JPH0614518B2 - Surface reaction control method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for controlling a surface reaction, and more particularly to a method for controlling a surface reaction suitable for etching or modifying a solid surface with high accuracy.

[Background of the Invention]

In the conventional semiconductor manufacturing process using high-energy particles, since the temperature of the solid sample and the solid material is kept at the water temperature, the solid temperature is relatively high and the active gas and the solid easily react with each other. There is a drawback in that it is difficult to control the surface reaction acceleration effect by energetic particles such as a laser with high precision. In particular, in dry etching, it is difficult to control the reaction between reactive neutral particles such as radicals in plasma and solids, and etching under the mask, that is, side etching becomes large,
There is a drawback that it becomes difficult to perform high-precision etching.

[Object of the Invention]

It is an object of the present invention to provide a method for highly accurately controlling a surface reaction on a surface where the energetic particles are not incident when the energetic particles are incident on the solid to process the solid.

[Outline of Invention]

In dry etching, on the horizontal surface of the solid to be etched,
While high-energy particles such as ions and electrons and neutral particles such as radicals are simultaneously incident, the side wall is
Only neutral particles are incident. As a result of conducting the mechanism analysis, on the horizontal surface of the solid, by irradiation with high energy particles,
A pseudo "high temperature" state is created on the very solid surface,
Therefore, it was found that the reaction between the gas particles or radicals and the surface electrons is greatly activated.

On the other hand, in the solid side wall, the reaction between the radical and the solid, and the gas molecule and the solid occurs at the water-cooled temperature.

Therefore, in order to reduce the side etching without changing the etching in the depth direction, it was understood that the temperature of the sample (solid) should be lowered and the etching should be performed.

Example of Invention

 An embodiment of the present invention will be described below with reference to FIG.

FIG. 1 shows a sample table 1 and a counter electrode 2 of a high frequency discharge parallel plate type cathode couple plasma etching apparatus.
Shows a device equipped with a cooling device (water temperature or lower, −120 ° C. or higher). The cooling device uses the principle of the heat pipe, and is composed of the refrigerant reservoir 3, the pipe 4, and the exhaust device 5. By changing the refrigerant, the above temperature can be easily realized and the stability is excellent. However, it is an apparatus that can typically hold the set temperature ± 1.5 ° C. for 1 hour. High-frequency power is applied to the sample stage 1 to generate plasma between both electrodes. The gas inlet is port 6.

FIG. 2 shows the result of etching poly-Si with SF ₆ gas using this apparatus. Etching condition is 5 ×
10 Pa, high frequency power: 200 W (power density 0.2 W /
cm ² ), and a photoresist (AZ1350J) film was used as a mask of poly-Si (thickness 1.2 μm).
FIG. 2 shows the sample table temperature and the side etching amount when the etching is completed (dimension shift amount: shows the dimension from the mask edge).
It is understood that the dimensional shift becomes smaller as the temperature is lowered in this etching. Further, the side etching amount is below a temperature at which the vapor pressure of SiF ₄ which is a reaction product of poly-Si and SF ₆ gas plasma is 1/10 or less of the vapor pressure at room temperature, that is, below about −10 ° C. At this temperature, the side etching amount at 20 ° C. was reduced to ¼ or less of 0.8 μm. At this time, the etching speed in the depth direction does not change, which is a great feature of the present invention. The same phenomenon was confirmed with other electronic materials such as Al, W, resist, and Mo. That is,
In this method, side etching can be made extremely small by holding the sample at a temperature at which the vapor pressure of the reaction product becomes 1/10 or less of the vapor pressure at room temperature. However, if the temperature is too low, gas adsorption to the cooling part occurs, making etching impossible. In this gas adsorption, the vapor pressure of the introduced gas SF _{6 at} the sample temperature is
It has been found that this occurs when the gas pressure in the vacuum container becomes lower than the gas pressure.

Therefore, it is necessary to set the sample temperature to a temperature at which the vapor pressure of the gas introduced into the vacuum container becomes equal to or higher than the gas pressure in the vacuum container.

At a temperature in the above range, the present invention can reduce the amount of side etching extremely, as shown in FIG. 2, and is an excellent method for etching when manufacturing an LSI having a high integration density.

This reaction control method is also effective when etching is performed using another etching device such as a microwave etching device or an ion beam etching device, and the cooling of the vacuum container itself is not related to the control of the plasma etching reaction. It turned out to be. However, in this case, countermeasures against dew drops, such as a double structure, were necessary.

The present invention is also effective for lithography using an ion beam or an electro beam. With lithography, it was possible to form high-precision patterns with the lateral spread of these beams limited.

[Brief description of drawings]

FIG. 1 is a sectional view of an etching apparatus used for carrying out the present invention, and FIG. 2 is a curve diagram showing the effect of the present invention. 1 ... Sample (electrode), 2 ... Counter electrode, 3 ... Refrigerant reservoir, 4 ... Pipe, 5 ... Pump, 6 ... Gas inlet,
7 ... rt power supply, 8 ... sample, 9 ... exhaust.

Claims (4)

[Claims] 1. A method of etching or modifying a workpiece placed in a vacuum container using gas plasma, wherein the etching or reforming is performed by changing the temperature of the workpiece to the etching temperature. Alternatively, the vapor pressure of the reaction product generated during the reforming is equal to or lower than the temperature at which the vapor pressure of the reaction product at room temperature is equal to 1/10, and the vapor pressure of the gas is within the vacuum container. A method for controlling a surface reaction, which is carried out at a temperature equal to or higher than the pressure of 1. 2. The method for controlling a surface reaction according to claim 1, wherein the etching or modification is performed by using a parallel plate type device. 3. The method for controlling a surface reaction according to claim 1, wherein the etching or modification is performed using a microwave plasma device. 4. The method for controlling a surface reaction according to claim 1, wherein the etching or modification is performed by using an ion beam device.