JPH1131827A - Solar cell and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell and its manufacturing method, wherein mass- production is easily available and surely, even if a large output solar cell is constituted with multiple solar cell elements. SOLUTION: On a photodetecting surface side of a semiconductor substrate 24, wherein a semiconductor layer constituting a plurality of solar cell elements 16 is formed, a light-transmitting type carrier substrate 23 is jointed, and from the rear surface side opposite to the photodetecting surface side of the semiconductor substrate 24, recessed parts 26 are formed among adjoining solar cell elements. A separation insulating layer 18 where a porous layer is oxidized is formed on the inside wall of the recessed part 26. A photodetecting surface side electrode 20 or an end part of its interconnection 21 of each solar cell element 16 is formed on the recessed part in an extending manner, while a rear surface side electrode 29 or the end part of its interconnection 30 is extendedly formed on the recessed part 26. At the recessed part 26, the photodetecting surface side electrode 20 of the other solar cell element 16 or its interconnection and the rear surface side electrode 25 or its interconnection are mutually connected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell, particularly to a solar cell in which a plurality of solar cells are arranged on a common semiconductor substrate, and a method of manufacturing the same.

[0002]

2. Description of the Related Art When a solar cell is constituted by a plurality of solar cell elements, a large output solar cell is obtained by connecting each light receiving surface side electrode and the back surface side electrode to the other back surface side electrode and the light receiving surface side electrode, respectively. Is performed. As described above, the connection between the light receiving surface side electrode and the rear surface side electrode is generally made directly by, for example, a conductive wire. in this case,
For example, a conductive wire is bonded to a light-receiving surface electrode of a solar cell, then a light-transmitting substrate is bonded thereon, and a conductive wire derived from the light-transmitting substrate is bonded to a back-surface electrode. Work is done. Since such an operation is extremely complicated, a structure has been proposed in which a plurality of element layers are connected on the light receiving surface side. This is, for example, H.
Takato et al., Japn. J. Appl. Phys. Vol. 33 (1994) pp. L139
As described in Section 6, SOI (Silicon on Insul
ator) A solar cell element was formed on a substrate, a light receiving surface side electrode terminal and a back surface side electrode terminal were formed on one side, and these were connected by an Al thin film.

[0003] An amorphous Si solar cell can be manufactured by using a laser patterning method.
For example, Katsunobu Sayama et al., Proceedings of the 3rd "High Efficiency Solar Cell" Workshop, Toyama (1992), Organized by IEEJ Semiconductor Power Conversion Technical Committee, p80 By patterning, TCO (transparent conductive oxide film) on glass substrate, amorphous S
An element can be formed while forming and cutting the i-active layer and the metal thin film, respectively.

[0004]

SUMMARY OF THE INVENTION In the present invention, even when a large-output solar cell is constituted by a large number of solar cell elements, it can be easily and reliably mass-produced. A solar cell and a method for manufacturing the same are provided.

[0005]

In a solar cell according to the present invention, a light-transmitting carrier substrate is joined to a light-receiving surface side of a semiconductor substrate on which semiconductor layers constituting a plurality of solar cell elements are formed. A concave portion is formed between the adjacent solar cell elements from the back surface side opposite to the light receiving surface side of the substrate, and a separation insulating layer formed by oxidizing a porous layer is formed on the inner wall of the concave portion. And, for each solar cell element,
An end of the light-receiving surface-side electrode or its wiring, for example, a metal wire, is formed to extend over the concave portion, and an end of the back-side electrode or its wiring is formed to extend to the concave portion. Further, the light receiving surface side electrode of another solar cell element or its wiring and the back surface side electrode or its wiring are connected to each other.

In the method of manufacturing a solar cell according to the present invention, a step of forming a porous layer composed of two or more layers having different porosity by changing the surface of the semiconductor substrate, A step of forming a common semiconductor layer constituting a plurality of solar cell elements on the surface, and selectively forming a porous portion at least at a depth crossing the semiconductor film in a pattern crossing between formation portions of the solar cell elements. A step of oxidizing the porous portion to form an isolation insulating layer; and, ohmic contacting each light receiving surface side electrode of each solar cell element on the semiconductor layer, forming an end of these electrodes or their wiring. ,
A step of forming and extending on the isolation insulating layer, a step of bonding the light-transmitting supporting substrate to the light-receiving surface side of the semiconductor substrate, and a step of peeling the semiconductor layer in the porous layer together with the light-transmitting supporting substrate. A separation step of forming a semiconductor substrate on which a plurality of solar cell elements are arranged, and formation of an extension of an end portion of a light-receiving-surface-side electrode of a solar cell element or an end of its wiring in a portion where a separation insulating layer is formed from the separation surface side An etching step of forming a concave portion reaching the extending portion at the position to expose an end of the light receiving surface side electrode or the wiring extending on the isolation insulating layer; A step of extending the ends of the wiring, for example, metal wires, and connecting them to the light receiving surface side electrode of another solar cell or the end of the wiring in the concave portion to form a solar cell.

