JP2000277439A - Plasma cvd method for crystalline silicon thin-film and manufacture of silicon thin-film photoelectric conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a film of high-quality crystalline silicon photoelectric conversion layer at a high speed for improved throughput and performance, by calculating the residence period of reactive gas between electrodes from a specific relational expression between the pressure and volume of a reactive vessel and the flow rate of reactive gas for specification between them. SOLUTION: Related to the plasma CVD method, in a film-forming process, a residence period τ (sec) of reactive gas between first and second electrodes 3 and 5 is calculated from τ=(p.v)/Q where the pressure in a reactive vessel 1 is P (Torr), the flow rate of reactive gas is Q (Torr.cm3/sec), and the volume of the reactive vessel 1 is V (cm3). With τ and P set to be 1-10 sec and 5-20 Torr, respectively, Q and V are so selected as to satisfy the expression. Such a plasma CVD method having this relational expression allows a high-quality crystalline silicon thin-film to be film-formed at high speed on a substrate 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a silicon-based thin film photoelectric conversion device, which includes a step of forming a crystalline silicon-based thin film photoelectric conversion layer by the plasma CVD method for a silicon thin film.

[0002] In the present specification, the terms "crystalline" and "microcrystal" are intended to include those partially including an amorphous state.

[0003]

2. Description of the Related Art An amorphous silicon solar cell is known as a typical thin film photoelectric conversion device. Since the amorphous photoelectric conversion material used for this solar cell can be formed by a plasma CVD method under a low film formation temperature of about 200 ° C., inexpensive materials such as glass, stainless steel, and organic films can be used as the substrate. . As a result, an amorphous photoelectric conversion material is expected as a leading material for manufacturing a low-cost photoelectric conversion device. Further, since amorphous silicon has a large absorption coefficient in the visible light region, 500 n
A short-circuit current of 15 mA / cm ² or more has been realized in a solar cell having a photoelectric conversion layer made of amorphous silicon having a thin film thickness of not more than m.

However, amorphous silicon-based materials suffer from problems such as deterioration of photoelectric conversion characteristics due to the Stebler-Wronsky effect when exposed to light for a long period of time. It is.
Therefore, in a photoelectric conversion device using an amorphous silicon-based material, its reliability and high performance are limited, and the inherent advantages of the freedom of substrate selection and the use of a low-cost process are sufficient. Has not been utilized.

[0005] For these reasons, in recent years, photoelectric conversion devices using thin films containing crystalline silicon such as polycrystalline silicon and microcrystalline silicon have been vigorously developed. These developments attempt to achieve both low-cost and high-performance photoelectric conversion devices by forming high-quality crystalline silicon thin films on low-cost processes on inexpensive substrates. It is expected to be applied to various photoelectric conversion devices.

As a method of forming a crystalline silicon thin film,
For example, a method of directly depositing on a substrate by CVD or sputtering, or a method of crystallizing by once depositing an amorphous film by a similar process and then performing thermal annealing or laser annealing is known. ing. In any method, in order to use the inexpensive substrate described above, the temperature at the time of film formation needs to be 550 ° C. or less.

By the way, in each of the film forming processes,
The method of directly depositing a crystalline silicon thin film by the plasma CVD method is the easiest to lower the temperature of the process and increase the area of the thin film, and it is expected that a high-quality crystalline thin film can be obtained by a relatively simple process. Have been.

In the plasma CVD method, a plasma CVD apparatus having a structure in which first and second electrodes are arranged opposite to each other in a reaction vessel having an exhaust pipe and a reaction gas introduction pipe is generally used. In such a CVD apparatus, a substrate on which one of the electrodes is to be formed is held, a predetermined reaction gas (for example, a gas containing a silane-based gas) is introduced into the reaction vessel from the introduction pipe, and the gas is exhausted. After evacuation through a tube to make the inside of the reaction vessel a predetermined degree of vacuum, a desired electric power is supplied between the electrodes to generate plasma between the electrodes to decompose the reaction gas, thereby forming a predetermined gas on the substrate. (For example, a silicon thin film) is formed.

When a polycrystalline silicon thin film is formed by a plasma CVD method, a high-quality silicon thin film containing a crystalline material is formed on a substrate in advance, and then the thin film is used as a seed layer or a crystallization control layer. By forming a film by the method, a high-quality polycrystalline silicon thin film can be formed at a relatively low temperature.

On the other hand, in a plasma CVD method, a reaction gas obtained by diluting a silane-based source gas by 10 times or more with hydrogen is introduced into a reaction vessel, and the pressure inside the reaction vessel is set to 10 mTorr.
By forming a film in the range of ~ 1 Torr,
It is well known that a microcrystalline silicon thin film can be obtained, and a microcrystalline silicon thin film can be easily formed even at a temperature of about 200 ° C.

