JP3513505B2 - Plasma CVD apparatus, photoelectric conversion element, and method of manufacturing photoelectric conversion element - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma CVD apparatus, a photoelectric conversion element, and a method for manufacturing a photoelectric conversion element, and more particularly, plasma CVD with an improved supply mode of source gas.
Apparatus, a photoelectric cell such as a solar cell in which a substantially intrinsic i-type microcrystalline silicon layer or polycrystalline silicon layer of a microcrystalline silicon layer or a polycrystalline silicon layer having a pin structure is formed by the plasma CVD apparatus. The present invention relates to a conversion element and a method for manufacturing a photoelectric conversion element.

[0002]

2. Description of the Related Art Conventional surface treatment equipment such as plasma C
As shown in FIG. 4, the VD device includes a reaction container 101, a support electrode 102 disposed in the reaction container for supporting an object to be processed and having a heater for heating, and the support in the reaction container 101. A hollow flat plate electrode 104, which is arranged in parallel with the electrode 102 at a desired distance and has a plurality of gas blowing holes 103 on the support electrode side, and high frequency power is passed through the flat plate electrode 104 through an impedance matching device 105. A high frequency power supply 106 for supplying the flat plate electrode 104 to the flat plate electrode 104 via an insulating tube 107.
A gas supply pipe 108 for supplying a mixed gas containing a raw material gas and a carrier gas, which is connected so as to communicate with the hollow part of the chamber, and an exhaust facility such as a vacuum pump for exhausting the gas in the reaction vessel 101 ( (Not shown) is connected to the exhaust pipe 109.

In such a CVD apparatus, for example, p
The i-type microcrystalline silicon layer or polycrystalline silicon layer, which is a power generation layer in a photoelectric conversion element such as a solar cell, having an in-structure thin film crystalline silicon layer (microcrystalline silicon layer or polycrystalline silicon layer) is The film is formed by the method described above. That is, after supporting the object 110 to be processed on the supporting electrode 102 having the ground potential, the vacuum pump is operated to discharge the gas in the reaction vessel 101 to the exhaust pipe 109.
Evacuated through further heating an object 110, while further continuing the exhaust, is for example SiH ₄ source gas
Gas supply pipe 1 for mixing mixed gas of H ₂ and carrier gas
No. 08 is supplied to the hollow portion of the flat plate electrode 104, and the flat plate electrode 104 is blown out toward the support electrode 102 from a plurality of gas blowing holes 103. At this time, in order to form a microcrystalline silicon layer or a polycrystalline silicon layer, H ₂ /
The flow rate ratio of SiH ₄ is set to 10 times or more. After the inside of the reaction vessel 101 reaches a predetermined pressure, the high frequency power source 10
By supplying high frequency power from 6 to the plate electrode 104 through the impedance matching device 105, plasma 111 is generated between the plate electrode 104 and the supporting electrode 102 at the ground potential. The generation of the plasma 111 causes the Si
H ₄ is dissociated to form an i-type microcrystalline silicon layer or polycrystalline silicon layer on the surface of the object 110 to be processed.

The above-described CVD apparatus supplies a mixed gas of SiH ₄ and H ₂ from the gas supply pipe 108 to the plate electrode 104 through the insulating tube 107, and the mixed gas is supplied from a plurality of blowing holes 103 of the plate electrode 104. When the object to be processed 110 is blown out toward the supported support electrode 102, the support electrode 102 (the object to be processed 110) and the flat plate electrode 104.
By shortening the distance between the SiH _{4 and} the plasma 111, the flight distance of the SiH _{4 in} the plasma 111 is shortened, and as a result, the residence time of the SiH ₄ is shortened. Can be prevented from being captured.
However, as described above, the support electrode 102 and the flat plate electrode 1 are
04, the object 110 to be treated is blown out from the plurality of blowing holes 103 of the plate electrode 104 for the purpose of increasing the film formation rate of the microcrystalline silicon layer or the polycrystalline silicon layer with the distance from the plate electrode 104 being shortened.
When the flow rate of the gas (mainly SiH ₄ which is the raw material gas) blown out toward the supporting electrode 102 on which Si is supported is increased, the thickness of the formed silicon layer becomes non-uniform. That is,
The gas blown out from the blowout hole 103 is H ₂ / S.
Since iH ₄ is a mixed gas of SiH ₄ and H ₂ having a flow ratio of 10 times or more, a large amount of mixed gas will be blown out from the blowing hole 103 as the flow rate of SiH ₄ is increased, and the supporting Since the distance between the electrode 102 and the plate electrode 104 is short, the workpiece 11 of the supporting electrode 102 is processed.
The directivity of the mixed gas with respect to 0 becomes high. As a result, the film thickness varies between the surface portion of the object to be processed 110 facing the gas blowing hole 103 and the surface portion of the object to be processed 110 other than that, resulting in non-uniformity.

On the other hand, in the conventional plasma CVD apparatus, it is important to make the thickness of the microcrystalline silicon layer or the polycrystalline silicon layer uniform, that is, in order to suppress the directivity of the mixed gas, the supporting electrode 102 (the object 110 to be processed). If the distance between the flat plate electrode 104 and the plate electrode 104 is increased, the flight distance of the SiH _{4 in} the plasma 111 is increased, and as a result, the S
Since the retention time of iH ₄ becomes long, fine particles are easily generated and the amount of fine particles taken into the silicon layer during film formation increases. Fine particles are incorporated into the formed i-type microcrystalline silicon layer or polycrystalline silicon layer, and defects are generated in the i-type microcrystalline silicon layer or polycrystalline silicon layer.
The photoelectric conversion efficiency of a photoelectric conversion element having an i-type microcrystalline silicon layer or a polycrystalline silicon layer having such a defect is significantly reduced.

