WO2008088298A1

WO2008088298A1 - Method for producing thin semiconductor films

Info

Publication number: WO2008088298A1
Application number: PCT/UA2007/000005
Authority: WO
Inventors: Volodymyr Sergiyovych Khokhlachov; Victor Andreevich Philippenko
Original assignee: Khokhlachov Volodymyr Sergiyov
Priority date: 2007-01-17
Filing date: 2007-01-17
Publication date: 2008-07-24

Abstract

The invention relates to novel and improved thin semiconductor films and to methods for producing thin crystalline semiconductor films which are applicable to different types of substrates. Said films can be flexible. The inventive methods consist in forming a multi-porous semiconductor structure comprising two or more different porosity layers by producing the combined through time action of anode oxidation, electromagnetic radiation, magnetic and electric fields and ultrasonic oscillations. The thin semiconductor film is grown on a porous structure. Electrodes and/or required carrier substrate can be connected to the grown layer. The grown layer is separated from a semiconductor substrate where the porous structure has the lowest strength. The separated semiconductor layer secured on the carrier substrate can be, afterwards, used for producing improved film devices, solar batteries, solar cells and light-emitting diodes. The inventive thin semiconductor films are perfect in terms of the crystalline structure thereof and, therefore, are cheap in production and are suitable for producing low-cost solar cells and light-emitting diodes.

Description

METHOD FOR MANUFACTURING THIN FILMS OF SEMICONDUCTORS

Technical field

This invention relates to the field of semiconductor technology and electronics, and in particular to methods for manufacturing thin films of semiconductors, including for solar cells and emitting diodes. In particular, the invention relates to methods for forming semiconductor film layers on a substrate with a plurality of porous layers described herein that have controlled and relatively different porosities.

State of the art

The properties of a large number of materials for their possible application for the manufacture of solar cells were studied on this topic. Silicon, which is the second most abundant element in the earth's crust (silicon makes up 26% of the earth’s mass) and whose properties do not cause concern about possible environmental pollution, is of particular interest for research. The vast majority of solar cells (more than ninety percent of the production of solar cells) in the world are made on the basis of silicon. The challenges facing the developers of solar cells are to reduce the cost of the solar cell, increase the efficiency of conversion of the electromagnetic radiation of the Sun into electricity, increase operational reliability and minimize the time period for returning the energy spent for the manufacture of solar cells. To meet the requirements for a high conversion efficiency and high reliability, monocrystalline silicon is currently the best material for its use for the production of solar cells, but at the same time it is difficult to obtain monocrystalline silicon of solar quality at a low price. Therefore, in the field of solar cells, in particular in the field of solar cells with large surface area, active research and development work on solar cells using thin films based on polycrystalline silicon or amorphous silicon is ongoing. In thin-film solar cells based on polycrystalline silicon, the purity of silicon is increased by the technology of distillation from the initial - metallurgical silicon. An ingot is formed by the casting process, while the substrate is formed using multi-wire cutting or other high speed separation technology. However, the process for removing phosphorus and boron from metallurgical silicon, the preparation of a high-quality ingot by casting into molds, increasing the surface area of the substrate, and the multi-wire cutting process or other high-speed separation process require a very high level of technology, therefore the substrates that were substantially would be cheaper and have good performance at the moment have not yet been produced. In addition, the thickness of the substrate films is approximately 200 micrometers, and this fact makes it difficult to manufacture a flexible substrate.

Amorphous silicon on the surface of the substrate can be formed from plastic using vapor deposition technology. Therefore, the formation of a flexible thin layer of amorphous silicon is possible. As a result, solar cells having a wide range of applications can be formed. However, there are disadvantages of amorphous silicon in that the conversion coefficient is lower than that of polycrystalline silicon and single-crystal silicon, and the conversion coefficient very much and quickly degrades during operation.

Monocrystalline silicon allows to obtain high values of the coefficient of conversion of solar energy into electrical energy and high operational reliability. Thin films based on single-crystal silicon can be fabricated using silicon on an insulator technology, which is used in integrated circuits, but this technology has low productivity. Using this technology, manufacturing costs become very significant, and this is a problem for the application of this technology for the production of cheap solar cells.

Also, the temperature of the technological process in the production of single-crystal silicon is relatively high; therefore, this process is difficult to carry out on a plastic or glass substrate with low thermal resistance of the substrates. Difficulties in producing single-crystal silicon on a plastic substrate make it difficult to produce flexible thin films based on single-crystal silicon.

The prior art [US6326280] discloses a method for manufacturing thin semiconductor films in the manufacture of thin single-crystal silicon solar cells, in accordance with which at least one anodizing of a semiconductor substrate in a solution of hydrofluoric acid and ethyl alcohol electrolyte (HF + C ₂ H ₅ OH) and form three porous layers. Two with low porosity and one with high porosity. After that, a high-temperature annealing of the semiconductor substrate is carried out with a surface porous layer formed at the stage of anodizing in a hydrogen reducing atmosphere. After that, a thin-film single-crystal structure of a solar cell having a pth junction with a p ⁺ region is grown on the surface of a low-porous layer using an epitaxial growth process. A flexible support substrate is adhered to the resulting thin semiconductor film. A flexible support substrate with a thin semiconductor substrate is separated from the semiconductor substrate using an external tensile force. Metallization is carried out and an antireflection coating is applied.

The disadvantages of this method, in particular, include the impossibility of producing thin single-crystal films of large area and, accordingly, solar cells consisting of them, which significantly affects the cost and efficiency of the latter. Due to the fact that it is not possible to produce thin single-crystal films and large-area solar cells, their cost cannot to be low. It is not possible to obtain solar cells with high rates of conversion of solar radiation to electricity. So, the indicated solar corporation [US6326280] and its employees obtained solar cells with the best efficiency indicators for converting solar radiation into electricity equal to efficiency = 12.5% and the maximum solar cell area of 4.0 cm ² .

Also, which is very important in this process of manufacturing thin single-crystal films and solar cells, the anodization process in this prototype is relatively poorly controlled, which can cause destruction of the porous layer at the stage of its formation during the anodization process, especially when anodizing at high density anodizing current. The critical factors ensuring the success of photovoltaic energy for industrial manufacturing and commercial use are: the efficiency of converting solar radiation into electricity, the production of large area solar cells (substrates with formed solar cells based on them with dimensions of 150 x 150 cm or more) at low the cost of production, production, ensuring ease of manufacture and reliability, stability of reproduction of the characteristics of solar cells, the service life of the solar cell, the efficiency degradation value during operation, payback of a solar cell during its operation for generating electric energy. In the prototype of the method cannot reproduce the characteristics of the solar cell. In particular, such characteristics as the peeling of the formed solar cell over the entire area from the substrate, which is associated with a wide range of strength properties of the formed porous structure, on which the solar cell is held during the manufacturing process. It is not possible to separate the formed thin single-crystal structure from the initial semiconductor substrate — separation occurs by parts of the area of the formed semiconductor single-crystal structure. So, during the process of separation of a thin single-crystal silicon solar cell, destruction often occurs solar cell. This destruction of the solar cell is caused by the heterogeneity of the strength of the structure of the porous structure, which in turn is caused by the heterogeneity of the process of anodizing the surface of the semiconductor substrate during the formation of the porous structure. Also, the disadvantages of this prototype method include a rather large thickness of the porous layer formed by anodizing. So the minimum thickness of the porous layer formed by anodizing is S / Jt -

2OjUm, which is an essential part of the semiconductor substrate and, accordingly, determines the cost of a future solar cell or device formed on a given porous structure, i.e. the structure of the future device includes the cost of the material of the semiconductor substrate used to obtain the porous structure, as well as the cost of chemicals, electricity, staff wages (during such a long anodizing process). Such substantial thicknesses of the porous structure increase the cost of the solar cell and, accordingly, reduce its competitiveness. The disadvantages of this method include the relatively low efficiency of converting solar radiation into electricity. Thus, the efficiency of converting solar radiation into electricity by companies producing solar cells based on monocrystalline silicon on an industrial scale reaches 22%, and laboratory samples reach 25%. Such differences in the efficiency of converting solar radiation into electric energy of solar cells manufactured by employees of the Japanese corporation [US6326280] and industrially manufactured, for example, by the SшiРоwer-Sorroratiop corporation producing solar cells based on single-crystal silicon, are associated with an unsatisfactory porous structure, as well as the entire solar cell and its structure as a whole. The nonuniform area of the semiconductor substrate and the non-optimal porous structure, on which the single-crystal silicon structure of the solar cell subsequently epitaxially grows, causes stresses on the surface in contact with the epitaxially growing single-crystal layer and these stresses generate dislocations and crystal defects structure of the future single-crystal silicon solar cell. In turn, these defects in the crystal structure cause the capture of electric charge carriers generated during the illumination of the solar cell by electromagnetic radiation of the Sun, and their combination, which in turn reduces the efficiency of conversion of solar radiation into electricity.

The essence of the invention

The objective of the invention is to provide a method for manufacturing thin semiconductor films, which allows to obtain thin semiconductor films of large surface areas with a high degree of crystalline perfection including to create solar cells with high photovoltaic conversion efficiency of a solar cell at low manufacturing costs and high process performance.

The problem is solved by creating a method for manufacturing thin semiconductor films in which the following are successively carried out: at least one anodizing of the semiconductor substrate in a hydrofluoric acid based electrolyte solution to produce a porous layered structure; high temperature annealing in a reducing atmosphere of hydrogen; epitaxial build-up of a thin semiconductor film; bonding a flexible support substrate to the resulting thin semiconductor film; the destruction of the highly porous layer and the separation of the flexible supporting substrate with a thin semiconductor film from the semiconductor substrate; metallization. Moreover, in accordance with the invention:

- the anodization current density is set in the range from 1 mA / cm ² to 2 mA / cm ² ; - when anodizing a semiconductor substrate, an additional effect is exerted by a magnetic field and / or an electric field and / or electromagnetic radiation and / or ultrasound;

- high-temperature annealing is carried out for 1 minute to 1 hour at a temperature of 900-1400 ° C; - epitaxial build-up of a thin semiconductor film is carried out at a temperature of 800-1400 ° C for from 1 minute to 1 hour; breaking stress for separating a thin semiconductor film from a semiconductor substrate is caused by application of: thermal stresses (occurring during cooling and / or heating), and / or ultrasound, and / or mechanical stresses by dissection by mechanical incorporation.

Moreover, in accordance with the invention, the wavelength of electromagnetic radiation during anodization is set in the range from gamma radiation to 100 μm.

Moreover, in accordance with the invention, the value of the magnetic field energy density during anodization is set in the range 1 - 1 - W ³ J / cm ³ .

Moreover, in accordance with the invention, the value of the energy density of the electric field during anodization is set in the range of 1 - 1 - IQ ³ J / cm ³ .

Moreover, in accordance with the invention, the value of magnetic induction during anodization is set in the range of 1 to 10 T.

Moreover, in accordance with the invention, the value of the magnetic field during anodization is set in the range of 1 A / m - 1-10 ³ AZM.

Moreover, in accordance with the invention, the value of the electric field during anodization is set in the range of 1 V / m - 1 - 10 ³ V / m. Moreover, in accordance with the invention, the value of the power density of ultrasonic vibrations during anodization is set in the range 1 - 10 ^"1 W / cm ² - 1 W / cm ² .

Moreover, in accordance with the invention, the value of the frequency of ultrasonic vibrations during anodization is set in the range of 1 10 Hz to 1-10 Hz. Moreover, in accordance with the invention, a semiconductor substrate with a resistance of 0.001 Ω • cm - 1 Ω • cm is used for anodizing.

Moreover, in accordance with the invention, a semiconductor substrate with a dopant concentration of 10 ¹⁸ -10 ²² atoms / cm ^{3 is} used during anodization. Moreover, in accordance with the invention, the concentration of hydrofluoric acid in the electrolyte solution is in the range of 1-100%. Moreover, in accordance with the invention, during anodization, the electrolyte solution has a pH of 1-7.

Moreover, in accordance with the invention, with anodizing, permanent magnets and / or solenoids (inductors) are used to create a magnetic field.

Moreover, in accordance with the invention, a direct current source and / or an alternating current source and / or a pulse current source are used as an anodizing current source.

Moreover, in accordance with the invention, an electromagnetic radiation source with a constant and / or variable and / or pulsed power density of electromagnetic radiation is used as the source of electromagnetic radiation during anodization.

Moreover, in accordance with the invention, a lamp and / or a matrix of emitting diodes and / or a laser are used as a source of electromagnetic radiation with a constant and / or variable and / or pulsed power density of electromagnetic radiation.

Moreover, in accordance with the invention, the electromagnetic radiation source is structurally made in the form of a perforated plate, permeable to the electrolyte solution in the places of its perforation, transparent to electromagnetic radiation and resistant to the chemical effect of the electrolyte.

Moreover, in accordance with the invention, in the anodizing process, exposure to a magnetic field and / or an electric field and / or electromagnetic radiation and / or ultrasound is carried out periodically or continuously.

Moreover, in accordance with the invention, when anodizing, the effect of a magnetic field and / or electric field and / or electromagnetic radiation and / or ultrasound is constantly in the direction of action and / or changes in the Cartesian coordinate system, for example, it is concentrated and / or decreases per unit area processed semiconductor substrate.

Moreover, in accordance with the invention, the energy density of the magnetic field and / or the energy density of the electric field and / or the power density of electromagnetic radiation and / or the power density of ultrasound at doping is left unchanged and / or increased and / or decreased, including pulse and / or periodically and / or with a constant component of the increment, where the constant component lies in the range from 1 to 100% of the numerical value of the physical influencing factor, and the change in the influencing factor lies in the time range from 10 ^bp . up to 5 minutes

As a result of this, we obtain an ultrathin silicon monocrystalline solar cell of perfect quality with a thickness of 1 to 100 μm, peeled from the original substrate with a surface area of 100, 1000 or more cm ^{2 of} pre-anodized surface. DETAILED DESCRIPTION OF THE INVENTION

A part of the surface of the semiconductor substrate is treated with at least one exposure that is simultaneous with the process of anode treatment — electromagnetic radiation, magnetic field, electric field, and ultrasonic vibrations to form many porous layers having varying degrees of porosity adjacent to the surface of the semiconductor substrate.

