JPH09312258A - Polycrystal silicon thin film laminate, its manufacture and silicon thin film solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a polycrystal silicon thin film having (111) orientation with a large grain diameter on the surface of a substrate. SOLUTION: On the surface of a substrate 2, an amorphous or crystallite silicon thin film 4 is formed and laser beams are applied on the surface to form a polycrystal silicon seed layer 5 having (111) orientation. Then, a polycrystal silicon deposited layer 6 having (111) orientation is formed by accumulating silicon atoms or silicon compound molecules, while applying energy beams on the surface of the seed layer 5. The polycrystal silicon thin film 3 having (111) orientation has less defects and is formed for a desired thickness with large diameter grains by such a manufacturing method. The polycrystal silicon thin film 3 with a large grain diameter with less defects can be used, for instance, for a highly efficient light carrier generating layer of a silicon solar cell.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polycrystalline silicon thin film laminate, a method for manufacturing the same, and a silicon thin film solar cell.

[0002]

2. Description of the Related Art Currently, solar cells that convert light rays into electric power are used in various devices, and there is a demand for improvement in their efficiency. A general solar cell uses amorphous silicon, which has good productivity but is insufficient in photoelectric conversion efficiency. Therefore, use of polycrystalline silicon has been studied.

A method of manufacturing a polycrystalline silicon thin film laminate which realizes this is disclosed in Japanese Patent Laid-Open Nos. 5-109638 and 4-35021.
JP-A No. 5-136062, and the like.
For example, in the solid layer growth method described in JP-A-5-109638, an amorphous silicon thin film is formed on the surface of a substrate by the CVD (Chemical Vapor Deposition) method, and this silicon thin film is about 600 (° C). The polycrystalline silicon thin film layered product is manufactured by annealing at a high temperature and crystallizing.
Further, in the layer-by-layer method and the chemical annealing method described in JP-A-4-35021 and JP-A-5-136062,
By repeating deposition of an amorphous silicon thin film and exposure with hydrogen plasma in the plasma CVD method, a polycrystalline silicon thin film laminate is manufactured.

[0004]

The polycrystalline silicon thin film laminate can be manufactured by the above-mentioned method. However, the above-mentioned method produces a high-quality polycrystalline silicon thin film laminate with good productivity. Is difficult.

That is, in the solid layer growth method described in Japanese Patent Laid-Open No. 5-109638, since annealing is performed at a high temperature of 600 (° C.), the substrate is required to have heat resistance, and an inexpensive glass substrate or the like should be used. I can't. Moreover, since the annealing takes a long time, the throughput is low.

In this respect, Japanese Patent Laid-Open No. 4-35021 and Japanese Patent Laid-Open No. 5-35021
With the layer-by-layer method and the chemical annealing method described in Japanese Patent No. 136062, a polycrystalline silicon thin film laminate can be manufactured at a low temperature with a relatively good throughput, but this method cannot increase the crystal grain size.

In the polycrystalline silicon thin film laminate manufactured by the various methods as described above, silicon is (11
It has been found that the crystal grains are oriented in the 0) orientation, and it has been confirmed that defects such as twins frequently occur in the crystal grains grown in this orientation.

[0008]

A polycrystalline silicon thin film laminate according to the present invention comprises a substrate and a (111) oriented polycrystalline silicon thin film formed on the surface of the substrate. Therefore, since the polycrystalline silicon thin film is formed with the (111) orientation, defects such as twins are unlikely to occur in the crystal grains. The (111) orientation referred to here is that most of the crystal planes parallel to the surface of the substrate are (111) planes (in other words, most of the crystal axes perpendicular to the surface of the substrate are the <111> axes. It means that. Mostly referred to here means, for example, that the ratio to the whole is 0.5 or more, which is twice the ratio 0.25 when the orientation is completely random.

According to a second aspect of the present invention, in the polycrystalline silicon thin film laminate of the first aspect, the polycrystalline silicon thin film is a crystal grain of (111) -oriented polycrystalline silicon formed on the surface of the substrate. And a growth layer of (111) -oriented polycrystalline silicon deposited on the surface of the seed layer. Therefore, (11) is formed on the surface of the seed layer made of (111) -oriented polycrystalline silicon.
1) Since a growth layer made of oriented polycrystalline silicon is deposited, a (111) oriented polycrystalline silicon thin film is formed to a desired thickness.

