JP2003119567A - Method and apparatus for forming deposition film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously form a deposition film with high quality without dispersion of characteristics, on a substrate having a large area. SOLUTION: The apparatus for forming the deposition film on the substrate 306 by a microwave plasma CVD method, has a film forming vessel 302 capable of evacuating the inside, a substrate transfer means for continuously passing the substrate 306 into the film forming vessel 302, slit-shaped openings 304 and 305 for passing the substrate 306, which are installed in both sides of a wall of the film forming vessel 302, a dielectric window 316 for introducing microwave into the film forming vessel 302, and electrodes 328 and 329 for applying several bias voltages, which are installed in the film forming vessel 302, wherein at least one or more of the electrodes 328 and 329 for applying the bias voltages is installed in a position within 50 mm from the slit-shaped openings 304 and 305.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deposited film forming method and a deposited film forming apparatus by a plasma CVD method, and in particular,
The present invention relates to a deposited film forming method and a deposited film forming apparatus for continuously forming various functional deposited films on a large-area substrate.

[0002]

2. Description of the Related Art In recent years, the demand for electric power has rapidly increased all over the world and the production of electric power has become active.
The problems of environmental pollution and global warming associated with thermal power generation and nuclear power generation have become apparent. Under such circumstances, solar cell power generation using sunlight does not cause problems of environmental pollution and global warming, and the uneven distribution of the resource of sunlight is small. ing.

In order to put solar cell power generation into practical use, it is required that the solar cell used has sufficiently high photoelectric conversion efficiency, excellent characteristics and stability, and is suitable for mass production. It In addition, a large-area solar cell is required due to the scale of power generation. For this reason, an amorphous material formed by depositing a semiconductor thin film such as amorphous silicon on a relatively inexpensive substrate such as glass or a metal sheet by decomposing an easily available source gas such as silane by glow discharge. Silicon-based solar cells have been proposed. This amorphous silicon-based solar cell is noted to have excellent mass productivity and low cost as compared with a solar cell manufactured from single crystal silicon or the like, and various proposals have been made regarding its manufacturing method.

In solar cell power generation, unit modules of solar cells are often connected in series or in parallel to form a unit so as to obtain a desired current and voltage, and no disconnection or short circuit occurs in each unit module. Is required
Further, it is required that there is little variation in output voltage and output current between unit modules. Therefore, at least at the stage of manufacturing the unit module, the uniformity of the characteristics of the semiconductor layer itself, which is the largest factor for determining the characteristics, is required. In addition, in order to simplify the module design and simplify the module assembly process, the ability to form a semiconductor deposited film with excellent characteristics over a large area improves the mass productivity of solar cells and reduces production costs. Will be significantly reduced.

A semiconductor layer, which is an important constituent element of a solar cell, includes a semiconductor junction such as a pn junction or a pin junction. These semiconductor junctions are formed by sequentially laminating semiconductor layers having different conductivity types or having a certain conductivity. It is formed by ion-implanting or thermally diffusing dopants of different conductivity types into the semiconductor layer of each type. In the production of the above-mentioned amorphous silicon solar cell, a raw material gas containing an element serving as a dopant such as phosphine (PH ₃ ) or diborane (B ₂ H ₆ ) is mixed with silane gas which is a main raw material gas and mixed. A semiconductor film having a desired conductivity type is obtained by decomposing the raw material gas by glow discharge,
It is known that a semiconductor junction can be easily obtained by sequentially stacking these semiconductor films on a desired substrate. Therefore, when manufacturing an amorphous silicon solar cell, it is common to provide an independent film forming chamber corresponding to each semiconductor layer and form each semiconductor layer in this film forming chamber.

As a method for forming a deposited film by a plasma CVD method suitable for producing such an amorphous silicon solar cell, US Pat. No. 4,400,409 describes rolls.
A roll-to-roll method is disclosed. This deposited film forming method is provided with a plurality of glow discharge regions, a long strip-shaped substrate is arranged along a path through which each substrate sequentially penetrates the glow discharge regions, and a required conductive type semiconductor layer is formed. Is deposited and formed in each glow discharge region, and the belt-shaped substrate is continuously conveyed in the longitudinal direction thereof. As a result, a solar cell having a desired semiconductor junction can be continuously formed. In this deposited film forming method, in order to prevent the dopant gas used in each glow discharge region from diffusing and mixing into other glow discharge regions, each glow discharge region is formed by a slit-shaped separation passage called a gas gate. They are separated from each other and, for example, A
A flow of scavenging gas such as r, H ₂ is formed. With this configuration, roll-to-roll
The method of forming a deposited film by the roll method is suitable for manufacturing a semiconductor element such as a solar cell.

On the other hand, as an attempt to improve the photoelectric conversion efficiency of amorphous silicon solar cells, a-Si
Ge: H, a-SiGe: F, a-SiGe: H: F, a-S
When a group IV alloy semiconductor such as iC: H, a-SiC: F, a-SiC: H: F is used as an i-type (intrinsic) semiconductor layer, the inhibition of the i-type semiconductor layer from the light incident side is prohibited. The open circuit voltage (V _oc ) and fill factor (FF) of the solar cell can be significantly improved by continuously and appropriately changing the body width (band gap: E _g ^opt ) in the film thickness direction. Has been found (20th IEEE PVSC, 1988, " A Novel
Design for Amorphous Silicon Solar Cells ",
S. Guha, J. Yang, et al.).

Further, for semiconductor devices, electrophotographic photosensitive devices, image input line sensors, image pickup devices and various other electronic elements, or optical elements, amorphous semiconductors such as hydrogen and / or halogen (fluorine, fluorine, Deposited films such as amorphous silicon compensated with chlorine) have been proposed, and some of them have been put to practical use. Such a deposited film is also generally formed by the plasma CVD method. That is,
It is formed by decomposing the raw material gas by direct current, high frequency or microwave glow discharge, and forming a thin deposited film on the substrate made of glass, quartz, heat resistant synthetic resin film, stainless steel, aluminum, etc. There is.

Here, the plasma CVD method will be described in more detail. The plasma CVD method is a method in which energy such as electromagnetic waves is added to a specific substance and discharged,
This is a method of forming a deposited film on a substrate by bringing a specific substance into a chemically active radical and bringing the radical into contact with a substrate or a substrate. The plasma CVD apparatus is an apparatus designed and manufactured to carry out the plasma CVD method.

Conventionally, the plasma CVD apparatus has a film forming chamber which is a vacuum container having a film forming gas inlet and an exhaust port, and a gas supply means for supplying the film forming gas to the film forming chamber through the film forming gas inlet. A gas discharging means for discharging the film forming gas in the film forming chamber through the film forming gas exhaust port; and an energy supplying means for supplying energy such as electromagnetic waves for dissociating the film forming gas supplied to the film forming chamber. And a substrate carrying means for carrying the substrate for forming the deposited film into the film forming chamber.

By the way, the plasma CVD method relies on the strong activity of radicals, and a desired deposited film is formed by appropriately selecting the radical generation density and the temperature of the substrate. In order to increase the processing speed and to form a uniform deposited film over a large area, it is necessary to select plasma conditions that generate radicals uniformly and in large quantities over a large area.

Conventionally, a high frequency (RF) of 13.56 MHz has been used as energy for dissociating a film forming gas, but in recent years, a wavelength of 2.45 GHz, which has a shorter wavelength, has been used.
Since high density plasma can be efficiently generated by using the microwave of, there is a possibility that the deposition film formation rate can be improved in the plasma CVD method.
A plasma CVD method using microwaves has been drawing attention, and many plasma CVD apparatuses have been proposed for that purpose. For example, various microwave plasma CVD apparatuses have been proposed on a desired substrate made of amorphous silicon (hereinafter, referred to as “a-Si”) as an element material used for various electronic elements and optical elements as described above.

For example, Japanese Patent Publication No. 58-49295 and Japanese Patent Publication No. 59-4399.
1, Japanese Utility Model Publication No. 62-36240 discloses that a gas tube is inserted into or brought into contact with a rectangular or coaxial waveguide to generate plasma. As a device of this type, the device shown in FIG. 4 can be mentioned as a typical device. This device consists of an outline, a vacuum system, an exhaust system,
It is composed of a microwave introduction system.

