JP5327785B2 - Impedance matching device and impedance matching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the loss of control in impedance matching. <P>SOLUTION: In an impedance matching device for adjusting the impedance of a high-frequency power supply and a load, the impedance matching device includes: an impedance matching circuit in which the impedance variable element between the high-frequency power supply and the load is provided; and an impedance control section for performing impedance matching by controlling the phase difference of voltage and current and the absolute value of the input impedance of the impedance matching circuit so as to conform with each target value, by changing the impedance value of the impedance variable element of the impedance matching circuit. By carrying out the impedance matching for combining a seek control and a following control, the loss of control in the impedance matching is prevented. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an impedance matching apparatus and an impedance matching method that are provided between a high-frequency power source and a load and match the impedance of the high-frequency power source and the load.

  Plasma processing is used in manufacturing processes of liquid crystal panels and semiconductor integrated circuits. Impedance matching (matching control) is a technique indispensable for a high-frequency power supply system in order to stably generate plasma used at that time. Impedance matching maximizes transmission efficiency by making the power transmitter and receiver impedances equal to the characteristic impedance of the transmission line.

  As a device for matching, an LC circuit including a transformer, a capacitor, and an inductance is known. The high-frequency power supply system includes a high-frequency power supply and a matching device (Matcher), and the matching device includes a matching box including an LC circuit for impedance matching with a load, and a controller.

  As a plasma chamber used for plasma processing, as an energy source for generating plasma, a device that applies a high-frequency voltage in a radio frequency band in addition to a device that applies a DC voltage or a microwave voltage is known. In the plasma chamber using the radio frequency voltage in the radio frequency band, an impedance matching device is provided to match the impedance of the high frequency power source with the impedance of the plasma chamber load, thereby reflecting the reflected power from the load to the high frequency power source. Is controlled so as to maximize the power supplied to the load.

  As control of the impedance matching device, following control (see Patent Document 1) and seek control (see Patent Documents 2 and 3) are known.

  In the following control, the absolute value, phase difference, and sensor of the input impedance are detected by the sensor, and the detected value is fed back to the impedance matching circuit to control the impedance element of the capacitor and the inductance. Absolute value control to be controlled and phase control to control the phase difference of the input impedance are performed.

  Patent Document 1 discloses a phase difference detector that detects a phase difference between a high-frequency voltage and a high-frequency current from a high-frequency power source, an impedance difference detector that detects an impedance difference between a matching impedance and a load circuit impedance, and a phase difference of zero. A configuration including a matching variable circuit including a second variable capacitor having a variable capacitance and a first variable capacitor having a variable capacitance that sets an impedance difference to zero is shown.

  The seek control is control for calculating a final target value of the impedance element in a state where impedance matching is performed and changing the impedance element toward the target value.

  Patent Document 2 discloses input impedance calculation means for calculating the input impedance of an impedance matching circuit, and load circuit side impedance calculation means for calculating load side impedance using the input impedance, the impedance of a variable impedance element, and other circuit constants. And a configuration with adjustment unit target position calculation means for calculating the target position of the adjustment unit of the variable impedance element necessary to make the input impedance of the impedance matching circuit equal to the power supply side impedance.

  Patent Document 3 discloses high frequency information detection means for detecting information on a traveling wave traveling to a high frequency power supply side, variable element information detection means for detecting information on a variable value of an impedance variable element, and characteristic parameters of the impedance matching device. A first storage means for storing, a first calculation means for calculating the traveling wave and the reflected wave using the characteristic parameter, a second calculation means for calculating the input reflection coefficient using the characteristic parameter, and the calculated input reflection coefficient The second storage means for storing and the input reflection coefficient close to the target input reflection coefficient from the input reflection coefficients stored in the second storage means, and the variable value information of the impedance variable element corresponding to the selected input reflection coefficient is specified. And the adjustment means to adjust the impedance of the variable impedance element based on the specified variable value

  Also, as a positioning control for controlling the position of the object to a target position, a seek control method is known in which seek control is performed and then switching to following control (see Patent Document 4). This Patent Document 4 is applied to seek control for moving a head to a target track in positioning of a medium storage device such as a magnetic disk device or an optical disk device. In this seek control, by switching to fine control (following control) in the vicinity of the target position, both movement to a high-speed target position and high-accuracy positioning are realized.

Japanese Examined Patent Publication No. 7-10041 (page 3, left column, lines 30 to 50) Japanese Patent No. 3183914 (paragraphs 0017, 0018) JP 2006-166212 A (paragraph 0016) JP 2008-84103 A (paragraphs 0002 to 0006)

  The following control disclosed in Patent Document 1 has a problem in that it may be in an uncontrollable state. In the absolute value control and phase control performed by the following control, the absolute value control generates a maximum value in the absolute value of the input impedance with respect to the capacitance adjustment of the capacitor. When the target absolute value exceeds or exceeds this maximum value, even if the capacitance of the capacitor of the impedance matching circuit is changed, it cannot be adjusted to the target absolute value of input impedance.

  FIG. 12 shows the change in the absolute value of the input impedance with respect to the change in the capacitance of the capacitor. In this case, 13.56 MHz used for the plasma load is used as the high-frequency power source, the absolute value | Zin | is 50Ω, and the phase difference θ is 0 [rad] (or [deg]) as the target value as the characteristic impedance. Is shown.

  As shown in FIG. 12, the maximum value of the absolute value | Zin | of the input impedance with respect to the capacitance C of the capacitor is 50Ω. In this case, since there is an intersection with 50Ω, the control of 50Ω is possible. This characteristic is the same regardless of the magnitude of the load resistance R.

  When an impedance matching circuit is considered as an LC circuit (not shown) of a capacitor C connected in parallel on the input side and an inductance L (inductance obtained by combining Lm and Cm in FIG. 3) connected in series on the output side, The absolute value control of the input impedance is performed by adjusting the capacitance of the capacitor C, and the phase control of the input impedance is performed by adjusting the inductance L. In the process, when the reflected power becomes a specified value or less, it is considered that matching is completed, and the control operation is temporarily stopped. Further, when the reflected power exceeds a specified value due to load fluctuations, impedance is controlled again to perform matching (matching).

  The absolute value | Zin | of the input impedance has an extreme value with respect to the change of C, and the maximum value Zin-max of the input impedance Zin is a pure resistance.

On the other hand, in the phase control, when θ = 0 is controlled, the value of the input impedance Zin when θ = 0 is also the maximum value Zin-max, and the input impedance Zin is always the maximum value when matching is achieved. Zin-max. FIG. 12 shows an example in which the maximum value Zin-max is 50Ω. When ωL is increased in this state, the maximum value of Zin-max changes in a direction increasing from 50Ω. On the other hand, when ωL is decreased, the maximum value of Zin-max changes in a direction of decreasing from 50Ω. At this time, when the control is resumed due to a change in load or the like, the control may become impossible depending on the level of ωL. In FIG. 13, for example, in the case of R = 5Ω, “F-shaped” characteristics having an extreme value Zin (θ = 0) = 2R = 10Ω in the vicinity of C = 1200 pF are shown. From the matching point | Zin _{θ = 0} | <50, if | Zin _{θ = 0} | <10Ω = 2R due to load fluctuations, it will jump into the uncontrollable region indicated by point B in FIG. It becomes out of control.

