JPH05218464A - Semiconductor substrate and solar cell and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a semiconductor substrate composed of a metal substrate and an epitaxial layer of high quality formed on it and a thin film crystal solar cell formed thereof. CONSTITUTION:A porous Si layer 102 is formed on an Si wafer 101 by anodization, and a non-single crystal Si layer 104 previously laid on a metal substrate 103 is brought into contact with the porous Si layer 102, which is thermally treated not only to turn the non-single crystal Si layer 104 into a single crystal silicon layer 106 through solid-phase growth making the porous Si layer 102 serve as seed crystal but also to form a silicide layer at an interface between the metal substrate 103 and the single crystal silicon layer 106. The porous Si layer 102 is removed through a selective etching method to separate the single crystal silicon layer 106 from the Si wafer 101, whereby a semiconductor substrate of two-layered structure composed of metal a metal layer and a single crystal Si layer. Furthermore, an epitaxial Si layer 107 is grown on the single crystal Si layer 106, and thus a solar cell can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor substrate and a solar cell, and more particularly to a method for manufacturing a substrate having a semiconductor laminated on a metal and a solar cell.

[0002]

2. Description of the Related Art It is desired that photoelectric conversion elements, particularly solar cells, can be formed on a metal, especially a low-priced substrate such as SUS, in view of cost requirements. Therefore, how to form a good-quality semiconductor layer on metal is important.

Silicon is generally used as a semiconductor constituting a solar cell, and the form of silicon is single crystal,
There are polycrystalline and amorphous. Amorphous silicon is considered to be advantageous from the viewpoints of large area and cost reduction, but it is preferable to use single crystal silicon from the viewpoint of efficiency and stability of converting light energy into electromotive force. Further, in recent years, use of polycrystalline silicon has been studied for the purpose of obtaining low cost as amorphous silicon and high energy conversion efficiency as single crystal silicon. However, the method conventionally proposed in such single crystals and polycrystalline silicon, it is difficult to reduce the thickness to 0.3 mm or less in order to use this by slicing a massive crystal into a plate-like body, and therefore The thickness was unnecessarily sufficient to absorb the amount of light, and the material was not effectively used in this respect. That is, it is necessary to sufficiently reduce the thickness in order to reduce the cost. Recently, a method of forming a silicon sheet by spin method in which molten silicon droplets are poured into a mold has been proposed, but the thickness is at least 0.1 mm to 0.2 mm, which is a film sufficient as light absorption for crystalline silicon. Thickness (20-50
μm), but not yet thin enough. Further, with such thinning, it is no longer possible for the silicon sheet itself to have strength as a substrate, and inevitably another substrate supporting the silicon sheet is required.

[0004]

Therefore, the fact that a thin film epitaxial layer grown on a single-crystal silicon substrate is separated (peeled) from the substrate and attached to another substrate is used for a solar cell. Attempts to achieve energy conversion efficiency and cost reduction have been proposed (Milnes, AG
and Feucht, DL, "Peeled Film Technology Solar Cell
s ", IEEE Photovoltaic Specialist Conference, p.33
8, 1975).

However, according to the above-mentioned method, an intermediate layer of SiGe is inserted between the single crystal silicon as a substrate and the growth epitaxial layer for heteroepitaxial growth, and this intermediate layer is further selectively melted to grow the growth layer. Need to be peeled off. Generally, when heteroepitaxial growth is performed, defects are likely to be induced at the growth interface because the lattice constants are different. In addition, it cannot be said that it is advantageous in terms of process cost because different materials are used.

Further, a single crystal silicon wafer is brought into contact with the amorphous silicon film deposited on SiO ₂ to perform heat treatment,
Method for obtaining crystalline thin film by solid phase growth (Spring 1991, 3rd
The 8th Joint Lecture on Applied Physics 28p-X-10) has been reported. However, since the silicon wafer and the solid-phase growth layer are firmly adhered, it is difficult to separate them after growth, and sufficient heat treatment is required. It has not been possible to obtain a perfect single crystal.

The method of the present invention eliminates the above-mentioned drawbacks of the prior art, obtains a good-quality thin film single crystal on a metal substrate, and further provides a good method for producing a solar cell by using this.

An object of the present invention is to provide an inexpensive metal / crystal semiconductor two-layer substrate by single-crystallizing a non-single crystal layer formed on a metal substrate by solid phase growth.

Another object of the present invention is to provide a high quality solar cell by using a single crystal semiconductor.

[0010]

The present invention has been completed as a result of earnest research by the present inventors in order to solve the above-mentioned problems in the prior art and achieve the above object. And a solar cell obtained by the method. That is,
The method for producing a semiconductor substrate of the present invention is the method for producing a semiconductor substrate having a metal / semiconductor two-layer structure, comprising the steps of i) depositing a non-single crystal silicon layer on the metal substrate, and ii) forming a surface of the single crystal silicon substrate. The step of making porous, iii) the step of contacting the surface of the non-single-crystal silicon layer on the metal substrate with the surface of the porous layer on the single-crystal silicon substrate, and iv) heat-treating the porous layer Forming a silicide layer at the interface between the metal substrate and the non-single-crystal silicon at the same time by solid-phase epitaxially growing the facing non-single-crystal silicon layer to form a single crystal; and v) the porous layer by selective etching. Is removed to separate the single-crystal silicon substrate from the single-crystallized silicon layer on the metal substrate.

