JP2001007027A - Method and device for form deposition film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously form a deposition film having a composition distribu tion in the film-thickness direction on a mobile substrate by introducing a plural ity of source gases from a discharge space forming a region, where a in-film composition ratio of group III, IV, or V elements contained in such a material gas as of small dissociation energy is maximum in the film-thickness direction. SOLUTION: Related to the deposition film forming method, a long length base body 5 is moved continuously in a discharge space 7 and a deposition film, where a composition changes in the film-thickness direction is formed continuously on the lengthy mobile base body 5 by a plasma CVD method. At the introduction of a plurality of source gases containing each kind of group III, IV, or V elements from the moving direction position of the base body 5 in the discharge space 7, a plurality of source gases is introduced from a position of the discharge space 7 for forming a region where the in-film composition ratio of group III, IV, or V elements contained in a source gas, among a plurality of source gases, whose dissociation energy is small is maximum in the film-thickness direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method and an apparatus for continuously forming a deposited film on a long substrate by a plasma CVD method. In particular, the present invention relates to a method and an apparatus for forming a deposited film having a composition distribution in a thickness direction, particularly a functional deposited film such as a photovoltaic element.

[0002]

2. Description of the Related Art In recent years, while the demand for electric power has rapidly increased worldwide, as power production has been activated to meet such demand, greenhouses such as carbon dioxide released into the atmosphere in thermal power generation have been developed. Concerns about the effects on the environment, such as its effects, the destruction of rivers and forests by hydropower, and the danger of radioactive contamination in nuclear power, have become more serious. Under these circumstances, solar cell power generation using sunlight has attracted attention as a clean energy source. By the way, in order to put solar cell power generation into practical use, the solar cell (photovoltaic element) used must have sufficiently high photoelectric conversion efficiency, excellent characteristics and stability, and be suitable for mass production. Is required. In addition, a large-area solar cell is required in view of the power generation scale. For this reason, a readily available raw material gas such as silane is decomposed by glow discharge to deposit a semiconductor thin film such as amorphous silicon on a relatively inexpensive substrate such as glass or a metal sheet. Silicon-based solar cells have been proposed. This amorphous silicon-based solar cell has attracted attention as being excellent in mass productivity and low in cost as compared with a solar cell manufactured from single crystal silicon or the like, and various proposals have been made on a method for manufacturing the same.

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

As a method for remarkably improving the mass productivity of the above-mentioned so-called stacked element, US Pat.
No. 9 describes “Roll to Roll”.
A continuous plasma CVD method employing the (Roll) method is disclosed. FIG. 4 shows a continuous plasma CVD apparatus employing a roll-to-roll method. According to this method, a conductive semiconductor required in a plurality of glow discharge regions 111, 112, and 113 separated by gas gates 106, 107, 108, and 109 using a long base (band-shaped member) 110 as a substrate. By continuously moving the substrate in the longitudinal direction while depositing and forming a layer, an element having a semiconductor junction can be continuously formed. On the other hand, as an attempt to improve the photoelectric conversion efficiency of an amorphous silicon-based photovoltaic device, a-SiGe, a
-When a Group IV alloy semiconductor such as SiC is used as the i-type (intrinsic) semiconductor layer, the forbidden band width (band gap) of the i-type semiconductor layer is continuously and appropriately adjusted in the film thickness direction from the light incident side. It has been found that the variation greatly improves the open-circuit voltage and fill factor as a photovoltaic element. A method for forming a film having a composition continuously changed in the thickness direction on a moving substrate is disclosed in JP-A-5-121338.
And JP-A-5-234918.

In Japanese Patent Application Laid-Open No. 5-121338, a flow of a source gas is formed in a direction parallel to a moving direction of a substrate,
A method is described in which plasma is generated by a plurality of discharge means arranged in the direction of movement of the substrate to form a deposited film on the surface of the substrate. In Japanese Patent Application Laid-Open No. Hei 5-234918, in microwave plasma CVD, the concentration of any of the elements constituting a film to be deposited is changed in a film formation space, and the concentration of any of the elements is increased. A method is disclosed in which a deposited film is formed so as to have an extreme value at a specific location in a film space and to have an extreme reaction pressure at a specific film forming space location. By the way, from a demand for reduction of photodeterioration (Stabler-Wronski effect) of a photovoltaic element and improvement of conversion efficiency, we have used an i-type semiconductor in a plasma CVD method using VHF power (hereinafter referred to as a VHF plasma CVD method). We focus on the formation of layers. VH
When an amorphous silicon or amorphous silicon germanium film is formed by the F plasma CVD method, a high-speed film formation with a deposition rate of 30 ° / sec or more can be performed;
Discharge and film formation are possible at low pressures of the order of 1 to 100 mTorr as compared with RF discharge, and the growth of poly-like substances in the gas phase can be suppressed. In addition, there is a feature that the discharge distribution due to the wavelength and the standing wave in the discharge furnace is small.

[0006]

However, the above V
In producing a photovoltaic device having better photoelectric characteristics in the HF plasma CVD method, a further problem to be solved is a film thickness of an i-type semiconductor layer such as amorphous silicon, alloy-based silicon germanium, and silicon carbide. Controlling the composition distribution in the direction, or changing the composition at the interface with the adjacent n-type layer or p-type layer based on the electrical and optical characteristics and the film structure of the i-type semiconductor layer obtained by VHF film formation. Controlling and forming an ideal bonding surface to produce a photovoltaic device having good photoelectric characteristics, and the like, are desired, and it is desired to achieve these problems more effectively.

In order to solve the above-mentioned problems, the present invention provides a method of forming a deposited film capable of continuously forming a deposited film having a composition distribution in a thickness direction on a moving substrate without variation in characteristics. And equipment, especially VHF plasma CV
Providing a method and an apparatus for forming a deposited film by a D method;
In particular, it is an object of the present invention to provide a method and an apparatus for forming an i-type semiconductor layer having an optical band gap distribution in a film thickness direction by a VHF plasma CVD method in producing a pin-type semiconductor photovoltaic device. It is.

