JPH05234918A - Deposition film forming method using microwave plasma cvd method and roll-to-roll method - Google Patents

Abstract

PURPOSE:To form an ideal junction surface, by continuously changing the concentration of either one element out of a plurality of elements in a film forming space, and making the concentration have an extremal value at a specified portion in the film forming space. CONSTITUTION:The arrangement of holes formed in the bottom part of a film forming space is characteristic. When an alpha-SiGe film which has the smallest band gap, i.e., the highest Ge content, in the vicinity of a gas discharging vent is to be obtained, exhaust vents are concentrically arranged at the portion corresponding to said film. From gas discharging vents 112a-112d, SiH4 gas and GeH4 gas are made to flow while the flow rates are suitably adjusted, and microwave is introduced into all applicators 110a-110d. When a film is deposited in the above state, the Ge content in the film forming space is made zero, and a film whose band gap is indentical to that of a-Si can be formed. Thereby an ideal junction surface can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generates a uniform microwave plasma over a large area, and decomposes and excites a raw material gas by a reaction caused by the microwave plasma, thereby continuously forming a large area functional deposited film. To the method of forming.

More specifically, it is a method of forming a large-area photovoltaic element using an amorphous semiconductor, and in particular, an amorphous silicon-germanium (hereinafter referred to as amorphous silicon-germanium containing at least hydrogen) forming a stacked photovoltaic element. a-SiGe) film and an amorphous silicon carbide (hereinafter abbreviated as a-Sic) film containing at least hydrogen are ideally controlled in the respective ratios of the above elements to improve the photovoltaic device. On how to do.

[0003]

2. Description of the Related Art In recent years, the demand for electric power has rapidly increased all over the world, and the problem of environmental pollution has become more serious as electric power production has been activated to meet such demand.

[0004] Incidentally, in nuclear power generation, which is expected as a power generation method to replace thermal power generation and has already entered a practical period, serious radioactive contamination damages the human body as typified by the Chernobyl nuclear power plant accident. In addition, there is a situation in which the natural environment is invaded and the spread of nuclear power generation is threatened in the future, and even countries that have stipulated laws that actually prohibit the construction of new nuclear power plants have come out.

Further, even in the case of thermal power generation, the amount of fossil fuels typified by coal and oil continues to increase in order to meet the increasing power demand, and the amount of carbon dioxide emitted increases accordingly. By increasing the concentration of greenhouse gases such as carbon dioxide in the atmosphere and inducing global warming, the annual average temperature of the earth is steadily increasing.
(International Energy Age
ncy) will reduce carbon dioxide emissions by 2005 to 2
It is recommended to reduce by 0%.

Against this background, population growth in developing countries and accompanying increase in power demand are inevitable, and per capita power consumption due to further promotion of electronic lifestyles in developed countries. Coupled with the increase in power supply, the problem of electricity supply has become a situation that must be considered globally.

Under such circumstances, the power generation system using a solar cell utilizing sunlight does not cause the above-mentioned problems such as radioactive contamination and global warming, and the sunlight spreads all over the earth. Since there is little uneven distribution of energy sources, it is possible to obtain relatively high power generation efficiency without the need for complicated and large-scale equipment. Has attracted attention as a clean power generation method that can be applied without any effort, and various research and development are being made toward its practical application.

By the way, regarding a power generation method using a solar cell, in order to establish it as a method for supplying power demand, the solar cell to be used must have a sufficiently high photoelectric conversion efficiency and excellent characteristic stability. It is basically required to be available and capable of mass production.

Incidentally, the electric power required in a general household is about 3 kW per household. On the other hand, if the energy of the sun is 1 KW / m ² at the peak and the photoelectric conversion efficiency of the solar cell is, for example, about 10%, the area of the solar cell is 3 to cover the required power.
It will be about 0 m ² . And, for example, in order to supply the necessary power for 100,000 households, 3,000,000 m ²
A solar cell with such an area is required.

For this reason, an easily available gaseous raw material gas such as silane is used, and this is subjected to glow discharge decomposition to form amorphous silicon (hereinafter referred to as “a” on a relatively inexpensive substrate such as glass or a metal sheet). -Si ")
A solar cell that can be produced by depositing a semiconductor thin film such as is highly producible, and has attracted attention as a possibility that it can be produced at a lower cost than a solar cell that is produced using single crystal silicon or the like. Various proposals have been made regarding the basic layer structure, manufacturing method, and the like.

Looking at the conventional basic layer structure of such a photovoltaic element, the output voltage is low because the band gap of the a-Si film is about 1.7 ev, which is not sufficiently large, and Particularly, for a light source such as a fluorescent lamp having a large proportion of short wavelength light, there is a problem that sufficient photoelectric conversion efficiency cannot be obtained. Therefore, application to consumer equipment is limited to equipment with extremely low power consumption. Further, the a-Si film has a so-called Staebler-Wr photoelectric property that deteriorates when it is continuously irradiated with strong light.
In many cases, it has a property called the onski effect. For these reasons, the above-mentioned photovoltaic element is not practical for use as a solar cell for electric power that is required to maintain stable characteristics for a long period of time.

By the way, particularly in the design of a solar cell for electric power using a photovoltaic element, it is important to effectively photoelectrically convert sunlight, and especially sunlight having a broad spectrum distribution is used as much as possible. It is important to have a layer structure capable of photoelectrically changing in a wide wavelength range.

For example, when a photovoltaic element is formed of a semiconductor material having a small energy band gap, the wavelength range of light absorbed by the film spreads over a wide range from the short wavelength side to the long wavelength side. The amount of energy that is photoelectrically converted and extracted is determined by the energy band gap of the semiconductor material used, so long-wavelength components effectively contribute to photoelectric conversion, but the energy of short-wavelength light components is not effectively used for photoelectric conversion. ..

When the photovoltaic element is made of a semiconductor material having a large energy band gap,
The wavelength component of sunlight that is absorbed by the film and contributes to photoelectric conversion is a short-wavelength light component having an energy equal to or more than the energy band gap of the semiconductor material used, and the long-wavelength light component is not photoelectrically converted.

In any case, the maximum voltage taken out to the outside as a photovoltaic element, that is, the open end voltage (Voc)
Is determined by the value of the energy bandgap of the semiconductor material to be joined, and a semiconductor material having a large bandgap is effective for obtaining a high Voc.

However, even if an attempt is made to form a photovoltaic element by using only one semiconductor material so as to perform desired photoelectric conversion as a solar cell, the photoelectric conversion efficiency is naturally limited.

Taking these points into consideration, a plurality of photovoltaic elements are stacked by using a plurality of semiconductor materials having different energy band gaps, and are formed of semiconductor materials having different energy band gaps. There is a proposal of a method of improving the photoelectric conversion efficiency of sunlight by dividing the wavelength region to be photoelectrically converted by the photovoltaic element.

The layer structure of the proposed solar cell has a so-called electrically series structure in which a plurality of photovoltaic elements are laminated. The conversion efficiency cannot be obtained.

FIG. 16 is a schematic view showing an example of such a laminated solar cell.

In FIG. 16, reference numeral 1601 denotes a conductive substrate, 1
Reference numeral 602 denotes a lower photovoltaic element (hereinafter abbreviated as “bottom cell”), which specifically uses a-SiGe as a material. Reference numerals 1602a to 1602c are layers constituting a bottom cell, and are n-type a-Si and i-type a-SiG.
e, p-type microcrystal (μC) -Si layer. Reference numeral 1603 denotes an upper photovoltaic element (hereinafter abbreviated as “top cell”), which specifically uses a-Si as a material. 1603
Reference numerals a to 1603c are layers constituting the top cell, and are n-type a-Si, i-type a-Si, and p-type μC-Si layers. 1604 is a transparent electrode, specifically, ITO,
It consists of materials such as IO. 1605 is a collector electrode. In FIG. 16, light enters from the top and the a-S of the top cell
Photocarriers are generated by being absorbed by the i layer and the a-SiGe layer of the bottom cell, and photoelectric conversion is performed.

By the way, the photocarriers generated in the a-Si and a-SiGe films, specifically the electrons of the electron-hole pairs, have high mobility and travel relatively easily in all layers to generate photoelectrons. Although holes can contribute to electric power, holes have low mobility, and for example, carriers generated in the a-SiGe layer cannot be traversed in the a-SiGe layer and are trapped in the film. As a result, there is a problem that the electromotive force cannot be effectively extracted. Against such a situation, a-
Improvements using hydrogen dilution method, three-electrode method, etc. have been tried in order to improve the quality of the SiGe film and further improve the running property of holes.
A certain amount of results are coming out. However, when it is limited to the a-SiGe film, it is still difficult to say that a material having a sufficient hole traveling property was obtained despite various attempts.

Therefore, a method recently proposed as a means for improving the traveling property of holes in the a-SiGe layer is as follows.
There is a method of continuously changing the optical band gap of an a-SiGe layer (hereinafter abbreviated as a graded band gap method). In FIG. 17A, the energy band of an a-SiGe film formed by the graded band gap method is shown. The schematic diagram showing an example is shown.

In FIG. 17A, light enters from the left side. 1701 is the energy level of the conduction band (Ec), and 1702 is the energy level of the valence band (Ev). In FIG. 17A, the band gap (Ec-E) is changed by continuously changing the content rates of Si and Ge.
A large area and a small area of v) can be created.
As a result, a stronger internal electric field is created on the light incident side. The reason why the narrow bandgap portion is closer to the p-layer side is that light is incident from the p-layer side, so that more carriers are generated on the p-layer side, and holes among the generated carriers are p-layers. Because it moves to the side.

In FIG. 17A, the holes can run through the a-SiGe film by being assisted by the strong internal electric field, but there is no energy change portion shown in FIG. 17B. In the conventional a-SiGe film, holes cannot travel and remain in the a-SiGe film, which does not contribute to electromotive force.

Also, the graded band gap a-
It should be noted that the SiGe layer has a Ge content of about 0% at the p-layer side interface and the n-layer side interface, and has good energy matching with the p-layer and the n-layer. Forming a bond. By forming a good junction, the carrier injection efficiency is increased, and as a result, the solar cell efficiency is also improved.

As described above, the a-Si top cell having the structure shown in FIG. 16 and the graded band gap a
-SiGe bottom cells or a stacked photovoltaic element in which a middle cell is further added is currently under different study as a solar cell having good photovoltaic characteristics.

By the way, the research and development relating to the layer structure as described above or the improvement of the band profile of the graded band gap has not been carried out by the conventional badge type production apparatus, that is, without moving the substrate in one film forming space. The composition of the deposition gas was changed by changing the composition of the deposition gas, switching the layers, and continuously changing the composition when creating the graded band gap. Therefore, in the badge type, for example, a graded band gap a-Si
It should be noted that it was possible to drop the Ge content to 0 at the interfaces of the Ge layer on the p-layer side and the n-layer side relatively easily, and to form a good bond.

Next, let us turn to the mass production method of such photovoltaic elements.

As one of the efficient mass production methods for photovoltaic elements, when an amorphous silicon solar cell is manufactured,
A method has been proposed in which an independent film forming chamber for forming each semiconductor layer is provided and each semiconductor layer is formed in the film forming chamber.

Incidentally, US Pat. No. 4,400,409 discloses a roll-to-roll (Roll to R) method.
There is disclosed a continuous plasma CVD apparatus adopting the Oll system. According to this device, a plurality of glow discharge regions are provided, and a sufficiently long flexible substrate having a desired width is arranged along a path through which the substrates sequentially pass through the glow discharge regions. It is said that an element having a semiconductor junction can be continuously formed by continuously transporting the substrate in the longitudinal direction while depositing and forming a conductive type semiconductor layer required in the discharge region.
In this specification, a gas gate is used to prevent the dopant gas used when forming each semiconductor layer from diffusing and mixing into other glow discharge regions. Specifically, a means for separating each glow discharge region from each other by a slit-shaped separation passage and forming a flow of a scavenging gas such as Ar or H _{2 in the} separation passage is adopted. .. From this, it can be said that the roll-to-roll method is suitable for mass production of semiconductor devices.

