JPH06151090A - Plasma generating device - Google Patents

Abstract

PURPOSE:To solve the problem accompanying a conventional ECR discharge type plasma generating device or magnetron discharge type plasma generating device, and allow the uniform plasma radiation or ion generation in a large area with good power efficiency. CONSTITUTION:A plurality of cusp magnetic field generating coils 2 are juxtaposed along the axial direction on the outer circumference of a cylindrical vessel 1 capable of vacuum exhausting, and these cusp magnetic field generating coils 2 are alternately excited by direct currents in reversed directions. A plurality of high frequency electrodes 4 are arranged in a position within the cylindrical vessel 1 where the magnetron discharge is effective to the cusp magnetic field generated by each cusp magnetic field generating coil 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma generator by magnetron discharge using high frequency.

[0002]

2. Description of the Related Art FIG. 3 of the accompanying drawings shows a conventional ECR discharge type plasma generator, which introduces microwaves from a waveguide B into a plasma chamber A through a microwave introduction window C. The plasma chamber A is provided with an axial magnetic field generator D, which is configured to generate plasma by causing an electric discharge in the plasma chamber A. A coil or a plurality of permanent magnets that generate a magnetic field in the axial direction are alternately arranged on the circumference of N poles and S poles.
It is arranged so that the poles come. Plasma is efficiently generated in the plasma chamber A by the resonance phenomenon between the magnetic field and the microwave. The plasma or ions generated in the plasma chamber A in this way is carried to the sample F by the action of the (divergent) magnetic field or plasma generated by the excitation of the axial magnetic field generator D, and the electric field from the ion extracting electrode portion E to irradiate the sample F for etching. The sample F can be processed by processing such as sputtering, deposition or the like.

FIG. 4 shows a conventional bucket type plasma generator, in which a heater or a microwave G is used to generate an electric discharge in a plasma chamber H to generate plasma. In order to generate a magnetic field in the axial direction of the plasma chamber H, a plurality of permanent magnets I are arranged so that N poles and S poles are alternately arranged on the circumference. The plasma or ions generated in the plasma chamber H by the permanent magnet I (divergence)
The sample K is carried by the action of the magnetic field or plasma, and the electric field from the ion extracting electrode portion J to the sample K for irradiation, and the processing such as etching, sputtering or deposition is performed so that the sample K can be processed. There is.

Further, FIG. 5 shows a conventional plasma generator using magnetron discharge, in which L is a cathode, and an annular (or oval) magnet M and an inside of this magnet M are arranged along the central axis. The central magnet N is provided. An anode O is arranged at a position facing the cathode L. The magnets M and N generate a magnetic field in front of the cathode L, and an electric field orthogonal to this magnetic field is applied to the cathode L.
An orthogonal electromagnetic field is formed on the surface of the. And the cathode L
When secondary electrons or exoelectrons are emitted from the surface of
These electrons move in a racetrack shape in the direction perpendicular to the action of the orthogonal electromagnetic field on the surface of the cathode L. During this time, the electrons that lost part of their energy by colliding with the molecules of the carrier gas cannot return to the cathode L, which has a high potential for the electrons, and drift in the magnetic field while drawing a racetrack orbit in the orthogonal electromagnetic field. Go on. During this time, the gas collides with the carrier gas to be ionized, and the generated ions are accelerated toward the cathode L and collide with each other, and secondary electrons are emitted. Then, the emitted secondary electrons behave similarly to the electron first emitted from the cathode L. In this way, the plasma grows and racetrack-shaped plasma is generated in front of the cathode L.

In the operation of such a conventional device, the microwave or heater introduced from the waveguide through the microwave introduction window serves as an energy source, that is, an electron supply source, and the electrons resonantly absorb the energy. The gas is ionized by the ionization action of the electrons, and plasma is generated. In this case, when an external magnetic field is present, electrons are wrapped around the magnetic lines of force and the chances of collision with the gas are increased without going directly to the discharge wall, and plasma is easily formed. Therefore, as the external magnetic field forming device, a cylindrical coil, a mirror coil, a multicusp permanent magnet or a magnetron magnet is usually used.