The above-described solar cell according to the present invention has a configuration in which a plurality of solar cell elements are provided and connected in series, so that a high-output solar cell can be formed. According to the configuration of the present invention, the plurality of solar cell elements are configured as a common semiconductor substrate, and their serial connection is performed, that is, the light-receiving surface-side electrode of each solar cell element and the back-side electrode of another solar cell element. Is formed so as to penetrate the semiconductor substrate, so that its structure is simplified.

Further, according to the structure of the present invention, as described above, a plurality of solar cell elements are formed as a common semiconductor substrate, and the solar cell elements are connected in series with each other, that is, the light-receiving-surface-side electrode of each solar cell element and the other. The connection with the back side electrode of the solar cell element can be mass-produced since it is formed so as to penetrate the semiconductor substrate.

In the manufacturing method of the present invention, a porous layer is formed on a semiconductor substrate to form a separation (peeling) layer, and a porous portion is formed. Selectively oxidize the part to form an isolation insulating layer, form a recess in this isolation insulating layer, and communicate with the light receiving surface side electrode and the back surface side electrode to be connected to it, thereby manufacturing Can be formed in mass production and reliably.

In the present invention, the semiconductor substrate on which the solar cell element is formed is separated from the semiconductor substrate.
That is, since the thin film semiconductor is formed into a sufficiently thin thin film comprising a part of the thickness of the semiconductor substrate, an efficient solar cell can be formed.

Further, the semiconductor substrate used in the method of the present invention comprises:
Although a porous layer is formed on the surface layer, since this is a substantially thin layer, the semiconductor substrate left after the separation can be used again, for example, for manufacturing a similar solar cell. For a substrate whose thickness becomes insufficient due to repeated use, a semiconductor layer can be further repeatedly used by epitaxially growing a semiconductor layer on the substrate, so that the semiconductor substrate can be used without waste. It is possible to use resources efficiently and reduce costs.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a solar cell according to the present invention, as described above, a light-transmitting carrier substrate is bonded to a light-receiving surface side of a semiconductor substrate on which semiconductor layers constituting a plurality of solar cell elements are formed. A concave portion is formed between adjacent solar cell elements from the back surface side opposite to the light receiving surface side of the semiconductor substrate, and a separation insulating layer formed by oxidizing a porous layer is formed on an inner wall of the concave portion. Consisting of And, for each solar cell element,
The end of the light receiving surface side electrode or its wiring is formed to extend over the concave portion, and the end of the back surface electrode or its wiring is formed to extend to the concave portion.
The light receiving surface side electrode of another solar cell element or its wiring and the back surface electrode or its wiring are connected to each other.

In the method of manufacturing a solar cell according to the present invention, a step of forming a porous layer composed of two or more layers having different porosity by changing the surface of the semiconductor substrate, A step of forming a common semiconductor layer constituting a plurality of solar cell elements on the surface, and selectively forming a porous portion at least at a depth crossing the semiconductor film in a pattern crossing between formation portions of the solar cell elements. A step of oxidizing the porous portion to form an isolation insulating layer; and, ohmic contacting each light receiving surface side electrode of each solar cell element on the semiconductor layer, forming an end of these electrodes or their wiring. ,
A step of forming and extending on the isolation insulating layer, a step of bonding the light-transmitting supporting substrate to the light-receiving surface side of the semiconductor substrate, and a step of peeling the semiconductor layer in the porous layer together with the light-transmitting supporting substrate. A separation step of forming a semiconductor substrate on which a plurality of solar cell elements are arranged, and a light-receiving surface-side electrode or a wiring thereof extending on the separation insulating layer by forming a recess in the formation portion of the separation insulating layer from the separation surface side An etching step for exposing the end of the solar cell, the concave portion, the back surface side electrode of each solar cell or the end of the wiring thereof is extended, these are, in the concave portion, the light receiving surface side electrode of another solar cell or its electrode. Connecting to the end of the wiring to obtain a solar cell.

