JP2002009317A - Non-single-crystal semiconductor thin film forming method, photovoltaic element forming method, and functional deposited film forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an effective hydrogen plasma treatment process and a method for forming a non-single-crystal semiconductor thin film capable of obtaining a high photoelectric conversion efficiency and forming a photovoltaic element at high speed and continuously. . SOLUTION: Prior to hydrogen plasma treatment, preheating is performed at a substrate temperature or higher at the time of forming a semiconductor layer. Belt substrate 10
7. The unwinding substrate 108 and the winding substrate 109 are adapted for production. In the preheating and the post-heating, the atmosphere gas is desirably hydrogen, and if 50% or more of the atmosphere gas is hydrogen, a gas other than hydrogen, such as an inert gas such as He, Ne, or Ar, may be included. N ₂ , H ₂ , H ₂
In the case of a gas containing an element which may be taken in as an impurity for a semiconductor such as O and HF, a smaller amount is preferable, and 1% or less with respect to hydrogen is preferable. By this procedure,
A good interface can be formed while relaxing the structure of the amorphous semiconductor layer, and a photovoltaic element having good photoelectric conversion efficiency can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a non-single-crystal semiconductor thin film, a method for forming a photovoltaic element, and an apparatus for forming a functional deposited film. The present invention relates to a method for forming a non-single-crystal semiconductor thin film made of a crystalline silicon semiconductor, a method for forming a photovoltaic element, and a functional deposited film forming apparatus.

[0002]

2. Description of the Related Art Conventionally, a method for forming a non-single-crystal semiconductor thin film,
The method for forming a photovoltaic element and the apparatus for forming a functional deposited film are applied to, for example, a semiconductor device.

In recent years, semiconductor devices using a non-single-crystal silicon semiconductor such as hydrogenated amorphous silicon have been actively developed. A non-single-crystal silicon semiconductor is an amorphous, microcrystalline, or polycrystalline silicon film that is not a single crystal. The non-single-crystal silicon semiconductor referred to here also includes a film made of a non-single-crystal silicon alloy containing carbon or germanium in silicon. In addition, this non-single-crystal silicon semiconductor generally contains hydrogen,
It is a so-called hydrogenated non-single-crystal silicon semiconductor.
For example, in the case of amorphous silicon, unlike single crystal silicon, a film can be formed over a low-temperature substrate or a glass substrate, the area can be easily increased, and light absorption is larger than that of crystalline silicon. For this reason, application fields different from crystalline silicon have been developed. Main semiconductor elements using a non-single-crystal silicon semiconductor include a photovoltaic element such as a solar cell, a solid-state imaging element, a thin film transistor for driving a liquid crystal display, and an electrophotographic photosensitive member.

[0004] However, when the above-mentioned non-single-crystal silicon semiconductor is used for photoelectric conversion elements, a photo-deterioration phenomenon (so-called Stab) greatly affects the deterioration of the characteristics of these elements.
ler-Wronski effect). As a cause thereof, it is considered that dangling bonds and weak bonds between Si atoms existing in the non-single-crystal silicon semiconductor are broken by light irradiation, so that the photoelectric conversion efficiency is reduced. It is known that the lower the density of the semiconductor, the greater the photodegradation. It is also said that excess hydrogen in the semiconductor causes photodegradation.

Therefore, recently, as a method for preventing the light deterioration, Japanese Patent Application Laid-Open Nos. Hei 5-166733 and Hei 6-12015 are disclosed.
No. 2, JP-A-60-163429, JP-A-59-72
As disclosed in Japanese Patent No. 176 and Patent Publication No. 2723224, there has been proposed a method of forming a non-single-crystal silicon semiconductor while repeating a hydrogen plasma treatment on a growth surface. This is because atomic hydrogen extracts excess hydrogen in the deposited film by hydrogen plasma treatment, and at the same time, the structure of the film is relaxed. As a result, a dense film structure is formed and the light caused by the excess hydrogen is reduced. It is said that deterioration is suppressed. Here, the substrate temperature of the hydrogen plasma treatment is considered to be an important factor. However, in Japanese Patent Publication No. 2723224,
It is only specified that the temperature is below the semiconductor formation temperature. Further, other reports only describe that the temperature is equal to the semiconductor formation temperature.

Further, there is a roll-to-roll method as a method for increasing the mass productivity of a solar cell using a non-single-crystal silicon semiconductor. Japanese Patent Application Laid-Open No. Hei 6-232482 discloses a conventional high quality roll-to-roll apparatus in which a hydrogen plasma processing chamber is provided and hydrogen plasma processing is performed after forming an i-type layer and before forming an impurity layer. It is disclosed that it is effective for forming a photovoltaic element.

