JP2012174668A - High-frequency power supply device, plasma processing apparatus, and method for manufacturing semiconductor thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-frequency power supply device and a plasma processing apparatus which are capable of improving power utilization efficiency, and to obtain a method for manufacturing a semiconductor thin film.SOLUTION: The high-frequency power supply device for supplying high-frequency power to a fluctuating load comprises: a high-frequency power source; a circulator which is disposed between the high-frequency power source and the fluctuating load and separates reflected power received from the fluctuating load; an adjustment unit for adjusting a phase and an amplitude of the reflected power separated by the circulator; a power combining unit which combines power outputted from the high-frequency power source with the reflected power adjusted by the adjustment unit and outputs combined power to the circulator.

Description

  The present invention relates to a high-frequency power supply apparatus, a plasma processing apparatus, and a method for manufacturing a semiconductor thin film.

  A plasma processing apparatus is widely used as an apparatus for forming a thin film such as an amorphous silicon thin film or a microcrystalline silicon thin film on a substrate. Nowadays, a plasma processing apparatus capable of forming a thin film having a large area such as a thin film transistor used for a power generation layer of a thin film silicon solar cell or a flat display panel at a high speed at a time has been developed. In order to form a silicon thin film having a large area, it is common to use a parallel plate type plasma processing apparatus. Hereinafter, the parallel plate type plasma processing apparatus will be mainly described.

The parallel plate type plasma processing apparatus has a first electrode and a second electrode facing each other with a distance of several mm to several tens mm in the vacuum chamber. Usually, these electrodes are installed in a horizontal plane, supply high-frequency power to the first electrode, and the second electrode is grounded. When forming a silicon thin film, a film forming gas such as silane (SiH ₄ ) or hydrogen (H ₂ ) is supplied to the gap between the electrodes serving as a discharge region through a large number of apertures formed in the first electrode. The gas supplied to the discharge region is turned into plasma by high frequency power. The deposition gas is decomposed in the plasma, becomes radicals and ions, and enters the deposition target substrate to form a silicon film on the substrate. In general, the second electrode on the grounded side is used as a stage, and a deposition target substrate is placed on the stage.

  In recent years, in order to meet the needs for improving film formation quality and film formation speed, VHF plasma generated using high frequency power in the VHF (Very High Frequency) band, which is higher than the conventional 13.56 MHz frequency, is formed. It has been actively studied for use. Since VHF plasma has a high density and a low electron temperature, it is expected as a solution to the above needs.

  However, due to the increase of the frequency of the high frequency power, the high frequency power causes interference in the electrode surface, and the standing wave is formed, resulting in nonuniform electric field strength distribution, resulting in nonuniform plasma density, and finally In addition, the film formation rate and the film quality itself tend to be non-uniform. In general, it is desirable that the electrode size is 1/10 or less of the wavelength λ of the high-frequency power to be used. For example, in the case of 13.56 MHz, the electrode size is limited to over 2 m, and in the VHF band, for example, 60 MHz, about 50 cm is the limit. Become.

  Here, the variation in film formation characteristics, for example, the film thickness distribution, in the solar cell field, ensures reproducibility and achieves about ± 10%, which is one indicator of practical use. In the conventional VHF plasma technology, for example, in the case of an amorphous silicon film deposition rate, a substrate area of about 50 cm × 50 cm is about ± 10 to 15%, which is barely satisfied with a small area substrate, which is about 100 cm × 100 cm. It has reached about ± 20 to 40% and does not reach the above index.

  Since the formation of standing waves is caused by the fundamental physical phenomenon of wave interference, the fundamental solution is very difficult. Therefore, as a suboptimal measure, many of the prior arts allow the formation of standing waves themselves, and take a guideline that the generation of uniform plasma as a time average and thus film formation is achieved by controlling the distribution of the standing waves over time. ing.

  In Patent Document 1, in a plasma CVD apparatus, a phase difference between power voltages supplied from two opposite sides of a rectangular electrode is changed with time, and two pulse-modulated two-output high-frequency power sources are used. It is described to provide temporally separated pulse power. Thus, according to Patent Literature 1, the first standing wave whose antinode position matches the positions of the first and second feeding points, and the node position of the first and second feeding points. It is said that the second standing wave that matches the position is generated alternately in time, and the plasma can be made uniform on a time average.

Japanese Patent No. 4022670 JP 2010-182683 A JP 2000-138501 A

  As described above, film formation using high-frequency power in the VHF band capable of generating high-density plasma at a low electron temperature has been actively studied in recent years as a technology that can solve both film quality improvement and high-speed film formation. Has been done. However, due to the deterioration of film formation uniformity due to the formation of standing waves, many of the conventional techniques guide the generation of uniform plasma as a time average and thus film formation by controlling the distribution of standing waves over time. Have taken.

