JPS61194726A - Plasma processing unit - Google Patents

Abstract

PURPOSE:To attempt uniform plasma processing of wafers by rotating or fluctuating the high frequency field pattern, imposed in the interior of a reaction bath, around the center axis. CONSTITUTION:A couple of semi-circular high frequency electrodes 2, 3 are mutually adhered with an insulator 8 and the lower electrode is provided with an electrode supporting mechanism 9 and a driving mechanism 10 to fluctuate the electrodes 2,3 along the circumferential direction. A high frequency voltage is applied to the wafers 7 loaded on a support stand 6 in the reaction bath 1. When the electrodes are rotated by an angle of 90 deg. with the driving mechanism, the field pattern shown in the figure is displaced by the same angle to reverse the intensity pattern in the periphery, enabling to compensate ununiformity of the field by swinging the electrodes back and fourth in the range of + or -45 deg. about the center axis.

Description

[Detailed Description of the Invention] [Summary] In an external electrode type plasma processing apparatus that performs etching, ansing, deposition, etc. using the function of plasma, improvements have been made to the means for applying high frequency voltage to generate plasma. , which aims to make the plasma action uniform over the entire surface of the substrate.

[Industrial application field]

The present invention relates to an improvement in means for applying a high frequency voltage in a plasma processing apparatus that is often used in dry processes such as etching, ashing, and deposition.

The structure of a plasma processing device consists of an airtight reaction tank in which the material to be processed is placed, gas introduction and exhaust means, and a pair of electrodes for generating a high-frequency electric field within the reaction tank. There is.

In general, large-sized plasma processing apparatuses generally have a reaction tank with a metal wall structure, while small-sized ones often use a cylindrical quartz tube as a container.

In the former case, parallel plate electrodes enclosed in a reaction tank are often used as high-frequency electrodes. In the latter case, since a quartz tube is used as the material for the reaction tank, a pair of high-frequency electrodes that are divided into shapes that surround the quartz tube are used on the outside.

In the case of a reaction tank using a small quartz tube, when the wafer size as the material to be processed is 3 to 4 inches, the wafer size is The wafer, which is sufficiently small compared to the electrode and placed in the center of the reaction chamber, is exposed to a highly uniform high-frequency electric field, and the processing is considered to be uniform over the entire surface of the wafer.

As the wafer size has recently increased from 5 inches to 6 inches, and as it approaches the diameter of the high-frequency electrode, the influence of the non-uniform area of the field pattern due to the edge effect at the dividing part of the high-frequency electrode becomes large. This causes non-uniformity in processing, which cannot be ignored and improvements are desired.

[Conventional technology]

In a plasma processing apparatus, when a high frequency electrode is installed inside a reaction tank, a parallel plate type electrode is generally used.

At this time, in order to maintain uniformity of processing, methods are used such as dividing the electrodes and changing their shape or the gap between the electrodes, or using auxiliary electrodes to uniformize the electric field applied to the wafer.

In addition, a method of maintaining uniformity by controlling the flow of the reaction gas has also been adopted.

Since the high-frequency electrode is installed inside the reaction tank, it is extremely difficult to move the electrode itself due to its airtight structure, so measures have been taken to obtain a uniform electric field in a fixed state due to the design. .

On the other hand, the small external electrode type uses a quartz tube for the reaction tank, so it is difficult to enlarge it, but the equipment is simple and easy to handle, so it is very useful when the wafer size is small. It is used as a convenient plasma processing device.

The high-frequency electrode of this small-sized plasma processing apparatus has a shape as shown in FIG. 3. That is, it consists of a pair of high-frequency electrodes 2.3 arranged to surround a reaction tank 1 made of a quartz tube, and a wafer 7 mounted on a wafer support 6 is arranged perpendicular to the tube axis as shown in the figure. ing.

The reaction tank is equipped with a gas inlet 4 and an exhaust port 5, a reaction gas is introduced through the inlet 4, and a high frequency voltage is applied to the electrodes.

The field pattern at this time should be as shown in FIG. 4 if the quartz tube reaction tank 1, the wafer 7 as the material to be processed, etc. are not present between the electrodes.

In FIG. 4, the solid line represents the direction of the electric field, and the dotted line represents the equipotential surface.

However, in reality, the presence of these component materials disturbs the field pattern, but the basic pattern structure shown in FIG. 4 remains unchanged.

That is, in FIG. 4, the electric field is strong in region A near the dividing portion, and the electric field becomes weaker in region B and then region CN.

[Problem that the invention seeks to solve]

In the above-mentioned external electrode type plasma processing apparatus, if the wafer size is as small as 3 to 4 inches and is relatively small with respect to the field pattern of the electric field generated by the high-frequency electrode, there will be a large processing speed penalty on the wafer. Uniformity is not allowed.

However, as the wafer size increases to 5 to 6 inches, problems arise with non-uniform processing due to edge effects of the high frequency electrodes on the wafer.

[Means for solving problems]

The above problem is solved by a plasma processing apparatus having a cylindrical reaction tank 1, which is equipped with an even number of high-frequency electrodes divided concentrically around the reaction tank. This can be solved by providing means for rotating or swinging the high frequency field pattern by more than ±45 degrees with respect to the central axis.