The mechanism of the extraction of excess hydrogen from the semiconductor film and the relaxation of the film structure by the hydrogen plasma treatment will be described.
JP-A-5-166733 discloses the following two models. In the first model, active atomic hydrogen arriving at the semiconductor deposition surface diffuses between the deposition surface and the semiconductor film, attacks Si-H bonds present in excess on the film surface and in the film, and from this bond, Withdraw hydrogen. The dangling bonds generated at this time are recombined with each other, and as a whole, excessive hydrogen is extracted and the structure is relaxed. Second
According to the model, active atomic hydrogen coming to the film surface diffuses and moves only on the surface of the film, and the Si—H
Reacts with the hydrogen in the bond and abstracts this hydrogen. Dangling bonds generated on the surface by this diffuse from the surface into the film. This diffusion proceeds with the movement of hydrogen atoms between sites in the film, so that the hydrogen in the film moves toward the surface, and the hydrogen in the film is always supplied to the surface. The diffused hydrogen is subsequently extracted by a surface reaction, and as a whole, the excess hydrogen is extracted and the structure is relaxed.

In either of these two models, the diffusion of atomic hydrogen in the film or the diffusion of dangling bonds in the film leads to the extraction of excess hydrogen and excessive Si—H bonds. Thermal energy plays a role in promoting these diffusions.

[0009]

However, in the above prior art, after the i-type layer is formed or after the hydrogen plasma treatment, the substrate surface is cooled non-uniformly and rapidly in the gas gate which always exists in the roll-to-roll apparatus. As a result, the effect of the hydrogen plasma treatment is impaired. Therefore, in order to prevent the photodeterioration of the non-single-crystal semiconductor thin film by performing the hydrogen plasma treatment, it is necessary to not only perform the hydrogen plasma treatment but also to devise a more effective hydrogen plasma treatment process. Has been requested.
Further, there is a need for a method and an apparatus capable of obtaining a high photoelectric conversion efficiency and forming a photovoltaic element at high speed and continuously.

The present invention relates to an effective hydrogen plasma process, a method for forming a non-single-crystal semiconductor thin film, which can obtain a high photoelectric conversion efficiency and can form a photovoltaic element at high speed and continuously. It is an object of the present invention to provide an element forming method and a functional deposited film forming apparatus.

[0011]

In order to achieve the above object, a method for forming a non-single-crystal semiconductor thin film according to the present invention is characterized in that a non-single-crystal semiconductor film is subjected to a hydrogen plasma treatment after depositing an amorphous semiconductor layer. The method for forming a semiconductor thin film is characterized in that preheating is performed at a substrate temperature or higher at the time of forming a semiconductor layer before hydrogen plasma treatment.

According to the second aspect of the present invention, the preheating according to the first aspect is preferably performed in a hydrogen atmosphere.

According to the third aspect of the present invention, the hydrogen plasma treatment according to the first or second aspect is preferably performed at a temperature lower than the preheating temperature.

According to a fourth aspect of the present invention, the hydrogen plasma treatment according to any one of the first to third aspects is preferably performed at a temperature lower than the formation temperature of the amorphous semiconductor.

According to the fifth aspect of the present invention, after the hydrogen plasma processing according to any one of the first to fourth aspects, it is preferable to perform the second-stage heating at a temperature lower than the temperature of the hydrogen plasma processing.

In the invention described in claim 6, the post-stage heating according to any one of claims 1 to 5 may be performed in a hydrogen atmosphere.

According to a seventh aspect of the invention, there is provided a method for forming a photovoltaic element, comprising the steps of forming a first conductive type semiconductor layer of a non-single-crystal semiconductor, a substantially intrinsic semiconductor layer (hereinafter referred to as an i-type semiconductor layer) on a substrate. 7.) A method for forming a photovoltaic device having a pin-type semiconductor junction in which a second conductivity type semiconductor layer is sequentially laminated, wherein the i-type semiconductor layer is a non-single-layer semiconductor device according to claim 1. It is characterized by being formed by a method of forming a crystalline semiconductor thin film.

In the functional deposited film forming apparatus according to the present invention, the belt-like substrate is continuously moved in the longitudinal direction.
Functional deposition that passes a plurality of deposition chambers connected by gas gates with gas inlets for introducing scavenging gas into slit-shaped separation passages, and sequentially deposits functional deposition films on strip substrates in each deposition chamber In the continuous film forming apparatus, at least one hydrogen plasma processing chamber, one preheating area before the hydrogen plasma processing chamber, and one post-heating area after the hydrogen plasma processing chamber are provided. And

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a method for forming a non-single-crystal semiconductor thin film, a method for forming a photovoltaic element, and an apparatus for forming a functional deposited film according to the present invention will be described in detail with reference to the accompanying drawings. . 1 to 3 show an embodiment of the method for forming a non-single-crystal semiconductor thin film, the method for forming a photovoltaic element, and the apparatus for forming a functional deposited film according to the present invention.

In the hydrogen plasma treatment of the present invention, DC plasma, low frequency plasma, high frequency (RF) plasma, VH
A known method such as F plasma or microwave (MW) plasma is used as required. As conditions suitable for each of these hydrogen plasma treatments, the following were obtained from the results of experiments.

When the hydrogen plasma treatment of the present invention is performed by RF, a preferable frequency range is 1 MHz to 29 MHz.
Range. When the hydrogen plasma treatment of the present invention is performed by VHF, a preferable frequency range is from 30 MHz to 50 MHz.
The range is 0 MHz. The hydrogen plasma treatment of the present invention is performed by M
When operating at W, the preferred frequency range is 0.51 GH
The range is from z to 10 GHz.

