JP2001284254A - Plasma cvd system and method for forming non-single crystal semiconductor thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a plasma CVD system and a method for forming a non- single crystal semiconductor thin film in which a high quality semiconductor thin film can be formed at a high deposition rate while suppressing defects. SOLUTION: At least one surface of a hydrogen adsorption alloy 46 is exposed in a plasma discharge space or at a position contiguous thereto. The hydrogen adsorption alloy 46 is cooled to a specified temperature, as required, using a water cooling mechanism 47, e.g. a water cooling jacket. According to the arrangement, a species containing no group 4A atom generated through plasma discharge decomposition is removed from a gas composed of a compound containing group 4A atoms and hydrogen atoms in a plasma discharge atmosphere thus lowering partial pressure of the species containing no group 4A atom. Consequently, a high quality photovoltaic element having excellent uniformity and reduced defects can be produced by forming a semiconductor thin film while satisfying contradictory purposes of high deposition rate and high film quality at high level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a plasma CVD apparatus and a method for forming a non-single-crystal semiconductor thin film.
The present invention relates to a plasma CVD apparatus and a method for forming a non-single-crystal semiconductor thin film for forming an amorphous silicon thin film or an amorphous silicon alloy thin film constituting an optical superpower element layer of a solar cell or the like.

[0002]

2. Description of the Related Art Conventionally, a plasma CVD apparatus and a method for forming a non-single-crystal semiconductor thin film are applied as a technique for forming a non-single-crystal semiconductor thin film such as an amorphous silicon thin film.

FIG. 5 shows an example of a conceptual configuration of a conventional plasma CVD apparatus. The conventional plasma CVD apparatus shown in FIG. 5 includes a gas introduction pipe 91, a vacuum vessel 92, a power application electrode (cathode electrode) 93, an insulation insulator 94, a high frequency power supply 95, an exhaust pipe 96, and a ground electrode (anode electrode).
97, a substrate 98, and a pressure gauge 99 in a vacuum vessel. A typical example for forming a non-single-crystal semiconductor thin film such as an amorphous silicon thin film in a conventional plasma CVD apparatus having this configuration is as follows.

[0004] Silane (SiH ₄ ) is used as a source gas in a vacuum vessel having a parallel plate type electrode structure equipped with a gas exhaust mechanism.
And a high-frequency power source 95 is applied to a power applying electrode (cathode electrode) 93 of a parallel plate electrode, and a glow discharge is placed in a vacuum vessel 92. Is generated, the source gas is decomposed by plasma (plasma CVD), and a non-single-crystal semiconductor thin film is formed on a desired substrate 98. Further, a hydrogen gas is mixed and introduced as a diluent gas with respect to a source gas composed of a compound containing a Group 4A atom and a hydrogen atom.

[0005]

However, according to the above-mentioned prior art, a gas (for example, silane gas) composed of a compound containing a Group 4A atom and a hydrogen atom in a source gas itself is generated by plasma decomposition. Hydrogen molecules, hydrogen atoms, hydrogen ions, hydrogen radicals, and the like are not selectively and actively removed from the plasma atmosphere. Rather, a thin film has been formed in a system in which the “species not containing Group 4A atoms” is increased by a method such as using hydrogen gas as a diluent gas. For this reason, the partial pressure of these “species not containing Group 4A atoms” is increased, and as a result, the partial pressure of the species contributing to film formation is reduced. For this reason, a sufficient amount of "species containing Group 4A atoms" is not supplied onto the substrate growth surface, and it has been relatively difficult to increase the deposition rate of the thin film.

On the other hand, when forming an amorphous silicon thin film by plasma CVD, SiH ₃ radicals generated by the decomposition of silane gas are said to contribute to the film formation as main active species. According to the literature ("Amorphous Silicon", co-authored by Tanaka-Yiura / Ohm Co., Ltd.), although it is an experimental result in a triode type reaction vessel, among SiH ₃ radicals existing in an atmosphere generated by plasma discharge decomposition, The probability of adhesion after reaching the surface of the film-formed substrate, that is, the probability of film formation is 3
It is stated that the ratio is less than a certain percentage. This may be because most of the SiH ₃ radicals are hardly attached to the substrate surface, or even if they are attached, they are removed again by obtaining energy from plasma or the like.

[0007] Since SiH ₃ radicals are considered to greatly contribute to the formation of a thin film among the species existing in the plasma, about 70% or more of the SiH ₃ radicals existing in the plasma atmosphere contribute to the film formation. It can be said that this is one indicator that indicates that waste (exhaust) is being carried out without doing anything. For example, when manufacturing an amorphous silicon solar cell element having a pin structure, particularly when forming an i-type semiconductor layer, a layer thicker than a p-type layer and an n-type layer must be formed. Low rates were a major problem. Therefore, when an amorphous silicon thin film is formed by plasma decomposition of a source gas composed of a compound containing a Group 4A atom and a hydrogen atom, the utilization efficiency of the source gas is poor, and more than half of the source gas does not contribute to film formation and is wasted (exhaust). ) It's likely to be. Furthermore, when this source gas is diluted and introduced with hydrogen gas or the like, it is presumed that there is a great possibility that the usage efficiency of the source gas is further deteriorated, and it is natural to increase the deposition rate of the thin film. There are limitations. Under such conditions, conventionally, as a method for increasing the deposition rate of the thin film, a method of increasing a source gas to be introduced or increasing a high-frequency power applied to the plasma has been performed.