[0008]

According to the present invention, in order to achieve the above object, a method and an apparatus for forming a deposited film are configured as follows. That is, in the method of forming a deposited film of the present invention, a long substrate is continuously moved to a discharge space, and a deposited film whose composition changes in a film thickness direction is formed on the moving long substrate by a plasma CVD method. In the method of forming a deposited film, a plurality of source gases each containing one group III, IV, or V element are introduced from a position in the discharge space in which the substrate moves in the discharge space. The group III or IV contained in the source gas having a low dissociation energy out of the gas, the composition ratio of the element in the film, from the position of the discharge space to form a region where the maximum in the film thickness direction, the plurality of It is characterized by introducing a source gas. Further, in the method of forming a deposited film according to the present invention, the introduction position of the source gas into the discharge space is unified on the upper side or the lower side in the moving direction of the substrate in the discharge space of a plurality of adjacent discharge furnaces. The substrate is sequentially moved along the plurality of adjacent discharge furnaces to form a deposited film on the substrate. Further, in the method of forming a deposited film according to the present invention, the plasma CVD method is a plasma CVD method in which an n-type semiconductor layer, an i-type semiconductor layer, and a p-type semiconductor layer are stacked in this order, and the n-type semiconductor layer is formed by a VHF plasma CVD method. It is characterized in that an i-type semiconductor layer whose optical band gap becomes narrower from the side toward the p-layer side is formed. Further, in the method of forming a deposited film according to the present invention, the plasma CVD method is a plasma CVD method in which an n-type semiconductor layer, an i-type semiconductor layer, and a p-type semiconductor layer are stacked in this order, and the n-type semiconductor layer is formed by a VHF plasma CVD method. Forming an i-type semiconductor layer having an optical band gap narrower from the side toward the p-layer side, and then increasing the optical band gap toward the p-type layer side by RF-CVD. Is formed. Further, in the method of forming a deposited film according to the present invention, the i-type semiconductor layer formed by the VHF plasma CVD method may be made of amorphous silicon germanium (SiGe).
It is characterized by being. Further, the method of forming a deposited film according to the present invention is characterized in that the plurality of source gases are introduced from a lower side in a moving direction of the substrate in a discharge space of a plurality of adjacent discharge furnaces. In the method for forming a deposited film according to the present invention, the plurality of source gases include Si and Ge elements, and Ge / (Ge +
The value of Si) satisfies the relationship: discharge furnace located upstream in the moving direction of the substrate <discharge furnace located downstream in the moving direction of the substrate. Further, in the deposited film forming method of the present invention, in the deposited film formed by the VHF plasma CVD method, the Ge concentration in the film is such that the film formed on the upstream side in the moving direction of the substrate <the downstream in the moving direction of the substrate. It is characterized by satisfying the relationship of the film formed on the side. Further, in the method of forming a deposited film according to the present invention, the plurality of source gases include Si and C, and C in a supply amount of the source gases.
It is characterized in that the value of / (C + Si) satisfies the relationship: discharge furnace located upstream in the moving direction of the substrate> discharge furnace located downstream in the moving direction of the substrate. Further, in the deposited film forming method of the present invention, in the deposited film formed by the VHF plasma CVD method, the C concentration in the film is such that the film formed on the upstream side in the moving direction of the substrate> the downstream in the moving direction of the substrate. It is characterized by satisfying the relationship of the film formed on the side. Further, the method of forming a deposited film according to the present invention is characterized in that the i-type semiconductor layer formed by the VHF plasma CVD method is amorphous silicon carbon (SiC). Further, the deposited film forming apparatus of the present invention includes a device for continuously moving a long substrate, and the device continuously moves the long substrate to a discharge space by the device. In a deposition film forming apparatus for continuously forming a deposition film having a composition that changes in the film thickness direction on a long substrate to be formed,
A source gas introduction section for introducing a plurality of source gases each containing one group III element, a group IV element, and a group V element, and an introduction section for introducing the source gas into the discharge space; Among the source gases, the composition ratio of the group III or IV, group V element contained in the source gas having a small dissociation energy in the film is disposed at a position where a region having the maximum in the film thickness direction can be formed. It is characterized by having. Further, in the deposited film forming apparatus of the present invention, the introduction position of the raw material gas into the discharge space is unified on the upper side or the lower side in the moving direction of the substrate in the discharge space of a plurality of adjacent discharge furnaces. It is characterized by being. Further, the deposited film forming apparatus of the present invention is characterized in that the plasma CVD method is a plasma CVD method using VHF power. In the present invention, VHF refers to a frequency of 30 MHz to 500 MHz.

[0009]

According to the present invention, a deposited film having a composition distribution in a film thickness direction is formed on a moving substrate by a structure having the above-mentioned features. In particular, when producing a pin-type semiconductor photovoltaic device, an i-type semiconductor layer having an optical band gap distribution in the film thickness direction is formed by a VHF plasma CVD method. It is based on the following findings of the inventors. That is, when the source gas is introduced during the discharge in which the discharge power is uniformly supplied, the concentration of the source gas decreases as the distance from the introduction position of the source gas increases. As the gas diffuses into the discharge space,
The dissociated source gas is adsorbed on the substrate and members around the discharge space,
This is because they are deposited. Also, the dissociation energy is different,
When a plurality of source gases having different elements are introduced into the discharge space from the same place, the composition ratio of the gas (mixing ratio of the plurality of gases) changes as the source gas diffuses from the introduction position to the periphery. come. This is because a raw material gas having a low dissociation energy has a higher decomposition rate and is absorbed and deposited on a member and is consumed quickly. Therefore, the ratio of a raw material gas having a high dissociation energy increases as the distance from the introduction position increases. As described above, the present invention has been completed through a number of experiments and the like as described below.

(Experiment 1) Source gases having different dissociation energies, SiH ₄ and GeH ₄ (dissociation energy: S
iH ₄ > GeH ₄ ), a deposited film was formed on a fixed substrate exposed to electric discharge, and the deposition area distribution of the content ratio of Si to Ge in the deposited film was examined by XMA. . Also,
The optical band gap of the deposited film was investigated. FIG. 2 shows the discharge furnace used. The raw material gas is mixed and supplied from a gas supply pipe to the discharge space of the discharge furnace, and discharge generation power is supplied from an external power supply through the electrodes. Further, the atmosphere gas in the discharge space is uniformly exhausted from the surface facing the base. The substrate was fixedly installed so as to cover the discharge space and to be exposed to the discharge. The conditions for forming the deposited film are as follows: source gas SiH ₄ is 200 sccm;
eH ₄ was supplied at 200 sccm and H ₂ was supplied at 1000 sccm, and a DC bias of +100 V (with respect to the substrate) was superimposed on the electrode at VHF of 100 MHz and 1 kw. Pressure 20m
Torr, substrate temperature 320 ° C. The middle part of FIG. 2 shows the Ge concentration (Ge / Ge + Si) in the formed deposited film. It is highest at the position where the raw material gas is blown out, and decreases as the distance from the blowout position increases. Since the dissociation energy of GeH ₄ is smaller than that of SiH ₄ , the gas decomposition rate with respect to the supplied amount is larger in GeH _{4. In} the diffusion process, the mixing ratio of SiH ₄ increases as the distance from the gas introduction position increases, and the Ge in the film increases. Concentration (Ge / (Ge + Si))
Decreases. When the optical band gap (forbidden band width) of the deposited film was measured, it was narrow at the gas introduction position corresponding to the Ge concentration distribution in the film and widened as the distance increased.