For example, Appl, Phys, Lett., Vol. 65, 19
94, p. 860 discloses a photoelectric conversion device including a photoelectric conversion unit composed of a microcrystalline silicon pin junction.
This photoelectric conversion unit is composed of a p-type semiconductor layer, an i-type semiconductor layer serving as a photoelectric conversion layer, and an n-type semiconductive layer which are sequentially stacked by a plasma CVD method, and all of these semiconductor layers are microcrystalline silicon. . However, in order to obtain a high-quality crystalline silicon film and further a high-performance silicon-based thin film photoelectric conversion device, the film formation rate is so slow as to be less than 0.6 μm / hr under conventional manufacturing methods and conditions. ,
There is a problem that it is about the same as or less than that of the amorphous silicon film.

Japanese Patent Application Laid-Open No. 4-137725 discloses that a silicon film is formed by a low-temperature plasma CVD method under a relatively high pressure of 5 Torr. However, this silicon film is directly deposited on a substrate such as glass, and the quality of the film is low and cannot be applied to a photoelectric conversion device. In general, when the pressure conditions of the plasma CVD method are increased, a large amount of powdery products and dust are generated in the plasma reaction vessel. For this reason, there is a high risk that the dust or the like will fly to the surface of the film being deposited and be taken into the deposited film, which may cause pinholes in the film. In order to reduce the deterioration of the film quality, the inside of the reaction vessel must be frequently cleaned. In particular, when forming a film under a low temperature condition of 550 ° C. or less by increasing the pressure of the reaction vessel,
These problems become significant. In addition, in the manufacture of a photoelectric conversion device such as a solar cell, a large-area thin film needs to be deposited, which causes problems such as a reduction in product yield and an increase in labor and cost for maintaining and managing the film formation device.

Therefore, when a photoelectric conversion layer to be incorporated in a thin film photoelectric conversion device is manufactured by a plasma CVD method, a pressure condition of usually 1 Torr or less has been conventionally used as described above.

[0014]

As described above, plasma CVD
When a conventional film forming technique by the method is applied to the formation of a thin film such as polycrystalline silicon or microcrystalline silicon partially containing an amorphous phase, for example, a crystalline silicon-based photoelectric conversion layer in the manufacture of a photoelectric conversion device However, it was difficult to improve the quality of the film.

It is an object of the present invention to provide a plasma CVD method capable of forming a high-quality crystalline silicon thin film on a substrate to be processed.

According to the present invention, when a photoelectric conversion unit having a crystalline silicon-based photoelectric conversion layer is laminated, the plasma C
An object of the present invention is to provide a method of manufacturing a silicon-based thin-film photoelectric conversion device in which a high-quality crystalline silicon-based photoelectric conversion layer is formed at a high speed under a predetermined condition by a VD method to achieve an improvement in throughput and an improvement in performance. Aim.

[0017]

According to the present invention, there is provided a plasma CVD method comprising: a reaction vessel having an exhaust member; a first electrode disposed in the reaction vessel and holding a substrate to be processed;
A hollow second electrode disposed in the reaction vessel so as to face the first electrode and having a blowing portion for the reaction gas on a surface facing the first electrode; and introducing the reaction gas into the second electrode. Using a plasma CVD apparatus provided with a gas introduction unit for performing the process and a power supply for applying power to the second electrode, holding the substrate to be processed on the first electrode, And a reaction gas containing silane-based gas and hydrogen is blown out from the gas introduction tube toward the substrate to be processed through the blow-out portion of the hollow second electrode, and desired power is supplied from the power supply. When a crystalline silicon thin film is formed on the surface of the substrate to be processed by applying a plasma to the second electrode to generate plasma between the electrodes, the pressure in the reaction vessel is increased to P (Torr).
r), the flow rate of the reaction gas is set to Q (Torr · cm ³ / s).
ec), assuming that the volume of the reaction vessel is V (cm ³ ),
The residence time τ (sec) of the reaction gas between the electrodes is calculated from the following equation: τ = (PV) / Q (1), and the τ and P are respectively 1 to 10 s.
ec, more preferably 1 to 8 sec, 5 to 20 Torr
When Q is set, the film is formed by selecting Q and V so as to satisfy the expression (1).

A method of manufacturing a silicon-based thin-film photoelectric conversion device according to the present invention includes at least one photoelectric conversion unit formed on a substrate, wherein the photoelectric conversion unit is a one-conductivity type semiconductor sequentially stacked by a plasma CVD method. Layer, a crystalline silicon-based thin-film photoelectric conversion layer, and when manufacturing a silicon-based thin-film photoelectric conversion device including a semiconductor layer of the opposite conductivity type, the photoelectric conversion layer of the unit is formed by the plasma CVD method described above. The distance between the first and second electrodes is 2.0 m or less, and the reaction gas contains a silane-based gas and a hydrogen gas as main components, and a hydrogen gas with respect to the silane-based gas contained in all the reaction gases introduced into the reaction vessel Is 30 times or more, and the plasma discharge power density is 20 mW / c.
The film is formed under the condition of m ² or more.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plasma C according to the present invention will be described.
The VD method will be described in detail with reference to the plasma CVD apparatus shown in FIG.

