JP2001089291A - Liquid phase growth method, method of producing semiconductor member and method of producing solar battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a high quality epitaxial substrate at a low cost. SOLUTION: A coarse crystal surface of a base body 109 is brought into contact with a metal solution 112 which is not saturated with a semiconductor raw material and then the base body 109 is brought into contact with a metal solution 114 supersaturated with the semiconductor raw material, thereby the semiconductor layer 115 is grown on the crystal surface of the base body. The semiconductor layer is grown on a base body using this production method, which base body is used in the production method of a SOI substrate or a solar battery, or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid phase growth method, a method for manufacturing a semiconductor member, and a method for manufacturing a solar cell, and more particularly to a method for manufacturing a high quality epitaxial substrate suitable for manufacturing a bipolar LSI or a MOS-LSI. The present invention relates to a manufacturing method that can be suitably used, and a method for manufacturing a solar cell.

[0002]

2. Description of the Related Art In recent years, bipolar LSIs and CMOS-L
In the manufacture of SI, it has been recognized that the use of an epitaxial silicon substrate is extremely preferable.

First, in an epitaxial substrate, it is easy to independently control the impurity concentration in a bulk portion and an epitaxial layer (active layer) portion. Taking advantage of this feature, when a substrate in which an n ⁻ -type epitaxial layer is grown on a p-type substrate is manufactured to form a bipolar LSI, a deep p ⁺
By providing the diffusion region, the individual transistors can be easily cut off, and electrical interference between the individual transistors can be prevented. The p ⁺ (n ⁺⁾ type substrate ^{p -} (n -) type epitaxial layer to produce the substrate grow CMOS-L
When the SI is formed, a latch-up phenomenon via a parasitic thyristor between a p-channel transistor and an adjacent n-channel transistor can be prevented. In particular, it is reasonable to realize the latter substrate having a structure of “low-resistance substrate / active layer having the same conductivity type and high resistance” other than the epitaxial substrate.

[0004] In addition, the Czochralski silicon substrate which has been used conventionally has small voids called as-grown defects in which vacancies are aggregated, and a CMOS-LSI is formed by using such a substrate. It is said that when it is formed, as-grown defects become seeds to cause defects in the gate oxide film, thereby deteriorating the breakdown voltage of the oxide film. This phenomenon is caused by the progress of integration of LSI, and CMOS-
As the gate oxide film of the LSI is made thinner, it has become a serious problem. On the other hand, the epitaxial layer has a
It is said that s-grown defects are far less,
High reliability CMOS-
The manufacture of the LSI becomes easy.

Since heavy metal impurities contained in the substrate form recombination centers and significantly impair device characteristics, a process called gettering has recently been performed to remove heavy metal impurities near the surface. Many. It is known that in an epitaxial substrate, particularly an epitaxial substrate using a substrate containing boron (B) at a high concentration, the removal of heavy metal impurities by the gettering process is extremely effectively performed, and the device using the epitaxial substrate operates. Excellent characteristics.

[0006]

As described above, it has been widely recognized that it is desirable to use an epitaxial substrate for manufacturing various LSIs from various viewpoints. However, despite the simple manufacturing method, the epitaxial substrate is not suitable for manufacturing. It requires considerable cost and prevents its further spread.

One of the reasons is that, particularly when the substrate contains a high concentration of impurities, an epitaxial layer thicker than originally required as an active layer is required. That is, in the LSI manufacturing process, the substrate may be exposed to a high temperature of around 1000 ° C.
The thickness needs to be large enough (for example, 10 to 15 μm) so that impurities contained in the substrate do not diffuse to the surface. In general, a CVD (Chemical Vapor Deposition) method for thermally decomposing a source gas containing silicon such as dichlorosilane or trichlorosilane is used for growing the epitaxial layer. It is possible to grow an epitaxial layer of such a thickness by the CVD method, but the throughput in manufacturing is limited, for example, the number of sheets that can be input per batch is limited, or maintenance of the apparatus is required for each batch. Is low.

In addition, since epitaxial substrates are often used in the manufacture of highly integrated LSIs, their surfaces also require a high degree of smoothness, and the vicinity of the substrate surface generated by mechanical processing for smoothing is required. To remove the damage layer,
Generally, a CMP (Chemical Mechanical Polish) process is repeated about three times, which also causes a large cost increase. That is, it has been desired to develop a method for easily growing an epitaxial layer having excellent smoothness even on a substrate having a somewhat rough surface.

Japanese Patent Application Laid-Open Nos. 5-283722 and 7-302889 disclose a method of manufacturing a solar cell or SOI substrate by peeling a semiconductor thin film grown on a semiconductor substrate from the substrate. ing. These methods are characterized in that a semiconductor thin film grown on a single crystal substrate is transferred to another substrate, and the remaining substrate is reproduced and used again for growing the semiconductor thin film. If a substrate used an appropriate number of times by these methods is further used for manufacturing an epitaxial substrate, one or more semiconductor thin films and one epitaxial substrate can be obtained from one substrate. It can be expected that the manufacturing cost of an epitaxial substrate can be greatly reduced.

In particular, since a p ⁺ substrate is usually used in these steps, if an epitaxial layer having a low impurity concentration is formed on the surface, a p ⁺ / p ⁻ substrate or a p ⁺ / n, which is in high demand, is formed.
^- it is preferable to make the substrate. However, even in this case, the surface of the substrate from which the semiconductor thin film has been peeled has been roughened to a degree that is evident to the naked eye and needs to be smoothed. Does not go up.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has as its object to manufacture a high-quality epitaxial substrate having excellent characteristics and good smoothness at low cost.

Another object of the present invention is to construct a more economical semiconductor manufacturing process by combining a method for manufacturing a solar cell and an epitaxial substrate.

[0013]

The liquid phase growth method of the present invention comprises:
The crystal face of the substrate having a rough crystal face is brought into contact with a metal solution that is unsaturated with respect to the semiconductor raw material, and then brought into contact with a metal solution that has been supersaturated with the semiconductor raw material. Is grown.

In the liquid phase growth method of the present invention, the semiconductor material is brought into contact with an unsaturated metal solution while the crystal surface of the substrate having a rough crystal surface is held horizontally with the crystal surface facing downward. Contact the supersaturated metal solution with
A semiconductor layer is grown on the crystal plane of the base.

According to a method of manufacturing a semiconductor member of the present invention, a substrate having a first semiconductor layer formed by using the liquid phase growth method of the present invention is used as a raw material and a second semiconductor layer is provided on a separation layer. Forming a first member, and bonding the first member and the second member so that the second semiconductor layer is located inside; Separating the second semiconductor layer and transferring it to the second member side.

Further, in the method of manufacturing a semiconductor member according to the present invention, at least a member having a first semiconductor layer on a single crystal substrate via a separation layer is prepared, and the first semiconductor layer is formed by the separation layer. Step of separating from single crystal substrate (Step A)
And contacting the single crystal substrate after separation with a metal solution that is unsaturated with respect to the semiconductor raw material, and then contacting with a metal solution that is supersaturated with the semiconductor raw material to form a second semiconductor layer on the single crystal substrate. (Step B) of producing an epitaxial substrate by subjecting the compound to liquid phase epitaxial growth.

Further, in the method of manufacturing a semiconductor member according to the present invention, at least a first member having a first semiconductor layer on a single crystal substrate via a separation layer is prepared, and the first semiconductor is formed by the separation layer. A step (step A) of separating a layer from the single-crystal substrate, and contacting the separated single-crystal substrate with a metal solution that is unsaturated with respect to the semiconductor raw material, Contacting the liquid crystal layer to form a second semiconductor layer on the single crystal substrate by liquid phase epitaxial growth to form an epitaxial substrate (step B); After forming the second member having the third semiconductor layer,
A step of separating the third semiconductor layer from the single crystal substrate by the separation layer (step C) for the second member.

Further, in the method of manufacturing a semiconductor member according to the present invention, at least a first member having a first semiconductor layer is provided on a single crystal substrate via a separation layer, and the first semiconductor layer is provided inside. After the first member and the second member are bonded so as to be located, the first semiconductor layer is separated from the single crystal base by the separation layer and transferred to the second member side. (1) a step of preparing a semiconductor member (step A), and contacting the separated single crystal substrate with a metal solution that is unsaturated with respect to the semiconductor raw material and then with a metal solution that is supersaturated with the semiconductor raw material. Forming a second semiconductor member by liquid phase epitaxial growth of the second semiconductor layer on the single crystal substrate (process B).

