WO2018051447A1

WO2018051447A1 - Matching device

Info

Publication number: WO2018051447A1
Application number: PCT/JP2016/077211
Authority: WO
Inventors: 高橋　直人; 押田　善之; 規一加藤
Original assignee: 株式会社日立国際電気
Priority date: 2016-09-15
Filing date: 2016-09-15
Publication date: 2018-03-22
Also published as: JPWO2018051447A1

Abstract

This matching device is provided with: a directional coupler; a matching circuit comprising a first variable capacitor and a second variable capacitor; a control unit; and a storage unit that stores corrected setting values for the capacitance value of the first variable capacitor and the capacitance value of the second variable capacitor determined on the basis of set values for the capacitance values of a third variable capacitor and a fourth variable capacitor in a matching device serving as a reference and of the impedance of the matching device serving as the reference when the set values were set. The control unit corrects the set values for the capacitance value of the first variable capacitor and the capacitance value of the second variable capacitor on the basis of the corrected setting values for the capacitance value of the first variable capacitor and the capacitance value of the second variable capacitor in the storage unit.

Description

Matcher

The present disclosure relates to a matching device and can be applied to, for example, a matching device that matches the output of a high frequency power supply device to a load.

A plasma processing apparatus is used in a semiconductor manufacturing process in which etching or thin film formation is performed. A high frequency power supply device is used as a power supply source of the plasma processing apparatus. In order to efficiently supply power from the high frequency power supply device to the plasma processing apparatus, it is necessary to match the impedance between the high frequency power supply apparatus and the plasma processing apparatus (load). As a means for matching impedance, for example, as shown in Patent Document 1, a matching unit is inserted between a high frequency power supply device and a plasma processing apparatus. The matching unit is configured to include a matching circuit having a matching element for matching impedance between the high-frequency power supply device and the plasma processing apparatus. The matching circuit is configured to include a variable capacitor, an inductance, and a transmission line.

WO2015 / 129678

A variable capacitor uses a stepping motor to change the capacitance value, but due to the capacitance accuracy of the variable capacitor, there are rare instances where the capacitance value of the variable capacitor is completely different from the set value even if it is set. Exists. Matching devices equipped with the variable capacitors have the same impedance as other matching devices, but the impedance is completely different, so there is a significant difference in matching operation (trajectory, time) even when connected to a plasma load. The throughput of the device depends on the individual matchers and is not stable.
The subject of this indication is providing the matching device which reduces the capacity | capacitance error of a variable capacitor.

An outline of typical ones of the present disclosure will be briefly described as follows.
That is, the matching device includes a directional coupler, a matching circuit having a first variable capacitor and a second variable capacitor, a control unit, a third variable capacitor of the reference matcher, and a first variable capacitor. The capacitance value of the first variable capacitor obtained based on the set value of the capacitance value of the variable capacitor of 4 and the impedance of the reference matching device when the set value is set, and the second A storage unit that stores a correction setting value of the capacitance value of the variable capacitor. The control unit sets a capacitance value of the first variable capacitor and a set value of the capacitance value of the second variable capacitor, and sets the capacitance value of the first variable capacitor and the second variable of the storage unit. Correction is made based on the correction setting value of the capacitance value of the capacitor.

According to the matching device, the capacity error can be reduced.

FIG. 1 is a functional block diagram of the matching device according to the embodiment. FIG. 2 is a configuration diagram of the matching circuit according to the embodiment. FIG. 3 is a configuration diagram of a storage unit according to the embodiment. FIG. 4 is a diagram for explaining an example of the locus of the reflection coefficient when the capacitance of the variable capacitor is changed. FIG. 5 is a diagram for explaining another example of the locus of the reflection coefficient when the capacitance of the variable capacitor is changed. FIG. 6 is a diagram illustrating a locus of a reflection coefficient according to the example. FIG. 7 is a flowchart of impedance matching processing according to the embodiment. FIG. 8 is a diagram showing the impedance (with VC1 fixed) of a matching unit equipped with a correctly adjusted variable capacitor. FIG. 9 is a diagram showing the impedance (with VC2 fixed) of a matching device equipped with a correctly adjusted variable capacitor. FIG. 10 is a diagram illustrating the impedance (VC1 is fixed) of a matching device equipped with a variable capacitor that is not correctly adjusted. FIG. 11 is a diagram showing the impedance (VC2 is fixed) of a matching device equipped with a variable capacitor that is not correctly adjusted. FIG. 12 is a flowchart showing the capacity adjustment and matching operation of the variable capacitor. FIG. 13 is a diagram showing the relationship (VC2 fixed) between the VC step value and the reflection coefficient (U, V) value of the matching units (A) and (B). FIG. 14 is a diagram showing the relationship (VC1 fixed) between the VC step value and the reflection coefficient (U, V) value of the matching units (A) and (B). FIG. 15 is a diagram showing a conversion table (VC1). FIG. 16 shows the conversion table (VC2).

Hereinafter, examples will be described with reference to the drawings. However, in the following description, the same components may be denoted by the same reference numerals and repeated description may be omitted.

