JP2012186229A - Manufacturing method for single-crystal silicon thin film, manufacturing method for single-crystal silicon thin-film device, manufacturing method for solar cell device, single-crystal silicon thin film, and single-crystal silicon thin-film device and solar cell device including the single-crystal silicon thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a single-crystal silicon thin film, which easily performs etching of a sacrificial layer when a single-crystal silicon thin film is manufactured using epitaxial lift off (ELO), a manufacturing method for a single-crystal silicon thin-film device, a manufacturing method for a solar cell device, a single-crystal silicon thin film, and a single-crystal silicon thin-film device and a solar cell device including the single-crystal silicon thin film.SOLUTION: A sacrificial layer 2 which has etching selectivity to and has an epitaxial property with respect to silicon is provided on a surface of a single-crystal silicon substrate 1. A single-crystal silicon thin film 40 is epitaxially grown on the sacrificial layer 2. A plurality of penetration holes 42 are formed through the single-crystal silicon thin film 40. The sacrificial layer 2 is etched through the penetration holes 42, thereby separating a single-crystal silicon thin film 4.

Description

  The present invention relates to a method for producing a single crystal silicon thin film, a method for producing a single crystal silicon thin film device, a method for producing a solar cell device, a single crystal silicon thin film, a single crystal silicon thin film device using the same, and a solar cell device.

  As a conventional method for producing a single crystal silicon thin film, the following methods (a) to (e) are known.

(A) Oxygen ion implantation method A method of fabricating a single crystal silicon / silicon dioxide / single crystal silicon substrate structure by performing heat treatment after implanting oxygen ions into a single crystal silicon substrate (see Patent Document 1). .

  However, this method has a problem that, when oxygen ions are implanted into a single crystal silicon substrate, there are many defects in the upper single crystal silicon and the cost of ion implantation is high.

(B) Hydrogen ion implantation method After implanting hydrogen ions (H ⁺ and H ⁻ ) into a single crystal silicon substrate and bonding them to a support substrate, heat treatment is performed to destroy and peel off the layer into which hydrogen ions have been implanted. In this method, a single crystal silicon thin film on the order of sub-μm is formed on a support substrate.

  However, in this method, since the hydrogen injection depth remains on the order of sub-μm, for example, in the application of solar cells, a single-crystal silicon thin film is thickened to about 10 μm by chemical vapor deposition or physical vapor deposition at a high temperature of 1000 ° C. or higher. However, it is difficult to obtain an inexpensive substrate that satisfies the requirements of heat resistance and thermal expansion force. Further, it is impossible to thicken the hydrogen ion implanted layer before peeling it from the substrate because the hydrogen ion implanted layer is broken under the thickened condition (see Patent Document 2). There is also a problem that the cost of ion implantation is high.

(C) Porous silicon method When the surface of the single crystal silicon substrate is anodized, pores can be formed with high density. The surface of the pores is oxidized and the oxide layer is removed only in the vicinity of the outer surface with hydrofluoric acid. After annealing in a hydrogen atmosphere, the outermost surface returns to a single-crystal continuous film with many voids below it. Containing structure is possible. This is a method of separating a single crystal silicon thin film by pasting it on a support substrate and then chemically dissolving a layer containing voids by a liquid phase method or mechanically destroying it with a water jet or the like. (See Patent Document 3).

  However, in this method, the upper silicon film thickness is only about 1 μm, to which the surface tension contributes, and in order to apply it to a solar cell, it is essential to increase the film thickness by the CVD method. Furthermore, there is also a problem that the single crystal silicon substrate is damaged at the time of peeling due to mechanical breakage, and the repeated use is limited. Also, the process is complicated and requires many steps.

(D) Melt recrystallization method / melt crystallization method A silicon dioxide film, a polycrystalline or amorphous silicon thin film, and a protective film made of silicon dioxide are laminated in this order on a silicon substrate, and a linear melt zone formed by lamp heating or the like is formed. By performing scanning, a polycrystalline silicon thin film having a crystal grain size developed in the in-plane direction can be produced. Thereafter, the protective film is removed with a chemical solution, the polycrystalline silicon thin film is thickened by a CVD method, and then the silicon dioxide film is etched with hydrofluoric acid to separate the polycrystalline silicon thin film (Patent Document 4). reference).

  However, since a polycrystalline silicon thin film can only be obtained by this method, power generation efficiency is inferior, and there is a problem that the silicon substrate is deteriorated when the molten zone is scanned. It consists of steps and is complicated.

