JP2002164290A - Method of manufacturing polycrystalline silicone film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polycrystalline silicon thin film, having a proper crystallization in a short time and stably, using inductive- coupled plasma CVD method. SOLUTION: An inductive coupled plasma CVD apparatus includes a reaction chamber having a vacuum state kept therein, a reaction gas supply means for supplying a reaction gas including a silane-based gas into the reaction chamber, a reaction gas plasma generating means for plasmatizing the reaction gas to generate a reaction-gas inductive-coupled plasma by applying a high frequency power to a high frequency application coil of two or more turns, coated with an insulating material such as alumina or the like of 10 to 1000 μm in thickness and positioned inside or outside the reaction chamber, and a substrate-holding means for holding a substrate having a thin film formed on its surface. A polycrystalline silicon film is formed on the substrate at a reaction pressure of 5 to 50 pa with the use of the CVD apparatus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a polycrystalline silicon film using an inductively coupled plasma device, and a method for manufacturing a photovoltaic element using the method.

[0002]

2. Description of the Related Art Thin films such as amorphous silicon, polycrystalline silicon, silicon oxide and silicon nitride are widely used in semiconductor devices such as thin film transistors, photoelectric conversion devices and the like. In particular, among these, polycrystalline silicon has excellent electrical properties such as high photoconductivity and high durability, and thus has recently attracted particular attention as a material for photovoltaic devices such as solar cells.

As a general method for forming such a polycrystalline silicon thin film, a chemical vapor deposition (CVD) method, for example, a high-frequency plasma CVD method, an optical CVD method, an electron cyclotron resonance (ECR) CVD method, There is a thermal CVD method or the like.

Among these methods, a high-frequency plasma CVD method, which is a type of capacitively coupled plasma, suppresses the generation of structural defects such as dangling bonds (unbonded hands) and reduces the three-dimensional silicon network structure. It is widely used because it can be formed efficiently.

According to this method, a raw material gas such as monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is introduced into a vacuum reaction chamber while being accompanied by a hydrogen gas for dilution.
A high-frequency electric power is applied between two electrodes arranged opposite to each other in a vacuum reaction chamber to generate a high-frequency electric field. In this electric field, electrons collide with neutral molecules of a raw material gas, and a high-frequency plasma is generated. Is formed to decompose the raw material gas and form a silicon thin film on the surface of the base material provided on one of the electrodes.

In this high frequency plasma CVD method, a relatively high quality film is easily obtained because the plasma density is low, for example, 10 ⁹ cm ⁻³ or less, and the silicon thin film formation speed is low. However, since a high ratio of hydrogen gas dilution is required, the deposition rate is as low as about 0.1 nm per second, and
Since a large amount of hydrogen is used, there are problems in productivity and safety. In addition, there is a possibility that the quality of the thin film may be degraded due to the contamination of the electrode with the attached substance. For this reason, recently, low-pressure high-density plasma has attracted attention instead of capacitively-coupled plasma.

Therefore, the present inventors have paid attention to an inductively coupled (ICP) -CVD method using inductively coupled plasma. The ICP method is a method in which high-frequency power is applied to a high-frequency coil (antenna) to generate plasma, and a silicon thin film is formed on a base material arranged to face the high-frequency coil. In this ICP method, for example, 10 ¹⁰
10 ¹² cm ^{- 3} about a high plasma density can be obtained, it is also possible to generate more effective radical species (SiH ₃ radicals) by adjusting the plasma generating conditions. In addition, the generation of ions that are considered to have an adverse effect on the growth surface of the thin film or the interface at the time of lamination is small.
The reaction can be performed even at a pressure as low as 5 Pa.

Further, unlike the conventional capacitively-coupled plasma CVD apparatus, this ICP-CVD apparatus does not require the use of a counter electrode, and thus has a degree of freedom in the internal space of the apparatus. For this reason, for example, it is possible to increase the effective utilization rate of the reaction gas by installing a reaction gas supply nozzle facing the substrate stage.

