JPH0479319A - Optical endpoint monitor for dry - Google Patents

Abstract

PURPOSE:To protect the accuracy of endpoint detection from being affected by fouling of the view port of dry etching equipment by measuring the cloudiness of the surface of the view port window of an etching chamber for monitoring light intensity and by selecting an endpoint detect sensitivity program in conformity with the intensity of light from the monitor window relative to a critical light intensity. CONSTITUTION:An optical endpoint monitor for dry etching device of this invention is provided with a software that when the intensities (4) and (5) of light having a particular wavelength indicate an appropriate value x immediately after starting dry etching, a detection sensitivity program P1, or when indicating a value less than x, a detection sensitivity program P2 is automatically selected to detect an endpoint accurately at all times without being affected by the extent of fouling of a view port. The appropriate value x represents the critical intensity (6) of light having a particular wavelength and this critical intensity is a value representing a boundary that changes a light intensity sensitivity program for light having a particular wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical endpoint monitor used in a dry etching device used in IC manufacturing and the like.

[Conventional technology]

Conventionally, plasma etching, reactive ion etching,
In most dry etching processes, including magnetron etching, an optical endpoint monitor that utilizes the luminescent phenomenon of reaction residues, products, etc. is used to detect the endpoint and terminate the etching. At the end point, where the thin film to be etched is completely removed from the surface of the semiconductor substrate, chemical changes occur both in the gas phase and on the thin film, and the products disappear, while the reactant gas increases because it is no longer consumed by the reaction. . These chemical changes appear as changes in emission intensity at specific wavelengths. An optical endpoint monitor monitors changes in the intensity of light at a specific wavelength through a light intensity monitoring window (hereinafter referred to as the "viewport") fixed to the dry etching chamber, and defines the time when a large change in intensity occurs as the endpoint. In order to detect changes in the intensity of light at a point, many devices use -th order differentiation, second order differentiation, etc.

[Problem to be solved by the invention]

With the conventional optical endpoint monitor described above, especially when etching heavy metals such as gold, the view boat is likely to become dirty and cloudy due to product 2 reaction gas, reducing the sensitivity for detecting changes in light intensity and making it difficult to detect endpoints. It may disappear. In this case, it is necessary to change the light intensity detection sensitivity or open the chamber of the dry etching device and clean the view boat, but it is difficult to determine when to change the sensitivity, and cleaning the view boat is difficult. However, since the chamber must be opened, it takes time and effort. In addition, if you set the light intensity change detection sensitivity according to the state of the view boat when it is dirty, even the slightest change in intensity will be detected when the view boat is in a clean state, so you may misjudge the end point. There is a high possibility that you will make a judgment.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the above-mentioned drawbacks and to provide an optical endpoint monitor in which the accuracy of endpoint detection is not dependent on viewboat dirt.

Traditional optical endpoint monitors, as mentioned above,
In contrast, the present invention does not take into consideration the deterioration in detection sensitivity of changes in light intensity at specific wavelengths due to dirt on the view boat, whereas the present invention automatically measures dirt on the view boat and automatically changes the light intensity at specific wavelengths depending on the degree of dirt on the view boat. The difference is that the detection sensitivity is changed.

[Means to solve the problem]

The optical endpoint monitor of the present invention determines the degree of contamination of the view boat based on the light intensity of a specific wavelength measured immediately after the start of dry etching, and uses a pre-prepared light intensity change detection sensitivity program depending on the degree of contamination. It has software that automatically selects the most suitable one and detects the endpoint.

〔Example〕

Next, a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a graph showing the light intensity waveform of a specific wavelength monitored for endpoint detection when the viewboat is clean. FIG. 2 is a graph showing a light intensity waveform of a specific wavelength monitored for endpoint detection when the view boat is dirty. In the case of FIG. 2, compared to the case of FIG. 1, the intensity of light is about 1/2 to 1/3. In the case of a conventional optical endpoint monitor, if the detection sensitivity block that can detect the endpoint ■ in Figure 1 is Pl, it cannot detect the endpoint in Figure 2; If the possible detection sensitivity program is P2, there is a possibility that the correct end point (2) in FIG. 1 will not be detected, and the end point (2), which is likely to be mistakenly determined, will be detected as an end point.

Therefore, in the optical endpoint monitor of the present invention, if the light intensity ■, ■ of a specific wavelength immediately after the start of dry etching (after 5 seconds to 10 seconds) is greater than the appropriate value X, the detection sensitivity program P1 is changed to In the case of detection sensitivity program P2
We have developed software that automatically selects endpoints, so that endpoints can always be detected accurately regardless of how dirty the viewboard is. Also, multiple Xs are created as xl...xn, and the detection sensitivity program is changed accordingly to P,...
It is also possible to make more than one p n+1. In addition,
The above-mentioned appropriate value X is a preset critical light intensity (2) of a specific wavelength, and is a value serving as a boundary for changing the light intensity change detection program of a specific wavelength.

In the case of Example 1, the optimal light intensity change detection sensitivity program was automatically selected from a plurality of programs depending on the degree of dirt on the view boat. Apart from such a method, in Example 2, the amplifier gain value is automatically controlled in the detection sensitivity program according to the degree of dirt on the view boat, making it possible to continuously change the detection sensitivity. It is something. In the case of Example 2,
This has the advantage that the optimum detection sensitivity can be easily changed continuously.

〔Effect of the invention〕

As explained above, even if the view boat becomes dirty, the present invention automatically selects an appropriate light intensity change detection program depending on the degree of dirt and detects the end point. This has the effect of eliminating the trouble of appropriately changing the changing aspect ratio program and the case where an end point is not detected at times.

The light intensity of a specific wavelength is the boundary for changing the change detection program.

Claims (1)

[Claims] Equipped with a means for measuring the degree of clouding of a light intensity monitoring window attached to an etching chamber of a dry etching device and selecting an end point detection sensitivity program according to the light intensity from the monitoring window relative to a preset critical light intensity. An optical endpoint monitor for a dry etching system, characterized by: