JP3409397B2 - Ion source - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion source used in, for example, an ion implantation apparatus, a surface treatment apparatus using an ion beam, or the like, and more specifically, a thermal strain of an electrode constituting its extraction electrode system. Regarding means for reducing.

[0002]

2. Description of the Related Art An ion source is composed of a plasma source section for producing plasma by using a filament and an extraction electrode system for extracting an ion beam from the plasma source section and having one or more electrodes. There is.

Conventionally, carbon, copper, molybdenum, etc. have been used as the material of the electrodes constituting the extraction electrode system of such an ion source.

In particular, molybdenum has a large thermal stability in an ion source for generating a large area ion beam using a porous electrode, and has a small sputtering rate, a small change in shape due to sputtering, and a small amount of impurities. It is often used for reasons such as.

However, since the ion source uses a high-temperature filament to generate plasma, the temperature of the electrode rises due to heat radiation from the filament. Alternatively, at the downstream electrode, the temperature rises due to the incident ions due to divergence. In particular, the temperature rise due to the latter is remarkable when the ion current density is large as in an ion source for plasma heating or surface treatment.

Therefore, in order to suppress the deformation of the electrode caused by the temperature rise due to such a cause, conventionally, the electrode is usually cooled by a cooling structure in which the electrode is cooled by a cooling medium.

[0007]

However, when the electrode has a cooling structure, the structure around the electrode becomes complicated, and the cost of the ion source increases. Also,
Since a cooling system for supplying the refrigerant is required, there is also a problem that the cost increases accordingly.

Therefore, the main object of the present invention is to provide an ion source capable of simplifying the cooling structure of the electrode by reducing the deformation of the electrode due to the temperature rise.

[0009]

In order to achieve the above object, the first ion source according to the present invention has a layered structure in which at least one of the electrodes constituting the extraction electrode system has a crystal structure parallel to the plate surface. It is characterized by comprising a molybdenum plate having.

The second ion source according to the present invention is
At least one of the electrodes forming the extraction electrode system is formed of a molybdenum plate having a diffraction peak from the (200) plane measured by X-ray diffraction as a main peak.

[0011]

After the ion beam is generated using the electrode composed of the molybdenum plate having the above-mentioned layered structure or having the diffraction peak, the strain amount of the electrode is measured, and the strain amount of the electrode is I found it very small.
Therefore, by using the molybdenum plate as described above for the electrode, the deformation due to the temperature rise of the electrode is reduced,
The electrode cooling structure can be simplified.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic view showing an example of a high frequency type ion source together with a power source.

The ion source 2 includes a plasma source section 4 for producing a plasma 14 by high frequency discharge, and an extraction electrode system for extracting an ion beam 22 from the plasma source section 4 (more specifically, the plasma 14) by the action of an electric field. 1
6 and.

In this example, the plasma source part 4 has a plasma generating container 6 into which a gas 12 is introduced, and a high frequency electrode 7 attached to the back surface part thereof via an insulator 8. The high frequency electrode 7 also serves as the back plate of the plasma production container 6, and the plasma production container 6 also serves as the other high frequency electrode. When high-frequency power is supplied from the high-frequency power supply 23 through the matching circuit 24 between the plasma generation container 6 and the high-frequency electrode 7, high-frequency discharge occurs in the plasma generation container 6 and the gas 12 is decomposed to generate plasma 14. To be

In this example, the extraction electrode system 16 is on the most plasma side (most upstream side) and the extraction electrode 1 to which a positive voltage for extracting the ion beam is applied from the extraction power source 27.
7. An acceleration electrode 18 on the downstream side thereof to which a positive voltage for ion beam acceleration is applied from an acceleration power supply 28; and a suppression electrode on the downstream side thereof to which a negative voltage for backflow electron suppression is applied from a suppression power supply 29. 19 and a ground electrode 20 on the downstream side thereof and set to the ground potential. Each electrode 17
˜20 have a large number of small holes or slits for extracting the ion beam.

Among the electrodes 17 to 20 constituting the extraction electrode system 16 as described above, it is the second acceleration electrode 18 from the upstream side that the temperature rise is particularly large with the extraction of the ion beam 22. This is because the second acceleration electrode 18
This is because the ion beam 22 extracted from the extraction electrode 17 has a large divergence ratio and hits, and a large heat input is thereby received.

Further, the ion source 2 which does not use a filament as in this example is not so, but in the case of the filament type ion source 2a shown in FIG. The temperature rise of the extraction electrode 17 is also large.

In such an ion source 2, the following molybdenum plates A and B are used for the electrodes 17 to 19 constituting the extraction electrode system 16, and the cooling structure is not adopted for the electrodes and the extraction electrode 17 is used. The voltage between the ground electrodes 20 is 5
The amount of strain of each of the electrodes 17 to 19 after the ion beam 22 was generated in the range of KV to 110 KV was measured. The strain amount of the original plate material was about ± 0.1 mm for both molybdenum plates.