An example of manufacturing a polycrystalline silicon thin film by using such an ICP method is described in Japanese Journal of Applied Physics, Vol. 36, "Low Temperat.
ureGrowth of Amorphous and Polycrystalline Silicon
Films from a Modified Inductively Coupled Plasm
a ", M. Goto et.al., Jpn. J. Appl. Phys. Vol. 36
(1997), pp. 3714-3720｝, a monosilane gas was supplied to an ICP-CVD apparatus having a two-layer high-frequency coil (also referred to as an RF antenna) coated with a dielectric inside a reaction chamber to supply an RF antenna. 100W RF
When a substrate temperature is increased to 300 ° C. when a power is applied and a reaction is performed at a very low reaction pressure of 0.13 Pa (1 mTorr), a crystal phase can be seen in an amorphous silicon film. And further dilute the monosilane gas with hydrogen and apply R to the RF antenna.
It was described that when the F power was increased to 800 W and the reaction was performed at a reaction pressure and a substrate temperature of 2.5 mTorr and 250 ° C., respectively, a polycrystalline silicon thin film thought to contain relatively large crystal grains was obtained. Have been.

[0010] Also, Japanese Journal of Applied Physics, vol. 38, "Low Temperature Deposit
ion of Polycrystalline Silicon Films from a Mod
ified Inductively Coupled Silane Plasma '', K. Goshi
ma et. al., Jpn. J. Appl. Phys. Vol. 38 (1999), p.
p.3655-3659} shows that when a polycrystalline silicon thin film is manufactured by the ICP-CVD method, increasing the flow rate of the reaction gas increases the film forming speed, but tends to decrease the crystallinity, and It is shown that by coating the RF antenna with a dielectric, it is possible to increase the silicon crystal grain size and improve the film forming speed. In this document, as an example of obtaining a highly crystalline silicon thin film, an ICP plasma C provided with a single-turn RF antenna coated with a 3 mm-thick dielectric inside a reaction chamber is described.
2. Supply 0.3% hydrogen-diluted monosilane gas to the VD apparatus, RF power of 600 W, substrate temperature of 290 ° C.,
It is described that the reaction was carried out at a reaction pressure of 3 Pa (27.45 mTorr) to obtain a film having a crystallization ratio of 98%.

In the above-mentioned document, the reason why one turn of RF
Although the reason for using the antenna is not described, another report by the research group of the author of the above document states that a one-turn antenna was used to control the antenna impedance (No. 26th Seminar on Physical Properties of Amorphous Materials and Application Seminar (1999: Hakata)).

[0012]

However, according to the method described in the above-mentioned document, the deposition rate of a polycrystalline silicon thin film is at most 0.45 nm / even when the deposition rate is increased at the expense of crystallinity. This is on the order of seconds (about 0.3 nm / sec when a good crystalline film is obtained), which is not a satisfactory film forming speed in view of industrial production.

Therefore, in the present invention, the ICP plasma CV
It is an object of the present invention to provide a method for manufacturing a polycrystalline silicon film having good crystallinity at high speed by the D method.

[0014]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors first studied film forming conditions. As a result, the thickness of the insulator layer of the RF antenna covered with the insulator is reduced to 1000 μm or less, and the reaction speed is increased to about 10 nm by increasing the reaction pressure to, for example, 10 Pa.
/ Sec, and in this case, the resulting polycrystalline silicon film has reduced crystallinity, and, under some conditions, has a new problem that the plasma blinks and becomes unstable. Has led to the finding that phenomena occur. As a result of intensive studies to solve the above-mentioned problems of crystallinity deterioration and plasma instability, when an RF antenna having two or more turns is used, plasma is stably produced even at a high reaction pressure. Can be generated,
The inventors have found that it is possible to prevent a decrease in crystallinity and to increase the film forming speed, and have completed the present invention.