  Therefore, plasma having a different distribution, that is, a load having a different distribution, is formed in the electrode surface with the progress of the process time, and the reflected power is often increased in the conventional matching method. In general, passive element networks such as L-type, inverted L-type, and saddle-type are often used for matching variable loads represented by plasma. A variable element for controlling matching conditions in this network, such as a variable capacitor, is often used as a mechanical device to allow power necessary for plasma generation, and the response speed is approximately several tens of msec. It is slow with a few seconds. If the modulation speed is such that the response speed can be allowed, matching can always be achieved, so that the reflected power can be kept low.

  However, the modulation speed is usually set to several kHz to several hundred kHz according to a request from the film forming process. In this case, since the modulation speed greatly exceeds the response speed of the variable element, the value of the variable element, that is, the load matching condition, is expected to settle at a place where the reflected power becomes small on a time average basis.

  Therefore, the present inventor conducted an experiment to generate plasma by modulating high-frequency power so as to switch the distribution in which the antinodes and nodes of the standing wave are reversed at 1 kHz as shown in Patent Document 1. However, the time-average reflected power was about 30% of the supplied power, and settled at a very large value.

  Thus, when the reflected power increases, not only the power supply efficiency to the load decreases, but also a problem occurs in terms of protection of the power source. Therefore, there is a need for a system that protects a power supply from reflected power using an isolator that combines a circulator and a resistive load.

  In Patent Document 2, in the VHF plasma processing system, the first port of the circulator is connected to the power amplifier, the second port of the circulator is connected to the plasma load side, and the third port of the circulator is connected to the termination resistor. Via the ground potential. Thus, according to Patent Document 2, the reflected power caused by the plasma impedance is separated and applied to the terminating resistor, so that the stability of the system can be improved.

  However, when the circulator and the resistive load are used in this way, the reflected power is thrown away as heat in the resistive load, so that the power utilization efficiency seen in the total system is significantly reduced. For example, when about 30% of reflected power is generated as in the above-described experiment, power of several kW to 10 kW is wasted when power of several tens of kW class is used as in a microcrystalline silicon film forming process. Become.

  Patent Document 3 describes a microwave power feeding system in which a plurality of circulators are connected between one power source and a plurality of plasma welding machines. In this microwave power supply system, it is considered that the reflected power from one plasma welder is separated by one circulator and then supplied to another plasma welder via another circulator.

  In the microwave power feeding system described in Patent Document 3, since the reflected power is fed to another load, the reflected power from one plasma welding machine is not reused by the one plasma welding machine itself. The power utilization efficiency (= power consumed by the load / power supplied from the power source) is low when viewed with each plasma welding machine. Further, in the microwave power feeding system described in Patent Document 3, since the last-stage circulator discards the reflected power to the non-reflecting terminator, the power utilization efficiency when viewed as a whole system is low.

  On the other hand, when the reflected power is to be supplied again to the original load, there are the following problems. Usually, the reflected power has an amplitude and a phase difference different from those of the power supply output, and when the modulation is performed at a high speed as described above, the phase difference and the amplitude also change at a high speed. In the prior art, when it is attempted to synthesize power having an arbitrary phase difference and amplitude ratio, it is difficult to do so without loss, and the phase of the power after synthesis becomes uncertain. Therefore, it is difficult to apply to a power feeding method in which film formation characteristics and uniformity thereof are sensitive to the amplitude and phase difference of the supplied power, such as multiple power feeding and phase modulation power feeding. That is, it is difficult to improve power usage efficiency.

  This invention is made | formed in view of the above, Comprising: It aims at obtaining the manufacturing method of the high frequency electric power supply apparatus which can improve electric power utilization efficiency, a plasma processing apparatus, and a semiconductor thin film.

  In order to solve the above-described problems and achieve the object, a high-frequency power supply apparatus according to one aspect of the present invention is a high-frequency power supply apparatus that supplies high-frequency power to a variable load. A circulator arranged between a power source and the variable load and separating the reflected power from the variable load, an adjustment unit for adjusting the phase and amplitude of the reflected power separated by the circulator, and output from the high frequency power source And a power combining unit that combines the reflected power adjusted by the adjusting unit and outputs the combined power to the circulator.

  According to the present invention, the power utilization efficiency can be improved because the reflected power from the variable load can be supplied again to the original variable load while suppressing power loss during the synthesis.

FIG. 1 is a schematic diagram of a high-frequency power supply apparatus according to the first embodiment. FIG. 2 is a schematic diagram of the plasma processing apparatus in the first embodiment. FIG. 3 is a circuit diagram of the loaded line type phase shifter according to the first embodiment. FIG. 4 is a circuit diagram of the hybrid type phase shifter in the first embodiment. FIG. 5 is a circuit diagram of the Wilkinson coupler according to the first embodiment. FIG. 6 is a circuit diagram of the lumped constant circuit type Wilkinson coupler according to the first embodiment. FIG. 7 is a schematic diagram of a high-frequency power supply apparatus according to the second embodiment.

  Hereinafter, embodiments of a high-frequency power supply device according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
A high-frequency power supply apparatus 100 according to the first embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a configuration of the high-frequency power supply device 100.

  The high frequency power supply apparatus 100 supplies high frequency power to the variable load FL. The variable load FL is, for example, a plasma load. The plasma load is, for example, a plasma processing apparatus 200 as shown in FIG. The plasma processing apparatus 200 includes a vacuum chamber 201, a stage 202, an electrode block 203, a gas supply port 205, and a shower plate 204. The stage 202 is configured to be movable. The gas supply port 205 introduces a film forming gas into the electrode block 203. The shower plate 204 supplies a film forming gas to the discharge region 206. A substrate 207 to be processed (for example, a silicon wafer or a glass substrate) is placed on the stage 202.

  The high frequency power supply apparatus 100 is connected to, for example, an electrode block (first electrode) 203. A stage (second electrode) 202 placed opposite to the electrode block 203 is connected to the earth (ground potential). Thereby, a high-frequency electric field is formed between the electrode block 203 and the stage 202. When the high-frequency electric field exceeds the discharge threshold electric field, a film forming gas dissociation reaction or ionization reaction occurs, and plasma is generated. Then, film formation is performed by ions and radicals entering from the plasma onto the substrate 207 to be processed.

  Next, the high frequency power supply apparatus 100 will be described in detail. An RF to VHF band is selected as a frequency for supplying power from the high-frequency power supply apparatus 100 to the electrode block 203 in order to realize high-speed film formation. In order to supply high-frequency power in the VHF band to the electrode block 203 having a large area, a method of supplying power from a plurality of locations is preferable in order to reduce the influence of standing waves. For example, the arrangement and number of power feeding locations are selected depending on the size and structure of the apparatus, but the effect of this embodiment does not depend on the location and number of power feeding locations, so here one connected to those electrodes. Alternatively, one of the plurality of high-frequency power supply devices 100 will be described.

  The high frequency power supply apparatus 100 includes a high frequency power supply 104, a power combiner (power combiner) 101, a circulator 102, a phase / amplitude control circuit (adjuster) 105, and a matching unit 103. The phase / amplitude control circuit 105 includes a directional coupler (detection unit) 110, a reflected power adjuster (determination unit) 111, and a waveform shaping circuit (waveform shaping unit) 112. The waveform shaping circuit 112 includes a variable phase shifter 108 and a variable attenuator 109.

  The output of the high frequency power supply 104 is connected to the first input port 101 a of the power combiner 101, and the output port 101 c of the power combiner 101 is connected to the first port 102 a of the circulator 102. The second port 102 b of the circulator 102 passes only the input from the first port 102 a of the circulator 102, and is connected to the variable load FL through the matching unit 103. Further, the third port 102 c of the circulator 102 passes only the input from the second port 102 b of the circulator 102, that is, the reflected power from the variable load FL, and is connected to the directional coupler 110. Directional coupler 110 is connected to waveform shaping circuit 112. In the waveform shaping circuit 112, for example, a variable phase shifter 108 and a variable attenuator 109 are connected in series. The output of the waveform shaping circuit 112, that is, the output of the phase / amplitude control circuit 105 is connected to the second input port 101 b of the power combiner 101. The reflected power adjuster 111 is connected to the high frequency power supply 104, the directional coupler 110, and the waveform shaping circuit 112. The reflected power adjuster 111 acquires the phase / amplitude information of the power output power from the high-frequency power source 104, acquires the phase / amplitude information of the reflected power from the directional coupler 110, and moves to the waveform shaping circuit 112 based on them. Specify the phase amount and attenuation.

  The high frequency power source 104 includes a high frequency oscillator 106 and a high frequency amplifier 107. When there are a plurality of feeding points in the electrode block 203, for example, in order to synchronize the feeding points, the output of one high-frequency oscillator may be distributed and input to each high-frequency amplifier 107. The high-frequency oscillator 106 may be appropriately connected with a phase modulation system, a pulse modulation system, a frequency modulation system, and other various modulation systems in order to improve plasma processing characteristics such as improvement in uniformity in the VHF band. That is, the high frequency power source 104 may have at least one modulation mechanism. Thereby, for example, electromagnetic radiation (EMI) from the high frequency power supply 104 can be reduced.

  A matching unit 103 and a circulator 102 are used to connect the high-frequency power source 104 to the variable load FL. The matching unit 103 is installed in the immediate vicinity of the variable load FL, for example, and is connected to the load, for example, in the shortest time by a metal plate having a low resistivity such as copper or aluminum. The matching unit 103 is configured using a passive element network such as an L-type, an inverted L-type, or a saddle type. Based on input / reflected power information detected by a directional coupler (not shown) and a controller (not shown) connected to the inlet of the matching unit 103, the value of the variable element in the passive element network is set. Is done.

  Normally, the value of the variable element is determined so that the reflected power is minimized, that is, in a load matching state, but this embodiment requires a reflected power having a constant amplitude ratio with respect to the output power of the high frequency power supply 104. Therefore, the value of the variable element can be determined so as to be in a mismatched state, and control can be performed to ensure a certain amount of reflected power.