[0006]

In the conventional large-diameter plasma generator, for example, a bucket type ion source uses a hot filament, and therefore the life is extremely short when active gas ions such as oxygen are to be obtained. And EC again
Since the R type (including off-resonance) uses a vertical magnetic field, there is a problem that the in-plane uniformity of plasma density is extremely deteriorated. In order to irradiate a large-area substrate with plasma in accordance with the development of liquid crystal televisions and an increase in the diameter of a wafer in a semiconductor process, the area of a plasma source must be increased. However, in the plasma generator including the mirror-type or multi-cusp-type plasma source as described above, since the magnetic field exists in the plasma extraction portion, the uniformity of the plasma density is significantly deteriorated, and the TF for liquid crystal is increased.
When manufacturing T or irradiating a large-diameter substrate, there is a problem that the yield is low. Even if the area of the plasma source is increased, it is necessary to reduce the magnetic field, so the density is low and it is not practically usable. Further, if an attempt is made to increase the diameter, in the conventional ECR type device, the current flowing through the external magnetic field coil also increases, which causes a problem that power consumption increases. Further, in the magnetron discharge type device, since the plasma is limited to the region where electrons move in the magnetron, it is not possible to obtain a plasma having a good density uniformity.

Therefore, the present invention solves the problems of the conventional apparatus and provides a plasma generator capable of irradiating plasma or ion beam with a large area and uniform power consumption. It is an object.

[0008]

In order to achieve the above object, the plasma generator according to the present invention is arranged in parallel along the axial direction on the outer circumference in the circumferential direction of a cylindrical container that can be evacuated, and alternately in opposite directions. A plurality of cusp magnetic field generating coils that are excited by a direct current to generate cusp magnetic fields arranged along the axial direction, and a cylindrical container in which magnetron discharge is effective for the cusp magnetic field generated by each cusp magnetic field generating coil. It is characterized by having a plurality of high frequency electrodes arranged at the position of.

[0009]

In the plasma generator according to the present invention having the above-described structure, the axial line is generated by alternately passing a direct current in the opposite direction to the cusp-type magnetic field generating coils juxtaposed along the axial direction on the outer circumference of the cylindrical container. A cusp magnetic field that is aligned along the direction is generated. Then, each high-frequency electrode generates a high-frequency electric field in the middle of the adjacent cusp-type magnetic field generating coil, and (E × B) force acts in the middle of the cusp-type magnetic field generating coil, whereby the electrons generate (E × B) force. It makes a magnetron motion that drifts in the direction and spins around the inner surface of the cylindrical container. A number of such magnetron-moving electron rings are formed along the axial direction of the cylindrical container, and plasma is generated with good power efficiency and gas efficiency. Further, since the central portion along the axis of the cylindrical container has the minimum magnetic field orientation, it is possible to form the plasma having a good density.

[0010]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2 of the accompanying drawings. FIG. 1 shows an embodiment of the present invention. Reference numeral 1 denotes a cylindrical vacuum container, one end of which is closed and the other end of which is provided with a plasma drawing opening 1a. A plurality of cusp-type magnetic field generating coils 2 are arranged side by side along the axial direction on the outer circumference of the cylindrical vacuum container 1 in the circumferential direction, and these cusp-type magnetic field generating coils 2 are alternately excited by a direct current in opposite directions. , Thereby generating a cusp magnetic field aligned along the axial direction. At a position between the adjacent coils 2, the cylindrical vacuum chamber 1 has a gas inlet 3
And each gas inlet 3 is connected to a suitable gas supply source (not shown). Further, a plurality of annular high-frequency electrodes 4 extending along the inner peripheral wall of the cylindrical vacuum container 1 are arranged, and each high-frequency electrode 4 has a high-frequency power source 5 as shown in the drawing.
It is connected to the. Further, as shown in FIG. 2, the high-frequency electrode 4 has a cylindrical shape so as to form a high-frequency electric field (indicated by a solid arrow) between adjacent cusp-type magnetic fields (indicated by dotted lines) generated by the cusp-type magnetic field generating coil 2. Are positioned along the axial direction of the vacuum container 1. Also,
In FIG. 1, reference numeral 6 denotes a sample, and in the illustrated embodiment, the plasma is drawn from the drawing opening 1a of the vacuum container 1, but the drawing opening 1a of the vacuum container 1 is accelerating and decelerating electrodes in a usual manner. Can be provided, and the sample 6 can be extracted in the form of ions to subject the sample 6 to processing such as deposition and etching.