(Experiment 2) Next, the diffusion of gas in the discharge space and the exhaust direction will be considered. In the apparatus shown in FIG. 2 used in Experiment 1, the position of introducing the raw material gas into the discharge space was fixed, and the position of the exhaust port of the atmosphere gas was changed as in the conditions a, b, and c described later, and the discharge was started. Forming a deposited film on a substrate fixed to be exposed,
The content ratio of Ge was measured. The film forming conditions were the same as in Experiment 1. FIG. 3 shows the positional relationship between the source gas introduction position and the exhaust port,
And the distribution of the Ge concentration in the deposited film in the film formation region. The introduction position of the raw material gas is provided near the right end of the discharge space, and the exhaust port is provided at the left end of the discharge space under the condition (a). In the condition (c), the discharge space is provided at the right end of the discharge space. The distribution of the Ge concentration in the deposited film in the film formation region is defined as condition a,
Let's compare by b and c. A feature of the distribution common to the three conditions is that the Ge concentration in the film is maximized on the source gas introduction position. The difference between the three conditions is the gradient of the decrease in the Ge concentration in the film from the gas introduction position (right end of the discharge space) to the left end of the discharge space. The shape of the Ge concentration in the film under the condition (a) is that the source gas supplied to the right end of the discharge space diffuses and dissociates during the discharge and diffuses and moves to the exhaust port at the left end of the discharge space according to the pressure gradient. As a distribution. The shape of the Ge concentration in the film under the condition (b) reflects the distribution resulting from the decomposition and dissociation of the source gas supplied to the right end of the discharge space while diffusing to the left in the discharge space. The diffused source gas diffuses to the exhaust port at the bottom of the discharge space. The shape of the Ge concentration in the film under the condition (c) is a distribution generated as a result of decomposition and dissociation while the source gas supplied to the right end of the discharge space diffuses in the discharge in the opposite direction to the exhaust port (no flow). Is reflected. Condition (b) or condition (c)
From the results, it can be seen that the Ge concentration distribution in the film can be formed on the substrate in a direction perpendicular to or opposite to the flow direction of the source gas. In other words, it was found that a Ge concentration distribution (in the film formation region) in the film depending on the distance from the supply position of the source gas could be created regardless of the direction of the gas flow.

(Experiment 3) Next, based on the above results,
It is considered that a deposited film having a composition distribution in a film thickness direction is formed on a substrate while moving the substrate over a film forming region of a discharge furnace. In the discharge furnace used in Experiments 1 and 2, the introduction position of the raw material gas into the discharge space was changed in the moving direction of the substrate, and the substrate was moved along the discharge furnace while the substrate was moved in the film thickness direction. An i-type SiGe semiconductor deposited film having a changed composition was formed. The left side of FIG. 4 shows the conditions (ac) for introducing the source gas into the discharge space of the discharge furnace in the experiment. The substrate continuously moves along the discharge furnace from the left hand (n-layer side) to the right hand (p-layer side) in the drawing. The source gas introduction position under each condition is as follows: Condition (a): Introduce to the center of the discharge furnace in the substrate moving direction. Condition (b): The discharge furnace is introduced near the end (n-layer side) in the substrate moving direction. Condition (c): The discharge furnace is introduced near the lower end (p layer side) in the substrate moving direction. The film forming conditions such as the supply amount of the source gas, the VHF power, the pressure, and the substrate temperature were the same as in Experiment 2. The formation of the deposited film was performed in the following manner. Roll-to-roll (Ro) as shown in FIG.
continuous plasma C adopting the “ll to roll” method
Apparatus 100 for forming semiconductor layer of photovoltaic element in VD method
The discharge furnace under the above condition (a) was mounted in the i-type semiconductor layer forming chamber 105 to form an i-type SiGe semiconductor deposition film. The forming apparatus 100 includes a long strip-shaped substrate 108.
Vacuum chambers 101 and 107 for sending out and winding up, an n-type layer forming chamber 102, an i-type layer forming chamber 103, and an i-type layer forming chamber 104, i
The mold layer forming chamber 105 and the p-type layer forming chamber 106 are connected to gas gates 109, 110, 111, 112,
It is configured to be connected via 113 and 114. First, a delivery chamber 10 having a substrate delivery mechanism is provided.
1, a SUS430BA band-shaped base 108 (600 m wide)
m × length 100 m × thickness 0.13 mm) is set, and the substrate 108 is passed through a gas gate and each semiconductor layer forming chamber to a winding chamber 107 having a winding mechanism. The tension was adjusted to such an extent that there was no slack. Therefore, each chamber 1
01 to 107 were evacuated by a vacuum pump (not shown). Next, the gate gas introduction pipe 11 is connected to the gas gates 109 to 114.
From 5 to 120, 700 sc of H ₂ is used as a gate gas.
cm, and the base was heated to 320 ° C. in the i-type layer forming chamber 104 by a heater. And
SiH ₄ was introduced at 250 sccm into the discharge furnace 121 in the i-type layer forming chamber 104 through the raw material gas introduction pipe 122.
250 sccm of eH ₄ and 1000 sccm of H ₂ were introduced. The pressure in the discharge furnace was adjusted with a conductance valve (not shown) so as to be 25 mTorr. The other chambers were adjusted with a conductance valve (not shown) so that the pressure of the discharge furnace became 1 Torr. Then, the electrode 123
Then, a 100 MHz VHF power of 500 W was introduced to generate glow discharge in the discharge space. Next, the substrate 108 was transported at a speed of 50 cm / min in the direction of the arrow in the figure, and an i-type SiGe semiconductor deposited film was formed on the substrate. On the belt-like substrate 10
After the deposited film was formed on m, the inside of the chamber was purged with He, cooled, leaked to the atmosphere, and the substrate wound on the bobbin 140 of the winding chamber 107 was taken out. Hereinafter, the discharge furnace of the i-type semiconductor layer forming chamber is sequentially set under the condition (b),
Instead of (c), i-type SiGe is formed under the same film forming conditions and procedures.
A semiconductor deposition film was formed. Ten points were arbitrarily selected from each of the formed deposited films under the respective conditions, cut out, and elementary analysis in the depth direction was measured using a secondary ion mass spectrometer (SIMS). As a result, the distribution in the depth direction shown in FIG. 5 was obtained. Under the condition (a), the profile was such that Ge increased toward the middle of the film thickness and Si decreased. Under the condition (b), the profile was such that Ge decreased toward the film surface (from the n-layer side to the p-layer side) and Si increased. Further, under the condition (c), the profile was such that Ge increased toward the film surface (from the n-layer side to the p-layer side) and Si decreased. From this result, it was found that the bandgap profile in the thickness direction of the deposited film formed under each condition was as shown in the diagram on the right side of FIG. The band gap is narrowest at the position where the source gas is introduced,
It turned out that it became wider as the distance increased. Thus, by adjusting the introduction position of the source gas into the discharge space with respect to the moving direction of the substrate, the composition distribution in the thickness direction of the deposited film changes, and the optical band gap of the i-type SiGe semiconductor layer is changed. It was found that various distributions were formed in the film thickness direction.