According to a third aspect of the present invention, there is provided a method for producing a polycrystalline silicon thin film laminate, in which a seed layer made of (111) oriented polycrystalline silicon crystal grains is formed on the surface of a substrate, and the seed layer has a surface. A growth layer of (111) oriented polycrystalline silicon was deposited. Therefore, on the surface of the seed layer made of (111) -oriented polycrystalline silicon, (111)
Since a growth layer made of oriented polycrystalline silicon is deposited,
A polycrystalline silicon thin film having a (111) orientation is formed to a desired thickness, and a polycrystalline silicon thin film laminate having few crystal defects is manufactured.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a polycrystalline silicon thin film laminate, comprising:
The seed layer formation and the growth layer deposition were performed in vacuum. Therefore, since the seed layer and the growth layer are not exposed to an oxidizing atmosphere during the manufacturing process, the polycrystalline silicon thin film (1
11) Grow as it is oriented.

According to a fifth aspect of the present invention, there is provided a method for producing a polycrystalline silicon thin film laminate, wherein an amorphous or microcrystalline silicon thin film is formed on the surface of the substrate according to the third or fourth aspect of the invention. The silicon thin film was irradiated with a laser beam to form a seed layer. Therefore, (111) -oriented polycrystalline silicon is formed with a large grain size from an amorphous or microcrystalline silicon thin film.

According to a sixth aspect of the present invention, there is provided a method for producing a polycrystalline silicon thin film laminate, wherein in the third, fourth or fifth aspect of the present invention, the surface of the seed layer is irradiated with an energy beam while silicon atoms or silicon compound molecules are irradiated. Was deposited to form a growth layer. Therefore, (111)
On the surface of the seed layer made of oriented polycrystalline silicon, (1
11) Oriented polycrystalline silicon grows with a large grain size.

A silicon thin film solar cell according to a seventh aspect of the present invention has the polycrystalline silicon thin film laminate according to the first or second aspect as a photocarrier generation layer. Therefore, claim 1
Since the described polycrystalline silicon thin film laminate has few defects and a large grain size, a silicon thin film solar cell having this as a photocarrier generation layer has high conversion efficiency.

[0015]

FIG. 1 shows a first embodiment of the present invention.
The following description is based on FIG. First, as shown in FIG. 1C, the polycrystalline silicon thin film layered body 1 of the present embodiment has a Pyrex substrate 2 and a polycrystalline silicon thin film 3. The polycrystalline silicon thin film 3 is laminated on the surface of the substrate 2, and most of the crystal planes parallel to the surface of the substrate 2 are (111) oriented. The ratio of this orientation is defined based on the analysis intensity of X-rays, as shown below as a mathematical formula.

(111) Diffraction intensity ratio = 1 (constant) (220) Diffraction intensity ratio = [relative intensity of (220) of sample to (111)] / [relative intensity of (220) of powder to (111)] (311) Diffraction intensity ratio = [relative intensity of (311) of sample to (111)] / [relative intensity of (311) of powder to (111)] (400) Diffraction intensity ratio = [of (400) of sample Relative intensity to (111)] / [Relative intensity of (400) of powder to (111)] (111) orientation ratio = (111) diffraction intensity ratio / [(111) diffraction intensity ratio + (220) diffraction intensity ratio + (311) Diffraction intensity ratio +
(400) Diffraction intensity ratio] (110) Orientation ratio = (220) Diffraction intensity ratio / [(111) Diffraction intensity ratio + (220) Diffraction intensity ratio + (311) Diffraction intensity ratio +
(400) Diffraction Intensity Ratio] Most of the terms here mean that the ratio to the whole is 0.
It means that it is 5 or more.

Next, the structure of the manufacturing system 11 for manufacturing the above-mentioned polycrystalline silicon thin film laminate 1 will be described with reference to FIG. The manufacturing system 11 has first and second vacuum chambers 12 and 13, and these vacuum chambers 12 and 13 are connected via a gate valve 14. Inside the vacuum chambers 12 and 13,
A substrate transfer mechanism (not shown) is provided by a guide rail or the like, and the substrate 2 is transferred by this substrate transfer mechanism and held at a predetermined position.