In addition, the high frequency field pattern is
As a means for rotating or swinging, a pair of high-frequency electrodes 2.3 is provided, and the electrodes can be rotated or rocked by ±45 degrees or more with respect to the central axis of the reaction tank.

In addition, as another method, an even number of high frequency electrodes of 4 or more (2
1, 22, to 27, 28), and a sliding electrode 11. which slides on the contact point of the electrode while dividing the electrode into two electrode groups.
12, and the sliding electrode can be rotated or swung by ±45 degrees or more.

[Effect]

With the plasma processing apparatus equipped with the above means, the field pattern inside the reaction tank is rotated or oscillated by ±45 degrees or more with respect to the central axis of the reaction tank due to the voltage applied from the high-frequency electrode.

This makes it possible to compensate for plasma effects caused by non-uniform field effects on the wafer and to make processing uniform.

〔Example〕

An embodiment related to the present invention will be described in detail with reference to the drawings. In the drawings, explanations of symbols that can be explained in the section of the prior art will be omitted.

Figure 1(a) is a cross-sectional view of a plasma processing apparatus equipped with means for swinging a field pattern back and forth about a central axis using a pair of high-frequency electrodes. A side view of the movable part is shown.

That is, a pair of semicircular high-frequency electrodes 2 and 3 are fixed to each other by an insulator 8, and the lower electrode 2 has an electrode support mechanism 9 and a drive mechanism 1 for swinging the electrode in the circumferential direction.
0. The drive mechanism 10 may have a structure that rotates in the circumferential direction, but may also have a structure that swings back and forth by about 45 degrees as shown in the figure.

The wafer 7 housed inside the reaction chamber 1 is mounted on a wafer support 6, and a high frequency of, for example, 13.56 MzO is applied to the wafer 7.

At this time, the field pattern can be changed to 9 by moving the drive device.
If rotated by 0 degrees, change the field pattern in Figure 4 to 9.
A shift of the shape rotated by 0 degrees occurs.

This reverses the strength of the field at the periphery. That is, by swinging back and forth ±45 degrees from the center position, it is possible to compensate for non-uniformity of the field.

Of course, the same effect can be expected by rotating in one direction instead of rocking back and forth.

Alternatively, as shown in Figure 2, for example, 8
Split electrodes 21.22. 27 and 28 are arranged on the circumference, and are provided with sliding electrodes 11 and 12 that simultaneously contact four of the contacts of each electrode.

At the moment when there is a sliding electrode, (21, 22, 23, 24),
(25, 26° 27, 28), and at the next point (22, 23° 24.25), (26, 27
, 28, 21).

Furthermore, at the next point (23, 24, 25, 26), (27
, 2B, 21.22), in this case the field pattern will be rotated by 90 degrees to compensate for the non-uniformity, similar to the two-electrode case described earlier.

That is, compensation can be made by moving the position of the sliding electrode one contact point before and after a certain contact point position.

In addition, the number of divided high-frequency electrodes is an even number of 4 or more (i.e.,
This method is applicable if there are two or more electrodes on one side).

〔Effect of the invention〕

As explained above, in an external electrode type plasma processing apparatus, by rotating or swinging the high-frequency field pattern applied inside the reaction tank about the central axis, the plasma reaction on the wafer can be made uniform over the entire surface. This greatly contributes to improving processing speed and quality.

[Brief explanation of drawings]

Fig. 1 is a sectional view and side view of a plasma processing apparatus according to the present invention, Fig. 2 is another embodiment related to the present invention, Fig. 3 is a conventional external electrode type plasma processing apparatus, and Fig. 4 is a field pattern. Figure, shows. In the drawings, 1 is a reaction tank, 2.3 is a high-frequency electrode, 4 is a gas inlet, 5 is an exhaust port, 6 is a wafer support stand, 7 is a wafer, 8 is an insulator, 9 is an electrode support mechanism, and 10 is a drive mechanism , 11 and 12 are sliding electrodes, 21.22. ~27 and 2B indicate high frequency electrodes, respectively. 7'ibwq+:PIIh3? Last 2 models! the law of nature】

[Fig.

Claims (3)

[Claims] (1) A cylindrical reaction tank 1 made of a dielectric material and equipped with a means for introducing and exhausting a reaction gas, and concentrically divided parts arranged outside the cylindrical reaction tank so as to surround the reaction tank. An even number of high-frequency electrodes is provided, and a means is provided for rotating or swinging the high-frequency field pattern induced inside the reaction tank by an angle of ±45 degrees or more with respect to the central axis by means of a voltage applied to the high-frequency electrodes. A plasma processing apparatus characterized by the following. (2) A pair of high-frequency electrodes 2 and 3 are provided as means for rotating or swinging the high-frequency field pattern with respect to the central axis, and the electrodes are connected to the central axis of the reaction tank 1.
The plasma processing apparatus according to claim 1, further comprising means for rotating or swinging by ±45 degrees or more. (3) As a means for rotating or swinging the high-frequency field pattern about the central axis, an even number of high-frequency electrodes (21, 22, to 27, 28) of 4 or more and the electrodes are combined into two electrode groups. Claim No. 1, characterized in that it is provided with sliding electrodes 11 and 12 that slide on the contact points of the electrodes while being divided into two parts, and a means for rotating or swinging the sliding electrodes by ±45 degrees or more. 1) The plasma processing apparatus described in item 1).