JPS60180048A - Electric field type ion source - Google Patents

Abstract

PURPOSE:To obtain a high luminescent pattern irradiation capability in an electric field type ion source by forming the nib of an emitter tip with a porous metal and filling the cavity inside the tip with a liquefied gas to become ionization ions. CONSTITUTION:An electric field type ion source applied to such as the irradiation source of a lithographic device is formed by including an emitter tip 7 as an ionization electrode, which has a sharp curvature surface 10 at the nib made of a porous metal 8 solidified by sintering fine metal particles, an insulating body 9 of such as ceramics to support the emitter tip 7, and a draw-out electrode 2, and by filling the cavity 11 inside the tip 7 with liquefied gas such as hydrogen to become ionization ions. An amount of ionized gas is discharged in such a rapid process that when an ion source atom flown in from the porous metal 8 is ionized, the next atom flows in immediately and is ionized. Therefore, the luminance at the exposure ion irradiation source can be sharply increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to an electric field type ion source applied to an irradiation source of a lithographic apparatus.

(b) Background of the Technology In recent years, with the trend toward larger scale and higher density integrated circuits, ion beam exposure has attracted attention.

Compared to other exposure methods using X-rays or electron beams, this exposure method has high resolution because there is less lateral scattering and proximity effects during pattern exposure on resists or metal evaporation masks for fine pattern formation, and Extremely high exposure sensitivity.

The present invention relates to the formation of a fine pattern mask and the FIB (
This invention relates to improvements in irradiation sources (Focused Ion Beam) or ion sources.

(C) Prior Art and Problems An example of the configuration of this type of ion beam irradiation source will be explained with reference to a sectional view in FIG.

In Fig. 1, 1 is an electrode (commonly called an emitter tip) for gas ionization made of tungsten or the like that has been polished to a radius of curvature of the tip of about 0.1 μm, and 2 is an emitter tip. 1 is an ion extraction electrode that coaxially surrounds 1 and serves as the other side electrode for gas ionization; 3 is a high-purity hydrogen gas ejection hole on the side surface of the extraction electrode 2; and 4 is an ionization electrode formed at the axial center of the electrode 2. It is a radiation hole for hydrogen ions.

Although the electrodes I and 2 arranged in the above arrangement are not shown in detail, they are isolated by a highly thermally conductive insulator, and the isolated space is filled with the hydrogen gas at a pressure of about 10-2 Torr.

By applying a DC high voltage of 5 to 20 kV between the electrodes 1 and 2, the electric field strength near the curvature 6 of the tip of the emitter tip becomes sufficient for gas ionization. In this way, ionized hydrogen ions are generated, and the generated ions are extracted, accelerated, focused by a focusing lens system, etc., and irradiated onto a target object for fine pattern formation (a focusing lens, a scanning electrode for beam deflection, etc.) (not shown).

However, gas ionization at the tip of the emitter tip in the conventional ion source is rate-limited by the gas adsorption phenomenon on the tip surface, so the amount of ionized ions is limited, for example, 0.5 μ per unit solid circumference. Small, less than eight. Furthermore, the gas adsorption effect of the amount of ions emitted from the tip of the tip deteriorates depending on the cleanliness of the tip surface. For this reason, there are also problems such as a reduction in the brightness of beam irradiation as a radiation ion source.

(d) Purpose of the invention The present invention is to solve the above problems.

The object of the present invention is to embody a point gas ion source capable of pattern irradiation with high brightness in the FBI irradiation lithography apparatus and the like.

(e) Structure of the Invention The above-mentioned object is to provide an ion source that focuses and deflects an ion beam for irradiation, which is equipped with a porous metal emitter chip and filled with a cooling medium to draw out the gas. This can be achieved by

(f) Embodiments of the Invention Hereinafter, embodiments of an electric field type ion source of the present invention applied to an irradiation source of an ion beam lithography apparatus will be described in detail with reference to the drawings.

The present invention provides an emitter made of a sintered metal body that releases a large amount of ionized gas to speed up the process in which when the ion source atoms flowing into the tip of the emitter tip are ionized, the next atoms immediately flow in and are ionized. Chips are used.

FIG. 2 is a cross-sectional view of the ion source schematically showing the configuration of the emitter chip.

In the figure, 7 is an emitter tip as an ionization electrode whose tip has a sharply curved surface, 2 is the lead-out electrode explained in the conventional configuration diagram, and 8 is a sintered metal particle formed with a sharply curved surface 10 of the emitter tip 7. The solidified porous metal and 9 are insulators made of ceramic or the like that insulate and support the chip 7 and form an air-tight joint 13 that isolates it from the outside air, and is a wall that forms an ionization space for ions.

Further, the chip body 7 has an internal cavity 11 formed of porous metal, and the cavity is filled with a liquefied gas that becomes ionized ions. The filling gas is at atmospheric pressure or at a slightly higher pressure. The liquefied gas used is -25
An element such as hydrogen at 3°C (boiling point) or argon at -186°C is used.

As is clear from this, the ion source of the present invention is different from the conventional resistance heating type or induction heating type ion source using RF power, and is equipped with an emitter tip electrode 7 that can be filled with an extremely low temperature liquefied medium. -Also, the electrode tip 10 forming the ionization interface is made of porous sintered metal 8 into which the liquefied gas in the cavity 11 can infiltrate.

FIG. 3 is a schematic cross-sectional view of an electrode of another embodiment of the ion source of the present invention.

Compared to the embodiment shown in FIG. 2, the porous sintered metal 8 into which the liquefied gas filling the cavity 11 constantly permeates is disposed at the electrode tip 10, but the main differences are as follows. .

A coaxial double-tube electrode 12 surrounds the emitter tip electrode body 7 (see FIG. 2) in FIG. 3 and cools the area around the electrode. The liquefied gas to be filled in the coaxial electrode 12 is liquefied helium at -269°C in the external tube 14 (!lj) when used as the hydrogen ion source, and external liquefied helium at -269°C when used as the argon ion source. The tubes 14 are filled with liquefied nitrogen at -196° C. (boiling point) to cool the elements inside the inner tubes 15.

In this way, unnecessary loss or unnecessary vaporization of the ion source gas can be avoided, and the ion source gas that easily sublimates can be used efficiently.

According to the electric field type ion source equipped with the porous emitter tip electrode described in detail above, the gas partial pressure at the tip tip can be appropriately increased, and the ion current can be easily controlled. Therefore, a high-intensity beam irradiation source for forming fine patterns can be easily obtained.

(g) Effects of the Invention (5) According to the electric field type ion source equipped with the porous emitter tip electrode of the present invention, there is no restriction on the supply of ion source gas, and exposure ion irradiation for forming fine patterns, which has been a problem in the past. There are many advantages, such as increasing the brightness of the source.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of the main parts of a conventional ion source. FIG. 2 is a cross-sectional view schematically showing the main structure of the ion irradiation source of the present invention, and FIG. 3 is a cross-sectional view schematically showing another embodiment of the ion irradiation source of the present invention.

Claims (1)

[Claims] An electric field type ion source that focuses, deflects, and directs an ion beam, and is characterized by having a porous metal emitter tip and filling the tip with a cooling medium to draw out the gas.