  Since the reflected power is generated when the response of the matching unit 103 is not in time due to high-speed modulation or the like, the reflected power is separated using the circulator 102 for power supply protection. A 3-port Y-connection circulator is suitable for use at this time, but other types of circulators such as a 4-port can be used.

  The phase and amplitude of the reflected power separated by the circulator 102 are adjusted by the reflected power adjuster 111. Specifically, the phase and amplitude information of the reflected power separated by the circulator 102 is detected by the directional coupler 110, and the reflected power adjuster 111 performs phase shift amount (phase change) by feedback control based on the information. Amount) and attenuation (amplitude change amount) are determined, and an instruction for the change is sent to the phase / amplitude control circuit 105.

  For example, the reflected power adjuster 111 adjusts the phase and amplitude of the reflected power so as to have the same phase as the output power of the high-frequency power supply 104 and a constant amplitude ratio. In other words, the reflected power adjuster 111 matches the phase of the reflected power detected by the directional coupler 110 with the phase of the power output from the high frequency power supply 104 and the amplitude of the power output from the high frequency power supply 104. The phase shift amount (phase change amount) and attenuation amount (amplitude change amount) are determined so that the ratio of the amplitudes of the reflected power detected by the directional coupler 110 matches the target value.

  When the high-frequency power source 104 has a modulation mechanism, the reflected power adjuster 111 can modulate the high-frequency power source 104 because the fluctuation amount can be predicted to some extent based on the modulation signal in a load used for plasma processing such as film formation and etching. It is also possible to perform feedforward control based on the modulation signal from the mechanism. That is, the reflected power adjuster 111 may perform feedforward control based on the phase and amplitude of the reflected power predicted from the modulation signal of the high frequency power supply 104. Specifically, the reflected power adjuster 111 matches the phase of the predicted reflected power with the phase of the power output from the high frequency power supply 104 and the predicted reflected power with respect to the amplitude of the power output from the high frequency power supply 104. The amount of phase shift (phase change amount) and the amount of attenuation (amplitude change amount) may be determined so that the ratio of the amplitudes matches the target value. Thereby, the reflected power adjuster 111 can adjust the phase and amplitude of the reflected power.

  In addition, the reflected power adjuster 111 may simultaneously perform both feedback control and feedforward control.

  In the waveform shaping circuit 112, as described above, for example, the variable phase shifter 108 and the variable attenuator 109 are connected in series. The waveform shaping circuit 112 adjusts the phase and amplitude of the reflected power based on the instruction value from the reflected power adjuster 111. That is, the variable phase shifter 108 receives a phase shift amount instruction from the reflected power adjuster 111 and performs a phase shift of the reflected power in accordance with the phase shift amount instruction. The variable attenuator 109 receives an instruction of attenuation from the reflected power adjuster 111, and attenuates reflected power according to the instruction of attenuation.

  In FIG. 1, the reflected power is shown passing through the variable attenuator 109 after passing through the variable phase shifter 108, but the order of these may be reversed.

  As the variable phase shifter 108, a so-called transmission-type loaded line type phase shifter (see FIG. 3) or a reflective hybrid phase shifter (see FIG. 4) can be used.

  The transmission-type loaded line type phase shifter shown in FIG. 3 includes a transmission line 303 connected between the phase shifter input 300 and the phase shifter output 301, and a line connecting the phase shifter input 300 and the transmission line 303. A variable capacitor 302a is connected between the ground potential and a variable capacitor 302b is connected between the line connecting the transmission line 303 and the phase shifter output 301 and the ground potential. The characteristic impedance of the transmission line 303 is λ / 4 (λ: wavelength of the power signal), for example, 50Ω.

In the reflection type hybrid phase shifter shown in FIG. 4, a transmission line 303a is connected between a phase shifter input 300 and a phase shifter output 301, and a line connecting the phase shifter input 300 and the transmission line 303a and a ground. The transmission line 303b and the variable capacitor 302c are connected between the potential and the transmission line 303c and the variable capacitor 302d are connected between the line connecting the transmission line 303a and the phase shifter output 301 and the ground potential. A transmission line 303d is connected between a node connecting the transmission line 303b and the variable capacitor 302c and a node connecting the transmission line 303c and the variable capacitor 302d. The characteristic impedances of the transmission line 303a and the transmission line 303d are both λ / 4 (λ: wavelength of the power signal), for example, 50Ω. Characteristic impedance of the transmission line 303b and transmission line 303c are both, lambda / 4: a (lambda wavelength of the power signal), for example, _{Z 1.}

  The variable attenuator 109 can be a T-type or saddle-type network.

  However, when the reflected power reaches several tens of percent, that is, several hundred watts to several kW, variable phase shifters and variable attenuators that use solid state elements such as variable capacitance diodes are generally configured due to problems of withstand voltage and heat. It becomes difficult. In such a case, a lossless power combiner such as a Wilkinson coupler (see FIG. 5) described later may be used.