FIG. 1 is a functional block diagram of the matching device according to the embodiment. In FIG. 1, a matching device 10 is inserted between the high frequency power supply device 2 and the plasma processing device 3. By supplying high-frequency power output from the high-frequency power supply device 2 to the plasma processing device 3 via the matching unit 10, plasma is generated in the plasma processing device 3. In order to efficiently supply power from the high frequency power supply device 2 to the plasma processing apparatus 3, it is necessary to match the impedance between the high frequency power supply apparatus 2 and the plasma processing apparatus 3. Since the output impedance of the high-frequency power supply device 2 is normally 50Ω, the input impedance of the plasma processing device 3 may be converted by the matching device 10 so that the input impedance of the matching device 10 is 50Ω.

The input impedance of the plasma processing apparatus 3 varies depending on the type, flow rate, pressure, temperature, etc. of the gas input to the plasma processing apparatus 3. Therefore, the matching unit 10 needs to adaptively match according to the input impedance of the plasma processing apparatus 3 that changes with time.

1 includes a directional coupler 11 for detecting traveling waves and reflected waves, a matching circuit 30 having a matching element for matching impedance between the high-frequency power supply device 2 and the plasma processing device 3, The control unit 20 for controlling the circuit constant of the matching element of the matching circuit 30 and the storage unit 25 are configured.

The operation of the directional coupler 11 will be described. High-frequency power (traveling wave: Pf) traveling from the RFin terminal toward the RFout terminal is detected by the directional coupler 11 and output to the FORWARD terminal. High frequency power (reflected wave: Pr) traveling from the RFout terminal to the RFin terminal is detected by the directional coupler 11 and output to the REFLECT terminal. Further, the high-frequency power (Pf) traveling from the RFin terminal toward the RFout terminal is not detected by the REFECT terminal but is small even if detected. Similarly, the high-frequency power (Pr) traveling from the RFout terminal toward the RFin terminal is not detected at the FORWARD terminal and is small if detected.

The control unit 20 is configured to include a reflection coefficient calculation unit 21, a capacitance calculation unit 22, and a capacitance setting unit 23.

The traveling wave (Pf) and the reflected wave (Pr) detected by the directional coupler 11 are input to the reflection coefficient calculation unit 21 of the control unit 20. The reflection coefficient (Γ) is defined as in Expression (1) from the amplitude ratio (r) of the reflected wave (Pr) to the traveling wave (Pf) and the phase difference (θ).
Γ = r · exp (j · θ) (j: imaginary unit) (1)
Therefore, if the amplitude ratio (r) and the phase difference (θ) of the reflected wave (Pr) with respect to the traveling wave (Pf) are known, the reflection coefficient (Γ) can be obtained. The reflection coefficient calculator 21 calculates the amplitude ratio (r) and the phase difference (θ) based on the traveling wave (Pf) and the reflected wave (Pr), and calculates the reflection coefficient (Γ). As a specific method, the traveling wave (Pf) and the reflected wave (Pr) are converted into a frequency domain by FFT (Fast Fourier Transform), and the traveling wave is the same frequency as the high-frequency power output from the high-frequency power supply device 2. The amplitude ratio (r) and the phase difference (θ) may be calculated by comparing the amplitude and phase of (Pf) and the reflected wave (Pr).

The capacitance calculation unit 22 calculates a capacitor capacity for making the reflection coefficient (Γ) close to zero based on the reflection coefficient (Γ) calculated by the reflection coefficient calculation unit 21. A method for calculating the capacitor capacity will be described later. The capacitance setting unit 23 sets and changes the capacitance of the variable capacitance capacitor in the matching circuit 30 based on the capacitance of the capacitor calculated by the capacitance calculation unit 22.

FIG. 2 is a configuration diagram of the matching circuit according to the embodiment. The circuit configuration of the matching circuit 30 is determined by the range in which the input impedance of the plasma processing apparatus 3 serving as a load varies. Here, a description will be given by using a π-type matching circuit as an example. The matching circuit 30 includes a first variable capacitor 31, a second variable capacitor 32, an inductance 33, a transmission line 35, and a transmission line 36. The transmission line 35 and the transmission line 36 can be configured by a coaxial cable, a metal plate, or the like, or can be configured to include a lumped constant circuit of an inductor or a capacitor.

The transmission line 35 connects the input terminal 30 a of the matching circuit 30 and one end of the first variable capacitor 31. The other end of the first variable capacitor 31 is grounded. The transmission line 36 connects the output terminal 30 b of the matching circuit 30 and one end of the second variable capacitor 32. The other end of the second variable capacitor 32 is grounded.

The first variable capacitor 31, the second variable capacitor 32, and the inductance 33 are matching elements for impedance matching between the high frequency power supply device 2 and the plasma processing device 3. The matching circuit 30 includes a variable capacitor control terminal 31a for controlling the capacitance of the first variable capacitor 31 and a variable capacitor control terminal 32a for controlling the capacitance of the second variable capacitor 32. Is provided.