Further, in the method of manufacturing a semiconductor member according to the present invention, at least a first member having a first semiconductor layer on a single crystal substrate via a separation layer is prepared, and the separation layer is positioned inside. After the first member and the second member are bonded to each other, the first semiconductor layer is separated from the single crystal base by the separation layer, and is moved to the second member side, and the first semiconductor layer is moved to the second member side.
(A) preparing a semiconductor member (step A) and contacting the separated single crystal substrate with a metal solution that is unsaturated with respect to the semiconductor raw material, and then brought into contact with a metal solution that is supersaturated with the semiconductor raw material. A step of producing a second semiconductor member by liquid phase epitaxial growth of a second semiconductor layer on the single crystal substrate (step B); and forming a separation layer on the single crystal substrate using the second semiconductor member as a raw material. Forming a third member having a third semiconductor layer with the third member interposed therebetween, and bonding the third member and the fourth member so that the separation layer of the third member is located inside; The third layer is formed by the separation layer of the third member.
Separating the semiconductor layer from the single crystal substrate and transferring the semiconductor layer to the fourth member side to produce a third semiconductor member (Step C).

In the present invention, the crystals refer to single crystals, polycrystals, microcrystals and the like. That is, it means something other than non-crystal (amorphous). In the embodiments and examples described below, the case where the crystal is a single crystal is described, but the liquid phase growth method of the present invention is not particularly limited to the case where a single crystal layer is formed on a single crystal substrate, and the surface is polycrystalline. The present invention can also be applied to the case where a semiconductor layer such as a polycrystal or a microcrystal is formed on a base such as a microcrystal. Further, the entire substrate does not need to have crystallinity, and it is sufficient that the surface to be deposited has crystallinity.

The substrate and the single crystal substrate do not need to be flat, but may be a plate having a curved flat surface, a cylindrical body, a spherical body, or the like.

Conventionally, epitaxial substrates have been manufactured by a vapor phase epitaxial method using a CVD apparatus or a molecular beam epitaxial method. As another growth method, there is a liquid phase epitaxial (LPE) method. However, it has been hardly considered as a particularly demanding method for producing silicon. In the LPE method, a semiconductor layer is grown on a substrate surface by bringing a semiconductor substrate into contact with a solvent metal (melt) in which an element constituting a semiconductor such as silicon is dissolved to make the melt supersaturated. Although the principle is simple, it is difficult to handle a large amount of melt at a high temperature (generally around 1000 ° C.), and it is considered that the reason for the delay of the spread is that an appropriate growth apparatus at a mass production level has not been supplied from an apparatus maker.

However, as a result of intensive studies, the present inventors have made use of a large number of large-sized LPE growth apparatuses, which are described in detail in Japanese Patent Application Laid-Open No. 10-189924, and provided with an appropriate mechanism for handling a melt. A film having a thickness of several tens of μm could be easily grown on the area substrate at a growth rate of several μm / min or more, which is higher than the CVD method. In addition, it was found that the LPE device was easy to maintain after growth and was suitable for mass production. Further, the epitaxial growth film formed by the LPE method has an impurity concentration, a defect density, and the like that are equal to or lower than those of the epitaxial film formed by the ordinary CVD method. Moreover, in the LPE method, by adjusting the conditions of the melt,
It has been found that the smoothness of the substrate surface can be easily improved, and if another melt is used or the conditions of the melt are readjusted, the epitaxial layer can be grown on the substrate having the smoothed surface as it is.

Therefore, according to the method of the present invention, a plurality of semiconductor members are obtained from the same single crystal substrate,
Since the smoothing of the substrate surface and the epitaxial growth can be carried out as a series of steps by utilizing the characteristics of the PE method, it greatly contributes to the reduction in the cost of manufacturing the epitaxial substrate.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A description will be given with reference to FIG. First, a metal such as indium, gallium, tin, aluminum, copper, zinc, or a combination thereof put in the crucible 111 is heated to about several hundred to 1000 ° C. to be melted. In order to prevent oxidation of the metal or the substrate, it is desirable to maintain an inert gas such as nitrogen or argon, or a reducing atmosphere such as hydrogen. Semiconductor materials (silicon, germanium, arsenic, phosphorus, etc.) to be grown in advance are dissolved therein. Even if the semiconductor raw material is pulled up before the semiconductor raw material is completely melted, or if the semiconductor raw material is pulled up after being sufficiently melted, the melt becomes unsaturated with respect to the semiconductor raw material when the melt temperature is increased. The substrate 109 is immersed in the unsaturated melt 112 in which the semiconductor raw material is appropriately dissolved (FIG. 1A). Needless to say, the temperature may be increased after the substrate 109 is immersed, and an unsaturated melt may be obtained. Although FIG. 1A shows a substrate having a rough surface 120, the surface may of course be sufficiently smooth. For the unsaturated melt, the melt is melted from the substrate into the melt, and the surface of the substrate 109 is smoothed as shown by 113 (FIG. 1B). Here, the unsaturated melt 112
The reason for dissolving a certain amount of the semiconductor raw material is that if the concentration of the semiconductor raw material in the melt is extremely low, the semiconductor raw material melts out of the substrate surface extremely, causing spoon-cut irregularities on the substrate surface. Because. Unsaturated melt is 5 to 100 degrees saturated at a certain temperature,
Preferably, the unsaturated state is formed such that the temperature is increased by 10 to 50 degrees. Alternatively, 30% to 90%, preferably 50% to 90% of the time when the melt reaches saturation at a predetermined temperature.
Preferably, the unsaturated state is adjusted by dissolving the semiconductor raw material in the melt for 80% of the time. However, in this case, in order not to cause a significant non-uniform concentration of the semiconductor raw material inside the melt,
It is preferable to dissolve the semiconductor raw material while stirring the melt under predetermined conditions. The surface smoothing with the unsaturated melt is performed so that the surface roughness becomes 10 nm or less, more preferably 5 nm.

Next, the substrate 113 whose surface has been smoothed is
It is immersed in a melt 114 supersaturated with a semiconductor material (FIG. 1 (c)). In order to form a supersaturated melt, the temperature may be lowered slightly after dissolving a sufficient amount of the semiconductor material in the metal solution. Substrate 11 immersed in supersaturated melt 114
3 is deposited on the surface of the semiconductor material, which is no longer meltable from the melt.
15 grows. In FIG. 1C, the epitaxial film 115 is drawn so as to grow on only one surface of the substrate 113, but actually, the growth also occurs on the opposite surface. If it is necessary to avoid this, the growth may be performed by attaching a dummy substrate to the back surface or by growing the two substrates back to back. Several μm of epitaxial film 115
In order to grow the melt 114 thicker than m, the temperature of the melt 114 may be gradually lowered. Two crucibles with different melt temperatures may be prepared, but the melt placed in the same crucible 111 is first adjusted to be unsaturated, the substrate 109 is immersed to dissolve the surface, and then the melt temperature is lowered to supersaturate. Then, the epitaxial film 115 can be grown on the surface.

Thus, an epitaxial substrate 116 is formed. Note that the rough surface is specifically a surface that has not been mirror-polished, or a substrate that has a porous region exposed on at least a part of the surface. The porous material is formed through, for example, a process of anodizing a Si wafer and implanting hydrogen or the like into the Si wafer, which will be described later. According to this embodiment, an epitaxial wafer can be easily formed even on a substrate having a rough surface.

[Second Embodiment] Next, an application example using the first embodiment of the present invention will be described.

FIG. 2A shows an epitaxial wafer obtained by using the method shown in FIG.

First, the portion of the epitaxial layer 420 is anodized. A part of the surface may be formed, or the entire wafer may be formed. FIG. 2B shows the case where the chemical conversion is performed by the thickness of the epitaxial layer. However, the chemical conversion may be performed by the thickness smaller than the thickness of the epitaxial layer, or the chemical conversion may be performed to a depth deeper than the thickness of the epitaxial layer 420. May be. Also, the pore density can be changed by changing the current density during anodization. For example, a low-porosity porous layer can be formed on the outermost surface, and a high-porosity porous layer with low mechanical strength can be formed in the lower region.

Next, as shown in FIG. 2C, a non-porous single-crystal silicon layer 402 is formed. The formation is performed by thermal CV
D, a CVD method such as photo CVD or plasma CVD, a sputtering method, or an MBE method can be used.

Of course, the above-mentioned liquid phase growth method may be used.

FIG. 2 shows a case where a single crystal silicon layer is grown as a non-porous single crystal.
A compound semiconductor such as InP, GaN, InGaAsP, or AlGaAs may be used.

Next, an insulating layer 403 is formed on the surface of the non-porous single crystal layer 402 (FIG. 2D). For example, oxidize the surface. This insulating layer forming step can be omitted in a case where an insulating layer or the like is provided on the side to be bonded of the base to be bonded to the base 425 in FIG.

