JPH0997785A - Plasma processing device and plasma cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing device and a method capable of detecting an end point of plasma cleaning very accurately. SOLUTION: A plasma processing device is equipped with a window material 7 which transmits plasma emission from a vacuum chamber 1 and a lens optical system 8 focused on an empty space inside the vacuum chamber 1 through the window material 7, an optical device 9 which selectively transmits plasma emission in a specific range of frequency transmitted through the lens optical system 8, a plasma emission intensity measuring device 10 which measures the intensity of plasma emission in a specific frequency range, and a processing device 11 which calculates a change of emission intensity with time. Only plasma emission from the vicinity of a region where a disused deposit film is hard to remove and which takes a lot of time to clean up is spatially decomposed and extracted through the lens optical system 8 focused on it, and an intensity change in the spatially decomposed plasma emission of specific frequency range is measured and monitored, whereby an end point of plasma cleaning is accurately detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus such as a plasma CVD apparatus, a dry etching apparatus or a plasma ashing apparatus used in a thin film forming process for semiconductors, liquid crystal panels, solar cells or the like, or a fine processing process.

[0002]

2. Description of the Related Art In recent years, plasma processing apparatuses have been improved in quality in order to improve device functionality and reduce processing costs.
Efforts are being actively made to achieve high speed, large area, low damage, and low dust. Such a plasma processing apparatus performs plasma processing on a base material to perform film formation and etching, but at this time, unnecessary deposition film as a reaction product on the inner wall of the processing chamber other than the processing base material or components in the processing chamber. Is deposited. When the number of times the substrate is processed increases, the unnecessary deposited film is thickly deposited and eventually peels off to become a dust source, which causes a device failure. Therefore, although the actual production time (operating rate) of the apparatus is shortened, the deposited film is removed (cleaned) by plasma cleaning.

A conventional plasma processing apparatus will be described below. An example of a conventional plasma processing apparatus is disclosed as a plasma cleaning method in Japanese Patent Laid-Open No. 63-5532. FIG. 5 is a sectional view of a reaction chamber of the plasma processing apparatus disclosed in Japanese Patent Laid-Open No. 63-5532.

In FIG. 5, 21 is a vacuum container that can be evacuated, 22 is a processing substrate, 23 is a high-frequency electrode connected to a high-frequency power source 24, 25 is an opposite ground electrode installed, 2
Reference numerals 6 and 29 are quartz windows, and reference numerals 27 and 30 are devices for measuring emission intensity of a specific wavelength (for example, an interference filter and a photodiode), which are installed to measure the plasma emission spectrum intensity between the electrodes 23 and 25. There is. 28, 3
1 is an end point detection device.

A cleaning method of the plasma processing apparatus having the above structure will be described below. First, the vacuum container 21 on which an unnecessary film is deposited is evacuated, and a cleaning reaction gas (for example, oxygen gas) is introduced from the gas introduction port to adjust the pressure to 150 mTorr.
Next, 13.56 MHz high frequency power is supplied from the high frequency power supply 24 to the high frequency electrode 24 to generate plasma between both electrodes. By this plasma, unnecessary deposition films on the inner wall of the vacuum chamber 21 and both electrodes are removed by etching. At this time, the plasma emission spectrum between both electrodes is monitored through the quartz windows 26 and 29. That is, the emission spectrum intensity of the reaction product of the deposited film and the gas plasma or the substance consumed by the reaction in the plasma between both electrodes is monitored by the emission intensity measuring devices 27 and 30 of a specific wavelength, and the emission intensity is monitored. Changes at the end point of cleaning, the end point is detected by the end point detection devices 28 and 31.

