JPH10270728A - Method of manufacturing thin film semiconductor and semiconductor device - Google Patents

Abstract

(57) [Problem] To provide a semiconductor device such as a solar cell having excellent conversion efficiency or an integrated circuit having excellent characteristics, which can be manufactured at a low cost in mass production of a thin film semiconductor having excellent crystallinity. , So that it can be manufactured at low cost. SOLUTION: Through a step of forming a porous semiconductor layer having a layer whose strength is reduced inside by multi-step anodization on a semiconductor substrate, and a step of growing a semiconductor thin film on the surface of the porous layer Thereafter, the back surface of the semiconductor substrate is vacuum-sucked with the first suction force, and the semiconductor thin film is separated from the semiconductor substrate in the layer of the porous semiconductor layer having the reduced strength, thereby obtaining a target thin-film semiconductor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a thin film semiconductor and a semiconductor device, for example, a thin film semiconductor for obtaining various semiconductor devices such as a solar cell and a semiconductor integrated circuit, and a method for manufacturing these semiconductor devices.

[0002]

2. Description of the Related Art As a thin film semiconductor capable of forming a solar cell or a semiconductor integrated circuit having excellent characteristics, it is desired to form a thin film semiconductor having excellent crystallinity.

[0003] As a method for obtaining a conventional solar cell, for example, a thin polycrystalline Si solar cell, Si is highly purified by a purification technique from metal-grade Si using plasma or the like, an ingot is manufactured by a casting method, and a multi-wire or the like is manufactured. There has been proposed a method of obtaining a wafer, that is, thin polycrystalline Si by the high-speed slicing technique described above, and forming a solar cell thereon. However, such high-speed slicing techniques as removal of boron and phosphorus from metal-grade Si, production of high-quality crystal ingots by a casting method and enlargement of wafers, and high-speed slicing techniques such as multi-wire require high technology. Therefore, it has not been possible to produce sufficiently low-cost and high-quality thin polycrystalline Si. Further, the thickness of the thin polycrystalline Si thus manufactured is about 200 μm, and does not depend on the thin film configuration.

On the other hand, it has been proposed to form a thin film semiconductor made of amorphous Si on a resin substrate surface by a CVD (Chemical Vapor Deposition) method. However, when a solar cell or the like is formed from this amorphous thin film semiconductor, The light-
There is a problem that the electric conversion efficiency is lower than that of polycrystalline Si or single crystal Si.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a thin-film semiconductor having excellent crystallinity can be mass-produced at low cost, and a solar cell having excellent conversion efficiency can be obtained.
Another object of the present invention is to provide a thin film semiconductor and a method for manufacturing a semiconductor device, which can manufacture a semiconductor device such as an integrated circuit having excellent characteristics at low cost.

[0006]

In a method for manufacturing a thin film semiconductor according to the present invention, a porous semiconductor layer having a layer whose strength has been reduced inside or at an interface with the semiconductor substrate by multi-step anodization is provided on the semiconductor substrate. Forming a;
After the step of growing a semiconductor thin film on the surface of the porous layer, the back surface of the semiconductor substrate is vacuum-sucked with a first suction force, and the semiconductor thin film is removed from the porous semiconductor layer in the layer having the reduced strength. Separated from the semiconductor substrate, a desired thin film semiconductor is obtained.

In the method of manufacturing a semiconductor device according to the present invention, a step of forming a porous semiconductor layer having a layer whose strength has been reduced inside or at an interface with the semiconductor substrate by multi-step anodization on the semiconductor substrate. After a step of growing a semiconductor thin film on the surface of the porous layer and a step of forming a semiconductor element on the semiconductor thin film, or before forming the semiconductor element,
Then, the semiconductor thin film is separated from the semiconductor substrate in the layer of the porous semiconductor layer having the reduced strength by the vacuum suction with the suction force of the above, thereby manufacturing a semiconductor device.

As described above, in the manufacturing method of the present invention, the surface of the semiconductor substrate itself is changed by anodization to form a porous layer, on which a semiconductor thin film is grown. Since the thin film can be formed as a semiconductor thin film having excellent crystallinity by epitaxial growth, and can be formed to a necessary and sufficiently small thickness, the semiconductor thin film is broken at a porous layer or at an interface between the porous layers to form a semiconductor film. The target thin-film semiconductor or semiconductor device obtained by peeling from the base has excellent characteristics and can be formed in any sufficiently thin thickness.

Further, according to the method of the present invention, the peeling force for the separation can be held over a wide area, for example, over the entire surface by vacuum suction, so that the semiconductor thin film and the semiconductor substrate can be held together. In peeling (separation), an external force for this peeling can be applied over a wide area, for example, over the entire surface. Breakage or fouling can be avoided as compared with the case where the adhesive is peeled off by bonding to another substrate with an agent. The separation strength of the semiconductor thin film from the semiconductor substrate, that is, the strength required for separation, can be selected with a high degree of freedom by selecting the porosity of the porous layer. It is possible to select the optimum separation strength for the separation. Therefore, this separation can be performed satisfactorily, a breakage accident caused by this separation can be avoided, and a decrease in yield due to breakage can be avoided.

According to the above-described method of the present invention, the semiconductor thin film is separated and the porous layer and the semiconductor thin film are formed again on the remaining semiconductor substrate, and the thin film semiconductor or the semiconductor is repeatedly formed. Since the device can be manufactured, the target thin film semiconductor or semiconductor device can be manufactured at low cost.

[0011]

Embodiments of the present invention will be described.
In the present invention, the surface of the semiconductor substrate is changed by anodization to form a porous layer composed of two or more layers having different porosity from each other. Then, a semiconductor thin film is formed on the surface of the porous layer by, for example, epitaxial growth. Thereafter, the semiconductor thin film is peeled off from the semiconductor substrate via the porous layer to produce a target thin film semiconductor.

Anodization on the surface of the semiconductor substrate is as follows:
For example, in the case of Drurner in 1958,
A technique in which a Si wafer is used as an anode in a hydrofluoric acid aqueous solution, Pt is arranged as a counter electrode thereof, and a voltage is applied between the electrodes to apply a technique of causing the surface of the Si wafer to become porous. The Si thus anodized is referred to as porous (porous) Si.
Then, semiconductors other than Si, for example, SiGe, GaAs
It has been found that a porous layer can also be formed on an s, GaP substrate by anodization. In this specification, a layer formed by anodizing these semiconductors is called a porous semiconductor layer.

