JP2004266111A - Method for manufacturing microcrystal film and microcrystal film solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a microcrystal film and a microcrystal film solar cell which enhances qualities and deposition rate of the microcrystal film, and enhances performances, and reduces manufacturing costs of a thin-film semiconductor device, in particular a solar cell employing the microcrystal film. <P>SOLUTION: The microcrystal film is formed to satisfy such deposition requirements that a light generation section 5 caused in the vicinity of a high-frequency electrode 1 and a light generation section 6 caused in the vicinity of a ground electrode 2 are superposed. Further, letting d be a spatial distance between the electrode 1 and the electrode 2, s1 be a thickness of a dark section in the vicinity of the electrode 1, p1 be a thickness of the section 5, s2 be a thickness of a dark section in the vicinity of the electrode 2, and p2 be a thickness of the section 6, the following conditional equation should be satisfied: s1+p1+s2+p2>d>s1+s2+(p1+p2)/2. In the method for manufacturing the microcrystal film solar cell, at least an optical active layer consists of the microcrystal film, the microcrystal film is formed to satisfy the deposition requirements mentioned above, and the optical active layer is formed so that the crystal volume fraction of the microcrystal film falls within a range of 30-70%. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【００５７】
【発明の効果】
上記のとおり、この発明によれば、微結晶膜形成用基板の一側に配設した平板状の接地電極と、他側に平行して配設した平板状の高周波電極と、原料ガス供給口とを備えた成膜室に、膜形成用の原料ガスを導入し、プラズマ放電によって前記基板主面に微結晶膜を形成する微結晶膜の製造方法において、
前記高周波電極近傍に生ずる発光部とこの発光部に対向して接地電極近傍に生ずる発光部とが重なる成膜条件で微結晶膜を形成し、かつ、前記重なる成膜条件は、下記の条件式を満足することとした。
【００５８】
ｓ１＋ｐ１＋ｓ２＋ｐ２ ＞ ｄ ＞ ｓ１＋ｓ２＋（ｐ１＋ｐ２）／２
前記条件式において、ｄ は高周波電極と接地電極との空間距離、ｓ１は高周波電極近傍の暗部の厚さ、ｐ１は同発光部の厚さ、ｓ２は基板側電極近傍の暗部の厚さ、ｐ２は同発光部の厚さを示す。
【００５９】
また、微結晶薄膜太陽電池の製造方法の発明として、基板上に第１電極層、第１導電層、実効的に真性な光活性層、第２導電層、第２電極層が積層され、少なくとも前記光活性層が微結晶膜からなる微結晶薄膜太陽電池の製造方法において、前記微結晶膜は、前述の製造方法によって形成することとし、さらに、前記光活性層は、その微結晶膜の結晶体積分率が３０〜７０％の範囲となるように形成することとしたので、
微結晶膜の膜質の向上と成膜速度の増大を図り、さらに微結晶膜を用いた薄膜半導体デバイス、特に微結晶薄膜太陽電池の性能向上と製造コストの低減化を図ることができる。
【図面の簡単な説明】
【図１】この発明に関わり高周波プラズマＣＶＤの放電構造を模式的に示す図
【図２】この発明に関わり電極間距離と結晶分率との相関の実験結果の一例を示す図
【図３】この発明に関わり電極間距離と成膜速度との相関の実験結果の一例を示す図
【図４】この発明に係わる微結晶薄膜太陽電池の構造例を示す図
【図５】この発明に係わる微結晶薄膜太陽電池の図４とは異なる構造例を示す図
【符号の説明】
１：高周波電極、２：接地電極、３：基板、４：高周波電源、５：高周波電極側発光部、６：接地電極側の発光部、７：高周波電極側の暗部、８：接地電極側の暗部、９：発光部間の暗部、１０：基板（ガラス基板）、１１：金属電極、１２：反射増加層、１３：ｎ層、１４：光活性層、１５：ｐ層、１６，１７：透明電極層。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a microcrystalline film used for a thin-film semiconductor device such as a thin film transistor or a thin-film solar cell, and a method for manufacturing a microcrystalline thin-film solar cell in which at least a photoactive layer (i-layer) includes the microcrystalline film.
