JPH11167997A - Plasma monitoring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the measuring accuracy of the impedance of a plasma load or a voltage between peaks, in monitoring of the plasma state of the plasma load. SOLUTION: An impedance conversion circuit 3 is inserted between a power source 1 and a load 5. A voltage detection portion 3A1 for detecting a voltage V1 at the power source side end of the conversion circuit 3, and a current detection portion 3A2 detecting a current 11, and a phase difference detection portion 3A3 detecting the phase difference θ1 between the voltage and the current are provided. First input impedance computing portion 23c computing an impedance seeing a plasma load side from the power source side end of the conversion circuit 3 as the first input impedance Z1* from the phase difference between the voltage and the current, and a second impedance computing portion 23e for computing an impedance seeing a load side from the load side end of the conversion circuit 3 as the second input impedance Z2* from the constants ZC1*, ZC2*, ZL* of elements constituting the conversion circuit 3 and the first input impedance are also provided. A plasma impedance computing portion 23 for computing a load impedance from the impedance Zs* of a feeding line 4 which connects the load side end of the conversion circuit 3 and the second input impedance is further provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a plasma monitoring apparatus for monitoring a state of plasma of a plasma load to which power is supplied from a high frequency power supply.

[0002]

2. Description of the Related Art In the process of manufacturing semiconductor devices, LCDs (liquid crystal displays) and the like, a process using plasma (referred to as a plasma process) is performed when etching, sputtering, thin film growth and the like are performed. In the plasma process, high-frequency power is supplied to two electrodes provided in a chamber for performing processes such as etching, sputtering, and thin film growth, and plasma is generated between the electrodes.

As described above, when supplying high-frequency power to a plasma load for generating plasma, it is important to match the impedance between the high-frequency power supply and the plasma load, and the impedance matching between the two is important. If not taken, power is reflected at the output end of the high-frequency power supply, and high-frequency power cannot be efficiently supplied to the plasma load, so that good results cannot be obtained in the process.

Therefore, when power is supplied from a high-frequency power supply to a plasma load, it is indispensable to insert an impedance conversion circuit including an L / C circuit and a transformer between the high-frequency power supply and the plasma load.

FIG. 11 is a circuit diagram schematically showing a conventional circuit configuration for supplying power from a high frequency power to a plasma load. As shown, power is supplied from a high frequency power supply (hereinafter referred to as a power supply) 1 to a plasma load 5 through a coaxial cable 2, an impedance conversion circuit 3 ′, and a power supply line 4. The impedance conversion circuit 3 'includes, for example, a first variable capacitor C11 and a coil L11 whose inductance can be adjusted by selecting a tap.
And a second variable capacitor C22.
By changing the capacitances of the variable capacitor C11 and the second variable capacitor C22, impedance matching is performed.

First and second variable capacitors C11 and C11
In order to automatically perform the adjustment of 22, a detector (not shown) detects a voltage and a current at the power supply side end of the impedance conversion circuit 3 ′ and a phase difference between the voltage and the current, and detects the voltage and the current. From the power supply side end of the impedance conversion circuit 3 ', the impedance of the load 5 side is detected, and this impedance is made to match the output impedance of the power supply, and the capacitors C11 and Adjust C22.

[0007] Of the above adjustments, adjustment for matching the impedance seen from the load side to the output impedance of the power supply is mainly performed by adjusting the capacity of the first capacitor C11, and the phase difference is made zero. Is mainly adjusted by adjusting the capacity of the second capacitor C22.

As shown in FIG. 12, the plasma load 5 supplies power to the chamber 5a, the two electrodes 5b1 and 5b2, the power supply sections 5c1 and 5c2 for supplying power from the impedance conversion circuit 3 'to the chamber 5a, and the electrodes 5b1 and 5b2. Part 5c1
, 5c2 respectively. The power supply line 4 is provided in the chamber 5a, but includes a portion connecting the load side end of the impedance conversion circuit 3 'and the power supply units 5c1 and 5c2.

In the above-described plasma process, it is necessary to constantly monitor the state of the plasma in order to perform the process with good reproducibility and to improve the yield of semiconductor devices. It is well known that the state of the plasma can be monitored by, for example, measuring the impedance of the plasma or the peak-to-peak voltage of the plasma.

Incidentally, the impedance when the plasma load 5 side is viewed from the load side end of the impedance conversion circuit 3 'is defined as the internal resistance of the plasma and the impedance between the electrodes when the plasma is generated. There is a capacitance of the sheath generated between the two electrodes 5b1 and 5b2. Further, there is an inductance of the power supply line 4 connecting the load side end of the impedance conversion circuit 3 ′ and the plasma load 5. In many cases, the load-side end of the impedance conversion circuit 3 'cannot be directly connected to the power supply units 5c1 and 5c2. In this case, the power supply lines 4 are connected by a predetermined length.

When such an impedance exists, an equivalent circuit when the plasma load 5 side is viewed from the load side end of the impedance conversion circuit 3 'is as shown in FIG.
The voltage vector of this equivalent circuit is as shown in FIG. VD is the voltage on the load side end of the impedance conversion circuit 3 ', VL is the voltage generated on the feeder line 4, VR and VC are the voltage generated on the internal resistance of the plasma and the voltage generated on the combined capacitance of the sheath, VP, respectively. Are the electrodes 5b1 and 5b2
Voltage between the two.

