JP2000273643A - Plasma cvd device and production of silicon thin film photoelectric transferring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma CVD device capable of forming a thin film uniform in film thickness and film quality, particularly a crystalline silicon thin film on the substrate to be treated at a high speed. SOLUTION: This device is provided with a reaction vessel having an exhausting member, a 1st electrode 3 arranged in the reaction vessel and holding the substrate 9 to be treated, a hollow 2nd electrode 5 arranged oppositely to the 1st electrode, a gas introducing means for introducing reaction gas into the 2nd electrode and a power source for applying electric power on the 2nd electrode. The hollow 2nd electrode is arranged in such a manner that plural gas blow-off tubes 61, 62 and 63, in which many holes are opened at the parts opposite to the 1st electrode are arranged at prescribed intervals with each other, also, as each gas blow-off tube, as the gas blow-off tube having a big hole, it is situated at the 1st electrode side, and, moreover, they are arranged in such a manner that, based on the gas blow-off tube having the biggest hole, the hole corresponds to the holes of the other gas blow-off tubes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma CVD apparatus and a method for manufacturing a silicon-based thin film photoelectric conversion apparatus including a step of forming a crystalline silicon-based thin film photoelectric conversion layer using the plasma CVD apparatus.

[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. This silicon film is directly deposited on a substrate such as glass, and the quality of the film is low, so that it cannot be applied to a photoelectric conversion device. Also, generally, plasma CVD
If the pressure condition of the method is 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 this deterioration of film quality,
Frequent cleaning of the reactor is required. In particular, when a film is formed under a low temperature condition of 550 ° C. or less by increasing the pressure of the reaction vessel, these problems become remarkable. 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 Temperature, pressure in the reaction chamber,
Even if various film forming condition parameters such as a high frequency power and a gas flow rate ratio are examined, the film forming speed is equal to or less than that of an amorphous silicon film (for example, about 0.6 μm / hr). I can only do that. This is because the thickness of the crystalline silicon thin film photoelectric conversion layer needs to be at least several μm to several tens μm in order to sufficiently absorb sunlight from the relationship of the absorption coefficient of crystalline silicon. How many times more than amorphous silicon photoelectric conversion layer
This requires twice the film formation time, making it difficult to improve the throughput of the manufacturing process of the photoelectric conversion device, and hindering cost reduction.

It is an object of the present invention to provide a plasma CVD apparatus capable of forming a film having a uniform thickness and quality, particularly a crystalline silicon thin film, on a substrate to be processed at a high speed.

According to the present invention, when a photoelectric conversion unit having a crystalline silicon-based photoelectric conversion layer is laminated, the plasma C
Provided is 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 by a low-temperature process using a VD apparatus to achieve an improvement in throughput and an improvement in performance in a manufacturing process. The purpose is to:

[0017]

According to the present invention, there is provided a plasma CVD apparatus 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, gas introducing means for introducing a reaction gas into the second electrode, and applying power to the second electrode And a power supply for performing the operation, the hollow second electrode, a plurality of gas blowing plates having a large number of holes opened in a portion facing the first electrode are arranged at a desired interval from each other,
In addition, the gas blowout plate having a larger hole is located closer to the first electrode as the gas blowout plate has a larger hole, and the hole matches the hole of the other gas blowout plate with respect to the gas blowout plate having the largest hole. It is characterized by being arranged in such a way that

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 an opposite conductivity type semiconductor layer, the photoelectric conversion layer of the unit uses the plasma CVD device described above. Holding the substrate on the first electrode in the reaction vessel, and when the pressure in the reaction vessel is 5
At least rr, a plurality of gas blowing plates in the hollow second electrode are arranged at intervals of 2 mm or less, and the distance between the first electrode and the gas blowing plate of the second electrode adjacent to this electrode is 1 mm. 0.5 cm or less, the reaction gas contains silane-based gas and hydrogen gas as main components, the flow ratio of the hydrogen gas to the silane-based gas contained in all the reaction gases introduced into the reaction vessel is 100 times or more, and the plasma discharge power Density is 1
The film is formed under conditions of not less than 00 mW / cm ² .

