JPH0261140B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a plasma etching method for detecting the end point of etching when etching the surface of an article using gas plasma, particularly when performing plasma etching on the surface of a semiconductor in the manufacturing process of a semiconductor device. and regarding equipment.

Conventionally, when detecting the end point of this type of plasma etching, it has been considered to use a plasma monitor device as shown in FIG. In this device, 1 is a high-frequency power source for plasma generation, 2 is an electrode for applying a high-frequency electric field, 3 is a vacuum container, 4 is a reaction gas supply pipe, 5 is a reaction gas exhaust pipe, and 6 is a gas inside the vacuum container 3. pressure measurement gauge,
7 is a semiconductor substrate to be etched; 8 is a light extraction port from the vacuum container 3; 9 is a plasma radiation spectrum emitted from the vacuum container 3 through the light extraction port 8;
10 is a spectrometer, 11 is an entrance slit of the spectrometer 10, 12 is an exit slit of the spectrometer 10, 13 is a photoelectric conversion device for converting spectral light into an electric signal, 14 is an amplifier, and 15 is a self-recording recorder. It is.
That is, the plasma radiation spectrum 9 emitted from the gas plasma excited in the vacuum chamber 3 of this device is separated into spectra in the spectrometer 10, and then input into the photoelectric conversion device 13 where it is converted into an electrical signal and amplified. Appropriately amplified with device 14, then recorded with recorder 15
The spectral wavelength and intensity are recorded.

When etching a silicon oxide film with a fluorocarbon gas such as CF ₄ , C ₂ F ₆ , C ₃ F ₃ , or CHF ₃ using such a plasma monitoring device, the emission spectrum intensity changes over time during etching and after etching is completed. As shown in FIG. 2, the emission spectrum intensity changes rapidly at the etching end point, and by detecting this, the etching end point can be known. In FIG. 2, a indicates a high frequency discharge starting point, b indicates an etching end point, and c indicates a high frequency discharge stopping point.

By the way, the conventional plasma monitoring device shown in Fig. 1 uses a spectroscope to separate the emission spectrum from the plasma, but such a spectrometer has problems such as being large, complicated, and inconvenient to operate. Besides being problematic, it also has the disadvantage that it is extremely expensive, increasing the overall cost of the device.

The present invention has been made to eliminate the drawbacks of the prior art, and provides a plasma etching monitoring method and device that is simple and compact in structure, easy to operate, inexpensive, and highly reliable. The purpose is to

In order to achieve this object, the present invention provides a plasma etching method in which a sample in a vacuum container is etched with gas plasma. This plasma etching method is characterized in that the etching end point is detected based on the rapid change in gas pressure.

Further, the plasma etching apparatus according to the present invention includes a high frequency power source, a vacuum container containing a sample,
An electrode is provided in the vacuum container and generates plasma by gas discharge in the vacuum container using high frequency power from the high frequency power source, and a gas pressure is attached to the vacuum container and measures the gas pressure in the vacuum container. It consists of a detection mechanism, a signal processing device that processes electrical signals from the gas pressure detection mechanism, and a high frequency power source control device that controls the high frequency power source using the signals from this signal processing device.

The present invention will be further described below with reference to embodiments shown in the drawings.

FIG. 3 is a schematic diagram showing an embodiment of a plasma etching apparatus according to the present invention.

In this embodiment, reference numeral 20 is a high frequency power source for plasma generation, and this high frequency power source 20 is connected to a pair of electrodes 22 for applying a high frequency and high electric field provided in a vacuum vessel 21 for plasma generation, and A sample 23 is placed on the electrode 22 . The vacuum container 21 has a gas supply pipe 24 for introducing a gas for plasma etching, for example, a carbon fluoride gas such as CF ₄ , C ₂ H ₆ , C ₃ H ₈ , CHF ₃ , etc., and a gas supply pipe 24 for discharging the gas. A gas exhaust pipe 25 is provided. Furthermore, the vacuum container 21 includes
A vacuum gauge 26 is attached to measure the gas pressure within. This vacuum gauge 26 is connected to a signal processing device 27 that shapes, amplifies, calculates, and records the electrical signal from the vacuum gauge 26. The high frequency power supply 20 is connected to a high frequency power supply control device 29 for stopping the application of high frequency power from the high frequency power supply 20 to the electrode 22 after etching is completed, and this high frequency power supply control device 29 and the signal processing device A continuator 28 is provided between the two and 27.