[0012]

The electrodes 5b1, 5b
When the voltage VP generated during b2 must be detected, a lead wire for detecting this VP is connected to the chamber 5.
It is necessary to remodel the chamber in order to draw it out of a, but since this remodeling becomes complicated, the voltage VD at the load side end of the impedance conversion circuit 3 'has been conventionally detected. However, as is apparent from FIG. 14, VD is different from VP by the length of the feed line 4, that is, the voltage V generated on the feed line.
Due to the influence of L, the peak-to-peak voltage has a problem of detecting an inaccurate value.

For example, when a high frequency power of 13.56 (MHz), which is most frequently used in a plasma process, is supplied, the plasma reactance has a vacuum dielectric constant of 8.8.
^Assuming that 54 × 10 ⁻¹² , the relative dielectric constant of the sheath is 1, the electrode area is 0.032 (m ² ), and the sheath thickness is 1 (mm), the capacitance of one sheath is 283 (pF). .
Therefore, the combined capacitance of the sheath is about 142 (pF).
-J82.7 for 13.56 (MHz)
(Ω).

Here, the peak-to-peak voltage VDP of the voltage VD
Is compared with the peak-to-peak voltage VPP of the voltage VP, the power supplied to the plasma is 1 (KW), the internal resistance of the plasma is 10 (Ω), and the inductance of the power supply line is 100.
The accuracy when (nH), 500 (nH) and 1 (μH) are changed is calculated by 100 (VDP−VPP) / VDP (%).

As a result, when it is 100 (nH), -11
(%), -102 (%) at 500 (nH), 1
At (μH), the value is −707 (%), and the accuracy becomes worse as the inductance is obviously increased.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a plasma monitoring apparatus which improves the accuracy of measuring the impedance or peak-to-peak voltage of a plasma load when monitoring the state of the plasma of the plasma load.

[0017]

SUMMARY OF THE INVENTION The present invention relates to a plasma monitoring apparatus for monitoring the state of plasma in a plasma load to which power is supplied from a high frequency power supply via an impedance conversion circuit.

According to a first aspect of the present invention, there is provided a voltage detecting section for detecting a voltage at a load side end of an impedance conversion circuit;
A current detection unit that detects a current at the load side end of the impedance conversion circuit, a phase difference detection unit that detects a phase difference between the voltage and the current, and a voltage detection circuit that detects a phase difference between the voltage, the current, and the phase difference from the load side end of the impedance conversion circuit. A second input impedance calculator for calculating the impedance looking at the plasma load side as a second input impedance, an impedance of a feed line connecting the load side end of the impedance conversion circuit and the plasma load, and a second input impedance And a plasma impedance calculator for calculating the impedance of the plasma load from the computer.

The invention according to claim 2 further comprises a plasma peak-to-peak voltage calculation unit for calculating the peak-to-peak voltage of the plasma load from the impedance and the current of the plasma load.

In the first and second aspects of the present invention, the impedance of the power supply line, which affects the measurement accuracy of the impedance of the plasma load or the peak-to-peak voltage, is taken into account. I do.
Further, since the voltage and current are detected at a position near the plasma load, the calculation error is reduced.

According to a third aspect of the present invention, there is provided a voltage detecting unit for detecting a voltage at a load side end of an impedance conversion circuit,
A current detection unit that detects a current at the load side end of the impedance conversion circuit, a phase difference detection unit that detects a phase difference between the voltage and the current, and a load side end of the impedance conversion circuit based on the voltage, the current, and the phase difference. A feed line load side end voltage / current calculation unit that calculates the voltage and current at the load side end of the feed line connecting to the plasma load, and the impedance of the plasma load from the voltage and current at the load side end of the feed line. It is provided with a plasma impedance calculating section for calculating.

According to the third aspect of the present invention, the impedance of the power supply line does not need to be measured, so that the impedance of the plasma load can be measured efficiently. Further, since the voltage and current are detected at a position near the plasma load, the calculation error is reduced.

According to a fourth aspect of the present invention, there is provided a voltage detecting section for detecting a voltage at a power supply side end of an impedance conversion circuit;
A current detection unit that detects a current at the power supply side end of the impedance conversion circuit, a phase difference detection unit that detects a phase difference between the voltage and the current, and a power supply side end of the impedance conversion circuit from the voltage, the current, and the phase difference. A first input impedance calculation unit that calculates the impedance looking at the plasma load side as a first input impedance; and a load from the load side end of the impedance conversion circuit based on constants of elements constituting the impedance conversion circuit and the first input impedance. A second input impedance calculator for calculating the impedance looking at the side as a second input impedance, and a plasma from the impedance of the feeder line connecting the load side end of the impedance conversion circuit and the plasma load and the second input impedance. Plasma impedance calculation to calculate load impedance It is those with a.

According to a fifth aspect of the present invention, there is provided an impedance conversion circuit load-side current calculator for calculating a voltage, a current, and a current at a load-side end of the impedance conversion circuit from constants of elements constituting the impedance conversion circuit; A plasma peak-to-peak voltage calculator is further provided for calculating a peak-to-peak voltage of the plasma load from the impedance of the plasma load and the current at the load-side end of the impedance conversion circuit.

In the fourth and fifth aspects of the present invention, the impedance of the power supply line, which affects the measurement accuracy of the impedance of the plasma load or the peak-to-peak voltage, is taken into account. I do.
In addition, since the voltage and current are detected at locations where the detection accuracy is high, the measurement accuracy of the impedance of the plasma load or the peak-to-peak voltage is further improved.

