JPH10139413A - Microcrystalline film and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a microcrystalline film suitable for thin-film solar cells, capable of improving crystallinity and increasing film-making speed by specifying a crystal grain size distribution of the microcrystalline film in which a number of crystal grains are present in the amorphous phase. SOLUTION: This microcrystalline film contains a number of crystal grains in the amorphous phase deposited on a substrate, where the average crystal grain size is larger on the side of the substrate than on the opposite side. The microcrystalline film is deposited by decomposing a stock gas flowing into a reaction chamber into a plasma with electrons accelerated by an electron beam gun, where the stock gas is supplied into the reaction chamber at an increasing gas rate, either stepwise in 2 stages or continuously, to be deposited on the substrate to form a film thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microcrystalline film suitable for application to a thin-film solar cell and a method for manufacturing the same, and more particularly to improvement in crystallinity of the microcrystalline film and increase in film forming speed.

[0002]

2. Description of the Related Art A microcrystalline film is a film in which many fine crystal grains are mixed in an amorphous film. Among them, microcrystalline semiconductor films, particularly microcrystalline silicon, and microcrystalline silicon alloys have higher conductivity, higher doping efficiency, lower absorption coefficient for short wavelength light, higher absorption coefficient for long wavelength light, etc. Has features. BACKGROUND ART Microcrystalline silicon and microcrystalline silicon alloy doped with impurities are used as window layers and ohmic contact layers of amorphous thin-film solar cells expected as low-cost solar cells, and contribute to improvement in the efficiency of solar cells. In order to apply a microcrystalline semiconductor film to an amorphous solar cell, it is necessary to form the microcrystalline semiconductor film at a substrate temperature of 250 ° C. or lower in order to suppress damage to the amorphous layer and the transparent electrode layer.

FIG. 24 shows a conventional RF glow discharge plasma C.
The apparatus of the VD method is shown. High voltage port 2 from RF power supply 24
6, an RF high voltage is applied to the RF electrode 25.
The substrate 14 is placed on the ground electrode 27 having a built-in heater. Plasma 13 is generated between the RF electrode and the ground electrode 27 to decompose the source gas supplied from the source gas line 18 and deposit a microcrystalline film on the substrate 14. The source gas after film formation is exhausted from the source gas exhaust port 19. In order to obtain a microcrystalline film at a low substrate temperature of 250 ° C. or lower by the RF glow discharge plasma CVD method, it is necessary to dilute a source gas such as silane with hydrogen by a factor of 10 to 100. When the hydrogen dilution rate is increased as described above, the film forming speed is 10 to 50.
Å / min.

In the case of forming a microcrystalline film, it is difficult to use a gas having a high decomposition energy, for example, a halogenated gas such as SiF ₄ or CF ₄ as a source gas in the RF glow discharge plasma CVD method. The i-layer, which is the active layer of the pin-type thin-film solar cell, has a large thickness. The thickness of the i-layer is 30 in the case of amorphous silicon in consideration of the absorption coefficient.
00-5000Å, 10000 for microcrystalline silicon
The thickness of about Å is required, and the deposition rate of the conventional microcrystalline film requires a very long time for forming the i-layer, which makes it difficult to apply the microcrystalline film to the i-layer. There was a problem.

Further, the present applicants have stated that “the pressure of the source gas introduced into the reaction chamber is kept within a range of 0.5 to 50 mtorr, and the source gas is decomposed into a plasma state by electrons accelerated by an electron beam gun. And depositing ions or radicals of the source gas on a substrate. This method has a slight problem that crystallinity, for example, the crystallization ratio and the average crystal grain size are conversely reduced in a region where the film forming speed increases with an increase in pressure.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a microcrystalline film capable of increasing the speed of forming a microcrystalline film and a method of manufacturing the same.

Another object of the present invention is to form a microcrystalline film at a high speed and to improve the crystallinity thereof.

Another object of the present invention is to facilitate the use of a gas having a high decomposition energy as a raw material gas.

Still another object of the present invention is to facilitate application of a microcrystalline film to an i-layer which is an active layer of a pin type thin film solar cell.

[0010]

Means for Solving the Problems A microcrystalline film according to the present invention for solving the above-mentioned problems is a microcrystalline film in which a large number of crystal grains are mixed in an amorphous film formed on a substrate, The average crystal grain size is large on the substrate side and small on the side opposite to the substrate.

In order to solve the above-mentioned problems, a method of manufacturing a microcrystalline film according to the present invention is to decompose a raw material gas introduced into a reaction chamber into a plasma state by electrons accelerated by an electron beam gun to decompose a thin film. In this method, after the source gas is supplied to the reaction chamber at a first source gas supply amount to form a film, the source gas is supplied at a second source gas supply amount larger than the first source gas supply amount. It is characterized by forming a film.

Further, the method according to the present invention is characterized in that the film is formed while increasing the supply amount of the raw material gas during the film formation.

Further, the method according to the present invention is a method for producing a thin film by decomposing a raw material gas introduced into a reaction chamber into a plasma state by electrons accelerated by an electron beam gun to produce a thin film. After forming the film while maintaining the source gas pressure, the film is formed by changing the reaction gas pressure in the reaction chamber to a second pressure higher than the second pressure.

The method according to the present invention is characterized in that the film is formed while increasing the pressure in the reaction chamber during the film formation.

