JPS58192254A - Electrostatic-type deflector for charged particle rays - Google Patents

Abstract

PURPOSE:To obtain a charged-particle optical system which has a reduced size and a decreased aberration by integrating an electrostatic-type deflector with an astignatism corrector. CONSTITUTION:4N (N=2-6) electrodes are located symmetrical relative to an axis, and a deflecting voltage (Vx, Vy), an astigmatism-correcting voltage (Va, Vb) or a voltage which is the sum of the above voltages is applied to each of the 4N electrodes. Application of a deflecting voltage to each electrode is performed in order to remove a 4-times symmetrical deflectional aberration (named a rotation uncharged system). By applying an astigmatism-correcting voltage in addition to the deflecting voltage to each electrode as indicated in the figures, the astigmatism of charged particle rays can be corrected without disturbing a deflecting electric field. As a result, a deflector and an astigmatism corrector can be integrated with one another and a location space can be saved, thus the aberration of the entire optical system which suppresses its own deflectional aberration is reduced. In addition, since the deflector is the electrostatic type, it is suitable for high speed deflection and high speed correction as well compared to that of the magnetic field type.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic type I deflector and an astigmatism corrector that are particularly suitable for miniaturization in a charged particle beam optical system.

The conventional electrostatic deflector and astigmatism corrector are arranged separately in the traveling direction of the charged particle beam (generally, the beam passes through the astigmatism corrector and then the deflector). Ta. At this time, a space is required to arrange each of them, and in particular, in a self-cancelling optical system for deflection aberration such as that disclosed in JP-A-52-124873, it is difficult to obtain a sufficient effect due to the space in which the astigmatism corrector is arranged. There was a drawback that it could not be done.

An object of the present invention is to provide an integrated electrostatic deflector and astigmatism corrector in order to reduce the size and aberration of a charged particle optical system.

An electrostatic deflector or astigmatism corrector applies a desired voltage between a plurality of electrodes, and according to the electric field generated thereby, it is possible to deflect a charged particle beam and correct astigmatism. On the other hand, the electric field Fi
Since it is an A-type coupling, if the electrodes of the deflector and the astigmatism corrector are the same, the voltages between the electrodes can be simply added to integrate the deflector and the astigmatism corrector without disturbing their respective electric fields. The present invention has been devised in accordance with the principle of leverage, and special care has been taken to prevent the occurrence of four-fold symmetrical deflection aberration.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 3. Each figure is a cross-sectional view perpendicular to the traveling direction of the charged particle beam.

Figure 1: Fi8 electrodes (pt~P, l; Figure 2: F'i12 electrodes (Q, -Q□); Figure 3: Vi24 electrodes (R,~R14).
). Also, in each figure, (v-, V
y) is a deflection voltage that deflects the charged particle beam two-dimensionally (X@y orthogonal coordinates) on the sample surface.

Seriously, (V −, V b ) is the astigmatism correction voltage for correcting the astigmatism of the Fi charged particle beam. In each figure, the method of applying the deflection voltage to each electrode is done in order to eliminate the deflection aberration of four-fold symmetry (referred to as a rotational inhomogeneous system). is Japanese Patent Publication No. 53-13436
(This is shown in No. 1. Figure 3 can be easily inferred from Figure 2. If a stigma correction voltage is further applied as shown in each figure to the deflection voltage of each of these electrodes, the deflection electric field will be Astigmatism correction of the charged particle beam becomes possible without disturbing the charged particle beam.As a result, the deflector and the astigmatism corrector can be integrated.In this embodiment, the 16th electrode and 20th electrode are omitted, but the same Generally, 4N electrodes (N22) are sufficient.

The present invention is particularly effective when applied to a self-cancelling optical system for deflection aberration. At this time, in order to remove astigmatism caused by deflection caused by manufacturing errors in the optical system, it is sufficient to use the "@sag...b, ij coefficients. In particular, the embodiment shown in FIG. In the case of electrode R,
, R, 4 to V a ” a @ * R1 * Rlo to -V.

=-a, and V b -1) to R6 @ R+s
6 *R8 and *R14 may be applied with an astigmatism correction voltage of -Vb"bs, and the constant terms V- and Vb't"i of the 0.0 equation may be eliminated. At this time, fixed astigmatism correction using a lens or the like and deflection astigmatism correction can be performed separately. In the present invention, since both the deflector and the astigmatism corrector are electrostatic type,
Compared to the magnetic field type, it is extremely effective in high-speed deflection and high-speed correction.

In this example, the electrodes are plate-shaped (Fig. 1, Fig. 2) and inner rod (Fig. 2).
Although only the one shown in Fig. 3) is shown, it goes without saying that C may be used as long as it functions as an electrode.

According to the present invention, since the deflector and the astigmatism corrector can be integrated, there is an effect that the space for arrangement can be saved. This also has the effect of reducing the aberrations of the entire optical system in cases such as self-cancelling optical systems where deflection aberrations are self-cancelled. Additionally, since it is an electrostatic type, it is suitable for high-speed deflection and high-speed correction compared to magnetic field type.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view perpendicular to the advancing direction of the charged particle beam, and Figure 2 shows an embodiment of the present invention using 12 electrodes. The drawing is a sectional view similar to FIG. 1. FIG. 3 is a cross-sectional view similar to FIG. 1, showing an embodiment of the present invention using 24 electrodes.

Claims (1)

[Claims] 1. Arrange 4N electrodes (N = 2 to 6) axially symmetrically, and apply F′i deflection voltage (V, ,V, ) and astigmatism correction voltage (
An electrostatic deflector for a charged particle beam configured to apply either a voltage (Va, Vb) or the sum of the above voltages.