However, the formation of each semiconductor layer is performed by R
When the plasma CVD method using F (radio frequency) is used, there is a limit to the improvement of the film deposition rate while maintaining the characteristics of the continuously formed film. That is, for example, even when a semiconductor layer having a film thickness of 5000 Å at most is formed, it is necessary to constantly generate a predetermined plasma over a large area and maintain the plasma uniformly. However, doing so requires considerable skill and it is difficult to generalize the various plasma control parameters involved.
Further, the decomposition efficiency and utilization efficiency of the film-forming source gas used are not high, which is one of the factors that raise the production cost.

On the other hand, what has recently attracted attention is a plasma process using microwaves. Since the microwave has a short frequency band, the energy density can be increased as compared with the case where the conventional RF is used, and it is suitable for efficiently generating and sustaining plasma.

For example, US Pat. Nos. 4,517,223 and 4,504,518, deposit thin films on a small area substrate in a microwave glow discharge plasma under low pressure. Although a method of forming is disclosed, this method prevents polymerization of active species that causes deterioration of film characteristics due to the process under low pressure, and not only a high quality deposited film can be obtained. It is said that the generation of powder such as polysilane in plasma can be suppressed and the deposition rate can be dramatically improved. However, there is no specific disclosure for forming a uniform deposited film over a large area.

On the other hand, in US Pat. No. 4,729,341, a photoconductive semiconductor thin film is deposited on a large-area cylindrical substrate by a high power process using a pair of radiation waveguide applicators. Although a low-pressure microwave plasma CVD method and an apparatus for forming the same are disclosed, the large-area substrate is limited to a cylindrical substrate, that is, a drum as a photoreceptor for electrophotography. It has not been applied to substrates.

In view of the above situation, the microwave plasma CVD method (hereinafter referred to as “μW”) which is said to be suitable for mass production.
-Abbreviated as "CVD method") and a roll-to-roll production method can be reasonably combined to provide a mass production method with a higher throughput.

Next, a roll-to-roll μW plasma CVD method (hereinafter referred to as “R-Rμ
Abbreviated as "WCVD method"), an example of producing an a-SiGe single-layer (single) cell solar cell using an a-SiGe layer as an i-layer (photoelectric conversion layer) will be given, and an outline of the method will be given. State.

The production apparatus by the R-RμWCVD method is such that at least an n-type a-Si layer, i-type, which forms a solar cell by continuously sending out a band-shaped substrate for forming an a-SiGe film from a bobbin wound in a roll shape. a-SiGe layer, p-type a-S
A plurality of layers including a layer including i layer is formed in a film forming chamber which is a separate reaction container, but a plurality of film forming is performed on a substrate while maintaining a reduced pressure in each film forming space. It enables the movement between chambers and prevents the gas supplied to each film forming chamber, which is a raw material such as n-type a-Si layer and p-type a-Si layer, from diffusing and mixing with each other. And a connecting member (generally referred to as “gas gate” or simply “gate”) having the function of

FIG. 15 shows a- by the R-RμWCVD method.
It is a schematic diagram which shows the manufacturing apparatus of semiconductor elements, such as a SiGe solar cell, and in FIG. 15, 1501 is a strip | belt-shaped base | substrate (henceforth abbreviated as a base | substrate) which deposits an a-Si film, and it is usually deformable electroconductivity. A member in which a conductive thin film or the like is coated on a substrate, for example, a thin plate of stainless steel, aluminum or the like or a non-conductive thin plate is used. The base 1501 is wound around a circular bobbin 1511, and the delivery chamber 151
It can be installed within 0. The substrate 1501 delivered from a bobbin installed in the delivery chamber 1510 is a gas gate (hereinafter simply referred to as “gate”) 1520, an n-type a.
-Si film forming chamber 1530, gate 1540, i-type a-Si
After passing through the Ge film forming chamber 1550, the gate 1560, the p-type a-Si film forming chamber 1570, and the gate 1580, the winding chamber 1
It is wound up by a winding bobbin 1591 installed in 590.

Reference numerals 1530a, 1550a, and 1570a denote applicators composed of dielectric windows for radiating microwaves to the discharge space, and are not passed through rectangular waveguides 1530b, 1550b, and 1570b installed in the dielectric windows in the vertical direction. Electric power is applied from the illustrated microwave power source, and glow discharge is generated in the discharge space in each film forming chamber. 1
Reference numerals 502a to 1506a are filled with a gas serving as a raw material for forming a deposited film, 1502a is SiH ₄ gas, and 15 is a gas.
03a is GeH ₄ gas, 1504a is H ₂ gas, 150
5a is filled with PH ₃ gas, and 1506a is filled with B ₂ H ₆ gas.

Open / close valves 1502b to 1502 are used for the respective gases.
It is led to the gas mixers 1530c, 1550c, 1570c through 06b and the pressure reducers 1502c-1506c. Gas mixers 1530c-1570c with desired flow rates,
And the raw material gas having the mixing ratio is the gas introduction line 153.
It jets out into each film formation chamber through 0d, 1550d, and 1570d. The gas introduced into the film formation chamber was an oil diffusion pump,
Exhaust devices 1510e, 1530e, 155 including mechanical booster pumps and rotary pumps
By 0e, 1570e, and 1590e, the pressure in each chamber is adjusted so that the pressure in each chamber is adjusted to a desired value, and the gas is exhausted and guided to an exhaust gas treatment device (not shown). Also, 1530f, 1
Reference numerals 550f and 1570f are substrate heating heaters, and power is supplied from power sources 1530g, 1550g and 1570g, respectively.

Reference numerals 1541 and 1561 are parts for adjusting the opening cross-sectional area of the gate, and narrow the gas passage to reduce mutual diffusion of gas between the film forming chambers. Further, a gas that does not adversely affect the film formation, for example, a gas such as H ₂ or He is supplied from the cylinder 1507a to the pressure reducer 1507b and the flow rate controller 15 through the gas inlets 1542 and 1562 at the gate.
07c and 1507d are supplied to further suppress the mutual diffusion of the source gases in each film forming chamber.

The substrate 1501 delivered from the delivery chamber 1510 advances in each film forming chamber one after another, and an n-type a-Si film, an i-type a-SiGe film, and a p-type a-Si film are formed on the surface thereof. Finally, the winding room 1590 is entered.

First, in the n-type a-Si film forming chamber 1530, the substrate 1501 is heated by the heater 1530f to a desired temperature. Further, gases such as SiH ₄ , H ₂ and PH _{3 which} are raw materials of the n-type a-Si film are mixed at an optimum flow rate by the gas mixer 1530c and introduced into the film forming chamber 1530. At the same time, microwave power is applied through the waveguide 1530b and the applicator 1530a to cause glow discharge in the film-forming space and n on the surface of the substrate 1501.
A type a-Si film is formed.

Next, the substrate advances through the gate 1540, where i
Enter the mold a-SiGe film forming chamber 1550. Deposition chamber 155
Within 0, SiH ₄ set to the optimum flow rate as described above,
Optimum power is given to GeH ₄ and H ₂ gas, and the n-type a-
A desired i-type a-SiGe film is formed on the Si film. Similarly, the base 1501 is the gate 1560, and p-type a-Si.
Bobbin 1 in winding chamber 1590 through film forming chamber 1570
It is wound up in 591. In this way, since the substrate is successively passed through the n-type, i-type, and p-type film forming chambers, extremely high throughput can be obtained in the roll-to-roll type production apparatus.

The method of manufacturing an a-SiGe solar cell using the R-RμWCVD type deposited film forming apparatus has been described above. In this example, a-SiGe has a single band gap.

When the solar cell having the a-SiGe layer having the graded band gap described above was attempted to be realized by the R-RμWCVD type production apparatus, there were the following problems.

FIG. 18 shows a process for forming an i layer, that is, an a-SiGe layer, when a solar cell having an a-SiGe film having a graded band gap as a photovoltaic layer is manufactured by using the R-RμWCVD method. It is the schematic diagram which took out and showed the film space. Since the film forming space for depositing the p-type a-Si layer and the n-type a-Si layer is exactly the same as that in the above-mentioned case, it is omitted here. In FIG. 18, reference numeral 1801 is a strip-shaped substrate. 1802 is a vacuum chamber for creating a reduced pressure state, and through an exhaust port 1804 provided at the bottom,
It is connected to an exhaust unit 1805 including a diffusion pump and the like. Reference numeral 1803 denotes a film forming space chamber, which is a substrate 180.
Together with 1 forms the film formation space.

1820 is a SiH ₄ gas line, 182
1 is a GeH ₄ gas line and 1822 is an H ₂ gas line. Each gas is mixed in the gas mixer 1814a, 1814.
b, 1814c, and 1814d, and the gas mixed in the gas mixers 1814a to 1814d at a desired gas flow rate and ratio is respectively gas pipes 1813a and 1813a.
Gas discharge ports 1812a, 1812b, 1812c, 1812d through 13b, 1813c, 1813d, respectively.
More released into the film formation space.

1810a, 1810b, 1810c, 1
Reference numeral 810d is an applicator having a dielectric window for introducing microwaves into the film formation space, and is connected to a waveguide 1811a, 1811b, 1811 from a microwave power source (not shown).
Microwaves are injected through the c and 1811d, microwave glow discharge plasma is excited in the film formation space, and the substrate 1
The desired a-SiGe layer is deposited on 801.

Here, a of the graded band cap
-To deposit the SiGe layer, gas mixer 1814a-
The mixing ratio of the SiH ₄ gas and GeH ₄ gas mixed in 1814d may be changed. Specifically, for example, 100 sccc of SiH ₄ gas is used in the gas mixer 1814a.
m (GeH ₄₀ %) Gas mixer 1814b with SiH ₄ gas 90 scc
m GeH ₄ gas 10 sccm (GeH ₄ 10%) SiH ₄ gas 50 sccc in gas mixer 1814c
m GeH ₄ gas 50 sccm (GeH ₄ 50%) SiH ₄ gas 100 sccc in gas mixer 1814d
By setting m (GeH ₄₀ %), the ratio of Ge in the film is the maximum in the vicinity of the gas outlet 1812c, and therefore the graded band gap a-Si having the minimum band gap is obtained.
A Ge layer is formed. The band gap profile of the a-SiGe layer at this time is shown in FIG.

In FIG. 19, Ec represents the energy level in the conduction band, and Ev represents the energy level in the valence band.
Further, Ec ′ represents the energy level of the conduction band in the case of the a-Si single film, and Ev ′ represents the energy level of the valence band at that time. That is, a-SiG manufactured in this example
It is shown that the e film does not expand to the band gap of the a-Si film at both the p-layer side interface and the n-layer side interface and contains a considerable amount of Ge. As a result, good energy matching cannot be obtained on both the p-layer side and the n-layer side, and the injection efficiency of photocarriers is reduced, resulting in a problem of reduced solar cell efficiency.

In order to avoid such problems, the ratio of GeH ₄ gas in the source gas is lowered, that is, a-SiGe.
A method of reducing the Ge content in the glass is considered. However, in this method, the band gaps on the p-layer side and the n-layer side are certainly expanded, and good junctions with the respective layers can be formed, and the carrier injection efficiency is increased, but the band gap is expanded on average. As a result, the amount of carriers generated is reduced, and as a result, excellent solar cell efficiency cannot be obtained.

As another method for avoiding the above-mentioned problems, there is a method of further extending the film forming space and providing a larger number of gas discharge ports. That is, in FIG. 18, the film forming chamber 1803 is further extended to the left and right, new gas release ports are provided at the extended left and right positions, respectively, and only SiH ₄ gas is flown from both gas release ports to remove the gas in the a-SiGe layer. This is a method of extending a region having a high Si content to the p-layer side and the n-layer side. But,
This method also has a drawback in that a large number of gas lines, gas outlets and gas mixers are required, and the cost required for constructing the device increases significantly.

To summarize the problems described above, conventionally, it is preferable to freely change the film composition with a badge type production apparatus to produce a graded band gap a-SiGe film having any profile. It was known, but R that changes the composition not in time but in position
It is difficult to form such an ideal graded bandgap a-SiGe film by the −RμWCVD method.

The above description is based on aS in the photovoltaic element.
Although the iGe film has been particularly taken up and explained, such a problem is not limited to this example. That is, as an example, even if it is limited to the production of a photovoltaic element, a-
Even when trying to continuously change the composition of an amorphous semiconductor compound having a high band cap such as SiC or a-SiN,
It is difficult to control the ideal composition at the aforementioned interface, and
There is a problem that it is impossible to ideally control the composition containing the doping agent in the vicinity of the interface by the roll-to-roll method.

