JPS60744A - Dry etching method - Google Patents

Abstract

PURPOSE:To protect a mask form deterioration in an etching method, wherein a material to be etched and the mask are exposed to reactive gas in a non- contact state and ultraviolet ray or far ultraviolet ray is made to irradiate, by a method wherein the mask is coated with a stabilized material to the reactive gas. CONSTITUTION:A material 2 to be etched, such as a polycrystalline silicon to which a phosphorous has been added, etc., and a mask 9 are put under an atmosphere of Cl2. Ultraviolet light of a wavelength of 240-360nm emitted from an Hg-Xe lamp 4 is converged by a lens and projected to the material 2 to be etched for performing an etching. At this time, the mask 9 is formed by forming a pattern 11 made of a chrome oxide on an UV quartz plate 2, for example, depositing an SiO2 12 thereon by a plasma CVD method and covering the pattern 11 completely. Accordingly, an etching pattern faithful to the mask pattern can be formed, because deterioration doesn't effect in the SiO2 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a damage-free anisotropic dry etching method.

[Prior art and its problems] In recent years, integrated circuits have become increasingly finer, and recently, prototypes of ultra-LSIs with a minimum pattern size of 1 to 2 μm have been developed. Plasma etching technology is essential for this microfabrication.

This technology usually involves introducing a reactive gas such as CF4 into a container with parallel plate electrodes, placing a sample on an electrode (cathode) to which high frequency power such as 13.56MH2 is applied, and causing a blow discharge. The cathode drop voltage (e.g. H, S, B
utler and G, S, kino, Flu
ids, 6.1346 (1963)) to impact the sample and etch it, which is called reactive ion etching (R'IE) and is the mainstream of microfabrication technology. . However, in this method, since the sample is placed in plasma, the oxide film may be destroyed due to the charging of paper particles such as ions and '4L molecules, the threshold voltage may shift due to soft In addition to inducing traps, various radiation damages such as metal contamination from the inner walls of the chamber occur. These radiation damages include many factors that are fatal to VLSi devices, and a damage-free etching technique is desperately needed.

As a damage-free dry etching technique, for example, discharge chamber separated chemical dry etching (Y, Hori
ike and M, Shibagaki, Jpn, J
, Appl.

phys 5upp1.45.13 (1976) Fdt
l, ) Natkaal bs, its etching shape produces an isotropic undercut under the etching mask, and ■L
Not compatible with SI devices. On the other hand, recently,
Anisotropic etching (H, Aki
Ya.

proc, 3rd, Symp On Dry Proc
Reference Esses, pH 9 (1981) was reported and demonstrated the possibility of damage-free, anisotropic etching. Furthermore, one of the inventors of the present invention has recently proposed an etching method using ultraviolet or far ultraviolet light. As shown in Fig. 1, this method consists of the following steps:
For example, a phosphorus-doped polycrystalline silicon (2) is placed under an atmosphere, and ultraviolet light with a wavelength of 240 to 360 nm emitted from, for example, a mercury-Xe lamp (4) is focused by a lens (3) onto the sample. In this method, etching is performed only on the irradiated area, so as an etching mask, a mask such as M that sufficiently absorbs or reflects the irradiated light is used. It has become clear that by doing this, it is possible to obtain an etched shape that does not cause undercuts.This means that even without forming a mask pattern directly on the sample,
As shown in FIG. 2, it is possible to perform etching by placing a mask between the irradiation light and the sample. For this reason, when we attempted to etch phosphorus-doped polycrystalline silicon in a C7J2 atmosphere using a chromium oxide mask patterned on UV quartz, which is normally used for patterning photoresist, we found that it was not actually etched at all. Ta. The reason for this is that in the C/2 atmosphere, photo-dissociated CI atoms react with chromium oxide, producing decomposition products, which adhere to the unpatterned surface of the mask and cause light It has become clear that this phenomenon occurs even when an M mask is used for a long period of time. For this reason, it is stable against chlorine-based gases and has a resistance of 240 to 360
There is a strong need for a dry etching method that has a mask with excellent characteristics for wavelengths in the nm range.[Object of the Invention] An object of the present invention is to provide a damage-free anisotropic dry etching method that does not cause deterioration in mask depth. An etching method is provided.

[Summary of the Invention] The present invention provides for simultaneously applying ultraviolet or long-distance etching to a material to be etched placed in an atmosphere containing a reactive gas such as C/z, through an etching mask placed without contact with the material to be etched. When performing etching by irradiating ultraviolet light, etching is performed using a mask coated with a material that is sufficiently stable against reactive gases.

[Effects of the Invention] According to the present invention, it is possible to perform so-called resist-less etching in which there is no need to directly form a pattern on a sample because the mask does not deteriorate.

[Embodiment of the Invention] FIG. 3 is a cross-sectional view of a mask for explaining an embodiment of the invention. A pattern made of chromium oxide is formed with a thickness of 20001 on the UV quartz Ql with a thickness of 2-2. On this chromium oxide, 8i02α was deposited at 3000× by plasma CVD method.
This was used in place of the conventional mask of the dry etching apparatus described above in FIG. 2, and ultraviolet light was irradiated in a CI2 gas atmosphere to observe the deterioration of the mask and the etched state of the object to be etched. As a result, SiOz
No surface deterioration occurred on the etching target, and an etching pattern faithful to the mask pattern (turn) could be formed on the object to be etched.

In this example, an 8 i0z film was used as an example, but any material that is transparent to ultraviolet or deep ultraviolet light and stable to - and chlorine elements may be used, for example, even when lithium fluoride is used. Similar results were obtained.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic diagrams of an apparatus on which the present invention is based, and FIG. 3 is a cross-sectional view of a mask for explaining one embodiment of the present invention. (1)...sample stage, (2)...destructive etching material,
(3)...lens, (4)...ultraviolet light source such as Hg-Xe. (5)... Light irradiation point, (6)... Light path, (7)...
・C/2 molecule, (8)...filter, (9)...etching mask, (10)...UV quartz, (LL!・
...Chromium oxide, 0ri...S i02゜(7317)
Patent Attorney Noriyuki Chika (and 1 other person) Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) A mask placed in exclusive contact with the plate to be etched and the etching material is exposed to a reactive gas containing at least a halogen element, and at the same time ultraviolet or deep ultraviolet light is applied to the etching material through the mask. A dry etching method in which etching is performed by irradiating an etching material with the etching material, wherein the mask is coated with a material that is sufficiently stable against the reactive gas. (2) Claim 1, wherein the sufficiently stable material is 5IO2 or lithium fluoride.
Dry etching method described in section.