JP2005268682A - Semiconductor base material and manufacturing method of solar battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor base material and a manufacturing method of a solar battery capable of decreasing bubbles generated from a metallic paste when adhering a separation member to a semiconductor film with a metallic paste, the generation of non-adhered portions by improving an atmosphere at the time of sintering and a deterioration in strength of adhesion. <P>SOLUTION: In the manufacturing method of the semiconductor base material having a process for forming the semiconductor film 3 on a substrate 5 through a separation layer 4 and affixing a separation member 1 onto the semiconductor film 3 through an adhesive layer 6, and a process for separating the semiconductor film 3 and the base material 5 in a separation layer 4 by applying a force to a separation member 1, the process for affixing the separation member 1 characterized by comprising a process for coating the metallic paste functioning as at least the adhesive layer 6, a process for closely contacting the separation member 1 with a structure capable of discharging an exhaust from the surface of the adhesive layer and absorbing the exhaust into the surface of the adhesive layer, and a sintering process for hardening the metallic paste at ≥500°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a semiconductor substrate and a method for manufacturing a solar cell using a separation layer.

  As a method of manufacturing a semiconductor thin film for use in a thin film semiconductor device such as a semiconductor integrated circuit, a light emitting element, or a solar cell, a porous layer is formed on a semiconductor substrate, and a semiconductor thin film is formed on the porous layer. A method for manufacturing a semiconductor substrate by separating the semiconductor thin film from the semiconductor substrate is known.

  For example, in Patent Document 1, a porous layer is formed on an Si substrate by anodization, a semiconductor thin film is epitaxially grown on the porous substrate, a separation member is bonded to the semiconductor thin film, and the semiconductor thin film is combined with the separation member. Is peeled off from the Si substrate.

  Further, in Patent Document 2, a semiconductor layer is formed on a semiconductor substrate having a porous layer, and the substrate in which the semiconductor layer is bonded to a separation member is separated in the porous layer to obtain a semiconductor substrate. As a method for adhering the separating member and the semiconductor layer, there has been proposed a method in which a conductive metal paste is inserted between and closely adhered to each other, and is baked and fixed at a low temperature.

JP-A-10-79524 JP-A-10-189924

  However, in the above method, the conductive metal paste had a function as an adhesive and a collecting electrode for bonding the separating member and the semiconductor layer when obtaining the semiconductor substrate. In the bonding process for obtaining, the bubbles generated at the time of applying the metal paste or curing the metal paste remained in the adhesive layer only from the end of the adhesive layer, and an unbonded portion was generated. For this reason, when the semiconductor thin film is separated, the unbonded portion cannot be separated and remains on the base, and the thin film may be damaged, leading to a decrease in yield when a large-area semiconductor substrate is formed. .

  In addition, when using a metal paste that is fired at a high temperature, fresh air is required to burn the vehicle contained in the metal paste. The air was sandwiched between the separation members and the air was supplied only from the end of the metal paste, resulting in insufficient firing, leading to a decrease in adhesive strength and an increase in contact resistance with respect to electrical conduction.

  The above problem becomes more serious as the substrate becomes larger, which has been an obstacle to large area transfer.

In the case of manufacturing a solar cell, in the above method, in addition to the P ⁻ type Si layer and the n ⁺ type Si layer on the porous layer, the back surface field P widely used for crystalline solar cells is used. ^{Since the +} -type film is also formed, the film forming process becomes complicated, which hinders the improvement of mass productivity.

The present invention is a semiconductor that can reduce generation of bubbles generated from a metal paste when a separation member is bonded to a semiconductor film with a metal paste, generation of an unbonded portion by improving the atmosphere during firing, and a decrease in bonding strength. The present invention provides a method for manufacturing a base material and a solar cell, and further a method for manufacturing a solar cell that can simplify the film forming process by omitting the formation of a P ⁺ type for a back surface field.

In order to solve the above-described problems, the present invention includes a step of forming a semiconductor film on a substrate via a separation layer and bonding a separation member on the semiconductor film via an adhesive layer, and the separation member. In the method for manufacturing a semiconductor substrate, the method includes a step of applying force to separate the semiconductor film and the substrate in the separation layer.
The step of attaching the separation member to the semiconductor film via the adhesive layer includes at least a step of applying a metal paste that functions as the adhesive layer, and exhaust from the surface of the adhesive layer and intake of air to the surface of the adhesive layer. And a baking step of curing the metal paste at 500 ° C. or higher.

The method for producing a semiconductor substrate of the present invention as a further preferred feature,
"The metal paste contains an organic vehicle",
"The metal paste contains an organic solvent and is in a paste form",
"The metal paste contains Al",
"The separation member has heat resistance at the firing temperature of the metal paste",
"The separation member is a mesh substrate woven with a fibrous material",
"The separation member is a substrate in which a ventilation path from an end surface to the surface of the adhesive layer is formed",
“The separation member is a porous substrate having minute through holes”,
“The through hole has a diameter of 100 μm or less”,
"The separation layer comprises a porous layer formed by anodization",
including.

In order to solve the above-mentioned problems, the present invention includes a step of forming a semiconductor film on a substrate via a separation layer, and bonding a separation member on the semiconductor film via an adhesive layer, and the separation In the method for manufacturing a solar cell, the method includes a step of separating the semiconductor film and the substrate in the separation layer by applying a force to a member.
The step of attaching the separation member to the semiconductor film via the adhesive layer includes at least a step of applying a metal paste that functions as the adhesive layer and an electrode, and exhausting gas from the surface of the adhesive layer and to the surface of the adhesive layer. And a baking step of curing the metal paste at a temperature of 500 ° C. or higher.

