JPH0620060B2 - Dry etching equipment - Google Patents

Description

The present invention relates to a dry etching apparatus used for microfabrication of a semiconductor manufacturing apparatus.

[Conventional technology]

With higher integration of LSIs, a dry etching method is widely used as a fine processing means such as gate processing of polycrystalline silicon and patterning of wiring metal film.

In order to automate this dry etching device and stabilize the etching process, a monitor that determines the end point of the etching of the material to be processed is required, but in the conventional dry etching device, this is performed by optical emission spectroscopy. ing. That is, the end point of the etching is determined by dispersing the emission in the etching chamber and monitoring the emission intensity at an appropriate wavelength to measure the concentration change of the reaction gas species and the reaction product.

[Problems to be solved by the invention]

However, in the above-described conventional monitoring method, the etching depth and end point of the material to be processed cannot be known, and
If the stability of plasma or discharge is poor because the monitor is performed only at a certain wavelength, the fluctuation of the emission spectrum becomes large and the etching cannot be accurately monitored.

It is an object of the present invention to provide a dry etching apparatus which can eliminate the above-mentioned drawbacks and accurately determine the end point of etching of a material to be processed on a semiconductor wafer.

[Means for solving problems]

The dry etching apparatus of the present invention includes a light source that emits white light for irradiating a semiconductor wafer in an etching chamber,
A spectroscope for separating the light reflected by the semiconductor wafer;
It is configured to include a multi-channel analyzer that detects the separated light and a microcomputer that processes an input signal from the analyzer and calculates the etching depth.

〔Example〕

 Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a diagram showing a positional relationship among a light source, a spectroscope, and an etching chamber.

In FIGS. 1 and 2, light from a light source 11 that emits white light such as a mercury lamp or a halogen lamp is used as a semiconductor wafer in an etching chamber 12 (hereinafter simply referred to as a wafer).
After applying 23, the reaction gas introduced into the etching chamber 12 is discharged to start etching. The reflected light from the wafer is incident on the spectroscope 13 from which the exit slit has been removed and is dispersed.

That is, the light from the light source 11 passes through the aperture 21,
It is partially reflected by the half mirror 22 and applied to the wafer 23. A portion of the electrode 24 facing the wafer 23 is provided with a hole so that the incident light from the light source 12 and the reflected light from the wafer 23 can pass through. Wafer 23
The light reflected by is partially transmitted through the half mirror 22. The transmitted light is condensed by the quartz lens 25 and is incident on the spectroscope 13. The light from the light source 11 should not leak directly to the spectroscope 13.

The light dispersed by the spectroscope 13 is detected by the multi-channel analyzer 14 and displayed on the CRT 17 via the D / A converter 16 as a reflection spectrum in real time. The time required for measurement is about 1 second.
At this time, the emission spectrum in the etching chamber 12 is also obtained at the same time, but if the emission spectrum is strong and the reflection spectrum is not clear, a chopper is provided in front of the light source 11 to
By making the light from 1 a pulsed light having a constant frequency and applying a gate synchronized with the frequency to the multi-channel analyzer 14, a reflection spectrum which is not affected by the emission spectrum at all can be obtained.

The reflection spectrum gradually changes as the material to be processed on the wafer 23 is etched, but when the material to be processed is completely etched, the reflection spectrum changes greatly. Therefore, the end point of etching can be determined by monitoring the reflection spectrum from the wafer 23.

In order to automate the device, the microcomputer 15 is made to judge the change of the output of the multi-channel analyzer 14, and when the material to be processed is completely etched and the reflection spectrum is greatly changed, the reaction control system 18 is fed back, The discharge of the reaction gas is stopped and the etching is completed.

On the other hand, as a condition for monitoring the change in etching depth of the material to be processed, it is necessary that the reflection spectrum has a large film thickness dependency. An example will be described below.

The first example is a case where a silicon thin film provided on the aluminum wiring for preventing reflection during exposure is removed by dry etching. Since the silicon film has a large dependence of the reflection spectrum on the film thickness, if the data is stored in the microcomputer 15 in advance, the film thickness can be calculated from the reflection spectrum. Therefore, the etching depth is determined by the in-line process. It is possible to monitor with. 3 and 4 show an example of the reflection spectrum of the silicon thin film and an example of the correlation between the film thickness and the absorption peak wavelength.

In this case, the reflection spectrum as shown in Fig. 3 is shown during etching of the silicon thin film. Shifts to the short wavelength side as shown in FIG. When the silicon thin film is completely etched, the spectrum rapidly changes to a high reflectance spectrum of aluminum, so that the etching end point can be clearly determined.

The second example is the case of gate processing of polycrystalline silicon used in DRAM and the like.

During the etching of the polycrystalline silicon, the reflection spectrum as shown in FIG. 3 is also shown (actually, it also overlaps with the interference spectrum due to the resist film on the part to be the gate). Then, since the interference spectrum due to the oxide film or the like suddenly changes, the end point of etching can be clearly determined.

〔The invention's effect〕

As described above, the present invention configures a dry etching apparatus that includes a light source that emits white light, a spectroscope, a multi-channel analyzer, and a microcomputer, so that the material to be processed on the semiconductor wafer being etched is The depth of etching can be monitored by an in-line process by measuring a reflection spectrum, and the end point of etching can be clearly determined.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG.
FIG. 3 is a diagram showing the positional relationship between the light source, the spectroscope, and the etching chamber shown in the figure, FIG. 3 is a diagram showing the reflection spectrum of a silicon thin film, and FIG. 11 ... Light source, 12 ... Etching room, 13 ... Spectrometer, 14 ... Multi-channel analyzer, 15 ...
Microcomputer, 16 ... D / A converter, 17
...... Display (CRT), 18 ... Reaction control system, 2
1 ... Aperture, 22 ... Half mirror, 23 ...
Wafer, 24 ... Electrode, 25 ... Quartz lens.

Claims (1)

[Claims] 1. A light source that emits white light for irradiating a semiconductor wafer in an etching chamber, a spectroscope that disperses the light reflected by the semiconductor wafer, and a multi-channel analyzer that detects the disperse light. A dry etching apparatus comprising: a microcomputer that processes an input signal from an analyzer and calculates an etching depth.