JP2006228933A - High frequency plasma generator, surface treatment apparatus constituted thereof and surface treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment apparatus and a surface treatment method with which distribution of strength of plasma is made uniform by uniforming a standing wave generated between a pair of electrodes in application of VHF plasma to surface treatment, and uniform ultrahigh frequency plasma surface treatment of a large area is realized. <P>SOLUTION: A high frequency plasma generator is provided with a means for supplying pulse power which is hourly separated to at least two feeding points in a relation of opposite points on transmission of an electromagnetic wave in a pair of the electrodes, generating a plurality of standing waves whose positions of antinodes differ between a pair of the electrodes, and overlapping them. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a surface treatment apparatus and a surface treatment method for performing a predetermined treatment on a surface of a substrate using plasma. In particular, the present invention relates to a surface treatment apparatus using an ultrahigh frequency plasma having a low electron temperature and capable of generating a high density plasma, that is, a plasma generated by a high frequency power having a frequency in the VHF band (30 MHz to 300 MHz) and The present invention relates to a surface treatment method.

  Various kinds of processing are performed on the surface of the substrate using plasma to manufacture various electronic devices. LSI (Large Scale Integrated Circuit), LCD (Liquid Crystal Display) TFT (Thin Film Transistor), amorphous Si solar cell, thin film Already put into practical use in the fields of polycrystalline Si solar cells, photoconductors for copying machines, and various information recording devices. In addition, practical application is also progressing in the field of manufacturing ultra-hard films such as diamond thin films and cubic boron nitride (C-BN).

The above technical fields cover various fields such as thin film formation, etching, surface modification, and coating, all of which utilize the chemical and physical action of reactive plasma. The apparatus and method relating to the generation of the reactive plasma are roughly classified into three typical techniques.
The first representative technique is described in, for example, Patent Documents 1 to 3, and is characterized in that two parallel plate electrodes, which are a non-ground electrode and a ground electrode, are used as a pair for plasma generation. The second representative technique is described in, for example, Patent Documents 4 and 5, and is characterized by using a pair of rod electrodes or ladder-type electrodes and plate electrodes for plasma generation. The third representative technique is described in Patent Document 6, for example, and is characterized by an antenna system.

  For example, Patent Documents 2 and 3 describe techniques using a balance-unbalance converter as a technique for preventing power loss and suppressing generation of unnecessary plasma other than between electrodes.

The features of the technique described in the above document are roughly as follows. In the technique described in Patent Document 1, a non-grounded electrode is a square electrode, a plurality of first power supply points are arranged on the side surface of the first side of the rectangular electrode, and a second electrode facing the first side is provided. A plurality of second power supply points are arranged on the side surface of the side, and the voltage of power supplied to the plurality of first power supply points and the power supplied to the plurality of second power supply points By varying the voltage phase difference with respect to time, the electric field distribution between the pair of electrodes is averaged, and as a result, the spatial distribution of the plasma intensity is made uniform. In this technique, a standing wave can be generated by interfering with traveling waves of two electric power supplied so as to propagate in directions opposite to each other, and the position of the antinode of the standing wave can be changed with time. Is possible.
In the technique described in Patent Document 2, the pair of electrodes has a square shape, and the first and second sides of the electrodes positioned in directions orthogonal to each other are respectively provided in the output circuit of the power supply system. A plurality of connected power supply points are installed, and a reactance adjustment device corresponding to each of the plurality of power supply points is installed on the opposite side of the plurality of power supply points. . In this technology, by controlling the reactance adjustment device corresponding to the plurality of power supply points, by controlling the phase of the reflected wave, the traveling wave of the supplied power and the reflected wave are caused to interfere to generate a standing wave. And the position of the antinode of the standing wave can be moved.
In the technique described in Patent Document 3, a plurality of openings are installed in a pair of electrodes, power supply points are arranged at the edges of the openings, and the power supply system is connected to the balance-unbalance conversion device and the balanced transmission path. Power supply. In this technology, the power supplied from the adjacent apertures is superimposed on the standing wave generated by the relationship between the traveling wave and the reflected wave, and the spatial distribution of the plasma intensity between the electrodes is made uniform. It is possible to
The technique described in Patent Document 4 is characterized in that a phase adjustment circuit that adjusts the phase of reflected power is connected to the tip of the pair of electrodes on the opposite side of the power supply point. In this technique, by controlling the phase adjustment circuit, the phase of the reflected wave can be adjusted, the traveling wave of the supplied power can interfere with the reflected wave, and a standing wave can be generated, and The position of the antinode of the standing wave can be moved.
The technique described in Patent Document 5 changes temporally the phase difference between the voltage of power supplied to one power supply point on the electrode and the voltage of power supplied to at least one other power supply point. Thus, the electric field distribution between the pair of electrodes is averaged, and as a result, the spatial distribution of the plasma intensity is made uniform. In this technique, it is possible to generate a standing wave by interfering with traveling waves of two electric power supplied from opposite directions, and to change the position of the antinode of the standing wave with time. .
The technique described in Patent Document 6 is characterized in that the electrode is formed by folding a linear conductor so as to be included in a plane with reference to the central point, and the central point is used as a feeding point. The shape of this electrode is, for example, U-shaped or M-shaped. Further, the U-shaped or M-shaped electrode serves as an antenna to radiate supplied power to the space.

  The technique described in Non-Patent Document 1 is that an H-shaped feeding band is installed on the back side of the surface of the non-grounded electrode in contact with plasma, and a plurality of feeding points are installed on the H-shaped feeding band. It is a feature. The technique described in Non-Patent Document 2 is that a coil is installed on the opposite side of the feeding point of the non-grounded electrode, that is, on the end of the electrode located in the power propagation direction, and a feeding line connecting the power source and the pair of electrodes, It is characterized in that the position of the antinode of the standing wave generated in the electrode is shifted.

Japanese Patent Application Laid-Open No. 2002-12977 (second page, FIG. 1, FIG. 10-11) Japanese Patent No. 3575014 (page 1-3, FIG. 6-10) JP-A-2004-235673 (page 2-3, FIG. 9-11) JP-A-11-243062 (first page, FIG. 1, FIG. 7) Japanese Patent No. 3316490 (first page, FIG. 1, FIG. 8) JP 2000-345351 (Page 2, FIG. 1, FIG. 5, FIG. 7)

J. Kuske, U. Stephan, O. Steinke and S. Rohleck: Power feeding in large area PECVD of amorphous silicon, Mat. Res. Soc. Symp. Proc. Vol. 377 (1995), p.27-32. L. Sansonnens, A. Pletzer, D. Magni, AA Howling, Ch. Hollenstein and JPMSchmitt, A voltage uniformity study in large-area reactors for RF plasma deposition, Plasma Source Sci. Technol. 6 (1997), p. 170-178.

  The above-mentioned plasma surface treatment technology, that is, the plasma surface treatment apparatus and the plasma surface treatment method, reduce the product cost and increase the area of the product due to the improvement in productivity in any of the industrial fields such as LCD, LSI, electronic copying machine and solar cell. The need for large area, uniformization, and high-speed processing is increasing year by year for improving performance (specifications) such as wall-mounted TV. In particular, in the field of thin-film silicon solar cells, which are expected to accelerate the spread of practical use as a new energy source that responds to energy resource problems and global environmental problems, further reduction in production costs is required as a social need. ing.

  In order to meet the above needs, recently, as a technical trend, not only in industry but also in academic societies, both plasma CVD (chemical vapor deposition) technology and plasma etching technology are capable of high performance and high speed processing (low) Research on the practical application of plasma CVD technology using a power supply in the VHF band (30 MHz to 300 MHz), which is characterized by the fact that high-density plasma can be generated at an electron temperature, has become active. However, in the prior art, there are still problems as described below, and there is a problem in the field of the above needs.

  A first problem is to provide a VHF plasma surface treatment apparatus and a VHF plasma surface treatment method for a high productivity process capable of increasing the speed, large area, and uniformity (improvement of productivity and performance) of surface treatment using VHF plasma. This is a breakthrough of the technology involved. Generally, in the LCD field, the film thickness distribution ensures reproducibility of about ± 5%, and in the solar cell field, the film thickness distribution ensures reproducibility of about ± 10%. It has become. However, the technology for increasing the speed, area, and uniformity of VHF plasma, which appeared as the world's first attempt in 1987, has not made much progress. In the conventional VHF plasma technology, for example, in the case of manufacturing an a-Si film, assuming that reproducibility is ensured, when the substrate area is about 50 cm × 50 cm, the film thickness distribution is about ± 10 to 15%, and about 100 cm × 100 cm. The film thickness distribution is about ± 20 to 40%, and there is a problem that the above index cannot be cleared.

The direct cause of the non-uniformity of the film thickness distribution is the non-uniformity of the plasma density. The non-uniformity of the plasma density is caused by the standing wave caused by the wave interference phenomenon which is a problem inherent to the VHF. Occurs. Since this standing wave problem is a fundamental phenomenon associated with the propagation of electromagnetic waves, there has been no drastic solution in the past, and the idea described in Patent Documents 1 to 6 is being put into practical use as the next best measure. . However, both technologies have the following problems. That is, the problem of standing waves cannot be fundamentally solved.
(1) The technique described in Patent Document 1 changes the phase difference between the voltages of power supplied from two opposite sides of a rectangular electrode temporally, for example, at a frequency of several kilohertz, in a sawtooth shape, The position of the antinode of the generated standing wave is moved between the pair of electrodes, and the time average is made uniform. Regarding the film thickness distribution, in the case of amorphous Si film formation, a film thickness distribution of about ± 10 to 15% is obtained when the substrate area is about 50 cm × 50 cm, but it is considered to be ± 20 or more for about 100 cm × 100 cm. In addition, since the plasma fluctuates at a frequency of, for example, several kHz, there is a disadvantage that it is not suitable for high quality film manufacturing, high quality etching processing, and the like. In the case of a-Si film deposition, there is a research result that the amount of hydrogen in the film is remarkably increased in the case of a low frequency band compared with the case of a high frequency band at a power frequency of about 100 kHz to 1 MHz. .
(2) Since the technology described in Patent Document 2 controls the phase of the reflected wave of power by installing reactance adjustment devices corresponding to the plurality of power supply points on the opposite side of the plurality of power supply points, respectively. In the condition where the power absorption rate is high, for example, plasma generation at a pressure of several hundreds of Pa to several thousand Pa, the intensity of the reflected wave becomes weak, and the reflected wave cannot be controlled. That is, there is a drawback that it can be applied only when the plasma generation pressure is several hundred Pa or less.
(3) In the technique described in Patent Document 3, the strength of the plasma between the electrodes is obtained by superimposing standing waves generated by the power supplied from the openings adjacent to each other in the relationship between the traveling wave and the reflected wave. Therefore, it is necessary to select a distance corresponding to the power supply frequency, that is, the wavelength to be used. That is, it is an essential condition that the power supply frequency is selected in advance, and the wavelength of the propagation power is shortened according to the strength of the plasma density, so that the uniformity of the plasma depends on the strength of the plasma density. is there.
(4) The technique described in Patent Document 4 is similar to the technique described in Patent Document 2, in which a phase adjustment device is installed on the opposite side of the power supply point to control the phase of the reflected wave of power, so that power absorption In a high rate condition, for example, plasma generation at a pressure of several hundreds of Pa to several thousand Pa, the intensity of the reflected wave becomes weak and the reflected wave cannot be controlled. That is, there is a drawback that it can be applied only when the pressure of plasma generation is about several hundred Pa or less.
(5) The technique described in Patent Document 5 is similar to the technique described in Patent Document 1, in which the voltage of power supplied to one certain feeding point on the electrode and the power supplied to at least one other feeding point are described. VHF plasma surface treatment apparatus for processing, since the electric field distribution between a pair of electrodes is averaged by changing the phase difference of the voltage of the time, resulting in uniform spatial distribution of the plasma intensity The VHF plasma surface treatment method has a drawback that the plasma fluctuates at a frequency of, for example, several kHz, and is not suitable for high quality film production or high quality etching processing. As for the film thickness distribution, in the case of amorphous Si film formation, a film thickness distribution of about ± 10 to 15% is obtained for a substrate area of about 50 cm × 50 cm, but about 100 cm × 100 cm is considered to be ± 20 or more. Yes.
(6) Since the technique described in Patent Document 6 is an antenna system, that is, inductively coupled plasma generation, there is a restriction that the pressure condition is several Pa or less. That is, there is a disadvantage that it is impossible for an application in which the pressure condition such as microcrystalline Si is several hundred to several thousand Pa. In addition, it is presumed that it is difficult to grasp the appropriate conditions of the film forming conditions because it is easily influenced by the shape of the vacuum vessel around the electrode and the grounding conditions.

  Further, as a second problem, there is technical development of an electrode for generating VHF plasma that is highly applicable to a mass production apparatus. In general, the basic line of production equipment in a high-productivity process has three types: an inline type device, a multi-chamber type device, and a roll-to-roll type device. When a pair of electrodes in the plasma processing chamber is connected to the power supply cable, for example, when the shape of the pair of electrodes is rectangular, there is a need for means that can connect both using only one of the four surrounding sides. However, the conventional VHF plasma technology has a problem that it cannot respond to this need. Note that the techniques described in Patent Documents 1 to 6 are the only techniques described in Patent Document 6 that can meet this need. However, this technique is considered to have a low practical value because the pressure condition is limited to several Pa or less as described above.

  As described above, in the prior art, it is still difficult to apply VHF plasma CVD and plasma etching to a large area substrate necessary for mass productivity improvement and cost reduction, for example, a large area substrate of size 1 mx 1 m class, It seems difficult. That is, VHF plasma technology has attracted attention as one technology trend in order to cope with issues such as high-speed, large-area, and uniform plasma surface treatment. Due to technical difficulties, a successful example of a surface treatment apparatus capable of increasing the speed, area, and uniformity of VHF plasma using a large area substrate exceeding 1 mx 1 m class has not been announced.

  In other words, the specific technical problems that the VHF plasma field currently has are, first, the creation of a large area and uniform technology that can suppress the standing wave generated between a pair of electrodes, and second, the substrate transfer device It is the creation of a power supply means that places few restrictions on the installation of the power supply.

  Therefore, the present invention fundamentally suppresses the influence of standing waves necessary for solving the above-described problems of the prior art, enables high-speed, large-area, and uniform plasma surface treatment, and Creation of an idea capable of realizing a power supply means with little restriction on the installation of the substrate transfer apparatus, an electrode for generating an ultrahigh-frequency plasma for realizing the idea, a plasma surface treatment apparatus and a plasma surface composed of the electrode An object is to provide a processing method.

  In order to solve the above problems, the present invention is characterized in that a high-frequency plasma generator, a plasma surface treatment apparatus and a plasma surface treatment method constituted by the high-frequency plasma generator are configured as follows.

That is, the invention described in claim 1 of the present application is a high-frequency plasma generator used in a plasma surface treatment apparatus for processing the surface of a substrate disposed in a vacuum vessel using high-frequency plasma, A plurality of pulse powers separated in time are supplied to at least two feeding points that are opposed to each other in propagation of electromagnetic waves, and a plurality of positions of antinodes of standing waves of electromagnetic waves differ between the pair of electrodes. Means are provided for generating standing waves and superimposing them.
The invention according to claim 2 of the present application is characterized in that, in the high-frequency plasma generator according to claim 1, there is provided means for controlling positions of antinodes of a plurality of standing waves generated between the pair of electrodes. To do.
The invention according to claim 3 of the present application is the first invention according to claim 1 or 2, wherein any pulse modulation is possible, and the phase difference between the two outputs and the voltage of the two outputs can be arbitrarily set. A second high frequency power source capable of performing arbitrary pulse modulation synchronized with the pulse modulation signal of the first high frequency power source and the first high frequency power source and capable of arbitrarily setting the phase difference between the two outputs and the voltage of the two outputs And at any one of at least two feeding points arranged on the electrode, at one of the two output terminals of the first high-frequency power source and two of the second high-frequency power source. One of the output terminals is connected, and the other output terminal of the first high-frequency power supply and the other output terminal of the second high-frequency power supply are connected to the other feeding point. To do.
The invention according to claim 4 of the present application is characterized in that, in claims 1 to 3, a power distributor is connected to output terminals of the first and second high-frequency power supplies.
The invention according to claim 5 of the present application is characterized in that, in claims 1 to 4, a balance-unbalance conversion device is connected to the feeding point.
The invention according to claim 6 of the present application is characterized in that, in claims 1 to 5, the output frequency of the high-frequency power source belongs to a VHF band of 30 MHz to 300 MHz.
The invention according to claim 7 of the present application is that, in claims 1 to 6, the duty ratio of the pulse modulation of the output of the high frequency power source, that is, the ratio Hw / H0 of the pulse width Hw to the period T0 is set to 50% or less. Features.

  The invention according to claim 8 of the present application is a plasma surface treatment apparatus for treating a surface of a substrate disposed in a vacuum vessel using plasma, and the high frequency device according to any one of claims 1 to 7. It is characterized by comprising a plasma generator.

The invention according to claim 9 of the present application is a plasma surface treatment method for treating a surface of a substrate disposed in a vacuum vessel using plasma, and the high frequency wave according to any one of claims 1 to 7. A surface treatment of the substrate is performed using a plasma generator.
Further, the invention according to claim 10 of the present application is the method according to claim 9, wherein any one of the feeding points arranged at at least two points in the relation of opposing points on propagation of electromagnetic waves in the pair of electrodes. One of the two output terminals of each of the first and second high-frequency power supplies is connected to the feeding point, one by one, and the first and second high-frequency power supplies are connected to the other feeding point. The other output terminals are connected one by one, and the power output from the two output terminals of the first high-frequency power supply is pulse-modulated with a pulse width Hw and a pulse period T0, and the second high-frequency power supply Pulse modulation in which power output from two output terminals rises at a half cycle, that is, a time delayed by T0 / 2 from the rise time of pal-modulated power output from the output terminal of the first high-frequency power supply Thus, at least two of the pulse-modulated power output from the two output terminals of the first high-frequency power supply and the pulse-modulated power output from the two output terminals of the second high-frequency power supply The first standing wave and the second high-frequency power source, which are formed by the power output from the two output terminals of the first high-frequency power source between the pair of electrodes and separating the supply time zone to the feeding point The time points of occurrence of the second standing wave formed by the power output from the two output terminals of the first high-frequency power source are made different, and the voltage level of the power output from the two output terminals of the first high-frequency power source is made different. The phase difference between the phase difference and the voltage phase of the power output from the two output terminals of the second high frequency power supply is controlled, and the distance between the antinodes of the two standing waves, that is, the antinodes of the first standing wave And the distance between the position of the second standing wave and the position of the antinode of the second standing wave Set to 0.22 to 0.28 times, preferably 0.25 times, that is, 0.22 to 0.28λ, preferably λ / 4, of the wavelength λ of the electromagnetic wave propagating through the generated plasma between the electrodes. Thus, the substrate is subjected to a surface treatment.
In addition, the invention according to claim 11 of the present application is characterized in that, in claim 9 or 10, an amorphous Si-based material, a microcrystalline Si-based material, a polycrystalline Si-based material, a crystalline Si-based material, an oxide, Any one of a metal, an organometallic compound, an organosilicon compound, and an organic compound is formed.
The invention according to claim 12 of the present application is the amorphous silicon-based material, microcrystalline silicon-based material, polycrystalline silicon-based material, crystalline silicon-based material, oxide, which is fixed to the surface of the substrate according to the ninth or tenth invention. Any one of metal, organometallic compound, organosilicon compound, and organic compound is etched.