The manufacturing method of the solar cell of the present invention as a further preferable feature,
“In the firing step, the metal paste forms a P ⁺ type in the semiconductor film”, and “the metal paste contains Al”,
"In the firing step, the metal paste forms an n ⁺ type in the semiconductor film",
"The metal paste contains an organic vehicle",
"The metal paste contains an organic solvent and is in a paste form",
"The separation member has heat resistance at the firing temperature of the metal paste",
"The separation member is a mesh substrate woven with a fibrous material",
"The separation member is a substrate in which a ventilation path from an end surface to the surface of the adhesive layer is formed",
“The separation member is a porous substrate having minute through holes”,
“The through hole has a diameter of 100 μm or less”,
"The separation layer comprises a porous layer formed by anodization",
including.

  According to the manufacturing method of the present invention, since the separation member can be exhausted from the surface of the adhesive layer and sucked into the surface of the adhesive layer, bubbles generated on the surface of the adhesive layer of the metal paste at the time of bonding and at the time of firing The generated bubbles can be removed efficiently. Further, fresh air is required for burning the vehicle contained in the metal paste during firing, but in this case, sufficient air can be supplied to the surface of the adhesive layer. As a result, it is possible to reduce the unbonded portion when separating the semiconductor thin film and the decrease in the bonding strength, and it is possible to prevent breakage in the transfer of the large area semiconductor substrate, thereby achieving an improvement in yield.

Also, by using an Al paste as the metal paste and firing at 500 ° C. or higher to form an adhesive layer, the P ⁺ layer for the back surface field can be formed at the same time as the adhesive layer without forming a film such as CVD. It is possible to form the film, and the film forming process can be simplified and the mass productivity can be improved.

  Furthermore, when the adhesive layer formed of the metal paste is fixed to the separation member at 500 ° C. or higher, a heat resistant material is used for the separation member, so that the semiconductor film, the adhesive layer, and the separation layer after separation in the separation layer Since the semiconductor substrate made of a member has heat resistance, it is possible to cope with high-temperature processes such as impurity diffusion and high-temperature firing of electrodes. Therefore, even when producing a solar cell, the materials and processes of the existing crystalline solar cell can be used, and materials and devices can be shared, so that an inexpensive solar cell can be supplied.

  The present invention encompasses not only the embodiments described below but also all combinations of the embodiments described below. Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the embodiments, the same or corresponding parts are denoted by the same reference numerals.

A method of reducing bubbles generated from the metal paste when the separation member is bonded to the semiconductor film of the present invention with the metal paste, generation of an unbonded portion by improving the atmosphere at the time of firing, and a decrease in adhesive strength; and A method for simplifying the film forming process by omitting the formation of P ⁺ for the back surface field in film formation for a solar cell will be described with reference to FIG.

  First, the base 5 is prepared (FIG. 1A). The separation layer 4 is formed on the substrate 5, and this separation layer 4 uses a porous layer formed by anodizing the substrate 5 (FIG. 1B). A method for forming a porous Si layer by this anodizing method is well known (for example, T. Unagami and M. Seki J. Electrochem. Soc. 125, 8 (1978)), and as an HF-based etching solution, a concentrated solution is used. Hydrofluoric acid (49% HF) is used. Since the porous layer formed as a result of anodization has a large amount of voids formed therein, the mechanical strength such as tension, compression, and shearing is weak. In addition, when the anode is anodized, the structure in the porous layer is changed in advance by making it porous by rapidly raising to a high current level after a lapse of a certain time at a low current level for a short period of time, and forming it for a short time. It is also possible to provide it.

  As a method for forming the separation layer 4, in addition to the above-described anodizing method, ions such as hydrogen are implanted from the surface of the substrate 5, distributed in a layer form from the surface, and then subjected to heat treatment to form a large number of voids in the layer form. Then, a hydrogen ion separation method may be used.

In the case of forming a porous separation layer, the semiconductor film 3 is then grown by a vapor phase growth method such as a liquid layer growth method or a CVD method (FIG. 1C). It is possible to control the semiconductor film 3 to be p ⁻ type (or n ⁻ type) by mixing a small amount of dopant during the formation. Moreover, you may form joining as needed. When the separation layer is formed by the hydrogen ion separation method, film formation is not necessary, but film formation at a low temperature where separation does not occur may be performed as necessary.

  Next, after applying a metal paste 6 as an adhesive layer on the semiconductor film 3 to a desired location (FIG. 1 (d)), exhausting gas from the surface of the adhesive layer and applying it to the surface of the adhesive layer on the metal paste 6 The separation member 1 having a structure capable of sucking air is brought into close contact, and the solvent is volatilized and dried at about 150 ° C., and further, the metal paste 6 is cured by baking at 500 ° C. or more, so that the semiconductor film 3 and the separation member 1 are It is made to adhere (FIG.1 (e)).

  In addition, in order to use a semiconductor substrate as a solar cell, after bonding and further forming an antireflection layer on the semiconductor film 3, a grid was applied with a metal paste 6 as a bonding layer and a current collecting electrode by a printing method or the like. In this case, the separating member 1 may be adhered after applying a glass paste or the like to a place where the metal paste 6 is not further applied.