According to a sixth aspect of the present invention, there is provided a voltage detecting section for detecting a voltage at a power supply side end of the impedance conversion circuit,
A current detection unit that detects a current at the power supply side end of the impedance conversion circuit, a phase difference detection unit that detects a phase difference between the voltage and the current, and a power supply side end of the impedance conversion circuit from the voltage, the current, and the phase difference. A first input impedance calculator for calculating the impedance looking at the plasma load side as a first input impedance, and a plasma from a load side end of the impedance conversion circuit based on constants of elements constituting the impedance conversion circuit and the first input impedance. A second input impedance calculator for calculating the impedance looking at the load side as a second input impedance, an effective power calculator for calculating the active power of the high-frequency power supply from the voltage, current and phase difference; Calculate the voltage and current at the load end of the impedance conversion circuit from the impedance and active power Impedance conversion circuit load side voltage / current calculation unit, and voltage at the load side end of the feeder line connecting the load side end of the impedance conversion circuit and the plasma load from the voltage and current at the load side end of the impedance conversion circuit And a feed line load-side voltage / current calculation unit for calculating the current and the current, and a plasma impedance calculation unit for calculating the impedance of the plasma load from the voltage and current at the load end of the feed line.

According to a seventh aspect of the present invention, there is further provided a plasma peak-to-peak voltage calculation unit for calculating a peak-to-peak voltage of a plasma load from a voltage at a load side end of the power supply line.

According to the seventh aspect of the present invention, the peak-to-peak voltage of the plasma load can be measured efficiently because the impedance of the power supply line need not be measured. In addition, since the voltage and current are detected at locations where the detection accuracy is high, the measurement accuracy of the peak-to-peak voltage of the plasma load is further improved.

[0029]

<First Embodiment> FIG. 1 is a circuit diagram showing a first embodiment of a plasma monitoring apparatus according to the present invention. In the figure, 1 is a power supply, 2 is a coaxial cable,
Reference numeral 3 denotes an impedance conversion circuit (hereinafter, referred to as a conversion circuit), 4 denotes a power supply line, and 5 denotes a plasma load (hereinafter, referred to as a load). The conversion circuit 3 is an automatic impedance matching device conventionally used when supplying high-frequency power to the load 5.

The conversion circuit 3 includes a first variable capacitor C11, a second variable capacitor C22, and a coil L11 whose inductance can be adjusted by selecting a tap, similarly to the one shown in FIG. Have. An adjustment unit (operation shaft) for adjusting the respective capacitances of the first and second variable capacitors C11 and C22 is connected to an operation mechanism (not shown) using a motor as a drive source. Further, a control unit (not shown) for controlling a motor for driving an operator of each variable capacitor is provided.
By controlling the rotation of the operators 11 and C22, the capacitances of the respective variable capacitors are adjusted.

The load-side end of the conversion circuit 3 has a voltage detector 3B1 for detecting the voltage V2 at the load-side end, and a current I
2 and a load detector 3B having a phase difference detector 3B3 for detecting a phase difference .theta.2 between the voltage and the current at the load end.

The constants of the elements constituting the conversion circuit 3 are the first
And the capacitances C1, C2 of the second variable capacitors C11 and C22.
2 and the inductance L1 of the coil L11. Of these, the inductance L1 is known, but the first and second variable capacitors C, which are impedance adjusting means, are used.
The capacities of 11 and C22 change from time to time. Therefore, in order to calculate the capacitance of the variable capacitors C11 and C22, the variable resistor V
R1 and VR2 are provided, and the sliders of these variable resistors are connected to the drive mechanisms of the operators of the respective variable capacitors so as to interlock with the operators of the variable capacitors C11 and C22. A constant DC voltage is applied to both ends of the variable resistors VR1 and VR2, and the variable resistors VR1 and VR2
Between the slider and the ground, position detection signals Ep1 and Ep2 corresponding to the positions (rotation angles) of the operators of the capacitors C11 and C22 are obtained. The variable resistors VR1 and VR2 serve as impedance control means. An adjustment position detector 6 for detecting the position of the adjustment unit is configured.

The detection voltage V2, detection current I2, phase difference θ2
The position detection signals Ep1 and Ep2 are input to an analog / digital converter (A / D converter) 20 and converted into digital signals, and the respective digital signals are input to a computer 21.

The computer 21 calculates the plasma impedance and the voltage between the plasma peaks, and displays the result on the display device 25.

FIG. 2 is a block diagram showing the internal functions of the computer in the first embodiment of the plasma monitoring apparatus according to the present invention. The computer 21 has a power supply line for inputting the measured impedance ZS ^* of the power supply line 4. The input impedance Z of the feed line is obtained from the measured impedance value input section 21a and the detected voltage V2, detected current I2 and phase difference θ2.
Feed line input impedance calculator 21b that calculates 2 ^*
And Further, the impedance Z of the feeder line
Plasma impedance calculator 21c for calculating impedance ZP ^* of plasma load 5 from S ^* and feed line input impedance (second input impedance) Z2 ^*
When a plasma peak voltage calculation unit 21d for calculating a peak-to-peak voltage VPP of the plasma load from the detected current I2 and the plasma load impedance ZP ^*, display command for displaying the impedance ZP ^* and peak-to-peak voltage VPP of the plasma load A portion 21e. Note that "*"
Indicates that it is a complex number.