In a preferred embodiment, the substrate is anodized during the first anode treatment at a first current density, electromagnetic radiation power density, ultrasonic vibration power density, magnetic field energy density and electric field to provide a first porous layer adjacent to a surface having a first porosity. The second stage of anode processing is carried out after the first stage of processing, and a large current density is used, as well as a high power density of electromagnetic radiation, a high power density of ultrasonic vibrations, a high energy density of the magnetic field and electric field to provide a second porous layer adjacent to the first porous layer, moreover, the porosity of the second porous layer is greater than the porosity of the first porous layer. The difference in porosity between the first porous layer and the second porous layer provides an unremovable line or zone of relative mechanical weakness of the porous material relative to the adjacent layers, and this weakness is concentrated in the second porous layer or adjacent to it the interface between the first porous layer and the second porous layer. The line of low strength or brittleness introduced by deformation caused by the difference in the constant lattices of adjacent porous layers allows interlayer separation of the porous layers and any films grown on them from the remaining second porous layer and substrate. In a particularly preferred embodiment, the third stage of anode processing is performed at a third higher current density, as well as a third higher power density of electromagnetic radiation, power density of ultrasonic vibrations, magnetic field energy density and electric field to form a third porous layer having a third porosity greater than the second porous layer . The third porous layer is located inside the second porous layer or adjacent to the second porous layer. According to an embodiment, a relative line of low strength is defined by a third porous layer or on or an adjacent interface formed between the third porous layer and the second porous layer. After the construction of porous layers adjacent to the surface of the substrate, at least one semiconductor film layer is formed on the surface of the first porous layer. After that, the semiconductor film is separated from the semiconductor substrate along the line of relative fragility to obtain a semiconductor thin-film device. In accordance with the invention, a thin semiconductor film is made by changing the surface of the semiconductor substrate by forming a porous structure including two or more porous layers having different porosity, growing a semiconductor film on the surface of the porous structure, and separating, removing and / or peeling the semiconductor film from a semiconductor substrate in a controlled or controlled manner along the line of frailty created in a layered porous structure.

In addition, in the manufacturing process of solar cells in accordance with the claimed invention, solar cells are produced by a method comprising the steps of changing the surface of a semiconductor substrate to form a porous structure including two or more porous layers having different porosity, epitaxial a layer having different porosity, epitaxial build-up of a semiconductor film including a plurality of layers constituting the solar cell on the surface of the porous structure, and peeling or separation of the semiconductor film of the epitaxial multilayer from the semiconductor substrate along the friability line specified in the layered porous structure.

In addition, in the process for manufacturing emitting diodes in accordance with this invention, emitting diodes are manufactured by a method using the steps of changing the surface of a semiconductor substrate by forming a layered porous structure including two or more layers, including a first porous layer constituting the light emitting a region and a second porous separating layer having a large porosity located below and behind the light-emitting region, peeling or separation of the light-emitting region from uprovodnikovoy brittle substrate along a line defined in the separating layer layered porous structure.

As indicated above, in accordance with the process of the present invention, the surface of the semiconductor wafer is changed by the formation of a porous layer, the semiconductor layer is formed on the substrate by epitaxial growth, and this semiconductor layer is peeled off from the semiconductor substrate by destruction in the porous layer or on the interface with the porous layer, it turns out the intended thin semiconductor film or solar cell. Accordingly, an epitaxially extended semiconductor layer can be formed with any desired film thickness. Further, peeling of the semiconductor thin film from the substrate can be reliably performed by suitably selected strength of the porous layer, for example, by selecting porosity in the porous structure of the corresponding porous layers. As described above, in accordance with this invention, a thin film of a semiconductor can be obtained with any sufficient thickness with good performance. In addition, in the production of solar cells, solar cells with a high conversion rate of light into electricity can be formed on the basis of that the active part composed by this epitaxial layer can be composed substantially thin and it can be formed by a thin single-crystal semiconductor film that is grown epitaxially. In addition, since it is now possible to obtain a flexible structure, various applications, for example, applications for a solar car, etc., become easy to manufacture.

In addition, in the embodiment of the light emitting diode in accordance with this invention, the superstructure can be formed by porous layers having different porosities and therefore, an improvement in emissivity can be achieved.

In addition, in the design embodiment, a method for manufacturing thin semiconductor films is provided, comprising the following steps: forming a porous layer having a first porosity on a substrate surface, forming a second porous layer on its surface, inside or below said first porous layer having a second porosity of large than said first porosity, forming at least one thin semiconductor layer on said surface, separating said thin semiconductor layer from said of the substrate along the line with the relative lowest strength of the porous structure defined in or adjacent to the indicated first and second porous layers, wherein said first and second porous layer are formed by the joint action in time of electrochemical exposure (anodization), electromagnetic field, magnetic field, electric field and ultrasonic vibrations.

An embodiment provides a thin semiconductor film formed in accordance with a method including the steps of: providing a semiconductor substrate having a surface, forming a first porous layer having a first porosity on the surface of said substrate, forming a second porous layer on, in, or below said first porous a layer having a second porosity greater than that of the first porous layer, the formation of at least one thin semiconductor layer on a specified surface minute, and separating said semiconductor thin a nickel layer from said substrate along the line of relative least strength of a porous structure defined in or adjacent to said first and second porous layers to obtain said thin semiconductor structure, said first and second porous layers being formed by the combined action of the time of electrochemical exposure (anodizing) electromagnetic radiation, magnetic field, electric field and ultrasonic vibrations.

Hereinafter, the term “combined combined anode processing” refers to the combined time effect of electrochemical exposure (anodization), electromagnetic radiation, magnetic field and electric field and ultrasonic vibrations.

Hereinafter, the term "processing parameters" refers to the numerical values of physical quantities, namely: electrochemical effects (anodizing) expressed in

electromagnetic radiation expressed in [Bm / cm ² \, magnetic field and electric field expressed in the energy density of the electric and magnetic fields, B is the magnetic induction Tn = ψ у ₂ J ₅ H is the magnetic field strength γу J, E is the stress

electric field ψ // M \, D - electric displacement ψ / уM ₂ | and ultra

sound vibrations expressed in [W / cm ² ], which they take when processing a semiconductor substrate in a hydrofluoric acid based electrolyte solution.

A thin semiconductor film is formed, formed in accordance with a method including the steps of: providing a semiconductor substrate having a surface, combined combined anodic treatment of said semiconductor substrate with first processing parameters to provide a first porous layer adjacent to said surface having first porosity , combined combined anode treatment of the specified semiconductor substrate with second processing parameters greater than specified first processing parameters to ensure the second porosity adjacent to the specified first porous layer opposite of said surface, said second porous layer has a second porosity greater than said first porous layer, annealing said semiconductor substrate in a hydrogen atmosphere after said steps of anodizing said semiconductor substrate to provide a second porous layer, and forming at least one semiconductor layer on said surface .

An embodiment provides a thin semiconductor film formed in accordance with a method including the steps of: providing a semiconductor substrate having a surface, forming a first porous layer adjacent to the surface and having first porosity on the surface of said substrate, forming a second porous layer in said the first porous layer having a second porosity greater than that of the first porous layer, the formation of at least one thin semiconductor with laying on said surface, and separating said thin semiconductor layer from said substrate along a line of relative lowest strength of a porous structure defined in or adjacent to said first and second porous layers to obtain said thin semiconductor layer.

An embodiment provides a thin semiconductor film formed in accordance with a method including the steps of: providing a semiconductor substrate having a surface, forming one porous layer adjacent to a surface having porosity on the surface of said substrate, forming at least one thin semiconductor layer on said surface, and separating said thin semiconductor layer from said substrate along a line of relative least strength n Risto structure to obtain said thin semiconductor layer.

According to an embodiment of the present invention, the surface of the semiconductor substrate can be altered by combined combined anodic treatment to form a porous structure including two or more porous layers, each of which has a different porosity. Behind- thereby, a semiconductor film is grown on the surface of this porous structure by epitaxial. After that, this epitaxial semiconductor layer peels off or separates from the semiconductor substrate along the line of weakness formed in the porous structure to obtain the intended thin film of the semiconductor.

On the other hand, the remaining semiconductor substrate can be repeatedly reused for the production of the above thin semiconductor films. In addition, this semiconductor substrate, which becomes thinner due to repeated use, can be used as a thin semiconductor film.

At the stage of formation of the porous layer, a layer with low porosity is formed on the surface of the substrate. After that, a layer with high porosity is formed under the interface (in this description, the interface of the semiconductor substrate means the interface of the semiconductor substrate, which is made of a non-porous and porous layer) between the layer with low porosity and the semiconductor substrate.

In addition, in the step of forming a porous layer, for example, a layer with a low porosity on the substrate surface, an intermediate porous layer is formed below the low porosity layer having a higher porosity than the surface layer, and a layer with high porosity is formed in this intermediate porous layer or beneath the intermediate porous layer, can be formed having a greater porosity than that of the intermediate porous layer. The porous layer may be formed by a combined combined anode treatment. This combined combined anode treatment includes at least two or more steps carried out with different processing parameters.

In addition, for peeling off a thin semiconductor film, ultrasonic vibrations, thermal stresses, stresses caused by the action of a compressed liquid jet or air jet, guillotine knives, wire cutting, adhesion of supporting substrates to a thin one are used: a semiconductor layer, followed by separation of these supporting substrates together with a thin semiconductor layer, and a combination of these means.

In addition, in the joint combined anode treatment step, the composition of the electrolyte solution can be changed when the processing parameters are changed.

After the formation of the porous layer, the layer is preferably heated in an atmosphere of hydrogen. Furthermore, after the formation of the porous layer and before the step of heating in a hydrogen atmosphere, preferably the porous layer is thermally oxidized.

Various types of semiconductor substrates can be used for this invention. The semiconductor substrate may be composed of various semiconductor substrates, such as single crystal substrates of silicon, polycrystalline silicon, or a complex semiconductor substrate, such as, for example, a gallium arsenide single crystal.

Preferably, a single-crystal silicon substrate is used to produce single-crystal silicon thin films and solar cells in which single-crystal silicon thin films are used as the material of the solar cell. In addition, n is a type or p is a type of semiconductor substrate or an undoped semiconductor substrate can be used. For anodizing in the present invention, it is desirable to use a semiconductor substrate having a low resistance, doped with a p type of impurity at a high impurity content, that is, the so-called p ⁺ type silicon substrate. As a p ⁺ type of a silicon substrate, a silicon substrate in which boron is a p type of impurity is doped at _and

having its resistance at a level of from 0.01 to 0.02 Ωcm.

In addition, p - type or p - type of semiconductor substrate is used during joint combined anode processing. In addition, the concentration of impurities in the semiconductor substrates used during the joint combined anode treatment of p - type or p - type is at a level of \ tf ^b \ amomov /

^L / cm ¹

In addition, the electrical resistance of the semiconductor substrates used during the joint combined anode treatment of p - type or p - type is at a level of from 0.001Ωszh to lΩszh.

As indicated above, the semiconductor layer is epitaxially grown on the porous layer while it maintains its crystallinity. Due to this, it is possible to form a single crystal semiconductor layer. In addition, when a solar cell or other device is running, the grown semiconductor layer may include multi-semiconductor layers of various types of conductivity.

According to the present invention, a semiconductor layer epitaxially grown on a porous layer is separated from the semiconductor substrate due to direct fracture of the porous layer. Before peeling or peeling, the support substrate includes, for example, a flexible plastic sheet, and can be attached to the semiconductor film as a support substrate. The semiconductor film may be peeled off from the semiconductor substrate together with the support substrate by means of a porous layer formed on this semiconductor substrate.

This support substrate is not limited to a flexible sheet. As a supporting substrate, it is possible to use a glass substrate, a polymer substrate, or a flexible or rigid transparent printed circuit board on which the required printed attachments are applied.

Two or more porous layers having different porosity are formed on the surface of the semiconductor wafer. The first porous layer of the outermost surface is preferably formed as a thick porous layer that has a relatively low porosity to obtain improved growth of the epitaxial semiconductor film on this porous surface. that layer. By forming a second porous layer having a relatively large region of internal porosity adjacent to the surface and the first porous layer, the mechanical strength decreases due to the large porosity of the second porous layer or, in other words, the bond between the first and second porous layers becomes brittle due to stresses caused by the difference in the constant lattices of each of these layers. Due to this, the separation of the epitaxial semiconductor layer, or separation, can be easily done by means of a layer with high porosity. For example, it is also possible to form such a fragile porous layer that will separate by ultrasound.

The formed highly porous layer is easy to peel off due to its greater porosity, but if this porosity is very large, failure in the highly porous layer can occur before the stage of exfoliation of the semiconductor layer from the porous structure. Therefore, porosity in this highly porous layer is preferred at a level of 40 to 98 percent.

In addition, with increasing porosity, deformation increases. If the effect of this deformation becomes large, cracks in the surface layer may appear in the surface layer of the first porous layer. In addition, if the influence of deformation reaches the surface of the porous layer, crystal defects may appear in the epitaxial semiconductor film grown on the porous layer. Therefore, in the porous layer, an intermediate porous layer having an intermediate porosity that is greater than that of the surface layer but less than that of the layer with high porosity is preferably formed between the highly porous layer and the surface porous layer. In this case, the intermediate porous layer may be a stress relief buffer layer. The porosity of the highly porous layer can be made large enough so that the peeling of the epitaxial semiconductor layer can be reliably carried out. Additionally, an epitaxial semiconductor layer, which is perfect in crystallinity, can be formed on the porous layer. Anodizing to change the surface of a semiconductor substrate to form a porous layer can be carried out by a well-known method. For example, a double electrolytic bath method. The schematic structural view shown in FIG. 1., used in a double electrolytic bath process. In this method, the electrolyte solution of cell 1 has a first IA and a second IB cell. A semiconductor substrate 11 on which a porous layer is to be formed is installed between two cells IA and IB. Two platinum electrodes ZA and ZV are connected to a constant current source 2 installed between the first and second cells IA and IB. In the first and second cells IA and IB, the electrolyte solution 4 contains, for example, hydrofluoric acid and ethanol (ethyl alcohol) or hydrofluoric acid and methanol (methyl alcohol). The semiconductor substrate 11 is installed so that its two surfaces are in contact with the electrolyte solution 4 in the first and second cells IA and IB. Two platinum electrodes ZA and ZV are installed immersed in an electrolyte solution 4. Two sources of electromagnetic radiation A are immersed in an electrolyte solution in cells IA and IB and are located on each side of the anodized semiconductor substrate 11. A magnetic field source B made in the form of a solenoid encompasses an electrolytic bath 1 with its magnetic field inside the inductance coil 1. The source of ultrasonic vibrations B is connected to the electrolytic bath 1. The electric field source (not shown in the figure) acts on semiconductor substrate 11 with its field during its anodization in the electrolytic bath 1.

First, the magnetic field of the solenoid and the electric field of the corresponding sources are turned on. Then, the source of ultrasonic vibrations B is turned on, then the electromagnetic radiation source A, then, the current is supplied between the two electrodes of the electrodes ZA and ZV using a constant current source 2 and using the ZA electrode as a cathode. The current is supplied in such a way that the surface of the semiconductor substrate 11 facing its surface to the ZA electrode corrodes and becomes porous. According to the method of a double electrolytic cell, it becomes unnecessary to cover the semiconductor substrate with an ohmic electrode and the introduction of contaminants into the semiconductor substrate from the ohmic electrode is avoided. The structure of the porous layer can be changed by the selection of modes during the anodization process, whereby the crystallinity of the semiconductor layer is formed on the porous layer and the peeling properties change.

