of the plasma 1207. The electrode 1209 is applied with a negative potential, and has a function of extracting positive ions from the plasma 1207.

The vacuum chamber 1201 is depressurized, and a gas containing impurity atoms to be implanted into the substrate 1203 is introduced into the plasma generation chamber. Then, by exciting the plasma 1207 using the plasma generation unit, impurity atoms can be ionized, and p-type or n-type ions extracted through the

electrodes

1208 and 1209 can be implanted into the substrate 1203.

Here, the implantation amount of p-type ions and the implantation amount of n-type ions are determined in accordance with n after annealing treatment described later⁺Sheet resistance and p of site (B)104⁺The relationship between the sheet resistance of the site (a)103 and the photoelectric conversion efficiency of the HBC type crystal solar cell is determined as an optimum value in manufacturing the solar cell 100. However, n is⁺The concentration of n-type ions in the region (B)104 is set to be at least higher than the concentration of n-type ions in the substrate 101.

In addition, when the above-mentioned p-type ion implantation and n-type ion implantation are performed, a gas containing impurity atoms (for example, BF) may be used₃Etc.) and setting conditions to perform ion implantation of hydrogen into the amorphous Si layer. By performing ion implantation of hydrogen at the time of ion implantation, structural defects of the amorphous Si layer can be repaired, the effect of suppressing carrier recombination can be improved, and the total amount of electrons and holes reaching the site a or the site B can be increased, thereby improving the power generation efficiency.

As a method of efficiently implanting hydrogen into the amorphous Si layer, non-mass separation type ion implantation is employed. Mass fraction of ion implantation from n-type and P-type ions (e.g., P-type and B-type ions) aloneUnlike the release ion implantation, in the non-mass separation type ion implantation, pH is used₃、BH₂And the hydrogen-containing gas is used as the gas containing the impurity atoms. Accordingly, in the non-mass separation type ion implantation, hydrogen can be implanted into the substrate simultaneously with the n-type ions and the p-type ions, even if the process gas to which hydrogen is added is not used as described above. Further, in the non-mass separation type ion implantation, since a mechanism for separating ions is not required, there is an advantage that the occupied space is small as the device configuration.

In this way, by adding hydrogen to the process gas or selecting the non-mass separation type ion implantation, the hydrogen implanted into the amorphous Si layer simultaneously with the n-type ions and the p-type ions has a concentration distribution in the depth direction of the amorphous Si layer.

Next, the annealing treatment performed after the sixth step is performed using, for example, an annealing treatment apparatus 1300 shown in fig. 12. The annealing apparatus 1300 shown in fig. 12 employs a vertical heating furnace, and one substrate (substrate subjected to p-type and n-type ion implantation processes in the fourth and fifth processes) is placed in one cassette, and a plurality of such cassettes can be simultaneously heat-treated in a batch process.

The annealing apparatus 1300 shown in fig. 12 is composed of a heating chamber 1310 and a front chamber 1320, and an internal space 1312 of the heating chamber 1310 and an internal space 1322 of the front chamber 1320 can be isolated by a gate valve 1314.

In the internal space 1322 of the front chamber 1320, a cartridge frame 1303 is disposed on the cartridge base 1302, the cartridge frame 1303 is formed by stacking a plurality of cartridges 1301 in multiple stages, and the cartridges 1301 hold the outer peripheral portions of the substrates so that the front and back surfaces of the substrates are exposed.

The gate valve 1314 is opened with the internal space 1312 of the heating chamber 1310 open to the atmosphere, and the cartridge base 1302 in this state is raised (upward arrow) from the internal space 1322 of the front chamber 1320 toward the internal space 1312 of the heating chamber 1310 by the movement means (not shown). Then, the gate valve 1314 is closed, and the internal space 1312 of the heating chamber 1310 is set to a reduced pressure atmosphere by using the exhaust means (P) 1315. The internal space 1312 of the heating chamber 1310 may not be set to a reduced pressure atmosphere, and an annealing gas described later may be directly introduced to perform atmospheric pressure annealing.

