JPS5923875A - Dry etching method - Google Patents

Abstract

PURPOSE:To enable etching in the state of suppressing the contamination and damage of an Si object to be treated as far as possible and to clean the contaminated and damaged surface in the dry etching stage of said object, by using a gaseous mixture composed of SiF4 and H2. CONSTITUTION:Resist 1 is deposited on an SiO2 film 2; thereafter, the film 2 is selectively etched by reactive ion etching in the case of, for example, cleaning the surface of an Si substrate 3. Damages are formed on said surface in this stage. Thereupon, the surface is dry etched with a gaseous mixture composed of SiF4 and H2 and is then subjected to an O2 plasma treatment to remove a polymer layer and the resist 1; further the substrate is subjected to a soln. treatment. An SiO2 film 5 is selectively deposited on an Si substrate 4 and is etched with a gaseous mixture composed of SiF4 and H2 in selective etching of an Si type.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for dry etching a workpiece, and is capable of solving the problems of contamination and damage caused by dry etching.

Generally, semiconductors (Si, Ga, A
When performing dry etching on semiconductors and thin films, contamination and irradiation damage occur on the surface of the semiconductor or thin film, or within the vicinity of the surface.
If I or the like is created, the electrical characteristics will deteriorate. This is because a trap level is formed or a short circuit is caused. This is a well-known fact. The detailed classification of such contamination and irradiation damage is as follows.

■ Polymer film layer that adheres to the surface.

This is thought to be mainly due to the polymerization of the constituent elements of the gas used for etching due to the energy of the plasma.

■ Impurity elements that penetrate into the interior of semiconductors and thin films near their surfaces.

First, the constituent elements of the etching gas are ionized in the plasma, accelerated by the discharge internal electric field such as the cathode drop voltage, and then injected into the plasma. Second, heavy metals (Fe, Co, Ni, AQ, etc.), which are constituent materials of the etching apparatus, are made incident by sputtering.

■Crystal defects that occur inside the semiconductor near its surface.

This is due to the incidence of charged 1ft particles (ions and electrons) generated in the plasma, ultraviolet rays, X-rays, and the sputtering mold that is the constituent material of the chamber.

To clean such contamination and irradiation JJt scratches by dry treatment, O2 plasma treatment can be considered. In this plasma treatment, the above-mentioned (Cx, Fy) polymer film is oxidized in plasma and removed. Although this plasma treatment is also used for resist ashing, it has not been realized as a complete leaning method. Furthermore, no effective cleaning method has been provided for the above-mentioned contamination and damage.

This invention was made in consideration of these circumstances, and it is possible to produce 5iOz and 5I3N while minimizing contamination and damage.
It is an object of the present invention to provide a dry etching method which is capable of etching an object to be processed using etching material such as T4 as a base material or mask, and which is also suitable for dry cleaning a surface contaminated or damaged by other etching processes.

In order to achieve this purpose, the present invention etches silicon based material using a mixed gas of CF4 and Hz.

As silicon-based materials, single crystal silicon and polycrystalline silicon can be considered.

The first surface to be treated is the surface to be dry cleaned. That is, surfaces that have been contaminated or damaged by the etching process are dry cleaned by this etching process.

A second possibility is to etch a silicon-based material using a Si02 substrate or a thin film of Si3N4 as a base material or mask.

In dry cleaning, for example, the process shown in FIG. 1 is performed. That is, after the resist (1) is deposited on the 8102 film (2) (see FIG. 1), selective etching of the 51Oz film is performed. In this case, damage is formed on the surface of the silicon substrate (3) as shown by scattered dots in FIG. 1B. Therefore, dry cleaning was performed using a mixed gas of 5IF4 and Hz according to the present invention (Fig. 1C), and then 02 plasma treatment was performed to remove the polymer layer and the regimen) (
1) is removed (FIG. 1D), and then subjected to solution treatment (FIG. 1E). After this, move on to the next step 1j.

In silicon-based selective etching, for example, the process shown in FIG. 2 is performed. That is, 8 on the silicon thread body (4)
The 102 film (5) is selectively deposited (FIG. 2A), and etched thereon with a mixed gas of SiF4 and IIz (FIG. 2B).

The mixed gas is added at a mixing ratio of 20 to 80% by volume based on the total mixed gas. In particular, silicon-based products such as 5102 and S13. When selectively etching with respect to N4, it is preferable to set this to about 50% by volume.

As the apparatus, a cylindrical or parallel plate electrode type plasma etching apparatus, an ILIB apparatus, or the like can be used. In particular, when etching silicon based materials using Si3N4 etc. as a mask, RI is used to reduce side etching.
It is preferable to use an E device or the like.

According to the dry etching method of the present invention, etching can be performed without contamination or radiation damage. Furthermore, dry cleaning can be effectively performed on a surface to be treated that has been contaminated or damaged by radiation due to other etching treatments. This is thought to be due to the fact that carbon is not used in the present invention and Si is deposited. That is, when contaminant elements in Si produced when etching Si with a conventional CFA-based gas are analyzed by IMMA, CIFI is mainly detected as the contaminant element.