Conventionally, despite the inherently low probability of reaching and adhering to the substrate surface, the flow rate of the source gas is increased (in this case, the source gas utilization efficiency remains low), or the high frequency applied to the electrode is increased. In a certain sense, such as increasing the power, it was impossible.

There is also a conventional example in which a hydrogen gas is mixed and diluted with a raw material gas contributing to the formation of a thin film such as silane (SiH ₄ ) and introduced into a plasma discharge space. Mix hydrogen gas to increase,
It is not always desirable to perform the dilution.

[0010] However, for the above reasons, it cannot be said that the source gas component (in this example, a gas composed of a compound containing a Group 4A atom and a hydrogen atom) contributing to film formation is not essentially used effectively. This is apparently a problem from the viewpoint of manufacturing cost, and a new method capable of reducing cost has been desired. Further, from the viewpoint of improving the characteristics (film quality) of the thin film, when the deposition rate is increased by using the above-described method, the hydrogen content in the thin film is almost simultaneously increased.

FIG. 6 is a graph showing the relationship between the deposition rate using the substrate temperature as a parameter and the amount of hydrogen contained in the film. As can be seen from the characteristic diagram 6, as the deposition rate is increased, the film quality tends to deteriorate. In particular, when the film quality of the i-type layer, which is an important photocurrent generation layer in a pin-type solar cell, deteriorates, the characteristics of the solar cell itself deteriorate. Furthermore, if the applied high-frequency power is increased during the formation of the i-type layer whose deposition rate is to be increased, a large amount of powdery dust called so-called polysilane tends to be generated as a by-product in the film formation space. In addition to wasting the material gas to be consumed, the film quality may be degraded and defects may be increased due to the incorporation of polysilane into the film. It is generally known that the hydrogen content in a thin film is reduced by forming a thin film at a high substrate temperature. However, even when the substrate temperature is high, the deposition rate is increased. In that case, the hydrogen content in the film still tends to increase. Therefore, it has been desired to provide an effective means capable of achieving a high level of compatibility between a higher deposition rate and a higher film quality, which are mutually incompatible.

The present invention relates to the preparation of an amorphous silicon thin film or an amorphous silicon alloy thin film constituting an optical super power element layer of a solar cell or the like, and to form these thin films at a high deposition rate with few defects and high quality. Possible,
It is an object to provide a plasma CVD apparatus and a method for forming a non-single-crystal semiconductor thin film.

More specifically, an object to be solved by the present invention is to form a non-single-crystal semiconductor thin film such as an amorphous silicon thin film or an amorphous silicon alloy thin film constituting a functional element layer of a solar cell or the like. It is an object of the present invention to increase the deposition rate while effectively utilizing the source gas and to improve the film quality without increasing the hydrogen content in the thin film, as compared with the technique. That is, it is an object of the present invention to provide an apparatus and a method for forming a thin film of higher quality in terms of film quality at a lower cost in terms of manufacturing cost.

[0014]

In order to achieve the above object, a plasma CVD apparatus according to the first aspect of the present invention has a fourth aspect.
A raw material gas composed of a compound containing a group A atom and a hydrogen atom is introduced into a vacuum vessel having a gas exhaust mechanism, and a plasma discharge is generated to decompose the raw material gas. In a plasma CVD apparatus for depositing an i-type semiconductor thin film on a substrate, a species not containing Group 4A atoms generated by decomposition of a raw material gas itself is removed from a plasma atmosphere to remove the species not containing Group 4A atoms. It is characterized in that means for lowering the partial pressure is provided.

As described above, by selectively and positively removing species not containing Group 4A atoms present in the plasma atmosphere, the Group 4A atoms present in the plasma discharge space and directly contributing to thin film formation are obtained. The partial pressure of the species containing atoms becomes relatively large, increasing the probability that the species containing Group 4A atoms contributing to the formation of the thin film will reach and adhere to the substrate surface, the deposition rate of the thin film will increase, Gas utilization efficiency can be improved. In addition, by performing the method of the present invention, the deposition rate of the i-type semiconductor thin film can be essentially improved without difficulty. In this case, the utilization efficiency of the source gas is improved.

According to a second aspect of the present invention, in the plasma CVD apparatus according to the first aspect, a gasizable compound containing a carbon atom is used as a source gas composed of a compound containing a Group 4A atom and a hydrogen atom. It is preferable to use any of a gasizable compound containing a silicon atom and a gasizable compound containing a germanium atom.

According to a fifth aspect of the present invention, in the plasma CVD apparatus according to any one of the first to fourth aspects, a high frequency discharge may be used as a means for generating a plasma discharge.