Further, in the method according to the present invention, the mixed gas of the raw material gas and the diluent gas introduced into the reaction chamber is decomposed into a plasma state by the electrons accelerated by the electron beam gun, and decomposed.
In the method for producing a thin film, a film is formed with a ratio of the diluent gas to the source gas being a first ratio, and then a film is formed with a ratio of the diluent gas to the source gas being a second ratio smaller than the first ratio. It is characterized by the following.

According to the method of the present invention, a mixed gas of a raw material gas and a diluent gas introduced into a reaction chamber is decomposed into a plasma state by electrons accelerated by an electron beam gun and decomposed to produce a thin film. It is characterized in that a film is formed while reducing the ratio of gas to source gas.

In the above-described method for producing a microcrystalline film, the supply amount of the source gas is preferably 70 sccm or less, preferably 10 sccm or less, and more preferably 5 sccm.
It is as follows.

In the above-mentioned method, it is preferable that the supply amount of the source gas is 0.5 sccm or more;
More preferably, it is 4 sccm or more.

[0019] The ratio of the volume of the supply amount and the reaction chamber of the raw material gas may If it is 0.005 sccm · cm ^-3 or less, preferably 0.0007sccm · cm ^-3 or less, more preferably 0.0003sccm · cm ^{- 3} or less.

The ratio between the supply amount of the raw material gas and the volume of the reaction chamber is preferably 0.00003 sccm · cm ^-3 or more, more preferably 0.00025 sccm · c.
m ⁻³ or more.

The acceleration voltage of the electrons is preferably 40 V or more, and more preferably 60 V or more.

In the above method, at least one of silicon hydride and silicon halide can be used as the source gas, and at least one of silicon hydride and silicon halide as the source gas and a carbon atom are contained. A mixed gas with a gas can be used.

Hydrocarbons can be used as the gas containing carbon atoms, and at least one of methane, ethane, ethylene and acetylene can be used as the gas containing carbon atoms.

Also, a mixed gas of at least one of silicon hydride and silicon halide and a gas containing an oxygen atom can be used as the raw material gas, and at least one of oxygen and carbon dioxide is used as the gas containing an oxygen atom. One can be used.

Further, silicon hydride is used as the source gas,
A mixed gas of at least one silicon halide and a gas containing a nitrogen atom can be used, and at least one of nitrogen and ammonia can be used as the gas containing a nitrogen atom.

As the raw material gas, a mixed gas of at least one of silicon hydride and silicon halide and at least one of germanium hydride and germanium halide can be used, or as the raw material gas, germanium hydride, halogenated halogen At least one of germanium can be used.

Further, in the above method, the raw material gas is
It may be diluted with at least one of hydrogen and a rare gas.

A p-type impurity gas can be mixed with the raw material gas, and diborane can be used as the p-type impurity gas.

Further, an n-type impurity gas can be mixed with the source gas, and phosphine can be used as the n-type impurity gas.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a method of producing a microcrystalline film on a substrate by decomposing a raw material gas introduced into a reaction chamber into a plasma state by electrons accelerated by an electron beam gun (hereinafter, referred to as an electron beam). (Referred to as a beam-excited plasma CVD method).

The electron energy distribution of the plasma generated in the reaction chamber by the electron beam gun can be controlled by the acceleration voltage of the electron beam gun. This method makes it possible to create a plasma with a higher energy density of electrons having a higher energy than that of a normal RF glow discharge plasma. It is possible to produce a microcrystalline film at a high film forming rate at a low substrate temperature by producing a large density.

In particular, in the present invention, a film having high crystallinity is prepared at an early stage of film formation even if the film formation speed is low, and the film is formed as a base layer under the condition of a high film formation speed.
As a whole, a microcrystalline film having high crystallinity can be obtained at a high film forming rate.

In one embodiment of the present invention, the supply amount of source gas during film formation is changed.

As will be described later, the film forming speed can be remarkably increased with an increase in the supply amount of the raw material gas.
Conversely, the crystallinity such as the crystal grain size and the crystallization ratio is reduced. Therefore, in the initial stage of film formation, the supply amount of the raw material gas is reduced to form a layer having high crystallinity even if the film formation speed is low. Using this layer as a base layer, a microcrystalline film having high crystallinity is formed at a high film forming rate by increasing the supply amount of the source gas. The mode of the change of the source gas supply rate is that a microcrystalline film having high crystallinity is formed with a relatively small first supply amount, and the source gas supply amount is gradually increased to a second supply amount using the film as a base film. The film formation may be performed while the supply amount of the source gas is continuously increased from the first supply amount to the second supply amount. Furthermore, after forming the film at the first supply amount for a certain period of time, the film may be formed while gradually increasing the supply amount to the second supply amount, and then forming the film while maintaining the second supply amount.

In another embodiment of the present invention, the film is formed by changing the source gas pressure in the reaction chamber during the film formation in the electron beam excited plasma CVD method. The raw material gas pressure in the reaction chamber is formed at a first pressure having a low film forming rate but high crystallinity, and then gradually increasing the pressure to a second pressure having a high film forming rate using the base film as a base film. The first film may be formed.
The film formation may be performed while continuously increasing the pressure from the pressure of (2) to the second pressure. Furthermore, after forming the film at the first pressure for a certain period of time, the film may be formed while gradually increasing the pressure to the second pressure, and then forming the film while maintaining the second pressure.

