JPH04296500A - Method and device for generating plasma - Google Patents

Abstract

PURPOSE:To generate a plasma in discharge area with a satisfactory uniformity by changing the phase velocity in a waveguide to uniformalize the microwave electric field at the time of extending TE11 mode by a taper tube. CONSTITUTION:A magnetron 1 is mounted on a rectangular guide-wave 3 to generate an electric field of TE11 mode. A taper tube 6 is also regulated in taper angle and taper length so as to extend the TE11 mode, and a microwave tries to progress in the taper tube in TE11 mode. At that time, since a quartz tube 9 has a curvature, a difference in phase speed is caused between the center and the ends when the microwave propagates in the plasma, and the phase speed becomes slower the more it is closer to the center, whereby a more uniform electric field distribution can be obtained in the whole discharge chamber 7. Thus, a high density plasma can be generated with a satisfactory uniformity within the discharge chamber 7.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method and apparatus for generating microwave plasma, and is suitable for generating microwave plasma to uniformize the processing of samples such as semiconductor element substrates using microwave plasma. METHODS AND APPARATUS.

0002

[Prior Art] Conventional microwave generation techniques include, for example,
Semiconductor plasma process technology (written by Kanno, published by Sangyo Tosho,
As described in p. 139), a quartz discharge tube is provided within a waveguide that propagates microwaves, and plasma is generated within the discharge tube by the action of an external magnetic field and a microwave electric field. Then, the semiconductor wafer is processed using the plasma.

0003

[Problems to be Solved by the Invention] In the above-mentioned prior art, a magnetron is coupled to a waveguide, and a TE as shown in FIG.
The electric field of 11 modes is propagated. Therefore, the TE11 mode appears in the electric field distribution inside the discharge tube, and the electric field distribution becomes slightly higher at the center of the discharge tube axis. Therefore, sufficient uniformity is maintained for radical species that diffuse sufficiently from the plasma in the discharge tube and reach the surface to be treated of the sample, but it is somewhat insufficient for ions that are not sufficiently diffused. This results in uniformity. Furthermore, for this reason, control over the processing speed and shape of the surface of the sample to be processed becomes somewhat insufficient.

A first object of the present invention is to provide a plasma generation method and apparatus that can generate plasma with good uniformity in a discharge region.

A second object of the present invention is to provide a plasma processing method and apparatus that can control the processing speed and shape of the surface of a sample to be processed with good uniformity.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the diameter of the TE11 mode is increased using a tapered tube, and at that time, the phase velocity within the waveguide is changed, thereby generating a microwave electric field in the discharge region. This is to make the distribution more uniform.

[0007]

[Operation] Figures 3 and 4 show the electric field distribution and cross section of the TE11 wave at 0-
The potential distribution at 0' is shown. As shown in FIG. 3, the TE11 wave has a high electric field in the center of the discharge region. Therefore, by delaying the phase velocity of the microwave near the center and shifting it from the TE11 mode, the potential distribution can be corrected as shown by the solid line in Figure 2, and a more uniform microwave electric field distribution can be obtained over the entire discharge region. Can be done.

[0008] Therefore, by using a microwave electric field having such a uniform distribution, plasma is generated with good uniformity in the discharge region.

Furthermore, by using such plasma to process the surface of the sample to be processed, the processing speed and shape can be controlled with good uniformity.

0010

[Embodiment] An embodiment of the present invention will be explained using a magnetic field type microwave plasma processing apparatus shown in FIG. 1 is a magnetron, which is a microwave oscillation source. 3 to 6 are waveguides. Here, 3 is a rectangular waveguide, 4 is a circular rectangular waveguide, 5 is a circular waveguide, and 6 is a tapered tube. The discharge chamber 7 is made of, for example, highly pure Al, and also serves as a waveguide. 8 is a vacuum chamber. 9 is a quartz plate for supplying microwaves to the discharge chamber 7. 10,
A solenoid coil 11 applies a magnetic field to the discharge chamber 7. 12 is a semiconductor element substrate (hereinafter abbreviated as wafer) 14
It is a sample stage on which a bias power source, e.g.
The F power supply 13 can be connected. Reference numeral 15 denotes a gas supply system that supplies gas for processing such as etching and film formation into the discharge chamber 7. 16 is a vacuum pump system for evacuating the inside of the discharge chamber 7 and the vacuum chamber 8 under reduced pressure.