Next, it is bonded to the second substrate 404 (FIG. 2E).

In FIG. 2, SiO 2 is formed on the surface as a second substrate.
_Although a Si substrate having ₂ is shown, the present invention is not limited to this, and may be a simple Si substrate or a light-transmitting substrate such as quartz or plate-like or film-like plastic.

Here, the structure formed by bonding is referred to as a multilayer structure (FIG. 2 (f)).

When an SOI substrate is manufactured, the first
The second substrate and the second substrate may be attached to each other with an insulating layer interposed therebetween, and one example thereof is to form an insulating layer on the non-porous single crystal layer 402, for example. Instead, the second substrate itself may be used as an insulator, or the insulating layer 421 may be formed over the second substrate. In FIG. 2, the insulating layer is formed on both the first and second substrates. However, the insulating layer may be provided on one of the first substrate and the second substrate, and the insulating layer is not necessarily formed on both. do not have to. Needless to say, the first substrate and the first substrate can be attached to each other with an insulator such as an insulating sheet interposed therebetween.

Then, as shown in FIG. 2G, the multilayer structure is separated using a porous layer. Examples of the separation method include separation by external force such as pulling, shearing, and pressurization, a method of inserting a wedge or the like into or near the porous layer 401 serving as a separation layer, or a method in which a fluid such as water, an etching solution, or a gas is used in a thin nozzle. There is a method of spraying near the separation layer. In particular, it is preferable that separation is performed at the porous layer 401 by a water jet.

Thus, the semiconductor substrate 423 (SOI in the figure)
A substrate is formed. When a porous layer remains on the surface of the semiconductor substrate 423 or the surface property is poor, selective etching (for example, a solution containing HF, a solution containing HF + H ₂ O ₂ , a solution containing HF + H ₂ O ₂ + ethyl alcohol, Alternatively, a solution containing HF + H ₂ O ₂ + isopropyl alcohol), polishing (for example, CMP), or grinding is performed.

Further, the surface smoothness may be improved by hydrogen annealing. The hydrogen annealing temperature is 80
A temperature of about 0 ° C to 1200 ° C is preferably used.

When an SOI substrate is manufactured using an epitaxial substrate formed by the method of the present invention, stacking faults are more likely to occur on the surface of the SOI substrate than when a generally used Czochralski wafer is used as it is. Tend to be small. This is because the wafer of the Czochralski method contains considerable oxygen due to its manufacturing method, and this oxygen causes oxygen-induced defects on the substrate surface prior to the growth step of the non-porous single-crystal silicon layer 402, and this defect is While stacking faults occur in the non-porous single-crystal silicon layer 402 as nuclei, the liquid phase growth method employed in the method of the present invention has a low oxygen content in the grown epitaxial layer 420,
It is considered that the nucleus of the defect is hardly formed. In addition, it is most suitable for anodization but is relatively expensive and has low resistance (for example, P
⁺ Wafer) Without using a wafer, the epitaxial layer 42
Since the same effect can be obtained by doping 0, it is preferable from the viewpoint of reduction in manufacturing cost.

After the separation, a substrate 424 which is a part of the first substrate 400 is obtained as shown at 424 in FIG. The thickness of the porous layer in FIG.
If the thickness is sufficiently smaller than 0, the substrate 424 includes the entire first substrate 400. If necessary, the substrate 424 can be reused after being subjected to polishing, grinding, hydrogen annealing, selective etching, or a combination thereof to improve the surface flatness. It may be used again for forming the SOI, but of course, the substrate 424
May be subjected to the steps of Embodiment 1 described above to produce an epitaxial wafer.

As shown in FIG. 3, a substrate 425 having a non-porous single crystal layer on a porous silicon layer serving as a separation layer has hydrogen (positive ions or negative ions) and a rare gas (He , Ar, etc.) to form an ion-implanted layer 427 (microbubble layer or microbubble layer) serving as a separation layer. This point is described in detail in JP-A-5-211128.

[Third Embodiment] The present embodiment relates to a case where a solar cell is manufactured using the epitaxial wafer manufactured according to the first embodiment.

FIG. 4A shows an epitaxial wafer obtained by an application of the first embodiment.

First, a porous layer serving as a separation layer is formed by anodization (FIG. 4B). The formation region is the same as that of the second embodiment.

Next, as shown in FIGS. 4C and 4D, p
^- after the formation of the semiconductor thin film 102 of the mold, n using the diffusion method or the like
⁺ Layer 103 is formed. Of course, the conductivity types may be opposite to each other, and it is sufficient if a pn junction can be formed without using a diffusion method.

Thereafter, as shown in FIG. 4E, a grid electrode 104 is formed. Of course, even if an electrode is formed under the substrate shown in FIG. 4E, the electrode functions as a solar cell, but here, the following steps are further added.

That is, as shown in FIG. 4F, a transparent sheet (peeling substrate) 105 is attached with a transparent adhesive.

Then, as shown in FIG.
Separate by 01.

As shown in FIG. 4H, the back electrode 107 is attached, and the solar cell is completed.

The case where the porous layer 151 remains during the separation is shown. However, when the absorption of sunlight transmitted through the non-porous single-crystal silicon layer 402 by the remaining porous layer 151 cannot be ignored, or when the contact resistance between the porous layer 151 and the back electrode 107 is high, Porous layer 1
It is better to remove 51.

After removing the residual porous layer, the substrate 109 after peeling may be reused for manufacturing a solar cell again, or may be manufactured as an SOI substrate or subjected to the steps of Embodiment 1 to be diverted as an epitaxial wafer. Can also.

[Fourth Embodiment] A typical example of the method of the present invention will be described with reference to FIG. Here, the case of silicon will be described. Step A is a step of manufacturing a semiconductor thin film. In addition,
Here, a case where a semiconductor thin film is used as a solar cell will be particularly described, but the present invention is not limited to this.

First, as shown in FIGS. 5A and 5B, a separation layer is formed on the surface of the single crystal substrate 100. Here, a porous layer 101 is formed as the separation layer. Other separation layers will be described separately. In order to form the porous layer 101 with good controllability, it is preferable to use a low-resistance p-type (p ⁺ ) substrate having a specific resistance of about 0.005 to 0.1 Ωcm.
Even if the substrate has higher resistance, CVD, LP
Even if a p ⁺ layer is formed by a method such as E or thermal diffusion, it can be used similarly. The plane orientation of the crystal is (100)
Commonly distributed materials such as and (111) are preferably used.

First, the single crystal substrate 10 was placed in a solution of hydrofluoric acid.
0 and a counter electrode (not shown) are immersed and energized so that the substrate becomes positive (anodizing treatment). In this case, silicon is dissolved by an electrochemical reaction on the surface of the substrate 100. However, when the concentration of hydrofluoric acid is high and the flowing current is appropriately maintained, the dissolution of silicon proceeds locally, and the fineness of several hundred angstroms is reduced. Pores grow intricately and entangle, forming a porous layer 1
01 is formed. The proportion of the volume occupied by the pores in the porous layer 101 increases as the current flowing increases. If the current value is changed during the processing, a plurality of layers having different pore sizes can be formed.

Next, as shown in FIG. 5C, a semiconductor thin film 1 was placed on a single crystal substrate having a porous layer 101 formed on the surface.
Grow 02. Its thickness is typically 5-50 μm for solar cell applications. For growth, LPE
A method such as a CVD method, a thermal CVD method, or a plasma CVD method can be used. In particular, when the LPE method or the thermal CVD method is used, a high-quality epitaxially grown film can be obtained. When the LPE method is used, a film having a thickness of 20 μm or more can be easily grown.
The LPE method will be described later in detail.

In order to form a semiconductor junction for a solar cell, a dopant is added to the semiconductor thin film 10 during the growth.
2 or a method of applying a dopant diffusing agent to the grown semiconductor thin film and thermally diffusing the dopant into the semiconductor thin film 102. 103
Is the formed n ⁺ layer. Further, as shown in FIG. 5E, in order to extract a current from the surface, a comb-shaped conductive ink pattern is printed on the semiconductor surface and baked to form the grid electrode 104.

Next, as shown in FIG. 5 (f), a transparent sheet is adhered to the surface as a release substrate 105 with a transparent adhesive. As the peeling substrate 105, a transparent resin film having high flexibility such as polycarbonate or PET can be used, or a rigid substrate such as a glass plate can be used. Next, as shown in FIG. 5 (g), when the substrate 100 is fixed and a force is applied to the peeling substrate 105,
The portion of the porous layer 101 that has been made brittle by forming fine holes is broken, and the semiconductor thin film 102 is separated from this portion. In the case where a flexible peeling substrate 105 is used, the semiconductor thin film 102 can be sequentially peeled from the edge by applying a force to turn while rotating a roller holding the edge of the substrate. When a rigid substrate is used, the porous layer 10
The semiconductor thin film 102 can be separated by implanting wedges in the semiconductor thin film 102. Further, the semiconductor thin film 102 can be separated by applying a thermal shock such as rapid cooling or rapid heating of the peeling substrate 105 and a difference in thermal expansion coefficient from the substrate. The separation can also be performed by using the above-mentioned fluid jet such as water.

