JP3121669B2 - Microwave plasma generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave plasma generator used, for example, as an ion source for various devices.

[0002]

2. Description of the Related Art Conventionally, a microwave plasma generator has
It is used as an ion source for a neutral particle injection heating device for nuclear fusion, a plasma dry etching device used for manufacturing semiconductor devices, and an ion source such as a plasma vapor deposition device.

Hereinafter, a conventional example of an ion source which is one of the microwave plasma generators will be described with reference to FIGS. 4 is a cross-sectional view showing a schematic configuration of a first conventional example , FIG. 5 is a cross-sectional view showing an enlarged main part of FIG. 4, and FIG. 6 is an enlarged view of a main part of a second conventional example. FIG.

First, in the first conventional example shown in FIGS. 4 and 5, reference numeral 1 denotes a discharge vessel, which is provided at a microwave inlet 3 formed in an upper plate 2 of the discharge vessel 1. A microwave is not introduced into the discharge vessel 1 from the
One end of a waveguide 5 to be introduced through the vacuum window 4 is attached. 6 is an outer surface and a side wall 7 of the upper plate 2 of the discharge vessel 1.
The magnetic field and the magnetic filter that define the plasma confined region 8 in the discharge vessel 1 are formed by the permanent magnets disposed on the outer surface of the discharge vessel 1. Numeral 9 denotes magnetic lines of force schematically shown.

A predetermined gas is introduced into the discharge vessel 1 from a gas inlet (not shown), and an electrode portion 10 for extracting an ion beam from the discharge vessel 1 to the outside is provided. I have.

In the first conventional example configured as described above,
A predetermined gas introduced from the gas inlet is discharged by the microwave, and plasma is generated. The generated plasma is separated from the inner wall surface of the discharge vessel 1 by the magnetic field, and is confined in the plasma confinement region 8 so as to reduce the loss. And from the plasma through the electrode part 10
The ion beam is extracted to the outside.

However, in the above-mentioned first conventional example , the waveguide 5 is provided so that the vacuum window 4 is not directly exposed to the plasma.
And the inside of the waveguide 5 up to the vacuum window 4 has the same atmosphere as the inside of the discharge vessel 1 through the microwave introduction port 3. Also, a magnetic field is formed in one end of the waveguide 5 attached to the microwave introduction port 3 by the line of magnetic force 9 by the permanent magnet 6 crossing.

For this reason, plasma may be generated in the discharge vessel 1 and plasma may also be generated in one end of the waveguide 5. When plasma is generated in the waveguide 5, the microwaves reflected or blocked by the plasma propagate in the waveguide 5. By reflection or blocking
If the microwave is not sufficiently introduced into the discharge vessel 1,
Plasma cannot be generated efficiently.

On the other hand, in the second conventional example shown in FIG. 6, a magnetic field is formed in the discharge vessel 1 so that plasma is not generated in the waveguide 5 unlike the first conventional example. The permanent magnets 12 forming the plasma confinement region 11 are configured such that the arrangement intervals near the microwave inlet 3 are larger than those in the first example. Therefore, the permanent magnet 1
Among the two magnetic lines of force 12, few lines of magnetic lines 13 cross one end of the waveguide 5 attached to the microwave inlet 3.
The magnetic field in the waveguide 5 due to the lines of magnetic force 13 is weak.

In the second conventional example configured as described above,
Since the magnetic field generated in the one end of the waveguide 5 by the permanent magnet 12 is weak, even if plasma is generated in the discharge vessel 1, the discharge vessel 1 is generated through the microwave inlet 3.
Plasma is less likely to be generated in one end of the waveguide 5 communicating therewith.

However, in the plasma confinement region 11 formed in the discharge vessel 1, the microwave inlet 3
, The magnetic field is weak because the interval between the permanent magnets 12 is large. For this reason, the generated plasma cannot be confined enough to be separated from the inner wall surface of the discharge vessel 1, thereby causing a problem that the loss increases.

[0012]

As described above, since plasma is generated in the waveguide, microwaves cannot be sufficiently introduced, so that the density of the plasma cannot be increased, or the plasma confinement is poor due to poor plasma confinement. Plasma cannot be generated efficiently, for example, the loss of the plasma becomes large. The present invention has been made in view of such a situation, and an object of the present invention is to provide a microwave plasma generator capable of efficiently generating plasma.