In FIG. 4, the vacuum system is a reaction vessel 981.
And a microwave permeable tube 983 (for example, a quartz tube) having an inner diameter of about 40 mm or a window connected through a gas transport tube 982. The tube 983 (or window) is connected to the first gas introduction tube 982 and is at the same time orthogonal to the microwave waveguide 984. A second gas introduction pipe (not shown) is connected to the inside of the reaction vessel 981.
Gas introduced from the gas introduction pipe (for example, silane gas)
Is exhausted from an exhaust system constituted by an exhaust pipe 985 and a pump 986. In this device, the gas (oxygen gas or nitrogen gas) introduced through the first gas introduction pipe 982 is the microwave power source 98.
It dissociates by the microwave power input from 7. When discharging by microwave power, the sliding short-circuit plate (plunger) 988 can be moved to match the microwave input impedance. The radicals in the plasma thus generated react with the silane gas or the like introduced through the second gas introduction pipe, and the substrate 989 is formed.
A film of SiO ₂ , SiN, or the like will be formed on top. Further, with this apparatus, it is possible to form a photoconductive material or a photovoltaic material at a high deposition rate of several tens of liters / second.

Further, US Pat. No. 4,517,223 and US Pat. No. 4,504,518 disclose a method of depositing a thin film on a substrate having a small area in a microwave glow discharge plasma under low pressure. There is. Since this method is a process under low pressure, not only is it possible to prevent the polymerization of active species, which causes deterioration of film characteristics, to obtain a high-quality deposited film, but also to prevent the formation of powder such as polysilane in plasma. It is said that the generation can be suppressed and the deposition rate can be dramatically improved. On the other hand, U.S. Pat.
A low pressure microwave plasma CVD method and apparatus for depositing a photoconductive semiconductor thin film on a large area cylindrical substrate by a high power process using a pair of radiating waveguide applicators is disclosed.

In order to form a uniform deposition on a large area by using the microwave plasma CVD method, the microwave power and the spatial density (concentration) distribution of the source gas are controlled to
A homogeneous plasma must be created and maintained. Further, in the roll-to-roll method, that is, the substrate moving film forming method, it is necessary to control the plasma to have a spatial composition distribution in order to have a composition distribution in the film thickness direction of the deposited film.

In order to generate and maintain such plasma, a plurality of microwave introducing means are provided in the reaction vessel (deposited film forming vessel), and the energy of microwaves radiatively propagated from these microwave introducing means to the reaction vessel. The distribution is controlled, or a plurality of gas supply means are provided to adjust the concentration distribution of the raw material gas in the reaction vessel.

In order to maintain a homogeneous plasma for a long time, it is necessary to keep the microwave energy supplied to the reaction vessel constant. As a method of keeping the microwave energy constant, the traveling wave energy and the reflected wave energy of the microwave are respectively monitored,
There is a method of obtaining an effective supply energy by subtracting the reflected wave energy from the traveling wave energy and performing control so that the supplied energy becomes constant. However, since the traveling wave and the reflected wave are monitored on the waveguide on the way from the microwave power source to the reaction vessel, there is a problem that the actual energy supplied to the reaction vessel cannot be accurately obtained. On the other hand, there is also a method of monitoring the plasma parameter in the reaction vessel with a probe and controlling the microwave energy from the microwave power source so that each parameter value becomes constant. However, a large-area microwave plasma CV having a plurality of microwave introduction means
In the D device, it is difficult to monitor the plasma over a large area and maintain a uniform plasma due to mutual interference of microwaves.

Known plasma CVD as described above
Moving film forming type microwave plasma CV, which is a combination of the substrate moving film forming method for forming a film while moving the substrate.
Various types of D devices have been proposed, typically as shown in FIG.

In FIG. 5, slit-shaped openings 954,
Three film forming vessels 951 connected in series via 955
953 have vacuum-tight structures. Each of the slit-shaped openings 954 and 955 has a film-forming container 951 to
Gate gas introduction means (not shown) for injecting an inert gas are provided in order to suppress the mixture of the source gases with each other. Slit-shaped openings 954,955
Specific examples of the gas gate include those described in US Patent Application No. 204,493. Each of these film forming containers 951 to 953 and slit-shaped openings 954 and 9
A long strip-shaped substrate 956 is arranged so as to penetrate 55. The substrate 956 can be continuously conveyed in the longitudinal direction, is unwound from the unrolling roller 957 provided in the unwinding chamber 974, and is wound up in the winding chamber 97.
It is adapted to be wound up by a winding roller 958 provided inside 5. Feeding room 974 and winding room 97
5 communicates with exhaust devices 976 and 977, respectively.

The film forming containers 951 to 953 are respectively
Exhaust devices 971-973 through exhaust ports 968-970
Is in communication with. Further, in each of the film forming containers 951 to 953, a lamp heater 959 to heat a substrate 956 to
961 and dielectric windows 965-967 are provided. Each of the dielectric windows 965 to 967 is formed of a material capable of efficiently transmitting microwave power into the film forming container and maintaining vacuum tightness, such as quartz glass or alumina ceramics. A waveguide (not shown), which is a microwave transmission line and mainly made of metal, is connected to the outside of the film forming container of the dielectric windows 965 to 967, and a microwave is transmitted via a matching isolator (not shown). It is connected to a power source (not shown). Furthermore, two film forming containers 951 on the left and right in the figure,
953 is provided with source gas supply pipes 962 and 963,
A bias voltage applying rod 964 for applying a bias voltage also serves as a source gas supply pipe in the film forming container 952 in the center of the drawing.
Is provided.

Such conventional microwave plasma CVD
The deposition film formation by the apparatus is performed as follows.
That is, the exhaust devices 971 to 973 exhaust the insides of the film forming containers 951 to 953 to adjust the pressures to desired values. Next, the lamp heaters 959 to 961 are energized to heat and maintain the temperature of the substrate 956 at a temperature suitable for film deposition.
At this time, the substrate 956 is conveyed from the feeding roller 957 to the winding roller 958 at a suitable speed. For example, when a photovoltaic element having a pin structure is formed via the source gas supply pipes 962 and 963 and the bias voltage applying rod 964 that also serves as the source gas supply pipe, silane (SiH ₄ ) gas and diborane gas are used, respectively. The film forming containers 951 to 95 are formed using a mixed gas of (B ₂ H ₆ ) gas, a silane gas, a mixed gas of a silane gas and a phosphine (PH ₃ ) gas, and the like.
No. 3, and an appropriate DC bias voltage is applied by the bias applying rod 964. At the same time, a microwave power source (not shown) is operated in parallel to generate a microwave having a frequency of 500 MHz or more, preferably 2.45 GHz, and the microwave is passed through a waveguide (not shown) and dielectric windows 965 to 967. And are introduced into the film forming containers 951 to 953 via Thus, the source gas in the film formation containers 951 to 953 is excited by the energy of microwaves and dissociated, so that a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer are sequentially formed on the surface of the substrate 956. It will be.

[0023]

However, in the above-mentioned conventional method for forming a deposited film, a large amount of a deposited film is continuously and stably formed on a large-area substrate such as an electrophotographic photoreceptor or a solar cell. It was difficult and costly. There is also a problem that it is difficult to uniformly form a large-area deposited film whose composition continuously changes in the film thickness direction.

That is, as described above, the control method for keeping the microwave energy constant is insufficient, and it is difficult to uniformly form a large amount of deposited film.

When a member having a large area whose one side exceeds 300 mm is prepared, the reaction container (film forming container) has a capacity of about 10 liters or more. When a raw material gas such as silane or germane (GeH ₄ ) was introduced into the reaction vessel to generate a glow discharge at a pressure of 5 to 20 mTorr, the required microwave power was about 2 to 4 kW. Therefore, in order to facilitate the occurrence of glow discharge,
It has been proposed that a mechanism for causing an arc discharge for ignition be provided in the reaction vessel (Japanese Patent Laid-Open No. 59-158323). However, in this case, there is a new problem that the arc discharge electrode is sputtered and mixed in the deposited film as an impurity to deteriorate the electrical characteristics of the deposited film. As another method for facilitating the occurrence of glow discharge, electron cyclotron resonance (EC
The method of causing R) is generally known (Japanese Patent Publication Sho
63-67332), also in this case, enormous apparatus cost is required to form a uniform magnetic field over a large area having a diameter of 150 mm or more, and it is very insufficient in terms of economic efficiency.

Further, in the above-described method of forming a deposited film by the roll-to-roll method, the deposited film is formed while the strip-shaped substrate is continuously moved, so that the film is formed while the substrate passes through the glow discharge region. Done. Therefore, the film thickness of the deposited film can be controlled relatively easily by the deposition rate and the passing rate of the glow discharge region. On the other hand, in order to have the composition distribution in the film thickness direction, since the substrate is continuously moved, it is necessary to give the film forming atmosphere in the glow discharge region a distribution in the moving direction of the substrate. However, it is difficult to provide such a distribution with good reproducibility in the film forming atmosphere such as the composition of the source gas, the pressure, or the energy density of glow discharge. Even in the deposited film forming method of fixing the substrate, the film forming atmosphere is not provided with a distribution because the uniformity of the deposited film is impaired.