In the process of the present invention, as indicated above, a porous layer is formed composed of two or more layers having different porosities. In this case, a multi-stage anodizing method is used composed of two or more steps carried out at different current densities. More specifically, to prepare a relatively dense, porous layer with low porosity having small fine-grained pores on the surface of the semiconductor substrate, the first anodizing step is performed at a low current density. The film thickness of the porous layer is proportional to the anodizing time, therefore, at this stage, the anodizing time is selected to form the desired layer thickness. After this, the second anodization is carried out at a higher current density so as to form a highly porous layer under the formed porous layer with a low porosity. As a result, a porous layer is formed including at least a low porosity layer having a low porosity and a highly porous layer.

In this case, a large voltage can occur near the interface between the low-porosity layer and the highly porous layer due to the difference in the constant lattices. When this stress reaches a certain value or more, the porous layers are divided into two. By forming porous layers close to the critical anodizing parameters that cause separation due to stress or a decrease in mechanical strength, semiconductor films grown epitaxially on the porous layer can be easily separated due to the porous layer. Before turning on the anodizing current, turn on the lights. An incandescent lamp was used as a source and a luminous flux of electric electromagnetic radiation with a power density of 0.5 W / cm2. The luminous flux of electromagnetic radiation was turned on during the entire period of anodization and remained constant. The first anodizing step can be carried out at a low current density of 0.5 to 10 tL / cm ² over a period of 1 to 60 minutes, preferably 2 to 20 minutes, using a p-type single-crystal silicon semiconductor substrate with a resistance of 0.01 up to 0.02 Ωcm and the ratio of HF (49% solution) and C ₂ H ₅ OH (95% solution) at 1: 1 (volume parts) (hereinafter, HF and C ₂ H ₅ OH indicates volume parts of 49% solution HF and 95% solution of C ₂ H ₅ OH, respectively). Further, the second anodizing step can be carried out with a higher current density at a level of from 40 to 300 tA / cm ² over a period of 1 to 30 seconds, preferably for a period of about three seconds.

Before turning on the anodizing current, we turn on the lights. An incandescent lamp was used as a source and a luminous flux of electromagnetic radiation with a power density of 0.5 W / cm2 was created. The luminous flux of electromagnetic radiation was turned on during the entire period of anodization and remained constant. During the first and second stages of anodizing, stresses caused in the highly porous layer can become significant. Therefore, stress exposure can reach the low porosity layer. In this case, as indicated above, crystalline defects may appear in the epitaxial semiconductor film formed on the porous layer. Therefore, in the porous layer, an intermediate porous layer having a greater porosity than the surface layer but lower porosity than that of the highly porous layer is preferably formed between the highly porous and low porosity layer, as a buffer layer to relieve the stress generated by them. More specifically, the first anodization at a low current density is carried out first, the second anodization is carried out at a slightly higher current density than during the first anodization, and then the third anodization is carried out with a much higher current density than before. The conditions of the first anodization are especially unlimited, but when using the p-type single-crystal silicon substrate with a resistance of 0.01 to 0.02 Ωcm and an electrolyte solution is used (HF + C ₂ H ₅ OH = I :!), preferably the first, second and third anodizing can be carried out at a level of from 0.5 to 3 tAJcm ² , from 3 to 20 tA / cm ² , from 40 to 300 tA / cm ² , respectively. For example, when anodizing is performed at a current density of 1 tAJcm ² , 2.7 tA / cm ² , and 200 tA / cm ² , the porosity reaches 16%, 26%, and from 60 to 70%, respectively. According to the aforementioned method, a semiconductor layer having excellent crystalline properties can be epitaxially grown on a porous layer. In addition, during the anodization process, an intermediate porous layer can be formed under the low porosity layer. Accordingly, the porous layer becomes a bilayer structure of the low porosity layer and the intermediate porosity layer. Further, in the third anodizing step, if the current density is set at 90 tA / cm ² OR more, a highly porous layer is formed inside the intermediate porous layer, although the principle is not clear.

In addition, at the stage of formation of the intermediate layer, by changing the current density gradually or abruptly, an intermediate porous layer, with porosity which increases gradually or abruptly from the low porous layer to the highly porous layer, is formed between the low porous surface layer and the highly porous layer. As a result, the voltage between the low-porous layer and the high-porous layer decreases and the epitaxial semiconductor layer with good crystalline properties can be further reliably formed on the porous structure.

The separation will occur due to high stresses due to the difference in the constant lattices at the interfaces between the peeling layer (separating layer) of the highly porous layer and the buffer layer of the intermediate layer. If some special actions are carried out at the third stage of anodizing, separation becomes even easier. This is obtained by applying intermittent current in the third stage of anodizing with a high current density, for example, by applying current not continuously for 3 seconds, but by alternative steps, including applying current for one second and then switching current, with a preset time, for example, for one minute. By intermittently supplying current in discrete steps, a highly porous layer, like a separating layer, can be formed under the intermediate layer. In this case, the porous layer remaining with the semiconductor layer after separation can be removed by electrochemical polishing or other chemical or mechanical means.

As mentioned earlier, by forming a highly porous layer below the intermediate layer, the distance between the highly porous layer in which stresses are caused and the surface of the porous layer is larger and the buffer effect of the intermediate layer becomes large, so that a semiconductor layer with good crystalline properties can be formed. Moreover, when a highly porous layer is formed under the intermediate porous layer, the thickness of the whole porous layer can be reduced, and the thickness of the semiconductor substrate used to form this porous layer can be reduced, and the reuse of this semiconductor substrate can be increased.

Accordingly, by choosing the anodizing parameters it is possible to introduce large stresses into the separating layer and, in addition, protect the influence of this voltage from reaching the epitaxially growing surface of the semiconductor layer.

In order to produce epitaxial growth of a semiconductor on a porous layer with good crystalline properties, it is desirable to form the surface of the porous layer with small fine-grained pores that serve as seed crystal growth on the porous layer. For the production of small fine-grained pores, a highly concentrated solution of hydrofluoric acid can be used. In this case, at the anodizing stage with a low current density to form a low porous layer, an electrochemical solution of highly concentrated hydrofluoric acid is used. Then an intermediate porous layer is formed, which serves as a buffer layer, then the concentration of hydrofluoric acid in the electrolytic solution decreases and finally anodizing with high density is performed current. Using this process, it is possible to create the dimensions of the fine-grained pores of the surface layer very small, on which an epitaxial semiconductor layer having good crystalline properties can be formed on the porous layer. In addition, in the highly porous layer, the porosity can be increased to the required significant level, therefore, chipping of the epitaxial semiconductor layer can be carried out well.

By changing the electrolytic solution during the anodizing process, at the first stage of forming the surface of the low porous layer, anodizing is carried out using an electrolytic solution, for example, HF:

C ₂ H ₅ OH = 2: 1, at the second stage of formation of the intermediate porous layer serving as a buffer layer, anodization is carried out using a low concentration HF electrolytic solution, for example, HF: C ₂ H ₅ OH = I:!, And then, on the third stage of formation of a highly porous layer, anodizing with a high current density is carried out using an electrolytic solution with a reduced concentration of HF, for example, HF: C ₂ H ₅ OH = I :! before HF: C ₂ H ₅ OH =!:!.

In the anodizing process, when the current density changes during the period of the first stage to the second stage, the current supply can be cut off before the second stage. Or, after the first stage, the second stage can be carried out without interrupting the current supply.

In addition, the anodization process can be carried out in a dark place where light penetration is blocked, in order to make the surface irregularities of the porous layer smaller and increase the crystallinity of the semiconductor film epitaxially grown on the porous layer. Additionally, the anodized porous silicon layer can be used as a radiating diode. In this case, it is preferable that the anodizing is carried out by irradiation with light to increase the radiation efficiency. Further, by oxidizing the anodized porous layer, a purple mixing of the wavelengths of the emitting light is obtained. Further, the semiconductor substrate, which may be p-type or p-type, preferably has a high resistance so as not to introduce contamination. By using the above process, a semiconductor substrate formed on the surface (on one surface or on both surfaces) of the porous layer can be obtained. Further, the thickness of the whole porous layer is particularly unlimited, but the thickness can be from 1 to 50 μt, preferably from 3 to 15 μt, usually 8 μt. The thickness of the whole porous layer is preferably reduced as much as possible so that the semiconductor substrate can be reused.

Additionally, preferably, the porous layer is annealed prior to the epitaxial build-up of the semiconductor on the porous layer. This annealing can be hydrogen annealing, which can be carried out by heating hydrogen gas in a gas atmosphere. By hydrogen annealing, the natural oxide film formed on the surface of the porous layer can be completely removed and the oxygen atoms in the porous layer can be removed as much as possible. As a result, the surface of the porous layer becomes smoothed, and an epitaxial semiconductor layer with good crystalline properties can be formed. At the same time, with this annealing, the stress of the interface between the highly porous layer and the intermediate porous layer can be further reduced, and the separation of the epitaxial semiconductor layer from the substrate can be more easily performed. This hydrogen annealing can be carried out in the temperature range from 950 ⁰ C to 1350 ⁰ C.

In addition, the porous layer is oxidized at a low temperature before hydrogen annealing, and the inside of the porous layer is oxidized. Because of this, large structural changes do not appear in the porous layer even if heat treatment is applied in a hydrogen atmosphere. Accordingly, the stresses between the highly porous layer and the intermediate porous layer are isolated by a remote zone or separated from the surface of the first porous layer, and an epitaxial semiconductor film having good crystallinity can be formed. In this case, the low temperature Injection can be carried out in a dry oxidizing atmosphere at 400 ^° C for 1 hour.

After hydrogen annealing, as indicated previously, the semiconductor can be epitaxially grown on the surface of the porous layer. During the epitaxial growth of this semiconductor, a porous layer formed on the surface of a single crystalline semiconductor substrate maintains its crystallinity despite being porous. Therefore, epitaxial buildup onto this porous layer is possible. Epitaxial growth on the surface of this porous layer can be carried out using the process of deposition from the gas phase at temperatures, for example, 700-1300 C.

In addition, in both processes of hydrogen annealing and epitaxial growth of a semiconductor, both the method of heating a semiconductor substrate to a predetermined temperature, the so-called reactive heating system or a conductive heating system, conducting a current through a semiconductor substrate can itself be adopted for heating.

The aforementioned semiconductor layer epitaxially grown on a porous layer may be a single crystal layer of a semiconductor film or a multilayer semiconductor film formed by layering a plurality of semiconductor layers. In addition, this semiconductor layer may be from the same substance as that semiconductor substrate or another substance. As a semiconductor film, various kinds of semiconductor film or films can be used. For example, a single crystal silicon semiconductor film, a complex semiconductor gallium arsenide, etc., a complex silicon semiconductor Si Ge, or films suitably combined and composed can also be used.

In addition, in the case of a semiconductor film made of a complex semiconductor, the substrate of a complex semiconductor can be used as a substrate. In this case, by anodizing the composite semiconductor substrate, a composite semiconductor film can be formed on the porous layer. When a complex semiconductor is epitaxially dissociated tet on a porous layer made of a complex semiconductor, the mismatch of the crystal lattice parameters can be reduced in comparison with the case where the complex semiconductor is epitaxially grown on a silicon semiconductor substrate, and therefore a complex semiconductor having good crystallinity can be formed.

In addition, the p-type and p-type of impurities can be added to the semiconductor film formed on the porous layer during its epitaxial growth. As an alternative, it is also possible to add impurities over a continuous surface or selectively by ion implantation, diffusion, etc. after the formation of an epitaxial semiconductor layer. In this case, the type of conductivity and concentration and the type of impurities are selected in accordance with the object of its use.

In addition, the thickness of the epitaxial semiconductor layer may be suitably selected in accordance with the purpose of the thin semiconductor film. For example, when an integrated circuit is formed on a thin semiconductor film, since the active layer of the semiconductor element has a thickness of several micrometers, the semiconductor layer can be formed for example at a thickness of 5 μt (micrometers). Hereinafter, the sign μt indicates the unit of measurement of linear quantities - micrometers. When a semiconductor film made of monocrystalline silicon is epitaxially grown to form thin semiconductor films of solar cells, for example, a p ⁺ type semiconductor layer, an Γ type semiconductor layer, and n ⁺ a semiconductor layer type can be used in this order on the porous layer. The impurity concentrations and film thicknesses of these layers are in principle unlimited, but, for example, preferably, the p ⁺ - type semiconductor layer is specified by the film thickness in the range from 0 to 1 μt, usually 0.5 μt, and boron B, as p is the type of impurity, the concentration specified in the range from 10 ¹⁸ to 10 ²⁰ atoms / st ³ , usually at the level of 10 ¹⁹ atoms / st ³ ; p - type semiconductor layer is specified by the film thickness within the range from 1 to 100 μt, usually 5 μm, and the boron concentration is set in the range from 10 ¹⁴ to 10 ¹⁷ atoms / cm ^b , usually

10 ¹⁶ atoms / st ³ , and u ⁺ - the type of semiconductor layer is specified by the film thickness lying in the range from 0.0001 to 1 μt, usually 0.03 μt, and the concentration of phosphorus, P, arsenide, As ₅ in the range from 10 ¹⁸ up to 10 ²⁰ atoms / cm ^b , usually 10 ¹⁹ atoms / cm ³ .

In addition, the semiconductor film can be composed by epitaxial growth p ⁺ - type of silicon layer, p - type Si ^ _x Ge _x - step layer, undoped Si _x _ _y Ge _y layer, and - type Si ^ _x Ge _x - step layer, and n ⁺ - the type of silicon layer in this sequence and in this application for the preparation of a double heterostructured solar cell. Typical examples of layers for composing these double heterostructures, preferably for the p ⁺ type silicon layer, the concentration of impurities lies at 10 ¹⁹ atoms / st ³ and the layer thickness at 0.5 μt; for the p - type Sts_ _{_x} Ge _x - a stepped layer, the impurity concentration is at a level October ¹⁶ atoms / st ³ and the layer thickness at 1 μt; for an undoped Si _x _ _y Ge _y layer, the y-layer is 0.7 and the layer thickness is at level 1; for n - type Si _x _ _x Ge _x - step layer, the concentration of impurities lies at the level of 10 ¹⁶ atoms / 'st ³ and the layer thickness at the level of 1 μt; and for n ⁺ - type silicon layer, the concentration of impurities lies at the level of 10 ¹⁰ atoms / st ³ and the layer thickness at the level of 0.5 μt. In addition, the composition ratio x for Ge p - type and n - type Si _x _ _x Ge _x - step layer preferably gradually increases from x = 0 for existing layers on both sides to unalloyed Si _x _ _y Ge _y layers. Due to this, the lattice constants are comparable on the surface of the partitions, whereby good crystallinity can be achieved. In such a double heterostructured solar cell, charge carriers and light can be effectively separated in an undoped Si _x _ _y Ge _y layer, and therefore, high efficiencies of the conversion of light into electricity can be obtained. Alternatively, the manufacture of solar cells can be carried out before breaking off the semiconductor substrate. In this case, the peeling process will be carried out after the support substrate is attached to the semiconductor film formed on the porous layer and the semiconductor layer is peeled off from the semiconductor substrate together with the support substrate.