Then, the annealing gas is introduced into the internal space 1312 of the heating chamber 1310, and annealing is performed in accordance with a predetermined temperature distribution in a controlled atmosphere. Here, the introduced gas is nitrogen, and hydrogen may be added to the gas for use. In this way, by adding hydrogen to the annealing gas, hydrogen implanted into the i-type a-Si layer in the second and third steps can be released from the substrate by heating, and can be repaired. As an example, an annealing gas obtained by adding 3% of hydrogen to nitrogen gas is used.

After the substrate temperature is equal to or lower than the predetermined temperature, the introduction of the gas is stopped, and the gate valve 1314 is opened with the internal space 1312 of the heating chamber 1310 opened to the atmosphere. Then, the cartridge base 1302 is moved downward (downward arrow) from the internal space 1312 of the heating chamber 1310 to the internal space 1322 of the front chamber 1320 by a moving means (not shown).

The annealing treatment of the present invention is performed by the above steps. In this case, the conditions of the annealing process are determined to be optimum conditions according to the diffusion coefficients of n-type ions and p-type ions in the substrate. For example, the temperature of the annealing treatment is preferably 600 ℃. This is to prevent p from being included⁺Sites (A)103 and n⁺The i-type a-Si layer 102 in the region (B)104 is crystallized, and the function of the i-type a-Si layer as a passivation film is lowered. Further, the temperature of the annealing treatment is more preferably 400 ℃ or lower. This is to suppress hydrogen implanted simultaneously with n-type ions and p-type ions from being desorbed from the i-type a-Si layer during ion implantation. The time taken for the annealing treatment is preferably about 30 minutes to 60 minutes.

Then, as an electrode forming process, a process of forming an electrode so as to cover the electrode including p⁺Site (A)103, n⁺A metal film (e.g., Cu film) is formed over the entire outer surface 102B of the i-type a-Si layer including the photoresist PR and the site (B) 104. As the metal film, an Ag film or the like is preferably used in addition to the Cu film. However, the electrode is not limited to the metal film, and a transparent conductive film may be used instead of the metal film. Examples of the metal film or the transparent conductive filmSuch as by using a common sputtering apparatus.

Next, the photoresist PR is irradiated with, for example, UV light through the metal film, thereby peeling the photoresist PR from the outer surface of the a-Si layer 102 [ ninth step: fig. 5 (b) ]. At this time, the conductive member BM on the photoresist is also removed together.

Accordingly, the outer surface of the a-Si layer 102 remains only in the portion formed on the site a or the site B in the conductive member BM. As a result, p exists in a covering manner⁺Sites (A)103 and n⁺The electrode made of the conductive member BM arranged in the region of the portion (B)104 is stably formed. In the present invention, the ninth step is also referred to as a "peeling" step.

By sequentially performing the above steps, the HBC type crystal solar cell 100I (100) shown in fig. 1 can be produced.

In the case of the first embodiment [ HBC type crystal solar cell 100I (100) ], the n-type amorphous Si layer 113 and the anti-reflection layer 114 are formed on the one surface 101a side of the substrate 101 so as to cover the I-type amorphous Si layer α in an initial stage (before the formation of the portion a and the portion B by ion implantation).

In this way, it is preferable to form the antireflection layer 114 even in an initial stage (before the formation of the portion a and the portion B by ion implantation), in order to protect the light incident surface from the subsequent process such as ion implantation and BM formation.

Fig. 6 is a flowchart showing a manufacturing process of a solar cell according to a conventional example (fig. 25), and fig. 7 is a flowchart showing a manufacturing process of a solar cell according to the present invention (fig. 1 to 5).

As shown in fig. 6, the portion (a) and the portion (B) in the conventional HBC type crystal solar cell are formed after going through the process flow of fig. 25 (a) to 25 (j). That is, the manufacturing process is performed by sequentially performing 13 steps consisting of [ i-type a-Si film formation, n-type a-Si film formation, photoresist coating and patterning, etching, photoresist stripping, etching barrier layer film formation and patterning, i-type a-Si film formation, p-type a-Si film formation, photoresist coating and patterning, etching, photoresist stripping, etching barrier layer stripping, and i-type a-Si formation only in the partition portion ]. In the conventional manufacturing method, the coating and peeling process needs at least three times, and a complicated process flow is required.