It is known that when an amorphous deposited film such as a-Si is formed, the characteristics of the deposited film may be improved by applying an electric field by a bias voltage to the substrate in addition to microwave power. However, an optimum bias applying method in the moving film forming type microwave plasma CVD apparatus has not been found. FIG. 6 is a schematic diagram showing how a bias electric field is applied in a conventional device. Here, a bias applying rod 942 that extends parallel to the surface of the belt-shaped substrate 941 and perpendicular to the longitudinal direction of the substrate 941 is provided at substantially the center of the film forming container 943.
The arrow in the figure indicates the electric field. As is clear from this figure, the vicinity of the end of the film forming container 943 (section L in the drawing)
The magnitude of the electric field applied to the substrate 941 changes between the other places and the electric field applied to the substrate 941 during the transportation of the substrate 941. In particular, the film forming container 94
For the substrates immediately after entering the area 3 and immediately before exiting (when in the section L in the drawing), the DC bias is extremely weakened as compared with the substrate in the substantially central portion of the film forming container 941. As a result, the characteristics of the deposited film formed near the end of the film forming container 941 are inferior to those of the deposited film formed in the central portion of the film forming container 941. For example, when forming an i layer while applying a bias voltage in forming a pin type photovoltaic element, the characteristics are poor at the interface between the p layer and the i layer or the interface between the i layer and the n layer. Since the i-layer is deposited, the characteristics of the photovoltaic element are greatly deteriorated.

Further, in the plasma generated by microwaves, it is possible to control the plasma potential by applying a bias voltage to the plasma, but a stable and high-quality deposited film can be obtained in continuous film formation for a long time. In forming it, there are various problems that must be solved.

Specifically, a deposited film of desired quality can be formed over a relatively large area by applying a bias voltage to the microwave plasma, but the bias current by applying the bias voltage is: It is very sensitive to the state of the flowing wall surface, and the stability of the bias current greatly affects the characteristics of the deposited film. For example,
In the method of forming a deposited film by a roll-to-roll method using microwave plasma, a strip-shaped substrate forming one surface of a film forming container is continuously moved while a deposited film having a desired film thickness is formed on the substrate. While being formed, a large amount of deposited film will adhere to the inner wall of the fixed film forming container.
As a result, for example, when a bias voltage is applied by a bias applying rod or the like, the state of the wall surface into which the bias current flows, that is, the conductivity is constant on the moving substrate, but is large on the wall surface forming the film forming container. It will change. If the microwave energy and the bias voltage supplied to the film formation container in this state are constant, the bias current value apparently becomes constant, but the bias current flowing into the substrate actually increases and the film formation container The bias current that flows into the wall surface of is reduced. Therefore, the film quality of the film deposited on the substrate changes greatly with the change of the bias current, and it is difficult to form a deposited film having a constant characteristic continuously with good reproducibility.

Further, in the above-described method of forming a deposited film by the roll-to-roll system, a slit-shaped hole is provided in the film forming container surrounding the plasma region in order to pass the strip-shaped substrate through the microwave plasma region. The board is passed through the hole. For this reason, a gap is formed between the substrate and the film forming container in the hole portion, and microwave plasma or the raw material gas itself easily leaks through this gap, and it is difficult to stably maintain the film forming atmosphere.

An object of the present invention is to provide a deposited film forming method and a deposited film forming apparatus capable of forming a high quality deposited film on a large-area substrate continuously and with stable characteristics and with good reproducibility. To provide. Not only the deposited film whose composition does not change in the film thickness direction, but also the deposited film having a composition distribution in the film thickness direction can be formed continuously and with stable characteristics with good reproducibility. Is the purpose.

[0032]

A method for forming a deposited film according to the present invention comprises a film forming container capable of being evacuated to vacuum, a substrate conveying means for continuously passing a substrate through the film forming container, and the film forming process. Slit-shaped openings provided on both sides of the container for passing the substrate, microwave introducing means for introducing microwaves into the film forming container, and a plurality of bias voltage applying devices attached to the film forming container And a deposition film forming apparatus for forming a deposition film on the substrate by a microwave plasma CVD method, the method comprising:
At least one of the bias voltage applying means is provided at a position within 50 mm from the slit opening.

The deposited film forming apparatus of the present invention is provided with a film-forming container capable of being evacuated to vacuum, a substrate transfer means for continuously passing a substrate through the film-forming container, and both side walls of the film-forming container. A slit-shaped opening for passing the substrate, a microwave introducing unit for introducing microwaves into the film forming container, and a plurality of bias voltage applying units attached to the film forming container, Microwave plasma CVD
In the deposited film forming apparatus for forming a deposited film on the substrate by the method, one or more of the bias voltage applying means are provided at a position within 50 mm from the slit opening.

[0034]

In the present invention, one of the bias voltage applying means is used.
Since one or more of them are provided within 50 mm from the slit-shaped opening, it is possible to apply a suitable bias voltage to the strip-shaped substrate both at the center of the film formation space and near the end of the film formation space. Become. As a result, it has become possible to form a deposited film having good characteristics from the vicinity of the entrance of the film formation space to the vicinity of the exit of the strip-shaped substrate that is continuously conveyed. As a result, when a deposited film having a multilayer structure such as a photovoltaic element is formed, the quality of the film at the interface, which has a significant effect on the characteristics, is not deteriorated,
A good quality deposited film can be formed. Thereby, in the case of the photovoltaic element, the characteristics are improved.

Further, in the present invention, the bias applying means is installed in the vicinity of the gate portion connecting the two adjacent film forming spaces or in the vicinity of the gate portion connecting the film forming space and the substrate feeding chamber or the winding chamber. Therefore, the action of the bias electric field applied here can prevent charged particles from entering one film forming space into the other film forming space and from mixing impurities from the adjacent film forming space. . That is, the bias applying means also has the shield effect.

The bias voltage applied to the bias applying means may be direct current or alternating current. Further, in the case of the AC bias, it may be a sine wave, a rectangular wave, or a sawtooth wave, and the frequency thereof may be from several Hz to several tens MHz. The electric field strength generated by using a plurality of bias applying means is 15 V / cm, although it varies depending on the type of raw material gas used.
Or more and 500 Vcm or less is preferable, and 30 V / cm or more 1
It is more preferably 50 V / cm or less. When the electric field strength is in such a range, the film formation rate and the electric characteristics of the film are further improved.

Next, in order to examine the installation position of the bias applying means, an amorphous silicon single layer film is formed on the surface of the substrate, and it is parallel to the substrate surface from the side wall of the deposition container at the end of the deposition container toward the center of the deposition container. The distribution of the dark conductivity of the monolayer film with respect to the distance toward was measured. FIG. 7 is a schematic cross-sectional view showing the configuration of the experimental device used for this measurement.

First, a method for forming this amorphous silicon single layer film will be described. In contrast to a rectangular parallelepiped film forming container 994 having one surface opened, a belt-shaped substrate 991 is used as a film forming container 99.
4 extends so as to cover the opening. A bias applying rod 995, which extends parallel to the surface of the substrate 991 and perpendicular to the longitudinal direction of the substrate 991 and also serves as a source gas introduction tube, is provided at substantially the center of the film forming container 994. Then, a bias applying electrode 99 is formed at both ends of the film forming container 994 along the longitudinal direction of the substrate 991 via an insulator 993.
2 is provided so as to be close to the substrate 991. Further, the film forming container 994 is provided with a microwave introducing unit (not shown). Using this apparatus, a DC bias is applied by the microwave plasma CVD method to the substrate 991.
An amorphous silicon single layer film was formed on top.

FIG. 8 is a diagram showing the measurement results of the dark conductivity of the formed amorphous silicon single layer film. The horizontal axis is the distance measured from the end of the film forming container toward the center of the film forming container parallel to the substrate. As is clear from this figure, the bias applying means is preferably from 0 to 50 mm, and more preferably from 0 to 30 m from the side wall of the film forming container at the end of the film forming container.
m, more preferably 0 to 20 mm.

In the present invention, the temperature of the substrate during the formation of the deposited film is effective at any temperature, but it is 20 ° C. or higher and 5
The temperature is preferably 00 ° C or lower, more preferably 50 ° C or higher and 450 ° C or lower.