FIG. 1 is a schematic view showing a plasma CVD apparatus according to the present invention.

The rectangular reaction vessel 1 has exhaust pipes 2 and 2 as exhaust members connected to opposite side walls, respectively. The other ends of the exhaust pipes 2 and 2 are connected to a vacuum device (not shown) such as a mechanical booster pump and a dry pump. Valves (not shown) for taking in and out of the substrate are provided on opposite side walls of the reaction vessel 1.

The rectangular first electrode 3 is disposed on the lower side of the reaction vessel 1 and supported by a support shaft 4.
Above the first electrode 3, a heater (not shown) for heating the held substrate is incorporated. The first electrode 3 is connected to, for example, the ground.

The hollow second electrode 5 is disposed in the reaction vessel 1 so as to face the lower surface of the first electrode 3. A surface (opposing surface) 6 of the second electrode 5 facing the first electrode 3 is provided with, for example, a large number of gas blowing holes serving as a reactive gas blowing portion. The second electrode 5
Is connected to a power supply (not shown), for example, a high-frequency power supply. A gas introduction pipe 7 serving as a reaction gas introduction means is connected to the upper portion of the second electrode 5 from outside the reaction vessel 1.

The plasma CVD method of the present invention using the plasma CVD apparatus shown in FIG. 1 will be described.

First, the substrate 8 is held on the first electrode 3 in the reaction vessel 1 through a valve (not shown).
The film deposition portion of the substrate 8 is heated to, for example, 400 ° C. or less, at which an inexpensive substrate such as glass can be used by the heat generated by a heater (not shown) incorporated in the substrate. A reaction gas containing a silane-based gas and hydrogen is introduced into the hollow second electrode 5 through the introduction pipe 7, and the reaction gas is held on the first electrode 3 through a large number of gas blowing holes on the opposed surface 6. At the same time, the exhaust device (not shown) is driven to drive the reaction vessel 1
The inside gas is exhausted through the exhaust pipes 2 and 2 to maintain the inside of the reaction vessel 1 at a predetermined degree of vacuum. When the degree of vacuum in the reaction vessel 1 is stabilized, the second electrode 5 is supplied from a power source (not shown).
For example, by applying a high-frequency power to the plasma, a plasma 9 is generated in a region between the first and second electrodes 3 and 5. When the plasma 9 is generated, the reaction gas is decomposed therein, and silicon or the like is deposited on the surface of the substrate 8 heated to 400 ° C. or lower to form a silicon thin film.

As the silane-based gas, for example, monosilane, disilane and the like are preferable. In addition, silicon halide gas such as silicon tetrafluoride, silicon tetrachloride and dichlorosilane may be used. In addition to such a silane-based gas, an inert gas such as hydrogen, nitrogen, or a rare gas, preferably helium, neon, or argon may be used.

In the plasma CVD method according to the present invention, the pressure in the reaction vessel 1 is set to P (To
rr), the flow rate of the reaction gas is set to Q (Torr · cm ³ /
sec), assuming that the volume of the reaction vessel 1 is V (cm ³ ), the residence time τ (sec) of the reaction gas between the first and second electrodes 3 and 5 is represented by the following equation: τ = (P · V) / Q (1), and the τ and P are respectively 1 to 10 s
ec, 5 to 20 Torr, the above Q and V
Is selected so as to satisfy Expression (1). By the plasma CVD method having such a relational expression, a high-quality crystalline silicon thin film can be formed on the substrate 8 at a high speed.

In the plasma CVD apparatus used in the plasma CVD method according to the present invention, from the viewpoint of forming a crystalline silicon thin film with good reproducibility, the ends of the first and second electrodes 3 and 5 are respectively It is preferable to make the inner surface of the reaction vessel 1 approach.

When the residence time τ is less than 1 second,
Not only may the silicon thin film formed on the substrate 8 become amorphous, but also the film formation rate may be significantly reduced, and the gas utilization may be reduced. On the other hand, the residence time τ
Exceeds 10 seconds, the silicon thin film may become amorphous, and powder or particles may be generated, making it difficult to form a high-quality crystalline silicon thin film on the substrate 8. The more preferred residence time τ is 1 to
8 seconds.