According to the high-frequency plasma generator of claim 1 or 2, in the high-frequency plasma generator used in the high-frequency plasma surface processing apparatus for processing the surface of the substrate disposed in the vacuum vessel using the high-frequency plasma, It is possible to uniformly control the distribution of power intensity between a pair of electrodes, which is indispensable for the uniformization. That is, in the conventional apparatus, it is considered impossible to control the distribution of power intensity between the pair of electrodes, but this is possible. As a result, a large-area and uniform plasma surface treatment using high-frequency plasma for a large-area substrate, which is considered impossible with conventional devices, can be performed. That is, it is possible to provide an apparatus capable of realizing a large area and uniform plasma processing, which is an important issue in the application field of high-frequency plasma. The effect is of great value industrially.
According to the high-frequency plasma generator of claim 3, a specific device to which the high-frequency plasma generator of claim 1-2 is applied is provided, and a large-area, uniform, and high-density plasma is reliably generated. Is possible. The application value in industry is remarkably high.
The high-frequency plasma generators according to claims 4 to 7 are reliable means for realizing the plasma generators according to claims 1 to 3, respectively, and their application value in the industry is extremely high. That is, the plasma generator according to claim 4 has a high practical value in application to multi-point power feeding to a large area electrode capable of handling a large area substrate. Moreover, the plasma generator of Claim 5 can prevent the leakage current at the end of the coaxial cable that is generated when high-frequency power is supplied to the electrode using the coaxial cable. As a result, it is possible to suppress abnormal discharge and prevent power loss inside the high-frequency plasma generator. In addition, since the discharge frequency is in the VHF band, the plasma generator of claim 6 can generate high-density plasma at a low electron temperature, which is necessary for plasma applications. As a result, the value in plasma CVD and etching applications is significantly higher. Further, the plasma generator of claim 7 can surely realize the plasma generator of claims 1 to 3, and its application value in the industry is extremely high.

  According to the plasma surface processing apparatus of claim 8, the plasma surface that processes the surface of the substrate disposed in the vacuum vessel by using plasma generated by using the power of the output of the high frequency power source whose oscillation frequency belongs to the VHF band. In the processing apparatus, it is possible to control the distribution of power intensity between a pair of electrodes, which is indispensable for uniformizing large-area plasma, to be uniform. As a result, a large-area and uniform plasma surface treatment using VHF plasma targeting a large-area substrate, which is considered difficult with conventional apparatuses, can be achieved. That is, it is possible to provide an apparatus capable of realizing a large area and uniform plasma processing, which is an important issue in the application field of VHF plasma. The effect is of great value industrially.

According to the plasma surface treatment method of claim 9, the plasma surface that treats the surface of the substrate disposed in the vacuum vessel using plasma generated using the power of the output of the high-frequency power source whose oscillation frequency belongs to the VHF band. In the processing method, it is possible to control the distribution of power intensity between a pair of electrodes, which is indispensable for uniformizing a large area plasma. As a result, a large-area and uniform plasma surface treatment using VHF plasma targeting a large-area substrate, which is considered difficult by the conventional method, can be performed. That is, it is possible to provide a method capable of realizing a large area and uniform plasma treatment, which is an important issue in the application field of VHF plasma. The effect is of great value industrially.
The plasma surface treatment method according to claim 10, wherein the surface of a substrate disposed in a vacuum vessel is treated using plasma generated by using the power of an output of a high-frequency power source whose oscillation frequency belongs to the VHF band. Therefore, it is possible to reliably realize uniform control of the distribution of power intensity between a pair of electrodes, which is indispensable for uniformizing large-area plasma. As a result, a large-area and uniform plasma surface treatment using VHF plasma targeting a large-area substrate, which is considered difficult by the conventional method, can be performed. That is, it is possible to provide a method capable of realizing a large area and uniform plasma treatment, which is an important issue in the application field of VHF plasma. The effect is of great value industrially.
According to the plasma surface treatment method of claim 11, the plasma surface that treats the surface of the substrate disposed in the vacuum vessel using plasma generated using the power of the output of the high-frequency power source whose oscillation frequency belongs to the VHF band. In the treatment method, any of amorphous Si-based material, microcrystalline Si-based material, polycrystalline Si-based material, crystalline Si-based material, oxide, metal, organometallic compound, organosilicon compound, and organic compound is formed on the surface of the substrate. Can be formed uniformly in a large area. As a result, LSIs (Large Scale Integrated Circuits), LCD (Liquid Crystal Display) TFTs (Thin Film Transistors), amorphous Si solar cells, thin film polycrystalline Si solar cells, photoconductors for copying machines, and various information recording devices, etc. A drastic improvement in product productivity in each field is realized. Therefore, the effect is of great value.
According to the plasma surface treatment method of claim 12, the plasma surface that treats the surface of the substrate disposed in the vacuum vessel using plasma generated using the power of the output of the high-frequency power source whose oscillation frequency belongs to the VHF band. In the processing method, any of amorphous Si-based material, microcrystalline Si-based material, polycrystalline Si-based material, crystalline Si-based material, oxide, metal, organometallic compound, organosilicon compound, and organic compound fixed to the surface of the substrate It is possible to etch a large area and uniformly. As a result, LSIs (Large Scale Integrated Circuits), LCD (Liquid Crystal Display) TFTs (Thin Film Transistors), amorphous Si solar cells, thin film polycrystalline Si solar cells, photoconductors for copying machines, and various information recording devices, etc. A drastic improvement in product productivity in each field is realized. Therefore, the effect is of great value.

  Hereinafter, a high-frequency plasma generator according to an embodiment of the present invention, a plasma surface treatment apparatus constituted by the high-frequency plasma generator, and a plasma surface treatment method will be described with reference to the drawings. In the following description, as an example of a plasma surface treatment apparatus and a plasma surface treatment method, an apparatus and method for producing an a-Si thin film necessary for producing a solar cell are described. However, the present invention is not limited to the apparatus and method of the following example.

Example 1
A high-frequency plasma generating electrode of Example 1 relating to the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the electrodes will be described with reference to FIGS. .

  FIG. 1 is a schematic view showing the entire plasma surface treatment apparatus according to the first embodiment, FIG. 2 is an explanatory view of a power feeding portion to the first and second electrodes of the plasma surface treatment apparatus shown in FIG. 1, and FIG. FIG. 4 is an explanatory diagram showing a typical example of pulse-modulated output outputted from the first and second pulse modulation type variable-phase two-output transmitters shown in FIG. 1, and FIG. 4 shows the first and second pulse modulations shown in FIG. FIG. 5 is an explanatory diagram showing the propagation of a voltage wave generated between a pair of electrodes, and FIG. 6 is a pair of a pair of electrodes. FIG. 7 is an explanatory diagram showing the position of the antinode of the standing wave of the voltage generated between the electrodes, FIG. 7 is an explanatory diagram showing the distribution of the strength (value of the square of the amplitude) of the standing wave generated between the pair of electrodes; FIG. 8 is an explanatory diagram showing the strength of two standing waves generated between a pair of electrodes.

First, the configuration of the apparatus will be described. 1 and 2, reference numeral 1 denotes a vacuum vessel. The vacuum vessel 1 includes a pair of electrodes for converting a discharge gas, which will be described later, into plasma, that is, a first electrode 2 composed of a single non-grounded bar, and a grounded flat plate-like first member including a substrate heater 3 (not shown). Two electrodes 4 are arranged. The first electrode 2 is fixed to the vacuum vessel 1 via an insulator support 5 and a gas mixing box 6. The gas mixing box 6 has a function of uniformly supplying a discharge gas such as SiH 4 supplied from the discharge gas supply pipe 8 between the pair of electrodes 2 and 4 through the rectifying holes 7. The supplied discharge gas such as SiH 4 is converted into plasma between the pair of electrodes 2 and 4, and then discharged out of the vacuum vessel 1 by the exhaust pipe 9 and a vacuum pump 10 (not shown).

  The pressure in the vacuum vessel 1 is monitored by a pressure gauge (not shown), and is automatically adjusted and set to a predetermined value by a pressure adjustment valve (not shown). In the case of the present embodiment, when the discharge gas has a flow rate of about 500 sccm to 1, 500 sccm, the pressure can be adjusted to about 0.01 Torr to 10 Torr (1.33 Pa to 1330 Pa). The vacuum ultimate pressure of the vacuum vessel 1 is about 2 to 3E-7 Torr (2.66 to 3.99E-5 Pa).

  Reference numeral 11 denotes a substrate, which is installed on the second electrode 4 by opening and closing a gate valve 12 (not shown). Then, it is heated to a predetermined temperature by a substrate heater 3 (not shown).

  One feeding point, which is a position for feeding high-frequency power to the electrode, is one end of the first electrode 2 composed of the one bar, and this is a first feeding point 21. The other end portion of the electrode, which is in a position that is a point opposite to the feeding point 21 in the propagation of a high-frequency power wave, is a second feeding point 27.

Reference numeral 100 denotes a synchronization signal transmission cable, which uses a pulse modulation waveform signal output from a first pulse modulation system variable phase 2 output transmitter 15 described later as a synchronization signal, and outputs a second pulse modulation system variable phase 2 output described later. To the device 28.
Reference numeral 15 is a first pulse modulation type phase variable 2-output transmitter which generates a sine wave signal having an arbitrary frequency of 30 MHz to 300 MHz (VHF band), for example, 60 MHz, and pulses the sine wave signal. It is possible to arbitrarily set the phase difference between the two pulse-modulated sinusoidal signals that are modulated and output from the two output terminals.
The phase difference between the two sine wave signals output from the two output terminals of the phase-variable two-output transmitter 15 and the pulse width Hw and period T0 of the pulse modulation are attached to the phase-variable two-output transmitter 15. The phase difference adjuster and the pulse modulation adjuster can be set to arbitrary values. Further, the first pulse modulation system variable phase 2 output transmitter 15 transmits a pulse modulation to a second pulse modulation system variable phase 2 output transmitter 28 to be described later via the synchronization signal transmission cable 100 described above. Send a sync signal.
One output of two output terminals of the first pulse modulation type phase variable two-output transmitter 15 is a first power amplifier 16, a first impedance matching unit 17, a first current introduction terminal 18, 1 is supplied to the first feeding point 21 via the core wire 20 of the vacuum coaxial cable 19. As a typical example, this output is a sine wave pulse-modulated with a pulse width Hw and a period T0 as shown in W11 (t) shown in FIGS.
In addition, the connection between the transmitter 15 having the variable phase 2 output and the first power amplifier 16, the connection between the first power amplifier 16 and the first impedance matching unit 17, the first impedance matching unit 17 and the first power matching unit 17 A coaxial cable is used for connection to the current introduction terminal 18. The outer conductor of the first vacuum coaxial cable 19 is connected to the second electrode 4.
The other output of the two output terminals of the first pulse modulation type phase-variable two-output transmitter 15 is a second power amplifier 22, a second impedance matcher 23, a second current introduction terminal 24, a second 2 is supplied to the second feeding point 27 through the core wire 26 of the vacuum coaxial cable 25. This output is, as a typical example, a sine wave that is pulse-modulated with a pulse width Hw and a period T0 similar to W11 (t), such as W21 (t) shown in FIGS.
It should be noted that the phase variable 2-output transmitter 15 and the second power amplifier 22 are connected, the second power amplifier 22 and the second impedance matcher 23 are connected, and the second impedance matcher 23 and the second power amplifier 22 are connected. A coaxial cable is used for connection with the current introduction terminal 24. The outer conductor of the second vacuum coaxial cable 25 is connected to the second electrode 4.
Each of the first power amplifier 16 and the second power amplifier 22 is attached with a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. In addition, an isolator for protecting the electric circuit of the first and second power amplifiers 16 and 22 by the reflected wave is attached.

Reference numeral 28 is a second pulse modulation type variable phase 2 output transmitter that generates a sine wave signal of any frequency of 30 MHz to 300 MHz (VHF band) having different phases from the two output terminals, for example, 60 MHz. In addition, the first pulse modulation is performed by using the two sine wave signals from the first pulse modulation system phase-variable two-output transmitter 15 via the synchronization signal transmission cable 100. A pulse-modulated signal is output in synchronization with the pulse-modulated signal of the transmitter 15 having the system phase variable 2-output.
The phase difference between the two sine wave signals output from the two output terminals of the phase-variable two-output transmitter 28, the pulse width Hw and the period T0 of the pulse modulation are attached to the phase-variable two-output transmitter 28. The phase difference adjuster and the pulse modulation adjuster can be set to arbitrary values.
One output of the two output terminals of the second pulse modulation type phase-variable two-output transmitter 28 includes a third power amplifier 29, a third impedance matching unit 30, a third current introduction terminal 31, and a second output terminal. 3 is supplied to the first feeding point 21 via the core wire 33 of the vacuum coaxial cable 3. This output is typically a pulse width Hw, a period T0, and a pulse rise time of the pulse modulation of W11 (t) and W21 (t) as in W12 (t) shown in FIGS. It is a pulse-modulated sine wave that rises at a half cycle, that is, a time delayed by T0 / 2.
It should be noted that the second phase variable 2-output transmitter 28 and the third power amplifier 29 are connected, the third power amplifier 29 and the third impedance matching device 30 are connected, and the third impedance matching device 30 is connected. For the connection with the third current introduction terminal 31, a coaxial cable is used for both. The outer conductor of the third vacuum coaxial cable 32 is connected to the second electrode 4.
The other output of the two output terminals of the second pulse modulation type phase-variable two-output transmitter 28 includes a fourth power amplifier 34, a fourth impedance matching unit 35, a fourth current introduction terminal 36, 4 is supplied to the second feeding point 27 via the core wire 38 of the vacuum coaxial cable 37. This output is typically a pulse width Hw, a period T0, and a pulse rise time of the pulse modulation of W11 (t) and W21 (t) as shown in FIGS. 3 and 4 as W22 (t). It is a pulse-modulated sine wave that rises at a half cycle, that is, a time delayed by T0 / 2.
It should be noted that the second phase variable 2-output transmitter 28 and the fourth power amplifier 34 are connected, the fourth power amplifier 34 and the fourth impedance matching device 35 are connected, and the fourth impedance matching device 35 is connected. For the connection with the fourth current introduction terminal 36, a coaxial cable is used in all cases. The outer conductor of the fourth vacuum coaxial cable 37 is connected to the second electrode 4.
Each of the third power amplifier 29 and the fourth power amplifier 34 is accompanied by a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. Further, an isolator for protecting the electric circuit of the third and fourth power amplifiers 29 and 34 by the reflected wave is attached.

  Next, a method of forming an amorphous Si film for an a-Si solar cell using the plasma surface treatment apparatus having the above configuration will be described. In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. The first preliminary film forming step includes the step of determining the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15. In order to grasp the set value of the phase difference between the two outputs of the transmitter 28 having the second pulse modulation type variable phase two output, this film forming process is carried out for the purpose of manufacturing the target amorphous Si.

First, in the first first preliminary film-forming step, in FIGS. 1 and 2, the substrate 11 is previously set on the second electrode 4, and the vacuum pump 10 (not shown) is operated to operate the vacuum container. After removing the impurity gas and the like in 1, the substrate temperature is in the range of 80 to 350 ° C., for example 180, while the SiH 4 gas is supplied from the discharge gas supply tube 8 at 250 sccm and the pressure 0.5 Torr (66.5 Pa). Hold at ℃.
Next, the first pulse modulation type phase-variable two-output transmitter 15, the first power amplifier 16, the first impedance matching unit 17, the first current introduction terminal 18, and the first vacuum coaxial cable 19. A first power supply system comprising a core wire 20, a second power amplifier 22, a second impedance matching unit 23, a second current introduction terminal 24, and a core wire 26 of a second vacuum coaxial cable 25, High frequency power is supplied to the pair of electrodes 2 and 4, for example, with a frequency of 60 MHz, a pulse width Hw = 400 μsec, and a pulse period T0 = 1 msec, for example, 200 W in total.
That is, the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15 is set to, for example, zero, the pulse width Hw = 400 μsec, and the pulse period T0 = 1 msec. The output of the power amplifier 16 is set to 100 W, and the output is supplied to the first power supply via the first impedance matching unit 17, the first current introduction terminal 18, and the core wire 20 of the first vacuum coaxial cable 19. And the output of the second power amplifier 22 is set to 100 W, and the output is supplied to the second impedance matching unit 23, the second current introduction terminal 24, and the core wire of the second vacuum coaxial cable 25. 26 to the second feeding point.
In this case, by adjusting the first impedance matching unit 17 and the second impedance matching unit 23, the reflected wave of the supplied power does not return to the upstream side of the respective impedance matching units 17 and 23. Can do.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. As will be described later, the film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave, which is a phenomenon inherent to VHF plasma. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 15 having the first pulse modulation type variable phase two output as a parameter. Then, in the length direction of the first electrode, the distance from the center point of the substrate 11 to the position of the maximum thickness of the sinusoidal film thickness distribution and 2 of the transmitter 15 of the first pulse modulation system variable phase 2 output. The relationship between the phase differences of the two outputs is grasped as data. For example, it is understood that the phase difference for setting a position that is one-eighth of the wavelength λ from the center point of the substrate 11 in the direction of the first feeding point 21, that is, λ / 8, is, for example, Δθ1. Is done.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

By the way, the voltage wave of the power supplied in a pulse form from the first and second feeding points 21 and 27 oscillates from the same power source and propagates between the electrodes, that is, both face each other. Since they propagate from each other and overlap, an interference phenomenon occurs. This will be described with reference to FIGS.
In FIG. 5, the distance in the direction from the first feeding point 21 to the second feeding point 27 is x, the voltage wave propagating in the positive x direction is W11 (x, t), and the voltage propagating in the negative x direction. Assuming that a wave, that is, a voltage wave propagating from the second feeding point 27 toward the first feeding point 21 is W21 (x, t), it is expressed as follows.
W11 (x, t) = V1 · sin (ωt + 2πx / λ)
W21 (x, t) = V1 · sin {ωt−2π (x−L0) / λ + Δθ}
Where V1 is the amplitude of the voltage wave, ω is the angular frequency of the voltage, λ is the wavelength of the voltage wave, t is time, L0 is the interval between the first and second feeding points, and Δθ is supplied from the first feeding point 21. The phase difference between the voltage wave of the electric power and the voltage wave of the electric power supplied from the second feeding point 27. A composite wave W1 (x, t) of these two voltage waves is expressed by the following equation.
W1 (x, t) = W11 (x, t) + W21 (x, t)
= 2 · V1cos {2π (x−L0 / 2) / λ−Δθ / 2} · sin {ωt + (πL0 / λ + Δθ / 2)
The synthetic wave W1 (x, t) is conceptually shown in FIG. In FIG. 6, when Δθ = 0, the intensity of the generated plasma is strong in the central portion (x = L0 / 2) between the feeding points, and decreases as the distance from the central portion increases. When Δθ> 0, the strong plasma portion moves to one feeding point side, and when Δθ <0, it moves to the other feeding point side.
Here, the voltage waves of the power supplied to the first and second feeding points 21 and 27 using the first power supply system are respectively expressed as W11 (x, t) and W21 (x , T). Further, the combined wave of the two voltage waves is referred to as a first standing wave W1 (x, t).