According to a sixth aspect of the present invention, in the plasma CVD apparatus according to any one of the first to fifth aspects, it is preferable to use a long conductive strip as the substrate.

In the invention according to claim 7 or claim 8, in the plasma CVD apparatus according to any one of claims 1 to 6, hydrogen is used as a means for removing species not containing Group 4A atoms present in the plasma. It is advisable to use an adsorption alloy or an alloy containing palladium (Pd) as a main component and utilize the hydrogen filtration characteristics of this alloy.

Examples of hydrogen-absorbing alloys include Group 1A (Li,
Na, K, etc.), Group 2A (Mg, Ca, etc.), Lanthanum (LaNi ₅ etc.), Titanium (TiFe, TiMn)
Etc.), zirconium-based (ZrFeCr, ZrMn ₂ etc.)
However, it is desirable to select a material that can operate at a relatively high temperature in terms of adsorption characteristics. The form of the hydrogen-adsorbing alloy may be a solid, fibrous, sponge, powder, or the like, but is not particularly limited.

According to the ninth aspect of the present invention, in the plasma CVD apparatus according to any one of the first to eighth aspects, an oil diffusion pump may be used as a gas exhaust mechanism of the vacuum vessel.

According to a tenth aspect of the present invention, there is provided a method for forming a non-single-crystal semiconductor thin film, comprising introducing a source gas composed of a compound containing a Group 4A atom and a hydrogen atom into a vacuum vessel having a gas exhaust mechanism, and performing plasma discharge. Is generated to decompose this source gas and deposit a thin film on a predetermined substrate heated to a desired temperature.
Species not containing Group 4A atoms generated by decomposition of the raw material gas itself are removed from the plasma atmosphere to form
It is preferable to provide a step of lowering the partial pressure of a species not containing a group atom.

In the method of the present invention, a source gas composed of a compound containing a Group 4A atom and a hydrogen atom used as a source gas includes a gasizable compound containing a carbon atom and a hydrogen atom, a silicon atom and a hydrogen atom , A gasifiable compound containing germanium atoms and hydrogen atoms, and a mixed gas of compounds.

Specific examples of the gasifiable compound containing a carbon atom and a hydrogen atom include CH ₄ , C _n H _{(2n + 2)} ,
C _n H _2n , C ₂ H ₂ , C ₆ H _{6 and the} like, where n is an integer.

Specifically, it contains silicon atoms and hydrogen atoms.
The compound which can be gasified is SiH_Four, Si
H₆, SiFH_Three, SiF_TwoH_Two, SiF_ThreeH, Si_ThreeH₈,
SiHD _Three, SiH_TwoD_Two, SiH_ThreeD, SiD_ThreeH, Si_Two
D_ThreeH_ThreeAnd the like.

Specific examples of the gasifiable compound containing a germanium atom and a hydrogen atom include GeH ₄ , G
eFH ₃ , GeF ₂ H ₂ , GeF ₃ H, GeHD ₃ , GeH ₂
D ₂ , GeH ₃ D, GeH _{6 and the} like.

According to the invention as set forth in claims 11 to 13, in the method for forming a non-single-crystal semiconductor thin film according to claim 10, carbon atoms are used as a source gas composed of a compound containing a Group 4A atom and a hydrogen atom. It is preferable to use any of a gasizable compound containing a gas, a gasizable compound containing a silicon atom, and a gasizable compound containing a germanium atom.

According to the fourteenth aspect of the present invention, in the tenth aspect,
13. In the method for forming a non-single-crystal semiconductor thin film according to any one of the above items 13 to 13, the source gas introduced into the vacuum vessel may not be diluted with pure hydrogen gas.

In the method of the present invention, the compound capable of being gasified may be appropriately diluted with a gas such as He, Ne, Ar, Xe or Kr and introduced into the deposition chamber, but pure hydrogen (H ₂ ) gas Is characterized by not mixing and diluting the source gas.

[0030] According to the invention described in claim 15, in claim 10.
15. In the method for forming a non-single-crystal semiconductor thin film according to any one of the above items 14 to 14, high-frequency discharge may be used to generate plasma discharge.

According to the sixteenth aspect, in the tenth aspect,
In the method for forming a non-single-crystal semiconductor thin film according to any one of Items 1 to 15, it is preferable to use a long conductive strip-shaped member as the substrate.

In the invention according to claims 17 and 18,
17. The method for forming a non-single-crystal semiconductor thin film according to claim 10, wherein the substrate is heated to 300 ° C. or more and 550 ° C.
The heating may be performed at a predetermined constant temperature within the following range or within a range of 350 ° C. or more and 500 ° C. or less.

According to the invention as set forth in claims 19 to 21, in the method for forming a non-single-crystal semiconductor thin film according to any of claims 10 to 18, hydrogen is used as a species that does not contain Group 4A atoms present in the plasma. It is preferable to include at least one of a molecule, a hydrogen atom, a hydrogen neutral active species, and a hydrogen ion. These are mainly the species in which the raw material gas itself is decomposed and generated by the plasma.