By setting the pressure in the reaction vessel 1 to a high pressure of 5 Torr or more, it becomes possible to reduce ion damage to the crystalline silicon thin film formed on the substrate surface. As a result, even if the high-frequency power is increased (for example, the plasma discharge power density is, for example, 20 mW / cm ² or more) or the gas flow rate is increased in order to increase the film formation rate, ion damage to the thin film surface during film formation is prevented. This makes it possible to form a crystalline silicon thin film at a high speed. Further, by setting the pressure to a high pressure, the crystal grain boundaries and the defects in the grains are easily passivated by hydrogen, so that the defect density in the crystalline silicon-based thin film due to these can be reduced. At this time, it is important to define the conditions so that the residence time τ satisfies the relationship of 1 ≦ τ ≦ 10. However, if the pressure in the reaction vessel 1 exceeds 20 Torr, the first and second electrodes 3, 5
There is a possibility that the uniformity of the plasma generated during the process may be impaired and unstable.

The gas blowing structure of the second electrode is not limited to the configuration in which a large number of holes are provided on the surface facing the first electrode.
For example, the surface of the second electrode facing the first electrode may have a net shape.

The plasma CVD apparatus used in the plasma CVD method according to the present invention is not limited to the structure shown in FIG. For example, a structure in which a first electrode for holding a substrate and a second electrode for blowing out a reaction gas are arranged in an inverted manner, a frequency from a high frequency of 150 MHz or less to a VHF band,
Plasma CVD using microwave band as power source
An apparatus may be used.

Next, a method for manufacturing a silicon-based thin film photoelectric conversion device according to the present invention will be described with reference to FIG.

FIG. 2 is a perspective view schematically showing a silicon-based thin-film photoelectric conversion device manufactured according to one embodiment of the present invention.

(First Step) First, the back electrode 110 is formed on the substrate 101.

As the substrate 101, for example, a metal such as stainless steel, an organic film, or an inexpensive glass having a low melting point can be used.

The back electrode 110 is made of, for example, Ti, C
a metal thin film 102 including a layer made of at least one metal selected from r, Al, Ag, Au, Cu and Pt, or an alloy thereof; and at least one oxidation selected from ITO, SnO ₂ , and ZnO It is formed by laminating the transparent conductive thin films 103 which combine layers made of an object in this order. However, the back electrode 110 may be constituted only by the metal thin film 102 or the transparent conductive thin film 103. These thin films 102 and 103 are formed by, for example, an evaporation method or a sputtering method.

(Second Step) Next, the back electrode 110
The one conductivity type semiconductor layer 10 is formed thereon by a plasma CVD method.
4. The photoelectric conversion unit 111 is formed by sequentially laminating the crystalline silicon-based thin film photoelectric conversion layer 105 and the opposite conductivity type semiconductor layer 106. This photoelectric conversion unit 11
1 is not limited to one unit, and a plurality of units may be formed on the back surface electrode.

The one-conductivity-type semiconductor layer 104, the crystalline silicon-based thin-film photoelectric conversion layer 105, and the opposite-conductivity-type semiconductor layer 1
06 will be described in detail below.

1) One-Conductivity-Type Semiconductor Layer 104 This one-conductivity-type semiconductor layer 104 is formed of, for example, n doped with 0.01% by atom or more of phosphorus, which is a conductivity-type determining impurity atom.
A silicon layer or a p-type silicon layer in which boron is doped by 0.01 atomic% or more can be used. However, these conditions for the one-conductivity-type semiconductor layer 104 are not limited. For example, the impurity atoms may be aluminum or the like in a p-type silicon layer, or may be an alloy material such as silicon carbide or silicon germanium. Good.

The one-conductivity type silicon-based thin film 104 may be polycrystalline, microcrystalline or amorphous, and its thickness is preferably 1 to 100 nm, more preferably 2 to 30 nm.

2) Crystalline silicon-based thin film photoelectric conversion layer 10
5 The crystalline silicon-based thin-film photoelectric conversion layer 105 is formed, for example, by using the above-described plasma CVD apparatus shown in FIG.
4 holds the substrate 101 on which the film is formed, and the distance between the first and second electrodes 3 and 5 is 2.0 m or less, and the reaction gas contains a silane-based gas and a hydrogen gas as main components. Under the conditions that the flow ratio of hydrogen gas to silane-based gas contained in all the reaction gases introduced into the vessel is 30 times or more and the plasma discharge power density is 20 mW / cm ² or more, the pressure in the reaction vessel 1 is increased. The flow rate of a reaction gas containing P (Torr), a silane-based gas, and hydrogen is changed to Q (Torr · cm ³ / sec).
c), when the volume of the reaction vessel 1 is V (cm ³ ),
Residence time τ of the reaction gas between the first and second electrodes 3 and 5
(Sec) is calculated from τ = (P · V) / Q (1), and the τ and P are respectively 1 to 10 sec, 5
When the pressure is set to ２０20 Torr, the film is formed by selecting the Q and V so as to satisfy the expression (1).