[0006]

Unnecessary deposited films, which are dust sources, are deposited not only on both electrodes but also on the inner wall of the vacuum container and the side and back surfaces of the electrodes. Since it is away from the center of the plasma region, the time required for removal by plasma cleaning is longer than that on the electrode. However, in the above conventional configuration,
When monitoring the intensity of the emission spectrum, the plasma emission between both electrodes is monitored by an emission intensity measuring device that does not have spatial resolution, and it is vaguely monitored with a focus on the plasma emission between both electrodes. Therefore, the change in the emission spectrum between both electrodes is easy to detect, but it is difficult to remove by plasma cleaning deposited on the inner wall of the vacuum container, the side surface and the back surface of the electrode, and the end point of the cleaning of the deposited film that requires a long cleaning time. Is hard to detect. That is, it was impossible to detect the plasma cleaning end point of the deposited film on the inner wall of this vacuum container, the side surface of the electrode, and the back surface. Therefore, in the conventional configuration, the plasma cleaning is further continued excessively after the end point is detected. In such a conventional method, even if the deposited film on the inner wall of the vacuum container and the side and back surfaces of the electrode is actually removed by plasma cleaning,
There is a problem that the operating rate is unnecessarily reduced by cleaning for an excessive period of time, and cleaning is completed even if it is not sufficiently removed, and the remaining deposited film becomes a dust source during the subsequent plasma processing, which increases the yield. It had the problem of dropping it.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a plasma processing apparatus and a plasma cleaning method capable of performing highly accurate end point detection of plasma cleaning.

[0008]

To achieve this object, a plasma processing apparatus having a first structure according to the present invention comprises a lens optical system focused on a space in a substrate processing chamber and the lens optical system. An optical device that selectively transmits a specific wavelength region of the transmitted plasma emission, a plasma emission intensity measuring device of the specific wavelength region, and an end point detecting device that performs a calculation process of the temporal change of the emission intensity are provided.

Further, according to the second aspect of the present invention, it is preferable that the lens optical system is installed while focusing on a space other than the space sandwiched between the plasma generating portion of the plasma generating source and the processing substrate. .

Further, according to the third aspect of the present invention, it is preferable that the lens optical system is installed in focus near the inner wall of the substrate processing chamber.

In the plasma cleaning method according to the present invention, plasma light emission other than the main plasma region sandwiched between the plasma generating portion of the plasma source and the processing substrate is spatially decomposed by focusing with a lens optical device. Next, the end point of plasma cleaning is detected by measuring and monitoring the emission intensity of the spatially decomposed plasma emission in a specific wavelength region.

[0012]

According to the first aspect of the present invention, the end point of plasma cleaning of the unnecessary deposited film, which is a dust source, is increased by spatially and wavelength-resolving the plasma emission and monitoring the intensity change. It can be detected accurately.

According to the second aspect of the present invention, the lens optical system is focused on the plasma other than the space sandwiched between the plasma generating portion having a high plasma cleaning speed of the unnecessary deposited film and the processing substrate. By spatially decomposing the light emission and then wavelength-decomposing it and monitoring its intensity, the end point of the plasma cleaning of the unnecessary deposited film in the portion that is difficult to remove by plasma cleaning can be detected with high accuracy.

Further, according to the third structure of the present invention, it becomes easy to detect with high accuracy the end point of the plasma cleaning of the inner wall of the base material processing chamber which takes the longest cleaning time.

Further, according to the method of the present invention, only the plasma emission in the vicinity of the portion of the unnecessary deposited film that is difficult to remove and requires a long cleaning time is spatially decomposed and extracted by focusing with the lens optical device. Next, the end point of plasma cleaning can be detected with high accuracy by measuring and monitoring the emission intensity change of the spatially decomposed plasma emission in a specific wavelength region.

[0016]

EXAMPLE An example of a plasma processing apparatus according to the present invention will now be described with reference to plasma C in which a SiN film is deposited inside a vacuum container.
Taking the application to plasma cleaning of VD equipment as an example,
This will be described with reference to the drawings.

