JPH06101308B2 - Microwave plasma processing equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a microwave plasma processing apparatus that performs a surface treatment of a sample with plasma generated by an interaction between a microwave and a magnetic field.

[Conventional technology]

Plasma is generated by microwave power, and a solenoid coil is arranged around the chamber for generating plasma. The magnetic field generated by this solenoid coil and the cyclotron motion of electrons due to the electric field of the microwave are used to further generate plasma. , A microwave plasma processing apparatus that performs surface treatment of a sample with ions in plasma is
For example, it is known from JP-A-57-177975.
The outline of such a microwave plasma processing apparatus will be described with reference to the drawings.

FIG. 8 is a sectional view of a conventional microwave plasma processing apparatus. In the figure, 1 is a microwave oscillator for generating microwaves, 2 is a waveguide for transmitting the microwave power generated by the microwave oscillator 1, 3 is a container connected to the waveguide 2, 4
Denotes a plasma generation chamber formed by the container 3, 5 denotes an entrance window for introducing microwaves into the plasma generation chamber 4, and 6 denotes plasma generated in the plasma generation chamber 4. Reference numerals 7a and 7b are solenoid coils provided outside the container 3, 8 is an ion extraction electrode for extracting the ions in the plasma 6, and 9 is a processing device for performing various processes by the extracted ions. Ten
Is a sample supported by a holder (not shown) in the processing device 9, 11 is ions extracted by the ion extracting device 8,
Reference numeral 12 denotes an evacuation device that evacuates the plasma generation chamber 4 and the processing device 9.

When a predetermined gas is introduced into the plasma generation chamber 4 while microwaves are being radiated into the plasma generation chamber 4, the gas causes
Electrons that have been turned into plasma and that are present in the plasma 6 undergo cyclotron motion under the influence of the magnetic field formed by the solenoid coils 7a and 7b. Due to the cyclotron motion of the electrons, the electrons collide with neutral particles such as molecules and atoms in the container 16 and ionize the particles to generate ions. By repeating such an operation, the introduction gas is turned into plasma significantly, and the plasma generation efficiency is improved. When 2.45GHz, which is industrially assigned by the Radio Law, is used as the microwave frequency, the magnetic flux density that satisfies the cyclotron resonance (ECR) condition for causing cyclotron motion in electrons is 0.0875 Tesla.

Ions existing in the plasma 6 thus formed are extracted by the ion extracting device 8 (consisting of a plurality of electrodes) and introduced into the processing device 9 together with the ion shower 11. Using the ion shower 11, processing such as milling and etching on the sample 10 is performed.

[Problems to be solved by the invention]

By the way, in the microwave plasma processing apparatus as described above, when the processing such as milling and etching for the sample 10 is completed, the sample 10 is taken out, replaced with an unprocessed sample, and the same processing is repeated again. Be done. Therefore, in order to improve the processing efficiency (productivity efficiency), it is necessary to process a larger number of samples at one time, and for that purpose, the cross-sectional area of the plasma generation chamber 4 may be increased. However, in order to obtain a good degree of coupling of microwaves incident on the plasma generation chamber 4, the cross-sectional area of the plasma generation chamber 4 must be selected to approximate the cross-sectional area of the microwave waveguide 2. As a result, it was impossible to increase the cross-sectional area of the plasma generation chamber 4 and improve the processing efficiency of the sample 10.

In a microwave plasma generator that does not use ECR with an external magnetic field, a means for gradually expanding the plasma in the plasma generating unit is disclosed, for example, as described in Japanese Patent Application Laid-Open No. 56-1124722. However, this method is to generate plasma by ionizing by the microwave electric field of the inner conductor of the coaxial waveguide.Unlike plasma generation by ECR, this plasma is the surface of the plasma generation unit, that is, the insulation that constitutes the plasma generation unit. It is generated on the inner wall surface. Such plasma contains impurities from the wall surface,
In addition, there is a problem that it is difficult to obtain a high-density and highly pure product because the loss on the wall surface is large.

