JP2003046359A - Impedance matching device with load active power measurement function - Google Patents

Abstract

An object of the present invention is to accurately measure effective power consumption of a plasma chamber load using values of circuit elements of an impedance matching device. An apparatus is inserted between a high-frequency power source having a known internal impedance Z0 and a plasma chamber load 3. The device has a first variable reactance 1 for amplitude adjustment and a second variable reactance 2 for phase adjustment,
By controlling these reactances in accordance with the detection values of the phase detection and amplitude detection sections 6, respectively, the load impedance is matched. The power source side impedance viewed from the output terminal Out side of the device is calculated, the load impedance Zc = R ± jX is determined using the conjugate impedance, and the power factor Cos θ = R / √ (R ² + X ² ) is calculated. Power calculation means is provided for calculating the active power consumed by the high-frequency load from the equation P = VICosθ obtained by multiplying the product of the effective voltage V of the input terminal and the effective current value I by the power factor Cosθ.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an impedance matching device to be inserted in a transmission line for transmitting high frequency power from a high frequency power source to a plasma chamber load, and more particularly to an impedance matching device having a load power calculation function.

[0002]

2. Description of the Related Art In order to efficiently transfer energy to a high frequency plasma chamber, it is necessary to automatically match the impedances on the power source side and the load side by an impedance matching device to minimize loss. The impedance matching device is used for this purpose and has a function of automatically adjusting its own impedance according to the power transmission state.

The impedance matching device typically includes a fixed inductance inserted as a main body element in a transmission line, a variable capacitor for phase adjustment connected in series to the fixed inductance, and a power supply side terminal of the fixed inductance and a ground potential. If there is a variable capacitor for amplitude adjustment that is shunt connected between them, and if the power source impedance is, for example, 50Ω, this is automatically adjusted so that the matching load impedance seen from the power source side of the impedance matching circuit is also 50Ω. Match and adjust.

If the impedances match, the high frequency power is ideally supplied with maximum efficiency. However, due to the difference in the material and size of the wiring before and after the impedance matching device and the coil conductor inside the impedance matching device, it is mainly due to Joule heat. Passage loss occurs. Therefore, even if the same power is supplied from the power supply side, the power consumption of the plasma chamber load does not directly occur and the amount of passage loss is reduced.

On the other hand, the impedance inside the chamber also changes depending on the plasma processing recipe (plasma state and time setting depending on the type of gas, etc.). For example, when the actual resistance part R of the plasma chamber load becomes low, the current flowing through the coil of the impedance matching device increases, and the loss (resistance loss) due to the coil increases. As described above, the internal coil loss of the impedance matching device is not constant, and accordingly, the power consumption of the plasma chamber load also changes.

By the way, in the plasma chamber of the same model, the effective power amount of the plasma, that is, the energy consumption amount of the plasma (as a main factor of the process rate (etching rate, deposition rate, ashing rate, etc.)) There is a demand to accurately measure the actual work amount. This is because the factors that affect the process rate consist of complicated entanglement of factors such as pressure, temperature, gas species, vessel shape, and gas flow, and the overall effect of these factors appears as plasma impedance, which in turn This is because the difference in plasma power consumption appears.

Conventionally, the power consumption of the plasma chamber load is limited to the assumption that it is substantially equal to the power supplied from the high frequency power source after impedance matching due to the difficulty of measurement, and the effective power of the load is forced at the load terminal. In order to measure, for example, the instantaneous values of voltage and current (e,
Attempts have been made to determine the average power by measuring i) and integrating the product (instantaneous power) at each instant. However, this method cannot be used at a high frequency because the operation speed of the ei multiplier normally does not catch up with the fluctuation of the instantaneous value, and it is possible only when an ultra-high speed multiplier is used.

[0008]

SUMMARY OF THE INVENTION The present invention determines the work of the real part in the electrical equivalent circuit of the plasma chamber load, that is, the effective power consumption consumed by the plasma,
An object of the present invention is to provide a method and an apparatus for calculating / measuring using an impedance specific value of an impedance matching device.