In order to effectively carry out the hydrogen plasma treatment of the present invention, the pressure is an important factor for maintaining the plasma, and the preferable pressure when conducting in the RF frequency band is 1 P.
a to 1000 Pa.

When hydrogen plasma treatment is performed in the VHF frequency band, the preferable pressure is 0.01 Pa to 100 Pa.
Range.

The preferred pressure for performing the hydrogen plasma treatment in the MW frequency band is in the range of 0.01 Pa to 1 Pa.

In the hydrogen plasma treatment of the present invention, hydrogen
Injected into chamber to generate plasma
Power density effectively performs the hydrogen plasma treatment of the present invention
Is an important factor. Such power densities
Depends on the frequency of the electromagnetic wave. Uses RF frequency band
Power density is 0.01 to 10 W / cm ^Two
Is a preferable range. The reason is 0.01 W / cm
^TwoThis is because the above does damage.

When using the VHF frequency band,
A preferred range is from 0.01 to 1 W / cm ³ . In particular, in the case of the VHF frequency band, plasma discharge can be maintained in a wide pressure range. When performing hydrogen plasma processing at a high pressure, it is preferable to perform hydrogen plasma processing at a relatively low power density. . The reason is that when the pressure is high, the density of atoms, molecules, and ions is high, and when the power density is high, the film quality is unnecessarily affected.

On the other hand, when the hydrogen plasma treatment is performed at a low pressure, it is preferable to perform the treatment at a relatively high power density.
When the hydrogen plasma treatment of the present invention is performed using the MW frequency band, the preferable power density is 0.1 to 10 W / cm ³ . The reason is that if the pressure is low, the density of atoms, molecules, and ions is low, and if the power density is low, the film cannot be sufficiently modified.

In the hydrogen plasma treatment of the present invention, the substrate temperature during the hydrogen plasma treatment is a very important factor for making the effect of the present invention effective, and the substrate temperature is 100%.
To 400 ° C. is a preferred range. Within that range,
It is desirable to carry out at a temperature lower than the preheating temperature.
Further, it is preferable to perform the process at a temperature lower than the formation temperature of the amorphous semiconductor.

When performing the hydrogen plasma treatment of the present invention, the above-described power density, gas flow rate, substrate temperature, pressure, and the like may be changed with respect to the treatment time. Usually, a substrate has many defects and many impurities near the surface. Therefore, the hydrogen plasma treatment is preferably performed at a relatively high power density and a high pressure at the start of the treatment.

In the preheating of the present invention, the substrate temperature at the time of preheating is a very important factor for making the effect of the present invention effective, and the substrate temperature is set to be higher than the formation temperature of the amorphous semiconductor. It is desirable.

In performing the preheating and the post-heating in the present invention, there is a close relationship between the heating time and the atmospheric gas pressure, and when the atmospheric gas pressure is high, the shorter the heating time, the better. preferable. Further, when the atmospheric gas pressure is low, it is effective that the heating time is relatively long. However, when performing continuous film formation, if the heating time is long, the productivity cannot be increased. For this reason, the range of 1 sec to 1000 sec is preferable. The ambient gas pressure in the pre-heating chamber and the post-heating chamber is from 0.01 Pa to 1000 P
The range of a is preferred, but 5 Pa to 500 Pa, which is close to the pressure at the time of forming the amorphous semiconductor, is desirable.

The semiconductor layer is made of a non-single-crystal material of silicon-based material ranging from amorphous (including so-called microcrystal) to polycrystal. As a method for forming a semiconductor layer, a vapor deposition method,
Known methods such as sputtering, high-frequency plasma CVD, VHF plasma CVD, microwave plasma CVD, ECR plasma CVD, thermal CVD, and optical CVD,
Use as desired. As a method adopted industrially, a high-frequency plasma CVD method in which a raw material gas is decomposed by plasma and deposited on a substrate is preferably used. In the case of the high-frequency plasma CVD method, a parallel plate capacitive coupling type or a type having different areas of the cathode electrode and the anode electrode may be used. However, to form microcrystalline silicon or the like, it is more preferable that the area ratio of the anode electrode to the cathode electrode is small. In the case of the high frequency plasma CVD method, S
A mixed gas of iH ₄ , Si ₂ H ₆ , hydrogen, He, or the like is decomposed by plasma, so that a substantially intrinsic silicon-based non-single-crystal semiconductor can be formed.

As a valence electron controlling agent for obtaining an n-type semiconductor, a compound containing an element of Group V of the periodic table is used. Group V elements include P, N, As, and Sb. PH ₃ or the like is used as a compound containing a Group V element. As a valence electron controlling agent for obtaining a p-type semiconductor, a compound containing an element of Group III of the periodic table is used. Group III elements include B, Al, Ga,
In is mentioned. BF ₃ , B ₂ H ₆ or the like is used as the compound containing a Group III element.