  At this time, conventionally, a solid plate-like or flexible sheet-like material has been used as the separating member 1, so that the bubbles included in the metal paste 6 as the adhesive layer can be removed only from the end of the adhesive layer. It remains in the adhesive layer. In addition, in order to burn the vehicle contained in the metal paste 6 when the paste is fired at a high temperature following drying, it is necessary to have an oxygen-containing atmosphere or an air atmosphere, but only from the end of the metal paste 6. Insufficient firing without being supplied resulted in a decrease in adhesive strength and an increase in contact resistance.

  In the present invention, the separation member 1 has a structure capable of exhausting air from the surface of the adhesive layer and sucking air to the surface of the adhesive layer, so that bubbles and solvents contained in the adhesive layer at the time of bonding are efficiently removed from the surface of the adhesive layer. Well removed. In addition, an atmosphere necessary for the metal paste 6 as the adhesive layer at the time of curing is supplied from the separating member 1 to the surface of the adhesive layer.

  FIG. 2 shows an example of the structure of the separating member 1. This is a substrate having a mesh structure in which a fibrous material is woven as a structure capable of exhausting air from the surface of the adhesive layer and intake air to the surface of the adhesive layer. 2A is a cross-sectional view, and FIG. 2B is a top view. 50 is a material portion, and 51 is an opening for supplying and exhausting gas.

  FIG. 3 shows another structural example of the separating member 1. This is a substrate having a structure in which a groove-like air passage from the end face to the surface of the adhesive layer is formed as a structure capable of exhausting air from the surface of the adhesive layer and sucking air to the surface of the adhesive layer. 3A is a cross-sectional view, and FIG. 3B is a top view showing a surface in contact with an adhesive layer. FIG. 3C shows a perspective view. Reference numeral 50 denotes a material portion, and reference numeral 51 denotes an opening (groove-shaped ventilation path) for supplying and exhausting gas from the side surface.

  FIG. 4 shows still another structural example of the separation member 1. This is a substrate having a porous structure with minute through holes as a structure capable of exhausting air from the surface of the adhesive layer and sucking air to the surface of the adhesive layer. 4A shows a cross-sectional view, and FIG. 4B shows a top view. 50 is a material part, and 51 is an opening (through hole) for supplying and exhausting gas. Since it is sufficient that such a through hole can supply and exhaust only gas, a hole diameter of 100 μm or less is sufficient, but an opening ratio with respect to the surface of the adhesive layer is preferably 30% or more.

  The material of the separating member 1 has heat resistance that can withstand firing at 500 ° C. or higher, and metal materials such as SUS, glass, ceramic, carbon, SiC, and the like can be used.

As the metal paste 6 as the adhesive layer (and the current collecting electrode), a paste containing an organic vehicle and an organic solvent is used. Cellulose or the like is used for the vehicle. As the metal material, it is desirable that Al is contained when the P ⁺ layer is formed at the same time when baking the paste. In addition to Al, any of metals such as Ag, Cu, Ni, and Pd may be contained. Further, Ag, Ag-Pd, Cu, or the like is preferable as the collector electrode on the n ⁺ layer side. Furthermore, a dopant such as P may be contained when forming an n ⁺ type in the semiconductor film during firing of the metal paste.

  Next, the semiconductor film 3 serving as a semiconductor substrate and the substrate 5 are separated in the separation layer 4 (FIG. 1 (f)). Since the separation layer 4 made of a porous layer has a larger amount of voids inside than the substrate 5 and the formed semiconductor film 3, the mechanical strength such as tension, compression, and shear is weak. For this reason, it can be separated at the portion of the separation layer 4 by applying a force between the separation member 1 and the substrate 5 in the direction of separating them from each other.

  When the separation layer 4 is formed by the hydrogen ion separation method, a hydrogen microcavity in the implanted defect layer is grown and separated by performing a heat treatment.

  Thus, the semiconductor substrate 7 including the semiconductor film 3, the metal paste 6 as the adhesive layer, and the separating member 1 is obtained (FIG. 1 (g)).

  Thereafter, the substrate 10 after peeling the semiconductor substrate shown in FIG. 1 (f) has a porous residue and irregularities after peeling the hydrogen ions, but is easily smoothed by polishing, chemical etching or the like. Examples of the chemical etchant include an etchant such as a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution, and a hydrofluoric acid-nitric acid-acetic acid mixed solution. The substrate 10 after the semiconductor substrate is peeled after being smoothed is reused as the substrate 5.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, this invention is not limited at all by these Examples.

[Example 1]
In Example 1, a semiconductor film is formed on a substrate having a porous layer formed thereon by a liquid phase growth apparatus by the process shown in FIG. 5 and then separated from the porous layer as a separation layer to create a semiconductor substrate. After that, a solar cell was manufactured by forming current collecting electrodes and the like.

(Formation of porous layer as separation layer)
As shown in FIG. 5A, a 5-inch single crystal Si wafer 11 is prepared. This single crystal Si wafer 11 has a P-type specific resistance of 0.01 to 0.02 Ω · cm. A solution of HF (49%): H ₂ O = 1: 2 is injected into the anodizing apparatus to obtain a single crystal. The Si wafer 11 is set. For example, after the formation current is applied at a current density of 10 mA / cm ² for about 5 minutes, the current density is abruptly changed without stopping the current application. The current density to be changed is, for example, 25 mA / cm ² and the time is applied for about 2 minutes. Thereby, the porous layer 12 is formed (FIG.5 (b)).

(Formation of semiconductor film)
A semiconductor film is grown by epitaxial growth by a liquid phase growth method.
First, the substrate shown in FIG. 5 (b) is introduced into a liquid phase growth apparatus, heated to 1100 ° C. in a hydrogen atmosphere, and then subjected to high temperature treatment for 1 minute to smooth the porous layer surface, A void to be a separation layer is formed.