By the way, the strength of power between the pair of electrodes is proportional to the square of the amplitude value of the first standing wave W1 (x, t) of the voltage. That is, the power intensity I1 (x, t) is
I1 (x, t) ∝cos ² {2π (x−L0 / 2) / λ−Δθ / 2}
It is expressed. This I1 (x, t) is conceptually shown in FIG.
FIG. 7 shows that the uniformity of plasma between a pair of electrodes is, for example, in the range of 0.9 to 1.0, due to the generation of a standing wave that is a problem in the generation of VHF plasma. This indicates that the distance in the propagation direction is limited to the range of −0.05 to + 0.05λ (that is, the range where the film thickness is uniform is 0.1λ).
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.
Further, the distance from the center point of the substrate acquired in the first preliminary film forming step to the position of the maximum thickness of the sinusoidal film thickness distribution and the two outputs of the transmitter 15 having the first phase variable and two outputs. For example, the position of the maximum thickness of the film thickness distribution can be set at a position that is one eighth of the wavelength λ, that is, a position that is λ / 8 away from the center point of the substrate.
Here, the intensity distribution of the first standing wave W1 (x, t) is referred to as I1 (x, t).

Next, in the second preliminary film forming step, in FIGS. 1 and 2, the substrate 11 is previously set on the second electrode 4, the vacuum pump 10 (not shown) is operated, and the inside of the vacuum container 1 is operated. After removing the impurity gas, etc., the substrate temperature is in the range of 80 to 350 ° C., for example, 180 ° C. while supplying the SiH 4 gas from the discharge gas supply tube 8 at 250 sccm and the pressure of 0.5 Torr (66.5 Pa) Hold.
The second pulse modulation type phase-variable two-output transmitter 28, the third power amplifier 29, the third impedance matching device 30, the third current introduction terminal 31, and the third vacuum coaxial cable 32 Using a second power supply system comprising a core wire 33, a fourth power amplifier 34, a fourth impedance matching device 35, a fourth current introduction terminal 36, and a core wire 38 of a fourth vacuum coaxial cable 37, a pair The electrodes 2 and 4 are supplied with high frequency power, for example, with a frequency of 60 MHz, a pulse width Hw = 400 μsec, and a pulse period T0 = 1 msec, for example, 200 W in total.
That is, the phase difference between the two outputs of the second pulse modulation type phase-variable two-output transmitter 28 is set to, for example, zero, the pulse width Hw = 400 μsec, and the pulse period T0 = 1 msec. The output of the power amplifier 29 is set to 100 W, and the output is supplied to the first power supply via the third impedance matching device 30, the third current introduction terminal 31, and the core wire 33 of the third vacuum coaxial cable 32. And the output of the fourth power amplifier 34 is set to 100 W, and the output is the core wire of the fourth impedance matching device 35, the fourth current introduction terminal 36, and the fourth vacuum coaxial cable 37. It is supplied to the second feeding point via 38.
In this case, by adjusting the third impedance matching unit 30 and the fourth impedance matching unit 35, the reflected wave of the supplied power can be prevented from returning to the upstream side of the respective impedance matching units 30 and 35.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 has a sinusoidal distribution due to the generation of a standing wave that is a phenomenon inherent to the VHF plasma. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 28 of the second pulse modulation type variable phase output 2 as a parameter. Then, in the length direction of the first electrode, the distance from the center point of the substrate to the position of the maximum thickness of the sinusoidal film thickness distribution and the two transmitters 28 of the second pulse modulation type phase variable two output Grasp the relationship of output phase difference as data.
Also in this case, similarly to the first preliminary film forming step, in the case where the second power supply system is used, the distance from the center point of the substrate to the position of the maximum thickness of the sinusoidal film thickness distribution and the first The position of the maximum thickness of the film thickness distribution, for example, from the center point of the substrate to the second feeding point 27 is obtained from data indicating the relationship between the two output phase differences of the two pulse modulation type phase-variable two-output transmitters 28. It can be seen that the phase difference for setting the position to one-eighth of the wavelength λ in the direction, that is, the position separated by λ / 8 is, for example, Δθ2.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

In the second preliminary film-forming step, the voltage wave of power supplied in a pulse form from the first and second feeding points 21 and 27 is oscillated from the same power source and propagates between the electrodes. That is, the two propagate from each other and overlap each other, causing an interference phenomenon. This is shown in FIGS.
In FIG. 5, the distance in the direction from the first feeding point 21 to the second feeding point 27 is x, the voltage wave propagating in the positive direction of x is W12 (x, t), and the voltage propagating in the negative direction of x. When a wave, that is, a voltage wave propagating from the second feeding point 27 toward the first feeding point 21 is W22 (x, t), it is expressed as follows.
W12 (x, t) = V2 · sin (ωt + 2πx / λ)
W22 (x, t) = V2 · sin {ωt−2π (x−L0) / λ + Δθ}
Where V2 is the amplitude of the voltage wave, ω is the angular frequency of the voltage, λ is the wavelength of the voltage wave, t is the time, L0 is the interval between the first and second feed points, and Δθ is supplied from the first feed point 21. The phase difference between the voltage wave of the electric power and the voltage wave of the electric power supplied from the second feeding point 27 The voltage composite wave W2 (x, t) is expressed by the following equation.
W2 (x, t) = W12 (x, t) + W22 (x, t)
= 2 · V2cos {2π (x−L0 / 2) / λ−Δθ / 2} · sin {ωt + (πL0 / λ + Δθ / 2)
The synthetic wave W2 (x, t) is conceptually shown in FIG. In FIG. 6, when Δθ = 0, the intensity of the generated plasma is strong in the central portion (x = L0 / 2) between the feeding points, and decreases as the distance from the central portion increases. When Δθ> 0, the strong plasma portion moves to one feeding point side, and when Δθ <0, it moves to the other feeding point side.
Here, the voltage waves of the power supplied to the first and second feeding points 21 and 27 using the second power supply system are respectively expressed as W12 (x, t) and W22 (x, t). The combined wave of the two waves is called a second standing wave W2 (x, t).

By the way, the strength of the power between the pair of electrodes is proportional to the square of the amplitude value of the composite wave W2 (x, t) of the voltage. That is, the power intensity I2 (x, t) is
I2 (x, t) ∝cos ² {2π (x−L0 / 2) / λ−Δθ / 2}
It is expressed. This I2 (x, t) is conceptually shown in FIG.
FIG. 7 shows that the uniformity of plasma between a pair of electrodes is, for example, when the strength is in the range of 0.9 to 1.0 due to the generation of standing waves that are a problem in the generation of VHF plasma. This indicates that the distance in the direction is limited to the range of −0.05 to + 0.05λ (that is, the range where the film thickness is uniform is 0.1λ).
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.
Here, the intensity distribution of the second standing wave W2 (x, t) is referred to as I2 (x, t).

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIGS. 1 and 2, the substrate 11 is previously set on the second electrode 4, the vacuum pump 10 (not shown) is operated to remove the impurity gas in the vacuum vessel 1, and then the discharge gas is supplied. While supplying SiH4 gas from the tube 8 at, for example, 300 sccm and a pressure of 0.5 Torr (66.5 Pa), the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C.
Next, two preliminary outputs of the first pulse modulation type phase-variable two-output transmitter 15 of the constituent members of the first power supply system, for example, a phase difference of a sine wave having a frequency of 60 MHz are used as a first preliminary film forming step. Is set to Δθ1 grasped as data, and pulse width Hw and period T0 in W11 (t) and W21 (t) shown in FIGS. 3 and 4 are set to Hw = 400 μsec and T0 = 1 msec, for example. The first and second feeding points 21 and 27 are each supplied with, for example, 100 W of power, and the second pulse modulation type phase variable two-output transmitter of the component of the second power supply system. 28, for example, a phase difference of a sine wave having a frequency of 60 MHz is set to Δθ2 grasped as data of the second preliminary film-forming process, and its pulse modulation is W12 (t) shown in FIG. 3 and FIG. And W22 ( The pulse width Hw and period T0 at t) are, for example, Hw = 400 μsec and T0 = 1 msec, and a half period, ie, T0 / 2 delay from the pulse rise time of the pulse modulation of W11 (t) and W21 (t). For example, 100 W is supplied to the first and second feeding points 21 and 27, respectively. That is, the voltage waves W11 (x, t), voltage waves W21 (x, t), W12 (x, t) and W22 (x, t) are supplied to the first and second feeding points 21 and 27. Is done.
Here, the first pulse modulation type phase variable 2 output transmitter 15 and the second pulse modulation type phase variable 2 output transmitter set in the first preliminary film forming step and the second preliminary film forming step, respectively. For example, the values of 28 pulse widths Hw and period T0 can be changed from Hw = 400 μsec to 1 msec or the like, and T0 = 1 msec to 5 msec or the like.

When four voltage waves are supplied between the pair of electrodes 2, 4, as described above, W 11 (x, t) and W 21 (x, t) interfere with each other and the first standing wave W 1 (x, t t), and W12 (x, t) and W22 (x, t) interfere to form a second standing wave W2 (x, t). However, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t) because they are temporally separated. Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
Therefore, considering a general film formation time of several seconds or longer, which is significantly longer than the pulse modulation period T0, the distribution of the strength of the power generated between the pair of electrodes 2 and 4 is the first standing wave. The intensity distribution I1 (x, t) of W1 (x, t) and the intensity distribution I2 (x, t) of the second standing wave W2 (x, t) are superimposed. This is conceptually shown in FIG.
Here, if the center point of the substrate is the origin of the x-axis and the direction from the origin toward the first feeding point 21 is a positive direction, the strength of the first standing wave W1 (x, t) Distribution I1 (x, t) is
I1 (x, t) ∝cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the second standing wave W2 (x, t) is
I2 (x, t) ∝cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2 and 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1
As a result, the distribution of power intensity I (x, t) generated between the pair of electrodes 2 and 4 is a constant value independent of x, that is, the position in the power propagation direction, and is uniform. It shows that there is.

This result also shows that the high-frequency plasma used in the surface treatment apparatus that processes the surface of the substrate placed in the vacuum vessel using the plasma generated using the power of the output of the high-frequency power source whose oscillation frequency belongs to the VHF band. In the generator, the first standing wave and the second standing wave are generated at different antinode positions of the standing wave of the electromagnetic wave having an electric field substantially in the same direction as the normal direction of the surface of the substrate, In addition, the provision of means for superimposing the first and second standing waves makes it possible to control the distribution of power intensity between the electrodes, which is indispensable for plasma uniformity.
Further, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, a pair of electrodes The power intensity distribution I (x, t) generated between 2 and 4 has a constant value and does not depend on the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide an apparatus capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of UHF plasma and UHF plasma. Yes.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the power distribution between the pair of electrodes 2 and 4 is uniform on a time average basis as described above, the deposited film becomes uniform.
This indicates that the apparatus and method of the present invention can form a uniform film thickness distribution even when a substrate having a size exceeding one half of the wavelength λ is targeted. That is, even when a substrate having a size exceeding one-half of the wavelength λ, which is impossible with the conventional VHF plasma surface treatment apparatus and method, is targeted, the present invention can realize a uniform film thickness distribution. It means that.
Therefore, the above is an epoch-making discovery in the application field of VHF plasma, and its practical value is extremely large.
It is a well-known technique that microcrystalline Si, thin-film polycrystalline Si, or the like can be formed by optimizing the flow ratio, pressure, and power of SiH4 and H2 in the film forming conditions.

In this embodiment, since the first electrode 2 is a single bar, the substrate size is limited to the above-mentioned 1200 mm × 100 mm. However, if the number of the rod electrodes as the first electrode 2 is increased, the width of the substrate size is increased. Of course, it is expandable.

Further, in the manufacture of a-Si solar cells, thin film transistors, and photosensitive drums, there is no problem in performance as long as the film thickness distribution is within ± 10%. According to the above embodiment, even when a power supply frequency of 60 MHz is used, the distribution of power intensity I (x, t) between the pair of electrodes 2 and 4 that is impossible with the conventional apparatus and method is uniform. Is possible. In other words, the film thickness distribution can be within ± 10%. This means that the industrial value related to productivity improvement and cost reduction in the manufacturing field of a-Si solar cells, thin film transistors, and photosensitive drums is remarkably large.

(Example 2)
Referring to FIG. 9 and FIG. 10, a high-frequency plasma generator of Example 2 relating to the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described. explain.

  First, the configuration of the apparatus will be described. However, the same members as those shown in the first embodiment are denoted by the same reference numerals and description thereof is omitted. FIG. 9 is a schematic view showing the entire plasma surface treatment apparatus according to the second embodiment, and FIG. 10 is an explanatory view of a power feeding portion to the first and second electrodes of the plasma surface treatment apparatus shown in FIG.

  First, the concept of the apparatus will be described. The overall configuration of the apparatus is the same as that of the first embodiment shown in FIGS. 1 and 2, but in the apparatus configuration shown in FIGS. 1 and 2, the first impedance matching unit 17 and the first Between the feeding points 21, between the second impedance matching unit 23 and the second feeding point 27, between the third impedance matching unit 30 and the first feeding point 21, and between the fourth impedance matching unit 35 and the second feeding point 21. It is characterized in that a balanced / unbalanced conversion device composed of an LC bridge type balanced / unbalanced conversion device and a balanced transmission circuit is inserted between the feeding points 27 of each.

In FIG. 9 and FIG. 10, one of the feeding points that is a position for feeding high-frequency power to the electrode is one end of the first electrode 2, and this is the first feeding point 21. The other end portion of the electrode, which is in a position that is a point opposite to the feeding point 21 in the propagation of a high-frequency power wave, is a second feeding point 27.
One output terminal of the two output terminals of the first pulse modulation type phase-variable two-output transmitter 15 is a first power amplifier 16, a first impedance matching unit 17, a first LC bridge type balanced unbalanced. Two coaxial cables 44 and 45 connected to two output terminals of the conversion device 40 and the first LC bridge type unbalanced conversion device 40 and whose outer conductors are short-circuited, a first current introduction terminal 18 are connected to the first feeding point 21 and the second electrode 4 through the core wires 48 and 49 of the vacuum coaxial cables 46 and 47 in which the outer conductors at both ends are short-circuited.
The power supplied to the feeding point 21 is a sine wave that is pulse-modulated with a pulse width Hw and a period T0 as shown in W11 (t) in FIGS. 3 and 4 as a typical example.
The other output terminal of the two output terminals of the first pulse modulation type phase-variable two-output transmitter 15 is a second power amplifier 22, a second impedance matching unit 23, a second LC bridge type balanced unbalanced. Two coaxial cables 50 and 51 connected to two output terminals of the conversion device 41, the second LC bridge type unbalanced conversion device 41, and the outer conductors are short-circuited, a second current introduction terminal 24, the external conductors at both ends are connected to the second feeding point 27 and the second electrode 4 via the core wires 54 and 55 of the vacuum coaxial cables 52 and 53, respectively.
The phase difference between the two sine wave signals output from the two output terminals of the phase-variable two-output transmitter 15 and the pulse width Hw and period T0 of the pulse modulation are attached to the phase-variable two-output transmitter 15. The phase difference adjuster and the pulse modulation adjuster can be set to arbitrary values. Further, the first pulse modulation system variable phase 2 output transmitter 15 transmits a pulse modulation to a second pulse modulation system variable phase 2 output transmitter 28 to be described later via the synchronization signal transmission cable 100 described above. Send a sync signal.
The power supplied to the feeding point 27 is typically a sine pulse-modulated with a pulse width Hw and a period T0 similar to that of W11 (t) as shown in W21 (t) shown in FIGS. It is a wave.

9 and 10, the second pulse modulation system variable phase 2 output transmitter 28 is the pulse modulation of the first pulse modulation system variable phase 2 output transmitter 15 transmitted via the synchronization signal cable 100. Using the waveform synchronization signal, the power of the pulse modulation synchronized with the pulse modulation waveform of the output of the transmitter 15 having the first pulse modulation system variable phase 2 output is output.
One output terminal of the two output terminals of the second pulse modulation system variable-phase two-output transmitter 28 is a third power amplifier 29, a third impedance matching unit 30, and a third LC bridge type balanced unbalanced. Two coaxial cables 56 and 57 connected to two output terminals of the converter 42 and the third LC bridge type unbalanced converter 42 and whose outer conductors are short-circuited, a third current introduction terminal 31, the external conductors at both ends are connected to the first feeding point 21 and the second electrode 4 via the core wires 60 and 61 of the vacuum coaxial cables 58 and 59, respectively.
As a typical example, the power supplied to the feeding point 21 has a pulse width Hw, a period T0, and W11 (t) and W21 (t) as shown in W12 (t) shown in FIGS. This is a pulse-modulated sine wave that rises at a time that is half a cycle, that is, T0 / 2 later than the pulse rise time of the pulse modulation.
The other of the two output terminals of the second pulse modulation type phase-variable two-output transmitter 28 is a fourth power amplifier 34, a fourth impedance matching unit 35, and a fourth LC bridge type balanced / unbalanced. Two coaxial cables 62 and 63 connected to two output terminals of the conversion device 43 and the fourth LC bridge type unbalanced conversion device 43 and whose outer conductors are short-circuited, a fourth current introduction terminal 36, the external conductors at both ends are connected to the second feeding point 27 and the second electrode 4 via the core wires 66 and 67 of the vacuum coaxial cables 64 and 65, respectively.
As a typical example, the power supplied to the feeding point 27 has a pulse width Hw, a period T0, and W11 (t) and W21 (t) as shown in W22 (t) shown in FIGS. This is a pulse-modulated sine wave that rises at a time that is half a cycle, that is, T0 / 2 later than the pulse rise time of the pulse modulation.

  Next, a method of forming an amorphous Si film for an a-Si solar cell using the plasma surface treatment apparatus having the above configuration will be described. In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. The first preliminary film forming step includes the step of determining the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15. In order to grasp the set value of the phase difference between the two outputs of the transmitter 28 having the second pulse modulation type variable phase two output, this film forming process is carried out for the purpose of manufacturing the target amorphous Si.