As shown in FIG. 5 (i), a back electrode 107 such as a metal sheet is attached to the back surface of the separated semiconductor thin film 102 in order to extract a current.
8 is completed. A porous layer may be left on the semiconductor thin film 102 to increase the absorptance of incident sunlight.

The substrate 109 which has been peeled off usually has unevenness due to the residue of the porous layer 101 and the like, and the gloss is completely lost. Such a surface condition can be greatly improved by etching with an alkaline solution or electrolytic polishing. The substrate 110 thus regenerated as shown in FIG. 5H can be used again as the single crystal substrate 100 in the step A. In particular, when the (111) substrate is used, it can be suitably reused in the step A if the film is regenerated to a state where slight clouding remains visually. The thickness of the porous layer 101 is usually about 5 to 10 μm, and the thickness of the single crystal substrate 100 is reduced by about 5 to 10 μm each time the process A is performed once.
If a single crystal substrate of about m is used, it is not difficult to repeat step A about 10 times.

When the step A, which is repeated once or twice or more, is completed, the substrate 109 is left at the end, and the substrate B is used to perform the step B to manufacture an epitaxial substrate.

In an epitaxial substrate, smoothness is required strictly on the surface of a crystal after growth. Specifically, in the case of an epitaxial substrate, the permissible smoothness is determined from the depth of focus of the exposure apparatus used in the photolithography process, and the design rule is a guideline inside the exposure area (about 20 × 20 mm). It is required to be 0.3 μm or less, and it is difficult to use it in a state where roughness is visually observed. To achieve this accuracy, generally wrapping,
A series of steps of etching and polishing are required.

In the method of the present invention, the above precision is achieved in a simpler process B, and epitaxial growth is subsequently performed. First, a metal such as indium, gallium, tin, aluminum, copper, zinc or the like put in the crucible 112 is heated to several hundred to 1000 ° C
Heat to the desired level and dissolve. To prevent oxidation of metals and substrates,
It is desirable to maintain an inert gas such as nitrogen or argon, or a reducing atmosphere such as hydrogen. Semiconductor materials (silicon, germanium, arsenic, phosphorus, etc.) are previously dissolved therein. Even if the semiconductor raw material is pulled up before the semiconductor raw material is completely melted, or if the semiconductor raw material is pulled up after being sufficiently melted, the melt becomes unsaturated with respect to the semiconductor raw material when the melt temperature is increased.

As shown in FIG. 5J, the peeled substrate 109 is immersed in the unsaturated melt 112 in which the semiconductor raw material is appropriately melted. As shown in FIG. 5 (k), for the unsaturated melt, melting from the substrate to the melt occurs, the residue of the porous layer remaining on the surface of the substrate 109 melts, and the surface is smoothed. The substrate 113 is manufactured. Here, the reason for dissolving a certain amount of the semiconductor raw material into the unsaturated melt 112 is that if the concentration of the semiconductor raw material in the melt is extremely low, the semiconductor raw material is extremely dissolved from the substrate surface, and rather the substrate surface is melted. This is because spoon-cut irregularities occur on the surface.

Next, as shown in FIG. 5 (l), the substrate 113 whose surface has been smoothed is immersed in a melt 114 supersaturated with a semiconductor material in another crucible. In order to form a supersaturated melt, the temperature may be lowered slightly after dissolving a sufficient amount of the semiconductor material in the metal solution. Supersaturated melt 11
On the surface of the substrate 113 immersed in 4, a semiconductor raw material that is no longer melted from the melt is deposited, and the epitaxial film 115 grows because the substrate is a single crystal. By pulling up from the melt 114, an epitaxial substrate 116 shown in FIG. In FIG. 5 (l), the epitaxial film 115 is drawn so as to grow only on one surface of the substrate 109, but actually, the growth also occurs on the opposite surface. If it is necessary to avoid this, the growth may be performed by attaching a dummy substrate to the back surface or by growing the two substrates back to back. In order to grow the epitaxial film 115 to a thickness of several μm or more, the temperature of the melt 114 may be gradually lowered. Alternatively, the melt placed in the same crucible 111 may be first adjusted to be unsaturated, the substrate 109 may be immersed to melt the surface, and then the melt temperature may be lowered to make the melt supersaturated, and the epitaxial film 115 may be grown on the surface.

Referring to FIG. 6, a possible mechanism for producing an epitaxial substrate having high smoothness by the method of the present invention will be described. FIG. 6A shows a state in which a single crystal substrate 202 that has been separated and held horizontally is immersed in an unsaturated melt 201 with its main surface facing down. In this state, the melt of the semiconductor occurs with the passage of time, and the melt whose density has decreased due to an increase in the concentration of the semiconductor raw material accumulates along the main surface of the substrate 202 facing downward. At that time, the convex part 2
Melting occurs preferentially from 03, while melt having a high density of the semiconductor raw material is concentrated in the concave portion 204, so that the semiconductor raw material is less likely to be melted. The surface 205 immediately after being immersed in the melt in this way gradually becomes a surface in which the contrast of the surface irregularities is reduced as indicated by 206. In this case, the semiconductor is leached out only on the main surface facing down, but actually leaching also occurs from the opposite surface. In order to avoid this, a dummy substrate may be attached to the back surface to perform melting.

This substrate 202 is immersed in a supersaturated melt 207. Also in this case, the density of the semiconductor raw material is higher in the vicinity of the surface of the concave portion 204 than in the vicinity of the surface of the remaining convex portion 203, so that the growth is faster and the surface 208 immediately after being immersed in the melt.
Is expected to eventually become almost completely smooth as shown in 209.

In the method of the present invention, the single crystal substrate 202
The thickness unevenness existing over the entire surface can be reduced to some extent, but if the initial unevenness is large and the improvement is insufficient, it is effective to wrap the surface of the single crystal substrate 202 before entering the step B. It is a target. Lapping alone does not provide sufficient smoothness and leaves a damaged layer near the surface of the substrate, but these can be effectively improved by the method of the present invention.

In the above description, an example of manufacturing a plurality of thin-film single-crystal silicon solar cells and one silicon epitaxial substrate by repeatedly using one single-crystal silicon substrate has been described. A plurality of SOI substrates and one silicon epitaxial substrate can be manufactured by using the method of the present invention. Needless to say, a plurality of SOI substrates, a plurality of thin-film single-crystal silicon solar cells, and one epitaxial substrate can be manufactured by repeatedly using one piece of single-crystal silicon. In addition, GaAs,
A plurality of thin film compound semiconductors and one semiconductor substrate are obtained by using a single crystal substrate of a compound semiconductor such as GaN or InP, or a plurality of thin film compounds are obtained from one single crystal silicon substrate by using a heteroepitaxial method. The method of the present invention can also be used to obtain a semiconductor and a single silicon epitaxial substrate. As described above, a more economical semiconductor manufacturing process is constructed by combining the SOI or solar cell manufacturing method using the separation layer with the liquid phase epitaxial growth method (Embodiment 1) that also has a surface planarization function. be able to.

Of course, using the epitaxial wafer 116 obtained in this embodiment,
An OI substrate and a solar cell can also be manufactured.

In this case, since the epitaxial layer is always stacked, a decrease in the film thickness due to the formation of the separation layer or the like can be prevented.

[0074]

Embodiments of the present invention will be described below in detail with reference to the drawings.

[Embodiment 1] In this embodiment, an example in which an epitaxial substrate is manufactured using a wafer in a state where a single crystal silicon ingot is sliced as a substrate will be described. Conventionally, in the production of an epitaxial substrate, a substrate whose surface has been smoothed by lapping, etching, and polishing after slicing has been used. That is, the surface as sliced has not only poor smoothness but also damage to the inside, and when an epitaxial layer is grown thereon, defects are likely to occur.

