KR101707276B1 - Plasma processing apparatus - Google Patents

Abstract

A plasma processing apparatus capable of accurately detecting occurrence of an arc discharge is provided.
A plasma processing apparatus (10) for performing a process on a substrate (G) by using plasma is provided with a chamber (11) in which a plasma is generated by a high frequency power supplied thereto, and a high frequency power source DVr / dt-dVf / dt, and outputs the calculated dVr / dt-dVf / dt to the first differential circuit 21. The second differential circuit 23 demultiplexes the reflected wave voltage Vr of the high- dVr / dt-dVf / dt is set to a value equal to or greater than the dVr / dt-dVf / dt when the dVf / dt is negative, the comparator 22 determines that an arc discharge has occurred in the chamber 11 when the dt exceeds the arc discharge detection value, And a diode 25 for setting dVf / dt to 0 so as to be smaller.

Description

PLASMA PROCESSING APPARATUS

The present invention relates to a plasma processing apparatus for preventing occurrence of an arc discharge.

In a plasma processing apparatus for performing a predetermined process on a substrate, for example, a glass substrate or a semiconductor wafer used for manufacturing a substrate, for example, a FPD using plasma generated by supplying high-frequency power, arc discharge occurs in a processing chamber where plasma is generated There is work. If the arc discharge is continued, there is a fear of damaging the parts in the processing chamber, the glass substrate or the semiconductor wafer. Therefore, if the occurrence of the arc discharge is detected, it is necessary to stop the supply of the high frequency power for generating the plasma quickly.

When arc discharge occurs, a peak occurs in the reflected wave voltage of high frequency electric power. Therefore, it is generally performed to monitor the reflected wave voltage and to interrupt the supply of the high frequency electric power when detecting the occurrence of a peak.

The supply form of the high-frequency electric power has various forms according to the contents of a predetermined process, but a form in which the supply form is changed is a form in which the supplied high-frequency electric power is gradually increased.

However, when the high frequency power is stepwise increased, the traveling wave voltage also increases. In this case, until the matching circuit can match the impedance of the traveling wave voltage and the reflected wave voltage, a peak occurs in the reflected wave voltage have.

Therefore, in order to prevent the occurrence of the peak of the reflected wave voltage due to the increase of the traveling wave voltage as the occurrence of the peak of the reflected wave voltage caused by the occurrence of the arc discharge, in general, It is determined that a peak of the reflected wave voltage has occurred (see, for example, Patent Document 1).

dVr / dt-dVf / dt > The arc discharge detection value

Here, Vr is the reflected wave voltage, Vf is the traveling wave voltage, and the arc discharge detection value is a predetermined threshold value set in advance.

In the above equation, when the traveling wave voltage increases, the value of dVr / dt-dVf / dt becomes small, so that even when a peak of the reflected wave voltage due to the increase of the traveling wave voltage occurs, the above formula hardly occurs.

(Prior art document)

(Patent Literature)

(Patent Document 1) International Publication No. 03/037047

In recent years, along with the complication of the plasma processing, there has been demanded not only an increase in high frequency electric power (traveling wave voltage) but also a supply form of high frequency electric power accompanied by a decrease in traveling wave voltage as shown in Fig.

Even when the traveling wave voltage drops, a peak may occur in the reflected wave voltage until the impedance of the traveling wave voltage and the reflected wave voltage can be matched by the matching circuit. At this time, if dVf / dt of the above expression is negative Value, the value of dVr / dt-dVf / dt becomes excessively large, so that the above equation is established, and there is a possibility that a peak of the reflected wave voltage caused by the occurrence of the arc discharge is erroneously determined.

When the arc discharge detection value is made large, the possibility of defining the misfire is lowered. However, when the peak of the reflected wave voltage due to the arc discharge which is not so strong occurs and dVr / dt does not become large, There is a possibility that it will be lost.

An object of the present invention is to provide a plasma processing apparatus capable of accurately detecting the occurrence of an arc discharge.