In the present invention, a porous semiconductor layer having a layer whose strength is reduced inside or at the interface with the semiconductor substrate is formed on the semiconductor substrate by multi-step anodization,
A semiconductor thin film is grown on the surface. The back surface of the semiconductor substrate is vacuum-sucked with the first suction force to separate the semiconductor thin film from the semiconductor substrate in the layer of the porous semiconductor layer having the reduced strength, and the thin film semiconductor made of the separated semiconductor thin film To form

In this case, generally, the vacuum adsorption is 1 kg / c
m ² , the separation strength in the porous layer of the semiconductor thin film, that is, the strength required for separation, is 1 kg /
cm ² or less.

Alternatively, in the present invention, in the step of separating the semiconductor thin film from the semiconductor substrate, the back surface of the semiconductor substrate is vacuum-adsorbed with the above-mentioned first attraction force, and the semiconductor thin film side on the opposite side is vacuum-adsorbed. The semiconductor thin film is separated from the semiconductor substrate in the layer of the porous semiconductor layer having the reduced strength by vacuum suction with the suction force of 2, to form a thin film semiconductor composed of the separated semiconductor thin film.

As described above, when the separation is performed by holding the first and second vacuum suctions on both sides, the separation strength of the semiconductor thin film in the porous semiconductor layer is equal to the first and second suction forces. The sum, that is, as described above, the vacuum adsorption is generally about 1 kg / cm ^2, so that the separation strength can be selected and set to ² kg / cm ² or less.

However, for example, in the case of manufacturing a semiconductor device, for example, in a step of forming a semiconductor element on a semiconductor thin film, or in a step of forming various materials, a semiconductor substrate on which the porous layer is formed is subjected to vacuum, That is, there may be a step of arranging in a negative pressure space.
In this case, the space is usually applied with a negative pressure of about 1 kg / cm ^2, so that the above-mentioned separation strength is reduced to 1 kg / cm ^2.
If the weight is not more than kg / cm ² , the semiconductor thin film may be separated during the manufacturing process. Therefore, in the present invention, when such a step is involved, the above-mentioned separation strength is selected to be 1 kg / cm ² or more, and 2 kg / cm ² or less which can be separated by the first and second adsorptions. To be selected.

Further, each of the above-mentioned separation strengths of the semiconductor thin film,
That is, the breaking strength at a predetermined portion of the porous layer is the separation strength at the time of separation of the semiconductor thin film, and after the formation of the porous layer, due to the semiconductor thin film forming process, the heating process in other processes, and the like. If the strength changes, the separation strength considering the change is determined in advance by selecting the conditions for forming the porous layer.

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

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

The form of the porous layer to be formed can be changed by selecting the conditions for the anodization. Representative examples of the form of the porous layer include the following first and second forms. That is, in the first mode, a layer having a low porosity is formed facing the surface of the porous layer, and the interface between the porous layer and the semiconductor substrate, that is, anodization of the porous layer and the semiconductor substrate is performed. This is a mode in which a layer having a high porosity is formed on the interface side of the part where the porosity is not made. In the second mode, a surface layer having a low porosity, an intermediate porosity layer formed below the surface layer,
A higher porosity than the intermediate porosity layer in the intermediate porosity layer or at the interface side of the intermediate porosity layer with the semiconductor substrate, that is, at the interface side of the portion where the porous layer and the semiconductor substrate are not made porous by anodization. And a high porosity layer having the following.

These anodizations are performed in at least two steps with different current densities. That is, a step of anodizing at least the semiconductor substrate surface at a low current density, and thereafter,
Anodizing at a high current density.

For example, in the anodization, a step of anodizing the surface of the semiconductor substrate at a low current density, a step of anodizing at an intermediate low current density slightly higher than the low current density, and a step of further anodizing at a higher current density And a step of chemical formation.

Further, the anodization at a high current density in the anodization can be carried out intermittently at a high current density.

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

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

The first anodization at a low current density is carried out, for example, by using 0.1%.
HF (49% solution): C ₂ H ₅ OH (95% solution) using a p-type silicon single crystal substrate of 01 to 0.02 Ωcm
= 1: 1 (volume ratio) (hereinafter, the ratio of HF to C ₂ H ₅ OH indicates the volume ratio of a 49% solution and a 95% solution, respectively), and is as low as about 0.5 to ¹⁰ mA / cm ² . This is performed at a current density for several minutes to several tens of minutes. The second anodization with a high current density is performed at a current density of, for example, about 40 to 300 mA / cm ^{2 for} 1 to 10 seconds, preferably about 3 seconds.

In the first and second anodization processes described above, since the strain generated in the highly porous layer inside the porous layer is considerably large, the influence of the strain extends to the surface of the porous layer. In this case, as described above, cracks occur,
There is a risk that crystal defects may occur in the epitaxial semiconductor film formed thereon. Therefore, in the porous layer, between the low porosity surface layer and the high porosity layer, as a buffer layer for relaxing the strain generated by these, the porosity is higher than the surface layer, and the high porosity layer An intermediate porosity layer having a relatively low porosity can be formed. Specifically, a first anodization at a low current density is first performed, a second anodization at a current density slightly higher than the first anodization is performed, and then the third anode is formed at a much higher current density than those. Perform chemical conversion. The conditions for the first anodization are not particularly limited. For example, a p-type silicon single crystal substrate of 0.01 to 0.02 Ωcm is used, and HF: C ₂ H ₅ is used as an electrolytic solution.
When OH = 1: 1, the current density of the second anodization is, for example, 3 to 20 mA / cm ^2.
/ Cm ² , and the current density of the third anodization is, for example, 40
It is preferably performed at about 300 mA / cm ² . For example, when anodizing is performed at a current density of 1 mA / cm ² , the porosity is about 16%, and when anodizing is performed at a current density of 7 mA / cm ² , the porosity is about 26%, and the current is 200 mA / cm ² . When anodizing at a density, the porosity is about 40-70%
About. When epitaxial growth is performed on such an anodized porous layer, an epitaxial semiconductor film having good crystallinity can be formed.

In the case where the anodization is performed at three current densities as described above, the surface layer having a low porosity formed by the first anodization maintains the low porosity as it is and is formed by the second anodization. The intermediate porosity layer having a somewhat higher porosity, ie, the buffer layer, is formed inside the surface layer, that is, on the interface side with the semiconductor substrate, and the porous layer has a two-layer structure of the surface layer and the intermediate porosity layer. Becomes The principle of the high porosity layer having a high porosity formed by the third anodization is not known, but if the current density is about 90 mA / cm ² or more, the intermediate layer formed by the second anodization may be used. It is formed in the porosity layer, that is, at an intermediate portion in the thickness direction of the intermediate porous layer.