Therefore, in the conventional plasma CVD apparatus, if the fine particles are prevented from being taken in during the film formation, the uniformity of the film thickness is sacrificed. There was a problem that importation occurred.

[0007]

SUMMARY OF THE INVENTION The present invention is intended to provide a plasma CVD apparatus capable of both reducing the amount of fine particles incorporated into a film during film formation and making the film thickness uniform.

According to the present invention, in the production of a photoelectric conversion element having a microcrystalline silicon layer or a polycrystalline silicon layer having a pin structure or a nip structure, at least a substantially i-type microcrystalline silicon layer or a polycrystalline silicon layer. A photoelectric conversion device capable of significantly reducing the amount of fine particles taken in during the film formation and uniformizing the thickness thereof, and further enabling the (110) preferential orientation of the i-type microcrystalline silicon layer or polycrystalline silicon layer. It is intended to provide a method for manufacturing a conversion element.

The present invention has a microcrystalline silicon layer or a polycrystalline silicon layer having a pin structure or a nip structure,
The amount of fine particles taken into the film of the at least substantially intrinsic i-type microcrystalline silicon layer or polycrystalline silicon layer can be remarkably reduced, and the thickness thereof can be made uniform. It is intended to provide a photoelectric conversion element in which a layer or a polycrystalline silicon layer is (110) preferentially oriented more effectively.

[0010]

Means for Solving the Problems Plasma C according to the present invention
A VD device is disposed in the reaction vessel and the reaction vessel,
A support electrode containing a heater for heating and supporting the object to be treated and having a ground potential, is arranged in parallel in the reaction container at a desired distance from the support electrode, and a plurality of gas is blown to the support electrode side. A ladder-type electrode having a combination of hollow rods with holes, a high-frequency power source for supplying high-frequency power to the ladder-type electrode, and a ladder-type electrode connected to the ladder-type electrode through an insulating pipe to supply a source gas. A first gas supply means, a second gas supply means arranged in the reaction vessel on the side of the ladder electrode opposite to the support electrode, for supplying a carrier gas to the support electrode side, and the reaction And a gas exhaust means for exhausting the gas in the container.

The method of manufacturing a photoelectric conversion element according to the present invention comprises:
In manufacturing a photoelectric conversion element having a microcrystalline silicon layer or a polycrystalline silicon layer having a pin structure or a nip structure on a substrate, at least one of the microcrystalline silicon layer or the polycrystalline silicon layer having the pin structure or the nip structure is used. The substantially intrinsic i-type microcrystalline silicon layer or polycrystalline silicon layer causes the support electrode in the reaction container in the plasma CVD apparatus according to claim 1 to support the object having the substrate, and Gas is exhausted by the gas exhaust means, the object to be processed is heated by the heater of the supporting electrode, and the Si-containing gas as the raw material gas is supplied from the first gas supplying means and the gas blowing hole of the ladder electrode to the supporting electrode. wherein of H ₂ as a carrier gas from the second gas supply means of the ladder-type electrode back to supply toward the object to be treated in And supplied toward the object to be processed in the lifting electrodes,
High-frequency power is supplied from the high-frequency power source to the ladder-shaped electrode to generate plasma between the ladder-shaped electrode and the supporting electrode at the ground potential for film formation.

Another method for manufacturing a photoelectric conversion element according to the present invention is the method for manufacturing a photoelectric conversion element having a microcrystalline silicon layer or a polycrystalline silicon layer having a pin structure or a nip structure on a substrate, wherein The plasma C according to claim 1, wherein among the microcrystalline silicon layer or the polycrystalline silicon layer having a nip structure, at least the substantially intrinsic i-type microcrystalline silicon layer or the polycrystalline silicon layer is formed.
The object to be processed having the substrate is supported by the supporting electrode in the reaction container in the VD apparatus, the gas in the reaction container is exhausted by the gas exhausting means, and the object to be processed is heated by the heater of the supporting electrode, First, SiH _{4 as a} source gas and at least one silicon chlorinated compound gas selected from SiH ₂ Cl ₂ , SiHCl ₃ and SiCl ₄
Gas is supplied from the gas supply means and the gas blow-out holes of the ladder-shaped electrode toward the object to be processed of the supporting electrode, and H ₂ which is a carrier gas is supplied from the second gas supply means on the back surface of the ladder-shaped electrode to the processing of the supporting electrode. The film is formed by supplying a high frequency power from a high frequency power source to the ladder electrode to generate plasma between the ladder type electrode and the supporting electrode at a ground potential.

The photoelectric conversion element according to the present invention is characterized by being manufactured by any of the methods described above.

The tandem photoelectric conversion element according to the present invention is
It is characterized by including at least one set of pin type units or nip type units manufactured by any of the above-mentioned methods.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

(First Embodiment) FIG. 1 is a schematic view showing a plasma CVD apparatus according to the first embodiment, and FIG. 2 is a perspective view showing a ladder electrode incorporated in the plasma CVD apparatus shown in FIG.

In the reaction vessel 1, a support electrode 2 for holding an object to be treated 13 and incorporating a heater (not shown) is arranged. The support electrode 2 is grounded. The ladder-shaped electrode 3 is arranged below the support electrode 2 so as to face each other at a desired distance. As shown in FIG. 2, the ladder-shaped electrode 3 has a plurality of gas blowing holes 4 on the support electrode 2 side.
It has a rectangular shape in which hollow rods having openings are combined, and has a structure which also serves as a source gas supply member.

The first gas supply pipe 5 for supplying the raw material gas penetrates the reaction vessel 1 from the outside and is connected to the ladder-shaped electrode 3 via an insulating pipe 6. The high frequency power supply 7 is connected to the ladder electrode 3 through an impedance matching device 8. The insulating tube 6 serves to prevent high frequency power from flowing into the first gas supply tube 5 when high frequency power is supplied from the high frequency power supply 7 to the ladder electrode 3.