Next, the operation of this embodiment will be explained. When etching the sample 23 placed on the electrode 22, the sample 23 is The etching process is performed by gas plasma generated by gas discharge of the electrode 22. At that time, the vacuum container 21
Changes in the gas pressure inside are measured and recorded by a vacuum gauge 26 and a signal processing device 27, which constitute a monitoring mechanism.

For example, the SiO ₂ film of sample 23 can be treated with CF ₄ , C ₂ F ₆ ,
When etching is performed using a carbon fluoride gas such as C ₃ F ₈ or CHF ₃ , the gas pressure inside the vacuum chamber 21 is
Changes as shown in the figure. In other words, in Fig. 4, point A is the start point of high-frequency discharge, and the gas pressure is kept high and stable during etching, but it drops rapidly at etching end point B, so this change must be monitored. By doing so, the etching end point B can be detected.

After the etching is completed, the signal processing device 27 is
sends an electric signal from to the high frequency power supply control device 29,
The application of high frequency power from the high frequency power source 20 to the electrode 22 is stopped. As a result, the high-frequency discharge stops, but the point at which such high-frequency discharge stops is the fourth
This is indicated by C in the figure, and at this time the gas pressure drops rapidly.

In this way, in this embodiment, the vacuum container 2
Vacuum gauge 2 detects sudden changes in gas pressure from a stable state during the etching process of sample 23 in
6, and the electric signal from the vacuum gauge 26 is shaped, amplified, and calculated by a signal processing device 27,
By recording the end point of etching, it is possible to easily and accurately detect the end point of etching, but the vacuum gauge 26 and signal processing device 27 that constitute the monitoring mechanism may be those used in ordinary etching equipment.
The structure is simple and compact, the operation is simple, and the reliability is high. Moreover, in this embodiment, not only can the etching end point be automatically detected, but also the application of high frequency power can be automatically stopped, making it possible to significantly improve work efficiency.

As described above, according to the present invention, accurate and highly reliable monitoring can be automatically performed at low cost with a simple, compact, and easily operated structure.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing a conventional monitor device;
FIG. 2 is a diagram showing changes over time in the emission spectrum intensity in the apparatus shown in FIG. 1, FIG.
The figure is a diagram showing changes in gas pressure over time in the embodiment of FIG. 3. 20... High frequency power supply, 21... Vacuum container, 22
... Electrode, 23 ... Sample, 26 ... Vacuum gauge,
27... Signal processing device, 28... Relay, 29...
...High frequency power supply control device, A...High frequency discharge start point, B...Etching end point, C...High frequency discharge stop point.

Claims (1)

[Claims] 1. In a plasma etching method in which a sample in a vacuum container is etched with gas plasma, a rapid change in gas pressure in the vacuum container from a stable state during etching of the sample is measured, and this A plasma etching method characterized by detecting an etching end point based on a sudden change in gas pressure. 2. A high frequency power source, a vacuum container containing the sample,
An electrode is provided in the vacuum container and generates plasma by gas discharge in the vacuum container using high frequency power from the high frequency power source, and a gas pressure is attached to the vacuum container to detect gas pressure in the vacuum container. A plasma etching apparatus comprising a detection mechanism, a signal processing device for processing electrical signals from the gas pressure detection mechanism, and a high frequency power supply control device for controlling the high frequency power supply using signals from the signal processing device.