In order to achieve the above object, a plasma processing apparatus according to a first aspect of the present invention is a plasma processing apparatus that includes a processing chamber to which a high-frequency power is supplied, generates plasma in the processing chamber, A second time differentiator for temporally differentiating the reflected wave voltage of the high frequency power returning from the process chamber; and a second time differentiator for temporally differentiating the reflected wave voltage of the high frequency power returning from the process chamber, Calculating a value corresponding to a time differential value and a time differential value of the progressive wave voltage and judging that an arc discharge has occurred in the processing chamber when a value corresponding to the calculated difference exceeds a predetermined threshold value; And when the time derivative of the traveling wave voltage becomes negative, a value corresponding to the difference And a differential value changing unit that changes at least one of a time differential value of at least the reflection wave voltage and a time differential value of the traveling wave voltage so that the difference value becomes smaller than a predetermined threshold value.

In the plasma processing apparatus according to the second aspect of the present invention, in the plasma processing apparatus of the first aspect, the determination section may include: a first input section to which the time derivative of the traveling wave voltage is input; 2-input section, and the differential value changing section is connected to at least one of the first input section and the second input section.

In the plasma processing apparatus according to the third aspect of the present invention, in the plasma processing apparatus of the first or second aspect, the value corresponding to the difference is obtained by subtracting the time derivative of the traveling wave voltage from the time derivative of the reflected wave voltage Value.

In a plasma processing apparatus according to a fourth aspect of the present invention, in the plasma processing apparatus according to any one of the first to third aspects, when the time derivative of the progressive wave voltage becomes negative, And the time differential value of the voltage is set to zero.

In the plasma processing apparatus of the fifth aspect of the present invention, in the plasma processing apparatus of the fourth aspect, the differential value changing section is formed of a diode.

In a plasma processing apparatus according to a sixth aspect of the present invention, in the plasma processing apparatus according to any one of the first to third aspects, when the time derivative of the progressive wave voltage becomes negative, And the absolute value of the time differential value of the voltage is made small.

In a plasma processing apparatus according to a seventh aspect of the present invention, in the plasma processing apparatus according to any one of the first to third aspects, when the time derivative of the traveling wave voltage becomes negative, And the time differential value of the voltage is made small.

According to the present invention, when the time differential value of the traveling wave voltage becomes negative, the time differential value of the reflected wave voltage of the high frequency power and the time differential value of the traveling wave voltage and the time differential value of the traveling wave Any one of the time differential values of the voltage is changed, so that the value corresponding to the calculated difference is less likely to exceed the predetermined threshold value. This makes it possible to suppress erroneous determination that a peak of the reflected wave voltage due to the occurrence of the arc discharge has occurred even if a peak of the reflected wave voltage due to the reduction of the traveling wave voltage is generated and to detect the occurrence of the arc discharge more accurately have.

1 is a view schematically showing a configuration of a plasma processing apparatus according to an embodiment of the present invention.
Fig. 2 is a diagram for explaining a process of changing the time differential value of the traveling wave voltage to be executed in the plasma processing apparatus of Fig. 1. Fig.
FIG. 3 is a view schematically showing a configuration of a first modification of the plasma processing apparatus of FIG. 1;
Fig. 4 is a view for explaining a process of changing the time differential value of the traveling wave voltage, which is executed in the plasma processing apparatus of Fig. 3;
Fig. 5 is a view schematically showing a configuration of a second modification of the plasma processing apparatus of Fig. 1;
FIG. 6 is a diagram for explaining a process of changing the time differential value of the reflected wave voltage to be executed in the plasma processing apparatus of FIG. 5; FIG.
7 is a view showing a supply mode of high frequency power according to a complicated plasma process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 is a view schematically showing a configuration of a plasma processing apparatus according to an embodiment of the present invention.

1, the plasma processing apparatus 10 includes a rectangular parallelepiped chamber 11 (processing chamber) in which the inside is reduced in pressure and a high frequency power source 12, and the chamber 11 has a pedestal shape And a showerhead 14 disposed in the ceiling portion. The high frequency power source 12 is connected to the susceptor 13 and supplies the high frequency power to the susceptor 13. The susceptor 13 functions as a lower electrode, and the showerhead 14 functions as an upper electrode. As a result, the radio frequency power supplied to the susceptor 13 can be applied to the processing space S between the susceptor 13 and the showerhead 14.

In the chamber 11, a glass substrate (hereinafter simply referred to as "substrate") G as an object to be processed is mounted on the susceptor 13, and the showerhead 14 introduces a process gas into the process space S And the susceptor 13 applies a high frequency power to the processing space S to generate plasma from the processing gas in the processing space S. The ions or radicals in the plasma reach the substrate G, and the substrate G is subjected to a predetermined plasma treatment, for example, a dry etching treatment.