A hollow rectangular gas supply member 9 is arranged in the reaction vessel 1 so as to be positioned below the ladder electrode 3. The gas supply member 9 has a plurality of gas blowing holes 10 communicating with the hollow portion on the surface facing the ladder electrode 3. The second gas supply pipe 11 for supplying a carrier gas penetrates the reaction vessel 1 from the outside and is connected to the gas supply member 9. The second gas supply pipe 11 is grounded. The gas supply member 9 and the second gas supply pipe 11 constitute second gas supply means.

The exhaust pipe 12 is connected to the lower side surface of the reaction vessel 1 and has the other end connected to an exhaust facility such as a vacuum pump (not shown).

The distance (d) between the ladder-shaped electrode 3 and the surface of the object 13 to be treated supported by the supporting electrode 2 is 10 to 2
It is preferably 0 mm. This distance (d) is 10m
If it is less than m, the directivity of the raw material gas blown from the plurality of gas blowing holes 4 of the ladder-type electrode 3 toward the object 13 to be treated is increased, and the formed film thickness may become non-uniform. On the other hand, when the distance (d) exceeds 20 mm,
There is a possibility that the film forming speed may decrease and the crystallinity may decrease.

Next, the operation of the plasma CVD apparatus described above will be described.

After holding the object 13 to be processed on the supporting electrode 2 of the plasma CVD apparatus shown in FIG. 1, a vacuum pump (not shown) is operated to evacuate the inside of the reaction vessel 1 through the exhaust pipe 12. Then, the heater incorporated in the supporting electrode 2 is energized to heat the object to be processed 13 to a desired temperature. After the heating temperature by the heater is sufficiently stabilized, the carrier gas is supplied to the gas supply member 9 from the second gas supply pipe 11, and the supporting electrodes in the reaction vessel 1 are supplied from the plurality of gas blowing holes 10 of the gas supply member 9. 2, and at the same time, the source gas is supplied from the first gas supply pipe 5 to the ladder-shaped electrode 3, and the supporting electrode 2 in the reaction vessel 1 is passed through a plurality of gas-blowing holes 4 of the ladder-shaped electrode 3.
And the inside of the reaction vessel 1 is controlled to a predetermined pressure. After the temperature of the object to be treated 13 and the pressure in the reaction vessel 1 are sufficiently stabilized, high-frequency power is supplied from the high-frequency power source 7 to the ladder-shaped electrode 3 through the impedance matching device 8, so that the ladder-shaped electrode 3 and the ground potential are grounded. Plasma 14 is generated between the substrate 13 and the supporting electrode 2 to form a predetermined film on the object to be processed 13 held by the supporting electrode 2.

In such a film formation, by shortening the distance between the ladder electrode 3 and the front surface (back surface) of the object 13 to be processed supported by the supporting electrode 2, the raw material gas is transferred to the ladder electrode 3. Since the flight distance in the plasma 14 generated between the support electrodes 2 can be shortened, the amount of fine particles generated in the plasma 14 can be significantly reduced.

In addition, the source gas and the carrier gas having a flow rate of at least 10 times the source gas are used as the first gas.
The gas is supplied separately from the gas supply pipe 5 and the second gas supply pipe 11, and only the raw material gas is passed through the ladder-type electrode 3 and through the plurality of gas blowing holes 4 of the ladder-type electrode 3 in the reaction vessel 1. By blowing out toward the support electrode 2, the flow velocity of the blown-out gas is higher than that in the case where the mixed gas of the raw material gas and the carrier gas is blown out toward the object to be processed from the plurality of gas blowing holes of the flat plate electrode as in the conventional case. It can be significantly reduced to 1/10 or less. Therefore, even if the distance between the ladder electrode 3 and the front surface (back surface) of the object 13 supported by the supporting electrode 2 is shortened, the directivity of the gas to be sprayed can be relaxed. As a result, it is possible to prevent the film thickness from varying between the surface portion of the object to be processed 13 facing the gas blowing hole 4 of the ladder electrode 3 and the surface portion of the other object to be processed 13 to form a uniform film. Can be formed into a film.

Further, since the ladder-shaped electrode 3 shown in FIG. 2 arranged to face the supporting electrode 2 has a higher electric field strength when high frequency power is supplied than the conventional flat plate electrode,
It is possible to improve the distance (d) to the supporting electrode 2 and the pressure margin in the reaction vessel 1 which are plasma generation conditions.

As described above, according to the plasma CVD apparatus of the first embodiment, it is possible to reduce the amount of fine particles taken into the film at the time of film formation and to make the film thickness uniform. A desired film having a uniform film thickness can be formed.

Next, a method for manufacturing a photoelectric conversion element, such as a solar cell, according to the present invention will be described with reference to the plasma CVD apparatus shown in FIGS.

(First Step) A first transparent electrode is formed on a transparent insulating substrate.

The transparent insulating substrate is made of, for example, soda-lime glass showing light transmission.

The first transparent electrode is, for example, tin oxide (Sn).
O _2), is made from a metal oxide such as indium tin oxide (ITO). Here, in order to suppress reduction of the first transparent electrode by hydrogen, a zinc oxide film (not shown) having a thickness of several tens nm is formed on the first transparent electrode.