In the present invention, a waveguide or a coaxial cable can be used as a microwave transmission path from a microwave power source such as a magnetron to a film forming container. Further, as a method of introducing the film into the film forming container, there is a method of introducing from one or a plurality of dielectric windows or providing an antenna in the film forming container. At this time, the material of the dielectric window is not particularly limited, but for example, microwave loss of alumina, aluminum nitride, silicon nitride, silicon carbide, silicon oxide, beryllium oxide, polytetrafluoroethylene, polystyrene, etc. A material having a small amount is preferably used.

<< Example of Deposited Film Formed by Method and Apparatus of Present Invention >> The present invention has been described above. Here, an example of a deposited film formed by the method and apparatus for forming a deposited film of the present invention. Will be described.

As such a deposited film, Si, Ge, C
Representative examples thereof include Group IV semiconductor thin films such as those described above, and those containing a valence electron control element. In addition, Si
I such as Ge, SiC, GeC, SiSn, GeSn, SnC
Group V alloy semiconductor thin film, GaAs, GaP, GaSb, In
III-V group compound semiconductor thin films such as P and InAs, Zn
II-VI group compound semiconductor thin films such as Se, ZnS, ZnTe, CdS, CdSe, CdTe, CuAlS ₂ , CuAlS
e ₂ , CuAlTe ₂ , CuInS ₂ , CuInSe ₂ , CuI
nTe ₂ , CuGaS ₂ , CuGaSe ₂ , CuGaTe, A
I-III-VI compound semiconductor thin film such as _{gInSe 2, AgInTe 2, ZnSiP 2} , ZnGeAs 2, CdSiAs
₂ , II-IV-V group compound semiconductor thin films such as CdSnP ₂ ,
Cu ₂ O, TiO ₂ , In ₂ O ₃ , SnO ₂ , ZnO, CdO, B
Examples thereof include oxide semiconductor thin films such as i ₂ O ₃ and CdSnO ₄ , and those in which these semiconductor thin films contain a valence electron control element for controlling valence electrons. Of course, these thin film semiconductors are
It may be any of polycrystal, microcrystal, and single crystal. As an example of a deposited film having a composition changed in the film thickness direction, the hydrogen and / or fluorine content was changed in an amorphous semiconductor such as a-Si: H or a-Si: H: F. It is a thing.

The raw material gas for forming the deposited film used for forming the above-mentioned deposited film is introduced into the film forming space by appropriately adjusting the mixing ratio according to the desired composition of the deposited film.

The above-mentioned Group IV semiconductor or Group IV alloy semiconductor thin film
Group IV of the periodic table, which is preferably used for forming a film
Examples of compounds containing elements include Si atom, Ge atom, and C atom.
A compound containing a child, Sn atom, and Pb atom,
For SiH_Four, Si₂H₆, Si₃H₈, Si₃H₆, Si_FourH₈, S
i_FiveH_TenSilane compounds such as SiF_Four, (SiF₂)_Five, (S
iF₂)₆, (SiF₂)_Four, Si₂F₆, Si₃F₈, SiHF₃, S
iH₂F₂, Si₂H₂F_Four, Si₂H₃F₃, SiCl_Four, (SiC
l₂)_Five, SiBr_Four, (SiBr₂)_Five, Si₂Cl₆, Si₂B
r₆, SiHCl₃, SiHBr₃, SiHI₃, Si₂Cl₃F
₃Halogenated silane compounds such as GeH_Four, Ge₂H₆Na
Which germane compound, GeF_Four, (GeF₂)_Five, (GeF₂)₆,
(GeF₂)_Four, Ge₂F₆, Ge₃F₈, GeHF₃, GeH₂F₂,
Ge₂H₂F_Four, Ge₂H₃F₃, GeCl_Four, (GeCl₂)_Five, G
eBr_Four, (GeBr₂)_Five, Ge₂Cl₆, Ge₂Br₆, GeH
Cl₃, GeHBr₃, GeHI₃, Ge₂Cl₃F₃Ha
Germanium Rogenide Compound, CH_Four, C₂H₆, C₃H₈Na
Which methane series hydrocarbon, C₂H_Four, C ₃H₆Such as ethylene
Row hydrocarbon, C₆H₆Cyclic hydrocarbons such as CF_Four, (C
F₂)_Five, (CF₂)₆, (CF₂)_Four, C₂F₆, C₃F₈, CHF₃, CH
₂F₂, CCl_Four, (CCl₂)_Five, CBr_Four, (CBr₂)_Five, C₂Cl
₆, C₂Br₆, CHCl₃, CHI₃, C₂Cl₃F₃Such as halo
Genated carbon compound, SnH_Four, Sn (CH₃)_FourTinization such as
Compound, Pb (CH₃)_Four, Pb (C₂H_Five)₆Lead compounds such as
Can be mentioned. Use one of these compounds
Also, two or more kinds may be mixed and used.

The valence electron control agent used to control the valence electrons of the above-mentioned group IV semiconductor or group IV alloy semiconductor is, as a p-type impurity, an element of group III of the periodic table, such as B or Al. , Ga, In, Tl and the like are preferable, and as the n-type impurities, elements of Group V of the periodic table, for example, N, P, As, Sb and Bi are preferable. Especially, B, Ga, P, Sb, etc. are most suitable. The amount of impurities to be doped is appropriately determined according to the required electrical and optical characteristics. As such a raw material for introducing impurities, a substance that is in a gas state at room temperature and atmospheric pressure or that can be easily gasified under at least the film forming conditions is adopted. Specific examples of the starting material for introducing such impurities include PH ₃ , P ₂ H ₄ , PF ₃ , PF ₅ , and PC.
l ₃ , AsH ₃ , AsF ₃ , AsF ₅ , AsCl ₃ , SbH ₃ , Sb
F ₅ , BiH ₃ , BF ₃ , BCl ₃ , BBr ₃ , B ₂ H ₆ , B ₄ H ₁₀ ,
_{B 5 H 9, B 5 H} 11, B 6 H 10, B 6 H 12, AlCl 3 , and the like. The compound containing the above impurity element is 1
They may be used alone or in combination of two or more.

The compound containing a Group II element of the periodic table, which is used to form the above II-VI group compound semiconductor, is specifically Zn (CH ₃ ) ₂ or Zn (C ₂ H ₅ ) ₂ , Zn
(OCH ₃ ) ₂ , Zn (OC ₂ H ₅ ) ₂ , Cd (CH ₃ ) ₂ , Cd (C ₂ H
_{5) 2, Cd (C 3} H 7) 2, Cd (C 4 H 9) 2, Hg (CH 3) 2, Hg
_{(C 2 H 5) 2,} Hg (C 6 H 5) 2, Hg [C≡ (C 6 H 5)] 2 , and the like. Specific examples of the compound containing a Group VI element of the periodic table include NO, N ₂ O, CO ₂ , CO, H ₂ S and SCl.
_{2, S 2 Cl 2, SOCl} 2, SeH 2, SeCl 2, Se 2 Br 2,
_{Se (CH 3) 2, Se} (C 2 H 5) 2, TeH 2, Te (CH 3) 2, T
e (C ₂ H ₅ ) _{2 and the} like. Of course, these raw materials may be used alone or in combination of two or more.

The group II-VI compound semiconductor is controlled by valence electrons.
The valence electron control agent used for
Compounds containing elements of groups I, III, IV and V are considered effective
Can be listed. Specifically, the inclusion of Group I elements
As a compound, LiC₃H₇, Li (sec-C_FourH₉), Li₂S,
Li₃N and the like can be mentioned as preferable ones.
Further, as a compound containing a Group III element, BX₃, B₂H₆,
B_FourH_Ten, B_FiveH₉, B_FiveH₁₁, B₆H_Ten, B (CH₃)₃, B (C₂H
_Five)₃, B₆H₁₂, AlX₃, Al (CH₃)₂Cl, Al (CH₃)₃,
Al (OCH₃)₃, Al (CH₃) Cl₂, Al (C₂H_Five)₃, Al
(OC₂H_Five)₃, Al (CH₃)₃Cl₃, Al (i-C_FourH₉)₃, A
l (i-C₃H₇)₃, Al (C₃H₇)₃, Al (OC_FourH₉)₃, Ga
X₃, Ga (OCH₃)₃, Ga (OC₂H_Five)₃, Ga (OC
₃H₇)₃, Ga (OC_FourH₉)₃, Ga (CH₃)₃, Ga₂H₆, Ga
H (C₂H_Five)₂, Ga (OC₂H_Five) (C₂H_Five)₂, In (CH₃)₃,
In (C₃H₇)₃, In (C_FourH₉)₃, Compounds containing group V elements
As NH₃, HN₃, N₂H_FiveN₃, N₂H_Four, NH_FourN₃, PX
₃, P (OCH₃)₃, P (OC₂H_Five)₃, P (OC ₃H₇)₃, P (OC
_FourH₉)₃, P (CH₃)₃, P (C₂H_Five)₃, P (C₃H₇)₃, P (C_FourH
₉)₃, P (SCN)₃, P₂H_Four, PH₃, AsH₃, AsX₃, As
(OCH₃)₃, As (OC₂H_Five)₃, As (OC₃H₇)₃, As (O
C_FourH₉)₃, As (CH₃)₃, As (C₂H_Five)₃, As (C₆H_Five)₃,
SbX₃, Sb (OCH₃)₃, Sb (OC₂H_Five)₃, Sb (OC₃
H₇)₃, Sb (OC_FourH₉)₃, Sb (CH₃)₃, Sb (C₃H₇)₃,
Sb (C_FourH₉)₃And so on. X is halogen
The elements (F, Cl, Br, I) are shown. Of course, these
The raw material may be one kind, but two or more kinds
You may use together. Furthermore, as a compound containing a group IV element
For the above, the compounds described above can be used.

