JPS58140126A - Dry etching method - Google Patents

Abstract

PURPOSE:To facilitate the detection of the finish point of a dry etching by a method wherein etching gas in a fixed amount is introduced into an etching chamber and exhausted, and the finish point of etching is judged by the integral amount of pressure which varies as the etching advances. CONSTITUTION:A vacuum meter 2 is installed in an etching chamber 1, and the output from the vacuum meter 2 is inputted in a control part 6 as it is via differentiators 3 and 4, and an integrater 5. The etching gas in a fixed amount is introduced into the etching chamber 1 and exhausted, and the finishing point of etching is judged at the control part 6 by the integral amount of pressure which varies as the etching advances.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention applies to dry etching techniques used for microfabrication of semiconductor devices, etc., before and during etching.

This provides a method for determining the end point of etching from the subsequent change in pressure.

SUMMARY OF THE INVENTION An object of the present invention is to provide a determination method suitable for estimating the end point from the state of pressure change during etching.

In recent years, in order to miniaturize and increase the degree of integration of semiconductor devices, the conventionally used wet etching method has been replaced by dry etching, which uses plasma or ions generated by high-frequency discharge as an etching species. With dry etching technology, it has become possible to form a pattern of about 1 μm, but compared to the wet method, the etching speed ratio with the underlying layer cannot be very large, and after a certain amount of the film to be etched has been etched, the etching rate is too high. There are problems such as etching in the side direction, and a highly accurate end point detection method is needed.

In particular, when etching M1, A, and alloys, there is a delay in the etching start time and a decrease in the etching speed due to the natural oxide film on the surface of the M1 alloy film, moisture and residual oxygen in the etching equipment, It is difficult to control the amount of etching depending on the time.

End point detection methods include mass spectrometry, 9 spectroscopic analysis, etc. Spectroscopic analysis is used to detect the end point of people, Si, etc. by detecting the luminescence of the object to be etched.

On the other hand, when etching A/ using act 4 as the etching gas, the degree of vacuum is the same as before etching.

It is known that it changes later and that the change corresponds to the progress of etching. This example will be explained below using figures. Figure 1 shows R,1,! This is a record of changes in pressure when a mulch was etched by GCjta using a (reactive ion etching) device. Etching conditions were CC1a, 208eeM, 0,2 W/
c, 4. In FIG. 1, high frequency power is applied at time t1 and discharge is started.

In the case of ke etching in which the pressure rises to a constant value (Ll), the etching progresses with a time delay, so that the etching has not yet occurred at this time. At 12 hours, the pressure drops rapidly to the level of L2. At this point, etching of A/ is started, and the emission of light from E atoms is also confirmed by spectroscopic analysis. At t3, the etching is nearing completion, and the pressure also rises from the L2 level and reaches the L3 level. The pressure L4 in the etching chamber after etching is not uniform (it takes an appropriate value lower than Lo, and the difference between LO and L4 is a balanced value).

The problems of the narrow alley point detection method that has been commonly used will be explained. In the electrode voltage method, the voltage value changes greatly due to a slight change in tuning, and the way it changes is unpredictable. Therefore, it is difficult not only to predict the voltage value at the end point but also to estimate the end point by integration. In mass spectrometry, due to the corrosive atmosphere, the sensitivity of the photomultiamplifier gradually decreases and the signal S/
It is difficult to determine the end point due to the poor N ratio. Spectroscopy is an excellent method because it is not affected much by tuning, like electrode voltage method, and it does not change sensitivity due to corrosion like mass spectrometry. In the case of etching of l, 39 of the mul atom
The emission (4.396 nm) cannot be said to have a one-to-one correspondence with the etching reaction, and is easily quenched by trace amounts of impurities in the reaction apparatus. Furthermore, since the 87M ratio is worse than when measuring pressure, if the area to be etched is small, the emission intensity will be weak and determination will be difficult.

Therefore, it is currently desired to establish a good method for detecting the end point in dry etching.

By the way, when using the conventionally known pressure change to detect the end point, the etching chamber pressure before the start of etching (Lo in FIG. 1) and the etching chamber pressure after the end point of etching (L4 in FIG. 1) must match. There is a need. For LO and L4 in FIG. 1, the amount of leakage before and after etching and the amount of gas generated from the etching chamber must be balanced with the amount of exhaust gas.

The inventor of the present invention has proposed, for example, to perform sufficient preliminary evacuation (for example, 5X1o-5 Torr) before starting etching, and to wait 16 to 29 minutes after introducing the reaction gas to ensure sufficient stability.
The butterfly valve used to adjust the exhaust volume is located in the middle part with the highest accuracy, and by manual operation (the butterfly valve is not controlled from the reaction chamber pressure), the etching chamber pressure before and after etching can be kept constant. It's done. This situation is shown in FIG.

By keeping the etching chamber pressure constant before and after etching, the following things became clear.

That is, the integral amount of pressure change has a constant relationship with the area to be etched.