[0034]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a plasma CVD apparatus and a method of forming a non-single-crystal semiconductor thin film according to the present invention. 1 to 4 show a plasma CVD apparatus and a non-single-crystal semiconductor thin film forming method according to an embodiment of the present invention.

(First Embodiment) FIG. 1 shows a conceptual schematic configuration example of a plasma CVD apparatus of a first embodiment. The plasma CVD apparatus of the present embodiment shown in FIG. 1 includes a gas introduction pipe 41, a vacuum vessel 42, a power application electrode (cathode electrode) 43, an insulating insulator 44, a high frequency power supply 45, a hydrogen adsorption alloy 46, a water cooling mechanism 47, and a vacuum vessel. The exhaust pipe 48, a ground electrode (anode electrode) 49, a substrate 50, and a pressure gauge (G 1) 51 in a vacuum vessel are configured.

In the plasma CVD apparatus of this configuration, at least one surface of the hydrogen adsorption alloy 46 must be exposed at a position in or adjacent to the plasma discharge space. It is also desirable to cool the hydrogen adsorption alloy 46 to a predetermined temperature by using a water cooling mechanism 47 such as a water cooling jacket, if necessary. By using this configuration, “a species that does not contain Group 4A atoms” generated by plasma discharge decomposition is removed from a plasma discharge atmosphere from a gas composed of a compound containing Group 4A atoms and hydrogen atoms. It becomes possible.

In the method of the present invention, another means for positively removing the “species not containing Group 4A atoms” present in the plasma uses an alloy containing palladium (Pd) as a main component. It is characterized by utilizing the hydrogen filtration (permeation) characteristics of the alloy. The palladium (Pd) alloy has a property of selectively permeating only hydrogen in the direction of lower hydrogen partial pressure by a pressure difference between before and after the alloy when heated and maintained at a temperature of about 400 ° C. The form of the palladium (Pd) alloy may be solid, fibrous, sponge, powdery, or the like, but is not particularly limited.

(Second Embodiment) FIG. 2 shows a conceptual schematic configuration example of a plasma CVD apparatus according to a second embodiment. The plasma CVD apparatus of the present embodiment shown in FIG. 2 includes a gas introduction pipe 61, a vacuum vessel 62, a power application electrode (cathode electrode) 63, an insulation insulator 64, a high frequency power supply 65, a gas suction duct 66, a palladium (Pd) alloy diaphragm. 67, hydrogen removal exhaust pipe 68, vacuum vessel exhaust pipe 69, ground electrode (anode electrode) 70, substrate 71, vacuum vessel pressure gauge (G1) 72, hydrogen removal exhaust pipe pressure gauge (G2) 7
3 is configured.

In the plasma CVD apparatus of this configuration, the gas suction duct 6 installed adjacent to the plasma discharge space
From 6, the “species not containing Group 4A atoms” present in the plasma atmosphere are exhausted to the hydrogen removal exhaust pipe 68 through the palladium (Pd) alloy diaphragm 67. Palladium (P
d) The alloy diaphragm 67 is heated to 40 mm by a heater (not shown).
Heated to 0 ° C. Also, the gas flow rate introduced from the gas introduction pipe 61 and the hydrogen removal exhaust pipe 68, the vacuum vessel are set so that the measurement value of the hydrogen removal exhaust pipe pressure gauge 73 becomes lower than the measurement value of the vacuum vessel pressure gauge 72. Exhaust pipe 69
Adjust the conductance of By using this configuration, “species not containing Group 4A atoms” generated by plasma discharge decomposition from a gas composed of a compound containing Group 4A atoms and hydrogen atoms is removed from the plasma discharge atmosphere. Becomes possible.

The method of the present invention is characterized in that high-frequency power is applied to a source gas in a vacuum vessel as means for generating plasma. As the frequency band of the high frequency power, an RF band represented by 13.56 MHz, a VHF band which is higher in frequency than the RF band, and a microwave band represented by 2.45 GHz can be considered. However, the frequency is not particularly limited as long as it can generate plasma discharge. Further, the high frequency power introducing means may be a parallel plate empty electrode structure represented by a structure in which a cathode / anode electrode is paired,
A rod-shaped antenna structure may be used. Further, an applicator structure (dielectric window structure), which is effective as a microwave band power introduction means and is representative of an electrodeless discharge in which an insulating dielectric material is transmitted and power is introduced into a vacuum vessel. Is also good.

The method of the present invention is characterized in that a long strip having conductivity is used as a substrate on which a thin film is formed. The material is not particularly limited as long as it is a roll material obtained by rolling a conductive material such as stainless steel represented by SUS304 or the like or an aluminum material to a thickness of about 0.2 mm.

In the method of the present invention, the heating temperature of the substrate on which the thin film is to be formed is a constant temperature in the range of 300 ° C. to 550 ° C., more preferably 350 ° C. to 50 ° C.
It is desirable that the temperature be maintained at a constant temperature within the range of 0 ° C. or less. Substrate temperature is closely related to the deposition mechanism of the thin film,
Selection of the set value is an important factor. In plasma CVD of amorphous silicon, generally 300 ° C.
It is said that the surface of the substrate is covered with bonded hydrogen atoms in the following temperature range, and the desorption of bonded hydrogen increases in a high temperature range of 300 ° C. or more, and as a result, 4A It is said that dangling bonds of group atoms (in this case, silicon atoms) increase. The increase in unbonded species means that, when the species contributing to film formation reaches the substrate surface, the bonding is relatively easily performed and is easily fixed.