The substrate 101 may be formed by forming a conductive film on a translucent green body such as a glass substrate or the like, or a non-transparent conductor such as a stainless steel substrate or an Ag as a reflection layer on the non-transparent conductor. Alternatively, a material in which a light-transmitting conductive layer such as ZnO or SnO ₂ is formed as a buffer layer may be used.

(Example 1) A photovoltaic element was manufactured as follows using a general parallel plate capacitive coupling type high frequency plasma CVD apparatus (not shown).

A transparent conductive layer of about 1 μm was laminated on stainless steel by sputtering to form a substrate having a fine uneven surface (size: 50 mm & time).
s; 100 mm).

An n-type layer composed of an amorphous silicon film, an i-type layer composed of an i-type amorphous silicon film, and a p-type layer composed of a microcrystalline silicon film are sequentially deposited on a substrate, and a pin junction is formed. It was formed under the conditions shown in Table 1.

[Table 1]

In this embodiment, the i-th layer is formed at a film forming temperature.
After forming at 220 ° C., H_Two300 sccm, temperature 2
Preheating at 50 ° C. for 1 minute_Two300 sccm,
High-frequency power of 100 W, processing temperature of 220 ° C for 1 minute
Plasma treatment and H _Two300 sccm, temperature 1
The latter stage heating was performed at 70 ° C. for 1 minute.

The substrate on which the semiconductor layer is formed has an area of 50 cm ^2.
And cut by ITO (In ₂ O ₃ + S
Fifty transparent conductive layers having a thickness of 87 nm and an area of 0.25 cm ^{2 made of} an nO ₂ ) film were formed as upper electrodes, and fifty small area cells (actual one element) were produced. AM in these cells
Irradiate 1.5 (100 mW / cm ² ) pseudo sunlight,
The photoelectric conversion characteristics were evaluated. The photodegradation was measured by installing a solar cell whose initial photoelectric conversion efficiency was measured in advance in an environment of 55% humidity and 25 ° C.
AM after irradiating 5 (100 mW / cm ² ) light for 500 hours
The evaluation was performed based on the rate of decrease in photoelectric conversion efficiency under irradiation of 1.5 (100 mW / cm ² ) (photoelectric conversion efficiency after light degradation test / initial photoelectric conversion efficiency).

For comparison, a semiconductor layer was formed without preheating and without performing hydrogen plasma treatment.
Fifty small area cells (1-1 element ratio) were prepared in the same manner as the element, and the same measurement as in Example 1 was performed.

For comparison, a semiconductor layer was formed by performing a hydrogen plasma treatment without preheating, and
Fifty small area cells (1-2 elements in ratio) were prepared in the same manner as the element, and the same measurement as in Example 1 was performed.

For comparison, the preheating temperature was set to 1
After performing at a temperature as low as 70 ° C., a hydrogen plasma treatment is performed to form a semiconductor layer, and 50 small area cells (1 to 3 elements in comparison) are formed in the same manner as the actual 1 element, and the same as above. A measurement was made.

[Table 2]

Table 2 shows the measurement results. The photoelectric conversion efficiency of the actual one element normalized by the value of 1-1 element, in which the semiconductor layer was formed without preheating and without hydrogen plasma treatment, was 1.017.
In fact, the open-circuit voltage of one device was significantly increased. Also,
The rate of decrease in photoelectric conversion efficiency due to light degradation is also greatly suppressed. Therefore, it was confirmed that the actual single element that had been subjected to the preliminary heating at a temperature equal to or higher than the film formation temperature of the i-type layer and then subjected to the hydrogen plasma treatment had high photoelectric conversion efficiency and suppressed light degradation.

The ratio 1-2 element where preheating was not performed, or the ratio 1−1 where the preheating temperature was lower than the film formation temperature of the i-type layer.
The three elements have a photoelectric conversion efficiency of 1.011 standardized at a ratio of 1-1 element, and the photoelectric conversion efficiency is almost close to the actual one element, but the light deterioration rate is slightly inferior.

(Embodiment 2) In Embodiment 2, the layer structure of the photovoltaic element is the same as that of Embodiment 1, and a photovoltaic element forming apparatus is formed on a strip-shaped substrate as shown in FIG. The present embodiment is different from the first embodiment in that a roll-to-roll type apparatus capable of forming a semiconductor film in a stacked manner is used. The apparatus for forming a photovoltaic element shown in FIG.
01, n-layer film forming chamber 102, i-layer film forming chamber 103, p-layer film forming chamber 104, band-shaped substrate winding chamber 105, gas gate 10
6. It is composed of an H ₂ plasma processing chamber 111. Note that the substrates to be formed are a band-shaped substrate 107, an unwinding substrate 108, and a winding substrate 109. This will be described below according to the manufacturing procedure.

FIG. 2 is a schematic view of the semiconductor layer film forming chamber and the hydrogen plasma processing chamber. The vacuum chamber 202, the gas gate 203, the discharge chamber 205, the discharge electrode 206, the source gas introduction pipe 207, the exhaust pipe 208, Block heater 20
9. Discharge chamber outside exhaust port 210, adjustment plate 21 between film formation regions
1, lid 212, lamp heater 213, thermocouple 214,
It has a reflector 215, a support roller 216, and a gate gas introduction pipe 217.

