JPH10303442A - Substrate for forming semiconductor film and semiconductor device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable crystal growth at a sufficiently high speed and supply an inexpensive thin film crystal silicon substrate, by sequentially stacking a crystal oxide layer containing aluminum or the like and a crystal silicon layer on a main surface of a base, and thus carrying out crystal silicon growth of a thin film at a relatively low temperature. SOLUTION: First, a thin film crystal silicon layer 5 is formed on a glass substrate 1 with an Al2 O3 layer 4 provided between the layer 5 and the substrate 1. Next, using the thin film crystal silicon layer 5 as a first silicon layer, a second thin film crystal silicon layer 6 is stacked thereon by using a vacuum film forming technique such as a CVD method. The two-layer structure is formed for the following reason. That is, if there is only a lower layer, the doping impurity concentration is too high and recombination of carriers due to an Auger recombination mechanism becomes problematical. Thus, it becomes difficult to obtain the quality suitable for an optical active layer of a solar battery. The surface of the optical active layer thus obtained is dry-etched by using a RIE method, and a semiconductor forming substrate S having a rough surface of a randomly recessed and protruding structure is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor film forming substrate for forming, for example, a thin crystalline semiconductor film on an upper surface thereof.
And a semiconductor device using the same, such as a solar cell, an optical sensor, and a thin film transistor.

[0002]

2. Description of the Related Art Conventionally, thin film crystalline silicon has been actively studied in various fields relating to semiconductor devices. Examples of research in the field of semiconductor devices typified by semiconductor integrated circuits are described in detail in, for example, "SOI Structure Forming Technology" (edited by Seijiro Furukawa: Sangyo Tosho 1987). The field of is described.

[0003] In the field of solar cells, crystalline silicon solar cells using crystalline silicon wafers have been put to practical use. However, since a large amount of crystalline silicon wafers must be used, there are problems such as shortage of raw materials and expensive raw material costs. The development and commercialization of a low-cost and high-efficiency thin-film crystalline silicon solar cell using thin-film crystalline silicon that can solve the above problems are greatly expected.

Generally, in order to manufacture a thin-film solar cell at low cost, the substrate to be used needs to be low-cost. In this connection, it is more preferable that the temperature of the element process is relatively low because the degree of freedom in selecting a substrate is increased. Further, as for the conversion efficiency of the element, the higher the value, the lower the manufacturing cost per watt. Therefore, a higher conversion efficiency is desired.

[0005] Examples of such thin-film crystalline silicon solar cells are listed below. In Japan, thermal CVD is performed on a thin-film polycrystalline silicon underlayer by ZMR (melt recrystallization).
Method for forming a thin-film polycrystalline silicon photoactive layer by the plasma method 1
(Proc. 1st. WCPEC (1994) 1287-1290, 1311-131)
4, 1394-1397, JP-A-2-28315, JP-A-3-228324,
JP-A-4-91482, JP-A-6-204539, JP-A-7-135332, JP-A-7-226528, and JP-A-7-335660). Also, p-
Method 2 for forming a thin film polycrystalline silicon photoactive layer by the CVD method (see Proc. 1st. WCPEC (1994) 1575-1578, JP-A-6-163957, JP-A-7-94766), and SPC (solid phase crystal). Method for polycrystallizing amorphous silicon formed by p-CVD using the method (Proc. 1st. W)
CPEC (1994) 1315-1318, JP 2-28315, JP 6-
204539, JP-A-7-135332 and JP-A-7-335660), and a method of forming a polycrystalline silicon layer by melting and injecting silicon particles by a plasma spraying method 4 (JP-A-5-31525).
8, JP-A-5-315259, JP-A-5-315260, JP-A-5-32641
4, Japanese Patent Application Laid-Open Nos. 6-208960 and 6-208961), and a method of applying a paste composed of silicon powder and aluminum powder on an aluminum substrate and heat-treating the paste 5 (see Japanese Patent Application Laid-Open No. 55-140278). Furthermore, there is a method 6 in which a thin film of a high-melting-point metal, a thick film of a low-melting-point metal, and silicon microcrystal grains are sequentially deposited and heat-treated on a substrate 6 (see JP-A-1-110776).

