JPH0628252B2 - Plasma processing end point determination method and apparatus - Google Patents

Description

TECHNICAL FIELD The present invention relates to a plasma processing end point determination method and apparatus,
In particular, the present invention relates to a plasma processing end point determining method and apparatus suitable for determining the end point of plasma processing of a sample by emission spectroscopy.

[Conventional technology]

As a technique for determining the end point of plasma processing such as dry etching of a sample such as a semiconductor element substrate by an emission spectroscopy, conventionally, for example, a spectral amount is converted into an electric signal as described in JP-A-59-94423. It is known that the function of the electric signal and the processing time is converted, and the function of the processing time is secondarily differentiated, and the end point of the plasma processing of the sample is determined based on the relationship between the second derivative and the preset level value.

[Problems to be solved by the invention]

The above-mentioned prior art does not consider both the time delay of the determination of the plasma processing end point and the certainty of the determination (noise resistance). Therefore, when the certainty of the determination is emphasized, If the determination time is delayed and the determination time is emphasized, on the contrary, there is a problem that an erroneous determination is made for a slight change in the light amount due to noise or the like.

An object of the present invention is to provide a plasma processing end point determination method and apparatus capable of suppressing a time delay in determining the plasma processing end point of a sample and ensuring the certainty of the determination.

[Means for solving problems]

The above-mentioned object is a plasma processing end point determination method, a step of spectrally separating the light emission of a specific wavelength from among the light emission generated during the plasma processing of the sample, a step of converting the light amount of the spectral light into an electrical signal, A step of smoothing with a time constant, a step of detecting a change tendency of the smoothed electric signal,
A step of smoothing the electric signal with a small time constant after detecting the change tendency of the smoothed electric signal; and a step of determining the plasma processing end point of the sample by the temporal change of the electric signal smoothed with the small time constant. And a plasma processing end point determination device, a means for spectrally splitting light emission of a specific wavelength from among the light emission generated during plasma processing of the sample, a means for converting the light amount of the spectral light into an electrical signal, and the electrical signal A means for smoothing with a large time constant, a means for detecting a change tendency of the smoothed electric signal, a means for smoothing the electric signal with a small time constant, and an electric signal smoothed with the small time constant. Means for determining the plasma processing end point of the sample by aging, means for smoothing the electric signal with a large time constant, and means for smoothing the electric signal with a small time constant. With those and means for switching the change trend detection of the serial smoothed electrical signal,
To be achieved.

[Work]

The light amount of the light emission of a specific wavelength, which is separated from the light emission during the plasma processing of the sample, is converted into an electric signal. This electric signal is smoothed with a large time constant. By smoothing with a large time constant in this way, it is not affected by minute fluctuations in the light amount of the spectrum (excellent in noise resistance). The change tendency of the smoothed electric signal, that is, the decreasing tendency or the increasing tendency is detected (the noise resistance is excellent and the processing end tendency can be surely grasped.) After that, in this state, that is, the smoothing of the electric signal with a large time constant is performed. In the case where the charge is maintained, the change from the decrease or increase of the smoothed electric signal to the steady state cannot be immediately detected. Therefore, when the change tendency of the smoothed electric signal is detected (the tendency of the end of processing is surely grasped), the smoothing of the electric signal is performed from the smoothing with a large time constant to the smoothing with a small time constant (spectral Sensitive to slight changes in light intensity)
The end point of the plasma processing of the sample is determined by the change with time of the electric signal smoothed by the small time constant, that is, the relationship between the electric signal and the function of the processing time, for example, the relationship between the second derivative and a preset level value. To be done.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows an example of a device configuration to which the present invention is applied. A reaction processing chamber 1 in which an upper electrode 2 connected to a ground potential and a lower electrode 3 connected to a high-frequency power source 6 are provided internally, and a reaction gas introduction unit 4, a vacuum exhaust unit 5, and a quartz glass window 8 are provided. A spectroscope 9, a photoelectric converter 10, an amplifier circuit 11, an A / D converter 12, and a digital signal processing device 13. A sample 7 is placed on the lower electrode 2 and a reaction gas is introduced. While causing blow discharge, the spectroscope 9 selects a specific wavelength for the amount of light emitted during etching.
The photoelectric converter 10 converts the signal into an electric signal, and the amplifier circuit 11
Is amplified by the A / D converter 12, converted into a digital signal by the A / D converter 12, and input to the digital signal processing device 13.