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a plasma C according to the present invention will be described.
The VD device will be described in detail with reference to FIGS.

FIG. 1 is a schematic view showing a plasma CVD apparatus according to the present invention, FIG. 2 is a sectional view of a main part of the plasma CVD apparatus shown in FIG. 1, and FIG. It is a partial cutaway plan view at the time of seeing-through.

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 pump or the like (not shown). 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 in the reaction vessel 1 while being supported by a support shaft 4. The first
A heater (not shown) for heating a substrate to be mounted is built in the upper portion of the electrode 3. The first electrode 3 is connected to, for example, the ground.

The rectangular hollow second electrode 5 is disposed in the reaction vessel 1 so as to face the upper surface of the first electrode 3. A plurality, for example, three, first, second, and third gas blowing plates 6 ₁ , 6 ₂ , and 6 ₃ are provided on the second electrode 5 facing the first electrode 3 as shown in FIGS. The parts (bottom) are arranged at a desired distance from each other. Wherein the first to third gas blowout plate 6 _1, 6 _2, 6 _3, a large number of holes (gas blow holes) 7 _1, 7 _2, 7 ₃ are opened. Third gas blowout plate 6 having the most large pores 7 _3
3, the most proximate to the position in the first electrode 3 upper surface, the third gas blowout plate 6 ₃ small holes 7 ₂ than this upward, 7 ₁ second with a first gas blowout plate 6 ₂ , 6 ₁
Are sequentially arranged. That is, the magnitude relation of the hole is in the third gas blowing plate 6 ₃ (closest to the first electrode 3 upper surface is located)> second gas blowout plate 6 _2> first gas blowout plate _61. Each of the gas blowing plates 6 ₁ , 6 ₂ , 6 ₃
The hole 7 of the largest hole 7 ₃ third gas blowout plate 6 ₃ the holes 6 ₃ based on the the other gas having a balloon plate (second, first gas blowout plate 6 _2, 6 _{1) 2,} 7 ₁ and are arranged to match.

[0024] Specifically, the largest hole 7 ₃ third gas blowout plate 6 ₃ small holes 7 ₂ than this from having, 7 ₁
Second having, when viewed toward the first gas blowout plate 6 _2, 6 _1, each gas flow-out plates 6 _1, 6 _2, 6 ₃ holes (gas blow holes) 7 _1, 7 _2, 7 ₃ Are arranged on the same normal to form a truncated cone.

The second electrode 5 is connected to a power supply (not shown), for example, a high-frequency power supply, to which high-frequency power having a frequency of 150 MHz or less and from an RF band to a VHF band is applied. A gas introduction pipe 8 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 first to third gas blowing plates 6
It is preferable that the distance between ₁ , 6, ₂ and 6 ₃ be 2 mm or less. Thus the gas blowout plate 6 _1, 6 _2, 6 ₃
Is set to 2 mm or less, the specific holes 7 ₁ , 7 ₂ , and 7 ₃ of the gas blow-out plates 6 ₁ , 6 ₂ , 6 ₃ are supplied by supplying a reaction gas described later, applying high frequency power to the second electrode, or the like.
It is possible to generate a stable and uniform plasma 7 _3.

Next, the operation of the plasma CVD apparatus having the structure shown in FIGS. 1 to 3 will be described.

First, the substrate 9 is placed on the first electrode 3 in the reaction vessel 1 through a valve (not shown).
The substrate 9 is heated to a desired temperature by the heat generated by a heater (not shown) incorporated in the substrate. A reaction gas (for example, a reaction gas containing a silane-based gas and hydrogen) is introduced through the introduction pipe 8 into the hollow second gas.
Was introduced into the electrode 5, the bottom first to third gas spouting plate arranged on part 6 _1, 6 _2, 6 ₃ holes (gas blow openings)
7 _1, 7 _2, 7 ₃ sequentially through by the blows towards the reaction gas to the substrate 9 on the first electrode 3. At the same time, an exhaust device such as a vacuum pump (not shown) is driven to exhaust the gas in the reaction vessel 1 through the exhaust pipes 2 and 2 to maintain the inside of the reaction vessel 1 at a predetermined degree of vacuum.

With the degree of vacuum in the reaction vessel 1 being stable,
For example, high-frequency power is applied to the second electrode 5 from a power source (not shown). Such a by application of high frequency power first to the third gas blowout plate 6 _1, 6 _2, holes 7 ₁ in 6 _3, 7 _2, 7 out of the _3, conically hole which is matched each other in the vertical direction Is generated and confined in those holes. When the plasma 10 is generated,
The reaction gas (silane-based gas) is decomposed therein, and silicon is deposited on the surface of the substrate 9 heated to the desired temperature (for example, 550 ° C. or lower) to form a silicon thin film.

At the time of the above-mentioned film formation, first to third gas blowing plates 6 ₁ , 6 ₂ , 6 ₃ are arranged at a portion of the hollow second electrode 5 facing the first electrode 3. By
The reactant gas (for example, a reactant gas containing a silane-based gas and hydrogen) introduced into the second electrode 5 is supplied to the gas blow-out plate 6.
_1, 6 _2, 6 a number of holes 7 _{1 3,} 7 _2, 7 also through ₃ as blown in a large amount toward the substrate 9 on the first electrode 3, can be made uniform and the gas flow. At the same time, the first third to the substrate 9 near the surface of the electrode 3 and the first gas blowout plate 6 ₃ As described above, 6 _2, 6 ₁ of the holes 7 _3, 7 _2, 7 ₁ to reach for example conical The plasma 10 can be generated stably. As a result, a thin film having a uniform and uniform thickness (for example, a silicon thin film) can be formed on the substrate 9 at a high speed.

In particular, as shown in FIGS.
Third gas blowing plate 6₁, 6_Two, 6 _ThreeOut of them
(The third gas blowing plate 6)_ThreeBig
Hole 7_Three), The holes 7_Three, 7_Two, 7₁By frustum cone
A stable discharge as well as a hollow cathode.
Between the first and second electrodes 3 and 5.
It is possible to generate plasma 10 of uniform density stably
become.

When the plasma 10 is generated, the reaction gas is supplied to the first gas blowing plate 6 ₁ on the upper side of the second electrode 5.
Is supplied to the plasma 10 through the gaps between the first, second and third gas blowing plates 6 ₁ , 6 ₂ and 6 ₃ from the hole 7 ₁ where plasma does not stand out of the large number 7 _1. A higher density plasma 10 can be generated.

Therefore, it is possible to avoid non-uniformity and instability of the plasma density due to a large amount of the reaction gas blown out. Can be formed at speed.

The second electrode has a hollow shape,
When a single-stage gas blowing portion having a large number of holes opened only on the bottom surface facing the electrode is used, and the distance between the first and second electrodes is reduced, the plasma flows from the hole of the gas blowing portion to the hollow gas outlet. Silicon is deposited inside the two electrodes, and silicon is deposited on the inner surface of the hollow second electrode 5 to become a source of particles such as powder and dust. In particular, when the distance between the first and second electrodes 3 and 5 is shortened to increase the plasma density, plasma is easily generated even in the hollow second electrode.

[0035] In contrast, in the present invention the first to third gas blowout plate ₆₁ as described above, 6 _2, hole 7 in the 6 _{3 1,} 7 _2, 7 of the _three, are matched each other in the vertical direction Since the conical plasma 10 can be generated by confining the conical plasma in the holes, the plasma is generated even in the hollow portions above the gas blow-out plates 6 ₁ , 6 ₂ , 6 ₃ of the hollow second electrode 5. Can be avoided. As a result, it is possible to prevent silicon from being deposited on the inner surface of the hollow second electrode 5, prevent particles such as powder and dust from adhering to the surface of the substrate 9 during deposition, and prevent pinholes and the like. A high-quality thin film without generation can be formed.

In the plasma CVD apparatus according to the present invention, the number of gas blowout plates disposed at the portion of the hollow second electrode 5 facing the first electrode 3 is not limited to three. For example, two or four or more gas blowing plates may be sequentially arranged at a portion of the hollow second electrode 5 facing the first electrode 3.