In addition, outside of Japan, a method of growing a thin-film polycrystalline silicon from a liquid phase using the LPE method has been proposed.
(Proc. 1st. WCPEC (1994) 1250-1253 and 1254-1257
, 1339-1342, 1391-1393, 1398-1401, 157
9-1582, Solid State Phenomena 37-38 (1994) 459-46
4.Journal of Materials Science: Materials in Ele
ctronics. 5 (1994) 305-309, J. Electrorochem. Soc.
Vol. 140, No. 11 (1993) 3290-3293).

[0007]

Problems to be solved by the above research examples in manufacturing a thin-film crystalline silicon solar cell at low cost and high efficiency are as follows.

The method 1 is not suitable for mass production at low cost because the large area recrystallization rate by the ZMR method is slow and precise temperature control is required. ZMR method, thermal CVD
Since both methods are high-temperature processes, the degree of freedom in the device structure and device process for cost reduction is limited.

The method 2 is not suitable for mass production at low cost because the large area recrystallization speed by the laser annealing method is low. Further, the crystal grain size of the recrystallized crystal cannot be sufficiently increased to a maximum of about 1 μm, and the existence of crystal grain boundaries increases. Therefore, the influence of recombination there increases, and this is not suitable for high efficiency. Further, since the p-CVD method is used,
It takes several hours to form the main photoactive layer, which is not suitable for reducing the cost.

In the method 3, it takes several hours to form an amorphous silicon layer to which the SPC method is applied, and about 10 hours to solid-phase crystallization, and there is a problem in low-cost mass production. In addition, since the recrystallized crystal grain size is about 1 μm at the maximum and cannot be made sufficiently large, and the existence of crystal grain boundaries increases, the amount of recombination there increases, which is not suitable for high efficiency.

In the method 4, although the film formation speed is very high, there is a problem in the controllability of the film thickness. At present, the film thickness is several hundred μm, which is almost the same as that of a crystal wafer. There is a problem in cost reduction. In addition, since the process is a high-temperature process, the degree of freedom in the device structure and device process for cost reduction is limited.

In method 5, since a small amount of aluminum is used to sinter the silicon powders, there are many gaps between the powders. Further, since silicon in the sintered portion is doped with aluminum at a high concentration and Auger recombination becomes a problem, high efficiency cannot be expected.

In method 6, since the silicon particles are sintered using tin, Auger recombination does not pose a problem. However, since tin has a very low solubility of silicon at low temperatures, the particles are sintered without gaps. For this purpose, tin of a considerable thickness is required or heat treatment at a high temperature is required, so that there is a problem in mass production at low cost.

In the method 7, it is difficult to develop a device suitable for a solar cell class large-area element using the current LPE method, and there is a problem in low-cost mass production because the film formation speed is not sufficient. In addition, since a silicon substrate is used as a substrate, there is a problem in that silicon material cannot be saved.

In order to manufacture a thin-film crystalline silicon solar cell at low cost, the substrate to be used is inexpensive and the process is performed at a relatively low temperature, so that the degree of freedom of the element structure and the element process is large, and the thin film forming speed is increased. It is necessary to operate at a sufficiently high speed, and an issue is to provide an inexpensive thin film crystal Si substrate that satisfies this condition.

In order to increase the efficiency of the thin-film crystalline silicon solar cell, it is necessary to provide an element structure in which the crystal grain size of the thin-film crystalline silicon is sufficiently large and the utilization efficiency of incident light is high. Therefore, an object of the present invention is to provide a semiconductor film forming substrate that solves the above-mentioned problems when obtaining such a semiconductor device such as a thin film crystalline silicon solar cell, and a semiconductor device using the same.

[0017]

In order to achieve the above object, a substrate for forming a semiconductor film according to the present invention is provided on a main surface of a substrate.
A crystalline oxide layer containing at least one of aluminum, magnesium, and calcium, and a crystalline silicon layer are sequentially laminated, and thin-film crystalline silicon is grown at a relatively low temperature. A thin-film crystalline silicon substrate can be supplied at a low cost by enabling use of a simple substrate and enabling crystal growth at a sufficiently high speed, and a thin-film crystalline silicon solar cell using the same can be manufactured at low cost.