An object of the present invention is to solve the above-mentioned problems of the prior art, and to improve the processing efficiency by increasing the processing area without impairing the coupling degree of the microwave incident on the plasma generation chamber. To provide the equipment.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention transmits microwave power generated by a microwave oscillator through a waveguide and introduces it into a plasma generation chamber, and generates a magnetic field inside the plasma generation chamber. Ions are extracted from the generated plasma into the processing chamber with an ion extraction device,
In a microwave plasma processing apparatus that performs processing on a sample using these ions, the plasma generation chamber has a cross-sectional area of the plasma generation chamber between the opening of the waveguide and the ion extractor, which is closer to the opening of the waveguide. From the ion extraction device side toward the ion extraction device side.

[Action]

Microwaves transmitted by a waveguide of a predetermined shape have a mode that is determined by the shape of the waveguide, and if the shape of the waveguide is changed abruptly, the above mode cannot be maintained,
Reflections and losses are significantly increased. According to the present invention, in the plasma generation chamber, the cross-sectional area of the plasma generation chamber increases substantially continuously from the opening side of the waveguide toward the ion extraction device side between the opening to the waveguide and the ion extraction device. Since the portion to be provided is provided, the cross-sectional area on the side of the ion extracting device can be increased while maintaining the above mode, and the ions can be extracted from a large area.

〔Example〕

 Hereinafter, the present invention will be described based on the illustrated embodiments.

FIG. 1 (a) is a sectional view of a microwave plasma processing apparatus according to the first embodiment of the present invention, and FIGS. 1 (b) and 1 (c) are respectively lines Ib-Ib, of FIG. 1 (a). A sectional view taken along Ic-Ic,
FIG. 1 (d) is a magnetic field distribution diagram in the plasma generation chamber of the apparatus shown in FIG. 1 (a). In the figure, those parts that are the same as those corresponding parts in FIG. 8 are designated by the same reference numerals, and a description thereof will be omitted. Reference numeral 15a denotes a plurality of permanent magnets arranged on the same circumference in the vicinity of the entrance window 5 as shown in FIG. 1 (b), so that the S pole of each permanent magnet faces the plasma generation chamber 4. It is arranged.

Reference numeral 15b denotes a plurality of permanent magnets which are adjacent to the permanent magnet 15a and are arranged on the same circumference larger than the circumference thereof, and like the permanent magnet 15a, its S pole faces the plasma generation chamber 4. Reference numeral 15c denotes a plurality of permanent magnets arranged away from the permanent magnet 15b on the processing device 9 side, and each N pole is arranged on the same circumference larger than the permanent magnet 15b so as to face the plasma generation chamber 4. As shown in FIG. 1 (c), 15d is a plurality of permanent magnets arranged adjacent to the permanent magnet 15c on the processing device 9 side, and each N pole is on the same circumference larger than the permanent magnet 15c. Are arranged so as to face the plasma generation chamber 4. Reference numeral 16 is a container configured to be inscribed in each of the permanent magnets 15a to 15d. Reference numeral 17 denotes an ion extraction electrode provided at the end of the container 16 on the side of the processing device 9. In order to extract a positive ion from the plasma 6 by applying a negative potential to the plasma electrode 17a in contact with the plasma 6 and the plasma electrode 17a. Of the extraction electrode 17b and the grounding electrode 17c that is set to the ground potential similarly to the processing device 9.

Next, the operation of this embodiment will be described with reference to the magnetic flux distribution chart shown in FIG. In FIG. 1 (d), the horizontal axis represents the magnetic flux density, and the vertical axis represents the axial distance of the plasma generation chamber 4. After the whole is evacuated to a high vacuum of about 10 ^-6 Torr by the vacuum exhaust device 12, the plasma generation chamber 4 is filled with a required gas such as argon or CF ₄ at 10 ^-3 to 10 ^-4 Torr.
When the microwave is incident on the gas, the filled gas is turned into plasma.