[0013]

A microwave plasma generator according to the present invention has a discharge vessel in which a predetermined gas is introduced to form plasma therein, and one end attached to a microwave inlet of the discharge vessel. In a microwave plasma generator comprising a waveguide that has been subjected to plasma and plasma confinement means for confining plasma by forming a magnetic field in the discharge vessel, the plasma confinement means is provided at a portion adjacent to the microwave introduction port by the plasma confinement means. A magnetic field adjustment unit for reducing the strength of a magnetic field in one end of the waveguide is provided.

[0014]

In the microwave plasma generator constructed as described above, a magnetic field adjusting section for reducing the strength of the magnetic field in one end of the waveguide is provided at a portion adjacent to the microwave inlet of the plasma confining means. In the case where the magnetic field is weak in a limited area inside the microwave inlet and the waveguide attached to the microwave inlet and plasma is generated in the discharge vessel, the same as in the discharge vessel. No plasma is generated in the waveguide, which is a gas atmosphere. Therefore, introduction of the microwave into the discharge vessel is not hindered,
Plasma can be efficiently generated.

[0015]

BRIEF DESCRIPTION which is one ion source embodiment the microwave plasma generator of the present invention with reference to the drawings.

First, a first embodiment will be described with reference to FIGS. FIG. 1 is a sectional view showing a schematic configuration, and FIG. 2 is an enlarged sectional view showing a main part of FIG.

In FIG. 1 and FIG. 2, the discharge vessel 21 is
The lower end is a substantially cylindrical container having an opening 23 having a flange 22 on the outer periphery and an upper end closed by an upper plate 24. The inside of the discharge vessel 21 is reduced to a pressure of, for example, 0.1 Pa by an exhaust device (not shown), and the predetermined pressure is maintained.

A predetermined gas for forming plasma, for example, hydrogen gas (H ₂ ) is introduced into the discharge vessel 21 from a gas inlet (not shown).

Further, the discharge vessel 21 has a microwave inlet 25 formed at the center of the upper plate 24. The microwave inlet 25 has a waveguide 26 and one end 27 thereof.
Are attached so as to open into the discharge vessel 21. The other end of the waveguide 26 is connected to a microwave generation source (not shown) that generates a microwave of, for example, 2.45 GHz. Then, the microwave from the microwave generation source propagates in the waveguide 26, passes through the microwave inlet 25, and is introduced into the discharge vessel 21.

The waveguide 26 has a bent portion 28 provided at one end of the intermediate portion to bend the microwave transmission line at a substantially right angle, and further has a microwave introduction port on the other end side of the bent portion 28. A vacuum window 29 made of a material transparent to microwaves, for example, alumina ceramic or the like is mounted at a position that cannot be directly viewed from the position 25. The vacuum window 29 is mounted so that the main surface thereof intersects the microwave transmission path of the waveguide 26, whereby the waveguide 26 is airtightly divided at one end 27 side and the other end side. You.

On the other hand, the opening 23 on the lower end side of the discharge vessel 21
The electrode portion 31 is attached and closed so that the insulating ring 30 is interposed between the electrode portion 31 and the flange 22. The electrode section 31 includes a plurality of electrodes 32 to which a predetermined voltage is applied by a power supply (not shown).
Are provided so as to be insulated and separated. A plurality of negative ion extraction holes 34 are formed in the center of each electrode 32.

On the outer surface of the discharge vessel 21, there is provided plasma confinement means 35 for confining the generated plasma by a magnetic field, whereby a plasma confinement region 36 is defined in the discharge vessel 21.

That is, on the outer surface of the disc-shaped upper plate 24,
On a concentric circle centered on the microwave introduction port 25, a material having high magnetic permeability, for example, iron (F
e) the magnetic field adjusting member 37, etc.
5 is arranged so as to surround the periphery. Further, the upper plate 24
Outside the magnetic field adjusting member 37 on the outer surface, a plurality of annular permanent magnets 38 are arranged concentrically at predetermined intervals.