  In the Wilkinson coupler shown in FIG. 5, a transmission line 403 a is connected between the combiner input 401 a and the combiner output 400, and a transmission line 403 b is connected between the combiner input 401 b and the combiner output 400. Further, a non-equilibrium absorption resistor 402 is connected between a node connecting the transmission line 403a and the combiner input 401a and a node connecting the transmission line 403b and the combiner input 401b. The characteristic impedances of the transmission line 403a and the transmission line 403b are both λ / 4 (λ: wavelength of the power signal), for example, 70.7Ω. The non-equilibrium absorption resistor 402 is, for example, 100Ω.

  Note that a lossless power combiner such as a Wilkinson coupler can also be used as a power distributor if the input and output are interchanged. That is, in the Wilkinson coupler shown in FIG. 5, the synthesizer output 400 and the synthesizer inputs 401a and 401b are set as a distributor input 400 and distributor outputs 401a and 401b, respectively.

  With this power distributor, the reflected power is first distributed to a power value that can be used by the solid state element. Then, phase shift and attenuation are performed using a plurality of variable phase shifters corresponding to the number of distributions, or a variable attenuator, or a plurality of waveform shaping subunits including variable phase shifters and variable attenuators, and then lossless again. You may synthesize | combine using a type | mold power combiner | synthesizer. That is, the waveform shaping circuit 112 includes one waveform shaping unit, and the waveform shaping unit may include a reflected power distributor, a plurality of waveform shaping subunits, and a reflected power synthesizer. The waveform shaping circuit 112 may have a plurality of waveform shaping units. With this waveform shaping unit, even when the reflected power reaches several tens of percent, that is, several hundred W to several kW, the phase and attenuation of the reflected power can be performed.

  In the waveform shaping unit, the reflected power distributor distributes the reflected power separated by the circulator 102 into a plurality of reflected powers. The reflected power distributor is obtained by switching the input and output of a lossless power combiner such as a Wilkinson coupler (see FIG. 5). The plurality of waveform shaping subunits perform at least one of phase shifting and attenuation on the plurality of reflected power distributed by the reflected power distributor. That is, each waveform shaping subunit may include at least one of the variable phase shifter and the variable attenuator as described above. The variable phase shifter is, for example, a transmission type loaded line type phase shifter (see FIG. 3) or a reflection type hybrid phase shifter (see FIG. 4). The reflected power combiner combines a plurality of reflected powers output from the plurality of waveform shaping subunits. The reflected power combiner is a lossless power combiner such as a Wilkinson coupler (see FIG. 5). Note that a filter may be provided in the waveform shaping subunit to remove harmonics and the like at the same time.

  The reflected power phase-shifted and attenuated by the waveform shaping circuit 112 is input to the power combiner 101. The power output from the high frequency power supply 104 is also input to the power combiner 101. The power combiner 101 combines the output power of the high frequency power supply 104 and the reflected power, and supplies the combined power to the variable load FL again via the circulator 102 and the matching unit 103.

  The power combiner 101 is preferably a lossless combiner such as a Wilkinson coupler (see FIG. 5) or a branch line coupler. For example, a Wilkinson coupler circuit for 1: 1 synthesis is shown in FIG. In FIG. 5, the 1: 1 synthesis is illustrated, but it is also possible to configure the circuit so that the 1: n (n ≠ 1) synthesis. The Wilkinson coupler includes a non-equilibrium absorption resistor 402. However, if the amplitude and phase are input together, the potentials at both ends of the non-equilibrium absorption resistor 402 are equalized, so that loss can be minimized.

  Wilkinson couplers and branch line couplers usually require a λ / 4 line, so the installation area tends to be large at a relatively low oscillation frequency of about 10 MHz to 100 MHz. Therefore, the lumped constant circuit type shown in FIG. 6 may be used. In this case, the installation area can be greatly reduced.

  The lumped constant circuit type Wilkinson coupler shown in FIG. 6 has an inductor 403a1 connected between the synthesizer input 401a and the synthesizer output 400, and an inductor 403b1 connected between the synthesizer input 401b and the synthesizer output 400. ing. A capacitor 403c is connected between the line connecting the inductor 403a1, the inductor 403b1, and the combiner output 400 and the ground potential, and the capacitor 403a2 is connected between the line connecting the inductor 403a1 and the combiner input 401a and the ground potential. And a capacitor 403b2 is connected between the line connecting the inductor 403b1 and the combiner input 401b and the ground potential. Further, a non-equilibrium absorption resistor 402 is connected between a node connecting the inductor 403a1, the capacitor 403a2, and the combiner input 401a and a node connecting the inductor 403b1, the capacitor 403b2, and the combiner input 401b. The inductances of the inductor 403a1 and the inductor 403b1 are both 187.6 nH, for example. The capacitances of the capacitor 403a2 and the capacitor 403b2 are both 37.5 pF, for example. The capacity of the capacitor 403c is, for example, 70.5 pF. The non-equilibrium absorption resistor 402 is, for example, 100Ω.