A DC cut capacitor 15, a matching circuit 16, a coaxial cable 17 and a power meter 18 are interposed between the chamber 11 and the RF power supply 12 in order from the chamber 11 side, Thereby forming a current supply path. In the high-frequency current supply path, the power meter 18 measures the progressive wave voltage Vf and the reflected wave voltage Vr of the high-frequency power supplied from the high-frequency power source 12 to the susceptor 13, and outputs the respective values.

The output side of the traveling wave voltage Vf of the power meter 18 is connected to the first amplifier 19 and the first amplifier 19 amplifies or attenuates the input traveling wave voltage Vf to a signal of an appropriate size. The output side of the reflected wave voltage Vr of the power meter 18 is connected to the second amplifier 20 and the second amplifier 20 amplifies or attenuates the inputted reflected wave voltage Vr to a signal of an appropriate size.

The traveling wave voltage Vf output from the first amplifier 19 is temporally differentiated by the first differential circuit 21 (first time differential section), and the differential traveling wave voltage Vf (hereinafter referred to as " dVf / dt " .) (Time differential value of the traveling wave voltage) is inputted to the negative input side 22a (first input portion) of the comparator 22 (judgment portion).

The reflected wave voltage Vr output from the second amplifier 20 is temporally differentiated by the second differentiating circuit 23 (second time differentiating section), and the differentiated reflected wave voltage Vr (hereinafter referred to as " dVr / dt " .) (Time differential value of the reflected wave voltage) is input to the plus input side 22b (second input section) of the comparator 22. [

Whether or not the arc discharge has occurred in the processing space S can be determined by monitoring the time derivative of the reflected wave voltage Vr. However, in order to exclude the variation of the reflected wave voltage Vr due to the traveling wave voltage Vf, By using an evaluation value obtained by subtracting the time derivative of the progressive wave voltage Vf from the measured value, and judging whether or not the evaluation value exceeds a predetermined threshold value. Specifically, it is determined whether or not the following equation (1) is satisfied in the comparator 22. When the following equation (1) is established, a signal is output from the comparator 22 to the output interrupting circuit 24 .

dVr / dt-dVf / dt > Arc discharge detection value (predetermined threshold value) ... (One)

Since the arc discharge occurring in the processing space S affects the reflected wave voltage but does not affect the traveling wave voltage or has a small influence even if it affects it, It is possible to judge whether or not an arc discharge has occurred in the case where the traveling wave voltage Vf does not increase even if a peak of the reflected wave voltage Vr is generated or the variation is small This corresponds to the case where an arc discharge occurs in the processing space S.

When the above equation (1) is established and the signal transmitted from the comparator 22 is received, the output interruption circuit 24 determines that arc discharge has occurred in the processing space S and outputs an output cutoff signal to the high frequency power supply 12 . The high frequency power supply 12, which has received the output cutoff signal, stops the supply of the high frequency power for a predetermined period. This prevents the generation of the arc discharge in the processing space S from being continued.

However, when the progressive wave voltage Vf decreases according to the plasma processing recipe, dVf / dt becomes a negative value. Therefore, when the reflected wave voltage Vr does not fluctuate (dVr / dt is 0), a small peak of the noise level Or when only a small peak is generated in the reflected wave voltage Vr until the matching circuit 16 can match the impedance of the traveling wave voltage Vf and the reflected wave voltage Vr (1) is satisfied, it is determined that an arc discharge has occurred in the processing space S, and there is a fear that supply of the high-frequency electric power is stopped. That is, when the traveling wave voltage Vf decreases, there is a fear that the arc discharge is erroneously determined to have occurred in the processing space S.

The dVf / dt input to the negative input side 22a of the comparator 22 is set to 0 (zero) so that the dVr / dt-dVf / dt does not excessively increase when the progressive wave voltage Vf decreases, . Specifically, a diode 25 (differential-value changing unit) for rectifying the current from the first amplifier 19 to the comparator 22 is disposed between the first differential circuit 21 and the comparator 22 . When the potential difference is generated in the rectifying direction of the diode 25 or when dVf / dt is 0, that is, when the dVf / dt obtained in the first differentiating circuit 21 is positive, that is, (DVf / dt) is negative, that is, when a potential difference is generated in a direction opposite to the rectifying direction of the diode 25, the current It outputs 0 by blocking.