A supporting substrate in solar cells can be composed of a plurality of substrates, for example, a sheet of glass such as window glass, a metal substrate, a ceramic substrate, or a flexible substrate composed of a transparent resinous film or sheet (hereinafter, simply provided for consideration as a sheet) and so on.

Next, the steps for compiling the solar cell will be explained. It is possible to carry out these steps after or before peeling of the semiconductor film from the semiconductor substrate. In the process of compiling a solar cell, as indicated above, a multilayer silicon semiconductor film is epitaxially grown on a semiconductor substrate, on the surface of which a porous layer is formed. Further, for example, a thermal oxidation process is conducted to form an oxidized layer having a thickness of 10 to 200 pts on the surface of the semiconductor film. Then, the oxidized surface film of the semiconductor film is screened to form a bonding layer using photolithography. Alternatively, it is also possible to form holes only in areas where connections to the semiconductor layer are necessary. Further, for example, a conductive layer for composing the electrode and the interconnect layer, for example, a single metal layer such as Al or multilayer metal layers formed by layering a plurality of metal layers, are finally formed on a continuous surface by vacuum deposition, and so on, and this is a pattern for forming the required electrodes and wiring pattern by photolithography and etching. Alternatively, the electrodes and wiring pattern can be formed using screen printing, for example, contact stencil- printing, which is used in the manufacture of metallization of single-crystal and multicrystalline solar cells.

Further, the so-called printed circuit board made of a transparent polymer sheet on which the required electrodes and wiring patterns are made, that is, the so-called printed hinged elements are formed, prepared in advance and this printed circuit board is connected to the semiconductor film formed on the porous a layer for forming an electrical contact of the respective parts. At the same time, the electrodes of the semiconductor film and the printed circuit are connected, for example, by solder. Further, other parts, unlike electrodes, can be attached using a transparent bonding element, such as epoxy resin.

In this case, the adhesion of a printed circuit board and a single-crystal silicon thin film, which was not possible in the past, can be carried out especially easily in this invention. Further, in the present invention, the support substrate is not limited to a printed circuit board — a transparent sheet of material can also be adhered. After a supporting substrate such as a printed circuit board or a transparent sheet of material is attached, tensile stress can be applied to the semiconductor substrate, thereby causing destruction in the high porous layer or on the interface between the highly porous layer and the intermediate porous layer or the interface between the highly porous layer and a semiconductor substrate, the epitaxial semiconductor layer is easily peeled off from the semiconductor substrate on the supporting substrate. In this case, flexible solar cells made up of a thin semiconductor film on a support substrate such as a printed circuit board can be obtained.

After the peeling process, sometimes the porous layer remains on the back of the semiconductor film opposite the supporting substrate. In this case, it is possible to remove this porous layer, for example, by etching. Alternatively, a metal film such as silver paste used as another ohmic electrode or as a reflective film can be formed on a porous layer without removing it. This reflective surface will improve the efficiency of photoelectric conversion. Further, it is also possible to adhere a metal sheet or a polymer sheet to the back of the semiconductor film as a protective layer. On the other hand, the semiconductor substrate, from which the semiconductor film is peeled off, can be a base on its surface and is subjected to many times the same operation to form a porous layer and solar cells and so on. The thickness of the semiconductor substrate can be made, for example, at a level of 200 to 300 μt, while the thickness of the semiconductor substrate spent on the preparation of the solar cell is from 3 to 20 μt, so even the thickness consumed after ten repeated uses is from 30 to 200 μt. Therefore, the semiconductor substrate can be reused quite a lot. According to the process of the present invention, expensive single-crystal semiconductor substrates can be reused repeatedly, and therefore, solar cells can be produced with low energy consumption, while costs are reduced. Further, the semiconductor substrate obtained during processing becomes significantly thinner. After such a multiple procedure, it can itself be used to perform a solar cell.

Next, embodiments of the present invention will be explained. However, the present invention is not limited to these embodiments. First of all, an embodiment of a process for manufacturing thin semiconductor films in accordance with this invention will be explained. Brief Description of the Drawings:

Fig. L is a schematic side view of an example of an anode device for operating the present invention.

FIG. 2 (A) - 2 (C) is a cross-sectional view illustrating a sequence of steps for forming a porous structure on a semiconductor substrate in accordance with an embodiment of the method of the present invention. FIG. 3 (A) - 3 (D) is a cross-sectional view illustrating the growth stages of an epitaxial semiconductor layer, the relationship of the structural support of the semiconductor layer, the separation of the semiconductor layer from the substrate along the line of relative least strength of the porous structure defined in the porous structure to obtain a separated thin semiconductor product .

FIG. 4 (A) - 4 (D) is a cross-sectional view illustrating the steps of forming a second porous structure in accordance with an alternative embodiment. FIG. 5 (A) - 5 (B) is a cross-sectional view illustrating the steps of growing a semiconductor layer on the porous structure shown in FIG. 4 (A) - 4 (D) and separating the semiconductor layer from the semiconductor substrate. FIG. 6 (A) - 6 (E) is a cross-sectional view illustrating a sequence of steps for forming a multilayer porous structure in accordance with a third embodiment of the invention.

FIG. 7 (A) - 7 (B) is a cross-sectional view illustrating a sequence of steps for forming a semiconductor film on a porous structure made in FIG. 6 (A) - 6 (E) and the separation of the semiconductor layer from the semiconductor substrate. FIG. 8 (A) - 8 (F) is a cross-sectional view illustrating another embodiment of a process for forming a multilayer porous structure on a semiconductor substrate, forming a semiconductor film on a porous structure, and separating the semiconductor film from the semiconductor substrate. FIG. 9 (A) - 9 (D) is a cross-sectional view illustrating another embodiment of the method of the present invention for forming a multilayer porous structure on a semiconductor substrate.

FIG. 10 (A) to 10 (D) is a cross-sectional view illustrating the formation of a multilayer semiconductor film on the porous structure shown in FIG. 9 (A) - 9 (D) and the separation of the multilayer semiconductor film from the semiconductor substrate. FIG. H (A) - H (C) is a cross-sectional view illustrating the formation of a multilayer porous structure on a semiconductor substrate.

FIG. 12 (A) - 12 (B) is a cross-sectional view illustrating the formation of a multilayer semiconductor film on the porous structure shown in FIG. H (A) - P (C) and the formation and copying of the pattern of the insulating layer afterwards to determine the contact holes, respectively. FIG. 13 (A) to 13 (B) is a cross-sectional view illustrating the formation of electrodes in the contact windows of the substrate prepared in FIG. 1 (C) and the connection of the printed circuit board to the electrodes and the semiconductor substrate, respectively.

FIG. 14 (A) - 14 (B) is a cross-sectional view illustrating the separation of the structure of the solar cell panel from the semiconductor substrate and the attachment of the rear metal electrode, respectively. FIG. 15 (A) - 15 (D) is a cross-sectional view illustrating the formation of a multilayer porous structure on a semiconductor substrate. FIG. 16 (A) - 16 (B) is a cross-sectional view illustrating the formation of an epitaxially grown thin semiconductor film on a porous substrate shown in 15 (D) and the separation of a thin semiconductor film from a semiconductor film, respectively.

FIG. 17 (A) - 17 (E) is a cross-sectional view illustrating the formation of another porous structure on a semiconductor substrate and the formation of an epitaxially grown thin semiconductor film on it. FIG. 18 (A) - 18 (E) is a cross-sectional view illustrating the formation of another porous structure on a semiconductor substrate and the formation of a thin semiconductor film on it.

FIG. 19 (A) - 19 (B) is a cross-sectional view illustrating the formation of an electrode structure on a semiconductor thin film and the attachment of a conductive structural member and a transparent substrate to the structure of the solar panel, respectively. FIG. 20 (A) - 20 (B) is a cross-sectional view illustrating the separation of the structure of the solar panel from the semiconductor substrate and the attachment of the back electrode, respectively.

FIG. 21 (A) - 21 (C) is a side view of views of a plurality of solar panel structures indicating a method of the present invention through an intermediate formation step.

FIG. 22 (A) - 22 (B) is a side view of the views illustrating the shown method of the final stages of forming the solar panels prepared in FIG. 21 (A) - 21 (C). FIG. 23 is a schematic cross-sectional view of a micrograph of a main part of a porous layer during the manufacturing process of the present invention in cross-section before heat treatment.

FIG. 24 is a schematic cross-sectional view of a micrograph of a major part of a porous layer during the manufacturing process of the present invention after heat treatment.

FIG. 25 (A) - 25 (E) is a cross-sectional view illustrating the formation of a heterojunction and a porous structure on a semiconductor substrate in accordance with an embodiment of the method of the present invention for the manufacture of emitting diodes. FIG. 26 (A) - 26 (D) is a cross-sectional view illustrating the steps of attaching electrodes and a supporting substrate and separating a diode substrate from a semiconductor substrate in accordance with an embodiment of the present invention. FIG. 27 (A) - 27 (C) is a cross-sectional view illustrating the subsequent steps of attaching a second array of electrodes and a second supporting substrate in accordance with an embodiment of the present invention. FIG. 28 (A) and FIG. 28 (B) composite views of the process.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS The following are embodiments of the present invention, which, however, do not limit its scope. Implementation Example 1.

In FIG. 2 and FIG. 3 shows a process diagram of an example of implementation 1. First, a semiconductor substrate 11 was made of monocrystalline silicon, doped with boron B at a high concentration, and having a resistance of 0.02 to 0.03 Ωst (Fig. 2A).

Then, the surface of this semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. In this embodiment, anodizing was carried out using an anodizing apparatus having a two-sided structure of an electrochemical cell explained in FIG. A semiconductor substrate 11 made of monocrystalline silicon was installed between the first and second cells IA and IB, and the electrolyte solution composed of HF: C ₂ H ₅ OH = 1: 1 was filled into two cells IA and IB. Then, a current was passed between the Pt electrodes ZA and ZV immersed in the electrolyte solution of cells IA and IB using a constant current source 2.

Using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1 T was created, at the same time a source of ultrasonic vibrations B was turned on with a power density of ultrasonic vibrations of 0.1 W / cm ² , at the same time a source of electromagnetic radiation A with a power density of electromagnetic radiation of 0.1 W / cm ² , at the same time, an anodization current was applied through electrodes ZA and ZV with a current density of 8 tL / st ² for 15 minutes. At the same time, sources A, B and C were turned on continuously throughout the entire stage of anodization and their characteristics did not change over time.

An incandescent lamp was used as a source of electromagnetic radiation A. An inductor (solenoid) was used as a source of magnetic field B.

By this step, a surface layer 12S was formed having a porosity of 27% and a thickness of 11 μt (Fig. 2B). The current supply was stopped for a moment, and then using a magnetic field source B (Fig. 1) a magnetic field with a magnetic induction of 2 T was created, at the same time a source of ultrasonic vibrations B with a power density of ultrasonic vibrations OD W / cm ² was turned ^on , at the same time, the electromagnetic radiation source A was switched on with an electromagnetic radiation power density of 0.1 W / cm ² ; at the same time, the anodizing current was supplied through ZA and ZV electrodes with a current density of 150 tA / st ² for 1.5 seconds . In this case, source A was turned on for 0.5 s, source B was turned on continuously, and source B for 0.7 s and their characteristics did not change over time.

By this step, a highly porous 12H layer having a porosity of 60% greater than that of the surface layer 12S was formed in the surface layer

12S. A highly porous layer is located between the previous formed surface layer 12S (Fig. 2C). Thus, a porous layer 12 composed of a surface layer 12S and a highly porous layer 12H was formed.

In the porous layer 12, the surface layer 12S and the highly porous layer 12H have large differences in porosity, therefore, large stresses are introduced at the interface between the surface layer 12S and the highly porous layer 12H, and the strength of the material becomes extremely small around the vicinity of the interface.

After the formation of the porous layer 12, for silicon epitaxial growth of the device, heat treatment, which is annealing at 1100 C, was carried out for the semiconductor substrate 11 in an atmosphere of H ₂ at atmospheric pressure. Annealing step was carried out by increasing the temperature from room temperature to 1100 C for about 20 minutes and holding at 1100 ⁰ C for approximately 30 minutes. With this annealing in an H ₂ atmosphere, the surface of the porous layer 12 becomes smooth and the strength porous material near the interface between the intermediate porous layer 12M and the highly porous layer 12H was made even more brittle.

After that, the temperature was reduced from the annealing temperature of 1110 ° C to 1020 ° C in an H ₂ atmosphere and the epitaxial growth of silicon was carried out for 18 minutes using 5Ϊ2 ₂ gas as a gas source. As a result, an epitaxial semiconductor film 13 made of single crystal silicon having a thickness of 5 μt was formed on the surface of the porous layer 12 (FIG. 3A). In the next step, the epitaxial semiconductor layer 13 was peeled off from the semiconductor substrate 11. For this peeling step, a bonding element 14 was deposited on the surface of the epitaxial semiconductor film 13 and on the back side of the semiconductor substrate 11, respectively, and the flexible supporting substrate 15 made of a poly ethylene terephthalate was adhered to this connecting element 14 (Fig. 3B). The bond strength of the support substrate 15 with this bonding element 14 was selected more durable than the separation strength in the porous layer 12.

Then, by mechanical insertion using a guillotine, a breaking stress was caused to separate the resulting thin semiconductor film from the semiconductor substrate along the line of strength in the brittle porous layer 12 with separation in the highly porous layer 12H, or, on or near the interface with the highly porous layer 12H and epitaxi The alalic semiconductor film 13 was peeled from the semiconductor substrate 11 (Fig. 3C).

In this way, a thin semiconductor film 23 composed of an epitaxial semiconductor film 13 is separated (FIG. 3D). In this example, any remaining porous layer delaminated with a thin film of semiconductor 23 was removed by chemical or mechanical etching. The result was an ultrathin silicon monocrystalline solar cell with a surface area of 150 xl50mmxmm. Implementation Example 2.

FIG. 4-5, the process diagram of implementation example 2. First, similarly to implementation example 1, a semiconductor substrate 11 was made of single-crystal silicon, doped with boron B at a high concentration, and having a resistance of 0.02 to 0.03 Ωst (Fig. 4A )

Then, the surface of this semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. Also in the second embodiment, similar to the first embodiment, the anodization was carried out using an anodizing apparatus having a two-sided structure of the electrochemical cell explained in FIG. one. A semiconductor substrate 11 made of single-crystal silicon was installed between the first and second cells IA and IB, and the electrolyte solution HF: C ₂ H ₅ OH = 1: 1 was filled into two cells IA and IB. Then, a current was passed between the Pt electrodes ZA and ZV immersed in the electrolyte solution of cells IA and IB using an alternating current source 2 with a frequency of 60 Hz.

