JPH0479220A - Dry etching method - Google Patents

Abstract

PURPOSE:To improve the accuracy of an etching pattern and facilitate the control of processing time by removing the difference in level between the material to be etched and the electrode at the periphery of the electrode, and arranging the material to be etched such that specified intervals are made on the two axes which cross each other at right angles passing through the center of an electrode. CONSTITUTION:Four sheets of wafers 1,... are arranged tmm apart from each other in the directions which cross each other at right angle passing through the center of the electrode. That is, the interval t between adjacent wafers 1 are all set to not less than 0.5mm and not more than 5mm. Dummy wafers 2,... as thick as the wafer 1 are arranged, around the wafers 1,..., in contact so that they surround the wafers 1,..., whereby the difference in level between the wafers 1 and the periphery of the electrode can be removed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for dry etching a material made of 5iO7, SiO, etc., and particularly to a method for uniformly etching a material using a reactive ion etching method. It is something.

[Conventional technology]

Conventionally, when etching a wafer on which a film made of silicon oxide such as St, 2.3iO, etc. has been formed, reactive ion etching has been used.
ing ) method (hereinafter referred to as RIE method) is used. The RIE method is one of the dry etching methods, and is characterized in that it causes less side etching and can form fine patterns compared to chemical etching using hydrofluoric acid or the like.

Furthermore, compared to dry etching methods such as the ion silling method and the sputtering method, selective etching is possible because it has selectivity with respect to the processing material.

Normally, in parallel plate type dry etching equipment,
Two parallel electrodes (anode electrode, cathode electrode) for applying high frequency power are arranged one above the other, and the material to be etched is placed on the cathode electrode to perform etching.

[Problem to be solved by the invention]

Here, 3 Xl0-2 Torr using CF gas,
During etching under the condition of 175 W, the electrode (
FIG. 2 shows a distribution diagram of the etching rate within a diameter of 300 mm. I and If each indicate the distribution on two orthogonal lines within the electrode. As shown in FIG. 2, it can be seen that the cutting/notching speed within the electrode is lowest at the center of the electrode and increases toward the outer periphery.

This tendency was similar even when the gas pressure, type of gas, and distance between the electrodes were changed. In addition, when considering the selectivity between the underlying film and the film to be etched, it is necessary to increase the gas pressure to reduce sputtering. As shown in Figure 2, there is a tendency for the difference in etching rate between the central part and the outer peripheral part of the electrode to become even larger.

Table 1: When etching is performed under the above etching conditions using a wafer in which a 5iO7 film is sputtered on a 50 mm square substrate as the material to be etched, as shown in FIG. It can be seen that the etching rate at the outer circumference is considerably faster than at the center. Furthermore, as shown in FIG. 4, regarding the distribution of etching rates when four wafers 6 are placed on the electrode 5, the etching rate at the outer periphery of each wafer 6 is large, as described above. This is a difference of about 23% compared to the central part. This is an etching distribution different from the positional distribution within the electrode described above.

Therefore, when etching is performed by simply placing a wafer on an electrode, the overall etching rate distribution will be the velocity distribution inside the electrode plus the speed distribution inside the wafer, and the etching rate will be the distribution between the center and outer periphery of the wafer. The problem is that the difference in etching speed between the two methods is quite large.

[Means to solve the problem]

The dry etching method according to the present invention is a dry etching method for a plurality of materials to be etched placed on a flat electrode, in which the level difference between the material to be etched and the electrodes at the outer periphery of the electrode is removed using, for example, a jig or a dummy wafer. The material to be etched is arranged at an interval of 0.5 mm or more and 5 mm or less on two axes passing through the center of the electrode and orthogonal to each other.

[Function] According to the above configuration, it is possible to reduce the difference in etching speed inside the material to be etched and between the materials to be etched. As a result, it becomes easier to improve etching pattern accuracy and control processing time.

[Example 1] An example of the present invention will be described below with reference to FIG.

FIG. 1(a) shows the arrangement of sea urchin hearts, which are the material to be etched during etching by the RIE method. This wafer 1 has Si on a ferrite substrate or a glass substrate.
This is an Oz film formed by sputtering.

At the center of the electrode 3, 1.4 sea urchin hearts are arranged at intervals of 20 mm from each other in a direction orthogonal to each other passing through the center of the electrode. That is, the sea urchin hearts are arranged so that the distance t between adjacent wafers 1 is 2[[lIn]. Further, around the sea urchin heart..., dummy wafers 2... having the same thickness as the wafer 1 are placed in contact with the sea urchin heart... so as to surround the sea urchin heart... Eliminate.

Next, use an oil diffusion pump etc. to pump the inside of the chamber for 10 minutes.
-' Evacuate to a high vacuum of about Torr. Next, introduce etching gas consisting of CF at a predetermined flow rate, and in this state, switch to a pump with an appropriate pumping speed such as a mechanical booster pump and adjust the conductance valve so that a vacuum level of about 3 Xl0-2 Torr is maintained. do.