On the other hand, in a high temperature region exceeding 600 ° C., the energy applied from the heater to the deposited thin film is too large, and the deposited thin film is likely to be crystallized. This means that when a non-single-crystal semiconductor thin film is formed in the present invention, a situation is created in which the probability of the species containing Group 4A atoms contributing to the thin film formation reaching and adhering to the substrate surface is increased. It is preferable that the set value of the substrate temperature be in the range of 300 ° C. or more and 550 ° C. or less.
It can be said that it is more desirable that the temperature be set in the range of 50 ° C. or more and 500 ° C. or less. The reason for this will be described in detail below, particularly in the description of the embodiments.

The method of the present invention is characterized in that an oil diffusion pump is used as a gas exhaust mechanism for exhausting the inside of the vacuum vessel. The oil diffusion pump is different from other typical vacuum pumps, for example, a mechanical booster pump, a rotary pump, a turbo molecular pump, and the like.
It has characteristics that it is easy to increase both the gas exhaust amount and the exhaust speed, and is excellent in the characteristic of selectively exhausting a gas (such as hydrogen) which is lighter than a gas having a high molecular weight. Due to this exhaust characteristic, the present invention provides a means for selectively and positively removing “species not containing Group 4A atoms” such as hydrogen molecules, hydrogen atoms, hydrogen neutral active species, and hydrogen ions from the plasma atmosphere. Can be said to be convenient.

According to the above embodiment, when forming an amorphous silicon thin film or a non-single-crystal semiconductor thin film such as an amorphous silicon alloy constituting a photovoltaic element layer of a solar cell or the like, a Group 4A atom and a hydrogen atom are used. It is possible to effectively use the source gas composed of the containing compound, and at the same time, it is possible to increase the deposition rate of the thin film. Further, even when the deposition rate is increased, deterioration of the film quality can be suppressed and improved without increasing the hydrogen content in the thin film. Further, it becomes possible to form a thin film of higher quality in terms of film quality at a lower cost in terms of manufacturing cost.

[0046]

(Embodiment 1) FIG. 3 is a schematic conceptual view showing an example of a non-single-crystal semiconductor single-type photovoltaic device manufacturing apparatus of the present invention. It has a structure in which the feeding container 1, the first conductive layer forming container 2, the i-type layer forming container 3, the second conductive layer forming container 4, and the winding container 5 are connected to each other via respective gas gates 6, and has a strip shape. A transport system capable of continuously transporting the members in a vacuum is provided. The i-type layer forming vacuum vessel 3 is constituted by a vacuum vessel equivalent to a structure having a palladium (Pd) alloy diaphragm as shown in FIG.

With such an apparatus configuration, a roll-to-roll (Roll t-roll) capable of continuously transporting the conductive strip 8 can be used.
o) A single-type photovoltaic device was manufactured based on a continuous plasma CVD method employing a (roll) method (device-actual 1). A specific production example will be described below.

First, the vacuum vessel 1 having a substrate sending-out mechanism is sufficiently degreased and cleaned, and as a lower electrode, a band member 8 made of SUS430BA having a silver thin film of 100 nm and a ZnO thin film of 1 μm deposited by sputtering.
A bobbin 17 wound around (width 120 mm × length 200 m × thickness 0.13 mm) is set.
Through a gas gate, a vacuum vessel for making each non-single-crystal layer,
The sheet was passed through a vacuum vessel 5 having a belt-like member winding mechanism, and the tension was adjusted to a level where there was no slack.

Therefore, the vacuum containers 1, 2, 3, 4, and 5 were evacuated to 1 × 10 ⁻⁴ Torr or less by a vacuum pump (not shown).

Next, 800 sccm of H ₂ was flowed as a gate gas from the gate gas inlet pipe 14 to the gas gates, and the strip members 8 were moved by the lamp heaters 9 to 3 g each.
Heated to 50 ° C, 350 ° C, 300 ° C. And the first
60 sccm of SiH ₄ gas in the conductive layer forming container of
PH ₃ gas (2% H ₂ diluted product) is 50 sccm, H ₂ gas is 500 sccm, SiH ₄ gas is 100 sccm in the i-type layer forming container, SiH ₄ gas is in the second conductive layer forming container.
20 sccm of ₄ gases, 100 sccm of BF ₃ gas (diluted with 2% H ₂ ), and 2000 sccm of H ₂ gas were introduced from the gas introduction pipe 12 respectively.