(L) A strip-shaped stainless steel plate made of SUS430BA (width 12 cm × length 20 om &
(time; thickness: 0.15 mm) Ag was deposited as a reflective conductive layer to a thickness of 400 nm by DC sputtering, and ZnO was deposited to a thickness of 1 μm as a buffer layer to form a band-shaped substrate having minute uneven surfaces. (2) The substrate manufactured in the above (1) was set in the unwinding chamber 101 of the belt-like substrate while being wound around the bobbin 108. (3) The band-shaped substrate is made to pass through the film forming chambers 102, 103, 110, 111, and 104 through the respective gas gates 106,
The sheet was transferred to the winding chamber 105 of the band-shaped substrate, and tension was applied to such an extent that it did not loosen. After setting the strip-shaped substrate, each chamber 101-
The inside of 111 was evacuated. (4) He gas is introduced while evacuating, and about 200P
The inside of each deposition chamber was heated and baked at about 350 ° C. in the He atmosphere of a. (5) After the heating and baking, each gas gate 106 is supplied with 500 sccm of hydrogen as a gate gas in each of the film forming chambers 102 to 102.
A predetermined flow rate of each raw material gas was introduced into 104, and the internal pressure of each chamber was set to a predetermined pressure. (6) Take-up bobbin 1 in take-up chamber 106 for belt-like substrate
09, the belt-like substrate 107 is
It was continuously moved at a constant speed of 60 cm / min in the direction toward 04. Further, temperature control was performed by a temperature control device (not shown) provided in each of the film forming chambers 102 to 111 so that the moving band-shaped substrate had a predetermined temperature in the film forming space of each film forming chamber. (7) When the temperature of the belt-shaped substrate is stabilized, the film forming chamber 10
In steps 2, 103 and 104, film formation is started by a high-frequency plasma CVD method. Film forming chambers 102, 103 and 1
Reference numeral 04 denotes a structure as shown in FIG. 2, in which a discharge chamber is arranged on the surface of a continuously moving strip-shaped substrate such that a semiconductor film is formed in the order of gas supply-side plasma and gas exhaust-side plasma. To 13.56 MHz from a power source (not shown) via a matching device. The source gas in each deposition chamber is turned into plasma by the input of discharge power, and the strip-shaped substrate 2 continuously moves in each deposition chamber.
A semiconductor film was formed on the surface of Sample No. 01. The preheating chamber 110 and the hydrogen plasma processing chamber 111 had the same structure as the film forming chambers 102, 103 and 104 as shown in FIG. 2, and hydrogen was introduced instead of the source gas. (8) In each deposition chamber, a high-speed deposition amorphous n-type layer composed of an amorphous silicon film, an i-type layer composed of an amorphous silicon film,
A p-type layer made of a microcrystalline silicon film is formed under the film forming conditions shown in Table 3, and after the i-type layer is formed, pre-ripening is performed in a pre-heating chamber 110, and hydrogen plasma processing is performed in a hydrogen plasma processing chamber 111. Was. The processing temperatures of the preheating chamber 110 and the hydrogen plasma processing chamber 111 were changed as shown in Table 4.

[Table 3] (9) The belt-shaped substrate is continuously moved from the start of the transfer by 180
Moved for a minute. During that time, the formation of the semiconductor laminated film was performed continuously for 170 minutes. (10) After forming the semiconductor laminated film over about 100 m, the supply of the discharge power, the introduction of the raw material gas, and the heating of the belt-like substrate and the film forming chamber were stopped, and the film forming chamber was purged. Thereafter, the apparatus was opened after sufficiently cooling the band-shaped substrate and the inside of the apparatus, and the band-shaped substrate wound around the bobbin 109 was taken out of the apparatus from the band-shaped substrate winding chamber 105.

Further, the strip-shaped substrate taken out is continuously processed by a continuous modularization apparatus, and a transparent electrode is formed on the entire surface of the semiconductor laminated film formed by the apparatus of the present invention as a transparent electrode.
by forming a thin film of ITO (In ₂ O ₃ + SnO ₂ ) thin film, forming thin Ag electrodes at regular intervals as current collecting electrodes, and performing modularization such as serialization of unit elements. 35cm & tim composed by
es; A 35 cm solar cell module (actual two elements) was continuously produced. The characteristics of the fabricated solar cell module were evaluated under simulated sunlight irradiation of AM 1.5 (100 mW / cm ² ).

For comparison, after forming the i-th layer,
The semiconductor layer was formed without performing the hydrogen plasma treatment. Otherwise, 35 cm × 35 as in the case of the actual two elements
cm solar cell module (2 elements in comparison) was prepared, and the same measurement as in Example 2 was performed.