On the other hand, a magnetic field having the magnetic flux density distribution shown in FIG. 1D is generated in the plasma generation chamber 4 by the permanent magnets 15a to 15d. The magnetic flux density of this magnetic field has a region A that gradually decreases from the position where the magnetic flux density is maximum toward the ion extraction electrode side. Due to the presence of such a magnetic field, cyclotron motion of electrons in the plasma 6 occurs, the electrons collide with neutral particles, and ions with relatively low kinetic energy (low ion temperature) are generated. The generation efficiency of the plasma 6 is highest near the maximum magnetic flux density, and the plasma 6 generated near this is transported to the ion extraction electrode 17 by the magnetic flux density gradient in the region A.

Since the container 16 is inscribed in each of the permanent magnets 15a to 15d, the magnetic flux density near the inner surface of the container 16 is substantially equal on both the microwave incident side and the ion extraction electrode 17 side, and is substantially the same distance from the wall surface of the container 16. From this point, it is possible to obtain a magnetic flux density that satisfies the ECR condition. As a result, as shown in FIG. 1A, the plasma generation region can be gradually widened from the microwave incident side toward the ion extraction electrode 17, and the ion extraction area can be widened.

The ions extracted from the plasma 6 by the ion extraction electrode 17 are generally positively charged ions 11, and the extracted ions 11 are accelerated and irradiated on the sample 10.
The pattern processing is performed on 10 by a required process such as milling or etching.

As described above, in this embodiment, the magnet array radius is small on the microwave incident side and the magnet array radius is large on the ion extraction electrode side, and the container 16 is formed inscribed in each of these magnets. The ion extraction area can be increased without impairing the coupling degree of the microwave incidence, and the processing efficiency can be improved by increasing the processing area. In addition, when rare earth is used as a permanent magnet, a magnetic field of 0.1 Tesla or more can be easily obtained, which makes it possible to provide a stable DC power supply and cooling device for the magnetic field generation required when an electromagnetic coil is used. It can be omitted, and thus cost reduction and occupancy area reduction can be achieved.

FIG. 2 is a sectional view of the microwave plasma processing apparatus according to the second embodiment of the present invention. In the figure, the same parts as those shown in FIG.
Reference numerals 19a and 19b are electromagnetic coils, and the diameter of the electromagnetic coil 19a on the microwave incident side is the electromagnetic coil 19b on the ion extraction electrode 17 side.
Is smaller than the diameter of. By supplying a current to these electromagnetic coils 19a and 19b, a magnetic flux density distribution near the central axis of the plasma generation chamber forms a magnetic field that gradually decreases from the microwave incident side toward the ion extraction electrode 17 as in the previous embodiment. can do. Therefore, also in this embodiment, the ion extraction area can be widened and the processing capacity can be improved without impairing the coupling degree of the microwave incidence on the plasma generation chamber.

FIG. 3 is a sectional view of the microwave plasma processing apparatus according to the third embodiment of the present invention. In the figure, the same parts as those shown in FIG.
Reference numeral 20 denotes an electromagnetic coil arranged near the microwave entrance. A current is supplied to the electromagnetic coil 20 so as to form a magnetic field in the same direction as the magnetic field formed by the permanent magnets 15a and 15b. The magnetic field of the electromagnetic coil 20 can maximize the magnetic flux density in the vicinity of the microwave entrance of the plasma generation chamber 4, thereby suppressing the diffusion loss of the generated plasma in the direction of the microwave entrance window 5. The plasma density can be increased.

In this embodiment, since the electromagnetic coil is used together with the permanent magnet, the magnetic field distribution can be controlled with high accuracy, and the plasma generation efficiency can be increased. The effect of widening the ion extraction area and improving the processing capacity is the same as that of the first embodiment.