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. 4 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 on the first electrode 3 in the reaction vessel 1 by using the plasma CVD apparatus shown in FIGS.
4 holds the substrate 101 on which the film is formed, the pressure in the reaction vessel 1 is 5 Torr or more, and the plurality of gas blowing plates 6 ₁ , 6 ₂ , 6 _{3 in} the hollow second electrode 5 have an interval of 2 mm or less. The distance between the first electrode 3 and the gas blowing plate (third gas blowing plate 6 ₃ ) of the second electrode 5 adjacent to the electrode 3 is 1.5 cm or less, and the reaction gas is mainly It contains a silane-based gas and a hydrogen gas as components, the flow ratio of the hydrogen gas to the silane-based gas contained in all the reaction gases introduced into the reaction vessel is 100 times or more, the plasma discharge power density is 100 mW / cm ² or more, The film is formed under the following conditions.

In the film forming step, the pressure in the reaction vessel 1 is set to a high pressure of 5 Torr or more.
It is possible to reduce ion damage to the crystalline silicon thin film formed on the substrate surface. As a result, in order to increase the deposition rate, the high frequency power is increased (for example, the plasma discharge power density is 100 mW / cm ² or more),
Even if the gas flow rate is increased, ion damage to the thin film surface during film formation can be reduced, and a crystalline silicon-based thin film photoelectric conversion layer can be formed 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. More preferably, the pressure in the confined region 18 is 5 to 20 Torr.

In the film forming step, the distance between the gas blowing plate (third gas blowing plate 6 ₃ ) of the first electrode 3 and the second electrode 5 is shortened to 1.5 cm or less, so that the reaction vessel third to the pressure in 1 from the substrate 9 near the surface of the first electrode 3 as well in the above 5Torr the aforementioned first gas blowout plate 6 _3, 6 _2, 6 ₁ of the holes 7 _3,
7 _2, 7 leading example conical plasma 10 to ₁ can be generated stably.

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 550 ° C. or less which enables the 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 100 times or more, so that the activated hydrogen is easily etched off 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.

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 a rare gas, preferably helium,
Neon, argon, or the like may be used.

The plasma CVD shown in FIGS.
Using a device, the reaction gas (containing a silane-based gas and a hydrogen gas as a main component) is introduced into the hollow second electrode 5 through the gas introduction tube 8 under the above conditions, and the second reaction gas is disposed at the bottom thereof. blown toward the third gas blowout plate 6 _1, 6 _2, 6 ₃ holes (gas blow holes) 7 _1, 7 _2, 7 substrate 9 ₃ successively through the reaction gas on the first electrode 3 At the same time, by applying, for example, high-frequency power to the second electrode 5 respectively, the substrate 9 (10
1) A high-quality crystalline silicon-based thin film photoelectric conversion layer having a film thickness and quality can be formed at a deposition rate of 1 μm / h or more over the entire surface of the one conductivity type semiconductor.

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 disposed on a surface facing the second electrode is disposed opposite 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.

For this reason, by reducing the distance between the electrodes to 1.5 cm or less, stable and uniform plasma can be generated between the electrodes.

On the other hand, the hollow second electrode for blowing out the reaction gas generally has 0.5 to 2 gas blowing holes having a diameter of 0.5 to 1 mm on the surface facing the first electrode. / C
m are provided in the order of ² density. However, with such a hole density, the uniformity of the blown gas flow may be insufficient, and a nonuniform photoelectric conversion characteristic may be locally generated in the completed photoelectric conversion device.

In order to eliminate such non-uniformity of gas flow, it is generally considered that the distance between gas blowing holes must be less than half the distance between electrodes. That is,
Under the condition that the distance between the electrodes is small, it is necessary to arrange the gas blowing holes densely. However, if the number of gas blowout holes is too large, the flow speed of gas blowout becomes slow, and radicals generated from silane and hydrogen recombine before reaching the substrate, so that powder and dust are likely to be generated, and between the electrodes. In order to escape from the plasma space to another space, it is difficult to reach the substrate, and the deposition rate of silicon decreases.