(Second Step) After the transparent insulating substrate having the first transparent electrode formed thereon is held as the workpiece 13 on the supporting electrode 2 of the plasma CVD apparatus shown in FIG.
A vacuum pump (not shown) is operated to evacuate the inside of the reaction vessel 1 through the exhaust pipe 12. Then, the heater incorporated in the supporting electrode 2 is energized to heat the object to be processed 13 to a desired temperature. After the heating temperature by the heater is sufficiently stabilized, H ₂ which is a carrier gas is supplied from the second gas supply pipe 11 to the gas supply member 9, and the gas supply holes 9 of the gas supply member 9 cause the inside of the reaction container 1 to flow. Of the Si-containing gas (for example, Si, which is a raw material gas) from the first gas supply pipe 5 at the same time.
H ₄ ) and p-type impurity gas are supplied to the ladder-type electrode 3, and the supporting electrode 2 and the ladder-type electrode 3 in the reaction vessel 1 are passed through a plurality of gas blowing holes 4 of the ladder-type electrode 3.
It blows out in the area between and and the inside of the reaction container 1 is controlled to a predetermined pressure. After the temperature of the object to be treated 13 and the pressure in the reaction vessel 1 are sufficiently stabilized, high-frequency power is supplied from the high-frequency power source 7 to the ladder-shaped electrode 3 through the impedance matching device 8, so that the ladder-shaped electrode 3 and the ground potential are grounded. Then, plasma 14 is generated between the supporting electrode 2 and the above-mentioned supporting electrode 2 to form a p-type microcrystalline silicon layer or a polycrystalline silicon layer on the first transparent electrode of the object to be processed 13.

As the p-type impurity, for example, B ₂ H ₆ or the like can be used.

(Third Step) After the p-type microcrystalline silicon layer or the polycrystalline silicon layer is formed, the supply of high frequency power and the raw material gas is stopped and the inside of the reaction vessel 1 is evacuated.
Subsequently, the heater incorporated in the support member 2 is energized to heat the substrate of the object to be processed 13 to a desired temperature. After the heating temperature by the heater is sufficiently stabilized, H ₂ which is a carrier gas is supplied from the second gas supply pipe 11 to the gas supply member 9, and the gas supply holes 9 of the gas supply member 9 cause the inside of the reaction container 1 to flow. While being blown toward the supporting electrode 2 of the above, at the same time, a Si-containing gas (for example, SiH ₄ ) which is a raw material gas is supplied from the first gas supply pipe 5 to the ladder-shaped electrode 3, and a plurality of gases of the ladder-shaped electrode 3 are supplied. The gas is blown into the region between the supporting electrode 2 and the ladder-shaped electrode 3 in the reaction container 1 through the blowing hole 4 to control the inside of the reaction container 1 to a predetermined pressure. Temperature of object to be treated 13 and reaction vessel 1
After the internal pressure is sufficiently stabilized, high-frequency power is supplied from the high-frequency power source 7 to the ladder-shaped electrode 3 through the impedance matching device 8, so that the ladder-shaped electrode 3 and the supporting electrode 2 at the ground potential are connected to each other. Plasma 14 is generated to form a substantially intrinsic i-type microcrystalline silicon layer or polycrystalline silicon layer on the p-type microcrystalline silicon layer or polycrystalline silicon layer of the object to be processed 13.

The heating of the object 13 by the heater of the supporting electrode 2 is preferably 120 to 400 ° C.

The pressure in the reaction vessel 1 is set to 0.1 to 5 To.
It is preferable to set it in the range of rr.

When SiH ₄ is used as the Si-containing gas supplied from the first supply means 5, the flow rate ratio between this SiH ₄ and the carrier gas H ₂ supplied from the second supply means 11 is H ₂ / It is preferable to set SiH ₄ to 30 to 70 times. By setting the H ₂ / SiH ₄ flow rate ratio within the above range, it becomes possible to form a microcrystalline silicon layer or a polycrystalline silicon layer without lowering the film forming rate.

The source gas supplied into the reaction vessel 1 is Si
It is allowed to further contain at least one silicon chlorinated compound gas selected from H ₂ Cl ₂ , SiHCl ₃ and SiCl ₄ . By adding such a chlorinated silicon compound gas to the raw material gas, the transparent insulating substrate of the object to be treated by the heater of the supporting electrode 2 is
Under relatively low temperature heating conditions of 20 to 300 ° C (11
0) It becomes possible to form a substantially intrinsic i-type microcrystalline silicon layer or polycrystalline silicon layer having a preferred orientation.

The silicon chlorinated compound gas is the S
It is preferable that the iH ₄ and the silicon chlorinated compound gas are supplied to the reaction vessel 1 at a flow rate ratio of 1 to 80% with respect to the total flow rate. When the flow rate ratio of the silicon chlorinated compound gas is less than 1%, an i-type microcrystalline silicon layer or a polycrystalline silicon layer having good film quality is formed under a relatively low temperature heating condition of 120 to 300 ° C. Will be difficult to do. On the other hand, when the flow rate ratio of the silicon chlorinated compound gas exceeds 80%, the i-type microcrystalline silicon layer or the polycrystalline silicon layer is etched by Cl, Cl _2, etc., and the film formation rate is lowered. The layer may become amorphous. A more preferable flow ratio of the silicon chlorinated compound gas is 10% to 40%.

The flow rate ratio of the silicon chlorinated compound gas is
By setting 1-80%, (110) priority allocation
Direction is improved and chlorine is 1 × 10¹⁸cm^-3~ 8x
10 ²⁰cm^-3Containing substantially authentic i-type microcrystalline silly
Capable of forming con-layer or polycrystalline silicon layer
Become.