[0002]
[Prior art]
2. Description of the Related Art Solar cells that convert sunlight into electric energy have attracted attention as an inexhaustible clean energy device. Above all, amorphous silicon (a-Si) thin-film solar cells have the advantage that they can be easily mass-produced at a low manufacturing cost, although their efficiency is lower than that of crystalline solar cells, but they are characteristic when irradiated with light. As a defect, that is, light degradation. On the other hand, a microcrystalline silicon (μc-Si) solar cell can be applied to the same process as that of an a-Si solar cell, so that the cost can be reduced and the problem of photodeterioration does not occur. (For example, see Patent Document 1).
[0003]
Patent Document 1 is an application filed by the same applicant as the present invention. In order to improve the performance of a thin-film semiconductor device using a microcrystalline film, a fine crystalline film having a high crystal volume fraction can be formed. For the purpose of providing a method for manufacturing a crystal film, the following manufacturing method is disclosed.
[0004]
That is, a plate-like ground electrode provided on one side of the microcrystalline film forming substrate, a plate-like high-frequency electrode provided parallel to the other side, and a film forming chamber provided with a source gas supply port. In a method for producing a microcrystalline film, in which a source gas for film formation is introduced and a microcrystalline film is formed on the main surface of the substrate by plasma discharge, by reducing the distance between the two electrodes, Due to the decrease, both the light emitting portion generated near the high-frequency electrode and the light emitting portion generated near the ground electrode opposite to the light emitting portion form a microcrystalline film under adjacent or overlapping film forming conditions.
[0005]
[Patent Document 1]
JP-A-2002-64066 (page 1-5, FIG. 1-5)
[0006]
[Problems to be solved by the invention]
However, as a result of subsequent studies, it has been found that the method for manufacturing a microcrystalline film disclosed in Patent Document 1 has the following problems.
[0007]
First, it is clear from subsequent research that if the distance between the electrodes is too short, electron and ion losses in the electrode part increase and the film deposition rate decreases, and further damage tends to increase and the film quality tends to decrease. became.
[0008]
Further, when a method of manufacturing a microcrystalline film as disclosed in Patent Document 1 is applied to a photoactive layer of a microcrystalline thin film solar cell, as described in Patent Document 1, the crystal volume of the microcrystalline film is reduced. The higher the percentage, the better it is, the better it is. As will be described in detail later, there is an appropriate range for improving the characteristics of the solar cell, and this volume fraction has a close relationship with the hydrogen dilution rate. Is known.
[0009]
Furthermore, in a microcrystalline thin film solar cell, an amorphous layer is easily formed in the initial stage of film formation of the microcrystalline thin film, but the conductive layer needs to be thinned so as not to deteriorate the characteristics of the solar cell. For this reason, particularly for forming the conductive layer on the substrate side, a condition with a high hydrogen dilution rate is applied, and a microcrystalline thin film having less amorphous components in the film has been used. On the other hand, if the hydrogen dilution ratio is too high, there is a problem that the electrode and the film are strongly damaged during the film formation, leading to deterioration of the characteristics. Therefore, it is necessary to form the conductive layer while simultaneously suppressing the damage and the formation of the amorphous layer.
[0010]
Furthermore, since the photoelectric conversion layer needs to have a large film thickness of about several μm, it is necessary to increase the film forming rate in order to reduce the manufacturing cost. Further, as in the case of the conductive layer, if the film is strongly damaged, the characteristics are deteriorated. Therefore, it is necessary to increase the film forming speed while suppressing the damage.
[0011]
The present invention has been made in view of the above points, and an object of the present invention is to improve the film quality of a microcrystalline film and increase the film formation rate, and further to provide a thin film semiconductor device using a microcrystalline film, It is an object of the present invention to provide a microcrystalline film and a method of manufacturing a microcrystalline thin film solar cell which improve the performance of the crystalline thin film solar cell and reduce the manufacturing cost.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, a flat ground electrode provided on one side of a microcrystalline film forming substrate, a flat high frequency electrode provided in parallel with the other side, and a raw material In a method for producing a microcrystalline film, in which a source gas for film formation is introduced into a film forming chamber having a gas supply port and a microcrystalline film is formed on the main surface of the substrate by plasma discharge, the gas is generated in the vicinity of the high-frequency electrode. A microcrystalline film is formed under a film forming condition in which the light emitting portion and the light emitting portion generated near the ground electrode facing the light emitting portion overlap, and the overlapping film forming condition satisfies the following conditional expression. (Invention of claim 1).