In FIG. 1, 1 is a vacuum container, 2 is a vacuum exhaust system, 3 is a ground electrode for holding a substrate (not shown) having a heater for heating a substrate (not shown), 4 has a reaction gas introduction port, and 13. 5
A high-frequency electrode to which a 6-MHz high-frequency power source 6 is connected, 5 is an insulator, 7 is a quartz window that transmits plasma emission, and 8 is a quartz glass lens (focal length = 150 mm), which is a space 3 mm away from the side surface of the ground electrode 3. Focus on. Reference numeral 9 is an interference filter which transmits a specific wavelength region, and 10 is a conversion of the plasma emission transmitted by the photodiode into an electric signal. Reference numeral 11 is an end point detection device.

Here, the plasma emission to be monitored may be an emission spectrum of a reaction product of the deposited film and the gas plasma in the plasma, or a substance consumed by the reaction. Since it is cleaning, the emission intensity at 674 nm, which is the emission spectrum of N (nitrogen) of the reaction product, is monitored. Therefore, the interference filter 9 has a transmission center near 674 nm.

Plasma processing apparatus configured as described above
The operation will be described with reference to FIG. First,
Evacuate the vacuum container 1 with the necessary SiN film deposited inside.
The reaction gas CF_Four90cc / min, O₂10cc
/ Min at the same time, the pressure is adjusted to 800 mTorr. Next, 8
A high frequency power of 00 W is applied to the high frequency electrode 4. Do
And F (fluorine) in the vacuum chamber 1 centered between the electrodes 3 and 4.
Plasma of an elementary gas is generated. Deposited SiN
The film is etched by F radicals and SiF_FourAnd N ₂gas
As the reaction product of the
Be used. Normally, the deposited film between both electrodes can be removed quickly.
However, it takes longer than this to remove the deposited film on the side of the ground electrode.
It takes time and is difficult to remove.

FIG. 2 shows changes in the emission intensity of 674 nm, which is the emission spectrum of N (nitrogen) of the reaction product in a space of 3 mm on the side surface of the ground electrode of this example, and the emission spectrum between both electrodes in the conventional method. The intensity change was shown. In the prior art, the emission intensity changes greatly when the SiN film between both electrodes can be removed, and the end point is detected near point A. However, in reality, the SiN film still remains on the side surface of the ground electrode. Accurate end point cannot be detected due to accumulation.

On the other hand, according to this embodiment, since only the emission spectrum on the side surface of the ground electrode is selectively monitored, the emission spectrum is changed at the time (point B) when the SiN film on the side surface of the ground electrode is removed. There is a large change, and the end point can be detected at this point. That is, it is possible to detect the cleaning end point with high accuracy by spatially selectively monitoring the emission spectrum intensity in the vicinity of the portion that is difficult to clean.

As described above, according to this embodiment, the lens optical system focused on the space in the substrate processing chamber, and the optical device selectively transmitting the specific wavelength region of the plasma emission transmitted through the lens optical system. By providing the plasma emission intensity measuring device for the specific wavelength region and the arithmetic processing device for the time variation of the emission intensity, only the plasma emission in the vicinity of the portion of the unnecessary deposited film, which is difficult to remove and requires cleaning time, Detecting the end point of plasma cleaning with high accuracy by focusing and spatially decomposing and extracting with a lens optical device, and then measuring and monitoring the change in emission intensity of the spatially decomposed plasma emission in a specific wavelength region. Can
It is possible to save unnecessary extension of the cleaning time and improve productivity, and to keep the inside of the vacuum container in a clean state without leaving an unnecessary deposited film that has not been removed.

In the present embodiment, the area of plasma emission for focusing the lens and spatially selectively monitoring is defined as follows.
Although it is set on the side surface of the ground electrode, the present invention should not be limited to this, and it is desirable to set it in the vicinity of a portion that is difficult to remove by plasma cleaning. For example, as shown in FIG. B: near the back surface of the electrode, C: near the side surface of the high frequency electrode, D: on the inner wall of the vacuum container, or the like. It is desirable to set the optimum location according to the device depending on the plasma generation method, process conditions, vacuum container structure, gas supply and exhaust structure, and the like.