(Fourth Step) After the i-type microcrystalline silicon layer or the polycrystalline silicon layer is formed, the supply of high frequency power and the raw material gas is stopped and the inside of the reaction vessel 1 is evacuated.
Then, the heater incorporated in the supporting electrode 2 is energized to heat the object to be processed 13 to a desired temperature. After the heating temperature by the heater is sufficiently stabilized, the carrier gas H ₂ is supplied from the second gas supply pipe 11 to the gas supply member 9
To the supporting electrode 2 in the reaction vessel 1 from a plurality of gas blowing holes 10 of the gas supply member 9, and at the same time, from the first gas supply pipe 5 as a source gas Si.
A containing gas (for example, SiH ₄ ) and an n-type impurity gas are supplied to the ladder-type electrode 3, and the supporting electrode 2 and the ladder-type electrode 3 in the reaction vessel 1 are passed through a plurality of gas blowing holes 4 of the ladder-type electrode 3. The reaction vessel 1 is blown into a region between and the inside of the reaction vessel 1 is controlled to a predetermined pressure. After the temperature of the object to be processed 13 and the pressure in the reaction vessel 1 are sufficiently stabilized, the high frequency power source 7
By supplying high-frequency power from the above through the impedance matching device 8 to the ladder-shaped electrode 3, plasma 14 is generated between the ladder-shaped electrode 3 and the supporting electrode 2 at the ground potential, and the plasma 14 is generated. An n-type microcrystalline silicon layer or a polycrystalline silicon layer is formed on the i-type microcrystalline silicon layer or the polycrystalline silicon layer. Thereafter, the object to be processed is taken out of the reaction container 1 of the plasma CVD apparatus, and the second transparent electrode and the back electrode are sequentially formed on the n-type microcrystalline silicon layer or the polycrystalline silicon layer to manufacture a solar cell. . This solar cell is generated by injecting light such as sunlight from the transparent insulating substrate side and photoelectrically converting the light in the pin structure microcrystalline silicon layer or the polycrystalline silicon layer.

As the n-type impurity gas, for example, PH
₃ etc. can be used.

The second transparent electrode is made of, for example, indium tin oxide (ITO), tin oxide or zinc oxide.

The back electrode is made of, for example, Al or Ag.

In manufacturing the solar cell of the type in which light is incident from the transparent insulating substrate side, the p-type, i-type, and n-type microcrystalline silicon layers or polycrystalline silicon layers are sequentially formed from the first transparent electrode side. The film was formed into a pin structure, but n
Type, i-type, and p-type microcrystalline silicon layers or polycrystalline silicon layers may be sequentially formed to have an nip structure.

The arrangement of p, i, and n between the first transparent electrode and the microcrystalline silicon layer or the polycrystalline silicon layer having the pin structure or the nip structure is the microcrystalline silicon layer or the polycrystalline silicon layer. It is allowed to place an amorphous silicon layer having a pin structure or a nip structure similar to the layer.

Further, the present invention can be similarly applied to a method of manufacturing a solar cell of the type in which light is incident from the second transparent electrode side in the present invention. In the production of this solar cell,
An n-type, i-type, p-type microcrystalline silicon layer or a polycrystalline silicon layer is sequentially formed from the first transparent electrode side to form a nip structure, or a p-type, i-type, n-type microcrystalline silicon layer or a polycrystal silicon layer is formed. A crystalline silicon layer may be sequentially formed to have a pin structure, or any of them may be used. The arrangement of p, i, and n between the microcrystalline silicon layer or the polycrystalline silicon layer having the nip structure or the pin structure and the second transparent electrode is the same as that of the microcrystalline silicon layer or the polycrystalline silicon layer. It is allowed to dispose an amorphous silicon layer having a proper nip structure or a pin structure.

As described above, in the production of the photoelectric conversion element described above, the workpiece 13 having the substrate is supported on the supporting electrode 2 by using the plasma CVD apparatus shown in FIGS. 1 and 2, and is exhausted through the gas exhaust pipe 12. The object 13 to be processed is heated, and the Si-containing gas (for example, SiH ₄ ) that is a raw material gas is directed from the first gas supply pipe 5 and the gas blowing hole 4 of the ladder-type electrode 3 toward the object 13 to be processed of the support electrode 2. At the same time as being blown out, H ₂ which is a carrier gas is supplied to the ladder type electrode 3
The second gas supply pipe 11 on the rear surface and the gas supply holes 9 of the gas supply member 9 blow out toward the object 13 to be processed of the supporting electrode 2, and high-frequency power is supplied from the high-frequency power supply 7 to the ladder-shaped electrode 3 to be grounded. It is possible to generate a plasma 14 having a remarkably small amount of suspended fine particles between the support electrode 2 and the electric potential, and it is possible to remarkably reduce the incorporation of fine particles into the surface of the object 13 to be processed. Therefore, it is possible to form a substantially intrinsic i-type microcrystalline silicon layer or polycrystalline silicon layer having a small amount of fine particles taken in, a good film quality with few defects, and a uniform film thickness. It will be possible. As a result, it is possible to manufacture a photoelectric conversion element exhibiting high photoelectric conversion efficiency.

The Si-containing gas (for example, SiH ₄ ) which is a raw material gas is separately supplied from the first gas supply pipe 5, and the H ₂ which is a carrier gas is separately supplied from the second gas supply pipe 11. By generating a plasma 14 between the supporting electrode 2 and the supporting electrode 2 having a ground potential, the i
Type microcrystalline silicon layer or polycrystalline silicon layer (11
0) Preferential orientation can be performed, and a photoelectric conversion element having higher photoelectric conversion efficiency can be manufactured.

Further, the ladder type electrode 3 is fed from the first gas supply pipe 5 with a mixed gas of SiH ₄ and at least one silicon chlorinated compound gas selected from SiH ₂ Cl ₂ , SiHCl ₃ and SiCl ₄ as a source gas. It is supplied toward the object to be treated 13 supported by the supporting electrode 2 via the plasma, and plasma 14 is generated between the supporting electrode 2 and the ladder-shaped electrode 3, thereby heating at a relatively low temperature of 120 to 300 ° C. Under the conditions, it becomes possible to form a substantially intrinsic i-type microcrystalline silicon layer or polycrystalline silicon layer having a higher (110) preferential orientation. As a result, it is possible to manufacture a photoelectric conversion element having a higher photoelectric conversion efficiency.