Control of the variable capacitor of the matching circuit 30 is controlled so that the magnitude of the reflection coefficient (Γ) calculated from the traveling wave (Pf) detected by the directional coupler 11 and the reflected wave (Pr) becomes small. .

As described above, the control unit 20 calculates the reflection coefficient based on the traveling wave and the reflected wave detected by the directional coupler 11, and uses the reflection coefficient to determine the capacitance value of the first variable capacitor 31. (VC1) and the capacitance value (VC2) of the second variable capacitor 32 are controlled. The storage unit 25 stores circle information and the like described later. As shown in FIG. 3, the storage unit 25 includes a CPU built-in SRAM 251, an external SRAM (volatile memory) 252, and an external EEPROM (nonvolatile memory) 253.

Here, the circle information is the circle information drawn by the locus of the reflection coefficient (Γ) passing through the matching point (the point where the real part and the imaginary part of the reflection coefficient (Γ) are zero) on the Smith chart. Information on the position and size of the circle. It is known that this circle information is determined based on the condition of the transmission line 35, that is, the characteristic impedance (ZL) and the line length (L) of the transmission line 35.

The capacitance calculation unit 22 is a matching circuit corresponding to the calculated reflection coefficient (Γ) based on the reflection coefficient (Γ) calculated by the reflection coefficient calculation unit 21 and the circle information stored in the storage unit 25. The capacitance value (VC1) of the 30 first variable capacitor 31 and the capacitance value (VC2) of the second variable capacitor 32 are calculated. That is, VC1 and VC2 that reduce the calculated reflection coefficient (Γ) are calculated.

Specifically, the capacitance calculation unit 22 is configured so that the reflection coefficient (Γ) calculated by the reflection coefficient calculation unit 21 approaches the circle stored in the storage unit 25. A capacity value (VC2) of 32 is calculated. Then, the capacitance setting unit 23 changes the capacitance value (VC2) of the second variable capacitor 32 so that the calculated capacitance is obtained. Thereby, the capacitance setting unit 23 positions the reflection coefficient Γ on the circle.

After that, the capacitance calculation unit 22 calculates the capacitance value (VC1) of the first variable capacitor 31 of the matching circuit 30 so that the reflection coefficient Γ calculated by the reflection coefficient calculation unit 21 becomes small. Then, the capacitance setting unit 23 changes the capacitance value (VC1) of the first variable capacitor 31 so that the calculated capacitance is obtained. Thereby, the capacity setting unit 23 positions the reflection coefficient (Γ) at the matching point (the point where the reflection coefficient (Γ) is 0).

In the storage unit 25, circle information corresponding to the transmission line 35 is stored in advance. As described above, the information (position and size) of the circle is determined based on the condition of the transmission line 35, that is, the sex impedance (ZL) and the line length (L) of the transmission line 35. For example, when the transmission line 35 is short enough to be ignored, the circle becomes a circle R1 shown in FIG. Further, when the transmission line 35 has a characteristic impedance of 50Ω and a line length of λ / 4, the circle is a circle R2 shown in FIG. 5 and a circle R3 shown in FIG.

Here, the concept of the matching algorithm of this embodiment will be described. When the impedance between the high frequency power supply device 2 and the plasma processing device 3 matches (that is, the reflection coefficient (Γ) is 0) at a certain plasma load, the values of VC1 and VC2 are VC1 = X and VC2 = Y. And For easy understanding, the locus of the input impedance of the matching circuit 30, that is, the locus of the reflection coefficient (Γ) when VC1 is changed from the matching conditions VC1 = X and VC2 = Y. This is shown in the Smith chart of FIG. In this case, the transmission line 35 is assumed to be negligibly short compared to the wavelength (λ) of the traveling wave or the reflected wave.

4, when VC1 is changed, the locus of the reflection coefficient (Γ) draws a circle R1 whose diameter is a line segment connecting the F point and the G point in a matched state. The reflection coefficient (Γ) at point F has zero imaginary part (Γi) and zero real part (Γr) (the input impedance of the matching device 10 is 50Ω). The reflection coefficient (Γ) at point G has an imaginary part of zero and a real part of −1.

Specifically, in FIG. 4, when VC1 is increased in a state of matching (point F), the reflection coefficient (Γ) moves on the circle R1 from the point F to the point A. Further, when VC1 is decreased, it moves on the circle R1 from the point F to the point B. This is because the first variable capacitor 31 is connected (grounded) to the ground in the π-type matching circuit 30 of FIG. 2 including the first variable capacitor 31, the second variable capacitor 32, and the inductance 33. Since it is generally known as an impedance locus when it is, detailed description is omitted.

FIG. 4 shows a case where the transmission line 35 can be ignored, but in reality it may not be ignored. The Smith chart of FIG. 5 shows the locus of the reflection coefficient (Γ) when the characteristic impedance of the transmission line 35 is 50Ω and the line length is λ / 4. In FIG. 4, it is known that the locus of the reflection coefficient (Γ) draws a circle R2 whose diameter is a line segment connecting the F point and the H point in a matched state. The reflection coefficient (Γ) at point H has an imaginary part of zero and a real part of 1 (the input impedance of the matching device 10 is infinite).