Further, when the phase control is performed from the time when the value of the input impedance | Zin | is as small as | Zin _{θ = 0} | <2R, the absolute value | Zin even if the capacitance of the capacitor is changed due to the “f character” characteristic. It becomes an uncontrollable state in which | cannot be controlled to a desired value.

  In the impedance matching circuit, when θ = 0 is controlled by phase control, the imaginary part of the input impedance Zin becomes zero.

At this time, the input impedance Zin (θ = 0) at θ = 0 has an extreme value of Zin (θ = 0) = 2R with respect to the change of the capacitor C. R is the load resistance. FIG. 13 shows an example of the change of the input impedance Zin (θ = 0) with respect to the capacitor C at θ = 0. In FIG. 13, for example, in the case of R = 5Ω, “F-shaped” characteristics having an extreme value Zin (θ = 0) = 2R = 10Ω in the vicinity of C = 1200 pF are shown. In this “F” characteristic, when the phase control is started from the value indicated by the capacitor C at the point A in FIG. 13 (| Zin _{θ = 0} | <10Ω = 2R), for example, at the point B in FIG. The absolute value of the impedance does not change at the extreme value shown and becomes uncontrollable.

  In this way, the absolute value control and phase control in the impedance matching circuit have an extreme value with respect to the capacitance change of the capacitor, and in the absolute value control, when matching is resumed due to load fluctuation from the matching state, it becomes impossible to control In addition, in phase control, control may be impossible due to the “f” character characteristic.

  Conventionally, when the control becomes impossible, a variable element included in the impedance matching device is reset and control is performed again.

  In addition, the seek control disclosed in Patent Documents 2 and 3 has a problem that the convergence time until convergence to the target value is longer than in the following control. In Patent Document 3, in order to acquire variable value information of an impedance variable element, it is necessary to use characteristic parameters of an impedance matching device such as an S parameter and a T parameter.

  Accordingly, an object of the present invention is to solve the above-described problems and prevent control failure in impedance matching.

  More specifically, in the absolute value control in following control, the purpose is to prevent control failure caused by the input impedance becoming an extreme value at the time of re-matching after matching and being unable to take a value exceeding the extreme value. .

  It is another object of the present invention to prevent inability to control due to the U-shaped characteristics caused by the input impedance having an extreme value of pure resistance in phase control in following control.

  Note that Patent Document 4 shows that in positioning control for controlling the position of an object to a target position, speeding up is achieved by combining seek control and following control. When moving, the purpose is to move to a high-speed target position and positioning with high accuracy, and in the absolute value control and phase control by the impedance matching device, an uncontrollable state occurs due to having an extreme value. It does not solve the problems inherent in the impedance matching device.

  The impedance matching apparatus and the impedance matching method of the present invention solve the problem of uncontrollable impedance matching by combining seek control and following control in impedance matching.

  By performing seek control prior to following control, seek control is performed at the time of re-matching after matching, thereby preventing an inability to control due to the input impedance becoming an extreme value at the time of re-matching after matching.

  In addition, by setting a condition for switching from seek control to following control, it is possible to prevent control failure due to the U-shaped characteristic caused by the input impedance having the extreme value of the pure resistance in the phase control in the following control.

  An impedance matching device according to the present invention is an impedance matching device for matching impedance between a high frequency power source and a load, an impedance matching circuit in which an impedance variable element is provided between the high frequency power source and the load, and an impedance variable element of the impedance matching circuit. The impedance control unit performs impedance matching by controlling the absolute value of the input impedance of the impedance matching circuit and the phase difference between the voltage and the current to the respective target values by changing the impedance value.

  The impedance control unit includes seek control means for performing seek control to change the impedance value of the variable impedance element to a target impedance value at the time of impedance matching, and a deviation between each measured value of the absolute value of the input impedance, the phase difference, and each target value Is provided with following control means for performing following control to increase or decrease the impedance value of the variable impedance element, and control switching means for switching control between the seek control means and the following control means.

  The control switching means of the present invention prioritizes the seek control means over the following control means, and after the impedance value is brought close to the target value by seek control of the seek control means, the seek control means is switched to the following control means, Impedance matching is performed in the vicinity of the target value by following control of the following control means. This control switching means gives priority to seek control over following control.

  Further, the control switching means of the present invention has a switching range set by a predetermined threshold value determined for each of the target value of the absolute value of the input impedance and the target value of the phase difference in the vicinity of the target value. The control switching means compares each measured value of the input impedance absolute value and phase difference with the switching range, selects the seek control means when the measured value is outside the switching range not including the target value, and the measured value is the target value. If it is within the switching range including, the following control is selected.

  This switching range sets conditions when switching from seek control to following control. In the switching range of the control switching means, the switching range with respect to the absolute value of the input impedance is at least a range in which the absolute value of the input impedance is larger than the pure resistance value of the input impedance when the phase difference is zero. By adopting this switching range, it is possible to prevent control failure due to the U-shaped characteristics caused by the input impedance having the extreme value of the pure resistance in the phase control in the following control.

  The seek control means of the present invention calculates the target impedance value at the time of impedance matching by using the measured values of the absolute value and the phase difference of the input impedance, and the impedance value of the impedance variable element toward the calculated target impedance value To change.

  In the impedance matching circuit, in the configuration including the first variable capacitor connected in parallel on the input side and the second variable capacitor connected in series on the output side as the impedance variable element, the seek control means of the present invention includes: The measured values of the absolute value and phase difference of the input impedance, the capacitance (Ct) of the first variable capacitor of the impedance matching circuit, the capacitance (Cm) of the second variable capacitor, and the inductance (Lm) of the impedance matching circuit The load reactance component (Xo) and the load resistance component (Ro) are calculated based on the following equation, and the absolute value of the input impedance and the load resistance component (Ro) are calculated using the calculated load reactance component (Xo) and the load resistance component (Ro). The capacitance (Ctref) of the first capacitor and the capacitance of the second capacitor of the impedance matching circuit when the phase difference reaches each target value Cmref) is calculated.