In still another embodiment of the present invention,
In the electron beam excited plasma CVD method, a raw material gas is diluted with a diluent gas and supplied to a reaction chamber. At this time, the ratio of the diluent gas to the raw material gas is changed during film formation. The change in the ratio is such that a film is formed by supplying a diluent gas and a source gas at a first ratio having a low film forming speed but high crystallinity, and using the base film as a base film to form a second gas having a low ratio of the diluent gas to the source gas. The film formation may be performed by supplying the diluent gas and the raw material gas stepwise to the ratio, or may be performed by continuously changing from the first ratio to the second ratio. Further, after forming a film for a certain period of time while supplying the diluent gas and the source gas at the first ratio, the film is formed while the ratio of the diluent gas to the source gas is continuously reduced to the second ratio, and then the second film is formed. The film formation may be performed by supplying the diluent gas and the raw material gas while maintaining the ratio.

In the above-described electron gas excited plasma CVD method, it is preferable to form a film at a supply rate of the raw material gas of 70 sccm or less, preferably 10 sccm or less, more preferably 5 sccm or less. This is because, when the supply amount of the source gas is 70 sccm or less, a change from amorphous to microcrystalline starts, a microcrystalline film having a large grain size of 100 ° or more is obtained at 10 sccm or less, and 150 μm or less at 5 sccm.
This corresponds to obtaining a microcrystalline film having a larger grain size exceeding 200 °.

In addition to the control of the crystallinity by the supply amount of the raw material gas, the supply amount of the raw material gas is 0.5 sccm or more.
Desirably, the film is formed at 4 sccm or more. this is,
Corresponding to a high film formation rate of 100 ° / min or more when the supply amount of the raw material gas is 0.5 sccm or more, and obtaining a higher value of 200 ° / min or more for a film formation rate of 4 sccm or more. Corresponding to When the range of the supply amount of the source gas is used, a microcrystalline film having a high film forming speed and high crystallinity can be obtained. Physically, it is considered that the ratio between the film forming speed and the supply amount of the raw material gas corresponds to the gas use efficiency, and this is closely related to the crystallinity.

Further, in the electron beam excited plasma CVD method, the ratio of the supply amount of the source gas to the volume of the reaction chamber is 0.005 sccm · cm ⁻³ or less, preferably 0.005 sccm · cm ⁻³ or less.
07 sccm · cm ^-3 or less, more preferably 0.00
The problem can be solved by forming the film at 03 sccm · cm ⁻³ or less. This concerns the control of crystallinity. Also,
The ratio of the supply amount of the raw material gas to the volume of the reaction chamber is 0.0000.
³ sccm · cm ^-3 or more, preferably 0.00025 s
The above-described problem can be solved by forming a film at ccm · cm ⁻³ or more. This relates to the control of the film forming speed. The ratio between the amount of source gas supplied and the volume of the reaction chamber is proportional to the reciprocal of the residence time of the source gas in the reaction chamber, and is useful as an index for controlling the film forming speed and crystallinity when the size and arrangement of the equipment are different. It is.

In the electron beam excited plasma CVD method, it is preferable to form a film at an electron acceleration voltage of 40 V or more, preferably 60 V or more. This corresponds to the fact that the change from amorphous to microcrystal starts at 40 V or higher, and that microcrystals having a particle size of 100 ° or more are obtained at 60 V or higher. At this time, as the acceleration voltage increases, the film forming speed also increases.

In the present invention, a film having high crystallinity is prepared in the early stage of film formation even if the film formation speed is low, and this film is used as an underlayer, so that fine films having high crystallinity can be obtained even under the condition of high film formation speed. A crystalline film is obtained. As conditions for controlling the crystallinity and the film forming rate, the supply amount of the raw material gas is changed from small to large, the pressure is changed from small to large, and the ratio of the dilution gas and the raw material gas is changed stepwise from large to small, or during the film formation. By continuously changing,
It is possible to shift from a condition where the film forming speed is low and the crystallinity is high to a condition where the film forming speed is high.

By defining the range of the supply amount of the raw material gas or the range of the ratio of the supply amount of the raw material gas to the volume of the reaction chamber, a microcrystalline film having a high film forming speed and high crystallinity can be obtained. can get. Also, by defining the range of the acceleration voltage of the electron beam, a microcrystalline film having a high film forming speed and high crystallinity can be obtained.

[0043]

FIG. 1 shows an example of a microcrystalline film manufacturing apparatus for carrying out the present invention. The electron beam gun 1 includes a discharge area 2 and an acceleration area 3 and is connected to a reaction chamber 4. Discharge is generated between the cathode 7 and the discharge electrode 9 via the auxiliary electrode 8 by the DC discharge power supply 5. A voltage is applied between the discharge electrode 9 and the acceleration electrode 10 by the acceleration power source 6 to extract electrons from the discharge portion, accelerate the electrons, generate an electron beam 12, and introduce the electron beam 12 into the reaction chamber 4. Coil 11
Is provided to converge the electron beam 12. The source gas introduced from the source gas line 18 is decomposed by the electron beam introduced into the reaction chamber 4, and the plasma 1
3 results. For example, glass installed on the heater 15,
A microcrystalline film is deposited on a substrate 14 such as crystalline silicon.
The source gas after film formation is exhausted from an exhaust port 19. The electron beam gun supplies argon through an argon gas line 16 and exhausts the exhaust gas through an exhaust port 17, and is maintained at a pressure independent of the reaction chamber 4. Although FIG. 1 shows an arrangement in which the electron beam and the substrate are parallel to each other, the same operation and effect can be obtained even when the electron beam and the substrate are in a vertical or other angular positional relationship. It is also possible to improve the uniformity of the film thickness distribution by rotating the substrate.