First, in the first preliminary film-forming step, in FIGS. 9 and 10, the substrate 11 is previously set on the second electrode 4, the vacuum pump 10 (not shown) is operated, After removing the impurity gas and the like, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at, for example, 250 sccm and a pressure of 0.5 Torr (66.5 Pa). To do.
Then, the first pulse modulation type phase-variable two-output transmitter 15, the first power amplifier 16, the first impedance matching unit 17, the first LC bridge type unbalanced converter 40, the first current Introduction terminal 18, core wires 48 and 49 of coaxial cables 46 and 47 for vacuum, second power amplifier 22, second impedance matching unit 23, second LC bridge type balun device 41, second current introduction Using the first power supply system including the terminal 24 and the core wires 54 and 55 of the vacuum coaxial cables 52 and 53, high-frequency power is applied to the pair of electrodes 2 and 4, for example, a frequency of 70 MHz and a pulse modulation pulse width Hw = 400 μm. The power of the second and the pulse period T0 = 1 msec, for example, 200 W in total is supplied.
That is, the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15 is set to, for example, zero, the pulse width Hw = 400 μsec, and the pulse period T0 = 1 msec. The output of the power amplifier 16 is set to 100 W, and the output is set to the first impedance matching unit 17, the first LC bridge type balun device 40, the first current introduction terminal 18, the vacuum coaxial cable 46, The power is supplied between the first feeding point 21 and the second electrode 4 via the 47 core wires 48 and 49, the output of the second power amplifier 22 is set to 100 W, and the output is supplied to the second impedance. The second feeding point 27 and the second feeding point 27 are connected via the matching unit 23, the second LC bridge type balun device 41, the second current introduction terminal 24, and the core wires 54 and 55 of the vacuum coaxial cables 52 and 53. Between the electrodes 4
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 15 having the first pulse modulation type variable phase two output as a parameter. Then, in the length direction of the first electrode, the distance from the center point of the substrate 11 to the position of the maximum thickness of the sinusoidal film thickness distribution and 2 of the transmitter 15 of the first pulse modulation system variable phase 2 output. The relationship between the phase differences of the two outputs is grasped as data. For example, it is understood that the phase difference for setting a position that is one-eighth of the wavelength λ from the center point of the substrate 11 in the direction of the first feeding point 21, that is, λ / 8, is, for example, Δθ1. Is done.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Next, as a second preliminary test, in FIGS. 9 and 10, the substrate 11 is previously placed on the second electrode 4, the vacuum pump 10 (not shown) is operated, and impurities in the vacuum container 1 are operated. After removing the gas and the like, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at, for example, 250 sccm and a pressure of 0.5 Torr (66.5 Pa). .
Then, the second pulse modulation type phase-variable two-output transmitter 28, the third power amplifier 29, the third impedance matching device 30, the third LC bridge type balun device 42, the third current Introduction terminal 31, cores 60 and 61 of vacuum coaxial cables 58 and 59, fourth power amplifier 34, fourth impedance matching unit 35, fourth LC bridge type unbalanced converter 43, fourth current introduction Using a second power supply system including the terminal 36 and the core wires 66 and 67 of the vacuum coaxial cables 64 and 65, high-frequency power is applied to the pair of electrodes 2 and 4, for example, a frequency of 70 MHz, a pulse width Hw = 400 μsec, a pulse A power of period T0 = 1 msec, for example, 200 W in total is supplied.
That is, the phase difference between the two outputs of the second phase variable 2-output transmitter 28 is set to, for example, zero, the pulse modulation is set to a pulse width Hw = 400 μsec, and a pulse period T0 = 1 msec. The output of the power amplifier 29 is set to 100 W, and the output is set to the third impedance matching device 30, the third LC bridge type balance-unbalance conversion device 42, the third current introduction terminal 31, the vacuum coaxial cable 58, The power is supplied between the first feeding point 21 and the second electrode 4 via the 59 core wires 60 and 61, and the output of the fourth power amplifier 34 is set to 100 W, and the output is set to the fourth impedance. The second feeding point 27 and the second feeding point 27 are connected via the matching unit 35, the fourth LC bridge type unbalanced conversion device 43, the fourth current introduction terminal 36, and the core wires 66 and 67 of the vacuum coaxial cables 64 and 65. Between the two electrodes 4.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 28 of the second pulse modulation type variable phase output 2 as a parameter. Then, in the length direction of the first electrode, the distance from the center point of the substrate 11 to the position of the maximum thickness of the sinusoidal film thickness distribution and 2 of the transmitter 28 of the second pulse modulation type phase variable 2 output. The relationship between the phase differences of the two outputs is grasped as data. For example, it is understood that the phase difference for setting a position that is one-eighth of the wavelength λ from the center point of the substrate 11 toward the second feeding point 27, that is, a position separated by λ / 8 is, for example, Δθ2. Is done.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIG. 9 and FIG. 10, the substrate 11 is set on the second electrode 4 in advance, the vacuum pump 10 (not shown) is operated, the impurity gas in the vacuum vessel 1 is removed, and then the discharge gas is supplied. While supplying SiH4 gas from the tube 8 at, for example, 300 sccm and a pressure of 0.5 Torr (66.5 Pa), the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C.
Next, two outputs of the first pulse modulation system variable phase two output transmitter 15 of the constituent members of the first power supply system, for example, a phase difference of a sine wave with a frequency of 70 MHz are used as the first preliminary test data. The detected Δθ1 is set, and the pulse modulation is set such that the pulse width Hw and period T0 in W11 (t) and W21 (t) shown in FIGS. 3 and 4 are set to Hw = 400 μsec and T0 = 1 msec, for example. The first and second feeding points 21 and 27 are each supplied with, for example, 100 W of power, and the two outputs of the second phase variable and two-output transmitter 28 of the constituent members of the second power supply system, For example, the phase difference of a sine wave with a frequency of 70 MHz is set to Δθ2 grasped by the second preliminary test data, and the pulse modulation is performed with the pulse width Hw at W12 (t) and W22 (t) shown in FIGS. And period T For example, 0 is set to rise at Hw = 400 μsec and T0 = 1 msec, and at a time that is half a cycle, ie, T0 / 2 delayed from the pulse rise time of the pulse modulation of W11 (t) and W21 (t). For example, electric power of 100 W is supplied to the first and second feeding points 21 and 27, respectively.
That is, the voltage waves W11 (x, t), voltage waves W21 (x, t), W12 (x, t) and W22 (x, t) are supplied to the first and second feeding points 21 and 27. Is done.
Here, the first pulse modulation type phase variable 2 output transmitter 15 and the second pulse modulation type phase variable 2 output transmitter set in the first preliminary film forming step and the second preliminary film forming step, respectively. For example, the values of 28 pulse widths Hw and period T0 can be changed from Hw = 400 μsec to 1 msec or the like, and T0 = 1 msec to 5 msec or the like.

When four voltage waves are supplied between the pair of electrodes 2, 4, as described above, W 11 (x, t) and W 21 (x, t) interfere and the first standing wave W 1 (x , T), and W12 (x, t) and W22 (x, t) interfere to form a second standing wave W2 (x, t). However, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t) because they are temporally separated. Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
Therefore, considering a general film formation time of several seconds or longer, which is significantly longer than the pulse modulation period T0, the distribution of the strength of the power generated between the pair of electrodes 2 and 4 is the first standing wave. The intensity distribution I1 (x, t) of W1 (x, t) and the intensity distribution I2 (x, t) of the second standing wave W2 (x, t) are superimposed. This is conceptually shown in FIG.
Here, if the center point of the substrate is the origin of the x-axis and the direction from the origin toward the first feeding point 21 is a positive direction, the strength of the first standing wave W1 (x, t) Distribution I1 (x, t) is
I1 (x, t) = cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the second standing wave W2 (x, t) is
I2 (x, t) = cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2 and 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1
As a result, the distribution of power intensity I (x, t) generated between the pair of electrodes 2 and 4 is a constant value independent of x, that is, the position in the power propagation direction, and is uniform. It shows that there is.

This result also shows that the high-frequency plasma used in the surface treatment apparatus that processes the surface of the substrate placed in the vacuum vessel using the plasma generated using the power of the output of the high-frequency power source whose oscillation frequency belongs to the VHF band. In the generator, the first standing wave and the second standing wave are generated at different antinode positions of the standing wave of the electromagnetic wave having an electric field substantially in the same direction as the normal direction of the surface of the substrate, In addition, the provision of means for superimposing the first and second standing waves makes it possible to control the distribution of power intensity between the electrodes, which is indispensable for plasma uniformity.
Further, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, a pair of electrodes The power intensity distribution I (x, t) generated between 2 and 4 has a constant value and does not depend on the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide an apparatus capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of UHF plasma and UHF plasma. Yes.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the power distribution between the pair of electrodes 2 and 4 is uniform as described above, the deposited film becomes uniform.
This means that it is possible to achieve a uniform film thickness distribution that is impossible with the conventional VHF plasma surface treatment apparatus and method for a substrate having a size exceeding one-half of the wavelength λ. Means. Therefore, the above is an epoch-making discovery in the VHF plasma and UHF plasma application fields, and its practical value is remarkably great.

  In the case of the apparatus configuration of the first embodiment, the leakage current generated near the power feeding points 21 and 27, which is one of the factors hindering the realization of plasma uniformity, becomes a problem. The leakage current is obtained by the functions of a balanced / unbalanced conversion device and a balanced transmission path inserted between the points 21 and 27 and the first, second, third and fourth impedance matching units 17, 23, 30 and 35, respectively. Therefore, the uniform deposition film can be realized more reliably than in the first embodiment.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the power distribution between the pair of electrodes 2 and 4 is uniform in time average as described above, the deposited film becomes uniform.
This indicates that the apparatus and method of the present invention can form a uniform film thickness distribution even when a substrate having a size exceeding one half of the wavelength λ is targeted. That is, even when a substrate having a size exceeding one-half of the wavelength λ, which is impossible with the conventional VHF plasma surface treatment apparatus and method, is targeted, the present invention can realize a uniform film thickness distribution. It means that.
Therefore, the above is an epoch-making discovery in the application field of VHF plasma, and its practical value is extremely large.
It is a well-known technique that microcrystalline Si, thin film polycrystalline Si, or the like can be formed by optimizing the flow ratio, pressure, and power of SiH4 and H2 in the film forming conditions.

(Example 3)
Referring to FIG. 11 to FIG. 13, a high-frequency plasma generator of Example 3 relating to the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described. explain.

  First, the configuration of the apparatus will be described. However, the same members as those shown in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted. FIG. 11 is a schematic view showing the entire plasma surface treatment apparatus according to the third embodiment. 12 and 13 are wiring diagrams of the first and second power supply systems used in the plasma surface treatment apparatus shown in FIG. 11, respectively.

  First, the concept of the apparatus will be described. As shown in FIG. 11, this apparatus uses a plurality of rod-shaped electrodes 2a, 2b, 2c, 2d as first electrodes, and power supply points 21a, 21b, 21c, 21d, and 27a, 27b, 27c, and 27d are arranged, and the first power supply system using the first pulse modulation type phase-variable two-output transmitter 15 as an oscillation source at the power supply points at both ends and the first power supply system From the second power supply system using the second pulse modulation type phase variable 2-output transmitter 28 that oscillates using the synchronization signal from the pulse modulation type phase-variable 2-output transmitter 15 as an oscillation source, A voltage wave W11 (x, t), a voltage wave W21 (x, t), and W12 (x, t) and W22 (x, t) are supplied.

11 and 12, one output terminal of the two output terminals of the first pulse modulation type phase-variable two-output transmitter 15 is a first power amplifier 16, a first impedance matching unit 17, and a first output terminal. The second power distributor 71, one output terminal of the second power distributor 71, the current introduction terminal 18 a, and the core wire 20 a of the vacuum coaxial cable 19 a are connected via one output terminal of the power distributor 70. Is connected to the feeding point 21a via the other output terminal of the second power distributor 71, and is connected to the feeding point 21b via the current introduction terminal 18b and the core wire 20b of the vacuum coaxial cable 19b. In addition, the power is supplied via the other output terminal of the first power distributor 70 via one output terminal of the third power distributor 72, the current introduction terminal 18c, and the core wire 20c of the vacuum coaxial cable 19c. Is connected to a point 21c, it is connected the other output terminal of the third power divider 72, a current introduction terminal 18 d, to the feeding point 21d via the core wire 20d of the vacuum coaxial cable 19d.
The power supplied to the power supply points 21a to 21d is, as a typical example, a sine wave that is pulse-modulated with a pulse width Hw and a period T0 as shown in W11 (t) shown in FIGS.
The other output terminal of the two output terminals of the transmitter 15 having the first pulse modulation system variable phase output 2 is one of the second power amplifier 22, the second impedance matcher 23, and the fourth power distributor 73. Is connected to the feeding point 27a via one output terminal of the fifth power distributor 74, the current introduction terminal 24a, and the core wire 26a of the vacuum coaxial cable 25a, and the fifth power The other output terminal of the distributor 74, the current introduction terminal 24b, and the core wire 26b of the vacuum coaxial cable 25b are connected to the feeding point 27b, and the other output terminal of the fourth power distributor 74 is connected. The sixth power distributor 75 is connected to the feeding point 27c via one output terminal of the sixth power distributor 75, the current introduction terminal 24c, and the core wire 26c of the vacuum coaxial cable 25c. An output terminal of the current introduction terminal 24d, is connected to a feeding point 27d via the core wire 26d of the vacuum coaxial cable 25d.
Note that the power supplied to the feeding points 27a to 27b is pulse-modulated with the same pulse width Hw and period T0 as W11 (t) as shown in FIG. 3 and FIG. 4 as a typical example. Sine wave.
Each of the first power amplifier 16 and the second power amplifier 22 is attached with a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. In addition, an isolator for protecting the electric circuit of the first and second power amplifiers 16 and 22 by the reflected wave is attached.
Here, the power supply for supplying the two outputs of the first phase variable two-output transmitter 15 to the first and second feeding points 21a to 21d and 27a to 27d using the power amplifiers 16 and 22, respectively. The system is called a first power supply system.

11 and 13, one output terminal of the two output terminals of the second pulse modulation type phase variable two-output transmitter 28 includes a third power amplifier 29, a third impedance matcher 30, Through one output terminal of the seventh power distributor 76, the eighth power distributor 77, one output terminal of the eighth power distributor 77, the current introduction terminal 31 a, and the core wire of the vacuum coaxial cable 32 The power supply point 21a is connected to the power supply point 21a through the other output terminal of the eighth power distributor 77 and the power supply point 21b through the core wire 33b of the vacuum coaxial cable 32b. Through the other output terminal of the seventh power distributor 76, one output terminal of the ninth power distributor 78, the current introduction terminal 31c, and the core wire 33c of the vacuum coaxial cable 32c are connected. Is connected to the feeding point 21c Te, is connected the other output terminal of the power distributor 78 of said 9, cable terminal 32d, the feeding point 21d via the core wire 33d of the vacuum coaxial cable 32d.
Note that the power supplied to the feeding points 21a to 21d typically has a pulse width Hw, a period T0, and the W11 (t) and W21 ( This is a pulse-modulated sine wave that rises at a time that is half a period, ie, T0 / 2 later than the pulse rise time of the pulse modulation of t).
In addition, each of the branched coaxial cable lines has a structure, a material and a length so that the length of the propagation path of the power wave from the seventh power distributor 76 to the first feeding points 21a to 21d is the same. Are equal.
The other output terminal of the two output terminals of the transmitter 28 of the second pulse modulation type phase variable two output is one of the fourth power amplifier 34, the fourth impedance matching unit 35, and the tenth power distributor 79. To the feeding point 27a via the eleventh power distributor 80, one output terminal of the eleventh power distributor 80, the current introduction terminal 36a, the vacuum coaxial cable 37a and the connection line 38a. And connected to the feeding point 27b via the other output terminal of the eleventh power distributor 80, the current introduction terminal 36b, the vacuum coaxial cable 37b and the connection line 38b, and the tenth power. Via the other output terminal of the distributor 79, the feed point 27c via one output terminal of the twelfth power distributor 81, the current introduction terminal 36c, the vacuum coaxial cable 37c, and the connection line 38c. Is connected, it is connected the other output terminal of the power distributor 81 of the said 12, the current introduction terminal 36d, the feeding point 27d via the coaxial cable 37d and the connecting wire 38d vacuum.
The power supplied to the feeding points 27a to 27b is typically a pulse width Hw, a period T0, and the W11 (t) and W21 () as shown in W22 (t) shown in FIGS. This is a pulse-modulated sine wave that rises at a time that is half a period, ie, T0 / 2 later than the pulse rise time of the pulse modulation of t).
Further, each of the branched coaxial cable lines has a structure, a material, and a length so that the length of the propagation path of the power wave from the tenth power distributor 79 to the second feeding points 27a to 27d is the same. Are equal.
The third power amplifier 29 and the fourth power amplifier 34 are each accompanied by a monitor for output value (traveling wave) and a monitor for reflected wave that returns from the downstream side. Further, an isolator for protecting the electric circuit of the third and fourth power amplifiers 29 and 34 by the reflected wave is attached.
Here, the power supply for supplying the two outputs of the second phase variable and two-output transmitter 28 to the first and second feeding points 21a to 21d and 27a to 27d using the power amplifiers 29 and 34, respectively. The system is called a second power supply system.

  Next, a method for manufacturing an amorphous Si film for an a-Si solar cell using the plasma surface treatment apparatus having the above configuration will be described. In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. The first preliminary film forming step includes the step of determining the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15. In order to grasp the set value of the phase difference between the two outputs of the transmitter 28 having the second pulse modulation type variable phase two output, this film forming process is carried out for the purpose of manufacturing the target amorphous Si.

First, in the first preliminary film-forming step, in FIGS. 11 and 12, a substrate 11 (not shown) is previously placed on the second electrode 4 and a vacuum pump 10 (not shown) is operated to operate the vacuum vessel 1. After removing the impurity gas in the substrate, the substrate temperature is in the range of 80 to 350 ° C. while supplying SiH 4 gas from a discharge gas supply pipe 8 (not shown) at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa). Hold at 180 ° C.
Then, using the first power supply system, high-frequency power is supplied to the first and second feeding points 21a to 21d and 27a to 27d, for example, power having a frequency of 60 MHz, for example, 500 W in total.
That is, the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15 is set to, for example, zero, the pulse width Hw = 400 μsec, and the period T0 = 1 msec. The outputs of the amplifier 16 and the second power amplifier 22 are respectively set to 250 W at a frequency of 60 MHz and supplied to both ends of the first electrode.
Here, typical examples of power supplied to the first and second feeding points 21a to 21d and 27a to 27d are shown as W11 (t) and W21 (t) in FIGS. The W11 (t) and W21 (t) are sine waves having a pulse width Hw and a pulse modulation with a period T0, for example, 60 MHz. The pulse width Hw and period T0 are set to arbitrary values, for example, Hw = 400 μsec and period T0 = 1 msec, by a regulator attached to the first pulse modulation system phase variable 2-output transmitter 15.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 15 having the first phase variable and two outputs as a parameter. Then, in the length direction of the first electrode, the distance from the center point of the substrate 11 to the position of the maximum thickness of the sinusoidal film thickness distribution and the two outputs of the transmitter 15 of the first phase variable two outputs Understand the relationship of phase difference as data. For example, the phase difference for setting a position that is one-eighth of the wavelength λ, that is, λ / 8 away from the center point of the substrate 11 in the direction of the first feeding points 21a to 21d is, for example, Δθ1. Is grasped.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Next, in the second preliminary film forming step, in FIGS. 11 and 13, a substrate 11 (not shown) is previously set on the second electrode 4 and a vacuum pump 10 (not shown) is operated to operate a vacuum container. After removing the impurity gas and the like in 1, the substrate temperature is in the range of 80 to 350 ° C. while supplying SiH 4 gas from a discharge gas supply tube 8 (not shown) at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa). For example, it is maintained at 180 ° C.
Then, using the second power supply system, high-frequency power is supplied to the first and second feeding points 21a to 21d and 27a to 27d, for example, power having a frequency of 60 MHz, for example, 500 W in total.
That is, the phase difference between the two outputs of the second pulse modulation type phase-variable two-output transmitter 28 is set to, for example, zero, the pulse width Hw = 400 μsec, and the pulse period T0 = 1 msec. The outputs of the power amplifier 29 and the second power amplifier 34 are set to 250 W at a frequency of 60 MHz, respectively, and supplied to both ends of the first electrode.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 28 having the first phase variable and two outputs as a parameter. Then, in the length direction of the first electrode, the distance from the center point of the substrate 11 to the position of the maximum thickness of the sinusoidal film thickness distribution and 2 of the transmitter 28 of the second pulse modulation type phase variable 2 output. The relationship between the phase differences of the two outputs is grasped as data. For example, it is understood that the phase difference for setting a position that is one-eighth of the wavelength λ from the center point of the substrate 11 toward the second feeding point 27, that is, a position separated by λ / 8 is, for example, Δθ2. Is done.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIGS. 9 to 11, the substrate 11 is previously set on the second electrode 4, the vacuum pump 10 (not shown) is operated, the impurity gas in the vacuum vessel 1 is removed, and then the discharge gas is supplied. While supplying SiH 4 gas from the tube 8 at 800 sccm and a pressure of 0.5 Torr (66.5 Pa), the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C.
Next, two outputs of the first pulse modulation system variable phase two output transmitter 15 of the constituent members of the first power supply system, for example, a phase difference of a sine wave with a frequency of 60 MHz are used as the first preliminary test data. The detected Δθ1 is set, and the pulse modulation is set such that the pulse width Hw and period T0 in W11 (t) and W21 (t) shown in FIGS. 3 and 4 are set to Hw = 400 μsec and T0 = 1 msec, for example. For example, electric power of 500 W is supplied to the first and second feeding points 21a to 21b and 27a to 27b, respectively, and the second pulse modulation method phase variable two-output transmission of the constituent members of the second power supply system The phase difference between the two outputs of the device 28, for example, a sine wave having a frequency of 60 MHz, is set to Δθ2 grasped by the second preliminary test data, and the pulse modulation thereof is shown as W12 (t) and W22 (t ) The pulse width Hw and the period T0 are, for example, Hw = 400 μsec and T0 = 1 msec, and a half cycle, that is, T0 / 2 delayed from the pulse rise time of the pulse modulation of W11 (t) and W21 (t). For example, electric power of 500 W is supplied to the first and second feeding points 21a to 21b and 27a to 27b, respectively.
That is, a voltage wave W11 (x, t) with a power of 250 W, a voltage wave W21 (x, t) with a power of 250 W, and a W12 with power of 250 W are applied to the first and second feeding points 21a to 21b and 27a to 27b, respectively. (X, t) and W22 (x, t) with a power of 250 W are supplied.
Here, the first pulse modulation type phase variable 2 output transmitter 15 and the second pulse modulation type phase variable 2 output transmitter set in the first preliminary film forming step and the second preliminary film forming step, respectively. For example, the values of 28 pulse widths Hw and period T0 can be changed from Hw = 400 μsec to 1 msec or the like, and T0 = 1 msec to 5 msec or the like.