  In the impedance matching circuit, in the configuration including the first variable capacitor connected in parallel on the input side as the impedance variable element and the second variable capacitor connected in series on the output side, the following control according to the present invention. The means controls the phase difference to zero by increasing or decreasing the second variable capacitor according to the sign of the phase difference, and increases or decreases the first variable capacitor according to the absolute value of the input impedance. And an absolute value control means for matching the absolute value of the input impedance to the absolute value of the characteristic impedance on the power supply side, and the phase control means and the absolute value control means have an initial value near the target value controlled by the seek control means. Control starts as

  According to the impedance matching method of the present invention, an impedance matching circuit provided with an impedance variable element is provided between a high-frequency power supply and a load, and the impedance value of the impedance variable element is changed to thereby obtain an absolute impedance of the impedance matching circuit. Impedance matching method for matching the impedance of the high-frequency power supply and the load by impedance control that matches the value and the phase difference between the voltage and current to the target value, respectively, and the impedance value of the variable impedance element is Seek control to change to target impedance, and following control to increase / decrease impedance value of variable impedance element so that deviation between absolute value of input impedance and each measured value of phase difference and each target value becomes zero Turn off And switching control to give priority to the seek control over the following control, the impedance value is brought close to the target value by the seek control, and the seek control is switched to the following control. Adjust the impedance value to the target value.

  In the impedance matching apparatus and matching method of the present invention, the target value of the absolute value of the input impedance can be the characteristic impedance on the power supply side, and the target value of the phase difference can be zero.

  According to the impedance matching device and the matching mode of the present invention, combining the seek control and the following control, and prioritizing the seek control over the following control, the conventional matching control in which the variable element is reset when the control is impossible is performed. Since it is not necessary to perform the treatment again, the control time can be shortened.

  In addition, the vicinity of the target value can be quickly reached by seek control, and the convergence time to the target value can be shortened by switching from seek control to following control in the vicinity of the target value. This is because the following control can be performed faster than the seek control near the target value.

  According to the impedance matching device and matching mode of the present invention, as a switching condition from seek control to following control, the absolute value of the input impedance is a pure resistance value of the input impedance when the phase difference is zero. By setting the range larger than the above, it is possible to avoid the inability to control due to the U-shaped characteristic in the phase control of the following control.

  The seek control according to the present invention uses a lumped constant such as the capacitance of the capacitor of the impedance matching circuit and controls toward the target value by this lumped constant. In comparison, the processing can be performed with simple processing.

  Furthermore, the seek control according to the present invention does not require calculation using characteristic parameters such as S parameter and T parameter, and has a function of switching from seek control to following control even when calibration is rough. Thus, it is possible to control the driving to the matching point.

  In other words, the seek control of the present invention is performed by the first capacitor of the impedance matching circuit used for calculating the capacitance (Ctref) of the first capacitor of the impedance matching circuit and the capacitance (Cmref) of the second capacitor in the seek control. The absolute value and phase difference of the input impedance due to the error of each value of the capacitance (Ct), the capacitance (Cm) of the second capacitor, and the inductance (Lm) of the impedance matching circuit follow the deviation control of each target value. It can be reduced by switching to.

  Further, according to the present invention, the switching operation from the seek control to the following control can be performed at a high speed by performing the control to the target value by the concentrated constant.

  As described above, according to the impedance matching device and the matching method of the present invention, it is possible to prevent control failure in impedance matching.

  Further, according to the present invention, in the absolute value control in the following control, the input impedance becomes an extreme value at the time of re-matching after matching, and it is possible to prevent control failure caused by being unable to take a value higher than the extreme value. it can.

  Further, in the phase control in the following control, it is possible to prevent control failure due to the U-shaped characteristic caused by the input impedance having the extreme value of the pure resistance.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a system diagram of a high-frequency power supply system. Impedance matching (impedance matching) relates to high-frequency transmission technology by maximizing transmission efficiency by making the impedance on the power transmission (high frequency power supply) side and the impedance on the reception (load) side equal to the characteristic impedance of the transmission line. is there. Examples of equipment for matching include a transformer and an LC circuit (consisting of a capacitor and an inductance). Below, matching (matching) control shows the example by LC circuit in the matching box (Matching Box) in a high frequency power supply system.

  Here, an example of an RF (Radio Frequency) power source is shown as the high frequency power source. As shown in FIG. 1, the configuration of the RF power source system includes an RF power source (RF Generator) 100 that is an RF power generation source and a matcher 101 of a matching device. The matcher 101 includes a matching box including an LC circuit for impedance matching with a load, and a controller thereof. As the load, for example, a process chamber 102 of a plasma generator can be used.

  How far the impedance viewed from the input side of the matching box (Matching Box) 101 is with respect to the reference characteristic impedance is expressed by “voltage standing wave ratio”, that is, “VSWR” (Voltage Standing Wave Ratio). can do. When impedance matching is expressed using VSWR, VSWR = 1. At this time, since the reflected wave power = 0, the traveling wave power from the RF power source (RF Generator) 100 is transmitted to the process chamber 102 with the maximum transmission efficiency.

  The control of the RF power supply system is shown in the flowchart of FIG. In FIG. 2, after the power supply from the RF power supply is started (S1), the reflected wave power returning from the load to the power supply side is monitored. When the reflected wave power is smaller than the allowable limit value (S2), traveling wave power control is performed (S3). On the other hand, when the reflected wave power is larger than the limit value (S2), reflected wave power control is performed (S4).

  By controlling the reflected wave power to 0 by the traveling wave power control (S4), the power supply and the load are matched (S5). When the reflected wave power is not controlled to 0 by the traveling wave power control and when the reflected wave power control is performed (S6), impedance matching is performed using a matching box (S7). The RF power supply system performs control so as to maintain the matching state by repeating the above steps S2 to S7.

Hereinafter, matching control (matching control) will be described. According to polar coordinates, the input impedance Zin when looking at the matching box from the input side
Zin = | Zin | ∠θin (1)
It is represented by

  The impedance value of the RF power supply is 50 [Ω], which is generally used for high-frequency circuits. If the characteristic impedance of the transmission line connecting the RF power supply and the matching box (Matching Box) is 50Ω, the absolute value of the input impedance Impedance matching is performed by controlling | Zin | and the phase difference θin so that | Zin | = 50 [Ω] and θin = 0 [deg] ([rad]), respectively.

When the matching box matches the load, the input impedance Zin is
Zin = | 50Ω | ∠0rad (2)
It is represented by

Also, the input impedance Zin is set to Zin = R + jX (3)
When the absolute value | Zin | and the phase difference θin between the voltage and the current are represented by | Zin | = √ (R ² + X ² ) (4)
θin = tan ⁻¹ X / R (5)
It is represented by Impedance matching can be performed by the absolute value | Zin | and the phase difference θin.

  FIG. 3 shows an equivalent circuit example of the LC circuit in the matching box. In the equivalent circuit shown in FIG. 3, a variable capacitance capacitor (hereinafter referred to as a variable capacitor) Ct is provided in parallel on the input side of the matching box (Matching Box), and a variable capacitor Cm and an inductance Lm are provided in series on the reception side (load). Prepare. The absolute value of the input impedance Zin is changed by changing the capacitance of the variable capacitor Ct in the LC circuit, and the phase of the input impedance Zin is changed by changing the capacitance of the variable capacitor Cm or the inductance Lm in the LC circuit. Thus, the absolute value | Zin | and the phase difference θin of the input impedance are set to | Zin | = 50 [Ω] and θin = 0 [deg], respectively.