A transparent window 15 is formed on the tube wall of the first vacuum chamber 12, and a laser light source 16 made of, for example, an ArF excimer laser is arranged at a position facing the transparent window 15. ing.

A beam generator 17 is provided in the second vacuum chamber 13, and a silicon source 18 and an evaporation source 19 are arranged therein. The silicon source 18 is a crucible filled with silicon, and the evaporation source 19 is
It consists of a crucible filled with boron. The beam generator 17 has an electron gun (not shown) here, and this electron gun emits an electron beam as an energy beam. This electron gun is, for example, a filament, an accelerating electrode,
It has a converging lens and a deflecting lens, and deflects and scans the emitted electron beam.

Next, a method of manufacturing the polycrystalline silicon thin film stack 1 using the manufacturing system 11 as described above will be described below. First, on the surface of Pyrex substrate 2,
An amorphous or microcrystalline silicon thin film 4 having a film thickness of 500 (nm) is formed by a thin film technique such as an electron beam evaporation method, an ion plating method, a sputtering method, and a plasma CVD method.
Hereinafter, the film is preferably formed to a thickness of 10 to 200 (nm). The substrate 2 on which the silicon thin film 4 is thus formed is set in the substrate transfer mechanism inside the first vacuum chamber 12, and after this setting, the inside of the vacuum chamber 12 is evacuated.

Next, as shown in FIG. 1B, the silicon thin film 4 is irradiated with a laser beam from the laser light source 16,
The seed layer 5 is formed by polycrystallizing silicon. In this case, the energy of the excimer laser is 200 to 500 (mJ / c
m ² ) and the number of shots is 20 to 200. In this case, the temperature of the substrate 2 is 300 to 500 (° C.), preferably 400 (° C.) or less. In this way, the amorphous or microcrystalline silicon thin film 4 is polycrystallized by laser irradiation in a vacuum to form the seed layer 5
Is formed by crystal grains of (111) oriented polycrystalline silicon.

Next, the inside of the second vacuum chamber 13 is evacuated, and after this is completed, the gate valve 14 is opened and the substrate 2 is transferred from the first vacuum chamber 12 to the second vacuum chamber 13 by the substrate transfer mechanism. To do. After this transfer, the gate valve 14 is closed to set the internal pressure of the second vacuum chamber 13 to 1 × 10 ⁴ (Pa) or less, and the substrate 2 is irradiated with an electron beam as an energy beam by the beam generator 17. In this case, the energy of the electron beam has an accelerating voltage of 1
00 (V) to 100 (kV), preferably 1.0 (kV) to 30 (kV), and a current density of 1.0 (μA / cm ² ) to 1.0 (A / cm ² ), preferably 10 (μA / cm ^2). ) To 1.0 (mA / cm ² ). Also in this case, the temperature of the substrate 2 is 300 to 500 (° C), preferably 400 (° C)
The following is assumed. Simultaneously with this, for example, silicon atoms are generated from the silicon source 18 by the electron beam evaporation method and are deposited on the surface of the seed layer 5.

Since the mobility of silicon atoms on the surface of the seed layer 5 is increased by the above beam irradiation, FIG.
As shown in FIG. 5, a growth layer 6 of polycrystalline silicon having a large grain size and high orientation is formed. The growth layer 6 is formed to have a film thickness as necessary. For example, when the polycrystalline silicon thin film stack 1 is used in a silicon solar cell, the growth layer 6 has a thickness of 1.0-5.
It is formed with a film thickness of about 0 (μm).

When the growth layer 6 is deposited on the surface of the seed layer 5 made of (111) -oriented polycrystalline silicon in vacuum as described above, the growth layer 6 also grows as (111) -oriented polycrystalline silicon. The (111) oriented polycrystalline silicon thin film 3 is formed on the surface of the.

That is, in the method for manufacturing the polycrystalline silicon thin film laminate 1 of the present embodiment, the amorphous silicon thin film 4 formed by a general thin film technique is polycrystallized by laser irradiation, so that the crystal is formed. It is possible to easily form the seed layer 5 of (111) orientation having a large grain size. Since the growth layer 6 is deposited on the surface of the seed layer 5, the (111) oriented polycrystalline silicon thin film 3 having a large crystal grain size can be easily formed.

