JP6009931B2 - High frequency power supply - Google Patents

Description

  The present invention relates to a high frequency power supply apparatus that supplies high frequency power to a load such as a plasma processing apparatus.

  When plasma processing such as etching of a semiconductor is performed, as shown in FIG. 8, a high frequency power supply device 1 that converts an AC input at a commercial frequency into a high frequency output is provided, and the output of the high frequency power supply device 1 is converted into an impedance matching device. 2 is supplied to the plasma processing apparatus (load) 3.

  For example, as shown in FIG. 9, the high-frequency power supply 1 includes a variable DC power supply 11, a power amplifier 12 including a switching amplifier that operates using the output of the variable DC power supply 11 as a power supply, and a high-frequency signal having a fundamental frequency of high-frequency power A high-frequency oscillator 13 for generating power, a driver 14 for driving the power amplifier 12 with a high-frequency signal output from the high-frequency oscillator 13 in order to amplify the high-frequency signal and output high-frequency power from the power amplifier 12, A low-pass filter 15 that removes harmonic components from the output; a high-frequency power output terminal 1a that outputs high-frequency power that has passed through the low-pass filter toward the load; a traveling wave that is supplied to the load through the high-frequency power output terminal 1a; And a traveling wave power detection signal Pf and a reflected power detection signal are detected. The variable DC power source 11 is inputted with the power detector 16 that outputs r, the traveling wave power detection signal Pf and the reflected power detection signal Pr, the traveling wave power setting signal PS, and the reflected power protection level setting signal Pr-S. It is comprised by the control part 17 which controls.

  The variable DC power source 11 includes, for example, a rectifier circuit that rectifies an AC input at a commercial frequency, an inverter that converts the DC output of the rectifier circuit into an AC output, and a rectifier / smoothing circuit that rectifies and smoothes the output of the inverter. Therefore, the AC power of the inverter is PWM controlled to output DC power whose level is adjusted.

  The switching amplifier constituting the power amplifier 12 is constituted by a full bridge type inverter in which the output of the variable DC power source 11 is applied to the DC input terminal, for example. The driver 14 gives a drive signal to the control terminal of the switch element of each arm of the inverter constituting the switching amplifier according to the high-frequency signal output from the high-frequency oscillating unit 13, and turns on / off the switch element of the inverter according to the high-frequency signal. As a result, the power amplifier 12 outputs high-frequency power with the frequency of the high-frequency signal output from the high-frequency oscillator 13 as the fundamental frequency. In this case, the level of the high frequency power is controlled by controlling the output of the variable DC power supply 11.

  The control unit 17 compares the traveling wave power setting signal PS with the traveling wave power detection signal Pf, and adjusts the traveling wave power detection signal Pf output from the power detector 16 to be equal to the traveling wave power setting signal PS. While performing steady state output control for controlling the output of the amplifier, the reflected power detection signal Pr is compared with the reflected power protection level setting signal Pr-S, and the reflected power detection signal Pr exceeds the protection level setting signal Pr-S. When the reflected power exceeds the protection level, the output of the power amplifier 12 is suppressed, and the output of the power amplifier is controlled so that the reflected power detection signal Pr is equal to the protection level setting signal Pr-S. Perform protection control. The control unit 17 also performs on / off of the output of the driver 14, adjustment of the amplitude of the output of the driver 14, and the like. This type of high-frequency power supply is disclosed in Patent Document 1, for example.

  In the above example, a switching amplifier is used as the power amplifier 12 that converts DC power into high-frequency power. However, as shown in Patent Document 2, the output of the DC power source is used as the power source and the output of the high-frequency oscillation unit is used. A power amplifier may be configured by a linear amplifier that amplifies power. FIG. 10 shows a configuration example of the high-frequency power supply device 1 using a power amplifier composed of a linear amplifier. This high frequency power supply device 1 generates a high frequency signal having a fundamental frequency of a high frequency output, a DC power source 21 that outputs a constant DC voltage, a power amplifier 22 that is a linear amplifier that operates using the output of the DC power source 21 as a power source. Passes through the high-frequency oscillator 23, the preamplifier 24 that amplifies the high-frequency signal output from the high-frequency oscillator 23, and inputs it to the power amplifier 22, the low-pass filter 25 that removes harmonic components from the output of the power amplifier 22, and the low-pass filter The high frequency power output terminal 1a for outputting the high frequency power directed to the load, the traveling wave power supplied to the load through the high frequency power output terminal 1a, and the reflected power returning from the load side to the high frequency power output terminal 1a are detected. A power detector 26 for outputting a traveling wave power detection signal Pf and a reflected power detection signal Pr, and a traveling wave power detection The preamplifier 24 is controlled with the signal Pf, the reflected power detection signal Pr, the traveling wave power setting signal PS, and the reflected power protection level setting signal Pr-S as inputs, and the output voltage of the DC power supply unit 21 is kept constant. And a control unit 27 for controlling the above. The control unit 27 protects the reflected power detection signal Pr and the steady-state output control that controls the output of the power amplifier so that the traveling wave power detection signal Pf output from the power detector 26 is equal to the traveling wave power setting signal PS. When the level setting signal Pr-S is exceeded, the output of the power amplifier 22 is suppressed, and protection control is performed to control the power amplifier so that the reflected power detection signal Pr is equal to the protection level setting signal Pr-S. . The control unit 27 shown in FIG. 10 also performs on / off of the output of the DC power supply 21, adjustment of the output level of the DC power supply 21, and the like.

  The high-frequency power supply device shown in FIGS. 9 and 10 has substantially the same configuration of each main part, except that the power amplifier is configured by a switching amplifier or a linear amplifier. . For example, the control units 17 and 27 used in this type of high-frequency power supply device are configured as shown in FIG.

  The control unit shown in FIG. 11 is configured so that the reflected power is set and the steady-state output control means 31 that controls the power amplifier 12 or 22 so as to keep the traveling wave power at the set level at the steady state when the reflected power is equal to or lower than the protection level. Reflected power protection means 32 for controlling the power amplifier 12 or 22 so that the reflected power is kept at the protection level when the protection level is exceeded, DC current output from the DC power supply, DC voltage, and high-frequency current supplied to the load And other factor protection means 33 for controlling the power amplifier so that the other factor is kept at the protection level when other factors such as loss caused by the power amplifier exceed the protection level.