  As described above, in the first embodiment, the circulator 102 separates the reflected power, the phase / amplitude adjustment circuit adjusts the phase and amplitude of the separated reflected power, and the power combiner adjusts the adjusted power. The reflected power and the output power from the high frequency power source 104 are combined and input to the circulator 102. As a result, the reflected power from the variable load can be supplied again to the original variable load while suppressing the power loss during synthesis, so that the power utilization efficiency (= power consumed by the load / power supplied from the power source) ) Can be improved.

  In particular, experimental results show that the reflected power reaches several tens of percent when modulation is applied to improve film formation uniformity, while power of several tens of kW class may be used for film formation of microcrystalline silicon and the like. For this reason, such a technique for improving the power utilization efficiency is very useful industrially.

  Specifically, the reflected power adjuster 111 determines the amount of phase and amplitude change for the reflected power separated by the circulator 102, and the waveform shaping circuit 112 determines the phase and amplitude determined by the reflected power adjuster 111. The phase and amplitude of the reflected power separated by the circulator 102 are changed according to the change amount. Thereby, the phase and amplitude of reflected power can be adjusted.

  More specifically, the directional coupler 110 detects the phase and amplitude of the reflected power separated by the circulator 102, and the reflected power adjuster 111 detects the phase, amplitude, and direction of the power output from the high frequency power supply 104. Feedback control is performed based on the phase and amplitude of the reflected power detected by the sex coupler 110. Thereby, the phase and amplitude of reflected power can be adjusted.

  More specifically, the reflected power adjuster 111 has the phase of the power output from the high-frequency power source 104 coincides with the phase of the reflected power detected by the directional coupler 110 and is output from the high-frequency power source 104. The amount of change in phase and amplitude is determined so that the ratio of the amplitude of the reflected power detected by the directional coupler 110 to the amplitude of the power matches the target value. Thereby, the reflected power adjuster 111 can perform feedback control.

  Further, in the first embodiment, the matching unit 103 disposed between the circulator 102 and the variable load FL is configured so that the reflected power that enables the power combiner 101 to be supplied from the variable load FL to the circulator 102. Has matching conditions. As a result, it is possible to reflect an amount of power that the power combiner 101 can always operate by deviating the matching conditions so that the load matching is not lost and the reflection is not lost, that is, the mismatch is made.

Embodiment 2. FIG.
A high frequency power supply apparatus 600 according to the second embodiment will be described with reference to FIG. FIG. 7 is a diagram illustrating a configuration of the high-frequency power supply device 600. Below, it demonstrates centering on difference with Embodiment 1. FIG.

  The high frequency power supply apparatus 600 further includes a switch 602a, a resistance load 601 and a switch 602b as a configuration mainly used when power is supplied to an unknown variable load FL.

  The switch 602 a is arranged so that the connection of the output of the high-frequency power source 104 can be switched between the first input port 101 a of the power combiner 101 and the first port 102 a of the circulator 102. That is, the switch 602 a switches between a first state in which the high-frequency power source 104 is connected to the power combiner 101 and a second state in which the high-frequency power source 104 is connected to the circulator 102.

  The resistive load 601 is disposed between the directional coupler 110 and the ground potential. For example, the switch 602b is connected between the ground potential.

  The switch 602b is arranged so that the output connection of the directional coupler 110 can be switched between the waveform shaping circuit 112 and the resistance load 601. That is, the switch 602b switches between the third state in which the directional coupler 110 is connected to the waveform shaping circuit 112 and the fourth state in which the directional coupler 110 is connected to the resistive load 601.

  For example, when power is supplied to an unknown variable load FL with the configuration of FIG. 1, the control parameters in the high-frequency power supply apparatus 100 are unknown immediately after the power supply, so that the control of the amount of phase shift and attenuation of the reflected power can diverge. There is sex. In addition, there is a possibility that the amplitude ratio between the output power and the reflected power of the high frequency power supply 104 does not reach a desired value. In such a case, the power combiner 101 may be overloaded and damaged.

  Therefore, in the present embodiment, when power is supplied to the unknown variable load FL, first, the output of the high-frequency power source 104 is directly connected to the first port 102a of the circulator 102 by the switch 602a, and the directional coupler is connected by the switch 602b. The output of 110 is connected to the resistance load 601. Thereby, the high frequency power supply apparatus 600 is configured to discard the reflected power to the resistance load 601. In this configuration, information on the amplitude and phase of the reflected power is acquired, and control parameters of a controller (not shown) that controls the reflected power adjuster 111 and the matching unit 103 are set appropriately.

  Thereafter, the output of the high-frequency power source 104 is connected to the first input port 101a of the power combiner 101 by the switch 602a, and the output of the directional coupler 110 is connected to the waveform shaping circuit 112 by the switch 602b. Thereby, the high frequency electric power supply apparatus 600 becomes the structure similar to the structure which supplies the reflected power shown in Embodiment 1 again to the fluctuation | variation load FL.

