JPH0374454B2 - - 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㎜, supplies helium gas to the tip of the tip, and ionizes the helium gas molecules attached to the tip using an electric field. , is an ion source that ionizes.

[Problems to be Solved by the Invention] Now, in this ion source, it is desired to efficiently cool the emitter tip to a level below.

For this reason, it is conceivable to introduce a refrigerant such as liquid helium contained in a container through a conduit to a refrigerant tank for cooling the emitter chip, but since the emitter is floating at a high voltage, it is not suitable in the past. There was no proper means of cooling.

The present invention aims to solve such problems.

[Means for Solving the Problems] Therefore, the present invention provides an emitter held at a high voltage, a means for providing ionized gas near the tip of the emitter, and a high-voltage emitter disposed opposite to the emitter. In an ion source having an extraction electrode held at a voltage, a container containing a refrigerant for cooling the emitter or the extraction electrode and floating at a high voltage;
A conduit for transporting the refrigerant from the container to the vicinity of the emitter or the extraction electrode, a pedestal for supporting the container while insulating it from earth potential, and an electric field relaxation ring provided to surround the container. It is characterized by having the following.

[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. 2 is a holder made of a good heat conductor to hold this chip, and a ring-shaped refrigerant tank 3
It is removably attached to the center of the 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 from the container 5D through the metal tube 5, and at the same time, the helium gas vaporized here is discharged to the outside through the pipe 6. As will be described later, since the refrigerant tank 3 is floating at a high voltage, the container 5D is also floating at a high voltage. 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 from the container 11D through the heat exchanger 10 and the metal tube 11 to the space 8S inside the support, and at the same time, nitrogen gas vaporized in the space 8S is discharged through the pipe 12. Ru. Since the support stand 7 is also floating at a high voltage as described later, the container 1
1D is also floating on high voltage. 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. A space A isolated in the upper part of the lens barrel by these bellows 13 and 14 is thermally insulated from spaces B and C. 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 vicinity of the emitter tip 1 in the space A. 17 is a focusing lens, 18a, 18b, ...,
18j is an accelerating electrode. 19 is a blanking electrode, and 20 is a blacking aperture. 21 is an objective lens, and 22 is a deflector that controls the position of helium ions on the target 23. 24 is
This is a voltage dividing resistor for determining the divided voltage of the acceleration voltage applied to each of the acceleration electrodes 18a, 18b, . . . , 18j. One end p of this voltage dividing resistor is connected to the extraction electrode 6, and the other end is connected to the ground. 25 is a variable extraction power source that generates an extraction voltage to be applied between the holder 2 and the extraction electrode 6; 26 is an acceleration power source that generates an acceleration voltage that is applied between one end p of the voltage dividing resistor 24 and the ground. be. A control circuit 27 is supplied with signals representing the output voltages of the extraction power source 25 and the acceleration power source 26, and controls the output voltage of the acceleration power source 26 so that the sum of both signals becomes a predetermined set value.

Now, the mechanism for supplying liquid helium to the refrigerant tank 3 through the metal tube 5 and the mechanism for supplying liquid nitrogen into the space 8S of the support base 8 through the metal tube 11 are as follows. It is configured.

As shown in FIG. 2, the container 5D containing liquid helium and the container 11D containing liquid nitrogen are placed on an insulating stand 29 insulated from ground potential via stable insulators 28A and 28B. It is being These insulators are placed on a floor 30 near the mirror body of the ion beam device with an iron plate 31 interposed therebetween. This floor is at earth potential. An electric field relaxation ring 32 is provided around the insulating frame in a cage shape surrounding the containers 5D and 11D. Further, in order to eliminate vibrations to these containers, a vibration-proofing rubber sheet 33 is laid on the top surface of the pedestal.
The metal tubes 5 and 11 are selected to have a diameter (30 mm) such that the surface electric field strength is approximately 1 K volts/mm in consideration of safety to the outside. In order to obtain the pressure to send liquid helium and liquid nitrogen from the containers 5D and 11D, respectively, these containers 5
D and 11D are respectively helium gas cylinders 5B,
Pressure is applied by a nitrogen gas cylinder 11B. These gas cylinders are at earth potential,
These gases can only withstand an electric field of about 0.6K volts/mm at the above pressure, so nylon tubes 5T and 11T for connecting the respective containers and cylinders are given a length of about 1m. ing.