(E) Epitaxial lift-off (ELO) method using sacrificial layers having different elemental compositions In the epitaxial lift-off (ELO) method, a single crystal substrate is used as a mold, a sacrificial layer is epitaxially grown thereon, and a target film is further formed thereon. Is epitaxially grown and the sacrificial layer is removed to obtain a single crystal thin film of the target material.

  By the way, the single crystal silicon substrate is excellent in power generation efficiency, safety and stability when used as a solar cell, but its cost is a problem. At present, high-purity silicon raw materials used for solar cells account for most of the cost of solar cells. Therefore, if single crystal silicon can be replaced with a thin film from the substrate, the problem of cost can be solved.

  Therefore, the present inventor has proposed a method of manufacturing a single crystal silicon thin film by the ELO method (see Patent Documents 5 and 6).

  Here, it is proposed that the ELO method can be applied even to silicon by using a metal silicide, a doped silicon layer, or a silicon layer including crystal defects as a sacrificial layer. Specifically, on a single crystal silicon substrate, a layer having a composition different from that of pure silicon, specifically, a metal silicide, highly doped silicon, or a silicon layer containing crystal defects is epitaxially grown as a sacrificial layer (intermediate layer). Further, a single crystal silicon thin film is formed by epitaxially growing silicon thereon, and the single crystal silicon substrate and the single crystal silicon thin film are separated by chemically etching and removing the sacrificial layer. A method of manufacturing a single crystal silicon thin film while repeatedly reusing a substrate was proposed.

  However, even the method using the sacrificial layer as described above has a problem that it takes a long time to remove the sacrificial layer by etching. That is, when removing the sacrificial layer, it is removed by etching through a through hole provided in the single crystal silicon substrate. However, the pitch of the through holes that can be formed in the single crystal silicon substrate is approximately the same as the thickness of the substrate. Considering the pitch of the through holes and the thickness of the sacrificial layer, it is necessary to perform an etching process with an aspect ratio of about 1000 times. Even if an etchant having a large etching rate difference between the sacrificial layer and the single crystal silicon is used, the etching process takes a long time. There was a problem that it was necessary to do.

JP 2000-077732 A Japanese Patent Laid-Open No. 11-040785 JP 05-275663 A Japanese Patent Application Laid-Open No. 07-226528 International Publication No. 2002/040751 Pamphlet International Publication No. 2005/069356 Pamphlet

  The present invention relates to a method for manufacturing a single crystal silicon thin film, a method for manufacturing a single crystal silicon thin film device, a method for manufacturing a solar cell device, and a method for manufacturing a solar cell device, which facilitate etching of a sacrificial layer when manufacturing a single crystal silicon thin film using ELO. An object is to provide a single crystal silicon thin film, a single crystal silicon thin film device using the same, and a solar cell device.

  According to a first aspect of the present invention for achieving the above object, a sacrificial layer having etching selectivity with respect to silicon and having an epitaxial relationship is provided on the surface of a single crystal silicon substrate, and the single crystal silicon is provided on the sacrificial layer. Epitaxially growing a thin film, forming a plurality of through holes in the single crystal silicon thin film, etching the sacrificial layer through the through holes, and separating the single crystal silicon thin film, Is in the way.

  According to a second aspect of the present invention, in the method for producing a single crystal silicon thin film according to the first aspect, the step of forming a crystal growth inhibiting portion is performed after the sacrifice layer is provided or before the sacrifice layer is provided. A crystal growth inhibiting portion is partially provided on the sacrificial layer, the single crystal silicon thin film is grown on the sacrificial layer provided with the crystal growth inhibiting portion, and the crystal growth inhibiting portion of the single crystal silicon thin film is formed on the sacrificial layer. In the method of manufacturing a single crystal silicon thin film, the silicon including a crystal defect in a corresponding portion is selectively etched to form the through hole.

  According to a third aspect of the present invention, there is provided the method for producing a single crystal silicon thin film according to the second aspect, wherein the crystal growth inhibition portion is made of an amorphous material or a silicon compound. It is in the manufacturing method of a thin film.

  According to a fourth aspect of the present invention, there is provided the method for producing a single crystal silicon thin film according to the second aspect, wherein the crystal growth inhibiting portion is provided in a predetermined pattern. is there.