  As described above, in the second embodiment, the control parameters of the controller (not shown) that controls the reflected power adjuster 111 and the matching unit 103 are appropriately set and switched to the same configuration as in the first embodiment. Therefore, problems such as damage to the power combiner 101 can be avoided.

  If the controller (not shown) determines that the reflected power is smaller than the threshold based on the result detected by the directional coupler 110, the output of the high-frequency power source 104 is sent to the first circulator 102 by the switch 602a. It is also possible to use the configuration in which the output of the directional coupler 110 is connected directly to the port 102a and the output of the directional coupler 110 is connected to the resistance load 601 by the switch 602b, and the reflected power is discarded to the resistance load 601. Further, based on the result detected by the directional coupler 110, if a controller (not shown) determines that the reflected power is larger than the threshold value, the same operation as in the second embodiment is performed. Good.

Embodiment 3 FIG.
In the present embodiment, the high-frequency power supply apparatus 100 shown in FIG. 1 is connected to the plasma processing apparatus 200 shown in FIG. 2, and a mixed plasma of silane gas (SiH ₄ ) and hydrogen gas (H ₂ ) is generated, whereby a glass substrate is obtained. An example in which a microcrystalline silicon film is deposited thereon will be described.

In order to form a silicon thin film on a substrate to be processed, for example, monosilane (SiH ₄ ) gas is used as a silicon source, hydrogen (H ₂ ) gas is used as a carrier gas, and a gas obtained by mixing them is used as a film forming gas. The deposition gas is supplied into the electrode block 203 through the gas supply port 205 and is introduced into the discharge region 206 between the opposing stages 202 through a large number of apertures formed in the shower plate 204. High frequency power is supplied to the electrode block 203, and the deposition gas in the discharge region 206 is decomposed by the high frequency power to generate high frequency plasma. In this process, active species such as SiH ₃ , SiH ₂ , SiH, Si, and H are generated, and these active species enter the substrate 207 to be processed, and amorphous or microcrystalline silicon is formed on the surface of the substrate 207 to be processed. Form. As a result of continuing the high frequency plasma for a certain time, an amorphous or microcrystalline silicon thin film is formed on the substrate 207 to be processed.

1 is connected to the plasma processing apparatus shown in FIG. 2, and high-frequency plasma is generated with a mixed gas of silane gas (SiH ₄ ) and hydrogen gas (H ₂ ), and then finely formed on the glass substrate. An experiment in which a crystalline silicon film is deposited will be described.

A 1400 mm × 1100 mm glass substrate (thickness: 4 mm) was placed on the stage 202 in the vacuum chamber 201 that had been evacuated, and heated to 200 ° C. using a sheath heater (not shown) built in the stage 202. Next, the height position of the stage 202 was set so that the distance between the electrode block 203 and the substrate to be processed 207 was 5 mm. In this state, SiH ₄ gas and H ₂ gas were supplied to the gas supply port 205 of the electrode block 203 at flow rates of 1 slm and 50 slm, respectively, and the exhaust speed was adjusted so that the gas pressure in the discharge region 206 was 1000 Pa. After the gas pressure was stabilized, the high-frequency power supply apparatus 100 was connected to the electrode block 203 side to generate a SiH ₄ / H ₂ mixed plasma, and film formation was performed for 20 minutes in a state where high-frequency power was fed at an average of 20 kW. When film formation was performed with phase modulation at a modulation frequency of 10 kHz to make the film formation characteristics uniform, when a 1 μm-thick silicon thin film was formed under the above conditions, a reflected load of about 30% was applied to the resistance load. The power use efficiency was about 70% on an average over time.

  On the other hand, when film formation was performed using the apparatus shown in FIG. 1 under the same conditions, this time, since synthesis is performed with the output power of the high-frequency power source: reflected power = 4: 1, the output power of the high-frequency power source is effectively 125. % Will be supplied to the load. Therefore, since the power reflectance is 30%, the power utilization efficiency is improved to 125 × (1−0.3) = 87.5%. Assuming that the prepared thin film is used for solar cells, the formation ratio of crystalline silicon was investigated by Raman spectroscopy. A sufficient peak intensity ratio was obtained, and the in-plane uniformity of the formation ratio was within the practical range. I was able to confirm that. From this, it was concluded that a silicon film having excellent characteristics can be formed even with a practical substrate size.

In the present embodiment, numerical values are shown for parameters such as gas flow rate, pressure, and high frequency power, but these numerical values can be changed as appropriate. Further, the description has been given of the mixed gas of SiH ₄ and H ₂ as the film forming gas for forming a silicon thin film, further, Ar, may be added to rare gas Ne, and the like. In addition, an appropriate gas type is selected according to the purpose of the process.