  At regular times (when the reflected power is below the set protection level), only the steady-state output control means 31 operates. Here, the protection level is a level set below the maximum level of reflected power that can be operated without damaging the power amplifier, and the power amplifier is damaged if the reflected power is below this protection level. It can operate without

  The constant power control means 31 compares the traveling wave power setting signal PS and the traveling wave power detection signal Pf, and controls the control signal P-CNT so that the values of both are equal (the variable DC power supply 11 or the preamplifier). 24). The controlled object (variable DC power supply 11 or preamplifier 24) changes its output in accordance with the control signal P-CNT so that the traveling wave power setting signal PS is equal to the traveling wave power detection signal Pf. Adjust the high frequency output.

  Protection in which the impedance of the load suddenly changes and impedance matching between the impedances of the high frequency power supply device and the load cannot be achieved by the impedance matching unit 2 and the reflected power returning from the load side to the high frequency power supply device side is set. When it becomes larger than the level, the reflected power protection means 32 operates.

  The reflected power protection means 32 compares the reflected power detection signal Pr with the reflected power protection level setting signal Pr-S, and the level of the reflected power detection signal Pr is higher than the level of the reflected power protection level setting signal Pr-S. When it becomes larger, the control signal P-Pr (LMT) is given to the steady-state output control means 31 so that both values are equal. At this time, the steady-state output control means 31 changes the control signal P-CNT according to the control signal P-Pr (LMT) so that the reflected power detection signal Pr becomes equal to the reflected power protection level setting signal Pr-S. In addition, the high frequency output of the high frequency power supply device is adjusted (restricted).

  Further, when other factors such as a direct current output from the direct current power source, a direct current voltage, a high frequency current supplied to the load, and a loss generated in the high frequency power supply device exceed a protection level, the other factor protection means 33 operates. The other factor protection means 33 compares the other factor detection signal Other-D for detecting the level of each other factor with another factor protection level setting signal that gives a protection level set for each other factor. When the level of each other factor detection signal exceeds the level of the set other factor protection level setting signal, the control signal P-other (LMT) is set so that the other factor becomes equal to the protection level. ) To the steady-state output control means 31. At this time, the steady-state output control means 31 changes the control signal P-CNT in accordance with the control signal P-other (LMT) to change each other factor detection signal other-D to another factor protection level setting signal other- Adjust (limit) the high-frequency output of the high-frequency power supply device to be equal to S.

In FIG. 11, the other factor protection means 33 is represented as one block, but this protection means is provided for each of other factors to be protected. “Loss” to be protected as another factor is obtained from the following equation.
Loss = (DC voltage × DC current + reflected power Pr) −traveling wave power Pf (1)

JP 2003-143861 A Japanese Patent Laid-Open No. 61-16314

  The operation of the power amplifier when supplying high-frequency power from the high-frequency power supply to a load that does not match the impedance of the output impedance of the high-frequency power supply (unmatched load) Side impedance). Even if the reflected power is the same (even if the reflection coefficient is the same), if the phase is different, the operation of the power amplifier (switching amplifier or linear amplifier) is different, and the components of the amplifier such as a MOSFET Loss, voltage applied to the component, and current flowing through the component are different. This is especially true when switching amplifiers are used as power amplifiers.If the load is close to a short circuit, or if the load impedance is capacitive, there is no impedance mismatch or the load impedance is Compared to the inductive case, the loss is greatly increased.

  For this reason, in the conventional high-frequency power supply device, the reflection power protection level setting signal Pr-S is determined assuming the worst load condition that can be expected. As a result, depending on the phase of the load impedance, the high-frequency output may be suppressed and the high-frequency power supplied to the load may be insufficient even though there is room in the usage state of the components of the high-frequency power supply device. It was. Especially when the load is a plasma load, the plasma may become unstable during processing and its impedance may become unstable, and the output of the high-frequency power supply device is suppressed when the impedance of the plasma load is unstable. As a result, the plasma becomes more unstable, and in some cases, the plasma may disappear.

  In general, an impedance matching unit 2 for automatically matching impedance as shown in FIG. 8 is installed between the high frequency power supply device for generating plasma and the plasma load. The high-frequency power supply device operates in a state where it is not in a period of several hundreds msec to several seconds from when the plasma is generated until the impedance matching device 2 performs the matching operation, and abnormal discharge occurs in the process processing device, etc. It was when the load condition suddenly changed. However, in recent semiconductor processing apparatuses, a complicated process is performed in which high-frequency power having different frequencies is superimposed and supplied to a load (process chamber), or pulse-modulated high-frequency power is supplied to the load. The matching unit 2 cannot perfectly match the impedance, and the high frequency power supply device is often operated in a state where the impedance matching with the load is not achieved (in a mismatched state). Therefore, recently, there is a need for a high-frequency power supply device that can output a sufficient high-frequency power even when the reflection resistance is large and impedance matching with the load is not achieved.

  In addition, the control system (control unit) of the high-frequency power supply device made the control response faster and the control gain was set high, so that the impedance when the load amplifier viewed from the power amplifier became capacitive or short-circuited In some cases, the control tends to become unstable. By reducing the control response and gain, it is possible to stabilize the control operation regardless of whether the impedance seen from the power amplifier is capacitive, inductive, short-circuited, or open. If the responsiveness or gain is reduced, not only the control with good sensitivity cannot be performed, but also the output value cannot be quickly converged to the target value, so that the controllability is inevitably deteriorated. If the load fluctuation range can be narrowed from the matched load to the inductive load range, control can be stabilized without degrading responsiveness and gain, but it may become unstable like a plasma load. When supplying high frequency power to a certain load, it is difficult to narrow the load fluctuation range from the matched load to the inductive load range.

  An object of the present invention is to provide a high-frequency output capable of obtaining a high-frequency output close to the performance limit of the apparatus without excessively suppressing the high-frequency output even when the reflection resistance is large and impedance matching with the load is not achieved. It is to provide a power supply device.

  Another object of the present invention is not only to obtain a high frequency output close to the performance limit of the apparatus without excessively suppressing the high frequency output, but also to speed up the response of the control system and set the control gain high. An object of the present invention is to provide a high-frequency power supply device that can perform the above-mentioned.