FIG. 2 shows the inside of the digital signal processing device 13. A series of a filter means 14 having a large time constant, a secondary difference calculating means (large difference interval) 16 and a judging means 18, a filter means 15 having a small time constant, and a secondary difference calculating means (small difference interval) 17 , A sequence consisting of the judging means 19 and a sequence controlling means 20. The sequence control signal is a judgment start signal,
The determination means 18 sends the first-stage determination signal 22 to the determination means 19 at the time when the increase or decrease tendency of the monitor light amount is detected. The determination means 19 determines the etching end point. Second stage judgment signal 23
Is transmitted to the sequence control means 20. The sequence control means 20 gives an electric discharge stop command to the high frequency power source 6 after performing overetching.

FIG. 3 shows the case where the light emission by the reaction product during etching is selected as the monitor specific wavelength, and the monitor waveform 24 is
The waveform 25 that has been subjected to the difference calculation in a series with a large time constant is determined by the determination threshold value 27, and is used as the first stage determination. After that, the waveform 26 for which the difference has been calculated is determined by the determination threshold value 28 in a series having a small time constant, and is set as the end point of the second stage.

FIG. 4 shows a case where light emission by reaction radicals during etching is selected as the monitor specific wavelength, and is the same as the case of FIG. 3 if the sign of the determination threshold value is reversed.

In the present embodiment, it is possible to determine the time delay of the determination of the end point of the dry etching process of the sample, and also it is possible to reliably grasp the etching end tendency with excellent noise resistance and prevent erroneous determination. Further, the etching end point can be accurately determined.

In the above embodiment, the digital signal is smoothed by the filter means, but the analog electric signal may be smoothed by the filter means. Further, in the above embodiment, the function of the electric signal and the processing time is second-order differentiated, but the function may be first-differentially differentiated. Further, although the parallel plate type dry etching apparatus is taken as an example of the semiconductor manufacturing apparatus in the above-mentioned embodiment, an apparatus for processing a sample by plasma, for example, a magnetic field microwave plasma processing apparatus, a non-magnetic field microwave plasma processing apparatus. It can also be applied to other devices without any problem.

〔The invention's effect〕

According to the present invention, by considering both the time delay of the determination of the plasma processing end point of the sample and the certainty of the determination,
It is possible to suppress the time delay of the determination of the plasma processing end point of the sample and ensure the certainty of the determination.

[Brief description of drawings]

FIG. 1 is a block diagram of a plasma processing end point determining apparatus according to an embodiment of the present invention, FIG. 2 is a block diagram of a digital processing apparatus of FIG. 1, and FIGS. 3 and 4 are of FIG. FIG. 7 is a relational diagram of emission intensity, secondary difference value, and elapsed time showing an example of a monitor waveform in the device. 1 ... Reaction processing chamber, 7 ... Sample, 8 ... Quartz glass window, 9 ... Spectrometer, 10 ... Photoelectric converter, 12 ... A / D converter, 13 ... Digital signal processor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hiroji Nishihata Hiroji Nishihata 794, Higashitoyoi, Kudamatsu, Yamaguchi Prefecture Inside the Kasado Plant, Hitachi, Ltd. (72) Shoji Ikuhara 794, Toyoi, Higamatsu, Yamaguchi Prefecture Hitachi Techno Engineering Co., Ltd. Kasado Plant (72) Inventor Shoji Okiguchi 794 Azuma Higashitoyo, Kudamatsu City, Yamaguchi Prefecture Hitachi Techno Engineering Co., Ltd. Kasado Plant

Claims (2)

[Claims] 1. A step of spectrally splitting a light emission of a specific wavelength from among the light emission generated during plasma processing of a sample, a step of converting the light amount of the spectral light into an electric signal, and smoothing the electric signal with a large time constant. A step of detecting a change tendency of the smoothed electric signal, a step of smoothing the electric signal with a small time constant after detecting the change tendency of the smoothed electric signal, and a step of smoothing with the small time constant And a step of determining a plasma processing end point of the sample based on a temporal change of an electric signal. 2. A means for spectrally separating the light emission of a specific wavelength from the light emitted during plasma processing of the sample, a means for converting the light quantity of the spectral light into an electric signal, and smoothing the electric signal with a large time constant. Means, means for detecting a change tendency of the smoothed electric signal, means for smoothing the electric signal with a small time constant, and plasma of the sample due to the temporal change of the electric signal smoothed with the small time constant. A means for determining a processing end point, a means for smoothing the electric signal with a large time constant, and a means for smoothing the electric signal with a small time constant by means of detecting a change tendency of the smoothed electric signal. A plasma processing determination device characterized in that.