FIG. 3 is a flowchart showing an algorithm of a program executed by a computer according to the first embodiment.

Feeding line impedance measured value input section 21a
Is supplied with the feeder line impedance ZS ^* measured by the impedance analyzer (step S
1). In this feed line, the resistance component can be ignored, and only the inductance LS as the reactance component is provided. The impedance is measured by short-circuiting the electrodes 5b1 and 5b2.

The feeder line input impedance calculator 21b first reads the detection voltage V2, the detection current I2, and the phase difference θ2, which are the outputs of the detector 3B (step S2). 5, that is, the impedance looking at the load side from the power supply end of the feed line 4 is the feed line input impedance Z2
^* , The absolute value Z2 of the input impedance is obtained from V2 and I2 by the equation (1) (step 3). Z2 = V2 / I2 (1)

Next, the absolute value of the impedance Z2
Then, the feeder line input impedance Z2 ^* is determined from the phase difference θ2 (step 4). The resistance component of the impedance Z2 ^* is R2, the reactance component is X2, and Z2 ^* = R2
+ JX2, R2 and X2 are given by equations (2) and (3). R2 = Z2 · cos θ2 (2) X2 = Z2 · sinθ2 (3)

The plasma impedance calculation section 21c calculates the impedance of the load side from the load end of the feed line 4 to the plasma impedance ZP ^{* based on the} resistance R2, the reactance X2, and the reactance ωLs (ω: angular frequency) of the feed line ^. (Step S5). If the resistance component of the impedance ZP ^* is RP and the reactance component is XP, and ZP ^* = RP + jXP, then RP and XP are given by equations (4) and (5). RP = R2 (4) XP = X2 -ωLs (5)

In the plasma peak-to-peak voltage calculation section 21d,
First, the absolute value ZP of the plasma impedance is obtained from RP and XP obtained by the equations (4) and (5) by the equation (6) (step S6). Zp = {R2 ² + (X2 -ωLs) ² } ^1/2 (6)

Next, the plasma peak-to-peak voltage V is calculated from the detected current I2 and the absolute value ZP of the plasma impedance.
PP is obtained by equation (7) (step S7). Note that I
2 is the effective value. ^{VPP = 2 · 2 1/2 · I2} · ZP ... (7)

The display command section 21e issues a display command for the plasma impedance ZP ^* and the plasma peak-to-peak voltage VPP (step S8), and returns to step S2 again.

<Second Embodiment> FIG. 4 is a block diagram showing internal functions of a computer in a second embodiment of the plasma monitoring apparatus according to the present invention. Note that a circuit diagram showing the present embodiment is the same as that of the first embodiment, and a description thereof will be omitted.

The computer 22 detects the detection voltage V 2,
From the current I2 and the phase difference θ2, the load-side terminal voltage V of the feeder line 4 is obtained.
Three^* And current I3^* Power supply line load side voltage and power
It has a flow calculation unit 22a. Also, the load of the above feeder line
Side end voltage V3^* And current I3 ^* From the plasma load 5
Impedance ZP^* To calculate the plasma impedance
The calculation unit 22b and the load-side end voltage V3 of the power supply line^* From
Plasma peak to calculate peak-to-peak voltage VPP of plasma load
Peak voltage calculator 22c and the impedance of the plasma load.
-Dance ZP^* And a display finger for displaying the peak-to-peak voltage VPP
Command part 22d.

FIG. 5 is a flowchart showing an algorithm of a program executed by a computer according to the second embodiment.

The feed line load side end voltage / current calculation unit 22a first reads the detection voltage V2, the detection current I2, and the phase difference θ2, which are the outputs of the detector 3B (step S1).
, I2 and .theta.2, the power supply side terminal voltage V2 ^* and the current I2 ^* of the feed line are obtained (step S2). This V2 ^* , I
2 ^* is (8), (9) when V2 and I2 are the effective values.
Given by the formula. V2 ^* = 2 ^1/2 · V2 ε ^{j ω t} .. (8) I2 ^* = 2 ^1/2 · I2 ε ^{j ( ωt - θ 2)} (9)

Next, the power supply line is treated as a four-terminal network,
The load side terminal voltage V3 ^* and the current I3 ^* are obtained (step S3). The voltage V2 ^* and the current I2 ^* are expressed by equation (10) using the four-terminal constants A2, B2, C2, and D2 and the load-side voltage V3 ^* and the load-side current I3 ^* .

[0049]

(Equation 1)

Equation (10) is obtained by multiplying V2 ^* and I2 ^* by the inverse matrix of the four-terminal constant, and is expressed by equation (11).

[0051]

(Equation 2)

Load-side voltage V3 ^* and current I3 of the feed line
^* Is obtained from Expression (11) by Expressions (12) and (13). A2, B2, C2, and D2 are (21), (22), (23), and (2), respectively, as shown below.
4) It is obtained by the equation. V3 ^* = {1 / (A2D2−B2C2)} (D2V2 ^* −B2I2 ^* ) (12) I3 ^* = {1 / (A2D2−B2C2)} (− C2V2 ^* + A2I2 ^* ) … (13)

The plasma impedance calculator 22b calculates the plasma impedance ZP ^* from the load-side voltage V3 ^* and the current I3 ^{* of} the power supply line obtained by the equations (12) and (13) by the equation (14) (step S4). ). ZP ^* = V3 ^* / I3 ^* (14)

In the plasma peak-to-peak voltage calculation unit 22c,
(12) obtains its maximum value V3' ^* from the resulting V3 ^* by formula, obtained by the plasma peak voltage VPP (15) equation (step S5). VPP = 2 · V3 ′ ^* (15)

The display command section 22d issues a display command for the plasma impedance ZP ^* and the plasma peak-to-peak voltage VPP (step S6), and returns to step S1 again.