When power consisting of four voltage waves is supplied between the pair of electrodes 2a to 2d and 4 via the first and second feeding points 21a to 21b and 27a to 27b, as described above, W11 (X, t) and W21 (x, t) interfere to form a first standing wave W1 (x, t), and W12 (x, t) and W22 (x, t) interfere with each other. 2 standing waves W2 (x, t) are formed. However, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t) because they are temporally separated. Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
Therefore, considering a general film formation time of several seconds or longer, which is significantly longer than the pulse modulation period T0, the distribution of the strength of power generated between the pair of electrodes 2a to 2d and 4 is the first constant. The intensity distribution I1 (x, t) of the standing wave W1 (x, t) and the intensity distribution I2 (x, t) of the second standing wave W2 (x, t) are superimposed. . This is conceptually shown in FIG.
Here, assuming that the center point of the substrate is the origin of the x axis and the direction from the origin toward the first feeding points 21a to 21d is a positive direction, the strength of the first standing wave W1 (x, t) is strong. The distribution of thickness I1 (x, t) is
I1 (x, t) = cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the second standing wave W2 (x, t) is
I2 (x, t) = cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2a to 2d, 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1
As a result, the distribution of power intensity I (x, t) generated between the pair of electrodes 2 and 4 is a constant value independent of x, that is, the position in the power propagation direction, and is uniform. It shows that there is.

This result also shows that the high-frequency plasma used in the surface treatment apparatus that processes the surface of the substrate placed in the vacuum vessel using the plasma generated using the power of the output of the high-frequency power source whose oscillation frequency belongs to the VHF band. In the generator, the first standing wave and the second standing wave are generated at different antinode positions of the standing wave of the electromagnetic wave having an electric field substantially in the same direction as the normal direction of the surface of the substrate, In addition, the provision of means for superimposing the first and second standing waves makes it possible to control the distribution of power intensity between the electrodes, which is indispensable for plasma uniformity.
Further, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, a pair of electrodes The power intensity distribution I (x, t) generated between 2 and 4 has a constant value and does not depend on the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide an apparatus capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of UHF plasma and UHF plasma. Yes.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the power distribution between the pair of electrodes 2 and 4 is uniform as described above, the deposited film becomes uniform.
This means that it is possible to achieve a uniform film thickness distribution that is impossible with the conventional VHF plasma surface treatment apparatus and method for a substrate having a size exceeding one-half of the wavelength λ. Means. Therefore, the above is an epoch-making discovery in the VHF plasma and UHF plasma application fields, and its practical value is remarkably great.

In this embodiment, the size of the rod electrode used for the first electrode is about 5 to 20 mm in diameter, the interval is about 5 to 30 mm, the length is about 1400 mm to 1800 mm, and the first rod electrode and the second flat plate are used. By setting the distance of the electrode (ground electrode) to about 5 to 40 mm, the amorphous Si film can be formed at a film forming speed of about 1 to 3 nm / s and a film thickness distribution within ± 10%.
Naturally, the width of the substrate size can be increased by increasing the number of rod electrodes and the number of power supply systems.
Note that it is a known technique that microcrystalline Si or thin-film polycrystalline Si can be formed by optimizing the flow rate ratio, pressure, and power of SiH4 and H2 in the film forming conditions, and the film thickness distribution ± 10 % Film formation is possible.

  In the present embodiment, the balance-unbalance conversion device and the balanced transmission line used in the second embodiment are not used. However, if the balance-unbalance conversion device and the balanced transmission path are used, the plasma is uniformized as follows. Of course it will be more certain.

Example 4
A high-frequency plasma generator of Example 4 relating to the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIG.

  First, the configuration of the apparatus will be described. However, the same members as those shown in the first to third embodiments are denoted by the same reference numerals, and description thereof is omitted. FIG. 14 is a schematic view showing the entire plasma surface treatment apparatus according to the fourth embodiment.

First, the concept of the apparatus will be described. The device is characterized in that a rectangular flat plate is used for the first electrode.
Specifically, the first electrode 2 is a rectangular flat plate conductor having a hole with a diameter of 3 mm and installed with an aperture ratio of 50% or more, for example, about 55%. The thickness is about 6 mm and the area is about 1500 mm × 300 mm. The second electrode is a rectangular flat conductor with a built-in substrate heater. The thickness is about 70 mm and the area is about 1500 mm × 500 mm. The electrode interval can be arbitrarily set in the range of about 5 to 50 mm. As the substrate 11, a glass substrate with an area of about 4 mm thickness: about 1200 mm × 200 mm is used.

In FIG. 14, one of the two output terminals of the first pulse modulation type phase variable 2-output transmitter 15 is a first power amplifier 16, a first impedance matching unit 17, a first current introduction. The terminal 18 and the core wire 20 at the end of the first vacuum coaxial cable 19 are connected to the first feeding point 21. The outer conductor at the end of the first vacuum coaxial cable 19 is connected to the second electrode 4.
The power supplied to the feeding point 21 is a sine wave that is pulse-modulated with a pulse width Hw and a period T0 as shown in W11 (t) in FIGS. 3 and 4 as a typical example.
The other output terminal of the two output terminals of the first pulse modulation type phase-variable two-output transmitter 15 is the second power amplifier 22, the second impedance matching unit 23, the second current introduction terminal 24, and the second output terminal. 2 is connected to a second feeding point 27 via a core wire 26 at the end of the vacuum coaxial cable 25. The outer conductor at the end of the second vacuum coaxial cable 19 is connected to the second electrode 4.
Note that the power supplied to the feeding point 27 is a sine wave that is pulse-modulated with a pulse width Hw and a period T0, as typically shown in W21 (t) in FIGS.
Each of the first power amplifier 16 and the second power amplifier 22 is attached with a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. In addition, an isolator for protecting the electric circuit of the first and second power amplifiers 16 and 22 by the reflected wave is attached.
Here, the power supply system for supplying the two outputs of the first pulse modulation type phase-variable two-output transmitter 15 to the first and second feeding points 21 and 27 using the power amplifiers 16 and 22, respectively. Is called a first power supply system.

Further, in FIG. 14, the second pulse modulation system phase capable of performing the pulse modulation synchronized with the pulse modulation signal of the transmitter 15 having the first pulse modulation system phase variable 2 output transmitted through the synchronization signal transmission cable 100. One output terminal of the two output terminals of the variable two-output transmitter 28 includes a third power amplifier 29, a third impedance matcher 30, a third current introduction terminal 31, and a third vacuum coaxial cable 32. It is connected to the first feeding point 21 via the core wire 33 at the end.
As a typical example, the power supplied to the feeding point 21 has a pulse width Hw, a period T0, and W11 (t) and W21 (t) as shown in W12 (t) shown in FIGS. This is a pulse-modulated sine wave that rises at a time that is half a cycle, that is, T0 / 2 later than the pulse rise time of the pulse modulation.
The other output terminal of the two output terminals of the transmitter 28 having the second variable phase output is a fourth power amplifier 34, a fourth impedance matching unit 35, a third current introduction terminal 31, and a fourth vacuum. The end of the coaxial cable 37 is connected to the second feeding point 27 via a core wire 38.
As a typical example, the power supplied to the feeding point 27 has a pulse width Hw, a period T0, and W11 (t) and W21 (t) as shown in W22 (t) shown in FIGS. This is a pulse-modulated sine wave that rises at a time that is half a cycle, that is, T0 / 2 later than the pulse rise time of the pulse modulation.
Each of the third power amplifier 29 and the fourth power amplifier 34 is accompanied by a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. In addition, an isolator is attached to protect the electric circuits of the first and second power amplifiers 29 and 34 by the reflected wave.
Here, the power supply system that supplies the two outputs of the second pulse modulation type phase variable 2-output transmitter 28 to the first and second feeding points 21 and 27 using the power amplifiers 29 and 34, respectively. Is called a second power supply system.

  Next, a method for manufacturing an amorphous Si film for an a-Si solar cell using the plasma surface treatment apparatus having the above configuration will be described. In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. The first preliminary film forming step includes the step of determining the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15. In order to grasp the set value of the phase difference between the two outputs of the transmitter 28 having the second pulse modulation type variable phase two output, this film forming process is carried out for the purpose of manufacturing the target amorphous Si.

First, in the first preliminary film-forming step, in FIG. 12, the substrate 11 is previously set on the second electrode 4 and the vacuum pump 10 (not shown) is operated, so that the impurity gas in the vacuum vessel 1 and the like. Then, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at 500 sccm and a pressure of 0.5 Torr (66.5 Pa), for example.
Then, using the first power supply system, high-frequency power, for example, power at a frequency of 70 MHz, for example, 400 W in total is supplied to the pair of electrodes 2 and 4.
That is, the phase difference between the two outputs of the transmitter 15 having the first pulse modulation method phase variable 2 output is set to, for example, zero, and the pulse modulation is set to a pulse width Hw = 400 μsec and a pulse period T0 = 1 msec. The output of the first power amplifier 16 is set to 200 W, and the output is connected to the first feeding point 21 via the first impedance matching device 17, the first current introduction terminal 18 and the vacuum coaxial cable 19. While being supplied between the second electrodes 4, the output of the second power amplifier 22 is set to 200 W, and the output is supplied to the second impedance matching unit 23, the second current introduction terminal 24, and the vacuum coaxial cable 25. And supplied between the second feeding point 27 and the second electrode 4.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 15 having the first pulse modulation type variable phase two output as a parameter. Then, in the length direction of the first electrode 2, the distance from the center point of the substrate 11 to the position of the maximum thickness of the sinusoidal film thickness distribution and the transmitter 15 of the first pulse modulation type phase variable 2 output The relationship between the phase differences between the two outputs is grasped as data. For example, it is understood that the phase difference for setting a position that is one-eighth of the wavelength λ from the center point of the substrate 11 in the direction of the first feeding point 21, that is, λ / 8, is, for example, Δθ1. Is done.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Next, as a second preliminary test, in FIG. 12, the substrate 11 is set on the second electrode 4 in advance, the vacuum pump 10 (not shown) is operated, and the impurity gas in the vacuum vessel 1 is removed. After the removal, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa).
Then, using the second pulse modulation system power supply system, high-frequency power, for example, power at a frequency of 70 MHz, for example, 400 W in total is supplied to the pair of electrodes 2 and 4.
That is, the phase difference between the two outputs of the second pulse modulation method phase variable 2-output transmitter 28 is set to, for example, zero, and the pulse modulation is set to a pulse width Hw = 400 μsec and a pulse period T0 = 1 msec. The output of the third power amplifier 29 is set to 200 W, and the output is connected to the first feeding point 21 via the third impedance matching device 30, the third current introduction terminal 31 and the vacuum coaxial cable 32. While being supplied between the second electrodes 4, the output of the fourth power amplifier 34 is set to 200 W, and the output is set to the fourth impedance matching unit 35, the fourth current introduction terminal 36, and the vacuum coaxial cable 37. And supplied between the second feeding point 27 and the second electrode 4.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 28 having the second phase variable and two outputs as a parameter. Then, in the length direction of the first electrode, the distance from the center point of the substrate 11 to the position of the maximum thickness of the sinusoidal film thickness distribution and the two outputs of the transmitter 28 of the second phase variable two output Understand the relationship of phase difference as data. For example, it is understood that the phase difference for setting a position that is one-eighth of the wavelength λ from the center point of the substrate 11 toward the second feeding point 27, that is, a position separated by λ / 8 is, for example, Δθ2. Is done.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIG. 14, the substrate 11 is set on the second electrode 4 in advance, and the vacuum pump 10 (not shown) is operated to remove the impurity gas and the like in the vacuum vessel 1, and then from the discharge gas supply pipe 8. The substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C., while supplying SiH 4 gas at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa).
Next, the phase difference of two outputs of the first pulse modulation system variable phase two output transmitter 15 of the first power supply system component, for example, a sine wave with a frequency of 70 MHz, is used as the first preliminary test data. Is set to Δθ1 grasped in step S1, and the pulse modulation is set to pulse width Hw and period T0 in W11 (t) and W21 (t) shown in FIGS. 3 and 4, for example, Hw = 400 μsec and T0 = 1 msec, The first and second feeding points 21 and 27 are each supplied with, for example, 200 W of power, and the second pulse modulation type phase-variable two-output transmitter 28 of the component of the second power supply system. A phase difference between two outputs, for example, a sine wave having a frequency of 70 MHz, is set to Δθ2 grasped by the second preliminary test data, and the pulse modulation is performed at pulses at W12 (t) and W22 (t) shown in FIGS. Width H w and period T0 are set to rise at, for example, Hw = 400 μsec and T0 = 1 msec, and a half cycle, ie, T0 / 2 delayed from the pulse rise time of the pulse modulation of W11 (t) and W21 (t). For example, electric power of 200 W is supplied to the first and second feeding points 21 and 27, respectively.
That is, a voltage wave W11 (x, t) having a power of 200 W and a voltage wave W12 (x, t) having a power of 200 W are supplied to the first feeding point 21, and a W21 (x , T) and 22 (x, t) of power 200W are supplied.
Here, the first pulse modulation type phase variable 2 output transmitter 15 and the second pulse modulation type phase variable 2 output transmitter set in the first preliminary film forming step and the second preliminary film forming step, respectively. For example, the values of 28 pulse widths Hw and period T0 can be changed from Tw = 400 μsec to 1 msec or the like, and T0 = 1 msec to 5 msec or the like.

When four voltage waves are supplied between the pair of electrodes 2, 4, as described above, W 11 (x, t) and W 21 (x, t) interfere and the first standing wave W 1 (x , T), and W12 (x, t) and W22 (x, t) interfere to form a second standing wave W2 (x, t). However, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t) because they are temporally separated. Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
Therefore, considering a general film formation time of several seconds or longer, which is significantly longer than the pulse modulation period T0, the distribution of the strength of the power generated between the pair of electrodes 2 and 4 is the first standing wave. The intensity distribution I1 (x, t) of W1 (x, t) and the intensity distribution I2 (x, t) of the second standing wave W2 (x, t) are superimposed. This is conceptually shown in FIG.
Here, if the center point of the substrate is the origin of the x-axis and the direction from the origin toward the first feeding point 21 is a positive direction, the strength of the first standing wave W1 (x, t) Distribution I1 (x, t) is
I1 (x, t) = cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the second standing wave W2 (x, t) is
I2 (x, t) = cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2 and 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1
As a result, the distribution of power intensity I (x, t) generated between the pair of electrodes 2 and 4 is a constant value independent of x, that is, the position in the power propagation direction, and is uniform. It shows that there is.

This result also shows that the high-frequency plasma used in the surface treatment apparatus that processes the surface of the substrate placed in the vacuum vessel using the plasma generated using the power of the output of the high-frequency power source whose oscillation frequency belongs to the VHF band. In the generator, the first standing wave and the second standing wave are generated at different antinode positions of the standing wave of the electromagnetic wave having an electric field substantially in the same direction as the normal direction of the surface of the substrate, In addition, the provision of means for superimposing the first and second standing waves makes it possible to control the distribution of power intensity between the electrodes, which is indispensable for plasma uniformity.
Further, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, a pair of electrodes The power intensity distribution I (x, t) generated between 2 and 4 has a constant value and does not depend on the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide an apparatus capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of UHF plasma.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the power distribution between the pair of electrodes 2 and 4 is uniform as described above, the deposited film becomes uniform.
This means that it is possible to achieve a uniform film thickness distribution that is impossible with the conventional VHF plasma surface treatment apparatus and method for a substrate having a size exceeding one-half of the wavelength λ. Means. Therefore, the above is an epoch-making discovery in the VHF plasma application field, and its practical value is remarkably large.

In this example, by setting the electrode interval to about 5 to 40 mm, an amorphous Si film with a glass substrate size of 1200 mm × 200 mm has a film forming speed of about 1 to 3 nm / s and a film thickness distribution within ± 10%. Film formation is possible.
Note that it is a known technique that microcrystalline Si or thin-film polycrystalline Si can be formed by optimizing the flow rate ratio, pressure, and power of SiH4 and H2 in the film forming conditions, and the film thickness distribution ± 10 % Film formation is possible.

  In the present embodiment, the balance-unbalance conversion device and the balanced transmission line used in the second embodiment are not used. However, if the balance-unbalance conversion device and the balanced transmission path are used, the plasma is uniformized as follows. Of course it will be more certain.

(Example 5)
A high-frequency plasma generation apparatus according to Embodiment 5 of the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIGS. explain.

  First, the configuration of the apparatus will be described. However, the same members as those shown in the first to fourth embodiments are denoted by the same reference numerals, and description thereof is omitted. FIG. 15 is a schematic view showing the entire plasma surface treatment apparatus according to the fifth embodiment, and FIG. 16 is a sectional view of the inside of the vacuum vessel of the plasma surface treatment apparatus shown in FIG.