[0013]
s1 + p1 + s2 + p2>d> s1 + s2 + (p1 + p2) / 2
In the above conditional expression, d is the spatial distance between the high-frequency electrode and the ground electrode, s1 is the thickness of the dark portion near the high-frequency electrode, p1 is the thickness of the light-emitting portion, s2 is the thickness of the dark portion near the substrate-side electrode, p2 Indicates the thickness of the light emitting portion.
[0014]
In the first aspect of the present invention, s1 + p1 + s2 + p2> d on the left side of the conditional expression indicates a film forming condition in which a light emitting portion generated near the high-frequency electrode and a light emitting portion generated near the ground electrode opposite to the light emitting portion overlap. However, by further satisfying the condition d> s1 + s2 + (p1 + p2) / 2 on the right side, the conventional problem described above, that is, the problem that the electron and ion losses in the electrode portion increase and the film forming speed decreases, The problem that the damage is increased and the film quality is reduced can be solved.
[0015]
Specifically, the composition of the source gas, the frequency, the pressure at the time of film formation, the power density, and the like are set in advance in accordance with the specifications of the target microcrystalline film, and the dark portion and the light emitting portion can be completely formed. S1, p1, s2, and p2 are measured below the electrode gap, and then the electrode gap d is narrowed to form a film so as to satisfy the above conditional expression.
[0016]
As an embodiment of the invention of claim 1, the following inventions of claims 2 and 3 are preferable. That is, in the method of manufacturing a microcrystalline film according to claim 1, the microcrystal of the microcrystalline film to be formed is any one of microcrystalline silicon, microcrystalline germanium, microcrystalline silicon alloy, and microcrystalline germanium alloy. (The invention of claim 2). In the method of manufacturing a microcrystalline film according to claim 2, the microcrystalline silicon alloy is any one of microcrystalline silicon germanium, microcrystalline silicon carbide, microcrystalline silicon oxide, and microcrystalline silicon nitride. Item 3 invention).
[0017]
Further, as the invention of the method of manufacturing a microcrystalline thin film solar cell, the following inventions 4 and 5 are preferable. That is, a first electrode layer, a first conductive layer, an effective intrinsic photoactive layer, a second conductive layer, and a second electrode layer are laminated on a substrate, and at least the photoactive layer is a microcrystal made of a microcrystalline film. In the method for manufacturing a thin-film solar cell, the microcrystalline film is formed by the method according to any one of claims 1 to 3 (invention of claim 4).
[0018]
Further, in the method for manufacturing a microcrystalline thin film solar cell according to claim 4, the photoactive layer is formed such that the crystal volume fraction of the microcrystalline film is in a range of 30 to 70% (claim). 5 invention). The method for producing a microcrystalline film is applied to the formation of a photoelectric conversion layer of a microcrystalline thin film solar cell as described in the invention of claim 5, and the hydrogen dilution rate during the film formation is controlled as described later. By controlling the crystal volume fraction to be 30 to 70%, it is possible to improve the film forming rate and the characteristics of the solar cell. Furthermore, when the method for producing a microcrystalline film is applied to the formation of a conductive layer of a microcrystalline thin film solar cell, a thin film having a small thickness, an amorphous layer, and a film having a high conductivity suppresses damage to electrodes and films. To form a microcrystalline solar cell with good characteristics. That is, according to the fourth and fifth aspects of the present invention, it is possible to improve the performance of the microcrystalline thin-film solar cell and reduce the manufacturing cost by increasing the film forming rate. This will be described later in detail together with the experimental results.
[0019]
The significance of setting the crystal volume fraction of the microcrystalline film in the range of 30 to 70%, the reason thereof, and the relationship with the hydrogen dilution rate according to the invention of claim 5 are described below.
[0020]
Crystals are characterized by higher mobility and longer mean free path than amorphous. Therefore, charge can be collected even when the film thickness is large. In addition, defects (crystal grain boundaries) contained in the crystal serve as traps for electric charges, causing deterioration in characteristics.
[0021]
In the case of microcrystals (a mixed state of crystal and amorphous), if amorphous exists at the grain boundaries of crystal grains, the effect of trapping charges is reduced, and the electrical characteristics are improved. However, when the amount of the amorphous component is too large and the crystal grains are not connected to each other, the flow of the electric charge is hindered by the amorphous, so that the electric characteristics are deteriorated. The crystal volume fraction of about 30% is the lower limit at which the crystal grains are connected to each other to allow a current path.