Fig. 2 is a diagram for explaining a process of changing the time differential value of the traveling wave voltage to be executed in the plasma processing apparatus of Fig. 1. Fig.

In Fig. 2, there is shown a case where a fine peak not caused by the arc discharge occurs in the reflected wave voltage Vr, but the traveling wave voltage Vf decreases. The dVf / dt in the figure is partially projected in the negative direction as indicated by the broken line. In the plasma processing apparatus 10, the dVf / dt obtained by the first differentiating circuit 21 is set so that the protrusion of dVf / dt is changed to zero by the diode 25. As a result, dVr / dt-dVf / dt, which is changed as indicated by the broken line in the drawing and which exceeds the arc discharge detection value, is offset as shown by the solid line (see arrows in the figure) It disappears. That is, the above equation (1) does not hold. This makes it possible to prevent the arc discharge in the processing space S from being misjudged to have occurred.

According to the plasma processing apparatus 10 of the present embodiment, even when the progressive wave voltage Vf is lowered and dVf / dt becomes negative, the negative input side of the comparator 22 is controlled so that dVr / dt-dVf / dt does not become too large DVr / dt-dVf / dt becomes less likely to exceed the arc discharge detection value, because dVf / dt input to the gate electrode 22a is set to zero. As a result, when the reflected wave voltage Vr does not fluctuate and only a small peak of the noise level is generated, or when the matching circuit 16 can match the impedance of the traveling wave voltage Vf and the reflected wave voltage Vr , It is incorrectly assumed that a peak of the reflected wave voltage Vr caused by the occurrence of the arc discharge is generated even if the traveling wave voltage Vf is lowered by executing the recipe of the plasma processing for reducing the high frequency power only when a small peak occurs in the reflected wave voltage Vr The occurrence of the arc discharge can be detected more accurately.

Further, by precisely detecting the occurrence of the arc discharge, it is possible to suppress the supply stop of unnecessary high-frequency electric power, and the plasma can be more stably maintained in the processing space S.

The present invention has been described using the embodiments, but the present invention is not limited to the embodiments described above.

In the above-described embodiment, the comparator 22 determines whether the arc discharge has occurred by directly using the difference obtained by subtracting the time derivative of the progressive wave voltage Vf from the time derivative of the reflected wave voltage Vr as an evaluation value. However, The presence or absence of the occurrence of the arc discharge may be determined by using another evaluation value calculated using, for example, an evaluation value converted into a step-wise varying value or an evaluation value obtained by extracting only the absolute value of the difference.

In the above-described plasma processing apparatus 10, the diode 25 is used as the means for setting dVf / dt to 0, but when dVf / dt is positive or 0 instead of the diode 25, dVf / And an electric circuit for outputting 0 when dVf / dt is negative may be disposed between the first differential circuit 21 and the negative input side 22a of the comparator 22. [

In the above plasma processing apparatus 10, dVf / dt is set to 0 when the progressive wave voltage Vf is lowered and dVf / dt becomes negative. However, dVf / dt is not necessarily set to 0, / dt may be reduced.

FIG. 3 is a view schematically showing a configuration of a first modification of the plasma processing apparatus of FIG. 1;

3, the plasma processing apparatus 26 includes a first differential circuit 21 instead of the diode 25 and a differential reduction circuit 27 disposed between the negative input side 22a of the comparator 22 Respectively.

The differential value decreasing circuit 27 outputs dVf / dt as it is when the dVf / dt obtained by the first differentiating circuit 21 is positive or zero, and when the dVf / dt is negative, the absolute value of dVf / dt is small And outputs it.

Fig. 4 is a view for explaining a process of changing the time differential value of the traveling wave voltage, which is executed in the plasma processing apparatus of Fig. 3;

FIG. 4 shows a case in which a fine peak not caused by the arc discharge occurs in the reflected wave voltage Vr, but the traveling wave voltage Vf decreases. The absolute value of dVf / dt obtained by the first differentiating circuit 21 is smaller than the absolute value of dVf / dt obtained by the first differentiating circuit 21 so that the amount of protrusion of dVf / dt decreases, Is reduced by the value decreasing circuit (27). As a result, dVr / dt-dVf / dt, which is changed as indicated by the broken line in the drawing and which exceeds the arc discharge detection value, is offset as shown by the solid line (see arrows in the figure) It disappears. This makes it possible to suppress misjudgment that arc discharge has occurred in the processing space S.

