JPH0719771B2 - Discharge abnormality detection device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a plasma processing apparatus using AC power, such as a high frequency sputtering apparatus and a high frequency plasma etching apparatus,
In particular, the present invention relates to an apparatus suitable for detecting and recording an abnormality in a discharge state.

[Conventional technology]

In a conventional plasma processing apparatus using AC power, a high-frequency reflection wattmeter or an electrode DC voltmeter is used as a method of knowing the discharge state, and the above power meter is used to detect an abnormality in the discharge state. Or, the only choice was to see the fluctuation of the voltmeter or to visually observe the inside of the processing chamber.

[Problems to be solved by the invention]

In the above conventional technique, a relatively large discharge abnormality can be observed, but a high-speed pulsed discharge cannot be detected. In addition, no consideration was given to quantitative analysis such as the magnitude, frequency, and total number of discharge abnormalities.For discharge abnormalities, there is a rise in local temperature, electrostatic charge, etc., which damages the object to be processed and foreign matter occurs. However, since it is not possible to know the discharge state during processing, no measures could be taken.

An object of the present invention is to detect the occurrence state of the discharge abnormality in order to reduce the damage of the processing body due to the discharge abnormality and improve the yield.

[Means for solving problems]

The above-mentioned object is the potential of the AC discharge electrode of the plasma processing apparatus,
Or, the signal from the high frequency power supply system such as the output of the high frequency power meter is passed through a filter that removes the frequency component of the steady signal,
This is achieved by detecting and recording the occurrence of abnormal discharge by discriminating the level of the obtained signal.

[Action]

Since the potential level measured in the AC power feeding system is closely related to the state of the discharge field that is the load, it changes with the change in impedance due to abnormal discharge. This signal is
Since the power carrier is the main component, the discharge abnormality cannot be detected as it is, but by deleting the frequency component of the power carrier, which is a stationary signal, by the filter, only the signal generated by the discharge abnormality remains. Therefore, if the output is above a certain threshold value, it can be judged that the discharge abnormality has occurred.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows the high frequency sputtering apparatus to which the present invention is applied.

A target electrode 1 and a substrate electrode 2 are installed in the vacuum chamber 10. The substrate electrode 2 is grounded via a capacitor 11. The target electrode 1 is supplied with a high frequency power of 13.56 MHz from a high frequency power source 6 through a power meter 4 and a matching unit 5.

The power meter reflected wave output 13 of the power meter 4 is input to the discharge abnormality detection device 12 of the present invention. The discharge abnormality detection device 12
Is composed of a signal detection unit 6, a filter unit 7, a comparison unit 8, and a recording unit 9.

In the above structure, the vacuum chamber 10 is kept at a constant pressure by an exhaust system (not shown) and an atmosphere gas (inert gas such as Ar) supply system (not shown). Plasma is generated between the electrodes by the high frequency power supplied from the high frequency power supply 3 to the target electrode 1 via the power meter 4 and the matching unit 5.

The frequency components of the signal of the power meter reflected wave output 13 during normal discharge are shown in FIG. Power carrier 13.56M for this signal
A low frequency component of 50 Hz to 300 Hz generated due to the Hz component and fluctuation of the carrier power (due to the fact that the high frequency power supply 11 is supplied with power from the commercial power supply line) is included as a stationary signal.

The power meter reflected wave output 13 undergoes level conversion and impedance conversion in the signal detection unit 6 of the discharge abnormality detection device 12, and is input to the filter unit 7 at the optimum level. The frequency characteristic of the filter section 7 is designed based on FIG. 2 and as shown in FIG. 3 so that almost only the standing wave component of the signal sent from the power meter reflected wave output 13 is deleted. Therefore, during normal discharge, nothing is output from the filter unit 7.

When a discharge abnormality occurs between the target electrode 1 and the substrate electrode 2 or between the electrode and the wall of the vacuum chamber 10, a change in the impedance of the discharge system seen from the target electrode 1 occurs and the matching device 5 The reflected power from the power source fluctuates and appears at the power meter reflected wave output 13. Since this signal caused by the occurrence of discharge abnormality is generally an irregular signal including a wide frequency component, it almost passes through the filter section 7 having the frequency characteristic shown in FIG. That is, the output of the filter unit 7 emits a signal only when a discharge abnormality occurs.

The comparison unit 8 compares the output of the filter unit 7 with a signal level that is higher than the minute noise level generated inside the filter unit 7 and the comparison unit 8. If there is a signal that passes through the filter unit 7, that is, if a discharge abnormality occurs,
It will be directly detected by the comparison unit 8. When the occurrence of the discharge abnormality is detected, it is recorded in the recording unit 9, and the occurrence time, the total number, the frequency, and the signal waveform of the discharge abnormality can be known.

As described above, according to the present embodiment, it is possible to detect the discharge abnormality occurrence and to know the occurrence state by utilizing the difference between the stationarity of the power carrier and the non-stationary irregularity of the discharge abnormality signal. Therefore, it is possible to utilize it for the mechanism of occurrence of discharge abnormality, analysis of monetary damage due to occurrence of discharge abnormality, and countermeasures.

〔The invention's effect〕

According to the present invention, it is possible to detect only the signal caused by the discharge abnormality from the AC power supply system, and thus it is possible to know the number of occurrences, the magnitude, and the generation time of the discharge abnormality. Therefore, problems such as damage to the processed object and adhesion of foreign matter caused by abnormal discharge can be accurately grasped, sufficient measures can be taken against these abnormal discharge, and the yield of semiconductor plasma processing steps can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an abnormal discharge detection device according to an embodiment of the present invention, FIG. 2 is a frequency power spectrum distribution diagram of a steady signal of a reflected wave output of a power meter of FIG. 1, and FIG. It is a filter characteristic view of the filter unit 7 in the figure. 1 ... Target electrode, 2 ... Substrate electrode, 3 ... High-frequency power supply, 4 ... Power meter, 5 ... Matching device, 6 ... Signal detection unit, 7 ... Filter unit, 8 ... Comparison unit, 9 …… Recording unit, 10 …… Vacuum chamber, 11 ・ ・ ・
… Capacitor.

Claims (1)

[Claims] 1. A discharge abnormality detecting apparatus for a plasma processing apparatus for processing a sample by generating plasma with AC power, comprising signal detection means for detecting the AC power and a signal detected by the signal detection means. It has a filter means for removing the standing wave component and outputting only the non-standing wave component, a comparing means for identifying the signal level of the non-standing wave component, and a recording unit for recording the generation state of the non-standing wave component. Discharge abnormality detection device.