In FIG. 1, a circular waveguide 5, a tapered tube 6,
The sample mounting surfaces of the quartz plate 9 and the sample stage 12 have substantially coaxial central axes. Further, the wafer 14 is installed on the sample installation surface of the sample stage 12 using, for example, mechanical pressing force, electrostatic adsorption force, or the like. Further, the sample stage 12 includes a temperature control means (not shown), and the temperature of the wafer 12 placed on the sample installation surface of the sample stage 12 is adjusted to a predetermined temperature by the means.

In FIG. 1, the magnetron 1 is conventionally attached to a rectangular waveguide 3, thus generating an electric field in the TE11 mode. In addition, the tapered pipe 6 is also TE11
The taper angle and taper length are adjusted to expand the mode, and the microwave attempts to travel in the TE11 mode within the tapered tube. At this time, in this embodiment, since the quartz plate 9 has a curvature, when the microwave propagates within the plasma, a difference occurs in phase velocity between the center and the edges, and the microwave is delayed closer to the center. Along with this, TE1 towards the center
1 mode, and as shown in the potential distribution (solid line) in FIG. 2, it is possible to obtain a potential distribution with a uniform slope in the cross section 0-0', that is, a more uniform electric field distribution throughout the discharge chamber 7. Therefore, in the discharge chamber 7, high-density plasma is generated with good uniformity due to the synergistic effect of the electric field having a more uniform distribution throughout the discharge chamber 7 and the magnetic field produced by the coils 10 and 11. Sufficient uniformity is maintained for radical species that have sufficiently diffused to reach the processing surface of the wafer 14 and for ions that have been somewhat insufficiently diffused.

In this embodiment, the following effects can be obtained.

(1) By correcting the TE11 mode, a more uniform electric field distribution can be obtained throughout the discharge chamber. Therefore, in the discharge chamber, high-density plasma is generated with good uniformity due to the synergistic effect of the electric field and magnetic field, which have a more uniform distribution throughout the discharge chamber, and is sufficiently diffused from the plasma in the discharge chamber to the surface to be processed of the wafer. Sufficient uniformity is maintained for each of the arriving radical species as well as ions that are somewhat poorly diffused.

(2) Both ions and radicals in the plasma uniformly reach the surface of the wafer to be processed, and etching processing and deposition processing are performed. Especially in the etching process, the uniformity of ions improves, so the uniformity of the etching rate and the uniformity of the etched shape within the processed surface of the wafer,
Precision is improved.

In the above embodiment, the phase velocity of the microwave was changed in the radial direction within the plasma, but the thickness of the quartz plate 9 was changed in the radial direction, and the phase velocity of the microwave within the quartz plate 9 was changed. The same effect can be obtained.

[0017]

According to the present invention, the microwave electric field distribution in the discharge region can be made more uniform, and plasma can be generated with good uniformity.

Furthermore, according to the present invention, the distribution of ions in the plasma becomes more uniform, and the processing speed and shape can be controlled more uniformly.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a magnetic field type microwave plasma processing apparatus showing one embodiment of the present invention.

FIG. 2 is a diagram showing a microwave potential distribution within the discharge chamber of FIG. 1;

FIG. 3 is a schematic plan view showing electric lines of force and electric field distribution in TE11 mode.

FIG. 4 shows the potential distribution in the waveguide in TE11 mode.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Magnetron, 3... Rectangular waveguide, 4... Circular rectangular waveguide, 5... Circular waveguide, 6... Tapered tube, 7... Discharge chamber, 8... Vacuum chamber, 9... Quartz plate, 10, 11... Coil, 12...sample stand, 14...wafer, 15...gas supply system, 16...vacuum pump system.

Claims (4)

[Claims] 1. A plasma generation method characterized in that when increasing the diameter of the TE11 mode using a tapered tube, the phase velocity is changed within the waveguide to make the microwave electric field uniform. 2. A plasma generation device comprising means for uniformizing the microwave electric field by changing the phase velocity within the waveguide when increasing the diameter of the TE11 mode using a tapered tube. 3. The plasma generation apparatus according to claim 2, wherein the uniformizing means is constituted by a quartz plate having a curvature constituting a microwave introduction chamber of the discharge tube. 4. The plasma generating apparatus according to claim 2, wherein the uniformizing means is provided within the tapered tube.