  According to a fifth aspect of the present invention, in the method for producing a single crystal silicon thin film according to any one of the second to fourth aspects, the crystal growth inhibition portion is 1 to 100 times the thickness of the single crystal silicon thin film. In the method of manufacturing a single crystal silicon thin film, the first crystal silicon thin film is provided at intervals of

According to a sixth aspect of the present invention, in the method for producing a single crystal silicon thin film according to any one of the first to fifth aspects, the sacrificial layer is highly doped silicon doped with other elements, silicon containing crystal defects. And a method for producing a single crystal silicon thin film, characterized by being formed of a material selected from calcium fluoride (CaF ₂ ).

According to a seventh aspect of the present invention, in the method for producing a single crystal silicon thin film according to any one of the first to sixth aspects, the opening area of the through hole is 100 to 10,000 μm ^2. It is in the manufacturing method of a thin film.

  An eighth aspect of the present invention is the method for producing a single crystal silicon thin film according to any one of the first to seventh aspects, wherein the single crystal silicon thin film has a thickness of 5 to 100 μm. It exists in the manufacturing method of a silicon thin film.

  A ninth aspect of the present invention is the method for producing a single crystal silicon thin film according to any one of the first to seventh aspects, wherein the single crystal silicon thin film has a thickness of 5 to 50 μm. It exists in the manufacturing method of a silicon thin film.

  According to a tenth aspect of the present invention, there is provided a method for manufacturing a single crystal silicon thin film device, wherein a single crystal silicon thin film device is manufactured using the method for manufacturing a single crystal silicon thin film according to any one of the first to ninth aspects. It is in.

  An eleventh aspect of the present invention resides in a method for producing a solar cell device, comprising producing a power generation layer for a solar cell using the method for producing a single crystal silicon thin film according to any one of the first to ninth aspects. .

  A twelfth aspect of the present invention is a single crystal silicon thin film having a thickness of 5 to 100 μm and having a plurality of through holes.

  A thirteenth aspect of the present invention is the single crystal silicon thin film according to the twelfth aspect, wherein the single crystal silicon thin film has a thickness of 5 to 50 μm.

  A fourteenth aspect of the present invention is the single crystal silicon thin film according to the twelfth or thirteenth aspect, wherein the through holes are formed in a predetermined pattern.

According to a fifteenth aspect of the present invention, in the single crystal silicon thin film according to any one of the twelfth to fourteenth aspects, an opening area of the through hole is 100 to 10,000 μm ² , and a surface of the through hole is made of silicon (111 ) Surface, the single crystal silicon thin film is characterized.

  A sixteenth aspect of the present invention is a single crystal silicon thin film device characterized by using the single crystal silicon thin film according to any one of the twelfth to fifteenth aspects.

  A seventeenth aspect of the present invention is a solar cell device using the single crystal silicon thin film according to any one of the twelfth to fifteenth aspects.

It is sectional drawing which shows the manufacturing process of the single crystal silicon thin film which concerns on one Embodiment of this invention. It is sectional drawing which shows the manufacturing process of the crystal growth inhibition part of this invention. It is sectional drawing which shows the other example of the manufacturing process of the crystal growth inhibition part of this invention. It is a figure which shows schematic structure of the single crystal silicon thin film of one Embodiment of this invention. It is sectional drawing which shows the other example of the formation process of the sacrificial layer of this invention. It is sectional drawing which shows the manufacturing process of the single crystal silicon thin film which concerns on other embodiment of this invention. It is sectional drawing which shows the manufacturing process of the single crystal silicon thin film which concerns on other embodiment of this invention. It is the scanning electron microscope image (a) of the surface of the single crystal silicon thin film which has the polycrystalline-silicon part which has a crystal defect, and the scanning electron microscope image (b) of a cross section. It is a photograph of the single crystal silicon thin film peeled off from the single crystal silicon substrate and transferred onto the glass substrate.

Hereinafter, the present invention will be described in detail based on embodiments.
FIG. 1 is a cross-sectional view showing a process of a method for producing a single crystal silicon thin film according to an embodiment.

  First, as shown in FIG. 1A, a single crystal silicon substrate 1 is prepared. The single crystal silicon substrate 1 is, for example, a (100) single crystal silicon wafer, and for example, a substrate having a thickness of 400 to 700 μm can be used.

Next, as shown in FIG. 1B, a sacrificial layer 2 is epitaxially grown on the surface of the single crystal silicon substrate 1. Here, the sacrificial layer 2 only needs to have etching selectivity with respect to silicon, and a single crystal silicon thin film or a single crystal silicon substrate to be manufactured is preferably not mixed with a metal element. Preferably, a material selected from highly doped silicon highly doped with other elements, silicon containing crystal defects, and calcium fluoride (CaF ₂ ) can be used.