That is, the present invention provides a reaction chamber capable of maintaining the inside thereof in a vacuum state, a reaction gas supply means for supplying a reaction gas containing a silane-based gas into the reaction chamber, Placed outside,
Reaction gas plasma generating means for generating a reaction gas inductively coupled plasma by applying a high frequency power to a high frequency application coil having two or more turns covered with an insulator having a thickness of 10 to 1000 μm to convert the reaction gas into plasma. And performing chemical vapor deposition at a reaction pressure of 5 to 50 Pa using an inductively coupled plasma CVD apparatus having a substrate holding means for holding a substrate on which a thin film is formed. A method for manufacturing a polycrystalline silicon film, comprising forming a polycrystalline silicon film thereon.

According to the manufacturing method of the present invention, a polycrystalline silicon thin film having a uniform and good crystallinity can be manufactured stably at a high speed of, for example, 10 nm / sec with good reproducibility. In the production method of the present invention, a silane-based gas concentration of 10 to 100 vol. % Of the silane-based gas, particularly hydrogen, to dilute the silane-based gas to a concentration of 10%.
-50 vol. When using gas diluted to%,
A polycrystalline silicon film can be efficiently manufactured with a higher film forming speed.

Although the present invention is not limited by theory, in the manufacturing method of the present invention, a high-frequency application coil (RF) having two or more turns covered with an insulating film having a relatively small thickness is used.
The use of an antenna widens the space in which the plasma is confined, enables the plasma to exist in a stable state even when the reaction pressure is increased to 5 to 50 Pa, and increases the generation efficiency of the inductively coupled plasma. Thus, it is considered that the above-described effects were obtained.

According to another aspect of the present invention, a silicon-based thin film layer that is an n-type impurity semiconductor and a silicon-based thin film layer that is a p-type impurity semiconductor are joined directly or via a silicon-based thin film layer that is an intrinsic semiconductor. A method for manufacturing a photovoltaic element having a stacked structure as a component, wherein at least one of the silicon-based thin film layers is manufactured by the method for manufacturing a polycrystalline silicon film according to claim 1 or 2. This is a method for manufacturing a photovoltaic element.

In the method of manufacturing a photovoltaic element according to the present invention, at least one of the silicon thin film layers is formed by the method of manufacturing a polycrystalline silicon film according to the present invention. Can be formed at a high speed.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION In the manufacturing method of the present invention, a reaction chamber capable of maintaining the inside thereof in a vacuum state, a reaction gas supply means for supplying a reaction gas containing a silane-based gas into the reaction chamber, The reaction gas is turned into plasma by applying high-frequency power to a high-frequency application coil having two or more turns covered with an insulator having a thickness of 10 to 1000 μm and disposed inside or outside the reaction chamber to convert the reaction gas into a plasma. A polycrystalline silicon film is manufactured using an inductively coupled plasma CVD apparatus having a reactive gas plasma generating means for generating plasma and a substrate holding means for holding a substrate on which a thin film is formed on its surface. .

Inductively coupled plasma CV used in the present invention
The D apparatus is not particularly different from the conventional inductively coupled plasma CVD apparatus except that it has a reactive gas plasma generating means using a high frequency application coil having two or more turns as described above as the high frequency application coil.

For example, the reaction chamber is a container whose inside can be maintained in a vacuum state by an exhaust means such as a vacuum pump or the like, and a high-frequency application coil is installed inside or outside thereof, and inside the inside thereof, The container is not particularly limited as long as it can supply a reaction gas and further has a substrate holding means therein.
A cylindrical or spherical container made of a metal material such as stainless steel used in the method can be used without any limitation.