The surface roughness of the p-type substrate as sliced was measured with a stylus type surface roughness meter (50 μm was scanned using an alpha-step 200 manufactured by Tencor Instruments, and the peak-to-valley was scanned). The same apparatus was used for the measurement of plane roughness of about μm in Examples described later.), The average roughness was 1 μm, and there was no gloss visually. Then, after polycrystalline silicon was dissolved in indium at 900 ° C. in a crucible of a liquid phase growth apparatus, the temperature was increased to 10 ° C.
The temperature was raised to 00 ° C. to adjust the unsaturated melt. The wrapped substrate was immersed therein while keeping the main surface downward and horizontal. After leaving the substrate for about 20 minutes in this state, the substrate was pulled up, and the substrate was taken out for confirmation.
Gloss was obtained when the average roughness of the surface was 5 nm or less. The average surface roughness is Nanos manufactured by Rank Taylor Hobson.
Scanning was performed at 50 μm using tep, and the height difference of peak-to-valley was measured (the average roughness of the surface was measured using the same apparatus in the examples described later). Then 900 ° C
Another melt prepared by dissolving polycrystalline silicon in indium was gradually cooled at −0.5 ° C./min. When the temperature reached 880 ° C., the main surface was kept horizontal with the main surface facing downward in the melt 114. While the substrate was immersed for 10 minutes, a single-crystal silicon film of about 5 μm grew epitaxially. The average roughness of the surface of this film was 2 nm or less. The average roughness of the surface was measured using a Nanostep (manufactured by Rank Taylor Hobson) at 50 μm, and the height difference of peak-to-valley was measured (the average roughness of the surface was also measured using the same apparatus in Examples described later). Was measured.). According to the SIMS method, C
And the concentration of O is 10 ¹⁶ cm ⁻³ or less, and the concentration of indium is 10 ¹⁵ cm ^−3.
It could not be detected below cm ^-3 . From the hole mobility measurement, it was found that this epitaxial film was p ^- type. The surface density of stacking faults was 10 ² cm ^-2 or less, and a p / p ^- substrate having good characteristics was obtained.

For comparison, a single-crystal Si film was epitaxially grown to a thickness of 5 μm by a CVD apparatus using a substrate as sliced in the same manner. The growth conditions are as follows. Dichlorosilane (SIH ₂ C) diluted with hydrogen as a source gas
l ₂ ) was flushed. The flow rate is 180 L / min of hydrogen and 0.5 L / min of dichlorosilane. The pressure was 80 Torr, and the growth temperature was 950 ° C. The average roughness of the surface of the grown film is 1
With a thickness of at least μm, the roughness of the substrate surface was inherited. Further, the stacking fault was 10 ⁵ cm ⁻² or more, which proved to be unsuitable for practical use as an epitaxial substrate.

[Embodiment 2] In this embodiment, an example in which a plurality of thin-film single-crystal silicon solar cells and one p ⁺ / p ^- epitaxial substrate are manufactured from one single-crystal silicon substrate will be described. .

(Step A) The steps of this embodiment will be described with reference to FIG. Plane orientation (111) p of specific resistance 0.01Ωcm
^{A +} type 5 inch φ single crystal silicon substrate 100 and a platinum electrode (not shown) of the same size as this were opposed to each other at an interval of 5 cm and held in a Teflon bat. This was filled with a mixed solution of hydrofluoric acid (49% by weight) and ethanol at a volume ratio of 1: 0.1. In this state, a voltage is applied so that the substrate 100 becomes positive, and 1 A for 5 minutes at the beginning and 3 A for 1 minute at the end.
When a current of?
01 was formed. Here, the porous layer 101 was composed of two types of layers having different volume ratios (porosity) of the micropores corresponding to the increase in the current value on the way, and the porosity increased in the layer deeper from the surface. Subsequently, the substrate was set in a liquid phase growth apparatus.

In the inside of the liquid phase growth apparatus, a reducing atmosphere is maintained by constantly flowing hydrogen. 95 indium in crucible
While heating and melting at 0 ° C., the polycrystalline silicon substrate made p-type with B was left for a sufficient time to form a melt. With the substrate on which the porous layer was formed kept outside the melt, the hydrogen reducing atmosphere was heated to 1050 ° C. and left for 10 minutes.
During this time, the surface of the porous layer 101 was modified. Thereafter, the atmosphere was cooled, and the substrate was immersed in the melt at 930 ° C. Thereafter, cooling was continued for 15 minutes at a rate of -1 ° C./min.
m of the silicon film 102 was grown. When this film was measured for hole conductivity, it was found to be weak p (p ⁻ ) type. A diffusing agent containing phosphorus was applied to the surface of the silicon film 102 by a spin coater, placed in a diffusion furnace, and thermally diffused in a nitrogen atmosphere at 900 ° C. for 30 minutes to form an n ⁺ layer 103 on the surface to form a semiconductor junction.

Further, the grid electrode 104 was formed by printing and baking silver paste on the surface in a comb tooth pattern using a screen printing machine. A passivation layer (not shown) for suppressing surface recombination may be provided on the surface of the n ⁺ layer. As the passivation layer, for example, silane (SiH ₄ ) and ammonia (NH ₃ ) are used to form a plasma CV.
A silicon nitride film deposited by the method D is preferably used.
Thereafter, a polycarbonate sheet 105 was attached with a transparent epoxy adhesive.

Next, when cold air at −70 ° C. was blown onto the surface of the polycarbonate sheet 105, the semiconductor thin film 102 was separated from the substrate 100 by thermal shock. This is because the sheet 105 is cooled and contracted, and the stress is applied to the porous layer 101.
Layer that has become brittle due to the formation of micropores
It seems that 01 was destroyed. A copper sheet was adhered to the rear surface of the peeled semiconductor thin film with a conductive adhesive mainly containing silver to form a rear electrode 107, thereby forming a thin film single crystal silicon solar cell.

On the other hand, the surface of the substrate 100 from which the semiconductor thin film 102 has been peeled off has no gloss at all because a part of the porous layer 101 remains, but when it is etched with an alkaline solution, a slight clouding is visually observed. However, an almost smooth surface was obtained. The porous layer 101 was formed again on the surface of the substrate, and the process A was repeated in the same manner as described above to form nine thin-film single-crystal silicon solar cells 108.

(Step B) An epitaxial substrate was manufactured using the substrate 109 left in the step A. When the surface roughness of the substrate 109 was measured with a stylus type surface roughness meter, the average roughness was 2 μm.
And there was no gloss visually. When the thickness unevenness over the entire surface of the substrate was measured, it was ± 25 μm. First, lapping the substrate surface with alumina powder,
It was 10 μm. The average roughness was also improved to 0.5 μm, but there was still no gloss visually. Next, after melt | dissolving polycrystalline silicon in 900 degreeC indium in the crucible 111 of a liquid phase growth apparatus, the temperature was raised to 1000 degreeC and the unsaturated melt 112 was adjusted.

The wrapped substrate 109 is placed therein.
Was immersed while keeping the main surface downward and horizontal. After leaving the substrate for about 10 minutes in this state, the substrate was pulled up, and the substrate 113 was taken out for confirmation. The gloss was obtained when the average roughness of the surface was 0.03 μm or less. Then 900 ° C
Another melt 114 prepared by dissolving p-type polycrystalline silicon sufficiently doped with B in indium is gradually cooled at −0.5 ° C./min. When the substrate 113 was immersed for 30 minutes while maintaining the horizontal position downward, an epitaxially grown film 115 of about 15 μm grew. The average roughness of the surface of this film is 0.01
μm or less. According to the SIMS method, the doping concentration of B is 10 ¹⁶ cm ^-3 and the concentrations of C and O are 10 ¹⁶ cm ^-3.
In the following, In was not detectable at 10 ¹⁵ cm ⁻³ or less. The surface density of stacking faults is 10 ² cm ^-2 or less,
It was found that ap ⁺ / p ^- substrate having good characteristics was obtained. [Embodiment 3] In this embodiment, a plurality of thin-film single-crystal silicon solar cells manufactured by a method different from that of Embodiment 1 and one n / n ^- epitaxial substrate are manufactured from one single-crystal silicon substrate. Will be described.

(Step A) As shown in FIG. 7B, the hydrogen ion acceleration energy is set to 1 MeV and the dose is set to 1 on the 6-inch square n-type silicon substrate 300 shown in FIG.
Hydrogen ions 301 were implanted at 0 ¹⁷ cm ^-2 . As a result, an atomic hydrogen implantation region 302 was formed in the silicon substrate. The implantation depth was about 25 μm. Next, FIG.
(C) As shown in FIG.
At a temperature of 00 ° C., a p ⁺ -type microcrystalline silicon film 305 was deposited on the surface of silicon to form a semiconductor junction. Further, a mask is hung thereon to deposit Ni with a thickness of 0.1 μm to form a grid electrode pattern, and Cu is plated with a thickness of 10 μm along this pattern to form a grid as shown in FIG. The electrode 306 was used. As shown in FIG. 7 (e), a coating solution of titanium oxide is applied to the surface of the glass substrate, and the glass plate is covered with the glass plate. Simultaneously with the bonding, hydrogen is liberated in the hydrogen ion implanted region 302 to form fine holes to form a hole region 304, and the semiconductor thin film 303 is finally separated from this portion (FIG. 7).
(F)). As shown in FIG. 7H, a back electrode 309 was formed on the back surface of the semiconductor film 303 in the same manner as in Example 1 to obtain a thin-film single-crystal Si solar cell 310. In addition, a fluid (for example, a liquid such as water or an etching liquid or a gas such as a rare gas or a nitrogen gas) may be sprayed on the side surface of the bonded substrate to be separated.