  First, the concept of the apparatus will be described. The overall configuration of the apparatus is the same as in the case of FIGS. 1 and 2 in the first embodiment, but is characterized in that the place where the substrate 11 is installed is different. That is, as shown in FIGS. 15 and 16, by providing a plurality of openings in the pair of electrodes 2 and 4, the radical species in the plasma generated between the electrodes is diffused to the outside through the openings. It is. A feature of this configuration is that the installation place of the substrate 11 is not between the pair of electrodes 2 and 4 but between the electrodes. This means that the film forming conditions at the time of plasma generation can be selected without being affected by the thickness and material of the substrate. In particular, even when the pressure condition during plasma generation is as high as several hundreds of Pa to several thousand Pa (several Torr to several tens of Torr), the distance between the pair of electrodes 24 can be set as narrow as 10 to 15 mm without being affected by the substrate. Is possible. This is a feature that cannot be achieved with the conventional configuration.

  In FIG. 16, reference numeral 109 denotes a substrate support material that incorporates a substrate heater 3 (not shown). The first and second electrodes 2 and 4 have a rectangular flat plate shape, and holes with a diameter of about 3 mm are installed with an aperture ratio of about 55%. The thickness is about 6 mm, and the area is about 1500 mm × 300 mm. The feeding point 21 is installed at the center of one side of the rectangular plate electrode, and the feeding point 27 is installed at the center of the opposite side. The distance between the electrodes 2 and 4 can be arbitrarily set to about 5 to 50 mm. As the substrate 11, a glass substrate having a thickness of about 4 mm and an area of 1400 mm × 200 mm is used. The discharge gas is supplied from the discharge gas supply pipe 8 through the rectifying hole 7 of the gas mixing box 6.

  Next, a method for manufacturing an amorphous Si film for an a-Si solar cell using the plasma surface treatment apparatus having the above configuration will be described. In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. In the first preliminary film-forming process, in order to grasp the set value of the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15, In order to ascertain the set value of the phase difference between the two outputs of the two pulse modulation type phase-variable two-output transmitter 28, this film-forming step is performed for the production of the target amorphous Si.

First, in the first first preliminary film forming step, in FIGS. 15 and 16, the substrate 11 is previously set on the substrate support material 109, the vacuum pump 10 (not shown) is operated, and the vacuum container 1 is operated. After removing the impurity gas and the like in the substrate, the substrate temperature is in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at 500 sccm and the pressure of 0.5 Torr (66.5 Pa) Hold on.
Next, the first pulse modulation type phase-variable two-output transmitter 15, the first power amplifier 16, the first impedance matching unit 17, the first current introduction terminal 18, and the first vacuum coaxial cable 19. A first power supply system comprising a core wire 20, a second power amplifier 22, a second impedance matching device 23, a second current introduction terminal 24, and a core wire 26 of a second vacuum coaxial cable 25, The pair of electrodes 2 and 4 is supplied with high frequency power, for example, power with a frequency of 60 MHz, for example, 400 W in total.
That is, the phase difference between the two outputs of the first pulse modulation system phase variable 2-output transmitter 15 is set to, for example, zero, pulse modulation pulse width Hw = 400 μsec, and pulse period T0 = 1 msec. The output of the first power amplifier 16 is set to 200 W, and the output is passed through the first impedance matching unit 17, the first current introduction terminal 18, and the core wire 20 of the first vacuum coaxial cable 19. 1 is supplied to one feeding point 21, the output of the second power amplifier 22 is set to 200 W, and the output is supplied to the second impedance matching unit 23, the second current introduction terminal 24, and the second vacuum coaxial. This is supplied to the second feeding point 27 via the core wire 26 of the cable 25.
In this case, by adjusting the first impedance matching unit 17 and the second impedance matching unit 23, it is possible to prevent the reflected wave of the supplied power from returning to the upstream side of the respective impedance matching units 17 and 23.
Here, typical examples of power supplied to the first and second feeding points 21 and 27 are shown as W11 (t) and W21 (t) in FIGS. 3 and 4, respectively. W11 (t) and W21 (t) are sine waves of ultrahigh frequency, for example, 60 MHz, pulse-modulated with a pulse width Hw = 400 μsec and a period T0 = 1 msec, respectively. The pulse width Tw and the period T0 are set to arbitrary values, for example, Tw = 400 μsec and the period T0 = 1 msec by an adjuster attached to the transmitter 15 having the first pulse modulation system variable phase 2 output.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 15 having the first pulse modulation type variable phase two output as a parameter. Then, in the length direction of the first electrode, the distance from the center point of the substrate 11 to the position of the maximum thickness of the sinusoidal film thickness distribution and 2 of the transmitter 15 of the first pulse modulation system variable phase 2 output. The relationship between the phase differences of the two outputs is grasped as data. For example, it is understood that the phase difference for setting a position that is one-eighth of the wavelength λ from the center point of the substrate 11 toward the first feeding point 21, that is, a position that is separated by λ / 8 is Δθ1, for example. Is done.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Next, in the second preliminary film forming step, in FIGS. 15 and 16, the substrate 11 is previously set on the substrate support material 109, the vacuum pump 10 (not shown) is operated, After removing the impurity gas and the like, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at 500 sccm and a pressure of 0.5 Torr (66.5 Pa), for example. To do.
The second pulse modulation type phase-variable two-output transmitter 28, the third power amplifier 29, the third impedance matching unit 30, the third current introduction terminal 31, and the third coaxial coaxial cable 32 are provided. Using a second power supply system comprising a core wire 33, a fourth power amplifier 34, a fourth impedance matching device 35, a fourth current introduction terminal 36, and a core wire 38 of a fourth vacuum coaxial cable 37, a pair The electrodes 2 and 4 are supplied with high-frequency power, for example, power with a frequency of 60 MHz, for example, 400 W in total.
That is, the phase difference between the two outputs of the second pulse modulation method phase-variable two-output transmitter 28 is set to, for example, zero, the pulse width of the pulse modulation = 400 μsec, and the pulse period = 1 ms, The output of the power amplifier 29 is set to 200 W, and the output is supplied to the first impedance matcher 30, the third current introduction terminal 31, and the core wire 33 of the third vacuum coaxial cable 32 through the first impedance matching unit 30. The power is supplied to the feeding point, the output of the fourth power amplifier 34 is set to 200 W, and the output of the fourth impedance matching unit 35, the fourth current introduction terminal 36, and the fourth vacuum coaxial cable 37 is set. It is supplied to the second feeding point via the core wire 38.
As a result, plasma of the SiH 4 gas is generated and, for example, amorphous Si is deposited on the substrate 11.

In the above manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 has a sinusoidal distribution due to the generation of a standing wave that is a phenomenon inherent to the VHF plasma. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 28 of the second pulse modulation type variable phase output 2 as a parameter. Then, in the length direction of the first electrode, the distance from the center point of the substrate to the position of the maximum thickness of the sinusoidal film thickness distribution and the two transmitters 28 of the second pulse modulation type phase variable two output Grasp the relationship of output phase difference as data.
Also in this case, similarly to the first preliminary film forming step, in the case where the second power supply system is used, the distance from the center point of the substrate to the position of the maximum thickness of the sinusoidal film thickness distribution and the first The position of the maximum thickness of the film thickness distribution, for example, from the center point of the substrate to the second feeding point 27 is obtained from data indicating the relationship between the two output phase differences of the two pulse modulation type phase-variable two-output transmitters 28. It can be seen that the phase difference for setting the position to one-eighth of the wavelength λ in the direction, that is, the position separated by λ / 8 is, for example, Δθ2.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIG. 15 and FIG. 6, the substrate 11 is previously set on the substrate support member 109, the vacuum pump 10 (not shown) is operated to remove the impurity gas and the like in the vacuum vessel 1, and then the discharge gas supply pipe The substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while SiH 4 gas is supplied from 8 at 500 sccm and a pressure of 0.5 Torr (66.5 Pa).
Next, two preliminary outputs of the first pulse modulation type phase-variable two-output transmitter 15 of the constituent members of the first power supply system, for example, a phase difference of a sine wave having a frequency of 60 MHz are used as a first preliminary film forming step. Is set to Δθ1 grasped as data, and pulse width Hw and period T0 in W11 (t) and W21 (t) shown in FIGS. 3 and 4 are set to Hw = 400 μsec and T0 = 1 msec, for example. The first and second feeding points 21 and 27 are each supplied with, for example, 200 W of power, and the second pulse modulation type phase-variable two-output transmitter of the constituent member of the second power supply system. The phase difference between the two outputs of 28 is set to Δθ2 grasped as the data of the second preliminary film forming step, and the pulse modulation is performed with the pulse width Hw at W12 (t) and W22 (t) shown in FIGS. And period T0 For example, Hw = 400 μsec and T0 = 1 msec, and set to rise at a time that is half a cycle, ie, T0 / 2 later than the pulse rise time of the pulse modulation of W11 (t) and W21 (t), For example, electric power of 200 W is supplied to the first and second feeding points 21 and 27, respectively.
That is, at the first and second feeding points 21 and 27, a voltage wave W11 (x, t) with a power of 200 W, a voltage wave W12 (x, t) with a power of 200 W, and a W21 (x, t) with a power of 200 W, respectively. ) And W22 (x, t) with power of 200 W are supplied.
Here, the first pulse modulation type phase variable 2 output transmitter 15 and the second pulse modulation type phase variable 2 output transmitter set in the first preliminary film forming step and the second preliminary film forming step, respectively. For example, the values of 28 pulse widths Hw and period T0 can be changed from Tw = 400 μsec to 1 msec or the like, and T0 = 1 msec to 5 msec or the like.

When four voltage waves are supplied between the pair of electrodes 2, 4, as described above, W 11 (x, t) and W 21 (x, t) interfere with each other and the first standing wave W 1 (x, t t), and W12 (x, t) and W22 (x, t) interfere to form a second standing wave W2 (x, t). However, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t) because they are temporally separated. Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
Therefore, considering a general film formation time of several seconds or longer, which is significantly longer than the pulse modulation period T0, the distribution of the strength of the power generated between the pair of electrodes 2 and 4 is the first standing wave. The intensity distribution I1 (x, t) of W1 (x, t) and the intensity distribution I2 (x, t) of the second standing wave W2 (x, t) are superimposed. This is conceptually shown in FIG.
Here, if the center point of the substrate is the origin of the x-axis and the direction from the origin toward the first feeding point 21 is a positive direction, the strength of the first standing wave W1 (x, t) Distribution I1 (x, t) is
I1 (x, t) ∝cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the second standing wave W2 (x, t) is
I2 (x, t) ∝cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2 and 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1
As a result, the distribution of power intensity I (x, t) generated between the pair of electrodes 2 and 4 is a constant value independent of x, that is, the position in the power propagation direction, and is uniform. It shows that there is.

As a result, the high-frequency plasma generator used in the surface treatment apparatus that processes the surface of the substrate disposed in the vacuum vessel using the plasma generated using the power of the output of the high-frequency power source whose oscillation frequency belongs to the VHF band. And generating a first standing wave and a second standing wave having different antinode positions of the standing wave of the electromagnetic wave having an electric field substantially in the same direction as the normal direction of the surface of the substrate, and By providing the means for superimposing the first and second standing waves, it is meaningful that the distribution of the power intensity between the electrodes, which is indispensable for making the plasma uniform, can be controlled.
Further, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, a pair of electrodes The power intensity distribution I (x, t) generated between 2 and 4 has a constant value and does not depend on the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide an apparatus capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of UHF plasma.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the power distribution between the pair of electrodes 2 and 4 is uniform as described above, the deposited film becomes uniform.
This means that it is possible to achieve a uniform film thickness distribution that is impossible with the conventional VHF plasma surface treatment apparatus and method for a substrate having a size exceeding one-half of the wavelength λ. Means. Therefore, the above is an epoch-making discovery in the VHF plasma and UHF plasma application fields, and its practical value is remarkably great.
It is a well-known technique that microcrystalline Si, thin-film polycrystalline Si, or the like can be formed by optimizing the flow ratio, pressure, and power of SiH4 and H2 in the film forming conditions.

In this embodiment, since the feeding point of the first electrode 2 is one point at the central part of the opposite side, the substrate size is limited to about 1400 mm × 200 mm, but the width of the electrode is increased and the feeding point is increased. Of course, by increasing the number of points, the width of the substrate size can be expanded. However, in this case, the interval between adjacent feeding points is preferably about 100 mm to 300 mm.

Further, in the manufacture of a-Si solar cells, thin film transistors, and photosensitive drums, there is no problem in performance as long as the film thickness distribution is within ± 10%. According to the above embodiment, even if a power supply frequency of 60 MHz is used, it is possible to obtain a film thickness distribution that is significantly better than the conventional apparatus and method, for example, within ± 10%. This means that the industrial value related to productivity improvement and cost reduction in the manufacturing field of a-Si solar cells, thin film transistors, and photosensitive drums is remarkably large.

(Example 6)
A high-frequency plasma generation apparatus according to Embodiment 6 of the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIGS. explain.

  First, the configuration of the apparatus will be described. However, the same members as those shown in the first to fifth embodiments are denoted by the same reference numerals and the description thereof is omitted. FIG. 17 is a schematic view showing the entire plasma surface treatment apparatus according to the sixth embodiment, and FIG. 18 is an explanatory diagram showing a power supply system wiring diagram of the plasma surface treatment apparatus shown in FIG.

  First, the concept of the apparatus will be described. The device configuration is characterized in that the first and second feeding points installed on the ungrounded first electrode are arranged in the vicinity of one of the four sides of the second electrode 4 that is a rectangular plate-type ground electrode. It is to be done. Further, the first electrode has a U-shape formed by folding back one bar-like conductor so as to be included in a plane parallel to the first electrode. Preferably, the total length of the U-shaped bar is a half of the wavelength λ of the power used, that is, an integral multiple of λ / 2. Further, the bent portion of the U-shaped electrode is covered with a dielectric such as alumina.

  Specifically, the first electrode 2 uses a U-shaped electrode made of a SUS rod having a diameter of about 5 to 20 mm. The length of the U-shaped straight portion is about 1400 mm, and the distance between the straight bars is about 10 to 40 mm. The distance between the U-shaped electrode and the second plate electrode can be arbitrarily set to about 5 to 50 mm. As the substrate 11, a glass substrate having a thickness of about 4 mm and a glass substrate area of about 1200 mm × 200 mm is used.

Next, the configuration of the apparatus will be described. In FIG. 17 and FIG. 18, one output terminal of the two output terminals of the first pulse modulation type phase variable two-output transmitter 15 is the first power amplifier 16, the first impedance matching device 17, and the first output terminal. The current introduction terminal 18 and the core wire 20 at the end of the first vacuum coaxial cable 19 are connected to the first feeding point 21. The outer conductor at the end of the first vacuum coaxial cable 19 is connected to the second electrode 4.
The other output terminal of the two output terminals of the first pulse modulation type phase-variable two-output transmitter 15 is the second power amplifier 22, the second impedance matching unit 23, the second current introduction terminal 24, and the second output terminal. 2 is connected to a second feeding point 27 via a core wire 26 at the end of the vacuum coaxial cable 25. The outer conductor at the end of the second vacuum coaxial cable 19 is connected to the second electrode 4.
Each of the first power amplifier 16 and the second power amplifier 22 is attached with a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. In addition, an isolator for protecting the electric circuit of the first and second power amplifiers 16 and 22 by the reflected wave is attached.
Here, a power supply system for supplying the two outputs of the first pulse modulation type phase-variable two-output transmitter 15 to the first and second feeding points 21 and 27 by the power amplifiers 16 and 22 respectively. This is called a first power supply system.

17 and 18, the second pulse modulation system variable phase 2 output transmitter 28 is the pulse modulation of the first pulse modulation system variable phase 2 output transmitter 15 transmitted via the synchronization signal cable 100. Using the waveform synchronization signal, the power of the pulse modulation synchronized with the pulse modulation waveform of the output of the transmitter 15 having the first pulse modulation system variable phase 2 output is output.
One of the two output terminals of the second pulse modulation type phase-variable two-output transmitter 28 has a third power amplifier 29, a third impedance matching device 30, a third current introduction terminal 31, and a second output terminal. 3 is connected to the first feeding point 21 through the core wire 33 at the end of the vacuum coaxial cable 32. The outer conductor at the end of the third vacuum coaxial cable 32 is connected to the second electrode 4.
The other output terminal of the two output terminals of the second pulse modulation type phase-variable two-output transmitter 28 is a fourth power amplifier 34, a fourth impedance matching device 35, a fourth current introduction terminal 36, and a second output terminal. 4 is connected to the second feeding point 27 via the core wire 38 at the end of the vacuum coaxial cable 37. The outer conductor at the end of the second vacuum coaxial cable 19 is connected to the second electrode 4.
Each of the third power amplifier 29 and the fourth power amplifier 34 is accompanied by a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. In addition, an isolator for protecting the electric circuit of the main body of the first and second power amplifiers 29 and 34 by the reflected wave is attached.
Here, the power supply system for supplying the two outputs of the second phase variable two-output transmitter 28 to the first and second feeding points 21 and 27 by the power amplifiers 29 and 34, respectively, This is called a power supply system.

  Next, a method for manufacturing an amorphous Si film for an a-Si solar cell using the plasma surface treatment apparatus having the above configuration will be described. In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. The first preliminary film forming step includes the step of determining the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15. In order to grasp the set value of the phase difference between the two outputs of the transmitter 28 having the second pulse modulation type variable phase two output, this film forming process is carried out for the purpose of manufacturing the target amorphous Si.

