JPS6398944A - Charged particle ray application device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a charged particle beam application device, and particularly to a charged particle optical system suitable for energy filters and mass separations.

[Conventional technology]

Conventionally, in order to improve the resolution of scanning electron microscopes, an electron optical system shown in Fig. 4, in which the sample is placed inside an objective lens to reduce aberrations, has been used (Japan Society of Electron Microscopy, Vol. Proceedings of the 40th Academic and Technical Conference, p.211). Even when such an optical system is used, there is a drawback that resolution is reduced due to chromatic aberration, especially in a low acceleration region. In order to solve this problem, it is necessary to reduce the energy width of the electron beam to reduce chromatic aberration. Therefore, we have already devised an electron optical system using an energy filter.

This electron optical system is shown in FIG. Here, filter 10
A so-called Wien filter in which the electric field and magnetic field are orthogonal is suitable. In addition, from the viewpoint of the aberration of the filter 10, the electron beam 8
It is also known that it is most desirable for the lens 3 to form an image on the deflection fulcrum 20 of the filter 10. However, in the method shown in FIG. 3, since this deflection fulcrum is fixed, the usage conditions of the lens 3 are fixed. Normally, the lens 3 is used to adjust the reduction ratio of the entire electron optical system and the current of the electron beam, and there is a risk that this function will be impaired.

[Problem that the invention seeks to solve]

1. The prior art had the drawback that it was not possible to sufficiently adjust the reduction ratio of the entire electron optical system and the current of the electron beam.The purpose of the present invention is to compensate for this drawback.

[Means for solving problems]

In order to achieve the above object, the deflection fulcrum of the filter may be changed. In this way, the imaging point that changes when the conditions of use of the condenser lens are changed can be made to coincide with the deflection fulcrum of the filter. In order to realize this, the filter is divided into two stages and the strength of each filter is adjusted, thereby making it possible to arbitrarily change the deflection fulcrum of the filter as a whole.

[Effect]

A Wien filter allows beams with a desired energy to travel straight, while beams with other energies are deflected and bent. In other words, it is a kind of deflector.

FIG. 2 shows a diagram of the principle of the present invention. The beam 8 incident on the filter 10 has an energy different by Δ■ from the desired energy.
1 is placed at the edge of the aperture 11, beams with different energies can be completely cut out. The incident beam 81 is first bent by 01 at the filter 101,
Next, the filter 102 bends 02 again. At this time, the deflection angle θ after passing through the filter 10 is θ=01+02
becomes. If the radius of the aperture 11 is ro, then the deflection fulcrum 20
is located above the aperture by rolo. As can be seen in FIG. 2, there are an infinite number of combinations of 731 and O2 to bring the beam 81 to the edge of the aperture 11, and the deflection angle θ can be changed arbitrarily. In other words, the deflection fulcrum can be changed freely.

〔Example〕

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

The electron beam 8 emitted from the FEffi sub-gun 1 is accelerated to a desired voltage by an accelerating lens 2. After the electron beam 8 passes through the condenser lens 3, it passes through the Wien filters 101 and 10.
2, the energy of the electron beam is reduced, and only the electron beam with a desired energy width passes through the aperture 11. This electron beam is imaged onto the surface of the sample 7 by the objective lens 6. The secondary electrons 9 completely generated on the surface of the sample 7 are detected by the detector 5 and become a video signal.

Here, the lens 3 and filters 101 and 102 can be adjusted as follows. First, the lens 3 is used to adjust the reduction ratio and the amount of current of the electron beam. At this time, the electron beam 8 is ξ
1. Focus the image on a suitable location.

First, the deflection fulcrum 2 is where the filter 101 is operated.
1 is located at the center of the filter 101, which is different from the position of the image forming groove. Therefore? Since the irradiation position of the single beam on the sample surface changes, for example, when the SEM image is lltF%, the image becomes 8e1. Therefore, if the filter 102 is operated to bring this image to its original position, the deflection fulcrum 20 formed by the filters 101 and 102 will coincide with the above image formation point.Sixth order, the energy sensitivity of the filter will be adjusted. However, this can be done without changing the strength ratio of filters 101 and 102. In this manner, the filter of the present invention can be used with the deflection fulcrum 20 and the imaging point of the lens 3 always being aligned.

That is, the filter can be used in a state where the aberration G of the filter is minimized.

In the present invention, sample F) 7 was placed inside the objective lens 6, and the secondary electron detector 5 was placed on the electron gun side of the objective lens 6, but this placement is limited to the embodiment shown in FIG. Needless to say, this is not something that can be done. Further, the type of lens (magnetic field type, static T!! type), number of lenses, and type of electron gun are not limited to the embodiments of the present invention, and the present invention can be used.

The present invention has been described with respect to an energy filter for electron beams. However, regardless of the application, for example, when a Wien filter is used as a mass separation filter for ion beams in a device in which the electron gun is replaced with an ion gun, the same result can be obtained.
can be done. In other words, it can be used in general application equipment for electric particle beams.

〔Effect of the invention〕

As described above, according to the present invention, the imaging point of the condenser lens and the deflection fulcrum of the energy filter can always be made to coincide, so that the aberration caused by this filter can be minimized when used. At this time, for example, it becomes possible to provide a scanning electron microscope with high resolution even at a low acceleration voltage.

[Brief explanation of the drawing]

FIG. 1 is a basic configuration diagram of a scanning electron microscope showing an embodiment of the present invention, FIG. 2 is a principle diagram showing the operation of the present invention, and FIG. 3 is a basic configuration diagram of a conventional scanning electron microscope. Figure 4 shows the basic configuration of a conventional scanning electron microscope with high resolution. 1... Field emission type electron gun, 2... Accelerating lens, 3...
... Condenser lens, 4... Deflector, 5... Secondary electron detector, 6... Objective lens, 7... Sample, 8...
...Electron beam, 9...Secondary electron, 10,101,102
...Wien filter, 11...Aperture, 20.21
. . . Deflection fulcrums of Wien filters 0 and 101, respectively, 80 . . . Electron beam with desired energy, 81.
82...Electron beam with energy other than the desired energy. i′

Claims (1)

[Claims] 1. A charged particle source, a lens means for narrowing the charged particle beam emitted from the charged particle source, a scanning means for two-dimensionally scanning the particle beam on the sample surface, and an electric field and a magnetic field are configured to be perpendicular to each other. A charged particle beam application device comprising deflection-type energy filter means, characterized in that the filter means is arranged in two stages, so that the position of the deflection fulcrum of the charged particle beam by these filters can be changed. Particle beam application equipment.