Using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1 T was created, at the same time a source of ultrasonic vibrations B was switched on with a power density of ultrasonic vibrations of 0.1 W / cm ^2, at the same time a source of electromagnetic radiation was turned on A with a power density of electromagnetic radiation of 0.1 W / cm; at the same time, an anodizing current was applied through electrodes ZA and ZV with a current density of 1 mA / cm ^g for 7 minutes. Moreover, sources A, B and C were included periodically with a period of 0.7 minutes. throughout the anodizing stage and their characteristics increased over time (up to 2 T for the value of magnetic induction, 0.2 W / cm ² for the power density of ultrasonic vibrations, and 0.11 W / cm for the power density of electromagnetic radiation. ) with a constant component of the increment.

An incandescent lamp and a matrix of emitting diodes were used as a source of electromagnetic radiation A. An inductor (solenoid) was used as a source of magnetic field B. By this step, a surface layer 12S having a porosity of 16% and a thickness of 1.7 μt having a very small pore diameter was formed (Fig. 4B).

The current supply was stopped for a moment, then using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 2 T was created; at the same time, an ultrasonic vibration source B was switched on with a power density of ultrasonic vibrations of 0.01 W / cm ² at the same time, the electromagnetic radiation source A was switched on with an electromagnetic radiation power density of 0.1 W / cm ² ; at the same time, the anodizing current was supplied through the ZA and ZV electrodes with a current density of 8 tA / st ² for 8 minutes. At the same time, sources A, B and C were switched on continuously throughout the entire anodizing stage and their characteristics increased over time by 40% with a constant increment component.

An incandescent lamp and a matrix of emitting diodes were used as a source of electromagnetic radiation A. An inductor (solenoid) was used as a source of magnetic field B.

By this step, an intermediate porous layer 12M having a porosity of 26% and a thickness of 6, bμm and having a greater porosity compared to the surface layer 12S, was formed under the surface layer 12S (Fig. 4C). The current supply was stopped again for a moment and then using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 2 T was created, at the same time a source of ultrasonic vibrations B with a power density of ultrasonic vibrations of 0.1 W / cm ² was turned ^on at the same time, the electromagnetic radiation source A was switched on with an electromagnetic radiation power density of 0.1 W / cm ² ; at the same time, the anodizing current was supplied through ZA and ZV electrodes with a current density of 210 tA / st ² for 4 seconds . At the same time, sources A, B and C were turned on continuously throughout the entire stage of anodizing and their characteristics increased over time by 10% with a constant increment component. As a source of electromagnetic radiation A, a matrix of emitting diodes was used. As a source of magnetic field B using an inductance coil (solenoid). By this step, a highly porous layer 12H having a higher porosity than this intermediate porous layer 12M having a porosity of 61% and a thickness of 0.05 μm was formed in the intermediate porous layer 12M (Fig. 4D). Thus, a porous layer 12 was formed including a surface layer 12S, an intermediate porous layer 12M, and a highly porous layer 12H.

After the formation of the porous layer 12, annealing, silicon epitaxial growth, and peeling is carried out in the same sequence as described in embodiment 1. After the formation of the porous layer 12, for silicon epitaxial growth of the device, the heat treatment, which is annealing at 1300 ° C was carried out for the semiconductor substrate 11 in an atmosphere of H ₂ at atmospheric pressure. The annealing step was carried out by increasing the temperature from room temperature to 1300 C for approximately 25 minutes and holding at 1300 C for approximately 40 minutes. With this annealing in an H ₂ atmosphere, the surface of the porous layer 12 becomes smooth, and the strength of the porous material near the interface between the intermediate porous layer 12M and the highly porous layer 12H has been made even more fragile. After that, the temperature was reduced from the annealing temperature of 1300

C to 1040 C ° in an atmosphere of H ₂ and epitaxial growth of silicon was carried out for 20 minutes, and the gas source was SiH ₂ . By doping this film, an epitaxial semiconductor film 13 made of monocrystalline silicon having a thickness of 5 μt was formed on the surface of the porous layer 12S (Fig. 5A).

In the next step, the epitaxial semiconductor layer 13 was peeled off from the semiconductor substrate 11. For this peeling step, a bonding element 14 was deposited on the surface of the epitaxial semiconductor film 13 and on the back side of the semiconductor substrate 11, respectively, and a flexible supporting substrate 15 made of sheet poly- ethylene terephthalate was bonded by this bonding element 14. The bond strength of the support substrate 15 with this bonding element 14 was selected to be stronger than the separation strength in the porous layer 12. Then, a directional compressed jet of water caused a breaking stress to separate the resulting thin semiconductor film from a semiconductor substrate. This resulted in separation along the line of weakness in the brittle porous layer 12 with separation occurring in the highly porous layer 12H, or, on or near the interface with the highly porous layer 12H, and the epitaxial semiconductor film 13 was peeled from the semiconductor substrate 11 (Fig. 5B) .

In this way, a thin film of semiconductor 23 composed of an epitaxial semiconductor film 13 is separated. In this example, any remaining porous layer delaminated with a thin film of semiconductor 23 was removed by chemical or mechanical etching. The result was an ultra-thin silicon-based single-crystal solar cell with a surface area of 150 xl50mmxmm.

Implementation Example 3.

FIG. 6 and FIG. 7 is a process diagram of an example of implementation 3. First, similarly to example of implementation 1, a semiconductor substrate 11 was made of monocrystalline silicon, doped with boron B at a high concentration, and having a resistance of 0.02 to 0.03 Ost (Fig. 6A).

Then, the surface of this semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. In the third embodiment, similarly to the first embodiment, anodizing was performed using an anodizing apparatus having a two-sided structure of the electrochemical cell explained in FIG. A semiconductor substrate 11 made of single-crystal silicon was installed between the first and second cells IA and IB, and the electrolyte solution HF: C ₂ H ₅ OH = 1: 1 was filled into two cells IA and IB. Then, a current was passed between the Pt electrodes ZA and ZV immersed in the electrolyte solution of cells IA and IB using a constant current source 2. Using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1 T was created, at the same time a source of ultrasonic vibrations B with a power density of ultrasonic vibrations of 0.02 W / cm ² was turned ^on , at the same time an anodized current was applied. through electrodes ZA and SV with a current density of 1 tA / st ² for 7 minutes. At the same time, sources B and C were turned on continuously throughout the entire anodizing stage and their characteristics decreased by 5% over time with a constant increment component.

An incandescent lamp was used as a source of electromagnetic radiation A. An inductance coil (solenoid) and permanent magnets were used as a source of magnetic field B.

By this step, a surface layer 12S was formed having a porosity of 16% and a thickness of 1.7 μt (Fig. 6B).

The current supply was stopped for a moment, and then using a magnetic field source B (Fig. 1), a magnetic field with magnetic induction was created

2 T, at the same time, the source of ultrasonic vibrations B was switched on with a power density of ultrasonic vibrations of 0.05 W / cm ² , and at the same time, an anodizing current was supplied through ZA and ZV electrodes with a current density of 4 tA / st ² for 3 minutes . In this case, sources B and C were switched on continuously throughout the entire anodizing stage and their characteristics decreased by 5% over time with a constant increment component.

An incandescent lamp was used as a source of electromagnetic radiation A. An inductance coil (solenoid) and permanent magnets were used as a source of magnetic field B. By this step, an intermediate porous layer 12Ml having porosity

22% and a thickness l, 8μm and having a greater porosity compared to the surface layer 12S, was formed under the surface layer 12S (Fig. 6C).

The current supply was stopped again for a moment, and then using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1.5 T was created, at the same time the ultrasonic source was turned on oscillations of B with a power density of ultrasonic vibrations of 0.02 W / cm ² ; at the same time, an anodization current was supplied through electrodes ZA and SV with a current density of 10 tA / st ² for 6 minutes. At the same time, sources B and C were turned on continuously throughout the entire stage of anodization and their characteristics increased over time with 10% with a constant increment component.

An incandescent lamp was used as a source of electromagnetic radiation A. An inductance coil (solenoid) and permanent magnets were used as a source of magnetic field B. By this step, a second intermediate porous layer 12M2 having an intermediate porosity of 30% and a thickness of 6.6 μt was formed under the first intermediate porous layer 12Ml (Fig. 6D).

Further, the current supply was stopped again for a moment, and using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 2 T was created at the same time as the source of ultrasonic vibrations B with a power density of ultrasonic vibrations of 1 W / cm ² , at the same time, the anodizing current was supplied through the electrodes ZA and ZV with a current density of 200 tA / st ² for 3 seconds. At the same time, sources B and C were turned on continuously throughout the entire stage of anodizing and their characteristics remained constant over time.

By this step, in the second intermediate porous layer 12M2, a highly porous layer 12H having a greater porosity than the intermediate porous layer 12M2 having a porosity of 60% and a thickness of 0.5 μt was formed (Fig. 6E). Thus, a porous layer 12 was formed including a surface layer 12S, first and second intermediate layers 12Ml and 12M2, and a highly porous layer 12H.

After the formation of the porous layer 12, annealing is carried out as in the first and second embodiment, the epitaxial semiconductor film 13 is formed by the epitaxial growth of silicon (Fig. 7A), and the polyethylene terephthalate sheet (not shown) serving as a support substrate was bonded. Flaking epitaxial semiconductor film 13 and the semiconductor substrate 11 was carried out by the destruction of the highly porous layer 12H of the porous layer 12 or in its vicinity (Fig. 7B). Destructive stresses of highly porous 12 were created by tensile stress to the polyethylene terephthalate film. In Embodiment 3, between the highly porous layer 12H and the surface layer 12S, the first and second intermediate layers 12Ml and 12M2 having porosities increasing towards the highly porous layer 12H are created. These intermediate layers perform the task of buffer layers. Therefore, the magnitude of the effect of stress due to the highly porous 12H layer can be more effectively reduced.

As a result, an ultrathin silicon monocrystalline solar cell with a surface area of 150 x 150 mm x mm was obtained.

Implementation Example 4 FIG. 4 and FIG. 5 is a process diagram of an example of implementation 4. First, similarly to example of implementation 1, a semiconductor substrate 11 was prepared made of single-crystal silicon doped with boron B at a high concentration and having a resistance of 0.02 to 0.03 Ωst (Fig. 4A).

Then, the surface of this semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. Also in the fourth embodiment, similarly to the first embodiment, anodizing was carried out using an anodizing apparatus having a double-sided structure of the electrochemical cell explained in FIG. one. A semiconductor substrate 11 made of single-crystal silicon was installed between the first and second cells IA and IB, and the electrolyte solution HF: C ₂ H ₅ OH = 1: 1 was filled into two cells IA and IB. Then, a current was passed between the Pt electrodes ZA and ZV immersed in the electrolyte solution of cells IA and IB using a constant current source 2.

Using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1 T was created, at the same time a source of ultrasonic vibrations B was switched on with a power density of ultrasonic vibrations of 0.1 W / cm ² , at the same time, an anodization current was applied through electrodes ZA and ZV with a current density of 1 tA / st ² for 8 minutes. At the same time, sources B and C were turned on continuously throughout the entire anodizing stage and their characteristics decreased by 5% over time with a constant increment component. A laser was used as the source of electromagnetic radiation A. An inductor (solenoid) was used as a source of magnetic field B.

During this step, a surface layer 12S having a porosity of 16% and a thickness of 1.7 μt having a very small pore diameter was formed compared to the surface layer 12S in the first embodiment (FIG. 4B).

Further, in this example, after the formation of the surface layer 12S, without stopping the current supply, the anodization was carried out by gradually increasing the current density from 1 tA / st ² to 10 tA / st ^{2 for} 16 minutes, with a speed of increasing current density I mA / ' st ² per minute. In this case, the magnetic field source B was switched on (Fig. 1) and a magnetic field with a magnetic induction of 1.5 T and a source of ultrasonic vibrations B with a power density of ultrasonic vibrations of 0.01 W / cm were created. By this action, an intermediate porous layer 12M having a varying porosity of 16% to 30% and a thickness of 6, Sμm was formed under the surface layer 12S (Fig. 4C).

The current supply was stopped for a moment, and then the current was supplied with a current density of 200 tA / st ² for 3 seconds. In this case, the magnetic field source B was switched on (Fig. 1) and a magnetic field with a magnetic induction of 2 T and a source of ultrasonic vibrations B with a power density of ultrasonic vibrations of 0.02 W / cm ^{2 were created} . By this action, was formed (Fig. 4D) in an intermediate porous layer 12M, a highly porous layer 12H having a greater porosity of 60% and a thickness of 0.05 μt than this intermediate porous layer 12M. Thus, a porous layer 12 was formed including a surface layer 12S, an intermediate porous layer 12M, and a highly porous layer 12H. In the porous layer 12, the porosity of the intermediate porous layer 12M is very different from that of the highly porous layer 12H. Therefore, large stresses are created at the interface between the highly porous layer 12H and the intermediate layer 12M and close to this surface, thus, the mechanical strength of the porous structure in this vicinity becomes very small.

After the formation of the porous layer 12, for silicon epitaxial growth of the device, heat treatment, which is annealing at 1100 C, was carried out for the semiconductor substrate 11 in an atmosphere of H ₂ at atmospheric pressure. The annealing step was carried out by increasing the temperature from room temperature to 1100 ° C for approximately 20 minutes and holding at 1100 ° C for approximately 30 minutes. With this annealing in an H ₂ atmosphere, the surface of the porous layer 12 becomes smooth, and the strength of the porous material near the interface between the intermediate porous layer 12M and the highly porous layer 12H has been made even more fragile.

After that, the temperature was reduced from the annealing temperature of 1100 C to 1030 C ⁰ B in an H ₂ atmosphere and the epitaxial growth of silicon was carried out for 17 minutes, and SiH ₄ gas was used as a gas source. By doping this film, an epitaxial semiconductor film 13 made of monocrystalline silicon having a thickness of 5 μt was formed on the surface of the porous layer 12S (Fig. 5A).

After the above steps, which are identical, as in Example 2, the adhesion of a sheet of polyethylene terephthalate (not shown) serving as a supporting substrate was carried out and peeling (Fig. 5B), epitaxial semiconductor film 13 and semiconductor substrate 11 was carried out by destruction of the highly porous layer 12H the porous layer 12 or in the vicinity thereof by applying tensile forces to the supporting substrates directed in opposite directions.

In the fourth embodiment, the surface layer 12S which has a small and dense porosity and becomes smoother due to annealing in price. Therefore, the semiconductor film 13 epitaxially grown on the surface layer 12S is formed and has even better crystallinity. As a result, an ultrathin silicon single-crystal solar cell with a surface area of 150 x 150 mm x mm was obtained. Implementation Example 5.