FIGS. 4 (a) and 4 (b) are a longitudinal sectional view and a lateral sectional view of a microwave plasma processing apparatus according to the fourth embodiment of the present invention. In the figure, the same parts as those shown in FIG. In each of the above-described embodiments, the container 16 forming the plasma generation chamber 4 is only a truncated cone, but in the present embodiment, it is connected to the ion extraction electrode 17 side of the truncated cone container 16. It has a cylindrical container 21. Reference numeral 22 is a permanent magnet arranged around the container 21. FIG. 4 (b) is a sectional view taken along line IVb-IVb in FIG. 4 (a), which shows the arrangement and polarity of the permanent magnets 22. Reference numeral 23 is a plasma expansion chamber formed by the container 21. The plasma expansion chamber 23 communicates with the plasma generation chamber 4.

The permanent magnets 22 are arranged such that the adjacent magnets have opposite polarities as shown in FIG. 4 (b). Therefore, a magnetic field toward the adjacent magnet is formed near the inner wall surface of the container 21 in the plasma expansion chamber 23, and the magnetic field can confine the plasma 6 at a position away from the wall surface of the container 21.

In the present embodiment, the magnetic field in the vicinity of the center of the plasma expansion chamber 23 is very small, and the plasma density distribution in the plasma expansion chamber 23 has a characteristic that the radial direction plasma density distribution is substantially uniform. By arranging the ion extracting electrode 17 at the same position, not only the same effect as in the first embodiment can be obtained, but also an ion beam having a uniform distribution can be obtained, and as a result, the plasma processing apparatus can obtain a uniform processing characteristic with high accuracy. You can also get

FIG. 5 is a sectional view of a microwave plasma processing apparatus according to the fifth embodiment of the present invention. In the figure, the same parts as those shown in FIG.
Reference numeral 25 denotes a permanent magnet magnetized in the axial direction, and a plurality of permanent magnets 25 are arranged outside the plasma generation chamber so that the magnetic poles coincide with each other in the axial direction. By using such a permanent magnet 25, the present embodiment has the same effects as the first embodiment, can maximize the characteristics of the permanent magnet, and can be easily attached. It also has the effect of reducing the radial dimension.

FIG. 6 is a sectional view of a microwave plasma processing apparatus according to the sixth embodiment of the present invention. In the figure, the same parts as those shown in FIG.
27 is a semi-circular or U-shaped permanent magnet. This permanent magnet
A plurality of 27 are arranged on the outer periphery of the plasma generation chamber 4,
Each of the permanent magnets 27 is magnetized in the arc direction and arranged so that the polarities of their respective magnetic poles match in the axial direction. This embodiment has the same effect as the first embodiment, and since the magnetic field created by the permanent magnet 27 is closed inside the magnet outside the plasma generation chamber 4, the leakage flux is reduced and the magnetic field inside the plasma generation chamber is reduced. It also has the effect that it can be strengthened, and by extension, the plasma generation efficiency can be increased.

FIG. 7 is a sectional view of the microwave plasma processing apparatus according to the seventh embodiment of the present invention. In the figure, the same parts as those shown in FIG.
Reference numeral 29 denotes a permanent magnet arranged on the outer circumference of the plasma generation chamber 4 with an inclination. These permanent magnets 29 are magnetized in the width (or thickness) direction so that the magnetization direction becomes the radial direction,
The adjacent permanent magnets are arranged so that their polarities are reversed. It is clear that the magnetic flux density of the magnetic field formed by these permanent magnets 29 becomes gradually smaller from the microwave incident side toward the ion extraction electrode 17 side, as in the previous embodiments, and FIG. As shown in b), the vicinity of the wall surface of the plasma generation chamber is large and gradually decreases toward the center of the plasma generation chamber 4. In such a magnetic flux density distribution,
If the strength of the magnet is made sufficiently large and the magnetic flux density satisfying the ECR condition is given, plasma can be efficiently generated. The plasma generated near the wall surface of the plasma generation chamber 4 is transported to the center of the plasma generation chamber 4 and toward the ion extraction electrode 17 due to the gradient of the magnetic field.