[0022]
In addition, since the crystal has a smaller band gap than an amorphous state, the charge density is high. The lower the charge density in the power generation layer of the solar cell, the better the characteristics. Therefore, from this point, the more the amorphous component, the better the characteristics. In view of the above, there is an appropriate crystal volume fraction, and a preferable range thereof is 30 to 70%.
[0023]
Further, the crystal volume fraction can be controlled mainly by the hydrogen dilution rate during film formation when the electrode gap, frequency, pressure during film formation, and power density are fixed. A gas obtained by diluting silane gas with hydrogen is used as a source gas, and the hydrogen dilution ratio is determined by the flow rate ratio. The characteristics of the amorphous silicon thin film formed by plasma CVD are improved when radicals are sufficiently diffused on the film surface during film formation, and can be promoted by the hydrogen dilution rate. When the hydrogen dilution rate is increased to some extent, the structure of the film changes, and a crystal component is formed. When the dilution ratio is further increased, the crystal component increases, and is substantially saturated at about 80 to 90%.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below. First, a discharge mode of high-frequency plasma CVD related to the film forming conditions of the method for manufacturing a microcrystalline film will be described.
[0025]
FIG. 1 schematically shows a discharge structure of high-frequency plasma CVD. FIG. 1A is a schematic diagram according to an embodiment of the present invention, and FIG. 1B is a conventional general structure in which light emitting portions are not overlapped. FIG. 1C is a schematic diagram according to the manufacturing method, and is a schematic diagram in a case where the light emitting units overlap excessively. First, FIG. 1B, which is an exploded view of each part of the plasma, will be described. The plasma shown in FIG. 1B is a system including a high-frequency electrode 1 for applying a high frequency, a ground electrode 2 on the substrate side, a substrate 3 for forming a film, and a high-frequency power supply 4. It is generated by application. This plasma is composed of light emitting portions 5 and 6 on the high frequency electrode side and the ground electrode side, dark portions 7 and 8 near each electrode, and dark portion 9 between the light emitting portions. In this range, radicals generated in the light emitting portion on the high-frequency electrode side are damaged by recombination while diffusing to the substrate side.
[0026]
As shown in FIG. 1B, the gap distance between the two electrodes is d, the thickness of the dark part near the high-frequency electrode and the thickness of the light emitting part are s1 and p1, respectively, the thickness of the dark part near the ground electrode, and the light emitting part. Are s2 and p2, respectively, in FIG. 1B, d> s1 + p1 + s2 + p2, and a dark portion 9 is present in the middle. Note that s1, s2, p1, and p2 hardly change even if the inter-electrode distance d is changed, as long as the light emitting portions of the respective electrodes do not overlap.
[0027]
On the other hand, in the range of s1 + s2 + (p1 + p2) / 2 <d <s1 + p1 + s2 + p2 according to the present invention, as shown in FIG. 1A, there is no dark portion in the light emitting portion, and the light emitting portions of both electrodes overlap. Absent. In this region, by reducing the distance between the electrodes, the rate at which radicals formed in the light emitting portion reach the substrate increases.
[0028]
Furthermore, if the distance between the electrodes is reduced and d <s1 + s2 + (p1 + p2) / 2, the plasma finally becomes a state where the light emitting portions of both electrodes are completely overlapped as shown in FIG. 1 (c). By setting d <s1 + s2 + (p1 + p2) / 2, there was a tendency that the film-forming speed was reduced with a decrease in the electrode interval. This is considered to be due to an increase in loss of electrons and ions at the electrodes.
[0029]
Next, specific film forming conditions other than the discharge mode of the microcrystalline film according to the embodiment of the present invention will be described below. The electrode diameter of the apparatus used for film formation is 16 mm. Although the frequency of the applied high-frequency power is 100 MHz here, the film can be formed in a range of 10 MHz to 200 MHz. Although the power is set to 20 W, the film can be formed in a range of 2 W to 200 W.
