JPS6314369Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a field ionization type ion source, and particularly to an ion source capable of generating high-intensity gas ions.

In recent years, the use of gas ions has been considered as a means of selectively etching minute areas of semiconductor wafers in the manufacturing process of VLSI devices.
Gas ion sources suitable for this purpose are being developed. FIG. 1 shows an example of a field ionization type gas ion source suitable for this ion etching and also for an ion probe microanalyzer, and numeral 1 in the figure is a vacuum chamber for ionization. In the vacuum chamber 1, an emitter tip 4 having a sharp tip is supported by struts 2 and 3 made of a material that is electrically conductive and has good thermal conductivity. An extraction voltage of about 5 to 10 KV from an appropriate current is applied between the chip 4 and the extraction electrode 5, and a voltage of 20 to 10 KV is applied between the chip 4 and the cathode 6 at ground potential.
An accelerating voltage of about 50KV is applied. The pillar 3,
4 is taken out to the outside of the vacuum chamber 1 through an insulator 7 disposed above the vacuum chamber and a cooling tank 9 in which a refrigerant 8 such as liquid nitrogen is placed inside the insulator 7. 10 is a gas cylinder filled with argon gas, for example, and the argon gas from the gas cylinder 10 enters the vacuum chamber 1 through a valve 11, a Teflon gas introduction pipe 12, and a passage 13 provided in the insulator 7. be introduced.

In the configuration as described above, emitter tip 4
The electric field is concentrated near the sharp tip, and a strong electric field is formed. As a result, when the valve 11 is opened and argon gas is introduced into the vacuum chamber 1, the argon gas near the tip of the chip 4 is ionized in the electric field and extracted as ions, which are further accelerated by the cathode 6. and used for purposes such as etching. Incidentally, the ion beam current i generated in such an ion source is a function of the gas pressure P and temperature T as shown below.

i∝PV/T ^3/2 In the above equation, V is the extraction voltage. Therefore, in order to increase the beam current and increase the brightness, it is sufficient to lower the gas temperature. Therefore, in the conventional ion source shown in FIG. 1, the gas introduction tube 12 is placed in a refrigerant 8 such as liquid nitrogen to lower the temperature of the gas introduced into the vacuum chamber 1, and 2, 3 Furthermore, the emitter chip 4 is cooled by a refrigerant 8 to lower the gas temperature within the vacuum chamber 1. However, in the above-described configuration, the insulator 7 must be made long in order to prevent creeping discharge between the pillars 2, 3, etc. to which high voltage is applied and the outer wall 14 of the vacuum chamber 1. Therefore, the distance between the cooling tank 9 containing the refrigerant 8 and the tip of the emitter chip 4 where ionization is performed inevitably becomes long, and the cooling efficiency of the tip of the chip 4 is poor, resulting in a decrease in the temperature of the gas to be ionized. It cannot be made as low as desired.

This invention was made in view of the above points,
It is an object of the present invention to provide a field ion source that can lower the temperature of ionized gas and generate a high-intensity ion beam.

A field ionization type ion source based on the present invention includes a member disposed in a vacuum chamber for ionization and having a sharp tip, means for forming a strong electric field at the tip of the member, and a support member for supporting the member. a gas introduction pipe for supplying gas to be ionized into the vacuum chamber; an insulator disposed above the vacuum chamber and partially hollow; and an insulator disposed close to the insulator. The support member and a part of the gas introduction pipe are disposed in the refrigerant in the hollow part of the insulator.

An embodiment of the present invention will be described in detail below with reference to FIG.

In FIG. 2, the same parts as in FIG. 1 are given the same numbers and their explanations are omitted, but in this embodiment, a bottomed cylindrical insulator 15 is used in place of the insulator 7 in FIG. There is. The hollow part of the insulator 15 communicates with the inside of the cooling tank 9, and a refrigerant 8 such as liquid nitrogen is in communication with the inside of the cooling tank 9.
is filled by. The struts 2 and 3 supporting the emitter chip 4 and the gas introduction pipe 12 for introducing gas into the vacuum chamber 1 are arranged in the refrigerant in the hollow part of the insulator 15.

With the configuration shown in FIG. 2, the distance between the refrigerant and the tip of the emitter chip 4 can be significantly shortened even though a sufficiently long insulator is used, so that the distance between the refrigerant and the tip of the emitter chip 4 can be significantly shortened. As a result, the temperature of the gas that reaches the tip of the chip can be lowered, and the cooling efficiency of the pillars and the chip in the vacuum chamber is improved, so the gas near the tip of the chip is maintained at a low temperature and the generated ion beam is Current can be increased.

As detailed above, the present invention provides an ion source capable of generating a high-intensity ion beam.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional ion source, and FIG. 2 is a sectional view showing a field ion source which is an embodiment of the present invention. 1: Vacuum chamber, 2, 3: Strut, 4: Emitter chip, 5: Extraction electrode, 6: Cathode, 7: Insulator, 8: Refrigerant, 9: Cooling tank, 10: Gas cylinder,
11: Valve, 12: Gas introduction pipe, 13: Passage, 1
4: Exterior wall, 15: Insulator.

Claims (1)

[Scope of utility model registration request] A member arranged in a vacuum chamber for ionization and having a sharp tip, means for forming a strong electric field at the tip of the member, a support member for supporting the member, and supplying gas to be ionized into the vacuum chamber. an insulator placed in the upper part of the vacuum chamber and partially hollow; and an insulator placed close to the insulator and communicating with the hollow part of the insulator, A field ionization type ion source comprising a cooling tank into which a refrigerant is placed, and wherein the support member and a part of the gas introduction pipe are disposed in the refrigerant in the hollow part of the insulator.