In such an apparatus, liquid helium and liquid nitrogen from containers 5D and 11D are transferred to metal tubes 5 and 11D.
11, it is supplied to the refrigerant tank 3 and the heat exchanger 10. The liquid nitrogen supplied to this heat exchanger is supplied into the support base 8 through the metal tube 11. The holder 2 in contact with the cooling tank 3 supplied with liquid helium is sufficiently cooled and the emitter tip 1
is cooled to about 4㎜. And heat exchanger 10
Helium gas that has been sufficiently cooled inside is introduced into the space A through the pipe 16, and its gas molecules adhere to the tip of the tip. At this time, the extraction voltage from the extraction power supply 25 is applied between the holder 2 and the extraction electrode 7, and the extraction voltage from the extraction power supply 25 is applied between the acceleration electrode 18a (extraction electrode 7).
Accelerating voltages are applied from 6 to 6, respectively. In this way, helium ions are extracted by applying an extraction voltage,
By applying an accelerating voltage, it is accelerated in the direction of the target. During this ion extraction, ions from the emitter tip 1 hit the extraction electrode 7, but since this extraction electrode is cooled by the support 8, there is no radiant heat from the extraction electrode to the emitter 1. Therefore,
This prevents the temperature of the emitter from rising.

Now, since the metal tubes 5 and 11 of the containers 5D and 11D are connected to the refrigerant tank 3 and the support stand 8, they are at the same potential as the refrigerant tank 3 and the support stand 8, but are grounded by the insulators 28A and 28B. Since it is insulated from the ground, it is possible to safely ensure insulation from the ground side. In addition, because the shapes and processing of these containers 5D and 11D are insufficient, there are protrusions on their surfaces.
There is a risk that the electric field will concentrate on this protrusion and a discharge will occur between it and the ground, but since the containers 5D and 11D are surrounded by the electric field relaxation ring 32 in a cage shape, the outside of the electric field relaxation ring There is no leakage of strong electric fields that can cause discharge.

[Effects of the Invention] According to the present invention, the emitter or extraction electrode held at a high voltage can be sufficiently cooled, and electric discharge between the refrigerant container and the ground side can also be prevented.

[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 the apparatus. 1: Emitchi tip, 2: Holder, 3: Refrigerant tank, 4: Lens barrel, 5, 11: Metal tube, 5
D, 11D: Container, 5T, 11T: Nylon tube, 5B: Helium gas cylinder, 11B: Nitrogen gas cylinder, 6, 12, 16: Pipe, 7: Support, 8: Space, 9: Hole, 9G: Good thermal conductor, 1
0: heat exchanger, 13, 14: bellows, 15: bypass pipe, 17: focusing lens, 18a, 18b,
..., 18j: accelerating electrode, 19: blanking electrode, 20: blanking aperture, 21: objective lens, 22: deflector, 23: target, 24:
voltage dividing resistor, 25: extraction power supply, 26: acceleration power supply,
27: Control circuit, 28A, 28B: Insulator, 29:
Insulating frame, 30: floor, 31: iron plate, 32: electric field mitigation ring, 33: vibration-proof rubber sheet.

Claims (1)

[Claims] 1. In an ion source equipped with an emitter held at a high voltage, a means for supplying ionized gas near the tip of the emitter, and an extraction electrode placed opposite the emitter and held at a high voltage. ,
a container floating at high voltage containing a refrigerant for cooling the emitter or the extraction electrode; a conduit for transporting the refrigerant from the container to the vicinity of the emitter or the extraction electrode; A gas phase ion source characterized by comprising a pedestal for insulating support and an electric field relaxation ring provided to surround the container.