Although the surface of the remaining substrate 300 shown in FIG. 7 (g) was not glossy, when it was treated with an alkaline solution, a smooth surface was obtained. Hydrogen ions were implanted into this substrate again, and step A was repeated in the same manner as above to produce four more thin-film single-crystal silicon solar cells 310. The implantation of hydrogen ions is performed by a plasma ion implantation technique (for example,
PIII (Plasma immersion) described in WO98 / 52216
ion implantation) can also be used.

(Step B) Using the remaining substrate 308, an epitaxial substrate was manufactured. The average roughness of the surface of the substrate 308 was 1.0 μm, and the thickness unevenness was ± 15 μm. In this example, lapping was not performed because the thickness unevenness was relatively small. First, polycrystalline silicon converted into n-type with phosphorus is melted into indium at 980 ° C. in crucible 312 of the liquid phase growth apparatus, and then the temperature is increased to 1000 ° C.
Unsaturated melt 313 was prepared. In this, the substrate 308 after peeling was immersed while holding the main surface horizontally with the main surface facing down. Subsequently, the melt was gradually cooled at a rate of −0.2 ° C./min while stirring well. As the temperature decreased, the unsaturated melt became a supersaturated melt 315. Melt is 950
When the temperature reached ° C., when the substrate 308 was pulled up, an epitaxially grown film 315 having a thickness of about 10 μm was grown on the surface. The average roughness of the surface is 1 nm or less.
According to the MS method, the doping concentration of P was 10 ¹⁶ cm ⁻³ , the concentrations of C and O were 10 ¹⁶ cm ⁻³ or less, and In was not detected at a concentration of 10 ¹⁵ cm ⁻³ or less. Also, when the surface density of stacking faults was evaluated, it was found that it could be manufactured on an n / n ^- substrate with good characteristics at 10 ² cm ^-2 or less.

[Embodiment 4] In this embodiment, a single single crystal silicon substrate is used, and a plurality of SOI substrates and one
An example of manufacturing one p / n / p ⁺ epitaxial substrate will be described.

(Step A) A 5-inch φ (100) p ⁺ -type (single-resistance 0.01 Ωcm) first single-crystal Si substrate 400 shown in FIG. In a 2: 1 chemical solution, the cells were differentiated into 12 at a current of 1 A.
As shown in (b), a porous Si layer 401 was formed.
This substrate was oxidized at 400 ° C. for 1 hour in an oxygen atmosphere. Due to this oxidation, the inner wall of the hole of the porous Si layer 401 was covered with the thermal oxide film. Next, as shown in FIG.
On the layer 401, while maintaining a pressure of 80 Torr and a substrate temperature of 950 ° C. by a thermal CVD method, dichlorosilane and hydrogen are flowed as source gases at 0.5 L and 180 L per minute, respectively, to form a single-crystal Si layer 402 having a thickness of 1 μm. It was epitaxially grown. Further, as shown in FIG.
100 nm of Si is formed on the surface of the i-layer 402 by thermal oxidation.
An O ₂ layer 403 was formed.

[0091] Next Figure 8 (e), the and the SiO ₂ layer 403 surface, a thickness of 500nm separately prepared SiO ₂
After the layer and the Si substrate 404 having a layer formed on the surface were brought into contact with each other, they were heat-treated at 900 ° C. for 2 hours and bonded.
The two SiO ₂ layers 403 and 404 are bonded to form the SiO ₂ layer 405 (FIG. 8F). Next, a plate was adhered to both sides of the bonded substrate with an adhesive (not shown), and a force was applied in a direction to separate the two plates from each other.
Separated from the porous Si layer 401 (FIG. 8 (g)). Further, the remaining porous Si layer was immersed in a mixed solution of hydrofluoric acid and 30% hydrogen peroxide at a volume ratio of 1: 5, and was selectively etched while stirring. The epitaxial Si layer 402 remained without being etched, and the porous Si remaining after the peeling was selectively etched using single-crystal Si as a material for the etch stop, and completely removed. The etching rate of single-crystal Si with respect to the etching solution is extremely low, and the selectivity with the etching rate of the porous layer reaches 10 ⁵ or more.
The etching amount of i (about several tens angstroms) can be practically ignored.

Thus, as shown in FIG.
An SOI substrate 406 in which a single-crystal Si layer having a thickness of 1 μm was stacked on the oxide film was formed. Porous Si401
Epitaxial layer 40 by selective etching of
There was no change in 2. Further, as shown in FIG. 8H, the porous layer remaining on the Si substrate separated by the porous Si layer 401 was removed by the same etching, and the surface was polished. Regenerated Si substrate 407
By repeating the above-described steps using the method, three SOI substrates having a high-quality semiconductor layer were obtained.

(Step B) An epitaxial substrate was manufactured using the substrate 409 (without polishing) left in the step A. The surface roughness of this substrate 408 was 0.5 μm, and the thickness unevenness was ± 10 μm, but it was not visually glossy.
First, polycrystalline silicon was dissolved in indium at 950 ° C. in a crucible, and then the temperature was raised to 1000 ° C. to prepare an unsaturated melt 408. In this, the substrate 409 was immersed while keeping the main surface downward and horizontal (FIG. 8 (j)). In this state, the substrate 409 was pulled up after being left for about 10 minutes.
When the substrate was taken out for confirmation, the average roughness of the surface was 5 nm and gloss was observed.

Next, B was added to indium at 900 ° C. in another crucible.
Another melt 410 prepared by dissolving doped p-type polycrystalline silicon is gradually cooled at a rate of -0.5 ° C / min to 880 ° C.
Then, when the substrate 408 was immersed in the melt for 20 minutes while keeping the main surface downward and horizontal, a p-layer 411 having a thickness of 10 μm grew (FIG. 8 (k)). In another crucible, melt 412 prepared by dissolving P-doped n-type polycrystalline silicon in tin at 900 ° C. was heated to −0.5 ° C.
When the substrate 409 was immersed in the melt for 4 minutes while keeping the main surface face down, the n-layer 413 having a thickness of 2 μm was grown (at 880 ° C.). FIG. 8 (l)). In yet another crucible, melt 414 prepared by dissolving B-doped p ⁺ -type polycrystalline silicon in indium at 900 ° C. was gradually cooled at a rate of −0.5 ° C./min to 880 ° C. After immersing the substrate in the melt for 6 minutes while keeping the main surface facing down,
A p ⁺ layer 415 having a thickness of 3 μm was grown (FIG. 8 (m),
(N)).

The average roughness of the surface of this film was 1 nm or less. Further, when the cross-sectional profile of the impurity was measured by SIMS analysis, the B-doping concentration of the p-layer 411 was 1
0 ¹⁶ cm ⁻³ , P concentration of n layer 413 is 10 ¹⁸ cm ⁻³ , p ⁺
The B concentration of the layer 415 is 10 ²⁰ cm ⁻³ , and C and O
Was less than 10 ¹⁷ cm ^-3 , and In was less than 10 ¹⁵ cm ^-3 and was undetectable. The surface density of stacking faults is 10 ²
cm ^-2 or less.

The substrate is processed into a mesa shape and electrodes are attached. The p ⁺ layer 415 is an emitter, the n layer 413 is a base,
A pnp bipolar transistor was formed using the layer 411 as a collector, and the characteristics were evaluated. As a result, an amplification factor of h _fe = 60 was obtained.

Embodiment 5 In this embodiment, a plurality of thin-film single-crystal solar cells are manufactured from one single-crystal silicon substrate, and then a semiconductor layer is grown by the liquid phase epitaxial growth method of the present invention. An example in which a separation layer is formed on a semiconductor layer and a plurality of thin-film single-crystal solar cells are manufactured again will be described.

(Step A) Ten thin-film single-crystal silicon solar cells were manufactured in the same steps as in Example 2.

(Step B) As shown in FIG. 5, a thickness of about 50 μm is
A μm epitaxial layer was grown and the substrate was reclaimed.