From the above, FIG. 1 to FIG.
As shown in the plasma CVD apparatus of the present invention shown in FIG.
Plural, for example, in the opposing hollow second electrode 5 portion (bottom)
For example, three first, second, and third gas blowing plates 6₁, 6_Two,
6_ThreeAre arranged at an interval of 2 mm or less.
The system contained in all the reaction gases introduced into the empty second electrode 5
Increase the flow ratio of hydrogen gas to run gas by 100 times or more
As a result, the reaction gas is
1, 2nd, 3rd gas blowing plate 6₁, 6_Two, 6 _ThreeLarge number of
Hole (gas blowing hole) 7₁, 7_Two, 7_ThreeThrough the first train
Large volume can be blown out to pole 3 with uniform and high-speed gas flow
The deposition rate of silicon on the substrate surface on the first electrode
The degree can be improved. At the same time, as described above,
Third to first gas blowing from near the surface of the substrate 9 of one electrode 3
Slab 6_Three, 6_Two, 6₁Hole 7_Three, 7_Two, 7₁Eg cones leading to
Plasma 10 can be generated stably. As a result,
High reaction pressure that can increase the film speed to, for example, 1 μm / h or more
Force, increase the ratio of hydrogen to silane based gas, etc.
To stably generate high-density plasma under the conditions
As a result, the entirety of the one conductivity type semiconductor layer of the substrate 9 (101) is obtained.
Crystalline silicon thin film photoelectric conversion with uniform thickness and quality
The replacement layer can be formed at a high film forming rate.

When the pressure inside 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.

The secondary reaction was activated by increasing the flow ratio of the hydrogen gas to the silane-based gas contained in all the reaction gases introduced into the reaction vessel 1 to 100 times or more. It is possible to prevent deposition of a thin film of silicon or the like, which is low in quality and easily peeled off, on the inner surface of the reaction vessel 1 due to the etching action of hydrogen and 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.

Accordingly, a high-quality crystalline silicon-based thin-film photoelectric conversion layer 105 can be formed on the one-conductivity-type semiconductor layer 104 at a higher deposition rate (for example, 1 μm / h or more) as compared with the conventional plasma CVD.

Further, 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.

More specifically, the crystalline silicon-based thin-film photoelectric conversion layer 105 is grown such that most 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 2/5 or less, more preferably 1/10 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% 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) Then, 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 Al, Ag, Au, Cu, Pt or the like, 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 shown in FIG. 4 manufactured by such a method, light 109 is incident on the transparent conductive oxide film 107 to be photoelectrically converted, and
10 of the metal thin film 102 and the metal electrode 108
Are output between the terminals.

FIG. 4 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, the crystalline silicon-based photoelectric conversion layer for improving the throughput is formed with high quality, uniform thickness, and high speed. Therefore, it is possible to greatly contribute to higher performance and lower cost of the silicon-based thin film photoelectric conversion device.

[0073]

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 placed 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 is formed by applying a plasma CV under a substrate temperature of 400 ° C. and a pressure in the reaction vessel of 5 Torr.
Formed by Method D. The second electrode used at this time has a gas blowing hole having a diameter of 0.5 mm on the surface facing the first electrode.
The distance from the first electrode, which is provided at intervals of 1 cm and holds the substrate, was set to 1.5 cm. In the reaction gas blown from the gas blowout hole of the second electrode, the flow ratio of silane / hydrogen was set to 1/18, and the discharge power was set to 80 mW / cm ² .

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 was 4/5.
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 0.302 V,
Short circuit current density is 14.8 mA / cm ² and fill factor is 3.
The conversion efficiency was 6.2% and the conversion efficiency was 1.6%.

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, silane /
The hydrogen flow ratio was changed to 1/120 and the discharge power was 12
Increased to 0 mW / cm ² . Under the partially changed conditions, the film formation rate of the photoelectric conversion layer 105 is 1.
It was 4 μm / h. From this result, it can be seen that, although the flow rate ratio of hydrogen to silane is greatly increased, the film forming speed can be improved by appropriately increasing the discharge power accordingly.

