JPS61114530A - Method and device for dry etching - Google Patents

Abstract

PURPOSE:To obtain the prescribed etching characteristics by a method wherein more than one of etching parameters are made to vary secularly and continuously. CONSTITUTION:Pressure, one of etching parameters, is made to input in advance in the computer of a control system 4 by the plasma etching device, wherein an upper and lower pair of parallel plate electrodes 2 and 3 are provided in a decompression vessel 1, in such a way as to be able to be made to vary automatically and continuously, the signal from the control system 4 is transmitted to a variable conductance valve 5, the valve 5 is made to vary and the pressure is varied. The flow rate of gas to flow in from a gas introducing port 6 is held to a constant and the opening ratio of the variable conductance valve 5, which is situated midway between an exhaust vent 7 and the exhaust system of gas, is made to vary little by little automatically and continuously according to the electrical signal from the control system 4 using a mechanical booster pump 8 and a rotary pump 9.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a drying and etching method and apparatus used in the manufacturing process of semiconductor devices.

<Prior art> In recent years, as the integration of semiconductor integrated circuits has increased, the demand for microfabrication has been increasing year by year.In the etching process, the proportion of dry etching has increased from wet etching, which causes large side etching, to dry etching. Reactive ion etching (which has anisotropic etching characteristics)
RIE) is increasingly being used. This reactive ion etching technology enables processing with extremely small differences in etching conversion, making microfabrication possible.

FIG. 5 is a diagram illustrating the cross-sectional shape of a material to be etched according to the conventional technique. Board 1 using the conventional method
The etching film 13 coated on the resist film 1
3 as a mask, the film to be etched 13 is etched at an angle of 90' as shown.

In conventional dry etching, which is usually performed, etching pressure, gas flow rate, gas mixture ratio, applied power, etc.
22 meters was kept constant during etching. In addition, after etching was performed for a predetermined time under predetermined conditions, which may be a step etching, the high frequency application was stopped once, the gas introduction was stopped, and the chamber was brought to a background pressure state, and then the next predetermined conditions were set, and a steady state was achieved. At this point, high frequency is applied again to perform etching.

In addition, another configuration example of the conventional technology is disclosed in Japanese Patent Application Laid-Open No. 56-1376.
It is disclosed in No. 38. In this technique, isotropic etching is performed halfway, and anisotropic etching is performed on the remainder b'. FIG. 6 shows the cross-sectional shape of the material to be etched using this technique.

<Problems to be solved by the invention> However, the above-mentioned reacti! In processing using ion etching/etching technology, the cross-sectional shape becomes steep as shown in FIG. When such a steep cross section is formed, processing in the next step becomes extremely difficult. That is,
In the next step, there was a problem in that the thickness of the wire changed at the stepped portion, and in extreme cases, defects such as wire breakage occurred.

Therefore, there is a technique described in the above-mentioned publication aimed at solving this problem. However, even with this technique, as shown in FIG. 6, the cross-sectional shape of the material to be etched is very steep (1), and the above-mentioned problem has not been satisfactorily solved.

<Means for Solving the Problems> Therefore, in order to solve the above problems, in a dry etching method using a plasma etching apparatus, one or more etching/-? The present invention provides a method in which predetermined etching characteristics are obtained by continuously changing the etching parameters over time.

Additionally, one or more etching/? The present invention provides a plasma etching apparatus comprising means for changing the etching parameter and control means for controlling the means.

<Operation> According to the above-mentioned invention, the parameters in etching,
For example, by changing one or more of pressure, gas flow rate, gas mixing ratio, applied power, etc. over time and continuously, the etched cross-sectional shape can be changed as appropriate.

This is because the matching follows as the conditions inside the reaction vessel change, and the reflection loss of the input power into the reaction vessel changes.

<Example> Here, an example of the present invention will be described using FIG. 1. This embodiment shows an example in which the variable parameter is pressure.

In Fig. 1, a control system is used to automatically and continuously change the pressure, which is one of the etching parameters, using an apparatus equipped with a pair of upper and lower parallel plate electrodes 2 and 3 in a reduced pressure vessel 1. By inputting the signal into the computer 4 and transmitting the signal to the variable conductance valve 5, the conductance pulp 5 changes and the pressure increases to, for example, 10
It becomes possible to change at a speed corresponding to PaZ. At this time, by varying the rate of change of the conductance pulp, it is possible to vary the degree of pressure fluctuation. This can be achieved by changing the open area ratio of the conductance pulp by 5%/min.

In general, in a pressure reduction system, once the exhaust capacity and inflow gas flow rate are determined, the ultimate degree of vacuum, that is, the pressure, is constant. Therefore, the pressure can be changed by changing the exhaust capacity or the inflow gas flow rate.

In this embodiment, first, the flow rate of gas flowing in from the gas inlet 6 is kept constant. and mechanical booster pon f
The porosity of the variable conductance pulp 5, which is attached in the middle of the exhaust system that exhausts gas from the exhaust lower using the rotary pump 8 and the rotary pump 9, is automatically and continuously changed gradually by electric signals from the control system. let Thereby, the pressure inside the reduced pressure container 1 can be changed automatically.

In the figure, 10 is a matching box, and 1 is a high frequency power source.

For example, if the gas flow rate is 100 SCCM (Standard
dCubicCentimeter/Minite
), and the porosity of the variable conguctance bulb was set to 10.
% to 15% (change rate of 5%/min when done in 1 minute), the pressure changes from 70 Pa to 60 Pa. However, this value varies depending on the pumping capacity of the exhaust system.