The molybdenum plate A is an ordinary molybdenum plate which has been conventionally used for an electrode, and as a result of microscopic observation of the structure, as shown in FIG. 2 and FIG. Was observed.

The molybdenum plate B constitutes the electrode of the ion source according to the present invention. As a result of microscopic observation of the structure, no crystal grains are observed on the surface and the cross section as shown in FIGS. It was What was seen on the surface was scratches during polishing. As for the cross section, a layered crystal structure along the surface was confirmed.

The molybdenum plate A is used as the electrode 1 of the ion source 2.
FIG. 6 shows an example of the measurement results of both strains of the electrodes 17 to 19 when used in Nos. 7 to 19. A gap gauge was used to measure both strains. The measurement position on the horizontal axis is the measurement position in the plane of the electrode (the same applies to FIG. 7).

As can be seen from this figure, when the molybdenum plate A was used, the amount of strain was very large, and a maximum of 2.4 mm was observed.

On the other hand, FIG. 7 shows an example of the measurement results of the strain amounts of the electrodes 17 and 18 when the molybdenum plate B is used as the electrodes 17 to 19 of the ion source 2. Since the amount of strain is small in measuring the amount of strain, a three-dimensional measuring device having higher accuracy than the gap gauge was used. Since the amount of strain of the electrode 19 was almost 0, illustration of the measurement result was omitted. Further, in the case of this three-dimensional measuring device, it is easy to increase the number of measuring points, so the number of measuring positions is increased.

As can be seen from this figure, the strain amount when the molybdenum plate B is used is +0.3 mm to −0.
It was confirmed that it was about 1 mm, which was significantly smaller than that of the molybdenum plate A.

As described above, it was confirmed that the electrode composed of the molybdenum plate having a layered structure whose crystal structure is parallel to the plate surface has a very small thermal strain. This is considered to be due to the following reasons. That is, the molybdenum plate is usually manufactured by sintering and rolling powdered molybdenum. In that case, when molybdenum is not recrystallized and is rolled under sufficient pressure, no crystal grains can be observed in the cross section of the molybdenum plate, and the crystal structure forms a layered structure parallel to the plate surface. In such a state, it is considered that the mechanical strength is high and therefore the amount of deformation due to the temperature rise is small.

Therefore, by using a molybdenum plate made of a material such as the molybdenum plate B for the electrodes constituting the extraction electrode system 16, the deformation of the electrode due to the temperature rise is reduced and the electrode cooling structure is simplified. be able to. In a high-frequency ion source that does not use a filament,
It is also possible to omit the electrode cooling structure. As a result, the structure around the electrodes is simplified, and the cost of the ion source can be reduced. In addition, as the cooling structure of the electrode is simplified, the cost of the refrigerant system for supplying the refrigerant to the electrode can be reduced.

When the extraction electrode system is composed of a plurality of electrodes, it is of course most preferable to use the above molybdenum plates for all the electrodes from the viewpoint of reducing thermal strain. However, without doing so, an electrode having a particularly large heat input, for example, the second accelerating electrode 18 in the case of the above-mentioned ion source 2 and, if necessary, the electrodes 17 and 19 on the upstream and downstream sides thereof, The molybdenum plate as described above may be used, and in such a case, the effect of simplifying the cooling structure by reducing the amount of thermal strain described above can be obtained for at least the electrode. More generally speaking, there is no particular electrode, and if at least one electrode using a molybdenum plate as described above is included, at least that electrode has a cooling structure by reducing the thermal strain described above. The effect of simplification is obtained.

Instead of using a molybdenum plate as described above for the electrodes constituting the extraction electrode system, a molybdenum plate whose plate surface is mainly parallel to the (200) plane of the molybdenum crystal, that is, X-ray diffraction measurement As a result of measurement by the θ-2θ method according to, a molybdenum plate in which the X-ray diffraction peak intensity corresponding to the (200) plane appears stronger than other peak intensities may be used, which also reduces the thermal strain of the electrode. It can be kept very small. An example will be described below.

In the X-ray diffraction intensity measurement of the molybdenum plate, (1
The electrodes of the molybdenum plate C having the diffraction peak from the (10) plane as the main peak and the molybdenum plate D having the diffraction peak from the (200) plane as the main peak in the ion source 2 that does not adopt the same cooling structure as described above. 17-19
And the voltage between the extraction electrode 17 and the ground electrode 20 is 5
The amount of strain of each of the electrodes 17 to 19 after the ion beam 22 was generated in the range of KV to 110 KV was measured. Even in this case, the strain amount of the original plate material is ± 0.
It was about 1 mm.

Table 1 shows the diffraction peak intensity ratios of both molybdenum plates C and D. Further, FIG. 8 shows an X-ray diffraction pattern of the molybdenum plate D.