[0056]

As described above, according to the present invention, an amorphous semiconductor compound such as a-SiGe, a-SiC, or the like, whose composition changes continuously by using the R-RμWCVD method, or When a device such as a photovoltaic device including a film in which the doping amount of a valence electron control agent into a semiconductor device continuously changes, is manufactured, by stacking with an end face of the device or a film of another kind. In some cases, composition control at an interface with another film can be realized as desired, an ideal bonding surface is formed, and a method for producing a device having excellent characteristics is provided.

A further object of the present invention is to provide a method capable of producing, for example, a photovoltaic device having the above-mentioned favorable characteristics in a large area in a large amount and at a low cost.

[0058]

According to the present invention for achieving the above object, the strip-shaped substrate is continuously moved in the longitudinal direction in a depressurized state, and the strip-shaped substrate is moved in the middle of the side wall of the film forming space. The film forming gas is introduced into the film forming space through the gas supply means while being made to be one, and at the same time, microwave energy is radiated into the film forming space by the microwave applicator means to generate microwaves. In a deposited film forming method using a microwave plasma CVD method and a roll-to-roll method in which a plasma is generated and a deposited film is continuously formed on the surface of the moving strip-shaped substrate, the deposited film is deposited on the strip-shaped substrate. The film is made of a plurality of elements, and the concentration of any of the plurality of elements continuously changes in the film formation space. In the particular location to have an extreme value at the point, the reaction pressure is characterized in that performing the film deposition three conditions are satisfied at or above to have an extremum in the film forming space.

[0059]

Operation: For example, i- of the graded band gap
A three-layer solar cell having an a-SiGe layer (paS)
(i / ia-SiGe / na-Si) is continuously produced in the form of a strip substrate by the method of the present invention, a-Si
The Ge content in the Ge layer is set to n-a-Si and p-a-Si.
It becomes possible to make it substantially 0 at the interface with. That is,
The band gap near the interface between the p-layer side and the n-layer side is a-Si.
Since it is possible to approach the film as close as possible, it is possible to form an ideal junction. As a result, a solar cell having excellent photovoltaic characteristics can be manufactured over a large area at low cost.

[0060]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described in detail below with reference to embodiments.

The inventor of the present invention has a discharge space for producing a graded band cap a-SiGe shown in FIG.
As a result of earnest research using the roll to roll production apparatus of No. 5, the following facts were found.

In the discharge space shown in FIG. 18, SiH ₄ 100% gas is used as a film forming gas, and a gas discharge port 1812a.
Equal amount of -1812d is discharged to the film formation space. Microwaves are applied only from the applicator 1810c to cause glow discharge, and microwave power is not applied to other applicators. In this state, a
The i-film was deposited. The solid line 2001 in FIG. 20 shows the result of examination of the film thickness distribution of the a-Si film thus deposited on the strip substrate along the longitudinal direction of the substrate.

In FIG. 20, 2011a and 2011
b, 2011c and 2011d are gas release holes 1812a, 1812b, 1812c and 1812 in FIG. 18, respectively.
The position corresponding to d is shown. As shown in this figure, the film thickness of the a-Si film shows a distribution close to a Gaussian shape with the maximum value at the position 2011c where microwave power is applied.

On the other hand, in exactly the same manner, GeH ₄ gas was introduced from all the gas discharge ports, and the applicator 18
The result of examining the film thickness distribution of amorphous germanium (hereinafter abbreviated as "a-Ge") deposited by applying microwave power only from 10c is shown by a broken line 2002 in FIG.

From the above results, the distribution of the a-Ge film deposition rate in the film-forming space is narrower and sharper than the a-Si film deposition distribution, but a considerable deposition rate is obtained even at the end of the discharge space. I know that I have it. It is considered that these are because the precursor used for depositing the a-Si film and the a-Ge film has a certain diffusion distance. On the other hand, actually graded band cap a-SiGe
When the layers are to be produced, 2011a, 20a of FIG.
At all positions 11c and 2011d, microwave power is applied from the applicator to cause microwave glow discharge to increase the film deposition rate of the a-Si film at that position. Since the deposition rate of a-Ge is finite even at the space end, it is clear that reducing the Ge content in the film is finite.

In other words, in the above experiment, a-
Without devising a method in which the deposition rate of the Ge film is substantially zero, it is not possible to make the band gap near the p-side and n-layer side interfaces of the a-SiGe film the same as that of the a-Si film. It is possible.

As a result of earnest studies based on the above findings, the present inventor has made the film thickness distribution of the a-Ge film abrupt in the above experiment, and the method of rapidly reducing the film formation rate to 0, That is, the actual graded band gap a
The inventors have found a method of the present invention for making the band gap near the p-layer side and n-layer side interfaces in the -SiGe film as close as possible to that of the a-Si film.

A specific example will be described below with reference to FIG.

FIG. 1 is a schematic view showing an example of an apparatus in which the conventional graded band gap a-SiGe film forming chamber shown in FIG. 18 is improved according to the method of the present invention.

In FIG. 1, 101 is a belt-shaped substrate.
Reference numeral 102 denotes a vacuum chamber for creating a reduced pressure state, which is connected to an exhaust means 105 such as a diffusion pump through an exhaust port 104 provided in the lower part. 103
Is a film forming chamber and forms a film forming space together with the substrate 101.

120 is a SiH ₄ gas line, 121 is a GeH ₄ gas line, and 122 is an H ₂ gas line. Each gas is mixed in the gas mixer 114a, 114b, 11
4c, 114d, gas mixer 114a
The gas mixed at a desired gas flow rate and ratio at ~ 114d is gas pipes 113a, 113b, 113c, 1 respectively.
13d through the gas discharge ports 112a, 112b,
It is discharged from the film forming space 112c and 112d.

110a, 110b, 110c, 110d
Is an applicator having a dielectric window for introducing microwaves into the film formation space. Microwaves are introduced from a microwave power source (not shown) through the waveguides 111a, 111b, 111c and 111d, and the film formation space is formed. Microwave glow discharge plasma is excited on the substrate 101, and a desired a-
A SiGe film is deposited.

Further, 115a, 115b, 115c, 11
Reference numeral 5d is a pressure gauge, and gas discharge ports 112a and 112, respectively.
It is installed so that the pressure near b, 112c, 112d can be examined.

Here, in order to deposit the a-SiGe layer having the graded band gap, SiH ₄ gas and GeH mixed in the gas mixers 114a to 114d as described above are used.
_It suffices to change the ratio of the _four gases to each gas mixer.

The difference between the means for embodying the method of the present invention shown in this figure and the conventional one lies in the arrangement of the holes formed at the bottom of the film formation space 103. That is, when the a-SiGe film having the smallest band gap, that is, the highest Ge content in the vicinity of the gas discharge port 112c is to be obtained, the exhaust ports are centrally provided at the position corresponding to the position. There is. FIG. 2 schematically shows the gas flow at this time.

In FIG. 2, 201 is a vacuum container, and 202
Is an exhaust means such as a diffusion pump, 203 is a chamber for forming a film forming space, 204a to 204d are gas discharge holes, 205 is an exhaust hole provided at the bottom of the chamber 203, and 206 is a belt-shaped substrate.

In the configuration of FIG. 2 of the present invention, the pressure is 20
4a and 204d are high, and 204b and 204c are low, and the gas flow has a flow toward the exhaust hole as shown by the arrow in the figure. By creating such a gas flow, for example, GeH ₄ gas flowing out from the gas release holes 204b and 204c into the film formation space and excited by the microwave power of the GeH ₄ gas become a precursor before film deposition. The component is obstructed by the flow of gas released from the gas outlets 204a and 204d, and these precursors do not reach the end of the discharge space, and the G at the point is substantially reduced.
The deposition rate of the e component becomes almost zero.

The above facts were confirmed by the following experiments.

In the discharge space shown in FIG. 1, as the film forming gas, GeH ₄ 100% gas is used as the gas discharge ports 112a-1.
The same amount is discharged from 12d into the film formation space. Microwaves are applied only from the applicator 110c to cause glow discharge, and microwave power is not applied to other applicators. In this state, the a-Ge film was deposited on the belt-shaped substrate which was stationary. The a-G thus deposited on the strip substrate
The solid line in FIG. 3 shows the result of examining the film thickness distribution of the e film along the longitudinal direction of the substrate.

In FIG. 3, 301a, 301b, 301
c and 301d are gas release holes 112a and 112a in FIG. 1, respectively.
The positions corresponding to 112b, 112c and 112d are shown.
Similar to the experiment described above, the thickness of the a-Ge film shows a distribution close to a Gaussian shape with the maximum value at the 301c position, but the distribution shape is sharper, and the film formation space end The film deposition rate of the a-Ge film in the part is 0.

According to the deposited film forming method of the present invention, the above facts are obtained by adjusting the flow rates of the SiH ₄ gas and the GeH ₄ gas from the gas discharge ports 112a to 112d as appropriate, and then 110a to 11a.
When the microwave is introduced into all the applicators of 0d and the film is deposited, the content ratio of Ge at the end of the film formation space is set to 0, and the film having the same band gap as that of a-Si can be manufactured. It is shown that.

Next, the graded band gap a-SiGe was actually deposited using the above-mentioned apparatus based on the deposited film forming method of the present invention.

Graded bandgap a-Si
In order to deposit the Ge layer, the mixing ratio of the SiH ₄ gas and the GeH ₄ gas mixed in the gas mixtures 114a to 114d may be changed. Specifically, for example, 100 sccm of SiH ₄ gas is used in the gas mixer 114a.
(GeH ₄ 0%) SiH ₄ gas 90 sccm in gas mixer 114 b GeH ₄ gas 10 sccm (GeH ₄ 10%) SiH ₄ gas 50 sccm GeH ₄ gas 50 sccm (GeH ₄ 50%) gas mixer 114 d At SiH ₄ gas 100 sccm
By setting (GeH ₄₀ 0%), the graded band gap a-SiG is such that the Ge ratio in the film is maximum in the vicinity of the gas outlet 112c and therefore the band gap has a minimum value.
An e-layer is formed. The bandgap profile of the a-SiGe layer actually deposited under the above conditions is shown in FIG.
Shown in.

In FIG. 4, 401a to 401d correspond to the positions of the gas discharge ports 112a to 112d, Ec indicates the energy level of the conduction band, and Ev indicates the energy level of the valence band. Further, Ec 'indicates the energy level of conduction in the case of the a-Si single film, and Ev' indicates the energy level of the valence band at that time. That is, in the a-SiGe film manufactured in this example, both the p-layer side interface and the n-layer side interface have a
It can be seen that the band gap has been expanded to the -Si film and an almost perfect a-Si film is formed on the end face.

As a result, good energy matching and junctions are formed on both the p-layer side and the n-layer side, the photocarrier injection efficiency is good, and a photovoltaic element having excellent solar cell efficiency can be formed. it can.

At this time, the pressure distribution in the film formation space measured by the pressure gauges 115a to 115d is shown in FIG. In FIG. 5, 501a to 501d are gas discharge ports 112a to 112d, respectively.
It corresponds to the position of 12d.

From the above, the method of the present invention in which the pressure at the location where the Ge content is maximum is minimized reduces the Ge content at the edge of the film formation space and is good for both the p-layer side and the n-layer side. It has been revealed that various joints can be formed.

As described above, the inventor of the deposited film forming method of the present invention has been invented by using the apparatus shown in FIG. 1, but the intention of the present invention is to concentrate only on a part of the bottom of the film forming chamber as shown in FIG. Except for controlling the gas flow by providing an exhaust port, any method can be used as long as the pressure is low at a high Ge content rate, and other means can be considered. .. An example of such a case is described below.

