JPS6013460B2 - plasma monitor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plasma monitor, and more specifically, a plasma monitor for measuring the emission intensity of a desired part of plasma to elucidate reactions in plasma etching or deposition, or to detect the end point of processing. Regarding plasma monitors.

2. Description of the Related Art In fields that require microfabrication, such as the manufacture of various semiconductor devices and memory devices, methods of etching and deposition using plasma have been proposed. In particular, etching using plasma is called plasma etching or reactive sputter etching, depending on the shape of the equipment.
It has many features such as less undercuts and excellent fidelity, so it is often used for microfabrication.

When performing etching or deposition using plasma, it is clear that there is a significant relationship between the state of the plasma and the etching process. , it is possible to obtain practically important information. FIG. 1 is a diagram schematically showing an example of a conventional method performed for this purpose, and shows an example in which spectroscopic measurement of plasma was performed.

That is, parallel plate electrodes 2, 6 having a gas introduction system 1,
A viewing window 5 is provided in a plasma etching apparatus consisting of an evacuation system 8, a workpiece 7, a vacuum chamber 3, etc., and the state of the plasma is measured through the viewing window 5 using a spectrometer 4.

(In order to simplify the drawing, components such as high-frequency power supplies are omitted.) However, such conventional methods have several drawbacks as described below, and their practical effects are not as expected. Can not.

That is, as is clear from FIG. 1, since the spectrometer 4 remains fixed, it is not possible to selectively perform spectroscopic measurements of only a desired portion of the plasma.

Therefore, it is hardly useful for practically important purposes such as the distribution of plasma between electrodes and the relationship between the plasma state and processing conditions. Furthermore, the installation location of the spectrometer is limited, and the required area becomes large. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and provide a plasma monitor useful for plasma etching and thin layer deposition.

In order to achieve the above object, the present invention measures plasma through a slit using, for example, a spectrometer, thereby dividing the plasma into layers and sequentially determining the emission intensity distribution.

Hereinafter, the present invention will be explained in detail using Examples.

FIG. 2 is a diagram showing one embodiment of the present invention, in which the viewing window 5
A slit 9 substantially parallel to the flat electrodes 2 and 6 is placed between the spectrometer 4 and the spectrometer 4 .

By not sequentially moving the slit 9 and the spectrometer 4, the plasma generated between the flat electrodes 2 and 6 is divided into layers, and spectroscopic measurements are performed sequentially. FIG. 3 shows another embodiment of the invention, in which the slit 9 and the spectrometer 9
An optical system consisting of two mirrors 11 and 11' is provided between them.

Although the slit 12 of the spectrometer 4 is provided in the vertical direction, the horizontally long image 10 obtained on the mirror 11 through the lateral (horizontal) slit 9 is rotated by 90 degrees to form a vertically long image. The light is converted and made incident on the slit 12 of the spectrometer 4.

In this embodiment, the spectroscope 4 and the mirror 11' are fixed, and only the slit 9 and one mirror 11 are moved to scan between the electrodes 2 and 6, which is similar to the embodiment shown in FIG. It has the advantage of higher plasma condensing efficiency than the example.

Figure 4 shows the transmission of light from the slit 9 to the spectrometer 4.
An example using an optical fiber 15 will be shown.

The entrance end face 14 and the output face 16 of the optical fiber 16 are formed into shapes that match the slit 9 and the slit 12 of the spectrometer 4, respectively, which are arranged near the viewing window of the plasma etching device, and The optical fiber 15 is twisted 900 times so that the slits 16 and 16 face the slits 9 and 12, respectively.

The slits 9 and 12 have different ratios of vertical and horizontal dimensions, but in the case of glass fiber, the shapes of both end surfaces can be easily matched. Therefore, as is clear from FIG. 4, the light of the layered portion 18 of the plasma 17 generated between the flat electrodes 2 and 6 enters the optical fiber 15 through the slit 9 and the cylindrical lens 13.
It is guided to a spectrometer 4.

In this embodiment, a cylindrical lens 13 is disposed between the slit 9 and the input device surface 14 so that all of the light beams 18 entering the slit 9 are focused onto the input end surface 14.