Here, the heavily doped silicon is silicon doped with other elements selected from Group III to Group V elements at a high concentration, and a silicon source and a dopant source are supplied to the surface of the single crystal silicon substrate 1 at a predetermined ratio. Thus, the sacrificial layer 2 made of highly doped single crystal silicon can be formed. Here, preferably, other elements include boron (B) and phosphorus (P). Further, high concentration means that the dopant concentration is 10 ¹⁸ atoms / cm ³ or more.

  Highly doped silicon can also be formed by doping the surface of the single crystal silicon substrate 1 with another element selected from group III or group V elements by thermal diffusion or ion implantation. Details of this method will be described later.

In addition, silicon containing crystal defects has etching selectivity with respect to silicon including crystal defects. Examples of crystal defects include twins, vacancies, interstitial atoms, edge dislocations, and screw dislocations. Can be mentioned. Here, the crystal defect has etching selectivity with respect to silicon if the number density is 1 / μm ² to 1 / nm ² at the interface between the single crystal silicon substrate 1 and the sacrificial layer 2.

  A method for forming the sacrificial layer 2 made of silicon containing such crystal defects is, for example, by growing silicon epitaxially under film forming conditions with a relatively high residual gas pressure and a relatively low temperature. The sacrificial layer 2 made of single crystal silicon containing can be grown. In the case of the sacrificial layer 2 made of silicon containing such crystal defects, as will be described later, before the single crystal silicon thin film is epitaxially grown on the sacrificial layer 2, twin crystal or the like is obtained by annealing in a reducing atmosphere. It is preferable to eliminate the twins on the surface of the sacrificial layer 2 made of silicon containing the above crystal defects.

Further, when the sacrificial layer 2 made of calcium fluoride is used, it can be formed by, for example, vacuum deposition using calcium fluoride as a raw material.
Here, the thickness of the sacrificial layer 2 is preferably, for example, 100 nm to 1000 nm.

  Next, as shown in FIG. 1C, crystal growth inhibition units 3 are provided in a predetermined pattern, for example, arranged in a lattice pattern with a predetermined interval.

Here, the crystal growth inhibiting part 3 is made of an amorphous material or a silicon compound, and examples thereof include SiO _x , SiN _x , SiC, and SiO _x N _y . The crystal growth inhibiting unit 3 may be any unit that inhibits epitaxial growth and forms silicon containing crystal defects when the single crystal silicon thin film 40 is epitaxially grown on the sacrificial layer 2. Crystals that do not match may be used.

  An example of a method of providing the crystal growth inhibition unit 3 arranged in such a predetermined pattern is shown in FIGS.

In the first method, as shown in FIG. 2 (a), a sacrificial layer 2 is provided on a single crystal silicon substrate 1, and then, as shown in FIG. 2 (b), in a predetermined pattern made of a resist or the like. After providing the mask 6 having the provided opening 6a, as shown in FIG. 2C, a material such as SiO _{2 is formed in the} opening 6a by sputtering or the like, as shown in FIG. In addition, the crystal growth inhibiting portion 3 is formed in a predetermined pattern.

In the second method, a sacrificial layer 2 is provided on a single crystal silicon substrate 1 as shown in FIG. 3A, and then crystal growth inhibition such as SiO _{2 is} inhibited as shown in FIG. 3B. After the film 30 is provided on the entire surface, a resist mask 7 of a dot-shaped pattern 7a patterned by photolithography is provided, and then the crystal growth inhibition film 30 whose surface is exposed is removed by etching, and FIG. ), The crystal growth inhibiting portion 3 is formed in a predetermined pattern.

  The formation method of the crystal growth inhibition part 3 is not limited to this, and the formation method is not particularly limited as long as it can be formed in a predetermined pattern. For example, the crystal growth inhibiting portion 3 may be pattern printed on the sacrificial layer 2 by an inkjet method.

Moreover, the crystal growth inhibition part 3 may be arrange | positioned at random. For example, by spraying silica sol on the sacrificial layer 2, the crystal growth inhibiting portion 3 made of randomly disposed SiO ₂ can be formed.

  A process after providing the crystal growth inhibiting part 3 on the sacrificial layer 2 will be described.

  As shown in FIG. 1D, a high-purity single crystal silicon thin film 40 with few crystal defects is epitaxially grown on the sacrificial layer 2 provided with the crystal growth inhibiting portion 3.