Next, In was used as a solvent, and necessary amounts of dopants to be Si and N ^{+ as} raw materials were dissolved in advance before growth, and kept at 960 ° C. for a certain time to form a saturated state. Thereafter, when the substrate and the solvent were gradually cooled and reached a certain degree of supersaturation, the solvent was brought into contact with the substrate surface, and the temperature of the solvent was gradually lowered, whereby an N ⁺ Si layer 13 was grown on the porous layer 12. The film thickness was 0.2 to 0.3 μm (FIG. 5C).

Thereafter, the solvent that contains N ⁺ Si P ^- replacing the solvent for Si growth In the same manner as above, the substrate for inclusive dissolved P ^- Replace the Si narrowing dissolved in a solvent, a single crystal P ^- The Si layer 14 is also grown by liquid phase growth. The growth conditions are a solvent temperature of 950 ° C. → 940 ° C. and a slow cooling rate of 1 ° C./min. The immersion time is about 30 minutes, and a P ⁻ Si layer 14 of about 30 μm grows (FIG. 5D).

After the single crystal N ⁺ Si layer 13 and the P ⁻ Si layer 14 are formed as described above, the substrate is taken out from the liquid phase growth apparatus.

(Lamination process)
After applying an Al paste 16 having a viscosity of 150 Pa · s to the entire surface of the P ⁻ Si layer 14 by a screen printing method (FIG. 5E), a separating member 17 is bonded (FIG. 5F).

  In this embodiment, as the separating member 17, a substrate having a mesh structure in which SUS fine wires are woven is used as shown in FIG. If the fiber diameter and the opening ratio when weaving are selected in consideration of the viscosity of the adhesive (Al paste 16), bubbles and solvent on the surface of the adhesive layer generated at the time of bonding are efficiently removed from the surface of the adhesive layer. The atmosphere required for the adhesive layer at the time of curing is supplied from the separating member to the surface of the adhesive layer. The fiber has a wire diameter of 0.5 mm, an aperture ratio of about 30% when interwoven, and a plurality of layers are interwoven.

  Thereafter, drying is performed by heating at 150 ° C. for 10 minutes, but bubbles generated on the Al paste 16 during bonding and a solvent generated from the Al paste 16 during drying are efficiently removed.

Further, the substrate 17 was heated in an air atmosphere at 700 ° C. for 2 minutes, and the paste was baked to fix the substrate 17 having a mesh structure in which a P ⁻ Si layer 14 as a semiconductor film and a SUS fine wire as a separating member were woven. Atmosphere is required for vehicle combustion at the time of firing, but the substrate in FIG. 6 sufficiently supplies air to the surface of the adhesive layer. Moreover, since the material of the separating member is SUS, conductivity is also ensured.

(Separation process)
At this time, a pulling force is applied between the substrate 17 having a mesh structure in which fine wires of SUS as a separating member are woven and the single crystal Si wafer 11, so that the semiconductor substrate 18 including the separating member is formed from the porous layer 12. Separate (FIG. 5 (g)).

(Manufacture of solar cell unit cells)
The residue of the porous layer remaining on the semiconductor substrate 18 is removed with a HF: H ₂ O ₂ = 1: 1 solution to expose the N ⁺ Si layer 13 (FIG. 5 (h)).

Since the adhesive layer formed of the Al paste 16 and the separating member 17 made of SUS have heat resistance, the semiconductor substrate 18 after separation has heat resistance. Therefore, Ag paste 24 used in a crystalline solar cell as a collecting electrode is applied to the surface of the N ⁺ Si layer 13 in a comb shape by a screen printing method, heated and dried at 120 ° C. for 5 minutes, and further 700 ° C. for 2 minutes. Firing was performed to form a current collecting electrode. Further, the antireflection layer 19 is formed on the surface of the N ⁺ Si layer 13 to complete the unit cell of the solar cell (FIG. 5 (i)). In addition, the single crystal Si wafer 20 after separating the semiconductor substrate 18 shown in FIG. 5G is used as a substrate again after removing the porous layer residue with HF: H ₂ O ₂ = 1: 1. Reused.

According to the method of the present invention, the separation member and the semiconductor film can be bonded to each other with an adhesive layer made of an Al paste, and damage can be prevented in the transfer of the semiconductor substrate, thereby improving the yield. In addition, by using Al as the metal paste, it is possible to simultaneously form the P ⁺ layer for the back surface field and the adhesive layer in the P ⁻ layer, simplifying the film forming process and improving mass productivity. Achieved.

[Example 2]
In Example 2, a semiconductor film is formed on the surface of a porous layer in a CVD apparatus on a substrate on which a porous layer is formed by anodization by the process shown in FIG. Is formed from a porous layer as a separation layer, and a solar cell is manufactured.

(Formation of porous layer as separation layer)
As shown in FIG. 7A, a polycrystalline Si substrate 23 of 15 cm square and 1 mm thick is prepared. This polycrystalline Si substrate 23 has a P-type specific resistance of 0.01 to 0.02 Ω · cm, and a polycrystal is injected by injecting a solution of HF (49%): H ₂ O = 1: 1 into the anodizing apparatus. The Si substrate 23 is set. For example, after the formation current is applied at a current density of 8 mA / cm ² for about 10 minutes, the current density is abruptly changed without stopping the current application. The current density to be changed is, for example, 20 mA / cm ² and the time is applied for about 30 seconds. Thereby, the porous layer 12 is formed (FIG. 7B).

