JP2728417B2 - Ion source with microwave heating type evaporating furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an ion source used in an ion implantation apparatus and an ion processing machine for forming a thin film and modifying a surface.
The present invention relates to an ion source having a function suitable for stably extracting ions of a sample having a vapor pressure of about 10 ⁻³ Torr at a temperature of 0 ° C. for a long time.

[Conventional technology]

As described in Example 1 of JP-A-56-132754, a conventional sample heating furnace for an ion source is one in which a tungsten heater or a sheath heater is wound around the furnace.

[Problems to be solved by the invention]

In the above-mentioned conventional technology, in the case of a tungsten heater, disconnection is easily caused, so handling during sample replacement and furnace cleaning is difficult. On the other hand, in the case of the sheath heater, there was a problem that the maximum operating temperature was low at around 500 ° C.

SUMMARY OF THE INVENTION An object of the present invention is to realize an ion source having an evaporating furnace having a high maximum operating temperature, which is easy to handle during sample exchange and furnace cleaning.

[Means for solving the problem]

The above problems are unavoidable to a greater or lesser extent as long as a tungsten heater or a sheath heater is used. Therefore, in order to achieve the above object, a heating method that does not use a heater is required. Specifically, this is achieved by using microwaves for heating.

[Action]

In general, a carbon-based material used as a constituent material of an evaporating furnace is a substance that efficiently absorbs microwaves. Therefore, it is possible to efficiently heat only the evaporating furnace with a simple configuration in which the evaporating furnace made of a carbon-based material is placed in a rectangular waveguide or a coaxial line. Then, the temperature of the evaporating furnace is controlled by the power of the introduced microwave.

In the case of the above configuration, since the carbon evaporating furnace can be installed at an arbitrary position in the waveguide, the degree of freedom of the structure is large, and the evaporating furnace with good operability at the time of sample exchange and cleaning in the furnace can be obtained. .

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG. In this embodiment, the microwave is also used for generating the plasma, and one microwave generator is used to heat both the sample evaporating furnace and generate the plasma. The ion source consists of a microwave generator 1, a branch waveguide 2, microwave power regulators 3a and 3b, microwave introduction flanges 4a and 4b, a discharge electrode 5, a plasma chamber 6, a gas sample introduction pipe 7, and an evaporating furnace. Heating waveguide
8, a solid sample evaporating furnace 9, an ion beam extraction electrode system 10, and a magnetic field generator 11.

In the figure, a microwave generated by a microwave generator 1 passes through a branch waveguide 2, a microwave power adjuster 3a, and a microwave introduction flange 4a, and a plasma chamber 6 installed in a discharge electrode 5 is provided. A microwave electric field is generated inside.
On the other hand, microwaves are supplied to the solid sample evaporating furnace 9 through the branch waveguide 2, the microwave power controller 3b, the microwave introducing flange 4b, and the evaporating furnace heating waveguide 8. In the case of the present embodiment, all the microwave three-dimensional circuits use rectangular waveguides, and the branch waveguide 2 has a characteristic of branching an incident microwave to both sides by an equal amount. A flap type variable attenuator is used for the microwave power adjusters 3a and 3b. Therefore, the microwave generator 1 has only a function of always generating a constant microwave. With the microwave electric field generated in the plasma chamber 6, a magnetic field is applied to the vicinity of the plasma chamber 6 in a direction orthogonal to the microwave electric field by the magnetic field generator 11, and further, the gas sample introduction pipe 7 or the solid sample introduction furnace is used. By introducing a gaseous sample from 9, plasma of the introduced gas can be generated in the plasma chamber 6. Then, the ion beam 21 is extracted from the plasma by the ion beam extraction electrode system 10.