The reaction gas supply means is not particularly limited as long as it is a means for supplying a reaction gas, which is converted into a plasma and reacts as a raw material of a silicon thin film, into a reaction chamber, but is usually a gas cylinder (cylinder). This is a pipe for introducing a reaction gas from a gas storage container such as the above via a pressure regulating valve or a flow controller, and if necessary, via a gas mixer or a temperature controller to the reaction chamber. Here, the reaction gas means a gas (raw material gas) directly serving as a raw material of the polycrystalline silicon thin film or a gas obtained by diluting the gas as needed (diluted raw material gas). As the raw material gas, monosilane, disilane, and the general formula SiH _m Cl _(4-m) (where m is 0 to 0)
It is an integer of 3. A silane-based gas such as a chlorosilane-based gas represented by the formula (1) is generally used, and such a raw material gas can be used in the present invention. When a diluent raw material gas is used, non-depositable gases such as hydrogen, helium, argon, and xenon can be used as the diluent gas. In the production method of the present invention, from the viewpoint of film formation speed,
As the reaction gas, use a monosilane or a mixed gas of monosilane and dichlorosilane without dilution,
Alternatively, these gases are hydrogen gas and the silane-based gas concentration is 10 v
ol. % Gas is preferably used. From the viewpoint of the crystallinity of the obtained film, the silane-based gas is hydrogen gas and the concentration of the silane-based gas is 10 to 50 v.
ol. %, It is particularly preferable to use a gas diluted to be%.

Further, a dopant gas may be mixed with the reaction gas for the purpose of controlling the semiconductor properties of the obtained polycrystalline silicon thin film. For example, when it is desired to obtain a polycrystalline silicon thin film that is a p-type impurity semiconductor, a gas of a compound containing a Group III element of the periodic table such as boron or gallium serving as a dopant may be mixed with the silane-based gas, When it is desired to obtain a polycrystalline silicon thin film which is an n-type impurity semiconductor, a gas of a compound containing a Group V element of the periodic table, such as phosphorus or arsenic, which serves as a dopant may be used.

The substrate on which the thin film is formed in the reaction chamber and on which the thin film is formed is not particularly limited, and any substrate used for forming various silicon-based thin films can be used. As such a substrate, a substrate made of a material such as quartz glass, soda lime glass, heat-resistant polymer, single crystal silicon, polycrystalline silicon, stainless steel, ceramics or the like can be used without any limitation. The thickness and shape of these substrates may be appropriately determined according to the purpose, but generally, a plate or sheet having a thickness of about 50 nm to 5 mm can be suitably used.

ICP-CV used in the production method of the present invention
The D apparatus has a thickness of 10 to 10 disposed inside or outside the reaction chamber as a reaction gas plasma generating means.
It is necessary to have a reactive gas plasma generating means for generating a reactive gas ICP plasma by applying a high frequency power to a high frequency applying coil having two or more turns covered with an insulator of 00 μm to convert the reactive gas into plasma.

The thickness of the high frequency application coil is 10 to 100.
By using an inductively coupled plasma CVD apparatus using a high-frequency coil having two or more turns covered with an insulator of 0 μm, the reactive gas inductively coupled plasma can be easily stabilized even when the reaction pressure is increased. Thus, a polycrystalline silicon film having high crystallinity can be manufactured at a high speed. If the number of turns is one even when a high-frequency application coil covered with an insulator is used, it is difficult to reduce the crystallinity or set conditions for obtaining stable plasma.

Here, the high frequency application coil is, for example, SU
It is a coil of two or more turns made of a conductive material such as stainless steel such as S304, copper, and aluminum, and has an insulator layer (coating layer) having a thickness of 10 to 1000 μm on its surface. It is not particularly limited as long as it is performed. As the insulator, alumina, aluminum nitride, quartz, or the like can be used. Further, it is preferable that the coating layer is formed such that the entire surface of the coil which can come into contact with the reactive gas plasma is coated with a uniform thickness.
When the thickness of the coating layer is less than 10 μm, the effect of stabilizing the plasma is low. When the thickness exceeds 1000 μm, not only is it difficult to coat with a uniform thickness, but also the crystallinity of the obtained film is reduced. However, it is difficult to obtain a high-quality polycrystalline silicon film at a high film forming speed.