(Experiment 4) Next, as shown in FIGS. 4 (d) and 4 (e), the substrate is sequentially passed through a plurality of discharge furnaces to obtain a distribution in which the composition continuously changes in the film thickness direction. A deposited film was formed on the substrate. The feature of each condition is as follows: Condition (d): two discharge chambers are arranged adjacent to each other in the moving direction of the substrate (good in the substrate moving direction = discharge chamber A, the furnace on the n-th layer side)
The furnace on the lower layer side is referred to as a discharge chamber B), and both A and B have independent source gas supply control systems, and the gas is introduced into the discharge chamber from the lower side of the substrate moving direction on the p layer side. The exhaust port is provided at the end on the n-layer side in A and on the p-layer end in B, and a conductance valve is installed on a pipe connected to an exhaust device (vacuum pump) outside the discharge chamber, so that the pressure can be controlled independently. . In addition, discharge power is supplied from an independent power supply to the electrodes of the respective discharge chambers. The shape (length, volume) of one discharge chamber is the same as the discharge chamber used in Experiment 3. Condition (e): Three discharge chambers are disposed adjacent to each other in the moving direction of the substrate (discharge chambers A, B, and C are described from the upper side (n-layer side) to the lower side (p-layer side) in the substrate moving direction. ), The raw material gas is discharged into the discharge chamber A by an independent raw material gas supply control system.
Both B and C are introduced from the lower side (p layer side) in the substrate moving direction. The exhaust port is provided at the end on the n-layer side in A, in the lower part of the discharge chamber in B, and at the p-layer end in C, and a conductance valve is provided on a pipe connected to an exhaust device (vacuum pump) outside the discharge chamber. Is installed and pressure can be controlled independently. In addition, discharge power is supplied from an independent power supply to the electrodes of the respective discharge chambers. The shape (length, volume) of one discharge chamber is the same as the discharge chamber used in Experiment 3. The discharge furnaces under the conditions (d) and (e) were sequentially mounted in the i-type semiconductor layer formation chamber of the deposition film forming apparatus used in Experiment 3, and an i-type SiGe semiconductor layer was formed in the procedure of Experiment 3.
Creating conditions, condition (d): the raw material gas deposition chamber A, respectively B (Conditions _{d-1) SiH 4 250sccm,} GeH 4 250sccm H 2 1000sccm and (Condition d-2) the film forming chamber A SiH ₄ 300 sccm, GeH ₄ 200 sccm H ₂ 1000 sccm Deposition chamber B Two conditions of SiH ₄ 220 sccm and GeH ₄ 280 sccm H ₂ 1000 sccm Power VHF 100 MHz 500 w DC + 100 v Superposed pressure 18 mTorr Substrate temperature 320 ° C. Substrate moving speed 1 m / min Condition (e): source gas deposition chamber _{A SiH 4 300sccm, GeH 4 200sccm} H 2 1000sccm film formation chamber _{B SiH 4 250sccm, GeH 4 250sccm} H 2 1000sccm deposition chamber _{C SiH 4 220sccm, GeH 4 280sccm} H 2 10 0 sccm or less, power is applied to each of the film forming chambers A, B, and C. VHF 100 MHz 500 w DC + 100 v superimposed pressure 15 mTorr substrate temperature 320 ° C. substrate moving speed 1.5 m / min. 10 points are arbitrarily selected from the deposited films under each condition prepared. Cutting out, secondary ion mass spectrometer (SIMS)
Was used to measure the elemental analysis in the depth direction. As a result, it was found that a deposited film having the optical band gap shown in the conditions (d) and (e) of FIG. 4 was formed. When the moving speed of the substrate is high, a long film formation region (distance) must be secured in the discharge space in order to increase the film thickness. However, a plurality of film formation regions as in conditions (d-2) and (e) are required. If a film is formed by a film furnace, a deposited film having a continuous composition distribution in the film thickness direction can be formed.

The present invention is applied to forming a composition distribution in a thickness direction of a semiconductor layer of a photovoltaic element. Specifically, it is applied to optical band gap control, Fermi level control, refractive index control, crystallinity control, and the like. As a semiconductor material constituting the semiconductor layer, a-Si: H, a-
Si: F, a-Si: H: F, a-SiC: H, a-S
iC: F, a-SiC: H: F, a-SiGe: H, a
-SiGe: F, a-SiGe: H: F, poly-S
i: H, poly-Si: F, poly-Si: H:
F, μc-Si: H, μc-Si: F, μc-Si:
H: A group IV semiconductor material such as F and a group IV alloy-based semiconductor material are exemplified. Other examples include II-VI group compound semiconductor materials and III-V group compound semiconductor materials.

Examples of the raw material gas for introducing the group III, IV, and V atoms into the film composition include hydrides, halides such as fluorides and chlorides. As a source gas for supplying silicon atoms, hydrides such as SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ , SiF ₄ , Si ₂ F ₆ , Si ₃ F ₈ , SiHF ₃ ,
SiH ₂ F ₂ , SiH ₃ F, SiH ₂ Cl ₂ , SiHCl ₃ ,
Halides such as SiCl ₄ . As a source gas for supplying germanium atoms, GeH ₄ , Ge ₂ H
₆ , hydrides such as Ge ₃ H ₈ , GeHF ₃ , GeH
₂ F ₂ , GeH ₃ F, GeF ₄ , GeHCl ₃ , GeH ₂ Cl
_And halides such as ₂ , GeH ₃ Cl and GeCl ₄ . As a source gas for supplying carbon atoms, CH ₄ ,
Saturated hydrocarbons such as C ₂ H ₆ and C ₃ H ₈ , ethylene hydrocarbons such as C ₂ H ₆ , acetylene hydrocarbons such as C ₂ H ₂ , CF ₄ , CHF ₃ and CH ₂ F ₂ , CH ₃ F, CC
halides such as l ₄ , CHCl ₃ , CH ₂ Cl ₂ , and CH ₃ Cl. Examples of the source gas for supplying Group III atoms include hydrides and halides such as B ₂ H ₆ , BF ₃ , and BCl ₃ . Further, examples of the source gas for supplying Group V atoms include hydrides and halides such as PH ₃ , PF ₃ , and PCl ₃ .

[0016]

Embodiments of the present invention will be described below.
The present invention is not limited by these examples. [Example 1] In Example 1, a pin type amorphous silicon germanium photovoltaic device having the structure shown in FIG. 10A was formed by using the method of the present invention. n-type layer 5
03 is amorphous silicon, and the p-type layer is microcrystalline silicon 505. The i-type semiconductor layer 504 has a band gap structure of the conditions (a) to (d) shown in FIG. 1 in order to form the optical band gap distribution in the film thickness direction.
The goal was to create an in-type SiGe photovoltaic device. Condition (a): i is determined by VHF plasma CVD to reduce the optical band gap from the n-layer side to the p-layer side.
Type SiGe layer is formed, and RF plasma CV
An amorphous SiGe layer was formed by the RF plasma CVD method in which the optical band gap was widened from the n-layer side to the p-layer side by the D method (embodiment 1-1).

Condition (b): An i-type SiGe layer is formed by VHF plasma CVD so that the optical band gap becomes narrower from the n-layer side to the p-layer side, and VHF is formed thereon.
An amorphous SiGe layer was formed by the plasma CVD method, in which the optical band gap was widened from the n-layer side toward the p-layer side, by the RF plasma CVD method (Comparative element 1-1). Condition (c): n is formed on the silicon layer by RF plasma CVD by VHF plasma CVD so that the optical band gap becomes narrower from the n-layer side toward the p-layer side.
An i-type SiGe layer is formed by a VHF plasma CVD method so that an optical band gap becomes narrower from the layer side toward the p layer side. Of the amorphous SiGe layer with a wide dynamic band gap (embodiment 1-
2).

Condition (d): A silicon layer having a flat optical band gap is formed by RF plasma CVD, and a SiGe layer having a flat optical band gap is formed thereon by VHF plasma CVD. Further, a silicon layer having a flat optical band gap was formed thereon by RF plasma CVD (Comparative element 1-2).

For the pin type semiconductor layer of the photovoltaic element, a deposition film forming apparatus by a continuous plasma CVD method using a roll-to-roll method shown in FIG. Was. In the i-type layer forming chamber 104, a VHF having a structure shown in FIG.
A plasma CVD discharge furnace was installed. The VHF electrode was provided in the discharge furnace so that power was uniformly applied to the discharge space. The n-type semiconductor layer forming chamber 102, the i-type semiconductor layer forming chambers 103 and 105, and the p-type semiconductor layer forming chamber 106 contained an RF plasma CVD discharge furnace having a plate electrode facing a substrate as shown in FIG. (The evacuation direction and the source gas introduction position are appropriately adjusted according to the film forming conditions.) The photovoltaic element under the above conditions was prepared in the following procedure. First, the delivery chamber 101 having the substrate delivery mechanism is sufficiently degreased and washed to provide a lower electrode (FIG. 1).
0 502) by the sputtering method.
A SUS430BA band-like substrate 108 (width 600 mm × length 100 m × thickness 0.13 mm) on which a silver thin film is deposited to a thickness of 100 nm and a ZnO thin film is deposited to a thickness of 1 μm is set, and a bobbin 139 is set. 109-114, each semiconductor layer forming chamber 102-1
Through 06, the sheet was passed to a take-up chamber 107 having a band-shaped member take-up mechanism, and the tension was adjusted to a level where there was no slack.

Therefore, each of the chambers 101 to 107 is disabled.
Vacuum was drawn by the illustrated vacuum pump. Next, gas gate 1
The gate gas inlet pipes 115-120
H as the source gas_TwoFlow each at 700 sccm
Lamp built in body layer forming chambers 102 to 106
The belt-shaped substrate 108 was heated by the heater. (Heating conditions
Are shown in Tables 1 and 2. ) And each semiconductor layer formation channel
Feed gas (see Tables 1 and 2) to discharge furnaces 102 to 106
) Is supplied from source gas introduction pipes 122, 125 to 128.
did. Pressure in the discharge furnace in each semiconductor layer formation chamber
So that the conductance bar becomes the value shown in Table 1 and Table 2.
Adjusted with a lube (not shown). Thereafter, each semiconductor layer forming chip is
See Tables 1 and 2 for Chamber electrodes 123 and 135-138.
Glow discharge was generated by applying the indicated power. Next,
The body 108 is transported at a speed of 100 cm / min in the direction of the arrow in the figure.
To form an i-type SiGe semiconductor deposited film on the substrate.
Was. First, after forming a 10 m film on the belt-like substrate under the condition (a),
According to the condition (b), a film was formed to have a thickness of 10 m.
m was formed. The substrate on which the film was formed is a winding chamber
After being wound on 107, the inside of each chamber is purged with He.
After cooling, the air leaks to the winding chamber 10
The substrate wound around the bobbin 140 of No. 7 was taken out. Next
Then, a transparent electrode (FIG. 10 506) is formed on the second conductivity type layer.
As ITO (In _TwoO_Three+ SnO_Two) By vacuum evaporation
80 nm deposited and further connected to a collecting electrode (507 in FIG. 10).
Then, Al is vapor-deposited by vacuum vapor deposition to a thickness of 2 μm,
It was created.

Next, the i-type semiconductor layer forming chamber 105
The VHF plasma CVD discharge furnace shown in FIG. 8 was attached to the discharge furnace described above, and a photovoltaic element was prepared under the same procedure as described above under the condition (b) (comparative element 1-1). In the discharge furnace shown in FIG. 8, the source gas is introduced into the discharge space from the upper side (n-layer side) in the moving direction of the substrate. Further, the discharge furnace in the i-type semiconductor layer formation chamber 105 is returned to its original state, and the VHF plasma CVD discharge furnace shown in FIG. It was produced in the same procedure as above (Comparative element 1-2). The discharge furnace shown in FIG. 7 has a configuration in which the raw material gas is uniformly supplied to the discharge space in the moving direction of the substrate. I of the above photovoltaic element
Table 1 shows the conditions for forming the type semiconductor layers, and Table 2 shows the conditions for forming the n-type and p-type semiconductor layers.