The compound containing a group III element of the periodic table, which is used for forming the group III-V compound semiconductor described above, is a group III element used for valence electron control of a group II-VI compound semiconductor. The above-mentioned compounds can be used as they are as compounds containing
As the compound containing a group element, the compound described above as a compound containing a group V element used for controlling valence electrons of a II-VI group compound semiconductor can be used as it is. Of course, these raw materials may be used alone or in combination of two or more.

As the valence electron controlling agent used for controlling the valence electrons of the III-V group compound semiconductor, a periodic table is used.
Compounds containing Group II, IV, and VI elements can be cited as effective ones. As such a compound, the compound containing the group II element described above, the compound containing the group IV element described above, and the compound containing the group VI element described above can be used.

The above-mentioned raw material gases are He, Ne, Ar,
Noble gas such as Kr, Xe or H ₂, HF, HCl, etc.
It may be mixed with the dilution gas of the above and introduced into the deposited film forming apparatus.
Yes. In addition, these rare gases and dilution gases are independent of the source gas.
Alternatively, it may be introduced into the deposited film forming apparatus.

When forming a deposited film of these semiconductor thin films, molecules containing nitrogen atoms such as N ₂ and NH ₃ , O ₂ and NO ₂ are used as a characteristic improving gas for changing the band gap width of the deposited film. Molecules containing oxygen atoms such as CH ₄ , C ₂
Hydrocarbons such as H ₆ , C ₂ H ₄ , C ₂ H ₂ , C ₃ H ₈ and SiF ₄ , S
Examples thereof include fluorides such as i ₂ F ₆ and GeF ₄ , or mixed gas thereof.

In the present invention, it is possible to form a controlled composition distribution in the film thickness direction of the deposited film. However, by performing composition control in the above-mentioned semiconductor thin film, forbidden band width control and valence electron control are performed. , Refractive index control, crystal control, etc. are performed. By forming a deposited film whose composition is controlled in the film thickness direction on a belt-shaped substrate, a large area thin film semiconductor device having excellent electrical, optical and mechanical characteristics can be manufactured. That is, by changing the forbidden band width and / or the valence electron density in the film thickness direction of the deposited semiconductor layer, carrier mobility is enhanced, and carrier recombination at the semiconductor interface is prevented to prevent electrical recombination. The characteristics are improved. Further, by continuously changing the refractive index, an optical non-reflecting surface can be obtained, and the light transmittance into the semiconductor layer can be improved. Furthermore, by changing the hydrogen content and the like, a structural change can be given, internal stress is relieved, and a deposited film having high adhesion to the substrate can be formed.

The substrate on which the deposited film is formed in the present invention is not particularly limited in its material, but for example, Al, Cr, Mo, Au, In, Nb, Te, V, Ti,
Metals such as Pt and Pd, alloys of these and stainless steel,
Synthetic resin such as polycarbonate whose surface is treated to be conductive,
Glass, ceramics and paper are usually used.

<< Structural Example of Solar Cell >> A photovoltaic element, that is, a solar cell is an example of a semiconductor device suitably manufactured by using the deposited film forming method and the deposited film forming apparatus of the present invention. An amorphous silicon solar cell, which is a typical layer structure, will be described with reference to FIGS. 9 (a) to 9 (d).

The solar cell shown in FIG. 9A has a substrate 901.
A lower electrode 902, an n-type semiconductor layer 903, an i-type semiconductor layer 904, a p-type semiconductor layer 905, and a transparent electrode 906 are sequentially laminated on the transparent electrode 906, and a grid-shaped collector electrode 907 is formed on the transparent electrode 906. It has a structured structure. This solar cell is based on the premise that light is incident from the transparent electrode 906 side. The lower electrode 902 is an electrode that faces the transparent electrode 906 with the semiconductor layers 903 to 905 interposed therebetween.

The solar cell shown in FIG. 9B has a substrate 901.
Is transparent, and light is incident from the side of the substrate 901, and the transparent electrode 90 is formed on the substrate 901.
6, the p-type semiconductor layer 905, the i-type semiconductor layer 904, the n-type semiconductor layer 903, and the lower electrode 902 are sequentially stacked.

Each of the above solar cells has only one set of pin junctions, but two sets of pin junctions are stacked to improve the utilization efficiency of incident light. FIG. 9 (c) shows the structure of a solar cell having two pairs of pin junctions (so-called tandem solar cell),
This solar cell comprises a substrate 901, a lower electrode 902,
The first pin junction 911, the second pin junction 912, the transparent electrode 906, and the collector electrode 907 are sequentially stacked. Light enters from the transparent electrode 906 side.
Each of the pin junctions 911 and 912 has, of course, a structure in which an n-type semiconductor layer 903, an i-type semiconductor layer 904, and a p-type semiconductor layer 905 are stacked. To the first and second
The band gap and the film thickness are made different depending on each of the pin junctions 911 and 912.

Furthermore, in order to improve the photoelectric conversion efficiency,
Lamination of three sets of pin junctions is performed. Figure 9
(d) shows a structure of a solar cell having three sets of pin junctions (so-called triple solar cell), which is a lower electrode 902, a first p-type electrode on a substrate 901.
in junction 911, second pin junction 912, third pi
The n-junction 913, the transparent electrode 906, and the collector electrode 907 are sequentially stacked. Light enters from the transparent electrode 906 side. Also in this solar cell, in order to improve the photoelectric conversion efficiency, the band gap and the film thickness of the i-type semiconductor layer 904 are made different in each of the pin junctions 911 to 913.

Next, details of each component of the above-mentioned solar cell will be described. In each of the solar cells shown in FIGS. 9A to 9D, when the n-type semiconductor layer 903 and the p-type semiconductor layer 905 are compared, the p-type semiconductor layer 905 is located on the light incident side. However, the n-type semiconductor layer 90
It is also possible to have a layer structure in which 3 is located on the light incident side.

First, the substrate 901 will be described.

Substrate 90 used in this solar cell
1 is preferably made of a material that can be easily bent to form a curved shape, and may be conductive or electrically insulating. The substrate 901 may be translucent or non-translucent, but when light is incident from the side of the substrate 901, it is needless to say that it is translucent. Is. Specifically, a strip-shaped substrate as used in each example of the present invention can be mentioned. By using the belt-shaped substrate, the solar cell can be continuously formed on the substrate by the method and apparatus of the present invention, and the weight and strength of the solar cell can be improved, and the transportation space can be reduced.

Next, the electrodes for extracting electric power from the solar cell will be described.

In this solar cell, an appropriate electrode is selected and used according to its configuration. Examples of these electrodes include a lower electrode 902, a transparent electrode 906, and a collector electrode 907. (However, the transparent electrode 906 referred to here
Means the one provided on the light incident side, and the lower electrode 90
2 is a transparent electrode 9 sandwiching each semiconductor layer 903-905.
It will be shown that it is provided so as to face 06. ) These electrodes will be described in detail below.

(I) Lower Electrode 902 As the lower electrode 902, the surface on which the light for generating photovoltaic is irradiated differs depending on whether or not the material of the substrate 901 described above is translucent (for example, the substrate 901). Is a non-translucent material such as metal, light is emitted from the transparent electrode 906 side, as shown in FIG.

Specifically, in the case of the layer structure shown in FIGS. 9 (a), 9 (c) and 9 (d), the substrate 9 is used as an electrode for current extraction.
The lower electrode 902 is provided between 01 and the n-type semiconductor layer 903. Note that when the substrate 901 is conductive, this substrate 901 can also serve as the lower electrode 902, so that the lower electrode 902 can be omitted. However, when the substrate 901 is conductive but has a high sheet resistance value, the lower part is used as an electrode having a low resistance for current extraction or for the purpose of effectively utilizing incident light by increasing the reflectance on the support surface. The electrode 902 may be installed.