In FIG. 8 shows a process diagram of an example of implementation 5. First, a semiconductor substrate 11 made of single-crystal silicon, doped with boron B at a high concentration, and having a resistance of 0.02 to 0.03 Ω.cm was prepared (Fig. 8A). Then, the surface of this semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. In this embodiment, anodizing was carried out using an anodizing apparatus having a two-sided structure of an electrochemical cell explained in FIG. A semiconductor substrate 11 made of single crystal silicon was installed between the first and second cells IA and IB, and the electrolyte solution composed of HF: C ₂ H ₅ OH = 1: 1 was filled into two cells IA and IB. Then, a current was passed between the Pt electrodes ZA and ZV of the cells IA and IB immersed in the electrolyte solution using a direct current source 2. Using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1 T was created at the same time the source of ultrasonic vibrations B was switched on with a power density of ultrasonic vibrations of 0.02 W / cm ² ; at the same time, the anodizing current was supplied through the electrodes ZA and SV with a current density of 1 tL / st ² for 8 minutes. At the same time, the source of electromagnetic radiation A was switched on with a power density of electromagnetic radiation of 0.018 W / cm ^2. The sources A, B and C were turned on continuously throughout the entire anodizing stage and their characteristics decreased by 5% over time with a constant increment component. As a source of electromagnetic radiation A, a matrix of emitting diodes was used. An inductor (solenoid) was used as a source of magnetic field B.

By this step, a surface layer 12S was formed having a porosity of 16% and a thickness of 1.7 μt (Fig. 8B).

The current supply was stopped for a moment, and then using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1.5 T was created, at the same time a source of ultrasonic vibrations B with a power density of ultrasonic vibrations of 0.02 W / cm ² , at the same time, the electromagnetic radiation source A was switched on with a power density of electromagnetic radiation of 0.18 W / cm ² , at the same time, the anodizing current was supplied through electrodes ZA and ZV with a current density of 7 tA / st ² for 8 minutes. Moreover, sources A, B and C were turned on continuously throughout the entire anodizing stage and their characteristics decreased by 5% over time with a constant increment component.

As a source of electromagnetic radiation A, a matrix of emitting diodes was used. An inductor (solenoid) was used as a source of magnetic field B.

By this step, an intermediate porous layer 12M having a porosity of 26% and a thickness of 6, bμm and having a greater porosity compared to the surface layer 12S, was formed under the surface layer 12S (Fig. 8C). The current supply was stopped again for a moment, and then using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 2 T was created, at the same time a source of ultrasonic vibrations B with a power density of ultrasonic vibrations of 0.07 was turned on W / cm ² , at the same time, the source of electromagnetic radiation A with an electromagnetic power density of 0.18 W / cm ² was turned ^on , at the same time, an anodizing current was supplied through the ZA and ZV electrodes with a current density of 200 tA / st ² at 0.7 min ut, then the current supply was again stopped for a minute, then a current of 200 tA / st ² was supplied for 0.7 seconds. Moreover, sources A, B and C were turned on continuously throughout stages of anodization and their characteristics over time remained constant.

Anodizing was carried out intermittently at a high current density three times. Thereby, a highly porous 12H layer was formed having a porosity of 60% and a thickness of 50 rш and larger compared to the intermediate porous layer 12M, and a highly porous layer 12H was formed under the intermediate porous layer 12M (Fig. 8D). Thus, a porous layer 12 was formed including a surface layer 12S, an intermediate porous layer 12M, and a highly porous layer 12H.

After the formation of the porous layer 12, for silicon epitaxial growth of the device, heat treatment, which is annealing at 1100 C, was carried out for the semiconductor substrate 11 in an atmosphere of H ₂ at atmospheric pressure. The annealing step was carried out by increasing the temperature from room temperature to 1100 ° C for approximately 20 minutes and holding at 1100 ° C for approximately 3 minutes. With this annealing in an H ₂ atmosphere, the surface of the porous layer 12 becomes smooth, and the strength of the porous material near the interface between the intermediate porous layer 12M and the highly porous layer 12H has been made even more brittle.

After that, the temperature was reduced from the annealing temperature of 1100 C ⁰ to 1030 CB in an H ₂ atmosphere and epitaxial silicon growth was carried out for 17 minutes using SzH ₄ B gas as a gas source. As a result, an epitaxial semiconductor film 13 made of single-crystal silicon having a thickness of 5 μt was formed on the surface of the porous layer 12 (Fig. 8E).

Further, as in the above described embodiments, the epitaxial semiconductor film 13 and the semiconductor substrate 11 are separated (Fig. 8F). By periodically applying a current of high power density, a highly porous layer 12H is formed at the bottom or under the intermediate porous layer 12M, and a highly porous layer 12H can be formed with very high porosity. The porosity of the highly porous layer is significantly improved during high-temperature annealing in an H ₂ atmosphere. Accordingly, the epitaxial semiconductor film 13 on the porous layer 12 can be very easily peeled off along the high porous layer 12H or in its vicinity.

FIG. 23 and FIG. 24 are schematic views based on microphotographs with a magnification of 100,000 of a cross section of an intermediate porous layer 12M and a highly porous layer 12H in this embodiment before and after high-temperature annealing in an H ₂ atmosphere. As is evident from a comparison of these two species, the growth of crystalline grains is caused by high-temperature annealing in an H ₂ atmosphere.

As a result, an ultrathin silicon monocrystalline solar cell with a surface area of 150x150lx x mm was obtained.

Implementation Example 6.

In FIG. 8 shows a process diagram of an example of implementation 6. First, a semiconductor substrate 11 made of single-crystal silicon, doped with boron B at a high concentration, and having a resistance of 0.01 to 0.02 Ωst (Fig. 8A) was prepared.

Then, the surface of this semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. In this embodiment, anodizing was carried out using an anodizing apparatus having the two-sided structure of the electrochemical cell explained in FIG. A semiconductor substrate 11 made of monocrystalline silicon was installed between the first and second cells IA and IB, and the electrolyte solution composed of HF: C ₂ H ₅ OH = 1: 1 was filled into two cells IA and IB. Then, a current was passed between the Pt electrodes ZA and ZV immersed in the electrolyte solution of cells IA and IB using a constant current source 2. Using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1 T was created, at the same time a source of ultrasonic vibrations B with a power density of ultrasonic vibrations of 0.02 W / cm ² was turned ^on , at the same time an anodized current was applied. through electrodes ZA and SV with a current density of 1 tA / st ² for 8 minutes. At the same time, the electromagnetic radiation source A was switched on with a power density of electromagnetic radiation of 0.18 W / cm. At the same time, sources A, B and C were turned on continuously throughout the entire anodizing stage and their characteristics decreased by 5% over time with a constant increment component.

The current supply was stopped for a moment, and then the current was supplied with a current density of 7 tA / st ² for 8 minutes. By this step, an intermediate porous layer 12M having a porosity of 26% and a thickness of 6, bμm and having a greater porosity compared to the surface layer 12S, was formed under the surface layer 12S (Fig. 8C).

The current supply was stopped again for a moment, and then the current was supplied for 2 seconds with a current density of 60 tA / st ² and a magnetic field with a magnetic induction of 2 T was created, as well as ultrasonic vibrations with an oscillation power density of 0.02 W / cm ² . By this step, a highly porous 12H layer with a porosity of 60% and a thickness of 50 pm was formed. Moreover, this highly porous layer 12H was formed on the interface of the semiconductor substrate 11 under the intermediate layer 12M (Fig. 8D).

Thus, a porous layer 12 was formed including a surface layer 12S, an intermediate porous layer 12M, and a highly porous layer 12H. In this porous layer 12 formed in this way, the porosity is very different between the highly porous layer 12H, the intermediate layer 12M and the substrate 11, therefore, large stresses are introduced on the interface of these layers and in its vicinity, thus the strength of the highly porous layer and the surrounding area becomes very unstable.

After the formation of the porous layer 12, heat treatment, which is annealing at 1100 C, was carried out for the semiconductor substrate 11 in an atmosphere of H ₂ at atmospheric pressure. The annealing step was carried out by increasing the temperature from room temperature to 1100 ° C for approximately 20 minutes and holding at 1100 ° C for approximately 3 minutes. Using this annealing in an H ₂ atmosphere, the surface of the porous layer 12 becomes smooth and the strength of the porous material near the interface between the intermediate porous layer 12M and the highly porous layer 12H was made even more brittle.After that, the temperature was reduced from the annealing temperature 1100

C to 1030 C in an atmosphere of Tf ₂ and epitaxial growth of silicon was carried out for 17 minutes using SiH ₄ B gas as a gas source. As a result, an epitaxial semiconductor film 13 made of single-crystal silicon having a thickness of 5 μt was formed on the surface of the porous layer 12 (FIG. 8E).

Further, as in the above-described embodiments, the epitaxial semiconductor film 13 is separated from the semiconductor substrate 11, thereby producing the intended thin semiconductor film 23 (FIG. 8F). As a result, an ultrathin silicon monocrystalline solar cell with a surface area of 150xl50lxlxl was obtained.

Implementation Example 7.

In FIG. 8 shows a process diagram of an example of implementation 7. First, a semiconductor substrate 11 was prepared made of monocrystalline silicon, doped with boron B at a high concentration and having a resistance of 0.01 to 0.02 Ωst (Fig. 8A). Then, the surface of this semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. In this embodiment, anodizing was carried out using an anodizing apparatus having a two-sided structure of an electrochemical cell explained in FIG. A semiconductor substrate 11 made of monocrystalline silicon was installed between the first and second cells IA and IB, and the electrolyte solution composed of HF: C ₂ H ₅ OH = 1: 1 was filled into two cells IA and IB. Then, a current was passed between the Pt electrodes ZA and ZV immersed in the electrolyte solution of cells IA and IB using a constant current source 2.

Using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1.5 T was created, at the same time a source of ultrasonic vibrations B with a power density of ultrasonic vibrations of 0.02 W / cm ² was turned ^on , at the same time a current was applied anodizing through electrodes ZA and ZV with a current density of 1 tA / st ² for 6 minutes. At the same time, the source of electromagnetic radiation A was switched on with a power density of electromagnetic radiation of 0.18 W / cm ^2. Moreover, sources A, B and C were switched on continuously throughout the entire anodizing phase and their characteristics decreased by 5% over time with a constant increment component.

By this step, a surface layer 12S was formed having a porosity of 16% and a thickness of 1.5 μt (Fig. 8B).

The current supply was stopped for a moment, and then the current was supplied with a current density of 4 tA / st ² for 13 minutes. By this step, an intermediate porous layer 12M having a porosity of 22% and a thickness of 6, bμm and having a higher porosity compared to the surface layer 12S was formed under the surface layer 12S (Fig. 8C). The current supply was stopped again for a moment, and then the current was supplied for 2 seconds with a current density of 60 tL / st ² , and a magnetic field with a magnetic induction of 2 T was created, as well as ultrasonic vibrations with an oscillation power density of 0.02 W / cm ² . By this step, a highly porous 12H layer was formed with a porosity of 60% and a thickness of 50 pm. Moreover, this highly porous layer 12H was formed on the interface of the semiconductor substrate 11 under the intermediate layer 12M (Fig. 8D).

Thus, a porous layer 12 was formed including a surface layer 12S, an intermediate porous layer 12M, and a highly porous layer 12H.

In this porous layer 12 formed in this way, the porosity varies greatly between the highly porous layer 12H, the intermediate layer 12M and the substrate 11, therefore, large stresses are introduced on the interface of these layers and in its vicinity, so the strength of the highly porous layer and the surrounding area becomes very not durable.

After the formation of the porous layer 12, heat treatment, which is annealing at 1100 C, was carried out for the semiconductor substrate 11 in an atmosphere of H ₂ at atmospheric pressure. The annealing step was carried out by increasing the temperature from room temperature to 1100 ° C for approximately 20 minutes and holding at 1100 ° C for approximately 3 minutes. With this annealing in an H ₂ atmosphere, the surface of the porous layer 12 becomes smooth, and the strength of the porous material near the interface between the intermediate porous layer 12M and the highly porous layer 12H has been made even more brittle. After that, the temperature was reduced from the annealing temperature of 1100

From up to 1030 C ⁰ B atmosphere of H ₂ and epitaxial growth of silicon was carried out for 17 minutes using SiH ₄ B gas as a gas source. As a result, an epitaxial semiconductor film 13 made of single-crystal silicon having a thickness of 5 μt was formed on the surface of the porous layer 12 (FIG. 8E). Further, as in the above-described embodiments, the epitaxial semiconductor film 13 is separated from the semiconductor substrate 11, thereby obtaining the intended thin semiconductor film 23 (Fig. 8F). As a result, an ultrathin silicon single-crystal solar cell with a surface area of 150 x 150 mm x mm was obtained.

Implementation Example 8.

In FIG. 8 shows a process diagram of an example of implementation 8. First, a semiconductor substrate 11 was prepared made of monocrystalline silicon, doped with boron B at a high concentration, and having a resistance of 0.01 to 0.02 Ω.cm (Fig. 8A).

Then, the surface of this semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. In this embodiment, anodizing was carried out using an anodizing apparatus having a two-sided structure of an electrochemical cell explained in FIG. A semiconductor substrate 11 made of monocrystalline silicon was installed between the first and second cells IA and IB ₅ in the first electrochemical cell IA, an electrolyte solution HF: C ₂ H ₅ OH = 2: 1 was poured, and an electrolyte solution HF was poured into the second IB electrochemical cell : C ₂ H ₅ OH = 1: 1. Then, a current was passed between the Pt electrodes ZA and ZV immersed in the electrolyte solution of cells IA and IB using a constant current source 2.

Using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1 T was created, at the same time a source of ultrasonic vibrations B was switched on with a power density of ultrasonic vibrations of 0.02 W / cm ² , at the same time, an anodization current was applied through ZA and ZV electrodes with current density at the level of 1 tA / st ² for 5 minutes. At the same time, the source of electromagnetic radiation A was switched on with a power density of electromagnetic radiation of 0.18 W / cm ² , while sources A, B and C were turned on continuously throughout the entire anodizing phase. and their characteristics over time decreased by 5% with a constant component of the increment.

By this step, a surface layer 12S was formed having a porosity of 13% and a thickness of 1.5 μt (Fig. 8B).

The current supply was stopped for a moment, and then the current was supplied with a current density of 5 tA / st ² for 5 minutes. By this step, an intermediate porous layer 12M having a porosity of 18% and a thickness of 5 μt was formed under the surface layer 12S (Fig. 8C).

The current supply was stopped again for a moment, and then the current was supplied for 3 seconds with a current density of 80 tA / st ² and a magnetic field with a magnetic induction of 2 T was created, as well as ultrasonic vibrations with an oscillation power density of 0.02 W / cm ² . By this step, a highly porous 12H layer was formed with a porosity of 60% and a thickness of 50 pm. Moreover, this highly porous layer 12H was formed on the interface of the semiconductor substrate 11 under the intermediate layer 12M (Fig. 8D).

Thus, a porous layer 12 was formed comprising a surface layer 12S, an intermediate porous layer 12M, and a highly porous layer 12H.

In this porous layer 12 formed in this way, the porosity varies greatly between the highly porous layer 12H, the intermediate layer

12M and substrate 11, therefore, large stresses are introduced on the interface of these layers and in its vicinity, so the strength of the highly porous layer and the surrounding area becomes very unstable.

After the formation of the porous layer 12, heat treatment, which is annealing at 1100 C, was carried out for the semiconductor substrate 11 in an atmosphere of H ₂ at atmospheric pressure. The annealing step was carried out by increasing the temperature from room temperature to 1100 C during about 20 minutes and holding at 1100 C ⁰ for about

ZOMIN. With this annealing in an H ₂ atmosphere, the surface of the porous layer 12 becomes smooth, and the strength of the porous material near the interface between the intermediate porous layer 12M and the highly porous layer 12H has been made even more brittle.