[0022]

[Table 1]

[0023]

[Table 2] For the created solar cell module, the AM value was 1.
When the characteristics were evaluated using pseudo sunlight having an energy density of 100 mW / cm ² at 5, the photoelectric conversion efficiency of the working device was 9% or more. Implementation element 1-1 and comparison element 1
-1, the i-type layer having an optical bandgap wider from the n-layer side to the p-layer side on the VHF layer has a higher R band than VHF.
Voc and fill factor were slightly higher when formed by the FCVD method. In addition, when an RF silicon layer was formed under the VHF layer, Voc was improved. In general, in the working element and Comparative Example 1-1, the Voc and the FF were improved as compared with the flat band gap Comparative Element 1-2, and the working element further improved the Voc compared to the element in Comparative Example 1-1. It was observed. Further, the variation in the characteristics between the solar cell modules of the working element was within 5%. Even after continuously irradiating the artificial sunlight with the AM value of 1.5 and the energy density of 100 mW / cm ² for 500 hours, the fluctuation of the photoelectric conversion efficiency was within 8% of the initial value. .

[Embodiment 2] In Embodiment 2, an amorphous SiC having a band gap structure shown in FIG. 1A is applied to the i-type semiconductor layer, and a pin having a configuration shown in FIG. A photovoltaic element (p-type layer on the light incident side) having a single SiC single cell structure was prepared in the same procedure as in Example 1. The i-type semiconductor layer 504 is made of VHF by applying the present invention.
An amorphous SiC layer (layer) having a narrow optical band gap is provided from the n-type layer side to the p-type layer side by the CVD method, and an optical band gap is formed from the n-type layer side to the p-type layer side by the RFCVD method. Amorphous SiC
It was configured to provide a layer (layer). n-type layer 503 is RFC
Amorphous silicon by the VD method, p-type layer 505 is R
Microcrystalline amorphous silicon was obtained by the FCVD method (embodiment 2).

The apparatus used for forming the semiconductor layer is a roll-to-roll type continuous film forming apparatus similar to that shown in FIG.
A mold layer forming chamber, an i-type layer forming chamber by VHFCVD (discharge furnace of FIG. 4D), an i-type layer forming chamber by RFCVD (discharge furnace of FIG. 9), and a p-type layer forming chamber through a gas gate. Are located. As a comparative example, the discharge furnace shown in FIG. 7 was mounted in an i-type semiconductor layer forming chamber, and the light where the i-type layer was amorphous SiC (layer) formed by a VHF plasma CVD method with a flat optical band gap. An electromotive element was also prepared (comparative element 2). Table 3 shows the conditions for forming the i-type semiconductor layer. The conditions for forming the n-type and p-type semiconductor layers were the same as in Example 1 (Table 2).

[0026]

[Table 3] The resulting solar cell module was evaluated for characteristics using simulated sunlight having an AM value of 1.5 and an energy density of 100 mW / cm ^{2, and} a photoelectric conversion efficiency of 5% or more was obtained in the working element. Was done. The Voc was more improved than the comparative device having the flat band gap in the i-layer, and the decrease in FF was small. In addition, the variation in characteristics among the respective solar cell modules was within 5%. A above
Even after continuously irradiating 500 hours of pseudo sunlight with M value of 1.5 and energy density of 100 mW / cm ² ,
The fluctuation of the photoelectric conversion efficiency was within 6% of the initial value.

[Third Embodiment] In the third embodiment, FIG.
Pin type Si / SiGe / SiG having the configuration shown in FIG.
An e (top / middle / bottom) triple cell photovoltaic element (light incident side p layer) was prepared. Top cell 52
The fourth i-type semiconductor layer 518 is amorphous silicon formed by RFCVD. According to the present invention, an amorphous silicon layer is formed on the i-type semiconductor layers 515 and 512 of the middle cell 523 and the bottom cell 522 by the RFCVD method in the same manner as in the first embodiment. An amorphous SiGe layer having a composition distribution in which the optical band gap is narrowed was formed on the p-layer side, and an amorphous silicon germanium layer having a composition distribution in which the optical band gap was widened from the n-layer side to the p-layer side was formed by RFCVD. .

The apparatus used for forming the semiconductor layer is a roll-to-roll type continuous film forming apparatus similar to that shown in FIG. 6, and a chamber for forming each semiconductor layer is provided between the substrate sending chamber and the winding chamber. The configuration arranged via a gas gate was adopted. As a comparative example, the photovoltaic device in which the i-type semiconductor layers 512 and 515 of the bottom cell and the middle cell are an amorphous silicon layer formed by an RF plasma CVD method and amorphous SiGe formed by a VHF plasma CVD method having a flat optical band gap sandwiched therebetween. An element was produced (Comparative Element 3). The i-type semiconductor layer having a flat optical band gap was formed by using a VHF discharge furnace in a formation chamber with a structure in which a source gas was uniformly supplied to a discharge space as shown in FIG. Table 4 shows the conditions for forming the i-type semiconductor layers of the working element and the comparative element. Also, n
Table 5 shows the conditions for forming the p-type and p-type semiconductor layers.

[0029]

[Table 4]

[0030]

[Table 5] For the created solar cell module, the AM value was 1.
5, the characteristics were evaluated using simulated sunlight having an energy density of 100 mW / cm ² , and the photoelectric conversion efficiency was 9.5.
% Was obtained. The FF and the Voc of the device 2 were higher than those of the device 2 in which the i-type layer had a flat band gap. In addition, the variation in characteristics among the respective solar cell modules was within 5%. Even after the above-mentioned AM value of 1.5 and the energy density of 100 mW / cm ² simulated sunlight were continuously irradiated for 500 hours, the variation of the photoelectric conversion efficiency of the working element was within 7.5% of the initial value. It was in.

[Embodiment 4] p of the structure shown in FIG.
A photovoltaic element (light incident side p layer) having an in-type SiC / SiGe / SiGe (top / middle / bottom) triple cell configuration was prepared in the same procedure as in Example 4. The present invention is applied to the i-type layer 518 of the top cell 524 to provide an amorphous SiC layer having a narrow optical band gap from the n-type layer side to the p-type layer side as in the second embodiment. R
An amorphous SiC layer having a wide optical band gap was provided from the n-type layer side to the p-type layer side by the FCVD method. The present invention is applied to the i-type layers 512 and 515 of the bottom cell 522 and the middle cell 523, and an amorphous silicon layer is formed by the RFCVD method in the same manner as in the first embodiment. An amorphous SiGe layer having a composition distribution in which the optical band gap is narrowed is formed on the layer side.
An amorphous silicon germanium layer having a composition distribution in which the optical band gap was widened from the layer side to the p layer side was formed (Example element 4).