  As a method for epitaxially growing the single crystal silicon thin film 40, there is a physical vapor deposition (PVD; Physical Vapor Deposition) method. Generally, it is used as a method of growing silicon slowly at low temperature in an ideal environment (ultra-high vacuum or the like) in a laboratory. On the other hand, in a production process, a chemical vapor deposition (CVD) method is used as a method for depositing a semiconductor layer at a high speed at a high speed.

When the single crystal silicon thin film is epitaxially grown by the CVD method, for example, when chlorosilane is used as a raw material, the film formation rate is rate-determined by desorption of chemical species such as SiCl ₂ and HCl, and the vicinity of 1200 ° C. is 1-10 μm / min. The growth rate is the limit. Although the speed can be increased by increasing the temperature, it is likely to be the rate of raw material supply, and a practical upper limit is several μm / min. This is almost the same speed as the lower limit of the film formation rate for preventing the sacrificial layer 2 from being deteriorated, and it is difficult to suppress the deterioration of the sacrificial layer 2 by the CVD method. Further, when doped silicon is used as the sacrificial layer 2, when a single crystal silicon thin film is grown on the sacrificial layer 2 of the doped silicon by the CVD method, a single crystal silicon thin film of 10 μm is formed at the above growth rate. Since it takes 1-10 minutes and the dopant diffuses into the single crystal silicon thin film 40 within that time, there is a problem that the sacrificial layer 2 cannot be maintained.

  On the other hand, in the PVD method, since only silicon is adsorbed, there is no desorption of chemical species. Therefore, the upper limit of the desorption rate limit is exceeded, and the film formation rate can be increased arbitrarily. However, if the film formation rate is increased too much, silicon does not grow epitaxially at low temperatures, and becomes polycrystalline or amorphous. However, for example, melt growth of silicon at a melting point of 1410 ° C. is known to epitaxially grow at a rate of 10 mm / s, that is, 600,000 μm / min. Therefore, if the temperature is raised to near the melting point, epitaxial growth can also be performed by a rapid vapor deposition (RVD) method.

The characteristics of the RVD method will be specifically described in the case of using heavily doped silicon using B or P as the sacrificial layer 2. If the thickness of the target single crystal silicon thin film 40 is 10 μm, the thickness of the sacrificial layer 2 is desirably 1/10 or less, that is, 1 μm or less. When the dopant (B, P) diffuses by 1 μm, the structure of the sacrificial layer 2 deteriorates. The time constant is represented by (1 μm) ² / D, where D is the diffusion coefficient. Since it is necessary to grow the single crystal silicon thin film 40 by 10 μm or more within this time, the film formation speed GR needs to be GR> 10D / 1 μm. By using the relationship between the known diffusion coefficient D and temperature T, GR> 2 × 10 ¹² exp (−325 [kJ / mol] /8.31 [J / mol · K] / (T + 273) [K]) A relational expression is obtained. Actually, when PVD was performed at a substrate temperature of 800 ° C. and a silicon melt temperature of 1800 ° C., the single crystal silicon thin film 40 was successfully epitaxially grown at 10 μm / min. This means that the growth was 20000 times faster than the target film formation rate, and it is clear that the structure deterioration of the sacrificial layer 2 can be easily suppressed.

  As described above, when the single crystal silicon thin film 40 is epitaxially grown, since it does not grow epitaxially on the crystal growth inhibiting portion 3, a polycrystalline silicon portion 41 containing many crystal defects is formed. That is, in the present invention, when the single crystal silicon thin film 40 is epitaxially grown, the polycrystalline silicon portion 41 is formed in the region corresponding to the crystal growth inhibiting portion 3 in the single crystal silicon thin film 40.

  Since such a polycrystalline silicon portion 41 has etching selectivity with respect to single crystal silicon, as shown in FIG. 1E, only the polycrystalline silicon portion 41 is mixed with, for example, hydrofluoric acid and an oxidizing agent. The through-hole 42 can be formed by removing by selective etching with a solution. Note that the polycrystalline silicon portion 41 formed on the crystal growth inhibiting portion 3 does not necessarily have to be polycrystalline, as long as it is made of silicon containing crystal defects and has etching selectivity with respect to single crystal silicon. Good.

  Next, as shown in FIG. 1 (f), the sacrificial layer 2 is selectively etched through the through holes 42 to remove the sacrificial layer 2 to manufacture the single crystal silicon thin film 4 having the through holes 4a. it can. Here, the crystal growth inhibition portion 3 is also removed by selective etching, or the boundary between the crystal growth inhibition portion 3 and the single crystal silicon thin film 40 is etched, and the through hole 42 reaches the sacrifice layer 2. Note that the single crystal silicon substrate 1 from which the single crystal silicon thin film 4 is separated can be reused.