Thereafter, a high frequency of 175 W is applied between the cathode electrode 3 and an anode electrode (not shown) to perform etching to a predetermined depth.

At this time, the difference in etching speed between the outer periphery and the center of the four sea urchin hearts was 5.2% and 5.5%, respectively.
．． The results were 3%, 5.4%, and 7%. In other words, according to the above arrangement method, the difference in etching speed within the uniheart is within 10%, and each wafer
The difference in etching speed between the two also becomes smaller.

Table 2 also shows the difference in etching speed between the outer periphery and the center of the sea urchin heart when the etching conditions are changed, together with the results obtained using the conventional arrangement method. The etching conditions were as follows: CF containing 20% 02 was used as the etching gas, and the gas pressure was 1.2×10 = Torr.

As shown in Table 2, even when the type of gas and gas pressure were changed, the difference in etching speed within the sea urchin heart was approximately 10%, and the etching speed was lower than that of the conventional method. The difference is getting smaller.

By the way, as the above-mentioned dummy wafer 2, a glass substrate coated with a resist over the entire surface is used. This is because the material to be etched, such as a wafer, is usually patterned with a resist, so the surface condition is the same and the factors that cause the difference in etching speed are eliminated.

As described above, by eliminating the difference in level between the wafer 1 on the electrode 3 and the electrode 3 using the dummy wafer 2, concentration of the electric field at the edge of the wafer 1 can be removed and an increase in the etching rate can be suppressed. Furthermore, in the area where the etching rate is low near the center of the electrode 3, the etching rate can be increased by taking advantage of the effect that the etching rate at the outer periphery of the wafer 1 is increased. -1 The overall etching rate can be made uniform.

[Example 2] Another example of the present invention will be described below using FIG. 1(b). It should be noted that members having the same functions as those in the previous embodiment will be denoted by the same reference numerals and their explanation will be omitted.

In this example, as shown in FIG. 1(b), the first
The dummy wafers 2 in Figure (a) are replaced with sea urchin hearts, and dummy wafers 4 are placed in contact with the sea urchin hearts so as to surround the sea urchin hearts.

When etching is performed by the RIE method using the sea urchin heart, which is the material to be etched, arranged as described above,
For example, the wafer 1 at position A shown in FIG. 1(b)
In this case, the difference in etching speed was 15%. However, the etching conditions at this time were that the etching gas was CF and the gas pressure was 1.2×10-' Torr. Therefore, although the difference in etching speed within the wafer 1 is somewhat larger than the result in Example 1, it is smaller than the difference in etching speed according to the conventional method, and the etching speed within the wafer 1 can be made uniform.

On the other hand, regarding the spacing between the wafers at the center of the electrode, if it is less than 0.5 mm, the increase in the etching rate at the center will be small, and if it exceeds 5 mm, the etching rate at the center will become too high. As a result, uniformity cannot be achieved.

In the first and second embodiments described above, a dummy wafer was used to eliminate the difference in level between the wafer and the electrode, but a jig may be used instead.

(Effects of the Invention) As described above, the dry etching method according to the present invention has the following effects:
Eliminate the difference in level between the material to be etched and the electrode on the outer periphery of the electrode, and the distance between the materials to be etched in the directions of two axes orthogonal to each other passing through the center of the electrode is 0.5 mm or more and 5 mm.
Since the material to be etched is arranged as follows, it is possible to reduce the difference in etching speed inside the material to be etched and between the materials to be etched. As a result, the accuracy of etching patterns can be improved, fine patterns can be processed, and processing time can be easily controlled.

[Brief explanation of drawings]

FIG. 1(a) shows an embodiment of the present invention,
FIG. 3 is a plan view showing a method of arranging wafers and dummy wafers on electrodes. FIG. 1(b) shows another embodiment of the present invention, and is a plan view showing a method of arranging wafers and dummy wafers on electrodes. FIG. 2 is a graph showing the distribution of etching rates within the electrode. 3 and 4 show conventional examples. FIG. 3 is a graph showing the distribution of etching rates within a wafer. FIG. 4 is a plan view showing the arrangement of wafers on the electrodes. 1 is a wafer, 2 and 4 are dummy wafers, and 3 is an electrode. Figure 1 (a) Figure (b) Length (mm)

Claims (1)

[Claims] 1. In a dry etching method for etching a plurality of materials to be etched arranged on a flat plate electrode, a step between the material to be etched and the electrode at the outer periphery of the electrode is eliminated, and the material passes through the center of the electrode and intersects perpendicularly. A dry etching method characterized in that the materials to be etched are arranged so that the distance between the materials to be etched in two axes is 0.5 mm or more and 5 mm or less.