First, in the first preliminary film forming step, in FIGS. 17 and 18, the substrate 11 is previously set on the second electrode 4, the vacuum pump 10 (not shown) is operated, After removing the impurity gas and the like, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at 500 sccm and a pressure of 0.5 Torr (66.5 Pa), for example. To do.
Then, using the first power supply system, high-frequency power, for example, pulse-modulated power of 70 MHz, for example, 400 W in total is supplied to the pair of electrodes 2 and 4.
That is, the phase difference between the two outputs of the first pulse modulation system phase variable 2-output transmitter 15 is set to, for example, zero, pulse modulation pulse width Hw = 400 μsec, and pulse period T0 = 1 msec. The output of the first power amplifier 16 is set to 200 W, for example, and the output is supplied to the first feeding point 21 via the first impedance matching unit 17, the first current introduction terminal 18 and the vacuum coaxial cable 19. And the output of the second power amplifier 22 is set to 200 W, for example, and the output is supplied to the second impedance matching unit 23, the second current introduction terminal 24, and the coaxial for vacuum. It is supplied between the second feeding point 27 and the second electrode 4 via the cable 25.
In this case, the power wave supplied from the feeding points 21 and 27 is attenuated by some influence because the shape of the first electrode as the propagation path is bent at the intermediate point, but is attenuated at the bent portion. The covered dielectric film 92 suppresses power loss in that region. As a result, the above-described standing wave is generated by the power waves W11 (x, t) and W21 (x, t) in the propagation path.
As a result, plasma of the SiH 4 gas is generated, and amorphous Si having a sinusoidal distribution, for example, is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 15 having the first pulse modulation type variable phase two output as a parameter. Then, on the line segment along the U-shape of the rod of the U-shaped electrode 2, the distance from the center point of the U-shaped electrode 2 to the position of the maximum thickness of the sinusoidal film thickness distribution and the first The relationship of the phase difference between the two outputs of the transmitter 15 having the pulse modulation system variable phase 2 output is grasped as data. For example, the phase difference for setting at a position away from the center point of the U-shaped electrode 2 by one-eighth of the wavelength λ in the direction of the first feeding point 21, that is, λ / 8 is, for example, Δθ1. That is understood.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Next, as a second preliminary test, in FIGS. 17 and 18, the substrate 11 is previously set on the second electrode 4, the vacuum pump 10 (not shown) is operated, and impurities in the vacuum container 1 are operated. After removing the gas and the like, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa). .
Then, using the second power supply system, high-frequency power, for example, pulse-modulated power at a frequency of 70 MHz, for example, a total of 400 W is supplied to the pair of electrodes 2 and 4.
That is, the phase difference between the two outputs of the second pulse modulation type phase variable 2-output transmitter 28 is set to, for example, zero, the pulse width of the pulse modulation Hw = 400 μsec, and the pulse period T0 = 1 msec. The output of the first power amplifier 16 is set to 200 W, the output of the third power amplifier 29 is set to 200 W, and the output is set to the third impedance matching device 30, the third current introduction terminal 31, and the vacuum. The power is supplied between the first feeding point 21 and the second electrode 4 via the coaxial cable 32, the output of the fourth power amplifier 34 is set to 200 W, and the output is set to the fourth impedance matching unit. 35, the fourth current introduction terminal 36, and the vacuum coaxial cable 37 are supplied between the second feeding point 27 and the second electrode 4.
In this case, the power wave supplied from the feeding points 21 and 27 is attenuated by some influence because the shape of the first electrode as the propagation path is bent at the intermediate point, but is attenuated at the bent portion. The covered dielectric film 92 suppresses power loss in that region. As a result, the above-mentioned standing wave is generated by the power waves W12 (x, t) and W22 (x, t) in the propagation path.
As a result, plasma of the SiH 4 gas is generated, and amorphous Si having a sinusoidal distribution, for example, is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. As described above, the film thickness distribution of, for example, amorphous Si deposited on the substrate 11 has a sinusoidal distribution due to the generation of a standing wave, which is a phenomenon inherent to VHF plasma. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 28 of the second pulse modulation type variable phase output 2 as a parameter. On the line segment along the U-shape of the rod of the U-shaped electrode 2, the distance from the center point of the U-shaped electrode 2 to the position of the maximum thickness of the sinusoidal film thickness distribution and the second The relationship of the phase difference between the two outputs of the pulse-modulation phase-variable two-output transmitter 28 is grasped as data. For example, the phase difference for setting at a position away from the center point of the U-shaped electrode 2 by one eighth of the wavelength λ in the direction of the second feeding point 27, that is, λ / 8 is, for example, Δθ2. That is understood.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIG. 17 and FIG. 18, the substrate 11 is set on the second electrode 4 in advance, and the vacuum pump 10 (not shown) is operated to remove the impurity gas and the like in the vacuum vessel 1 and then supply the discharge gas. While supplying SiH4 gas from the tube 8 at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa), the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C.
Next, two outputs of the first pulse modulation system variable phase two output transmitter 15 of the constituent members of the first power supply system, for example, a phase difference of a sine wave with a frequency of 70 MHz are used as the first preliminary test data. The detected Δθ1 is set, and the pulse modulation is set such that the pulse width Hw and period T0 in W11 (t) and W21 (t) shown in FIGS. 3 and 4 are set to Hw = 400 μsec and T0 = 1 msec, for example. The first and second feeding points 21 and 27 are each supplied with, for example, 200 W of power, and the second pulse modulation type phase-variable two-output transmitter 28 of the second power supply system component. Two outputs, for example, a phase difference of a sine wave having a frequency of 70 MHz, is set to Δθ2 grasped as data of the second preliminary film forming process, and the pulse modulation thereof is shown by W12 (t) and W22 (t) shown in FIGS. Pal in The width Hw and the period T0 are, for example, Hw = 400 μsec and T0 = 1 msec, and a half cycle from the pulse rise time of the pulse modulation of W11 (t) and W21 (t), that is, a time delayed by T0 / 2. It sets so that it may stand up, and power 200W is supplied to the 1st and 2nd feeding points 21 and 27, respectively.
That is, a voltage wave W11 (x, t) having a power of 200 W and a voltage wave W12 (x, t) having a power of 200 W are supplied to the first feeding point 21, and a W21 (x , T) and a voltage wave W22 (x, t) having a power of 200 W are supplied.
Here, the first pulse modulation type phase variable 2 output transmitter 15 and the second pulse modulation type phase variable 2 output transmitter set in the first preliminary film forming step and the second preliminary film forming step, respectively. For example, the values of 28 pulse widths Hw and period T0 can be changed from Hw = 400 μsec to 1 msec or the like, and T0 = 1 msec to 5 msec or the like.

When four voltage waves are supplied between the pair of electrodes 2, 4, as described above, W 11 (x, t) and W 21 (x, t) interfere and the first standing wave W 1 (x , T), and W12 (x, t) and W22 (x, t) interfere to form a second standing wave W2 (x, t). However, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t) because they are temporally separated. Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
Therefore, the intensity distribution of the power generated between the pair of electrodes 2 and 4 is the intensity distribution I1 (x, t) of the first standing wave W1 (x, t) and the second standing wave. The intensity distribution I2 (x, t) of the wave W2 (x, t) is superposed. This is conceptually shown in FIG.
Here, if the center point of the U-shaped electrode 2 is the x-axis origin, and the direction toward the first feeding point 21 on the line segment along the U-shape from the origin is the positive direction, The intensity distribution I1 (x, t) of one standing wave W1 (x, t) is
I1 (x, t) = cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the first standing wave W2 (x, t) is
I2 (x, t) = cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2 and 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1
As a result, the distribution of power intensity I (x, t) generated between the pair of electrodes 2 and 4 is a constant value independent of x, that is, the position in the power propagation direction, and is uniform. It shows that there is.

This result also shows that the high-frequency plasma used in the surface treatment apparatus that processes the surface of the substrate placed in the vacuum vessel using the plasma generated using the power of the output of the high-frequency power source whose oscillation frequency belongs to the VHF band. In the generator, the first standing wave and the second standing wave are generated at different antinode positions of the standing wave of the electromagnetic wave having an electric field substantially in the same direction as the normal direction of the surface of the substrate, In addition, the provision of means for superimposing the first and second standing waves makes it possible to control the distribution of power intensity between the electrodes, which is indispensable for plasma uniformity.
Further, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, a pair of electrodes The power intensity distribution I (x, t) generated between 2 and 4 has a constant value and does not depend on the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide an apparatus capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of VHF plasma.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the distribution of power intensity between the pair of electrodes 2 and 4 is uniform on a time average as described above, the deposited film becomes uniform. This is an epoch-making discovery in the application field of VHF plasma, and its practical value is remarkably large.
That is, one side of the first electrode of the rectangular type that is required in the improvement of the plasma generating device for improving the productivity of the in-line type, multi-chamber type or roll-to-roll type plasma surface treatment apparatus. This can be realized as one new means relating to a means for supplying VHF power only from the vicinity. This means that when the cross section of the main body of the plasma surface treatment apparatus is viewed in a cross section perpendicular to the substrate transport direction, if the cross section is a rectangular cross section, for example, one side of the four sides of the rectangular cross section It is possible to realize a novel power supply means for generating VHF plasma using only the above.
In this example, by setting the distance between the first and second electrodes to about 5 to 40 mm, the amorphous Si film with a glass substrate area of about 1200 mm × 200 mm has a film forming speed of about 1 to 3 nm / s. Film thickness distribution can be within ± 10%.
In this embodiment, since the number of U-shaped first electrodes 2 is one, the width of the substrate size is limited to about 200 mm. However, if the number of the first electrodes is increased, the substrate size is reduced. Of course, the width can be expanded.
Note that it is a known technique that microcrystalline Si or thin-film polycrystalline Si can be formed by optimizing the flow rate ratio, pressure, and power of SiH4 and H2 in the film forming conditions, and the film thickness distribution ± 10 % Film formation is possible.

  In the present embodiment, the balance-unbalance conversion device and the balanced transmission line used in the second embodiment are not used. However, if the balance-unbalance conversion device and the balanced transmission path are used, the plasma is uniformized as follows. Of course it will be more certain.

(Example 7)
A high-frequency plasma generator of Example 7 relating to the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIG. FIG. 19 is a schematic view showing the entire plasma surface treatment apparatus according to the seventh embodiment.

As shown in FIG. 19, the feature of this apparatus is that a plurality of, for example, two U-shaped first electrodes described in Example 6 are installed so as to be included in a plane parallel to the second electrode. The first and second feeding points are arranged at the end portions of the plurality of U-shaped first electrodes, and the first and second feeding points of the U-shaped first electrodes are The configuration is such that the outputs of the first and second power supply systems are supplied.
In the configuration shown in FIG. 19, the same members as those shown in the first to sixth embodiments are given the same reference numerals, and the description thereof will be omitted.
The U-shaped electrode 2 is formed of a SUS rod having a diameter of about 5 to 20 mm, and the distance from the second electrode can be arbitrarily set to about 5 to 50 mm.

(Example 8)
A high-frequency plasma generation apparatus according to an eighth embodiment of the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIG. FIG. 20 is a schematic view showing the entire plasma surface treatment apparatus according to the eighth embodiment.

The feature of this apparatus is that one of the four sides of the rectangular plate-type ground electrode in which the first and second feeding points 21 and 27 arranged on the ungrounded first electrode are the second electrode 4 is provided. And the first electrode has a W-shaped shape formed by folding a single rod-shaped conductor so as to be included in a plane parallel to the first electrode. Preferably, the total length of the W-shape is one half of the wavelength λ of the power used, that is, an integral multiple of λ / 2. In addition, the bent portion of the W-shaped electrode is characterized by being covered with a dielectric such as alumina.
As shown in FIG. 20, the apparatus of Example 8 has first and second feeding points 21 and 27 arranged at the respective ends of the W-shaped first electrode, and the first and second feeding points. It has the structure which supplies the output of the said 1st and 2nd electric power supply system to a point.
The configuration shown in FIG. 20 is made up of the same members as those shown in the first to seventh embodiments and is given the same reference numerals, and therefore the description thereof is omitted.
The W-shaped electrode 2 is formed of a SUS rod having a diameter of about 5 to 20 mm, and the distance from the second flat plate electrode can be arbitrarily set at 5 to 50 mm.

Example 9
A high-frequency plasma generator of Example 9 relating to the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIG. FIG. 21 is a schematic view showing the entire plasma surface treatment apparatus according to the ninth embodiment.

The apparatus of the present embodiment is an ultrahigh frequency plasma generating electrode used in a plasma surface treatment apparatus for a cylindrical substrate, and the configuration thereof is W-shaped as described in Embodiment 8 as shown in FIG. A plurality of first electrodes of the mold, for example, two are installed so as to be included in a cylindrical surface surrounding a second electrode having a cylindrical shape, and each of the plurality of W-shaped first electrodes is arranged. First and second feeding points 21 and 27 are arranged at the ends, and the first and second feeding points 21 and 27 of the respective W-shaped first electrodes are arranged at the first and second feeding points 21 and 27, respectively. It has the structure which supplies the output of this electric power supply system. Preferably, the total length of each W-shaped electrode is a half of the wavelength λ of power used, that is, an integral multiple of λ / 2.
The configuration shown in FIG. 21 is made up of the same members as those shown in the first to eighth embodiments and is given the same reference numerals, and therefore the description thereof is omitted.
The W-shaped electrode 2 is formed of a SUS rod having a diameter of about 5 to 20 mm, and the distance from the second flat plate electrode can be arbitrarily set at 5 to 50 mm.

(Example 10)
A high-frequency plasma generator of Example 10 relating to the present invention, a plasma surface treatment apparatus (plasma CVD apparatus) and a plasma surface treatment method (plasma CVD method) constituted by the high-frequency plasma generation apparatus will be described with reference to FIG.

First, the configuration of the apparatus will be described. However, Examples 1 to 9 are used.
The same members as those shown in FIG. FIG. 22 is a schematic view showing the entire plasma surface treatment apparatus according to the tenth embodiment.

First, the concept of the apparatus will be described. The feature of the device configuration is that a rectangular flat conductor is divided into two by a W-shaped slit, one of the conductors is a first electrode, the other is a second electrode, and the end of the W-shaped slit. This is to have a structure in which a feeding point is arranged in the part.
The slit may have a shape other than the W shape, for example, a U shape and a zigzag shape. Further, the shape of the conductor is not limited to a rectangular flat plate. For example, when the shape of the substrate is cylindrical, it can be made cylindrical correspondingly.

Next, the configuration of the apparatus will be described. In FIG. 22, reference numeral 91 is a slit. Here, a W-shaped slit is used. The width of the slit is about 2 mm to 50 mm, for example, 8 mm in consideration of the pressure condition described later: 0.5 Torr (66.5 Pa).
Reference numeral 2 is a first electrode, and reference numeral 4 is a second electrode. The size of the first and second electrodes is, for example, about 1400 mm × 200 mm with a pair of outer dimensions. Reference numeral 21 is a first feeding point, and reference numeral 27 is a second feeding point, which are arranged at the ends of the W-shaped slit 91 in an opposed manner. Reference numeral 90 denotes a discharge gas passage hole, which is installed on the first and second electrodes. The diameter of the hole is preferably about 1 to 5 mm, and the aperture ratio is preferably about 50% or more.
In FIG. 22, one output terminal of the two output terminals of the first pulse modulation type phase-variable two-output transmitter 15 is a first power amplifier 16, a first impedance matching unit 17, and a first current introduction. The terminal 18 and the core wire 20 at the end of the first vacuum coaxial cable 19 are connected to the first feeding point 21. The outer conductor at the end of the first vacuum coaxial cable 19 is connected to the second electrode 4.
The other output terminal of the two output terminals of the first pulse modulation type phase-variable two-output transmitter 15 is the second power amplifier 22, the second impedance matching unit 23, the second current introduction terminal 24, and the second output terminal. 2 is connected to a second feeding point 27 via a core wire 26 at the end of the vacuum coaxial cable 25. The outer conductor at the end of the second vacuum coaxial cable 19 is connected to the second electrode 4.
Each of the first power amplifier 16 and the second power amplifier 22 is attached with a monitor for an output value (traveling wave) and a monitor for a reflected wave returning from the downstream side. In addition, an isolator for protecting the electric circuit of the first and second power amplifiers 16 and 22 by the reflected wave is attached.
Here, the first power supply system for supplying the two outputs of the first phase variable two-output transmitter 15 to the first and second feeding points 21 and 27 by the power amplifiers 16 and 22, respectively, is the first power supply system. This is called a power supply system.

In FIG. 22, one output terminal of the two output terminals of the second pulse modulation type phase variable two-output transmitter 28 is a third power amplifier 29, a third impedance matching unit 30, a third current introduction. The terminal 31 and the core wire 33 at the end of the third vacuum coaxial cable 32 are connected to the first feeding point 21. The outer conductor at the end of the third vacuum coaxial cable 32 is connected to the second electrode 4.
The other output terminal of the two output terminals of the second pulse modulation type phase-variable two-output transmitter 28 is a fourth power amplifier 34, a fourth impedance matching device 35, a fourth current introduction terminal 36, and a second output terminal. 4 is connected to the second feeding point 27 via the core wire 38 at the end of the vacuum coaxial cable 37. The outer conductor at the end of the second vacuum coaxial cable 19 is connected to the second electrode 4.
The third power amplifier 29 and the fourth power amplifier 34 are each accompanied by a monitor for an output value (traveling wave) and a monitor for a reflected wave reflected and returned from the downstream side. In addition, an isolator for protecting the electric circuit of the main body of the first and second power amplifiers 29 and 34 by the reflected wave is attached.
Here, a power supply system for supplying the two outputs of the second pulse modulation type phase variable 2-output transmitter 28 to the first and second feeding points 21 and 27 by the power amplifiers 29 and 34, respectively, is provided. This is called a second power supply system.

  Next, a method for manufacturing an amorphous Si film for an a-Si solar cell using the plasma surface treatment apparatus having the above configuration will be described. In the implementation or application of the present invention, the first and second preliminary film forming steps and the main film forming step are necessary as procedures. The first preliminary film forming step includes the step of determining the phase difference between the two outputs of the first pulse modulation type phase-variable two-output transmitter 15. In order to grasp the set value of the phase difference between the two outputs of the transmitter 28 having the second pulse modulation type variable phase two output, this film forming process is carried out for the purpose of manufacturing the target amorphous Si.

First, in the first preliminary film forming step, in FIG. 22, the substrate 11 is previously set on the second electrode 4 and the vacuum pump 10 (not shown) is operated, so that the impurity gas in the vacuum vessel 1 and the like. Then, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at 500 sccm and a pressure of 0.5 Torr (66.5 Pa), for example.
Then, using the first power supply system, ultra high frequency power, for example, power at a frequency of 70 MHz, for example, 400 W in total is supplied to the pair of electrodes 2 and 4.
That is, the phase difference between the two outputs of the first pulse modulation system variable-phase two-output transmitter 15, for example, a pulse-modulated sine wave having a frequency of 70 MHz, is set to, for example, zero, and the first power amplifier 16 The output is set to 200 W, for example, and the output is connected between the first feeding point 21 and the second electrode 4 via the first impedance matching unit 17, the first current introduction terminal 18 and the vacuum coaxial cable 19. And the output of the second power amplifier 22 is set to 200 W, for example, and the output is passed through the second impedance matching unit 23, the second current introduction terminal 24, and the vacuum coaxial cable 25 to 2 between the second feeding point 27 and the second electrode 4.
Here, typical examples of power supplied to the first and second feeding points 21 and 27 are shown as W11 (t) and W21 (t) in FIGS. W11 (t) and W21 (t) are sine waves having a pulse width Hw and a pulse modulation with a period T0, for example, 70 MHz. The pulse width Hw and period T0 are set to arbitrary values, for example, Hw = 400 μsec and period T0 = 1 msec, by a regulator attached to the first pulse modulation system phase variable 2-output transmitter 15.
In this case, the power wave supplied from the feeding points 21 and 27 is attenuated slightly because the W-shaped slit that is the propagation path is bent in the middle, but is attenuated but is covered by the bent portion. The dielectric 92 that is present suppresses power loss in that region. As a result, the above-described standing wave is generated by the power waves W11 (x, t) and W21 (x, t) in the propagation path.
As a result, plasma of the SiH 4 gas is generated, and amorphous Si having a sinusoidal distribution is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 15 having the first pulse modulation type variable phase two output as a parameter. Then, in the length direction of the W-shaped slit 91, the distance from the center point of the W-shaped slit 91 to the position of the maximum thickness of the sinusoidal film thickness distribution and the first pulse modulation system phase variable 2 output The relationship between the phase differences between the two outputs of the transmitter 15 is grasped as data. For example, the phase difference for setting at a position away from the central point of the W-shaped slit 91 in the direction of the first feeding point 21 by an eighth wavelength λ, that is, λ / 8 is, for example, Δθ1. That is understood.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Next, as a second preliminary test, in FIG. 22, the substrate 11 is previously set on the second electrode 4, the vacuum pump 10 (not shown) is operated, and the impurity gas in the vacuum container 1 is removed. After the removal, the substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C. while supplying SiH 4 gas from the discharge gas supply tube 8 at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa).
Then, using the second power supply system, ultra high frequency power, for example, power at a frequency of 70 MHz, for example, a total of 400 W is supplied to the pair of electrodes 2 and 4.
That is, the phase difference between the two outputs of the second pulse modulation type phase-variable two-output transmitter 28, for example, the pulse-modulated sine wave of 70 MHz, is set to, for example, zero, and the third power amplifier 29 The output is set to 200 W, and the output is connected between the first feeding point 21 and the second electrode 4 via the third impedance matching unit 30, the third current introduction terminal 31 and the vacuum coaxial cable 32. In addition, the output of the fourth power amplifier 34 is set to 200 W, and the output is passed through the fourth impedance matching unit 35, the fourth current introduction terminal 36, and the vacuum coaxial cable 37 to the second Supply is performed between the feeding point 27 and the second electrode 4.
Here, typical examples of power supplied to the first and second feeding points 21 and 27 are shown as W12 (t) and W22 (t) in FIGS. W12 (t) and W22 (t) are sine waves of a very high frequency, for example, 70 MHz, which are pulse-modulated with a pulse width Tw and a period T0, respectively, from the rise time of the W11 (t) and W21 (t). The relationship is such that it rises with a delay of T0 / 2. The pulse width Tw and the period T0 are set to arbitrary values, for example, Tw = 400 μsec and the period T0 = 1 msec, by a regulator attached to the transmitter 28 of the second pulse modulation type phase variable 2 output.
In this case, the power wave supplied from the feeding points 21 and 27 is attenuated slightly because the W-shaped slit that is the propagation path is bent in the middle, but is attenuated but is covered by the bent portion. The dielectric 92 that is present suppresses power loss in that region. As a result, the above-mentioned standing wave is generated by the power waves W12 (x, t) and W22 (x, t) in the propagation path.
As a result, plasma of the SiH 4 gas is generated, and amorphous Si having a sinusoidal distribution, for example, is deposited on the substrate 11.