In the case of FIG. 9B, a transparent substrate 901.
Since light is incident from the side of the substrate 901, the lower electrode 902 faces the substrate 901 and faces each of the semiconductor layers 903 to 90 for the purpose of current extraction and light reflection.
It is provided with 5 in between.

The material of the lower electrode 902 is Ag, A
Examples include metals such as u, Pt, Ni, Cr, Cu, Al, Ti, Zn, Mo, and W, or alloys thereof. Thin films of these metals are formed by vacuum evaporation, electron beam evaporation, sputtering, or the like. In addition, care must be taken so that the formed metal thin film does not become a resistance component for the output of the solar cell, and the sheet resistance value of the lower electrode 902 is preferably 50.
It is desirable to be Ω or less, more preferably 10 Ω or less.

A diffusion prevention layer (not shown) such as conductive zinc oxide may be provided between the lower electrode 902 and the n-type semiconductor layer 903. As an effect of the diffusion prevention layer, not only the metal element forming the lower electrode 902 is prevented from diffusing into the n-type semiconductor layer 903, but also a slight resistance value is provided, so that each of the semiconductor layers 903 to 905. Lower electrode 902 and transparent electrode 906 due to defects such as pinholes generated in
It is possible to prevent a short circuit between the light source and the light source, and to cause multiple interference by the thin film to trap the incident light in the solar cell.

(Ii) Transparent Electrode 906 The transparent electrode 906 has a light transmittance of 85% or more in order to efficiently absorb the light from the sun or the white fluorescent lamp into each of the semiconductor layers 903 to 905. It is desirable that the sheet resistance value is 100Ω or less so that it does not electrically become a resistance component to the output of the solar cell. As a material having such characteristics, SnO ₂ ,
In ₂ O ₃ , ZnO, CdO, Cd ₂ SnO ₄ , ITO (In ₂ O
₃ + SnO ₂₎ and metal oxides such as, Au, Al, a metal thin film extremely thin deposited semitransparent a metal such as Cu and the like. The transparent electrode is laminated on the p-type semiconductor layer 905 in the solar cells shown in FIGS. 9 (a), (c), and (d), and on the substrate 901 in the solar cell shown in FIG. 9 (b). Since they are laminated, it is necessary to select those that have good mutual adhesion. As a method for manufacturing the transparent electrode 906, a resistance heating vapor deposition method, an electron beam heating vapor deposition method, a sputtering method, a spray method, or the like can be used, and is appropriately selected as desired.

(Iii) Collecting Electrode 907 The collecting electrode 907 is provided on the transparent electrode 906 in a grid pattern for the purpose of effectively reducing the surface resistance value of the transparent electrode 906. The material of the collector electrode 907 is Ag, C
Examples thereof include thin films of metals such as r, Ni, Al, Ag, Au, Ti, Pt, Cu, Mo and W or alloys thereof. These thin films can be laminated and used. The shape and area of the semiconductor layers 903 to 905 are appropriately designed so that a sufficient amount of light can be ensured.

For example, it is desirable that the shape is uniformly spread over the light receiving surface of the solar cell, and the area is preferably 15% or less, more preferably 10% or less with respect to the light receiving area. The sheet resistance value is preferably 50Ω or less, more preferably 10Ω or less.

Next, the n-type semiconductor layer 903, the i-type semiconductor layer 904, and the p-type semiconductor layer 905 will be described.

(I) i-Type Semiconductor Layer 904 The semiconductor material forming the i-type semiconductor layer 904 is a
-Si: H, a-Si: F, a-Si: H: F, a-SiC:
H, a-SiC: F, a-SiC: H: F, a-SiGe: H,
a-SiGe: F, a-SiGe: H: F, poly-Si: H, p
Examples thereof include group IV semiconductor materials such as oly-Si: F, poly-Si: H: F, and group IV alloy-based semiconductor materials. other than this,
Examples thereof include II-VI group compound semiconductor materials and III-V group compound semiconductor materials.

In the i-type semiconductor layer 904, the composition is changed in the film thickness direction so that the band gap is changed for the purpose of improving the photoelectric conversion efficiency and the like. FIGS. 10A to 10D show specific examples of how the bandgap in the i-type semiconductor layer 904 changes (bandgap profile). The symbol → in the figure represents the incident side of light.

The bandgap profile shown in FIG.
The file has a band gap in the i-type semiconductor layer 904.
It's a constant amount. Bandugi shown in Fig. 10 (b)
The cap profile is the incidence of light on the i-type semiconductor layer 904.
Side band gap is narrow, and band gap is gradually widening
It is of the type that is rugged. This is the shape of the bandgap
By doing so, fill factor (FF)
Is effective in improving. The band gap shown in FIG.
The profile has a wide bandgap on the light incident side.
It is a type that the band gap gradually narrows.
Open circuit voltage (V _oc) Is effective in improving. Figure 10 (d)
The bandgap profile shown in Fig.
Wide band gap, relatively steep band gap
It is a type that narrows and then expands again.
To obtain the effects of both by combining (b) and (c)
Is something that can be done. The band gap changes like this
In order to have
Yes. For example, a-Si: H (E_g ^opt= 1.72 eV) and a
-SiGe: H (E_g ^opt= 1.45 eV)
And the bandgap profile shown in FIG.
The i-type semiconductor layer 904 can be manufactured. Also,
a-SiC: H (E_g ^opt= 2.05 eV) and a-Si: H
(E_g ^opt= 1.72 eV) and shown in Fig. 10 (c).
I-type semiconductor layer 904 having bandgap profile
Can be manufactured.

Further, the Fermi level of the i-type semiconductor layer 904 is changed by changing the concentration of the impurity added to the i-type semiconductor layer 904 in the film thickness direction, while keeping the conductivity type as the i-type. be able to. A specific example of the Fermi level change state (Fermi level profile) in the i-type semiconductor layer 904 whose bandgap profile is that shown in FIG. 10A (that is, the bandgap does not change) is shown in FIG. 11A. ~ (D). The symbol → in the figure represents the incident side of light.

FIG. 11A shows the Fermi level profile of the i-type semiconductor layer 904 without the addition of impurities. On the other hand, the one shown in FIG. 11 (b) is of a type in which the Fermi level on the light incident side is closer to the valence band and the Fermi level is gradually closer to the conduction band. It is effective in preventing the above and improving the traveling property of the carrier. FIG. 11C shows a type in which the Fermi level gradually approaches the valence band from the light incident side, and when the n-type semiconductor layer is provided on the light incident side, FIG.
The same effect as in the case of 1 (b) is obtained. The type shown in FIG. 11 (d) is of a type in which the Fermi level changes from the valence band to the conduction band almost continuously from the light incident side.
Although these exemplify the case where the bandgap is constant, the Fermi level can be similarly controlled in the case of the bandgap profile shown in FIGS. 10B to 10D.

By appropriately designing the bandgap profile and the Fermi level profile, a solar cell with high photoelectric conversion efficiency can be manufactured. Especially, the control of these band gap profile and Fermi level profile is shown in FIG. 9 (c), (d).
It is preferably applied to the i-type semiconductor layer 904 of the so-called tandem type or triple type solar cell shown in FIG.

(Ii) p-type semiconductor layer 905 and n-type semiconductor layer 903 For the p-type semiconductor layer 905 or the n-type semiconductor layer 903, a valence electron control agent is publicly known as a semiconductor material forming the above-mentioned i-type semiconductor layer 904. It is obtained by doping with the method of.

[0081]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of a microwave plasma CVD apparatus used for carrying out the deposited film forming method in this embodiment.

In FIG. 1, slit-shaped openings 304,
Three film forming containers 301 connected in series via 305
Each of to 303 has a vacuum airtight structure. Each of the slit-shaped openings 304, 305 has a film deposition container 301-
Gate gas introducing means (not shown) for injecting an inert gas are provided in order to suppress mixing of the raw material gases between the 303. Slit-shaped openings 304, 305
Specific examples of the gas gate include those described in US Patent Application No. 204,493. Each of these film forming containers 301 to 303 and slit-shaped openings 304, 3
A long strip-shaped substrate 306 is arranged so as to penetrate 05. The substrate 306 is capable of being continuously conveyed in the longitudinal direction, is fed from a grounded feed roller 307 provided in the feed chamber 324, and is taken up by a take-up roller 308 provided in a take-up chamber 325. It is designed to be wound up. Sending room 324 and winding room 3
25 communicates with exhaust devices 326 and 327, respectively.