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 1/10, and the hydrogen content was 1.6 atomic%. . That is, in Reference Example 2, the crystal orientation of the photoelectric conversion layer 105 is significantly improved as compared with Reference Example 1, and the preferable hydrogen content for suppressing defects in the film is also increased. Understand.

In such a solar cell of Reference Example 2,
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 0.520 V, the short-circuit current density was 27.4 mA / cm ² , the fill factor was 75.1%, and the conversion efficiency was 10.7%. From this, Reference Example 2
It can be seen that the solar cell of No. 1 has significantly improved photoelectric conversion efficiency as compared with the solar cell of Reference Example 1.

However, in the solar cell of Reference Example 2, the solar cell formed on one substrate is divided into a plurality of solar cells having a predetermined small light receiving surface, and the photoelectric conversion efficiency is measured. Examination of local location dependence revealed a 1.5% change in conversion efficiency. That is, it was observed that the conversion efficiency varied within the range of 9.2 to 10.7% depending on the local location of the light receiving surface.

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

That is, in the first embodiment, the first plasma CVD apparatus having the structure shown in FIGS.
The temperature of the substrate held by the electrode 3 was reduced to 200 ° C.

Further, first, second, and third gas blowing plates 6 ₁ , 6 ₂ , 6 are provided at a portion (bottom) facing the first electrode 3.
₃ used the 2nd electrode 5 arrange | positioned at intervals of 1.5 mm. Wherein the first gas blowout plate _61,
Diameter hole 0.2 mm (gas blow holes) 7 ₁ 0.5c
The openings are provided at intervals of m. The second gas blowing plate 6
₂ has a hole of 2 mm in diameter (gas blowing hole) 7 ₂ of 1 cm
It is opened at intervals. The third gas blowing plate 6 ₃
The diameter 3mm holes (gas blow holes) 7 ₃ 1cm
It is opened at intervals. The biggest hole 7 ₃ third gas blowout plate 6 ₃ small holes 7 ₂ than this from having, 7 ₁
Second having, when viewed toward the first gas blowout plate 6 _2, 6 _1, each gas flow-out plates 6 _1, 6 _2, 6 ₃ holes (gas blow holes) 7 _1, 7 _2, 7 ₃ Are arranged on the same normal so as to form a truncated cone. The second electrode 5 was spaced of 15mm the third gas blowing plate 6 ₃ having the largest pores 7 ₃ relative to the first electrode 3 upper surface.

Further, the ratio of silane / hydrogen was changed to 1/150, and the discharge power was increased to 150 mW / cm ² .

Under these partially modified conditions,
The film formation rate of the photoelectric conversion layer 105 was 4.0 μm / h. That is, in Example 1 in which the structure of the second electrode was improved, although the flow rate ratio of hydrogen to silane was further increased as compared with Reference Example 2, the discharge power was further increased accordingly. It can be seen that the deposition rate can be further increased.

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 1/10, and the hydrogen content was 1.3 atomic%.

In the solar cell of the first embodiment, the incident light 109 shown in FIG.
Output characteristics when irradiated with a light amount of cm ² were examined. As a result, the open-circuit voltage was 0.524 V and the short-circuit current density was 2
7.0 mA / cm ² , fill factor was 74.8%, and conversion efficiency was 10.6%. For this reason, the solar cell of Example 1 maintains almost the same excellent photoelectric conversion characteristics as the solar cell of Reference Example 2 even though the film formation rate is further increased. You can see that.

The local variation of the photoelectric conversion efficiency in the solar cell of Example 1 was examined by the same method as in Reference Example 2, and found to be about 1.0%, that is, the conversion efficiency was 9.6.
１10.6%. This is shown in Example 1
The first, second, and third gas blowing plates 6 ₁ having holes (gas blowing holes) 7 ₁ , 7 ₂ , and 7 ₃ having predetermined dimensions in a portion (bottom portion) facing the first electrode 3 as shown in FIG. , 6 ₂ , and 6 ₃ are arranged at a predetermined distance from each other, so that the second electrode 5 having the gas blowing hole only on the surface facing the first electrode as in the second embodiment is used. The film formation rate is improved as compared with the case where a photoelectric conversion layer is formed using a plasma CVD apparatus provided with electrodes, and local fluctuations in conversion efficiency in a solar cell can be significantly reduced. It can be seen that a solar cell can be obtained.

