JPH06120169A - Plasma generating apparatus - Google Patents

Abstract

PURPOSE:To rotate a plasma and obtain the uniformity of the plasma generated non axialsymmetrically by installing a center electrode in a holding vessel in substantially parallel with a magnetic field and installing an outer circumferential electrode paired with the center electrode in the circumference and applying a voltage of DC or AC to these electrodes. CONSTITUTION:A center electrode 1 is mounted in a treating chamber 4 on the upper surface of a discharge tube 10 and an outer circumferential electrode 2 is mounted in the outer circumference of the discharge tube 10. The center electrode 1 and the outer circumferential electrode 2 are connected to a power source 3 for control and a radial electric field around the center electrode 1 in the treating chamber 4 is formed through a DC component of a voltage applied by the power source 3. Since an electric line 13 of force of the radial electric field generated by the center electrode 1 and the outer circumferential electrode 2 intersects a magnetic line 14 of force of a magnetic field generated by a coil 9 for generating the magnetic field, a plasma is drifted perpendicular to both the electric line 13 of force and the magnetic line 14 of force, and the plasma rotates around the center electrode 1. As a result, the uniformity of a plasma density distribution around a center axis can be obtained and a plasma treatment with the high uniformity can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma processing apparatus equipped with a plasma generator, and more particularly to a plasma processing apparatus suitable for fine processing of semiconductor elements.

[0002]

2. Description of the Related Art Various inventions have been made to generate uniform plasma in a dry etching apparatus and a chemical vapor deposition (CVD) apparatus using plasma. For example,
In the invention of Japanese Patent Laid-Open No. 2-46627, a uniform plasma density is obtained by providing an ECR surface that is substantially parallel to the ion extraction electrode near the ion extraction electrode for introducing plasma from the plasma generation chamber into the processing chamber. It is supposed to be obtained. Here, ECR means electron cyclotron resonance (El
ectron Cyclotron Resonance).

In the invention of Japanese Patent Laid-Open No. 2-139924, EC
In addition to the magnetic coil used to form the R-plane, a magnetic coil for controlling the plasma density distribution is provided to oscillate the magnetic field to make the plasma density uniform.

In the invention disclosed in Japanese Patent Laid-Open No. 3-79771, a large number of electrode plates placed substantially in parallel are provided between the plasma generating section and the sample to be processed, and the plasma generated in the plasma generating section flows toward the sample. When passing, make sure to pass between these electrode plates. By providing a means for controlling the flow of plasma by applying a voltage to this electrode plate, the plasma density is made uniform.

In the invention disclosed in Japanese Patent Laid-Open No. 3-229859, the stator winding coil is provided outside the processing chamber, and the stator winding coil is provided with control means for generating a rotating magnetic field in the processing chamber. The plasma flow is also rotated to make the plasma density uniform.

[0006]

Some current methods of generating plasma can make it difficult to generate plasma with an axisymmetric distribution under certain conditions.

For example, in the invention of Japanese Patent Application Laid-Open No. 2-139924, when the mode of microwave propagation is not such a mode that a uniform electric field is generated, uniform plasma is not generated and the plasma is not generated. The density distribution becomes non-uniform.

In the invention disclosed in Japanese Patent Laid-Open No. 2-139924, the coil must be moved to oscillate the magnetic field, which complicates the mechanism.

In the invention of Japanese Patent Application Laid-Open No. 3-79771, since a large number of electrodes are provided in the processing chamber, the processing chamber becomes crowded, and contamination by dust becomes a problem. Further, if the plasma generation distribution is not uniform, the amount of plasma flowing between the electrode plates will be non-uniform, so it is difficult to make the plasma density sufficiently uniform by this method.

In the invention of Japanese Patent Laid-Open No. 3-229859, the device is complicated because a rotating magnetic field is generated, and the magnetic field in the plasma generation chamber is also affected by the addition of the rotating magnetic field, so that the plasma is generated. Since the generated ECR plane also fluctuates, it may be difficult to control the plasma state.

In the prior art, assuming that an axisymmetric plasma is generated, only homogenization in the radial direction is considered, or even if homogenization in the circumferential direction is considered, the structure of the device is considerably complicated. It was a method that would become a thing.