The film forming containers 301 to 303 are respectively
Exhaust devices 321 to 323 via exhaust ports 318 to 320
Is in communication with. Further, in each of the film forming containers 301 to 303, a lamp heater 309 to heat the substrate 306 is formed.
311 and dielectric windows 315 to 317 are provided. Each of the dielectric windows 315 to 317 is formed of a material capable of efficiently transmitting microwave power into the film forming container and maintaining vacuum tightness, such as quartz glass or alumina ceramics. A waveguide (not shown), which is a microwave transmission path and is mainly made of metal, is connected to the outside of the film forming container of the dielectric windows 315 to 317, and a microwave is transmitted via a matching isolator (not shown). It is connected to a power source (not shown). Further, two film forming containers 301 on the left and right in the figure,
303 is provided with source gas supply pipes 312 and 313,
A bias voltage applying rod 314 for applying a bias voltage also functions as a source gas supply pipe in the film forming container 302 at the center of the drawing.
Is provided.

Film forming containers 301 to 303 connected in series
In the center of the film forming container 302, electrodes for bias application 328, 3 connected to a DC bias power source (not shown) are provided.
29 are provided. FIG. 2 is a schematic view showing an enlarged main part of the film forming container 302. The connection between the film forming container 302 and the gas gates 304, 305 is a right-angled ridge longer than the width of the substrate 306. The insulators 330, 331 having an inverted L-shaped cross section are attached to the ridge. The electrodes 328 and 329 are attached to the insulators 330 and 331. The insulators 330 and 331 extend in the width direction of the substrate 306 so as to cover the respective ridges, so that the electrodes 328 and 329 extend in the width direction of the substrate 306 and are close to the substrate 306. At this time, the electrodes 328, 3
29 and the side wall at the end of the film forming container 302 has a distance of about 2
It is 0 mm or less. The bias voltage applying rod 314 in the film forming container 302 has a through hole T
It is composed of a hollow hollow tube.

The deposition film formation by this microwave plasma CVD apparatus is performed as follows. That is, the film forming container 301 is respectively controlled by the exhaust devices 321 to 323.
The inside of ~ 303 is evacuated and adjusted to a desired pressure. Next, the lamp heaters 309 to 311 are energized to heat and maintain the temperature of the substrate 306 at a temperature suitable for film deposition. At this time, the substrate 306 is transferred from the delivery roller 307 to the take-up roller 3
No. 08 is conveyed at a suitable speed. For example, in the case of forming a photovoltaic element having a pin structure via the source gas supply pipes 312 and 313 and the bias voltage applying rod 314 also serving as the source gas supply pipe, silane (SiH
₄ ) A mixed gas of gas and diborane (B ₂ H ₆ ) gas, a mixed gas of silane gas, a mixed gas of silane gas and phosphine (PH ₃ ) gas, and the like are introduced into the film formation containers 301 to 303.
Regarding the center film forming container 302 (in the case of manufacturing a photovoltaic device having a pin structure, a film forming container for forming an i-type semiconductor layer), the bias applying rod 314 and each electrode 3 are used.
Appropriate DC bias is applied to each of 28 and 329. In this case, the potentials of the bias applied to the electrodes 328 and 329 are equal, but they may be different from each other. Further, a microwave power source (not shown) is simultaneously operated in parallel to generate a microwave having a frequency of 500 MHz or more, preferably 2.45 GHz, and the microwave is passed through a waveguide (not shown) to the dielectric window 315.
To 317 and introduced into the film forming containers 301 to 303, respectively. Thus, the source gas in the film forming containers 301 to 303 is excited and dissociated by the energy of microwaves,
A p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer are sequentially deposited on the surface of the substrate 306.

In this apparatus, it is possible to apply a suitable bias voltage near the end of the film forming space, so that the substrate 306 that is continuously transported is in the vicinity of the inlet to the outlet of the film forming container 302. Thus, it is possible to form a deposited film having good characteristics. Pin as above
When manufacturing a photovoltaic element having a structure, the characteristics of the i-type semiconductor layer are improved, and a photovoltaic element having excellent characteristics can be manufactured. Further, the electrodes 328, 32
Due to the shielding effect of No. 9, mutual diffusion of charged particles between adjacent film forming containers is suppressed, and a better deposited film can be obtained.

Next, the experiments carried out in this embodiment will be described with specific numerical values.

Experimental Example 1 The deposited film forming apparatus shown in FIG.
Using the pin structure of the layer structure shown in FIG. 9 (a).
Morphos silicon solar cells were made continuously. substrate
For 901, a strip-shaped substrate made of SUS430BA is used.
The lower electrode 902 is made of aluminum and chromium.
A layer structure was used. The n-type semiconductor layer 903 is an n-type semiconductor layer.
The i-type semiconductor layer 90 is a rufus silicon (n-Si) layer.
4 is an i-type amorphous silicon (a-Si) layer, which is p-type
The semiconductor layer 905 is p-type microcrystalline silicon (p-type μx-S
i) each layer. In addition, as the transparent electrode 906
ITO (In₂O₃+ SnO ₂) Use a membrane to collect current
Aluminum was used for the pole 907.

First, a strip-shaped substrate made of stainless steel (substrate 9
01) was thoroughly washed and degreased, and then Al and Cr were continuously vapor-deposited using a continuous vacuum vapor deposition device (not shown) to form a lower electrode 902. The strip-shaped substrate on which the lower electrode 902 is formed is mounted on the apparatus shown in FIG. 1 so that the surface on which the lower electrode 902 is formed faces downward in the figure, and the n-type semiconductor is formed under the film forming conditions shown in Table 1. Layer 903 (n-Si layer; film thickness 300)
Å), i-type semiconductor layer 904 (i-Si layer; film thickness 4000)
Å), p-type semiconductor layer 905 (p-type μx-Si layer; film thickness 1
The deposited films were successively laminated in the order of 00Å). At this time, in the film forming container 302 for forming the i-type semiconductor layer 904, a DC bias of 80 V was applied to the bias voltage applying rod 314. The DC bias voltage applied to each of the electrodes 328 and 329 was changed from 0V to 50V in steps of 10V, and a solar cell was prepared for each DC bias condition. Note that the film formation containers 301 and 303 corresponding to the n-type semiconductor layer 903 and the p-type semiconductor layer 905, respectively.
Then, the DC bias voltage is not applied. n-type semiconductor layer 903, i-type semiconductor layer 904, p-type semiconductor layer 9
The film deposition rates of 05 are 20Å / s and 100Å / s, respectively.
s, 6Å / s, which was independent of the value of the DC bias applied to the electrodes 328 and 329.

[0090]

[Table 1]

Then, IT is formed on the p-type semiconductor layer 905.
An O film was vapor-deposited to form a transparent electrode 906, Al was vapor-deposited to form a collector electrode 907, and a resin was applied as a surface protective layer (not shown) to complete a solar cell. The thus obtained solar cell has an AM value of 1.5.
100mW / cm ² from the solar simulator
Then, the photoelectric conversion efficiency was obtained by irradiating the artificial sunlight. Figure 3
4 is a graph showing the relationship between the value of the DC bias for the electrodes 328 and 329 in the film forming container 302 for forming the i-type semiconductor layer 904 and the photoelectric conversion efficiency.

From these results, the photoelectric conversion efficiency was improved when the DC bias was applied from the electrodes 328 and 329 installed at the end of the film forming container 302, compared with the case where the DC bias was not applied. This is because the electric field, which was lacking in the substrate 306 near the edge of the film forming container 302, was compensated for, and cations collided with the surface of the substrate 306 in that part, and the annealing effect increased, and at the interface of the deposited film. It is considered that the film quality was improved. This effect reaches almost the maximum when the DC bias is 20V,
Although it decreased to 40 V, the photoelectric conversion efficiency was higher than that when no DC bias was applied. This is considered to be because the collision of cations with the substrate becomes excessive, and the influence of deterioration due to structural destruction such as the generation of dangling bonds in the film due to collision cannot be ignored. 40V
Sparks occur frequently when a DC bias that exceeds the
The discharge was not stable.

Further, each of the film forming containers 301 to 301 during the formation of the deposited film.
The impurity concentration in 303 is determined by the photoionization mass spectrometer (ULV
ACQ, MSQ-400 type). When the DC bias was not applied to the electrodes 328 and 329 of the film forming container 302, the source gas mixed from other film forming containers was detected in the order of 10 ² ppm, while the DC bias was 10 V or more. When applied, the concentration of the source gas mixed from another film forming container was on the order of 10 ppm. From this, it was confirmed that the application of the DC bias to the electrodes 328 and 329 can suppress the mixture of the raw material gas between the film forming containers.