The results of the operation are shown in Tables 4 and 5. Table 4 shows by symbol the amount of change in the photoelectric conversion efficiency of the actual two elements normalized by the value of the ratio two elements without performing the hydrogen plasma treatment.
That is, the symbol ○ has a change of 2% or more, and the symbol △ has a change of 1%.
% Or more and less than 2%, and the sign-indicates that the change amount is less than 1%. In Table 5, the rate of decrease in photoelectric conversion efficiency due to light deterioration of the actual two elements, that is, the light deterioration rate is indicated by symbols. That is,
The symbol ○ indicates that the light deterioration rate is 91 to 100%, the symbol △ indicates that the light deterioration rate is 86 to 90%, and the sign-indicates that the light deterioration rate is 80 to 85%.

If the temperature of the preheating is higher than the film forming temperature of the i-type layer and the temperature of the hydrogen plasma treatment is lower than the film forming temperature of the i-type layer, the amount of change in photoelectric conversion efficiency is 1% or more. A good photovoltaic element having a deterioration rate of 86% or more was obtained. In addition, a change in photoelectric conversion efficiency of 2% or more was confirmed when the preheating temperature was in the range of 250 to 280 ° C and the hydrogen plasma treatment temperature was in the range of 150 to 170 ° C. Further, the light deterioration rate was suppressed as the amount of change in the photoelectric conversion efficiency increased.

As described above, the first hydrogen plasma treatment is performed at a temperature equal to or higher than the film formation temperature of the i-type layer, and the second hydrogen plasma treatment is performed at a temperature lower than the film formation temperature of the i-type layer. It was confirmed that the photoelectric conversion efficiency was improved by forming the semiconductor layer.

[Table 4]

[Table 5]

(Embodiment 3) This embodiment is different from the embodiment 2 in that a photovoltaic element forming apparatus uses a roll-to-roll type apparatus as shown in FIG. In this example, the semiconductor layer was formed under the film forming conditions shown in Table 6. Otherwise, a semiconductor layer was formed in the same manufacturing procedure as in Example 2, a 35 cm & 35 cm solar cell module (actual 3 elements) was prepared in the same manner as in Example 2, and the same measurement as in Example 2 was performed. .

The apparatus for forming a photovoltaic element shown in FIG. 3 includes an unwinding chamber 301 for a strip substrate, a film forming chamber 302 for an n-type semiconductor layer,
i-type semiconductor layer deposition chamber 303, p-type semiconductor layer deposition chamber 3
04, strip substrate winding chamber 305, gas gate 30
6, strip-shaped substrate 307, unwinding bobbin 30 for strip-shaped substrate
8. Winding bobbin 309 for strip-shaped substrate, hydrogen plasma processing chamber 310, discharge chamber 311, exhaust pipe 312, preheater 313, heater 314, first heater 315, second
It has a heater 316 and a third heater 317.

[Table 6]

Comparative Example 3-1 For comparison, a semiconductor layer was formed without performing a hydrogen plasma treatment. Except for this, a 35 cm & 35 cm solar cell module (comparative 3-1 element) was prepared in the same manner as the actual three elements.
The same measurement as described above was performed.

Comparative Example 3-2 For comparison, a semiconductor layer was formed without performing preheating. Otherwise, a 35 cm & 35 cm solar cell module (3-2 elements in comparison) was prepared in the same manner as the actual three elements, and the same measurement as in Example 3 was performed.

(Comparative Example 3-3) For comparison, preheating was performed at a temperature lower than the i-type layer forming temperature to form a semiconductor layer. Other than that, 35cm & ti like the real three elements
mes; 35 cm solar cell module (3-3 elements in comparison) was prepared, and the same measurement as in Example 3 was performed.

Comparative Example 3-4 For comparison, a semiconductor layer was formed without performing post-stage heating. Otherwise, a 35 cm & 35 cm solar cell module (3-4 elements in comparison) was prepared in the same manner as the actual three elements, and the same measurement as in Example 3 was performed.

(Comparative Example 3-5) For comparison, post-stage heating was performed at a temperature higher than the i-type layer forming temperature to form a semiconductor layer. Other than that, 35cm & ti like the real three elements
mes; 35 cm solar cell module (3-5 elements in comparison) was prepared, and the same measurement as in Example 3 was performed.

Comparative Example 3-6 For comparison, a hydrogen plasma treatment was performed at a temperature higher than the i-type layer forming temperature to form a semiconductor layer. Other than that, 35c like the real three elements
m &time; 35 cm solar cell module (3 ratio)
−6 elements), and the same measurement as in Example 3 was performed.

Table 7 shows the results of the operation. Table 7 shows the amount of change in the photoelectric conversion efficiency of the actual 3 elements and the ratio 3-2 to 3-6 elements normalized by the value of the ratio 3-1 element where the hydrogen plasma treatment was not performed, and the photoelectric change due to light degradation. Conversion efficiency decrease rate,
Characteristic unevenness and the crystallinity of the p-type microcrystalline silicon layer formed on the i-type layer are shown.

Compared to the 3-1 device having the semiconductor layer formed without performing the hydrogen plasma treatment, the actual three devices have a photoelectric conversion efficiency of 1.05 times and an improved light degradation rate. In addition, characteristic unevenness was suppressed, and the crystallinity of the p-layer was high.