The present embodiment has the same effect as the first embodiment, and has the effect that a uniform ion beam can be extracted.

〔The invention's effect〕

As described above, in the present invention, between the microwave introduction part and the ion extraction electrode, the plasma generation chamber is a part where the cross-sectional area continuously increases from the microwave introduction part side toward the ion extraction electrode side. Since it is configured so that the ion extraction area can be widened without deteriorating the coupling degree of the microwave incident on the plasma generation chamber, the processing area can be increased and the processing efficiency can be improved.

[Brief description of drawings]

FIG. 1 (a) is a sectional view of a microwave plasma processing apparatus according to the first embodiment of the present invention, and FIGS. 1 (b) and 1 (c) are respectively lines Ib-Ib shown in FIG. 1 (a). , Ic-Ic cross-sectional view, FIG. 1 (d) is a magnetic flux density distribution diagram of the apparatus shown in FIG. 1 (a), and FIGS. 2 and 3 are second and third embodiments of the present invention, respectively. 4A is a sectional view of a microwave plasma processing apparatus according to an example, FIG. 4A is a sectional view of a microwave plasma processing apparatus according to a fourth embodiment of the present invention, and FIG. ) Is a cross-sectional view taken along line IVb-IVb shown in FIG. 5, FIG. 6, FIG. 6 and FIG. 7 are cross-sectional views of a microwave plasma processing apparatus according to fifth, sixth and seventh embodiments of the present invention, respectively. FIG. 8 is a sectional view of a conventional microwave plasma processing apparatus. 1 ... Microwave oscillator, 2 ... Waveguide, 4 ... Plasma storage chamber, 6 ... Plasma, 9 ... Processor, 10 ... Sample, 15a-15d, 25,27,29 ... Permanent Magnet, 16 ... container, 17
...... Ion extraction electrodes, 19a, 19b, 20 …… electromagnetic coils.

Claims (6)

[Claims] 1. A microwave oscillator, a waveguide for transmitting microwave power generated by the microwave oscillator, a plasma generation chamber having an opening for the waveguide, and a magnetic field generated in the plasma generation chamber. In a microwave plasma processing apparatus comprising a magnetic field generator, an ion extractor for extracting ions from the plasma generated in the plasma generating chamber, and a processing chamber utilizing the extracted ions,
In the plasma generation chamber, the cross-sectional area of the plasma generation chamber is substantially continuous from the opening side of the waveguide toward the ion extraction device side between the opening to the waveguide and the ion extraction device. A microwave plasma processing apparatus, characterized in that the microwave plasma processing apparatus has an increasing portion. 2. The microwave plasma processing apparatus according to claim 1, wherein the magnetic field generation device is an electromagnetic coil arranged along an outer surface of the plasma generation chamber. 3. The magnetic field generating device according to claim 1, wherein the magnetic field generating device is a permanent magnet arranged so as to form an axial magnetic field along the outer surface of the plasma generating chamber. Microwave plasma processing equipment. 4. The permanent magnet according to claim 3, wherein the permanent magnets are arranged such that adjacent magnetic poles have the same polarity along the circumferential direction of the outer periphery of the plasma generation chamber. Microwave plasma processing equipment. 5. The permanent magnet according to claim 3, wherein the permanent magnets are arranged such that adjacent magnetic poles along the circumferential direction of the outer periphery of the plasma generation chamber have opposite polarities. Microwave plasma processing equipment. 6. The plasma generation chamber according to claim 1, wherein the plasma generation chamber has an opening on the ion extractor side, the plasma storage chamber having a larger area than the opening, and the magnetic poles adjacent to each other along the outer periphery of the plasma storage chamber. The microwave plasma processing apparatus is characterized in that a permanent magnet is provided so that the magnets have opposite polarities.