(Formation of semiconductor film)
Next, the substrate shown in FIG. 7B is introduced into a thermal CVD apparatus. First, the temperature is raised from room temperature to 1000 ° C. over about 20 minutes, and high temperature treatment is performed in a hydrogen gas atmosphere for 1 minute. As a result, the surface of the porous layer becomes smooth, and a void serving as a separation layer is formed inside.

After the high-temperature treatment with hydrogen gas, about 30 μm of P ⁻ Si layer 14 was deposited in hydrogen and SiH ₂ Cl ₂ gas at 1050 ° C. for 30 minutes (FIG. 7C).

Thereafter, the dopant gas was changed to PH ₃ to form an N ⁺ layer 13 doped with P (FIG. 7D).

(Lamination process)
An Ag paste 24 having a viscosity of 100 Pa · s is applied on the N ⁺ Si layer 13 as a grid electrode for collecting current in a comb shape by screen printing (FIG. 7E). Thereafter, a light transmissive glass paste 25 is applied to a portion other than the grid electrode with a dispenser (FIG. 7F).

  Thereafter, the separating member 26 is bonded. In the present embodiment, as the separating member 26, a substrate made of glass and having grooves formed on the surface contacting the adhesive layer from the end face as shown in FIG. 8 was used. 8A is a cross-sectional view, FIG. 8B is a top view, and FIG. 8C is a perspective view. 50 is a material portion, and 51 is an opening (groove) for supplying and exhausting gas.

  The separating member 26 has a light-transmitting property, and light enters through the light-transmitting glass paste 25.

  At the time when the separating member 26 is pasted, drying is performed by heating at 100 ° C. for 30 minutes. The bubbles at the time of pasting the Ag paste 24 and the light-transmitting glass paste 25 and the solvent at the time of drying are separated by the separating member 26. Is removed from the end face through the opening 51 (FIG. 7G).

  Further, the substrate was heated in an air atmosphere at 650 ° C. for 2 minutes, and the Ag paste and the glass paste were fired to fix the semiconductor film and the substrate 26 on which the ventilation path from the end surface as the separating member to the surface of the adhesive layer was formed. . Although air is necessary for vehicle combustion at the time of firing, sufficient air is supplied to the surface of the adhesive layer in the substrate of FIG.

  The Ag paste 24 is directly bonded to the separating member 26, so that the electrodes are fired and bonded simultaneously. The light-transmitting glass paste 25 is used except for the current collecting electrode, and the semiconductor film in the necessary region and the separating member can be fixed by firing simultaneously with the firing of the electrode (FIG. 7 (h)). .

(Separation process)
At this time, a pulling force is applied between the substrate 26 on which the ventilation path from the end surface to the surface on the adhesive layer side is formed and the polycrystalline Si substrate 23, so that the semiconductor substrate 29 including the substrate 26 is separated from the porous layer 12. (FIG. 7 (i)).

(Manufacture of solar cell unit cells)
The porous layer residue remaining on the semiconductor substrate 29 is removed by immersing in a TMAH (2.38%): H ₂ O = 1: 1 solution at 85 ° C. for 5 minutes to expose the P ⁻ Si layer 14. .

Thereafter, an Al paste 16 is applied to the entire surface of the P ⁻ Si layer 14 by a screen printing method, heated at 120 ° C. for 5 minutes to remove the solvent, and further heated in an air atmosphere at 700 ° C. for 2 minutes to form an Al electrode on the back surface. Formed. By baking the Al paste 16 at a high temperature, Al diffused into the P ⁻ Si layer 14 to form a P ⁺ Si layer 15 (FIG. 7J).

  Further, an Ag paste 24 for taking out the output is partially printed on the back Al electrode, heated at 120 ° C. for 5 minutes, and then heated in air at 600 ° C. for 1 minute to form an Ag electrode on the back surface to form a solar cell unit. The cell is completed (FIG. 7 (k)).

  The polycrystalline Si substrate 30 after separation of the semiconductor substrate 29 shown in FIG. 7 (i) is reused after removing the porous layer residue by polishing.

By using the method of the present invention, the separation member and the semiconductor film are bonded to the Ag paste portion as the current collecting electrode and the other portion with the light-transmitting glass paste and fixed to the adhesive layer without any unbonded portion. In addition, it was possible to prevent breakage in the transfer of solar cells, and the yield was improved. In addition, by using Ag paste that is fired at high temperature and light transmissive glass paste, and by providing heat resistance to the separating member, high temperature process adaptability to the semiconductor substrate after separation can be achieved. It is possible to obtain the same effect without forming a P ⁺ Si layer, and it is also possible to form an Ag electrode for taking out an output by using a material and a method usually used in a crystalline solar cell.

Example 3
In Example 3, a semiconductor film is formed on the surface of a porous layer in a CVD apparatus on a substrate on which a porous layer has been formed by anodization according to the process shown in FIG. This is an example of manufacturing a solar cell by forming an n + layer and the like after separating the base material.

(Formation of porous layer as separation layer)
The porous layer 12 is formed on the 5-inch single crystal Si wafer 11 by anodization in the same manner as in Example 1 (FIG. 9A). Thereafter, it is introduced into a thermal CVD apparatus, heated to 1100 ° C., and subjected to a high temperature treatment for 2 minutes in a hydrogen gas atmosphere, the surface of the porous layer is smoothed, and a void serving as a separation layer is formed inside.

(Formation of semiconductor film)
After the high-temperature treatment with hydrogen gas, a P ⁻ Si layer 14 of about 30 μm was deposited in hydrogen and SiH ₂ Cl ₂ gas at 1050 ° C. for 30 minutes (FIG. 9B).