  The present invention relates to a power amplifier that amplifies a high-frequency signal and outputs high-frequency power, a low-pass filter that removes harmonic components from the output of the power amplifier, and high-frequency power that outputs high-frequency power that has passed through the low-pass filter toward a load. A power detector for detecting the output terminal, the traveling wave power supplied to the load through the high frequency power output terminal and the reflected power returning from the load side to the high frequency power output terminal, and the traveling wave power detected by the power detector And a high-frequency power supply device including a control unit that controls the output of the power amplifier according to the reflected power.

  In the present invention, provided between the output terminal of the power amplifier and the high frequency power output terminal, the impedance phase viewed from the output terminal of the power amplifier viewed from the load side is the impedance phase viewed from the high frequency power output terminal. The first circuit configuration having the characteristic of rotating approximately 180 degrees with respect to the phase, and the impedance phase viewed from the output end of the power amplifier and the impedance phase viewed from the high frequency power output terminal are approximately A phase converter configured to take a second circuit configuration having the same characteristics; a switch circuit that switches the circuit configuration of the phase converter to the first circuit configuration and the second circuit configuration; A reflection coefficient calculation unit for calculating the magnitude of the reflection coefficient Γ and the phase angle θ at the position of the high frequency power output terminal from the traveling wave power and the reflected power detected by the power detector And determining the state of the impedance viewed from the high frequency power output terminal from the reflection coefficient calculated by the reflection coefficient calculation unit so that the impedance viewed from the output end of the power amplifier is always inductive. And a switch control unit for controlling the switch circuit.

  In the present specification and claims, it is assumed that the phase of the impedance viewed from the output end of the power amplifier is rotated by “approximately 180 degrees” with respect to the phase of the impedance viewed from the high frequency power output terminal. The impedance phase seen from the output side of the power amplifier as viewed from the load side and the impedance phase seen from the high frequency power output terminal as viewed from the load side are said to be “substantially the same”. And the resistance component, stray inductance, and stray capacitance of the inductor cannot be made zero, and the impedance phase seen from the output side of the power amplifier and the impedance phase seen from the high frequency power output terminal This is because even if the difference is 180 degrees or 0 degrees in theory, this may not be the case. .

  If comprised as mentioned above, the impedance which looked at the load side from the output terminal of power amplifier can always be made to look inductive. With this configuration, loss generated in the power amplifier can be reduced, so the protection level of reflected power (maximum allowable reflected power) is assumed under the worst possible load conditions that can be expected. There is no need to set, and there is no need to suppress the high frequency output more than necessary. Therefore, even when high-frequency power is supplied to the mismatched load, it is possible to obtain a high-frequency output close to the performance limit of the device without increasing the reflection tolerance and excessively suppressing the high-frequency output.

  In addition, if the impedance seen from the output side of the power amplifier as viewed from the load side is always inductive as described above, stable control operation can be achieved even if the control system response is accelerated or the control gain is increased. Therefore, it is possible to cause the control unit to perform a control operation that is more responsive and stable than the conventional one.

  The switch controller determines from the reflection coefficient whether the impedance viewed from the high frequency power output terminal is inductive, capacitive, short-circuited, or open, and the impedance is capacitive or Switch circuit so that the circuit configuration of the phase conversion unit is the first circuit configuration when in the short circuit state, and the circuit configuration of the phase conversion unit is the second circuit configuration when the impedance is inductive or open state It is preferable to control the above.

  In a preferred aspect of the present invention, the low-pass filter has a characteristic of rotating the phase of the impedance viewed from the input end to the load side by approximately 180 degrees with respect to the phase of the impedance viewed from the output end to the load side. The low-pass filter (λ is the wavelength of the high-frequency voltage output from the power amplifier) can be configured, and the low-pass filter also serves as a phase converter. In this case, the switch circuit uses the first circuit configuration to enable the odd number of λ / 4 low-pass filters connected in cascade, and enables the even number of λ / 4 low-pass filters connected in cascade. The circuit configuration to be used is the second circuit configuration, and the circuit configuration of the low-pass filter is switched.

  Since the λ / 4 type low-pass filter has a characteristic of rotating the phase of the impedance viewed from the input end to the load side by approximately 180 degrees with respect to the phase of the impedance viewed from the output end to the load side, It can be used as a phase conversion element that rotates the phase of the impedance approximately 180 degrees with the output end. When an odd number of λ / 4 low-pass filters connected in cascade are enabled in the low-pass filter, the impedance phase viewed from the input end of the load side is compared to the impedance phase viewed from the output end of the load side. When an even number of λ / 4 low-pass filters connected in cascade can be rotated approximately 180 degrees, the impedance phase viewed from the input end to the load side is changed to the impedance phase viewed from the output end to the load side. The phase can be substantially the same. As described above, when the low-pass filter, which is an essential component of the high-frequency power supply device, is also used as the phase conversion unit, the configuration of the device can be simplified.

  When the low-pass filter is also used as the phase conversion unit as described above, the circuit configuration of the low-pass filter can be a circuit configuration that can form a two-stage λ / 4-type π-type low-pass filter. In this case, the switch circuit for switching the circuit configuration of the low-pass filter enables only the one-stage λ / 4-type T-type low-pass filter by separating part of the elements constituting the two-stage π-type low-pass filter. The circuit configuration of the low-pass filter is switched with the first circuit configuration as the first circuit configuration and the circuit configuration in which the two-stage π-type low-pass filter is enabled as the second circuit configuration.

  Further, when the low-pass filter is constituted by a two-stage λ / 4-type π-type low-pass filter as described above, the switch circuit has a circuit configuration in which only one of the two-stage π-type low-pass filters is made effective as the first circuit. A circuit configuration in which both of the two-stage π-type low-pass filters are enabled may be configured as a second circuit configuration so that the circuit configuration of the low-pass filter is switched.

  When the low-pass filter is also used as the phase conversion unit as described above, the low-pass filter may have a circuit configuration that can form a two-stage λ / 4-type T-type low-pass filter. In this case, the switch circuit has a circuit configuration in which only one of the two-stage T-type low-pass filters is enabled as the first circuit configuration, and a circuit configuration in which both of the two-stage T-type low-pass filters are enabled is the second circuit configuration. As a circuit configuration, the circuit configuration of the low-pass filter is switched.

