CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2021-029008 filed on Feb. 25, 2021 in Japan, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

One aspect of the present invention relates to a cathode mechanism of an electron gun, an electron gun, and an electron beam writing apparatus.

Description of Related Art

The lithography technique that advances miniaturization of semiconductor devices is extremely important as a unique process whereby patterns are formed in semiconductor manufacturing. In recent years, with high integration of LSI, the line width (critical dimension) required for semiconductor device circuits is becoming increasingly narrower year by year. The electron beam writing technique which intrinsically has excellent resolution is used for writing or “drawing” a mask pattern on a mask blank with electron beams.

For example, as a known example of employing the electron beam writing technique, there is a writing apparatus using multiple beams. Since it is possible for multi-beam writing to apply multiple beams at a time, the writing throughput can be greatly increased in comparison with single electron beam writing. For example, a writing apparatus employing the multi-beam system forms multiple beams by letting portions of an electron beam emitted from an electron gun individually pass through a corresponding one of a plurality of holes in a mask, performs blanking control for respective formed beams, reduces by an optical system beams that were not blocked in the blanking process to reduce a mask image, and deflects the reduced beams by a deflector to irradiate a desired position on a target object or “sample”.

In a thermal electron gun emitting electron beams, the operating temperature of the cathode increases along with achieving higher luminance of the cathode. The conventional cathode is assembled by mechanically combining a plurality of parts through which currents flow. Therefore, there exist a plurality of electric contact portions, resulting in a problem that resistance of the entire cathode becomes unstable. Moreover, when a plurality of parts through which currents flow are fixed within a ceramic serving as an insulating part, the temperature of the ceramic also increases at the time of heating, resulting in a problem that insulation breakdown tends to occur easily.

There is disclosed a cathode mechanism, integrated from glassy carbon, composed of a pair of energizing terminals, a pair of legs each extending from each of the terminals such that the sectional area of the leg gradually becomes small, and a support part which connects the pair of legs at the narrowest portions and on which lanthanum hexaboride (LaB6) powder is placed (e.g., refer to Japanese Patent Application Laid-open (JP-A) No. 2001-084932).

BRIEF SUMMARY OF THE INVENTION

According to one aspect of the present invention, a cathode mechanism of an electron gun includes a crystal configured to emit a thermal electron from an end surface by being heated, a holding part configured to hold the crystal in a state where the end surface is exposed and at least a part of other surfaces of the crystal is covered, a first supporting post and a second supporting post each configured to support the holding part and extend while maintaining an unchanged sectional size, a first base part configured to fix the first supporting post, and a second base part configured to fix the second supporting post, wherein the holding part, the first supporting post, the second supporting post, the first base part, and the second base part are formed in an integrated structure made of a same material, and the crystal is heated by supplying a current to the integrated structure.

According to another aspect of the present invention, an electron gun includes the cathode mechanism of the electron gun described above, and an anode electrode configured to be controlled to have a potential more positive than that of a crystal and to pull out a thermal electron emitted from the crystal.

According to yet another aspect of the present invention, an electron beam writing apparatus includes the electron gun described above, and a writing mechanism configured to write a pattern on a target object using a thermal electron emitted from the electron gun.