The method of manufacturing a solar cell according to the present invention is the method of manufacturing a solar cell using a solid phase epitaxial film, comprising the steps of i) depositing a non-single crystal silicon layer on a metal substrate, and ii) single crystal silicon. The step of making the surface of the substrate porous, iii) the step of contacting the surface of the non-single-crystal silicon layer on the metal substrate with the surface of the porous layer on the single-crystal silicon substrate, and iv) the heat treatment A step of forming a silicide layer at the interface between the metal base and the non-single-crystal silicon at the same time by solid-phase epitaxially growing the non-single-crystal silicon layer facing the porous layer into a single crystal, and v) by selective etching Removing the porous layer to separate the single crystal silicon substrate from the single crystal silicon layer on the metal substrate; and vi) on the single crystal silicon layer by a thin film epitaxial growth method. It is characterized in that comprises a step of growing a silicon epitaxial layer.

In the semiconductor substrate of the present invention, i) a step of depositing a non-single-crystal silicon layer on the metal substrate, ii) a step of making the surface of the single-crystal silicon substrate porous, and iii) the metal substrate Contacting the surface of the non-single-crystal silicon layer with the surface of the porous layer on the single-crystal silicon substrate, and iv) heat-treating the non-single-crystal silicon layer facing the porous layer by solid phase epitaxial growth Forming a silicide layer at the interface between the metal substrate and the non-single-crystal silicon at the same time as single-crystallizing, and v) removing the porous layer by selective etching to remove the porous layer on the single-crystal silicon substrate and the metal substrate. And a step of separating the single-crystallized silicon layer from 1.

Further, in the solar cell of the present invention, i) a step of depositing a non-single crystal silicon layer on the metal substrate, ii) a step of making the surface of the single crystal silicon substrate porous, and iii) the metal substrate Contacting the surface of the non-single crystal silicon layer with the surface of the porous layer on the single crystal silicon substrate, and iv) heat-treating the non-single crystal silicon layer facing the porous layer by solid phase epitaxial growth. Forming a silicide layer at the interface between the metal substrate and the non-single-crystal silicon at the same time as single crystallizing, and v) removing the porous layer by selective etching to remove the single crystal silicon substrate and the metal substrate. Separating the upper single crystallized silicon layer,
vi) a step of growing a silicon epitaxial layer on the single crystallized silicon layer by a thin film epitaxial growth method, and vii) a step of forming a semiconductor junction on the surface of the epitaxial layer. is there.

As shown in FIG. 1, the characteristic feature of the present invention is that the surface of a silicon wafer is made porous by anodization in an HF solution (FIG. 1 (a)), and amorphous silicon is previously deposited on a metal substrate. The surface and the formed porous surface are heat treated together to form a single crystal of amorphous silicon using the porous side as a seed crystal, and at the same time, a silicide layer is formed at the metal substrate / amorphous silicon interface, which is favorable. Obtaining ohmic contact (Fig. 1 (b)), the porous layer is removed by selective etching to separate the silicon wafer from the solid phase growth layer (Fig. 1 (c)), and if necessary, solid phase growth. This is to form a single crystal silicon thin film on a metal substrate by laminating an epitaxial layer to a desired thickness on the layer by a normal crystal growth method (FIG. 1 (d)).

The formation of porous silicon by anodization requires holes for the anodic reaction, so that it is said that the p-type silicon in which holes are mainly present is used to make the porous (T. Unagami, J. Electrochem. Soc., Vol. 127, 476 (1
980)). However, on the other hand, there is also a report that low resistance n-type silicon is made porous (RP Holmstrom and J.
Y.Chi, Appl. Phys. Lett., Vol.42, 386 (1983)), p
Regardless of type n type, low resistance silicon can be used to make it porous. Porous silicon obtained by anodizing single crystal silicon has pores with a diameter of several hundreds as observed by a transmission electron microscope, and the density thereof is less than half that of single crystal silicon. Nevertheless, single crystallinity is maintained, and it is generally well known that an epitaxial layer grows on porous silicon by the LPCVD method or the like. Furthermore, since porous silicon has a large amount of voids inside as described above, the surface area increases dramatically compared to the volume.
The chemical etching rate is remarkably increased as compared with the etching rate of normal single crystal silicon.

Further, as an ordinary selective etching solution for crystalline silicon and porous silicon, only a NaOH aqueous solution has been conventionally used. In the selective etching of porous silicon using this NaOH aqueous solution, Na ions are adsorbed on the etching surface. Therefore, there is a problem of causing impurity contamination.

The inventors of the present invention have conducted repeated experiments to bring a non-single-crystal silicon layer, particularly an amorphous silicon layer, deposited on a metal substrate into contact with the upper surface of the porous silicon layer to perform heat treatment. Non-single-crystal layer can be solid-phase-grown by using as a seed crystal to form a single crystal, and only a porous silicon layer can be formed with a mixed solution of hydrofluoric acid, which has no etching action on crystalline silicon, and alcohol and hydrogen peroxide It has been found that selective etching is possible. As a result, they have found that a good-quality thin film single crystal silicon layer can be formed on a metal substrate, and completed the present invention. The experiment conducted by the present inventors will be described below with reference to FIG.