Further, by utilizing the fact that the crystal is grown through the liquid phase, the crystal grain size of the thin crystalline silicon layer can be sufficiently increased, and the surface of the crystalline silicon layer is suitable for optical confinement. By using a random uneven structure,
It enables the production of highly efficient thin film crystalline silicon solar cells.

Further, the crystalline silicon layer is in a polycrystalline state, and the crystal orientation of the crystalline silicon layer is mainly <111.
> Azimuth. Thereby, even if the crystalline silicon is polycrystalline, the surface can be made almost flat, and when the above-described random uneven structure on the surface of the crystalline silicon layer is formed, the structure is spread over the entire substrate. It can be formed almost uniformly and easily, and an excellent solar cell substrate and a solar cell having particularly low reflectance can be obtained.

When the crystalline silicon layer has a plurality of layers (at least a two-layer structure), the upper layer has an electrical resistivity of 1 to 10 ⁻³ Ω · cm, and the lower layer has an electrical resistivity of 10 ⁻² to 10 ⁻² . 1
0 ^-6 Ω · cm. Alternatively, the doping impurity concentration of the upper layer is 10 ¹⁶ to 10 ¹⁹ / cm ³ ,
The doping impurity concentration of the lower layer is 10 ¹⁸ to 10 ²² / cm
³ is characterized. In this case, the lower layer is a crystalline silicon layer formed on the above-described crystalline oxide layer, and the upper layer is a crystalline silicon layer formed in a subsequent process. As described above, in the two-layer structure, the doping impurity concentration is too high only in the lower layer, and the carrier recombination by the Auger recombination mechanism becomes a problem, and the quality suitable for the photoactive layer of the solar cell is obtained. Because it is difficult. If the electric resistance and the doping impurity concentration of the upper layer deviate from the above-specified ranges, characteristics such as a decrease in open-circuit voltage in solar cell characteristics are reduced.
Further, if the electric resistance of the lower layer deviates from the upper limit value or the lower limit value of the doping impurity concentration, surface recombination on the back surface of the element becomes large, thereby causing deterioration in characteristics such as reduction in open-circuit voltage in solar cell characteristics.

The thickness of the crystalline silicon layer is 1-5.
0 μm. This is because if the thickness of the crystalline silicon layer is too thin, the incident light cannot be sufficiently utilized and the short-circuit current decreases, while if it is too thick, the open-circuit voltage generally decreases depending on the film quality.

Also, the reflectance of the surface of the crystalline silicon layer is 5% or less with respect to light having a wavelength of 400 to 1000 nm. For example, in the case of a solar cell, it is important to lower the surface reflectance in order to improve the characteristics. In the present invention, the surface of the thin-film crystalline silicon is finely and randomly formed using a dry etching technique such as an RIE method. Due to the concavo-convex structure, the surface reflectivity is much smaller than the surface reflectivity according to the conventional technology, and a more efficient solar cell can be manufactured.

A flux underlayer containing at least one of aluminum, magnesium, and calcium and forming a eutectic system with silicon is formed on the substrate, and thereafter, aluminum, magnesium, calcium, tin, zinc, and antimony are formed. A mixture of silicon and a flux body containing at least one of indium, bismuth, and gallium and forming a eutectic system with silicon is provided on the flux underlayer, these are melted, and crystalline silicon is grown on the surface layer. It is characterized by comprising. In particular, the particle size of the silicon powder and the flux body (in the case of powder) is 50 μm.
m or less. In the heat treatment, the deposition rate of the thin-film polycrystalline silicon is 0.1 μm / mi.
It is characterized in that a temperature gradient is applied to the front and back surfaces of the base so as to be n or more.

By forming the flux underlayer on the substrate as described above, the wettability between the substrate and the powder is improved, and the mixture of silicon and the flux applied on the flux underlayer is heated to the melting point of the flux. By heating as described above to obtain a melt and supersaturating the melt, silicon can be grown on the substrate. In order to realize the supersaturation, a temperature gradient may be provided so that the back surface of the substrate is lower in temperature than the front surface of the substrate. Since this crystal growth utilizes the eutectic phenomenon with a low melting point metal, it is possible to grow the crystal at a relatively low temperature and at a sufficiently high speed. A thin-film polycrystalline silicon solar cell using this thin-film polycrystalline silicon Can be manufactured at low cost. In addition, by utilizing the crystal growth via the liquid phase, it is possible to manufacture a highly efficient thin-film polycrystalline silicon solar cell by sufficiently expanding the crystal grain size of the thin-film polycrystalline silicon layer. is there.

