JPS63231853A - Focusing and deflecting device - Google Patents

Abstract

PURPOSE:To eliminate the adverse effect of the magnetic field change based on the operation and deflect a charged particle beam at a large angle and a high speed by arranging a magnetic field type deflecting unit and an electrostatic type deflecting unit with the specific specification and operating them. CONSTITUTION:A magnetic field type deflecting unit 33 and an electrostatic type deflecting unit 34 are arranged between a lens 2 and a sample 4, and the distance LM between the deflecting unit 33 and the sample 4 is set to nearly twice as large as the distance LS between the deflecting unit 34 and the sample 4. Both deflecting unit 33, 34 are arranged to avoid the arranged position of the lens 2, and the fluctuation of the magnetic field generated during their operation gives no disturbance to the lens 2. The operation is performed so that the deflection quantity RM of the deflecting unit 33 on the sample 4 is nearly twice as large as the deflection quantity RS, of the deflecting unit 34 on the sample 4 and the deflection directions are made opposite to each other. That is, respective deflection angles by the deflecting units 33, 34 are the same in size and different in direction, a charged particle beam 1 is made vertical to the sample 4 face and deflected at a high speed, high precision, and a large angle.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a charged particle beam device, and particularly to a charged particle optical system suitable for deflecting a charged particle beam at a large angle and at high speed.

[Conventional technology]

In order to deflect the charged particle beam to a large angle while keeping it narrow,
A charged particle optical system with self-cancelling deflection aberration has been devised as shown in Japanese Patent Publication No. 14495/1982. This charged particle optical system is shown in FIG. The lenses and deflector of this optical system are constructed of magnetic field type. The charged particles [1 deflected by the first deflector 31 are subjected to the deflection action of the charged particle beam by the lens 2 and the deflection action of the second deflector 32.

At this time, the structure and operation are such that the deflection aberration caused by the deflector 31 can be canceled by the off-axis aberration of the lens 2 and the deflection aberration of the deflector 32.

However, in this optical system, at least the second deflector 32 must be placed inside the lens 2.

For this purpose, when the deflector is operated at high speed, the deflection magnetic field changes at high speed, and this alternating magnetic field generates a current in the coil of the lens. This current disturbs the lens magnetic field and affects the properties of the lens. Therefore.

There was a problem in that the charged particle beam could not be deflected at high speed.

[Problem that the invention seeks to solve]

In the above conventional technology, a deflector is installed inside the lens in order to self-cancel the deflection aberration. Il! This was caused by operating the deflector at high speed.

The purpose of the present invention is to solve this problem.

[Means for solving problems]

In order to achieve the above object, it is not necessary to arrange a deflection coil inside the lens. However, in general, the deflection aberration cannot be self-cancelled using a deflector alone. Therefore, if this self-cancellation can be achieved by combining only deflectors, the above object can be achieved.

To this end, we devised a charged particle optical system that can be realized by appropriately combining magnetic field type and electrostatic type deflectors.

[Effect]

There are two types of deflectors: magnetic field type and electrostatic type, and deflection aberrations occur when they are operated. There are various types of deflection aberrations, but they can be broadly divided into geometric aberrations and chromatic aberrations. For the former, third-order aberrations have the greatest influence on optical characteristics, and for the latter, first-order aberrations have the greatest influence on optical characteristics. When a deflector is used alone, the former aberration changes depending on the shape and dimensions of the deflector, but the latter is uniquely determined. Therefore, in order to simply explain the principle of the present invention, chromatic aberration will be explained.

Now, if a charged particle beam accelerated by an accelerating voltage V is deflected by a distance R on the sample surface by a deflector, a charged particle beam whose energy differs from the accelerating voltage V by ΔV is deflected by a distance R + ΔR. , 8R are expressed by the following formula.

ΔR=KT-R・Δ■/v...(1)
Here, Kr is a deflection chromatic aberration coefficient, and KT=1.5 for the magnetic field type and KT=1 for the electrostatic type.