(Experiment 1) Formation of Porous Silicon A p-type (100) single crystal silicon wafer 101 having a specific resistance of 0.01 Ω · cm and a thickness of 500 μm was anodized in an HF aqueous solution. Table 1 shows anodization conditions.

[0019]

[Table 1]

Observation of the surface of the obtained porous silicon layer 102 with a transmission electron microscope revealed that pores having an average diameter of about 600 Å were formed. Also, when the cross section of the porous silicon layer was observed with a high resolution scanning electron microscope, it was confirmed that minute holes were similarly formed in the direction perpendicular to the substrate.
Moreover, when the anodization time was increased under the conditions of Table 1 to increase the thickness of the porous silicon layer and the density was measured, it was found that the density of the porous silicon layer was 1.1 g / cm ^3. It was about half that of crystalline silicon.

(Experiment 2) Solid phase growth using porous silicon as a seed crystal 0.1 μm of amorphous silicon 104 was deposited by vacuum evaporation on a 0.8 mm thick W (tungsten) substrate 103. After the surface of the porous silicon layer on the wafer formed in Experiment 1 was brought into contact with the upper surface of the amorphous silicon, heat treatment was once performed at a temperature lower than the crystallization temperature of the amorphous silicon, and the surface of the porous silicon 102 and the amorphous silicon were amorphous. The silicon 104 surface was brought into close contact.

Next, the closely adhered substrate was heat-treated again at 630 ° C. to grow a solid phase epitaxial layer 106 of an amorphous silicon layer using the porous silicon 102 as a seed crystal.
The heat treatment was completed when a sufficient time had passed. In order to observe the structural change of the amorphous silicon layer, the cross section of the substrate was examined with a transmission electron microscope.The amorphous silicon layer in contact with the porous silicon was completely single-crystallized, and a good crystal was obtained. It was confirmed that the sex was maintained.

Further, W substrate 103 / single-crystallized silicon layer 1
It was found by composition analysis that the WSi ₂ layer 105 was formed at the interface of No. 06.

(Experiment 3) Selective Etching of Porous Silicon The etching of porous silicon produced under the same conditions as in Experiment 1 with a mixed solution of hydrofluoric acid, alcohol, and hydrogen peroxide was examined.

In FIG. 2, porous silicon and single crystal silicon were infiltrated into a mixed solution (10: 6: 50) of 49% hydrofluoric acid, 100% ethyl alcohol and 30% hydrogen peroxide without stirring. The time dependence of the thickness of the etched porous silicon and the single crystal silicon at this time is shown. The thickness of porous silicon and single crystal silicon before etching is 300μ each.
m and 500 μm.

When porous silicon and single crystal silicon were infiltrated into the above mixture at room temperature and the reduction in thickness was measured,
Porous silicon is rapidly etched, and in about 40 minutes 107
.mu.m, 244 .mu.m was also etched in 80 minutes. Despite such a high etching rate, the surface after etching was very flat. In contrast, with single crystal silicon, the etched thickness is 50 even after 120 minutes.
It was below Å, and it was revealed that it was hardly etched.

Next, when the bonded substrate obtained in Experiment 2 was soaked in the same mixed etching solution as above and allowed to stand,
Only the porous silicon layer 102 was selectively etched and separated into the wafer 101 side and the metal substrate 103 side. After rinsing / drying, the state on the metal substrate (the side facing the porous layer) was observed with a high-resolution scanning electron microscope. As a result, a single-crystal silicon layer with a very flat surface was about 0.1 μm.
Was formed with a thickness of. Also, when the surface of the wafer (the side facing the porous layer) was observed in the same manner, it was also very flat.

As described above, it was shown that a good quality single crystal silicon layer can be formed on a metal substrate by the solid phase growth method using a porous layer as a seed crystal.

The present inventors further attempted to manufacture a solar cell using the obtained metal / single crystal silicon two-layer substrate.

(Experiment 4) Crystal Growth on Solid Phase Growth Layer Solid phase epitaxial layer 1 on metal substrate obtained in Experiment 3
Further, the epitaxial layer 107 was grown by using 06. A normal LPCVD method is used as a crystal growth method,
Growth was performed under the conditions shown in Table 2.

When the state of the crystal growth surface after the growth was observed with an optical microscope and a scanning electron microscope, a flat surface was obtained, and when the cross section of the growth layer was observed with a transmission electron microscope, it was excellent. It was confirmed that it was a single crystal epitaxial layer having excellent crystallinity.