In the formation of the intermediate porosity layer, the low porosity surface layer and the high porosity can be obtained by performing the anodic oxidation for forming the intermediate porosity layer in multiple stages or gradually, for example, under conditions in which the current density is changed. An intermediate porosity layer whose porosity is increased stepwise or inclined from the surface layer toward the high porosity layer side is formed between the porosity layer and the porosity layer. By doing so, the strain between the surface layer and the high porosity layer is alleviated (buffered), and a semiconductor thin film having good crystallinity can be more reliably grown epitaxially.

The separation surface is formed by a large strain caused by a difference in lattice constant at the interface between the release layer (separation layer) of the high porosity layer performed last and the buffer layer having a small porosity performed immediately before the separation layer. However, if a device is devised when performing the final anodization, the separation surface is more easily separated. That is, in the last anodization of high current density, for example, instead of energizing for a constant time of 3 seconds, anodizing is stopped after energizing for 1 second, and after elapse of a required time, for example, after leaving for about 1 minute, 1 at the same or different high current density
A method of intermittent energization, in which anodization is stopped for a minute and then anodization is stopped, and after elapse of a required time, for example, left for about one minute, and then anodized again at the same or different high current density for one second to stop anodization. It is. When an appropriate anodizing condition is selected by using this method, a release layer of the porous layer is formed at the interface with the semiconductor substrate, that is, on the lowermost surface of the porous layer. That is, in this case, the separation surface is not the inside of the intermediate porous layer, that is, the buffer layer as described above, but the interface side of the porous layer with the semiconductor substrate. The porous layer left on the semiconductor layer after the separation is removed by, for example, electrolytic polishing.

As described above, when the buffer layer, that is, the intermediate porosity layer is formed only on the surface layer side of the high porosity layer, the high porosity layer and the surface where distortion occurs in the porous layer are formed. Are maximized, the buffer effect of the intermediate porosity layer is maximized, and a semiconductor thin film having good crystallinity can be formed. Further, when the intermediate porous layer is formed only on the surface side as described above, the entire thickness of the porous layer can be reduced by the consumption thickness of the semiconductor substrate for forming the porous layer. Can be reduced, and the number of repeated use of the semiconductor substrate can be increased.

Thus, by selecting the anodizing conditions,
On the separation surface, a large strain can be applied, and the influence of the strain can be prevented from being exerted on the epitaxial growth surface of the semiconductor thin film.

Further, in order to epitaxially grow a semiconductor with good crystallinity on the porous layer, it is desired to reduce micropores which are seeds for crystal growth on the surface layer of the porous layer.
As one of means for reducing the fine pores in the surface layer, there is a method of increasing the HF concentration in the electrolytic solution during anodization. That is, in this case, in the low current anodization for forming the surface layer, an electrolytic solution having a high HF concentration is used. Next, an intermediate porosity layer serving as a buffer layer is formed,
Then, after lowering the HF concentration of the electrolytic solution, anodization with a high current density is finally performed. By doing so, the fine pores in the surface layer can be reduced, so that an epitaxial semiconductor thin film having better crystallinity can be formed thereon, and in the high porosity layer, Since the porosity can be made sufficiently high, the epitaxial semiconductor film can be satisfactorily peeled off.

The change of the electrolytic solution in the anodization of the porous layer may be performed, for example, in the formation of the surface layer, by anodizing using an electrolytic solution of HF: C ₂ H ₅ OH = 2: 1 as the electrolytic solution. In the formation of the intermediate porosity layer as the buffer layer, anodization using an electrolytic solution having a slightly lower HF concentration, for example, an electrolytic solution of HF: C ₂ H ₅ OH = 1: 1 is performed to further increase the porosity. In forming the layer, the HF concentration of the electrolytic solution is further reduced, and high current density anodization is performed using, for example, an electrolytic solution of HF: C ₂ H ₅ OH = 1: 1 to 1: 2.

In the formation of the porous layer described above,
When changing the current density from the formation of the surface layer to the formation of the intermediate porosity layer, it is possible to temporarily stop the anodization and then start the energization for the next anodization, or to perform the anodization once. The current density can be continuously changed without stopping, that is, without stopping energization.

In addition, when performing anodization, it is performed in a dark place where light is blocked, so that the irregularities on the surface of the porous layer are reduced.
The crystallinity of the semiconductor thin film epitaxially grown thereon can be improved.

Through the above steps, a semiconductor substrate having a porous layer formed on the surface (one or both surfaces) can be obtained. The thickness of the entire porous layer is not particularly limited, but is 1 to 50 μm, preferably 3 to 15 μm, and usually 8 μm.
It can be about as thick. It is preferable that the thickness of the entire porous layer be as small as possible so that the semiconductor substrate can be used as repeatedly as possible.

It is preferable to anneal the porous layer before epitaxially growing a semiconductor on the porous layer. The annealing may be a heat treatment in a hydrogen gas atmosphere, that is, a hydrogen annealing. When performing this hydrogen annealing, the natural oxide film formed on the surface of the porous layer can be completely removed, and oxygen atoms in the porous layer can be removed as much as possible, so that the surface of the porous layer becomes smooth. Thus, an epitaxial semiconductor film having good crystallinity can be formed. At the same time, the strength of the interface between the high porosity layer and the intermediate porosity layer can be further reduced by this pretreatment, and the epitaxial semiconductor film can be more easily separated from the substrate. In this case, the hydrogen annealing is performed in a temperature range of, for example, about 950 ° C. to 1150 ° C.

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

Then, the semiconductor is epitaxially grown on the surface of the porous layer as described above. In the epitaxial growth of this semiconductor, since the porous layer formed on the surface of the single crystal semiconductor substrate maintains the crystallinity while being porous, the epitaxial growth on the porous layer is possible. The epitaxial growth on the surface of the porous layer can be performed by, for example, a CVD method at a temperature of, for example, 700C to 1100C.

In any of the above-described hydrogen annealing and the epitaxial growth of a semiconductor, a method of heating a semiconductor substrate to a predetermined substrate temperature may be a so-called susceptor heating method, or a method in which a current is directly applied to the semiconductor substrate itself. An electric heating method of flowing and heating can be employed.

The semiconductor thin film epitaxially grown on the porous layer may be a single-layer semiconductor film or a multi-layer semiconductor thin film formed by laminating a plurality of semiconductor layers. Also,
This semiconductor thin film may be the same material as the semiconductor substrate or a different material. For example, a single crystal Si semiconductor substrate is used, and a porous layer formed on the surface thereof is made of Si or Ga.
A compound semiconductor such as As, or a Si compound such as Si
Toka epitaxially growing a _1-y Ge _y, equal to appropriately combined stack can grow various semiconductor thin films.