  The phase conversion unit can also be configured by a plurality of lines (1/4 wavelength lines) having a length of 1/4 of the wavelength of the high frequency voltage output from the power amplifier.

  The switch circuit for switching the circuit configuration of the phase conversion unit is preferably configured by a vacuum switch or a pin diode switch.

  As described above, according to the present invention, since the impedance viewed from the output side of the power amplifier as viewed from the load side is always inductive, it is possible to reduce the loss generated in the power amplifier. Therefore, according to the present invention, it is not necessary to set the protection level of the reflected power assuming the worst possible load condition, and it is not necessary to suppress the high frequency output more than necessary. Even when power is supplied, a high-frequency output close to the performance limit of the apparatus can be obtained without increasing the reflection resistance and excessively suppressing the high-frequency output. In addition, according to the present invention, since the impedance viewed from the output side of the power amplifier is always inductive, stable control can be achieved even if the control system response is increased or the control gain is increased. The action can be performed. Therefore, it is possible to cause the control unit to perform a control operation that is more responsive and stable than the conventional one.

  In particular, according to the invention described in claims 3 to 6, since the low-pass filter, which is an essential component of the high-frequency power supply device, is used as the phase conversion unit, the configuration of the device can be simplified. .

It is the block diagram which showed the structure of embodiment of this invention. FIG. 2 is a circuit configuration diagram specifically showing a low-pass filter portion of FIG. 1. FIG. 6 is a circuit configuration diagram showing another specific configuration example of the low-pass filter portion of FIG. 1. FIG. 6 is a circuit configuration diagram showing still another specific configuration example of the low-pass filter portion of FIG. 1. FIG. 6 is a circuit configuration diagram showing still another specific configuration example of the low-pass filter portion of FIG. 1. It is the block diagram which showed the structure of other embodiment of this invention. It is the block diagram which showed the structure of the principal part of other embodiment of this invention. It is the block diagram which showed the structural example of the circuit which supplies high frequency electric power to load from a high frequency power supply device. It is the block diagram which showed the structural example of the conventional high frequency power supply device. It is the block diagram which showed the other structural example of the other conventional high frequency power supply device. It is the block diagram which showed the structural example of the control part of the conventional high frequency power supply device.

  Embodiments of a high-frequency power supply device according to the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of a high frequency power supply device according to the present invention. In the figure, reference numeral 11 is a DC-DC converter or the like, which is a variable DC power supply that outputs DC power in a form that can be adjusted in size, 12 is a power amplifier that operates using the variable DC power supply 11 as a power supply, and 13 is a load. A high-frequency oscillating unit that generates a high-frequency signal having a fundamental frequency of the high-frequency power to be supplied, and a driver that drives the power amplifier 12 according to the high-frequency signal output from the high-frequency oscillating unit 13 in order to output high-frequency power from the power amplifier 12 It is.

  The power amplifier 12 used in the present embodiment is configured by a full-bridge inverter in which each arm of the bridge is configured by a parallel circuit of a switch element and a feedback diode, and the output of the variable DC power supply 11 is applied to a DC input terminal. The switching element of the bridge is driven by the output of the high frequency oscillating unit 13 via the driver 14 to amplify the high frequency signal output from the high frequency oscillating unit 13 and thereby generate high frequency power. Is output.

  In FIG. 1, 15 is a low-pass filter that removes harmonic components from the output of the power amplifier 12 and supplies it to the high-frequency power output terminal 1a, and 16 is a directional coupler, from the high-frequency power that has passed through the low-pass filter 15. The traveling wave supplied to the load and the reflected wave returning from the load side are detected, and the traveling wave voltage detection signal Vf and the traveling wave power detection signal Pf, and the reflected voltage detection signal Vr and the reflected power detection signal Pr are obtained. Output power detector. Reference numeral 17 denotes a variable DC power supply 11 using the traveling wave power detection signal Pf and the reflected power detection signal Pr output from the power detector 16, the traveling wave power setting signal PS, and the reflected power protection level setting signal Pr-S as inputs. And a control unit for controlling the driver 14.

  The control unit 17 compares the traveling wave power setting signal PS with the traveling wave power detection signal Pf, and adjusts the traveling wave power detection signal Pf output from the power detector 16 to be equal to the traveling wave power setting signal PS. While performing steady state output control for controlling the output of the amplifier, the reflected power detection signal Pr is compared with the reflected power protection level setting signal Pr-S, and the reflected power detection signal Pr exceeds the protection level setting signal Pr-S. When the reflected power exceeds the protection level, the output of the power amplifier 12 is suppressed, and the output of the power amplifier is controlled so that the reflected power detection signal Pr is equal to the protection level setting signal Pr-S. Perform protection control. The control unit 17 also performs on / off of the output of the driver 14, adjustment of the amplitude of the output of the driver 14, and the like. Similarly to the example shown in FIG. 11, the control unit 17 includes a steady-state output control unit 31 that controls the power amplifier 12 so that the traveling wave power is maintained at a set level during the steady state where the reflected power is equal to or lower than the protection level, and the reflected power. Reflected power protection means 32 for controlling the power amplifier 12 so as to keep the reflected power at the protection level when the value exceeds the set protection level, the DC current output from the DC power supply, the DC voltage, and the high frequency supplied to the load. When other factors such as current and loss generated in the power amplifier exceed the protection level, other factor protection means 33 that controls the power amplifier 12 so as to keep the other factor at the protection level.

  In the present embodiment, the first characteristic is that the phase of the impedance viewed from the output end of the power amplifier 12 is rotated by approximately 180 degrees with respect to the phase of the impedance viewed from the high frequency power output terminal 1a. A circuit configuration and a second circuit configuration having characteristics that make the phase of the impedance viewed from the output end of the power amplifier 12 substantially the same as the phase of the impedance viewed from the high-frequency power output terminal 1a. A phase conversion unit configured to be able to be provided is provided between the output terminal of the power amplifier 12 and the high frequency power output terminal 1a, and the circuit configuration of the phase conversion unit is changed to the first circuit configuration and the second circuit configuration. A switch circuit 18 for switching is provided, and the switch circuit 18 is controlled according to the state of impedance when the load side is viewed from the high-frequency power output terminal 1a. More, the impedance viewed load side from the output terminal of the power amplifier 12 is always visible to the inductive.