[0009]

In order to solve the above-mentioned problems, the present invention provides an impedance matching device which is inserted between a high-frequency power source having a known internal impedance Z0 and a high-frequency load composed of a plasma chamber. A phase detection unit and an amplitude detection unit are inserted at the input end, a first variable reactance for amplitude adjustment is connected immediately after the detection units, and a second variable reactance for phase adjustment is provided after the first variable reactance connection position. And a voltage detection unit and a current detection unit are inserted immediately before the output end (that is, the load input end) after the second variable reactance, and the first and second variable reactances are respectively connected to the phase detection unit. Impedance impedance matching between the high frequency power supply side and the load side is controlled by controlling according to the detection value of the amplitude detection section. The impedance on the power source side as viewed from the output side of the matching circuit and the impedance matching circuit in the matching state is calculated, and the conjugate impedance thereof is set as the load impedance Zc = R ± jX (1) and the power factor Cosθ is Cos θ = R / √ (R ² + X ² ) (2) Calculated from (2) and multiplying the product of the voltage effective value V and the current effective value I detected by the voltage detection unit and the current detection unit by the power factor Cos θ P = VICosθ (3) The power calculation means for calculating the active power consumed by the high frequency load is provided.

According to the above configuration, when it is difficult to obtain the product of the instantaneous value of the voltage and the current of the load itself due to the so-called ultra-high frequency at which the power supply frequency is plasma generation, it is difficult to obtain the product. However, the effective power consumed by the high frequency load (plasma chamber) can be calculated by a reliable method of multiplying the effective value of the voltage and the current, which is easily obtained, by the product of these and the power factor Cosθ calculated as described above. it can. Further, by feeding back the measured and calculated power value to the power supply side, the effective power consumption can be maintained constant.

[0011] Typically, the first variable reactance is composed of a series circuit of a first variable capacitor for phase adjustment and a fixed inductance, and a second variable reactance of a second variable capacitor for amplitude adjustment and a fixed inductance. In the case where the potentiometer is configured by a series circuit, the power calculation means controls the electrostatic capacitances of the first and second variable capacitors at the equilibrium positions of the first and second servomotors that control the capacitors. Can be used for calculation of the load impedance in the impedance matching state by determining the values of the first and second variable reactances by using these capacitances.

Further, the power calculation means is provided with a means for displaying the calculated load active power or is externally attached, which contributes to the convenience of the operator and the process designer.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Before explaining the embodiments of the present invention,
The impedance calculation process of the high frequency load (plasma chamber) will be described with the equivalent circuit of FIG. 1, and the voltage and current detection principle for load power consumption calculation will be described with the equivalent circuit of FIG. First, in FIG. 1, the internal impedance Z0 of the high frequency power source connected to the input terminal In of the impedance matching device is a real number (Z0 = realZ0 = 50Ω).
And

The impedance matching device has an inductive (L3) pre-stage reactance X3 connected to the input terminal In,
Between the rear end of the reactance X3 and the so-called ground line, a fixed inductance (coil L1) for adjusting the amplitude (50Ω) and a variable capacitance (first variable capacitor, so-called variable capacitor:
Amplitude adjusting reactance 1 consisting of a series branch of VC1)
(First variable reactance: X1) is inserted, and a fixed inductance for phase adjustment (coil L2) and a variable capacitance (second variable capacitor: between the rear end of the reactance X3 and the output end Out on the non-ground line side). It is composed of a T-type circuit to which a phase adjusting reactance 2 (second variable reactance: X2) consisting of a series branch of VC2) is connected. In addition,
A variable element of the reactances for amplitude adjustment and phase adjustment may be a variometer (variable inductance), and a fixed capacitor may be connected to this.

These variable capacitors VC1 and VC2
The values C1 and C2 of are specified by the potentiometer positions (that is, variable condenser designated positions x% and y%) that determine the rotational displacements of the drive control servomotors M1 and M2.
For example, set the position where the capacitor
%, The position where the rotary plate is completely pulled out from between the fixed plates is 0%, and the capacity increase amount x · {C1 (C1 (0) is added to each capacity C1 (0) or C2 (0) at 0%. 100) -C1 (0)} / 10
The values obtained by adding 0 or y · {C2 (100) -C2 (0)} / 100 are C1 and C2. (Where C1 and C2 are (100)
The ones with (0) and (0) indicate the capacitance value at 100% position and the capacitance value at 0% position of each variable capacitor. )