In contrast, as shown in fig. 7, the portion (a) and the portion (B) in the HBC type crystal solar cell of the present invention are formed by the process flow shown in fig. 2 to 5. According to the present invention, since the coating and peeling process can be performed only once, a simple process flow can be realized.

Since the HBC type crystal solar cell can be manufactured by a very small number of steps compared to the conventional manufacturing method, the HBC type crystal solar cell of the present invention can greatly reduce "the expensive photolithography step and etching step" compared to the conventional steps. Therefore, according to the present invention, since the complicated process required in the past can be reduced, the manufacturing can be performed in a more stable process management. That is, according to the first embodiment, since an expensive manufacturing apparatus is not required, the present invention contributes to providing an inexpensive HBC type crystal solar cell.

However, as shown in FIG. 1, in the HBC type crystal solar cell of the present invention, [ p ] is affected by annealing⁺Site (A)103]And [ n⁺Site (B)104]Beta 102 existing in [ i-type a-Si film]The annealing conditions need to be taken into consideration.

Specifically, the temperature [ ° c ] at the time of annealing is preferably 600 or less for preventing the i-type a-Si layer from deteriorating its function as a passivation film, and is preferably 400 or less for suppressing hydrogen separation from the i-type a-Si layer, as described above.

< second embodiment >

(Process B)

(HBC type crystal solar cell)

Fig. 13 is a diagram illustrating the structure of the HBC type crystal solar cell 200I (200) according to the second embodiment of the present invention. In the structure after the production, the HBC type crystal solar cell 200I (200) is the same as the HBC type crystal solar cell 100I (100) described above, but the HBC type crystal solar cell 200I (200) differs from the HBC type crystal solar cell 100I (100) described above in terms of the production step (production process).

Specifically, in the case of the first embodiment [ HBC type crystal solar cell 100I (100) ], the n-type amorphous Si layer 113 and the anti-reflection layer 114 are formed on the one surface 101a side of the substrate 101 so as to cover the I-type amorphous Si layer α in an initial stage (before the formation of the site a and the site B by ion implantation).

In contrast, in the case of the second embodiment [ HBC type crystal solar cell 200I (200) ], the antireflection layer 214 is not formed at the initial stage (before the formation of the portion a and the portion B by ion implantation). That is, the n-type amorphous Si layer 213 is formed on the one surface 201a side of the substrate 201 so as to cover the i-type amorphous Si layer α. The antireflection layer 214 of the second embodiment is formed at a later stage (after the portions a and B are formed by ion implantation).

In the second embodiment, the antireflection layer 214 is formed at a later stage (after the portion a and the portion B are formed by ion implantation), and thus can be formed simultaneously with BM by sputtering, which is preferable in terms of improvement in productivity.

(method for producing HBC type Crystal solar cell)

A method for manufacturing the HBC type crystal solar cell 200I (200) according to the second embodiment shown in fig. 13 will be described. Fig. 14 to 17 are schematic cross-sectional views showing steps of manufacturing the HBC type crystal solar cell shown in fig. 13. Fig. 18 is a flowchart showing a manufacturing process of the HBC type crystal solar cell shown in fig. 13. Hereinafter, "amorphous Si" is abbreviated as "a-Si" as in the first embodiment.

Hereinafter, differences between the first embodiment and the second embodiment will be described by using fig. 1 to 5 and fig. 7 showing the first embodiment as appropriate.

The respective steps for manufacturing the HBC type crystal solar cell 200 according to the second embodiment will be described in detail. First, in the texturing step, the substrate 201 is subjected to a wet etching process using, for example, potassium hydroxide (KOH) or sodium hydroxide (NaOH) as an etchant. Then, organic matter and metal contaminants remaining on the treated substrate 201 are removed using nitric fluoride acid. Accordingly, the one surface 201a and the other surface 201b of the substrate 201 are processed to have a textured shape [ first step: fig. 14 (a) ].