On the other hand, when a thin film semiconductor made of a compound semiconductor is formed, a compound semiconductor substrate can be used as a semiconductor substrate. In this case, if anodization is performed on the compound semiconductor substrate, a porous layer is similarly formed on the surface. A semiconductor substrate can be configured. When a compound semiconductor is epitaxially grown on the porous layer, a lattice mismatch can be reduced as compared with, for example, the case where a compound semiconductor is epitaxially grown on a Si semiconductor substrate. A thin film semiconductor formed of a compound semiconductor having excellent crystallinity can be obtained.

Further, an n-type or p-type impurity can be introduced into the semiconductor thin film formed on the porous layer during the epitaxial growth. Alternatively, after the epitaxial semiconductor thin film is formed, the introduction of impurities can be performed entirely or selectively by ion implantation, diffusion, or the like. In this case, the conductivity type, impurity concentration, and type are selected according to the purpose of use.

The thickness of the semiconductor thin film can be appropriately selected according to the use of the thin film semiconductor. For example, when a semiconductor integrated circuit is formed on a thin film semiconductor, the operating layer of the semiconductor element has a thickness of about several μm, and thus can be formed to a thickness of about 5 μm, for example.

When a solar cell is constituted by a thin film semiconductor made of a single crystal silicon semiconductor thin film, the semiconductor thin film may be, for example, a p-type high impurity concentration p ⁺ semiconductor layer and a p-type low A multilayer semiconductor thin film can be formed by epitaxially growing a p ⁻ semiconductor layer with an impurity concentration and an n ⁺ semiconductor layer with an n-type high impurity concentration in this order. Although the impurity concentration and the film thickness of these layers are not particularly limited, for example, the p ⁺ type semiconductor layer has a film thickness in the range of 0 to 1 μm, typically about 0.5 μm, and a boron B concentration of 10 μm.
^{18 ~10 20} atoms / cm ³ range, typically about 10 ¹⁹ the atom
s / cm ³ , the p-type semiconductor layer has a thickness of 1 to 30 μm, typically about 5 μm, and a boron concentration of 10 ¹⁴ to 10
^The thickness of the n ⁺ type semiconductor layer is in the range of 0.1 to 1 μm, in the range of ¹⁷ atoms / cm ³ , typically about 10 ¹⁶ atoms / cm ³ ,
Typically, the concentration of phosphorus P or arsenic As is in the range of 10 ¹⁸ to 10 ²⁰ atoms / cm ³ , typically about 1 μm.
It is preferable to be about 0 ¹⁹ atoms / cm ³ .

Further, the semiconductor thin film is formed by p ⁺
Semiconductor epitaxially grown in the order of a p-type Si layer, a p-type Si _1-x Ge _x graded layer, an undoped Si _1-y Ge _y layer, an n-type Si _1-x Ge _x graded layer, and an n ⁺ type silicon layer A solar cell having a double hetero structure can be manufactured. A typical example of each layer constituting the double hetero structure is p
^{The +} type Si layer has an impurity concentration of about 10 ¹⁹ atoms / cm ³ and a film thickness of about 0.5 μm. The p-type Si _1-x Ge _x graded layer has an impurity concentration of about 10 ¹⁶ atoms / cm ^3. The thickness of the undoped Si _1-y Ge _y layer is about 0.7 μm, the thickness is about 1 μm, and the n-type Si
_1-x Ge as the _x graded layer, an impurity concentration of 1
0 ¹⁶ atoms / cm ³ or so, the thickness is 1μm or so, as the and n ⁺ -type Si layer, an impurity concentration of ¹⁰ 10 cm ^-3 or so, it is preferable that the film thickness is set to about 0.5 [mu] m. In addition, p-type,
The composition ratio x of Ge in the n-type Si _1-x Ge _x graded layer may be gradually increased from x = 0 of each of the layers present on both sides to _{y of} undoped Si _1-y Ge _y. preferable. Thereby, since lattice constants are matched at each interface, good crystallinity can be obtained.

In such a solar cell having a double hetero structure, carriers and light can be effectively confined in the undoped Si _1-y Ge _y layer at the center thereof, so that high conversion efficiency can be obtained.

The above semiconductor thin film can be peeled off from the semiconductor substrate and used as it is as a thin film semiconductor.

Alternatively, while the semiconductor thin film is weakly fixed to the semiconductor substrate via the porous layer, the semiconductor thin film can be subjected to a process required for a solar cell, for example.

The shape of the semiconductor substrate can take various configurations. For example, it can take various shapes such as a wafer shape, that is, a disk shape, or a rod-shaped body having a curved substrate surface.

As described above, the semiconductor substrate can be composed of various semiconductor substrates such as a single crystal substrate of silicon Si, a polycrystalline substrate of Si in some cases, or a compound semiconductor substrate of SiGe, GaAs, GaP or the like. But,
It is preferable to use a Si single crystal substrate for manufacturing a Si single crystal thin film or a solar cell using the Si single crystal thin film.

The semiconductor substrate can be constituted by a semiconductor substrate doped with n-type or p-type impurities or a semiconductor substrate containing no impurities. However, in the case of performing anodization, it is desirable to use a so-called p ⁺ Si substrate, which is a low-resistivity semiconductor substrate doped with p-type impurities at a high concentration. When ap ⁺ -type Si substrate is used as the semiconductor substrate, a p-type impurity such as boron B
However, it is desirable to use a Si substrate doped with about 10 ¹⁹ atoms / cm ³ and having a resistance of about 0.01 to 0.02 Ωcm. Then, when the p ⁺ -type Si substrate is anodized, fine pores elongated in a direction substantially perpendicular to the surface of the substrate are formed, and the p ⁺ -type Si substrate becomes porous while maintaining the crystallinity. Thus, a desirable porous layer is formed.

Next, an embodiment of the method of the present invention will be described. First, an embodiment in which a thin film semiconductor is obtained by the method of the present invention will be described. [Embodiment 1] FIGS. 2 to 4 show the manufacturing steps of this embodiment 1. FIG. First, single crystal Si doped with boron B at a high concentration and having a specific resistance of, for example, 0.01 to 0.02 Ωcm.
A wafer-like semiconductor substrate 11 was prepared (FIG. 2A).
₁ ).

Then, the surface of the semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. In this example, anodization was performed using the anodizing apparatus having the two-tank structure described with reference to FIG. That is, the semiconductor substrate 11 made of single crystal Si is arranged between the first and second tanks 1A and 1B, and both the tanks 1A and 1B have:
Both HF (49% solution): C ₂ H ₅ OH (95% solution)
= 1: 1 electrolyte solution was injected. Then, a current was supplied by the DC power supply 2 between the Pt electrodes 3A and 3B immersed in the electrolytic solutions of the electrolytic solution tanks 1A and 1B.