The present invention takes advantage of this property. That is,
The magnetic field type deflector is operated so that the amount of deflection RM on the sample surface is opposite to the amount of deflection R3 of the electrostatic type deflector and is approximately twice as large (RM knee 2Rs). At this time, the nine aberrations are ΔR=KT-RM・ΔV/V −(2)Δ
R=KT-Rs' ΔV/V
-(3), and the overall aberration ΔR is ΔR=ΔRM+Δ
Rs=0. In other words, aberrations are canceled out. Therefore, it can be seen that the deflection aberration can be self-cancelled without arranging the magnetic field type deflector inside the lens.

In the above explanation, no restrictions are given regarding the arrangement of the magnetic field type and the electrostatic type. That is, these arrangements can be made arbitrarily. Conversely, adding constraints to these arrangements will produce effects other than those described above. Regarding this, please refer to [
Example].

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

First, the configuration and operation of the present invention will be explained. A charged particle beam 1 emitted from a charged particle gun is narrowly focused and irradiated onto a sample 4 by a lens 2 .

A magnetic field type deflector 33 is provided between the lens 2 and the sample 4.
and an electrostatic deflector 34 are provided.

Further, if each is used alone, the deflection amount (Rn v Rs ) of each is the same and the direction is opposite. If these deflectors are operated simultaneously under such conditions, the deflection aberration can be canceled as explained in [Operation].

In this embodiment, the distance (LH) between the deflector 33 and the sample 4 is approximately twice the distance (Ls) between the deflector 34 and the sample 4. At this time, the charged particle 1 is
If 7A1 is deflected at an angle of OM, the deflector 34 may deflect this charged particle beam at an angle of θ5 (=-0M). With this configuration, as can be easily seen from FIG. 1, there is also an effect that the charged particle beam 1 is incident perpendicularly to the sample 4.

Although only one example has been shown above, for example, the magnetic field type deflector 33 and the electrostatic type deflector 34 may be placed at the same location (LH=LS).
, fJM=-os/2. With this configuration, the distance between the lens 2 and the sample 417j can be shortened.

The key is to place a magnetic field type and an electrostatic type deflector between the lens and the sample, so that when each is operated independently, the amount of deflection on the sample surface is approximately twice as much for the former as for the latter. If it works, there will be no problem with the essence of the invention.

In this embodiment, only one nons 2, one magnetic field deflector 33, and one electrostatic deflector 34 are used, but it should be noted that the number of these deflectors is not limited to the embodiments of the present invention and a plurality of them can be used. It's no good. Further, although the lens 2 is shown as a magnetic field type lens, there is no problem even if it is an electrostatic type lens.

〔Effect of the invention〕

As described above, according to the present invention, deflection aberration can be canceled without arranging a deflector inside the lens.
In addition, since the charged particle beam can be applied perpendicularly to the sample, it can be used at high speed and with high precision, like an electron beam lithography system.
A focusing/deflecting system capable of deflecting at a large angle can be provided.

[Brief explanation of drawings]

DESCRIPTION OF SYMBOLS 1... Charged particle beam, 2... Objective lens, 3... Magnetic field type side device, 4... Sample, 31... First deflector, 3
2... Second deflector, 33... Magnetic field type deflector, 34...
...An electrostatic deflector.

Claims (1)

[Scope of Claims] 1. An apparatus comprising a plurality of lens means for narrowing a charged particle beam emitted from a charged particle gun, and a deflection means for two-dimensionally deflecting the charged particle beam on a sample surface, The deflection means is composed of a magnetic field type deflector and an electrostatic type deflector, and is arranged between the above lens and the sample, and the amount of deflection of the magnetic field type deflector on the sample surface is controlled by the amount of deflection of the electrostatic type deflector. A focusing/deflecting device characterized in that the amount of deflection is approximately twice that on the sample surface, and the deflection is operated in opposite directions. 2. The above magnetic field deflector and electrostatic deflector are characterized in that the distance between the magnetic field deflector and the sample is approximately twice the distance between the electrostatic deflector and the sample. A focusing/deflecting device according to claim 1.