Thereafter, the temperature was reduced from an annealing temperature of 1100 ⁰ C to 1030 C ° in an atmosphere of H ₂ and epitaxial silicon growth was carried out for 17 minutes using a gas 5 / H ₄ B as a gas source. As a result, an epitaxial semiconductor film 13 made of single-crystal silicon having a thickness of 5 μt was formed on the surface of the porous layer 12 (FIG. 8E).

Further, as in the above-described embodiments, the epitaxial semiconductor film 13 is separated from the semiconductor substrate 11, thereby obtaining the intended thin semiconductor film 23 (Fig. 8F).

As a result, an ultrathin silicon monocrystalline solar cell with a surface area of 150 hlSОmmkhmm was obtained.

Implementation Example 9.

In FIG. 4 and FIG. 5 shows a process diagram of an example of implementation 9. First, a semiconductor substrate 11 was made of single-crystal silicon doped with boron B at a high concentration, and having a resistance of 0.01 to 0.02 Ωst (Fig. 4A).

Then, the surface of this semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. In this embodiment, anodizing was carried out using an anodizing apparatus having the two-sided structure of the electrochemical cell explained in FIG. A semiconductor substrate 11 made of monocrystalline silicon was installed between the first and second cells IA and IB, and the electrolyte solution composed of HF: C ₂ H ₅ OH = 1: 1 was filled into two cells IA and IB. Then, the current was passed between Pt electrodes ZA and ZV immersed in the electrolyte solution of cells IA and IB using a constant current source 2.

Using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1 T was created, at the same time a source of ultrasonic vibrations B was switched on with a power density of ultrasonic vibrations of 0.02 W / cm ² , at the same time, an anodization current was applied through ZA and ZV electrodes with a current density of 1 tA / st ² for 8 minutes. At the same time, the source of electromagnetic radiation A was switched on with a power density of electromagnetic radiation of 0.1 W / cm ^2. Moreover, sources A, B and C were turned on continuously throughout the entire anodizing phase and their characteristics decreased by 5% over time with a constant increment component.

By this step, a surface layer 12S was formed (Fig. 4B). The current supply was stopped for a moment, and then the current was supplied with a current density of 7 tA / st ² for 8 minutes. By this step, an intermediate porous layer 12M was formed under the surface layer 12S (Fig. 4C). The current supply was stopped again for a moment, and then the current was supplied for 3 seconds with a current density of 200 tA / st ² and a magnetic field with a magnetic induction of 2 T was created. By this step, a highly porous 12H layer was formed. Moreover, this highly porous layer 12H was formed inside the intermediate porous layer 12M. Thus, a porous layer 12 was formed comprising a surface layer 12S, an intermediate porous layer 12M, and a highly porous layer 12H (Fig. 4D).

After that, in this implementation example, an oxidation step was carried out. This oxidation step was carried out by dry oxidation, which included high-temperature heating to 400 C in an oxygen atmosphere. By this process, the inner-lying portion of the porous layer 12 was oxidized, a large structural changes in the porous layer were prevented even during subsequent heat treatment in an H ₂ atmosphere, and the stress caused by the proximity of the interface of the highly porous layer 12H straining the surface layer can be effectively reduced or completely eliminated.

After this, as in the previous implementation examples, the processes of high-temperature annealing in a hydrogen atmosphere were carried out, then the process of epitaxial growth, and finally the process of peeling the epitaxially grown thin semiconductor film from the semiconductor substrate by applying a breaking voltage to the highly porous layer.

After the formation of the porous layer 12, heat treatment, which is annealing at 1100 C, was carried out for the semiconductor substrate 11 in an atmosphere of H ₂ at atmospheric pressure. Annealing step was carried out by increasing the temperature from room temperature to 1100 C for about 20 minutes and holding at 1100 ⁰ C for approximately ZOminut. With this annealing in an H ₂ atmosphere, the surface of the porous layer 12 becomes smooth, and the strength of the porous material near the interface between the intermediate porous layer 12M and the highly porous layer 12H has been made even more brittle. After that, the temperature was reduced from the annealing temperature of 1100

From 1030 C ° in an atmosphere of H ₂ and epitaxial growth of silicon was carried out for 17 minutes using SiH ₄ gas as a gas source. As a result, an epitaxial semiconductor film 13 made of single-crystal silicon having a thickness of 5 μt was formed on the surface of the porous layer 12 (Fig. 5A).

Further, as in the above-described embodiments, the epitaxial semiconductor film 13 is separated from the semiconductor substrate 11, thereby obtaining the intended thin semiconductor film 23 (Fig. 5B). As a result, an ultrathin silicon single-crystal solar cell with a surface area of 150X150LShXLSh was obtained. Implementation Example 10.

In FIG. 4 and FIG. 5 shows a process diagram of an embodiment 10. First, a semiconductor substrate 11 made of single-crystal silicon doped with boron B at a high concentration and having a resistance of 0.01 to 0.02 Ω, cm was prepared (Fig. 4A).

Then, the surface of this semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. In this embodiment, anodizing was carried out using an anodizing apparatus having the two-sided structure of the electrochemical cell explained in FIG. A semiconductor substrate 11 made of monocrystalline silicon was installed between the first and second cells IA and IB, and the electrolyte solution HF - was poured into the first electrochemical cell IA. C ₂ H ₅ OH = 2: 1, and the electrolyte solution HF: C ₂ H ₅ OH = 1: 1 was poured into the second IB electrochemical cell. Then, a current was passed between the Pt electrodes ZA and ZV of cells IA and immersed in the electrolyte solution and IB using a DC source 2.

Using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1 T was created, at the same time a source of ultrasonic vibrations B was switched on with a power density of ultrasonic vibrations of 0.02 W / cm ² , at the same time, an anodization current was applied through ZA and ZV electrodes with a current density of 1 rpA / st ² for 8 minutes. At the same time, the source of electromagnetic radiation A was switched on with a power density of electromagnetic radiation of 0.18 W / cm ^2. Moreover, sources A, B and C were switched on continuously throughout the entire anodizing stage and their characteristics decreased by 5% over time. with a constant component of the increment.

As a source of electromagnetic radiation A, a matrix of emitting diodes was used. An inductor (solenoid) was used as a source of magnetic field B. By this step, a surface layer 12S was formed having a porosity of 16% and a thickness of 1.7 μt (Fig. 4B).

The current supply was stopped for a moment, and then the current was supplied with a current density of 7 tA / st ² for 8 minutes. By this step, an intermediate porous 12M layer was formed having a porosity of 26% and a thickness of 6.3 μt (Fig. 4C).

Then, the composition of the electrolyte solution in the first electrolytic cell IA was changed to HF -. C ₂ H ₅ OH = 1: 1. Then, the current density was increased to

200 tA / st ² , and the current was supplied for 3 seconds, and a magnetic field with a magnetic induction of 2 T was created. By this step, a highly porous 12H layer with a porosity of 60% and a thickness of 0.5 μt was formed. Moreover, this highly porous layer 12H was formed inside the intermediate porous layer 12M (Fig. 4D).

Thus, a porous layer 12 was formed comprising a surface layer 12S, an intermediate porous layer 12M, and a highly porous layer 12H (Fig. 4D).

After this, as in the previous implementation examples, the processes of high temperature annealing in a hydrogen atmosphere were carried out, then the process of epitaxial growth, and finally the process of peeling the epitaxially grown thin semiconductor film from the semiconductor substrate by applying a breaking voltage to the highly porous layer.

After the formation of the porous layer 12, heat treatment, which is annealing at 1100 C, was carried out for the semiconductor substrate 11 in an atmosphere of H ₂ at atmospheric pressure. The annealing step was carried out by increasing the temperature from room temperature to 1100 ° C for approximately 20 minutes and holding at 1100 ° C for approximately 3 minutes. With this annealing in an H ₂ atmosphere, the surface of the porous layer 12 becomes smooth, and the strength of the porous material near the interface between the intermediate porous layer 12M and the highly porous layer 12H has been made even more brittle. After that, the temperature was reduced from the annealing temperature.

1100 C ⁰ to 1030 C ⁰ In an H ₂ atmosphere and epitaxial silicon growth was carried out for 17 minutes using SiH ₄ R gas as a gas source. As a result, an epitaxial semiconductor film 13 made of single crystal silicon having a thickness of 5 μrn was formed on the surface of the porous layer 12 (FIG. 5A).

Further, as in the above described embodiments, the epitaxial semiconductor film 13 is separated from the semiconductor substrate 11, thereby producing the intended thin semiconductor film 23 (FIG. 5B).

In this embodiment, during the formation of the surface of the porous layer 12, that is, the surface layer 12S and the intermediate porous layer 12M, the concentration of hydrofluoric acid increased. When the concentration of hydrofluoric acid increased in the electrolyte, the porosity of the porous layer became smaller. Therefore, in this case, since a porous layer is formed having extremely fine-grained small pores on the surface of the porous layer 12, an epitaxially grown epitaxial semiconductor film formed on this porous layer is a film with perfect crystallinity. Further, in this case, during the formation of the highly porous 12H layer, if the concentration of hydrofluoric acid in the electrolyte solution is high, significant porosity cannot be achieved by applying current with a current density of 200 tA / st ² in 3 seconds, but in this example, at the stage of formation of a highly porous 12H layer, the concentration of hydrofluoric acid in the electrolyte solution was reduced — by replacing the electrolyte before the formation of a highly porous layer, so a highly porous 12H layer having a large porosity could be produced.

The result was an ultrathin silicon single crystal solar cell with a surface area of 150 x 150 mm x mm.

An implementation example 11. In FIG. 6 and FIG. 7 shows a process diagram of an example implementation 11. First, a semiconductor substrate 11 was made of mono crystalline silicon doped with boron B at high concentration and having a resistance of 0.01 to 0.02 Ωst (Fig. 6A).

Using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1 T was created, at the same time a source of ultrasonic vibrations B was switched on with a power density of ultrasonic vibrations of 0.02 W / cm ² , at the same time, an anodization current was applied through ZA and ZV electrodes with a current density of 1 tA / st ² for 8 minutes. At the same time, the source of electromagnetic radiation A was switched on with a power density of electromagnetic radiation of 0.18 W / cm ^2. Moreover, sources A, B and C were switched on continuously throughout the entire anodizing stage and their characteristics decreased by 5% over time. with a constant component of the increment.

By this step, a surface layer 12S was formed having a porosity of 14% and a thickness of 2 μt (Fig. 6B).

The current supply was stopped for a moment, and then the current was supplied with a current density of 7 tA / st ² for 6 minutes. This stage was formed a first intermediate 12Ml porous layer having a porosity of 20% and a thickness of 6.4 μt (Fig. 6C).

Then, the composition of the electrolyte solution in the first electrolytic cell IA was changed to HF: C ₂ H ₅ OH = 1: 1. Then, the current was supplied with a current density of 7 tA / st ² for 2 minutes. By this step, a second intermediate porous layer 12M2 was formed having a porosity of 26% and a thickness of 1.7 μt (Fig. 6D).

Then, the current supply was stopped for a moment, and the composition of the electrolyte solution in the first electrolytic cell IA was changed to HF: C ₂ H ₅ OH = 1: 1.5. In this state, the current density has been increased to

200 tA / st ² , and the current was supplied for 2 seconds, and a magnetic field with a magnetic induction of 2 T was created, as well as ultrasonic vibrations with an oscillation power density of 0.02 W / cm ² . By this step, a highly porous 12H layer with a porosity of 60% and a thickness of 0.5 μt was formed. Moreover, this highly porous layer 12H was formed inside the second intermediate porous layer 12M2 (Fig. 6E).

Thus, a porous layer 12 was formed including a surface layer 12S, a first intermediate porous layer 12Ml, a second intermediate layer 12M2 and a highly porous layer 12H. After this, as in previous implementation examples, high-temperature annealing in a hydrogen atmosphere was carried out, then the process of epitaxial growth, and finally the process of peeling an epitaxially grown thin semiconductor film from a semiconductor substrate by applying a breaking voltage to the highly porous layer. After the formation of the porous layer 12, heat treatment, which is annealing at 1100 C ⁰ , was carried out for the semiconductor substrate 11 in an atmosphere of H ₂ at atmospheric pressure. Annealing step was carried out by increasing the temperature from room temperature to 1100 ⁰ C for approximately 20 minutes and holding at 1100 ⁰ C for approximately ZOminut. Using this annealing in an H ₂ atmosphere, the surface of the porous layer 12 becomes smooth, and the strength of the porous material near the interface between the intermediate porous layer 12M and the highly porous layer 12H has been made even more brittle.

After that, the temperature was reduced from the annealing temperature of 1100 C to 1030 C ° in an H ₂ atmosphere and the epitaxial growth of silicon was carried out for 17 minutes using SiH ₄ B gas as a gas source. As a result, an epitaxial semiconductor film 13 made of single-crystal silicon having a thickness of about 5 μt was formed on the surface of the porous layer 12 (Fig. 7A). Further, as in the above-described embodiments, the epitaxial semiconductor film 13 is separated from the semiconductor substrate 11, thereby obtaining the intended thin semiconductor film 23 (Fig. 7B).

In this embodiment, the first and second porous layers 12Ml and 12M2 were formed. At the stage of formation of the second intermediate porous layer 12M2, the concentration of hydrofluoric acid was reduced. The concentration of hydrofluoric acid was further reduced during the formation of the highly porous 12H layer. Therefore, the porosity increased stepwise from the surface layer 12S to the highly porous layer 12H, and therefore, the stress effect on the surface of the porous layer 12 by the highly porous layer 12H can be effectively reduced, and the crystallinity of the epitaxially grown epitaxial semiconductor layer 13 on the porous layer 12 can be made large.

Further, when anodizing the highly porous 12H layer, the concentration of hydrofluoric acid was further reduced, so the fragility of this porous 12H layer could be further increased, and the peeling, that is, the delamination property of the epitaxial semiconductor film 13 from the semiconductor substrate 11, could be increased .

As a result, an ultrathin silicon monocrystalline solar cell with a surface area of 150x150mm x mm was obtained.

Implementation Example 12. This implementation example demonstrates the case where an epitaxial semiconductor film, that is, a thin semiconductor film, has a multi-layer structure, i.e., a p + / p- / n + structure.

FIG. 9 and FIG. 10 is a process diagram of an example of implementation 12. First, similarly to example of implementation 1, a semiconductor substrate 11 was made of single-crystal silicon, doped with boron B at a high concentration, and having a resistance of 0.01 to 0.02 Ω.cm (FIG. 9A).