In the matching circuit 30 of FIG. 2, assuming that the input impedance viewed from the right end of the transmission line 35 is Z1, and the input impedance viewed from the left end of the transmission line 35 is Z2, Z2 is determined by the following equation (2). In Expression (2), Z1 is an input impedance when the transmission line 35 can be ignored (FIG. 4), and Z2 is an input impedance when the transmission line 35 cannot be ignored (FIG. 5). When the transmission line 35 cannot be ignored (FIG. 5), the circle R1 in FIG. 4 becomes the circle R2 in FIG.

As described above, since the transmission line 35 having the characteristic impedance of 50Ω and the line length of λ / 4 is inserted in the locus in FIG. 5, the real part and the imaginary part of the reflection coefficient (Γ) are in the locus in FIG. The state is rotated by 180 ° around the zero point (F point). Therefore, in FIG. 5, when VC1 is increased in a matched state (point F), the reflection coefficient (Γ) becomes the direction of the point A ′ on the circle R2 (the imaginary part of the reflection coefficient (Γ) is positive). Direction). When VC1 is decreased, the reflection coefficient (Γ) moves on the circle R2 in the direction of the point B ′ (the imaginary part of the reflection coefficient (Γ) is negative). That is, on the circle R2 in FIG. 5, when the imaginary part of the reflection coefficient (Γ) is positive, VC1 is larger than the matching value X, and when the imaginary part of the reflection coefficient (Γ) is negative, VC1 is matched. Less than value X.

As described above, in FIG. 5, when VC1 is increased or decreased at the matching point (point F), the reflection coefficient (Γ) follows a locus that draws a circle R2. This indicates that when VC1 is changed in a state where VC2 is at the matching value, the reflection coefficient (Γ) moves on the circle R2 shown in FIG. Therefore, it can be understood that VC1 is first controlled so that the reflection coefficient (Γ) is on the circle R2 in FIG. 5, and then VC1 is controlled so that the reflection coefficient (Γ) becomes zero.

FIG. 6 shows a reflection coefficient (when the impedance matching is performed according to the embodiment in the case of the matching circuit 30 similar to FIG. 5, that is, when the characteristic impedance of the transmission line 35 is 50Ω and the line length is λ / 4. It is a Smith chart which shows the locus | trajectory of (GAMMA). The point C is the reflection coefficient (Γ) when VC1 and VC2 are initial values (for example, the minimum value of the variable capacitor), that is, the input impedance of the matching unit 10 when the plasma load is at a certain input impedance value. It is.

First, the control unit 20 increases only VC2 until the reflection coefficient (Γ) reaches the point D in contact with the circle R3 from the initial point C of VC1 and VC2. The circle R3 is the same as the circle R2 in FIG. Information on the circle R3 is stored in the storage unit 25. When the reflection coefficient (Γ) reaches the point D in contact with the circle R3, VC2 becomes Y which is the capacity at the time of matching. In this state, VC2 is controlled to the matching value, but VC1 remains at the initial value. Therefore, the control unit 20 then increases VC1. When VC1 is increased, as described above, the reflection coefficient (Γ) moves on the circle R3. Therefore, it is only necessary to increase VC1 and stop increasing VC1 when the reflection coefficient (Γ) becomes zero. VC1 at that time is X, which is a capacity at the time of matching.

6 is an example when the input impedance of the plasma load is at a certain value. However, if the input impedance of the plasma load is changed, the positions of the point C and the point D naturally change. However, when VC2 is the capacitance at the time of matching, the reflection coefficient (Γ) is on the circle R3.

In the case of point C in FIG. 6, the minimum value of the variable capacitor is selected as the initial value of VC1 and VC2, but it may be the maximum value of the variable capacitor or any other value. In that case, of course, the position of the point C changes. However, regardless of the initial values of VC1 and VC2, if VC2 is the value at the time of matching, the phenomenon that the reflection coefficient (Γ) moves on the circle R3 when VC1 is changed. Will not change.

Therefore, until the reflection coefficient (Γ) touches the circle R3, only the VC2 is controlled, and after touching the circle R3, only the VC1 is controlled. In the control of VC2, when VC2 is larger than the matching value Y, the reflection coefficient (Γ) is outside the circle R3, so that by reducing VC2, the reflection coefficient (Γ) is in contact with the circle R3. Control. On the contrary, when VC2 is smaller than the matching value Y, the reflection coefficient (Γ) is in the circle R3. Therefore, by increasing VC2, control is performed so that the reflection coefficient (Γ) is in contact with the circle R3. .