As the film forming apparatus, an apparatus of the type shown in FIG. 18 in which exhaust ports at the lower part of the film forming space are uniformly arranged is used.
The pressure is controlled by the flow rate of the diluent gas. As a concrete example, 100 sccc of SiH ₄ gas is used in the gas mixer 1814a.
mH ₂ gas 500sccm Gas mixer 1814b SiH ₄ gas 90scc
m GeH ₄ gas 10 sccm H ₂ gas 150 sccm Gas mixer 1814 c SiH ₄ gas 50 sccc
m GeH ₄ gas 50 sccm SiH ₄ gas 100 sccc in gas mixer 1814d
By setting the m H ₂ gas to be 500 sccm, the pressure at the end of the film formation space can be made higher than the pressure at the portion having the highest Ge content. Even with such a method, G in the film deposited at the end of the film formation space
The present inventors have confirmed that the content rate of e is extremely small, and this result will be described in detail in Examples and will be omitted here.

As described above, the graded band gap a-
Although the case of forming a SiGe film has been described with particular reference to the present invention, the present invention is not limited to the above examples, and it is possible to create a different type of bandgap profile and control the composition of various semiconductors and alloys. Further, in the case of ideally changing the doping profile of the valence electron control agent when controlling the valence electrons of the semiconductor, microwave plasma CVD
It goes without saying that the method and the roll-to-roll method can be applied to various applications of film deposition.

Such an example will be described below.

First, variations of bandgap profiles in amorphous semiconductor materials and alloys thereof will be described.

As the semiconductor material forming the i-type semiconductor layer that is preferably used in the photovoltaic element manufactured according to the present invention, a-Si: H, a-Si: F, a-S
i: H: F, a-SiC: H, a-SiC: F, a-S
iC: H: F, a-SiGe: H, a-SiGe: F,
a-SiGe: H: F, poly-Si: H, poly
-Si: F, poly-Si: H: F and the like so-called group IV and group IV alloy semiconductor materials, as well as group II-VI and group I
Examples include so-called compound semiconductor materials of II-V group. Among them, a-SiGe: H, a-SiGe: F, a-
SiGe: H: F, a-SiC: H, a-SiC: F,
When a so-called group IV alloy-based semiconductor such as a-SiC: H: F is used for the i-type semiconductor layer, the characteristics can be improved by appropriately changing the forbidden band width (bandgap: E _g opt) from the light incident side. It has already been mentioned that it can be improved.

FIGS. 6A to 6D show specific examples of bandgap profiles of various variations.
The arrow (→) in the figure represents the incident side of light.

The bandgap profile shown in FIG. 6A has a constant bandgap from the light incident side. The bandgap profile shown in FIG. 6B is a type in which the bandgap on the light incident side is narrow and the bandgap gradually widens.
Factor: It is effective in improving the fill factor. Figure 6
The bandgap profile shown in (c) is of a type in which the bandgap on the light incident side is wide and the bandgap gradually narrows, and is effective in improving Voc: open circuit voltage.

The bandgap profile shown in FIG. 6D is of the type already described in which the bandgap on the light incident side is wide, the bandgap narrows relatively steeply, and then widens again. By combining (b) and FIG. 6 (c), both effects can be obtained at the same time.
Good characteristics can be obtained by creating an ideal joint surface.

By the method of the present invention, for example, a-Si:
By using H and a-SiGe: H, an i-type semiconductor layer having a bandgap profile shown in FIG. 6D can be manufactured. In addition, a-SiC: H (E _g opt = 2.
05 eV) and a-Si: H (E _g opt = 1.72 eV), an i-type semiconductor layer having a bandgap profile shown in FIG. 6C can be manufactured.

In addition, according to the method and apparatus of the present invention, FIG.
A semiconductor layer having a doping profile shown in (a) to (d) can be produced. The arrow (→) in the figure represents the incident side of light.

FIG. 7A shows the profile of the non-doped i-type semiconductor layer. On the other hand, FIG. 7B shows a type in which the Fermi level on the light incident side is higher than the valence band and the Fermi level gradually approaches the conduction band, which prevents recombination of photogenerated carriers and It is effective in improving the running performance. FIG. 7C is of a type in which the Fermi level gradually approaches the valence band from the light incident side, and is similar to the case of FIG. 7B when an n-type semiconductor layer is provided on the light incident side. Has the effect of. FIG. 7D shows a type in which the Fermi level changes from the valence band to the conduction band almost continuously from the light incident side.

When it is attempted to form the deposited film in which the Fermi level is continuously changed as shown in FIGS. 7B to 7D, the method of the present invention, for example, in the case of FIG. 7B, Since high-concentration doping is performed on the light incident side, the pressure should be low at the position in the film formation space that corresponds to depositing the light incident side.
Since the i-type semiconductor is used on the side opposite to the film formation space, a high pressure is set to prevent the inflow of the dopant. In the case of FIG. 7C, the shape is symmetrical to that of FIG. 7B, and the pressure setting is reversed.
Similarly, in FIG. 7D, the Fermi level is the i-layer type in the middle part of the film, and the dopant concentration is the lowest,
The pressure at the position in the film formation space corresponding to the deposition of the i-layer type film is set to be the highest.

By appropriately designing these bandgap profile and Fermi level profile, a photovoltaic element with high photoelectric conversion efficiency can be manufactured. In particular, these profiles are preferably applied to the i-type semiconductor layer of the tandem-type or triple-type photovoltaic element shown in FIG.

Hereinafter, such a part of the present invention will be described in more detail.

The method of the present invention is an apparatus for continuously forming a functional deposition film on a continuously moving strip-shaped member by a microwave plasma CVD method, wherein the strip-shaped member is continuously formed in its longitudinal direction. While moving, it has a film forming chamber capable of holding a substantially vacuum inside the discharge chamber which forms a discharge space in the middle thereof, and a microwave chamber for generating microwave plasma is formed in the film forming chamber. Wave applicator means, exhaust means for exhausting the film forming chamber, means for introducing a deposition film forming source gas into the film forming chamber, and temperature control means for heating and / or cooling the belt-shaped member. And a deposition film whose composition is ideally controlled is formed on the surface of the continuously moving strip-shaped member exposed to the microwave plasma. A continuous method for forming a deposited film to be.

In the present invention, the microwave energy is applied to at least one or more of the microwave applicator means at the end surface or the opposite end surfaces of the film forming space formed by using the film forming chamber and the strip-shaped member as a side wall. The light is emitted into the film formation space.

Also, the microwave applicator means is arranged in a direction perpendicular to the end face so that the microwave energy is radiated in a direction parallel to the side wall.

In the method of the present invention, the microwave energy is radiated through a dielectric window provided at the tip of the microwave applicator means.

The dielectric window is used to keep the microwave applicator means and the film forming space airtight.

In the method of the present invention, in order to uniformly generate and confine microwave plasma in the film forming space, microwave energy is radiated from one side or both sides of both end surfaces of the film forming space, and the film forming is performed. Try to confine microwave energy in space.

When the width of the belt-shaped member is relatively narrow,
Even if the microwave energy is radiated from only one side, the uniformity of the microwave plasma generated in the film formation space is maintained, but the width of the belt-shaped member exceeds, for example, one wavelength of the microwave. In order to maintain the uniformity of microwave plasma, it is preferable to radiate microwave energy from both sides.

When the microwave energy is radiated from one microwave applicator means, the microwave energy emitted from one microwave applicator means is received by the other microwave applicator means, and the received microwave energy is the microwave energy of the other microwave applicator means. Special consideration needs to be taken so as not to reach the microwave power source connected to the wave applicator means and damage the microwave power source or cause an adverse effect such as abnormal oscillation of the microwave. There is. Specifically, the microwave applicator is arranged so that the electric field directions of the microwaves traveling in the microwave applicator means are not parallel to each other.

In the method of the present invention, when the microwave energy is radiated from only one side of the both end surfaces of the film forming space, it is necessary to prevent the microwave energy from leaking from the other end surface. The end surface is sealed with a conductive member, or the hole diameter is preferably 1/2 wavelength or less of the microwave wavelength used, and more preferably 1/4 wavelength.
It is desirable to cover it with a wire mesh of a wavelength or less, a punching board, or the like.

Of course, the uniformity of the microwave plasma generated in the film forming space requires that microwave energy be sufficiently transmitted in the film forming space, and the film forming space is a so-called waveguide. It is desirable to have a similar structure.
For that purpose, the film forming chamber and the strip-shaped member are preferably made of a conductive material, but the strip-shaped member may have at least one surface thereof subjected to a conductive treatment.

The microwave permeable member is provided at the tip of the microwave applicator means, separates the vacuum atmosphere in the film forming chamber from the outside air in which the microwave applicator means is installed, and between the inside and outside thereof. It is designed to withstand existing pressure differentials. Specifically, the cross-sectional shape with respect to the traveling direction of the microwave is preferably circular, rectangular, elliptical flat plate, bell jar shape,
It is desirable to have a doublet shape or a conical shape.

The thickness of the microwave transmitting member with respect to the traveling direction of the microwave is designed in consideration of the permittivity of the material used so that the reflection of the microwave here is suppressed to the minimum. For example, if it is flat, it is preferable that the wavelength is approximately equal to 1/2 of the microwave wavelength. Further, as the material thereof, the microwave energy radiated from the microwave applicator means can be transmitted into the film forming chamber with a minimum loss, and the airtightness is such that the air does not flow into the film forming chamber. Is preferably excellent, specifically, quartz, alumina, silicon nitride, beryllia, magnesia, zirconia,
Examples thereof include glass such as boron nitride and silicon carbide, fine ceramics and the like.

Further, it is preferable that the microwave transmitting member is uniformly cooled in order to prevent thermal deterioration (cracking, destruction) and the like due to heating by microwave energy and / or plasma energy.

The specific cooling means may be a cooling air flow blown toward the surface of the microwave permeable member on the atmosphere side, or the microwave applicator means itself may be cooled air, water, The microwave permeable member may be cooled through a portion contacting the microwave applicator means by cooling with a cooling medium such as oil or freon. By cooling the microwave permeable member to a sufficiently low temperature, even if microwave energy having a relatively high power is introduced into the film forming chamber, the generated heat may cause cracks or the like in the microwave permeable member. A high electron density plasma can be generated without causing destruction.

Further, in the method of the present invention, film deposition occurs in the portion where the microwave permeable member is in contact with microwave plasma, as in the case of the band-shaped member. Therefore,
Depending on the type and characteristics of the deposited film, the deposited film absorbs or reflects the microwave energy that should be radiated from the microwave applicator means, and the microwave into the film forming chamber formed by the strip-shaped member. When the amount of energy emitted decreases and the amount of change significantly increases compared to immediately after the start of discharge, it is difficult to maintain the microwave plasma itself, and the deposition rate of the deposited film decreases. And changes in characteristics may occur. In such a case, the initial state can be restored by removing the film deposited on the microwave permeable member by dry etching, wet etching, or a mechanical method. In particular, dry etching is preferably used as a method for removing the deposited film while maintaining the vacuum state.

With the microwave applicator means, while keeping the vacuum state in the film forming chamber, the film is taken out of the film forming chamber by a so-called load lock method, and the film deposited on the microwave permeable member is wet-etched or It may be peeled off by mechanical removal or the like for reuse, or may be replaced with a new one.

Further, a sheet made of a material having a microwave permeability substantially equal to that of the microwave permeable member is continuously fed along the surface of the microwave permeable member on the film forming chamber side. It is also possible to adopt a method in which a deposited film is attached and formed on the surface of the sheet and discharged to the outside of the microwave plasma region.

The microwave applicator means in the method of the present invention may be of the same standard as the microwave transmission waveguide, or may be of another standard. In addition, the microwave transmission mode in the microwave applicator means enables efficient transmission of microwave energy in the film forming chamber and stable generation, maintenance and control of microwave plasma. Therefore, it is desirable that the size and shape of the microwave applicator be designed so as to be a single mode. However, even if a plurality of modes are transmitted, it can be used by appropriately selecting microwave plasma generation conditions such as a raw material gas to be used, pressure, and microwave power. When the transmission mode is designed to be a single mode, for example, TE ₁₀ mode, TE ₁₁ mode, eH
₁ mode, TM ₁₁ mode, TM ₀₁ mode and the like can be mentioned, but TE ₁₀ mode, TE ₁₁ mode,
The eH ₁ mode is selected. A waveguide capable of transmitting the above-mentioned transmission mode is connected to the microwave applicator means, and preferably the transmission mode in the waveguide and the transmission mode in the microwave applicator means are matched. Is desirable. The type of the waveguide is appropriately selected according to the frequency band (band) and mode of the microwave used, and it is preferable that at least the cutoff frequency thereof is smaller than the frequency used. Is JIS, EIAJ, IEC, J
In addition to AN, etc. standard rectangular waveguide, circular waveguide, or elliptic waveguide, etc., as a company standard for 2.45 GHz microwaves, a square cross section with an inner diameter of 96 mm and a height of 27 mm Etc. can be mentioned.