The hydrogen plasma treatment was not applied to the 3-2 element in which the semiconductor layer was formed without preheating and the 3-3 element in which preheating was performed at a temperature lower than the i-layer forming temperature. No improvement in photoelectric conversion efficiency and light deterioration rate was observed, and unevenness in characteristics was large as compared with the element of the ratio 3-1.

The element having a ratio of 3-4, in which the semiconductor layer was formed without performing post-stage heating, improved the photoelectric conversion efficiency and the light deterioration rate as compared with the element having the ratio of 3-1.

The post-heating was performed at a temperature higher than the i-type layer formation temperature, and the semiconductor layer was formed at a ratio of 3-5. The actual post-heating was performed at a temperature lower than the i-type layer formation temperature. In comparison, the crystallinity of the p-type layer is reduced, and the photoelectric conversion efficiency and the light deterioration rate are low. It is considered that this is because hydrogen on the surface of the i-type layer was desorbed by the latter-stage heating, the interface state between the p-type layer and the i-type layer was deteriorated, and travel of the photo-generated carriers was hindered. In addition, it is considered that the crystallinity of the p-type layer formed by the microcrystalline silicon semiconductor formed on the i-type layer is reduced, and the p-type layer becomes a resistance component, thereby lowering the photoelectric conversion efficiency.

The hydrogen plasma treatment was performed at a temperature higher than the i-type layer formation temperature, and the ratio 3-6 element in which the semiconductor layer was formed was compared with the element 3-1 in which the hydrogen plasma treatment was not performed. Conversion efficiency and light deterioration rate, characteristic unevenness,
Although the crystallinity of the p-type layer is improved, the photoelectric conversion efficiency and the light deterioration rate are lower than those of the actual three devices in which the hydrogen plasma treatment is performed at a temperature lower than the i-type layer formation temperature. This is because the hydrogen plasma treatment causes structural relaxation, but the temperature is too high, so that the relaxation in the i-type layer film proceeds, but the relaxation of the i-type layer surface proceeds with the desorption of hydrogen, and the surface has a dangling bond. The process of the hydrogen plasma treatment is terminated while the structural disturbance remains, and a good interface is not formed.

As described above, the preheating is performed at a temperature equal to or higher than the film forming temperature of the i-type layer, the hydrogen plasma treatment is performed, and then the subsequent heating is performed at a temperature lower than the film forming temperature of the i-type layer. By forming the semiconductor layer in this manner, it was confirmed that the photoelectric conversion efficiency and the light deterioration rate were improved, and the characteristic unevenness was improved.

[Table 7]

In the above embodiment, after depositing the semiconductor film,
Prior to performing the hydrogen plasma treatment, preheating is performed at a temperature equal to or higher than the temperature at which the semiconductor film was formed. This allows
Sufficient thermal energy is given to excessive Si—H bonds and dangling bonds in the film, and the film is set in a state where structural relaxation easily occurs in the film before performing the hydrogen plasma treatment. Alternatively, a part of excess hydrogen, Si—H bond, and dangling bond are diffused to relax the structure in the film.

When the hydrogen plasma treatment is performed in this state, the diffusion of atomic hydrogen into the film or the diffusion on the deposition surface causes
Excessive hydrogen and Si—H bonds can be effectively extracted in a short time. As a result, the relaxation of the structure in the film is promoted, and the light deterioration can be suppressed and the film quality can be improved.

Thereafter, when the substrate is rapidly cooled, the structure relaxation process is rapidly completed and the structure is not sufficiently relaxed, and the film structure is fixed while forming a part where dangling bonds remain. Is done. In addition, since the cooling rate has a distribution at the edge and the center even in the substrate, the light deterioration rate and the photoelectric conversion characteristics become uneven. Therefore, in the present invention, after the hydrogen plasma treatment, the latter-stage heating is performed in which the semiconductor film is heated at a temperature lower than the temperature at the time of formation. by this,
The diffusion of atomic hydrogen into the film is suppressed, and the structural relaxation in the film is suppressed, so that the structural relaxation process by the hydrogen plasma treatment is uniformly and slowly completed. By performing the latter-stage heating at a temperature lower than the temperature at the time of forming the semiconductor as described above, hydrogen near the deposition surface is not desorbed, and the termination of dangling bonds on the deposition surface can be maintained. That is, when a photoelectric conversion element is manufactured by further forming a semiconductor layer on the semiconductor film implemented according to the present invention, the photoelectric conversion element has a good interface with little light degradation and does not hinder the movement of photocarriers. A conversion element can be obtained.

Also, in the roll-to-roll apparatus, after the i-type layer is formed, the substrate surface which has been rapidly cooled by the gas gate is sufficiently heated again to a temperature effective for hydrogen plasma treatment. Thus, the effect of the hydrogen plasma treatment can be more expected.

Further, by giving a temperature and time sufficient to sufficiently relax the structure before the substrate surface subjected to the hydrogen plasma treatment is rapidly cooled by the gas gate, a semiconductor forming apparatus which does not impair the effect of the hydrogen plasma treatment is provided. Realize.