The impedance Zc of the plasma chamber load 3 is typically represented by the above equation (1) including the capacitive imaginary part (-jX), Zc = R-jX, and the impedance between the power source side and the load side is The matched state means a state in which the load impedance Zc has a conjugate complex value of the impedance Zm of the load end, that is, the impedance Zm as seen from the output end (Out) of the impedance matching device to the power supply side. That is,

[0017]

[Equation 1]

(However, Z0 = realZ0 = 50Ω, X1 = ωL1 =
1 / ωC1, X2 = ωL2 = 1 / ωC2, X3 = ωL3, ω =
2πf. ) Therefore, the load impedance Zc is

[0019]

[Equation 2]

Therefore, the resistance component R of the load impedance Zc
Is

[0021]

[Equation 3]

Further, the capacitive reactance X is

[0023]

[Equation 4]

It can be obtained from

Therefore, the load impedance Zc = R-j
At X, the power factor Cosθ is calculated by: Cosθ = R / √ (R ² + X ² ) ... (Formula 2), and the current detection unit 4 and the voltage detection unit 5 shown in FIG.
I = K1 * Ei and V = K2 * Ev converted from Ei and Ev measured respectively (K1 and K2 are constants)
The active power consumed by the high frequency load can be accurately calculated by the following equation: P = VICosθ (Equation 3) obtained by multiplying the product of by by the power factor Cosθ. (Note that the sign of the imaginary number X may be positive (inductivity: + jX) depending on the recipe of the plasma process and at one point after the startup.)

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the impedance matching device of the present invention will be described below with reference to FIG.
The input end In of the impedance matching circuit including the basic elements as described with reference to FIG. 1 and the pre-stage reactance coil L3
An amplitude detection and phase detection circuit 6 for detecting the current values of the amplitude adjustment and the phase adjustment is inserted between and. The impedance matching circuit includes the detected amplitude and phase, and the variable capacitors C1 and C2 described above.
Value (potentiometer indication), current and voltage detection values are received for control and calculation A / D conversion
The converter 7 and the control / calculator 8 that receives the converted digital output and calculates at least the potentiometer displacement (servo motor drive amount) necessary for amplitude adjustment and phase adjustment, and the motor drive in response to the displacement instruction. A servo motor driving amplifier 9 for generating an output is provided.

Referring again to the main body of the impedance matching circuit, the servomotors M1 and M2 rotate in accordance with the control output signal of the motor drive amplifier until the partial pressure values of the potentiometers VRx and VRy are balanced with the control output. , Variable amplitude control capacitor VC1 at this time
And capacitance C1 and C2 of the phase adjusting variable capacitor VC2 is confirmed, VRx and divided voltage value V _c1, V of VRy
_c2 is supplied to the A / D converter 7 as the angular voltage of the variable capacitors VC1 and VC2, that is, the values of C1 and C2.

Next, the output terminal O of the impedance matching circuit
current detector 4 and voltage detector 5 inserted immediately before ut
, The former (4) is composed of a current transformer inserted at the end of the line, and the fact that the induced voltage Ei of the secondary coil of the current transformer is proportional to the line termination current, that is, the load current is used, and the latter (5) is It consists of a pair of series capacitors at the end of the line, and the fact that the divided voltage value Ev of the capacitors is proportional to the line end voltage, that is, the load voltage is used.
And Ev are both given to the rectification and integration circuit 10 and A / D as values proportional to the effective current I and the effective voltage V, respectively.
It is supplied to the conversion unit 7.

In a preferred embodiment, the control / operation unit 8
Is the capacitance C1 required for the load impedance calculation described above.
And C2 are calculated and supplied to the power calculation computer 11 together with the load current and load voltage (effective value) received from the A / D converter 7. The power calculation computer 11 performs load impedance calculation, power factor calculation, and load active power calculation at the time of impedance matching described above, and therefore circuit constants such as L1, L2, and L3, high-frequency frequency f or angular frequency ω, and the like. Parameter input unit 12 and a calculation formula for deriving the above Zc formula (1)
(4) to (7), and equations (2) and (3) for obtaining the power factor and power
CP operated by software for sequentially calculating
U and a display unit 13 for displaying these calculated values are provided.