Hereinafter, the configuration of the present invention will be explained using the drawings. Figure 3 (a
) The chart shown in (b) is the pressure value as it is.
(C1) shows the differentiated signal, and (C1) shows the integrated signal. In the chart of the integrated signal shown in (0), the sharp fall (12) of the differentiated signal in (b)
Integration starts from the time (time), and the zero level is assumed to be the pressure value at the end of etching.

The pressure value at the end of etching can be estimated from the pressure value before discharge. This situation will be explained below using figures. FIG. 4 shows the relationship between the etching chamber pressure before discharge (corresponding to LO in FIG. 2) and the etching chamber pressure at the end of etching (corresponding to L3 in FIG. 3). In this way, both parties are doing well,
The etching pressure at the end of etching can be predicted from the etching chamber pressure before discharge. There are other methods for estimating the pressure at the end of etching in advance. for example,
From the etching chamber pressure immediately after the start of discharge (corresponding to Ll in Figure 2) and the steady state etching chamber pressure during etching (corresponding to L2 in Figure 2), the pressure L3 at the end of etching is L3zαL1 + βL2 + r (α, β, γ is a constant). In any case, it is possible to estimate the pressure at the end of etching.

As mentioned above, an integral curve as shown in FIG. 3(C) can be obtained. The level at which this integral curve saturates, that is, the third
Experiments have revealed that the shaded area in the figure (&) is related to the area of the wafer to be etched. This situation is shown in FIG. FIG. 6 shows the relationship between the area to be etched and the integral amount of pressure change. In this way, the two show a nearly proportional relationship.

The present invention estimates the etching end point using the relationship shown in FIG. That is, the integral amount of pressure change is estimated in advance from the area to be etched, and when a predetermined integral amount is reached during etching, the etching end point is determined.

Next, the specific configuration of the end point determination device used in the present invention will be explained using the drawings. FIG. 6 is an example of an end point determination device. In FIG. 6, reference numeral 1 denotes an etching chamber to which a vacuum gauge 2 is attached. The output from the vacuum gauge 2 is inputted to the control unit 6 directly or via differentiators 3 and 4 and an integrator 5. The control unit 6 includes a memory circuit, a logic circuit, and the like.

Also, these three signals are from the pen recorder.

It is connected to a display recording unit 7 such as a CRT.

Here, the differentiator 4 is not necessarily necessary. Differentiator.

The sampling cycle of the integrator, control signals, etc. are set by the control section, and input thereof is made from the input section 8. The output section 9 has a function of outputting by a relay or generating sound by a buzzer, for example.

It is possible to turn off the high frequency power supply using the end point determination signal outputted from the output section 9.

The pressure gauge used in the present invention is an indispensable device for the etching device, and because it simply extracts its output and determines the etching end point from the change, it is extremely simple and inexpensive as an end point determining device. . For example, spectroscopic analysis requires a diffraction grating, a photomultiamplifier, etc., and mass spectrometry requires a diffusion pump, a mass filter, etc. In comparison, the method of detecting pressure changes requires only a pressure gauge, which is only a part of the structure of the etching apparatus, and is extremely simple.

Conventionally, the end point determination has relied on human judgment, but by using the end point determination method described above, individual differences among the people making the determination can be eliminated, and it can also be semi-automated or fully automated. Effective in reducing dust and oil power in clean rooms.

Although the embodiment of the present invention has been described in the case of mud dry etching using GO14 gas, it is of course applicable to etching other types of objects using other etching gases. Moreover, it goes without saying that it can be used in combination with other end point detection means. In addition, the vacuum level needle used in the present invention is optimally a vacuum needle with a diaphragm (situation manometer, for example, MK
Baratron vacuum gauge manufactured by S, CM manufactured by Vacuum General
, CMT series, etc. Both are less affected by high-frequency power sources and have a structure that is resistant to corrosion.

As described above, the present invention makes it possible to easily detect the end point of dry etching, and greatly contributes to the manufacture of highly accurate semiconductor devices.

[Brief explanation of the drawing]

Fig. 1 is a characteristic diagram of pressure change known in the past, Fig. 2 is a characteristic diagram of an example of pressure coupling in the present invention, and Fig. 3 (iL
(C1 is an explanatory diagram of the end point detection method of the present invention, FIG. 4 is a diagram showing the relationship between pressure before discharge and at the end of etching, and FIG. 6 is a diagram showing the relationship between the integral value of the pressure signal and the area to be etched. The diagram shown in FIG. 6 is a schematic configuration diagram of an example of the end point determination device used in the present invention. 2...Pressure gauge, 5...Integrator, 6...
...control section. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 4
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Claims (3)

[Claims] (1) Introducing a certain amount of etching gas into the etching chamber,
A dry etching method characterized in that the end point of etching is determined based on the integrated amount of pressure that changes as the etching progresses. (2) The dry etching method according to claim 1, wherein the etching gas is carbon tetrachloride. (3) The dry etching method according to claim 1, wherein the object to be etched is aluminum.