JP2669005B2 - Plasma generator and ion source using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plasma generator that excites plasma by electron cyclotron resonance (ECR) using microwaves, and an ion source using the same.

[Conventional technology]

A conventional example of this type of plasma generator is disclosed in
No. 62-31999.

In summary, as shown in FIG. 6, in this plasma generator, a plurality of permanent magnets 4 are arranged inside the side surface 2a of the plasma generation container 2 so as to create a cusp magnetic field, and further microwave radiation is performed. The antenna 10 for the ECR on the center line 6 of each permanent magnet 4 is shown in FIG.
It is arranged at each point of the magnetic field strength that satisfies the condition (for example, 875 gauss for 2.45 GHz). Numeral 8 in both figures indicates the lines of magnetic force.

Then, when the inside of the plasma generating container 2 is evacuated and a gas is introduced into the plasma generating container 2 so as to have a predetermined pressure, and microwave power is supplied to each antenna 10, the microwave discharge satisfying the ECR condition causes each antenna 10 to be discharged. Around the plasma 14, and this is diffused along the diverging magnetic field of the permanent magnet 4 to the center of the plasma generating vessel 2.

[Problems to be solved by the invention]

However, in the above-mentioned device, the magnetic field lines 8 of the permanent magnet 4 and the electric field lines 12 (see FIG. 7) emitted from the antenna 10 are substantially orthogonal to each other, and the region satisfying the ECR condition is the The plasma 14 exists only in a very small area between the antenna 10 and the plasma 14 diffused from such a very small area.
Since the plasma regions 16 are overlapped with each other to form the central plasma region 16, there is a large difference in the density of the plasma density there, which makes it difficult to obtain a two-dimensionally uniform plasma.

Electrons and ions also concentrate at the strongest point of the cusp magnetic field where the magnetic lines of force 8 concentrate.
Due to the presence of 10, there is also a problem that the antenna 10 is sputtered by these particles, thereby easily generating impurities.

Accordingly, it is an object of the present invention to provide a plasma generator having the above-mentioned improvement and an ion source using the same.

[Means for solving the problem]

The plasma generator of the present invention is a device for exciting plasma by electron cyclotron resonance using microwaves, wherein a plurality of permanent magnets are provided in the circumferential direction of at least the side surface portion of the plasma generation container, and gaps are provided between them. hand,
In addition, the antennas for microwave radiation are arranged so that the polarities of the adjacent magnetic poles appear alternately, and an antenna for microwave radiation is provided in the plasma generation container on or near the center line between the adjacent permanent magnets. It is characterized in that it is arranged along the inner wall surface of.

Further, the ion source of the present invention is characterized in that an opening is provided in the plasma generating container as described above, and an extracting electrode for extracting an ion beam from the plasma generated in the plasma generating container is provided in the opening.

[Action]

In the above plasma generator, the lines of electric force emitted from the respective antennas are substantially orthogonal to the lines of magnetic force of the adjacent permanent magnets over a wider area than in the case of the conventional example. Therefore, the discharge region satisfying the electron cyclotron resonance condition is increased as compared with the conventional example.

Then, the plasma diffused from such a wide area is superimposed to form a central plasma area,
A plasma having a two-dimensionally uniform plasma density can be obtained.

Moreover, since each antenna avoids a place where the cusp magnetic field is strong, it is less likely to be sputtered by ions or electrons. As a result, generation of impurities is reduced.

In the above-mentioned ion source, an ion beam having a two-dimensionally uniform ion density and containing few impurities can be extracted for the same reason.

〔Example〕

FIG. 1 is a sectional view in the radial direction of the plasma generator according to the embodiment, and FIG. 2 is an axial sectional view of the apparatus in FIG.

In the plasma generator of this embodiment, for example, a plurality of permanent magnets 24 are provided inside the side surface 22a of the plasma generation container 22 having a cylindrical shape, more specifically, inside the side surface 22a with a gap between them, and It is arranged such that the polarities of the matching magnetic poles appear alternately as N, S, N... To create a cusp magnetic field.