[0073]

As is clear from the above description, claim 1
In the method for forming a non-single-crystal semiconductor thin film according to the invention described above, preheating is performed at a substrate temperature or higher at the time of forming the semiconductor layer and before hydrogen plasma treatment after deposition of the amorphous semiconductor layer. Thereby, a good interface can be formed while relaxing the structure of the amorphous semiconductor layer, and a photovoltaic element having good photoelectric conversion efficiency can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a mass production type film forming apparatus used in Example 2 which is applied to a method for forming a non-single-crystal semiconductor thin film, a method for forming a photovoltaic element, and a functional deposited film forming apparatus according to the present invention. .

FIG. 2 is a schematic view of a semiconductor layer deposition chamber and a hydrogen plasma processing chamber by a high-frequency plasma CVD method in FIG.

FIG. 3 is a schematic diagram of a mass production type film forming apparatus used in Example 3.

[Explanation of symbols]

 101, 301 Unwinding chamber for strip-shaped substrate, 102, 302 Deposition chamber for n-type semiconductor layer, 103, 303 Deposition chamber for i-type semiconductor layer, 104, 304 Deposition chamber for p-type semiconductor layer, 105, 305 Substrate winding chamber, 106, 306 gas gate, 107, 307 strip substrate, 108, 308 strip substrate unwinding bobbin, 109, 309 strip substrate winding bobbin, 110 preheating chamber, 111, 310 hydrogen plasma processing chamber, 201 band-shaped substrate, 202 vacuum vessel, 203 gas gate, 205 discharge chamber, 206 discharge electrode, 207 source gas introduction pipe, 208 exhaust pipe, 209 block heater, 210 discharge chamber outside exhaust port, 211 film formation area opening adjusting plate, 212 lid , 213 lamp heater, 214 thermocouple, 215 reflector, 216 support row Chromatography, 217 gate gas inlet pipe, 311 the discharge chamber, 312 exhaust pipe, 313 preheater, 314 heater, 315 a first heater, 316 a second heater, 317 a third heater.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yuzo Koda 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Masahiro Kanai 3- 30-2 Shimomaruko, Ota-ku, Tokyo Canon F term in reference (reference) 5F045 AA08 AA09 AA10 AB04 AC01 AD05 AD06 AE17 AE19 AE21 AF10 DP22 EB14 EB15 EH13 EK11 HA11 HA16 5F051 AA03 AA04 AA05 BA14 CA16 CA22 CA34 CA36 CB12 CB24 CB29 CB30 DA04

Claims (9)

[Claims] 1. A method for forming a non-single-crystal semiconductor thin film on a substrate, comprising: a deposition step of depositing a non-single-crystal semiconductor layer on the substrate; and wherein the temperature of the substrate is higher than the substrate temperature in the deposition step. A method of forming a non-single-crystal semiconductor thin film, comprising: a heating step of heating the substrate so that the non-single-crystal semiconductor layer is exposed to hydrogen plasma; 2. The method according to claim 1, wherein the heating of the substrate is performed in a hydrogen atmosphere. 3. The method for forming a non-single-crystal semiconductor thin film according to claim 1, wherein the substrate temperature in the hydrogen plasma processing step is lower than the substrate temperature in the heating step. 4. The method for forming a non-single-crystal semiconductor thin film according to claim 1, wherein a substrate temperature in said hydrogen plasma treatment step is lower than a substrate temperature in said deposition step. 5. The method according to claim 1, further comprising a second heating step of heating or cooling the substrate after the hydrogen plasma processing step so that the substrate temperature is lower than the substrate temperature in the hydrogen plasma processing step. 5. The method for forming a non-single-crystal semiconductor thin film according to any one of items 1 to 4. 6. The method for forming a non-single-crystal semiconductor layer according to claim 5, wherein the heating of the substrate in the second heating step is performed in a hydrogen atmosphere. 7. A step of sequentially laminating a non-single-crystal semiconductor thin film having a first conductivity type, a substantially intrinsic non-single-crystal semiconductor thin film, and a second non-single-crystal semiconductor thin film having a conductivity type on a substrate. The method for manufacturing a photovoltaic device having the above, wherein the substantially intrinsic non-single-crystal semiconductor layer is provided.
3. A method for forming a photovoltaic element, comprising: 8. The photovoltaic device according to claim 7, wherein a non-single-crystal semiconductor thin film is sequentially stacked while using the strip-shaped substrate as the substrate and moving the strip-shaped substrate in the longitudinal direction. Forming method. 9. While continuously moving the strip-shaped substrate in the longitudinal direction, the strip-shaped substrate is passed through a plurality of film forming chambers connected by a gas gate having a gas inlet for introducing a scavenging gas into a slit-shaped separation passage. In a functional deposition film continuous forming apparatus for sequentially laminating a functional deposition film on the belt-like substrate in a film forming chamber, at least one hydrogen plasma processing chamber; and one preheating region before the hydrogen plasma processing chamber; And a post-heating area after the hydrogen plasma processing chamber.