[0030]
As a raw material gas, a silane gas was supplied in a range of 3 to 20 sccm, and a hydrogen gas flow rate was controlled in a range of 150 to 500 sccm by a mass flow controller. Then, the film was evacuated by a turbo pump through a pressure control valve, and the film was formed while maintaining the pressure at 200 Pa (1.5 torr). The unit of flow rate sccm indicates standard cc / min (flow rate cm ³ / min in standard condition conversion). As a source gas, a silane gas was used to form a microcrystalline silicon thin film. In addition, a hydride of silane such as SiH ₄ or Si ₂ H _{6, a} hydride of higher order silane, or hydrogen Gases replaced with hydrogen, fluorine, and chlorine are suitable. Further, when a film of microcrystalline germanium or an alloy thereof is formed, GeH ₄ or a gas obtained by replacing hydrogen thereof with deuterium, fluorine, or chlorine is suitable as a raw material of germanium. Although H ₂ was used as the diluent gas, Ar, He, etc. are also suitable. The pressure may be set in a range of about 13.3 Pa (0.1 torr) to about 2660 Pa (20 torr).
[0031]
Although a 50 mm square glass substrate was used as the substrate, a ceramic substrate, a stainless steel substrate, or a resin substrate such as polyester, polyethylene, polyamide, polyimide, polypropylene, polyvinyl chloride, polycarbonate, or polystyrene may also be used. it can. The substrate temperature was controlled by setting the heater temperature of the ground electrode on the substrate side to 300 ° C. The substrate temperature can be in the range of 50 ° C. to 600 ° C. within the range of the heat resistant temperature of the substrate, but is preferably in the range of 100 ° C. to 400 ° C.
[0032]
Next, with respect to an example of the results of various experiments in which the distance between the electrodes is changed, the relationship between the crystal volume fraction (hereinafter, also simply referred to as the crystal fraction) related to the microcrystalline thin-film solar cell described later, the film formation rate, and the like. Is described.
[0033]
FIG. 2 shows an example of an experimental result of a correlation between a distance between electrodes and a crystal fraction. The experimental conditions in FIG. 2 are a film forming pressure of 200 Pa (1.5 torr), a hydrogen dilution ratio of 20 times, a frequency of 100 MHz, and a power density of 75 mW / cm ² . When the distance between the electrodes (gap distance) is reduced from 14 mm under these conditions, as shown in FIG. 2, the flux of hydrogen radicals reaching the substrate side increases, so that the crystal fraction (%) gradually increases. Increase. Here, the flux of the radical derived from the silane gas hardly changes, and thus the film forming speed does not change. Further, when the distance between the electrodes (gap distance) is reduced to 4 mm, the loss in the electrodes increases, and the crystal fraction decreases.
[0034]
FIG. 3 shows that the photoactive layer of the microcrystalline thin-film solar cell desirably has a crystal fraction in the range of 30 to 70%. Therefore, the hydrogen dilution rate is reduced and the crystal fraction is constant (for example, 60%). 4) shows an example of an experimental result of an experiment performed under the condition that satisfies the following condition, and an example of an experimental result of a correlation between a distance between electrodes and a deposition rate. As shown in FIG. 3, when an experiment is performed so that the crystal fraction does not change, the necessary dilution ratio decreases and the film forming speed increases when the electrode interval is reduced. The film formation speed is almost inversely proportional to the dilution ratio. Further, when the electrode interval is set to 4 mm, the loss at the electrodes increases, so that the dilution ratio increases and the film formation speed decreases.
[0035]
The above experimental results are, as described above, an example of the back data indicating that the range of s1 + s2 + (p1 + p2) / 2 <d <s1 + p1 + s2 + p2 is preferable, and is preferable when applied to a microcrystalline thin film solar cell.
[0036]
Next, the embodiment of the method for manufacturing a microcrystalline thin-film solar cell according to the present invention will be described. First, the structure of the microcrystalline thin-film solar cell will be described. FIG. 4 shows a structural example of a microcrystalline thin-film solar cell according to the present invention. The structure of this solar cell is a substrate-type single structure, in which a conductive metal electrode 11, a reflection increasing layer 12, an n-type semiconductor layer 13, a photoactive layer 14, and a p-type semiconductor layer 15 are formed on a substrate 10. , And a transparent electrode 16. The solar cell is irradiated with light from the transparent electrode 16 side.