(Lamination process)
After the Al paste 16 is applied to the entire surface of the P ⁻ Si layer 14 by screen printing, a separation member 27 is bonded (FIG. 9C).

  In this embodiment, as the separating member 27, a substrate having a porous structure with minute through holes 51 as shown in FIG. The material is low-resistance metal grade Si, and the whole substrate is made porous using anodization or the like so that the hole diameter is 50 nm and the aperture ratio is about 50%. Metal grade Si is Si obtained by direct reduction from silica sand, and usually has a purity lower than 99.99%, but can be obtained at a much lower cost than semiconductor grade or solar cell grade Si.

  After the separation member 27 was bonded, heating was performed at 120 ° C. for 30 minutes, and the atmosphere was reduced in pressure to remove the bubbles of the Al paste 16 and the solvent. Thereafter, heating was performed at 700 ° C. for 2 minutes in an air atmosphere, the paste was fired, and the semiconductor thin film and the separating member 27 were fixed. In addition, since the separating member 27 is low-resistance metal grade Si, conductivity is also ensured.

(Separation process)
At this time, a pulling force is applied between the single-crystal Si wafer 11 and the substrate 27 having a porous structure with minute through holes as a separation member, and the semiconductor substrate 29 including the separation member from the porous layer 12. Are separated (FIG. 9D).

(Manufacture of solar cell unit cells)
Furthermore, after removing the residue of the porous layer remaining on the semiconductor substrate 29, thermal diffusion of P was performed at a temperature of 830 ° C. using POCl ₃ as a diffusion source to form an N ⁺ Si layer 13 (FIG. 9 (e)). )).

Next, a SiN film 28 was deposited as an antireflection layer on the N ⁺ Si layer 13 by a P-CVD apparatus (FIG. 9F).

Next, Ag paste 24 containing a dopant having a viscosity of 100 Pa · s as a grid electrode for collecting current on SiN film 28 was applied in a comb shape by a screen printing method, dried and baked at 750 ° C. for 2 minutes. A contact could be formed in the N ⁺ Si layer 13 through the SiN film 28 (FIG. 9G).

  Further, an Ag paste 24 for taking out the output is partially printed on the back surface of the metal grade Si (separating member 27), heated at 120 ° C. for 5 minutes, then heated at 600 ° C. for 1 minute in the air atmosphere, and the Ag electrode on the back surface To complete the unit cell of the solar battery (FIG. 9 (h)).

  The single crystal Si wafer 20 after separating the semiconductor substrate 29 shown in FIG. 9D is reused after removing the porous layer residue as in the first embodiment.

According to the method of the present invention, the separation member and the semiconductor film can be bonded to each other with an adhesive layer made of an Al paste, and damage can be prevented in the transfer of the semiconductor substrate, thereby improving the yield. Moreover, using the Al paste is fired at a high temperature, the use of metal-grade Si to the separation member a heat resistance, it is high temperature process adaptability to separation after the semiconductor substrate, n in CVD ⁺ It has become possible to perform a high-temperature impurity diffusion step on the separated semiconductor substrate without forming a Si layer. Furthermore, the formation of an Ag electrode for output extraction has become possible with the materials and methods normally used in crystalline solar cells.

Example 4
In Example 4, a semiconductor film was formed in a liquid layer growth apparatus on a substrate on which a porous layer was formed by anodization by the process shown in FIG. 10, and an n ⁺ layer and a P ⁺ layer region were further formed. This is an example in which a solar cell was manufactured after separation from a porous layer as a separation layer.

(Formation of porous layer as separation layer)
The porous layer 12 is formed on the polycrystalline Si substrate 23 as in the second embodiment (FIG. 10A).

(Formation of semiconductor film)
A semiconductor film is grown by epitaxial growth by a liquid phase growth method.
First, the substrate shown in FIG. 10A is introduced into a liquid phase growth apparatus, heated to 1100 ° C. in a hydrogen atmosphere, and then subjected to a high temperature treatment for 1 minute to smooth the surface of the porous layer. A void to be a separation layer is formed.

Next, In was used as a solvent, and necessary amounts of dopants to be Si and P ⁻ used as raw materials were dissolved in advance before growth, and kept at 960 ° C. for a certain time to form a saturated state. Thereafter, the substrate and the solvent are gradually cooled, and when the supersaturated state is reached to some extent, the solvent is brought into contact with the substrate surface and immersed for about 30 minutes at a solvent temperature of 950 ° C. → 940 ° C. and a slow cooling rate of 1 ° C./minute. A P ⁻ Si layer 14 was grown (FIG. 10B).

(Lamination process)
Next, comb-shaped n-electrodes and p-electrodes are formed on the P-Si layer 14.
For the n-electrode, Ag paste 24 containing phosphorus was applied to a comb-shaped pattern by screen printing (FIG. 10C). Next, a glass paste 31 is applied with a dispenser so as to surround the side surface of the Ag paste 24 (FIG. 10D). This top view is shown in FIG. The glass paste 31 at this time may not be translucent.

  The separating member 26 uses sintered mullite having insulating properties and has a structure shown in FIG. On the adhesive layer side of the separating member 26, the Al paste 16 was applied in a comb pattern not overlapping the Ag paste 24 by screen printing (FIG. 10E). This top view is shown in FIG.

After separating the separating member 26 and the P ⁻ Si layer 14 so that the pastes do not overlap each other, heating was performed at 150 ° C. for 15 minutes to remove the bubbles and the solvent in the paste (FIG. 10F).