  In the present embodiment, the low-pass filter 15 also serves as a phase converter, and the switch circuit 18 switches the circuit configuration of the low-pass filter between the first circuit configuration and the second circuit configuration to change the electrical length. Thus, the state in which the phase of the impedance seen from the output end of the power amplifier 12 is rotated about 180 degrees with respect to the phase of the impedance seen from the high-frequency power output terminal 1a and the load side, and the output end of the power amplifier 12 The impedance phase viewed from the load side is switched to the state where the phase of the impedance viewed from the high-frequency power output terminal 1a is substantially the same as the impedance phase viewed from the load side.

  For this reason, in this embodiment, the low-pass filter 15 has a circuit configuration capable of forming a plurality of λ / 4 type low-pass filters (λ is the wavelength of the high-frequency voltage output from the power amplifier), and is cascade-connected. The first circuit configuration that enables the odd number of λ / 4 low-pass filters and the second circuit configuration that enables the even number of λ / 4 low-pass filters connected in cascade The switch circuit 18 is configured to switch the circuit configuration of the low-pass filter 15 between the first circuit configuration and the second circuit configuration.

  The λ / 4 type low-pass filter is a filter having a characteristic in which the phase of impedance viewed from the input end viewed from the load side is rotated by approximately 180 degrees with respect to the phase of impedance viewed from the output end viewed from the load side. When a circuit in which a plurality of λ / 4 low-pass filters are cascade-connected (assuming the first circuit configuration), the impedance phase viewed from the input end to the load side is changed to the impedance phase viewed from the output end to the load side. On the other hand, a low-pass filter having a characteristic of rotating about 180 degrees can be configured. In addition, when a circuit in which an even number of λ / 4 low-pass filters are cascade-connected is configured (assuming a second circuit configuration), the impedance phase viewed from the input end to the load side is the impedance phase viewed from the output end to the load side. A low-pass filter having characteristics that are substantially the same in phase can be configured. As the number of stages in which the λ / 4 type low-pass filter is cascade-connected is increased, the attenuation amount of the harmonic can be increased.

In the present embodiment, in order to determine the state of impedance when the load side is viewed from the high frequency power output terminal 1a, the traveling wave voltage detection signal Vf and the reflected voltage detection signal Vr output from the power detector 16 are used as a reflection coefficient calculation unit. (Γ / θ calculation unit) 19 is input to calculate the magnitude and phase angle θ of the reflection coefficient Γ at the position of the high-frequency power output terminal 1a, and from the reflection coefficient Γ calculated by the reflection coefficient calculation unit 19, It is determined whether the impedance when the load side is viewed from the high frequency power output terminal 1a is inductive, capacitive, short-circuited or open. The reflection coefficient Γ can be obtained by the following equation (2) from the traveling wave voltage detection signal Vf and the reflection voltage detection signal Vr.
Γ = Vr / Vf = (| Vr | / | Vf |) ∠θ (2)

  When the phase angle θ is positive, the reflection coefficient calculation unit 19 determines that the impedance viewed from the high frequency power output terminal 1a is inductive, and when the phase angle θ is negative, the high frequency power It is determined that the impedance when the load side is viewed from the output terminal 1a is capacitive.

  In the present embodiment, the load-side impedance (high-frequency power) determined from the reflection coefficient Γ calculated by the reflection coefficient calculation unit 19 is set so that the impedance viewed from the output end of the power amplifier 12 is always inductive. A switch control unit 20 is provided for controlling the switch circuit 18 in accordance with the state of the impedance when viewing the load side from the output terminal 1a.

  The switch control unit 20 sets the circuit configuration of the phase conversion unit (low-pass filter) as the first circuit configuration when the impedance on the load side of the high-frequency power output terminal 1a is capacitive or short-circuited, and the high-frequency power By controlling the switch circuit 18 so that the circuit configuration of the phase converter is the second circuit configuration when the impedance on the load side of the output terminal 1a is inductive or open, the power amplifier 12 The circuit configuration of the low-pass filter 15 is switched so that the impedance viewed from the output end is always inductive.

  Referring to FIG. 2, an example of the circuit configuration of the low-pass filter 15 and the switch circuit 18 is shown. The low-pass filter 15 shown in FIG. 2 includes capacitors C1 to C4 and inductors L1 and L2 as reactance elements that constitute a low-pass filter. The inductors L1 and L2 and the capacitor C4 form a λ / 4 type T A state in which a low-pass filter is formed (first circuit configuration), a first λ / 4-type π-type low-pass filter F1 including a capacitor C1, an inductor L1, and a capacitor C4, a capacitor C2, an inductor L2, and a capacitor C3. The second λ / 4-type π-type low-pass filter F2 is connected in cascade to form a two-stage filter circuit (second circuit configuration).

  The illustrated switch circuit 18 includes switches SW1 and SW2 for turning on and off the capacitors C1 and C2 (enabling and disabling the capacitors C1 and C2 as components of the filter) and a switch SW3 for turning on and off the capacitor C3. When all of the switches SW3 are turned off, the low-pass filter 15 is set to a first circuit state in which a λ / 4 type T-type low-pass filter including inductors L1 and L2 and a capacitor C4 is configured, and the switches SW1 to SW3 Are all turned on, the low-pass filter 15 is a second circuit in which a first λ / 4-type π-type low-pass filter F1 and a second λ / 4-type π-type low-pass filter F2 are cascaded. It is supposed to be configured.

  When the switch control unit 20 determines from the reflection coefficient calculated by the reflection coefficient calculation unit 19 that the impedance viewed from the high-frequency power output terminal 1a is capacitive or short-circuited, the switch SW1 By turning off SW3, only the inductors L1 and L2 and the capacitor C4 are made effective as low-pass filter components, and the low-pass filter 15 functions as a λ / 4-type T-type low-pass filter (of the low-pass filter 15). From the reflection coefficient calculated by the reflection coefficient calculation unit 19 to the reflection coefficient calculated by the reflection coefficient calculation unit 19, the impedance when the load side is viewed from the high-frequency power output terminal 1a is determined. When it is determined that it is inductive or open, the switches SW1 to SW3 are turned on. By (the circuit configuration of the low-pass filter 15 and the second circuit configuration) to function the low-pass filter 15 as a low-pass filter of two-stage configuration of the lambda / 4 form the π form low-pass filters F1 and F2 connected in cascade.