Since this manufacturing method does not require heating at a high temperature, inexpensive glass or the like can be used as the substrate 2 and annealing for a long time is not required, so that the throughput is good. Moreover, since the formation of the seed layer 5 and the deposition of the growth layer 6 are performed in a vacuum, the seed layer 5 and the growth layer 6 are not exposed to an oxidizing atmosphere during the manufacturing process, and the polycrystalline silicon thin film 3 is (111). Since it is formed as an orientation, there are few defects.

Results of an experiment for verifying that the polycrystalline silicon thin film 3 thus formed with the (111) orientation has few defects will be described below with reference to FIG. First, the electrode 21 was attached to the polycrystalline silicon thin film laminate 1 manufactured by the above-mentioned method to manufacture the Schottky diode 22. However, the substrate 2 was formed of n-type single crystal silicon, and the polycrystalline silicon thin film 3 was formed of p-type by doping with boron. Also, this Schottky diode 2
As a sample material to be compared with 2, a Schottky diode (not shown) having a similar structure and a polycrystalline silicon thin film formed in a (110) orientation by a layer-by-layer method was also manufactured.

The diode factor n of these Schottky diodes 22 was determined from the current-voltage characteristics, and when the polycrystalline silicon thin film 3 had a (111) orientation, n = 1.2.
In the case where the polycrystalline silicon thin film has a (110) orientation, n =
1.6. The closer the diode factor is to “1”, the better the crystallinity. Therefore, the polycrystalline silicon thin film 3 has less crystal defects in the (111) orientation than in the (110) orientation.

It should be noted that the present invention is not limited to the above-mentioned form, and allows various modifications. For example, in the above-mentioned polycrystalline silicon thin film laminate 1, Pyrex is exemplified as the material of the substrate 2, but this may be heat-resistant plastic such as soda lime glass or polyimide, for example, glass, ceramic, plastic, metal, etc. Is also available.

In the method of manufacturing the polycrystalline silicon thin film laminate 1 described above, the seed layer 5 is directly formed on the surface of the substrate 2. However, a thermal buffer layer is formed in the middle of the seed layer 5 to form a polycrystalline layer. It is also possible to improve the crystallinity of the silicon thin film 3. When the seed layer 5 is formed through an appropriate heat buffer layer, the crystal grain size thereof is much larger than the film thickness, so that the polycrystalline silicon thin film 3 having a large crystal grain size can be easily obtained.

If such a thermal buffer layer is too thin, it is not effective, but if it is too thick, it is not effective.
(μm) or more, preferably 0.3 to 3.0 (μm). As the material, a material having a small thermal diffusivity (= thermal conductivity / density × specific heat) is preferable, and for example, Zr
O ₂ , TiO ₂ , SiO ₂ , etc. are suitable. Such a thermal buffer layer is formed by an electron beam evaporation method, an ion plating method, a plasma CVD method, an MO (Metal Organic) CVD method.
Method, sol-gel method, wet coating method and the like can be easily formed.

Further, in the above-mentioned manufacturing method, the seed layer 5
Although the growth layer 6 is deposited on the surface of the substrate by the electron beam evaporation method, it may be formed by, for example, an ion plating method, a sputtering method, a plasma CVD method or the like. In these cases, the second vacuum chamber 1
The atmosphere inside 3 corresponds to each state. For example, in the ion plating method or the sputtering method, 1 × 10 to ² to 10 (Pa) of Ar, He, N ₂ , H ₂ ,
Alternatively, in a plasma CVD method using a mixed gas of these, 1 × 10 to ^{2 to} 100 (Pa) of SiH ₄ , Si ₂ H ₆ , SiF ₄ ,
SiH ₂ Cl ₂ or a mixed gas of these and H ₂ . In case of electron beam evaporation method, the atmosphere is 1 × 10 ~ ³ (Pa)
The following H ₂ can also be used.