The conductance valve 2 is controlled so that the pressure in the vacuum vessel 1 becomes 1.0 Torr by the vacuum gauge 16 in the vacuum vessel.
Adjusted at 0. The pressure in the vacuum vessel 2 was adjusted with a conductance valve (not shown) so that the pressure in the vacuum vessel 2 became 1.5 Torr by the vacuum gauge 16 in the vacuum vessel. The pressure in the vacuum vessel 3 was adjusted with a conductance valve (not shown) so that the pressure in the vacuum vessel 3 became 2.0 Torr by the vacuum gauge 16 in the vacuum vessel. The pressure in the vacuum vessel 4 was adjusted by a conductance valve (not shown) so that the pressure in the vacuum vessel 16 became 1.6 Torr by the vacuum gauge 16 in the vacuum vessel. The conductance valve 20 adjusted the pressure in the vacuum vessel 5 to 1.0 Torr with the vacuum gauge 16 in the vacuum vessel. When the pressure of the hydrogen removal exhaust port 33 is 0.0
It was adjusted with a conductance valve (not shown) so that the pressure became 2 Torr.

Thereafter, 400 W of RF power was introduced to the cathode electrode in the first conductive layer forming container, and 400 W of RF power was introduced to the cathode electrode in the i-type layer forming container.
RF power is applied to the cathode electrode in the conductive layer forming container of
0W was introduced.

Next, the belt-shaped member 8 is transported in the direction of the arrow in the figure, and the first conductive type layer is placed on the belt-shaped member in the vacuum vessel 2.
Then, the i-type layer was formed in the vacuum vessel 3 and the second conductivity type layer was formed in the vacuum vessel 4 in this order.

When the i-type layer is formed, the palladium (Pd) alloy diaphragm 32 is heated to 400 ° C. by a heater (not shown).
Was maintained. The “species containing no Group 4A atom” present in the discharge space from the gas suction duct 31 is guided to the exhaust port for hydrogen removal through the heated palladium (Pd) alloy diaphragm 32 and is exhausted. Reduce the partial pressure of the "species not containing group 4A atoms" existing in the plasma discharge space to reduce the i
A mold layer thin film was formed.

Next, ITO (In ₂ O ₃ + SnO ₂ ) was applied as a transparent electrode on the second conductivity type layer by vacuum evaporation to a thickness of 80%.
Then, AI was vacuum-deposited at 2 μm as a current collecting electrode to form a photovoltaic device (device-Ex. 1).

Table 1 shows the conditions for producing the photovoltaic element described above. FIG. 4 is a conceptual cross-sectional view illustrating a configuration example of a single type photovoltaic element. The single-type photovoltaic element shown in FIG. 4 includes a SUS substrate 81, an Ag thin film 82, Zn
Each of the O thin film 83, the first conductivity type layer 84, the i-type layer 85, the second conductivity type layer 86, the ITO 87, and the current collecting electrode 88.

[0057]

[Table 1]

COMPARATIVE EXAMPLE 1 FIGS. 5 and 6 without any hydrogen removing means as the vacuum vessel for producing the i-type layer in FIG.
The procedure and film formation were the same as in Example 1, except that a vacuum vessel having a parallel plate electrode structure, which was a typical example of the related art, was used, and the manufacturing conditions shown in Table 2 were used. A single type photovoltaic element was manufactured under the conditions (element-ratio 1).

Example 1 (Element-Example 1) and Comparative Example 1
Conversion efficiency of the photovoltaic element prepared in (element-ratio 1),
Characteristics uniformity and yield were evaluated. The current-voltage characteristics were first obtained at an area of 5 cm square every 10 m, and AM-1.
5 (100 mW / cm ² ), and the photoelectric conversion efficiency was measured and evaluated. Table 2 shows the results. Each value is an arbitrary value when each characteristic of the element-ratio 1 is 1.00.

The uniformity of the characteristics was determined in Example 1 (element-actual 1),
The photovoltaic element on the belt-shaped member prepared in Comparative Example 1 (element-ratio 1) was cut out at an area of 5 cm square every 10 m, and the AM
It was installed under -1.5 (100 mW / cm ² ) light irradiation, and the photoelectric conversion efficiency was measured to evaluate the variation in the photoelectric conversion efficiency. Table 2 shows the results of the characteristic evaluation in which the reciprocal of the magnitude of the variation was determined based on the photovoltaic element of Comparative Example 1 (element-ratio 1).

The yield was determined by cutting out the photovoltaic elements on the belt-shaped member prepared in Example 1 (element-actual 1) and Comparative Example 1 (element-ratio 1) in an area of 5 cm square every 10 m. The shunt resistance in the dark state was measured, and those having a resistance value of 1 × 10 ³ ohm · cm ² or more were counted as non-defective products, and the ratio of all the products was expressed as a percentage and evaluated. Table 2 shows the results of the yields of the photovoltaic elements of Example 1 (element-actual 1) and Comparative Example 1 (element-ratio 1) thus determined.

[0062]

[Table 2]

In the device-actual 1, the conversion efficiency was improved to 1.08 times, the variation in the conversion efficiency was increased to 1.15 times, and the yield was increased to 1.23 times, respectively, as compared with the device-ratio 1.