An object of the present invention is to obtain non-axisymmetrically generated plasma to obtain uniform etching rate or film thickness within the wafer surface, and to achieve this with a simple structure. It is to be realized.

[0013]

In a plasma generation apparatus provided with a plasma generation source, a plasma holding container for holding plasma generated in the plasma generation source, and a magnetic field generation source for applying a magnetic field to the plasma, the holding container A center electrode is provided in a direction substantially parallel to the magnetic field, and an outer peripheral electrode that forms a pair with the center electrode is provided around the holding container, and DC is applied to these electrodes to rotate the plasma. Have means.

A microwave source, a waveguide for guiding the microwave generated by the microwave source to the plasma processing chamber, a magnetic field generating coil, a sample as a processing material for plasma processing, and a plasma for the sample. A plasma processing chamber to be processed, a gas introduction part for introducing a processing gas into the plasma processing chamber, an exhaust part for discharging the processing gas from the plasma processing chamber, and the plasma processing chamber for holding the sample. In a plasma generator with a sample table,
A central electrode is provided in the plasma processing chamber, and outer peripheral electrodes that form a pair with the central electrode are provided around the plasma processing chamber, and means for controlling plasma by applying DC or AC voltage to these electrodes is provided. Have.

A high-frequency power source for plasma generation, a plasma processing chamber, a sample as a processing material, a sample holder placed in the plasma processing chamber, and a flat plate placed in the processing chamber parallel to the sample holder. Shaped electrode, a power source for applying a voltage to the flat plate type electrode, and a portion for introducing a processing gas into the processing chamber,
In the plasma generation device provided with the discharge part of the processing gas from the processing chamber, the sample holding table forms an electrode,
A voltage is applied between the flat plate electrode and the flat plate electrode to generate plasma, but a magnetic field generation source that generates a magnetic field in a direction perpendicular to the flat plate electrode is provided, and a center electrode is provided in the plasma processing chamber. An outer peripheral electrode paired with the central electrode is provided around the plasma processing chamber, and means for controlling plasma by applying a DC or AC voltage to these electrodes is provided.

[0016]

Function: A magnetic field is generated by a magnet or a coil in the plasma generation chamber. This magnetic field may be a parallel magnetic field or a divergent magnetic field. Electron cyclotron resonance (E
In a plasma generator using CR), plasma is converted into EC
The divergent magnetic field for generation by R is used because it already exists in the plasma generation chamber. A center electrode is provided in the center of the plasma generation chamber in a direction substantially parallel to the magnetic force lines of the magnetic field, and an outer peripheral electrode is provided along the outer wall of the plasma generation chamber so as to be substantially parallel to the center electrode. By applying a voltage to the central electrode and the outer peripheral electrode, a radial electric field having electric lines of force centering on the central electrode and substantially perpendicular to the magnetic lines of force is generated in the plasma generation chamber.

In the present invention, the magnetic flux density vector of the magnetic field is B, the electric field vector of the electric field is E, and the central axis of the radial electric field is simply referred to as the central axis. Axial symmetry means symmetry around this central axis, and radial and circumferential directions mean the radial and circumferential directions, considering the cylindrical coordinate system around this central axis. To do. When an electric field and a magnetic field are present in the plasma at the same time, the plasma is subjected to a force due to the electric field drift in a direction perpendicular to both E and B, specifically, in the direction of the vector product of E and B. In the case of a magnetic field and a radial electric field, the plasma is subjected to a rotating force around the center electrode. By rotating the plasma around the center electrode with this force, even if the plasma is generated axisymmetrically,
The plasma density distribution can be made uniform. Since the rotating force can be controlled by the direct current component of the radial electric field, the plasma density can be controlled to be uniform in the circumferential direction.

Further, the strength and direction of the radial electric field can be changed by adding an AC component to the voltage applied to the central electrode and the outer peripheral electrode. This changes the distribution of the plasma density in the electric field direction, so that the plasma density can be made uniform in the electric field direction.

As described above, by applying a magnetic field to the plasma generating chamber and applying a radial electric field by the central electrode and the outer peripheral electrode, the circumferential distribution and the radial distribution of plasma can be made uniform.

[0020]

EXAMPLE FIG. 6 shows a microwave plasma etching apparatus as an example of a conventional plasma processing apparatus.