An example of etching performed by changing the pressure in this manner will be shown.

When etching contact holes, C2F6 is
00CC, flow CHF3 gas 50CC, fl p /
Discharge at 2.0 kW (high frequency 13.56 MHz). At this time, as shown in Figure 2, the initial pressure was set at 50 Pa, and the pressure was increased evenly for 5 minutes to 80 Pa.
Change it to Pa.

FIG. 3 shows the state in which etching has been performed in this manner. When etching is performed under the above conditions, the workpiece, chip/
The cheek angle θ of the cleaning film 13 is approximately 60'.

Further, in the above example, when etching is performed while maintaining the pressure at 80 Pa throughout, the taper angle θ is approximately 90 Pa.
becomes.

By appropriately setting the initial pressure to 50 Pa to 80 Pa, the chi-angle θ can be arbitrarily set within the range of 600 to 90 Pa.

Note that the Lenost film 14 in the above example may be a commonly used film (for example, OF PR (trade name) film thickness 1
．． 0,00X), the etching target film 13 can be similarly applied to ordinary etching target films such as SiO□, PolySi, At, and the like.

Here, as another embodiment, a configuration example in which the gas mixture ratio is selected as the parameter to be changed will be described.

First, FIG. 4 shows a system that automatically changes the gas mixture ratio.

As shown in FIG. 4, the etching apparatus is equipped with a pair of parallel plate electrodes 2 and 3 in a reduced pressure reaction vessel 1, and has a system in which gas is introduced through an inlet 6 and exhausted through an exhaust lower. Further, 10 is a matsingo, a box deshi, and 11 is a high frequency power source.

To introduce gas into such a system, first, three types of gas, for example, C2F6 + C) fF3 r He, are introduced into the gas mix chamber 18 through the mass flow controllers 15, 16, and 17.
1 into the vacuum reaction vessel. In this case, the amount of each gas introduced is controlled by the mass flow controllers 15.16.
17.

Mass flow controller 15 which controls this flow rate.
16 and 17 are grouted so that the amount of gas flow is changed over time by a control system 19 with a built-in computer. The signal is then transmitted to the mass flow controller, thereby changing the flow rate of gas actually flowing into the reduced pressure container I.

When etching an oxide film using such a system, the gas mixture ratio (CHF3)/(02F6) is
When +(CHF3) is changed from 0 to 30%, a shape with a chi and angle θ of approximately 70° can be obtained. Also,
The selection ratio PSG/St becomes 15 just before the end of etching. (PSG is 'phospho 5ilicate
(abbreviation of glass).

Through-cutting and etching 9 described in the explanation of the above two embodiments
RF discharge is stopped midway by automatically and continuously changing one or more of the parameters in small increments;
Etching characteristics can be changed automatically without the need to change the 2-layer meter and discharge again.

In addition to the gas pressure and gas flow rate shown in the above two embodiments, the system control system can also change set values over time. The discharge characteristics can also be changed by changing the , and the etching characteristics can also be changed accordingly, and it goes without saying that there are applications such as this.

What is the means for changing the RF input power? It is possible to install a volume unit.

Further, as a means for changing the electrode spacing, it is possible to install a motor unit that drives the electrode plates forward and backward in opposing directions.

Although each parameter has been explained above, desired etching characteristics can also be obtained by simultaneously changing two or more of the IP parameters.

<Effects of the Invention> The present invention allows the host control system to automatically and continuously change one or more of the etching parameters little by little so that the high-frequency 7y etching can follow, thereby eliminating the possibility of discharging during the process. This has the effect of changing the etching characteristics without stopping the etching process, making it possible to perform etching using R4E.

Furthermore, since there is no need to stop the RF' discharge midway, there is an effect that the etching processing time can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention. FIG. 2 is a diagram showing pressure changes in one aspect of the embodiment shown in FIG. FIG. 3 is a sectional view showing the state when etching is performed under the conditions shown in FIG. 2. FIG. 4 is a schematic configuration diagram showing another embodiment of the present invention. FIG. 5 and FIG. 6 are cross-sectional views showing the state when etching is performed by the technique used. 1: Decompression vessel, 2, 3: Parallel electrode, 4: Control system, 5: Conductance valve, 6: Gas inlet, 7: Gas exhaust port, 8: Mechanical booster pump, 9: Rotary pump, 10: Matching Bix , 11: High frequency power supply, 1
2: Substrate, I3: Film to be etched, 14: Renost film,
15.16.17: Mass 70-controller, 1g: Smix Champa, 19: Control system. Patent applicant Oki Electric Industry Co., Ltd. Figure 1 Clear rg1 (#) Figure 3 Figure 4 Figure 5 Figure 6 Cause

Claims (4)

[Claims] (1) A dry etching method using a plasma etching apparatus, characterized in that predetermined etching characteristics are obtained by continuously changing one or more etching parameters over time. (2) The dry etching method according to claim 1, wherein the etching parameters are gas pressure, gas flow rate, gas mixture ratio, input power, and electrode spacing. (3) A plasma etching apparatus comprising means for varying one or more etching parameters and a control device for controlling the means. (4) The means for changing the etching parameters includes:
Gas pressure control valve, gas flow control valve, gas mixing control device,
4. The plasma etching apparatus according to claim 3, wherein the plasma etching apparatus is an input power regulator and an electrode spacing regulator.