The diameter of the high-frequency application coil used in the present invention may be appropriately determined according to the size of the reaction chamber, and is usually 3 to 30 cm. From the viewpoint that a thin film having a uniform thickness can be obtained, the diameter is preferably 5 to 20 cm. The number of windings of the coil is not particularly limited as long as it is 2 or more, but is preferably 2 to 8 windings, and particularly preferably 2 to 4 windings from the viewpoint of the effect and ease of manufacturing the coil and storing it in the reaction chamber. It is.

A high-frequency generator is connected to the high-frequency application coil via a matching circuit so that high-frequency power in a normally used frequency range can be applied. Usually, high-frequency power of 5 to 200 MHz is preferably 10 to 1 from the viewpoint of adjustment by a matching circuit.
A high frequency power of 00 MHz is applied. The high-frequency power means high-frequency energy generated by the high-frequency generator, and a desired high-frequency power can be set by the high-frequency generator. For example, a commercially available general RF generator can generate RF with any high-frequency power in the range of 10 W to 3 kW.

In the manufacturing method of the present invention, a thin film is formed by adjusting the reaction pressure (film forming pressure) to 5 to 50 Pa using an ICP-CVD apparatus having the above-described reaction gas plasma generating means. When a film is formed at a reaction pressure of less than 5 Pa, the film formation speed and the crystallinity are reduced. Also, 50
At a pressure exceeding Pa, no plasma is generated,
Even if it occurs, it blinks and the thin film becomes amorphous, so that a good thin film cannot be obtained. Since a uniform, high-quality silicon thin film with few defects can be formed at a high speed, the reaction pressure is 5 to 30 Pa, especially 7 to 2 Pa.
It is desirable to set it to 0 Pa.

Inductively coupled plasma CVD shown in FIG.
The manufacturing method of the present invention will be described in detail by taking a case where a crystalline silicon film is manufactured using an apparatus as an example.

First, the inductively coupled plasma CV shown in FIG.
The D device 10 will be described. The device 10 includes, for example,
The apparatus includes a cylindrical reaction chamber 12 made of stainless steel such as SUS304 and maintained in a vacuum state, and is provided with a vacuum pump or the like via an exhaust port 13 formed in a bottom wall 16 of the reaction chamber 12. By connecting to a source, a constant vacuum is maintained. Further, a stage 14 that constitutes a base material setting part for setting a base material A on which a thin film such as a silicon thin film is deposited on the surface is disposed. This stage 14
The base material A is penetrated through the bottom wall 16 of the reaction chamber 12 so as to be slidable up and down by a drive mechanism (not shown) so that the position can be adjusted. Can be heated. Although not shown, a seal member such as a seal ring is provided in a sliding portion between the stage 14 and the bottom wall 16 to secure a degree of vacuum in the reaction chamber 12. Further, on the side of the reaction chamber 12, there is a gate valve (not shown),
Through this, it is connected to a pressure adjustment chamber (not shown) for taking in and out the substrate A to be treated.

On the other hand, a ring-shaped high frequency application coil 18 is provided above the reaction chamber 12, and its base end portions 20 and 22 pass through the top wall 17 of the reaction chamber 12, and It is connected to a high-frequency power supply 24 provided outside. Further, the entire surface of at least a portion of the coil located in the reaction chamber,
It is covered with an insulator such as alumina having a thickness of 10 to 1000 μm. Further, when heating the coil for the purpose of, for example, making it difficult for the silicon film attached to the coil to peel off, for example, a sheathed heater may be embedded inside the high-frequency coil 18 or silicone oil as a heat medium may be introduced into the coil. Of course, it is also possible to heat the high-frequency coil by a method such as circulation. This high frequency application coil 1
A matching circuit (not shown) is provided between the power supply 8 and the high frequency power supply 24 so that the high frequency generated by the high frequency power supply 24 can be transmitted to the high frequency application coil 18 without loss.