(Experimental Example 2) The thickness of the i-type semiconductor layer 904 is set to 3
000Å i-type amorphous SiC (i-SiC) layer, and p-type semiconductor layer 905 having a film thickness of 100Å i-type microcrystal S
Experimental Example 1 except that the iC (p-type μx-SiC) layer was used
A solar cell was prepared in the same manner as in. The film forming conditions at the time of formation are as shown in Table 2, and the i-type semiconductor layer 904
In the film deposition container 302 corresponding to
DC bias voltage applied to 29 from 0V to 50V 1
The same applies to the case where the solar cell was prepared by changing the voltage in steps of 0V.

As a result, the film forming rates of the n-type semiconductor layer 903, the i-type semiconductor layer 904, and the p-type semiconductor layer 905 are 13Å / s, 75Å / s, and 4Å / s, respectively, and the electrode 12
It was independent of the value of the DC bias applied to 8,129. In addition, when the photoelectric conversion efficiency of the solar cell produced in the same manner as in Experimental Example 1 was measured, it was found that applying a DC bias to the electrodes 328 and 329 compared to the case where it was not applied,
The photoelectric conversion efficiency was high. The relationship between the value of the DC bias and the photoelectric conversion efficiency is the same as in Experimental Example 1, and the value of 20
The photoelectric conversion efficiency became maximum at V, and the photoelectric conversion efficiency gradually decreased toward 40V.

[0096]

[Table 2]

Furthermore, an AM value of 1.5 and an energy density of 1
When photoelectric conversion efficiency was measured after irradiating simulated sunlight of 00 mW / cm ² for 500 hours continuously, the change was within 9% compared to the initial value (value before irradiating simulated sunlight). The effect of the DC bias value on the rate was not observed.

(Experimental Example 3) In the deposited film forming apparatus shown in FIG. 1, three film forming containers 301 to 303 are provided in series between the unwinding chamber 324 and the winding chamber 325.
A tandem solar cell shown in FIG. 9 (c) is produced by using a deposited film forming apparatus (a total of 6 film forming containers) in which the three film forming containers 301 to 303 are repeatedly provided. did.

As the substrate 901, a strip-shaped base material made of stainless steel was used, and as the lower electrode 502, one having two layers of an aluminum extraction electrode and a silver reflection layer was used. First p
In the in-junction 911, n is formed as the n-type semiconductor layer 903.
Type amorphous silicon (n-Si) layer is used, an i type amorphous silicon germanium (i-SiGe) layer is used as the i type semiconductor layer 904, and a p type semiconductor layer 905 is used.
A p-type microcrystalline silicon (p-type μx-Si) layer was used as. In the second pin junction 912, an n-type amorphous silicon (n-Si) layer is used as the n-type semiconductor layer 903, an i-type amorphous silicon (i-Si) layer is used as the i-type semiconductor layer 904, and a p-type semiconductor A p-type microcrystalline silicon (p-type μx-Si) layer was used as the layer 905.

The film forming conditions for each layer are as shown in Table 3, and a solar cell was prepared by the same procedure as in Experimental Example 1. The film formation container used for depositing the i-type semiconductor layer 904 in the first and second pin bonds 911 and 912 is the same as the film formation container 302 in Experimental Example 1, and a DC bias voltage is applied during film formation. I decided to do it. The i-type semiconductor layer 903 (i-Si) on the second pin junction 912 side
For the layer), from the results of Experimental Example 1, the DC bias applied to the bias applying rod 314 was set to 80 V, and each electrode 3
The DC bias voltage applied to 28,329 was set to 20V. The i-type semiconductor layer 904 on the first pin junction 911 side
For the (i-SiGe layer), a bias applying rod 314
The DC bias applied to the electrodes is set to 90V, and the electrodes 328, 32
DC bias applied to 9 from 0V to 50V 10V
Solar cells were created by changing the intervals.

[0101]

[Table 3]

As a result, regarding the first pin junction 911, the film forming rates of the n-type semiconductor layer 903, the i-type semiconductor layer 904, and the p-type semiconductor layer 905 are 13 Å / s and 75, respectively.
Å / s, 4Å / s, and with respect to the second pin junction 912, the film forming rates of the n-type semiconductor layer 903, the i-type semiconductor layer 904, and the p-type semiconductor layer 905 are 11 Å / s and 1, respectively.
25Å / s, 4Å / s, all electrodes 328,3
It was independent of the value of the DC bias applied to 29.
Further, when the photoelectric conversion efficiency was measured in the same manner as in Experimental Example 1, the i-type semiconductor layer 904 on the first pin junction side 911 was measured.
Electrodes 328 and 329 for depositing (i-SiGe layer)
The photoelectric conversion efficiency was improved in the case where the DC bias was applied to the case as compared with the case where the DC bias was not applied. Regarding the relationship between the value of the DC bias and the photoelectric conversion efficiency, Experimental Examples 1 and 2
The same tendency was observed.

Further, the AM value is 1.5 and the energy density is 1
When photoelectric conversion efficiency was measured after irradiating simulated sunlight of 00 mW / cm ² for 500 hours continuously, the change was within 9% compared to the initial value (value before irradiating simulated sunlight). The effect of the DC bias value on the rate was not observed.

[0104]

As described above, according to the present invention, by providing one or more of the plurality of bias voltage applying means at a position within 50 mm from the slit-shaped opening, the bias electric field at the end of the film forming container is reduced. The strength is improved, and the characteristics of the deposited film formed are improved.

[Brief description of drawings]

FIG. 1 is a microwave plasma CV according to an embodiment of the present invention.
It is a figure which shows the structure of D apparatus.

FIG. 2 is a perspective schematic view showing an enlarged main part of a film forming container.

FIG. 3 is a characteristic diagram showing a relationship between bias voltage and photoelectric conversion efficiency.

FIG. 4 is a schematic cross-sectional view showing the configuration of a conventional microwave plasma CVD apparatus.

FIG. 5 is a schematic cross-sectional view showing the structure of a conventional moving film forming type microwave plasma CVD apparatus.

FIG. 6 is a schematic diagram showing how a bias electric field is applied in a conventional microwave plasma CVD apparatus.

FIG. 7 is a schematic cross-sectional view showing the configuration of an experimental device used to study the installation position of bias applying means.

FIG. 8 is a characteristic diagram showing the relationship between the distance from the end of the film forming container and dark conductivity.

9 (a) to 9 (d) are schematic cross-sectional views each showing a configuration of a solar cell.

10A to 10D are diagrams showing bandgap profiles of an i-type semiconductor layer.

11A to 11D are diagrams showing Fermi level profiles of an i-type semiconductor layer.

[Explanation of symbols]

301-303 film forming container 306 substrate 312,313 Raw material gas supply pipe 314 Bias voltage applying rod 315-317 Dielectric window 328,329 electrodes 330,331 insulator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasushi Fujioka             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Akira Sakai             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Naoshi Yoshizato             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Yu Echizen             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation (72) Inventor Shuichiro Sugiyama             3-30-2 Shimomaruko, Ota-ku, Tokyo             Non non corporation F-term (reference) 4K030 AA06 AA07 AA08 BA30 CA02                       CA17 FA01 JA03 KA20 LA13                       LA16                 5F045 AA09 AB04 AC01 AC19 AD07                       AE17 AF10 BB01 BB16 CA13                       DA52 DA65 DP22 DQ15 EH03                       EH04 EH20                 5F051 AA04 AA05 BA12 BA14 CA02                       CA03 CA04 CA17 CA22 CA23                       DA04 FA04 FA06 GA02

Claims (2)

[Claims] 1. A film-forming container capable of being evacuated, a substrate transfer means for continuously passing a substrate into the film-forming container, and a side wall of the film-forming container for passing the substrate. Using a deposition film forming apparatus having a slit-shaped opening, a microwave introducing unit for introducing microwaves into the film forming container, and a plurality of bias voltage applying units attached to the film forming container. Wave plasma CV
In the deposited film forming method for forming a deposited film on the substrate by the D method, at least one of the bias voltage applying means is provided at a position within 50 mm from the slit-shaped opening. Method. 2. A film-forming container capable of being evacuated, a substrate transfer means for continuously passing the substrate into the film-forming container, and a side wall of the film-forming container for passing the substrate. A slit-shaped opening, a microwave introducing unit for introducing microwaves into the film forming container, and a plurality of bias voltage applying units attached to the film forming container, and the microwave plasma CVD method is used to A deposited film forming apparatus for forming a deposited film on a substrate, wherein at least one of the bias voltage applying means is provided at a position within 50 mm from the slit-shaped opening. .