Then, after controlling VC2 so that the reflection coefficient (Γ) is in contact with the circle R3, VC1 is controlled as follows. That is, when the imaginary part of the reflection coefficient (Γ) is positive, VC1 is a value larger than the matching value X. Therefore, the control is performed so that the reflection coefficient (Γ) becomes 0 by reducing VC1. To do. On the contrary, when the imaginary part of the reflection coefficient (Γ) is negative, VC1 is smaller than X. Therefore, by increasing VC1, control is performed so that the reflection coefficient (Γ) becomes zero.

Further, even when the input impedance of the plasma load changes during the control of VC1 and VC2, VC2 and VC1 are controlled as described above. That is, VC1 is controlled after controlling VC2 so that the reflection coefficient (Γ) is in contact with the circle R3.

In the description of FIG. 5 and FIG. 6, the case where the characteristic impedance of the transmission line 35 is 50Ω and the line length is λ / 4 in the matching circuit 30 of FIG. 2 has been described as an example. It is not limited to the case. If the condition of the transmission line 35 is different from the above condition, the locus of the circle when VC1 is changed under the condition that VC2 is the capacity at the time of matching is the locus of the circle R3 shown in FIGS. Since they are different, the locus of the circle may be set according to the condition of the transmission line 35 by the above-described equation (2).

FIG. 7 is a flowchart of impedance matching processing according to the embodiment. This process is executed by the control unit 20. First, as an initial setting, the circle information (position and size on the Smith chart) shown in FIGS. 5 and 6 is stored and stored in the storage unit 25 (step S1 in FIG. 7). As described above, since the information on this circle is determined by the transmission line 35, it is necessary to provide information according to the matching circuit 30. In step S1, initial values of VC1 and VC2 are also set.

Next, the reflection coefficient (Γ) at that time is calculated from the traveling wave (Pf) and the reflected wave (Pr) obtained from the directional coupler 11 (step S2). Next, the absolute value of the reflection coefficient (Γ) is compared with a predetermined value (L) (step S3). When the absolute value of the reflection coefficient (Γ) is L or less (Yes in Step S3), the process returns to Step S2, and the traveling wave (Pf) and the reflected wave (Pr) are obtained from the directional coupler 11, and again Then, the reflection coefficient (Γ) at that time is calculated.

If the absolute value of the reflection coefficient (Γ) is larger than L (No in step S3), the process proceeds to step S4. This L is a threshold value for determining that matching has been achieved and is ideally 0, but in reality, it is difficult to set the reflection coefficient (Γ) to 0. Judgment is made by providing (L). This L is a value determined by the reflection resistant power of the high frequency power supply device 2 and the required specifications of the plasma processing apparatus 3 using the high frequency power supply device 2.

In step S4, in order to determine whether or not there is a reflection coefficient (Γ) on the circle defined in the initial setting (step S1), information on the circle is acquired from the storage unit 25, and the reflection coefficient (Γ), the circle, The minimum value (P) of the distance is calculated. If this value (P) is larger than the predetermined threshold value (M) (Yes in step S5), since VC2 is not a matching value, control is performed to change VC2. Specifically, it is determined that the reflection coefficient (Γ) is not on a circle, and the process proceeds to step S6. This M is also ideally 0, but in reality it is difficult to make it 0, so it is set to a predetermined value.

If P is equal to or less than the predetermined threshold (M) (No in step S5), VC2 is a matching value, so there is no need to change VC2. Therefore, the process proceeds to the control operation of VC1 (that is, the first variable capacitor 31). That is, it is determined that the reflection coefficient (Γ) is on a circle, and the process proceeds to step S10.

In step S6, in order to determine the direction in which VC2 (that is, the second variable capacitor 32) is controlled, it is determined whether or not the reflection coefficient (Γ) is inside the circle. If the reflection coefficient (Γ) is inside the circle (Yes in step S6), VC2 is smaller than Y, so VC2 is increased (step S7). If the reflection coefficient Γ is outside the circle (No in step S6), VC2 is larger than Y, so VC2 is reduced (step S8). At this time, the amount to be reduced and the amount to be increased may be set in advance.

Thus, by repeating the processing from step S2 to step S7 or S8, P can be made equal to or less than a predetermined threshold value (M), that is, the reflection coefficient (Γ) can be placed almost on the circle. Thus, when it is determined in step S5 that P is equal to or less than M, the process proceeds to step S10, and the control operation of VC1 (that is, the first variable capacitor 31) is performed.

In step S10, it is determined whether or not the imaginary part of the reflection coefficient (Γ) is negative, that is, whether or not VC1 is smaller than X. As described above, VC1 is smaller than X when the imaginary part of the reflection coefficient (Γ) is negative, and VC1 is larger than X when the imaginary part of the reflection coefficient (Γ) is positive. Therefore, when the imaginary part of the reflection coefficient (Γ) is negative (Yes in step S10), VC1 is increased. If the imaginary part of the reflection coefficient (Γ) is positive (No in step S10), VC1 is decreased. Thus, by changing VC1, the reflection coefficient (Γ) is brought close to zero. The amount of increase / decrease at this time is also set in advance.