[0032]

[Table 2]

(Experiment 5) Formation of Solar Cell A solar cell was prepared based on the results of Experiments 1 to 4. In the same manner as in Experiment 1, the porous silicon layer 102 was formed on the silicon wafer 101 under the conditions shown in Table 1. Next, W board 10
Amorphous silicon 104 having a thickness of 0.1 μm was deposited on 3 by vacuum evaporation using p-type polycrystalline silicon of ρ = 0.01 Ω · cm as an evaporation source. The above-mentioned porous silicon layer 102 was brought into contact with the upper surface of the amorphous silicon layer 104, and was adhered thereto by heat treatment. The adhered substrates were heat-treated at 630 ° C. to carry out solid phase growth to form a solid phase epitaxial layer. Experiment 3
Similarly, the porous silicon 102 was infiltrated with a mixed solution of hydrofluoric acid / ethyl alcohol / hydrogen peroxide water to selectively etch the porous silicon 102, and the wafer 101 side and the metal substrate 103 side were separated. Solid phase growth layer 1 under the LPCVD conditions shown in Experiment 4
Epitaxially grow silicon 107 on 06,
A crystal layer having a thickness of about 50 μm was obtained.

Next, on the surface of the grown epitaxial layer,
Ion-implant P at 50 KeV, ^{1x10 15} cm ^-2 , 550 ℃,
A junction was formed by continuous annealing under conditions of 1 hour / 800 ℃, 30min / 550 ℃, and 1 hour to activate impurities and recover the damage caused by ion implantation. Finally, a transparent conductive film and a collecting electrode were vacuum-deposited on the surface of the epitaxial layer to manufacture a solar cell.

Under the irradiation of AM1.5 (100 mW / cm ² ) light of the epitaxial thin-film solar cell obtained by performing solid-phase growth using the porous material as a seed crystal in this manner and further growing it on this solid-phase growth layer. Current-voltage characteristics (IV characteristics) were measured, and an open-circuit voltage of 0.55 V, short-circuit photocurrent of 31 mA / cm ² , fill factor of 0.72, and conversion efficiency of 12.3% were obtained, and good crystalline solar cells were obtained.

As described above, the present invention completed based on the above experimental results forms a porous layer on a wafer, and uses the porous layer as a seed crystal to solidify a non-single crystal layer on a metal substrate. The present invention relates to a method for producing a substrate having a metal / semiconductor two-layer structure obtained by forming a single crystal layer by phase growth, and a method for producing a crystalline solar cell obtained by further epitaxially growing the substrate. A feature of the present invention is that the wafer forming the porous layer can be reused, which is advantageous in terms of cost.

A hydrofluoric acid solution is used in the anodization method for forming the porous silicon layer used in the present invention.
The amount of current passed during anodization is appropriately determined depending on the HF concentration and the desired thickness of the porous layer, etc.
mA / cm ² - several ten mA / cm ² range are suitable. In addition, by adding alcohol such as ethyl alcohol to the HF solution, bubbles of the reaction product gas generated during anodization can be removed from the reaction surface without instantaneous stirring, and porous silicon can be formed uniformly and efficiently. You can The amount of alcohol to be added is appropriately determined depending on the HF concentration and the desired thickness of the porous layer, and it is necessary to carefully determine so that the HF concentration does not become too low.

As the selective etching solution for porous silicon used in the present invention, a mixed solution of hydrofluoric acid, alcohol and hydrogen peroxide solution is used. In particular, the addition of hydrogen peroxide solution accelerates the oxidation of silicon, and therefore the reaction rate can be increased compared to that without addition, and the reaction rate can be controlled by changing the ratio of hydrogen peroxide solution. can do. Further, by adding alcohol such as ethyl alcohol, bubbles of the reaction product gas due to etching can be instantly removed from the etching surface without stirring, and the porous silicon can be uniformly and efficiently etched. The conditions of the concentration of each solution of the etching solution and the temperature at the time of etching are such that the etching rate of the porous silicon and the etching selection ratio between the porous silicon and the normal single crystal silicon are practically acceptable in the manufacturing process, and the above. It is appropriately determined as long as the effect of alcohol is not impaired.

As the metal substrate material used in the method of manufacturing the semiconductor substrate and the solar cell of the present invention, any metal that has good conductivity and forms a compound such as silicon and a silicide is used. , Mo, Cr
Etc. Of course, any other material may be used as long as the metal having the above-mentioned properties is attached to the surface thereof, and thus an inexpensive substrate other than the metal can be used. The thickness of the silicide layer is not specified, but it is 0.
It is desirable that the thickness is 01 to 0.1 μm.

In the present invention, amorphous silicon is mainly used as the non-single crystal silicon layer deposited on the metal substrate, but polycrystalline silicon may be used.

The temperature of the solid phase growth performed using porous silicon in the present invention is suitably 500 ° C. or higher, and 550 ° C. or higher, when amorphous silicon is used for the non-single crystal silicon layer. Is more preferable. However,
When using polycrystalline silicon, the solid phase growth temperature is 1000 ℃
The above high temperature process causes a structural change of the porous silicon and impairs the above-described characteristics of the enhanced etching. As the deposition method of non-single crystal silicon, vacuum deposition method,
Sputtering method, LPCVD method, plasma CVD method, optical CV
The D method or the like is used.