The i-type a-Si film (α)212 and the i-type a-Si film (β)202 are formed on the one surface 201a and the other surface 201b of the substrate 201 processed into the above-described textured shape by CVD under predetermined conditions [ second step: fig. 14 (b) ].

Next, an n-type a-Si film 213 is formed on the i-type a-Si film (α)212 disposed on the one surface 201a of the substrate 201 by a CVD method under predetermined conditions [ third step: fig. 14 (c) ].

In this embodiment, when the CVD apparatus 700 shown in fig. 10 is used, the i-type a-Si film 212, the i-type a-Si film 202, and the n-type a-Si film 213 are formed on the substrate 201 by sequentially passing through the respective processing chambers. That is, in the third step of the second embodiment, the anti-reflection layer formed in the first embodiment is not formed on the n-type a-Si film 213.

The method of forming the three layers [ i-type a-Si film 212, i-type a-Si film 202, and n-type a-Si film 213] using the CVD apparatus 700 is the same as that of the first embodiment, and the description thereof is omitted.

As shown in fig. 14 (c), the substrate 201 having the i-type a-Si film (α)212 and the n-type a-Si film 213 formed on one surface side and the i-type a-Si film (β)202 formed on the other surface side by the CVD apparatus 700 is moved to the film formation outlet chamber (EX)758, then moved to the take-out chamber (UL)760 through the transport chamber (T)759, and the interior of the take-out chamber is set to the atmospheric pressure, whereby the substrate is carried out of the sputtering apparatus.

Thereafter, a desired photoresist PR is applied to the i-type a-Si film 202 disposed on the other surface 201b of the substrate 201, followed by patterning. Accordingly, a photoresist PR having a predetermined opening in a region where ion implantation is performed in a later step is formed on the i-type a-Si film 202 [ fourth step: fig. 14 (d) ].

Next, p-type ions such as boron (B) ions are locally implanted near the outer surface 202B of the i-type a-Si film 202 through the mask M1 [ fifth step: FIG. 15 (a)]Thereby forming p⁺Site (a)203[ fifth step: FIG. 15 (c)]。

At this time, as shown in fig. 15 (b), a mask M1 is used which has an opening shape such that, when a portion a in which ions are implanted through the opening of the mask is viewed in plan, a portion of the photoresist PR defining the outer shape of the portion a can be seen.

In fig. 15 (b), a symbol M1e is defined as a position when the edge of the mask M1 is projected onto the photoresist PR, and a symbol pse is defined as a position of an edge defining an opening of the photoresist PR. At this time, the mask M1 was designed so that the difference between M1e and the pri (Δ M1A, Δ M1B) at each end of the mask M was greater than zero. In the present invention, by using the photoresist PR in addition to the mask M1, the outline of the region a can be defined more clearly than when only the mask M1 is used. Thus, according to the invention, for p⁺The portion (a)203 can be formed in a shape having a definite shape up to the outer edge thereof.

Next, n-type ions such as phosphorus (P) ions are locally implanted near the outer surface 202b of the i-type a-Si film 202 and at P-type by passing through a mask M2⁺Between the sites (A)203 and not with p⁺The position where the portions (a)203 overlap [ sixth step: FIG. 16 (a)]Thereby forming n⁺Portion (B)204[ sixth step: FIG. 16 (c)]。

At this time, as shown in fig. 16 (B), a mask M2 is used which has an opening shape such that, when the region B in which ions are implanted through the opening of the mask is viewed in plan, a region of the photoresist PR defining the outer shape of the region B can be seen.

