JPS6210305B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to an etching method, and more particularly to a method for performing dry etching with uniformity.

(2) Background of the technology For example, a mask used for exposing a wafer is made by coating a chromium (Cr) film on the entire surface of a glass substrate, then coating the entire surface with a resist film, and then patterning this resist film to use the resulting pattern as a mask. hand
It is made by etching a Cr film to form a chromium pattern.

The above-mentioned etching (reactive ion etching) is carried out using a plasma reactive gas in a cathode coupling type dry etching apparatus shown in FIG. ), 2 is a disk-shaped parallel plate counter electrode (anode), 3 is an electrode (cathode), 4 is a sample such as a mask, 5 is an insulator, 6 is a high frequency power source, and 7 is a reactive gas for etching. A reaction gas introduction pipe arranged in a ring shape is supplied into the chamber 1, and reference numeral 8 indicates a reaction gas exhaust port. The aforementioned Cr film is formed on the entire surface of the mask, and is patterned by reactive ion etching using the resist pattern as a mask. In etching chromium, for example, carbon tetrachloride gas (CCl ₄ ) is used as the reaction gas.
120SCCM, and oxygen gas (O ₂ ) is supplied at an introduction rate of 70SCCM.

(3) Prior Art and Problems The above-mentioned etching is carried out using a chamber resistant to reactive ion etching. There is a problem causing it. Such abnormal discharge is caused by, for example, the selectivity ratio when etching chromium using a resist pattern as a mask, that is, (chromium etching speed)/
This adversely affects (the etching speed of the resist), and it becomes necessary to form a thick resist film, and when the resist film is made thicker, the writing accuracy of the resist film decreases, resulting in a disordered pattern of the chromium film.

Next, in the etching described above, etching uniformity is required. If the etching rate is different for each location on the sample, there will be differences in the loss of the resist film, and as the resist pattern becomes thinner, the chromium pattern will become thinner, and the chromium pattern that is finally formed will be disordered and not uniform.

A reactive gas used for etching, for example (CCl ₄ +O ₂ ) gas used for etching chromium, is turned into plasma while flowing inside the chamber 1 .
Since this plasma formation requires a certain amount of time depending on each case, the length of residence time of the reaction gas in the chamber 1 has a significant influence on the uniformity of etching. In the conventional apparatus, the residence time of the reaction gas is short near the exhaust port 8 and long on the opposite side, and when viewed from the sample, this means that the residence time of the reaction gas above the exhaust port 8 is not uniform. Therefore, it is desired to slow down the space velocity of the reaction gas and uniformly lengthen the residence time of the reaction gas on the sample, but this has not been easy to achieve with conventional equipment.

(4) Purpose of the Invention In view of the above-mentioned conventional problems, the present invention provides a method for uniformly increasing the residence time of a reactive gas on a sample in dry etching using an etching chamber resistant to reactive ion etching. It is an object of the present invention to provide an etching method capable of performing reactive ion etching with uniformity.

(5) Structure of the Invention According to the present invention, a sample to be etched is placed on one of a pair of electrodes provided in a chamber facing each other, and A reactive ion etching is performed by ejecting a reactive gas in the direction of the other electrode from a reactive gas inlet tube arranged around the electrode at a position substantially in the same plane as the other electrode, and activating the reactive gas. This is accomplished by providing an etching method.

(6) Examples of the invention Embodiments of the present invention will be described in detail below with reference to the drawings.

As a result of studying the above-mentioned problems, the present inventor came up with a method for reducing the effect of exhausting the reaction gas through the exhaust port 8 in order to make the reaction gas stay above the sample placed in the chamber for as long as possible. Ta. An apparatus for carrying out such a method is shown in a schematic cross-sectional view in FIG. 2, in which parts that are the same as those shown in FIG. 1 are designated with the same reference numerals.

In the device shown in FIG.
are arranged so as to surround the electrode 3, at a position substantially flush with the electrode 3 on the side where the mask 4 is arranged, and further away from the exhaust port 8 than in the conventional device. For this purpose, the reaction gas introduction pipe 7 has an insulator 5
It is embedded in a flange 9 provided surrounding the flange 9.
Moreover, as shown in FIG. 3, which is a plan view of the part of the chamber where the mask 4 is placed, the reaction gas introduction tube is arranged so as to surround the insulator 5 on which the electrode 3 is placed. As shown in Fig. 2, the structure is such that it ejects upward.

When the reactive gas is ejected from the inlet pipe arranged as described above, the residence time of the reactive gas on the mask becomes longer and active plasma is more likely to be generated. Since it is almost unaffected, it moves on the mask 4 at a uniform spatial velocity, and etching is performed uniformly over the entire surface of the mask 4.

(7) Effects of the invention As explained in detail above, according to the method of the present invention, the residence time of the reaction gas becomes longer, and activated plasma is more likely to be generated over the entire surface of the sample.
In addition, since the reaction gas is ejected at the farthest point from the exhaust port of the chamber, the above-mentioned plasma gas flows uniformly over the sample, and dry etching is performed uniformly over the entire surface of the sample. This is highly effective in improving the reliability of manufactured semiconductor devices.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a conventional reactive ion etching chamber, FIG. 2 is a schematic sectional view of a chamber implementing the method of the present invention, and FIG.
FIG. 3 is a plan view of a portion of the illustrated apparatus on which a sample is placed; 1... Chamber, 2... Counter electrode (anode), 3... Electrode (cathode), 4... Mask, 5
... Insulator, 6 ... High frequency power supply, 7 ... Reaction gas introduction pipe, 8 ... Reaction gas exhaust port, 9 ... Flange.

Claims (1)

[Claims] 1. A sample to be etched is placed on one of a pair of electrodes provided facing each other in the chamber, and the sample is placed surrounding the electrode at a position substantially on the same plane as the one electrode. An etching method characterized in that reactive ion etching is performed by ejecting a reactive gas from a reactive gas introduction tube in the direction of the other electrode and activating the reactive gas.