The flux underlayer contains at least one of aluminum, magnesium and calcium, and since these elements have a strong oxidizing power, they are suitable for improving the wettability between the substrate and the powder. When the flux underlayer is not used, no thin-film polycrystalline silicon is grown. Further, the flux includes at least one of aluminum, magnesium, calcium, tin, zinc, antimony, bismuth, and indium in a powder state, or gallium which becomes a liquid at room temperature. These flux bodies individually have characteristics such as a melting point, a eutectic temperature, a solubility, and a solid solubility. However, the flux bodies are used in combination according to the purpose such as film forming conditions and film quality.
Further, the total amount of the flux body is set to 10 atomic% or more with respect to silicon. When the total amount of the flux is less than 10 atomic% based on the silicon powder, the amount of the melt is too small, so that most of the melt adheres to the silicon powder due to surface tension, and there is no melt in contact with the substrate. Therefore, the growth of thin-film polycrystalline silicon is not recognized.

The silicon powder in the powder state and the flux in the powder state have a particle size of 50 μm or less. Particle size of silicon powder is 50μ
If m or more, the surface area of the silicon powder in contact with the flux melt becomes small, so that the time until the melt becomes supersaturated becomes long. Furthermore, when the particle size of the flux in the powder state is 50 μm or more, it becomes difficult to apply the mixture uniformly when applying the mixture of the silicon powder and the flux, and the thin film polycrystalline silicon grows uniformly. Disappears.

Further, the heat treatment is performed by applying a temperature gradient so that the film forming speed of the thin-film polycrystalline silicon is 0.1 μm / min or more. Generally, in crystal growth from a melt, the film formation rate is proportional to the temperature gradient. Although a slight temperature gradient is required to grow the thin-film polycrystalline silicon on the substrate, it is necessary to reduce the process time in order to manufacture a thin-film polycrystalline silicon solar cell at low cost.

Further, the semiconductor device of the present invention is formed by depositing a crystalline silicon layer forming a semiconductor junction with the crystalline silicon layer on the crystalline silicon layer of the semiconductor film forming substrate.

[0029]

Embodiments of the present invention will be described below in detail with reference to the drawings. In addition, as a glass substrate suitably used as a substrate, a Corning 7059 substrate, a 1737 substrate, and a soda glass substrate most commonly commercialized by each glass manufacturer were used. Hereinafter, description will be made based on an example using a 7059 substrate, except that a difference due to a glass substrate causes a problem.

First, as shown in FIG.
On a glass substrate 1 containing O ₂ (silicon oxide), an Al (aluminum) layer 2 as a flux underlayer is formed to a thickness of about 1 to 5 μm by a vacuum evaporation method. Where Al
In forming the layer 2, a known vacuum film forming technique such as a CVD method and a sputtering method can be used in addition to the vacuum evaporation method. Also, instead of Al, Mg which is similarly oxidized more easily than Si
Even if a film of (magnesium) or Ca (calcium) is formed, the same effects as described below can be expected.

Next, on the deposited Al layer 2, if necessary, a mixture layer 3 composed of powdered Si and a flux is supplied and laminated by a printing method. Examples of the flux include powdered Al, Sn (tin), In (indium), Zn (zinc), Mg, Ca, Sb (antimony), Bi (bismuth), and Ga (gallium) which is liquid at normal temperature. ), Or a single element that causes a eutectic reaction with Si, or a mixture containing them. Note that the effects described below are basically achieved even if these mixtures are not particularly used, but it is more preferable to use these mixtures.

Next, the substrate 1 on which the Al layer 2 is formed and, if necessary, the mixture layer 3 composed of powdered Si and a flux body is laminated thereon, is subjected to a heat treatment under a predetermined condition,
The layer 2 and the mixture layer 3 are melted to form a liquid phase. The heat treatment is performed at a temperature of 577 ° C. or higher, which is the eutectic point of Si and Al, and, if necessary, a temperature exceeding 660 ° C., which is the melting point of Al. Here, in the case where an element other than Al is used, among the elements used, the one having the lowest eutectic point with Si is set as the lowest temperature of the heat treatment conditions, and if necessary. The heat treatment is performed under higher temperature conditions. The atmosphere may be an inert gas atmosphere such as Ar (argon) gas or N ₂ (nitrogen gas), or a gas atmosphere in which a reducing H ₂ (hydrogen) gas and an inert gas are mixed at an appropriate ratio. I do. The pressure is preferably a reduced pressure condition such as a vacuum, but may be a normal pressure. The heat treatment time is about 1 hour net, excluding the temperature rise and fall times.