As described above, the control unit 20 calculates a reflection coefficient based on the traveling wave and the reflected wave detected by the directional coupler 11, and a circle drawn by the locus of the reflection coefficient passing through the matching point on the Smith chart. And the calculated reflection coefficient is larger than a predetermined value, the capacitance value of the second variable capacitor 32 is changed, and the calculated reflection coefficient is changed to change the distance. When the distance is within the predetermined value and the distance is within the predetermined value, the capacitance value of the first variable capacitor 31 is changed, and the calculated reflection coefficient is reduced without changing the distance. That is, the control unit 20 calculates a reflection coefficient based on the traveling wave and the reflected wave detected by the directional coupler 11, and the first variable capacitance capacitor 31 is configured so that the calculated reflection coefficient becomes small. The capacitance value and the capacitance value of the second variable capacitor 32 are changed.

Next, adjustment of the capacitance value of the variable capacitor will be described with reference to FIGS. FIG. 8 is a diagram showing the impedance (with VC1 fixed) of a matching unit equipped with a correctly adjusted variable capacitor. FIG. 9 is a diagram showing the impedance (with VC2 fixed) of a matching device equipped with a correctly adjusted variable capacitor. FIG. 10 is a diagram illustrating the impedance (VC1 is fixed) of a matching device equipped with a variable capacitor that is not correctly adjusted. FIG. 11 is a diagram showing the impedance (VC2 is fixed) of a matching device equipped with a variable capacitor that is not correctly adjusted.

The matching unit is left to the capacitor manufacturer to adjust the capacitance value of the variable capacitor mounted inside, so even if the capacitance value of the variable capacitor is set due to human factors such as adjustment errors by the manufacturer There are rare individuals with completely different capacities. As shown in FIGS. 8 and 10, the reflection coefficients (U, V) when VC1 is fixed and VC2 is changed are completely different. Further, as shown in FIGS. 9 and 11, the reflection coefficients (U, V) when VC2 is fixed and VC1 is changed are completely different. In this way, a matching device equipped with variable capacitance capacitors with different capacitance values has a completely different impedance even if the same capacitance value is set as other matching devices, so matching operation (trajectory, time) even when connected to plasma load The throughput of the plasma processing apparatus depends on individual matching devices and is not stable.

In this embodiment, the capacitance value-impedance data of the variable capacitor of the reference matching device is prepared, and the capacitance of the variable capacitance capacitor is obtained by bringing the impedance of the other matching device closer to the data of the reference matching device. Differences in individual matching operations due to errors are solved, and uniform matching operations are performed uniformly. Details will be described below.

First, the capacity adjustment of the variable capacitor will be described with reference to FIGS. FIG. 12 is a flowchart showing the capacity adjustment and matching operation of the variable capacitor. FIG. 13 is a diagram showing the relationship (VC2 fixed) between the VC step value and the reflection coefficient (U, V) value of the matching units (A) and (B). FIG. 14 is a diagram showing the relationship (VC1 fixed) between the VC step value and the reflection coefficient (U, V) value of the matching units (A) and (B). FIG. 15 is a diagram showing a conversion table (VC1). FIG. 16 shows the conversion table (VC2).

Step S21: The data (C, D) as a set of the variable capacitor step value (C) of the reference matching unit (hereinafter referred to as matching unit (A)) and the impedance (D) at that time are measured in advance. prepare. For example, (C0, D0), (C1, D1), (C2, D2), (C3, D3), ..., (Cn, Dn), where C0 (= 0) is the minimum value of the step, Cn Is the maximum value of the step.

Specifically, the step value of the first variable capacitor 31 of the matching unit (A) is fixed at 80 steps from VC1 = 0 to 640, and the step value of the second variable capacitor 32 is fixed at VC2 = 320. The reflection coefficient (U, V) is measured. The reflection coefficient (U, V) is measured by fixing VC1 = 320 in steps of 80 steps of VC2 = 0 to 640. Here, C = (VC1, VC2) and D = (U, V).

Step S22: A matching unit on the correction side, that is, a matching unit equipped with a variable capacitor that is not correctly adjusted (hereinafter referred to as a matching unit (B)) is the matching unit (A) obtained in step S21. A step value (E) that becomes the impedance (D) of the variable capacitor is measured and prepared. For example, (E0, D0), (E1, D1), (E2, D2), (E3, D3), ..., (En, Dn).

Specifically, the reference is (U, V) = (− 399.82, 321.05) when (VC1, VC2) = (320, 320) of the matching unit (A) acquired in step S21. And The matching unit (B) searches for the step values of VC1 and VC2 in advance so that the reflection coefficient (U, V) = (− 399.82, 321.05) of the matching unit (A) is as close as possible. As a result of the search, for example, by setting the step value of the matching unit (B) to (VC1, VC2) = (347,363), (U, V) = (− 394.17,327.13). . From this result, the VC1 step value of the matching unit (B) is fixed at 347, and the VC2 value of the matching unit (A) is changed from 0 to 640 by changing the step value of VC2 (U, V) value. Search for the value of VC2 such that The result is shown in FIG. Similarly, the VC2 step value of the matching unit (B) is fixed at 363 from the search result in step S21, and the VC1 of the matching unit (A) is changed in 80 steps from 0 to 640 by changing the step value of VC1. Search for the value of VC1 that is the (U, V) value of. The result is shown in FIG. Here, E = (VC1, VC2) and D = (U, V).