The raw material gas is introduced from above the reaction chamber 12 so that the top wall 1
A shower-shaped or ring-shaped gas introduction nozzle 25 is provided so as to penetrate through the center 7 and pass through the center of the ring-shaped high-frequency application coil 18 and is introduced through a flow meter (not shown). From a reaction gas supply source (not shown in FIG. 1), a raw material gas such as, for example, monosilane (SiH ₄ ) or disilane (Si ₂ H ₆ ) is used as it is or for diluting hydrogen, helium, argon, xenon, or the like. Can be used as a mixture with the above gas.

Next, a method of forming a polycrystalline silicon film using the ICP plasma CVD apparatus having the above-described configuration will be described.

First, the inside of the reaction chamber 12 is maintained in a vacuum state by operating a vacuum source such as a vacuum pump to exhaust the gas through the exhaust port 13. By setting the inside of the reaction chamber 12 to a high vacuum, oxygen, carbon, nitrogen, and the like serving as an impurity source of the silicon film can be removed. The pressure at this time is preferably set to 1 × 10 ⁻⁶ Torr or less. Next, after a substrate A to be processed, for example, a glass substrate, a metal substrate, or the like to be processed is loaded into the pressure adjustment chamber connected to the side portion of the reaction chamber 12, the pressure in the pressure adjustment chamber is set in the reaction chamber 12. Adjust so that the degree of vacuum is the same as the pressure. Then, the gate valve is opened, and the substrate A is placed on the stage 14 in the reaction chamber 12. Then, while applying a high frequency to the high frequency application coil 18 from a high frequency power supply 24 provided outside the reaction chamber 12, a reaction gas is supplied from a reaction gas supply source (not shown) into the reaction chamber 12 through a gas introduction nozzle 25. Supply. Thus, an inductively coupled plasma is generated by the high frequency applied to the high frequency application coil 18, and a silicon thin film is deposited and formed on the surface of the substrate A mounted on the stage 14.

The introduction amounts of the reaction gas and the dilution gas are as follows:
The reaction gas alone is introduced into the reaction chamber, and the reaction gas is introduced into the reaction chamber together with the diluent gas. Is 30cc / min-3000
It is preferred that the pressure be cc / min. The mixing ratio between the reaction gas and the diluent gas is not particularly limited. However, by changing the flow ratio of the diluent gas to the reactant gas (diluent gas / reactant gas) depending on the type of the source gas used, the crystalline ratio is reduced. Although the deposition of the silicon film is dominant, if the dilution ratio is too large, the film formation efficiency is reduced. Therefore, the flow rate ratio is preferably set to 90/10 to 50/50. Since the structural change of the silicon film is greatly related to other deposition conditions, that is, high-frequency power, substrate temperature, and the like, it is difficult to uniquely define only the flow rate ratio. In general, the higher the high-frequency power, the higher the dilution ratio, and the higher the substrate temperature, the more the precipitation of crystalline silicon becomes dominant.

The distance L between the base material A and the high-frequency coil 18 is set to SiH which is considered to be a main deposition precursor.
₃ Considering the lifetime of neutral radicals, ₃ cm to 30 cm
The position may be adjusted by sliding the stage 14 up and down.

Further, the substrate A is heated to about 150 to about 250 ° C. by a heating device provided on the stage 14 so that a high-quality silicon thin film is easily deposited.

In this way, a silicon thin film is deposited and formed on the surface of the substrate A mounted on the stage 14 by the inductively coupled plasma generated by the high frequency applied to the high frequency application coil 18.

The time for forming the thin film depends on the use of the base material and the form of the apparatus. For example, the time for forming the thin film is 20 to 1000 nm so that the thickness of the silicon thin film is 200 to 1000 nm.
The reaction may be performed for about 00 seconds.

Although the vertical type apparatus has been described above, it is a matter of course that various changes can be made such as a horizontal type apparatus.