In this embodiment, first, the current density 1
A current was applied at a low current of mA / cm ² for 8 minutes. By doing so, a dense porosity of 16% due to small pores,
A 1.7 μm-thick surface layer 12S is formed (FIG. 2).
B ₁ ). After the current is stopped once, the current density is 7 mA / cm ²
For 8 minutes. By doing so, the porosity is 26% larger in diameter than the micropores in the surface layer 12S, and the thickness is 6.3 μm.
m of the intermediate porosity layer 12M was formed below the surface layer 12S, that is, inside (lower layer) than the surface layer 12S (FIG. 2C).
₁ ). Furthermore, after the current supply was once stopped, 200 mA / cm ²
At a high current density for 3 seconds. This way,
In the middle porosity layer 12M, that is, the middle porosity layer 12M
This intermediate porosity layer 1 is located at a position sandwiched by
About 40% to 70% approximately of the fragile high-porosity layer 12H of high porosity in comparison with 2M is formed (Fig. 3D _1). Thus, the porous layer 12 including the surface layer 12S, the intermediate porosity layer 12M, and the high porosity layer 12H was formed.

Thereafter, the semiconductor substrate 11 was first annealed in a normal pressure Si epitaxial growth apparatus in an H ₂ atmosphere. This annealing or heating step is performed from room temperature to 11
The heating and heating time to 00 ° C. was set to about 20 minutes, and then the temperature was kept at 1100 ° C. for about 30 minutes. Surface layer 12S of the porous layer by the H ₂ annealing became smoother.

Thereafter, the temperature was lowered from the annealing temperature of 1100 ° C. in H ₂ to 1060 ° C., and epitaxial growth of Si was performed for 17 minutes using SiH ₄ gas as a source gas. By doing so, an epitaxially grown semiconductor thin film 13 of single crystal Si having a thickness of about 5 μm is formed on the surface layer 12S of the porous layer 12 (FIG. 3E ₁ ). At this time, the strength of the high porosity layer 12H of the porous layer 12 was further weakened by recrystallization of the porous Si. Specifically, the separation strength was 1 kg / cm ² or less.

Therefore, in this state, the semiconductor thin film 13
Can be separated, that is, separated from the semiconductor substrate 11. In this separation operation, the support base 31 which is a resin film of, for example, PET (polyethylene terephthalate), for example, a reinforcing layer of a thin film semiconductor finally obtained, is firmly attached to the entire surface of the semiconductor thin film 13 with an adhesive, for example. Adhesion is performed with an adhesion strength greater than the above-mentioned separation strength. On the other hand, the back surface of the semiconductor substrate 11 is
To be absorbed.

The vacuum suction device 32 has a suction surface 32
A plurality of suction ports 32h are opened in s, and these are connected to a vacuum pump, that is, an exhaust device 33, to perform suction. The suction surface 32s is made to be suctioned with a force of 1 kg / cm ² or more over substantially the entire back surface of the semiconductor substrate 11 and over substantially the entire back surface of the semiconductor substrate 11 (FIG. 3F ₁ ).

In this way, the semiconductor thin film 13 is pulled up in a direction in which the support base 31 adhered to the semiconductor thin film 13 is separated from the semiconductor base 11 held by the vacuum suction device 32.
The semiconductor thin film 13 is peeled off from the semiconductor substrate 11. In this manner, separation is performed in the weakened porous layer 12, particularly in the highly porous layer 12H, and the semiconductor thin film 13 is separated.
Is separated from the semiconductor substrate 11 (FIG. 4G ₁ ).

Thus, in this example, the supporting base 31
Semiconductor 2 with semiconductor thin film 13 supported by
3 are configured. The semiconductor thin film 13 of the thin film semiconductor 23
The porous layer 12 deposited thereon can be removed by etching (FIG. 4H ₁ ).

On the other hand, with respect to the semiconductor substrate 11 after the thin film semiconductor 23 has been peeled off, the exhaust device 3 of the vacuum suction device 32
By stopping the evacuation by the step 3, the suction force is eliminated, the semiconductor substrate 11 is taken out from the vacuum suction device 32, the porous layer remaining on the semiconductor substrate 11 is removed by etching, and the operations shown in FIGS. By repeating this, the same thin film semiconductor 23 can be manufactured.

The thin-film semiconductor 23 thus formed
Is excellent in crystallinity and is thin enough to be used.
When 1 has flexibility, the whole can be configured as a flexible thin film semiconductor.

In the above embodiment, the semiconductor substrate 11
This is a case where only the side of the semiconductor substrate 11 is adsorbed by the vacuum suction device 32, adhered to the semiconductor thin film 13 and adhered to the support base 31, and then peeled off.
And the second vacuum suction device also causes the semiconductor thin film 13 to be sucked and held by the second vacuum suction device.
From the semiconductor substrate 11 can be performed. An example in this case will be described in a second embodiment.

[Embodiment 2] In this case as well, FIG.
_{1 to} C ₁ and the surface layer 12S on the semiconductor substrate 11 by using the same method as described in FIGS. 3D ₁ and 3E ₁ .
Intermediate porosity layer 12M and weakened high porosity layer 12H
To form a porous layer 12, on which an epitaxially grown semiconductor thin film 13 is formed.

In this embodiment, as shown in a schematic sectional view of FIG.
With respect to the surface of the semiconductor thin film 13, each of the suction surfaces 32s of the first and second vacuum suction devices 321 and 322 respectively.
Is adsorbed.

In this state, the semiconductor substrate 11 and the semiconductor thin film 13 are separated from each other by moving at least one of the first and second vacuum suction devices 321 and 322. In this manner, breakage occurs in the weakened porous layer 12, in this example, the high porosity layer 12 </ b> H, and the semiconductor substrate 11 is separated from the semiconductor thin film 13.
Are separated (FIG. 6A).

Thereafter, both vacuum suction devices 321 and 32
By stopping the evacuation of the semiconductor substrate 11, the suction force is lost and the semiconductor substrate 11 is removed from the suction devices 321 and 322.
Then, the semiconductor thin film 13 is taken out. Then, a thin film semiconductor 31 is obtained from the semiconductor thin film 13 (FIG. 6B). Also in this case, the porous layer left on the thin film semiconductor 31 can be removed by etching.