As shown in FIG. 13, for example, when it is desired to bring the impedance of the matching unit (B) closer to the impedance of VC1 = 0 step of the matching unit (A), this can be handled by correcting VC1 = 30 steps.

Step S23: The data acquired in step S22 is downloaded from an external terminal such as the PC 40 to the matching unit and stored in a nonvolatile storage medium such as an EEPROM in the storage unit.

Specifically, the VC1 data sets (0, 30), (80, 110), (160, 190), (240, 268), (320) of the matching units (A) and (B) shown in FIG. , 347), (400, 424), (480, 499), (560, 575), and (640, 640) are stored in the external EEPROM 253 of the storage unit 25 using an external terminal such as the PC 40. Similarly, the VC2 data sets (0, 34), (80, 122), (160, 202), (240, 283), (320, 363) of the matching units (A) and (B) shown in FIG. , (400, 443), (480, 523), (560, 603), and (640, 640) are stored in the external EEPROM 253 of the storage unit 25 using an external terminal such as the PC 40. The PC 40 and the control unit 20 transmit and receive via RS232C communication.

Step S24: When the matching unit is powered on, a table is created on a volatile storage medium such as SRAM of the storage unit with reference to the data stored in Step S23. The table interpolates between data depending on the resolution of the original data.

Specifically, the control unit 20 refers to the data stored in the external EEPROM in step S24 when the matching unit (B) is powered on, and determines the two points from the relationship shown in the graphs of FIGS. By repeating this interpolation, the correction step value for each step is obtained for each of the VC1 and VC2 steps 0 to 640 of the matching unit (B) with respect to the true step value. Then, as shown in FIGS. 15 and 16, the control unit 20 develops 0 to 640 in the external SRAM 252 of the storage unit 25 as indexes (addresses) on the memory (stores correction step values).

Step S25: The capacity of the matching device derived by the calculation and algorithm at the time of matching operation is step-converted by the table created in step S24, and the capacitance value actually set in the variable capacitor is determined from the step value and set.

Specifically, when the matching unit (B) is operated, the control unit 20 performs the capacity calculation of VC1 and VC2 to be set in the matching operation using the reflection coefficient and the algorithm in the capacity calculation unit 22 of FIG. Is actually set to the first variable capacitor 31 and the second variable capacitor 32 by the capacitance setting unit 23 to perform the matching operation. At this time, the calculation result in the capacity calculation unit 22 is compared with the capacity setting unit 23 in order from 0 to 640 of the indexes in the tables of FIG. 15 and FIG. 16, and the correction capacity value corresponding to the index that matches the calculation result is set. .

Further, the capacity calculation unit 22 acquires a step value from the first variable capacitor 31 or the second variable capacitor 32 as necessary, and uses it as a material for calculating the set capacity. In that case, the acquired step value and the correction capacitance value in the table are compared in order from the top, and the index of the matching correction capacitance value becomes the step value before correction.

In this embodiment, it is possible to correct the alignment operation by simply having a table on the memory without significantly changing the original algorithm.

】 The throughput of the plasma processing equipment does not depend on each matching unit and is stabilized. Even if an inexpensive variable capacitor with inferior capacity accuracy is used, capacity correction can be performed using a high performance variable capacitor as reference data, leading to cost reduction.

The matching device according to the embodiment is suitable for a microwave power source for generating plasma, and can be used in a wide frequency including ISM bands such as 13.56 MHz, 915 MHz, 2.45 GHz, and 5.8 GHz.

This specification includes at least the following configurations related to the present invention.

The matching device of the first configuration is:
A directional coupler for detecting traveling waves and reflected waves;
An input terminal, an output terminal, a first variable capacitor having one end connected to the input terminal via a first transmission line and the other end grounded, and one end connected to the output via a second transmission line A second variable capacitor connected to the terminal and grounded at the other end; one end connected to the one end of the first variable capacitor; the other end connected to the one end of the second variable capacitor. A matching circuit having an inductance; and
A control unit for controlling a capacitance value of the first variable capacitor and a capacitance value of the second variable capacitor based on a traveling wave and a reflected wave detected by the directional coupler;
The value obtained based on the set value of the capacitance value of the third variable capacitor and the fourth variable capacitor of the reference matching unit and the impedance of the reference matching unit when the set value is set A storage unit that stores a correction value of the capacitance value of the first variable capacitor and the capacitance value of the second variable capacitor;
With
The controller is
Based on the traveling wave and the reflected wave detected by the directional coupler, a reflection coefficient is calculated,
Changing the capacitance value of the first variable capacitor and the capacitance value of the second variable capacitor so that the calculated reflection coefficient becomes small;
Calculating a set value of the capacitance value of the first variable capacitor and the capacitance value of the second variable capacitor;
The capacitance value of the first variable capacitor and the set value of the capacitance value of the second variable capacitor are set as the capacitance value of the first variable capacitor and the capacitance of the second variable capacitor of the storage unit. Correction is performed based on the value correction setting value.