Subsequently, heating is performed at 800 ° C. for 5 minutes in the air atmosphere, and the paste is baked to fix the P ⁻ Si layer 14 which is a semiconductor film and the substrate 26 on which the ventilation path from the end surface as the separating member to the surface of the adhesive layer is formed. It was. Simultaneously with the baking of the paste, the phosphorus contained in the Ag paste 24 thermally diffuses into the P ⁻ Si layer 14 to form the n ⁺ Si layer 13 region, and Al in the Al paste thermally diffuses into the P ⁻ Si layer 14 and the P ⁺ Si layer. Fifteen regions were formed (FIG. 10 (g)). The glass paste 31 insulates between the n ⁺ electrode made of the Ag paste 24 and the P ⁺ electrode made of the Al paste 16.

(Separation process)
At this time, a pulling force is applied between the separation member 26 and the polycrystalline Si substrate 23 to separate the semiconductor substrate 29 including the separation member 26 from the porous layer 12 (FIG. 10H).

(Manufacture of solar cell unit cells)
Thereafter, the porous layer residue on the separation surface on the semiconductor substrate side was removed by TMAH, and then a SiN film 28 was deposited on the P ⁻ Si layer 14 as an antireflection layer (FIG. 10 (i)).

  Furthermore, the output extraction copper tab 32 is connected from the end face of the adhesive layer to complete the unit cell of the solar cell (FIG. 10 (j)).

  The polycrystalline substrate 30 after separating the semiconductor substrate 29 shown in FIG. 10 (h) is reused after removing the porous layer residue as in the second embodiment.

By using the method of the present invention, the separation member and the semiconductor film can be combined with Ag paste, Al paste, and insulating glass paste as a collecting electrode and fixed without an unbonded portion in an adhesive layer. As a result, it was possible to prevent breakage in the transfer of solar cells, and the yield was improved. In addition, by using Ag paste and Al paste containing phosphorus that is fired at high temperature and using heat-resistant ceramic for the separation member, it becomes n ⁺ diffusion, P ⁺ diffusion and electrode formation and separation member Can be realized by a single firing, and the manufacturing process can be simplified.

Example 5
In Example 5, a separation layer and a semiconductor film are formed in the same manner as in Example 4 by the process shown in FIG. 12, and then a P ⁺ layer region is formed following the n ⁺ layer, and then separated from the separation layer to manufacture a solar cell. This is an example.

(Formation of porous layer and semiconductor film as separation layer)
Similar to the fourth embodiment, the porous layer 12 and the P ⁻ Si layer 14 are formed on the polycrystalline Si substrate 23 (FIG. 12A).

(Formation of n ⁺ layer)
An Ag paste 24 containing phosphorus is applied to the comb pattern by screen printing on the P ⁻ Si layer 14, dried by heating at 150 ° C. for 15 minutes, and then heated at 800 ° C. for 5 minutes in an air atmosphere to fire the paste. did. Simultaneously with the baking of the paste, phosphorus contained in the Ag paste 24 was thermally diffused into the P ⁻ Si layer 14 to form the n ⁺ Si layer 13 region (FIG. 12B).

(Lamination process)
Next, a glass paste 31 was applied with a dispenser so as to cover the Ag paste 24, heated and dried at 120 ° C. for 10 minutes, and then heated in an air atmosphere at 550 ° C. for 10 minutes to fire the paste (FIG. 12C). ).

After the Al paste 16 is applied to the entire surface of the glass paste 31 and the P ⁻ Si layer 14 by screen printing, the substrate 26 on which a ventilation path from the end surface as the separating member to the surface of the adhesive layer is formed is formed on the Al paste 16. Pasted together. The separation member has the same structure as in Example 4, and the material used is copper having conductivity.

  Although drying was performed by heating at 150 ° C. for 10 minutes in a heating furnace, bubbles generated on the Al paste 16 during bonding and a solvent generated from the Al paste 16 during drying were efficiently removed.

Further, the Al paste 16 was baked by heating at 700 ° C. for 2 minutes in an air atmosphere to fix the semiconductor film and the separating member. During firing, Al in the Al paste 16 was thermally diffused into the P ⁻ Si layer 14 to form a P ⁺ Si layer 15 region (FIG. 12D). The glass paste 31 insulates between the Ag paste 24 and the Al paste 16.

(Separation process)
As in Example 4, the semiconductor substrate including the separating member 26 was separated.

(Manufacture of solar cell unit cells)
After removing the porous layer residue on the separation surface on the semiconductor substrate side with TMAH, an antireflection layer 19 was formed (FIG. 12E).

  Further, the output extraction copper tab 32 is connected from the end surface of the Ag paste adhesive layer to complete the unit cell of the solar cell (FIG. 12F).

  The polycrystalline substrate after separation of the solar cell is reused after removing the porous layer residue as in Example 4.

  According to the method of the present invention, thin film solar cells could be separated with high yield by using Al paste as an adhesive layer as in Example 1 and combining with a substrate having a structure capable of supplying and exhausting gas from the surface of the adhesive layer. In addition, the firing conditions can be easily optimized by sequentially firing Ag paste, glass paste, and Al paste containing phosphorus that is fired at a high temperature. In addition, since a conductive metal can be used for the separation member and the tab for output extraction only needs to be formed on the Ag paste side, the degree of freedom of electrode arrangement is increased.