In the sputtering method, a silicon target is used instead of the silicon source 18, and in the plasma CVD method, a cathode electrode is used instead of the silicon source 18. The energy beam emitted by the beam generator 17 is not limited to the electron beam, and an ion beam, a laser beam, an X-ray, or the like can be used. However, since the electron beam has a small mass of charged particles, the damage to the thin film layer is small, the growth layer 6 can be deposited with few defects, and the deflection is easy, so that the growth layer 6 having a large area can be easily controlled.
Can be uniformly deposited. When the chamber internal pressure during film formation is high, it is preferable to differentially exhaust the inside of the electron gun to stabilize the operation.

In the manufacturing system 11 described above, the seed layer 5 and the growth layer 6 are individually formed in the two vacuum chambers 12 and 13, but one of the layers 5 and 6 is formed. It is also possible to form inside the vacuum chamber.

Next, a second embodiment of the present invention will be described with reference to FIG.
It will be described below based on. First, the silicon solar cell 31 of the present embodiment has a structure similar to that of the polycrystalline silicon thin film stack 1 described above as a part thereof, and this part has a thermal buffer layer 32 on the surface of the substrate 2. ((11
1) A polycrystalline silicon thin film 3 including an oriented seed layer 5 and a growth layer 6 is laminated.

However, the seed layer 5 is doped with boron at a high concentration to form a p + type, and the silicon solar cell 31.
The growth layer 6 is doped with boron to form a p-type and acts as a photocarrier generation layer of the silicon solar cell 31. An n-type silicon thin film 33 is laminated on the surface of this polycrystalline silicon thin film 3, and a transparent conductive thin film 34 is laminated on this surface.

Next, a first example of a method of manufacturing the silicon solar cell 31 having the above-mentioned structure will be described below. First,
The thermal buffer layer 32 is formed on the surface of the Pyrex substrate 2 by Z
The substrate ₂ having a film thickness of 1.0 (μm) formed by sputtering with rO _{2 and} having the thermal buffer layer 32 formed therein is placed in the second vacuum chamber 13 of the manufacturing system 11 and then heated to 300 (° C.). ). Next, the internal pressure of the vacuum chamber 13 is set to 5.0 × 10 to ⁵ (Pa), silicon vapor is generated from the silicon source 18 and boron vapor is generated from the evaporation source 19 by electron beam heating, and the thermal buffer layer 32 is generated.
A p-type amorphous silicon thin film 4 having a film thickness of 80 (nm) is formed on the surface of the.

Next, the inside of the first vacuum chamber 12 is evacuated, the gate valve 14 is opened, the substrate 2 is transferred from the second vacuum chamber 13 to the first vacuum chamber 12, and then the gate valve 14 is opened. Close. This substrate 2
In the state of being heated to 400 (℃), the surface is irradiated with a laser beam at an energy density of 350 (mJ / cm ² ) for up to 100 shots to polycrystallize the silicon thin film 4 to form a (111) -oriented polycrystal. A silicon seed layer 5 is formed.

Next, the substrate 2 is transferred from the first vacuum chamber 12 to the second vacuum chamber 13 and the electron beam is heated to 400 (° C.) and the electron beam is accelerated to 200 (200) at an acceleration voltage of 10 (kV).
Irradiate with a current density of (μA / cm ² ). At this time, silicon vapor is generated from the silicon source 18 by electron beam heating, and boron vapor is generated from the evaporation source 19,
The growth layer 6 is formed on the surface of the seed layer 5 to a film thickness of 5.0 (μm). As a result, the (111) -oriented p-type polycrystalline silicon thin film 3 is formed on the surface of the substrate 2, so that the polycrystalline silicon thin film stack 1 is manufactured. When the growth layer 6 is deposited as described above, the amount of boron vapor generated is smaller than when the silicon thin film 4 is formed.

Next, the polycrystalline silicon thin film layered body 1 formed as described above is placed inside the vacuum chamber of a parallel plate type plasma CVD apparatus (not shown) and 300 (° C.).
The inside of the vacuum chamber to vacuum and then PH ₃
A source gas of / SiH ₄ = 0.5 (%) is introduced at a total flow rate of 50 (sccm). After setting the pressure of this source gas to 30 (Pa), RF (Radio-Frequency) power is supplied to the cathode of the plasma CVD apparatus to form an n-type silicon thin film 33 on the surface of the polycrystalline silicon thin film 3 with a film thickness of 20 (nm). To form a film.