In the figureIn (b) of fig. 16, the symbol M2e is defined as a position when the edge of the mask M2 is projected onto the photoresist PR, and the symbol pse is defined as a position of an edge defining an opening of the photoresist PR. At this time, the mask M2 is designed so that the difference between M2e and Pre (Δ M2A, Δ M2B) at each end of the mask M is greater than zero. In the present invention, by using the photoresist PR in addition to the mask M2, the outline of the region B can be defined more clearly than when only the mask M2 is used. Thus, according to the invention, for n⁺The portion (B)204 can be formed in a shape having a definite outer edge.

Accordingly, the HBC crystal solar cell 200G is formed ((c) of fig. 16)]Of the same conductivity type as the first conductivity type of the substrate (e.g., n)⁺Type) region (a)203 and a region (B)204 having a conductivity type different from the first conductivity type are arranged so as to be separated from each other so that the region is present inside the i-type a-Si layer (β)202 and a part of the region is exposed on the outer surface side of the a-Si layer (β) 202. At this stage, a photoresist PR is present on a portion (C) of the i-type a-Si layer (β)202 where a partition of the portion (a) and the portion (B) is formed.

Next, after the annealing treatment [ seventh step ], a conductive member BM functioning as an electrode is formed so as to cover the portion a, the portion B, and the photoresist PR. The annealing treatment will be described in detail later.

The conductive member BM is formed by a sputtering method under predetermined conditions [ eighth step: fig. 17 (a) ]. Accordingly, the conductive member BM formed in the portion a or the portion B is disconnected from the conductive member BM formed in the photoresist PR.

Since the conductive member BM is used as an electrode, a material having high conductivity (low resistance) is preferable, and examples thereof include Ag, Al, Cu, Ti, and the like. The conductive member BM may be a laminated film having two or more layers other than the single layer film. A typical example thereof is a laminated film of a transparent conductive film (such as ITO) and a metal film (such as Ag).

Next, after the conductive member BM is formed, the antireflection layer 214 is formed. Accordingly, as shown in fig. 17 (a), the HBC-type crystalline solar cell 200H (200) of the second embodiment has a structure in which an n-type amorphous Si layer 213 and an antireflection layer 214 are formed on the one surface 201a side of the substrate 201 so as to cover the i-type amorphous Si layer (α)212, as in the first embodiment.

Finally, the photoresist PR is peeled off from the outer surface of the a-Si layer 202 by irradiating, for example, UV light [ ninth process: fig. 17 (b) ]. At this time, the conductive member BM on the photoresist PR is also removed together. Accordingly, the outer surface of the a-Si layer 202 remains only in the portion formed on the site a or the site B in the conductive member BM. Therefore, the conductive member BM along the site a or the site B is formed and can be used as an electrode. This step is a process called "peeling".

By sequentially including the above steps, the HBC type crystal solar cell 200I (200) having the structure shown in fig. 13 can be produced.

In the HBC type crystal solar cell 200H (200) of the second embodiment as well, as in the first embodiment, as shown in fig. 14 (b), the i-type a-Si film (β)202 is originally formed as a single film in the thickness direction and in the in-plane direction. Therefore, even if p is formed near the outer surface 202b of the i-type a-Si film 202 in the third and fourth steps performed after the passage⁺Sites (A)203 and n⁺In the case of the portion (B)204, the portion (C) as the spacer, that is, the region where no ion is implanted, also exists as a single film in the thickness direction.

Further, the i-type a-Si film 202 as a single film is formed so as not to reach the other surface 201b of the substrate⁺Sites (A)203 and n⁺The region (B)204 is such that the i-type a-Si film 202 present in contact with the other surface 201B of the substrate is present as a single film continuous in the in-plane direction of the substrate.

In this manner, in the HBC type crystal solar cell 200I (200) of the present embodiment (fig. 13), the I-type a-Si film 202 is also formed in addition to p⁺Sites (A)203 and n⁺As a "single film" in the region other than the region (B)204"exists" (here, "a single film" means that there is no interface inside the i-type a-Si layer 202), and thus the i-type a-Si film 202 maintains its function as a passivation film.