FIG. 2 shows a first embodiment of the present invention. FIG.
Using 100% silane as the raw material gas and diluting silane with hydrogen using the apparatus shown in
The film forming speed of the produced microcrystalline silicon film with respect to the supply amount of the source gas, here, the flow rate of silane is shown. In the case of 100% silane, the pressure in the reaction chamber is 5 mtorr and 15 mtorr.
It shows about the case of. When diluted with hydrogen,
The combined flow rate of silane and hydrogen is maintained at 5 sccm, and the pressure in the reaction chamber is set at 5 mtorr. That is, the source gas supply amount is adjusted by changing the dilution ratio. The acceleration voltage of the electron beam gun is 100 V and the substrate temperature is 200
° C was used. In the range shown in the figure, the conventional hydrogen dilution was
A film formation speed of about 100 ° / min or more, which is faster than that of RF glow discharge plasma CVD performed 100 times from the above, is obtained. Further, as is apparent from the figure, the film formation speed increases remarkably as the supply amount of the raw material gas increases. A film forming rate of about 100 ° / min or more when the raw material gas supply amount is 0.5 sccm or more, and about 200 ° / mi when the raw material gas supply amount is 4 sccm or more.
A film formation speed of n or more is obtained. FIG. 3 shows the average crystal grain size of the microcrystalline film obtained under the conditions shown in FIG. The average particle size was measured from the half width of the peak in the X-ray diffraction pattern. With an increase in the supply amount of the source gas, the average particle diameter is significantly reduced to the supply amount of the source gas of 10 sccm, and gradually decreases at 10 sccm or more. It shows crystallinity when the source gas supply is 70 sccm or less, and about 10% when the source gas supply is
An average particle diameter of 0 ° or more is exhibited and the average particle diameter sharply increases, and a microcrystalline film having an average particle diameter of more than 150 ° can be obtained at a raw material gas supply of 5 sccm or less. FIG. 4 shows the crystallization ratio of the microcrystalline film obtained under the conditions shown in FIG. Here, the crystallization ratio is shown as a percentage of the volume of the crystallized portion with respect to the total volume of the microcrystalline film. As the supply of raw gas increases,
The crystallization rate monotonically decreases.

Focusing on crystallization, the source gas supply amount is 7
0 sccm or less is desirable, and the source gas supply amount is 10 sccm.
cm or less, and the supply amount of the source gas is 5 scc
m or less is more desirable. Further, when focusing on the film forming speed, the supply amount of the raw material gas is desirably 0.5 sccm or more.
The source gas supply rate is more desirably 4 sccm or more. When the above-described range of the supply amount of the raw material gas is used, the crystallinity is high and a microcrystalline film can be obtained at a high film forming speed.

FIG. 5 shows a second embodiment of the present invention. A certain period of time from the start of film formation, for example, 500 to 1000 in film thickness
A microcrystalline film is formed with a relatively small first source gas supply amount for a film formation time corresponding to Å. As a result, as is clear from FIGS. 2, 3, and 4, a film having a low film formation rate but a large crystallization ratio and a large crystal grain size is obtained, and the next film formation is performed using this as an underlayer. Next, a microcrystalline film is formed with a second source gas supply amount larger than the first source gas supply amount. In this case, as apparent from FIG. 2, the film forming speed is high. Here, since a film having high crystallinity, that is, a film having a large crystallization rate and a large crystal grain size is used as the underlayer, fine films having higher crystallinity than the case where all the films are formed at the second source gas supply amount are used. A crystalline film is obtained. Further, the film formation time is shortened as compared with the case where the film formation is performed at the first raw material gas supply amount during the entire film formation period.

FIG. 6 shows a third embodiment of the present invention. FIG.
(A) shows a case where a thick microcrystalline film is formed under the condition that the supply amount of the source gas is relatively small during the entire film forming time. The microcrystalline film 20 is deposited on the substrate 14 under the condition that the supply amount of the source gas is relatively small. In this case, a film with high crystallinity is obtained. However, the deposition time is long because the deposition rate is low. For example, using silane as a source gas,
When a film is formed at a pressure of 5 mtorr and a raw material gas supply rate of 2.5 sccm at 10,000 °, a crystal grain size of about 190 ° is obtained, but it takes about 59 minutes. FIG. 6B shows a case where a thick film is formed under the condition that the supply amount of the raw material gas is relatively large in the entire period of the film formation time. A microcrystalline film 21 is deposited on the substrate 14 under a condition that the supply amount of the source gas is relatively large. In this case, the film has a lower crystallinity than that of FIG. However, the film forming time can be shortened because the film forming speed is high. For example, silane is used as a source gas, the pressure in the reaction chamber is 5 mtorr, the source gas supply amount is 6 sccm, and
When 0000 ° is formed, the crystal grain size is about 125 °, but the film formation time is about 30 minutes. Therefore, as shown in FIG. 6C, a microcrystalline film 22 is formed on the substrate 14 under the condition of a relatively small supply amount of the first source gas at the initial stage of film formation, and the film is used as a base layer. As shown in FIG. 6D, the microcrystalline film 23 is formed under the condition of the second source gas supply amount larger than the first source gas supply amount. As a result, a film formation time is shorter than in the case of FIG. 6A, and a microcrystalline film having higher crystallinity than in the case of FIG. 6B is obtained. For example, when silane is used as a source gas and the reaction chamber is at a pressure of 5 mtorr and the source gas is supplied at a rate of 2.5 sccm at 1000 ° and the source gas is supplied at a rate of 6 sccm at 9000 °, a crystal grain size of about 180 ° is obtained. The film time is greatly reduced to about 33 minutes.