The matching device of the second configuration is the first configuration,
The correction set values of the first variable capacitor and the second variable capacitor are set values of the first variable capacitor and the second variable capacitor of the matching device that are the impedance of the reference matching device. Is obtained by measuring.

The matching device of the third configuration is the second configuration,
The storage unit includes a nonvolatile storage medium,
The setting values of the capacitance values of the third variable capacitor and the fourth variable capacitance capacitor, the correction values of the capacitance values of the first variable capacitance capacitor, and the capacitance value of the second variable capacitance capacitor are non-volatile. Stored in a sexual storage medium.

The matching device of the fourth configuration is the third configuration,
The storage unit further includes a volatile storage medium,
The control unit sets a set value of capacitance values of the third variable capacitor and the fourth variable capacitor, a capacitance value of the first variable capacitor, and the second variable when the matching unit is powered on. Interpolation data is calculated based on the correction setting value of the capacitance value of the capacitor and a table is created and stored in the volatile storage medium.

The matching device of the fifth configuration is the fourth configuration,
The table includes a first table configured to read out a correction setting value of the capacitance value of the first variable capacitor using the setting value of the capacitance value of the third variable capacitor as an index, and the fourth table And a second table configured to read out a correction setting value of the capacitance value of the second variable capacitor using the setting value of the capacitance value of the variable capacitor as an index.

As mentioned above, although the invention made by the present inventor has been specifically described based on the embodiments, it is needless to say that the present invention is not limited to the above embodiments and can be variously modified.

DESCRIPTION OF SYMBOLS 2 ... High frequency power supply device, 3 ... Plasma processing apparatus, 10 ... Matching device, 11 ... Directional coupler, 20 ... Control part, 21 ... Reflection coefficient calculating part, 22 ... Capacity calculating part, 23 ... Capacity setting part, 25 ... Storage unit 30 ... matching circuit 30a ... input terminal 30b ... output terminal 31 ... first variable capacitor 32 ... second variable capacitor 31a ... control terminal 32a ... control terminal 33 ... inductance 35, 36 ... transmission lines.

Claims

A directional coupler for detecting traveling waves and reflected waves;
An input terminal, an output terminal, a first variable capacitor having one end connected to the input terminal via a first transmission line and the other end grounded, and one end connected to the output via a second transmission line A second variable capacitor connected to the terminal and grounded at the other end; one end connected to the one end of the first variable capacitor; the other end connected to the one end of the second variable capacitor. A matching circuit having an inductance; and
A control unit for controlling a capacitance value of the first variable capacitor and a capacitance value of the second variable capacitor based on a traveling wave and a reflected wave detected by the directional coupler;
The value obtained based on the set value of the capacitance value of the third variable capacitor and the fourth variable capacitor of the reference matching unit and the impedance of the reference matching unit when the set value is set A storage unit that stores a correction value of the capacitance value of the first variable capacitor and the capacitance value of the second variable capacitor;
With
The controller is
Based on the traveling wave and the reflected wave detected by the directional coupler, a reflection coefficient is calculated,
Changing the capacitance value of the first variable capacitor and the capacitance value of the second variable capacitor so that the calculated reflection coefficient becomes small;
Calculating a set value of the capacitance value of the first variable capacitor and the capacitance value of the second variable capacitor;
The capacitance value of the first variable capacitor and the set value of the capacitance value of the second variable capacitor are set as the capacitance value of the first variable capacitor and the capacitance of the second variable capacitor of the storage unit. A matcher that corrects based on the correction setting value.
In claim 1,
The correction set values of the first variable capacitor and the second variable capacitor are set values of the first variable capacitor and the second variable capacitor of the matching device that are the impedance of the reference matching device. It is obtained by measuring the matcher.
In claim 2,
The storage unit includes a nonvolatile storage medium,
The setting values of the capacitance values of the third variable capacitor and the fourth variable capacitance capacitor, the correction values of the capacitance values of the first variable capacitance capacitor, and the capacitance value of the second variable capacitance capacitor are non-volatile. Matching unit stored in a sexual storage medium.
In claim 3,
The storage unit further includes a volatile storage medium,
The control unit sets a set value of capacitance values of the third variable capacitor and the fourth variable capacitor, a capacitance value of the first variable capacitor, and the second variable when the matching unit is powered on. A matching unit that calculates interpolation data based on the correction setting value of the capacitance value of the capacitor and creates a table and stores it in a volatile storage medium.
In claim 4,
The table includes a first table configured to read out a correction setting value of the capacitance value of the first variable capacitor using the setting value of the capacitance value of the third variable capacitor as an index, and the fourth table And a second table configured to read out a correction setting value of the capacitance value of the second variable capacitor using the setting value of the capacitance value of the variable capacitor as an index.