JPS61240543A - Ion source - Google Patents

Abstract

PURPOSE:To enhance the efficiency of cooling, by providing a holder made of a material of high thermal conductivity to hold an emitter chip at a gas ion source, and by inserting the holder into the central portion of an annular coolant container to keep the holder in heat transfer contact therewith to reduce the heat resistance therebetween. CONSTITUTION:A holder 2 for holding an emitter chip 1 at the gas ion source of an ion beam apparatus is made of a material of high thermal conductivity. The holder 2 is inserted into the central portion of an annular coolant container 3 for supplying liquefied helium, so that the holder is kept in heat transfer contact with the container. A steel ball 2P attached to a spring 2C provided at the bottom of the coolant container 3 is fitted in the groove 2H of the tip portion of the holder 2 to secure it. Gaseous helium enough cooled by a heat exchanger 10 is supplied to the vicinity of the tip of the emitter chip 1 so that the helium is ionized and then led out by an electrode 7. The heat resistance between the coolant container 3 and the emitter chip 1 is thus much reduced to efficiently cool the emitter chip.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field 1] The present invention relates to a gas phase ion source most suitable for use in an ion beam device such as an ion beam lithography device.

[Prior Art] Recently, ion beam devices using gas phase ion sources have been developed.

This gas phase ion source cools an emitter tip with a sharp tip to about 4 degrees with liquid helium, and supplies helium gas to the tip of the tip.
This is an ion source that ionizes helium gas molecules attached to the tip using an electric field.

Now, in this ion source, it is desired to efficiently cool the emitter chip. In the conventional d3, as shown in Fig. 2, an emitter holder H made of an insulator is fixed under the coolant tank C to which liquid helium is supplied, and the emitter holder H is attached to the tip of this holder. We are trying to cool the chip E.The base of the emitter chip is a screw S that fixes this chip, and this screw is sandwiched between an insulating holder. An extraction voltage is applied between the extraction electrodes R.

[Problem to be solved by the invention] However, in this case, the cooling efficiency of the holder is not very good.

Also, since this holder is made of insulating material, it has high thermal resistance.
Therefore, the emitter chip is not efficiently cooled.

The present invention aims to solve such problems.

[Problems to be Solved by the Invention] Therefore, in the gas phase ion source of the present invention, the holder for holding the emitter chip is made of a good thermal conductor, and the holder has a part into which the holder is inserted while maintaining thermal contact. An annular coolant tank was provided to significantly reduce the thermal resistance up to the emitter chip.

[Embodiment] FIG. 1 is a schematic diagram of an ion beam apparatus shown as an embodiment of the present invention.

In the figure, reference numeral 1 denotes an emitter chip, the tip of which is formed in the shape of an ultra-fine circle with a radius of curvature of several hundred to several thousand angstroms. 2 is a holder made of a good thermal conductor for holding this chip. Reference numeral 3 denotes an annular refrigerant tank 3, which is made of a good thermal conductor and has a hole in its center for inserting the holder while maintaining thermal contact. A shallow groove 2H is carved near the tip of this holder, and a steel ball 2P attached to the tip of a spring 2c fixed to the lower surface of the refrigerant tank 3 is fitted into this groove. By holder 2
I am trying to fix it. If this refrigerant! Although not shown, f3 is fixed to the upper part of the lens barrel 4 by some kind of holder. Further, liquid helium is supplied to this refrigerant tank through the pipe 5, and at the same time, the helium gas vaporized here is discharged to the outside through the vibro. 7
1 is an extraction electrode disposed opposite to the depth 1, and has a small hole in the center thereof. This extraction electrode is fixed to the upper surface of a support base 8 made of an insulating material.