In the method of the present invention, since the microwave energy supplied from the microwave power source is efficiently radiated into the film forming chamber through the microwave applicator means, the reflected wave caused by the so-called microwave applicator is used. The problem related to is easy to avoid, and it is possible to maintain a relatively stable discharge in a microwave circuit without using a microwave matching circuit such as a three-stub tuner or an E-H tuner. If a strong reflected wave is generated due to abnormal discharge or the like even after the start, it is desirable to provide the microwave matching circuit for protecting the microwave power source.

The microwave frequency supplied from the microwave power source used in the method of the present invention is preferably 2.45 GHz which is preferably used for consumer, but comparison is made with other frequency bands. Any material that is easily available can be used. Further, in order to obtain a stable discharge, the oscillation mode is preferably so-called continuous oscillation, and the ripple width is preferably within 30%, and more preferably within 10% in the use output region.

Next, the strip member used in the deposited film forming apparatus of the present invention will be described. The material of the belt-shaped member that is preferably used in the method of the present invention is that it has a small amount of deformation and distortion at the temperature required for forming a functional deposited film by the microwave plasma CVD method, has a desired strength, and has a conductive property. It is preferable that the metal has a property, and specifically, a thin metal plate such as stainless steel, aluminum and its alloys, iron and its alloys, copper and its alloys, and their composites, and a metal of different materials on their surfaces. Thin film and / or SiO ₂ , Si ₃ N ₄ , Al
An insulating thin film such as ₂ O ₃ or AlN is formed by sputtering, vapor deposition,
A product that has been surface-coated by a plating method or the like.
Further, a heat-resistant resinous sheet of polyimide, polyamide, polyethylene terephthalate, epoxy or the like, or a metal simple substance or alloy, and a transparent conductive oxide on the surface of a composite of these with glass fiber, carbon fiber, boron fiber, metal fiber or the like. (TCO) etc. plating, vapor deposition,
Examples include those that have been subjected to a conductive treatment by a method such as sputtering or coating.

Of course, even if the band-shaped member is electrically conductive such as metal, the reflectance of long wavelength light on the substrate surface is improved, and the constituent elements between the substrate material and the deposited film are increased. A different kind of metal layer or the like may be provided on the side on which the deposited film is formed on the substrate for the purpose of preventing mutual diffusion of the above or as an interference layer for preventing a short circuit. Further, when the band-shaped member is relatively transparent and a solar cell having a layer structure in which light is incident from the side of the band-shaped member, a conductive thin film such as the transparent conductive oxide or a metal thin film is previously deposited. It is desirable to form it.

The surface property of the belt-shaped member may be a so-called smooth surface or a minute uneven surface.
In the case of forming a minute uneven surface, the uneven shape is spherical, conical, pyramidal, or the like, and its maximum height (Rmax)
Is preferably 500 Å to 5000 Å, and the light reflection on the surface becomes irregular reflection, resulting in an increase in the optical path length of the reflected light on the surface.

Further, the thickness of the belt-shaped member is preferably as thin as possible in consideration of cost, storage space and the like, as long as it is within a range in which the strength required at the time of carrying by the carrying means is exhibited. Specifically, preferably 0.0
1 mm to 5 mm, more preferably 0.02 mm to 2
The optimum strength is preferably 0.05 mm to 1 mm, but it is easier to obtain a desired strength by using a thin plate made of a metal or the like even if the thickness is reduced.

Regarding the width of the belt-shaped member,
When the microwave applicator means is used, it is preferable that the uniformity of the microwave plasma in the longitudinal direction is maintained and the curved shape is maintained, specifically, preferably 5 cm to 100 cm.
It is desirable that the thickness is cm, more preferably 10 cm to 80 cm.

Further, the length of the belt-like member is not particularly limited, and may be such a length that it can be wound into a roll, and a long one can be made longer by welding or the like. It may be one that has been made.

The gas supply means provided in the method of the present invention is constituted by a pipe-shaped gas introduction pipe, and one side or a plurality of gas discharge ports are opened on the side surface thereof.

As a material forming the gas introducing pipe, a material which is not damaged in microwave plasma is preferably used. Specifically, heat-resistant metals such as stainless steel, nickel, titanium, niobium, tantalum, tungsten, vanadium, molybdenum, and alumina,
Examples include ceramics such as silicon nitride and quartz that have been subjected to thermal spraying, ceramics such as alumina, silicon nitride, and quartz, and composites.

In the method of the present invention, the deposited film forming raw material gas discharged from the gas supply means is preferably uniformly discharged in the width direction of the belt-shaped member.

The gas supply means are arranged in parallel with the belt-shaped member.

The number of the gas supply means used in the method of the present invention is preferably at least equal to or more than the number of component elements of the functional deposition film to be formed. By appropriately changing the composition of the deposited film forming raw material gas to be released, an ideally composition-controlled functional deposited film can be formed.

It is desirable that each of the gas supply means is arranged so as to be included in the film formation space so that the released raw material gas for forming a deposited film is surely excited and decomposed. Further, in order to give the deposited film to be formed a desired composition distribution,
It is desirable to appropriately adjust the arrangement of the gas supply means.
Furthermore, in order to adjust and control the flow path of the raw material gas for forming a deposited film in the film forming space, a rectifying plate or the like may be provided in the film forming space.

In the method of the present invention, in order to control the plasma potential of the microwave plasma generated in the film forming chamber,
A bias voltage may be applied to the gas introduction pipe. The bias voltages applied to the plurality of gas introduction tubes may be the same or different from each other. As the bias voltage, it is desirable to apply a DC voltage, a pulsating current, and an AC voltage individually or in a superimposed manner.

To effectively apply the bias voltage,
It is desirable that the surfaces of both the gas introducing pipe and the strip-shaped member are electrically conductive.

By applying a bias voltage and controlling the plasma potential, plasma stability, reproducibility and film characteristics can be improved, and the occurrence of defects can be suppressed.

In the method of the present invention, a part or all of the deposited film forming raw material gas introduced into the columnar film forming chamber from the gas introducing pipe is decomposed to generate a deposited film forming precursor. Although a deposited film is formed, the raw material gas of undecomposition or the gas that has become a gas of a different composition due to decomposition must be promptly exhausted to the outside of the film forming chamber. However, if the area of the exhaust hole is made larger than necessary, microwave energy leaks from the exhaust hole, which may cause instability of plasma or adversely affect other electronic devices, human bodies, etc. . Therefore, in the method of the present invention, it is desirable that the exhaust hole has a wavelength of preferably ½ wavelength or less, more preferably ¼ wavelength or less of the wavelength of the microwave used in order to prevent microwave leakage. ..

In the method of the present invention, the film forming chamber and / or the isolation container is made continuous by disassembling a vacuum atmosphere having another film forming means into a vacuum atmosphere and allowing the strip-shaped member to penetrate therethrough. A gas gate means is preferably used for transporting to. In the apparatus of the present invention, the film forming chamber and / or
Or, since it is desirable that the inside of the isolation container is kept at a low pressure necessary for operation near the minimum value of the modified Paschen curve, the pressure in the vacuum chamber connected to the deposition chamber and / or the isolation container is Is often at least approximately equal to or higher than that pressure. Therefore, it is necessary for the gas gate means to have the ability not to diffuse the mutually used deposited film forming raw material gases due to the pressure difference generated between the containers. Therefore, the basic concept can employ the gas gate means disclosed in US Pat. No. 4,438,723, but its capabilities need to be further improved. Specifically, it is necessary to withstand a pressure difference of up to about 10 ⁶ times, and as the exhaust pump, an oil diffusion pump, a turbo molecular pump, a mechanical booster pump or the like having a large exhaust capacity is preferably used. In addition, the cross-sectional shape of the gas gate is a slit shape or a shape similar to this, and together with the total length and the exhaust capacity of the exhaust pump used, their dimensions are calculated using a general conductance calculation formula,
Designed. Further, it is preferable to use a gate gas together to enhance the separation ability. For example, Ar, He, Ne,
A rare gas such as Kr, Xe, or Rn or a diluted gas for forming a deposited film such as H ₂ can be used. The flow rate and pressure of the gate gas are appropriately determined depending on the conductance of the entire gas gate and the capacity of the exhaust pump used.However, if the point where the pressure is maximum is set at approximately the center of the gas gate, the gate gas will be vacuumed on both sides from the center of the gas gate. The gas flows to the container side, and on the other hand, if a point at which the pressure is minimized is set at the substantially central part of the gas gate, the gate gas is exhausted from the central part of the gas gate together with the deposited film forming raw material gas flowing from the containers on both sides. Therefore, in both cases, mutual gas diffusion between the containers on both sides can be minimized. In practice, the optimum conditions are determined by measuring the amount of gas that diffuses using a mass spectrometer and analyzing the composition of the deposited film.

The compositionally controlled functional deposited film formed by the method of the present invention includes SiGe, SiC and Ge.
So-called IV group alloy semiconductor thin films such as C, SiSn, GeSn, SnC, GaAs, GaP, GaSb, InP, InA
so-called III-V group compound semiconductor thin film, ZnSe, Z
nS, ZnTe, CdS, CdSe, CdTe, etc., so-called I
Group I-VI compound semiconductor thin film, CuAlS ₂ , CuAl
Se ₂ , CuAlTe ₂ , CuInS ₂ , CuInSe
₂ , CuInTe ₂ , CuGaS ₂ , CuGaSe ₂ ,
CuGaTe, AgInSe ₂ , AgInTe ₂ , etc., so-called I-III-VI group compound semiconductor thin films, ZnSiP ₂ ,
ZnGeAs _2, CdSiAs _2, CdSnP ₂ Hitoshishoi II-IV-V group compound semiconductor thin film, Cu ₂ O, TiO
₂ , In ₂ O ₃ , SnO ₂ , ZnO, CdO, Bi ₂ O
Examples thereof include so-called oxide semiconductor thin films such as ₃ , CdSnO ₄ , and those containing a valence electron controlling element for controlling valence electrons of these semiconductors.

Further, a so-called group IV semiconductor thin film such as Si, Ge, C containing a valence electron control element can be mentioned. Of course, an amorphous semiconductor such as a-Si: H, a-Si: H: F may have a different hydrogen and / or fluorine content.

By controlling the composition of the above-mentioned semiconductor thin film, forbidden band width control, valence electron control, refractive index control,
Crystal control and the like are performed. By forming a functionally deposited film whose composition is controlled on the band-shaped member, a large area thin film semiconductor device having excellent electrical, optical and mechanical properties can be manufactured.

That is, the carrier characteristics are improved by changing the forbidden band width and / or the valence electron density of the deposited semiconductor layer, or the recombination of carriers at the semiconductor interface is prevented, so that the electrical characteristics are improved. improves.

Further, by making the optical non-reflecting surface by continuously changing the refractive index, the light transmittance into the semiconductor layer can be improved.

Furthermore, stress is relieved by changing the hydrogen content and the like to provide a structural change, and a deposited film having high adhesion to the substrate can be formed.

In the present invention, the raw material gas for forming a deposited film used for forming the above-mentioned functional deposited film is formed into the above-mentioned film by appropriately adjusting the mixing ratio according to the desired composition of the functional deposited film. Introduce into space. A plurality of gas supply means are used at the time of introduction, but the composition of the deposited film forming raw material gas introduced from each gas supply means may be different, or may be the same depending on the purpose. In addition, the composition may be continuously changed with time if necessary.