As shown in Table 2, the photovoltaic element of Comparative Example 1 (element-ratio 1) was changed to Example 1 (element-actual 1).
Is excellent in all of conversion efficiency, characteristic uniformity and yield, and the photovoltaic element manufactured by the manufacturing method of the present invention has excellent characteristics, uniformity, It was also found that the properties were improved, and the effect of the present invention was demonstrated.

Example 2 In Example 2, the substrate temperature was examined, the control value of the lamp heater 9 in the i-type layer forming vacuum vessel was changed, and the substrate temperature was changed to 7 set values (250 ° C.). , 300 ° C, 400 ° C, 450 ° C, 500
° C, 550 ° C, and 600 ° C), and seven types of single-type photovoltaic elements were produced in the same procedure as in Example 1 (elements-Examples 2 to 8).

The conversion efficiency, characteristic uniformity and yield of the photovoltaic elements produced in Examples 2 to 8 were evaluated in the same manner as in Example 1. Table 3 shows the results. Each value is an arbitrary value when each characteristic of the element-real 2 is set to 1.00.
As for the value at 350 ° C., the data of the element (element-actual 1) manufactured in Example 1 is shown again.

[0067]

[Table 3]

As shown in Table 3, when the substrate temperature at the time of forming the i-type layer was in the range of 300 ° C. or more and 550 ° C. or less, it was found that each characteristic value was improved. Furthermore, it was found that each characteristic value was further improved in the range of 350 ° C. or more and 500 ° C. or less. That is, element-actual 3, element-actual 1, element-actual 4, element-actual 5, element-actual 6, element-actual 7
The six types of photovoltaic elements are excellent in conversion efficiency, characteristic uniformity, and yield. Furthermore, the element
The four types of photovoltaic elements, ie, element 1, element-element 4, element-element 5, and element-element 6, are more excellent in conversion efficiency, characteristic uniformity, and yield. The photovoltaic element produced by has excellent characteristics, uniformity,
The productivity was also found to be improved, demonstrating the effect of the present invention.

The above is a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the scope of the present invention.

[0070]

As is clear from the above description, the plasma CVD apparatus and the method for forming a non-single-crystal semiconductor thin film of the present invention employ a method in which a species not containing Group 4A atoms generated by decomposition of a raw material gas itself is removed from a plasma atmosphere. It is removed from the inside to lower the partial pressure of the species not containing the Group 4A atom. Therefore,
It is possible to form a semiconductor thin film by balancing the contradictory objectives of high deposition rate and high film quality at a high level, and when manufacturing photovoltaic devices continuously, it has high quality and excellent uniformity over a large area. In addition, it is possible to produce a large number of photovoltaic elements with few defects with high throughput and high reproducibility.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of a plasma CVD apparatus according to the present invention.

FIG. 2 is a schematic diagram showing another embodiment of the plasma CVD apparatus.

FIG. 3 is a conceptual schematic view of a non-single-crystal semiconductor single photovoltaic device manufacturing apparatus showing an application example.

FIG. 4 is a conceptual sectional view of a single-type optical superpower device formed by a non-single-crystal semiconductor thin film forming method.

FIG. 5 is a conceptual schematic diagram of a conventional plasma CVD apparatus.

FIG. 6 is a diagram for explaining the deposition rate dependence of the hydrogen content in the thin film.

[Explanation of symbols]

 1, 2, 3, 4, 5 Vacuum container 6 Gas gate 8 Band member 9 Lamp heater 11 Exhaust port for vacuum container 12 Gas inlet tube 14 Gate gas inlet tube 15 Exhaust port 16 Vacuum gauge in vacuum container 17 Delivery bobbin 18 Winding bobbin 20 Conductance valves 21, 22 Steering roller 30 Pressure gauge in exhaust pipe for hydrogen removal 31 Gas suction duct 32 Palladium (Pd) alloy diaphragm 33 Exhaust port for hydrogen removal 41 Gas introduction pipe 42 Vacuum container 43 Power supply electrode (cathode electrode) 44 Insulation insulator 45 High-frequency power supply 46 Hydrogen adsorption alloy 47 Water cooling mechanism 48 Exhaust pipe for vacuum vessel 49 Ground electrode (anode electrode) 50 Substrate 51 Pressure gauge in vacuum vessel 61 Gas introduction pipe 62 Vacuum vessel 63 Power supply electrode (cathode electrode) 64 Insulating insulator 65 High frequency power supply 66 Gas suction Cut 67 Palladium (Pd) alloy diaphragm 68 Exhaust pipe for removing hydrogen 69 Exhaust pipe for vacuum vessel 70 Ground electrode (anode electrode) 71 Substrate 72 Pressure gauge in vacuum vessel 73 Pressure gauge in exhaust pipe for hydrogen removal 81 SUS substrate 82 Ag thin film 83 ZnO thin film 84 first conductivity type layer 85 i-type layer 86 second conductivity type layer 87 ITO 88 current collecting electrode 91 gas introduction tube 92 vacuum vessel 93 power application electrode (cathode electrode) 94 insulating insulator 95 high frequency power supply 96 exhaust pipe 97 Ground electrode (anode electrode) 98 Substrate 99 Pressure gauge in vacuum vessel