< third embodiment >

(Process B +)

(HBC type crystal solar cell)

Fig. 19 is a diagram illustrating the structure of the HBC type crystal solar cell 300I (300) according to the third embodiment of the present invention. In the structure after the production, the HBC type crystal solar cell 300I (300) is different from the HBC type crystal solar cell 100I (100) and the HBC type crystal solar cell 200I (200) described above in that "an n-type amorphous Si layer is not included". Thus, the third embodiment differs from the first and second embodiments in the manufacturing steps (manufacturing steps). In the third embodiment, the antireflection layer is formed at the same timing as in the second embodiment.

In contrast, in the case of the third embodiment [ HBC type crystal solar cell 300I (300) ], the n-type amorphous Si layer and the antireflection layer are not formed at the initial stage (before the formation of the site a and the site B by ion implantation). That is, on the one surface 301a side of the substrate 301, there is no substance covering the i-type amorphous Si layer α. The anti-reflection layer 314 of the third embodiment is formed to cover the amorphous Si layer (α) at a later stage (after the formation of the portion a and the portion B by ion implantation).

In the third embodiment, since the anti-reflection layer is formed on the amorphous Si layer (α) at a later stage (after the formation of the portion a and the portion B by ion implantation), it can be formed simultaneously with the BM by sputtering, which is preferable in terms of improving productivity.

(method for producing HBC type Crystal solar cell)

A method for manufacturing the HBC type crystal solar cell 300I (300) according to the third embodiment shown in fig. 19 will be described. Fig. 20 to 23 are schematic cross-sectional views showing steps of manufacturing the HBC type crystal solar cell shown in fig. 19. Fig. 24 is a flowchart showing a manufacturing process of the HBC type crystal solar cell shown in fig. 19. Hereinafter, "amorphous Si" is abbreviated as "a-Si" as in the first mode.

Hereinafter, differences between the first embodiment and the third embodiment will be described by using fig. 1 to 5 and 7 showing the first embodiment as appropriate.

The respective steps for producing the HBC type crystal solar cell 300 according to the third embodiment will be described in detail. First, in the texturing step, the substrate 301 is subjected to a wet etching process using, for example, potassium hydroxide (KOH) or sodium hydroxide (NaOH) as an etchant. Then, organic matter and metal contaminants remaining on the treated substrate 301 are removed using nitric fluoride acid. Accordingly, the one surface 301a and the other surface 301b of the substrate 301 are processed to have a textured shape [ first step: fig. 20 (a) ].

The i-type a-Si film (α)312 and the i-type a-Si film (β)302 are formed on the one surface 301a and the other surface 301b of the substrate 301 processed into the above-described textured shape by CVD under predetermined conditions [ second step: fig. 20 (b) ].

Next, an n-type a-Si film 313 is formed on the i-type a-Si film (α)312 disposed on the one surface 301a of the substrate 301 by a CVD method under predetermined conditions [ third step: fig. 20 (c) ].

In this embodiment, when the CVD apparatus 700 shown in fig. 10 is used, the i-type a-Si film (α)312 and the i-type a-Si film (β)302 are formed on the substrate 301 by sequentially passing through the respective processing chambers. That is, in the third step of the third embodiment, the n-type a-Si film and the antireflection layer formed in the first embodiment are not provided on the i-type a-Si film (α) 312.

The method of forming the two layers, i.e., [ i-type a-Si film 312 and i-type a-Si film 302], using the CVD apparatus 700 is the same as in the first embodiment, and the description thereof is omitted.

As shown in fig. 20 (c), the substrate 301 having the i-type a-Si film (α)312 formed on one surface side and the i-type a-Si film (β)302 formed on the other surface side by the CVD apparatus 700 is moved to the film formation outlet chamber (EX)758, then moved to the take-out chamber (UL)760 through the transport chamber (T)759, and the inside of the take-out chamber is set to the atmospheric pressure, whereby the substrate is carried out of the sputtering apparatus.