FIG. 7 shows a fourth embodiment of the present invention. The supply amount of the raw material gas is continuously increased with the film forming time. In the initial stage of film formation, a microcrystalline film having a low film formation speed but high crystallinity is formed, and the film formation speed is continuously increased by continuously increasing the supply amount of source gas. As a result, without stopping the discharge and the supply of the raw material gas, the condition of the layer having high crystallinity is continuously shifted to the condition of the high film forming speed, and the microcrystalline film is formed with high crystallinity and at a high film forming speed. A film can be formed.

FIG. 8 shows a fifth embodiment of the present invention. Film formation is performed at a relatively small first source gas supply amount for a certain period of time at the beginning of film formation. Thereby, without stopping the discharge and the supply amount of the source gas, the film formation time at the first source gas supply amount, the increase time of the source gas supply amount, and the film formation time at the second source gas supply amount can be reduced. The optimum conditions of crystallinity and film forming speed can be determined by adjustment.

FIG. 9 shows a sixth embodiment of the present invention. With respect to the pressure in the reaction chamber, the film formation rate increases significantly up to about 15 mtorr, and decreases above 15 mtorr. As shown in FIG. 10, the average grain size of the crystals of the microcrystalline film decreases as the pressure increases. In order to obtain a microcrystalline film having a particle size of 100 ° or more, it is necessary to reduce the pressure to less than 15 mtorr, and the film forming speed tends to decrease. At this time, as shown in FIG. 11, a film is formed at a relatively low first pressure of 15 mtorr or less at the initial stage of film formation, and is used as a base layer at a pressure higher than the first pressure and at a pressure of 15 mtorr or less. Then, a microcrystalline film can be formed with high crystallinity and shortening the film forming time.

FIG. 12 shows a seventh embodiment of the present invention. Along with the film forming time, the pressure is continuously increased, and the condition is continuously shifted from a condition of good crystallinity to a condition of a high film forming speed. A film can be formed.

FIG. 13 shows an eighth embodiment of the present invention. A film is formed at a relatively low pressure for a certain period in the early stage of film formation, the pressure is increased during the film formation, and subsequently, the film is formed at a relatively large pressure. As a result, the film forming time at the first pressure, the pressure increasing time, the second
By adjusting the film forming time at the pressure described above, it is possible to determine the optimum conditions having high crystallinity and a high film forming speed.

FIG. 14 shows a ninth embodiment of the present invention. Silane is used as a source gas, and hydrogen is used as a diluent gas.
With respect to the ratio of the supply amount of hydrogen to the supply amount of silane, the film formation rate is significantly reduced at first, and gradually decreases when the ratio exceeds 4. As shown in FIG. 15, with respect to the ratio of the amount of hydrogen to the amount of silane supplied, the average crystal grain size of the microcrystalline film is:
It increases significantly up to a ratio of 4 and saturates at higher ratios.
At this time, as shown in FIG. 16, hydrogen and silane are supplied at the first ratio in which the ratio of hydrogen is relatively large at the initial stage of film formation, and a film is formed. When the film is formed by supplying hydrogen and silane at the second ratio in which the ratio of hydrogen is small, a microcrystalline film can be formed with high crystallinity and shortening the film forming time.

FIG. 17 shows a tenth embodiment of the present invention.
With the film forming time, the ratio of the supply amount of hydrogen to silane is continuously reduced, and the film is continuously shifted from a film forming condition having a high crystallinity to a film forming condition having a high film forming speed, and the crystallinity is high. In addition, a microcrystalline film can be formed by shortening the film forming time.

FIG. 18 shows an eleventh embodiment of the present invention.
Hydrogen and silane are supplied at the first ratio in which the ratio of hydrogen is relatively large during the initial period of film formation to form a film, and the supply ratio of hydrogen to silane is reduced during film formation. A film is formed by supplying hydrogen and silane at a relatively small second ratio. Thereby, without stopping the discharge and the supply amount of the source gas, the film formation time is determined by the supply ratio of the first hydrogen and the silane, the reduction time of the supply ratio of the hydrogen and the silane, and the second hydrogen and the silane are reduced. By adjusting the film forming time at the ratio of the supply amount, it is possible to determine the optimum conditions having high crystallinity and a high film forming speed.