That is, in the present invention, a semiconductor substrate is prepared, and a porous layer is formed on the semiconductor substrate. The porous layer is formed by changing the surface of the semiconductor substrate by, for example, anodizing to form a porous layer. (Porosity) 2
A porous layer composed of at least two layers is formed. Then, a semiconductor film for forming a plurality of solar cell elements is formed by forming a semiconductor film on the surface of the porous layer, for example, as a single crystal film or a polycrystalline film by epitaxial growth.

In the step of forming the porous layer, at least two layers having different porosity, a surface layer having a low porosity facing the surface thereof and a high porosity layer having a high porosity below the surface layer, are formed. A porous layer having a porous layer is formed. With this configuration, a layer weakened by the strain generated at or near the interface between the two porosity layers is formed, or a layer in which separation (peeling) easily occurs due to the fragility of the porosity layer itself is formed.

In the step of forming a porous layer, an intermediate porosity layer having an intermediate porosity is formed between the surface layer and the high porosity layer described above. By buffering the influence of the strain on the surface of the surface layer on which the semiconductor film is formed, it is possible to improve the film quality of the semiconductor film formed on the surface layer. For example, epitaxial growth of the semiconductor film is performed thereon. Make sure that it can be done easily and reliably.

The formation of such a porous layer can be carried out by anodization. The surface layer, high porosity layer, and intermediate porosity layer having different porosity can be formed by changing the current density during anodization. That is, at least a step of anodizing the surface of the semiconductor substrate with a low current density and a step of subsequently anodizing with a higher current density are employed. Alternatively, a step of anodizing the surface of the semiconductor substrate at a low current density, a step of further anodizing at an intermediate low current density slightly higher than the low current density, and a step of further anodizing at a higher current density are employed. .

In the anodization, the anodization at a high current density can be performed intermittently at a high current density.

Further, in the anodization at an intermediate low current density in the anodization for forming the porous layer, the current density can be increased gradually or stepwise.

The anodization can be performed in an electrolytic solution containing hydrogen fluoride and ethanol, or in an electrolytic solution containing hydrogen fluoride and methanol.

Further, in changing the current density in the anodizing step, the composition of the electrolytic solution can also be changed.

After the formation of the porous layer, it is preferable to heat in a hydrogen gas atmosphere at normal pressure or reduced pressure or in a vacuum, or in a Group 8 element gas such as He, Ne, Ar, or K. . It is preferable that the porous layer is thermally oxidized before the heating step.

The shape of the semiconductor substrate can take various configurations. For example, it can be formed into various shapes such as a wafer shape such as a disk shape, or a cylindrical ingot obtained by pulling a single crystal, and a peripheral surface thereof serving as a substrate surface.

The semiconductor substrate may include, for example, a p-type impurity such as boron B doped with an n-type or p-type impurity,
It is doped to about 10 ¹⁹ atoms / cm ^{3 and} has a resistance of 0.
It is desirable to use a Si substrate of about 01 to 0.02 Ωcm. Then, when the p ⁺ -type Si substrate is anodized, fine pores elongated in a direction substantially perpendicular to the surface of the substrate are formed, and the p ⁺ -type Si substrate becomes porous while maintaining the crystallinity. Thus, a desirable porous layer is formed.

A semiconductor film is formed on the porous layer while maintaining the crystallinity as described above. In this case, since the porous layer maintains the crystallinity, the semiconductor film can be epitaxially grown. The semiconductor film is formed by MOCVD (metal organic chemical vapor deposition), CV
D (chemical vapor deposition), MBE (molecular beam epitaxy), sputtering, etc.
It can be formed as a polycrystalline or amorphous film,
Furthermore, for example, after being formed as an amorphous film, it can be polycrystal or single crystal by annealing.

As described above, the semiconductor film formed on the semiconductor substrate is peeled off from the semiconductor substrate. Prior to this peeling, the light-transmissive carrier substrate is bonded onto the semiconductor film. Then, the semiconductor film is separated (separated) from the porous layer together with the carrier substrate.

This carrier substrate can be constituted by a glass substrate, a resin substrate, a flexible sheet or the like.