FIG. 2 is a diagram showing details of the solid sample evaporating furnace 9 and the plasma chamber 6. Dielectric insulators 12a, 12b, and 12c are inserted into the evaporating furnace heating waveguide 8 for the purpose of reducing the size of the waveguide and holding the solid sample evaporating furnace 9. The solid sample evaporation furnace 9 is made of carbon and has a furnace body 9a.
The furnace body 9a has an introduction hole for guiding the evaporated sample to the plasma chamber 6.
Then, on the microwave incident side (in the case of this embodiment, the holding lid 9b
The end is formed in a conical shape to reduce microwave reflection at this portion. Replacement and replenishment of solid samples
This is performed by removing the top end holding plate 8b of the evaporating furnace heating waveguide 8, and removing the dielectric insulator 12b and the holding lid 9b. A sheath-type thermocouple 13 is used for measuring the temperature of the solid sample evaporating furnace 9 so that the temperature measurement is not affected by microwaves. The temperature of the solid sample evaporation furnace 9 is controlled by feeding back the output of the thermocouple 13 to a microwave power attenuator. The microwave power required to heat the solid sample evaporating furnace 9 to 1000 ° C. depends on the installation conditions of the furnace, but can be roughly estimated to be 300 W at most even in a furnace capable of securing an internal volume of 10 cm ³ .

On the other hand, the microwave power required for plasma generation is on the order of several hundred W, and the present embodiment can exhibit sufficient performance by using the microwave generator 1 having an output of about 1 kW.

As described above, according to the present embodiment, since the generation of plasma and the evaporation of the solid sample can be simultaneously performed by one microwave generator, the heater power supply for the heating of the solid sample evaporation furnace, which is conventionally required, can be eliminated. Furthermore, since the microwave power supplied to the plasma and solid sample evaporating furnaces is adjusted by the variable attenuator, it is not necessary to make the microwave generator output variable, and the power source can be simplified.

In this example, the waveguide for heating the evaporating furnace was described as having a rectangular cross section. However, it is apparent that the same effect can be obtained by using another waveguide such as a circular waveguide. is there. Further, it is clear that even if a method other than the microwave discharge is used to generate the plasma, the effect of heating the solid sample evaporation furnace by the microwave described in the next section can be obtained.

Further, in this embodiment, only a solid sample having a low vapor pressure at normal temperature is targeted, but it is not necessary that the sample is a solid, and it is apparent that the same effect can be obtained for a liquid sample.

〔The invention's effect〕

According to the present invention, it is possible to transmit electric power only with a waveguide, and the apparatus is completed simply by placing a solid sample evaporating furnace made of an object that can absorb microwaves and withstand high temperatures therein. Therefore, the problems inherent in the solid sample evaporator, which heats by heating with a conventional heater, can be solved at once,
An ion source that is easy to replenish and has a furnace with a maximum operating temperature of about 1000 ° C. can be realized.

[Brief description of the drawings]

FIG. 1 is a view showing an embodiment of the present invention, and FIG. 2 is a detailed view of a portion I in FIG. 1 ... microwave generator, 2 ... branch waveguide, 3a, 3b ...
… Microwave power adjuster, 4a, 4b …… Microwave introduction flange, 5… Discharge electrode, 6… Plasma chamber, 7…
Gas sample introduction tube, 8 (8a, 8b) ... evaporating furnace heating waveguide, 9 (9a, 9b) ... solid sample evaporating furnace, 10 ... ion beam extraction electrode system, 11 ... magnetic field generator, 12a, 12b, 12c…
... dielectric insulator, 13 ... thermocouple, 21 ... ion beam.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Takayoshi Seki 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside Hitachi, Ltd. Central Research Laboratory (72) Inventor Kensuke Amemiya 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Hitachi, Ltd. Central Research Laboratory (56) References JP-A-62-256344 (JP, A)

Claims (3)

(57) [Claims] 1. A solid sample is heated and evaporated, and the solid sample is introduced into a discharge chamber to be used as a plasma gas, and the solid sample is heated by microwaves in an ion source for extracting ions from the plasma. An ion source equipped with a microwave heating evaporator. 2. The ion source according to claim 1, wherein microwaves are also used to generate plasma. 3. The microwave heating apparatus according to claim 2, wherein the generation of plasma and the heating of the solid sample are performed by microwaves generated by a single microwave generator. Ion source with evaporator.