In the present invention, the crystal growth method for growing the epitaxial layer on the solid phase growth layer includes LPCVD method, sputtering method, plasma CVD method, photo CVD method, liquid phase growth method and the like. For example, as the source gas used in the vapor phase growth method such as the LPCVD method, the plasma CVD method or the photo CVD method, SiH ₂ Cl ₂ , SiCl ₄ , SiHCl ₃ , SiH ₄ , Si ₂ H ₆ and SiH _{2 are used.}
Representative examples include silanes such as F ₂ and Si ₂ F ₆ and halogenated silanes. Further, H ₂ is added as a carrier gas or in addition to the above-mentioned raw material gas for the purpose of obtaining a reducing atmosphere for promoting crystal growth. The ratio of the amounts of the raw material gas and hydrogen is appropriately determined according to the formation method, the type of the raw material gas and the formation conditions as desired, but preferably 1:10 or more and 1: 1000 or less (introduction flow ratio), and It is preferable that the ratio is 1:20 or more and 1: 800 or less.

The temperature and pressure in the crystal growth method used in the present invention vary depending on the forming method, the type of the raw material gas used, the flow rate ratio of the raw material gas and H _2, and the like. For example, normal LPCV
In the method D, a temperature of 600 ° C. or higher and 1250 ° C. or lower is suitable, and more preferably 650 ° C. or higher and 1200 ° C. or lower. In the case of liquid phase epitaxy, depending on the type of solvent, when Sn is used, it is desirable to control the temperature to 850 ° C or higher and 1050 ° C or lower. In a low temperature process such as plasma CVD, a temperature of 200 ° C or higher and 600 ° C or lower is suitable, and more preferably 20 ° C or higher.
It is desirable to control the temperature from 0 ° C to 500 ° C.

Similarly, the pressure is about 10 ^-2 Torr to 760T.
orr is suitable, and more preferably 10 ^-1 Torr to 760 Torr.

The depth of the junction formed in the method for producing a solar cell of the present invention depends on the amount of impurities introduced, but is preferably in the range of 0.05 to 3 μm, preferably 0.1 to 1 μm. It is desirable to do.

[0046]

The present invention will be described in more detail below with reference to specific examples, but the present invention is not limited to these examples.

Example 1 As described above, a metal / single crystal silicon two-layer semiconductor substrate was manufactured by the process shown in FIG.

500 μm thick p-type (100) silicon wafer 10
1 (ρ = 0.01 Ω · cm) was anodized in an HF aqueous solution under the conditions shown in Table 3 to make the wafer 101 porous to form a porous silicon layer 102.

[0049]

[Table 3]

Mo is vacuum-deposited on a SUS substrate to a thickness of 500Å to form a metal substrate 103, and a normal LPCV is formed on the surface of the metal substrate 103.
An amorphous silicon layer 104 was deposited to a thickness of 0.2 μm using a D device. Table 4 shows the deposition conditions.

[0051]

[Table 4]

Next, after the surface of the porous silicon 102 and the surface of the amorphous silicon 104 are overlapped and brought into contact with each other,
Heat treatment was performed at 500 ° C for 30 minutes to improve the adhesion between the wafer and the SUS substrate.

Subsequently, in order to carry out solid phase epitaxial growth of the amorphous silicon layer 104 using the porous silicon layer 104 as a seed crystal, heat treatment was performed at 600 ° C. for 8 hours to completely crystallize the amorphous silicon layer.

Thereafter, the bonded substrates were mixed with 49% hydrofluoric acid and 1%.
Mixed solution of 00% alcohol and 30% hydrogen peroxide (10: 6: 5
0) and then selective etching was performed. After the porous silicon layer was completely removed and the wafer 101 side and the SUS substrate side were separated, the SUS substrate was washed / dried with water.

In this way, 0.1 μ is formed on the metal substrate 103.
A single crystal silicon layer 106 having a thickness of m could be formed. When the surface was examined by an optical microscope and a scanning electron microscope, the selective etching of porous silicon had no effect on the single crystal silicon layer.

As a result of cross-sectional observation with a transmission electron microscope, good crystallinity was maintained in the silicon layer,
A MoSi ₂ layer 105 is formed on the substrate 103 / silicon layer 106 interface.
Was confirmed to have been formed.

Example 2 In the same manner as in Example 1, metal / metal was produced by the process shown in FIG.
A single crystal silicon two-layer semiconductor substrate was produced.

500 μm thick n-type (100) silicon wafer 10
1 (ρ = 0.01 Ω · cm) was anodized in the HF aqueous solution under the conditions shown in Table 2, and the porous silicon layer 102 was formed on the wafer 101.
Formed.

Ti was vacuum-deposited on the SUS substrate 103 to a thickness of 500 Å, and an amorphous silicon layer 104 of 0.2 μm was deposited on the surface thereof by the LPCVD apparatus under the conditions shown in Table 4.

Next, after the surface of the porous silicon 102 and the surface of the amorphous silicon 104 are overlapped and brought into contact with each other,
The wafer 101 and SUS substrate 1 are heat-treated at 500 ° C for 30 minutes.
The adhesiveness of 03 was improved.

Subsequently, in order to carry out solid phase epitaxial growth of the amorphous silicon 104 using the porous silicon 102 as a seed crystal, heat treatment was performed at 650 ° C. for 6 hours to completely crystallize the amorphous silicon layer.