The above-mentioned anodization for making the surface of the semiconductor substrate porous is performed by a known method, for example, the surface technology Vo by Ito et al.
l. 46, no. 5, pp. 8-13, 1995 [Anodic formation of porous Si]. That is, for example, it can be performed by a double cell method whose schematic configuration diagram is shown in FIG. This method comprises a two-cell electrolytic solution tank 1 having first and second tanks 1A and 1B.
Is used. Then, a semiconductor substrate 11 on which a porous layer is to be formed is arranged between the two tanks 1A and 1B, and a pair of platinum electrodes 3A to which a DC power supply 2 is connected is provided in both tanks 1A and 1B.
And 3B are arranged. First of electrolytic solution tank 1
In the second tanks 1A and 1B, an electrolytic solution 4 containing, for example, hydrogen fluoride HF and ethanol C ₂ H ₅ OH, or hydrogen fluoride HF and methanol CH
An electrolytic solution 4 containing ₃ OH is accommodated, arranged in the first and second tanks 1A and 1B so that both surfaces of the semiconductor substrate 11 are in contact with the electrolytic solution 4 and both electrodes 3
A and 3B are immersed in the electrolytic solution 4. And
A tank 1A on the front side of the semiconductor substrate 11 on which a porous layer is to be formed.
With the electrode 3A side immersed in the electrolytic solution 4 inside as the negative electrode side, the DC power supply 2 is connected and electricity is supplied between the electrodes 3A and 3B. Thus, the semiconductor substrate 11
Power is supplied with the side facing the anode and the electrode 3A facing the cathode, whereby the surface of the semiconductor substrate 11 facing the electrode 3A is eroded and made porous.

According to the two-tank cell method, it is not necessary to form an ohmic electrode on the semiconductor substrate, and the introduction of impurities from the ohmic electrode into the semiconductor substrate is avoided.

The anodization is not limited to the above-described two-cell method, but may be, for example, a single-cell method schematically shown in FIG. In this example, a single electrolytic solution tank 1 is provided, and a semiconductor substrate 11 for performing anodization is placed in an O.
They are arranged in a liquid-tight abutment via a ring 5. The electrolytic solution 4 is accommodated in the electrolytic solution tank 1 so that the electrolytic solution 4 comes into contact with the surface of the semiconductor substrate 11 disposed at the bottom, on which the anode is formed. One electrode 3A made of, for example, a Pt electrode plate is immersed in the electrolytic solution 4 in the tank 1. On the back surface of the semiconductor substrate 11, the other electrode 3B made of, for example, a carbon electrode is placed in surface contact so as to face as much as possible over the entire surface on which anodization is performed. And
With the electrode 3A side immersed in the electrolytic solution 4 as the negative electrode side,
DC power supply 2 is inserted between both electrodes 3A and 3B, and electricity is supplied. Also in this case, the surface of the semiconductor substrate 11 on the side facing the electrode 3A is anodized.

The selection of the conditions for the anodization changes the structure of the porous layer to be formed, thereby changing the crystallinity and releasability of the semiconductor film formed thereon.

Although the thickness of the entire porous layer is not particularly limited, it is 1 to 50 μm, preferably 3 to 15 μm, usually 8 μm.
It can be about as thick. It is preferable that the thickness of the entire porous layer be as small as possible so that the semiconductor substrate can be used as repeatedly as possible.

Further, prior to the formation of a semiconductor layer on the porous layer, for example, prior to the epitaxial growth, when annealing is performed in a hydrogen gas atmosphere, for example, the completeness of the natural oxide film formed on the surface of the porous layer is reduced. It is possible to remove as much as possible and remove oxygen atoms in the porous layer as much as possible, so that the surface of the porous layer becomes smooth, and for example, an epitaxial semiconductor film having good crystallinity can be formed. In addition, the pretreatment by another annealing in hydrogen can further weaken the strength of the interface between the high porosity layer and the intermediate porosity layer, thereby making it easier to separate the epitaxial semiconductor film from the substrate. it can. In this case, the hydrogen annealing is performed in a temperature range of, for example, about 950 ° C. to 1150 ° C.

