US3835320A

US3835320A - Particle-beam device equipped with means for attenuating mechanical movements

Info

Publication number: US3835320A
Application number: US00039388A
Authority: US
Inventors: H Helwig
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1969-05-28
Filing date: 1970-05-21
Publication date: 1974-09-10
Anticipated expiration: 1991-09-10
Also published as: FR2048687A5; DE1927410A1; DE1927410B2; GB1290235A; NL7000300A

Abstract

A particle-beam device has a beam axis and is exposed to mechanical movements. The device also has a column assembly for housing electro-optical equipment needed for focus the particle beam and a support structure for supporting the column assembly. A damping system for damping the mechanical movements has a plurality of elastic pressure vessels communicating with the support structure and the column for holding the column. The damping system includes fluid actuating means connected to the pressure vessels for actuating the pressure vessels in response to the mechanical movements.

Description

United States Patent [191 Helwig PARTICLE-BEAM DEVICE EQUIPPED WITH MEANS FOR ATTENUATING MECHANICAL MOVEMENTS [75] Inventor: Hans Helwig, Berlin, Germany [73] Assignee: Siemens Aktiengesellschaft, Berlin,

Munich, Germany [22] Filed: May 21, 1970 [21] Appl. No; 39,388

[30] Foreign Application Priority Data May 28, 1969 Germany 1927410 [52] US. Cl 250/311, 73/430, 250/306,

- 250/396 [51] Int. Cl. H0lj 37/26, GOln 23/00 [58] Field of Search 73/430; 250/49.5 A

[56] References Cited UNITED STATES PATENTS 2,370,373 2/1945 Ruska et al. 250/495 11 3,835,320 [451 Sept. 10, 1974 OTHER PUBLICATIONS The Electron Microscope, Second Edition, by E. F. Burton et al., Reinhold Publishing Corp., New York, 1946, page 225.

Primary Examiner-William F. Lindquist Attorney, Agent, or Firm-Herbert L. Lerner 57 ABSTRACT A particle-beam device has a beam axis and is exposed tomechanical movements. The device also has a column assembly for housing electro-optical equipment needed for focus the particle beam and a support structure for supporting the column assembly. A

- damping system for damping the mechanical movements has a plurality of elastic pressure vessels communicating with the support structure and the column for holding the column. The damping system includes fluid actuating means connected to the pressure vessels for actuating the pressure vessels in response to the mechanical movements.

6 Claims, 5 Drawing Figures PATENIEB SEP 101974 saw 1 0r 2 Fig.1

My invention relates to a particle-beam device with a column supported by a base structure and containing apparatus for influencing a beam in a vacuum and means for attenuating mechanical movements. Although the invention is intended in the first instance for electron microscopes, it can nevertheless find application with advantage with other particle-beam devices such as ion microscopes and deflection devices. These devices tend, as a consequence of the construction of the vacuum space thereof and with the equipment functioning to focus the beam to form an enlarged image of the specimen, as a standing column, to be subject to mechanical movements.

With regard to the obtainable resolution of electron microscopes, not only are lense errors of the device disturbingly noticable, but also instabilities of the electrical operating values as well as the vibration sensitivity of the device.

An object of my invention is to substantially reduce the vibration sensitivity or susceptibility to mechanical movements in the columns of theabove-mentioned particle-beam devices.

The significance of this object becomes apparent when it is considered that modern high-power electron microscopes have a resolution in the order of magnitude of a few AE, so that the beam carrying through a specimen detail in the final image plane of the microscopes can practically not quiver. This condition is therefore already difficult to fulfill because the column of the microscope generally has a length of at least one meter and is therefore especially sensitive to vibrations and movements. Various equipment of the device such as thevacuum pump cause vibrations inoperation.

It is known to attenuate movements in an electron microscope by means of spring bodies that function between the support structure and the mounting pad of the entire microscope. However, this cushioning has shown itself to be inadequate to achieve an attenuation of movements in the region of the microscope column to the degree required by the resolution capability of modern high-power microscopes.

To correct the foregoing condition and according to a feature of my invention, the means for attenuating mechanical movements contains hydraulically or pneumatically operated, elastically formed vessels that grip on the column. Because the means to attenuate mechanical movements grips directly on the column, an especially good attenuation action is ensured. As opposed to the known arrangements of a support suspension, the actuating arm for the movements in the instant invention is considerably reduced. Also atenuated are vibrations caused by equipment such as pumps mounted on the support structure.