In the operation of the illustrated apparatus thus configured, the cylindrical vacuum container 1 is provided by applying a reverse direct current to each adjacent cusp magnetic field generating magnet 2 provided on the outer periphery of the cylindrical vacuum container 1. A cusp magnetic field is generated along the axial direction of, and a high-frequency electric field is applied by each high-frequency electrode 4 positioned at a position where magnetron discharge is effective for each cusp magnetic field. As a result, the electrons move in the magnetron near each high-frequency electrode, and the cylindrical vacuum chamber 1
A large number of electron rings that make a magnetron motion along the axis of are formed, and plasma is generated around each electrode 4. The plasma thus generated diffuses along the magnetic lines of force of each cusp magnetic field to the central region of the cusp magnetic field where the magnetic field strength is almost zero. This makes it possible to form a uniform plasma having a large area.

To test the significance of the device according to the invention,
As a result of the analysis of the uniformity of the plasma density distribution in the container using the spectrum analysis method, the intensity of the spectral line in the apparatus according to the present invention increases with the increase of the high frequency power applied to the high frequency electrode, and is flat in the central portion. It was confirmed that a uniform distribution of plasma was obtained. As a comparative example, when the conventional mirror type magnetic field was used, the strength of the central portion of the container was lower than that of the peripheral portion, and a uniform plasma distribution could not be obtained. In addition, as a result of measuring the ion current density using a Faraday cup, the device according to the present invention has a magnetic field strength substantially the same as that of a device using a conventional mirror type magnetic field and is three times or more at the same high frequency power. Ion current densities are obtained, which means that the device according to the invention can generate ions with higher power efficiency than the conventional devices.

By the way, in the illustrated embodiment, the plasma generating chamber is formed in a cylindrical shape, but it may be formed in a cylindrical shape having an arbitrary cross-sectional shape if necessary.

[0014]

As described above, according to the present invention, a plurality of cusp magnetic field generating coils are arranged side by side along the axial direction on the outer circumference of the cylindrical container that can be evacuated, and these cusp magnetic field generating coils are arranged. Are alternately excited by a direct current in the opposite direction, and a plurality of high-frequency electrodes are arranged at positions in the cylindrical container where magnetron discharge is effective for the cusp magnetic field generated by each cusp magnetic field generating coil. , A number of magnetron-moving electron rings can be formed along the axial direction of the cylindrical container, stable and high-density plasma can be generated at low pressure, and high-frequency power and direct current value for magnetic field generation It is possible to increase the diameter and the area without changing the temperature, and it is possible to easily provide a low-output, large-area plasma source.

[Brief description of drawings]

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

FIG. 2 is an enlarged line cross-sectional view of a main part of the device shown in FIG.

FIG. 3 is a schematic diagram showing the principle of a conventional ECR discharge type plasma generator.

FIG. 4 is a schematic view showing the principle of a conventional bucket type plasma generator.

FIG. 5 is a schematic diagram showing the principle of a conventional magnetron discharge type plasma generator.

[Explanation of symbols]

 1: Vacuum container 4: High frequency electrode 1a: Vacuum container extraction opening 5: High frequency power supply 2: Casp magnetic field generating coil 3: Gas inlet

Continued Front Page (72) Inventor Eiji Yabe 1-9 Tonosawa, Shimizu City, Shizuoka Prefecture

Claims (1)

[Claims] 1. A plurality of cusps that are arranged side by side along the axial direction on the outer circumference of a cylindrical container that can be evacuated, and are alternately excited by a direct current in the opposite direction to generate cusp magnetic fields arranged along the axial direction. A plasma generator comprising: a magnetic field generating coil; and a plurality of high-frequency electrodes arranged at positions in a cylindrical container where magnetron discharge is effective for a cusp magnetic field generated by each cusp magnetic field generating coil. .