  Of the suffixes attached to Cm, Lm, and Ct, “m” represents the first letter of Match, which means phase control, and “t” represents the first letter of Tune, which means absolute value control. .

  In the following control, the absolute value | Zin | of the input impedance and the phase difference θin sensor are detected, and this value is fed back so that | Zin | = 50 [Ω] and θin = 0 [deg]. Impedance matching is realized by controlling Ct, Cm or inductance Lm.

  Next, the impedance matching process of the present invention will be described. In the impedance matching according to the present invention, seek control for changing the impedance value of the variable impedance element to the target impedance value at the time of impedance matching, and the deviation between each measured value of the absolute value of the input impedance, the phase difference, and each target value is zero. As described above, the control is performed by following control that increases or decreases the impedance value of the impedance variable element, and seek control is performed with priority over following control.

  First, control is performed toward the target value of the absolute value and phase difference of the input impedance close to the matching point by performing seek control, and impedance matching is performed by performing following control from this target value point. In addition to avoiding impossible points, the matching points can be controlled at high speed.

  Switching control from seek control to following control will be described with reference to the flowchart of FIG. 4, the Smith chart of FIG. 5, and the characteristic diagram of the absolute value | Zin | of the input impedance of FIG.

  In the matching control according to the present invention, based on the absolute value | Zin | of the input impedance obtained by measurement and the phase difference θin, whether these values are within the preset switching range or outside the switching range. Whether to perform seek control or following control is selected depending on whether there is any. When performing seek control, first adjust the variable element toward the target value predicted by seek control and perform control to make the input impedance close to the target value, then switch from seek control to following control. The impedance is matched by changing the phase and the absolute value by following control.

  In the flowchart of FIG. 4, after the power supply from the high frequency power source to the load is started (S11), seek control is first performed (S12). If the input impedance obtained by this seek control is outside the predetermined switching range, seek control is performed again (S13, S14). Whether the phase difference θin is within the switching range is determined (S13) and whether the absolute value | Zin | is within the switching range (S14). To do.

  Here, a range of −θ1 ≦ θin ≦ θ2 is defined as the switching range of the phase difference θin, and a range of Z1 ≦ | Zin | ≦ Z2 is defined as the switching range of the absolute value | Zin |. As an example, this switching range can be set to −22.5 ° ≦ θin ≦ 22.5 ° and 33.3Ω ≦ | Zin | ≦ 75Ω. The threshold value of this switching range will be described later with reference to FIG.

  After the absolute value | Zin | of the input impedance reached by seek control and the phase difference θin are within the switching range of S13 and S14, switch from seek control to following control, and then perform impedance control by following control (S15).

  If the input impedance obtained by the following control is outside the predetermined switching range, the process returns to seek control (S16, S17). Whether the phase difference θin is within the switching range is determined by determining whether the phase difference θin is within the switching range (S16) and whether the absolute value | Zin | is within the switching range (S17). To do.

Here, as a switching range for performing switching control to return from following control to seek control, the switching range of the phase difference θin is a range of θin <−θ1 or θ2 <θin, and the switching range of the absolute value | Zin | is | Zin | < Z1 or Z2 <| Zin |. This switching range is, for example, | Zin | <33.3Ω or 75Ω <| Zin |, θin <−22.5 ° or 22.5 while considering so as to satisfy the condition of | Zin _{θ = 0} |> 2R. Set ° <θin.

  When the absolute value | Zin | of the input impedance reached by following control and the phase difference θin are within the switching range of S16 and S17, return to seek control from following control, and the switching range of S16 and S17. If it is outside, the following control is continued (S15).

  The switching range of S13 and S16 and the switching range of S14 and S17 are switching ranges determined by the same threshold value.

  FIG. 5 is a Smith chart showing the relationship between the absolute value of the impedance Zin and the phase, and switching from seek control to following control will be described using this Smith chart.

  In the Smith chart shown in FIG. 5, a circle 20a indicates | Zin | = 50Ω, and a point 32 on the circle 20a indicates a phase angle θin = 0 °, which represents an impedance matching point. In the present invention, impedance control is performed so that the absolute value | Zin | of the input impedance is 50Ω and the phase difference θin is 0 ° in accordance with the load variation. This impedance control corresponds to controlling the impedance Zin to the impedance matching point 32 on the Smith chart.

  In the Smith chart of FIG. 5, a circle 20a whose resistance component (real number) of Zin is 50Ω is indicated by a thick solid line, a circle 20c whose Zin resistance component (real number) is | Z1 |, and a Zin resistance component (real number) of | Z2 The circle | round | yen 20b of | is shown with the broken line. In the figure, | Z1 | <| Z2 |.

  The switching range 22 for switching from seek control to following control can be determined by the absolute value | Zin | of the impedance Zin and the phase θin. For example, when Z1 ≦ | Zin | ≦ Z2 is set as the range of the absolute value | Zin | and −θ1 ≦ θin ≦ θ2 is set as the range of the phase difference θin, the switching range 22 is set on the Smith chart of FIG. Z1 | ∠θ2, | Z2 | ∠θ2, | Z2 | ∠θ1, | Z1 | ∠θ1 can be represented by a hatched area surrounded by each point.

FIG. 5 shows an example in which θ1 and θ2 are the same size. In this case, Z ₂₂ (= | Z2 | ∠θ2) and Z ₁₁ (= | Z1 | ∠θ1) are contrasted with the Smith chart center (| Zin | = 50Ω, ∠θ = 0 °) as the center of the control. The positional relationship is as follows. At this time, ∠θ2 is a line (voltage V = m ·) indicating a line connecting point 0 and Z ₁₁ (corresponding to current I = n · | 1-Γ |) and a dot-dash line connecting point 0 and Z _22. | 1 + Γ |), and each line is the sum of ∠θ ₂₁ and ∠θ ₂₂ (∠θ ₂₁ + ∠θ ₂₂ ) formed by the horizontal line. Note that Γ is a reflection coefficient, and Z ₂₂ is expressed by the following equation.

Z ₂₂ = V / I = [m · | 1 + Γ | ε ^jθ22 ] / [n · | 1-Γ | ε ^jθ21 ]
= A [| 1 + Γ | / | 1-Γ |] × ε ^{j (θ21 + θ22)}
= | Z2 | ε ^jθ2

  In the switching range 22, control is performed by switching from seek control to following control.