In the film forming step, the residence time τ and the pressure in the reaction vessel 1 are defined for the same reason as described in the plasma CVD method.

In the film forming step, the temperature of the silicon deposition portion of the substrate by the heater built in the first electrode 3 is preferably set to 400 ° C. or less to enable use of an inexpensive substrate such as glass.

In the film forming step, the flow rate ratio of the hydrogen gas to the silane-based gas contained in all the reaction gases is set to 30 times or more, so that the activated hydrogen is easily removed at a low quality by the etching action or the like. It is possible to prevent crystalline silicon from being deposited in a region other than the film deposition portion that is a reaction field. A more preferable flow rate ratio of the hydrogen gas to the silane-based gas is 50 times or more.

According to the present invention described above, high-quality crystalline silicon is applied to one conductivity type semiconductor of the substrate 9 (101) mounted on the first electrode 3 by the plasma CVD method under the aforementioned conditions. The system thin film photoelectric conversion layer can be formed at a deposition rate of 1 μm / h or more.

That is, a conventional structure in which a first electrode is disposed in a reaction vessel, and a hollow second electrode having a large number of gas outlets on its opposite surface facing the second electrode. In the plasma CVD apparatus, the first
When a substrate is placed on an electrode and plasma is generated between the first and second electrodes, the pressure in the reaction vessel is reduced to 5 Torr.
When the pressure is set to the above high pressure, ion damage to the crystalline silicon thin film formed on the substrate surface can be reduced, so that the crystalline silicon thin film can be formed at a high speed as described above. However, when the pressure in the reaction vessel is set to a high pressure of 5 Torr or more, the uniformity of the plasma generated between the electrodes is lost, and the reaction becomes unstable.

Thus, by reducing the distance between the electrodes to 2.0 cm, preferably 1.5 cm or less, stable and uniform plasma can be generated between the electrodes.

However, it is sometimes difficult to form a high-quality crystalline silicon thin film with good reproducibility only by specifying the pressure in the reaction vessel and the distance between the electrodes.

From the above, the above-mentioned residence time τ and the pressure P in the reaction vessel are respectively set to 1 to 10 sec.
When the pressure is set to ２０20 Torr, the above Q and V are selected so as to satisfy the above formula (1), that is, by giving an appropriate residence time, gas decomposition products important for forming a high-quality film are generated, and 8 (101), a high-quality crystalline silicon-based thin film photoelectric conversion layer can be formed at a high deposition rate on the one conductivity type semiconductor layer.

When the pressure in the reaction vessel is set to a high pressure of 5 Torr or more, a crystalline silicon thin film of low quality and easy to peel off is generally deposited on the inner surface of the reaction vessel. Silicon particles may adhere to the surface of the substrate and deteriorate the crystallinity and the like of the formed crystalline silicon thin film.

For such a secondary reaction, the flow ratio of hydrogen gas to silane-based gas contained in all the reaction gases introduced into the reaction vessel 1 is 30 times or more, preferably 5 times or more.
By making it 0 times or more, it is possible to prevent the deposition of a thin film of silicon or the like that is low in quality and easily peeled off on the inner surface of the reaction vessel 1 due to the activated hydrogen etching action or the like. As a result, by reforming the reaction gas, a high-quality crystalline silicon-based thin-film photoelectric conversion layer that prevents contamination of particles and the like can be formed.

Also, by the improvement of the film forming speed described above,
Since the crystal nucleus generation time in the initial stage of film growth is short, the nucleus generation density is relatively reduced, and it is possible to form a crystalline silicon-based thin film having crystal grains having a large grain size and strong crystal orientation.

Specifically, the crystalline silicon-based thin-film photoelectric conversion layer 105 is grown so that many of the crystal grains contained therein extend upward from the one-conductivity-type semiconductor layer (base layer) 104 in a columnar manner. Many of these grains are parallel to the film plane (11
0), and the intensity ratio of the (111) diffraction peak to the (220) diffraction peak determined by X-ray diffraction is preferably 0.4 or less, more preferably 1/2 or less. .

Further, in the film forming step, the temperature of the silicon deposition portion (one conductivity type semiconductor layer) of the substrate is set to 100 to 100.
By setting the temperature at 400 ° C., 2
This makes it possible to form a crystalline silicon-based thin-film photoelectric conversion layer made of polycrystalline silicon containing 0 atomic% or less of hydrogen or microcrystalline silicon having a volume crystallization fraction of 80% or more.

The crystalline silicon thin film photoelectric conversion layer preferably has a thickness of 0.5 to 10 μm.

Further, even when the surface shape of the one conductivity type layer 104 as the underlayer is substantially flat, the photoelectric conversion layer 10
After the formation of 5, a surface texture structure having fine irregularities at intervals of about one digit smaller than the film thickness is formed on the surface.

3) Reverse conductivity type semiconductor layer 106 As the reverse conductivity type semiconductor layer 106, for example, a p-type silicon thin film doped with 0.01% by atom or more of boron, which is a conductivity type determining impurity atom, or a phosphorous layer containing 0.1% or less of phosphorus. 01 atomic%
An n-type silicon thin film doped as described above may be used. However, these conditions for the opposite conductivity type semiconductor layer 106 are not limited. As impurity atoms,
For example, in the case of p-type silicon, aluminum or the like may be used, or a film of an alloy material such as silicon carbide or silicon germanium may be used. The reverse conductive silicon-based thin film 106 may be polycrystalline, microcrystalline, or amorphous, and has a thickness in the range of 3 to 100 nm, more preferably in the range of 5 to 50 nm. You.

(Third Step) Next, a transparent conductive oxide film 107 and a comb-shaped metal electrode 108 are sequentially formed on the photoelectric conversion unit 111 to manufacture a photoelectric conversion device having a structure shown in FIG.

The transparent conductive oxide film 107 is made of, for example, I
At least one selected from TO, SnO ₂ , ZnO, etc.
It is formed from the above layers.

The comb-shaped metal electrode 108 (grid electrode) is formed by patterning a layer of at least one metal selected from, for example, Al, Ag, Au, Cu, Pt, or an alloy thereof. . These metal or alloy layers are formed by, for example, a sputtering method or an evaporation method.

In the photoelectric conversion device having such a structure,
The light 109 is incident on the transparent conductive oxide film 107 to be subjected to photoelectric conversion, and is output from the back electrode 110, for example, between the terminals of the metal thin film 102 and the metal electrode 108.

FIG. 2 illustrates only one of the silicon-based thin film photoelectric conversion devices, and the present invention relates to at least one crystalline thin film photoelectric conversion device including the silicon crystalline photoelectric conversion layer shown in FIG. In addition to the unit, the present invention can be applied to a tandem-type photoelectric conversion device including at least another amorphous-based thin film photoelectric conversion unit including an amorphous photoelectric conversion layer formed by a known method. .

According to the present invention described above, in a series of manufacturing steps of a silicon-based thin-film photoelectric conversion device, a crystalline silicon-based thin-film photoelectric conversion layer for improving throughput is formed with high quality and at a high speed. Therefore, it is possible to greatly contribute to higher performance and lower cost of the silicon-based thin film photoelectric conversion device.

[0065]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments according to the present invention will be described in detail below in comparison with a reference example.

Reference Example 1 A crystalline silicon thin-film solar cell as Reference Example 1 was manufactured in a manner similar to the embodiment of FIG.

First, the back electrode 11 is formed on the glass substrate 101.
0, a 300 nm thick Ag film 102 and a 100
Each of the ZnO films 103 of nm was sequentially formed by a sputtering method. 10 nm thick on the back electrode 110
N-type microcrystalline silicon layer 104 doped with phosphorus, non-doped polycrystalline silicon thin film photoelectric conversion layer 1 having a thickness of 3 μm
05 and a 10-nm-thick boron-doped p-type microcrystalline silicon layer 106 were each formed by a plasma CVD method to form a nip photoelectric conversion unit 111.
A transparent conductive ITO film having a thickness of 80 nm is deposited as a front electrode 107 on the photoelectric conversion unit 111 by a sputtering method, and a comb-shaped Ag electrode 10 for extracting a current is formed thereon.
8 was formed by a vapor deposition method and a patterning technique.

The n-type microcrystalline silicon layer 104 is made of RF
It was deposited by a plasma CVD method. The flow rates of the reaction gas used at this time were 5.0 sccm for silane, 200 sccm for hydrogen, and 0.05 sccm for phosphine. The pressure inside the reaction vessel was set to 1 Torr, and RF
The power density was set at 30 mW / cm ² .

The photoelectric conversion layer 105 holds the glass substrate after the phosphorus-doped n-type silicon layer is formed on the first electrode 3 of the reaction vessel 1 shown in FIG. It was deposited by an RF plasma CVD method for generating plasma in a region between the second electrodes 3 and 5.

The volume of the reaction vessel (V): 47600 cm
³ , the pressure (P) in the reaction vessel 1; 5.0 Torr, the structure of the hollow second electrode 3; gas blowing holes are opened at an interval of 1 cm at a diameter of 0.5 mm on the opposing surface of the first electrode 3. A distance between the first and second electrodes 3 and 5; 2 cm; a reaction gas blown from the second electrode 5; a flow rate ratio of silane and hydrogen of 1:75; and a blown gas from the second electrode 5. Reaction gas flow rate (Q);
30400 SCCM, the first and second electrodes 3, 5 determined from the above equation (1)
Residence time (τ) of the reaction gas between the electrodes; 0.62 sec; power applied to the second electrode 5; high-frequency power of 13.56 MHz; discharge power density; 150 mW / cm ² ; 200 ° C.

Under these conditions, the film formation rate of the photoelectric conversion layer 105 was 1.1 μm / h. In the obtained photoelectric conversion layer 105, the intensity ratio of the (111) diffraction peak to the (220) diffraction peak of X-ray diffraction is 2/5.
And the hydrogen content was 0.4 atomic%.

In the plasma CVD of the p-type microcrystalline silicon layer 106, the flow rate of the
sccm, hydrogen 500 sccm, diborane 0.01
sccm. Further, the pressure in the reaction vessel is set to 1 Torr.
And the RF power density was set to 150 mW / cm ² .

In the solar cell of Reference Example 1 thus obtained, the incident light 109 shown in FIG.
Was irradiated at a light amount of 100 mW / cm ² . As a result, the open-circuit voltage is 0.480V,
Short-circuit current density is 26 mA / cm ² , fill factor is 72%,
The conversion efficiency was 8.99%.

Reference Example 2 A solar cell was manufactured under the same conditions as in Reference Example 1 except that the plasma CVD conditions for the photoelectric conversion layer 105 were partially changed.

That is, in Reference Example 2, the flow rate (Q) of the reaction gas was changed to 600 SCCM, and the residence time (τ) of the reaction gas was set to 31 sec. Under such partially changed conditions, the film formation rate of the photoelectric conversion layer 105 was 0.7 μm / h.

In the obtained photoelectric conversion layer 105, the intensity ratio of the (111) diffraction peak to the (220) diffraction peak in X-ray diffraction was 2/5, and the hydrogen content was 0.5 atomic%. .

In the solar cell of Reference Example 2 described above,
As the incident light 109 shown in FIG.
Output characteristics when irradiated with a light amount of mW / cm ² were examined. As a result, the open-circuit voltage was 0.47 V, the short-circuit current density was 27 mA / cm ² , the fill factor was 72%, and the conversion efficiency was 9.13%.

Example 1 A solar cell was manufactured under the same conditions as in Reference Example 1 except that the plasma CVD conditions for the photoelectric conversion layer 105 were partially changed.

That is, in Example 1, the flow rate (Q) of the reaction gas was changed to 15200 SCCM, the residence time (τ) of the reaction gas was set to 1.24 sec, and the discharge power was increased to 150 mW / cm ² . Under such partially changed conditions, the film formation rate of the photoelectric conversion layer 105 is 2 μm / h, which is almost the same as that in Reference Example 1.

In the obtained photoelectric conversion layer 105, the intensity ratio of the (111) diffraction peak to the (220) diffraction peak in X-ray diffraction was 1/5, and the hydrogen content was 0.8 atomic%. .

In such a solar cell of Example 1,
As the incident light 109 shown in FIG.
Output characteristics when irradiated with a light amount of mW / cm ² were examined. As a result, the open-circuit voltage was 0.53 V, the short-circuit current density was 26.5 mA / cm ² , the fill factor was 76%, and the conversion efficiency was 10.67%. This indicates that the solar cell of Example 1 has better photoelectric conversion characteristics than that of Reference Example 2.

Example 2 A solar cell was manufactured under the same conditions as in Reference Example 1 except that the plasma CVD conditions for the photoelectric conversion layer 105 were partially changed.

That is, in Example 2, the flow rate (Q) of the reaction gas was changed to 3800 SCCM, the residence time (τ) of the reaction gas was 4.96 sec, and the discharge power was increased to 150 mW / cm ² . Under the partially changed conditions, the film formation rate of the photoelectric conversion layer 105 was 1.8 μm / h.

In the obtained photoelectric conversion layer 105, the intensity ratio of the (111) diffraction peak to the (220) diffraction peak in X-ray diffraction was 1/5, and the hydrogen content was 0.7 atomic%. .

In the solar cell of the first embodiment,
As the incident light 109 shown in FIG.
Output characteristics when irradiated with a light amount of mW / cm ² were examined. As a result, the open-circuit voltage was 0.52 V, the short-circuit current density was 27.0 mA / cm ² , the fill factor was 76%, and the conversion efficiency was 10.67%. This indicates that the solar cell of Example 2 has better photoelectric conversion characteristics than that of Reference Example 2.

[0086]

As described above in detail, according to the present invention, a high-quality crystalline silicon thin film can be formed on a substrate to be processed, which is effective for forming a film for a photoelectric conversion device of a solar cell, a liquid crystal display device and the like. A plasma CVD method that can be applied can be provided.