As shown in FIG. 4 in an enlarged manner, the antenna 30 for microwave radiation is provided in the plasma generation container 22 along the inner wall surface thereof and on the center line 26 between the adjacent permanent magnets 24. Alternatively, they are arranged in the vicinity thereof. In the figure
Reference numeral 28 denotes a magnetic field line.

In addition, in this embodiment, referring to FIG. 3 as well, the antennas 30 are connected together to the coaxial connector 38 by gathering them together at the central portion of the bottom surface 22b of the plasma generating container 22. One coaxial microwave cable (not shown) is connected to the coaxial connector 38.

Furthermore, in this embodiment, the bottom surface 22b of the plasma generation container 22
Also for each radial antenna 30 inside, the side surface 22 described above
In the same relationship as in the case of the permanent magnet 24 of a, the permanent magnet 24 that creates a cusp magnetic field is arranged.

Explaining the operation example of this device, the plasma generation container 22
The inside of the chamber is evacuated and gas is supplied at a predetermined pressure (for example,
1Torr ~ 10 ^-4 Torr) and when microwave power is supplied to each antenna 30 via the coaxial connector 38, a wide area around each antenna 30 is generated by microwave discharge that satisfies the ECR condition. At this time, the plasma 34 is excited, and is diffused along the diverging magnetic field of the permanent magnet 24 to the center of the plasma generating vessel 22.

In this case, in this embodiment, the adjacent permanent magnets 24
Lines of electric force 32 exiting from each antenna 30 placed in the middle of
For example, as shown in FIG. 4, the magnetic flux lines 28 of the adjacent permanent magnets 24 are substantially orthogonal to the magnetic field lines 28 over a wider area than in the conventional example. Therefore, the discharge region satisfying the ECR condition is greatly increased as compared with the conventional example.

And the plasma emitted from such a wide area 34
Are overlapped with each other to form a plasma region 36 (see FIG. 1) in the central portion, the difference in density of the plasma density there becomes small, so that the plasma 34 having a two-dimensionally uniform plasma density is obtained.

In addition, since the discharge region satisfying the ECR condition is increased as compared with the conventional example, the overall plasma density is also increased as compared with the conventional example.

Further, since each antenna 20 avoids a place where the cusp magnetic field 28 where the magnetic force lines 28 are concentrated, that is, a place where ions and electrons are concentrated, the antenna 30 is less likely to be sputtered by these particles, and thus the impurities Occurrence is reduced.

Further, as in this embodiment, it is preferable that a permanent magnet 24 is also provided at the portion of the antenna 30 on the bottom surface 22b of the plasma generation container 22 so that the ECR condition is satisfied there as well. Since the plasma generation source can be formed not only in the side surface 22a of the generation container 22 but also in the bottom surface 22b, and the extinction of the plasma 34 on the bottom surface 22b can be prevented, the plasma 34 having a higher density is also formed from this viewpoint. Can be obtained. That is, the inside of the bottom surface 22b can be effectively used.

Further, in the conventional device, although not shown, each antenna 10 is pulled out from the plasma generation container 2 through the through terminal one by one from the bottom surface of the plasma generation container 2, and is connected to a large number of micro coaxial cables there. , A complicated microwave circuit is required to connect many microwave coaxial cables to waveguides, etc.
In addition, there is a risk that microwaves leak from the connection portion into the atmosphere, and there is also a risk of vacuum leak at a large number of penetrating terminals.

In contrast, as in this embodiment, each antenna 30
Are preferably integrated into one in the bottom surface 22b of the plasma generation container 22 and pulled out from one coaxial connector 38, which simplifies the microwave circuit outside the plasma generation container 22. Also, the possibility of microwave leakage is reduced. Also, the possibility of vacuum leak is reduced.

By the way, the plasma generator as described above, for example,
The present invention can be used for a plasma CVD apparatus, an ion etching apparatus, and the like, and can be used as an ion source by further adding an extraction electrode.