[0037]
In this embodiment, a glass substrate is used as the substrate 10, but a ceramic substrate, a stainless steel substrate, and a resin substrate such as polyester, polyethylene, polyamide, polyimide, polypropylene, polyvinyl chloride, polycarbonate, and polystyrene are used. You can also. The metal electrode 11 is made of a metal such as Ni, Cr, Al, Ag, Pb, Zn, Ni, Au, Cr, Mo, Ir, Nb, Ta, V, Ti, Pt, or a thin film made of an alloy or a multilayer film thereof. Can be provided on the substrate surface by vacuum evaporation, electron beam evaporation, sputtering, a printing method, or the like.
[0038]
Suitable examples of the reflection increasing layer 12 include ITO, ZnO, SnO ₂ , In ₂ O ₃ , and TiO ₂ . Suitable methods for depositing the reflection increasing layer 12 include a vacuum deposition method, a sputtering method, a CVD method, and a spray method.
[0039]
For the n-type layer of the microcrystalline thin-film solar cell of this example, a microcrystalline material, particularly μc-Si, was used, but in addition, μc-Si: H, μc-SiC: H, μc-SiN: H, μc- Using a material in which an n-type valence electron controlling agent (Group V atom, P, As, Sb, Bi) is added in high concentration to SiO: H, μc-SiN: H, μc-SiGe: H, etc. Can be. The thickness of the n-type layer is preferably from 50 to 500 °.
[0040]
For the photoactive layer, μc-Si and μc-SiGe, which are effectively intrinsic, can be used. It is suitable that μc-Si has a thickness of 5000 to 40000 °, and μc-SiGe has a thickness of 3000 to 30000 °. As a source gas, a hydride of silane such as SiH ₄ or Si ₂ H ₆ or a gas obtained by replacing hydrogen thereof with deuterium, fluorine, or chlorine is suitable for supplying silicon. Similarly, as a raw material of germanium, GeH ₄ or a gas obtained by replacing hydrogen thereof with deuterium, fluorine, or chlorine is suitable. H ₂ is suitable as the diluent gas.
[0041]
For the p-type layer of the embodiment, a microcrystalline material, particularly μc-Si, was used, but a-Si may be used. In addition, μc-SiC: H, μc-SiN: H, μc-SiO: H, μc-Si Examples of such materials include SiN: H, μc-SiGe: H, and the like, in which B, which is a p-type valence electron controlling agent, is added at a high concentration. The thickness is preferably 20 to 200 °.
[0042]
As the p-type material for controlling valence electrons, B ₂ H ₆ was used, but other borohydrides such as B ₄ H ₁₀ and boron halides such as BF ₃ and BCl ₃ can be used.
[0043]
As the transparent conductive film of the present invention, ZnO, SnO ₂ , In ₂ O ₃ , ITO and the like are suitable. Further, the film thickness is preferably about 500 to 20000 °. As a film forming method, a vacuum evaporation method, magnetron sputtering, reactive sputtering, plasma CVD, or the like is suitable.
[0044]
Further, a grid electrode made of a metal such as Ag, Au, Cu, or Al may be used as the current collecting electrode.
[0045]
In the above description, the single structure of the substrate is described as the structure of the solar cell. However, the present invention can also be applied to a superstrate type shown in FIG. 5 or a tandem or triple structure in which a plurality of single cells are stacked. In FIG. 5, the same reference numerals are given to the same functional members as those shown in FIG. 4, and the detailed description is omitted. In FIG. 5, the transparent electrode 17 is placed directly above the substrate 10 made of, for example, glass. The light is provided from the substrate 10 side.
[0046]
Subsequently, the details of the example of the method for manufacturing the microcrystalline thin film solar cell shown in FIG. 4 will be described below together with a comparative example.
[0047]
(Example: Manufacturing method of microcrystalline thin film solar cell)
A 50 mm square glass substrate was used as the substrate 10, and Ag and ZnO metal electrodes 11 were stacked thereon by magnetron sputtering. Ag has a substrate temperature of 250 ° C. during film formation, and its film thickness is approximately 2000 °. ZnO was doped with Ga. The substrate temperature during film formation was 250 ° C., and the film thickness was about 500 °.
[0048]
A semiconductor layer made of silicon and its alloy was formed on the metal electrode 11 by plasma CVD. The plasma CVD apparatus is a capacitively-coupled plasma CVD apparatus having an electrode diameter of 160 mm, and each of the n-layer, the photoactive layer, and the p-layer can be manufactured in a different film-forming chamber.