  Here, the selective etching of the sacrificial layer 2 can be easily performed using, for example, a hydrofluoric acid / nitric acid / acetic acid mixed solution as an etchant when the sacrificial layer 2 is highly doped silicon. In the case where the sacrificial layer 2 is silicon containing crystal defects, it can be selectively etched with a mixed solution of hydrofluoric acid and an oxidizing agent, for example, in the same manner as the polycrystalline silicon portion 41. The selective etching of the crystalline silicon portion 41 can also be performed continuously. When the sacrificial layer 2 is made of calcium fluoride, selective etching can be performed using nitric acid, for example.

  In the present invention, the selective etching of the sacrificial layer 2 can be performed through the through-holes 42 formed at a predetermined pitch in the single crystal silicon thin film 40 that is significantly thinner than the single crystal silicon substrate 1. In a short time.

  In the method for manufacturing a single crystal silicon thin film of the present invention described above, the sacrificial layer 2 can be efficiently removed through the through hole 42 provided in the single crystal silicon thin film 40. Can be manufactured at cost. In particular, when the RVD method is adopted, not only the productivity is increased by increasing the epitaxial growth rate of the single crystal silicon thin film 40, but also the structure change of the sacrificial layer 2 is shortened because the time during which the entire substrate is exposed to high temperature is shortened. And the separation between the single crystal silicon thin film 4 and the single crystal silicon substrate 1 by selective etching of the sacrificial layer 2 becomes good, and as a result, a single crystal silicon thin film 4 having high purity and no defects can be obtained. It will be a promising process.

  A schematic configuration of the single crystal silicon thin film 4 thus formed is shown in FIG. The single crystal silicon thin film 4 has through holes 4a in a predetermined pattern. The through-hole 4a has a square opening in the drawing, but actually has various shapes depending on the shape of the crystal growth inhibiting portion. On the other hand, the surface (inner surface) of the through-hole 4a is formed by the (111) surface 5 of silicon.

  Here, the thickness of the single crystal silicon thin film 4 is not particularly limited, and a thickness of about 200 μm or more can be formed relatively easily, but the thickness of 5 μm to 50 μm which cannot be easily formed conventionally. A flexible single crystal silicon thin film can also be manufactured relatively easily.

Here, the size and interval of the through-holes 4a are the thickness of the single crystal silicon thin film 4 and the process time for selective etching of the sacrificial layer 2, and the arrangement state when the through-holes 4a are used in a later device fabrication process. It may be set as appropriate in consideration of the above, and is not particularly limited. For example, the opening area of the through-hole 4a is 100 μm ² (10 μm square) to 10,000 μm ² (100 μm square), the interval is 10 to 1000 μm, preferably 100 to 1000 μm, and the coverage is about 0.01 to 50%, preferably , About 0.01 to 10%.
Such a single crystal silicon thin film 4 cannot be manufactured conventionally.

  Further, when the single crystal silicon thin film 4 is used in a single crystal silicon thin film device, the through hole 4a may be effectively used for wiring or the like. Of course, it goes without saying that a single crystal silicon thin film device may be manufactured without using the through hole 4a.

  In the embodiment described above, the example in which the sacrificial layer 2 is formed by epitaxial growth has been described. However, the present invention is not limited to this. For example, the surface of the single crystal silicon substrate is doped with another element by a diffusion method or an ion implantation method and annealed. Thereby, a sacrificial layer (portion doped with other elements) can be provided on the surface of the single crystal silicon substrate. In this method, a sacrificial layer having an epitaxial relationship with a substantially continuous crystal structure with the single crystal silicon substrate is formed. Therefore, as in the above-described embodiment, after the crystal growth inhibition portion is provided, the single crystal silicon thin film is formed. Is grown epitaxially, and then the sacrificial layer is similarly removed, whereby a similar single crystal silicon thin film can be obtained.

  Further, in the method of doping other elements into the single crystal silicon substrate, the crystal growth inhibiting portion can be formed before the sacrifice layer is formed. An example of this is shown in FIG.

  In this method, as shown in FIG. 5A, after the crystal growth inhibiting portion 3 is provided in a predetermined pattern on the single crystal silicon substrate 1, other elements are doped as shown in FIG. 5B. . As a result, the surface layer portion of the single crystal silicon substrate 1 becomes the sacrificial layer 2A. The subsequent processes can be performed in the same manner as in the above-described embodiment.