Continuing on the front page (72) Inventor Takahiro Yajima 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masahiro Kanai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F term (reference) 4K030 AA06 AA17 BA30 CA02 CA17 FA03 GA14 JA10 KA30 LA16 5F045 AA08 AB04 AB05 AC01 AC14 AC16 AC17 AD07 AD08 AD09 AE21 BB09 CA13 DP22 EC05 EG01 EH13 5F051 AA04 AA05 CA15 CA16 CA26

Claims (21)

[Claims] 1. A source gas composed of a compound containing a Group 4A atom and a hydrogen atom is introduced into a vacuum vessel having a gas exhaust mechanism, and a plasma discharge is generated to decompose the source gas to a desired temperature. In a plasma CVD apparatus for depositing an i-type semiconductor thin film on a predetermined substrate heated to a temperature of, a species not containing Group 4A atoms generated by decomposition of the source gas itself is removed from a plasma atmosphere to remove the species. 4
A plasma CVD apparatus comprising means for lowering the partial pressure of a species not containing Group A atoms. 2. The plasma CVD apparatus according to claim 1, wherein a gasizable compound containing a carbon atom is used as a source gas composed of a compound containing a Group 4A atom and a hydrogen atom. 3. A gaseous compound containing a silicon atom is used as a source gas composed of a compound containing a Group 4A atom and a hydrogen atom.
The plasma CVD apparatus as described in the above. 4. The plasma CVD apparatus according to claim 1, wherein a gasizable compound containing a germanium atom is used as a source gas composed of a compound containing a Group 4A atom and a hydrogen atom. 5. A means for generating a plasma discharge,
The plasma CVD apparatus according to any one of claims 1 to 4, wherein a high-frequency discharge is used. 6. The plasma CVD apparatus according to claim 1, wherein a long strip having conductivity is used as the substrate. 7. The plasma CVD method according to claim 1, wherein a hydrogen-adsorbing alloy is used as a means for removing species not containing Group 4A atoms present in the plasma. apparatus. 8. A method for removing species that do not contain Group 4A atoms present in plasma by using an alloy containing palladium (Pd) as a main component and utilizing the hydrogen filtration characteristics of the alloy. The plasma CVD apparatus according to any one of claims 1 to 6, wherein 9. The plasma CVD apparatus according to claim 1, wherein an oil diffusion pump is used as a gas exhaust mechanism of the vacuum vessel. 10. A source gas composed of a compound containing a Group 4A atom and a hydrogen atom is introduced into a vacuum vessel having a gas exhaust mechanism, and a plasma discharge is generated to decompose the source gas to a desired temperature. I on a predetermined substrate heated to
A non-single-crystal semiconductor thin film forming method for depositing a semiconductor thin film of the type, wherein a species not containing Group 4A atoms generated by decomposition of the source gas itself is removed from a plasma atmosphere.
A method for forming a non-single-crystal semiconductor thin film, comprising a step of reducing a partial pressure of a species not containing a group A atom. 11. A gaseous compound containing a carbon atom is used as a source gas composed of a compound containing a Group 4A atom and a hydrogen atom.
The method for forming a non-single-crystal semiconductor thin film according to the above. 12. The method for forming a non-single-crystal semiconductor thin film according to claim 10, wherein a gasizable compound containing silicon atoms is used as a source gas composed of a compound containing Group 4A atoms and hydrogen atoms. . 13. The method for forming a non-single-crystal semiconductor thin film according to claim 10, wherein a gasizable compound containing a germanium atom is used as a source gas composed of a compound containing a Group 4A atom and a hydrogen atom. . 14. The raw material gas introduced into the vacuum vessel is not diluted with pure hydrogen gas.
14. The method for forming a non-single-crystal semiconductor thin film according to any one of items 13 to 13. 15. The method for forming a non-single-crystal semiconductor thin film according to claim 10, wherein a high-frequency discharge is used as a means for generating a plasma discharge. 16. The method for forming a non-single-crystal semiconductor thin film according to claim 10, wherein a long strip having conductivity is used as the substrate. 17. The non-single-crystal semiconductor according to claim 10, wherein the substrate is heated and maintained at a predetermined constant temperature in a range from 300 ° C. to 550 ° C. Thin film formation method. 18. The non-single-crystal semiconductor according to claim 10, wherein the substrate is heated and maintained at a predetermined constant temperature within a range from 350 ° C. to 500 ° C. Thin film formation method. 19. The non-monolithic device according to claim 10, wherein a hydrogen-adsorbing alloy is used in the step of removing species that do not contain Group 4A atoms present in the plasma. A method for forming a crystalline semiconductor thin film. 20. In the step of removing species not containing a Group 4A atom present in the plasma, the palladium (P
19. The method for forming a non-single-crystal semiconductor thin film according to any one of claims 10 to 18, wherein an alloy containing d) as a main component is used and the hydrogen filtration property of the alloy is used. 21. The method for forming a non-single-crystal semiconductor thin film according to claim 10, wherein an oil diffusion pump is used as a gas exhaust mechanism of the vacuum vessel.