The apparatus used for forming the semiconductor layer is a roll-to-roll type continuous film forming apparatus similar to that shown in FIG. 6, and a chamber for forming each semiconductor layer is provided between a substrate sending chamber and a winding chamber. It has a configuration arranged via a gas gate. In the discharge furnace of the VHFi type layer forming chamber of the top, middle and bottom cells, FIG.
The discharge furnace was incorporated. As a comparative example, bottom cell and middle cell i-type semiconductor layers 512 and 515 were sandwiched between amorphous silicon layers by RF plasma CVD.
VHF plasma CV with flat optical band gap
D-type amorphous SiGe, and the top cell i-type semiconductor layer 518 is made of amorphous SiC by VHF plasma CVD with a flat optical band gap.
Was manufactured (Comparative element 4). The i-type semiconductor layer having a flat optical band gap was formed by using a VHF discharge furnace in the formation chamber as the discharge furnace in FIG. 7 in which the source gas was uniformly supplied to the discharge space. Table 6 shows the conditions for forming the i-type semiconductor layers of the working element and the comparative element.
The conditions for forming the n-type and p-type semiconductor layers are the same as in Example 3 (Table 5).

[0033]

[Table 6] For the created solar cell module, the AM value was 1.
5, the characteristics were evaluated using pseudo sunlight having an energy density of 100 mW / cm ² , and the photoelectric conversion efficiency was 10%.
The above was obtained. In Example 2, the FF, Voc, and Jsc were improved as compared with Comparative Example 2 in which the i-type layer had a flat band gap. In addition, the variation in characteristics among the respective solar cell modules was within 5%. The above AM value is 1.5
Even after irradiation for 500 hours continuously with pseudo sunlight having an energy density of 100 mW / cm ² , the variation in photoelectric conversion efficiency was within 7% of the initial value.

[Embodiment 5] In Embodiment 5, FIG.
Pin type SiC / Si / SiGe having the configuration shown in FIG.
(Top / middle / bottom) A photovoltaic element (p-layer on the light incident side) having a triple cell configuration was prepared in the same procedure as in Example 4. The present invention is applied to the i-type layer 518 of the top cell 524 to provide an amorphous SiC layer having a narrow optical band gap from the n-type layer side to the p-type layer side as in the second embodiment. Amorphous Si whose optical band gap widens from the n-type layer side to the p-type layer side by RFCVD
The configuration provided with the C layer was adopted. I-type layer 5 of bottom cell 522
12, the present invention is applied, and the RF
An amorphous silicon layer is formed by a CVD method, and amorphous SiG having a composition distribution in which an optical band gap is narrowed from an n-layer side to a p-layer side by a VHFCVD method.
e layer is formed, and p layer is further formed from the n layer side by RFCVD.
An amorphous silicon germanium layer having a composition distribution in which the optical band gap was widened was formed on the layer side. An amorphous silicon layer was formed on the i-type layer 515 of the middle cell by VHFCVD (embodiment 4).

The apparatus used for forming the semiconductor layer is a roll-to-roll type continuous film forming apparatus similar to that shown in FIG. 6, and a chamber for forming each semiconductor layer is provided between a substrate sending chamber and a winding chamber. It has a configuration arranged via a gas gate. In the discharge furnace of the VHFi type layer forming chamber of the top, middle and bottom cells, FIG.
The discharge furnace was incorporated. As a comparative example, the bottom cell, i
The semiconductor layer 512 is amorphous SiGe formed by a VHF plasma CVD method with a flat optical band gap sandwiched between amorphous silicon layers formed by an RF plasma CVD method, and the i-type semiconductor layer 518 of the top cell is formed.
However, a photovoltaic element made of amorphous SiC by a VHF plasma CVD method with a flat optical band gap was manufactured (Comparative Element 4). The i-type semiconductor layer having a flat optical band gap is formed by VH of the formation chamber.
FIG. 7 shows that the source gas is uniformly supplied to the discharge space through the F discharge furnace.
And a discharge furnace. Table 7 shows the conditions for forming the i-type semiconductor layers of the working element and the comparative element. The conditions for forming the n-type and p-type semiconductor layers are the same as in Example 3 (Table 5).

[0036]

[Table 7] For the created solar cell module, the AM value was 1.
When the characteristics were evaluated using simulated sunlight having an energy density of 100 mW / cm ² in Example 5, the photoelectric conversion efficiency was 10.
More than 2% was obtained. The working element 2 is different from the comparison element 2 in which the i-type layer has a flat band gap by FF, Voc, Js
An improvement in c was obtained. In addition, the variation in characteristics among the respective solar cell modules was within 5%. Even after continuously irradiating the artificial sunlight with an AM value of 1.5 and an energy density of 100 mW / cm ² for 500 hours, the fluctuation of the photoelectric conversion efficiency falls within 6.5% with respect to the initial value. I was

[0037]

As described above, according to the present invention,
When introducing a plurality of source gases each containing one of Group III, IV, and V elements from the position of the substrate movement direction in the discharge space, the plurality of source gases are included in a source gas having a small dissociation energy among the plurality of source gases. Group III or I
The composition ratio of V and V elements in the film is moved by introducing the plurality of source gases from the introduction position into the discharge space for forming a region where the composition ratio is maximum in the film thickness direction. A deposited film having a composition distribution in a film thickness direction can be formed on a substrate. Further, according to the present invention, when a pin type photovoltaic element is formed on a moving long substrate by a plasma CVD method, a VHF plasma CVD method is used.
An i-type semiconductor layer having an optical band gap narrowing from the n-layer side to the p-layer side is formed by a method, and then an RF-
By forming an i-type semiconductor layer in which the optical band gap increases toward the p-type layer by the CVD method, an electromotive element with more improved photoelectric characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a band gap structure of an i-type semiconductor layer of a photovoltaic device employing the present invention.

FIG. 2 is a diagram showing a film formation region distribution and a band gap of an element concentration of a deposited film.

FIG. 3 is a diagram showing a film formation region distribution of an element concentration of a deposited film.

FIG. 4 is a diagram showing the relationship between the structure of a discharge furnace and the band gap of a deposited film.

FIG. 5 is a diagram showing an elemental analysis in a thickness direction of a deposited film by SIMS.