Next, a transparent conductive thin film 34 is formed on the surface of the silicon thin film 33 by the sputtering method using ITO (I
The silicon solar cell 31 is completed by forming a film with a film thickness of 100 (nm) using ndium-tin oxide. When the silicon solar cell 31 was actually manufactured and the conversion efficiency was measured as described above, it was confirmed that the efficiency was as high as 10.2 (%) [AM1.5, 100 (mW / cm ² )].

That is, in the method for manufacturing the silicon solar cell 31 of the present embodiment, the polycrystalline silicon thin film 3 of (111) orientation having a large crystal grain size can be easily formed similarly to the polycrystalline silicon thin film laminate 1 described above. Since this is used as the photocarrier generation layer, the silicon solar cell 31 with good conversion efficiency can be manufactured. When the crystal grain size of the polycrystalline silicon thin film 3 manufactured as described above was measured, it was confirmed to be as large as about 3.0 (μm).

The present invention is not limited to the above-described embodiment, but allows various modifications. For example, in the above-described silicon solar cell 31, the n-type silicon thin film 33 is laminated on the p-type polycrystalline silicon thin film 3, but the p-type and the n-type may be reversed. is there.

Further, in place of the silicon thin film 33, Pt or A
It is also possible to form the Schottky barrier with a metal thin film having a large work function such as u. In this case, the conductive thin film 34 can be omitted. Further, the thermal buffer layer 3
A metal thin film of Ag, Cu, Mo, etc. on the surface of No.
It is also possible to form a film at 00 (nm) and form a back surface reflection layer as a lower layer of the polycrystalline silicon thin film 3.

Further, in the above-described method for manufacturing the silicon solar cell 31, since the growth layer 6 is formed as a p-type, boron vapor is generated from the evaporation source 19 during the film formation. However, such boron or aluminum can be supplied from an evaporation source using a solid source or a gas source, or can be supplied by a Knudsen cell or an ion gun. In this case, the gas source is B
_{2 H 6, B (C 2} H 5 O) 3, Al (C 5 H 7 O 2) 3, Al (C 3 H 7
O) ₃ , etc. can be used.

The n-type silicon thin film 33 may be polycrystalline, amorphous or microcrystalline, and various general thin film techniques can be used for the film forming method. n
m) can be formed. When forming such a silicon thin film 33 as an n-type, P, As
Or the like, or by supplying PH ₃ , P (C
₂ H _{5) 3,} the AsH ₃ may be supplied as a CVD gas source.

The conductive thin film 34 is also formed by sputtering, electron beam evaporation, ion plating, MO.
Various thin film technologies such as the CVD method can be used, and the film thickness
It can be formed to have a thickness of about 10 (nm) to 1.0 (μm).

A second example of the method for manufacturing the silicon solar cell 31 will be described below. The description of the same parts as those in the first example of the manufacturing method described above will be omitted. First, the thermal buffer layer 32 is formed on the surface of the Pyrex substrate 2 by ECR (Ele
ctronic Cyclotron Resonance) Plasma CVD method was used to form a film of 2.0 (μm) of SiOx, and the thermal buffer layer 32
The substrate 2 on which is deposited is placed inside a parallel plate type plasma CVD apparatus (not shown) and heated to 300 (° C.). The inside of the vacuum chamber is evacuated to PH ₃ / SiH ₄
= 2.0 (%) of raw material gas was introduced at a total flow rate of 50 (sccm), the pressure of this raw material gas was set to 30 (Pa), and then RF power was supplied to the cathode to form an n + type silicon thin film 4 with a film thickness of 100 ( nm).