[0049]
The film formation of the n-layer was performed in the following procedure. The temperature of the heater for heating the substrate was set to 250 ° C., and the tray on which the substrate was placed was placed on the heater and heated. Then, SiH ₄ gas, H ₂ gas, and PH ₃ gas (hydrogen balance 1000 ppm) were introduced into the respective gas introduction pipes. From 3,300, and 20 sccm, and the pressure was adjusted to 266 Pa (2 torr) by a conductance valve. Subsequently, a high frequency of 13.56 MHz and 20 W was applied to the electrode. The glow discharge was stopped when the thickness of the microcrystalline n layer reached 300 °.
[0050]
Subsequently, a film was formed in a growth region of the photoactive layer. The distance between the electrodes was set to 6 mm so that the light emitting portions of both electrodes overlapped half. The temperature of the heater for heating the substrate was set to 200 ° C., the substrate was set and heated, and then SiH ₄ gas and H ₂ gas were introduced at 15, 200 sccm, respectively. The pressure was adjusted by a conductance valve so that the pressure became 200 Pa (1.5 torr). Subsequently, a high frequency of 100 MHz and 20 W was applied to generate glow discharge. When the film thickness reached 2.5 μm, the application of power was stopped, and the film formation in the growth region of the photoactive layer was completed. The film formation rate was 5 ° / s, and the crystal fraction was 60%.
[0051]
Subsequently, a p-layer was formed. SiH ₄ , H ₂ , and B ₂ H ₆ gases were introduced at 3,500 and 15 sccm, respectively, and the pressure was controlled at 266 Pa (2 torr). Then, a high frequency of 13.56 MHz and 10 W was applied, and the film thickness became 70 °. Then, the discharge was stopped. The distance between the electrodes was 10 mm. In this discharge, the light emitting portions of both electrodes were half overlapped. Further, a transparent conductive film made of ITO was formed on the p layer by sputtering at 800 °, and a grid electrode made of Ag was formed by vapor deposition.
[0052]
(Comparative Example 1)
A solar cell was prototyped under the same conditions as in the above example except that the distance between the electrodes at the time of forming the p-layer was 20 mm. Under this condition, when forming the p-layer, the thickness of the dark portion between the light-emitting portions of both electrodes was 7 mm.
[0053]
(Comparative Example 2)
It was prepared under substantially the same conditions as in the above example. However, the distance between the electrodes during the formation of the photoactive layer was set to 10 mm, and the source gas was introduced as SiH ₄ gas and H ₂ gas at 10, 200 sccm, respectively. The deposition rate was 3 ° / s and the crystal fraction was 60%. The thickness of the dark part between both electrodes was 3 mm.
[0054]
(Comparative Example 3)
It was prepared under substantially the same conditions as in the above example. However, the distance between the electrodes at the time of forming the photoactive layer was set to 4 mm, and the source gas was introduced as SiH ₄ gas and H ₂ gas at 15, 180 sccm, respectively. The film formation rate was 3 ° / s, and the crystal fraction was 60%.
[0055]
Table 1 shows comparison results of various characteristics (Voc, FF, Jsc, Eff) of the microcrystalline thin-film solar cells of the above-mentioned Example and Comparative Examples 1, 2, and 3. In Table 1, Voc indicates the open-end voltage, FF indicates the fill factor, Jsc indicates the short-circuit current, and Eff indicates the conversion efficiency. Table 1 confirms the superiority of the example to each comparative example.
[0056]
[Table 1]

[0057]
【The invention's effect】
As described above, according to the present invention, a flat ground electrode provided on one side of a microcrystalline film forming substrate, a flat high-frequency electrode provided in parallel on the other side, and a raw material gas supply port In a method for manufacturing a microcrystalline film, a source gas for forming a film is introduced into a film forming chamber provided with, and a microcrystalline film is formed on the main surface of the substrate by plasma discharge.
The microcrystalline film is formed under a film forming condition in which the light emitting portion generated near the high-frequency electrode and the light emitting portion generated near the ground electrode facing the light emitting portion overlap, and the overlapping film forming condition is defined by the following conditional expression. To be satisfied.