  In the present invention, the absolute value | Zin | and the phase difference θin are moved into the switching range 22 by seek control, and the phase θ and | Zin | To point 32 in a vector fashion. The vector control by simultaneous control of the phase θ and | Zin | can be performed by alternately switching the control of the phase θ and the control of | Zin |

  The range of the phase difference θin that defines the switching range 22 and the range of the absolute value | Zin | can be arbitrarily determined, but the absolute value | Zin | range is such that the absolute value of the input impedance is 0 ° and the phase difference is 0 °. By setting the input impedance to a range that is larger than the pure resistance value of the input impedance, the target value by seek control is changed to the range toward the matching position by changing the impedance of the variable element (variable capacitor). Inability to control due to character characteristics can be prevented.

  Here, the range of 33.3Ω ≦ | Zin | ≦ 75Ω, which is set as an example of the absolute value of impedance | Zin |, is a complex reflection coefficient Γ, voltage standing wave ratio (VSWR), reflected power Pr, and travel. It can be determined based on the relationship with the power Pf.

There is a relationship Pr = Γ ² × Pf among the complex reflection coefficient Γ, the reflected power Pr, and the traveling power Pf, and the reflected power Pr is expressed by Pr / Pf = Γ ^{2 with} respect to the traveling power Pf. In the impedance control, it is required to suppress the reflected power Pr by matching the input impedance. Accordingly, when the seek-controlled impedance matching target value is controlled, the reflected power Pr is expected to be sufficiently smaller than the traveling power Pf. Therefore, the switching range for switching from seek control to following control can be determined by a complex reflection coefficient Γ so that the reflected power Pr is sufficiently small with respect to the traveling power Pf.

  Therefore, for example, when the ratio of the magnitude of the reflected power Pr to the traveling power Pf is 0.04, for example, the magnitude of the complex reflection coefficient Γ is 0.2 from the relationship Pr / Pf = Γ2, and the voltage standing wave ratio (VSWR: Voltage Standing Wave Ratio) is 1.5.

  Here, the complex reflection coefficient Γ is represented by Γ = (Zin−Zo) / (Zin + Zo), and the voltage standing wave ratio is represented by (1+ | Γ |) / (1− | Γ |). When the magnitude of the complex reflection coefficient Γ is m, the absolute value | Zin | of the impedance is represented by {(1 + m) / (1-m)} Zin or {(1-m) / (1 + m)} Zin. be able to.

  When the ratio of the magnitude of the reflected power Pr to the traveling power Pf is 0.04, as described above, the magnitude m of the complex reflection coefficient is 0.2 and the voltage standing wave ratio (VSWR) is 1.5. The absolute value | Zin | of the impedance is 1.5Zo and 0.66Zo. Here, when Zo = 50Ω, the absolute value | Zin | of the impedance is 75Ω and 33.3Ω.

  Therefore, when the range of the absolute value | Zin | of the impedance is 33.3Ω ≦ | Zin | ≦ 75Ω, the ratio of the magnitude of the reflected power Pr to the traveling power Pf can be within 0.04.

  Further, the complex reflection coefficient Γ, the voltage standing wave ratio (VSWR), the reflected power Pr, and the travel are also set in the range of −22.5 ° ≦ θin ≦ 22.5 ° set as an example of the impedance phase difference θin. The voltage standing wave ratio (VSWR) = 1.5 when the ratio of the magnitude of the reflected power Pr to the traveling power Pf is 0.04, for example, can be determined based on the relationship with the power Pf. The phase difference θin is −22.5 ° and 22.5 °, and a range of −22.5 ° ≦ θin ≦ 22.5 ° is obtained.

  In general, the ratio of the reflected power Pr to the traveling power Pf is desirably 10% or less. As in the above example, the absolute value of impedance | Zin | and the range of the phase difference are obtained with the reflected power Pr being 4%. In this case, the reflected power Pr can be sufficiently reduced to 10% or less.

  When the absolute value | Zin | and the phase difference are obtained using the same value of the voltage standing wave ratio (VSWR), the switching range on the Smith chart is a square shape.

  FIG. 6 is a diagram for explaining the relationship between the character characteristics and the target value by seek control. FIG. 6 shows the change in the absolute value of the input impedance Zin (θin = 0) with respect to the change in the variable capacitor C when the in-phase operation is performed with the phase difference θin = 0. As described above, since this input impedance Zin is 2R and Zin (θin = 0) has an extreme value, when point A is set as a target value for seek control in the range of Zin indicated by D in the figure. When the capacitance C of the variable capacitor is increased, it stops at the extreme value B, making control difficult. Even when the capacitance C of the variable capacitor is decreased from the point A, it is difficult to reach a matching state of | Zin | = 50Ω.

  On the other hand, when the target value is set in the range of Zin indicated by E in the figure, it is possible to reach a matching state of | Zin | = 50Ω by increasing or decreasing the capacitance C of the variable capacitor.

As ωL is increased, the | Zin _{θ = 0} | level increases and exceeds the 50Ω line. When ωL is reduced, the | Zin _{θ = 0} | level decreases, falls below the 50Ω line, and finally reaches the uncontrollable region of the U-shaped characteristic. Once entering the uncontrollable area, control is disabled. Therefore, in the present invention, the impedance value (for example, ωL, C) of the variable impedance element is increased / decreased so that the reflected wave power becomes a specified value or less, and the speed at which the impedance value is increased / decreased depends on the magnitude of the reflected wave power. Change. Further, the variable speed speed of the variable operation of the plurality of impedance variable elements (for example, ωL and C) is arbitrarily variable, and the speed ratio for changing the plurality of impedance variable elements is set to an optimum ratio, thereby changing the impedance variable element ( The control of ωL and C) is prevented from entering the uncontrollable region of the F-characteristic, and remains in the controllable region, thereby realizing stable control.

  For example, when the reflected wave power is large, the speed of increasing or decreasing the impedance value is set fast to avoid the transition to the uncontrollable area, and when the reflected wave power is small, the impedance is The speed of increasing / decreasing the value is set to be slow, and the driving control near the matching is surely performed.

  Note that the ratio of the speed ratios for changing the plurality of impedance variable elements is set in accordance with the change characteristics in absolute value control or phase control undertaken by each impedance variable element. Since this change characteristic depends on the circuit configuration of the impedance matching circuit and the size and characteristics of each impedance variable element forming the circuit, the actual ratio of the speed ratio is set according to these circuit parameters.

  In the absolute value characteristic of FIG. 9C, the state where the curve indicating the absolute value characteristic intersects with 50Ω which is the absolute value of the matching point corresponds to the range where the absolute value characteristic passes 50Ω of the matching point in FIG. ing. FIG. 6 shows an absolute value characteristic when the in-phase operation is performed with the phase difference θin = 0.

Thus, by starting control from a relatively large ωL to obtain | Zin _{θ = 0} |> 2R, the absolute value characteristic shown in FIG. 6 does not pass the extreme value B of the characteristic, The following control can be performed toward | Zin _{θ = 0} | = 50Ω of the matching point without causing the uncontrollable state that the matching state of | Zin _{θ = 0} | = 50Ω is not reached.