The method for producing a polycrystalline silicon film according to the present invention comprises:
It can be suitably used as various semiconductor layer forming steps in the manufacture of a photovoltaic element such as a solar cell. That is, a photovoltaic element generally used at present has a silicon-based thin film layer that is an n-type impurity semiconductor and a p-type layer (also referred to as an n-layer).
A silicon-based thin film layer (also referred to as a p-layer), which is a type impurity semiconductor, is bonded directly or via a silicon-based thin film layer (also referred to as an i-layer), which is an intrinsic semiconductor. By manufacturing at least one of the system thin film layers by the method for manufacturing a polycrystalline silicon film of the present invention, a high-quality photovoltaic element can be efficiently manufactured as a result.

In the method of manufacturing a photovoltaic element, the steps other than the step of forming the silicon-based thin film layer are not particularly limited, and the silicon-based thin film formed by a plasma CVD method used in the conventional method of manufacturing a photovoltaic element is used. Known methods such as a forming method and a method of forming a metal thin film by a vapor deposition method can be used without limitation.

For example, a transparent electrode made of indium tin oxide (ITO) or the like is formed on a base material such as glass or resin by a sputtering method or the like, and a plasma using a silane-based gas or a dopant gas is formed on the formed transparent electrode. By sequentially forming a p-layer, an i-layer, and an n-layer by a CVD method, and then forming a transparent electrode again on the n-layer, a photovoltaic element having a so-called pin-type structure can be manufactured. At this time, at least one layer selected from the group consisting of a p-layer, an i-layer, and an n-layer may be formed by the method of manufacturing a polycrystalline silicon film of the present invention. A conventional plasma CVD method can be applied without limitation to a layer formed without employing the method of manufacturing a polycrystalline silicon film of the present invention. In addition, on a substrate such as glass, silicon, heat-resistant polymer or a metal substrate such as stainless steel,
After forming a metal electrode made of a metal such as aluminum or silver by a vapor deposition method, a transparent electrode is formed on the metal electrode, and then a plasma CVD method using a silane-based gas or a dopant gas thereon is performed in the same manner as described above. , N-layer, i-layer,
By sequentially forming a p-layer and finally forming a transparent electrode again on the p-layer, a photovoltaic element having a so-called nip-type structure can be manufactured.

[0047]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The evaluation of the crystallinity of the obtained film was made by RENI.
System2000 Raman M manufactured by SHAW
The measurement was performed by Raman scattering measurement using an microscope. According to this measurement, the wave number in the spectrum is 520 cm
A peak due to crystalline silicon is observed at ^−1, and the half-width can be estimated by curve fitting of this peak, and the crystallinity can be evaluated from the integrated intensity. That is, it can be said that the smaller the reversal width, the better the crystallinity.
Incidentally, when the measurement is performed on a silicon wafer having a crystallinity of 100%, the half width is about 3 cm ⁻¹ , and when the measurement is performed on a silicon thin film having a crystallinity of about 80% (containing about 20% of an amorphous phase). Is about 9cm
It is ^-1 .

Example 1 A substrate (quartz glass substrate, thickness: 0.5 mm, size: 10c) was mounted on the stage of the IPC plasma CVD apparatus shown in FIG.
m × 10 cm) substrate was set. The high-frequency application coil in the apparatus used was a two-turn coil having a coil diameter of 10 cm, and was coated with alumina having a thickness of about 50 μm.

A monosilane gas diluted with hydrogen gas (monosilane gas concentration: 25%) was supplied into the reaction chamber as a reaction gas. The flow rate of the monosilane gas was 30 cc / min, and the pressure in the reaction chamber was maintained at 10 Pa.
A high-frequency coil 50 mm away from the substrate stage
A high frequency was supplied from a 3.56 MHz high frequency power supply at an output of 1 kW. The substrate was heated to 200 ° C. An extremely stable plasma was obtained, and a 1.21 μm (about 10 nm / sec) polycrystalline silicon thin film was obtained by performing the treatment for 2 minutes. When this film was subjected to Raman scattering measurement, the half value width of the peak at a wave number of 520 cm ^-1 was 5.48 c.
m ⁻¹ , confirming that it has high crystallinity.