Thereafter, a desired photoresist PR is applied to the i-type a-Si film 302 disposed on the other surface 301b of the substrate 301, followed by patterning. Accordingly, a photoresist PR having a predetermined opening in a region where ion implantation is performed in a later step is formed on the i-type a-Si film 302 [ fourth step: fig. 20 (d) ].

Next, p-type ions such as boron (B) ions are locally implanted near the outer surface 302B of the i-type a-Si film 302 through the mask M1 [ fifth step: FIG. 21 (a)]Thereby forming p⁺Site (a)303[ fifth step: FIG. 21 (c)]。

At this time, as shown in fig. 21 (b), a mask M1 is used which has an opening shape such that, when a portion a in which ions are implanted through the opening of the mask is viewed in plan, a portion of the photoresist PR defining the outer shape of the portion a can be seen.

In fig. 21 (b), a symbol M1e is defined as a position when the edge of the mask M1 is projected onto the photoresist PR, and a symbol pse is defined as a position of an edge defining an opening of the photoresist PR. At this time, the mask M1 was designed so that the difference between M1e and the pri (Δ M1A, Δ M1B) at each end of the mask M was greater than zero. In the present invention, by using the photoresist PR in addition to the mask M1, the outline of the region a can be defined more clearly than when only the mask M1 is used. Thus, according to the invention, for p⁺The portion (a)303 can be formed in a shape having a definite shape up to the outer edge thereof.

Next, n-type ions such as phosphorus (P) ions are locally implanted near the outer surface 302b of the i-type a-Si film 302 and at P-type by passing through a mask M2⁺Between the sites (A)303 and not with p⁺Position where the portions (a)303 overlap [ sixth step: FIG. 22 (a)]Thereby forming n⁺Site (B)304[ sixth step: FIG. 22 (c)]。

At this time, as shown in fig. 22 (B), a mask M2 is used which has an opening shape such that, when the region B in which ions are implanted through the opening of the mask is viewed in plan, a region of the photoresist PR defining the outer shape of the region B can be seen.

In fig. 22 (b), a symbol M2e is defined as a position when the edge of the mask M2 is projected onto the photoresist PR, and a symbol pse is defined as a position of an edge defining an opening of the photoresist PR. At this time, the mask M2 was designed so that the difference between M2e and the pri (Δ M2A, Δ M2B) at each end of the mask M was greater than zero. In the present invention, by using the photoresist PR in addition to the mask M2, the outline of the region B can be defined more clearly than when only the mask M2 is used. Thus, according to the invention, for n⁺The portion (B)304 can be formed in a shape having a definite shape up to the outer edge thereof.

Accordingly, the HBC crystal solar cell 300G is formed ((c) of fig. 22)]Of the same conductivity type as the first conductivity type of the substrate (e.g., n)⁺Type) region (a)303 and a region (B)304 having a conductivity type different from the first conductivity type are arranged so as to be separated from each other so that the region is present inside the i-type a-Si layer (β)302 and a part of the region is exposed on the outer surface side of the a-Si layer (β) 302. At this stage, a photoresist PR is present on a portion (C) of the i-type a-Si layer (β)302 where a partition of the portion (a) and the portion (B) is formed.

The conductive member BM is formed by a sputtering method under predetermined conditions [ eighth step: fig. 23 (a) ]. Accordingly, the conductive member BM formed in the portion a or the portion B is disconnected from the conductive member BM formed in the photoresist PR.

Next, after the conductive member BM is formed, the antireflection layer 314 is formed. Accordingly, as shown in fig. 23 (a), the HBC-type crystal solar cell 300H (300) of the third embodiment has a structure in which the n-type amorphous Si layer is removed from the HBC-type crystal solar cell 200H (200) of the second embodiment, that is, the anti-reflection layer 314 is formed on the one surface 301a side of the substrate 301 so as to cover the i-type amorphous Si layer (α) 312.

Finally, the photoresist PR is peeled off from the outer surface of the a-Si layer 302 by irradiating, for example, UV light [ ninth process: fig. 23 (b) ]. At this time, the conductive member BM on the photoresist PR is also removed together. Accordingly, the outer surface of the a-Si layer 302 remains only in the portion formed in the portion a or the portion B in the conductive member BM. Therefore, the conductive member BM along the site a or the site B is formed and can be used as an electrode. This step is a process called "peeling".