In the above-described manner, an amorphous Si film is formed on the substrate 11 with a film formation time of, for example, 10 to 20 minutes. After film formation, the substrate 11 is taken out from the vacuum vessel 1 and the film thickness distribution of the amorphous Si film is evaluated. The film thickness distribution of, for example, amorphous Si deposited on the substrate 11 becomes a sinusoidal distribution due to the generation of a standing wave that is a phenomenon unique to the VHF plasma described above. Such a film forming test is repeatedly performed using the phase difference between the two outputs of the transmitter 28 having the second phase variable and two outputs as a parameter. Then, in the length direction of the W-shaped slit 91, the distance from the center point of the W-shaped slit 91 to the position of the maximum thickness of the sinusoidal film thickness distribution and the transmission of the second pulse modulation method phase variable 2 output The relationship of the phase difference between the two outputs of the device 28 is grasped as data. For example, the phase difference for setting at a position away from the central point of the W-shaped slit 91 in the direction of the second feeding point 27 by an eighth wavelength λ, that is, λ / 8 is, for example, Δθ2. It is understood.
However, the wavelength λ is not the wavelength of the electromagnetic wave in vacuum, but the wavelength λ in the above film forming conditions, and is shorter than the wavelength λ ₀ of the electromagnetic wave in vacuum. In general, in the plasma of SiH 4 gas, the ratio λ / λ ₀ between the wavelength λ in plasma and the wavelength λ _{0 in} vacuum is about 0.5 to 0.9.

Now, in response to the results of the first and second preliminary film forming steps, the main film forming step is started. First, in FIG. 22, the substrate 11 is previously set on the second electrode 4, and the vacuum pump 10 (not shown) is operated to remove impurity gas and the like in the vacuum vessel 1, and then from the discharge gas supply pipe 8. The substrate temperature is maintained in the range of 80 to 350 ° C., for example, 180 ° C., while supplying SiH 4 gas at, for example, 500 sccm and a pressure of 0.5 Torr (66.5 Pa).
Next, two outputs of the first pulse modulation system variable phase two output transmitter 15 of the constituent members of the first power supply system, for example, a phase difference of a sine wave with a frequency of 70 MHz are used as the first preliminary test data. The detected Δθ1 is set, and the pulse modulation is set such that the pulse width Hw and period T0 in W11 (t) and W21 (t) shown in FIGS. 3 and 4 are set to Hw = 400 μsec and T0 = 1 msec, for example. The first and second feeding points 21 and 27 are each supplied with, for example, 200 W of power, and the second pulse modulation type phase-variable two-output transmitter 28 of the second power supply system component. Two outputs, for example, a phase difference of a sine wave having a frequency of 70 MHz, is set to Δθ2 grasped as data of the second preliminary film forming process, and the pulse modulation thereof is shown by W12 (t) and W22 (t) shown in FIGS. Pal in The width Hw and the period T0 are, for example, Hw = 400 μsec and T0 = 1 msec, and a half cycle from the pulse rise time of the pulse modulation of W11 (t) and W21 (t), that is, a time delayed by T0 / 2. It sets so that it may stand up, and power 200W is supplied to the 1st and 2nd feeding points 21 and 27, respectively.
That is, a voltage wave W11 (x, t) having a power of 200 W and a voltage wave W12 (x, t) having a power of 200 W are supplied to the first feeding point 21, and a W21 (x , T) and a voltage wave W22 (x, t) having a power of 200 W are supplied.
Here, the first pulse modulation type phase variable 2 output transmitter 15 and the second pulse modulation type phase variable 2 output transmitter set in the first preliminary film forming step and the second preliminary film forming step, respectively. For example, the values of 28 pulse widths Hw and period T0 can be changed from Hw = 400 μsec to 1 msec or the like, and T0 = 1 msec to 5 msec or the like.

When four voltage waves are supplied between the pair of electrodes 2, 4, as described above, W 11 (x, t) and W 21 (x, t) interfere and the first standing wave W 1 (x , T), and W12 (x, t) and W22 (x, t) interfere to form a second standing wave W2 (x, t). However, W11 (x, t) does not interfere with W12 (x, t) and W22 (x, t) because they are temporally separated. Similarly, W21 (x, t) does not interfere with W12 (x, t) and W22 (x, t).
Therefore, considering a general film formation time of several seconds or longer, which is significantly longer than the pulse modulation period T0, the distribution of the strength of the power generated between the pair of electrodes 2 and 4 is the first standing wave. The intensity distribution I1 (x, t) of W1 (x, t) and the intensity distribution I2 (x, t) of the second standing wave W2 (x, t) are superimposed. This is conceptually shown in FIG.
Here, if the center point of the substrate, that is, the line connecting the apex of the wedge 90 and the slit is the origin of the x axis, and the direction from the origin to the first feeding point 21 is the positive direction, the first constant is defined. The intensity distribution I1 (x, t) of the standing wave W1 (x, t) is
I1 (x, t) = cos ² {2πx / 2 + 2π (λ / 8) / λ}
= Cos ² {2πx / 2 + π / 4}
The intensity distribution I2 (x, t) of the second standing wave W2 (x, t) is
I2 (x, t) = cos ² {2πx / 2-2π (λ / 8) / λ}
= Cos ² {2πx / 2−π / 4}
The distribution I (x, t) of the strength of power generated between the pair of electrodes 2 and 4 is
I (x, t)
= Cos ² {2πx / 2 + π / 4} + cos ² {2πx / 2−π / 4}
= 1
As a result, the distribution of power intensity I (x, t) generated between the pair of electrodes 2 and 4 is a constant value independent of x, that is, the position in the power propagation direction, and is uniform. It shows that there is.

This result also shows that the high-frequency plasma used in the surface treatment apparatus that processes the surface of the substrate placed in the vacuum vessel using the plasma generated using the power of the output of the high-frequency power source whose oscillation frequency belongs to the VHF band. In the generator, the first standing wave and the second standing wave are generated at different antinode positions of the standing wave of the electromagnetic wave having an electric field substantially in the same direction as the normal direction of the surface of the substrate, In addition, the provision of means for superimposing the first and second standing waves makes it possible to control the distribution of power intensity between the electrodes, which is indispensable for plasma uniformity.
Further, if the distance between the antinodes of the first and second standing waves is 0.25 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.25λ, a pair of electrodes The power intensity distribution I (x, t) generated between 2 and 4 has a constant value and does not depend on the position in the power propagation direction, and is uniform. This means that it is an epoch-making discovery in the sense that it is possible to provide an apparatus capable of realizing large-area and uniform plasma processing, which is an important issue in the application field of UHF plasma.
The distance between the antinodes of the first and second standing waves is 0.22 to 0.28 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.22 to 0.2. If it is 28λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 20% or less.
The distance between the antinodes of the first and second standing waves is 0.238 to 0.263 times the wavelength λ in the plasma of the electromagnetic wave used, that is, 0.238 to. In the case of H.263λ, the distribution I (x, t) of the intensity of power generated between the pair of electrodes 2 and 4 is ± 10% or less.

In the above process, when SiH 4 gas is turned into plasma, radicals such as SiH 3, SiH 2, and SiH existing in the plasma diffuse due to a diffusion phenomenon and are adsorbed on the surface of the substrate 11, thereby depositing an a-Si film. However, since the distribution of power intensity between the pair of electrodes 2 and 4 is uniform on a time average as described above, the deposited film becomes uniform. This is an epoch-making discovery in the application field of VHF plasma, and its practical value is remarkably large.
That is, one side of the first electrode of the rectangular type that is required in the improvement of the plasma generating device for improving the productivity of the in-line type, multi-chamber type or roll-to-roll type plasma surface treatment apparatus. This can be realized as one new means relating to a means for supplying VHF power only from the vicinity. This means that when the cross section of the main body of the plasma surface treatment apparatus is viewed in a cross section perpendicular to the substrate transport direction, if the cross section is a rectangular cross section, for example, one side of the four sides of the rectangular cross section It is possible to realize a novel power supply means for generating VHF plasma using only the above.
In this example, by setting the distance between the installation surface of the first and second electrodes and the substrate to about 5 to 40 mm, the amorphous Si film formation with a glass substrate size of about 1200 mm × 200 mm is performed at a film formation rate of 1 to 1. Film formation with a film thickness distribution within ± 10% is possible at about 3 nm / s.
In this embodiment, since the pair of electrodes 2 and 4 including the W-shaped slit 91 is one set, the width of the substrate size is limited to about 200 mm, but the pair of electrodes including the W-shaped slit 91 is included. It goes without saying that the substrate size width can be increased by increasing the number of electrodes 2 and 4.
Note that it is a known technique that microcrystalline Si or thin-film polycrystalline Si can be formed by optimizing the flow rate ratio, pressure, and power of SiH4 and H2 in the film forming conditions, and the film thickness distribution ± 10 % Film formation is possible.

  In this embodiment, the balance-unbalance conversion device and the balanced transmission line used in the second embodiment are not used. However, by using the balance-unbalance conversion device and the balanced transmission path, the plasma can be made uniform. Of course, it will be more certain.

1 is a schematic view showing an entire plasma surface treatment apparatus according to Embodiment 1. FIG. Explanatory drawing of the electric power feeding part to the 1st and 2nd electrode of the plasma surface treatment apparatus shown in FIG. FIG. 3 is an explanatory view showing a typical example of pulse-modulated output outputted from the first and second pulse modulation type phase-variable two-output transmitters shown in FIG. 1; FIG. 3 is an explanatory diagram illustrating a typical example of a pulse-modulated sine wave signal output from the first and second pulse modulation type phase-variable two-output transmitters illustrated in FIG. 1. Explanatory drawing which shows propagation of the voltage wave generated between a pair of electrodes. Explanatory drawing which shows the position of the antinode of the standing wave of the voltage generated between a pair of electrodes. Explanatory drawing which shows distribution of the intensity (value of the square of an amplitude) of the standing wave generated between a pair of electrodes. Explanatory drawing which shows the intensity | strength of two standing waves generated between a pair of electrodes. FIG. 3 is a schematic view showing the entire plasma surface treatment apparatus according to a second embodiment. Explanatory drawing of the electric power feeding part to the 1st and 2nd electrode of the plasma surface treatment apparatus shown in FIG. FIG. 6 is a schematic view showing the entire plasma surface treatment apparatus according to a third embodiment. The wiring diagram of the 1st electric power supply system used for the plasma surface treatment apparatus shown in FIG. The wiring diagram of the 2nd electric power supply system used for the plasma surface treatment apparatus shown in FIG. Schematic which shows the whole plasma surface treatment apparatus concerning Example 4. FIG. FIG. 6 is a schematic view showing the entire plasma surface treatment apparatus according to a fifth embodiment. FIG. 16 is a cross-sectional view of the inside of the vacuum vessel of the plasma surface treatment apparatus shown in FIG. FIG. 9 is a schematic view showing the entire plasma surface treatment apparatus according to a sixth embodiment. Explanatory drawing which shows the electric power supply system wiring diagram of the plasma surface treatment apparatus shown in FIG. FIG. 9 is a schematic view showing the entire plasma surface treatment apparatus according to Example 7. FIG. 10 is a schematic view showing the entire plasma surface treatment apparatus according to an eighth embodiment. FIG. 10 is a schematic view showing an entire plasma surface treatment apparatus according to a ninth embodiment. Schematic which shows the whole plasma surface treatment apparatus concerning Example 10. FIG.

Explanation of symbols

1. . . Vacuum vessel,
2. . . A first electrode,
3. . . Substrate heater (not shown),
4). . . A second electrode,
5. . . Insulator support material,
6). . . Gas mixing box,
7). . . Rectifying hole,
8). . . Discharge gas supply pipe,
9. . . Exhaust pipe,
10. . . Vacuum pump not shown,
11. . . substrate,
12 . . Gate valve not shown,
15. . . A first pulse modulation phase variable two-output transmitter;
16. . . A first power amplifier;
17. . . A first impedance matcher;
18. . . A first current introduction terminal;
19. . . First coaxial coaxial cable,
20. . . The core wire of the first vacuum coaxial cable,
21. . . A first feeding point,
100. . . Sync signal transmission cable,
22. . . A second power amplifier,
23. . . A second impedance matcher;
24. . . A second current introduction terminal,
25. . . A second coaxial coaxial cable,
26. . . The core wire of the second vacuum coaxial cable,
27. . . A second feeding point,
28. . . A second pulse modulation type phase variable two-output transmitter;
29. . . A third power amplifier,
30. . . A third impedance matcher;
31. . . A third current introduction terminal;
32. . . A third coaxial cable for vacuum,
33. . . A core wire of a third vacuum coaxial cable;
34. . . A fourth power amplifier,
35. . . A fourth impedance matcher;
36. . . A fourth current introduction terminal;
37. . . A fourth coaxial cable for vacuum,
38. . . A core wire of a fourth coaxial cable for vacuum.

Claims (12)

  A high-frequency plasma generator used in a plasma surface processing apparatus that processes the surface of a substrate disposed in a vacuum vessel using high-frequency plasma, and has a relationship that is an opposing point in the propagation of electromagnetic waves in a pair of electrodes A pulse power separated in time is supplied to at least two feeding points to generate a plurality of standing waves having different antinode positions of electromagnetic standing waves between the pair of electrodes, and superimpose them. A high-frequency plasma generator characterized by comprising means.   2. The high-frequency plasma generator according to claim 1, further comprising means for controlling positions of antinodes of a plurality of standing waves generated between the pair of electrodes.   Arbitrary pulse modulation is possible, and the first high-frequency power source capable of arbitrarily setting the phase difference between the two outputs and the voltage of the two outputs, and any one synchronized with the pulse modulation signal of the first high-frequency power source One of at least two feeding points arranged on the electrode, the second high-frequency power source capable of pulse modulation and having two outputs and capable of arbitrarily setting the phase difference between the voltages of the two outputs Either one of the two output terminals of the first high-frequency power source and one of the two output terminals of the second high-frequency power source are connected to one feeding point, and the first feeding point is connected to the first feeding point. 3. The high-frequency plasma generator according to claim 1, wherein the other output terminal of the high-frequency power supply and the other output terminal of the second high-frequency power supply are connected.   4. The high-frequency plasma generator according to claim 1, wherein a power distributor is connected to output terminals of the first and second high-frequency power supplies. 5.   The high-frequency plasma generator according to any one of claims 1 to 4, wherein a balance-unbalance converter is connected to the feeding point.   The high frequency plasma generator according to any one of claims 1 to 5, wherein an output frequency of the high frequency power source belongs to a VHF band of 30 MHz to 300 MHz.   7. The high frequency plasma generation according to claim 1, wherein a duty ratio of pulse modulation of the output of the high frequency power source, that is, a ratio Hw / H0 of the pulse width Hw and the period T0 is set to 50% or less. apparatus.   A plasma surface treatment apparatus for treating the surface of a substrate disposed in a vacuum vessel using plasma, comprising the high-frequency plasma generator according to any one of claims 1 to 7. Plasma surface treatment equipment.   In the plasma surface treatment method which processes the surface of the board | substrate arrange | positioned in a vacuum vessel using plasma, surface treatment of the said board | substrate is carried out using the high frequency plasma generator of any one of Claims 1-7. The plasma surface treatment method characterized by performing.   Each of the first and second high-frequency power sources is connected to any one of the feeding points arranged at least at two points that are the opposing points on the propagation of electromagnetic waves in the pair of electrodes. One of the two output terminals is connected one by one, and the other output terminal of the first and second high-frequency power sources is connected to the other feeding point one by one, and the first The power output from the two output terminals of the high frequency power supply is pulse-modulated with a pulse width Hw and a pulse period T0, and the power output from the two output terminals of the second high frequency power supply is By performing pulse modulation in such a way that it rises at a half cycle, ie, a time delayed by T0 / 2, from the rise time of the pal-modulated power output from the output terminal, the two high-frequency power supplies have two output terminals. Separating a supply time zone of the pulse-modulated electric power and the pulse-modulated electric power output from the two output terminals of the second high-frequency power supply to the at least two feeding points, and between the pair of electrodes The first standing wave formed by the power output from the two output terminals of the first high frequency power supply and the second formed by the power output from the two output terminals of the second high frequency power supply. And the phase difference between the power voltages output from the two output terminals of the first high-frequency power supply and the output from the two output terminals of the second high-frequency power supply. The phase difference between the two standing wave antinodes, ie, the distance between the antinode positions of the two standing waves, that is, between the antinode positions of the first standing wave and the antinode positions of the second standing wave. The distance of the wavelength λ of the electromagnetic wave propagating through the generated plasma between the pair of electrodes The surface treatment of the substrate is performed by setting to 0.22 to 0.28 times, preferably 0.25 times, that is, 0.22 to 0.28λ, preferably λ / 4. 10. The plasma surface treatment method according to any one of 8 and 9.   An amorphous Si-based material, a microcrystalline Si-based material, a polycrystalline Si-based material, a crystalline Si-based material, an oxide, a metal, an organometallic compound, an organosilicon compound, or an organic compound is formed on the surface of the substrate. The plasma surface treatment method according to claim 9, wherein the plasma surface treatment method is performed. Any material of amorphous Si-based material, microcrystalline Si-based material, polycrystalline Si-based material, crystalline Si-based material, oxide, metal, organometallic compound, organosilicon compound, and organic compound fixed on the surface of the substrate The plasma surface treatment method according to claim 9, wherein the plasma surface treatment method is performed by etching.

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