The substrate 2 having the silicon thin film 4 formed thereon is placed inside the first vacuum chamber 12 of the manufacturing system 11, and the surface is irradiated with a laser beam while being heated to 400 (° C.) ( A seed layer 5 of n + type polycrystalline silicon having a (111) orientation is formed. Next, the substrate 2 is transferred from the first vacuum chamber 12 to the second vacuum chamber 13 and the electron beam is heated to 400 (° C.) and the electron beam is accelerated to 200 (μA / cm ² at an accelerating voltage of 10 (kV). ) To the current density. At this time, silicon vapor is generated from the silicon source 18 and phosphorus vapor is generated from the evaporation source 19 by electron beam heating, and the n-type growth layer 6 is formed on the surface of the seed layer 5 to a thickness of 4.0.
(μm) is deposited. As a result, the (111) -oriented n-type polycrystalline silicon thin film 3 is formed on the surface of the substrate 2, so that the polycrystalline silicon thin film stack 1 is manufactured.

Next, the polycrystalline silicon thin film laminate 1 formed as described above is placed inside a parallel plate type plasma CVD apparatus and heated to 300 (° C.), and the inside of the vacuum chamber is evacuated. To B ₂ H ₆ / SiH ₄ = 0.1 (%) are introduced at a total flow rate of 50 (sccm). After setting the pressure of this source gas to 30 (Pa), RF power is supplied to the cathode of the plasma CVD apparatus to form a p-type silicon thin film 33 on the surface of the n-type polycrystalline silicon thin film 3 to a film thickness of 20 (nm). To film.

Next, a transparent conductive thin film 34 is formed on the surface of the silicon thin film 33 by sputtering to a thickness of 100 (nm) with ITO, whereby the silicon solar cell 31 is completed. When the silicon solar cell 31 was actually manufactured and the conversion efficiency was measured as described above, it was confirmed that the efficiency was as high as 9.5 (%).

That is, in the method for manufacturing the silicon solar cell 31 of the present embodiment, the (111) -oriented polycrystalline silicon thin film 3 having a large crystal grain size can be easily formed similarly to the polycrystalline silicon thin film stack 1 described above. Since this is used as the photocarrier generation layer, the silicon solar cell 31 with good conversion efficiency can be manufactured. When the crystal grain size of the polycrystalline silicon thin film 3 manufactured as described above was measured, it was confirmed to be as large as about 2.0 (μm).

Furthermore, the silicon solar cell 3 as described above is used.
In order to verify the effects of the first and second manufacturing methods of No. 1, a silicon solar cell was manufactured by the conventional method and the conversion efficiency was measured. In that case, the thermal buffer layer 32 and n are formed on the surface of the substrate 2.
Type seed layer 5 is formed and exposed to the atmosphere, and then a growth layer 6 of n-type polycrystalline silicon is formed to a thickness of 4.0 (μm) by a layer-by-layer method using microwave plasma.
Was formed. At this time, the substrate 2 is heated to 400 (° C), and P
A source gas of H ₃ / SiF ₄ = 0.5 (%) was introduced at a total flow rate of 60 (sccm). Film formation for 10 (sec) with this source gas and treatment for 30 (sec) with H ₂ gas are defined as one cycle.
Repeated until 00 cycle.

Since the (110) -oriented n-type polycrystalline silicon thin film 3 is thus formed on the surface of the substrate 2, a p-type silicon thin film 33 and a conductive thin film 34 are formed thereon to form a silicon film. A solar cell was formed. When the conversion efficiency of the silicon solar cell manufactured in this way was measured, it was 6.5 (%) [A
M1.5, 100 (mW / cm ² )] and low efficiency was confirmed. Furthermore, when the crystal grain size of the polycrystalline silicon thin film 3 was measured, it was confirmed that the diameter was as small as about 1.0 (μm).

[0055]

The polycrystalline silicon thin film laminate according to the first aspect of the present invention is formed on a substrate and the surface of the substrate (1
11) A polycrystalline silicon thin film laminate having a (111) -oriented polycrystalline silicon thin film with few defects such as twins in the crystal grains is obtained by having the oriented polycrystalline silicon thin film. Therefore, for example, by using this for a silicon solar cell, a silicon solar cell with high conversion efficiency can be obtained.

In the polycrystalline silicon thin film laminate according to the second aspect of the present invention, the polycrystalline silicon thin film comprises a seed layer formed on the surface of a substrate and made of (111) oriented polycrystalline silicon crystal grains, and this seed layer. Deposited on the surface of the layer (11
By having a growth layer of 1) oriented polycrystalline silicon, a (111) oriented polycrystalline silicon thin film can be easily formed to a desired thickness.