The sample 5 to be etched is at the core of the device.
Are installed on the sample table 6. This sample table also serves as an electrode, and a high-frequency bias voltage may be applied between it and the ground electrode 6a. The sample table can be moved up and down. The sample table is placed in the processing chamber by placing the sample on the sample table with the sample table lowered and raising the sample table. To remove the sample, reverse this procedure. As a mechanism for loading and unloading samples,
In some cases, a slide type sample carrying mechanism is provided on the side surface of the processing chamber. The sample and the sample table are covered with a cylindrical discharge tube 10 made of, for example, quartz. The shape of this discharge tube is various, such as a hemispherical shape or a conical shape in consideration of the microwave propagation mode. A vacuum seal 21 is used to attach the discharge tube so that the processing chamber can be maintained at a low pressure for plasma processing. A magnetic field is applied to the cylindrical discharge tube in a direction substantially parallel to the central axis of the discharge tube by a magnetic field generating coil 9 installed so as to surround the discharge tube. This magnetic field is formed so that the ECR surface that most absorbs microwaves is substantially parallel to the sample. Although the magnetic field generating coil has two stages in the figure, it may have one stage or multiple stages of three or more stages. Here, the two-stage coil is a coil in which the coil is divided into two and the voltage and current applied to each coil can be set to different values. A processing gas is supplied from the gas introduction unit 7 into the discharge tube. The apparatus may be provided with some mechanism for uniformly supplying the processing gas into the discharge tube. In addition, a gas exhaust unit 8 for exhausting gas is provided in the processing chamber. The processing chamber is composed of the discharge tube 10 and the outer wall 20, is sealed except for the gas supply part and the gas discharge part, and the pressure can be lowered.

A microwave of, for example, 12.5 GHz generated by the microwave generation source 11 propagates through the waveguide 12 and enters the discharge tube 10. This microwave is absorbed by the ECR surface due to the interaction between the magnetic field and the plasma to generate plasma. The plasma generated on the ECR surface is diffused while being restricted by the lines of magnetic force and spreads in the discharge tube. Radicals are generated in this plasma and etch the sample together with plasma ions. The processed gas is exhausted from the gas exhaust unit.

Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an embodiment in which the present invention is applied to the microwave etching apparatus for processing a semiconductor wafer shown in FIG. 6, and is a sectional view of the apparatus. The operation of the device is basically the same as the device of FIG.

In FIG. 1, a newly added portion to the apparatus of FIG. 6 is a central electrode 1 installed in the processing chamber 4 on the upper surface of the discharge tube 10 and an outer peripheral electrode 2 attached to the outer circumference of the discharge tube. Is. The center electrode may be attached to the discharge tube via an insulator, or directly if the discharge tube is an insulator. Further, the outer peripheral electrode may be directly attached to the discharge tube or may be attached to the discharge tube via an insulator.
Further, the outer peripheral electrode may be inside the discharge tube or outside the discharge tube. The central electrode and the outer peripheral electrode are connected to a control power source 3, and the DC component of the voltage applied from this power source forms a radial electric field centered on the central electrode in the processing chamber. FIG. 2 is a detailed view of the state inside the discharge tube of the device of FIG. 1, showing details of the electric force lines 13 of the radial electric field generated by the center electrode 1 and the outer peripheral electrode 2 and the magnetic force lines 14 of the magnetic field generated by the magnetic field generating coil. Represents Since the electric force lines 13 and the magnetic force lines 14 intersect with each other, the plasma drifts in a direction perpendicular to both the electric force lines and the magnetic force lines based on the above-described principle, so that the plasma rotates around the center electrode. As a result, the plasma density distribution around the central axis can be made uniform.

FIG. 3 shows another embodiment in which the present invention is applied to a microwave etching apparatus. The principle of the device is the same as the device of Fig. 1, but the upper part of the discharge tube is processed,
The difference is that the center electrode 1 is installed in the processing chamber so as to be insulated from the plasma in the processing chamber by the insulator 10a. The conductive tube 10 and the insulator 10a may be integrated or may be separate parts. In FIG. 3, it is an integrated type. Further, a method of treating the center electrode with an insulating coating is also conceivable. As described above, by disposing the center electrode in the plasma via the insulator, it is possible to prevent contamination by the electrode during etching.