[0094]

As described above in detail, according to the present invention, a thin film having a uniform thickness and quality, particularly a crystalline silicon thin film, can be formed on a substrate to be processed at a high speed, and the A plasma CVD apparatus which can be effectively applied to film formation of a conversion device, a liquid crystal display device, and the like can be provided.

The present invention provides a method for laminating a photoelectric conversion unit having a crystalline silicon-based photoelectric conversion layer on an inexpensive substrate.
A high-quality crystalline silicon-based photoelectric conversion layer having a uniform film thickness and film quality is formed at a high speed by a low-temperature process using the plasma CVD apparatus to improve the throughput (reduction in cost) and performance of the manufacturing process ( A high performance) can be provided.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of a main part of the plasma CVD apparatus of FIG.

3 is a partially cutaway plan view when the hollow second electrode of FIG. 2 is seen through from the bottom surface.

FIG. 4 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]

1 ... reactor 2 ... exhaust pipe, 3 ... first electrode, 5 ... second electrode, 6 _1, 6 _2, 6 ₃ ... gas blowing plate, 7 _1, 7 _2, 7 ₃ ... hole (gas blow openings) Reference numeral 9: substrate, 10: plasma, 102: thin film of Ag, etc. 103: thin film of ZnO, etc. 104: one-conductivity-type semiconductor layer, 105: crystalline silicon-based photoelectric conversion layer, 106: reverse-conductivity type semiconductor layer, 107 ... A transparent conductive film such as ITO; 110, a back electrode; 111, a crystalline silicon-based photoelectric conversion unit;

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 AA06 AA17 BA29 BB03 BB04 BB12 CA06 FA03 JA01 JA03 JA09 JA16 KA05 KA17 KA18 LA04 LA16 5F045 AA08 AB03 AB04 AC01 AC02 AC03 AC05 AD05 AD06 AD07 AD08 AD09 AE21 BB02 BB02 BB15 CA13 DA52 DP04 EE13 EF05 EF07 EH05 EH14 5F051 AA03 AA04 CA02 CA03 CA04 CA15 CB12 DA04 FA04 FA14

Claims (6)

[Claims] A reaction container having an exhaust member; and a first container disposed in the reaction container and holding a substrate to be processed.
An electrode; a hollow second electrode disposed in the reaction vessel so as to face the first electrode; gas introduction means for introducing a reaction gas into the second electrode; A power supply for applying electric power, wherein the hollow second electrode is provided with a plurality of gas blowing plates having a large number of holes opened in a portion facing the first electrode at a desired interval from each other. And the gas blowout plate is located closer to the first electrode side as the gas blowout plate has a larger hole, and the hole of the gas blowout plate is the hole of another gas blowout plate with respect to the gas blowout plate having the largest hole. Characterized by being arranged so as to match
VD device. 2. The gas blow-out plate according to claim 1, wherein the gas blow-out plates are arranged at intervals of 2 mm or less.
The plasma CVD apparatus as described in the above. 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 uses a plasma CVD device according to claim 1 and a first electrode in a reaction vessel thereof. The substrate is held and the pressure in the reaction vessel is 5 To
rr or more, a plurality of gas blowing plates in the hollow second electrode are 2 m
m, the distance between the first electrode and the gas blowing plate of the second electrode adjacent to this electrode is 1.5 cm or less, and the reaction gas is mainly composed of silane-based gas and hydrogen gas. And a plasma discharge power density of 100 mW / cm ² or more, wherein the flow rate ratio of the hydrogen gas to the silane-based gas contained in all the reaction gases introduced into the reaction vessel is 100 times or more. A method for manufacturing a silicon-based thin-film photoelectric conversion device, comprising: 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 preferential crystal orientation plane of (110) parallel to its surface, and the intensity ratio of the (111) diffraction peak to the (220) diffraction peak in X-ray diffraction is 2 / 5. The method according to claim 3, wherein the number is 5 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.