  The switches SW1 to SW3 constituting the switch circuit 18 are preferably constituted by vacuum switches or pin diodes.

  FIG. 3 shows a configuration example of the switch control circuit 20 provided for each of the switches SW1 to SW3 when the switches SW1 to SW3 are configured by pin diodes D1 to D3, respectively. 3 includes a PNP transistor Q11 in which the emitter is grounded through a resistor R11 and the resistor R12 is connected between the collector and the base, and a DC voltage -Va is applied to the collector from the power source Ba. Is connected to the base of the transistor Q11 through the resistor R13, the base is connected to the output terminal of the reflection coefficient calculation unit 19 through the resistor R14, and the PNP transistor Q12 in which the DC voltage Vb is applied from the power source Bb to the emitter, The diode D11 is connected between the base emitters with the anode facing the base side, the capacitor C11 is connected between the emitter of the transistor Q11 and the ground, and the inductor L11 has one end connected to the emitter of the transistor Q11. , Inductor L 1 of the other end is connected to the anode of the PIN diode D3. In FIG. 3, only the configuration of the switch control circuit 20 provided for the switch SW3 is specifically shown. However, the switch control circuit 20 provided for the other switches SW1 and SW2 is configured similarly. A voltage signal is given from the reflection coefficient calculation unit 19 to the base of the transistor Q12 of each switch control circuit 20 through the resistor R14. The other ends of the inductors L11 of the switch control circuit 20 provided for the switches SW1 and SW2, respectively, are connected to the anodes of the pin diodes D1 and D2 constituting the switches SW1 and SW2, respectively.

  In this example, when the impedance when the load side is viewed from the high frequency power output terminal 1a is capacitive or short-circuited, the reflection coefficient calculation unit 19 sets the potential of the output terminal to H level (high level), and switches The transistor Q12 of the switch control circuit 20 provided for each of SW1 to SW3 is turned off, and the transistor Q11 is turned on. At this time, since a reverse bias voltage is applied from the power source Ba to the pin diodes D1 to D3 through the inductor L11 and the transistor Q11 of the switch control circuit 20 provided for the switches SW1 to SW3, respectively, the pin diodes D1 to D3 Is turned off, disabling capacitors C1-C3. As a result, the low-pass filter 15 enters the first circuit state (a state in which the inductors L1 and L2 and the capacitor C4 constitute a one-stage λ / 4 type T-type low-pass filter), and the load side is viewed from the power amplifier 12. The phase angle of the impedance is 180 degrees different from the phase angle of the impedance when the load side is viewed from the high frequency output terminal 1a, and the impedance when the load side is viewed from the power amplifier 12 is inductive.

  When the impedance viewed from the high frequency power output terminal 1a when viewed from the load side is inductive or open, the reflection coefficient calculation unit 19 sets the potential of the output terminal to L level (ground potential), and switches SW1 to SW3. On the other hand, the transistor Q12 of the switch control circuit 20 provided for each is turned on, and the transistor Q11 is turned off. At this time, a forward voltage is applied to the pin diodes D1 to D3 from the power source Bb of the switch control circuit 20 provided for the switches SW1 to SW3 through the transistor Q12, the resistor R13, the diode D11, and the inkter L11. The diodes D1 to D3 are turned on. At this time, since the low-pass filter 15 is in the second circuit state (a state in which the capacitors C1 to C4 and the inductors L1 and L2 form a two-stage λ / 4 type π-type low-pass filter), The phase angle of the impedance viewed from the side becomes substantially the same as the phase angle of the impedance viewed from the high frequency output terminal 1a, and the impedance viewed from the power amplifier 12 becomes inductive.

  In the above embodiment, the low-pass filter 15 is configured so that a two-stage λ / 4-type π-type low-pass filter can be configured, and a one-stage λ / 4-type T-type low-pass filter is configured (first stage). The switch circuit 18 is configured so that it can be switched between a state (1 circuit state) and a state (second circuit state) constituting a two-stage λ / 4 type π-type low-pass filter, as shown in FIG. As described above, the low-pass filter 15 is configured so that the two-stage λ / 4-type π-type low-pass filter F1 and F2 can be configured, and only the one-stage λ / 4-type π-type low-pass filter F1 is enabled. The switch circuit 18 is configured to switch between the state (first circuit state) and the state (second circuit state) in which the cascaded two-stage λ / 4 type π-type low-pass filters F1 and F2 are enabled. You can also In the example shown in FIG. 4, the switch SW1 inserted between the output terminal of the power amplifier 12 and the filter F1, the switch SW2 provided to turn on and off between the filters F1 and F2, and the power amplifier 12 The switch circuit 15 is composed of the switch SW3 inserted between the output terminal of the filter and the filter F3.

  In the example shown in FIG. 4, when the impedance viewed from the high-frequency power output terminal 1a is capacitive or short-circuited, the switch controller 20 turns on the switch SW1 and turns off the switches SW2 and SW3. To. At this time, only the one-stage λ / 4-type π-type low-pass filter F1 is effective (the low-pass filter 15 is in the first circuit state), so that the phase angle of the impedance viewed from the power amplifier 12 on the load side is high frequency. The state is 180 degrees different from the phase angle of the impedance when the load side is viewed from the output terminal 1a, and the impedance when the load side is viewed from the power amplifier 12 is inductive.

  When the impedance viewed from the high-frequency power output terminal 1a when viewed from the load side is inductive or open, the switch control unit 20 turns off the switch SW1 and turns on the switches SW2 and SW3. At this time, since the cascaded two-stage λ / 4 type π-type low-pass filters F1 and F2 are effective (the low-pass filter 15 is in the second circuit state), the impedance when the load side is viewed from the power amplifier 12 Is substantially the same as the phase angle of the impedance when the load side is viewed from the high-frequency output terminal 1a, and the impedance when the load side is viewed from the power amplifier 12 is also inductive.