FIG. 4 shows an embodiment in which the present invention is applied to a radio frequency (RF) plasma etching apparatus. A flat plate-shaped electrode 18 is installed in the upper part of the inside of the processing chamber 4, and an electrode / sample base 19 is installed in parallel with the flat-plate-shaped electrode on the side facing it.
These electrodes are connected to the outer wall 20 via the insulator 15a.
Is attached to. High frequency power supply 16 for flat plate electrodes
, And ground the electrode and sample stand. In this case, a high-frequency power source is connected to the electrode / sample base, and the plate electrode may be grounded. One or more samples such as 5a and 5b are placed on the sample table. The processing chamber is provided with a gas introduction section 7 for introducing a processing gas and a gas discharge section 8 for exhausting the processed gas. The gas inlet may be incorporated in the flat plate electrode 18.

Magnets 17a and 17b are attached to the outside of the processing chamber in order to apply a parallel magnetic field in a direction substantially perpendicular to the sample and the electrodes. For this purpose, a magnetic field generating coil may be used instead of the magnet. The center electrode 1 is installed near the center of the processing chamber in a direction substantially parallel to the magnetic field, that is, in a direction substantially perpendicular to the electrodes. Although this center electrode is attached to the flat plate electrode 18 via an insulator, it may be attached to the outer wall via an insulator or may be attached to the sample stage via an insulator. Along the outer wall of the processing chamber, the outer peripheral electrode 2 is attached to the outer wall via the insulator 15a so as to be substantially parallel to the center electrode. It is not necessary to provide the outer peripheral electrode over the entire circumference in consideration of gas intake and exhaust. The central electrode and the outer peripheral electrode are connected to the control power supply 3.

A high frequency voltage is applied between the flat plate electrode 18 and the electrode / sample stage 19 by the high frequency power source 16, plasma is generated in the processing chamber, and spreads in the processing chamber by diffusion. When the processing gas is injected from the gas introduction part 7, it is turned into plasma in the processing chamber and at the same time, radicals are generated to etch the samples 5a and 5b. The processed gas is discharged from the gas exhaust unit 8.

A radial electric field is generated inside the processing chamber by the central electrode 1 and the outer peripheral electrode 2, and the magnets 17a and 17b are formed.
Along with the magnetic field generated by, the distribution is as shown in FIG. Therefore, the plasma can be rotated around the central axis by the drift, and the plasma density distribution around the central electrode can be made uniform.

As a result, the plasma densities on a plurality of samples can be made uniform, so that variations in etching rate among samples can be eliminated.

FIG. 5 shows another embodiment in which the present invention is applied to an RF plasma etching apparatus. The center electrode is installed by an insulator 15 so as to be insulated from the plasma inside the processing chamber. Fig. 4 in that it prevents contact between
Device.

By doing so, it is possible to prevent dust from adhering to the center electrode and contaminating the inside of the processing chamber with this dust.

[0033]

According to the present invention, since a uniform plasma density distribution can be obtained from a non-uniform plasma generation distribution, highly uniform plasma processing can be performed.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment of the present invention.

FIG. 2 is a detailed view of FIG.

FIG. 3 is a vertical sectional view of a second embodiment of the present invention.

FIG. 4 is a vertical sectional view of a third embodiment of the present invention.

FIG. 5 is a vertical sectional view of a fourth embodiment of the present invention.

FIG. 6 is a perspective sectional view of a conventional microwave plasma etching apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Central electrode, 2 ... External electrode, 3 ... Control power supply, 4 ... Processing chamber, 5 / 5a / 5b ... Sample, 6 ... Sample stand, 6a ... Ground electrode, 7 ... Gas introduction part, 8 ... Gas discharge part , 9 ... Magnetic field generating coil, 10 ... Discharge tube, 10a ... Insulator, 11 ... Microwave source, 12 ... Waveguide.

Claims (1)

[Claims] 1. A plasma generation apparatus comprising a plasma generation source, a plasma holding container for holding plasma generated by the plasma generation source, and a magnetic field generation source for applying a magnetic field to the plasma, wherein a magnetic field is provided in the holding container. Means for rotating the plasma by providing a center electrode in a direction substantially parallel to the outer circumference of the holding container, and providing a peripheral electrode paired with the center electrode around the holding container, and applying a DC or AC voltage to the center electrode and the peripheral electrode. A plasma generation device comprising: