JPH04328231A - Blanking method for charged particle beam - Google Patents

Abstract

PURPOSE:To make blanking with no generation of beam trailing while the beam converging characteristic is well held. CONSTITUTION:Between electrostatic lenses 3 and 7 in two-step arrangement, a charged particle beam 1 is made a parallel beam with which the aberration coefficient minimizes. Deflection with the same deflecting angle and with opposite signs, plus and minus, is made with electrostatic deflectors 11, 12 installed there in two-step arrangement, and blanking is performed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focused charged particle beam apparatus for performing fine processing and observation using a focused charged particle beam.

0002

[Prior Art] Conventionally, in order to perform blanking of a charged particle beam without creating streaks in the charged particle beam, the charged particle beam is once focused between a condenser lens and an objective lens, and the charged particle beam is focused once between a condenser lens and an objective lens. beam 11
Deflectors (upper deflector 12 and lower deflector 13) are provided above and below the focusing point A14, and the charged particle beam 11 deflected by the upper deflector 12 is further deflected by the lower deflector 13. By aligning the virtual light source of the charged particle beam 11 deflected by the deflector 13 with the focusing point A14 when the beam is not deflected, a streak is drawn on the sample surface where the charged particle beam 11 is finally focused by the objective lens. This made blanking possible without any problems.

0003

[Problem to be solved by the invention] In the prior art,
The charged particle beam is once focused between the electrostatic lens, condenser lens, and objective lens, but compared to the case where the charged particle beam runs parallel between the condenser lens and the objective lens, the aberrations of the condenser lens and objective lens are smaller. The coefficient is large, which is not preferable for further focusing the charged particle beam. The present invention does not impair the focusing property of the charged particle beam,
The object is to enable blanking of a charged particle beam without creating streaks due to blanking.

0004

[Means for Solving the Problems] In order to achieve the above object, the present invention converts a charged particle beam into a parallel beam using a condenser lens, minimizes aberrations of the condenser lens and object lens, and uses an upper deflector to make the charged particle beam a parallel beam. The charged particles are deflected at the same deflection angle as the upper deflector, but in the opposite direction.The charged particles deflected by the upper deflector are synchronized so that they are deflected by the lower deflector, and the charged particles are deflected by the lower deflector. Blanking of the charged particle beam is performed by blocking the charged particle beam with an aperture.

[0005]

[Embodiment] An embodiment of the present invention is shown in FIGS. 1 and 3. As shown in FIG. 1, a charged particle beam 2 generated from a charged particle source 1 is made into a parallel beam by an electrostatic lens/condenser lens 3, and an electrostatic lens/objective lens 7 focuses the charged particle beam 2 onto a sample surface 8. A two-stage electrostatic deflector, an upper-stage deflector 4 and a lower-stage deflector 5 are provided between the The lower deflector 5, which has rising and falling characteristics, is synchronized with a certain time delay so that the same charged particles receive a force in the opposite direction and by the same amount as the deflection angle by the upper deflector 4. Blanking aperture 6 provided at the bottom
The charged particle beam 2 is shielded by.

In order to satisfy the above conditions, as shown in FIG. 3, the gaps D1 and D2 of the upper deflector 21 and the lower deflector 22, the effective electric field lengths L1 and L2, and the voltage applied to both ends ±V1 are required. , ±V2, When the drift space between the two deflectors is La, the condition that the deflection angle by the upper deflector 21 and the deflection angle by the lower deflector 22 have opposite signs and the same magnitude is L1 ・V1 /D1 +L2 - Satisfied by dimensions or potential that satisfy V2/D2 = 0. In addition, in order for the same charged particle deflected by the upper deflector 21 to be deflected with the opposite sign and the same deflection angle by the lower deflector 22, the rise and fall times of the voltage are different from those of the upper deflector 21 and the lower deflector. 22 are the same, and the voltage applied to the lower deflector 22 is Δt=7.22×1 compared to the voltage applied to the upper deflector 22.
It is sufficient to delay the time by 0-5×(L1+La)×(M/φ0)1/2. However, the units of Δt are seconds, L1, L
The unit of 2 is meters, M is the mass number of charged particles, φ0
is the energy of a charged particle in electron volts. At this time, the amount of deflection Δx by these two deflectors is Δx=L1 ・V1 (L1 +L2 +2La)/
4D1 φ0, and the diameter of the blanking aperture is 2Δ, if the beam diameter on blanking is d0.
More than x-d0 is required.

By blanking the charged particle beam under the above conditions, the blanking is performed while the charged particle beam is incident perpendicularly to the objective lens as a parallel beam, and therefore, the blanking is performed with the charged particle beam entering the objective lens perpendicularly as a parallel beam. The position of the virtual light source does not change from the start of blanking to the end, and the irradiation position of the charged particle beam on the sample surface does not change. This makes it possible to avoid streaking of the charged particle beam.

[0008]

As described above, blanking can be performed with the charged particle beam in the best convergence state and without streaking on the sample surface due to blanking.

[Brief explanation of drawings]

FIG. 1 shows a charged particle beam blanking method according to the present invention.

FIG. 2 shows a conventional method.

FIG. 3 is a diagram for explaining the conditions of the present invention.

[Explanation of symbols]

1 Charged particle source 2 Charged particle beam 3 Condenser lens 4 Upper stage deflector 5 Lower deflector 6 Blanking aperture 7 Objective lenses 8 Sample surface 11 Charged particle beam 12 Upper stage deflector 13 Lower deflector 14 Focusing point A 15 Deflected charged particles 21 Upper stage deflector 22 Lower deflector 23 Deflected charged particles

Claims (1)

[Claims] 1. A charged particle source that generates charged particles, a condenser lens and an objective lens that constitute a two-stage electrostatic lens that focuses a charged particle beam generated from the charged particle source, and the condenser lens and the object lens. In between, two sets of electrostatic deflectors are arranged in series in the beam running direction so that the direction vectors perpendicular to the electrode plates of the two sets of electrostatic deflectors are parallel to each other so that the beam can be deflected in the same plane, In a charged particle device comprising an aperture that blocks the charged particle beam deflected by the two sets of electrostatic deflection plates, the charged particle beam is made parallel by the capacitor and deflected by the two sets of electrostatic deflectors. A charged particle beam blanking method characterized in that the directions of electric fields created by voltages applied to the two sets of electrostatic deflectors are reversed so that the deflection angles of the charged particle beams cancel each other out.