When the heat treatment is performed under the condition that a liquid phase is formed as described above, the powder Si melts into the liquid by eutectic reaction with the liquid. Further, the glass component in the surface layer of the glass substrate 1 also reacts with the liquid phase, and SiO ₂ (silicon oxide), which is a main component of the glass component, is reduced by molten Al to elute into Si as liquid, and conversely melts. Al is oxidized to Al ₂ O ₃ (aluminum oxide), and deposited on the surface of the glass substrate 1 in a polycrystalline state to form an Al ₂ O ₃ layer 4 which is a crystalline oxide layer.

On the other hand, the powdered Si and the Si eluted from the glass into the liquid phase are deposited on the above-mentioned Al ₂ O ₃ layer 4 under appropriate supersaturation conditions and crystallize. At this time, since the crystal is grown through the liquid phase, a particle size sufficient for use as a solar cell can be obtained. Here, the supersaturation condition is formed, for example, by lowering the temperature on the back surface side of the substrate 1 with respect to the front surface side (crystal silicon growth surface side) of the substrate 1 in a direction perpendicular to the substrate during the heat treatment. May be provided with a temperature gradient. In this way, as shown in FIG. 2, a thin-film crystalline silicon layer 5 is obtained on the glass substrate 1 with the Al ₂ O ₃ layer 4 interposed therebetween. When Mg or Ca is mainly used instead of Al, MgO (magnesium oxide) and CaO (calcium oxide) are generated instead of Al ₂ O ₃ as a crystal oxide layer. As a result, thin-film crystalline silicon is deposited and grown.

The cross section of the thin-film crystalline silicon layer (first silicon layer) 5 was observed with an SEM.
It was confirmed that the film thickness was about 1 to 30 μm and the particle size was several μm or more. In addition, structural analysis by an X-ray diffraction method confirmed that the polycrystalline silicon layer had a tendency to be preferentially oriented in the <111> crystal orientation. As a result, the surface of the obtained crystalline silicon thin film became almost flat. This is suitable for uniformly performing etching and film formation to be performed later on the substrate surface. For example, even when a random concavo-convex structure on the crystalline silicon surface is formed by the RIE method described later, the It could be formed uniformly. When the electric resistance was measured, a value of about 10 ⁻² to 10 ⁻⁵ Ω · cm was obtained.
Further, the presence of Al in the thin-film crystalline silicon was determined by SIMS.
As a result, values of 10 ¹⁸ to 10 ²¹ / cm ³ were confirmed. From these results, the carrier concentration was estimated to be about 10 ¹⁸ to 10 ²¹ / cm ³ . At this time, the film having a low electric resistivity, that is, a highly doped (high carrier concentration) film can be made to function as a back electrode of the device in device formation as described later.

Next, as shown in FIG. 3, the thin film crystalline silicon layer obtained above is used as a first silicon layer 5 and a second silicon layer 5 is formed thereon by a vacuum film forming technique such as a CVD method or a sputtering method. The thin film crystal silicon layer 6 is laminated. The doping concentration of the second silicon layer 6 is set to about 10 ¹⁶ to 10 ¹⁸ / cm ³ so as to function suitably as a photoactive layer of a solar cell together with the first silicon layer 5 (the first silicon layer 5). Is 10 ¹⁸ to 10 ²² / cm ³ ), and the electrical resistivity is 1 to 10 ^-2 Ω.
Cm (the first silicon layer 5 is 10 ^-2 to 10 ^-6 Ω · c
m). As described above, in the two-layer structure, the doping impurity concentration is too high only in the lower layer, and the carrier recombination by the Auger recombination mechanism becomes a problem, and the quality suitable for the photoactive layer of the solar cell is obtained. Because it is difficult.
If the electric resistance and the doping impurity concentration of the upper layer deviate from the above-specified ranges, characteristics such as a decrease in open-circuit voltage in solar cell characteristics are reduced. Further, if the electric resistance of the lower layer deviates from the upper limit value or the lower limit value of the doping impurity concentration, surface recombination on the back surface of the element becomes large, thereby causing deterioration in characteristics such as reduction in open-circuit voltage in solar cell characteristics.