First, when the surface roughness of the substrate 109 was measured by a stylus type surface roughness meter, the average roughness was 2 μm, and there was no gloss visually. When the thickness unevenness over the entire surface of the substrate was measured, it was ± 25 μm. First, the substrate surface was wrapped with alumina powder to make the thickness unevenness ± 10 μm. Further, the average roughness was improved to 0.5 μm, but there was still no gloss visually. Next, the crucible 1 of the liquid phase growth apparatus
11 was dissolved in 900 ° C. indium and the temperature was raised to 1000 ° C.
12 were adjusted.

The substrate 109 wrapped therein
Was immersed while keeping the main surface downward and horizontal. After leaving the substrate for about 10 minutes in this state, the substrate was pulled up, and the substrate 113 was taken out for confirmation. Gloss was obtained when the average roughness of the surface was 3 nm or less. Then slowly cooled to separate melt 114 to 950 ° C. Indium was adjusted crowded to dissolve the p ⁺ -type polycrystalline silicon of sufficient B-doped at -0.5 ° C. / min, the melt 114 at became 930 ° C. When the substrate 113 was immersed for 1 hour while keeping the main surface downward and horizontal, the epitaxial growth film 11 having a thickness of about 50 μm was obtained.
5 grew. The average roughness of the surface of this film was 1 nm or less. The specific resistance of an epitaxial film separately formed under the same conditions on a high-resistance substrate having a specific resistance of 10 Ωcm is approximately 0.01
Ωcm.

(Step C) In the step B, the substrate was regenerated to the state when it was put in the step A, so that ten thin-film single-crystal silicon solar cells were manufactured in the same steps as in the step A.
The solar cell thus obtained also exhibited the same characteristics as the solar cell obtained in step A.

Embodiment 6 In this embodiment, a plurality of SOI substrates are manufactured using one single-crystal silicon substrate, and then a semiconductor layer is grown by the liquid phase epitaxial growth method of the present invention. An example in which a separation layer is formed in a layer and a plurality of SOI substrates are manufactured again will be described.

(Step A) Three SOI substrates were manufactured in the same steps as in Example 4.

(Step B) An epitaxial layer having a thickness of 30 μm was grown on the surface of the substrate 409 whose thickness was reduced by about 30 μm in the step A, and the substrate was regenerated.

Although the surface roughness of this substrate was 0.5 μm and the thickness unevenness was ± 10 μm, the substrate was not visually glossy. First, melt polycrystalline silicon in indium at 950 ° C. in a crucible and raise the temperature to 1000 ° C.
08 was adjusted. In this, the substrate 409 was immersed while keeping the main surface downward and horizontal. In this state, the substrate 409 was pulled up after being left for about 10 minutes. When the substrate was taken out for confirmation, the average surface roughness was 5 nm.
Gloss was seen.

Next, B was added to indium at 900 ° C. in another crucible.
Another melt 410 prepared by dissolving doped p ⁺ -type polycrystalline silicon is gradually cooled at a rate of −0.5 ° C./min to 880.
When the temperature reached 0 ° C., the substrate 408 was immersed in the melt for 1 hour while keeping the main surface downward and horizontal.
A 30 μm thick p ⁺ layer 411 was grown. The average roughness of the surface of this film was 1 nm or less. Separate specific resistance 10Ωc
The specific resistance of the epitaxial film formed under the same conditions on the high-resistance substrate of m was approximately 0.01 Ωcm.

(Step C) In the step B, since the substrate was regenerated to the state when it was put in the step A, three SOI substrates were manufactured in the same step as the step A. S thus obtained
The OI substrate also exhibited the same characteristics as the SOI substrate obtained in step A.

[0109]

According to the present invention, a substrate which does not pass through a special process for improving the surface smoothness, or a substrate which is left for the production of a thin film single crystal solar cell or an SOI substrate, is used to simplify the process. The substrate can be smoothed by a simple method, and a film having few defects and excellent characteristics can be epitaxially grown by a method of high throughput. This greatly contributes to the high quality and low cost of the epitaxial substrate.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a manufacturing process according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a manufacturing process according to a second embodiment of the present invention.

FIG. 3 is an explanatory view showing another method for forming a separation layer.

FIG. 4 is an explanatory diagram of a manufacturing process according to a third embodiment of the present invention.

FIG. 5 is an explanatory diagram of a process of manufacturing a plurality of thin film single crystal solar cells and ap ⁺ / p epitaxial substrate by the method of the present invention.

FIG. 6 is an explanatory view of a mechanism for smoothing the surface of a substrate by the method of the present invention.

FIG. 7 is an explanatory diagram of a process of manufacturing a plurality of thin film single crystal solar cells and an n / n ⁻ epitaxial substrate by the method of the present invention.

FIG. 8 shows a plurality of SOI substrates and p
FIG. 4 is an explanatory diagram of a step of manufacturing a / n / p ⁺ epitaxial substrate.

[Explanation of symbols]

100, 300 Single crystal substrate 400 Single crystal Si wafer 101, 401 Separation layer (porous layer) 304 Separation layer (void region) 102, 303 Semiconductor thin film 402 Epitaxial growth layer 103 n ⁺ layer 305 p ⁺ layer 104, 306 Grid electrode 105, 307 Peeling substrate 106, 309 Back electrode 107, 311 Regenerated substrate 407 Polished substrate 108, 310 Solar cell 406 SOI wafer 111, 200, 312 Crucible 112, 201, 313, 408 Unsaturated melt 113 , 207, 314, 410, 411, 414 Supersaturated melt 116, 316, 416 Epitaxial substrate

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takao Yonehara 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kunio Watanabe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Kiyofumi Sakaguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Kazuaki Omi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Tetsuya Shimada 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. 4G077 AA03 BA01 BA04 BA05 CG02 CG06 5F051 AA02 AA08 BA14 CB02 CB12 CB15 CB29 FA06 FA10 FA18 GA04 GA15 5F053 A BB25 DD01 DD03 DD05 DD11 DD12 DD20 FF01 GG01 HH01 HH04 KK10 LL05 LL10 PP04 PP06 PP08 PP12 RR03 RR13

Claims (47)