According to a third aspect of the present invention, there is provided a method for producing a polycrystalline silicon thin film laminate, in which a seed layer made of (111) -oriented polycrystalline silicon crystal grains is formed on a surface of a substrate, and the seed layer has a surface. By depositing a growth layer of (111) -oriented polycrystalline silicon, a (111) -oriented polycrystalline silicon thin film can be easily formed to a desired film thickness, and a twin crystal or the like can be formed in a crystal grain. Few defects (111)
It is possible to easily manufacture a polycrystalline silicon thin film laminate in which an oriented polycrystalline silicon thin film is formed on the surface of a substrate.

In the method for producing a polycrystalline silicon thin film laminate according to the fourth aspect of the present invention, the seed layer and the growth layer are formed in a vacuum so that the seed layer and the growth layer are produced in the production process. Because it is not exposed to the oxidizing atmosphere,
It is possible to grow a polycrystalline silicon thin film in the (111) orientation.

In the method for producing a polycrystalline silicon thin film laminate according to the fifth aspect of the present invention, an amorphous or microcrystalline silicon thin film is formed on the surface of the substrate, and the silicon thin film is irradiated with a laser beam. By forming the seed layer, the amorphous or microcrystalline silicon thin film (1
11) Oriented polycrystalline silicon can be formed with a large grain size.

In the method of manufacturing a polycrystalline silicon thin film laminate according to the sixth aspect of the present invention, the surface of the seed layer is irradiated with an energy beam to deposit silicon atoms or silicon compound molecules to form a growth layer. As a result, (111) -oriented polycrystalline silicon can be grown with a large grain size on the surface of the seed layer made of (111) -oriented polycrystalline silicon.

The silicon thin film solar cell according to the invention of claim 7 has the polycrystalline silicon thin film laminate according to claim 1 or 2 as a photocarrier generation layer, so that the photocarrier generation layer has few defects and is polycrystalline. Since the particle size of silicon is large, a silicon thin film solar cell with high conversion efficiency can be obtained.

[Brief description of drawings]

FIG. 1 is a process drawing showing a method for producing a polycrystalline silicon thin film laminate according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing a manufacturing system for a polycrystalline silicon thin film laminate.

FIG. 3 is a cross-sectional view showing a Schottky diode including a polycrystalline silicon thin film stack as a part.

FIG. 4 is a cross-sectional view showing a silicon solar cell.

[Explanation of symbols]

 1 Polycrystalline Silicon Thin Film Laminate 2 Substrate 3 Polycrystalline Silicon Thin Film 4 Silicon Thin Film 5 Seed Layer 6 Growth Layer 31 Silicon Solar Cell

Claims (7)

[Claims] 1. A polycrystalline silicon thin film laminate comprising a substrate and a (111) oriented polycrystalline silicon thin film formed on the surface of the substrate. 2. A polycrystalline silicon thin film is formed on a surface of a substrate, a seed layer made of (111) -oriented polycrystalline silicon crystal grains, and deposited on the surface of the seed layer (1).
11) A growth layer made of oriented polycrystalline silicon, and the polycrystalline silicon thin film laminate according to claim 1. 3. A seed layer made of (111) -oriented polycrystalline silicon crystal grains is formed on a surface of a substrate, and a growth layer of (111) -oriented polycrystalline silicon is deposited on the surface of the seed layer. A method for manufacturing a polycrystalline silicon thin film laminate, comprising: 4. The method for producing a polycrystalline silicon thin film laminate according to claim 3, wherein the seed layer formation and the growth layer deposition are performed in a vacuum. 5. An amorphous or microcrystalline silicon thin film is formed on the surface of the substrate, and the silicon thin film is irradiated with a laser beam to form a seed layer. Alternatively, the method for manufacturing the polycrystalline silicon thin film laminate according to the item 4, 6. The polycrystal according to claim 3, 4 or 5, wherein the growth layer is formed by depositing silicon atoms or silicon compound molecules while irradiating the surface of the seed layer with an energy beam. Method for manufacturing silicon thin film laminate. 7. A silicon thin-film solar cell comprising the polycrystalline silicon thin-film laminate according to claim 1 or 2 as a photocarrier generation layer.