Then, with respect to the semiconductor substrate 11, the remaining porous layer is removed by etching, and the same operation as described above is repeated to obtain the same thin film semiconductor 23.
Can be manufactured.

[0072] In Figures 5 and 6A, the first and second vacuum suction devices 321 and 322, the respective portions corresponding to those of the vacuum suction device 32 of FIG. 3F ₁ and FIG. 4G ₁ are denoted by the same reference numerals A duplicate description is omitted.

The suction powers of the first and second vacuum suction devices 321 and 322 are equivalent, for example, 1 kg / c respectively.
m ^{2, in} which case the strength required for separation in the porous layer 12, that is, the separation strength, is 2 kg / cm.
² or less.

Next, an embodiment of the present invention for manufacturing a semiconductor device, for example, a solar cell, will be described. [Embodiment 3] In this embodiment, a porous layer 12 is formed on a semiconductor substrate 11 in the same manner as in Embodiment 1. That is, a wafer-shaped semiconductor substrate 11 made of single crystal Si doped with boron B at a high concentration and having a specific resistance of, for example, 0.01 to 0.02 Ωcm was prepared.

Then, the surface of the semiconductor substrate 11 was anodized to form a porous layer on the surface of the semiconductor substrate 11. In this example, anodization was performed using the anodizing apparatus having the two-tank structure described with reference to FIG. That is, the semiconductor substrate 11 made of single crystal Si is arranged between the first and second tanks 1A and 1B, and both the tanks 1A and 1B have:
Both HF (49% solution): C ₂ H ₅ OH (95% solution)
= 1: 1 electrolyte solution was injected. Then, a current was supplied by the DC power supply 2 between the Pt electrodes 3A and 3B immersed in the electrolytic solutions of the electrolytic solution tanks 1A and 1B.

In this embodiment, first, a current density of 1
A current was applied at a low current of mA / cm ² for 8 minutes. By doing so, the fine porosity is smaller than that of the surface layer 12S in Example 1, the dense porosity is 16%, and the thickness is 1.7 μm.
Is formed (FIG. 7A ₃ ). After the current was once stopped, current was applied at a current density of 7 mA / cm ² for 8 minutes.
By doing so, the intermediate porosity layer 1 having a porosity of 26%, which has a larger diameter than the micropores of the surface layer 12S, and a thickness of 6.3 μm.
2M was formed below the surface layer 12S, that is, inside the surface layer 12S (FIG. 7B ₃ ). Further, after the current supply was once stopped, current supply was performed at a high current density of 200 mA / cm ² for 3 seconds. In this way, the fragility of about 40 to 70% of a higher porosity than that of the intermediate porosity layer 12M is provided in the intermediate porosity layer 12M, that is, at a position vertically sandwiched by the intermediate porosity layer 12M. A high porosity layer 12H was formed (FIG. 7C ₃ ). Thus, the porous layer 12 including the surface layer 12S, the intermediate porosity layer 12M, and the high porosity layer 12H was formed.

Thereafter, the semiconductor substrate 11 was annealed in a normal pressure Si epitaxial growth apparatus in an H ₂ atmosphere. This annealing or heating step can be performed from room temperature to 110
The heating time to 0 ° C. was about 20 minutes, and then this 1
The test was carried out by maintaining the temperature at 100 ° C. for about 30 minutes. Surface layer 12S of the porous layer by the H ₂ annealing became smoother.

Thereafter, the temperature was lowered from the annealing temperature of 1100 ° C. in H ₂ to 1060 ° C., and SiH ₄ gas and B ₂ H ₆
Performing a high-concentration boron-doped Si epitaxial growth using a gas for 3 minutes to form a first semiconductor layer 131 composed of a p-type high-impurity-concentration Si epitaxial growth layer;
Next, a low-concentration boron-doped Si epitaxial growth is performed for 10 minutes using a SiH ₄ gas and a low-concentration B ₂ H ₆ gas to form a second semiconductor layer 132 made of a p-type low-impurity-concentration Si epitaxial growth layer. And then,
Si epitaxial growth is performed for 4 minutes using SiH ₄ gas and PH ₃ gas to form a third semiconductor layer 133 composed of an n-type Si epitaxial growth layer.
A semiconductor thin film 13 was formed by stacking a third semiconductor layer.

By the step of epitaxially growing the semiconductor thin film 13, the high porosity layer 12 H of the porous layer 12 is formed.
Porosity increases, its separation strength decreases, and 1 kg /
cm ² or less or slightly larger.

Next, in this embodiment, a SiO ₂ film, that is, a transparent insulating film 16 is formed on the epitaxial semiconductor thin film 13 by surface thermal oxidation, and pattern etching is performed by photolithography to make contact with an electrode or wiring. An opening 16W is formed (FIG. 8)
E ₃ ). The openings 16W can be formed in parallel with each other in a stripe shape extending in a direction perpendicular to the sheet of FIG. With the SiO ₂ film formed in this way, it is possible to minimize carrier generation and recombination at the interface.

Then, a metal film is vapor-deposited on the entire surface, and pattern etching is performed by photolithography to form an electrode or wiring 17 on the light receiving surface side in the stripe-shaped opening 1.
6W (FIG. 9F ₃ ). The metal film forming the electrode or the wiring 17 is, for example, a 30 nm thick T
An i film, Pd having a thickness of 50 nm, and Ag having a thickness of 100 nm are sequentially deposited, and a multilayer structure film formed by performing Ag plating with a thickness of 8 μm thereon may be used. Thereafter, annealing was performed at 400 ° C. for 20 to 30 minutes.

Next, the striped electrode or wiring 1
7 on each of which a conductive line 41, in this example a metal wire, is bonded, on which a transparent adhesive 2
1, a transparent substrate 4 such as a transparent resin substrate or a glass substrate
2 joining (Figure 9G _3). The bonding of the conductive member 41 to the electrode or the wiring 17 can be performed by soldering. These conductive wires 41 have one ends longer than the electrodes or wirings 17 and are led out.

Thereafter, the first and second vacuum suction devices 321 and 322 similar to those described with reference to FIG. 5 and the like are attached to the semiconductor substrate 11 and the transparent substrate 42, and the suction port of the exhaust device 33 is provided on each suction surface 32s. Adsorb by vacuum suction from 32h.

