JPH0724206B2 - Charged particle beam device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus including an extraction electrode for extracting a charged particle beam and an accelerating electrode for accelerating the charged particle beam extracted by the extraction electrode. .

[Prior Art] Recently, an ion beam apparatus using a gas phase ion source has been developed.

This gas phase ion source cools an emitter tip with a sharp tip to, for example, liquid helium at about 4 ° K, supplies helium gas to the tip of the tip, and causes helium gas molecules attached to the tip to be generated by an electric field. It is an ion source that is ionized and ionized.

Now, in the ion beam device, the ionized helium ions are extracted between the emitter tip and the extraction electrode by applying an extraction voltage Ve volt to the target direction, and the extracted ions are extracted by a plurality of acceleration electrodes. Furthermore, it accelerates Va bolt and irradiates the target. As a result, the total helium ion is (Ve + Va) volt =
It will be accelerated to Vt volt (Vt is 100k volt, for example) and will hit the target.

[Problems to be Solved by the Invention] However, in such an ion beam device, in order to change the amount of the ion beam extracted from the emitter tip, the voltage between the emitter tip and the extraction electrode is changed from Ve volt until then ( If changed to Ve + ΔVe) volts, the total acceleration voltage also changes from Vt volts to (Vt + ΔVe) volts, and the energy of the ion beam irradiated on the target deviates from the predetermined value.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a problem and to provide a charged particle beam device capable of constantly irradiating a target with a charged particle beam having a predetermined energy even when the ion beam current is changed. .

[Means for Solving Problems] In order to achieve such an object, the present invention includes an emitter,
An accelerating electrode arranged to face the emitter, an extraction electrode arranged between the emitter and the accelerating electrode, and between the emitter and the extraction electrode for extracting a charged particle beam from the emitter. A first power supply for applying a first voltage to the first electrode, and a first power supply between the extraction electrode and the acceleration electrode for accelerating the charged particle beam from the emitter together with the first voltage. A second power supply for applying the second voltage, and an output voltage of the first power supply so that the sum of the output voltage of the first power supply and the output voltage of the second power supply has a predetermined set value. According to the above, a means for automatically controlling the output voltage of the second power source is provided.

[Embodiment] The attached drawings are schematic views of an ion beam apparatus shown as an embodiment of the present invention.

In the figure, reference numeral 1 denotes an emitter tip, the tip of which is formed into an ultra-fine circular shape having a radius of curvature of several hundreds to several thousands angstroms. Reference numeral 2 is a holder for holding this chip. The holder 2 is inserted and mounted in a central portion of a refrigerant tank 3 formed of an annular heat conductor while maintaining thermal contact. Although not shown, this coolant tank is fixed to the upper portion of the lens barrel 4 by some holding body. Liquid helium is supplied to the refrigerant tank through the pipe 5, and at the same time, the helium gas vaporized here is discharged to the outside through the pipe 6. Reference numeral 7 is an extraction electrode which is arranged so as to face the chip 1, and has a small hole formed in the center thereof.
The extraction electrode is fixed to the upper surface of the support base 8 made of an insulating material. The support base is formed in an annular shape, and a circular truncated cone-shaped hole 9 is formed in the center thereof. The inner surface of this hole is made of a good thermal conductor. The smallest diameter portion of the truncated cone-shaped hole has the same size as the small hole of the extraction electrode. Liquid nitrogen is supplied to the space 8S inside the support through the heat exchanger 10 and the pipe 11, and at the same time, the nitrogen gas vaporized in the space 8S is discharged through the pipe 12. Reference numerals 13 and 14 respectively 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 8. The space A isolated at the upper part of the lens barrel by these bellows 13 and 14 is thermally insulated from the spaces B and C. Then, the space A passes through the valve 28,
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 tip 1 in the space A.