At this time, the total thickness of the first silicon layer 5 and the second silicon layer 6 was about 5 to 50 μm. This is because if the thickness of the crystalline silicon layer is too thin, the incident light cannot be sufficiently utilized and the short-circuit current decreases, while if it is too thick, the open-circuit voltage generally decreases depending on the film quality. As a method for forming the second thin-film crystalline silicon layer 5 at a relatively high speed at a relatively low temperature, in particular, cat-
There is a CVD method.

Next, the surface of the photoactive layer thus obtained is dry-etched by RIE (Reactive Ion Etching), and the surface as shown in FIG. And Regarding the formation of the surface random uneven structure by the RIE method, for example, see Technica
l Digest of the International PVSEC-9 (1996) 93-96,
109-110. This surface structure is not necessarily required for a simple device, but is particularly effective when there is a demand for increasing the use efficiency of incident light, such as in a thin-film crystalline Si solar cell. Here, as shown in FIG. 7, the reflectance of the surface of the second Si
A description will be given of a case where the structure is compared with a substantially regular uneven structure formed by ordinary wet etching called a ure structure. As shown by the broken line, in the case of the Texture structure, the reflectance of the light having a wavelength of 400 to 1000 nm including the visible light region is 10% or more, whereas the second Si layer 6 having the random uneven structure is provided. In case of 5
% Or less, which is a very suitable reflectance.

Next, a solar cell which is a semiconductor device having a semiconductor junction obtained using the semiconductor film forming substrate S shown in FIG. 4 will be described. As shown in FIG. 5, a third thin-film silicon layer 7 having a conductivity type opposite to the conductivity type of the second silicon layer 6 as the photoactive layer was formed, and a pn junction was formed. The third silicon layer 7 is formed by a CVD method,
A known vacuum thin film forming technique such as a sputtering method can be used. Further, the third silicon layer 7 may be a crystalline silicon film or an amorphous silicon film.
In the latter case, a so-called heterojunction is formed. However, if an intrinsic type amorphous silicon layer 6 is inserted between the second silicon layer 6 and the third silicon layer 7 (amorphous silicon layer) at a thickness of 20 to 400 °, the characteristics will be improved. It is more suitable for improvement.

Next, a transparent conductive film 8 typified by ITO is formed on the thin film silicon layer on which the pn junction is formed by using a vacuum film forming technique such as a sputtering method. After that, the front extraction electrode 10 is formed thereon by using a known technique such as a vapor deposition method, a plating method, and a printing method, so that a highly efficient solar cell P1 can be provided.

Incidentally, like the solar cell P2 shown in FIG.
Instead of ITO, a protective layer 11 of SiN or SiO
It may be formed using a vacuum film forming technique such as the VD method, and may be patterned into a surface electrode shape to form the surface extraction electrode 12 connected to the third silicon layer 7. In addition, IT
The thickness of the O film, SiN film or SiO film is AR
(Anti-Reflection) The thickness is controlled so as to fulfill the function.

On the other hand, as described above, the thin-film crystalline silicon layer (first silicon layer 5) which is heavily doped as described above fulfills its function. It is formed simultaneously with the formation of the front extraction electrodes 10 and 12. That is, etching or scribing is performed from the element surface using a wet or dry etching technique, a laser scribing technique, or a mechanical scribing technique to expose the first thin-film crystalline silicon layer. The take-out electrode may be formed in the same manner as the front electrode.

As described above, a very high efficiency thin film crystal silicon solar cell can be formed.

In FIG. 1, Al was formed as a flux layer on a carbon substrate by a vapor deposition method of about 5 μm.
Furthermore, silicon powder, powder Al
A paste composed of a flux, a binder, and a solvent may be applied by a printing method and dried.
Then, by subjecting this substrate to heat treatment in the same manner as in the above-described embodiment, thin-film polycrystalline silicon may be obtained on the carbon substrate. In addition, it has been found that when a polycrystalline silicon substrate is used, epitaxial growth occurs along the crystal orientation of the substrate.