[0051]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(Embodiment 1) In Embodiment 1, a manufacturing process of a solar cell of a type in which light is incident from the transparent insulating substrate side and having a pin structure made of microcrystalline silicon will be described with reference to FIG.

First, 50 mm × 50 mm having light transmission
On the transparent insulating substrate 21 made of soda lime glass having a size of 1 mm, the first transparent electrode 22 made of a two-layer film of tin oxide (SnO ₂ ) and zinc oxide (ZnO) thinner than the tin oxide (SnO ₂ ) was formed.

Next, the plasma CV shown in FIG.
The transparent insulating substrate 21 having the transparent electrode 22 formed on the supporting electrode 2 in the reaction vessel 1 of the D apparatus is processed 13
After holding as, the reaction vessel 1 in the 1 × 10 through the exhaust pipe 12 by operating the vacuum pump (not shown) ^{- 8} T
The chamber was evacuated to below orr. Next, the supporting electrode 2
The heating heater built in the heater is energized, and the workpiece 13
The substrate was heated to 160 ° C. After the heating temperature by the heater is sufficiently stabilized, the carrier gas H ₂ is supplied to the gas supply member 9 from the second gas supply pipe 11, and the reaction container 1 is supplied from the plurality of gas blowing holes 10 of the gas supply member 9.
The gas is blown toward the supporting electrode 2 inside, and at the same time, SiH ₄ and B ₂ H ₆ which are raw material gases are supplied from the first gas supply pipe 5 to the ladder type electrode 3, and a plurality of gases of the ladder type electrode 3 are supplied. The pressure inside the reaction vessel 1 was controlled to 500 mTorr by blowing out through the blow-out hole 4 to a region between the supporting electrode 2 and the ladder-type electrode 3 in the reaction vessel 1. After the temperature of the substrate 21 of the object to be processed 13 and the pressure in the reaction vessel 1 are sufficiently stabilized, the high frequency power from the high frequency power source 7 is supplied to the ladder type electrode 3 through the impedance matching device 8 to make the ladder type electrode 3 Plasma is generated between the support electrode 2 and the support electrode 2 at the ground potential, and a p-type microcrystalline silicon layer having a thickness of 30 nm is formed on the first transparent electrode 22 of the workpiece 13 supported by the support electrode 2. 23 was formed into a film.

Next, after the p-type microcrystalline silicon layer 23 is formed, the supply of high frequency power and source gas is stopped,
After evacuating the inside of the reaction vessel 1, a thickness of 1.5 is obtained under the following conditions.
A substantially intrinsic i-type microcrystalline silicon layer 24 having a thickness of μm was formed.

-Substrate temperature: 180 ° C-Pressure: 1 Torr-Ladder-type electrode-Substrate spacing: 15 mm-High frequency power: 10 W-Flow rate of source gas supplied from the first gas supply pipe 5: Monosilane gas (SiH ₄ ) 5 sccm, flow rate of carrier gas supplied from the second gas supply pipe 11: hydrogen gas (H ₂ ) 300 sccm.

Next, the film formation of the i-type microcrystalline silicon layer 24
After that, supply of high-frequency power and raw material gas is stopped, and the reaction volume
The inside of the reactor 1 is passed through the exhaust pipe 12 and the inside of the reaction vessel 1 is 1 × 1.
0^{− 8}It was evacuated below Torr. Next, supporting electricity
The heating heater built in the pole 2 is energized to generate the object to be treated.
The substrate 21 of No. 13 was heated to 160 ° C. For heating heater
After the heating temperature is sufficiently stabilized by the second gas supply pipe 11
H which is a carrier gas₂Is supplied to the gas supply member 9,
From the plurality of gas blowing holes 10 of this gas supply member 9,
At the same time, blow out toward the supporting electrode 2 in the reaction container 1.
From the first gas supply pipe 5 to the source gas SiH_FourAnd
And PH₃Is supplied to the ladder-shaped electrode 3 and the ladder-shaped electrode 3
Inside the reaction container 1 through a plurality of gas blowing holes 4 of the electrode 3.
Blown out into the area between the supporting electrode 2 and the ladder-shaped electrode 3 of
Then, the pressure inside the reaction vessel 1 is controlled to 700 mTorr.
It was The temperature of the substrate 21 of the workpiece 13 and the inside of the reaction container 1
After the pressure of is sufficiently stabilized, the high frequency power is supplied from the high frequency power supply 7.
To the ladder type electrode 3 through the impedance matching device 8.
By supplying this, the ladder type electrode 3 and the ground potential
The plasma 14 is generated between the support electrode 2 and
The i-type fine particles of the object to be processed 13 supported by the supporting electrode 2
An n-type microcrystalline silicon layer 25 is formed on the crystalline silicon layer 24.
The film was formed. Then, the object to be processed 13 is subjected to plasma CVD.
Of the n-type microcrystalline silicon taken out from the reaction container 1 of the layer
The layer 25 has a second transparent electrode made of indium oxide (ITO).
The pole 26 and the back electrode 27 made of Al are sequentially formed.
The solar cell shown in FIG. 3 was manufactured.

Comparative Example 1 An i-type microcrystalline silicon layer was formed under the following conditions using the plasma CVD apparatus shown in FIG.

Substrate size: 50 mm x 50 mm x 1 m
m, substrate temperature: 180 ° C., pressure: 1 Torr, parallel plate electrode-substrate spacing (d): 15 mm, high frequency power: 30 W, gas flow rate: monosilane gas (SiH ₄ ) 5 sccm, hydrogen gas (H ₂ ) 300 sccm, -Film thickness: 1.5 μm.

(Comparative Example 2) An i-type microcrystalline silicon layer was formed under the following conditions using the plasma CVD apparatus shown in FIG.