Thereafter, the bonded substrates were mixed with 49% hydrofluoric acid and 1%.
Mixed solution of 00% alcohol and 30% hydrogen peroxide (10: 6: 5
0) and then selective etching was performed. Since the porous silicon layer 102 is completely removed,
After separating the SUS substrate 103 side, the SUS substrate was washed / dried with water.

In this way, 0.1 μ is formed on the metal substrate 103.
A single crystal silicon layer 107 having a thickness of m could be formed. When the surface was examined by an optical microscope and a scanning electron microscope, the selective etching of porous silicon had no effect on the single crystal silicon layer.

As a result of cross-sectional observation with a transmission electron microscope, it was confirmed that the silicon layer 106 maintained good crystallinity and that the TiSi ₂ layer 105 was formed at the substrate / silicon layer interface. Was done.

Example 3 A metal / single crystal silicon two-layer semiconductor substrate was produced by the process shown in FIG. 1 in the same manner as in Examples 1 and 2.

500 μm thick p-type (100) silicon wafer 10
3 (ρ = 0.011 Ω · cm) was anodized in the HF aqueous solution under the conditions shown in Table 2 to form the porous silicon layer 102 on the wafer.

Mo was vacuum-deposited on the SUS substrate 103 to a thickness of 500 Å, and an amorphous silicon layer 104 of 0.2 μm was deposited on the surface thereof by the plasma CVD apparatus under the conditions shown in Table 5.

[0068]

[Table 5]

Next, after the surface of the porous silicon 102 and the surface of the amorphous silicon 104 are overlapped and brought into contact with each other,
The wafer 102 and SUS substrate 1 are heat-treated at 500 ° C for 30 minutes.
The adhesiveness of 03 was improved.

Then, in order to carry out solid phase epitaxial growth of the amorphous silicon 104 using the porous silicon 102 as a seed crystal, RTA (Rapid Thermal Annealing) method is applied to 1200.
Heat treatment was performed at 30 ° C. for 30 seconds to completely crystallize the amorphous silicon layer 104.

Thereafter, the bonded substrates were mixed with 49% hydrofluoric acid and 1%.
Mixed solution of 00% alcohol and 30% hydrogen peroxide (10: 6: 5
0) and then selective etching was performed. Since the porous silicon layer 102 is completely removed,
After being separated from the SUS substrate 103, the SUS substrate 103 was washed / dried.

Thus, a single crystal silicon layer having a thickness of 0.1 μm could be formed on the metal substrate. When the surface was examined by an optical microscope and a scanning electron microscope, the selective etching of porous silicon had no effect on the single crystal silicon layer.

As a result of cross-sectional observation with a transmission electron microscope, good crystallinity was maintained in the silicon layer,
It was confirmed that the MoSi ₂ layer 105 was formed at the substrate / silicon layer interface.

Example 4 A metal / single crystal silicon two-layer semiconductor substrate was prepared by the process shown in FIG. 1 in the same manner as in Examples 1 and 2, and a crystal was epitaxially grown thereon to prepare a solar cell.

500 μm thick n-type (100) silicon wafer 10
1 (ρ = 0.01 Ω · cm) was anodized in an HF aqueous solution under the conditions shown in Table 2 to make the wafer 101 porous and form a porous silicon layer 102.

Ti is vacuum-deposited on a SUS substrate 103 to a thickness of 500Å, and an amorphous silicon layer having a thickness of 0.2 μm is formed on the surface by vacuum vapor deposition using n-type polycrystalline silicon of ρ = 0.001 Ω · cm as a vapor deposition source. 104 was deposited.

Next, after the surface of the porous silicon 102 and the surface of the amorphous silicon 104 are overlapped and brought into contact with each other,
The wafer 102 and SUS substrate 1 are heat-treated at 500 ° C for 30 minutes.
The adhesiveness with the 03 side was improved.

Subsequently, in order to perform solid phase epitaxial growth of the amorphous silicon 104 using the porous silicon 102 as a seed crystal, heat treatment was performed at 650 ° C. for 6 hours to completely crystallize the amorphous silicon layer 104.

Thereafter, the bonded substrates were mixed with 49% hydrofluoric acid and 1%.
Mixed solution of 00% alcohol and 30% hydrogen peroxide (10: 6: 5
0) and then selective etching was performed. Since the porous silicon layer 102 is completely removed,
After separating from the SUS substrate 103 side, wash the SUS substrate with water /
Dried.

Epitaxial growth was performed under the conditions shown in Table 6 using an LPCVD apparatus to form silicon 107 with a film thickness of about 50 μm.
And

[0081]

[Table 6]

Next, BCl ₃ is formed on the surface of the epitaxial layer 107.
As a diffusion source, B was thermally diffused at a temperature of 950 ° C. to form a p ⁺ layer, and a junction depth of about 0.5 μm was obtained. P ⁺ formed
The dead layer on the layer surface was wet-oxidized and then removed by etching to obtain a junction depth having an appropriate surface concentration of about 0.2 μm.

Finally, ITO transparent conductive film (820Å) / collector electrode (Cr / Ag / Cr (200Å / 1 μm /
400Å)) was formed on the p ⁺ layer.

