JPH0646553B2 - Electronic beam device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam apparatus, and more specifically, to a deflector having a deflection lens made of a ferromagnetic material for electromagnetically deflecting an electron beam at a predetermined position. The present invention relates to a provided electron beam device.

[Prior Art] FIG. 4 shows a thermal processing machine such as an electron beam welding machine and an electron beam drawing apparatus as an example of a conventional electron beam apparatus. In the figure, an electron beam emitted from an electron gun (1) is shown. (2) is
It is focused on the target (5) by the focusing lens (3). The deflection lens (6) deflects the electron beam (2) by a deflection signal generated by a signal source such as a computer and accurately positions the electron beam (2) on the target (5). Generally, when the deflection area is large, a magnetic field deflection lens is used. But,
Since various errors are generated in the beam irradiation position in the magnetic field deflection due to the generation of eddy current and the hysteresis effect, various measures have been conventionally performed.

For example, FIG. 5 shows a focusing lens and a deflecting lens of a conventional electron beam apparatus disclosed in Japanese Patent Laid-Open No. 54-137977. In the figure, the magnetic pole (11) of the focusing lens (3) also serving as a magnetic shield is shown. A magnetic pole (12) of the focusing lens (3), a coil (13) of the focusing lens (3), a magnetic pole (14) of the deflecting lens (6) and a coil (15) of the deflecting lens (6).

With the above configuration, a high frequency current of several 100 KHz or more flows in the coil (15) of the deflection lens (6) to scan the electron beam (2) at high speed, and a high frequency magnetic field is generated in the deflection lens magnetic pole (14) or in the deflection lens. It occurs around the lens (6). Therefore, when the magnetic pole (14) of the deflecting lens is made of metal or when the metal is present near the deflecting lens (6), an eddy current is generated by the high frequency magnetic field, and the deflecting magnetic field is disturbed. Therefore, in this example, the magnetic pole (14) of the deflection lens and the magnetic pole (11) made of ferrite are provided at the tip of the magnetic pole (12) most susceptible to the high frequency magnetic field among the components of the focusing lens (3). The above-mentioned hysteresis is reduced by arranging them to reduce the generation of the above-mentioned eddy current and by selecting the ferrite material.

[Problems to be solved by the invention]

In the conventional electron beam apparatus, the deflection lens system is configured as described above, and a magnetic material such as ferrite is used for the components near the deflection lens system mainly to prevent the eddy current. However, since ferromagnets such as ferrite always have a hysteresis characteristic, an electron beam is used, which produces a residual magnetic field and accurately varies the beam irradiation position even in the same deflection current value and in the magnetic field deflection lens system. A high-precision processing or exposure apparatus has a serious problem.

The present invention has been made in order to solve the above problems, and a deflection lens system capable of accurately determining a beam irradiation position even in a magnetic field deflection lens system made of a material having a hysteresis characteristic is provided. The purpose of the invention is to obtain an electron beam device equipped with the device.

[Means for solving problems]

The electron beam apparatus according to the present invention includes a deflection lens system in which a ferromagnetic ring having a hysteresis characteristic is intentionally arranged above or below a deflection lens having a ferromagnetic core.

[Action]

The magnetic ring according to the present invention allows the leakage magnetic field of the deflecting lens to pass therethrough and generates the residual magnetic field in the opposite direction to the residual magnetic field of the deflector in the beam path, thereby causing an error in the beam irradiation position due to the residual magnetic field due to the hysteresis characteristic. Cancel.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, rings (21) made of ferrite, which is a ferromagnetic material, are disposed above and below the deflection lens (6). (22) is the deflection magnetic flux generated by the deflection current flowing in the coil (15), (23) is the leakage magnetic flux generated by the deflection current flowing in the coil (15), and (24) is the deflection magnetic flux when the deflection current is zero. The residual magnetic flux remaining in the beam path due to the hysteresis characteristic of the magnetic pole (14) of the lens (hereinafter referred to as the core residual magnetic flux), (25) is the ring (21) when the deflection current is zero.
The residual magnetic flux remaining in the beam path due to the hysteresis characteristic (hereinafter referred to as ring residual magnetic flux). Fig. 2
(a) and (b) show the direction of the magnetic flux in the deflection lens (6) and the ring (21) from the top.

With the above configuration, the deflection current flowing in the coil (15) generates the deflection magnetic flux (22) and the leakage magnetic flux (23). Bending magnetic flux (22)
Acts on the electron beam (2) to deflect it. When the magnetic flux leaks (23) exits the N pole of the magnetic pole (14), it enters the adjacent ring (21), passes through the ring (21), and again exits into the space near the S pole and the magnetic pole (14). Enter the S pole. As shown in FIG. 2, the directions of the magnetic flux in the deflection lens (6) and the magnetic flux in the ring (21) are opposite. Therefore, after the current flowing through the coil (15) is set to 0, the directions of the core residual magnetic flux (24) and the ring residual magnetic flux (25) are opposite to each other. Both act in the electron beam (1), but since their directions are opposite to each other, their influence on the irradiation position of each beam is canceled out.

The above operation will be described in more detail with reference to FIG.
(14), the total length of the ring (21) in the beam orbit direction, l _c and l _r, and the residual magnetic flux densities B _cr and B _{rr in} the beam orbit of the deflection lens (6) and the ring (21) are B _cr l _c 2B _{By selecting} the hysteresis characteristic or size of the magnetic material under the condition of _rr l _r , the error of the beam irradiation position can be completely canceled.

Further, since the ring (21) also functions as a shield material for the leakage magnetic flux, even when a metal such as a focusing lens is present near the deflection lens (6), there is a double effect that an eddy current is not generated.

In the above embodiment, the ring (2
Although the example in which 1) is provided is shown, the same effect can be obtained even with one ring.

Although an example of ferrite is shown as the deflecting lens and the ring material, a ferromagnetic material such as permalloy may be used when it is not operated at a high frequency.

Further, in the above embodiment, the case of the electron beam processing device and the exposure device was described, but it may be another device using high precision magnetic field deflection such as a high precision display, and the same effect as the above embodiment is obtained. Play.

〔The invention's effect〕

As described above, according to the present invention, since the ferromagnetic ring having the hysteresis characteristic is arranged on at least one of the upper and lower sides of the deflection lens, it is possible to cancel the influence of the hysteresis such as the deflection magnetic pole on the electron beam. A deflection lens system with high beam irradiation position accuracy can be obtained, and even when there is a metal such as a focusing lens near the deflection lens, the leakage magnetic flux is shielded and an eddy current is not generated.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention, FIG. 1 is a side sectional view of an essential part, FIG. 2 is a partial plan view for explaining the action, and FIG. 3 is for explaining the action. FIG. FIG. 4 and FIG. 5 are side sectional views of a main part of a conventional electron beam apparatus. (1) …… electron gun, (2) …… electron beam, (3) …… focusing lens, (5) …… target, (6) …… deflecting lens, (14) ……
Deflection magnetic pole, (15) …… deflection coil, (21) …… ring. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An electron gun for generating an electron beam, a focusing lens system for focusing the electron beam on a target, and a deflection magnetic pole made of a ferromagnetic material for electromagnetically deflecting the electron beam at a predetermined position on the target. An electron beam apparatus comprising: a deflection lens having a reflection lens; and a ring made of a ferromagnetic material disposed close to at least one of an upper side and a lower side of the deflection lens.