It is process drawing which shows one Embodiment of this invention. It is an example of 1 structure of the separation member which can supply and exhaust the gas from the surface of an adhesive layer in this invention. It is the other structural example of the separation member which can supply and exhaust the gas from the surface of an adhesive layer in this invention. It is the other structural example of the separation member which can supply and exhaust the gas from the surface of an adhesive layer in this invention. It is a figure for demonstrating the manufacturing process of the solar cell in Example 1 of this invention. It is the board | substrate which has the mesh structure of a SUS line as a structural example of the member for isolation | separation of this invention. It is a figure for demonstrating the manufacturing process of the solar cell in Example 2 of this invention. It is an example of composition of a separation member which can supply and exhaust gas from an adhesive layer surface in the present invention. It is a figure for demonstrating the manufacturing process of the solar cell in Example 3 of this invention. It is a figure for demonstrating the manufacturing process of the solar cell in Example 4 of this invention. It is a figure which shows the application pattern of the metal paste in Example 4 of this invention. It is a figure for demonstrating the manufacturing process of the solar cell in Example 5 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Separation member 3 Semiconductor film 4 Separation layer 5 Base 6 Metal paste 7 Semiconductor base 10 Substrate after semiconductor base peeling 11 Single crystal Si wafer 12 Porous layer 13 N ⁺ Si layer 14 P ^- Si layer 15 P ⁺ Si Layer 16 Al paste 17 Separation member 18 Semiconductor substrate 19 Antireflection layer 20 Single crystal Si wafer 23 after separation of semiconductor substrate 23 Polycrystalline Si substrate 24 Ag paste 25 Light transmissive glass paste 26 From end surface to adhesive layer side surface 27 A substrate having a porous structure with minute through-holes 28 SiN film 29 Semiconductor substrate 30 Polycrystalline Si substrate after solar cell separation 31 Glass paste 32 Copper tab for output extraction 50 Separation Material 51 opening

Claims (22)

Forming a semiconductor film on a substrate via a separation layer and bonding a separation member on the semiconductor film via an adhesive layer; and applying a force to the separation member to bond the semiconductor film and the substrate. In the method for producing a semiconductor substrate having a step of separating in the separation layer,
The step of attaching the separation member to the semiconductor film via the adhesive layer includes at least a step of applying a metal paste that functions as the adhesive layer, and exhaust from the surface of the adhesive layer and intake of air to the surface of the adhesive layer. The manufacturing method of the semiconductor base material characterized by including the process of closely_contact | adhering the separation member of an appropriate structure, and the baking process which hardens the said metal paste at 500 degreeC or more.   The method of manufacturing a semiconductor substrate according to claim 1, wherein the metal paste contains an organic vehicle.   The method of manufacturing a semiconductor substrate according to claim 1, wherein the metal paste contains an organic solvent and is in a paste form.   4. The method for manufacturing a semiconductor substrate according to claim 1, wherein the metal paste contains Al.   The method for manufacturing a semiconductor substrate according to claim 1, wherein the separating member has heat resistance at a firing temperature of the metal paste.   6. The method of manufacturing a semiconductor substrate according to claim 1, wherein the separating member is a mesh substrate woven with a fibrous material.   6. The method of manufacturing a semiconductor substrate according to claim 1, wherein the separating member is a substrate in which a ventilation path from an end surface to the surface of the adhesive layer is formed.   6. The method of manufacturing a semiconductor substrate according to claim 1, wherein the separating member is a porous substrate having minute through holes.   9. The method for manufacturing a semiconductor substrate according to claim 8, wherein the through hole has a diameter of 100 [mu] m or less.   The method for manufacturing a semiconductor substrate according to claim 1, wherein the separation layer comprises a porous layer formed by anodization. Forming a semiconductor film on a substrate via a separation layer and bonding a separation member on the semiconductor film via an adhesive layer; and applying a force to the separation member to bond the semiconductor film and the substrate. In the method for producing a solar cell having a step of separating in the separation layer,
The step of attaching the separation member to the semiconductor film via the adhesive layer includes at least a step of applying a metal paste that functions as the adhesive layer and an electrode, and exhausting gas from the surface of the adhesive layer and to the surface of the adhesive layer. The manufacturing method of the solar cell characterized by including the process of closely_contact | adhering the member for isolation | separation of the structure which can inhale of this, and the baking process which hardens the said metal paste at 500 degreeC or more. The method for manufacturing a solar cell according to claim 11, wherein the metal paste forms a P ⁺ type in the semiconductor film in the baking step.   The method for manufacturing a solar cell according to claim 11, wherein the metal paste contains Al. The method for manufacturing a solar cell according to claim 11, wherein the metal paste forms an n ⁺ type in the semiconductor film in the baking step.   The method of manufacturing a solar cell according to claim 11, wherein the metal paste contains an organic vehicle.   The method of manufacturing a solar cell according to claim 11, wherein the metal paste contains an organic solvent and is in a paste form.   The method for manufacturing a solar cell according to claim 11, wherein the separating member has heat resistance at a firing temperature of the metal paste.   The method for manufacturing a solar cell according to claim 11, wherein the separating member is a mesh substrate in which a fibrous material is woven.   The method for manufacturing a solar cell according to any one of claims 11 to 17, wherein the separating member is a substrate in which a ventilation path from an end surface to the surface of the adhesive layer is formed.   The method for manufacturing a solar cell according to claim 11, wherein the separation member is a porous substrate having minute through holes.   21. The method for manufacturing a solar cell according to claim 20, wherein the through hole has a diameter of 100 [mu] m or less.   The method for manufacturing a solar cell according to any one of claims 11 to 21, wherein the separation layer includes a porous layer formed by anodization.

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