The above four terminal constants A2, B2, C2, D2
Can be determined, for example, as follows. First, a resistor R having a known resistance value is connected between the electrodes 5b1 and 5b2,
Impedance Z looking at the load side from the power supply side end of the feed line 4
22 is measured using an impedance analyzer.

Next, a high frequency signal source having a predetermined voltage is connected to the power supply side end of the power supply line, and an input voltage V22 and an output voltage (inter-electrode voltage) V33 are measured. Assuming that the input current at this time is I22 and the output current is I33, V22 and I22 are calculated using four terminal constants A2, B2, C2, D2 and V33 and I33.
It is expressed by equation (16).

[0058]

(Equation 3)

Since I22 and I33 in the above equation (16) are I22 = V22 / Z22 and I33 = V33 / R, respectively,
It can be transformed as shown in equation 7).

[0060]

(Equation 4)

When the above equation (17) is expanded, (18),
Equation (19) is obtained. V22 = (A2 + B2 / R) V33 (18) V22 / Z22 = (C2 + D2 / R) V33 (19)

In the above equations (18) and (19), the impedance when the resistor Ra is connected is Z2a, the input voltage is V2a, the output voltage is V3a, the impedance when the resistor Rb is connected is Z2b, and the input voltage is Z2b. Assuming that V2b and the output voltage are V3b, the following simultaneous equation (20) is obtained.

[0063]

(Equation 5)

From the above equation (20), A2, B2, C2, D
2 is required. A2 = {1 / (Rb-Ra)} (V2a / V3a) .Ra + (V2b / V3b) .Rb (21) B2 = {(V2a / V3a)-(V2b / V3b)}. Ra. / (Rb−Ra)｝ · Rb (22) C2 = {1 / (Rb−Ra)} (− V2a / V3a · Z2a) · Ra + (V2b / V3b · Z2b) · Rb (23) D2 = [{(V2a / V3a−Z2a)} − (V2b / V3b · Z2b)] · Ra · {1 / (Rb−Ra)} · Rb (24)

<Third Embodiment> FIG. 6 is a circuit diagram showing a third embodiment of the plasma monitoring apparatus according to the present invention.
1 is a power supply, 2 is a coaxial cable, 3 is a conversion circuit, 4 is a power supply line, 5 is a load, 20 is an A / D converter, 23 is a computer, and 25 is a display device.

In the present embodiment, the voltage detection section 3A1 for detecting the voltage V1 at the power supply side end, the current detection section 3A2 for detecting the current I1 and the voltage at the power supply side end are provided at the power supply side end of the conversion circuit 3 respectively. A power supply side detector 3A having a phase difference detector 3A3 for detecting a phase difference θ1 with the current is provided.

FIG. 7 is a block diagram showing the internal functions of a computer in the third embodiment of the plasma monitoring apparatus according to the present invention. The computer 23 converts the known impedance ZL ^* among the constituent elements of the conversion circuit 3. It has a conversion circuit known impedance input section 23a for inputting, and a feeder line impedance measured value input section 23b for inputting the measured impedance Zs ^* of the feeder line 4. Also,
A conversion circuit input impedance calculation circuit 23c for calculating the input impedance Z1 ^* of the conversion circuit from the detection voltage V1, the detection current I1 and the phase difference θ1, a position detection signal EP1,
Of the constituent elements of the conversion circuit from EP2, the impedance for adjusting ZC1 ^*, and a conversion circuit for regulating the impedance calculation unit 23d for calculating a ZC2 ^*. Furthermore, the known impedance ZL of the conversion circuit ^*, the input impedance Z1 ^* and impedance for adjusting ZC1 ^*, the input impedance of the feed line from ZC2 ^* (second input impedance) Z2 feed line input impedance calculator for calculating a ^* 23e, a plasma impedance calculation unit 23 for calculating the impedance ZP ^{* of the} plasma load from the impedance ZS ^{* of the} power supply line and the input impedance Z2 ^*
f, a conversion circuit load-side current calculator 23g for calculating a load-side current I2 'of the conversion circuit from the detection voltage V1, the detection current I1, and the adjustment impedance ZC1, the impedance ZP ^{* of the} plasma load and the conversion. A plasma peak-to-peak voltage calculating unit 23h for calculating a peak-to-peak voltage VPP of the plasma load from the load-side current I2 'of the circuit; an impedance ZP ^{* of the} plasma load and a peak-to-peak voltage V
A display command unit 23i for displaying the PP.

FIG. 8 is a flowchart showing an algorithm of a program executed by a computer according to the third embodiment.

Conversion circuit known impedance value input unit 23
a represents the reactance ωL1 as the impedance ZL ^* by the known inductance L1 selected by tapping.
(Ω: angular frequency) is input (step S1), and the reactance ωLs is input as a measured feed line impedance Z S ^* into the feed line impedance measured value input section 23b.
Is input (step S1).