[0031]

[Table 1]

The measurement results of the strain amount of each of the electrodes 17 to 19 when the molybdenum plate C was used were almost the same as those in FIG. 6 described above, and thus duplicated illustration is omitted. Further, the measurement results of the strain amounts of the electrodes 17 and 18 when the molybdenum plate D is used are almost the same as those in FIG. 7 described above, and therefore, duplicated illustration is also omitted.

As described above, it was confirmed that the electrode composed of the molybdenum plate having the diffraction peak from the (200) plane as the main peak had a very small thermal strain. This is considered to be due to the following reasons. That is, a molybdenum plate is usually manufactured by sintering and rolling powdered molybdenum as described above. However, when the X-ray diffraction intensity from the (200) plane appears strongly, the crystal grains forming the molybdenum plate are It is due to being sufficiently small and rolled with sufficient pressure applied. In such a state, it is considered that the mechanical strength is high and therefore the amount of deformation due to the temperature rise is small.

Therefore, by using such a molybdenum plate D as an electrode, the same effect as that of the above-described molybdenum plate B can be obtained. That is, by using a molybdenum plate made of a material such as the molybdenum plate D for the electrodes forming the extraction electrode system 16, the deformation of the electrode due to the temperature rise can be reduced and the electrode cooling structure can be simplified. In a high-frequency ion source that does not use a filament, the electrode cooling structure can be omitted.
As a result, the structure around the electrodes is simplified, and the cost of the ion source can be reduced. In addition, as the cooling structure of the electrode is simplified, it is possible to reduce the cost of the cooling system that supplies the refrigerant to the electrode.

In the extraction electrode system, it is preferable to use a molybdenum plate made of the same material as the molybdenum plate D as described above.

Further, the molybdenum plates made of the above-mentioned materials such as molybdenum plates B and D have a great effect even when they are used for the electrodes constituting the extraction electrode system of the filament type ion source.

The ion source 2a shown in FIG. 9 is of such a filament type, and the plasma source section 4a includes, in this example, a plasma generation container 6 into which a gas 12 is introduced and a filament 10 for emitting thermoelectrons. The plasma 14 is created by the arc discharge between the two. The extraction electrode system 16a for extracting the ion beam 22 from the plasma 14 is, in this example, 3 without the acceleration electrode 18 described above.
It is composed of one sheet.

In such an ion source 2a, the molybdenum plates B and D are used as the first extraction electrode 17 and the second suppression electrode 19 which have a large heat input for the reason described above. When a molybdenum plate made of a material is used, the effect of reducing the amount of thermal strain is great.

[0039]

As described above, according to the present invention, since the molybdenum plate made of the above-mentioned material is used for the electrodes constituting the extraction electrode system, the deformation of the electrodes due to the temperature rise is reduced, and The cooling structure can be simplified. In a high-frequency ion source that does not use a filament, the electrode cooling structure can be omitted. As a result, the structure around the electrodes is simplified, and the cost of the ion source can be reduced. In addition, as the cooling structure of the electrode is simplified, it is possible to reduce the cost of the cooling system that supplies the refrigerant to the electrode.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a high-frequency ion source together with a power supply.

FIG. 2 is a micrograph of the surface structure of molybdenum plate A, having a magnification of 40 times.

FIG. 3 is a photomicrograph of the cross-sectional structure of the same molybdenum plate as in FIG. 2, with a magnification of 40 times.

FIG. 4 is a micrograph of the surface structure of molybdenum plate B, having a magnification of 40 times.

5 is a micrograph of a cross-sectional structure of the same molybdenum plate as in FIG. 4, with a magnification of 40 times.

FIG. 6 is a diagram showing an example of a measurement result of in-plane distribution of strain amount of an electrode using a molybdenum plate A in which crystal grains as shown in FIGS. 2 and 3 are observed.

FIG. 7 is a diagram showing an example of measurement results of in-plane distribution of strain amount of an electrode using a molybdenum plate B having a layered structure as shown in FIGS. 4 and 5.

FIG. 8 is a diagram showing an example of measurement results of X-ray diffraction intensity of molybdenum plate D.

FIG. 9 is a schematic view showing an example of a filament type ion source together with a power source.

[Explanation of symbols]

2,2a ion source 4,4a Plasma source part 14 plasma 16,16a Extraction electrode system 17 to 20 electrodes 22 Ion beam

Claims (2)

(57) [Claims] 1. An ion source comprising a plasma source part for producing plasma and an extraction electrode system for extracting an ion beam from the plasma source part and having one or more electrodes, wherein the extraction electrode system is constituted. An ion source, wherein at least one of the electrodes is composed of a molybdenum plate having a layered structure whose crystal structure is parallel to the plate surface. 2. The extraction electrode system is formed in an ion source including a plasma source part for producing plasma and an extraction electrode system for extracting an ion beam from the plasma source part and having one or more electrodes. An ion source, wherein at least one of the electrodes is composed of a molybdenum plate having a diffraction peak from a (200) plane measured by X-ray diffraction as a main peak.