Similarly, a plurality of annular permanent magnets 4 are arranged on the outer surface of the cylindrical side wall 39 of the discharge vessel 21 so as to be concentric with the permanent magnet 38 of the upper plate 24 in the axial direction of the side wall 39.
0 are arranged at predetermined intervals. Further, on the outer surface of the side wall 39 on the lower end side of the discharge vessel 21, a permanent magnet 41 is disposed coaxially with the permanent magnet 40 and forms a magnetic filter near the opening 23.

Each of the permanent magnets 38, 40, 41 is magnetized in a direction toward the inside of the discharge vessel 21, and the permanent magnets 38, 40 are
Arranged so that adjacent objects have different polarities
ing. Reference numeral 42 denotes magnetic lines of force schematically shown.

At this time, a magnetic field adjusting member 37 is provided between the permanent magnet 38 located on the innermost periphery of the upper plate 24 and the microwave introduction port 25 so as to surround the microwave introduction port 25. As a result, the magnetic lines of force coming out of the permanent magnets 38 and 40 enter the adjacent permanent magnets 38 and 40, but the magnetic lines of force coming out of the innermost permanent magnet 38 toward the center are collected by the adjacent magnetic field adjusting member 37. I will.

Therefore, the lines of magnetic force crossing the microwave inlet 25 and the one end 27 of the waveguide 26 attached thereto are very small, and the magnetic field in a narrow range within the inner circumference circle of the magnetic field adjusting member 37 is very small. Vulnerable to On the other hand, the magnetic field formed by the permanent magnets 38 and 40 in a range outside the inner circumference circle of the magnetic field adjusting member 37 is capable of confining the generated plasma in a state separated sufficiently from the inner wall surface of the discharge vessel 21. It has become. Therefore, the plasma confinement region 36 partitioned in the discharge vessel 21 has a portion where the magnetic field is weak only in a narrow limited range.

In the present embodiment thus constructed, the inside of the discharge vessel 21 is depressurized by an exhaust device (not shown) to a predetermined pressure of the order of 0.1 Pa. A hydrogen gas, which is a gas for forming plasma, is introduced from this.

After the atmosphere conditions in the discharge vessel 21 have been adjusted, the inside of the waveguide 26 is
The microwave transmitted through the vacuum window 29 on the way,
It is introduced into the discharge vessel 21 through the microwave introduction port 25.

As a result, the microwave converts electrons into high energy
The acceleration accelerates, and a discharge plasm is generated in the discharge vessel 21.
You. The discharge plasma generated at this time is stored in the plasma confinement region 36 by the magnetic field adjusting member 37 and the permanent magnets 38 and 4.
Confined by a magnetic field due to zero.

The hydrogen ions pass through the ion extraction holes 34 while being accelerated by the respective electrodes 32 of the electrode section 31, and are extracted as an ion beam to the outside.

At this time, as described above, inside the one end 27 of the waveguide 26, the microwave inlet 2
5, the same gas atmosphere as in the discharge vessel 21 is obtained, but the magnetic field lines from the permanent magnets 38 are collected by the magnetic field adjusting member 37, and the microwave introduction port 25 and the waveguide 2
6, the magnetic field in one end 27 is very weak. For this reason, in the one end 27 of the waveguide 26, there is little possibility that plasma is generated in the same atmosphere as in the discharge vessel 21.
No.

Therefore, the microwaves propagating in the waveguide 26 are reflected by the plasma, which makes it difficult for the microwaves to be introduced into the discharge vessel 21 or reduces the density of the plasma. In order to maintain the above, there is no problem that the power of the microwave needs to be excessively increased. Then, the plasma can be efficiently generated.

On the other hand, since the magnetic field adjusting member 37 is disposed between the permanent magnet 38 located at the innermost periphery and the microwave introduction port 25 so as to be adjacent to the microwave introduction port 25, the plasma confinement region 36 has a portion where the magnetic field is weak only in a narrow limited range. For this reason, the generated plasma is transferred to the plasma confinement region 3.
6 can be confined at a sufficient distance from the inner wall surface of the discharge vessel 21, and the loss related to confinement is very small.

Next, a second embodiment will be described with reference to FIG. FIG. 3 is an enlarged sectional view showing a main part.

In FIG. 3, on the outer surface of the discharge vessel 21,
As in the first embodiment, a plasma confinement means 51 for confining generated plasma by a magnetic field is provided.
As a result, the plasma confinement region 52 is
Is partitioned.