According to the present invention, when stacking a photoelectric conversion unit having a crystalline silicon-based photoelectric conversion layer,
A silicon-based photovoltaic layer of high quality is formed at a high speed under a predetermined condition by a method to improve the throughput (lower cost) and improve the performance (higher performance) of the manufacturing process. A method for manufacturing a thin film photoelectric conversion device can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one embodiment of a plasma CVD apparatus used for a plasma CVD method according to the present invention.

FIG. 2 is a perspective view schematically showing a silicon-based thin-film photoelectric conversion device manufactured according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reaction container, 2 ... Exhaust pipe, 3 ... 1st electrode, 5 ... 2nd electrode, 8, 101 ... Substrate, 9 ... Plasma, 102 ... Thin film, such as Ag, 103 ... Thin film, such as ZnO 104 ... One conductivity type Semiconductor layer: 105: crystalline silicon-based photoelectric conversion layer; 106: reverse conductivity type semiconductor layer; 107: transparent conductive film such as ITO; 110: back electrode; 111: crystalline silicon-based photoelectric conversion unit.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 AA06 AA17 BA29 BB01 BB03 BB04 FA01 JA05 JA10 JA11 JA16 KA14 KA17 LA16 5F045 AA08 AB03 AC01 AC02 AC03 AC05 AC15 AC16 AC17 AD05 AD06 AD07 AD08 AE21 AE23 AF07 AF10 BB08 BB08 BB09 DA52 EE13 EF05 EH04 EH05 EH14 EH19 5F051 AA03 AA04 CB12 DA04 DA07 FA03 FA04 FA06 FA14 FA18

Claims (6)

[Claims] 1. A reaction vessel having an exhaust member, a first electrode disposed in the reaction vessel and holding a substrate to be processed,
A hollow second electrode disposed in the reaction vessel so as to face the first electrode and having a blowing portion for the reaction gas on a surface facing the first electrode; and introducing the reaction gas into the second electrode. Using a plasma CVD apparatus provided with a gas introduction unit for performing the process and a power supply for applying power to the second electrode, holding the substrate to be processed on the first electrode, And a reaction gas containing silane-based gas and hydrogen is blown out from the gas introduction tube toward the substrate to be processed through the blow-out portion of the hollow second electrode, and desired power is supplied from the power supply. When forming a crystalline silicon thin film on the surface of the substrate to be processed by applying plasma to the second electrode to generate plasma between the electrodes, the pressure in the reaction vessel is set to P (Torr), and the reaction gas is Flow of Assuming that the amount is Q (Torr · cm ³ / sec) and the volume of the reaction vessel is V (cm ³ ), the residence time τ (sec) of the reaction gas between the electrodes is expressed by the following equation: τ = (P · V ) / Q (1), and τ and P are respectively 1 to 10 s
ec, 5 to 20 Torr, the above Q and V
Is selected so as to satisfy the above formula (1), and the film is formed. 2. The reaction vessel according to claim 1, wherein the first and second electrodes are arranged in the reaction vessel such that ends of the electrodes are close to an inner surface of the reaction vessel. Plasma CVD method. 3. A photoelectric conversion unit including at least one photoelectric conversion unit formed on a substrate, wherein the photoelectric conversion unit includes a one-conductivity-type semiconductor layer sequentially stacked by a plasma CVD method, a crystalline silicon-based thin-film photoelectric conversion layer, When manufacturing a silicon-based thin-film photoelectric conversion device including a semiconductor layer of the opposite conductivity type, the photoelectric conversion layer of the unit is disposed between the first and second electrodes in the plasma CVD method according to claim 1 or 2. The distance is 2.0 m or less, the reaction gas contains silane-based gas and hydrogen gas as main components, and the flow rate ratio of hydrogen gas to silane-based gas contained in all the reaction gases introduced into the reaction vessel is 30 times or more, A method for manufacturing a silicon-based thin-film photoelectric conversion device, wherein a film is formed under a condition that a plasma discharge power density is 20 mW / cm ² or more. 4. In the film forming step, the temperature of a silicon deposition portion of the substrate is set at 100 to 400 ° C., so that polycrystalline silicon containing 0.1 to 20 atomic% of hydrogen or 4. The method for manufacturing a silicon-based thin-film photoelectric conversion device according to claim 3, wherein a photoelectric conversion layer film having a thickness of 0.5 to 10 [mu] m made of microcrystalline silicon having a crystallization fraction of 80% or more is formed. 5. The photoelectric conversion layer has a (110) preferential crystal orientation plane parallel to its surface, and its X-ray diffraction has an intensity ratio of (111) diffraction peak to (220) diffraction peak of 0.1. 5. The method of manufacturing a silicon-based thin-film photoelectric conversion device according to claim 3, wherein the number is 4 or less. 6. The silicon-based thin film according to claim 3, wherein a tandem structure is obtained by laminating at least one amorphous silicon-based photoelectric conversion unit in addition to the photoelectric conversion unit. A method for manufacturing a photoelectric conversion device.