Then, the first and second vacuum suction devices 3
Move at least one of 21 and 322 to pull them apart. In this manner, the fragile high porosity layer 12H of the porous layer 12 is broken to cause the semiconductor substrate 11 to break.
And the semiconductor thin film 13 (FIG. 10). In this way, as shown in FIG. 11, the thin film semiconductor 2 having the epitaxial semiconductor thin film 13 bonded on the transparent substrate 42 is formed.
3 are configured. In this case, the porous layer 12 remains on the back surface of the thin film semiconductor 23, and a silver paste is applied on the porous layer 12 and a metal plate is further joined to form the other back electrode 24. In this way, p ⁺ −
A solar cell on which the thin film semiconductor 23 having the p ⁻ −n ⁺ structure is formed. This metal electrode 24 also functions as an element layer protective film on the back surface of the solar cell.

In the solar cell formed in this manner, although the light-receiving-side electrode or the wiring 17 is covered with the transparent substrate 42, the external electric conduction from the light-receiving-side electrode or the wiring 17 is carried out by the conductive wire 41 and the outside. Since it is derived, electrical connection with the outside is easily made. Further, as in the above-described embodiment, for example, the conductive lines 41 are respectively derived from the plurality of electrodes or wirings 17 that are in contact with the epitaxial semiconductor thin film 13, that is, the active portion of the solar cell. Therefore, the series resistance of the solar cell can be made sufficiently small.

The above-described conductive wire 41 is not limited to a metal wire, but may be made of, for example, a strip-shaped metal wire.

The transparent substrate 42 can be formed of a rigid substrate such as a glass substrate or a flexible substrate formed of a resin sheet. In the case of using a flexible substrate as described above, the entire solar cell can be configured flexibly.

As described above, when the solar cell is manufactured, the conductive wires can be led out from the respective electrodes 17 irrespective of the fact that the transparent substrate is disposed on the light receiving surface. The connection of the conductive line is mechanically strong in a state formed on the semiconductor substrate 11 before being separated as a thin-film solar cell, and Since the operation is performed in a stable state, mass production can be performed reliably and easily. In this manner, a plurality of solar cells can be easily connected to each other by leading out the conductive wire.

When the porous layer 12 remains on the back surface of the thin film semiconductor in the solar cell, the porous layer 1
2. If the semiconductor substrate 11 has a high impurity concentration, and if the semiconductor substrate 11 also has a high impurity concentration and there is a problem of absorbing photovoltaic power, it can be removed by, for example, etching.

In each of the above examples, the porous layer 1
2 is replaced with a middle porosity layer 12M.
The high porosity layer 12H is formed on the lowermost layer on the opposite side to the surface layer 12S, that is, by changing the conditions of the anodization.
Can be formed at the interface with the semiconductor substrate 11 where the porous layer 12 is not formed. That is, in this case, for example, 200 mA in forming the high porosity layer 12H is used.
By repeating the high current application several times intermittently, it can be formed at the interface between the interface of the intermediate porosity layer and the base region. In this case, the semiconductor thin film 13 and the semiconductor substrate 11 are separated from each other by the porous layer 12 and the porous layer 12.
Is formed at the interface with the semiconductor substrate 11 where no is formed.

In the above-described example, the case where a solar cell is obtained has been described as an example in which the present invention is applied to the manufacture of a thin film semiconductor device. However, the present invention is applied to the case where a thin film semiconductor device such as various other semiconductor integrated circuits is obtained. It goes without saying that it can be done.

As described above, according to the manufacturing method of the present invention, the porous layer is formed on the surface of the semiconductor substrate, the semiconductor is epitaxially grown thereon, and the semiconductor layer is peeled off. Although only the thickness of the epitaxial semiconductor thin film 13 described above is consumed,
After the formation and separation of the semiconductor substrate, the formation of the porous layer, the formation of the epitaxial semiconductor thin film, and the separation can be repeated by polishing the surface of the semiconductor substrate. it can. If the semiconductor substrate is thinned by repeated use, the semiconductor substrate itself can be used as a thin film semiconductor, and for example, a solar cell can be manufactured. Therefore, since the semiconductor substrate can be used almost without waste without being finally invalidated, the cost can be reduced.

Further, the semiconductor substrate whose thickness has been reduced by manufacturing the thin film semiconductor and the solar cell is subjected to epitaxial growth of a semiconductor having a thickness commensurate with the reduced thickness. By repeatedly performing the above, the same semiconductor substrate can be permanently used, so that semiconductor devices such as thin film semiconductors and solar cells can be manufactured at lower cost and with lower energy.

In the case where a method of simply epitaxially growing a semiconductor thin film on a porous layer having a single porosity is used, in order to improve the crystallinity of the semiconductor thin film, it is necessary to use a porous film which serves as a nucleus for crystal growth. Since it is necessary to reduce the porosity of the layer, it is necessary to lower the current density and increase the HF mixing ratio of the electrolytic solution during anodization. However, when the porosity is reduced as described above, the porous layer becomes hard, and it becomes difficult to separate the epitaxial semiconductor thin film. Therefore, in order to increase the porosity in order to weaken the separation strength, for example, if the current density is increased and the HF mixture ratio of the electrolytic solution is reduced among the anodizing conditions, the separation is facilitated in this case, In addition, the crystallinity of the epitaxial semiconductor thin film becomes extremely poor. However, by reducing the porosity of the surface portion of the porous layer and forming a porous layer having a two-sided property that the porosity inside the porous layer is large as in the above-described embodiment, The epitaxial semiconductor film can be favorably formed on the porous layer, and the epitaxial semiconductor film can be easily separated.

The high porosity layer formed on the porous layer is
The larger the porosity, the easier the peeling is, but the larger the strain, and the influence is exerted on the surface layer of the porous layer. For this reason, cracks may occur in the surface layer. In addition, when performing epitaxial growth, it causes defects in the epitaxial semiconductor film. In contrast, as described above, between the very high porosity layer and the low porosity surface layer, as a buffer layer to alleviate the strain generated from these layers, a slightly higher porosity than the surface layer By forming the intermediate porosity layer, a high-quality epitaxial semiconductor film that can be easily peeled off can be formed.

Further, in particular, in the method of the present invention, separation (peeling) of the semiconductor substrate 11 and the semiconductor thin film 13 is performed.
Since a vacuum suction device can be disposed on at least one of the surfaces to hold a substantially uniform suction force over the entire surface, the semiconductor substrate 11 and the semiconductor thin film 13 can be easily and reliably separated without being damaged. It can be carried out. In the case where reinforcement by a supporting substrate is not required in the finally obtained thin film semiconductor 23, by holding both the semiconductor substrate 11 and the semiconductor thin film 13 by a vacuum suction device,
Since the work of adhering and removing the supporting substrate and the holding substrate can be avoided, complicated work, and furthermore, the damage and contamination of the semiconductor thin film 13 or the thin film semiconductor 23 due to this work can be avoided.