Conversion circuit input impedance calculator 23c
First, the detection voltage V1, the detection current I1, and the phase difference θ1 which are the outputs of the detector 3A are read (step S2). (1 input impedance) Z1 ^*, and the absolute value Z1 of this input impedance is obtained from V1 and I1 by the equation (25) (step 3). Z1 = V1 / I1 (25)

Next, the absolute value Z1 of the impedance
And the phase difference θ1 from the conversion circuit input impedance Z1 ^*
Is obtained (step S4). This impedance Z1 ^*
Let R1 be the resistance component and X1 be the reactance component, and Z1 ^* =
If R1 + jX1, R1 and X1 are (26), (2
It is given by equation 7). R1 = Z1 · cos θ1 (26) X1 = Z1 · sin θ1 (27)

Conversion circuit adjusting impedance calculating section 23
In step d, the position detection signals EP1 and EP2 output from the adjustment position detector 6 are read (step S5), and then the capacitances C1 and C2 of the adjustment capacitors C11 and C22 are read from the position detection signals.
2 (step S6), and based on the result, the reactances XC1 and XC1 of the capacitors C11 and C22, respectively.
XC2 is obtained (step S7).

The feeder line input impedance calculator 23e calculates the impedance of the converter circuit 3 when the plasma load 5 is viewed from the load side end, that is, the impedance when the load side is viewed from the power supply side end of the feeder line.
^* (Step S8).

This impedance Z2 ^* is expressed as Z2 ^* = R2
+ JX2, R2 and X2 are unknown numbers, the resistance R1 and the reactance X1 of the input impedance Z1 ^* , and the reactance XC1,
R2 and X2 are determined using XC2 and XL1 as known numbers. These R2 and X2 are (28) and (29)
Given by the equation. ^{R2 = R1 · (XC1) 2} / B ... (28) X2 = {R1 2 · XC1 + (X1 + XC1) · XC1 · X1} / B + (XC2-XL1) ... (29) where, B = R1 ² + (X1 + XC1) ²

As in the first embodiment, the plasma impedance calculation unit 23f calculates the impedance of the load side from the load side end of the feed line based on the resistance R2, the reactance X2, and the reactance ωLs of the feed line to the plasma impedance. ZP ^* is obtained by the equations (4) and (5) (step S9).

In the conversion circuit load side current calculation unit 23g,
From the detection voltage V1, the detection current I1, and the reactance XC1 of the adjusting capacitor C11, the load-side current I
2 ′ is obtained by equation (30) (step S10). V1 and I1 are effective values. I2 '= I1 -XC1.V1 (30)

In the plasma peak-to-peak voltage calculation unit 23h,
First, the absolute value ZP of the plasma impedance is obtained from the above RP and XP by the equation (6) (step S11), and the plasma peak-to-peak voltage VPP is obtained from the above I2 'and ZP by the equation (31) (step S12). ^{VPP = 2 · 2 1/2 · I2'} · ZP ... (31)

The display command section 23i issues a display command for the plasma impedance ZP ^* and the plasma peak-to-peak voltage VPP (step S13), and returns to step S2 again.

<Fourth Embodiment> FIG. 9 is a block diagram showing the internal functions of a computer in a plasma monitoring apparatus according to a fourth embodiment of the present invention. Note that the circuit diagram showing the present embodiment is the same as that of the third embodiment, and therefore will be omitted.

The computer 24 is a component of the conversion circuit 3.
Child, known impedance ZL ^* Enter conversion times
Path known impedance input section 24a, detection voltage V1,
From the detected current I1 and the phase difference θ1, the input
-Dance Z1^* Conversion circuit to calculate the input impedance
The conversion circuit 24b converts the position detection signals EP1 and EP2 from the arithmetic circuit 24b.
Impedance ZC1 for adjustment among the components of the road^* , Z
C2^* Conversion circuit adjusting impedance calculating unit 2 for calculating
4c. In addition, a known input of the conversion circuit is used.
Peedance ZL^* , Input impedance Z1^* And adjustment
Impedance ZC1 for^* , ZC2^* Input line
Impedance (second input impedance) Z2^* Act
Feed line input impedance calculation unit 24d for calculating
From the voltage V1, the detection current I1 and the phase difference θ1
And an effective power calculation unit 24e for calculating the active power P of 1
doing. Further, the feeder line input impedance Z2
^*From the active power P and the load-side end voltage V2 of the conversion circuit 3^* 
And current I2^* Conversion circuit that calculates the load-side voltage and current
The calculation unit 24f and the load-side terminal voltage V2^* And current I2
^* From the load side end voltage V3 of the feed line 4^* And current I3^* To
The power supply line load side end voltage / current calculation unit 24g
Load-side voltage V3 of the feeder line^* And current I3 ^* From plastic
Zum load impedance ZP^* To calculate
Impedance calculation unit 24h, and a load-side terminal of the power supply line.
Pressure V3^* From the plasma load peak-to-peak voltage VPP
A plasma peak-to-peak voltage calculation unit 24i
Load impedance ZP^* And peak-to-peak voltage VPP
The display command unit 24j shown in FIG.

FIG. 10 is a flowchart showing an algorithm of a program executed by a computer according to the fourth embodiment. Steps S1 to S8
Until this is the same as FIG. However, in step S1, only the input of the conversion circuit known impedance ZL ^* is input.

