Electron gun used in an electron beam exposure apparatus

Details Electron gun used in an electron beam exposure apparatus Electron gun used in an electron beam exposure apparatus

1999-06-17

2001-06-26

Patel, Vip (Department: 2879)

Electric lamp and discharge devices

Cathode ray tube

Plural beam generating or control

C313S336000, C250S492230, C250S42300F, C250S346000, C250S492200

Reexamination Certificate

active

06252344

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exposure apparatus using a charged particle beam such as an electron beam. In particular, it relates to an electron gun for generating the electron beam used for drawing predetermined patterns on a material to be exposed (particularly, a wafer) in an electron beam exposure apparatus.
2. Description of the Related Art
Conventionally, there are many known electron beam exposure apparatuses, for example, a variable rectangular exposure apparatus, a block exposure apparatus, and a blanking aperture array (BAA) exposure apparatus. In these exposure apparatuses, there is a mask or block mask having a rectangular aperture in order to form a cross-sectional shape of the electron beam, art aperture having an optional shape used as a unit of repeating figure, and a plurality of apertures arranged in matrix. The electron beam is formed by irradiating a desired area of the aperture on the mask so that a desired pattern is drawn on the wafer.
In this case, the uniformity of the electron beam irradiated to the wafer has a large influence to a line width of the pattern to be drawn. For example, when it is assumed that an allowable line width is 0.01 &mgr;m when drawing a line having a width of 0.1 &mgr;m, the uniformity of beam irradiation is allowed for fluctuation of only a few percent. As a result, an irradiation area which appears to be uniform becomes narrow, and an exposure area is reduced so that the throughput of the electron beam exposure apparatus deteriorates.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an improved electron gun used in an electron beam exposure apparatus.
In accordance with the present invention, there is provided an electron gun and, in preferred embodiment, a four-pole electron gun, used in an electron beam exposure apparatus, including: a cathode for emitting an electron beam when a negative and high-accelerated voltage is supplied; a first grid provided at a downstream of the cathode for focusing a crossover image of the electron beam when supplying a voltage which becomes a reverse bias for the cathode, and the cathode and the first grid being arranged at a high voltage side of a high voltage insulator; an anode, for collecting the electron beam which passes through the first grid, arranged at a low voltage side of the high voltage insulator; and a second grid, provided at the high voltage side of the high voltage insulator and between the first grid and the anode, having an aperture for limiting an amount of the electron beam passing therethrough; wherein a voltage which becomes a forward bias for the cathode is supplied to the second grid, and the crossover image is focused at the aperture of the second grid.
In another preferred embodiment, the electron gun further includes an electromagnetic deflector for deflecting the electron beam emitted from the cathode toward the aperture of the second grid, wherein the electromagnetic deflector is arranged at a location insulated from the cathode and the first/second grids by the high voltage insulator, and is arranged at the location approximately corresponding to the location of the cathode for the direction of the electron beam.
In still another preferred embodiment, the electron gun further includes a difference detecting circuit for calculating a current (IB) passing through the aperture of the second grid based on a difference between an emission current (IE) emitted from the cathode and the current (IG
2
) inputting to the second grid, and for controlling at least one of the supply voltages (VG
1
, VG
2
) for the first and second grids (G
1
, G
2
) as the calculated current (IB) is kept constant.
In still another preferred embodiment, at least one of the supply voltages (VG
1
, VG
2
) for the first and second grids (G
1
, G
2
) is controlled as the emission current (IE) from the cathode is kept constant.
In still another preferred embodiment, at least one of the supply voltages (VG
1
, VG
2
) for the first and second grids (G
1
, G
2
) is controlled as the current (IG
2
) input to the second grid is kept constant.
In still another preferred embodiment, each of the supply voltages (VG
1
, VG
2
) for the first and second grids (G
1
, G
2
) is determined as a ratio (IB/IE) of the current passing through the aperture of the second grid and the emission current (IE) emitted from the cathode becomes maximum.


REFERENCES:
patent: 4200555 (1980-04-01), Joy et al.
patent: 4528474 (1985-07-01), Kim
patent: 5155412 (1992-10-01), Chang et al.
patent: 5449968 (1995-09-01), Terui et al.
patent: 5854490 (1998-12-01), Ooaeh et al.

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