JPS61250928A - Gas phase ion source - Google Patents

Abstract

PURPOSE:To fully cool an emitter and a lead-out electrode that are kept at high voltage by insulating supporting it, a container that accommodates coolant from ground potential, and providing an electric field relaxing ring around the container so as to form a structure for supplying the coolant. CONSTITUTION:A gas phase ion source is formed so that helium gas can be supplied on the tip of an emitter chip 1 provided in a coolant bath 3 that is cooled by liquid helium through a pipe 16 and be ionized, and then said ion source is drawn out by a lead-out electrode 7 that is cooled by liquid nitrogen. In this case, a container 5D in which liquid helium is contained is connected to the coolant bath 3 through a metal tube 5 and a container 11D in which liquid nitrogen is contained is connected to the lead-out electrode 7 through a metal tube 11. In addition, the containers 5D and 11D are insulated from ground potential by insulators 28A and 28B supported by them, and an electric field relaxing ring is provided around it in a cage form. As a result, an emitter 1 and the lead-out electrode 7 that are set at high voltage can fully be cooled.

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 degrees, supplies helium gas, for example, to the tip, and ionizes helium gas molecules attached to the tip by 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 about 4°.

Therefore, it is conceivable to introduce a refrigerant such as liquid helium contained in a container through a conduit to a refrigerant bath for cooling the emitter chip, but since the emitter is floating at a high voltage, conventionally 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 supplying ionized gas near the tip of the emitter, and a high-voltage emitter disposed opposite to the emitter. In an ion source equipped with 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, and a container that extends from the container to the vicinity of the emitter or the extraction electrode are provided. It is characterized by comprising a conduit for transporting a refrigerant, a pedestal for supporting the container while insulating it from the ground potential, and an electric field relaxation ring arranged to surround the container.

[Embodiment] FIG. 1 is a schematic diagram of an ion beam arrangement 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. Reference numeral 2 denotes a holder made of a good thermal conductor for holding this chip, and is detachably attached to the center of the annular refrigerant tank 3. Although not shown, this refrigerant tank 3 is fixed to the upper part of the mirror n4 by some kind of holder.

Further, liquid helium is supplied from the container 5D to the refrigerant tank through the metal tube 5, and at the same time, the helium gas vaporized here is discharged to the outside through the vibro. As will be described later, since the refrigerant tank 3 is floating at a high voltage,
Container 5D is also floated at high voltage. 7 is the chip 1
A small hole is made in the center of the extraction electrode placed opposite to the electrode. 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 part 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 to the space 8S inside the support base through the heat exchanger 10 and the gold-Iil tube 11, and at the same time, nitrogen gas vaporized in the space 8S is discharged through the pipe 12. be done. Support stand 7
As will be described later, since the container 11D is floating at a high voltage,
is also exposed to high voltage. 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. The space A isolated in the upper part of the lens barrel by these bellows 13, 14 is thermally insulated from the 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 periphery of the emitter chip 1 in the space 11IA.

17 is a focusing lens, 18a, 18b, etc.
. , 18j are accelerating electrodes. 19 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 18
This is a voltage dividing resistor for determining the divided voltage of the acceleration voltage applied to each of a, 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. 2
7 is the withdrawal %fll! This control circuit is supplied with signals representing the output voltages of the accelerating power source 25 and the accelerating power source 26, and controls the output voltage of the accelerating power source 26 so that the sum of both signals becomes a predetermined set value.

Now, a mechanism for supplying liquid helium to the refrigerant tank 3 via the metal tube 5, and a space 8S of the support base 8.
The mechanism for supplying liquid nitrogen into the interior through the metal scrap tube 11 is constructed as follows.

As shown in FIG. 2, the container 5D containing liquid helium and the container 110 containing liquid nitrogen are placed on two insulating stands 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. Around this insulating stand, an electric field relaxation ring 32 is provided in the shape of a bar, 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 volt/mm in consideration of safety to the outside.

In order to obtain pressure for sending liquid helium and liquid nitrogen from the containers 5D and 11D, respectively, these containers 5D and 11
D is pressurized by a helium gas cylinder 5B and a nitrogen gas cylinder 11B, respectively. Although these gas cylinders are at ground potential, these gases can only withstand an electric field of about 0.6 volts/mm at the above pressure, so nylon is used to connect each container to the cylinder. The manufactured tubes 5T and 11T are given a length of about 1 m.

In such an apparatus, liquid helium and liquid nitrogen from containers 5D and 11D are passed through gold tubes 5°11 to refrigerant tanks 3. Supplied to heat exchanger 10. The liquid nitrogen supplied to this heat exchanger is supplied to the inside of the support base 8 through the metal tube 11. 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 about 4 degrees. Then, the helium gas sufficiently cooled in the heat exchanger 10 is transferred to the via 1.
6 into the space A, and the gas molecules adhere to the tip of the tip. At this time, an extraction voltage is applied between the holder 2 and the extraction electrode 7 from the extraction power source 25 to the accelerating electrode 18a.
(Extracting electrode 7), an acceleration voltage is applied from an acceleration power supply 26 between each of them. In this way, helium ions are extracted by applying an extraction voltage, and accelerated toward the target by applying an accelerating voltage. 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, an increase in temperature of the emitter is prevented.

Now, the containers 5D and 11D are metal tubes 5°11
Refrigerant tank 3. Since it is connected to the support stand 8, these refrigerant tanks 3. Although it is at the same potential as the support stand 8, the insulators 28A and 28
Since it is insulated from the ground by B, insulation from the ground side can be safely ensured. Moreover, these containers 5D,
Due to the insufficient shape and processing of 110, there are protrusions on its surface, and there is a risk that the electric field will be concentrated on these protrusions and an electric discharge will occur between the container 5D and the ground. Since it is surrounded by the electric field relaxation ring 32, a strong electric field that causes discharge will not leak outside the electric field relaxation ring.

[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 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 the apparatus. 1: Emitch tip 2: Holder 3: Refrigerant tank
4: Lens barrel 5.11: Metal tube 5D, 11
0: Container 5T, 11T: Nylon tube 5B
: Helium gas cylinder 11B: Nitrogen gas cylinder 6.
12.16: Vibrator 7: Support stand 8: Space part
9: Hole 9G: Good thermal conductor 10: Heat exchanger 13゜1
4: Bellows 15: Bypass pipe 17: Focusing lens 18a, 18b, -------, 18j: Accelerating electrode 19 Niblanking electrode 20 Niblanking aperture 21: Objective lens 22: Deflector
23: Target 24: Voltage dividing resistor 25: Drawer type! 26: Acceleration power supply 27: Control circuit 28A
, 28B: Insulator 29: Insulating frame 30; Floor 31:
・Iron plate 32: Electric field relaxation ring 33: Rubber sheet for vibration isolation

Claims (1)

[Claims] An ion source comprising an emitter held at a high voltage, 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 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 gas phase ion source comprising: a pedestal for insulating support; and an electric field relaxation ring surrounding the container.