  In each of the embodiments described above, the low-pass filter 15 has a circuit configuration that can form the two-stage λ / 4-type π-type low-pass filters F1 and F2. The low-pass filter 15 is configured as shown in FIG. In addition, a λ / 4 T-type low-pass filter F1 ′ composed of inductors L1 and L2 and a capacitor C1 and a λ / 4 T-type low-pass filter F2 ′ composed of inductors L3 and L4 and a capacitor C2 can be configured. It may be. Also in this case, by configuring the switch circuit 18 in the same manner as the example shown in FIG. 4, the circuit configuration of the low-pass filter 15 is such that only the low-pass filter F1 ′ is enabled and two cascaded low-pass filters are connected. The filters F1 'and F2' can be switched to a valid state.

  In each of the above embodiments, the low-pass filter 15 has a characteristic of rotating the phase of the impedance viewed from the input end to the load side by approximately 180 degrees with respect to the phase of the impedance viewed from the output end to the load side. Although the circuit configuration capable of configuring two low-pass filters is provided, the low-pass filter has a circuit configuration capable of configuring three or more λ / 4 low-pass filters, so that an odd number of λ / s connected in cascade is provided. The circuit configuration of the low-pass filter is a circuit configuration that enables the 4-type low-pass filter as the first circuit configuration, and the circuit configuration that enables the even number of λ / 4 low-pass filters connected in cascade is the second circuit configuration. The switch circuit 18 may be configured to switch between the first circuit configuration and the second circuit configuration. In this case, the switch controller 20 determines from the reflection coefficient calculated by the reflection coefficient calculator 19 whether the impedance viewed from the high-frequency power output terminal 1a is inductive, capacitive, short-circuited, or open. When the impedance seen from the high-frequency power output terminal 1a as viewed from the load side is capacitive or short-circuited, the circuit configuration of the low-pass filter (phase conversion unit) is the first circuit configuration, and the high-frequency power output When the impedance when the load side is viewed from the terminal 1a is inductive or in an open state, the switch circuit is controlled so that the circuit configuration of the low-pass filter is the second circuit configuration.

  In the above embodiment, the power amplifier 12 including the switching amplifier is used. However, as illustrated in FIG. 6, the power amplifier 22 including the linear amplifier that operates using the output of the DC power source 21 as the power source is used. It goes without saying that the present invention can also be applied to a configuration in which the high-frequency signal output from 13 is input to the power amplifier 22 through the preamplifier 24.

  In the example shown in FIG. 6, the output of the power amplifier 22 is output from the high frequency power output terminal 1 a through the low pass filter 25 and the power detector 26. The power detector 26 is configured to output a traveling wave voltage detection signal Vf and a reflected voltage detection signal Vr. The traveling wave voltage detection signal Vf and the reflected voltage detection signal Vr are input to the reflection coefficient calculation unit 29 and reflected. The output of the coefficient calculation unit 29 is given to the switch control unit 30. The switch control unit 30 determines whether the impedance viewed from the high frequency power output terminal 1a is inductive, capacitive, short-circuited, or open, based on the calculated reflection coefficient, and the high-frequency power output terminal When the impedance viewed from the load side from 1a is capacitive or short-circuited, the circuit configuration of the low-pass filter (phase conversion unit) 25 is the first circuit configuration, and the load side is viewed from the high-frequency power output terminal 1a. When the impedance is inductive or open, the switch circuit 28 that switches the circuit configuration of the low-pass filter 25 is controlled so that the circuit configuration of the low-pass filter (phase conversion unit) 25 is the second circuit configuration. The control unit 27 protects the reflected power detection signal Pr and the steady-state output control that controls the output of the power amplifier so that the traveling wave power detection signal Pf output from the power detector 26 is equal to the traveling wave power setting signal PS. When the level setting signal Pr-S is exceeded, the output of the power amplifier 22 is suppressed, and protection control is performed to control the power amplifier so that the reflected power detection signal Pr is equal to the protection level setting signal Pr-S. . The control unit 27 also performs on / off of the output of the DC power supply 21, adjustment of the output level of the DC power supply 21, and the like.

  In each of the above embodiments, the low-pass filter is used as the phase conversion unit, but a phase conversion unit may be provided separately from the low-pass filter. For example, as shown in FIG. 7, between the low-pass filter 15 and the power detector 16, a first quarter-wave line 41 having one end connected to the output terminal of the low-pass filter 15, and a first quarter A second quarter wavelength line 42 having one end connected to the other end of the wavelength line 41 is provided, and the other end of the first quarter wavelength line 41 and the other second quarter wavelength line 42 are provided. The end may be selectively connected to the input terminal of the power detector 16 via the switch circuit 18. The 1/4 wavelength line is a line (for example, a coaxial cable) having a length of 1/4 of the wavelength of the high-frequency voltage output from the power amplifier, and the impedance phase viewed from one end to the other end is measured from the other end. Since it has a characteristic of rotating about 180 degrees with respect to the phase of the impedance viewed from the load side, the phase of the impedance viewed from the input end to the phase of the impedance viewed from the output end to the phase of the impedance viewed from the output end It can be used as a phase conversion element having a characteristic of rotating approximately 180 degrees.

  The switch control unit 20 shown in FIG. 7 determines from the reflection coefficient calculated by the reflection coefficient calculation unit 19 whether the impedance viewed from the high frequency power output terminal 1a is capacitive or short-circuited. When it is determined that the impedance viewed from the high-frequency power output terminal 1a on the load side is capacitive or short-circuited, the other end of the first quarter wavelength line 41 is input to the power detector 16. By connecting to the end, the phase of the impedance viewed from the output end of the power amplifier 14 is rotated 180 degrees with respect to the phase of the impedance viewed from the high frequency power output terminal 1a to the power amplifier 14 The impedance when the load side is viewed from the output end of the is inductive. When it is determined from the calculated reflection coefficient that the impedance when the load side is viewed from the high frequency power output terminal 1a is inductive or in an open state, the other end of the second quarter wavelength line 42 is switched. By connecting to the input terminal of the power detector 16 through the circuit 18, the phase of the impedance viewed from the output terminal of the power amplifier 14 is almost the same as the phase of the impedance viewed from the high frequency power output terminal 1a. Thus, the impedance when the load side is viewed from the output end of the power amplifier 14 is inductive.