If the porous layer is oxidized at a low temperature before hydrogen annealing, the inside of the porous layer is oxidized. Therefore, even if thermal annealing is performed in a hydrogen gas atmosphere, the porous layer has a large structure. No change occurs. That is, distortion from the peeling layer to the surface of the porous layer is not easily transmitted, and a high-quality crystalline epitaxial semiconductor film can be formed. In this case, the low-temperature oxidation is performed, for example, in a dry oxidation atmosphere at 40.degree.
It can be performed at 0 ° C. for about 1 hour.

The formation of the semiconductor film on the surface of the porous layer, for example, the epitaxial growth is carried out by, for example, CVD method, for example, by using
It can be performed at a temperature of from 00C to 1200C.

In both the annealing and the formation of the semiconductor film, the semiconductor substrate may be heated to a predetermined substrate temperature by a so-called susceptor heating method, or may be directly applied to the semiconductor substrate itself. It is possible to adopt an electric heating method or the like in which an electric current is applied to heat.

Next, an embodiment of the present invention will be described with reference to FIG. 3 and the following, but the present invention is not limited to this embodiment.

In this case, the single crystal S doped with boron B and having a specific resistance of, for example, 0.01 to 0.02 Ωcm
i, a wafer-like semiconductor substrate 11 is prepared (FIG. 3).
A), using the two-tank anodizing apparatus described in FIG. 1, HF (4
7-50% solution): C ₂ H ₅ OH (industrial ethanol (about 99.50% solution) = 1: 1 electrolyte is injected solution (volume ratio), the electrolyte solution of the electrolyte solution cells 1A and 1B An electric current was passed between the Pt electrodes 3A and 3B immersed and disposed by the DC power supply 2.

First, a current was applied for 8 minutes at a low current of 1 mA / cm ² to form a surface layer 12S having a porosity of about 16% (FIG. 3B). Once the current is stopped, the current density is 7m
A middle porosity layer 12M having a higher porosity than that of the surface layer S and having a porosity of about 26% by applying a current of 8 A / cm ² for 8 minutes.
Was formed (FIG. 3C). Furthermore, after stopping the energization once,
A current of 200 mA / cm ² was applied for 4 seconds. By doing so, a porosity of about 60% having a higher porosity than the surface layer 12S and the intermediate porosity layer 12M is provided in the intermediate porosity layer 12M.
Was formed (FIG. 3D). Thus, the porous layer 12 in which the surface layer 12S, the intermediate porosity layer 12M, and the high porosity layer 12H are laminated is formed.

After the formation of the porous layer 12, annealing was performed at 1100 ° C. in an H ₂ atmosphere in a normal pressure Si epitaxial growth apparatus. This annealing is performed from room temperature to 1100.
Temperature for about 20 minutes and then for about 40 minutes
It was kept at 00 ° C. By this annealing, the surface layer 12S of the porous layer 12 became smooth, and the strength near the interface between the intermediate porosity layer 12M inside the porous layer 12 and the high porosity layer 12H became weaker.

Thereafter, the temperature was reduced to 1030 ° C., and an annealed normal-pressure Si epitaxial growth apparatus was subjected to epitaxial growth using SiH ₄ gas and B ₂ H ₆ gas for 3 minutes, and boron B was reduced to 1 × 10 ¹⁹ atoms. The first semiconductor layer 131 is formed by p ⁺ Si doped at / cm ³ (FIG. 3E), and then the Si epitaxial growth is performed at 1030 ° C. for 30 minutes while changing the flow rate of B ₂ H ₆ gas. , Boron B doped at 1 × 10 ¹⁶ atoms / cm ³ ,
^- a second semiconductor layer 132 of Si is formed (FIG. 3
F) Further, a PH ₃ gas is supplied in place of the B ₂ H ₆ gas, and epitaxial growth is performed for 4 minutes, so that phosphorus P has a high concentration of 1 × 10 ¹⁹ atoms / cm ³ on the p ⁻ semiconductor layer 132. A third semiconductor layer 133 made of doped n ⁺ Si is formed, and finally a plurality of solar cell elements having a p ⁺ -p ^-- n ⁺ structure including the first to third semiconductor layers 131 to 133 are formed. A semiconductor film 13 which can be formed as shown in FIG.
G).

Next, on the semiconductor film 13, a portion where each solar cell element is to be finally formed is covered, and a portion corresponding to a portion between the solar cell elements is exposed to the outside. , By applying a photoresist, pattern exposure, and development (FIG. 4A).