This support base is formed in an annular shape, and a truncated conical hole 9 is formed in the center thereof. The inner surface of this hole is formed of nine thermally conductive bodies 9G. This circle♀1
[The smallest diameter part of the trapezoidal hole has approximately the same size as the small hole of the extraction electrode. Space 8 inside this support stand
Liquid nitrogen is supplied to S through the heat exchanger 10 and pipe 11, and at the same time, nitrogen gas vaporized in this space 8S is discharged fJl through the pipe 12. In order to efficiently perform cooling with this nitrogen gas, an opening is provided in the upper surface of the support base 8. 13 and 14 are bellows fixed between the side wall of the lens barrel 4 and the refrigerant tank 3, respectively;
This is a bellows fixed between the side wall of the lens barrel and the support base 8. A space A separated from the upper part of the lens barrel by these bellows 13 and 14 is thermally insulated from spaces B and C. The spaces B and C are connected by a bypass pipe 15. 16 is a pipe for guiding the helium gas sent through the heat exchanger 10 to the periphery of the emitter chip 1 in the space A. 17 is a focusing lens, 18'a, 18b, 18
j is an accelerating electrode. 19 is a blanking electrode, 20
is the aperture for blanking. 21 is an objective lens, 22
is a deflector that controls the position of helium ions on the target 23. 24 is the acceleration electrode 18a, 18b
, . . . are voltage dividing resistors for determining the divided voltage of the accelerating voltage applied to each of 18j. One end of this voltage dividing resistor @p is connected to the extraction electrode 7, and the other end is connected to the ground. Reference numeral 25 indicates a draw-out pressure control power source that controls the extraction voltage applied between the holder 2 and the extraction electrode 7, and 26 controls the accelerating voltage applied between one end p of the voltage dividing resistor 2/l and the ground. This is an accelerating voltage controlled power supply. 27 subtracts the extraction voltage controlled by the extraction voltage control power supply 25 from the acceleration voltage controlled by the acceleration voltage control power supply 26, and calculates an addition ai corresponding to the difference.
This is a control circuit that controls the accelerating voltage control power source 26, in which voltage is applied between one part of the voltage dividing resistor 24 and the ground.

The device constructed in this manner operates as follows.

First, the emitter chip 1 is attached to the holder 2, this holder is inserted into the hole in the center of the refrigerant tank 3, and the holder is fixed to the refrigerant tank by fitting the steel ball 2P into the groove 2H. Now, the holder 2 in contact with the cooling bath 3 supplied with liquid helium is sufficiently cooled, and the emitter chip 1 is cooled to a culm angle of 4 degrees. Then, the helium gas sufficiently cooled in the heat exchanger 10 is guided into the space Δ through the pipe 16, and the gas molecules adhere to the tip of the tip. At this time,
An extraction voltage control power source 25 is connected between the holder 2 and the extraction electrode 7.
The extraction voltage (25 volts) is applied to this extraction electrode and the accelerating electrode j8a, 18b, 18c,...

Accelerating voltage (R
100 volts) are applied, respectively. At this time, the control circuit 27 converts the acceleration voltage controlled by the acceleration voltage control power supply 26 into the extraction voltage control type? l! The accelerating voltage control power supply 26 is operated such that an accelerating voltage (volts at 75) corresponding to the difference is applied between one end p of the voltage dividing resistor 24 and the ground. control. Therefore, by applying an extraction voltage of 25 volts to 25, helium ions are extracted, and are finally accelerated to 100 volts and irradiated onto the target laser 1 at 23. During this ion extraction, ions from the emitter chip 1 hit the extraction electrode 7, but since this extraction electrode is cooled by the support 8, there is no radiant heat from this extraction electrode to the emitter 1. Therefore, the emitter temperature 1
Loans are prevented.

[Effects of the Invention] According to the present invention, the holder made of a good thermal conductor is inserted into the center of the annular refrigerant tank while maintaining thermal contact with it.
The emitter chip is very well cooled. Furthermore, the emitter chip can be easily replaced.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an ion beam apparatus shown as an embodiment of the present invention, and FIG. 2 is a partial schematic diagram of a conventional ion source.

Claims (1)

[Claims] an emitter chip; a holder made of a good thermal conductor for holding the chip; an annular coolant tank having a portion into which the holder is inserted while maintaining thermal contact; means for supplying ionized gas around the chip; An ion source with extraction electrodes placed opposite each other.