  Furthermore, in the above-described embodiment, in order to form a through-hole in the single crystal silicon thin film, a crystal growth inhibition portion is provided, and the single crystal silicon thin film is epitaxially grown to provide a polycrystalline silicon portion. Although the through hole is removed by selective etching, the method of forming the through hole in the single crystal silicon thin film is not limited to this.

6 and 7 show another example of forming a through hole in a single crystal silicon thin film.
6, the sacrificial layer 2 is formed on the single crystal silicon substrate 1 as shown in FIGS. 6A and 6B, and then the sacrificial layer 2 as shown in FIG. After the single crystal silicon thin film 40A is formed thereon, as shown in FIG. 6D, a mask 8 having openings 8a in a predetermined pattern is provided, and then as shown in FIG. 6E, the single crystal silicon thin film is formed. The region corresponding to the opening 8a of 40A is anisotropically etched to form the through hole 42A. Thereafter, as shown in FIG. 6F, the sacrificial layer 2 is removed by selective etching through the through-hole 42A, and the single crystal silicon thin film 4 is manufactured.

  7A, the sacrificial layer 2 is provided on the single crystal silicon substrate 1, and then the single crystal silicon thin film 40B is epitaxially grown on the sacrificial layer 2, as shown in FIG. As shown in b), a doped silicon portion 41B is provided in the single crystal silicon thin film 40B by doping other elements through a mask 9 having an opening 9a. Next, as shown in FIG. 7C, the doped silicon portion 41B is removed by selective etching to form a through hole 42B as shown in FIG. 7D. Thereafter, as shown in FIG. 7E, the sacrificial layer 2 is removed by selective etching through the through hole 42B, and the single crystal silicon thin film 4 is manufactured.

Example 1
The result of the study performed in the procedure of FIGS. 3 and 1 will be described. A sacrificial layer 2 was formed on the surface of the (100) single crystal silicon substrate 1 by doping phosphorus by ion implantation. The doping amount was 1 × 10 ²⁰ atoms / cm ³ or more, and the thickness of the sacrificial layer 2 was 120 nm. On the sacrificial layer 2, a 100 nm thick SiO ₂ film was formed by sputtering, and a resist layer was formed by spin coating. Further, a resist mask 7 having a dot-like pattern 7a was formed on the resist by UV lithography, and the SiO ₂ film was etched to form the dot-like crystal growth inhibiting portion 3. Here, the crystal growth inhibiting part 3 has a size of 20 μm square and is provided in a lattice shape with a pitch of 100 μm. A single crystal silicon thin film 40 having a thickness of about 10 μm was epitaxially grown on this substrate by depositing silicon at 1100 ° C. for 1 min by the RVD method. Then, the result of mild etching with a mixed solution of hydrofluoric acid, nitric acid and acetic acid is shown in FIG. FIG. 8A is a scanning electron microscope image of the surface of the single crystal silicon thin film, and it can be seen that etching of the surface of the single crystal silicon thin film starts with a pattern corresponding to the crystal growth inhibition portion. FIG. 8B is a scanning electron microscope image of the cross section of the same sample. It can be seen that polycrystalline silicon containing a crystal defect in a trapezoidal shape with the inhibition portion as the base is formed in the single crystal silicon thin film. .

(Example 2)
Here, the result of examining the lift-off method in the procedure of manufacturing the single crystal silicon thin film shown in FIGS. 3 and 1 will be described. After the single crystal silicon thin film 40 including the polycrystalline silicon portion 41 is provided on the single crystal silicon substrate 1 in the same manner as in the first embodiment according to the procedure shown in FIGS. Was immersed in an etchant composed of a mixed solution of hydrofluoric acid, nitric acid and acetic acid. This etchant is adjusted so that there is a difference in etching rate between the single crystal silicon thin film 40 and the polycrystalline silicon portion 41, and the etching rate of the polycrystalline silicon portion 41 is increased. As a result, only the polycrystalline silicon portion 41 was etched, and a through hole 4a leading from the surface to the sacrificial layer 2 was formed.