The IV characteristics of the thus obtained thin film crystalline silicon solar cell under AM1.5 (100 mW / cm ² ) light irradiation were measured, and an open circuit voltage of 0.59 V, a short circuit photocurrent of 31 mA / cm ² , The fill factor is 0.74, and the energy conversion efficiency is
Got 13.5%. Thus, solid-phase growth was performed using porous silicon as a seed crystal, and a thin-film crystal solar cell exhibiting good characteristics could be manufactured using the epitaxial layer grown on this solid-phase growth layer.

Example 5 A thin crystalline solar cell was prepared in the same manner as in Example 4.

500 μm thick p-type (100) silicon wafer 10
1 (ρ = 0.01 Ω · cm) was anodized in an HF aqueous solution under the conditions shown in Table 2 to form a porous silicon layer 102 on the wafer.

Mo is vacuum-deposited on the SUS substrate 103 to a thickness of 500Å, and an amorphous silicon layer having a thickness of 0.2 μm is formed on the surface by vacuum vapor deposition using p-type polycrystalline silicon of ρ = 0.001 Ω · cm as a vapor deposition source. 104 was deposited.

Next, after the surface of the porous silicon 102 and the surface of the amorphous silicon 104 are overlapped and brought into contact with each other,
The wafer 102 and SUS substrate 1 are heat-treated at 500 ° C for 30 minutes.
The adhesiveness with 03 was improved.

Subsequently, in order to perform solid phase epitaxial growth of the amorphous silicon 104 using the porous silicon 102 as a seed crystal, a heat treatment was performed at 600 ° C. for 8 hours to completely crystallize the amorphous silicon layer 104.

Thereafter, the bonded substrates were mixed with 49% hydrofluoric acid and 1%.
Mixed solution of 00% alcohol and 30% hydrogen peroxide (10: 6: 5
0) and then selective etching was performed. Since the porous silicon layer 102 is completely removed,
After being separated into the SUS substrate 103 side, the SUS substrate was washed / dried with water.

Epitaxial growth was performed by the LPCVD apparatus under the conditions shown in Table 7, and the film thickness of the silicon layer 107 was set to about 50.
μm.

[0092]

[Table 7] PSG was deposited at 6000Å using an atmospheric pressure CVD device, and using this as a diffusion source, thermal diffusion of P was performed at a temperature of 950 ° C to form an n ⁺ layer of 0.1μ.
m formed. Then, after removing PSG by etching, I
TO transparent conductive film (820Å) / collector electrode (Cr / Ag / Cr (200Å / 1
μm / 400Å)) was formed on the n ⁺ layer.

The IV characteristics of the thin-film crystalline silicon solar cell thus obtained were measured under AM1.5 (100 mW / cm ² ) light irradiation. The open-circuit voltage was 0.58 V, short-circuit photocurrent was 30 mA / cm ² , and The fill factor is 0.77, and the energy conversion efficiency is
13.4% was obtained.

Example 6 In the same manner as in Examples 4 and 5, p ⁺ μc-Si / crystalline silicon hetero solar cells were prepared.

Using the substrate prepared in Example 3, LPC
Epitaxial growth was performed by the VD apparatus under the formation conditions shown in Table 6 so that the thickness of the silicon layer was about 50 μm.

Ordinary plasma C on the epitaxial layer
Using a VD apparatus, 200 Å of p-type μc-Si was deposited under the conditions shown in Table 8. At this time, the dark conductivity of the μc-Si film was ˜10 S · cm ⁻¹ .

[0097]

[Table 8]

After forming the hetero-type pn junction in this manner, ITO as a transparent conductive film was vapor-deposited with about 850 Å electron beam, and the collector electrode (Cr / Ag / Cr (200 Å / 1 μm / 400
Å)) formed.

The IV characteristics of the p ⁺ μc-Si / crystalline silicon hetero solar cell thus obtained under AM1.5 light irradiation were measured. The open voltage was 0.62 V and the short-circuit photocurrent was 32 mA /
A cm ² and a fill factor of 0.7 were obtained, and a high conversion efficiency of 13.9% was obtained. By using the heterojunction in this way, a higher open circuit voltage can be obtained. As described above, according to the present invention, it has been shown that a good quality single crystal silicon layer can be formed on a metal substrate, and a high quality and inexpensive solar cell can be manufactured thereby.

[0100]

As described above, according to the present invention, it is possible to form a crystalline thin film solar cell having excellent characteristics on a metal substrate. As a result, it has become possible to provide a mass-produced, inexpensive, high-quality thin solar cell to the market.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a manufacturing process of a semiconductor substrate of the present invention.

FIG. 2 is a graph showing the time dependence of the thickness of porous silicon and single crystal silicon etched by a selective etching solution.