Therefore, all of the light incident on the slit 9 is introduced into the spectrometer 4, which dramatically improves the light collection efficiency and allows the user to freely select the installation location of the spectrometer 4, which provides practical benefits. is big. Furthermore, by using a plurality of slits 9 in combination, it is possible to further improve the resolution when dividing the plasma into layers.
Next, an example in which the emission spectrum of plasma was measured using the present invention will be described.

Example 1 One group of CF4 was placed in a parallel plate plasma etching system.
A high frequency power of 13.58 MHZ and 200 W was applied to the lower electrode to generate plasma.

In plasma using CF4, dissociation products, CF3, C
F2, F, etc. are generated, and among these, the emission spectrum of the F atom was examined using the apparatus shown in FIG. 4 to examine the distribution of the emission intensity between the two electrodes. As a result, the fifth
As shown in the figure, the emission intensity of F atoms at a wavelength of 703.7 nm' is large near the electrode to which the high frequency was applied, and becomes smaller as it approaches the opposing ground electrode.

If a Si wafer is also placed in this plasma, Si+4F
→S' is etched according to the reaction of SiF4.

As is clear from FIG. 5, the etching rate of Si at this time corresponds well to the emission intensity of F atoms, and the etching rate increases as it approaches the high frequency electrode. With conventional equipment, it was completely impossible to know such things, but according to the present invention, it is possible to know the distribution of luminescence intensity in extremely detail, and it is possible to know the mechanism of processing by plasma, etc. It is extremely useful for elucidating in detail.

Example 2 Using the same plasma etching apparatus as in Example 1,
The gas to be introduced is CC〆4, BC〆4, or a mixture of both, and the pressure is 1 tsubo a, 13.58MH2
High-frequency power was applied to generate plasma.

The distribution of the emission intensity of C Yuju at a wavelength of 50 m is the 6th
As shown in the figure, as in the case of Example 1, the intensity is strong near the high frequency electrode, and becomes weaker as it approaches the opposing ground electrode.

When exposing A to this plasma, A so ten sink → A so CZ3 By this reaction, A Yu is etched.

At this time, the A atoms generated by the above reaction enter the plasma, and as a result, the A atoms emit light. In this case, the distribution of the emission intensity of A-terminated atoms with a wavelength of 30 m or a 39-section plate was as shown in FIG. As is clear from FIG. 6, the emission intensity distribution of A. atoms is significantly different from the emission intensity distribution of chlorine ions, and is localized near the high frequency electrode.

Therefore, when etching the A film using the above gas, the progress and completion of the etching can be determined by measuring the change over time in the emission intensity of the A film.

Moreover, as mentioned above, the emission intensity is extremely high near the high-frequency electrode, so if the plasma emission in this area is measured, a large signal intensity can be obtained and highly accurate monitoring is possible. be. As is clear from the above description, the present invention has the following features.

'1} The plasma generated between the opposing electrodes is divided into layers, and the distribution of emission intensity can be sequentially measured spectroscopically.

[21] Since it has become possible to measure the state of plasma generation between both electrodes, it is possible to know the relationship between the state of plasma generation and the processing state.

[31 Optimal control of etching, etc. is possible.

[Brief explanation of drawings]

Figure 1 is a diagram to explain the subordinate plasma monitor.
FIGS. 2 to 4 are diagrams showing different embodiments of the present invention, and FIGS. 5 and 6 are curve diagrams showing measurement results according to the present invention. 2, 6... Flat plate electrode, 4... Spectrometer, 5... Viewing window, 9, 12... Slit, 15... Glass fiber. Chrysanthemum R *2 Leopard 3 Tsutomu 4 Chrysanthemum S Rare

Claims (1)

[Scope of Claims] 1. A plasma monitor equipped with means for measuring the emission intensity of a desired portion of plasma generated within a parallel plate type electrode through a slit substantially parallel to the electrode. 2. The plasma monitor according to claim 1, wherein the measurement of the emission intensity is performed using a spectrometer. 3. The plasma monitor according to claim 1 or 2, wherein the light incident on the slit is guided to the means for measuring the luminescence through a glass fiber. 4. The plasma monitor according to claim 3, wherein the input end face and the output end face of the glass fiber have different shapes. 5. The plasma monitor according to claim 1, 2, 3, or 4, comprising means for sequentially scanning and measuring the emission intensity of the plasma. 6. The plasma monitor according to claim 1 or 2, wherein the light incident on the slit is guided to the means for measuring the light emission via a mirror.