Using the mask layer 14 as a mask for anodizing, the anodizing apparatus shown in FIG. 1 and the electrolytic solution 4 were used to conduct electricity at a current density of 7 mA / cm ² for 18 minutes, for example. By doing so, a porous portion 15 is formed where the mask layer 14 is not formed and which is exposed to the outside, that is, between the portions where the solar cells are formed. In other words, the solar cell elements 16 each composed of a part of the semiconductor film 13 are formed by the porous portions 15 (FIG. 4B).

Thereafter, the mask layer 14 is removed, and a thermal oxidation treatment is performed in an atmosphere containing oxygen, for example, at 1000 ° C. for 30 minutes. In this case, the surface of the semiconductor film is oxidized to form the SiO ₂ oxide film 17 and, at the same time, the porous portion is easily oxidized, so that the porous portion 15 is also selectively oxidized. Here, a separation insulating layer 18 for electrically separating the solar cell elements 16 from each other is formed (FIG. 4C). The oxide film 17 thus formed can minimize generation of carriers at the interface and recombination.

Next, the oxide film 17 is subjected to pattern etching by photolithography, and a contact window 17w is formed in the formation portion of the light receiving surface side electrode of each solar cell element.
Is drilled (FIG. 4D).

Then, an ohmic contact is made to the semiconductor film 13 through the inside of the contact window 17w to form an electrode or a metal layer 19 for forming an electrode and a wiring (FIG. 5A). This metal layer 19 is, for example, 30n
m Ti film, 50 nm thick Pd, 100 nm thick A
g is sequentially deposited, and 8 μm of Ag plating is formed thereon. Then at 400 ° C for 20 ~
Annealing was performed for 30 minutes.

The metal layer 19 is pattern-etched by photolithography to form the light-receiving-surface-side electrode 20 for each solar cell element 16 (FIG. 5B). One end of each light-receiving surface electrode 20 of each solar cell element 16 is connected to an isolation insulating layer 18 formed adjacent to these solar cell elements 16.
It is formed over the top. The light-receiving-surface-side electrode 20 is formed on the light-receiving surface of each solar cell element 16 but is formed on a part of the light-receiving surface, so that a large area of the light-receiving surface is not blocked by the electrode 20. Placed in

Further, in this example, a metal wire 21 as a wiring for improving conductivity is bonded to each light receiving surface side electrode 20 by soldering (FIG. 5C). In this case, one end of the metal wire 21 is formed so as to extend on the isolation insulating layer 18, and soldering can be avoided in this extension.

Then, a rigid or flexible light-transmitting supporting substrate 23 made of glass, transparent resin, or the like is joined to the light-receiving surface via a light-transmitting adhesive 22 (FIGS. 5D and 6A). And, together with this light transmissive carrier substrate,
The semiconductor layer 13 is separated from the semiconductor substrate 11. In this case, separation (peeling) is performed in the porous layer 12, particularly in the weakened, for example, the high porosity layer 12H or in the vicinity thereof. In other words, the adhesive strength of the adhesive 22 to the transparent substrate 23 is selected to be larger than the separation strength of the porous layer 12. Thus, a semiconductor substrate 24 constituting a plurality of solar cell elements in which the semiconductor film 13 is carried by the light-transmissive carrier substrate 23 is formed.

On the back surface of the semiconductor substrate 24, an etching resist, for example, a photoresist is applied over the entire surface, subjected to pattern exposure and development processing, and the central portion of the formation pattern of the isolation insulating layer 18 formed between the solar cell elements 16. Opening 2
A mask layer 25 on which 5w is formed is formed (FIG. 6B).

An etching solution for etching the SiO ₂ of the isolation insulating layer 18 is etched with hydrofluoric acid to form a recess 26 between the solar cell elements 16 through the opening 25 w not covered by the mask layer 25 (FIG. 6C). . The width of the opening 25w of the mask layer 25 is selected such that the width of the concave portion 26 formed by etching through the opening 25w is such that the isolation insulating layer 18 is left on the side surface. Also, this recess 26
Is formed at least below the light-receiving-surface-side electrode 20 or the extending end of the metal wire 21 so that it can face the bottom of the concave portion 26. Can be formed along the formation portion of the isolation insulating layer 18, that is, in a pattern crossing between the respective solar cell elements 16. Then, the mask layer 2
5 is removed (FIG. 6D).