[Explanation of symbols]

 101 Silicon Wafer 102 Porous Silicon Layer 103 Metal Substrate 104 Non-Single Crystalline Silicon Layer 105 Silicide Layer 106 Solid Phase Epitaxial Layer 107 Epitaxial Silicon Layer

Claims (20)

[Claims] 1. A method of manufacturing a semiconductor substrate having a two-layer structure of metal / semiconductor, i) depositing a non-single crystal silicon layer on a metal substrate, and ii) a step of making the surface of the single crystal silicon substrate porous. Iii) contacting the surface of the non-single-crystal silicon layer on the metal substrate with the surface of the porous layer on the single-crystal silicon substrate, and iv) the non-single-crystal surface facing the porous layer by heat treatment. Solid phase epitaxial growth of the crystalline silicon layer to form a single crystal, and simultaneously forming a silicide layer at the interface between the metal substrate and the non-single crystalline silicon; and v) removing the porous layer by selective etching And a step of separating the single crystal silicon substrate and the single crystallized silicon layer on the metal substrate from each other. 2. The method for manufacturing a semiconductor substrate according to claim 1, wherein the non-single crystal silicon layer is an amorphous silicon layer. 3. The method for manufacturing a semiconductor substrate according to claim 1, wherein the porous layer is formed by anodization. 4. The method for manufacturing a semiconductor substrate according to claim 1, wherein the selective etching is performed using a mixed solution of hydrofluoric acid, alcohol, and hydrogen peroxide solution. 5. The method of manufacturing a semiconductor substrate according to claim 1, wherein impurities are introduced into the non-single crystal silicon layer during or after the deposition of the non-single crystal silicon layer. 6. A method of manufacturing a solar cell using a solid-phase epitaxial film, comprising the steps of i) depositing a non-single crystal silicon layer on a metal substrate, and ii) making the surface of the single crystal silicon substrate porous. Iii) contacting the surface of the non-single-crystal silicon layer on the metal substrate with the surface of the porous layer on the single-crystal silicon substrate, and iv) the non-single-crystal surface facing the porous layer by heat treatment. Solid phase epitaxial growth of the crystalline silicon layer to form a single crystal, and simultaneously forming a silicide layer at the interface between the metal substrate and the non-single crystalline silicon; and v) removing the porous layer by selective etching A step of separating the single crystal silicon substrate and the single crystal silicon layer on the metal substrate, and vi) forming a silicon epitaxial layer on the single crystal silicon layer by a thin film epitaxial growth method. Step and, vii) a method for manufacturing a solar cell characterized by comprising the steps of forming a semiconductor junction in the epitaxial layer surface that. 7. The method for manufacturing a solar cell according to claim 6, wherein the non-single-crystal silicon layer is an amorphous silicon layer. 8. The method for manufacturing a solar cell according to claim 6, wherein the porous layer is formed by anodization. 9. The method of manufacturing a solar cell according to claim 6, wherein the selective etching is performed using a mixed solution of hydrofluoric acid, alcohol, and hydrogen peroxide solution. 10. The method for manufacturing a solar cell according to claim 6, wherein impurities are introduced into the non-single crystal silicon layer during or after the deposition of the non-single crystal silicon layer. 11. A step of: i) depositing a non-single crystal silicon layer on a metal substrate; ii) a step of making the surface of the single crystal silicon substrate porous; iii) a non-single crystal silicon layer on the metal substrate. And the step of contacting the surface of the porous layer on the single crystal silicon substrate, and iv) by heat treatment to solid-phase epitaxially grow the non-single crystal silicon layer facing the porous layer at the same time. Forming a silicide layer at the interface between the metal substrate and the non-single-crystal silicon, and v) removing the porous layer by selective etching to remove the single-crystal silicon substrate and the single-crystal silicon on the metal substrate. A semiconductor substrate having a metal / semiconductor two-layer structure, which is obtained through a process of separating layers. 12. The semiconductor substrate according to claim 11, wherein the non-single crystal silicon layer is an amorphous silicon layer. 13. The semiconductor substrate according to claim 11, wherein the porous layer is formed by anodization. 14. The semiconductor substrate according to claim 11, wherein the selective etching is performed using a mixed solution of hydrofluoric acid, alcohol, and hydrogen peroxide solution. 15. The semiconductor substrate according to claim 11, wherein impurities are introduced into the non-single crystal silicon layer during or after the deposition of the non-single crystal silicon layer. 16. A step of: i) depositing a non-single crystal silicon layer on a metal substrate; ii) a step of making the surface of the single crystal silicon substrate porous; iii) a non-single crystal silicon layer on the metal substrate. And the step of contacting the surface of the porous layer on the single-crystal silicon substrate, and iv) heat-treating the non-single-crystal silicon layer facing the porous layer to form a single crystal by solid-phase epitaxial growth. Forming a silicide layer at the interface between the metal substrate and the non-single-crystal silicon; and v) removing the porous layer by selective etching to remove the single-crystal silicon substrate and the single-crystal silicon on the metal substrate. A step of separating the layers, vi) a step of growing a silicon epitaxial layer on the single crystallized silicon layer by a thin film epitaxial growth method, vii) a semiconductor junction on the surface of the epitaxial layer A solar cell characterized by being obtained through a process of forming. 17. The solar cell according to claim 16, wherein the non-single-crystal silicon layer is an amorphous silicon layer. 18. The solar cell according to claim 16, wherein the porous layer is formed by anodization. 19. The solar cell according to claim 16, wherein the selective etching is performed using a mixed solution of hydrofluoric acid, alcohol, and hydrogen peroxide solution. 20. The solar cell according to claim 16, wherein impurities are introduced into the non-single-crystal silicon layer during or after the deposition of the non-single-crystal silicon layer.