  Subsequently, the etchant reaches the sacrificial layer 2 through the formed through-hole 4a, the dissolution of the sacrificial layer 2 around the through-hole 4a starts, and the lateral direction (in the depth direction of the through-hole) with respect to the through-hole 4a. Etching in the orthogonal direction) proceeds. Finally, the etching of the sacrificial layer 2 proceeding laterally from the respective through holes 4a in the plane of the single crystal silicon thin film 40 is connected to each other, and the single crystal silicon thin film 4 which is epitaxially grown serves as a template. 1 was peeled off.

  FIG. 9 is a photograph of the single crystal silicon thin film 4 that was peeled from the single crystal silicon substrate 1 and transferred onto the glass substrate.

  The present invention is suitable for manufacturing a single crystal silicon thin film device, in particular, a power generation layer of a solar cell, a single crystal silicon thin film substrate of a semiconductor device, and the like.

DESCRIPTION OF SYMBOLS 1 Single crystal silicon substrate 2 Sacrificial layer 3 Crystal growth inhibition part 4 Single crystal silicon thin film 4a Through hole 40, 40A, 40B Single crystal silicon thin film 41 Polycrystalline silicon part 42, 42A, 42B Through hole

Claims (17)

A sacrificial layer having etching selectivity with respect to silicon and having an epitaxial relationship is provided on the surface of the single crystal silicon substrate,
Epitaxially growing a single crystal silicon thin film on the sacrificial layer;
A method for producing a single crystal silicon thin film, comprising: forming a plurality of through holes in the single crystal silicon thin film; and etching the sacrificial layer through the through holes to separate the single crystal silicon thin film. In the manufacturing method of the single-crystal silicon thin film of Claim 1,
After the sacrificial layer is provided or before the sacrificial layer is provided, a step of forming a crystal growth inhibition portion is performed to partially provide the crystal growth inhibition portion on the sacrificial layer,
The single crystal silicon thin film is grown on the sacrificial layer provided with the crystal growth inhibiting portion, and the silicon including crystal defects in a portion corresponding to the crystal growth inhibiting portion of the single crystal silicon thin film is selectively etched. A method for producing a single crystal silicon thin film, wherein the through-hole is used. In the manufacturing method of the single-crystal silicon thin film of Claim 2,
The method for producing a single crystal silicon thin film, wherein the crystal growth inhibition portion is made of an amorphous material or a silicon compound. In the manufacturing method of the single-crystal silicon thin film of Claim 2,
A method for producing a single crystal silicon thin film, wherein the crystal growth inhibiting portion is provided in a predetermined pattern. In the manufacturing method of the single-crystal silicon thin film of any one of Claims 2-4,
The method for producing a single crystal silicon thin film, wherein the crystal growth inhibiting portions are provided at an interval of 1 to 100 times the thickness of the single crystal silicon thin film. In the manufacturing method of the single-crystal silicon thin film of any one of Claims 1-5,
The sacrificial layer is formed of a material selected from highly doped silicon doped with other elements, silicon containing crystal defects, and calcium fluoride (CaF ₂ ). Method. In the manufacturing method of the single-crystal silicon thin film of any one of Claims 1-6,
The opening area of the through hole, the method for producing a single-crystal silicon thin film, which is a 100~10000μm ^2. In the manufacturing method of the single-crystal silicon thin film of any one of Claims 1-7,
The method for producing a single crystal silicon thin film, wherein the single crystal silicon thin film has a thickness of 5 to 100 μm. In the manufacturing method of the single-crystal silicon thin film of any one of Claims 1-7,
The method for producing a single crystal silicon thin film, wherein the single crystal silicon thin film has a thickness of 5 to 50 μm.   A method for producing a single crystal silicon thin film device, comprising producing a single crystal silicon thin film device using the method for producing a single crystal silicon thin film according to any one of claims 1 to 9.   A method for producing a solar cell device, comprising producing a power generation layer for a solar cell using the method for producing a single crystal silicon thin film according to any one of claims 1 to 9.   A single crystal silicon thin film having a thickness of 5 to 100 μm and comprising a plurality of through holes.   13. The single crystal silicon thin film according to claim 12, wherein the single crystal silicon thin film has a thickness of 5 to 50 [mu] m.   The single crystal silicon thin film according to claim 12 or 13, wherein the through holes are formed in a predetermined pattern. 15. The single crystal silicon thin film according to claim 12, wherein an opening area of the through hole is 100 to 10,000 μm ² , and a surface of the through hole is configured by a (111) plane of silicon. A single crystal silicon thin film characterized by comprising:   A single crystal silicon thin film device using the single crystal silicon thin film according to any one of claims 12 to 15. A solar cell device using the single crystal silicon thin film according to any one of claims 12 to 15.