Further, although the parallel plate type plasma CVD apparatus has been described as an example in the present embodiment, the method of generating plasma is not limited to this, and the plasma having the configuration shown in FIG. 4 is used. As the generation source 12, an induction heating plasma source (ICP) or an electron cyclotron resonance (EC
R) or a helicon wave plasma source may be used. The present invention may be used in a dry etching apparatus by changing the type of gas to a fluorine-based, chlorine-based, bromine-based, oxygen-based etching gas or the like. In this case as well, for example,
E: on the side surface of the substrate holder, F: on the back surface of the substrate holder,
G: Focusing on the inner wall of the vacuum container or the like, the intensity change of the spectrum may be monitored.

In this embodiment, the interference filter is used as the optical device for selectively transmitting the specific wavelength region of plasma emission, but an optical device such as a grating may be used.

Although a single-plate lens is used as the lens optical system in this embodiment, an optical system using a plurality of lenses may be used.

Further, in this embodiment, plasma CVD
Although the apparatus has been described, it may be used for a dry etching apparatus or a plasma ashing apparatus.

[0028]

As described above, according to the present invention, by plasma decomposition and wavelength decomposition of plasma emission and monitoring the intensity change thereof, the end point of plasma cleaning of an unnecessary deposited film as a dust source can be increased. It can be detected accurately.

Further, according to the method of the present invention, only plasma emission in the vicinity of the portion where it is difficult to remove an unnecessary deposited film and which requires a long cleaning time is spatially decomposed and extracted by focusing with a lens optical device. Next, the end point of plasma cleaning can be detected with high accuracy by measuring and monitoring the emission intensity change of the spatially decomposed plasma emission in a specific wavelength region.

[Brief description of drawings]

FIG. 1 is a sectional view of a reaction chamber in an embodiment of a plasma processing apparatus according to the present invention.

FIG. 2 is a diagram showing changes in emission spectra during plasma cleaning in the plasma processing apparatus according to the present invention and the conventional plasma processing apparatus.

FIG. 3 is a sectional view of a reaction chamber in another embodiment of the parallel plate type apparatus of the plasma processing apparatus according to the present invention.

FIG. 4 is a sectional view of a reaction chamber in another embodiment of the plasma processing apparatus according to the present invention.

FIG. 5 is a sectional view of a reaction chamber in a conventional plasma processing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Vacuum exhaust system 3 Grounding electrode 4 High frequency electrode 5 Insulator 6 High frequency power supply 7 Window material (quartz window) 8 Lens 9 Interference filter 10 Emission intensity measurement device 11 End point detection device 12 Plasma generation source

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01L 21/302 N

Claims (4)

[Claims] 1. A plasma processing apparatus having a plasma generation source for performing plasma processing on a base material, comprising: a lens optical system focused on a space in a base material processing chamber; and plasma emission light passing through the lens optical system. A plasma processing apparatus comprising: an optical device that selectively transmits a specific wavelength region, a plasma emission intensity measuring device in the specific wavelength region, and an end point detecting device that performs a calculation process of the time variation of the emission intensity. 2. The plasma processing apparatus according to claim 1, wherein the focal point of the lens optical system is located in a space other than the space sandwiched between the plasma generation portion of the plasma generation source and the processing substrate. 3. The plasma processing apparatus according to claim 2, wherein the focal point of the lens optical system is near the inner wall of the substrate processing chamber. 4. A plasma cleaning method for a plasma processing apparatus, which has a plasma generation source and performs plasma processing on a substrate, wherein plasma emission other than a region sandwiched between the plasma generation portion of the plasma source and the processing substrate is performed. Plasma cleaning characterized by detecting the end point of plasma cleaning by focusing and spatially decomposing with a lens optical device and then measuring and monitoring the emission intensity of the spatially decomposed plasma emission in a specific wavelength region. Method.