On the back surface of the semiconductor substrate 24, a metal layer 27 made of, for example, Al is deposited on the entire surface including the inside of the concave portion 26 (FIG. 7A).

On this metal layer 27, a mask layer 28 for pattern etching of this metal layer 27 is formed. The mask layer 28 is formed by, for example, application of a photoresist, pattern exposure, and development. The pattern of the mask layer 28 is formed on the back side electrode pattern of each solar cell element 16. In this case, each one end is extended so that the end is connected to the concave portion 26 facing the light receiving surface side electrode 20 of another adjacent solar cell element 16 or the extended portion to the concave portion of the metal wire 21. (FIG. 7B).

The mask layer 28 is not formed, and the metal layer 27 exposed to the outside is removed by etching (FIG. 7C).
After that, the mask layer 28 is removed. This way,
A back surface side electrode 29 formed of a metal layer 27 according to the pattern of the mask layer 28 has one end extending into a predetermined concave portion 26, and a light receiving surface side electrode formed facing the concave portion 26. It is formed so as to be connected to, or electrically connected to, the end of the metal wire 20 or its wiring (FIG. 7D).

Then, a wiring such as a metal wire 30 for improving the conductivity is adhered to the back surface side electrode 29 by, for example, an Ag paste (FIG. 8A).

A protective substrate 32 or a protective sheet made of, for example, a resin substrate is abutted on the entire back surface of the semiconductor substrate 24 with an adhesive 31 and is adhered by pressure (FIGS. 8B and 8C).
In this manner, the plurality of solar cell elements 16 are separated by the isolation insulating layer 18, and in the concave portion 26, for example, the light receiving surface side electrode 20 and the back surface side electrode 29 of the adjacent solar cell element 16 or their wirings For example, a solar cell connected by a metal wire and connected in series with each other is configured. Therefore, as shown by the arrow in FIG. 8C, when the input light is irradiated from the light transmission supporting substrate 23 side, the photoelectric conversion is performed in the respective solar cell elements 16 connected in series with each other, and the large output is obtained. Can be taken out as

In the above configuration, the solar cell element 1
Needless to say, 6 can be arranged in-line, or can be arranged in a large number in a two-dimensional plane. Further, the present invention is not limited to the above-described embodiment, and may be configured such that the conductivity type of each part is the opposite conductivity type. Further, in the above-described example, the operation unit configuring the solar cell element is configured by the semiconductor films including the first to third semiconductor layers 131 to 133 that are sequentially formed. Can be formed, and an operating portion can be formed by doping such as ion implantation and diffusion of impurities into the structure, and various configurations and manufacturing methods can be adopted.

[0058]

The solar cell according to the present invention has a structure in which a plurality of solar cell elements are provided and connected in series, so that a high-output solar cell can be formed. In particular, according to the configuration of the present invention, these solar cell elements are configured as a common semiconductor substrate,
The mutual series connection, that is, the connection between the light-receiving surface side electrode of each solar cell element and the back side electrode of the other solar cell element,
Since the semiconductor substrate is formed so as to penetrate the semiconductor substrate, its structure is simplified.

Further, according to the structure of the present invention, as described above, a plurality of solar cell elements are formed as a common semiconductor substrate, and the solar cell elements are connected in series with each other, that is, the light-receiving-surface-side electrode of each solar cell element and the other. The connection with the back side electrode of the solar cell element can be mass-produced since it is formed so as to penetrate the semiconductor substrate.

In the manufacturing method of the present invention, a porous layer is formed on a semiconductor substrate to form a separation (peeling) layer, and a porous portion is formed. Selectively oxidize the portion to form an isolation insulating layer, form a recess in this isolation insulating layer, and communicate with the light-receiving-side electrode and the back-side electrode to be connected to this through the recess. Can be formed in mass production and reliably.

According to the present invention, the semiconductor substrate on which the solar cell element is formed is formed as a thin film semiconductor having a sufficiently small thickness which is a part of the thickness of the semiconductor substrate separated from the semiconductor substrate. It is possible to constitute a good solar cell.

The semiconductor substrate used in the method of the present invention is
Although a porous layer is formed on the surface layer, since this is a substantially thin layer, the semiconductor substrate left after the separation can be used again, for example, for manufacturing a similar solar cell. For a substrate whose thickness becomes insufficient due to repeated use, a semiconductor layer can be further repeatedly used by epitaxially growing a semiconductor layer on the substrate, so that the semiconductor substrate can be used without waste. It is possible to use resources efficiently and reduce costs.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of an anodizing apparatus for performing a method of the present invention.