In the present invention, a compound containing a group IV element of the periodic table, which is preferably used for forming a group IV semiconductor or a group IV alloy semiconductor film, is a Si atom or Ge.
A compound containing an atom, a C atom, a Sn atom, and a Pb atom, specifically, SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ , and S
_{i 3 H 6, Si 4 H} 8, Si 5 H 10, silane compounds such _{as, SiF 4, (SiF 2)} 5, (SiF 2) 6, (S
iF ₂ ) ₄ , Si ₂ F ₆ , Si ₃ F ₈ , SiHF ₃ , S
iH ₂ F ₂ , Si ₂ H ₂ F ₄ , Si ₂ H ₃ F ₃ , SiC
l ₄ , (SiCl ₂ ) ₅ , SiBr ₄ , (SiBr ₂ )
₅ , Si ₂ Cl ₆ , Si ₂ Br ₆ , SiHCl ₃ , Si
HBr ₃ , SiHl ₃ , Si ₂ Cl ₃ F _{3 and} other halogenated silane compounds, GeH ₄ , Ge ₂ H _{6 and} other germane compounds, GeF ₄ , (GeF ₂ ) ₅ , and (GeF ₂ ) ₆ ,
(GeF ₂ ) ₄ , Ge ₂ F ₆ , Ge ₃ F ₈ , GeH
F ₃ , GeH ₂ F ₂ , Ge ₂ H ₂ F ₄ , Ge ₂ H
₃ F ₃ , GeCl ₄ , (GeCl ₂ ) ₅ , GeBr ₄ ,
(GeBr ₂ ) ₅ , Ge ₂ Cl ₆ , Ge ₂ Br ₆ , Ge
HCl ₃ , GeHBr ₃ , GeHl ₃ , Ge ₂ Cl ₃ F
Germanium halide compounds such as ₃ , CH ₄ , C ₂
H _6, C ₃ methane columns hydrocarbon gas such as H _8, C ₂ H _4,
Ethylene column hydrocarbon gas such as C ₃ H ₆ , cyclic hydrocarbon gas such as C ₆ H ₆ , CF ₄ , (CF ₂ ) ₅ , (C
F ₂ ) ₆ , (CF ₂ ) ₄ , C ₂ F ₆ , C ₃ F ₈ , CHF
₃ , CH ₂ F ₂ , CCl ₄ , (CCl ₂ ) ₅ , CB
r ₄ , (CBr ₂ ) ₅ , C ₂ Cl ₆ , C ₂ Br ₆ , CH
Halogenated carbon compounds such as Cl ₃ , CHl ₃ , and C ₂ Cl ₃ F ₃ , tin compounds such as SnH ₄ and Sn (CH ₃ ) ₄ ,
Examples thereof include lead compounds such as Pb (CH ₃ ) ₄ and Pb (C ₂ H ₅ ) ₆ . These compounds may be used alone or in combination of two or more.

In the present invention, so-called composition control is performed by appropriately mixing and using these compounds.

The valence electron controlling agent used for controlling the valence electrons of the group IV semiconductor or the group IV alloy semiconductor formed in the present invention is, as a p-type impurity, an element of group III of the periodic table, for example, , B, Al, Ga, In, T
1 and the like are preferable, and as the n-type impurity, an element of Group V of the periodic table, for example, N, P, As, S
Suitable examples include b and Bi, and in particular,
B, Ga, P, Sb, etc. are optimal. The amount of impurities to be doped is appropriately determined according to desired electrical and optical characteristics.

As such a raw material for introducing impurities, those which are in a gas state at room temperature and normal pressure or which can be easily gasified under at least the film forming conditions are adopted. Specifically, as a starting material for introducing such impurities, PH ₃ , P
₂ H ₄ , PF ₃ , PF ₅ , PCl ₃ , AsH ₃ , AsF
₃ , AsF ₅ , AsCl ₃ , SbH ₃ , SbF ₅ , Bi
_{H 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, AlC
1 _{3 and the} like can be mentioned. The compounds containing the above impurity elements may be used alone or in combination of two or more.

Specific examples of the compound containing a Group II element of the periodic table used for forming the II-VI group compound semiconductor in the present invention include Zn (CH ₃ ) ₂ and 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. Further, as a compound containing a Group VI element of the periodic table, specifically, NO,
N ₂ O, CO ₂ , CO, H ₂ S, SCl ₂ , S ₂ C
_{l 2, SOCl 2, SeH 2} , SeCl 2, Se 2 Br
_{2, Se (CH 3) 2} , Se (C 2 H 5) 2, Te
_{H 2, Te (CH 3)} 2, Te (C 2 H 5) 2 and the like.

Of course, these starting materials may be used alone or in combination of two or more.

As the valence electron control agent used to control the valence electrons of the II-VI group compound semiconductor formed in the present invention, compounds containing elements of the I, III, IV and V groups of the periodic table are effective. Can be listed as

Specifically, as the compound containing a group I element, LiC ₃ H ₇ , Li (sec-C ₄ H ₉ ), Li ₂ S,
Li ₃ N etc. can be mentioned as a suitable thing.

As the compound containing a group III element, BX ₃ , B ₂ H ₆ , B ₄ H ₁₀ , B ₅ H ₉ and B are included.
₅ H ₁₁ , B ₆ H ₁₀ , B (CH ₃ ) ₃ , B (C
₂ H ₅ ) ₃ , B ₆ H ₁₂ , AlX ₃ , Al (CH ₃ ) ₂ C
l, Al (CH ₃ ) ₃ , Al (OCH ₃ ) ₃ , Al (C
H ₃ ) Cl ₂ , Al (C ₂ H ₅ ) ₃ , Al (OC
₂ H ₅ ) ₃ , Al (CH ₃ ) ₃ Cl ₃ , Al (i-C _{4
H 9) 3, Al (i} -C 3 H 7) 3, Al (C 3 H 7)
₃ , Al (OC ₄ H ₉ ) ₃ , GaX ₃ , Ga (OC
_{H 3) 3, Ga (OC} 2 H 5) 3, Ga (OC 3 H 7)
₃ , Ga (OC ₄ H ₉ ) ₃ , Ga (CH ₃ ) ₃ , Ga _{2
H 6, GaH (C 2 H} 5) 2, Ga (OC 2 H 5) (C
₂ H ₅ ) ₂ , In (CH ₃ ) ₃ , In (C ₃ H ₇ ) ₃ ,
In (C ₄ H ₉ ) ₃ is N as a compound containing a group V element.
_{H 3, HN 3, N 2} H 5 N 3, N 2 H 4, NH 4 N 3,
PX ₃ , P (OCH ₃ ) ₃ , P (OC ₂ H ₅ ) ₃ , P
(C ₃ H ₇ ) ₃ , P (OC ₄ H ₉ ) ₃ , P (C
_{H 3) 3, P (C} 2 H 5) 3, P (C 3 H 7) 3, P
(C ₄ H ₉ ) ₃ , P (OCH ₃ ) ₃ , P (OC ₂ H ₅ )
₃ , P (OC ₃ H ₇ ) ₃ , P (OC ₄ H ₉ ) ₃ , P (S
CN) ₃ , P ₂ H ₄ , PH ₃ , AsH ₃ , AsX ₃ , A
s (OCH ₃ ) ₃ , As (OC ₂ H ₅ ) ₃ , As (OC
₃ H ₇ ) ₃ , As (OC ₄ H ₉ ) ₃ , As (C
_{H 3) 3, As (CH} 3) 3, As (C 2 H 5) 3, A
s (C ₆ H ₅ ) ₃ , SbX ₃ , Sb (OCH ₃ ) ₃ , S
b (OC ₂ H ₅ ) ₃ , Sb (OC ₃ H ₇ ) ₃ , Sb (O
C ₄ H ₉ ) ₃ , Sb (CH ₃ ) ₃ , Sb (C
₃ H _{7) 3,} such as Sb (C ₄ H _{9) 3} and the like.

In the above, X is halogen (F, Cl,
Br, I).

Of course, these starting materials may be used alone or in combination of two or more.

Further, as the compound containing the group IV element, the above-mentioned compounds can be used.

The compound containing a Group III element of the periodic table, which is used to form a III-V group compound semiconductor in the present invention, is specifically BX ₃ (where X represents a halogen atom). , B ₂ H ₆ , B ₄ H ₁₀ , B
₅ H ₉ , B ₅ H ₁₁ , B ₆ H ₁₀ , B ₆ H ₁₂ , AlX ₃ (where X represents a halogen atom), Al (CH ₃ ) ₂ C
l, Al (CH ₃ ) ₃ , Al (OCH ₃ ) ₃ , Al (C
H ₃ ) Cl ₂ , Al (C ₂ H ₅ ) ₃ , Al (OC
₂ H ₅ ) ₃ , Al (CH ₃ ) ₃ Cl ₃ , Al (i-C _{4
H 9) 3, Al (i} -C 3 H 7) 3, Al (C 3 H 7)
₃ , Al (OC ₄ H ₉ ) ₃ , GaX ₃ (where X represents a halogen atom), Ga (OCH ₃ ) ₃ , Ga (CO
₂ H ₅ ) ₃ , Ga (OC ₃ H ₇ ) ₃ , Ga (OC
₄ H ₉ ) ₃ , Ga (CH ₃ ) ₃ , Ga ₂ H ₆ , GaH
(C ₂ H ₅ ) ₂ , Ga (OC ₂ H ₅ ) (C ₂ H ₅ ) ₂ ,
In (CH ₃ ) ₃ , In (C ₃ H ₇ ) ₃ , In (C ₄ H
₉ ) ₃ etc. Specific examples of the compound containing a Group V element of the periodic table include NH ₃ , HN ₃ , N ₂ H _{5
N 3, N 2 H 4,} NH 4 N 3, PX 3 ( where, X is a halogen _{atom.), P (OCH 3)} 3, P (OC 2 H
₅ ) ₃ , P (C ₃ H ₇ ) ₃ , P (OC ₄ H ₉ ) ₃ , P
(CH ₃ ) ₃ , P (C ₂ H ₅ ) ₃ , P (C ₃ H ₇ ) ₃ ,
P (C ₄ H ₉ ) ₃ , P (OCH ₃ ) ₃ , P (OC
₂ H ₅ ) ₃ , P (OC ₃ H ₇ ) ₃ , P (OC
₄ H ₉ ) ₃ , P (SCN) ₃ , P ₂ H ₄ , PH ₃ , As
X ₃ (provided that X represents a halogen atom), AsH ₃ ,
As (OCH ₃ ) ₃ , As (OC ₂ H ₅ ) ₃ , As (O
_{C 3 H 7) 3, As} (OC 4 H 9) 3, As (CH 3)
₃ , As (CH ₃ ) ₃ , As (C ₂ H ₅ ) ₃ , As (C
₆ H ₅ ) ₃ , SbX ₃ (where X represents a halogen atom), Sb (OCH ₃ ) ₃ , Sb (OC ₂ H ₅ ) ₃ ,
Sb (OC ₃ H ₇ ) ₃ , Sb (OC ₄ H ₉ ) ₃ , Sb
_{(CH 3) 3, Sb (} C 3 H 7) 3, Sb (C 4 H 9)
₃ and so on. (However, X represents a halogen atom, specifically at least one selected from F, Cl, Br and I.) Of course, these raw materials may be used alone or in combination of two or more. You can

As the valence atom controlling agent used for controlling the valence atoms of the III-V group compound semiconductor formed in the present invention, compounds containing an element of group II, IV or VI of the periodic table are effective. Can be mentioned as.

Specifically, as the compound containing a group II element, Zn (CH ₃ ) ₂ , Zn (C ₂ H ₅ ) ₂ , Zn
(OCH ₃ ) ₂ , Zn (OC ₂ H ₅ ) ₂ , Cd (C
_{H 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, and examples of the compound containing a VI group element include NO, N ₂ O, CO ₂ , CO and H.
₂ S, 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, Te
(C ₂ H _{5) 2} or the like can be mentioned.

Of course, these starting materials may be used alone or in combination of two or more.

Further, as the compound containing the group IV element, the above-mentioned compounds can be mentioned.

In the present invention, the raw material compounds described above are H
Noble gases such as e, Ne, Ar, Kr, Xe, and Rn, and H
It may be introduced by mixing with a diluent gas such as ₄ , HF and HCl. Further, these dilution gases and the like may be independently introduced from the gas supply means.

[0165]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the examples.

Example 1 and Comparative Example 1 The following experiments were carried out by both the deposited film forming method of the present invention shown in FIG. 1 and the conventional deposited film forming method shown in FIG.

The specific working method, for example, gas mixing, introducing method and the like are as described above, and since they are redundant, they will be omitted here and the characteristic items performed in this embodiment will be described.