Conversion circuit known impedance value input section 24
The impedance ZL ^* due to the known inductance L1 selected by tapping is input to a (step S).
1) In the conversion circuit input impedance calculation unit 24b,
First, the detection voltage V1, the detection current I1, and the phase difference θ1 are read (step S2), then the absolute value Z1 of the conversion circuit input impedance is obtained (step 3), and then the conversion circuit input impedance Z1 ^* is obtained (step S4).
The conversion circuit adjusting impedance calculating section 24c first reads the position detection signals EP1 and EP2 (step S5), then obtains the capacitances C1 and C2 of the adjusting capacitors C11 and C22 from the position detection signals (step S6). Based on the result, the reactances XC1 and XC2 of the capacitors C11 and C22 are obtained (step S7). The feeder line input impedance calculator 24d determines the feeder line input impedance Z2 ^* (step S8).

In the active power calculating section 24e, in step S2
The detected voltage V1, the detected current I1 and the phase difference θ
The active power P of the high-frequency power supply 1 is obtained from equation (1) by using equation (32) (step S9). P = V 1 · I 1 · cos θ 1 (32)

Conversion circuit load side voltage / current calculation unit 24f
Assuming that the loss of the conversion circuit 3 is zero, the load-side terminal voltage V2 ^* and the current I2 ^* of the conversion circuit 3 can be calculated by using the feed line input impedance Z2 ^* = R2 + jX2 as shown in (33),
It is determined by equation (34) (step S10). I2 ^* = (P / R2) ^1/2 (33) V2 ^* = (P / R2) ¹ / 2.Z2 ^* (34)

In the feed line load side end voltage / current calculation unit 24g
Is similar to the second embodiment in that the feeder line 4 is a four-terminal network.
The load side voltage V2 of the above conversion circuit^* And current
I2 ^* To the load side end voltage V3 of the feed line^* And current I3^* 
Is obtained (step S11).

The plasma impedance calculating section 24h obtains the plasma impedance ZP ^* from the load side terminal voltage V3 ^* and the current I3 ^{* of} the power supply line by the equation (14) (step S12).

In the plasma peak-to-peak voltage calculation unit 24i,
The plasma peak-to-peak voltage VPP is obtained from the load-side end voltage V3 ^{* of the} power supply line by equation (15) (step S13).

The display command section 24i issues a display command for the plasma impedance ZP ^* and the plasma peak-to-peak voltage VPP (step S14), and returns to step S2 again.

The conversion circuit used in the above embodiment converts the input and output impedances, and it is sufficient if the constants of the constituent elements are known and the constants can be known. Various circuits can be used as the circuit.

The impedance Z S ^{* of the} feed line 4
Is obtained by an impedance analyzer, but can be calculated by, for example, an electromagnetic field simulator.

[0091]

As described above, according to the present invention, since the measurement accuracy of the impedance or the peak-to-peak voltage of the plasma load is improved, it can be used as a monitoring tool for reproducibility in a semiconductor process. Further, it can be used as an endpoint monitor for processes such as etching and ashing. Further, abnormalities such as unstable discharge and abnormal discharge in the chamber can be detected.

According to the first and third aspects of the present invention, since the voltage and the current are detected at a position near the plasma load, the calculation error can be reduced.

Further, according to the fourth and sixth aspects, since the voltage and current are detected at locations where the detection accuracy is high, the measurement accuracy of plasma impedance or peak-to-peak voltage can be further improved.

According to claims 3, 6 and 7,
The impedance or peak-to-peak voltage of plasma can be measured efficiently without using an impedance analyzer.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a plasma monitoring device according to the present invention.

FIG. 2 is a block diagram showing internal functions of a computer in the first embodiment of the plasma monitoring apparatus according to the present invention.

FIG. 3 is a flowchart illustrating an algorithm of a program executed by a computer according to the first embodiment.

FIG. 4 is a block diagram showing internal functions of a computer in a second embodiment of the plasma monitoring apparatus according to the present invention.

FIG. 5 is a flowchart illustrating an algorithm of a program executed by a computer according to the second embodiment.

FIG. 6 is a circuit diagram showing a third embodiment of the plasma monitoring apparatus according to the present invention.

FIG. 7 is a block diagram showing internal functions of a computer in a third embodiment of the plasma monitoring apparatus according to the present invention.

FIG. 8 is a flowchart illustrating an algorithm of a program executed by a computer according to the third embodiment.

FIG. 9 is a block diagram showing internal functions of a computer in a plasma monitoring apparatus according to a fourth embodiment of the present invention.

FIG. 10 is a flowchart illustrating an algorithm of a program executed by a computer according to the fourth embodiment.

FIG. 11 is a circuit diagram schematically showing a conventional circuit configuration for supplying power from a high-frequency power to a load.

FIG. 12 is a diagram schematically showing a load.

FIG. 13 is a diagram showing an equivalent circuit when the load side is viewed from the load side end of the impedance conversion circuit.