Substrate size: 50 mm x 50 mm x 1 m
m, substrate temperature: 180 ° C., pressure: 1 Torr, parallel plate electrode-substrate spacing (d): 30 mm, high frequency power: 30 W, gas flow rate: monosilane gas (SiH ₄ ) 5 sccm, hydrogen gas (H ₂ ) 300 sccm, -Film thickness: 1.5 μm.

Regarding the i-type microcrystalline silicon layer formed in Example 1 and Comparative Examples 1 and 2, the existence density of fine particle products having a diameter of 5 μm or more, 40 mm × 4 in the central portion
The film thickness distribution in the range of 0 mm and (22
The 0) / (111) orientation ratio was measured. Here, the orientation ratio is (2) out of X-ray diffraction peaks measured by the θ-2θ method.
It is represented by the ratio of the intensity diffracted by the (20) plane to the intensity diffracted by the (111) plane. The results are shown in Table 1 below.

[0063]

[Table 1]

As is clear from Table 1 above, the substantially intrinsic i-type microcrystalline silicon layer formed according to Example 1 has a low defect density due to fine particles and a uniform film thickness. , It has a higher (220) / (111) orientation ratio.

On the other hand, the i-type microcrystalline silicon layer formed according to Comparative Example 1 in which the distance (d) between the parallel plate electrodes and the substrate was set to 15 mm, although the defect density due to the fine particles was low, The thickness is uneven, and (220) /
It can be seen that the (111) orientation ratio is also low.

On the other hand, the i-type microcrystalline silicon layer formed in Comparative Example 2 in which the distance (d) between the parallel plate electrodes and the substrate was 30 mm, which was longer than that in Comparative Example 1, had a uniform film thickness. It can be seen that the defect density due to the fine particles is high and the (220) / (111) orientation ratio is also low.

Furthermore, the photoelectric conversion efficiency of the solar cell obtained in this Example 1 is higher than that of the solar cell of Comparative Example 1 in which an i-type microcrystalline silicon layer is formed by using the plasma CVD apparatus shown in FIG. Was 1.072 times.

Example 2 A solar cell was manufactured in the same manner as in Example 1 except that the i-type microcrystalline silicon layer was formed under the following conditions using the plasma CVD apparatus shown in FIG.

Substrate temperature: 180 ° C., Pressure: 1 Torr, Ladder electrode-Substrate spacing (d): 15 mm, High frequency power: 10 W, Raw gas flow rate supplied from the first gas supply pipe 5: Monosilane gas (SiH ₄ ) 4 sccm, dichlorosilane gas (SiH ₂ Cl ₂ ) 1 sccm ([monosilane gas + dichlorosilane gas] at a flow rate ratio of 20 to the total flow rate)
%)-Flow rate of carrier gas supplied from the second gas supply pipe 11: hydrogen gas (H ₂ ) 300 sccm.

Film thickness: 1.5 μm.

Regarding the substantially intrinsic i-type microcrystalline silicon layer formed in Example 2, the existence density of fine particle products having a diameter of 5 μm or more, 40 mm × 40 m in the central portion
film thickness distribution within m and X-ray diffraction (220)
The / (111) orientation ratio was measured. As a result, the existence density of the fine particle product was 7.5 particles / mm ² , and the film thickness distribution was ± 5.
%, The (220) / (111) orientation ratio was 26, and
It can be seen that a highly oriented i-type microcrystalline silicon layer can be formed as compared with the above.

Further, the photoelectric conversion efficiency of the solar cell obtained in the second embodiment is the plasma CVD shown in FIG.
It was 1.097 times that of the solar cell of Comparative Example 1 in which an i-type microcrystalline silicon layer was formed using the apparatus.

[0073]

As described in detail above, according to the present invention, it is possible to reduce the amount of fine particles incorporated in the film during film formation and to make the film thickness uniform, and to obtain a uniform film having a good quality with few defects. Plasma CVD capable of forming a desired film having a certain thickness
A device can be provided.

According to the present invention, the pin structure or nip
In manufacturing a photoelectric conversion element having a microcrystalline silicon layer or a polycrystalline silicon layer having a structure, the amount of fine particles to be incorporated into the film formation of at least substantially i-type i-type microcrystalline silicon layer or polycrystalline silicon layer Manufacture of a photoelectric conversion element having a significantly reduced thickness, a uniform thickness, and (110) preferential orientation of the i-type microcrystalline silicon layer or the polycrystalline silicon layer, which has improved photoelectric conversion efficiency. A method can be provided.

According to the present invention, the pin structure or nip
Having a microcrystalline silicon layer or a polycrystalline silicon layer having a structure, the amount of fine particles taken into the film of the at least substantially intrinsic i-type microcrystalline silicon layer or polycrystalline silicon layer is significantly reduced, and Its thickness can be made uniform,
Further, it is possible to provide a photoelectric conversion element in which the i-type microcrystalline silicon layer or the polycrystalline silicon layer is (110) preferentially oriented more effectively, and the photoelectric conversion efficiency is improved.

[Brief description of drawings]

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

FIG. 2 is a plan view showing a ladder-type electrode incorporated in FIG.

FIG. 3 is a cross-sectional view showing the structure of the solar cell manufactured in Example 1 of the present invention.

FIG. 4 is a schematic view showing a conventional plasma CVD apparatus.