With the circuit configuration as described above, the accurately calculated power consumption after starting the plasma chamber, the load resistance R and the reactance (± jX) which are the basis of the power consumption, and the transition of the power factor Cosθ are displayed on the display unit 13. In, for example, it is displayed as shown in FIG.

[0031]

As described above, according to the present invention, in the impedance matching device between the high frequency load composed of the plasma chamber and the power source, the load power is accurately measured and the plasma process is executed according to the recipe. (EN) An impedance matching device equipped with load power measuring / calculating means capable of properly verifying a relationship with a state or the like. Further, by feeding back the measured and calculated electric power value to the power supply side, it is possible to maintain the effective electric power consumption constant and execute a desired plasma process.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram of an impedance component portion in an impedance matching device of the present invention.

FIG. 2 is an equivalent circuit diagram of a current sensor and a voltage sensor unit in the impedance matching device of the present invention.

FIG. 3 is a circuit diagram showing a preferred circuit configuration example in the impedance matching device of the present invention.

FIG. 4 is a front view showing the display contents of the display unit of the power calculation means in the circuit configuration of FIG.

[Explanation of symbols]

1st variable reactance 2 Second variable reactance 3 load impedance 4 Current detector 5 Voltage detector 6 Phase and amplitude detector 7 A / D converter 8 control and computing unit 9 Motor drive amplifier 10 Rectification and integration circuit 11 Power calculation computer 12 Parameter input section 13 Display

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[Procedure amendment]

[Submission date] August 8, 2001 (2001.8.8)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

These variable capacitors VC1 and VC2
The values C1 and C2 of are specified by the potentiometer positions (that is, variable condenser designated positions x% and y%) that determine the rotational displacements of the drive control servomotors M1 and M2.
For example, set the position where the capacitor
%, The position where the rotary plate is completely pulled out from between the fixed plates is 0%, and the capacity increase x * {C1 (C1 (0)) is added to each capacity C1 (0) or C2 (0) at 0%. 100) -C1 (0)} / 10
The values obtained by adding 0 or y · {C2 (100) -C2 (0)} / 100 are C1 and C2. (Where C1 and C2 are (100)
The ones with (0) and (0) indicate the capacitance value at the 100% position and the capacitance value at the 0% position of each variable capacitor. )

Claims (3)

[Claims] 1. An impedance matching device to be inserted between a high frequency power source having a known internal impedance Z0 and a plasma chamber load, wherein a phase detection part and an amplitude detection part are inserted at an input end and the detection parts are inserted. A first variable reactance for amplitude adjustment is connected immediately after, a second variable reactance for phase adjustment is connected after the first variable reactance connection position, and a voltage immediately before the output end after the second variable reactance is connected. By inserting a detection unit and a current detection unit and controlling the first and second variable reactances according to the detection values of the phase detection unit and the amplitude detection unit, respectively, the impedance on the high frequency power supply side and the load side can be controlled. An impedance matching circuit that is adapted to match,
The impedance on the power source side as viewed from the output end side of the impedance matching circuit in the matching state is calculated, and the conjugate impedance thereof is defined as the load impedance: Zc = R ± jX (1), and the power factor Cosθ is: √ (R ² + X ² ) (2) Calculated from (2) and multiplying the product of the voltage effective value V and the current effective value I detected by the voltage detection unit and the current detection unit by the power factor Cosθ: P = VICosθ According to (3), an impedance matching device comprising power calculation means for calculating the active power consumed by the high frequency load. 2. The first variable reactance is composed of a series circuit of a first variable capacitor for phase adjustment and a fixed inductance, and the second variable reactance is a series circuit of a second variable capacitor for amplitude adjustment and a fixed inductance. The electric power calculating means controls the capacitances of the first and second variable capacitors to indicate the displacement of the potentiometer at the equilibrium positions of the first and second servomotors that control the capacitors. Decided from
The impedance matching device according to claim 1, wherein the capacitance values are used to specify the values of the first and second variable reactances. 3. The impedance matching device according to claim 1, wherein the power calculation means includes means for displaying the calculated active power.