That is, on the outer surface of the disk-shaped upper plate 24,
A plurality of annular permanent magnets 38 are arranged at predetermined intervals on a concentric circle centered on the microwave introduction port 25. Further, between the permanent magnet 38 located at the innermost circumference and the microwave introduction port 25, the strength of the magnetic pole is weaker than that of the permanent magnet 38, and is adjacent to the microwave introduction port 25 so as to surround the microwave introduction port 25. A magnetic field adjusting permanent magnet 5 which is manufactured in the same manner and has a magnetic pole area smaller than about 1/2
3 are provided.

On the outer surface of the cylindrical side wall 39 of the discharge vessel 21, an annular permanent magnet 40 coaxial with a permanent magnet 38 provided on the upper plate 24 and a permanent magnet 41 are arranged. Numeral 54 denotes lines of magnetic force schematically shown.

Then, between the permanent magnet 38 located on the innermost periphery of the upper plate 24 and the microwave introduction port 25, the permanent magnet 5 for magnetic field adjustment is adjacently disposed so as to surround the microwave introduction port 25.
3, the lines of magnetic force from each of the permanent magnets 38, 40 enter the adjacent permanent magnets 38, 40,
The lines of magnetic force coming out of the magnetic field adjusting permanent magnet 53 are collected by the adjacent innermost permanent magnet 38, and the magnetic field adjusting permanent magnet 53
The lines of magnetic force from the direction toward the center, that is, toward the microwave introduction port 25, almost disappear.

Therefore, the lines of magnetic force crossing the microwave inlet 25 and one end 27 of the waveguide 26 attached thereto are extremely small, and the magnetic field in a narrow range within the inner circumference circle of the magnetic field adjusting permanent magnet 53 is very small. Will be very weak. On the other hand, the magnetic field formed by the permanent magnets 38 and 40 in a range outside the inner circumferential circle of the magnetic field adjusting member 37 is capable of confining the generated plasma sufficiently away from the inner wall surface of the discharge vessel 21. It has become. Therefore, the plasma confinement region 36 partitioned in the discharge vessel 21 has a portion where the magnetic field is weak only in a narrow limited range.

Since the present embodiment is configured as described above, the magnetic field in one end 27 of the waveguide 26 becomes very weak, and the same operation and effect as those of the first embodiment can be obtained.

In each of the above embodiments, the magnetic field adjusting member 37 made of iron is used as the magnetic field adjusting portion of the plasma confinement means 35 and 51 in the first embodiment, but other materials having high magnetic permeability are used. In the second embodiment, the magnetic field adjusting permanent magnet 53 having a smaller magnetic pole area than the permanent magnet 38 surrounding the discharge vessel 21 is used. However, the present invention is not limited to this. It is sufficient that the permanent magnet is weaker than 38, and the present invention can be implemented with appropriate modifications without departing from the gist.

[0043]

As is apparent from the above description, according to the present invention, a magnetic field adjusting section for reducing the intensity of a magnetic field in one end of a waveguide is provided adjacent to a microwave inlet of a plasma confinement means. With such a configuration, an effect that plasma can be efficiently generated can be obtained.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view showing a main part of FIG.

FIG. 3 is an enlarged sectional view showing a main part of a second embodiment of the present invention.

FIG. 4 is a sectional view showing a schematic configuration of a first conventional example.

FIG. 5 is an enlarged sectional view showing a main part of FIG. 4;

FIG. 6 is an enlarged sectional view showing a main part of a second conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 21 ... Discharge container 25 ... Microwave introduction port 26 ... Waveguide 27 ... One end 35 ... Plasma confinement means 37 ... Magnetic field adjusting members 38, 40, 41 ... Permanent magnet

Continued on the front page (51) Int.Cl. ⁷ Identification code FI H05H 1/12 H01L 21/302 B

Claims (1)

(57) [Claims] 1. A discharge vessel in which a predetermined gas is introduced to form a plasma by introducing a gas, a waveguide having one end attached to a microwave introduction port of the discharge vessel, and a magnetic field in the discharge vessel. A microwave plasma generator comprising: plasma confinement means for forming and confining plasma.
The microwave confining means is provided with a magnetic field adjusting unit for reducing the strength of a magnetic field in one end of the waveguide by the plasma confining means adjacent to the microwave introduction port. Plasma generator.