[0058]
s1 + p1 + s2 + p2>d> s1 + s2 + (p1 + p2) / 2
In the above conditional expression, d is the spatial distance between the high-frequency electrode and the ground electrode, s1 is the thickness of the dark portion near the high-frequency electrode, p1 is the thickness of the light-emitting portion, s2 is the thickness of the dark portion near the substrate-side electrode, p2 Indicates the thickness of the light emitting portion.
[0059]
Further, as an invention of a method for manufacturing a microcrystalline thin film solar cell, a first electrode layer, a first conductive layer, an effective intrinsic photoactive layer, a second conductive layer, and a second electrode layer are laminated on a substrate, and at least In the method for manufacturing a microcrystalline thin film solar cell in which the photoactive layer is formed of a microcrystalline film, the microcrystalline film is formed by the above-described manufacturing method, and the photoactive layer is formed of a crystal of the microcrystalline film. Since the volume fraction was determined to be in the range of 30 to 70%,
It is possible to improve the film quality of the microcrystalline film and increase the film formation rate, and further to improve the performance and reduce the manufacturing cost of a thin film semiconductor device using the microcrystalline film, particularly a microcrystalline thin film solar cell.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a discharge structure of a high-frequency plasma CVD according to the present invention; FIG. 2 is a diagram showing an example of an experimental result of a correlation between a distance between electrodes and a crystal fraction according to the present invention; FIG. 4 is a view showing an example of an experimental result of a correlation between a distance between electrodes and a deposition rate according to the present invention. FIG. 4 is a view showing an example of a structure of a microcrystalline thin film solar cell according to the present invention. FIG. Diagram showing a structural example of a crystalline thin film solar cell different from that of FIG.
1: High frequency electrode, 2: Ground electrode, 3: Substrate, 4: High frequency power supply, 5: High frequency electrode side light emitting part, 6: Ground electrode side light emitting part, 7: High frequency electrode side dark part, 8: Ground electrode side Dark part, 9: dark part between light emitting parts, 10: substrate (glass substrate), 11: metal electrode, 12: reflection enhancement layer, 13: n layer, 14: photoactive layer, 15: p layer, 16, 17: transparent Electrode layer.

Claims (5)

The film is formed in a film forming chamber having a flat ground electrode provided on one side of the substrate for forming a microcrystalline film, a high-frequency flat electrode provided in parallel with the other side, and a material gas supply port. A method for producing a microcrystalline film, comprising introducing a source gas for formation and forming a microcrystalline film on the main surface of the substrate by plasma discharge,
The microcrystalline film is formed under a film forming condition in which the light emitting portion generated near the high-frequency electrode and the light emitting portion generated near the ground electrode facing the light emitting portion overlap, and the overlapping film forming condition is defined by the following conditional expression. A method for producing a microcrystalline film, characterized by satisfying the following.
s1 + p1 + s2 + p2>d> s1 + s2 + (p1 + p2) / 2
In the above conditional expression, d is the gap distance between the high frequency electrode and the ground electrode, s1 is the thickness of the dark portion near the high frequency electrode, p1 is the thickness of the light emitting portion, s2 is the thickness of the dark portion near the substrate side electrode, p2 Indicates the thickness of the light emitting portion. 2. The method for manufacturing a microcrystalline film according to claim 1, wherein the microcrystal of the microcrystalline film to be formed is any one of microcrystalline silicon, microcrystalline germanium, microcrystalline silicon alloy, and microcrystalline germanium alloy. A method for producing a microcrystalline film. 3. The method of manufacturing a microcrystalline film according to claim 2, wherein the microcrystalline silicon alloy is any one of microcrystalline silicon germanium, microcrystalline silicon carbide, microcrystalline silicon oxide, and microcrystalline silicon nitride. A method for manufacturing a microcrystalline film. A first electrode layer, a first conductive layer, an effective intrinsic photoactive layer, a second conductive layer, and a second electrode layer laminated on a substrate, and at least the photoactive layer is formed of a microcrystalline film; A method for manufacturing a microcrystalline thin-film solar cell, wherein the microcrystalline film is formed by the manufacturing method according to any one of claims 1 to 3. 5. The method for manufacturing a microcrystalline thin film solar cell according to claim 4, wherein the photoactive layer is formed such that the crystal volume fraction of the microcrystalline film is in the range of 30 to 70%. Manufacturing method of crystalline thin film solar cell.

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