FIG. 19 shows a twelfth embodiment of the present invention.
Using the apparatus shown in FIG. 1, when 100% silane was used as the source gas and when silane was diluted with hydrogen, the produced microcrystalline silicon film was formed with respect to the ratio between the supply amount of the source gas and the volume of the reaction chamber. Indicates speed. When the pressure is constant, the ratio between the supply amount of the source gas and the volume of the reaction chamber is proportional to the reciprocal of the residence time of the source gas in the reaction chamber. In the case of 100% silane, the case where the pressure in the reaction chamber is 5 mtorr and 15 mtorr is shown. When diluted with hydrogen, the combined flow rate of silane and hydrogen is maintained at 5 sccm, and the pressure is set at 5 sccm.
mtorr. The acceleration voltage of the electron beam gun was 100 V, and the substrate temperature was 200 ° C. In the range shown in the figure, about 100 ° / sec, which is faster than the conventional RF glow discharge plasma CVD in which hydrogen dilution is performed 10 to 100 times.
A film forming speed of at least min is obtained. Further, as is apparent from the figure, the film formation rate increases significantly with an increase in the ratio between the supply amount of the raw material gas and the volume of the reaction chamber. When the ratio between the supply amount of the source gas and the volume of the reaction chamber is 0.00003 sccm · cm ⁻³ or more, the film forming speed is about 100 ° / min or more, and when the ratio between the supply amount of the source gas and the volume of the reaction chamber is 0.00025 sccm · cm ⁻³ or more. A film forming speed of about 200 ° / min or more has been obtained.
FIG. 20 shows the average grain size of crystals of the microcrystalline film obtained under the conditions shown in FIG. With the increase of the ratio of the reaction chamber volume and the supply amount of the raw material gas, the average particle size is significantly reduced to a specific 0.0007sccm · cm ^-3 in the reaction chamber volume and the supply amount of the raw material gas, 0.0007sccm · cm ^-3 Above, it decreases gradually. Ratio of supply amount of source gas to volume of reaction chamber 0.005s
It shows crystallinity at ccm · cm ^-3 or less, and shows an average particle diameter of about 100 ° or more at 0.0007 sccm · cm ^-3 or less at the ratio of the supply amount of the raw material gas to the reaction chamber volume, and the average particle diameter rapidly increases. , The ratio of the supply amount of the raw material gas to the volume of the reaction chamber 0.0
A microcrystalline film having a particle size of 150 to 200 ° or less at 003 sccm · cm ⁻³ or less can be obtained. Focusing on crystallization, the ratio between the supply amount of the raw material gas and the volume of the reaction chamber is 0.005 sccm.
Cm ^-3 or less, the ratio of the supply amount of the source gas to the volume of the reaction chamber is more preferably 0.0007 sccm · cm ^-3 or less, and the ratio of the supply amount of the source gas to the volume of the reaction chamber is 0.00.
03 sccm · cm ⁻³ or less is more desirable. Further, when focusing on the film forming speed, the ratio between the supply amount of the raw material gas and the volume of the reaction chamber is preferably 0.00003 sccm · cm ^-3 or more.
The ratio between the supply amount of the raw material gas and the volume of the reaction chamber is 0.00025s.
More preferably ccm · cm ^-3 or more. When the above-described range of the ratio of the supply amount of the source gas to the volume of the reaction chamber is used, the crystallinity is higher and a microcrystalline film can be obtained at a high film forming speed.

FIG. 21 shows a thirteenth embodiment of the present invention.
Using the apparatus shown in FIG. 1, the film forming speed of the formed microcrystalline silicon film with respect to the acceleration voltage of the electron beam is shown for the case where 100% silane is used as the source gas. The reaction chamber pressure was 5 mtorr, the raw material gas supply was 6 sccm, and the substrate temperature was 200 ° C. As is clear from FIG. 21, the film forming speed increases as the acceleration voltage increases. FIG. 22 shows the average crystal grain size of the microcrystalline film with respect to the acceleration voltage. It shows crystallinity at an acceleration voltage of 40 V or more, and shows a particle size of about 100 ° or more at an acceleration voltage of 60 V or more. FIG. 23 shows the crystallization ratio of the microcrystalline film with respect to the acceleration voltage. Crystallinity is exhibited at an acceleration voltage of 40 V or more, and the crystallization ratio monotonically increases with respect to the acceleration voltage. It is desirable that the acceleration voltage is higher as well as the crystallinity and the film forming speed. Specifically, the acceleration voltage is preferably 40 V or more, and the acceleration voltage is more preferably 60 V or more.

In the above embodiment, the case where silane gas was used as the source gas was described. However, the source gas is not limited to silane gas, and silicon halide can be used. A mixed gas of silicon hydride and / or silicon halide and a gas such as methane, ethane, ethylene, and acetylene, or a gas containing a carbon atom; silicon hydride and / or hydrogen halide and oxygen or carbon dioxide And a mixed gas of silicon hydride and / or silicon halide and a gas containing nitrogen atom such as nitrogen or ammonia. Further, germanium hydride and / or germanium halide can be used as a source gas, and silicon hydride and / or a mixed gas of silicon halide and germanium hydride and / or germanium halide can be used as a source gas. .

As the gas for dilution, a rare gas can be used in addition to the hydrogen gas, and the rare gas can be used simultaneously with the hydrogen gas.

Further, a p-type impurity such as diborane or an n-type impurity such as phosphine can be added to the above-mentioned various source gases. Therefore, by applying the present invention, a pin having high conversion efficiency
The thin-film solar cell can be manufactured with high manufacturing efficiency.

[0061]

As described above, according to the present invention,
In a method of producing a thin film by decomposing a raw material gas introduced into a reaction chamber into a plasma state by electrons accelerated by an electron beam gun and forming a film with a first raw material gas supply amount, the first raw material gas is supplied. By forming a film with the second source gas supply amount larger than the supply amount, a microcrystalline film with high crystallinity can be manufactured at a high speed at a low substrate temperature.