14 is a diagram showing a voltage vector of the equivalent circuit in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 High frequency power supply 3 Impedance conversion circuit 3A1, 3B1 Voltage detector 3A2, 3B2 Current detector 3A3, 3B3 Phase difference detector 4 Feed line 5 Load 21a Feed line impedance measured value input unit 21b Feed line input impedance (second input impedance ) Calculation unit 21c Plasma impedance calculation unit 21d Plasma peak voltage calculation unit 21e Display command unit 22a Feed line load side voltage / current calculation unit 22b Plasma impedance calculation unit 22c Plasma peak voltage calculation unit 22d Display command unit 23a Impedance conversion circuit Known impedance input section 23b Feed line impedance measured value input section 23c Impedance conversion circuit input impedance (first input impedance) calculation section 23d Impedance calculation circuit for impedance conversion circuit adjustment 23e Feed line input Input impedance (second input impedance) calculation unit 23f Plasma impedance calculation unit 23g Impedance conversion circuit Load side current calculation unit 23h Plasma peak-to-peak voltage calculation unit 23i Display command unit 24a Impedance conversion circuit known impedance input unit 24b Impedance conversion circuit input Impedance (first input impedance) calculation unit 24c Impedance conversion circuit adjustment impedance calculation unit 24d Feed line input impedance (second input impedance) calculation unit 24e Active power calculation unit 24f Impedance conversion circuit load side terminal voltage / current calculation unit 24g Feed line load side end voltage / current calculation unit 24h Plasma impedance calculation unit 24i Plasma peak-to-peak voltage calculation unit 24j Display command unit

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI H05H 1/46 H01L 21/302 B

Claims (7)

[Claims] 1. A plasma monitoring apparatus for monitoring a plasma state of a plasma load to which power is supplied from a high-frequency power supply via an impedance conversion circuit, wherein a voltage at a load-side end of the impedance conversion circuit is detected. A current detection unit that detects a current at a load side end of the impedance conversion circuit; a phase difference detection unit that detects a phase difference between the voltage and the current; and A second input impedance calculator for calculating, as a second input impedance, an impedance when the plasma load side is viewed from the load side end of the impedance conversion circuit; The impedance of the plasma load is determined from the impedance of the feeder line to be connected and the second input impedance. Plasma monitoring device having a plasma impedance calculator for calculating the Nsu. 2. A plasma peak-to-peak voltage calculator for calculating a peak-to-peak voltage of the plasma load from the impedance and the current of the plasma load.
3. The plasma monitoring device according to claim 1. 3. A plasma monitoring apparatus for monitoring a plasma state of a plasma load to which power is supplied from a high-frequency power supply via an impedance conversion circuit, wherein a voltage at a load-side end of the impedance conversion circuit is detected. A current detection unit that detects a current at a load side end of the impedance conversion circuit; a phase difference detection unit that detects a phase difference between the voltage and the current; and A feed line load side end voltage / current calculation unit for calculating a voltage and a current at a load side end of a feed line connecting the load side end of the impedance conversion circuit and the plasma load; and a load side end of the feed line. A plasma monitoring device comprising a plasma impedance calculation unit for calculating the impedance of the plasma load from the voltage and the current. 4. A plasma monitoring apparatus for monitoring a state of a plasma of a plasma load to which power is supplied from a high-frequency power supply via an impedance conversion circuit, wherein a voltage at a power supply side end of the impedance conversion circuit is detected. A current detection unit that detects a current at a power supply side end of the impedance conversion circuit; a phase difference detection unit that detects a phase difference between the voltage and the current; and A first input impedance calculator for calculating, as a first input impedance, an impedance when the plasma load side is viewed from a power supply side end of the impedance conversion circuit; constants of elements constituting the impedance conversion circuit and the first input; Impedance when the plasma load side is viewed from the load side end of the impedance conversion circuit from impedance. A second input impedance calculation unit that calculates a dance as a second input impedance; and a power supply line connecting the load-side end of the impedance conversion circuit to the plasma load and the plasma from the second input impedance. A plasma monitoring device including a plasma impedance calculator for calculating a load impedance. 5. An impedance conversion circuit load-side current calculator for calculating a current at a load-side end of the impedance conversion circuit from the voltage, current, and constants of elements constituting the impedance conversion circuit; The plasma monitoring apparatus according to claim 4, further comprising a plasma peak-to-peak voltage calculation unit that calculates a peak-to-peak voltage of the plasma load from an impedance and a current at a load-side end of the impedance conversion circuit. 6. A plasma monitoring apparatus for monitoring a state of plasma of a plasma load to which power is supplied from a high-frequency power supply via an impedance conversion circuit, wherein a voltage at a power supply side end of the impedance conversion circuit is detected. A current detection unit that detects a current at a power supply side end of the impedance conversion circuit; a phase difference detection unit that detects a phase difference between the voltage and the current; and A first input impedance calculator for calculating, as a first input impedance, an impedance when the plasma load side is viewed from a power supply side end of the impedance conversion circuit; constants of elements constituting the impedance conversion circuit and the first input; Impedance when the plasma load side is viewed from the load side end of the impedance conversion circuit from impedance. A second input impedance calculation unit that calculates a dance as a second input impedance; an effective power calculation unit that calculates an active power of the high-frequency power supply from the voltage, current, and the phase difference; And an impedance conversion circuit load-side voltage / current calculation unit that calculates a voltage and a current at the load-side end of the impedance conversion circuit from the active power; and the voltage-current and a current at the load-side end of the impedance conversion circuit. A feed line load side end voltage / current calculator for calculating a voltage and a current at a load side end of a feed line connecting the load side end of the conversion circuit and the plasma load; A plasma monitoring device comprising a plasma impedance calculation unit for calculating the impedance of the plasma load from a voltage and a current. 7. The plasma monitoring apparatus according to claim 3, further comprising a plasma peak-to-peak voltage calculation unit that calculates a peak-to-peak voltage of the plasma load from a voltage at a load-side end of the power supply line.