[Explanation of symbols]

1 ... Reaction vessel, 2 ... Support electrodes, 3 ... Ladder type electrode, 4, 10 ... Gas blowing holes, 5 ... First gas supply pipe, 6 ... Insulation tube, 7. High frequency power supply, 8 ... Impedance matching device, 9 ... Gas supply member, 11 ... Second gas supply pipe, 12 ... Exhaust pipe, 13 ... Object to be processed, 14 ... Plasma, 21 ... Transparent insulating substrate, 22 ... First transparent electrode, 23 ... p-type microcrystalline silicon layer, 24 ... i-type microcrystalline silicon layer, 25 ... n-type microcrystalline silicon layer, 26 ... second transparent electrode, 27 ... Back electrode.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kaiji Nakano 1-8, Koura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture 1 Mitsubishi Heavy Industries, Ltd. Basic Technology Research Institute (72) Inventor, Shoji Morita, Kanazawa-ku, Yokohama-shi, Kanagawa Kochiura 1-chome 8 1 Mitsubishi Heavy Industries, Ltd. Basic Technology Research Laboratory (56) Reference JP-A-11-121381 (JP, A) JP-A-7-330488 (JP, A) JP-A-2001-77029 (JP, A) JP 2000-277439 (JP, A) JP 6-260434 (JP, A) JP 2000-232073 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/205 C23C 16/509 H01L 31/04

Claims (11)

(57) [Claims] 1. A reaction vessel, and a heating heater which is arranged in the reaction vessel and has a heater for heating.
A support electrode that supports the object to be processed and is at ground potential, and a hollow rod that is arranged in parallel in the reaction vessel at a desired distance from the support electrode and has a plurality of gas blowing holes on the support electrode side. A ladder-shaped electrode, a high-frequency power source for supplying high-frequency power to the ladder-shaped electrode, and a first gas supply means for supplying a source gas, which is connected to the ladder-shaped electrode through an insulating pipe. A second gas supply means arranged in the reaction vessel on the side of the ladder-type electrode opposite to the support electrode, for supplying a carrier gas to the support electrode side, and exhausting the gas in the reaction vessel And a gas evacuation unit for the purpose of providing a plasma CVD apparatus. 2. The plasma CVD apparatus according to claim 1, wherein the distance between the surface of the object to be processed supported by the supporting electrode and the ladder electrode is 10 to 20 mm. 3. When manufacturing a photoelectric conversion device having a microcrystalline silicon layer or a polycrystalline silicon layer having a pin structure or a nip structure on a substrate, a microcrystalline silicon layer or a polycrystalline silicon layer having the pin structure or the nip structure is produced. The at least substantially intrinsic i-type microcrystalline silicon layer or polycrystalline silicon layer among the layers causes a support electrode in a reaction container in the plasma CVD apparatus according to claim 1 to support an object to be processed having the substrate. The gas in the reaction vessel is exhausted by a gas exhaust unit, the object to be processed is heated by a heater of the supporting electrode, and a Si-containing gas as a raw material gas is blown out by a first gas supply unit and a ladder-type electrode. The H ₂ as a carrier gas is supplied from the hole toward the object to be processed of the supporting electrode, and the second gas is supplied on the back surface of the ladder-shaped electrode. Supply to the object to be treated of the supporting electrode from the means, and high-frequency power is supplied from the high-frequency power source to the ladder-shaped electrode to generate plasma between the supporting electrode at the ground potential and to form a film. A method for manufacturing a characteristic photoelectric conversion element. 4. The film containing at least an i-type microcrystalline silicon layer or a polycrystalline silicon layer, wherein the Si-containing gas supplied from the first supply means is SiH _4. Manufacturing method of photoelectric conversion element. 5. When manufacturing a photoelectric conversion element having a microcrystalline silicon layer or a polycrystalline silicon layer having a pin structure or a nip structure on a substrate, a microcrystalline silicon layer or a polycrystalline silicon layer having the pin structure or the nip structure is produced. The at least substantially intrinsic i-type microcrystalline silicon layer or polycrystalline silicon layer among the layers causes a support electrode in a reaction container in the plasma CVD apparatus according to claim 1 to support an object to be processed having the substrate. The gas in the reaction vessel is exhausted by a gas exhaust means, the object to be processed is heated by the heater of the supporting electrode, and SiH ₄ and SiH ₂ Cl ₂ , which are raw material gases, Si
At least one silicon chlorinated compound gas selected from HCl ₃ and SiCl ₄ is supplied to the object to be treated of the supporting electrode from the gas supply holes of the first gas supply means and the ladder-shaped electrode, and is also a carrier gas. H ₂ is supplied from the second gas supply means on the back surface of the ladder-shaped electrode toward the object to be processed of the supporting electrode, and high-frequency power is supplied from the high-frequency power source to the ladder-shaped electrode so that the H ₂ and A method for producing a photoelectric conversion element, characterized in that plasma is generated between the layers to form a film. 6. The film formation of at least the i-type microcrystalline silicon layer or the polycrystalline silicon layer is heated to a temperature of 120 to 400 ° C. by a heater of the supporting electrode. A method for manufacturing the described photoelectric conversion element. 7. The film formation of at least an i-type microcrystalline silicon layer or a polycrystalline silicon layer, wherein the pressure in the reaction vessel is set in the range of 0.1 to 5 Torr. Manufacturing method of photoelectric conversion element. 8. In the film formation of at least an i-type microcrystalline silicon layer or a polycrystalline silicon layer, SiH ₄ which is a raw material gas supplied from the first supply means and carrier gas which is supplied from the second supply means. the flow ratio of H ₂ H ₂
The method for manufacturing a photoelectric conversion element according to claim 4 or 5, wherein the ratio is set to 30 to 70 times with / SiH ₄ . 9. The chlorinated silicon compound gas is supplied to the reaction vessel at a flow rate ratio of 1 to 80% with respect to the total flow rate of the SiH ₄ and the chlorinated silicon compound gas. 6. The method for manufacturing a photoelectric conversion element according to claim 5. 10. A photoelectric conversion element manufactured by the method according to claim 3. 11. A tandem-type photoelectric conversion element comprising at least one set of a pin-type unit or a nip-type unit manufactured by the method according to any one of claims 3 to 9.