JPH0584019B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a gas phase ion source that is 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 mm with liquid helium, supplies helium gas to the tip, and uses an electric field to remove helium gas molecules attached to the tip. It is an ion source that ionizes and ionizes.

Now, in this ion source, it is desired to efficiently cool the emitter tip. Conventionally, as shown in Fig. 2, an emitter holder H made of an electrical insulator is fixed under a coolant layer C supplied with liquid helium, and an emitter tip E attached to the tip of this holder is cooled. It is said that
The base of the emitter tip is a screw S to which the tip is fixed, and this screw is screwed into a holder made of an insulating material. An extraction voltage is applied between this screw and the extraction electrode R.

[Problems to be Solved by the Invention] However, in this case, the cooling efficiency of the holder is not very good. Further, since this holder is made of an insulating material, its thermal resistance is large, and therefore the emitter tip is not efficiently cooled.

The present invention aims to solve such problems.

[Means for Solving the Problems] For this purpose, the ion source of the present invention includes an emitter chip, a holder made of a thermally conductive material having electrical insulation properties that holds the chip by directly contacting the end face of the holder, and an annular refrigerant tank that is removable and has a hole capable of maintaining at least substantially the entire holder in thermal contact when the holder is inserted; means for supplying ionized gas around the chip; An extraction electrode is provided facing the chip.

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

In the figure, numeral 1 is an emitter tip, the tip of which is formed into an ultra-fine circular shape with a radius of curvature of several hundred to several thousand angstroms. Reference numeral 2 denotes a holder made of a material such as sapphire, which is an electrically insulating and thermally conductive material, for holding the 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. The holder 2 is fixed by this. Although not shown, this coolant tank 3 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 a pipe 5, and at the same time, helium gas vaporized here is discharged to the outside through a pipe 6. Reference numeral 7 denotes an extraction electrode placed opposite to the chip 1, and has a small hole in the center. 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 bored in the center thereof. The inner surface of this hole is made of a good thermal conductor 9G. The smallest diameter portion of this truncated conical hole has approximately the same size as the small hole of the extraction electrode. Liquid nitrogen is supplied to the space 8S inside the support base through the heat exchanger 10 and the pipe 11, and at the same time, nitrogen gas vaporized in the space 8S is discharged 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. Reference numerals 13 and 14 denote a bellows fixed between the side wall of the lens barrel 4 and the coolant tank 3, and a bellows fixed between the side wall of the lens barrel and the support base 8, respectively. Space A, which is separated above the mirror surface by these bellows 13 and 14, is separated from spaces B and C.
thermally insulated from the And, Kutsu B and C are connected by a bypass pipe 15. 16 is
This is a pipe for guiding the helium gas sent through the heat exchanger 10 to the vicinity of the emitter tip 1 in the space A. 17 is a focusing lens, 18
a, 18b, . . . , 18j are accelerating electrodes. 1
9 is a blanking electrode, and 20 is a blanking aperture. 21 is an objective lens, and 22 is a deflector that controls the position of helium ions on the target 23. 24 is the acceleration electrode 18a, 18
This is a voltage dividing resistor for determining the divided voltage of the accelerating voltage applied to each of b, . . . , 18j. One end p of this voltage dividing resistor is connected to the extraction electrode 7, and the other end is connected to the ground. Reference numeral 25 denotes an extraction voltage control source for controlling an extraction voltage applied between the holder 2 and the extraction electrode 7. In reality, a conductor is embedded along the central axis of the holder 2, and one tip of the conductor is connected to a terminal attached to the center of one end of the holder. Since the structure is such that when the emitter tip 1 is attached to the other end of the holder, the attachment end of the emitter tip is connected to the other tip of the conductor.
The extraction voltage from the extraction control power source 25 is applied between the terminal attached to the center of the end of the holder 2 and the extraction electrode 7. 26 is an accelerating voltage control power source that controls an accelerating voltage applied between one end p of the voltage dividing resistor 24 and the ground. 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 the acceleration voltage corresponding to the difference is applied to the voltage dividing resistor 24. This is a control circuit that controls the acceleration voltage control power source 26 so that the acceleration voltage is applied between one end p and the ground.

The device constructed in this manner operates as follows.

First, the emitter tip 1 is directly attached to the front end surface of the holder 2, this holder is inserted into the hole in the center of the refrigerant tank 3, and the steel ball 2P is fitted into the groove 2H to fix the holder to the refrigerant tank. Now, the holder 2 in contact with the cooling bath 3 supplied with liquid helium is sufficiently cooled, and the emitter tip 1 is cooled down to about 4 degrees centigrade. Then, the helium gas sufficiently cooled in the heat exchanger 10 is introduced into the space A through the pipe 16, and the gas molecules adhere to the tip of the chip. At this time, between the holder 2 and the extraction electrode 7,
The extraction voltage (25k volts) from the extraction voltage control power supply 25 is applied to the extraction electrodes and the acceleration electrodes 18a, 18.
An accelerating voltage (maximum 100 kvolts) is applied from an accelerating voltage control power supply 26 between the accelerating voltages b, 18cc, . . . , 18j. At this time, the control circuit 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 controls the acceleration voltage ( The accelerating voltage control power source 26 is controlled so that 75 kV) is applied between one end p of the voltage dividing resistor 24 and the ground. Therefore,
Helium ions are extracted by applying an extraction voltage of 25 kV, and are finally accelerated to 100 kV and irradiated onto the target 23. During this ion extraction, the ions from emitter tip 1 are
This corresponds to the extraction electrode 7, but since this extraction electrode is cooled by the support stand 8, there is no radiant heat from this extraction electrode to the emitter 1. Therefore, the temperature of the emitter is prevented from rising.

[Effects of the Invention] According to the present invention, the holder made of a good thermal conductor having electrical insulation properties can be inserted and removed freely, and when the holder is inserted, it is possible to maintain thermal contact with at least substantially all sides of the holder. The emitter tip mounted on the holder in direct contact with the end face of the emitter tip is very well cooled because it is inserted into the hole of the annular refrigerant bath having a possible hole. Furthermore, since the holder can be attached and detached very easily, the emitter tip attached to the holder can also be replaced very easily.

[Brief explanation of the drawing]

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. 1: Emitsuta tip, 2: Holder, 2H: Groove,
2C: Spring, 2P: Claw, 3: Refrigerant tank, 4: Lens barrel,
5, 6, 11, 12, 16: Pipe, 7: Extraction electrode, 8: Support stand, 9: Hole, 9G: Good thermal conductor, 1
0: heat exchanger, 13, 14: bellows, 15: bypass tube, 17: focusing lens, 18a, 18
b, :, 18j: acceleration electrode, 19: blanking electrode, 20: blanking aperture, 21: objective lens, 22: deflector, 23: target, 2
4: Voltage dividing resistor, 25: Output voltage control power supply, 2
6: Acceleration voltage control power supply, 27: Control circuit.

Claims (1)

[Claims] 1 Emitsuta Chip, a holder made of a thermally good conductor with electrical insulation properties that holds the chip by directly contacting the end face of the chip can be inserted and removed freely, and when this holder is inserted, it comes into thermal contact with at least substantially all sides of this holder. an ion source comprising: an annular refrigerant tank having a hole capable of holding the chip; means for supplying ionized gas around the chip; and an extraction electrode disposed opposite the chip.