By sequentially including the above steps, the HBC type crystal solar cell 300I (300) having the structure shown in fig. 19 can be produced.

In the HBC type crystal solar cell 300H (300) of the third embodiment as well, as in the first embodiment, as shown in fig. 20 (b), the i-type a-Si film (β)302 is originally formed as a single film in the thickness direction and in the in-plane direction. Therefore, the third step and the fourth step are performed even after the passageThe step of forming p in the vicinity of the outer surface 302b of the i-type a-Si film 302⁺Sites (A)303 and n⁺In the case of the portion (B)304, the portion (C) as the spacer, that is, the region where no ion is implanted, also exists as a single film in the thickness direction.

Further, the i-type a-Si film 302 as a single film is formed so as not to reach the other surface 301b of the substrate⁺Sites (A)303 and n⁺The region (B)304 is such that the i-type a-Si film 302 present in contact with the other surface 301B of the substrate is present as a single film continuous in the in-plane direction of the substrate.

In this manner, in the HBC type crystal solar cell 300I (300) of the present embodiment (fig. 19), the I-type a-Si layer 302 is also present in addition to p⁺Sites (A)303 and n⁺The region other than the region (B)304 exists as a "single film" (here, the "single film" means that no interface exists inside the i-type a-Si layer 302), and thus the i-type a-Si film 302 maintains the function as a passivation film.

[ industrial applicability ]

The invention can be widely applied to HBC type crystal solar cells. Such an HBC type crystal solar cell is preferably used as a type of solar cell which requires weight reduction in operating conditions in addition to high power generation efficiency per unit area, for example.

Claims

1. A method for manufacturing a heterojunction back-contact HBC type crystal solar cell, wherein,

a substrate composed of crystalline silicon of a first conductivity type is used, and includes, in order:

a step of forming an i-type amorphous Si layer α and an i-type amorphous Si layer β separately or simultaneously, the i-type amorphous Si layer α covering one surface of the substrate on which light is incident, and the i-type amorphous Si layer β covering the other surface located on the opposite side of the one surface;

forming a photoresist so as to cover a region, in which an impurity is not introduced in a subsequent step, of an outer surface of the amorphous Si layer β;

forming a site a having the same conductivity type as the first conductivity type and a site B having a different conductivity type from the first conductivity type at positions separated from each other by the photoresist by an ion implantation method using a mask so that the sites a and B are internally present in the amorphous Si layer β and a part of the sites B is exposed on the outer surface side of the amorphous Si layer β;

annealing the ion-implanted amorphous Si layer β;

forming a conductive member so as to cover the portion a, the portion B and the photoresist on the outer surface side of the amorphous Si layer β; and

and removing the photoresist covered with the conductive member.

2. The HBC type crystal solar cell manufacturing method according to claim 1,

a mask having an opening shape such that a portion of the photoresist defining the outline of a portion A or a portion B into which ions are implanted can be seen when the portion A or the portion B is viewed in plan.

3. The method for manufacturing an HBC type crystal solar cell according to claim 1 or 2, wherein,

the method comprises the following steps in sequence before the step of forming the photoresist: forming an n-type amorphous Si layer so as to cover the i-type amorphous Si layer α; and forming a SiN layer so as to cover the n-type amorphous Si layer.

4. The method for manufacturing an HBC type crystal solar cell according to claim 1 or 2, wherein,

a step of forming an n-type amorphous Si layer so as to cover the i-type amorphous Si layer alpha, prior to the step of forming the photoresist,

the method further includes a step of forming a SiN layer so as to cover the n-type amorphous Si layer after the step of forming the conductive member.

5. The method for manufacturing an HBC type crystal solar cell according to claim 1 or 2, wherein,

the method further includes a step of forming a SiN layer so as to cover the i-type amorphous Si layer α after the step of forming the conductive member.