Then, the surface of this semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. In the third embodiment, similarly to the first embodiment, anodizing was carried out using an anodizing apparatus having a double-sided structure of the electrochemical cell explained in FIG. . A semiconductor substrate 11 made of single crystal silicon was installed between the first and second cells IA and IB, and the electrolyte solution HF -. C ₂ H ₅ OH = I:! was filled in two cells IA and IB. Then, a current was passed between the Pt electrodes ZA and ZV immersed in the electrolyte solution of cells IA and IB using a constant current source 2.

Using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1 T was created, at the same time a source of ultrasonic vibrations B with a power density of ultrasonic vibrations of 0.02 W / cm ² was turned ^on , at the same time an anodizing current was applied through electrodes ZA and ZV with a current density of 7 tL / st ² for 8 minutes (Fig. 9B). At the same time, the source of electromagnetic radiation A was switched on with a power density of electromagnetic radiation of 0.1 W / cm ^2. Moreover, sources A, B and C were turned on continuously throughout the entire anodizing phase and their characteristics decreased by 5% over time with a constant increment component.

As a source of electromagnetic radiation A, a matrix of emitting diodes was used. An inductor (solenoid) was used as a source of magnetic field B. By this step, an intermediate porous layer 12M was formed.

(Fig. 9C).

Further, the current supply was stopped again for a moment, and then the current was supplied with a current density of 200 shA / st ² for 3 seconds and a magnetic field with a magnetic induction of 2 T was created.

By doing this, a highly porous layer 12H was formed in the intermediate porous layer 12M (Fig. 9D).

Thus, a porous layer 12 was formed including a surface layer 12S, an intermediate layer 12M, and a highly porous layer 12H. After the formation of the porous layer 12, heat treatment, which is annealing at 1100 C, was carried out for the semiconductor substrate 11 in an atmosphere of H ₂ at atmospheric pressure. Annealing step was carried out by increasing the temperature from room temperature to 1100 ⁰ C for approximately 20 minutes and holding at 1100 ° C for approximately ZOminut. With this annealing in an H ₂ atmosphere, the surface of the porous layer 12 becomes smooth, and the strength of the porous material near the interface between the intermediate porous layer 12M and the highly porous layer 12H has been made even more brittle.

Thereafter, epitaxial growth of the first silicon semiconductor layer 131 doped with boron was carried out, and accordingly a thin p + type epitaxial semiconductor film doped with boron was formed at a high concentration (Fig. 10 A). This step was carried out at normal pressure using SiH ₄ and -S ₂ H ₆ gases for two minutes. Further, the gas flow rate of B ₂ H ₆ gas was changed and silicon epitaxial growth was carried out for 17 minutes to form the second epitaxial semiconductor layer 132 made in the form of a p-type silicon layer doped with boron at a low concentration (Fig. 10 B) .

After that, PH ₃ gas was supplied instead of B ₂ H ₆ gas, and silicon epitaxial growth doped with phosphorus at a high concentration was carried out on the p-epitaxial semiconductor layer 132 for 2 minutes to form the third epitaxial semiconductor layer 133 made in the form of n + silicon (Fig. 10 C).

By this step, the following were obtained: an epitaxial semiconductor layer 13 having a p + / p- / n + structure including a first 131, a second 132 and a third 133 epitaxial semiconductor layers.

Further, as in the above described embodiments, the epitaxial semiconductor film 13 is separated from the semiconductor substrate 11, and the processes were carried out to obtain the intended thin semiconductor film 23 (Fig. 10 D). In this embodiment, the porous layer adhered to the thin semiconductor film 23 has been removed by etching. A thin semiconductor film 23 made of a three-layer p + / p- / n + structure can constitute a solar cell.

Release Example 13.

This implementation example demonstrates the case when an epitaxial semiconductor film consists of a semiconductor with a complex chemical composition. In this implementation example, instead of the silicon film in the implementation process 12, the epitaxial semiconductor film 13 is formed as an epitaxial semiconductor film of gallium arsenide (GaAs).

In this embodiment, the steps from FIG. 9A to FIG. 9D were used, similar to the steps that were used in implementation example 12, and further, with the epitaxial growth of the epitaxial semiconductor layer 13, heteroepitaxial growth was carried out at a substrate temperature of 720 ° C for 1 hour at atmospheric pressure by the method of vapor deposition of organometallic compounds using trimethyl gallium gas, and AsH ₃ as the source gas in accordance with the deposition process from the gas phase of the metallo-connected s thus formed was epi- Taxi semiconductor film 13 made of GaAs and having a thickness of 3 μt.

Further, as in the above described embodiments, the epitaxial semiconductor film 13 was separated from the semiconductor substrate 11 to obtain a thin semiconductor film 23 made of an epitaxial semiconductor film 13.

As a result, an ultrathin silicon monocrystalline solar cell with a surface area of 150 x 150 lx x mm was obtained.

Implementation Example 14. This implementation example demonstrates the case when solar cells are produced. In the figures of FIG. 11 to FIG. 18 shows the production of solar cells. On Fig - Fig presents a diagram of the production of solar panels. In the drawings, the following positions are indicated: electrode or hinged element - pos.17; hinged element - pos.19; transparent substrate - pos. 18, 42, 104; electrodes - pos.24, 102, 106; printed circuit board - pos.20; glue - pos.21, 103; explorer - pos.41; semiconductor layer - keys 101 and 105. In this embodiment, an epitaxial semiconductor film, that is, a thin semiconductor film having a multi-layer structure, that is, p + / p- / n + structure, is formed by the same process as in the example implementations 12.

Namely, first, a semiconductor substrate 11 was prepared made of single-crystal silicon, doped with boron B at a high concentration, and having a resistance of 0.01 to 0.02 Ωst.

Then, the surface of this semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. In the third embodiment, similarly to the first embodiment, anodizing was performed using an anodizing apparatus having a double-sided electrochemical cell structure as explained in FIG. . A semiconductor substrate 11 made of single crystal silicon was installed between the first and second cells IA and IB, and the electrolyte solution HF -. C ₂ H ₅ OH = 1: 1 was filled in two cells IA and IB. Then current was passed between the Pt electrodes ZA and ZV immersed in the electrolyte solution of cells IA and IB using a constant current source 2.

In this implementation example, using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1 T was created, at the same time a source of ultrasonic vibrations B with a power density of ultrasonic vibrations of 0.01 W / cm ² was turned ^on , simultaneously with this was applied to the anodizing current through the electrodes ZA and SV with a current density of 1 tL / st ² for 8 minutes to form a surface layer 12S (Fig. 11 A). At the same time, the source of electromagnetic radiation A was switched on with a power density of electromagnetic radiation of 0.18 W / cm ^2. Moreover, sources A, B and C were switched on continuously throughout the entire anodizing stage and their characteristics decreased by 5% over time. with a constant component of the increment.

The current supply was stopped for a moment, and then using a magnetic field source B (Fig. 1), a magnetic field with a magnetic induction of 1 T was created at the same time as the source of ultrasonic vibrations B with a power density of ultrasonic vibrations of 0.02 W / cm ² , at the same time, the anodizing current was supplied through the electrodes ZA and ZV with a current density of 7 tA / st ² for 8 minutes (Fig. 9B). At the same time, the source of electromagnetic radiation A was switched on with a power density of electromagnetic radiation of 0.018 W / cm ^2. The sources A, B and C were turned on continuously throughout the entire anodizing phase and their characteristics decreased by 5% over time with a constant increment component .

(Fig. HB).

Further, the current supply was stopped again for a moment, and then the current was supplied with a current density of 200 tAJst ² for 3 seconds, and a magnetic field with a magnetic induction of 2 T was created, as well as ultrasonic vibrations with an oscillation power density of 0, 02 W / cm.

By this step, a highly porous layer 12H was formed in the intermediate porous layer 12M (Fig. 11 C).

Thus, a porous layer 12 was formed comprising a surface layer 12 S, an intermediate layer 12M, and a highly porous layer 12H.

After the formation of the porous layer 12, heat treatment, which is annealing at 1100 C, was carried out for the semiconductor substrate 11 in an atmosphere of H ₂ at atmospheric pressure. The annealing step was carried out by increasing the temperature from room temperature to 1100 ° C for approximately 20 minutes and holding at 1100 ° C for approximately 3 minutes. With this annealing in an H ₂ atmosphere, the surface of the porous layer 12 becomes smooth, and the strength of the porous material near the interface between the intermediate porous layer 12M and the highly porous layer 12H has been made even more brittle. After that, epitaxial growth was carried out for 2 minutes to form the first semiconductor epitaxial layer 131 made of p + type silicon layer having a thickness of 0.5 μt and doped with boron to a concentration of 10 to 19 atoms per centimeter cube. SiH ₄ and 2 gases were used as gas sources ₂ H ₆ . Further, the gas flow rate of ^ ₂ H ₆ gas was changed and silicon epitaxial growth was carried out for 17 minutes to form the second epitaxial semiconductor layer 132 of a thickness of 5 μm made in the form of a p-type silicon layer doped with boron at a low boron concentration of up to 10 to 16 atoms per centimeter cube After that, PH ₃ gas was supplied instead of B ₂ H ₆ gas and silicon epitaxial growth doped with phosphorus at a high concentration, until concentration was carried out on a p-epitaxial semiconductor

nickel layer 132 for 2 minutes to form a third epitaxial semiconductor layer 133 made in the form of n + silicon.

By this step, an epitaxial semiconductor layer 13 having a p + / p- / n + structure comprising a first 131, a second 132 and a third 133 epitaxial semiconductor layers (Fig. 12 A) was formed.

Further, in this embodiment, a silicon oxide film, that is, a transparent insulating film 16, was formed on the epitaxial semiconductor layer 13 by thermal oxidation and then stencilled using photolithography to form holes 16W for contacts with electrodes or attachments ( Fig. 12 B).

As a result, an ultrathin silicon monocrystalline solar cell with a surface area of 15O x 150mm x mm was obtained.

Claims

CLAIM

1. A method of manufacturing thin semiconductor films, comprising sequentially: at least one anodizing of a semiconductor substrate in a hydrofluoric acid based electrolyte solution to produce a porous layered structure; high temperature annealing in a reducing atmosphere of hydrogen; epitaxial build-up of a thin semiconductor film; bonding a flexible support substrate to the resulting thin semiconductor film; the destruction of the highly porous layer and the separation of the flexible supporting substrate with a thin semiconductor film from the semiconductor substrate; metallization, characterized in that:

- the anodization current density is set in the range from 1 mA / cm ² to 2 A / cm ² ;

- when anodizing a semiconductor substrate, an additional effect is exerted by a magnetic field and / or an electric field and / or electromagnetic radiation and / or ultrasound;

- high-temperature annealing is carried out for from 1 minute to 1 hour at a temperature of 900-1300 ⁰ C;

- epitaxial build-up of a thin semiconductor film is carried out at a temperature of 800-1350 ⁰ C for from 1 minute to 1 hour;

- destructive stress for separating a thin semiconductor film from a semiconductor substrate is caused by application of: thermal stresses (occurring during cooling and / or heating), and / or ultrasound, and / or mechanical stresses by dissection by mechanical incorporation.

2. The method according to claim 1, characterized in that the dissection by mechanical insertion is carried out by guillotining and / or using a directed compressed jet of liquid or gas.

3. The method according to claim 1, characterized in that the thermal stresses are caused by focused (concentrated) electromagnetic radiation, for example, by means of a CO ₂ laser.

4. The method according to p. 1, characterized in that the value of the power density of electromagnetic radiation during anodization is set in the range 1 -1 (T ¹ - 1 W / cm ² .

5. The method according to claim 1, characterized in that the wavelength of electromagnetic radiation during anodizing is set in the range from 10 ^"14 m to 10 ^{" 4} m.

6. The method according to claim 1, characterized in that the value of the magnetic field energy density during anodization is set in the range 1 - 10 ^"1 - 1 10 ³ J / cm ³ .

7. The method according to claim 1, characterized in that the value of the energy density of the electric field during anodization is set in the range 1 • 1 (T ¹ - 1 10 ³ J / cm ³ .

8. The method according to p. 1, characterized in that the value of magnetic induction during anodization is set in the range L0 ^"1 - 2 T.

9. The method according to claim 1, characterized in that the value of the magnetic field during anodization is set in the range of 1 A / m - 1-10 ³ 'A / m.

10. The method according to claim 1, characterized in that the value of the electric field during anodizing is set in the range of 1 V / m - 1-10 ³ V / m.

11. The method according to claim 1, characterized in that the value of the electric field displacement during anodization is set in the range of 1 C / m ² - 1 10 ³ C / m ² .

12. The method according to p. 1, characterized in that the value of the power density of ultrasonic vibrations during anodization is set in the range of 1 ^{-6 "} W / cm ² - 1 W / cm ² .

13. The method according to claim 1, characterized in that the frequency value of ultrasonic vibrations during anodization is set in the range from 1-10 ² Hz to 1-10 ⁶ Hz.

14. The method according to claim 1, characterized in that when anodizing a semiconductor substrate with a resistance of 0.001 Ω • cm - 1 Ω • cm is used.

15. The method according to p. L or p. 14, characterized in that during the anodization using a semiconductor substrate with a concentration of dopants at a level of 10 ¹³ -10 ²² atoms / cm ³ .

16. The method according to claim 1, characterized in that the concentration of hydrofluoric acid in the electrolyte solution is in the range of 1-100%.

17. The method according to p. 1, characterized in that during the anodization of the electrolyte solution has a pH of 1-7.

18. The method according to claim 1, characterized in that when anodizing to create a magnetic field using permanent magnets and / or solenoids (inductors).

19. The method according to claim 1, characterized in that a direct current source and / or an alternating current source and / or a pulse current source are used as the current source during anodizing.

20. The method according to p. 1, characterized in that the source of electromagnetic radiation during anodization using a source of electromagnetic radiation with a constant and / or variable and / or pulsed power density of electromagnetic radiation.

21. The method according to claim 1, characterized in that a lamp and / or a matrix of emitting diodes and / or a laser are used as a source of electromagnetic radiation with a constant and / or variable and / or pulsed power density of electromagnetic radiation.

22. The method according to p. 1 and p. 21, characterized in that the source of electromagnetic radiation is structurally made in the form of a perforated plate, permeable to the electrolyte solution in places of its perforation, transparent to electromagnetic radiation and resistant to chemical effects of electrolyte.

23. The method according to claim 1, characterized in that during the anodizing process, exposure to a magnetic field and / or an electric field and / or electromagnetic radiation and / or ultrasound is carried out periodically or continuously.

24. The method according to p. 1, characterized in that when anodizing the effect of a magnetic field and / or electric field and / or electromagnetic radiation and / or ultrasound is constantly in the direction of action and / or changes in a Cartesian coordinate system, for example, is concentrated and / or decreases per unit area of the processed semiconductor substrate.

25. The method according to p. 1, characterized in that the energy density of the magnetic field and / or the energy density of the electric field and / or the power density of electromagnetic radiation and / or the power density of ultrasound during anodization is left unchanged and / or increase and / or decrease including pulsed and / or periodically and / or with a constant component of the increment, where the constant component lies in the range from 1 to 100% of the numerical value of the physical factor, and the change in the factor is in the time range from 10 ^" to 5 minutes