FIG. 2 is a cross-sectional view of another example of the anodizing apparatus for performing the method of the present invention.

FIG. 3 is a process diagram (part 1) of one embodiment of the method of the present invention. 3A to 3G are cross-sectional views of the respective steps.

FIG. 4 is a process chart (part 2) of one embodiment of the method of the present invention. A to D are cross-sectional views of the respective steps.

FIG. 5 is a process diagram (part 3) of one embodiment of the method of the present invention. A to D are cross-sectional views of the respective steps.

FIG. 6 is a process chart (part 4) of one embodiment of the method of the present invention. A to D are cross-sectional views of the respective steps.

FIG. 7 is a process diagram (part 5) of one embodiment of the method of the present invention. A to D are cross-sectional views of the respective steps.

FIG. 8 is a process chart (part 6) of one embodiment of the method of the present invention. A to C are cross-sectional views of each step.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrolyte tank, 1A ... 1st tank, 1B ... 2nd tank, 2
... Power supply, 3A, 3B ... electrode, 4 ... electrolyte solution, 5 ... O-ring, 11 ... semiconductor substrate, 12 ... porous layer, 12S ... surface layer, 12M ... intermediate porosity layer, 12H ... high porosity layer, 13
... Semiconductor film, 131 ... First semiconductor film, 132 ... Second semiconductor film, 133 ... Third semiconductor film, 14 ... Mask layer,
15 ... porous part, 16 ... solar cell element, 17 ... oxide film,
18 ... isolation insulating layer, 19 ... metal layer, 20 ... light receiving surface side electrode, 21 ... metal wire, 22 ... adhesive, 23 ... light transmitting carrier substrate, 24 ... semiconductor substrate, 25 ... mask layer, 26 ...
Recesses, 27: metal layer, 28: mask layer, 29: back side electrode, 30: metal wire, 31: adhesive, 32: protective substrate

Claims (4)

[Claims] 1. A light-transmissive carrier substrate is bonded to a light-receiving surface side of a semiconductor substrate on which semiconductor layers constituting a plurality of solar cell elements are formed, and the semiconductor substrate has an opposite side to the light-receiving surface side. A concave portion is formed between adjacent solar cell elements from the back side of the substrate, and a separation insulating layer formed by oxidizing a porous layer is formed on an inner wall of the concave portion. A light-receiving surface electrode of each of the solar cell elements Alternatively, the end of the wiring is formed to extend on the concave portion, and the back electrode of each of the solar cell elements or the end of the wiring is formed to extend to the concave portion. A solar cell, wherein the light-receiving surface-side electrode or its wiring and the back-side electrode or its wiring of another solar cell element are connected to each other. 2. The solar cell according to claim 1, wherein said semiconductor substrate is a silicon substrate. 3. A step of forming a porous layer composed of two or more layers having different porosity by changing the surface of the semiconductor substrate, and forming a plurality of solar cell elements on the surface of the porous layer. Forming a semiconductor layer, and selectively forming a porous portion at least at a depth across the semiconductor film in a pattern crossing between the formation portions of the solar cell element; and oxidizing the porous portion. And forming an isolation insulating layer, on the semiconductor layer, ohmic contact of each light-receiving surface electrode of each of the solar cell elements, the end of the electrode or its wiring, on the isolation insulating layer Extending and forming; bonding the light-transmissive carrier substrate to the light-receiving surface side of the semiconductor substrate; and peeling the semiconductor layer in the porous layer together with the light-transmissive carrier substrate. The multiple solar cell elements are arranged A separating step of forming the arrayed semiconductor substrates, and a forming step of the light-receiving-surface-side electrode of the solar cell element or an extending portion of an end of the wiring of the solar cell element at the formation position of the separation insulating layer from the separation surface side. An etching step of forming a recess reaching the extension and exposing an end of the light-receiving surface-side electrode or its wiring extending on the isolation insulating layer; and in the recess, a back-side electrode of each of the solar cells or Extending the ends of the wiring, and connecting them to the light receiving surface side electrode of another solar cell or the end of the wiring in the concave portion. Production method. 4. The method according to claim 3, wherein the semiconductor substrate is a silicon substrate.