When the traveling wave voltage Vf is lowered and dVf / dt becomes negative, dVr / dt may be changed without changing dVf / dt.

Fig. 5 is a view schematically showing a configuration of a second modification of the plasma processing apparatus of Fig. 1;

5, the plasma processing apparatus 28 includes a differential detection circuit 29 disposed between the first differential circuit 21 and the negative input side 22a of the comparator 22 instead of the diode 25, And a differential value reducing circuit 30 connected to the differential value detecting circuit 29 and disposed between the second differential circuit 23 and the plus input side 22b of the comparator 22.

The differential value detecting circuit 29 transmits a signal to the differential value decreasing circuit 30 when detecting that the dVf / dt obtained by the first differential circuit 21 is negative, and outputs the signal to the differential value decreasing circuit 30 output the dVr / dt obtained by the second differentiating circuit 23 smaller.

FIG. 6 is a diagram for explaining a process of changing the time differential value of the reflected wave voltage to be executed in the plasma processing apparatus of FIG. 5; FIG.

6 shows a case in which a fine peak not caused by the arc discharge occurs in the reflected wave voltage Vr but the traveling wave voltage Vf decreases. The dVr / dt in the figure fluctuates vertically as indicated by a broken line. In the plasma processing apparatus 28, dVr / dt obtained by the second differentiating circuit 23 is reduced to a differential value Is reduced by the circuit (30). As a result, dVr / dt-dVf / dt, which is originally changed as shown by the broken line in the drawing and exceeds the arc discharge detection value, is decreased as shown by the solid line, and the arc discharge detection value is not exceeded. This makes it possible to suppress misjudgment that arc discharge has occurred in the processing space S.

Further, the present invention can be applied to any plasma processing apparatus that generates plasma using high-frequency power. For example, the present invention can be applied not only to the plasma processing apparatus 10 having the parallel plate type (CCP type) chamber 11 shown in Fig. 1 but also to the plasma processing apparatus having the ICP type chamber have.

10, 26, 28: Plasma processing apparatus
11: chamber
12: High frequency power source
18: Power meter
21: First differential circuit
22: Comparator
22a: Negative input side
22b: Plus input side
23: second differential circuit
24: Output cut-off circuit
25: Diode
29: Differential value detection circuit
27, 30: Differential value reduction circuit

Claims (7)

A plasma processing apparatus comprising a processing chamber to which a high frequency electric power is supplied and which generates plasma in the processing chamber and processes the object to be processed by using the plasma,
A first time differentiator for temporally differentiating a progressive wave voltage of a high frequency power toward the processing chamber,
A second time differential section for temporally differentiating the reflected wave voltage of the high-frequency power returned from the processing chamber,
A value corresponding to a time differential value of the reflected wave voltage and a time differential value of the progressive wave voltage is calculated and an arc discharge is generated in the processing chamber when a value corresponding to the calculated difference exceeds a predetermined threshold value A judging section for judging,
And a differential value changing means for changing at least one of a time differential value of at least the reflected wave voltage and a time differential value of the traveling wave voltage so that a value corresponding to the difference becomes smaller than a predetermined threshold value when the time differential value of the traveling wave voltage becomes negative part
The plasma processing apparatus further comprising:
The method according to claim 1,
Wherein the determination unit includes a first input unit to which the time derivative of the progressive wave voltage is input and a second input unit to which the time derivative of the reflected wave voltage is input,
Wherein the differential value changing unit is connected to at least one of the first input unit and the second input unit
And the plasma processing apparatus.
3. The method of claim 2,
Wherein the value corresponding to the difference is a value obtained by subtracting the time derivative of the progressive wave voltage from the time derivative of the reflected wave voltage.
4. The method according to any one of claims 1 to 3,
Wherein the differential value changing unit sets the time differential value of the traveling wave voltage to 0 when the time differential value of the traveling wave voltage becomes negative.
5. The method of claim 4,
Wherein the differential value changing unit comprises a diode. 4. The method according to any one of claims 1 to 3,
Wherein the differential value changing unit reduces the absolute value of the time derivative of the traveling wave voltage when the time differential value of the traveling wave voltage becomes negative.
4. The method according to any one of claims 1 to 3,
Wherein the differential value changing unit reduces the time differential value of the reflected wave voltage when the time differential value of the traveling wave voltage becomes negative.

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