[0097]

According to the manufacturing method of the present invention described above, the surface itself of the semiconductor substrate 11 is changed by anodization to form the porous layer 12, on which the semiconductor thin film 13 is grown. The semiconductor thin film 13 can be formed as a semiconductor thin film having excellent crystallinity by epitaxial growth, and can be formed to a thickness as small as necessary. Therefore, the semiconductor thin film 13 is formed at the interface between the intermediate layer of the porous layer 12 or the porous layer. The target thin film semiconductor or semiconductor device obtained by peeling from the semiconductor substrate by breaking is
Therefore, various thin-film semiconductor devices such as a solar cell with high photoelectric conversion efficiency and an integrated circuit device with excellent characteristics can be manufactured and formed.

Further, according to the method of the present invention, the peeling force for separation by vacuum suction, that is, the peeling force for the separation can be held over a wide area, for example, over the entire surface. In peeling (separation), an external force for this peeling can be applied over a wide area, for example, over the entire surface. Breakage or fouling can be avoided as compared with the case where the adhesive is peeled off by bonding to another substrate with an agent. The separation strength of the semiconductor thin film from the semiconductor substrate, that is, the strength required for separation, can be selected with a high degree of freedom by selecting the porosity of the porous layer. It is possible to select the optimum separation strength for the separation. Therefore, this separation can be performed satisfactorily, a breakage accident caused by this separation can be avoided, and a decrease in yield due to breakage can be avoided.

Further, according to the method of the present invention described above, the semiconductor thin film is separated, the porous semiconductor layer is formed again on the semiconductor substrate left behind, and the semiconductor thin film or the semiconductor device is repeatedly formed. Since the manufacturing can be performed, the target thin film semiconductor or thin film semiconductor device can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an example of an anodizing apparatus for performing a method of the present invention.

FIG. 2 is a process diagram (part 1) of one embodiment of the method of the present invention. A ₁ -C ₁ is a cross-sectional view of the respective steps.

FIG. 3 is a process diagram (part 2) of one embodiment of the method of the present invention. D _{1 to} F ₁ are cross-sectional views of each step.

FIG. 4 is a process diagram (part 3) of one embodiment of the method of the present invention. G ₁ and H ₁ are cross-sectional views of each step.

FIG. 5 is a process diagram (part 1) of another embodiment of the method of the present invention.
It is.

FIG. 6 is a process diagram (part 2) of another embodiment of the method of the present invention. A and B are cross-sectional views of the respective steps.

FIG. 7 is a process chart (part 1) of an embodiment of the method of the present invention. A ₃ -C ₃ are sectional views of the respective steps.

FIG. 8 is a process chart (part 2) of the embodiment of the method of the present invention. D ₃ and E ₃ are cross-sectional views of each step.

FIG. 9 is a process diagram (part 3) of another embodiment of the method of the present invention. F ₃ and G ₃ are cross-sectional views of the respective steps.

FIG. 10 is a sectional view (part 4) of a step in another embodiment of the method of the present invention.

FIG. 11 is a sectional view (part 5) of a step in another embodiment of the method of the present invention.

Claims (13)

[Claims] 1. A step of forming a porous semiconductor layer having a layer whose strength is reduced inside or at an interface with the semiconductor substrate by multi-step anodization on a semiconductor substrate, and forming a semiconductor thin film on a surface of the porous layer. And a separation step of separating the semiconductor thin film from the semiconductor substrate in the layer having the reduced strength of the porous semiconductor layer by vacuum-suctioning the back surface of the semiconductor substrate with a first suction force. A method for manufacturing a thin film semiconductor, comprising: 2. The semiconductor thin film according to claim 1, wherein said semiconductor thin film has a separation strength of
The method according to claim 1, wherein the method is selected to be smaller than the attraction force. 3. The semiconductor thin film having a separation strength of 1 kg /
^{2. The} method for producing a thin film semiconductor according to claim 1, wherein the thickness is selected to be not more than cm ² . 4. In the step of separating the semiconductor thin film from the semiconductor substrate, the back surface of the semiconductor substrate is vacuum-adsorbed with a first adsorption force, and the semiconductor thin film side is vacuum-adsorbed with a second adsorption force. 2. The method according to claim 1, further comprising the step of separating the thin film from the semiconductor substrate in the layer of the porous semiconductor layer having the reduced strength. 5. The method according to claim 1, wherein the separation strength of the semiconductor thin film is the first
5. The method according to claim 4, wherein the method is selected to be smaller than the sum of the attraction force and the second attraction force. 6. The semiconductor thin film having a separation strength of 2 kg /
5. The method for producing a thin film semiconductor according to claim 4, wherein the thickness is selected to be not more than cm ² . 7. A step of forming, on a semiconductor substrate, a porous semiconductor layer having a layer whose strength is reduced inside or at an interface with the semiconductor substrate by multi-step anodization, and forming a semiconductor thin film on the surface of the porous layer. Growing a semiconductor element on the semiconductor thin film; and vacuum-adsorbing the back surface of the semiconductor substrate with a first adsorption force to the semiconductor thin film, wherein the strength of the porous semiconductor layer is reduced. And a separating step of obtaining a semiconductor device by separating the semiconductor device from the semiconductor substrate. 8. The semiconductor thin film according to claim 1, wherein said semiconductor thin film has a separation strength of said first thin film.
8. The method for manufacturing a thin-film semiconductor device according to claim 7, wherein said method is selected to be smaller than said attraction force. 9. The separation strength of the semiconductor thin film is 1 kg /
8. The method for manufacturing a thin film semiconductor device according to claim 7, wherein the thickness is set to not more than cm ² . 10. In the step of separating the semiconductor thin film from the semiconductor substrate, the back surface of the semiconductor substrate is vacuum-adsorbed with a first adsorption force, and the semiconductor thin film side is vacuum-adsorbed with a second adsorption force. 8. The method for manufacturing a thin film semiconductor device according to claim 7, further comprising a separation step of separating the thin film from the semiconductor substrate in the layer having the reduced strength of the porous semiconductor layer. 11. The thin film semiconductor according to claim 10, wherein the separation strength of the semiconductor thin film is selected to be smaller than the sum of the first attraction force and the second attraction force. Device manufacturing method. 12. The separation strength of the semiconductor thin film is 2 kg.
/ Cm ² or less.
3. The method for manufacturing a thin film semiconductor device according to claim 1. 13. The method according to claim 1, further comprising a step including a treatment in a vacuum before separating the semiconductor thin film, wherein the separation strength of the semiconductor thin film is 1 k.
8. The method according to claim 7, wherein the g / cm ^{2 is 2} g / cm ^{2 to 2} kg / cm ² .