Fig. 5 shows an example of application to an ion source. That is, the ion source is provided with an opening 22c on one surface of the plasma generating container 22 as described above, and a porous (or mesh-like) extraction electrode is provided in the opening 22c through an insulator 40, for example. 42 is provided, and when an appropriate extraction voltage is applied to the extraction electrode 42, the plasma generated in the plasma generation container 22 as described above is generated by the action of the electric field.
From the ion beam 44.

In this case, as described above, the two-dimensional uniformity of the density of the plasma 34 is good, and the amount of impurities mixed into the plasma 34 is small, so that the ion beam has a two-dimensionally uniform ion density and a small amount of impurities. 44 can be pulled out.

Note that the configuration of the extraction electrode provided when the ion source is used is not limited to one as shown in the illustrated example, and various configurations can be adopted according to the purpose and the like.

Further, in each of the above-described plasma generator and ion source, an example in which the permanent magnet 24 is provided inside the plasma generation container 22 is shown, but these permanent magnets 24 are used in the plasma generation container.
It is also possible to arrange outside 22.

Further, the shape of the plasma generation container 22 is not limited to the cylindrical shape as in the above example, but may be various shapes such as a rectangular tube shape and a box shape.

〔The invention's effect〕

As described above, according to the plasma generator of the present invention,
Since the antennas are respectively arranged on or near the center lines between the adjacent permanent magnets, the lines of electric force emitted from each antenna are substantially orthogonal to the lines of magnetic force emitted from the adjacent permanent magnets on both sides over a wide area. The discharge area that satisfies the ECR condition is increased, so that a plasma having a two-dimensionally more uniform plasma density can be obtained. Further, since the discharge region satisfying the ECR condition increases, the overall plasma density also increases. Therefore, it is possible to obtain plasma with high uniformity in two dimensions and high density as a whole.

Moreover, by arranging the antennas at the above positions, it is possible to avoid the antennas from the place where the magnetic lines of force are concentrated and the ions and electrons are concentrated, so that each antenna is sputtered by the ions and electrons in the plasma. And the generation of impurities is also reduced. Therefore, plasma with few impurities can be obtained.

Further, according to the ion source of the present invention using the above-described plasma generator, for the same reason as above, an ion beam having a two-dimensionally uniform ion density, a high overall density, and a small amount of impurities can be generated. Can be withdrawn.

[Brief description of the drawings]

FIG. 1 is a sectional view in the radial direction of a plasma generator according to an embodiment. FIG. 2 is an axial sectional view of the apparatus of FIG. FIG. 3 is a front view showing the area around the antenna on the bottom surface of the apparatus shown in FIG. FIG. 4 is an enlarged view of a part around the permanent magnet of the apparatus shown in FIG. FIG.
It is sectional drawing which shows the ion source which concerns on an Example. FIG.
It is a radial sectional view of a conventional plasma generator.
FIG. 7 is an enlarged view of a part around the permanent magnet of the apparatus of FIG. 22 …… Plasma generating container, 22a …… Side, 22b …… Bottom,
22c ... opening, 24 ... permanent magnet, 30 ... antenna, 34
... plasma, 42 ... extraction electrode, 44 ... ion beam.

Claims (2)

(57) [Claims] 1. An apparatus for exciting plasma by electron cyclotron resonance using microwaves, comprising a plurality of permanent magnets in the circumferential direction of at least a side surface portion of a plasma generation container, with a gap between them, Antennas for microwave radiation are arranged so that the polarities of adjacent magnetic poles appear alternately and on the center line between adjacent permanent magnets in the plasma generation container or in the vicinity thereof, respectively. A plasma generator characterized by being arranged along an inner wall surface. 2. The plasma generator of the plasma generator according to claim 1, wherein an opening is provided in the plasma generator, and an extraction electrode for extracting an ion beam from the plasma generated in the plasma generator is provided in the opening. Ion source.