  Note that the plasma processing apparatus of the present invention can also be applied to a plasma etching apparatus, an ashing apparatus, a sputtering apparatus, an ion implantation apparatus, and the like.

  In the above description, the horizontal apparatus has been described. However, the plasma processing apparatus of the present invention can also be applied to a vertical apparatus. Which type is selected can be selected as appropriate according to the use of the plasma apparatus. The present invention can be variously modified, modified, combined, etc. other than those described above.

  As described above, the high-frequency power supply apparatus, plasma processing apparatus, and semiconductor thin film manufacturing method according to the present invention are useful for forming a semiconductor thin film.

DESCRIPTION OF SYMBOLS 100 High frequency electric power supply apparatus 101 Power combiner 102 Circulator 103 Matching device 104 High frequency power supply 105 Phase / amplitude control circuit 106 High frequency oscillator 107 High frequency amplifier 108 Variable phase shifter 109 Variable attenuator 110 Directional coupler 111 Reflected power adjuster 112 Waveform Molding circuit 200 Plasma processing apparatus 201 Vacuum chamber 202 Stage 203 Electrode block 204 Shower plate 205 Gas supply port 206 Discharge area 207 Substrate 300 Phase shifter input 301 Phase shifter output 302a, 302b Variable capacitor 303, 303a-303d Transmission line 400 Synthesizer output / distributor input 401a, 401b Synthesizer input / distributor output 402 Unbalanced absorption resistor 403a, 403b Transmission line 403a1, 403b1 Inductor 4 3a2,403b2,403c capacitor 600 high-frequency power supply device 601 resistive load 602 switches FL variable load

Claims (12)

A high frequency power supply device for supplying high frequency power to a variable load,
A high frequency power supply,
A circulator arranged between the high-frequency power source and the variable load, and separating reflected power from the variable load;
An adjustment unit for adjusting the phase and amplitude of the reflected power separated by the circulator;
A power combining unit that combines the power output from the high-frequency power source and the reflected power adjusted by the adjustment unit and outputs the combined power to the circulator;
A high-frequency power supply device comprising: The adjustment unit is
A determination unit for determining a change amount of a phase and an amplitude with respect to the reflected power separated by the circulator;
A waveform shaping unit that changes the phase and amplitude of the reflected power separated by the circulator according to the phase and amplitude change amount determined by the determination unit;
The high-frequency power supply device according to claim 1, comprising: The adjustment unit further includes a detection unit that detects the phase and amplitude of the reflected power separated by the circulator,
The said determination part performs feedback control based on the phase and amplitude of the electric power output from the said high frequency electric power source, and the phase and amplitude of the reflected electric power detected by the said detection part. High frequency power supply device. The determination unit is detected by the detection unit with respect to the amplitude of the power output from the high-frequency power source and the phase of the power output from the high-frequency power source matches the phase of the reflected power detected by the detection unit. 4. The high frequency power supply apparatus according to claim 3, wherein the amount of change of the phase and amplitude is determined so that the ratio of the amplitude of the reflected power matches the target value. The high-frequency power supply apparatus according to claim 2, wherein the high-frequency power source includes at least one modulation mechanism. The high-frequency power supply apparatus according to claim 5, wherein the determination unit performs feedforward control based on a phase and an amplitude of reflected power predicted from a modulation signal of the high-frequency power source. The corrugated part has at least one corrugated unit,
The corrugated unit is
A reflected power distributor for distributing the reflected power separated by the circulator to a plurality of reflected powers;
A plurality of waveform shaping subunits that perform at least one of phase shifting and attenuation with respect to the plurality of reflected power distributed by the reflected power distributor;
A reflected power combiner that combines a plurality of reflected powers output from the plurality of waveform shaping subunits;
The high-frequency power supply device according to claim 2, wherein The high-frequency power supply apparatus according to claim 1, wherein the power combining unit is configured as a lumped constant circuit. A first switch that switches between a first state in which the high-frequency power source is connected to the power combiner and a second state in which the high-frequency power source is connected to the circulator;
A resistive load disposed between the detection unit and the ground potential;
A second switch for switching between a third state in which the detection unit is connected to the waveform shaping unit and a fourth state in which the detection unit is connected to the resistive load;
The high-frequency power supply device according to claim 3, further comprising: The apparatus further includes a matching unit disposed between the circulator and the variable load, having a matching condition in which the reflected power that enables the power combiner to operate is supplied from the variable load to the circulator. The high-frequency power supply device according to any one of claims 1 to 9. A high-frequency power supply device according to any one of claims 1 to 10,
A vacuum chamber;
A shower plate disposed in the vacuum chamber, functioning as a first electrode to which power is supplied from the high-frequency power supply device, and supplying a plasma generation gas to a substrate to be processed;
A stage that is disposed in the vacuum chamber and functions as a second electrode on which the substrate to be processed is placed;
A plasma processing apparatus comprising: A method for producing a semiconductor thin film, comprising: forming a semiconductor thin film on a substrate to be processed using the plasma processing apparatus according to claim 11.

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