Alternatively, the raw material gas introduced into the reaction chamber is
In a method of producing a thin film by decomposing into a plasma state by electrons accelerated by an electron beam gun and increasing the amount of source gas supplied during film formation to form a film at low substrate temperature at high speed and with high crystallinity A high microcrystalline film can be manufactured.

Similarly, film formation is performed by increasing the pressure in the reaction chamber from small to large stepwise or continuously during film formation, and increasing the ratio of the diluent gas to the raw material gas from large to small stepwise or By continuously reducing the film thickness, a microcrystalline film having high crystallinity can be manufactured at high speed at a low substrate temperature.

Further, in a method of producing a thin film by decomposing a raw material gas introduced into a reaction chamber into a plasma state by electrons accelerated by an electron beam gun, a supply amount of the raw material gas is 70 sccm or less, preferably 10 sccm or less. More preferably, by controlling the supply amount of the source gas to 5 sccm or less and the supply amount of the source gas to 0.5 sccm or more, desirably to 4 sccm or more, a microcrystalline film with high crystallinity and high speed can be manufactured at a low substrate temperature.

Similarly, the ratio between the supply amount of the source gas and the volume of the reaction chamber is 0.005 sccm · cm ⁻³ or less, preferably 0.0007 sccm · cm ⁻³ or less, and more preferably 0.0003 sccm · cm ^−3. Under the following conditions, the ratio between the supply amount of the source gas and the volume of the reaction chamber is 0.00003 scc.
m · cm ⁻³ or more, desirably 0.00025 sccm ·
By controlling the ^{density to not} less than cm ⁻³ , a microcrystalline film having high crystallinity and high speed can be manufactured at a low substrate temperature.

Similarly, by controlling the acceleration voltage of the electron beam to desirably 40 V or more, more desirably 60 V or more, a microcrystalline film having high crystallinity and high speed can be manufactured at a low substrate temperature.

Thus, it is possible to reduce the cost of producing microcrystals by shortening the film forming time. Further, the improvement in crystallinity at a high film forming temperature can contribute to the improvement in the efficiency of the solar cell. In addition, it has become possible to apply a microcrystalline film to the i-layer of a pin type solar cell, which has been difficult due to the length of the conventional film formation time.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a microcrystalline film manufacturing apparatus capable of implementing the present invention.

FIG. 2 is a graph showing the dependence of the deposition rate of a microcrystalline film, which is a first embodiment of the present invention, on the amount of source gas supplied.

FIG. 3 is a diagram showing the dependence of the average particle diameter of the crystal of the microcrystalline film according to the first embodiment of the present invention on the source gas supply amount.

FIG. 4 is a graph showing the dependence of the crystallization ratio of a microcrystalline film on the amount of source gas supplied according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a second embodiment of the method for producing a microcrystalline film according to the present invention.

FIG. 6 is a diagram illustrating a third embodiment of the method for producing a microcrystalline film according to the present invention.

FIG. 7 is a diagram illustrating a fourth embodiment of the method for producing a microcrystalline film according to the present invention.

FIG. 8 is a diagram illustrating a fifth embodiment of the method for manufacturing a microcrystalline film according to the present invention.

FIG. 9 is a diagram showing the pressure dependence of the deposition rate of a microcrystalline film according to a sixth embodiment of the present invention.

FIG. 10 is a view showing the pressure dependence of the average grain size of crystals of a microcrystalline film according to a sixth embodiment of the present invention.

FIG. 11 is a diagram illustrating a sixth embodiment of the method for producing a microcrystalline film according to the present invention.

FIG. 12 is a diagram illustrating a seventh embodiment of the method for producing a microcrystalline film according to the present invention.

FIG. 13 is a diagram illustrating an eighth embodiment of the method for producing a microcrystalline film according to the present invention.

FIG. 14 is a diagram showing the dependency of the deposition rate of the microcrystalline film on the ratio of the dilution gas and the supply amount of the source gas according to the ninth embodiment of the present invention.

FIG. 15 is a diagram showing the dependence of the average particle size of the crystals of the microcrystalline film on the ratio of the dilution gas and the supply amount of the source gas according to the ninth embodiment of the present invention.

FIG. 16 is a diagram illustrating a ninth embodiment of a method for manufacturing a microcrystalline film according to the present invention.

FIG. 17 is a diagram illustrating a tenth embodiment of the method for manufacturing a microcrystalline film according to the present invention.

FIG. 18 is a diagram illustrating an eleventh embodiment of the method for manufacturing a microcrystalline film according to the present invention.

FIG. 19 is a diagram showing the dependence of the deposition rate of a microcrystalline film on the supply amount of source gas and the volume of a reaction chamber according to a twelfth embodiment of the present invention.

FIG. 20 is a diagram showing the dependence of the average particle size of the crystals of the microcrystalline film on the supply amount of the source gas and the volume of the reaction chamber according to the twelfth embodiment of the present invention.

FIG. 21 is a diagram showing the acceleration voltage dependence of the film forming speed of a microcrystalline film according to a thirteenth embodiment of the present invention.

FIG. 22 is a diagram showing the acceleration voltage dependence of the average grain size of crystals of a microcrystalline film according to a thirteenth embodiment of the present invention.

FIG. 23 is a diagram showing the acceleration voltage dependence of the crystallization ratio of a microcrystalline film according to a thirteenth embodiment of the present invention.

