JPH03259515A - Dry etching method - Google Patents

Abstract

PURPOSE:To enable low temperature etching wherein damage is very little by using the conventional reactive ion beam etching system, by a method wherein electrons and neutral radicals generated in produced plasma are led out and projected on a specimen to be processed. CONSTITUTION:The conventional reactive ion beam etching system is used. The potential VE of a plasma potential control electrode 8 and the potential V1 of an ion leading-out electrode 3a on the side of a plasma chamber 1 are kept to be VE, V1<VS, for the potential VS of a specimen. The potential of plasma of reaction gas in the plasma chamber 1 is made negative with respect to the potential VS, thereby preventing cations 4 generated in the plasma from reaching the specimen 5. Hence physical sputtering of cations are not caused, and etching wherein damage is not present or very little is enabled. Since electrons 9 and neutral radicals 5 can reach the specimen 5, the etching depending on the radicals 6 is promoted by electron irradiation. Thereby a specimen which is difficult to be etched only by radicals 6 at a low temperature can be easily processed without damage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for processing a semiconductor sample with extremely low damage using a reactive ion beam etching apparatus.

[Conventional technology]

Conventionally, one of the techniques for processing semiconductor samples is a method using a reactive ion beam etching device as shown in Figure 1 (Journal of Vacuum Science and Technology (J, Vac, Sci, T.
ech) vol, A4 (1986) p, 6771)
In this method, as shown in the figure, a plasma chamber 1 and a sample processing chamber 2 are formed separately, ion extraction electrodes 3a and 3b are provided at the interface between the chambers, and etching gas is discharged into the plasma chamber 1. and an electrode 3a for extracting positive ions 4 in the plasma.

3b, and irradiates the semiconductor sample 5 in the sample processing chamber 2 with the neutral radicals 6. At the same time, the neutral radicals 6 are also leaked from the openings 7 provided in the extraction electrodes 3a and 3b, and the sample 5 is irradiated with the neutral radicals 6. In this method, etching is performed using both positive ions 4 and neutral radicals 6.

[Problem to be solved by the invention]

Normally, the sample potential VS and the ion extraction electrode 3 on the processing chamber side
The potential V2 of b is kept at zero potential, and the potential VE applied to the plasma potential control electrode 8 and the potential Vl applied to the ion extraction electrode 3a on the plasma chamber 1 side are both kept at a positive potential with respect to V5. By doing so, the positive ions 4 in the plasma formed in the plasma chamber 1 are extracted from the electrode 3.
a.

3b to reach sample 5. This method has the advantages of being able to obtain a fast etching rate, obtaining an etched shape with a high aspect ratio, and being able to easily control the etching directionality, but the essential etching mechanism is ion etching. Since the method uses sputtering, there is a drawback that damage caused by ion bombardment is formed deep into the sample.

On the other hand, as a damage-free etching method, there has been a radical etching method. For example, in the reactive ion beam etching apparatus shown in FIG. 1, the sample 5 is rotated so that the plasma is not visible from the sample surface, and etching is performed by allowing only radicals to reach the sample surface. It is the law. This method has the advantage of no damage because the essential etching mechanism is only chemical etching, but if impurities such as carbon and oxygen are present on the sample surface, the sample temperature must be approximately 200°C or higher. However, there was a drawback that almost no etching occurred.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ultralow-damage, low-temperature etching method using conventional reactive ion beam etching equipment.

[Means to solve the problem]

The dry etching method of the present invention has a structure in which plasma is generated by generating electric discharge in an etching gas, and electrons and neutral radicals generated in the plasma 4 are extracted from the plasma and irradiated onto a workpiece. There is.

[Effect]

In the present invention, using the conventional reactive ion beam etching apparatus shown in FIG. 1, the potential VE of the plasma potential control electrode 8 and the ion extraction electrode 3a on the plasma chamber side
potential V, and VE, V+ with respect to the sample potential Vs.
<<Vs, and by making the potential of the plasma of the reactive gas in the plasma chamber 1 negative with respect to the sample potential Vs, the positive ions 4 generated in the plasma are prevented from flying to the sample 5. Since this can be prevented, physical sputtering by positive ions is not involved, resulting in etching with minimal or no damage. In addition, the electrons generated in the same plasma
Since the neutral radicals 6 can reach the sample 5, etching by the radicals 6 is promoted by electron irradiation, and the etching of the sample, which is difficult with the radicals 6 alone at low temperatures, becomes easier.

〔Example〕

Next, an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a reactive ion beam etching apparatus used in carrying out the present invention. First, each potential v, , v, , v2 . v5, respectively V,
=,V.

〈〈09V2=Vs=○ is maintained, and discharge is performed in the plasma chamber 1 filled with C1□ gas. In this case, the positive ions 4 in the plasma formed in the plasma chamber 1 are blocked by the potential difference V1 formed between the ion extraction electrodes 3a and 3b, and cannot reach the sample 5. In this case, in the sample processing chamber 2, as shown in FIG. Non-uniformity of current can be seen. However, this non-uniformity is eliminated by the rotation of the sample 5, and it becomes possible to perform uniform, damage-free etching at a temperature of 100° C. or less using only the electrons 9 and radicals 6.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to perform damage-free and low-temperature etching by simply applying a predetermined voltage to each electrode using a conventional reactive ion beam etching device. become.

Therefore, in the same device, a semiconductor sample is subjected to high-speed, anisotropic etching using an ion beam, and then damage-free etching using only electron irradiation and radicals is performed to remove the damaged layer induced by ion beam etching or remove surface contaminants. cleaning becomes possible.

Furthermore, according to the present invention, plasma potential control t'! Ii8
Also, among the ions of the ion extraction electrode 3a on the plasma chamber side and/or the ions of the electrode material elements generated by electron bombardment, positive ions with low kinetic energy cannot reach the sample. pollution can also be reduced.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional etching method using a known reactive ion beam etching apparatus and an etching method according to the present invention, and FIG. 2 is an explanatory diagram of an embodiment of the etching method according to the present invention. 1... Plasma chamber, 2... Sample processing room, 3a, 3b
...Ion extraction electrode, 4...Positive ion, 5...
- Sample, 6... Neutral radical, 7... Ion extraction electrode opening, 8... Plasma potential control electrode, 9...
・Electron, 10... Luminescent species.

Claims (1)

[Claims] A dry etching method characterized by generating plasma, extracting electrons and neutral radicals generated in the plasma from the plasma, and irradiating the sample to be processed.