Conversely, when control is started from a relatively small ωL that satisfies | Zin _{θ = 0} | <2R, control becomes impossible. This state corresponds to, for example, a state in which the absolute value characteristic indicated by the broken line in FIG. 9C does not cross 50Ω that is the absolute value of the matching point in FIG. 9C, and in FIG. 6, the range indicated by D in the figure. Corresponding to

  Next, seek control will be described with reference to FIG. FIG. 7 is a flowchart for explaining seek control.

  The seek control is control for calculating the final target impedance value of the variable element (variable capacitor) of the matching circuit and changing the impedance of the variable element (variable capacitor) toward the value.

Here, the following initial conditions (1) The capacitors Ct and Cm and the inductance Lm of the equivalent circuit shown in FIG. 3 are known.
(2) The input impedance | Zin | = | 1 / Yin | can be detected by a sensor.
(3) The phase difference θin can be detected by a sensor.
(4) In the equivalent circuit shown in FIG. 3, Cm, Lm, and Xo are collectively referred to as Xm.
Perform seek control based on

  In seek control, unknown Xm and Ro are first obtained, then Xo is obtained, Xmref, which satisfies | Zin | = 50Ω and θin = 0 [deg] using the obtained Xm, Ro, Xo and known values. Ctref and Cmref are obtained, and the capacitances of the capacitors Ct and Cm are controlled using the values of Ctref and Cmref as target impedance values.

  More specifically, in the flowchart of FIG. 7, after the power supply from the high frequency power source to the load is started (S21), when the phase difference θin is not 0 (S22), or the absolute value | Zin | of the input impedance is not 50Ω. In this case (S23), the current load impedance (Ro + jXo) is obtained by calculation using the absolute value | Zin | of the input impedance detected by the sensor and the phase difference θin (S24).

Ro and Xo can be expressed by the following formula.
Ro = Ao / (Ao ² + So ² ) (6)
^{Xo = So / (Ao 2 +} So 2) ... (7)

Here, Ao and So are expressed by the following equations.
Ao = | Yin | cosθin (8)
So = | Yin | sinθin + ωCt (9)

next,
jXm = (jωLm + 1 / jωCm + Xo) (10)
The unknown Xo is expressed by the following equation.
Xo = Xm-ωLm + 1 / ωCm (11)

  Since Xm, Lm, and Cm are known values, Xo can be obtained from equation (11).

next,
Xm / ω = Xmref (12)
And

  Xmref and Ctref can be expressed by the following equations by setting | Zin | = 50Ω and θin = 0 [deg] in FIG.

Xmref = √ {(50 Ro−Ro ² ) / ω ² } (13)
Ctref = Xmref / {Ro ² + (ωXmref) ² } (14)
Cmref = 1 / {ω ² (Lm−Xmref) + ωXo} (15)
As a result, Ctref and Cmref can be obtained (S25).

  Here, Ctref obtained by the equation (14) and Cmref obtained by the equation (15) are target impedance values, and the values of the variable elements Ct and Cm are changed toward this value, thereby performing matching (S26). ).

  Here, the known Ct and Cm used as initial conditions in the seek control described above can be obtained as follows.

  The capacitances of the variable capacitors Ct and Cm can be obtained from the installation position of the elements of the variable capacitor (variable capacitor). The capacity of the variable capacitor is proportional to the position (%) determined by the variable capacitor element in the entire variable region that can be changed by the variable capacitor element, and can be expressed by the following formula and converted from the position θx. Can be obtained.

    Cx = {(Cmax−Cmin) / 100%} · θx + Cmin (16)

  Here, Cmax is a capacitance value when the position θx (%) where the position of the variable capacitor element is displayed in percentage is 100%, and Cmin is when the position θx (%) where the position of the variable capacitor element is also displayed as a percentage is 0%. Capacity value. In Cx, when x is t, Ct is represented, and when x is m, Cm is represented.

  Lm can also be converted from its fixed inductance value when the coil element is a fixed element, and from the set position in the entire variable region, as with the variable capacitor described above, when it is a variable element.

  Next, the following control will be described with reference to the flowchart of FIG.

  If the reflected wave power is not 0, impedance matching is performed by matching processing (S31). Impedance matching by following control is performed by phase control (S32 to S35) and absolute value control (S36 to S39).

  In the phase control, when the phase difference θin is not 0 [deg] (S32), the phase control is performed by adjusting the variable capacitor Cm or the variable inductance Lm. Here, a case where phase control is performed by adjusting the variable capacitor Cm is shown.

  When the phase difference θin is negative (S33), the capacity of the variable capacitor Cm is increased (S34), and when the phase difference θin is positive (S33), the capacity of the variable capacitor Cm is decreased (S35). ).

  When the phase difference θin is 0 [deg], the phase control operation is not performed (S32), and the absolute value control is performed by S36 to S39.

  In the impedance control, when the absolute value | Zin | is not 50 [Ω] (S36), the absolute value control is performed by adjusting the variable capacitor Ct (S37 to S39). When the absolute value | Zin | is larger than 50 [Ω] (S37), the capacitance of the variable capacitor Ct is increased (S38), and when the absolute value | Zin | is smaller than 50 [Ω] (S37). ) Decrease the capacitance of the variable capacitor Ct (S39). If the absolute value | Zin | is 50 [Ω], the absolute value control operation is not performed (S36).

  Further, when the reflected wave power to be observed reaches a specified value or less, the control operation is temporarily stopped by assuming that matching is made. When the reflected wave power reaches a specified value or more due to load fluctuation or the like, the above-described control operation is resumed.

  FIG. 9 is a diagram for explaining phase characteristics of phase control and absolute value characteristics of absolute value control. 9A shows the change in the phase difference θin when ωL is used as a parameter, and FIG. 9B shows the change in the phase difference θin when C is used as a parameter. FIG. 9C shows a change in absolute value | Zin | when C is a parameter.

  In FIG. 9A, the solid line shows the change in the phase difference θin when the parameter ωL is changed. In the phase control, the parameter ωL is changed so that the phase difference θin becomes “0”. The phase range (−θ1 ≦ θ ≦ θ2) is set by seek control, and phase control of following control is performed from this point. In this phase control, when the phase difference θin is positive, the parameter ωL is decreased because it is a leading current (corresponding to S31), and when the phase difference θin is negative, the parameter ωL is increased because it is a lagging current ( Compatible with S32.)

  In FIG. 9B, the solid line indicates the change in the phase difference θin when the parameter C is changed. In the phase control, the parameter C is changed so that the phase difference θin becomes “0”. The phase range (−θ1 ≦ θ ≦ θ2) is set by seek control, and phase control of following control is performed from this point. In this phase control, when the phase difference θin is positive, the parameter C is decreased because it is a leading current (corresponding to S31), and when the phase difference θin is negative, the parameter C is increased because it is a lagging current ( Compatible with S32.)

  In FIG. 9C, the solid line indicates the change of the absolute value | Zin | when the parameter C is changed. In the absolute value control, the parameter C is changed so that the absolute value | Zin | becomes “50Ω”. The absolute value range (| Z1 | ≦ | Zin | ≦ | Z2 |) is set by seek control, and the absolute value control of the following control is performed from this point. In the absolute value control, when the absolute value | Zin | is larger than “50Ω”, the parameter C is decreased (corresponding to S38), and when the absolute value | Zin | is smaller than “50Ω”, the parameter C is decreased. Increase C (corresponding to S39).

  In FIG. 9C, when the absolute value | Zin | does not intersect with “50Ω” (characteristic indicated by a broken line in the figure), the absolute value | Zin | intersects with “50Ω” by phase difference control. Control.

  Table 1 below shows the control operation of the capacity of the variable capacitor Cm with respect to the phase difference θin of the following control, and Table 2 shows the control of the capacity of the variable capacitor Ct with respect to the absolute value | Zin | of the following control. The operation is shown.

  Hereinafter, one configuration example of the impedance matching apparatus of the present invention will be described with reference to FIG.

  The impedance matching apparatus 1 includes a high-frequency power source 10 and a load 11 and an impedance matching circuit 2 that performs impedance matching by connecting them. The impedance matching circuit 2 includes a variable capacitor Ct connected in parallel on the input side (power supply side), a variable capacitor Cm connected in series between the input side and the output side (load side), and an inductance Lm. An L-shaped matching circuit is configured. The variable capacitor Ct is a variable element that performs absolute value control, and the variable capacitor Cm and the inductance Lm are variable elements that perform phase control. In the phase control, only the variable capacitor Cm or the inductance Lm may be used as a variable element. Moreover, it is good also as a structure which replaced Cm and Lm.

  Hereinafter, an example in which the phase control uses the variable capacitor Cm as a variable element will be described.

  The variable capacitor Ct of the impedance matching circuit 2 includes a detector 2a that detects the% position θx (t) of the variable region, and a drive mechanism 2c that changes the capacitance of the variable capacitor Ct. The variable capacitor Cm includes a detector 2b that detects the% position θx (t) of the variable region and a drive mechanism 2d that changes the capacity of the variable capacitor Cm.

  When the variable capacitor Ct and the variable capacitor Cm are composed of variable capacitor elements, the% position θx of the variable region is the electrode position of the variable capacitor element, and the drive mechanism can be a motor mechanism that drives the electrodes.

  On the transmission line between the high-frequency power supply 10 and the impedance matching circuit 2, the detection means 3 of the impedance detection means 3a, the phase detection means 3b, and the reflected power detection means 3c are provided, and the absolute impedance of the input impedance of the impedance matching circuit 2 is provided. The value | Zin | and the phase difference θin are detected. The impedance detection means 3a and the phase detection means 3b can be constituted by a voltage detector, a current detector, and a calculation means for calculating the absolute value | Zin | and the phase difference θin from the voltage value and the current value. The reflected power detection means 3c can be configured by a voltage detector, a current detector, and a calculation means for calculating the reflected power from the voltage value and the current value.

  The impedance adjustment of the impedance matching circuit 2 is performed by controlling the capacitances of the variable capacitor Ct and the variable capacitor Cm included in the impedance matching circuit 2. The capacitances of the variable capacitor Ct and the variable capacitor Cm are controlled by switching between following control or seek control. Following control is performed by the following control means 6, and seek control is performed by the seek control means 7.

  Switching between following control and seek control is performed by the control switching means 8. The control switching means 8 has a set value for determining a switching range for determining which control is selected and switched for the absolute value | Zin | of the input impedance and the phase difference θin, and the input impedance detected by the impedance detection means 3a. The absolute value | Zin | and the phase difference θin detected by the phase detection means 3b are compared with the switching range.

  The following control means 6 switches between a phase control means 6a for controlling the capacity of the variable capacitor Cm to perform phase control, and an absolute value control means 6b for controlling the capacity of the variable capacitor Ct to perform absolute value control. Control selection means 6c is provided.

  The control selection means 6c receives the absolute value | Zin | of the input impedance detected by the impedance detection means 3a and the phase difference θin detected by the phase detection means 3b, and receives the absolute value | Zin | and a characteristic impedance (for example, 50Ω). ) And the phase difference θin and 0 [deg] (or [rad]), and the phase control by the phase control means 6a or the absolute value control by the absolute value control means 6b is selected.

  Further, the following control means 6 monitors the reflected power detected by the reflected power detection means 3c, and in the course of the input impedance control, it is considered that the matching is completed when the reflected power becomes a specified value or less, When the control operation is temporarily stopped and the reflected power exceeds a specified value due to load fluctuation, the impedance is controlled again to perform matching.

  The seek control means 7 inputs the variable capacitors Cm and Ct converted by the conversion means 5 and the inductance Lm, and the absolute value | Zin | of the input impedance detected by the impedance detection means 3a and the position detected by the phase detection means 3b. By inputting the phase difference θin, Ctref, Cmref, and Lmref which are target impedance values of the variable element are calculated, and the drive mechanism 2c of the variable capacitor Ct is driven by the calculated Ctref to control the capacitance of Ct. The drive mechanism 2d of the variable capacitor Cm is driven by the calculated Cmref to control the capacitance of Cm.

  The seek control means 7 may control Lm of the variable inductance by Lmref which is the target impedance value of the variable element. The inductance shown in FIG. 10 does not show a mechanism for controlling the inductance value.

  The conversion means 5 converts the capacity of the variable capacitor Ct from the% position θx (t) of the variable region of the variable capacitor Ct detected by the detector 2a, and% position θx of the variable region of the variable capacitor Cm detected by the detector 2b. The capacity of the variable capacitor Cm is converted from (m). In addition to storing a known value, the inductance Lm can be converted in the same way as the capacitor described above from the value detected by the detector in the case of a variable inductance.

  Here, the conversion means 5, the following control means 6, the seek control means 7, and the control switching means 8 constitute the impedance control unit 4 and control the impedance adjustment of the impedance matching circuit 2.

  The impedance matching circuit applicable to the impedance matching device of the present invention is not limited to the circuit shown in FIG. A configuration example of an impedance matching circuit that can be applied to the impedance matching device of the present invention will be described with reference to FIG. Note that the configuration example illustrated in FIG. 11 is an example and is not limited to this configuration example, and the number of variable elements used in the configuration can be arbitrarily determined.

  In the configuration example of the impedance matching circuit shown in FIG. 11A, a variable capacitor C1 and a variable capacitor C2 are connected in series, one end of an inductance L is connected to the connection end of both variable capacitors, and the other end of the inductance L is grounded. This is an example in which a T-type circuit is configured.