FIG. 24 is a schematic view illustrating a conventional method for manufacturing a microcrystalline film.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electron beam gun 2 Discharge area 3 Acceleration area 4 Reaction chamber 5 DC discharge power supply 6 Acceleration power supply 7 Cathode 8 Auxiliary electrode 9 Discharge electrode 10 Acceleration electrode 11 Coil 12 Electron beam 13 Plasma 14 Substrate 15 Heater 16 Argon gas line 17 Exhaust port 18 Raw material Gas line 19 Source gas exhaust port 20 Microcrystalline film obtained under relatively small amount of source gas supply 21 Microcrystalline film obtained under relatively large amount of source gas supply 22 First relatively small amount of first source gas supply 23 Microcrystalline film obtained under the condition of a relatively large amount of the second source gas supply 24 RF power supply 25 RF electrode 26 High voltage port 27 Ground electrode

Continuing on the front page (72) Inventor Ryuji Makoto 118 Futatsuka, Noda City, Chiba Prefecture Kawasaki Heavy Industries Noda Factory Co., Ltd. (72) Inventor Masakuni Tokai 118 Futatsuka, Noda City, Chiba Prefecture Kawasaki Heavy Industries, Ltd.

Claims (18)

[Claims] In a microcrystalline film in which a large number of crystal grains are mixed in an amorphous layer formed on a substrate, the average crystal grain size is large on the substrate side and small on the side opposite to the substrate. A microcrystalline film, comprising: 2. A method for producing a thin film by decomposing a raw material gas introduced into a reaction chamber into a plasma state by electrons accelerated by an electron beam gun to produce a thin film. And forming a film by supplying a source gas at a second source gas supply amount larger than the first source gas supply amount. 3. A method for producing a thin film by decomposing a raw material gas introduced into a reaction chamber into a plasma state by electrons accelerated by an electron beam gun, and forming a film while increasing a supply amount of the raw material gas during the film formation. A method for producing a microcrystalline film. 4. A method for producing a thin film by decomposing a source gas introduced into a reaction chamber into a plasma state by electrons accelerated by an electron beam gun to maintain a pressure in the reaction chamber at a first source gas pressure. After forming a film, the reaction gas pressure in the reaction chamber is increased to a second pressure higher than the second pressure.
A method for producing a microcrystalline film, wherein the film is formed by changing the pressure to a predetermined pressure. 5. A method for producing a thin film by decomposing a raw material gas introduced into a reaction chamber into a plasma state by electrons accelerated by an electron beam gun and increasing the pressure in the reaction chamber during film formation. A method for producing a microcrystalline film. 6. A method for producing a thin film by decomposing a mixed gas of a raw material gas and a diluent gas introduced into a reaction chamber into a plasma state by electrons accelerated by an electron beam gun to produce a thin film. Is formed as a first ratio, and then the second ratio is smaller than the first ratio. 7. A method for producing a thin film by decomposing a mixed gas of a raw material gas and a diluent gas introduced into a reaction chamber with electrons accelerated by an electron beam gun to produce a thin film. A method for producing a microcrystalline film, characterized in that a film is formed while reducing a ratio to a gas. 8. A method for producing a thin film by decomposing a raw material gas introduced into a reaction chamber into a plasma state by electrons accelerated by an electron beam gun, wherein a supply amount of the raw material gas is 70 sccm or less. Method for producing a microcrystalline film. 9. The supply rate of the source gas is 0.5 sccm.
9. The method for producing a microcrystalline film according to claim 8, wherein: 10. A method for producing a thin film by decomposing a raw material gas introduced into a reaction chamber into a plasma state by electrons accelerated by an electron beam gun to produce a thin film, wherein a ratio between a supply amount of the raw material gas and a volume of the reaction chamber is reduced. 0.005 sccm · cm ^-3
A method for producing a microcrystalline film, characterized in that: 11. The method for producing a microcrystalline film according to claim 10, wherein a ratio between the supply amount of the source gas and the volume of the reaction chamber is 0.00003 sccm · cm ⁻³ or more. 12. A method for producing a thin film by decomposing a raw material gas introduced into a reaction chamber into a plasma state by electrons accelerated by an electron beam gun, wherein an electron accelerating voltage is 40 V or more. A method for manufacturing a microcrystalline film. 13. The method for producing a microcrystalline film according to claim 2, wherein at least one of silicon hydride and silicon halide is used as said source gas. 14. The fine gas according to claim 2, wherein a mixed gas of at least one of silicon hydride and silicon halide and a gas containing a carbon atom is used as the raw material gas. Manufacturing method of crystalline film. 15. The fine gas according to claim 2, wherein a mixed gas of at least one of silicon hydride and silicon halide and a gas containing an oxygen atom is used as the raw material gas. Manufacturing method of crystalline film. 16. The fine gas according to claim 2, wherein a mixed gas of at least one of silicon hydride and silicon halide and a gas containing a nitrogen atom is used as the raw material gas. Manufacturing method of crystalline film. 17. The method according to claim 17, wherein the source gas is at least one of silicon hydride and silicon halide, and germanium hydride.
13. The method for producing a microcrystalline film according to claim 2, wherein a mixed gas with at least one of germanium halides is used. 18. The method for producing a microcrystalline film according to claim 2, wherein at least one of germanium hydride and germanium halide is used as the source gas.