JPH01202821A - Reactive ion etching apparatus - Google Patents

Abstract

PURPOSE:To reduce an irregularity in an etching rate by engaging a plurality of supporting bases for placing semiconductor wafers with a cathode plate, and separately rotating the bases in cooperation with the rotation of the plate. CONSTITUTION:A plurality of supporting bases 4 for placing semiconductor wafers are engaged with a cathode plate 3, and separately rotated through gears 5, 6 in cooperation with the rotation of the plate 3. Thus, in order to reduce an irregularity in the etching rate of the wafers due to the difference of a plasma state in a vacuum vessel 1 and the flows of etching gas, the plate 3 is rotated, and the bases 4 are additionally rotated. In this manner, the irregularity in the etching rates can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reactive ion etching apparatus, and more particularly to an improvement in a reactive ion etching apparatus in which a portion of an electrode on which a semiconductor wafer is placed is rotated.

[Conventional technology]

Conventionally, this type of reactive ion etching apparatus has fixed a plurality of semiconductor wafer mounting supports 4, as shown in FIG. 4, in order to improve the uniformity of the etching rate within the wafer I. , the cathode plate 3 was rotated within the vacuum container 1.

[Problem that the invention seeks to solve]

In the conventional reactive ion etching apparatus described above, when etching an object to be etched, the uniformity of the etching rate in the circumferential direction of the cathode plate is improved, but the uniformity of the etching rate in the radial direction cannot be improved. Therefore, for example, when a polycrystalline silicon film or an aluminum film on a semiconductor wafer is etched, undercuts occur in the photoresist mask due to remaining parts of the film to be etched or overetching, resulting in a drawback that the yield and quality of the product are reduced. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a reactive ion etching apparatus with less variation in wafer processing and etching rates.

[Means for solving problems]

The etching apparatus to which the present invention is applied has a pair of electrode plates facing each other in a vacuum container, one of which is rotatable, and a semiconductor wafer is placed on the electrode plate. A plurality of supporting stands placed on the electrode plate are locked, and the supporting stands rotate independently in conjunction with the rotation of the electrode plate.

[Effect]

In conventional equipment, the cathode plate is rotated in order to reduce variations in the etching rate of the wafer due to differences in plasma conditions and etching gas flows within the vacuum chamber, whereas the present invention rotates the cathode plate. In addition to this, by rotating the support base on which the semiconductor wafer /\ is stored, variations in the etching rate can be further reduced.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal cross-sectional view of the embodiment device, in which an anode plate 2 and a cathode plate 3 are arranged facing each other in a vacuum container l.
The cathode plate 3 is electrically insulated from the vacuum vessel 1 by an insulating member 8. The anode plate 2 is placed in contact with the vacuum container 1, and the cathode plate 3 is connected to a high frequency power source 17 via a matching box 16. The cathode plate 3 is rotated by a stepping motor 15 via a central rotating shaft 19 . A support rotation gear 5 for rotating the support base 4 is meshed with a drive gear 6 mounted on the rotation shaft 19.

A plurality of support stands 4 on which semiconductor wafers 7 are placed are arranged concentrically, as shown in FIG. 2(a) when cathode plate 3 is viewed from above. The support stand 4 is attached to the cathode plate 3 as shown in FIG.
), the bottom surface of the support base 4 is slidably connected to the cathode plate 3, or as shown in FIG. By frictionally coupling, it becomes locked with the cathode plate 3, and further rotates independently in conjunction with the rotation of the cathode plate 3. In this example, as shown in FIG. 2(a), it rotates in the opposite direction to the cathode plate 3 and at a faster rotation speed than the cathode plate 3.

In the etching apparatus configured in this way, for example, a photoresist is applied onto a polycrystalline silicon film formed on the semiconductor wafer 7, a mask with a desired pattern is printed using a projection exposure device, and after development, the photoresist is placed on the support base. 4, and the stepping motor 15 moves the cathode plate 3 onto 2.
While rotating at Or, p, +s, the support base 4 is rotated at 6 O.
Vacuum pump 13 (mechanical booster pump) from exhaust port 10 while rotating with r, p, +w.

14 (rotary pump) to create a low pressure (1 to 5
0 Pa), supplying etching gas from the gas inlet 18, generating plasma by a high frequency voltage applied between the anode plate 2 and the cathode plate 3, and etching the region to be etched by ion bombardment and chemical reaction in the plasma. to obtain the desired pattern. Note that 11 is a main valve, and 12 is a variable throttle valve, which is adjusted according to the degree of vacuum measured by a vacuum gauge 9.

Data on etching rate and uniformity when etching with this apparatus are shown in FIGS. 3(a) and 3(b) in comparison with those using a conventional apparatus. In the embodiment, as shown in FIG. 2(a), eight support stands 4 are arranged concentrically with the center of the cathode plate 3, and one semiconductor wafer 7 is mounted on each support stand 4. The semiconductor wafer 7 is stopped and rotated in the circumferential direction by the rotation of the cathode plate 3, and also rotates itself. When the semiconductor wafer 7 is initially placed on the support stand 4 in a stationary state, the direction perpendicular to the cut line B shown in FIG. 3(C) is directed toward the center of the cathode plate 3.

At this relative position, the positions of each point on the semiconductor wafer 7 are determined so that the TB line and the LR line are at right angles, and are defined as Xl-X9 points. FIGS. 3(a) and 3(b) illustrate the etching rate averaged at each point for eight semiconductor wafers 7, with the circumferential direction taken as the LR line and the radial direction taken as the TB line. The black dots are data for the device of the present invention, and the white dots are data for the conventional device. Note that this data is for polycrystalline silicon doped with phosphorus.

It can be seen from FIGS. 3(a) and 3(b) that there is little variation in the etching rate of each point by this apparatus. Numerically, as the uniformity of etching rate, the average value of 5 measurement points (X 1 to Xs) in one circumferential direction is X^, and the value of M a x - Min within the 5 points of x 1 to x 5 is R If (R^/also^) The uniformity of etching rate in the radial direction for five points is approximately 1.
Improved by 6%. When similar calculations are performed for all measurement points (X+-X9), the uniformity of the entire semiconductor wafer is improved by approximately 17%.

〔Effect of the invention〕

As explained above, in conventional reactive ion etching equipment, the cathode plate on which the semiconductor wafer is usually rotated in opposition to the stationary anode plate, so that the etching rate becomes uniform. Although it is possible to make the etching rate uniform in the circumferential direction, it is difficult to make the etching rate uniform in the radial direction because the support base on which the semiconductor wafer is mounted is fixed to the cathode plate. In contrast, in the present invention,
Since the support stand itself is rotated, a uniform etching rate can be obtained between a plurality of semiconductor wafers and at each point within a wafer.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of one embodiment of the present invention, FIG. 2 is a plan view of the cathode plate and support base, and a diagram illustrating the locked state of the support base, and FIG. 3 is a diagram showing the device of the present invention and a conventional device. FIG. 4 is a longitudinal sectional view of a conventional example. 1... Vacuum container, 2... Anode plate, 3...
Cathode plate, 4... Support stand, 5... Support stand rotation gear, 6... Drive gear, 7... Semiconductor wafer/\
, 15...Stepping motor. Figure 1 Cause 2 1a) (b)t C) Figure 3 (A)

Claims (1)

[Claims] A vacuum container includes a pair of electrode plates facing each other, one of which is rotatable, and a plurality of supports for placing semiconductor wafers on the electrode plates. A reactive ion etching apparatus characterized in that the support base is locked and independently rotates in conjunction with the rotation of an electrode plate.