Reference numeral 17 is a focusing lens, and 18a, 18b, ..., 18j are accelerating electrodes. Reference numeral 19 is a blanking electrode, and 20 is a blanking diaphragm. Reference numeral 21 is an objective lens, and 22 is a deflector for controlling the position of helium ions on the target 23. Reference numeral 24 is a voltage dividing resistor for determining the divided voltage of the DC high voltage voltage applied to the accelerating electrodes 18a, 18b, ... One end p of this voltage dividing resistor is connected to the extraction electrode 7, and the other end is connected to the ground.

25 is a first power source for applying a first voltage between the holder 2 and the extraction electrode 7 in order to extract the ion beam from the emitter tip 1 toward the target 23, and 26 is the In order to accelerate the ion beam from the emitter tip 1 together with the first voltage, a second voltage (DC high voltage) is applied between one end p of the voltage dividing resistor 24 and the ground. It is the second power source. 27 is the first power source
25 is a control circuit for automatically controlling the output voltage of the second power supply 26 so that a signal representing the output voltage of the second power supply 26 is supplied and the sum of both signals becomes a predetermined set value.

The device thus constructed operates as follows.

After the spaces A and B have been evacuated to a high vacuum state, the space A is closed by the valve 28 and 4 ° K by the liquid helium in the cooling tank 3.
The molecules of the helium gas introduced through the pipe 16 adhere to the tip of the chip cooled to some extent. At this time, the holder 2
From the first power source 25 to the extraction electrode 7 between the extraction electrode 7 and the extraction electrode 7, and between the acceleration electrode 18a (extraction electrode 7) and the ground (target 23) from the second power source 26 to the Va voltage. It is applied respectively.

Now, assuming that the output voltage of the first power supply 25 is increased by ΔVe volts in order to increase the amount of the ion beam with which the target 23 is irradiated, for example, the signal supplied from the first power supply 25 to the control circuit 27 is The control circuit 27 controls so as to maintain the sum of the signal from the first power source 25 and the signal from the second power source 26 at a predetermined set value because the voltage increases corresponding to ΔVe volt. A control signal is applied to the second power supply 26 to reduce its output voltage by .DELTA.Ve volts. As a result, the generated ions are (Ve +
ΔVe) Volt acceleration and (Va-ΔVe) by the acceleration electrode
Since the voltage is accelerated by a volt, the target 23 is irradiated with a total of (Ve + Va) volt, and the target can always be irradiated with ions having a predetermined energy even if the extraction voltage is changed.

Incidentally, the present invention is not limited to the above-mentioned embodiment, and various modifications can be made.

For example, in the above-described embodiments, the present invention is applied to the gas phase type ion beam generator, but the present invention is also applicable to field emission type electron beam generators and the like.

EFFECTS OF THE INVENTION According to the present invention, the target can be always irradiated with the charged particle beam having a predetermined energy even if the extraction voltage is changed because the amount of the charged particle beam to be extracted is changed.

[Brief description of drawings]

The attached drawings are schematic views of an ion beam apparatus shown as an embodiment of the present invention. 1: Emitch chip, 2: Holder, 3: Refrigerant tank, 4: Lens barrel, 5,6,
11,12,16: Pipe, 7: Extraction electrode, 8: Support, 9: Hole, 10: Heat exchanger, 13,14: Bellows, 15: Bypass pipe, 17: Focusing lens, 18a, 18b, ... , 18j: acceleration electrode, 19: blanking electrode, 20: blanking diaphragm, 21: objective lens, 22: deflector, 23: target, 24: voltage dividing resistor, 25: first power supply, 2
6: Second power supply, 27: Control circuit, 28: Valve

Claims (1)

[Claims] 1. An emitter, an accelerating electrode arranged to face the emitter, an extraction electrode arranged between the emitter and the accelerating electrode, and an extraction electrode for extracting a charged particle beam from the emitter. A first power supply for applying a first voltage between the emitter and the extraction electrode; and the extraction electrode for accelerating the charged particle beam from the emitter in combination with the first voltage. A second power supply for applying a second voltage between the accelerating electrode and a sum of the output voltage of the first power supply and the output voltage of the second power supply has a predetermined set value. According to the output voltage of the first power supply, the second
Charged particle beam device comprising means for automatically controlling the output voltage of the power source of