FIG. 6 is a diagram showing a roll-to-roll deposition film forming apparatus.

FIG. 7 is a view showing a VHF discharge furnace.

FIG. 8 is a view showing a VHF discharge furnace.

FIG. 9 is a view showing an RF discharge furnace.

FIG. 10 is a schematic sectional view showing a configuration of a photovoltaic element.

[Explanation of symbols]

1: Discharge furnace (discharge chamber) 2: Source gas inlet tube 3: Electrode 4: Exhaust port 5: Substrate 6: Deposition area adjusting plate 7: Discharge space 100: Roll-to-roll type deposited film forming apparatus 101: Discharge Chamber 102: n-type semiconductor layer forming chamber 103, 104, 105: i-type semiconductor layer forming chamber 106: p-type layer forming chamber 107: winding chamber 108: belt-like substrate 109, 110, 111, 112, 113, 114: gas gate 115, 116, 117, 118, 119, 120: Gate gas introduction tube 121: Discharge furnace (discharge chamber) 122, 125, 126, 127, 128: Source gas introduction tube 123, 135, 136, 137, 138: Electrode 124 130, 131, 132, 133, 134: exhaust pipes 139, 140: bobbins 501, 50 : Base 502, 510: Lower electrode (light reflecting layer) 503, 511, 514, 518: n-type semiconductor layer 504, 512, 515, 518: i-type semiconductor layer 505, 513, 516, 519: p-type semiconductor layer 506 520: Transparent electrode 507, 521: Current collecting electrode 508: Single cell 522: Bottom single cell 523: Middle single cell 524: Top single cell

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Sakai 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yuzo Kota 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Tadashi Sawayama 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Takahiro Yajima 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. ( 72) Inventor Masahiro Kanai 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H068 DA23 EA24 EA30 4K030 AA03 AA04 AA06 BA09 BA30 BA37 BA53 BA55 BA56 BB05 BB12 CA02 CA17 DA02 EA06 FA01 GA14 HA04 JA01 JA06 KA08 LA16 5F045 AA08 AB01 AB02 AB05 AC01 AD07 AE23 BB04 BB16 CA13 DA63 DA65 DP22 DQ12 DQ15

Claims (14)

[Claims] 1. A long substrate is continuously moved to a discharge space, and a deposited film whose composition changes in a film thickness direction is continuously formed on the moving long substrate by a plasma CVD method. In the method of forming a deposited film, when introducing a plurality of source gases each containing one group III, IV, or V element from the position of the substrate movement direction in the discharge space, Introducing the plurality of source gases from a position in a discharge space for forming a region where the composition ratio of a group III, IV, or V element contained in a small source gas in the film is maximum in the film thickness direction. A method for forming a deposited film. 2. The method according to claim 2, wherein the position of introduction of the source gas into the discharge space is
On the upper side or the lower side in the moving direction of the substrate in the discharge space of the plurality of adjacent discharge furnaces, the bases are uniformly arranged, and the base is sequentially moved along the plurality of adjacent discharge furnaces, and The method according to claim 1, wherein a deposited film is formed on the substrate. 3. The method according to claim 1, wherein the plasma CVD method comprises:
This is a plasma CVD method in which an i-type semiconductor layer and a p-type semiconductor layer are stacked in this order.
The method according to claim 1 or 2, wherein an i-type semiconductor layer having an optical band gap narrowing from an n-layer side to a p-layer side is formed by a D method. 4. The method according to claim 1, wherein the plasma CVD method comprises:
This is a plasma CVD method in which an i-type semiconductor layer and a p-type semiconductor layer are stacked in this order.
Forming an i-type semiconductor layer having an optical band gap narrower from the n-layer side to the p-layer side by Method D,
3. The method according to claim 1, wherein the i-type semiconductor layer is formed such that the optical band gap increases toward the p-type layer by a CVD method. 4. 5. The method according to claim 3, wherein the i-type semiconductor layer formed by the plasma CVD method using VHF power is amorphous silicon germanium (SiGe). 6. The method according to claim 5, wherein the plurality of source gases are introduced from a lower side in a moving direction of the substrate in discharge spaces of a plurality of adjacent discharge furnaces. 7. The plurality of source gases include Si and Ge elements, and Ge / (Ge +
7. The method according to claim 6, wherein the value of Si) satisfies the relationship: discharge furnace located upstream in the moving direction of the substrate <discharge furnace located downstream in the moving direction of the substrate. . 8. In the deposited film formed by the plasma CVD method using the VHF power, the Ge concentration in the film is such that the film formed on the upstream side in the moving direction of the substrate <the film formed on the downstream side in the moving direction of the substrate. 7. The method according to claim 6, wherein a relationship between the films is satisfied. 9. A discharge furnace> substrate, wherein Si and C are contained in the plurality of source gases, and a value of C / (C + Si) in a supply amount of the source gases is higher than a discharge furnace> substrate in a moving direction of the substrate. 6. The method according to claim 5, wherein the relationship of a discharge furnace located downstream of the moving direction is satisfied. 10. In the deposited film formed by the plasma CVD method using the VHF power, the C concentration in the film is such that the film formed on the upstream side in the moving direction of the substrate> the film formed on the downstream side in the moving direction of the substrate. 6. The method according to claim 5, wherein the relationship of the films is satisfied. 11. The method according to claim 3, wherein the i-type semiconductor layer formed by the plasma CVD method using the VHF power is amorphous silicon carbon (SiC). 12. An apparatus for continuously moving an elongated substrate, the apparatus continuously moving the elongated substrate to a discharge space, and the apparatus moves the elongated substrate by a plasma CVD method. A deposition film forming apparatus that continuously forms a deposition film having a composition that changes in a film thickness direction; A source gas introduction section for introducing a source gas into the discharge space for introducing the source gas, wherein the introduction section for the source gas into the discharge space is included in a source gas having a small dissociation energy among the plurality of source gases. II
An apparatus for forming a deposited film, wherein a composition ratio of a group I element, a group IV element, and a group V element in a film is provided at a position where a region where the composition ratio is maximum in a film thickness direction can be formed. 13. A method according to claim 1, wherein the introduction positions of the source gas into the discharge space are unified on the upper side or the lower side in the moving direction of the substrate in the discharge spaces of a plurality of adjacent discharge furnaces. The deposited film forming apparatus according to claim 12, wherein: 14. The plasma CVD method according to claim 1, wherein said plasma CVD method is a plasma CVD method using VHF power.
An apparatus for forming a deposited film according to claim 2 or claim 13.