If SiF4-based gas is used as in the present invention, it is possible to prevent C contamination that is harmful to semiconductor devices. Also, Si used in this example
F+ is easily decomposed during glow discharge, and deposition of 31 is likely to occur. Amorphous silicon films for solar cells are formed using this. It is believed that the damage is restored by such adhesion of silicon. Next, the present invention will be further explained with reference to examples.

[Example 1] Here, a cylindrical plasma etching device having an etch channel is used. Then, the etching characteristics of various treated surfaces were measured when the amount of H2 added was varied using a mixed gas of SiF4 at .degree. C. and Hz as a reaction gas.

The measurement conditions were a pressure of 0.8 torr and a high frequency power of 200W. The objects to be etched include single-crystal P-type silicon (etching surface 7 is (111) plane), polycrystalline silicon, P-type silicon, and
Implanted polycrystalline silicon, Si formed by low pressure CVD
3N4 and thermal oxidation 5i (Jz) were used. The etching effects of these etching objects are shown in Figure 3 as A, B, C,
Indicated by D and E.

As is clear from this figure 3, when only SiF4 is used, Si
3N4 (D) is etched, while 5I02°,
Si and the like are hardly etched. Furthermore, observation revealed that surface roughness of the single crystal silicon occurred. As the amount of H2 added increases, the etching rate of silicon-based materials, ie, single crystal silicon, polycrystalline silicon, P-implanted polycrystalline silicon, etc. increases. When the addition amount of Hz is in the range of 20 to 80% by volume, the etching rate of these silicon-based materials is 5iOz.
, becomes very large for Si3N<. Especially 1゛I2
When the amount added is about 50% by volume, it is 5 iOz.

Whereas Si 3N4 is hardly etched,
The etching rate of single crystal silicon, polycrystalline silicon, and P-implanted polycrystalline silicon reaches a peak of 150-200 l/min, St /5iOz, Si /Si: +N
The etching rate ratio of No. 4 is very large, several tens or more (high selectivity of silicon based on 5iOz and Si3N4 is shown. Also, according to the evaluation, there is no surface roughness of silicon based).

From this, the dry etching method according to the present invention can be applied to 5i.
7. Perform silicon-based etching using 02 or Si3N4 as a mask or base '4I material.7. It can be seen that it can be applied when In this case, contamination and radiation damage are extremely low.

[Example 2] Here, the electrode contact window of a bipolar transistor, etc. was formed by etching the 8102 layer on the silicon substrate by ILIE in the process and then dry cleaning it.

The small amount of Hz added to the mixed gas of SiF4 and 1 (2) was set to about 50% by volume.Then, the contact resistance of the As diffusion layer, AJ and other electrodes was determined.The area of the contact hole was The measurement was carried out over a range of about 2 to 100I blood 2.The variation of this contact resistance and force was used as an index of σ/Tt (%).Here, σ is the contact resistance value. The standard deviation of π is the average value of the measured contact resistance.) The measurement results are shown as A in Figures 4 and 5, respectively.This measurement result was extremely good compared to the previous one. .

Generally, when an S102 layer on a silicon substrate is etched by RIE, contamination and radiation damage occur, which increases the contact resistance between the As diffusion layer and the Ag electrode, and also causes large variations in the contact resistance value. Previously, dry cleaning or wet cleaning had been carried out, but it was not sufficient.

In Figs. 4 and 5, those indicated by B were solution-treated by boiling with acids (H2SO4 and HNO4) and light etching, and those indicated by C were CF4.
, Ar and 02 dry cleaning were performed. Compared to these conventional products shown by B and C in FIGS. 4 and 5, the present invention provides extremely good results.

As described above, according to the present invention, 5102 and St 3
Silicon-based selective etching can be performed using N4 or the like as a base material or mask, and contamination and irradiation damage can be suppressed as much as possible. The dry etching method according to the present invention is extremely effective when used for dry cleaning after other etching treatments.

[Brief explanation of drawings]

1 and 2 are cross-sectional views for explaining the present invention, and FIGS. 3 to 5 are similar graphs. Same Hide Matsukuma H1i,,ヂ,・9.・
1) Fig. 3 2 Capas contents f / set procedure Neili
JE Printing: October 22, 1981 Patent Application No. 134124 2° Light 1 1'1'2'' + IF' Dry cutting method: 3. Relationship with the case for stopping ?di Patent application Person address: 6-chome E+7: 35, Higashii I'l1 product ward, No. 35 Name: C!l!:) Soni - Macago (company representative director ti'l: role Ohga pll), fL4, agent Address: TIEL, 1-8-1 Nishi-Shinjuku, Shinjuku-ku, Tokyo
03-343-5821tl15 (Shintaku Building) (i
, ? +The number of inventions increasing by 7 in the city, sleeves 11-
Part 1 of the detailed description of the invention (
1) In page 5, line 19 of the specification, ``occurrence of deposition of st'' is defined as ``conditions that create a plasma state that is the boundary between plasma conditions that cause deposition of Si and plasma conditions that cause etching of Si. Please correct it to ``I have selected ``. (2) Correct "CIFl" in line 2 of page 6 to "C and F". (3) Delete "This is 5 clouds - I can think of it." on page 6, lines 7-9. Above 41

Claims (1)

[Claims] A dry etching method in which a workpiece is etched using a mixed gas of SiF4 and H2.