  The configuration example of the impedance matching circuit shown in FIG. 11B is an example in which an L-type circuit in which a variable inductance L and a variable capacitor C are connected in series to a variable capacitor C whose one end is grounded is connected in parallel. It is.

  In the above description, an example of 13.56 MHz as a high frequency power source and 50Ω as a characteristic impedance is shown. However, the impedance matching device and the matching method of the present invention are not limited to this, and can be applied to other high frequency power sources and characteristic impedances Can be applied.

  The present invention is not limited to the embodiments described above. Various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

  The impedance matching apparatus and matching method of the present invention can be applied when supplying power to a load whose impedance varies, not limited to a plasma load.

It is a systematic diagram of a high frequency power supply system. It is a flowchart for demonstrating control of RF power supply system. It is a figure which shows the equivalent circuit example of LC circuit in a matching box (Matching Box). It is a flowchart for demonstrating the seek control and following control of this invention. It is a Smith chart for demonstrating switching control from seek control to following control. It is a characteristic diagram of absolute value | Zin | of input impedance for explaining switching control from seek control to following control. It is a flowchart for demonstrating the seek control of this invention. It is a flowchart for demonstrating following control of this invention. It is a figure for demonstrating the phase characteristic of phase control, and the absolute value characteristic of absolute value control. It is a figure for demonstrating the example of 1 structure of the impedance matching apparatus of this invention. It is a figure for demonstrating the structural example of the impedance matching circuit which can be applied with the impedance matching apparatus of this invention. It is a figure which shows the change of the absolute value of input impedance with respect to the capacitance change of a capacitor | condenser. It is a figure which shows an example of the change with respect to the capacitor | condenser C of input impedance Zin ((theta) = 0) in (theta) = 0.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Impedance matching apparatus 2 Impedance matching circuit 2a, 2b Detector 2c, 2d Drive mechanism 3 Detection means 3a Impedance detection means 3b Phase detection means 4 Impedance control part 5 Conversion means 6 Following control means 6a Phase control means 6b Absolute value control means 6c Control selection means 7 Seek control means 8 Control switching means 10 High frequency power supply 11 Load 100 RF power supply 101 Matcher
102 Process Chamber

Claims (6)

In an impedance matching device that matches the impedance of a high-frequency power supply and a load,
An impedance matching circuit in which an impedance variable element is provided between a high-frequency power source and a load, and by changing the impedance value of the impedance variable element of the impedance matching circuit, the absolute value of the input impedance of the impedance matching circuit, voltage and current And an impedance control unit that performs impedance matching by controlling the phase difference of each to a target value,
The impedance controller is
Seek control means for performing seek control to change the impedance value of the impedance variable element to a target impedance value at the time of impedance matching;
The deviation between the absolute value of input impedance and each measured value of phase difference and each target value is zero.
Following control means for performing following control to increase or decrease the impedance value of the impedance variable element;
And a control switching means for switching control from the seek control unit to the following control unit,
The control switching means is
It has a switching range set by a predetermined threshold value determined for each target value of the absolute value of the input impedance and the phase difference,
In the switching range of the control switching means, the switching range of the absolute value of the input impedance is such that the phase difference is 0 and the impedance value of the input impedance indicates the extreme value when the impedance variable element is changed. It is a range larger than the absolute value of input impedance,
Prioritizing the seek control means over the following control means, and making the impedance value close to the target value by seek control of the seek control means, then measuring each of the absolute value and phase difference of the input impedance by the control switching means When the measured value is outside the switching range that does not include the target value, the seek control means is selected, and when the measured value is within the switching range that includes the target value, the following control means is selected. An impedance matching apparatus that selects and switches from the seek control means to the following control means and performs impedance matching by following control of the following control means in the vicinity of the target value.   The seek control means calculates a target impedance value at the time of impedance matching by using each measurement value of the absolute value and phase difference of the input impedance, and the impedance value of the impedance variable element toward the calculated target impedance value The impedance matching device according to claim 1, wherein the impedance matching device is changed. The impedance variable element of the impedance matching circuit includes a first variable capacitor connected in parallel on the input side, and a second variable capacitor connected in series on the output side,
The seek control means includes
The measured values of the absolute value and phase difference of the input impedance, the capacitance (Ct) of the first variable capacitor of the impedance matching circuit, the capacitance (Cm) of the second variable capacitor, and the inductance (Lm) of the impedance matching circuit Based on the above, the reactance component (Xo) of the load and the resistance component (Ro) of the load are calculated,
Using the calculated load reactance (Xo) and load resistance (Ro), the capacitance (Ctref) of the first capacitor of the impedance matching circuit when the absolute value and the phase difference of the input impedance are the target values. ) And the capacitance (Cmref) of the second capacitor, the impedance matching device according to claim 2 . The impedance variable element of the impedance matching circuit includes a first variable capacitor connected in parallel on the input side, and a second variable capacitor connected in series on the output side,
The following control means includes
Phase control means for controlling the phase difference to zero by increasing or decreasing the second variable capacitor according to the sign of the phase difference;
Absolute value control means for adjusting the absolute value of the input impedance to the absolute value of the characteristic impedance on the power supply side by increasing or decreasing the first variable capacitor according to the magnitude of the absolute value of the input impedance;
2. The impedance matching apparatus according to claim 1 , wherein the phase control unit and the absolute value control unit start control with an initial value in the vicinity of the target value controlled by the seek control unit. Target value of the absolute value of the input impedance is the characteristic impedance of the power supply side, and wherein the target value of the phase difference is 0, the impedance matching device according to any one of claims 1 to 4 . By providing an impedance matching circuit with an impedance variable element between the high-frequency power source and the load, and changing the impedance value of the impedance variable element, the absolute value of the input impedance of the impedance matching circuit and the voltage and current In the impedance matching method for matching the impedance of the high-frequency power supply and the load by impedance control that matches the phase difference to the target value,
Seek control to change the impedance value of the variable impedance element to a target impedance at the time of impedance matching;
Following control to increase or decrease the impedance value of the impedance variable element so that the deviation between each measured value and each target value of the absolute value and phase difference of the input impedance becomes zero,
Control switching to switch from the seek control to the following control,
The control switching is
It has a switching range set by a predetermined threshold value determined for each target value of the absolute value of the input impedance and the phase difference,
In the switching range of the control switching, the switching range of the absolute value of the input impedance is an input at the extreme value in the F-characteristic of the input impedance indicating the extreme value when the phase difference is 0 and the impedance variable element is changed. It is a range larger than the absolute value of impedance,
The seek control is prioritized over the following control, and after the impedance value is brought close to the target value by the seek control, the absolute value of the input impedance and each measured value of the phase difference are compared with the switching range by the control switching. When the measured value is outside the switching range not including the target value, the seek control is selected, and when the measured value is within the switching range including the target value, the following control is selected, Switching to following control, impedance matching is performed by the following control in the vicinity of the target value.