First, the deposited film forming method of the present invention shown in FIG. 1 and the conventional deposited film forming method shown in FIG. 18 are shown in FIG. 15 in the i-layer deposition chamber of the roll-to-roll system production apparatus. I captured it as 1550. In other words, only the i-layer film forming chamber in the roll-to-roll system production apparatus shown in FIG. 15 was replaced with the one by the deposited film forming method of the present invention and the one by the conventional deposited film forming method. is there.

The graded band gap aS
The gas mixer to the iGe layer deposition chamber further has a plurality of gas mixers for each gas discharge port therein.

In this embodiment, the n-layer film forming chamber 1530
The deposition gas and the doping gas did not flow in the p-layer deposition chamber 1570 at all, and the discharge by the microwave power did not occur. That is, in the present embodiment, one of the purposes is to grasp the single film characteristics of the film deposited in the i-layer film forming chamber. Secondly, in this embodiment, the strip-shaped substrate is fixed and does not move, and the strip-shaped substrate is arranged along the lengthwise direction of the substrate so as to face the deposition space at a position corresponding to the i-layer deposition chamber of the strip-shaped substrate. 7059 glass was installed. As a method for fixing the glass to the belt-shaped substrate, there are a method of making holes in the belt-shaped substrate and the glass and fixing them with screws, or a method of fixing with a high melting point inorganic adhesive such as Aron ceramic, etc. In, the former was adopted.

That is, in the present embodiment, the film is not examined in the state in which the films deposited at the respective positions from the inlet end face to the outlet end face of the i-layer chamber film formation chamber are stacked, and the film formation is not performed. It aims to separate and investigate the characteristics of each part of the chamber.

Thirdly, also in the conventional deposited film forming method shown in FIG. 18, as in the deposited film forming method of the present invention shown in FIG. 1, a plurality of vacuum gauges are provided along the longitudinal direction of the film forming chamber. The pressure at each point in the film forming chamber was monitored.

Under the above basic conditions, an a-SiGe film having a film thickness of about 1 μm was formed under the film forming conditions shown in Table 1. The deposition conditions in the deposited film forming method of the present invention and the conventional deposited film forming method are exactly the same except for the pressure.

Incidentally, the position a in the i-layer deposition chamber of Table 1,
b, c, and d are vacuum gauges 115a to 115 in FIG.
It corresponds to the measurement position by d.

[0175]

[Table 1] For the obtained film, an optical bandgap was measured using a spectroscope and an X-ray micro analyzer was used.
The composition analysis of Si and Ge was performed. i-layer chamber
FIG. 8 shows the results of the above measurements performed at various points in the longitudinal direction of the film forming chamber.

FIG. 8A shows the optical bandgap for each position. The solid line shows the deposited film forming method of the present invention, and the broken line shows the conventional deposited film forming method.
FIG. 8B shows the Ge content in the film at each position. The solid line shows the deposited film forming method of the present invention, and the broken line shows the conventional deposited film forming method.

As can be seen from FIGS. 8 (a) and 8 (b), in the conventional deposited film forming method, about several% of Ge is contained at the end portion of the film forming space, and accordingly the optical band gap is about 1. It is narrower than that of .65 eV and a-Si. Therefore, it has been found that the deposited film forming method of the present invention can ideally control the Ge content to form a film having a desired bandgap profile.

(Example and Comparative Example 2) The following experiments were conducted by both the deposited film forming method of the present invention shown in FIG. 1 and the conventional deposited film forming method shown in FIG.

Specific working methods, such as gas mixing and introducing methods, are as described above and will not be described here. The characteristic items performed in this embodiment will be described. First, the roll-to-roll system and the production apparatus shown in FIG. 15 are the deposition pattern forming method of the present invention shown in FIG. 1 and the conventional deposited film forming method shown in FIG. The i-layer film forming chamber 1550 of FIG.

Secondly, also in the conventional deposition forming method shown in FIG. 18, as in the deposition film forming method of the present invention shown in FIG. 1, a plurality of vacuum gauges are provided along the longitudinal direction of the film forming chamber to form a film. The pressure at each point in the chamber was monitored.

Thirdly, in the present embodiment, single
An n-type a-Si layer, an i-type graded bandgap a-SiGe layer, and a p-type a-Si layer that compose the cell solar cell were laminated. The thickness of each layer is 200 Å for n-type a-Si layer,
i-type graded bandgap a-SiGe layer 2
500 Å and p-type a-Si layer was 120 Å. Table 2 shows such film forming conditions.

[0182]

[Table 2] The deposition conditions of the deposited film forming method of the present invention and the conventional deposited film forming method are the same except for the pressure. The positions a, b, c, d in the i-layer type membrane chamber in Table 2 correspond to the measurement positions by the pressure gauges 115a to 115d in FIG.

Both the deposited film forming method of the present invention and the conventional deposited film forming method produced two samples, one of which was subjected to compositional analysis, and one of them was further subjected to vapor deposition to form a transparent electrode (I).
(TO) and a collector electrode (a laminate of Cr and Ag) were laminated to form a single solar cell. The composition analysis was performed by Auger electron spectroscopy, and the analysis proceeded from the p-layer side to examine the Ge content profile in the depth direction to the substrate. The result is shown in FIG. In FIG. 9, the solid line represents the deposited film forming method of the present invention, and the broken line represents the conventional deposited film forming method. As can be seen from FIG. 9, the conventional deposited film forming method contains approximately several percent Ge both in the vicinity of the p-layer side interface and in the vicinity of the n-layer side interface. It can be seen that Ge is not included and ideal film composition control is achieved.

On the other hand, the solar cell characteristics of the cell in which the transparent electrode and the current collecting electrode were laminated were examined. Pseudo sunlight of AM1.5 is used as irradiation light, and energy density is 1
It was set to 00 mW / cm ² . The measurement area of each subcell is 0.5 cm ² . The results are as follows.

The conversion efficiency of the cell manufactured using the conventional deposited film forming apparatus was 8.6%. The conversion efficiency of the cell manufactured using the deposited film forming apparatus of this example was 9.0% or more. It was found that the cells whose composition was ideally controlled by using the deposited film forming apparatus of 1) had a higher conversion efficiency than the conventional cells.

(Embodiment 3) 1812a to 1812 are formed by using the i-layer deposition chamber shown in FIG.
d. The deposited film forming method of the present invention was carried out by changing the amount of gas introduced from the gas discharge port.

Also in this example, a plurality of pressure gauges were provided along the lengthwise direction of the film forming chamber to monitor the pressure at the name of the film forming chamber, as in the deposited film forming method of the present invention shown in FIG.

In this example, the manufacturing conditions of the n-type a-Si layer and the p-type a-Si layer are exactly the same as in Table 2, and the thickness of each is 200 Å for the n-type a-Si layer and i-type. Graded bandgap a-SiGe 2500 Å, p-type a-
The Si layer was set to 100Å.

The experiment was performed on the i-layer chamber 1812a-181.
The amount of gas discharged from each gas discharge port of 2d was changed four times, and the experiments were conducted as Experiments 1 to 4, respectively.

Table 3 shows the gas amount and the pressure at each position at that time.

[0191]

[Table 3] In Experiment 1, the flow rate of H ₂ emitted from each gas outlet was 1812.
The same applies to a to 1812d, which corresponds to the conventional deposited film forming method. In Experiments 2 to 4, the flow rate of H ₂ gas discharged from the gas discharge port 1812c was minimized, and the amount of H ₂ gas flowing out from the other gas discharge ports was gradually increased.
The pressure gradient becomes tighter from Experiment 2 to Experiment 4.

Two samples were prepared for each, and the composition of one was analyzed for composition. One of the samples was further subjected to a vapor deposition method to form a transparent electrode (ITO) and a current collecting electrode (lamination of Cr and Ag). Were laminated to form a single solar cell.

The composition analysis was carried out by Auger electron spectroscopy, and the analysis was advanced from the p-layer side to examine the profile of Ge content in the depth direction to the substrate. The results for Experiments 1 to 4 are shown in FIG.

As shown in FIG. 10, the content ratio near the edge of the film formation space decreased from Experiment 1 to Experiment 4, and G
The e content has a steep gradient.

On the other hand, the solar cell characteristics of the cell in which the transparent electrode and the current collecting electrode were laminated were examined. Pseudo sunlight of AM1.5 is used as irradiation light, and energy density is 1
It was set to 00 mW / cm ² . The measurement area of each sub cell is 0.5 cm ² . Table 4 shows the measurement results for Experiments 1 to 4.

[0196]

[Table 4] As shown in Table 4, the conversion efficiency was improved from Experiment 1 to Experiment 3, and it was found that the deposited film forming method of the present invention was excellent.

In Experiment 4, the conversion efficiency is lower than that in Experiment 3, but it is superior to Experiment 1 or the conventional deposited film forming method. The conversion efficiency in Experiment 4 was lower than that in Experiment 3 because the bandgap profile became too steep at the location where the Ge content was high, and conversely the bandgap profile at the edge of the film formation space was flattened. It is probable that the running performance of the carrier deteriorated.

Example 4 A tandem solar cell in which the i layer of the top cell was made of amorphous silicon was prepared by using the method of the present invention.

FIG. 11 shows a schematic view of the apparatus used for the preparation. The production apparatus shown in FIG. 11 is basically the production apparatus shown in FIG. 15 with an additional film formation chamber for a tandem solar cell. In FIG. 11, 1100 is a substrate delivery chamber, 1110 is a bottom cell n-type a-Si layer deposition chamber,
1120 is an i-type graded bandgap a-SiGe layer deposition chamber for bottom cells, 1130 is a p-type a-Si layer deposition chamber for bottom cells, and 1140 is an n-type a-Si layer for top cells. Deposition chamber 1150 is i-type a-Si layer deposition chamber for top cell 1160 is p-type a-layer for top cell
It is a Si layer film forming chamber, and a gas mixer 11 is provided in each film forming chamber.
1161, a film forming gas mixed at a desired flow rate and a flow rate ratio is introduced, and electric power is applied from a microwave power source (not shown) to form a desired film on the substrate 1102. Graded bandgap a-SiG
The gas mixer for forming the film for forming e further has a plurality of gas mixers for each gas discharge port in the inside 3. The raw material cylinder of the film forming gas is basically the same as that shown in FIG.
Further, 1181 to 1187 are gates that connect the respective chambers.

Each gate is provided with a purge gas ejection port, and the purge gas cylinder supplies a desired flow rate of purge gas to each ejection port. Since the other parts relating to film formation and the steps for forming the a-Si film are the same as those shown in the prior art, the description thereof will be omitted.

Further, in this embodiment, the i-type graded band gap a- for the bottom cell in FIG.
As the SiGe film forming chamber 1120, the deposited film forming means of FIG. 12 based on the deposited film forming method of the present invention was used.

FIG. 12 shows a substrate used in the roll-to-roll method, which is curved in the i-layer deposition chamber to form the deposition chamber by the substrate itself.

With such a structure, the substrate occupies a considerable part of the film deposition surface, and the utilization efficiency of the deposition gas is improved.

Inside the columnar discharge space having a circular cross section formed by such a curved substrate, an exhaust adjusting plate for performing the pressure adjustment of the present invention was concentrically provided, and the pressure adjustment was performed.

Further, in this example, the microwave is provided with two applicators so as to face the end faces of the columnar discharge space.

In FIG. 12, reference numeral 1201 denotes a belt-shaped member having a width of 20 cm, which is made of SUS430BA material and is curved in a columnar shape with a radius of 12 cm. 1202, 1203
Is a roller 1 for bending the belt-shaped member 1201 into a columnar shape.
Reference numeral 204 is a carrying ring, and 1206a and 1206b are temperature adjusting mechanisms which are provided on the entire circumference. 1207, 1
Reference numeral 208 is a microwave introduction applicator, 1209 is a dielectric window, 1211 and 1212 are waveguides, which are connected to a microwave power source (not shown). 1213a-12
Reference numeral 13d is a gas introduction pipe, and 1214 is an exhaust port, which is connected to an exhaust means such as a diffusion pump (not shown). 1215
Is an exhaust control plate for pressure control.

The pressure at any position can be checked by a vacuum gauge (not shown). FIG. 13 schematically shows the flow of gas with such a configuration.