[Claims] 1. The method according to claim 1, wherein the crystal face of the substrate having a rough crystal face is
A liquid phase growth method in which a semiconductor material is brought into contact with an unsaturated metal solution and then brought into contact with a supersaturated metal solution with the semiconductor material to grow a first semiconductor layer on the crystal face of the base. 2. A substrate having a coarse crystal face, which is brought into contact with an unsaturated metal solution with respect to a semiconductor raw material while holding the crystal plane horizontally downward, and then the metal solution oversaturated with the semiconductor raw material is brought into contact with the metal solution. A liquid phase growth method in which a semiconductor layer is grown on the crystal face of the base by contacting the semiconductor layer. 3. The method according to claim 1, wherein the step of bringing the crystal face of the base into contact with a metal solution unsaturated with respect to the semiconductor raw material is a step of flattening the crystal face of the base. Liquid phase growth method. 4. The liquid phase growth method according to claim 1, wherein the rough crystal plane has an average surface roughness of 0.5 μm or more. 5. The liquid phase growth method according to claim 1, wherein the rough crystal surface is a surface that has not been mirror-polished. 6. The liquid phase growth method according to claim 1, wherein the rough crystal face is a face where a porous region is exposed on at least a part of the surface of the substrate. 7. A second semiconductor layer on a separation layer, using a substrate having a first semiconductor layer formed by using the liquid phase epitaxy method according to claim 1 as a raw material. Forming a first member having: and after bonding the first member and the second member so that the second semiconductor layer is located inside, the first member is attached to the first member by the separation layer. Separating the second semiconductor layer of the member and transferring it to the second member side. 8. The second member relocated to the second member side
8. The method for manufacturing a semiconductor member according to claim 7, wherein said semiconductor layer is provided on an insulating surface. 9. The solar cell according to claim 7, wherein the second semiconductor layer has a junction, and the second member to which the second semiconductor layer having the junction is transferred is a solar cell. A method for manufacturing a solar cell, comprising: 10. The method according to claim 7, wherein the separation layer is formed by anodizing at least a part of the first semiconductor layer. 11. The method according to claim 7, wherein the second semiconductor layer includes at least a part of the first semiconductor layer. 12. The method according to claim 7, wherein the separation layer is a layer formed by ion-implanting hydrogen or a rare gas. 13. The method according to claim 9, wherein the junction is a pn junction. 14. The method according to claim 7, wherein the first semiconductor layer has the same conductivity type as the base and has a higher resistance than the base. 15. A method for manufacturing a semiconductor member, comprising at least the following steps A and B. Step A) Step of preparing a member having a first semiconductor layer on a single crystal substrate via a separation layer, and separating the first semiconductor layer from the single crystal substrate by the separation layer. Step B) After bringing the single crystal substrate into contact with a metal solution that is unsaturated with respect to the semiconductor raw material, the substrate is brought into contact with a metal solution that has been supersaturated with the semiconductor raw material, and a second semiconductor layer is formed on the single crystal substrate by liquid phase epitaxial growth. Of making epitaxial substrate by 16. The step A is repeated a plurality of times by forming the member using the single crystal substrate after the separation in the step A as a raw material, and thereafter, the single crystal substrate after the separation in the step A is subjected to the step B. 16. Use according to claim 15
3. The method for manufacturing a semiconductor member according to item 1. 17. The method for manufacturing a semiconductor member according to claim 15, wherein, prior to the step B, the surface of the separated single crystal substrate is wrapped. 18. The semiconductor device according to claim 15, wherein the second semiconductor layer in the step B has the same conductivity type as that of the single crystal substrate and has a higher resistance than the single crystal substrate.
A method for manufacturing a semiconductor member according to claim 7. 19. The method according to claim 15, wherein the first semiconductor layer in the step A includes a plurality of semiconductor layers having different conductivity types, and the plurality of semiconductor layers have a semiconductor junction.
The method for manufacturing a semiconductor member according to claim 18. 20. In the step B, after bringing the single crystal substrate into contact with a metal solution that is unsaturated with respect to the semiconductor raw material, the metal solution is adjusted so as to be supersaturated with respect to the semiconductor raw material. 20. The method for manufacturing a semiconductor member according to claim 15, wherein a semiconductor layer is formed by liquid phase epitaxial growth thereon. 21. A method for manufacturing a solar cell, wherein the first semiconductor layer in the step A of the method for manufacturing a semiconductor member according to claim 19 is used as a photoelectric conversion region. 22. A method for manufacturing a semiconductor member, comprising at least the following steps A, B, and C. Step A) A step of preparing a first member having a first semiconductor layer on a single crystal substrate via a separation layer, and separating the first semiconductor layer from the single crystal substrate by the separation layer Step B) After the separated single crystal substrate is brought into contact with a metal solution that is unsaturated with respect to the semiconductor raw material, the substrate is brought into contact with a metal solution that has been supersaturated with the semiconductor raw material, and a second semiconductor layer is formed on the single crystal substrate. Step C) of Producing Epitaxial Substrate by Phase Epitaxial Growth Step C) Using the epitaxial substrate as a raw material, forming a second member having a third semiconductor layer on a single crystal substrate via a separation layer, Separating the third semiconductor layer from the single crystal substrate by the separation layer for the member 23. The step A is repeated a plurality of times by forming the first member using the single crystal substrate after the first semiconductor layer separation in the step A as a raw material, and thereafter, the first semiconductor layer separation. 23. The method for manufacturing a semiconductor member according to claim 22, wherein the subsequent single crystal substrate is used in the step B. 24. A method for manufacturing a solar cell using the first semiconductor layer in the step A and the third semiconductor layer in the step C in the method for manufacturing a semiconductor member according to claim 22 as a photoelectric conversion region. 25. A method for manufacturing a semiconductor member, comprising at least the following steps A and B. Step A) A first member having a first semiconductor layer is provided on a single crystal substrate with a separation layer interposed therebetween, and the first member and the second member are separated such that the semiconductor layer is located inside. A step of separating the first semiconductor layer from the single crystal base by the separation layer after the bonding and transferring the first semiconductor layer to the second member side to produce a first semiconductor member; step B) After the crystal substrate is brought into contact with a metal solution that is unsaturated with respect to the semiconductor raw material, the substrate is brought into contact with a metal solution that has been supersaturated with the semiconductor raw material, and a second semiconductor layer is formed on the single crystal substrate by liquid phase epitaxial growth. Step 2 of manufacturing a semiconductor member 26. The step A is repeated a plurality of times by forming the first member using the single-crystal substrate after the separation in the step A as a raw material, and thereafter, the single-crystal substrate after the first semiconductor layer separation. 26. The method of manufacturing a semiconductor member according to claim 25, wherein is used in the step B. 27. The method of manufacturing a semiconductor member according to claim 25, wherein the surface of the single-crystal substrate after the separation in the step A is wrapped prior to the step B. 28. The method according to claim 25, wherein the second semiconductor layer in the step B has the same conductivity type as that of the single crystal substrate and has a higher resistance than the single crystal substrate.
A method for manufacturing a semiconductor member according to claim 7. 29. The method according to claim 25, wherein the first semiconductor layer in the step A comprises a plurality of semiconductor layers having different conductivity types, and the plurality of semiconductor layers form a semiconductor junction.
The method for manufacturing a semiconductor member according to claim 28. 30. In the step B, after bringing the single crystal substrate into contact with a metal solution that is unsaturated with respect to the semiconductor raw material, the metal solution is adjusted so as to be supersaturated with the semiconductor raw material. 30. The method for manufacturing a semiconductor member according to claim 25, wherein the semiconductor layer is formed by liquid phase epitaxial growth thereon. 31. The semiconductor layer transferred to the side of the second member is provided on an insulating surface.
The method for manufacturing a semiconductor member according to claim 1. 32. A solar cell according to claim 29, wherein the second member to which the first semiconductor layer having the semiconductor junction is transferred is a solar cell. Production method. 33. A method for manufacturing a semiconductor member, comprising at least the following steps A, B, and C. Step A) A first member having a first semiconductor layer is provided on a single crystal substrate via a separation layer, and the first member and the second member are separated such that the separation layer is located inside. After the bonding, the first semiconductor layer is separated from the single crystal substrate by the separation layer, and is transferred to the second member side, so that the first semiconductor layer is formed.
Step B) After the separation, the single crystal substrate is brought into contact with a metal solution that is unsaturated with respect to the semiconductor raw material, and then brought into contact with a metal solution that is supersaturated with the semiconductor raw material. A step of producing a second semiconductor member by liquid phase epitaxial growth of a second semiconductor layer on a base; step C) using the second semiconductor member as a raw material, a third semiconductor on a single crystal base via a separation layer; Third with layer
Is formed, and after bonding the third member and the fourth member so that the separation layer of the third member is located inside, the third layer is separated by the separation layer of the third member. Forming a third semiconductor member by separating a semiconductor layer from the single crystal base and transferring the semiconductor layer to the fourth member side 34. The step A is repeated a plurality of times by forming the first member using the single crystal substrate after the separation of the semiconductor layer in the step A as a raw material, and thereafter, the single crystal substrate after the separation of the semiconductor layer is separated. The method for manufacturing a semiconductor member according to claim 33, wherein the method is used in the step B. 35. The semiconductor layer transferred to the second member side in the step A and the semiconductor layer transferred to the fourth member side in the step C are provided on an insulating surface. A method for manufacturing a semiconductor member according to claim 33 or claim 34. 36. The method for manufacturing a semiconductor member according to claim 33, wherein a junction is formed in the semiconductor layers of the first and third members, and the semiconductor layer on which the junction is formed is transferred. A method for manufacturing a solar cell, wherein the second member and the fourth member are solar cells. 37. The method for manufacturing a semiconductor member according to claim 15, wherein the single-crystal substrate is single-crystal silicon. 38. The method of manufacturing a semiconductor member according to claim 15, wherein the separation layer is a layer formed by anodization or implantation of hydrogen or a rare gas ion. Method. 39. The semiconductor member according to claim 7, wherein the separation is performed by heat-treating the bonded members or by applying an external force to the members. Manufacturing method. 40. The method according to claim 7, wherein the separation is performed by a fluid jet. 41. The unsaturated metal solution according to any one of claims 15, 22, 25, and 33, wherein the unsaturated metal solution is formed by increasing the temperature from 5 degrees to 100 degrees while being saturated at a certain temperature. Of manufacturing a semiconductor member. 42. The metal solution is formed by dissolving indium, gallium, tin, aluminum, copper, zinc, or a combination of these metals.
The method for manufacturing a semiconductor member according to any one of claims 2, 25, and 33. 43. The method for manufacturing a semiconductor member according to claim 25, wherein the bonding is performed via an insulating layer. 44. The method according to claim 22, wherein the third semiconductor layer includes at least a part of the second semiconductor layer. 45. The step A is repeated a plurality of times to obtain SOI
27. The method for manufacturing a semiconductor member according to claim 16, wherein the substrate or the solar cell is manufactured. 46. The liquid phase growth method according to claim 1, wherein the unsaturated metal solution is formed by increasing the temperature from 5 degrees to 100 degrees while being saturated at a certain temperature. 47. The liquid phase growth method according to claim 1, wherein the metal solution is formed by dissolving indium, gallium, tin, aluminum, copper, zinc, or a combination thereof.