  In the embodiment shown in FIG. 1, the switching amplifier constituting the power amplifier 12 is a full-bridge type inverter. However, the switching amplifier constituting the power amplifier 12 may be a half-bridge type inverter or a class D A push-pull amplifier circuit that performs the operation can also be used.

  In a plasma process for manufacturing a semiconductor, the process may be stabilized by optimizing the length of a coaxial cable that connects between the high-frequency power supply device 1 and the impedance matching device 2. However, it is difficult to select an optimal cable length for all processes, and when the cable length becomes long, the loss caused by the cable and the space for arranging the cable also become a problem. Changing the cable length is nothing but changing the electrical length. Therefore, a plurality of phase conversion elements (λ / 4 type low-pass filter and ¼ wavelength line) are provided in the high-frequency power supply device to generate high-frequency power. If the number of phase conversion elements to be passed is switched, the process can be stabilized without changing the coaxial cable connecting the high-frequency power supply device 1 and the impedance matching device 2.

DESCRIPTION OF SYMBOLS 1 High frequency power supply device 2 Impedance matching device 3 Plasma processing apparatus (load)
11 Variable DC power supply 12 Power amplifier (switching amplifier)
DESCRIPTION OF SYMBOLS 13 High frequency oscillation part 14 Driver 15 Low pass filter 16 Power detector 17 Control part 18 Switch circuit 19 Reflection coefficient calculating part 20 Switch control part 21 DC power supply 22 Power amplifier (linear amplifier)
23 High Frequency Oscillator 24 Preamplifier 25 Low Pass Filter 26 Power Detector 27 Controller 28 Switch Circuit 29 Reflection Coefficient Calculator 30 Switch Controller 31 Constant Output Control Unit 32 Reflected Power Protection Unit 33 Other Factor Protection Unit

Claims (9)

A power amplifier that amplifies a high-frequency signal and outputs high-frequency power; a low-pass filter that removes harmonic components from the output of the power amplifier; and a high-frequency power output terminal that outputs high-frequency power that has passed through the low-pass filter toward a load A power detector for detecting a traveling wave power supplied to the load through the high frequency power output terminal and a reflected power returning from the load side to the high frequency power output terminal, and a traveling wave detected by the power detector In a high-frequency power supply device comprising a control unit that controls the output of the power amplifier according to power and reflected power,
Provided between the output terminal of the power amplifier and the high-frequency power output terminal, the impedance phase viewed from the output terminal of the power amplifier viewed from the load side is the impedance phase viewed from the high-frequency power output terminal to the load side A first circuit configuration having a characteristic of rotating about 180 degrees with respect to the power amplifier, and a phase of impedance viewed from the output end of the power amplifier and a phase of impedance viewed from the high frequency power output terminal. A phase converter configured to be capable of taking a second circuit configuration having substantially the same characteristics;
A switch circuit for switching the circuit configuration of the phase conversion unit between the first circuit configuration and the second circuit configuration;
A reflection coefficient calculator for calculating the magnitude of the reflection coefficient Γ and the phase angle θ at the position of the high-frequency power output terminal from the traveling wave power and the reflected power detected by the power detector;
The state of impedance viewed from the high-frequency power output terminal on the load side is determined from the reflection coefficient calculated by the reflection coefficient calculation unit, and the impedance viewed from the output end of the power amplifier is always inductive. A switch controller for controlling the switch circuit,
A high frequency power supply device comprising:   The switch controller determines from the reflection coefficient whether the impedance viewed from the high frequency power output terminal is inductive, capacitive, short-circuited, or open, and the impedance is capacitive. When the impedance is inductive or open, the circuit configuration of the phase converter is set to the second circuit configuration. The high frequency power supply device according to claim 1, wherein the switch circuit is controlled to have a circuit configuration. The low-pass filter is a λ / 4 low-pass filter having a characteristic of rotating the phase of the impedance viewed from the input end toward the load side with respect to the phase of the impedance viewed from the output end approximately 180 degrees (λ is the power A plurality of high-frequency voltage wavelengths output from the amplifier), the low-pass filter also serves as the phase converter,
The switch circuit uses the first circuit configuration as a circuit configuration that enables an odd number of λ / 4 low-pass filters connected in cascade, and enables an even number of λ / 4 low-pass filters connected in cascade. The circuit configuration is configured to switch the circuit configuration of the low-pass filter as the second circuit configuration,
The high frequency power supply device according to claim 1 or 2, wherein The low-pass filter has a circuit configuration capable of constituting a two-stage λ / 4-type π-type low-pass filter,
The switch circuit has a circuit configuration in which only a one-stage λ / 4-type T-type low-pass filter is made effective by separating a part of elements constituting the two-stage π-type low-pass filter. The circuit configuration is configured to switch the circuit configuration of the low-pass filter as the second circuit configuration with the circuit configuration in which the two-stage π-type low-pass filter is enabled,
The high frequency power supply device according to claim 3. The low-pass filter has a circuit configuration capable of constituting a two-stage λ / 4-type π-type low-pass filter,
The switch circuit has a circuit configuration in which only one of the two-stage π-type low-pass filters is enabled as the first circuit configuration, and a circuit configuration in which both of the two-stage π-type low-pass filters are enabled is the first circuit configuration. The circuit configuration of the low-pass filter is switched as the circuit configuration of 2,
The high frequency power supply device according to claim 3. The low-pass filter has a circuit configuration capable of constituting a two-stage λ / 4-type T-type low-pass filter, and the switch circuit has a circuit configuration in which only one of the two-stage T-type low-pass filter is validated. The first circuit configuration is configured to switch the circuit configuration of the low-pass filter as the second circuit configuration is a circuit configuration in which both of the two-stage T-shaped low-pass filters are enabled.
The high frequency power supply device according to claim 3.   The high-frequency power supply device according to claim 1, wherein the phase conversion unit includes a plurality of lines having a length of ¼ of the wavelength of the high-frequency voltage output from the power amplifier.   The high frequency power supply device according to any one of claims 1 to 7, wherein the switch circuit is configured by a vacuum switch.   The high-frequency power supply device according to claim 1, wherein the switch circuit includes a pin diode.

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