In FIG. 13, 1301 is a belt-shaped substrate curved in a column shape, 1302 is a roller, 1303 is an exhaust control plate, and 1304 is a gas discharge port.

Using the apparatus shown in FIGS. 11 and 12, a tandem cell solar cell was produced by the deposited film forming method of the present invention. The layer structure of the cell is of the type shown in FIG.

The layer thicknesses of the bottom cell n-type a-Si layer are 200Å, the bottom cell i-type graded band gap i-type a-SiGe layer is 2800Å, and the bottom cell p-type a-Si layer is 120Å. , Top cell n-type a-Si
Layer is 180Å, top cell i-type a-Si layer is 2000
Å, the top cell p-type a-Si layer was 100 Å. Table 5 shows the film forming conditions. The positions a, b, c, and d in the i-type a-SiGe layer and the i-type a-Si layer in the table correspond to the positions of the gas discharge ports counted from the approach direction of the strip-shaped substrate.

[0211]

[Table 5] A transparent electrode and a collector electrode were further laminated on the prepared cell, and the solar cell characteristics thereof were examined. AM1.5 as the irradiation light
Energy density is 100mW / c
It was m ^2. The measurement area is 0.5 cm ² . As a result, it was confirmed that it had excellent properties such as an in-hand conversion efficiency of 12.4%.

(Example 5) An a-SiC film was deposited by the deposited film forming method of the present invention using the apparatus shown in FIG.

Specific working methods, such as gas mixing and introducing methods, are the same as those described above and will not be repeated here since they overlap, and the characteristic items performed in this embodiment will be described.

First, the deposited film forming method of the present invention shown in FIG. 1 was incorporated into the a-SiC film forming chamber 1550 of the roll-to-roll system production apparatus shown in FIG.

In this embodiment, the n-layer film forming chamber 1530 is used.
In the p-layer film forming chamber 1570, film forming gas and doping
No gas was flown at all, and no discharge was generated by microwave power, and the chamber was simply a chamber through which the strip-shaped substrate passed. That is, in this embodiment, one of the purposes is to grasp the single layer characteristics of the film deposited in the a-SiC film forming chamber.

Secondly, in this embodiment, the strip-shaped substrate is
The a-Si of the belt-shaped substrate is fixed and does not move.
# 7059 glass was placed along the lengthwise direction of the substrate on the side of the film formation space corresponding to the C film formation chamber. As a method for fixing the glass to the belt-shaped substrate, there are a method of making holes in the belt-shaped substrate and the glass and fixing them with screws, or a method of fixing with a high melting point inorganic adhesive such as Aron ceramic, etc. In, the former was adopted.

That is, in this embodiment, a-Si
C film forming chamber It is not intended to examine the film in the state where the film is deposited at each position from the inlet side end face to the outlet side end face of the film forming chamber. To separate and investigate.

In this embodiment, the cylinder 150 shown in FIG. 15 is used.
3a is replaced with a GeH ₄ gas cylinder and converted into a C ₂ H ₂ gas cylinder. Further, in this example, a DC power source was connected to all the gas discharge ports of the SiC layer deposition chamber and a bias voltage of +60 V was applied.

Under the above basic conditions, an a-SiC film having a film pressure of about 1 μm was formed under the film forming conditions shown in Table 6. Table 6 shows the position a in the SiC layer deposition chamber,
b, c, and d are gas discharge ports 112a to 112 in FIG.
It corresponds to the position of 12d.

[0220]

[Table 6] The C content of the obtained film was measured by an X-ray micro analyzer. Fig. 1 shows the results of the above measurements performed at various points in the i-layer chamber film formation chamber in the longitudinal direction.
4 shows.

As can be seen from FIG. 14, the C content at the edge of the film formation space was substantially 0, confirming the effect of the deposited film forming method of the present invention.

[0222]

As described above, the R-Rμ of the present invention is
The composition changes continuously according to the WCVD method, for example, a-
When an element such as a photovoltaic element including an alloy film such as SiGe or a-SiC, or a film in which the doping amount of a valence electron control agent into a semiconductor element continuously changes is produced, In the case of stacking with end faces or films of other types, composition control at the interface with other films can be realized as desired, ideal bonding surfaces can be formed, and devices with good characteristics can be manufactured. It will be possible.

Furthermore, according to the present invention, for example, a photovoltaic element having good characteristics as described above can be manufactured in a large area in a large amount at a low cost.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of an apparatus for realizing a deposited film forming method of the present invention.

FIG. 2 is a diagram schematically showing a gas flow in a deposited film forming apparatus adopting the deposited film forming method of the present invention.

FIG. 3 is a- produced by using the deposited film forming method of the present invention.
The graph which shows the film thickness distribution of a Ge film.

FIG. 4 is a schematic diagram showing energy bands of a graded band cap a-SiGe film produced by using the deposited film forming method of the present invention.

FIG. 5 is a graph showing the pressure in the film formation space when forming a deposited film based on the deposited film forming method of the present invention.

FIG. 6 is a schematic diagram showing various variations in the case where the band gap of the a-SiGe film is continuously changed.

FIG. 7 is a schematic diagram showing various variations in the case where the content of a valence electron control agent in a semiconductor is continuously changed and the Fel level is continuously changed.

FIG. 8 (a) is a graph showing the position dependence of the optical band gap of a film deposited using the present invention and the conventional deposited film forming method. FIG. 8B is a graph showing the position dependence of the Ge content in the film deposited using the present invention and the conventional deposited film forming method.

FIG. 9 is a graph showing the distribution of Ge content in the depth direction in a deposited film using the present invention and a conventional deposited film forming method.

FIG. 10 is a graph showing the distribution of Ge content in the depth direction in a film manufactured by variously changing the pressure distribution in the film formation space in the deposited film forming method of the present invention.

FIG. 11: a-SiG utilizing the deposited film forming method of the present invention
The schematic diagram which shows an example of the apparatus used when producing the laminated | stacked solar cell which consists of e and a-Si.

FIG. 12 is a deposition film forming apparatus using the deposition film forming method of the present invention, in which a belt-shaped substrate is curved to form a columnar film formation space, and microwaves are input from both end faces of the columnar film formation space. FIG.

13 is a diagram schematically showing a gas flow in the deposited film forming apparatus shown in FIG.

14 is a graded band gap a produced by the deposited film forming method of the present invention using the apparatus shown in FIG.
-The graph which shows the C content rate in a SiC film.

FIG. 15 is a schematic diagram showing a conventional roll-to-roll system production device.

FIG. 16 is a schematic diagram showing an example of a laminated solar cell.

FIG. 17 is an energy band diagram of an a-SiGe film. (A) In case of the graded band gap method (b) In case of the conventional method

FIG. 18 is a schematic diagram showing an arrangement of a conventional film forming space in a roll-to-roll system production apparatus.

FIG. 19 is an a-S manufactured using a conventional deposited film forming method.
The schematic diagram which shows the energy band of an iGe film.

FIG. 20: an a-S fabricated using a conventional deposited film forming method
The graph which shows the film thickness distribution of i film and a-Ge film.

[Explanation of symbols]

101 Belt-shaped substrate 102 Vacuum chamber for creating a reduced pressure state 104 Exhaust port 105 Exhaust means 103 Film forming chamber 120 SiH ₄ gas line 121 GeH ₄ gas line 122 H ₂ gas line 114a, 114b, 114c, 114d Gas mixer 113a, 113b, 113c, 113d Gas pipe 112a, 112b, 112c, 112d Gas outlet 110a, 110b, 110c, 110d Microwave applicator 111a, 111b, 111c, 111d having a dielectric window Waveguide 201 Vacuum chamber 222 Exhaust Means 203 Film-forming chamber 204a-204d Gas discharge port 205 Exhaust port 206 Band-shaped substrate 1100 Delivery chamber 1102 Substrate 1110 Bottom cell n-type a-Si layer film-forming chamber 1120 Bottom I-type a-SiGe layer deposition chamber for cell 1130 p-type a-Si layer deposition chamber for bottom cell 1140 n-type a-Si layer deposition chamber for top cell 1150 i-type a-Si layer for top cell Deposition chamber 1160 p-type a-Si layer deposition chamber for top cell 1111, 1121, 1161 Gas mixer 1190 SiH ₄ gas, GeH ₄ gas, H ₂ gas, B
₂ H ₆ gas, PH ₃ gas filling gas cylinder 1181 to 1187 Gate. 1201 Band-shaped member 1202, 1203 Roller for bending the band-shaped member 1201 into a column 1204 Transport ring 1206a, 1206b Temperature adjustment mechanism 1207, 1208 Microwave applicator 1209 Dielectric window 1211, 1212 Waveguide 1213a-1213d Gas introduction tube 1214 Exhaust port 1215 Exhaust control plate 1301 Column-shaped curved belt substrate 1302 Roller 1303 Exhaust control plate 1304 Gas emission port 1501 Band substrate 1511, 1591 Bobbin 1510 for winding each substrate 1501 Substrate delivery chamber 1530 n-type a-Si film forming chamber 1550 i-type a-SiGe film forming chamber 1570 p-type a-Si film forming chamber 1590 substrate winding chamber 1520, 1540, 1560, 1580 gate 1530a, 1550a, 1570 Microwave applicators 1530b, 1550b, 1570b waveguide 1502a~1506a material gas cylinders 1502a SiH ₄ gas cylinder 1503a GeH ₄ gas cylinder 1504a H ₂ gas cylinder 1505a PH ₃ gas cylinder 1506a B ₂ H ₆ gas cylinder 1502b to 1506b Gas cylinder opening / closing valve 1502c to 1506c Pressure reducer 1530c, 1550c, 1570c Gas mixer 1530d, 1550d, 1570d Gas introduction line 1510e, 1530e, 1550e, 1570e, 1
590e Exhaust pump 1530f, 1550f, 1570f Heater for heating substrate 1530g, 1550g, 1570g Power supply for heater for heating substrate 1507a Purge gas cylinder for gate 1507b Pressure reducer 1507c, 1507d Gas flow controller 1601 Conductive substrate 1602 Lower photovoltaic power Device (bottom cell) 1602 n-type a-Si, 1602b i-type a-SiGe, 1602c p-type microcrystalline μC-Si layer 1603 upper photovoltaic device 1603a n-type a-Si, 1603b i-type a-Si, 1603c p-type microcrystal μC-Si layer 1604 transparent electrode 1605 current collecting electrode 1801 belt-shaped substrate 1802 vacuum chamber 1803 deposition chamber 1804 exhaust port 1805 exhaust means 1820 SiH ₄ gas line 1821 GeH ₄ gas line Emissions 1822 H ₂ gas line 1814a~1814d gas mixer 1813a~1813d gas pipe 1812a~1812d gas outlet 1810a~1810d microwave applicator 1811a~1811d waveguide

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoshi Yoshito 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shotaro Okabe 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Akira Sakai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (4)

[Claims] 1. A film-forming gas is introduced into the film-forming space through a gas supply means while continuously moving in the longitudinal direction with the strip-shaped substrate as one of the side walls of the film-forming space. At the same time, microwave energy is radiated by microwave applicator means into the film forming space to generate microwave plasma, and microwave plasma CVD is used to continuously form a deposited film on the surface of the moving strip-shaped substrate.
Method and a roll-to-roll method for forming a deposited film, the film deposited on the strip-shaped substrate is composed of a plurality of elements, and the concentration of any one of the plurality of elements is continuous in the film formation space. The concentration of any of the plurality of elements has an extreme value at a specific location in the film formation space, and the reaction pressure has an extreme value at the specific location in the film formation space. Microwave plasma CVD method characterized by performing film deposition under the condition of 3 conditions and roll-to-roll
A deposited film forming method using a roll method. 2. The microwave plasma CVD method according to claim 1, wherein the plurality of elements are elements capable of forming an amorphous semiconductor thin film having different optical band gaps. And a deposited film forming method using a roll-to-roll method. 3. The microwave plasma CVD method and roll-to-roll method according to claim 2, wherein the plurality of elements include at least silicon, germanium, and hydrogen and / or halogen. A deposited film forming method using a roll method. 4. The microwave plasma CVD method and roll-to-roll method according to claim 2, wherein the plurality of elements include at least silicon, carbon, and hydrogen and / or halogen. A deposited film forming method using a roll method.