Comparative Example 1 In the same manner as in Example 1 except that a single-turn high-frequency application coil was set in the reaction chamber, a polycrystal having a thickness of 1.05 μm (8.75 nm / sec) was used. A silicon thin film was formed. When the Raman scattering measurement of this film was performed, the half width was 7.21 cm ^-1 . Compared with the result of Example 1, it can be seen that the film formation speed and the crystallinity of the film are reduced.

Comparative Example 2 The procedure of Example 1 was repeated, except that the reaction pressure was changed to 3 Pa, and the thickness was 0.62 μm (5.17 nm /
S) of a polycrystalline silicon thin film (Comparative product 2). When the Raman scattering measurement of this film is performed, the half width is 10.4 cm ^−1.
was gotten. Comparative Example 3 In Example 1, the reaction pressure was 8
The high-frequency power was turned on at 0 Pa, but no plasma was emitted.

COMPARATIVE EXAMPLE 4 In Example 1, except that a high-frequency applying coil not coated with alumina was used, a high-frequency power supply was turned on in the same manner to apply plasma, but a spark was generated and the plasma became unstable. became.

[0053]

According to the method of manufacturing a polycrystalline silicon film of the present invention, an ICP plasma C having excellent manufacturing characteristics is provided.
By the VD method, a high-speed, high-quality polycrystalline silicon film can be stably manufactured. Further, by applying the method to a method of manufacturing a silicon-based thin film at the time of manufacturing a photovoltaic element, a photovoltaic element having excellent characteristics can be efficiently manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a typical inductively coupled plasma CVD apparatus that can be suitably used for the method of manufacturing a polycrystalline silicon film of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Inductive coupling type plasma CVD apparatus 12 ... Reaction chamber 13 ... Exhaust port 14 ... Stage 16 ... Bottom wall 17 ... Top wall 18 ... High frequency application coil 20,22. ..Base end portion 24 ・ ・ ・ High frequency power supply 25 ・ ・ ・ Reaction gas introduction nozzle A ・ ・ ・ Base material

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 AA06 AA17 BA29 BB03 BB12 CA06 FA04 JA06 JA09 LA16 5F045 AA08 AB03 AC01 AC16 AC17 AE17 AE19 BB12 CA13 DP02 EH11 5F051 AA03 CB04 CB12

Claims (3)

[Claims] 1. A reaction chamber capable of maintaining the inside thereof in a vacuum state, a reaction gas supply means for supplying a reaction gas containing a silane-based gas into the reaction chamber, and disposed inside or outside the reaction chamber. , Thickness 10-10
Reaction gas plasma generating means for generating a reaction gas inductively coupled plasma by applying high frequency power to a high frequency application coil having two or more turns covered with an insulator of 00 μm to generate a reaction gas inductively coupled plasma, and a surface thereof Chemical vapor deposition is performed at a reaction pressure of 5 to 50 Pa using an inductively coupled plasma CVD apparatus having a substrate holding means for holding a substrate on which a thin film is to be formed. A method for manufacturing a polycrystalline silicon film, comprising forming a silicon film. 2. A silane-based gas having a concentration of 1 as a reaction gas.
0 to 100 vol. 2. The method according to claim 1, wherein a gas is used. 3. A laminated structure in which a silicon-based thin film layer as an n-type impurity semiconductor and a silicon-based thin film layer as a p-type impurity semiconductor are joined directly or via a silicon-based thin film layer as an intrinsic semiconductor. 3. A method of manufacturing a photovoltaic device having a photovoltaic device, wherein at least one of the silicon-based thin film layers is manufactured by the method of manufacturing a polycrystalline silicon film according to claim 1 or 2. Production method.