Although the present invention has been described by taking a solar cell as an example of a semiconductor device, the present invention is not limited to this. For example, an optical sensor such as a position detection sensor, a luminance sensor, a color sensor, or a TFT may be used. The present invention can be applied to a transistor and the like, and can be appropriately modified and implemented without departing from the gist of the present invention.

[0046]

As described above in detail, according to the substrate for forming a semiconductor film of the present invention, an inexpensive thin film crystalline silicon substrate using a glass substrate can be used, and the effect of high-speed film formation is added. As a result, a significant reduction in the manufacturing cost of the thin film crystalline silicon solar cell can be realized.

Further, by sufficiently expanding the crystal grain size of the thin-film crystalline silicon layer and introducing a random surface uneven structure suitable for optical confinement, a highly efficient thin-film crystalline silicon solar cell can be obtained particularly as a semiconductor device. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a process for manufacturing a substrate for forming a semiconductor film according to the present invention.

FIG. 2 is a cross-sectional view illustrating a manufacturing process of a substrate for forming a semiconductor film according to the present invention.

FIG. 3 is a cross-sectional view showing a step of manufacturing a substrate for forming a semiconductor film according to the present invention.

FIG. 4 is a cross-sectional view illustrating a substrate for forming a semiconductor film according to the present invention.

FIG. 5 is a cross-sectional view illustrating a semiconductor device obtained using a semiconductor film formation substrate according to the present invention.

FIG. 6 is a cross-sectional view illustrating another semiconductor device obtained using the semiconductor film formation substrate according to the present invention.

FIG. 7 is a graph showing the relationship between the wavelength of light on the surface of a substrate for forming a semiconductor film and the reflectance.

[Explanation of symbols]

 1: glass substrate (substrate) 4: aluminum oxide layer (crystal oxide layer) 5: first silicon layer 6: second silicon layer 7: third silicon layer S: semiconductor film forming substrates P1, P2: Solar cells (semiconductor devices)

Claims (8)

[Claims] A crystal oxide layer containing at least one of aluminum, magnesium, and calcium, and a crystal silicon layer sequentially laminated on a main surface of a base;
A semiconductor film forming substrate on which a semiconductor film is deposited on the crystalline silicon layer. 2. The semiconductor device according to claim 1, wherein said crystalline silicon layer is in a polycrystalline state, and its crystal orientation is selectively oriented mainly in a <111> orientation in a direction perpendicular to a main surface of said base. 4. The substrate for forming a semiconductor film according to item 1. 3. The semiconductor device according to claim 1, wherein the crystalline silicon layer has a plurality of layers, and an upper layer has an electric resistivity of 1 to 10 ⁻³ cm and a lower layer has an electric resistivity of 10 ⁻² to 10 ⁻⁶ Ωcm. The substrate for forming a semiconductor film according to claim 1, wherein: 4. The method according to claim 1, wherein the crystalline silicon layer has a plurality of layers, and an upper layer has a doping impurity concentration of 10 ¹⁶ to 10 ^19.
/ Cm ³ , the doping impurity concentration of the lower layer is 10 ¹⁸ -1
2. The substrate for forming a semiconductor film according to claim 1, wherein the substrate concentration is 0 ²² / cm ³ . 5. The crystalline silicon layer has a thickness of 1 to 50 μm.
2. The substrate for forming a semiconductor film according to claim 1, wherein m is m. 6. The semiconductor film forming substrate according to claim 1, wherein the reflectance of the surface of the crystalline silicon layer is 5% or less with respect to light having a wavelength of 400 to 1000 nm. 7. A flux underlayer containing at least one of aluminum, magnesium and calcium and forming a eutectic system with silicon is formed on a substrate, and thereafter aluminum, magnesium, calcium, tin, zinc and antimony are formed. A mixture of silicon and a flux body containing at least one of silicon, indium, bismuth, and gallium and forming a eutectic system with silicon is provided on the flux underlayer and melted, and crystal silicon is grown on the surface layer. Substrate for film formation. 8. A semiconductor device comprising: a semiconductor layer forming a semiconductor junction with the crystalline silicon layer on the crystalline silicon layer of the substrate for forming a semiconductor film according to claim 1;