In the preferred embodiment of the invention, pressure vessels are arranged between the support structure and the column. Insofar as the particle-beam device is provided with a swinging apparatus that grasps the column in a fork-like manner and functions to lift parts of the column such as the column part containing the beam generator, pressure vessels can be arranged between the fork and the column. In this instance it is advantageous to provide such an arrangement of pressure vessels so that they apply pressure forces directed in an upward or downward direction in dependence upon the operation of the swinging apparatus on the column. Such a swinging apparatus functions so that it first separates the column parts in the direction of the beam axis, the column parts being constructed so as to be swingable toward each other. That is, the parts constructed to be lifted are slightly raised, whereby the parts constructed so as to be swingable toward each other are disengaged- Only thereafter does the lifted part swing out. The first part of the swinging cycle of the swinging apparatus can at the same time be used, by using the always available play, for setting the direction of pressure force that is applied by the pressure vessels. I

With regard to the rotation-symmetry strived for in particle-beam devices with reference to the beam axis, the pressure vessels are arranged so as to operate in a rotational symmetrical relation to the beam axis. In

using pressure cylinders as pressure vessels, three pres sure cylinders can, for example, be grouped around the beam axis at the same angle so as to be opposed to each other.

For the arrangement between the fork of a swinging apparatus and the column, a pressure vessel is especially suitable which is constructed as an elastic hose surrounding the beam and filled with a pressure medium.

In the preferred embodiment of the invention, an equalizing vessel for a pressure medium is arranged between the pressure vessels and a pressure generator. Means for adjusting the pressure in the pressure vessels are arranged with respect to the pressure medium.

The invention will now be described with reference to the accompanying drawing, wherein:

FIG. 1 is a front view of an electron microscope equipped with a means for attenuating mechanical movements according to the invention;

FIG. 2 is a side view of the electron microscope according to FIG. 1;

FIG. 3 is a top view of the electron microscope illustrated in FIGS. 1 and 2;

FIG. 4 illustrates a pressure vessel constructed in the form of a hose and surrounding the microscope column; and

FIG. 5 illustrates a pressure vessel constructed in the A form of a pressure cylinder.

Referring to FIGS. 1 and 2, with regard to the invention, the electron microscope comprises two main parts, namely, the microscope column assembly 1 and the support assembly 2, the latter taking on the form of a desk because of its covering. A panel portion 3 is located on the desk and contains measuring and indicating instruments as well as control buttons for operating the microscope.

Because of the height of the microscope and especially because of the length of the column 1 in which the particle beam travels and which contains all the electro-optical assemblies as well as the specimen, the microscope has the tendency to undergo swinging movements in response to external mechanical vibrations. In older electron microscopes, the mere leaning on the console by the operator could result in the beam wandering at the final image screen.

The microscope column 1 is divided into several subparts. To swing the uppermost part 4 of the column away in a sideward direction from the other parts of the column, the latter is gripped by the fork-like swinging apparatus at the required elevation. The uppermost part 4 contains the beam generator and condensor lenses. The swinging apparatus 5 functions together with a collar 5a to first move the column part 4, as already mentioned, in the upward direction and then to swing the same.

The column 1 is placed with the base plate 6 on the support surface 7 of the support structure 2. According to a feature of the invention, three pressure cylinders 8 are disposed intermediate base plate 6 and support surface 7 and are disposed in rotation-symmetrical order with respect to the beam axis as shown in FIG. 3. The pressure cylinders can be equipped with cap-type gaskets. I

The pressure cylinder 8 is shown in FIG. 5 and comprises a stationary base 8a and a moveable cap portion 8b. The cap portion 812 is sealed against the base 8a by means of an elastic, flexible cap-type gasket 8c. For attenuating movements, the interior of cap portion 812 is divided by a plate 8d, the latter being provided with a bore 8e having a relatively small diameter. The interior of cap portion 8b is connected by line 13 with the compensator vessel 11 shown in FIGS. 1 and 2.

Because several pressure cylinders are applied at this location, a single pressure vessel 9 is arranged between the fork 5 and the column 1. The pressure vessel is in the form of an elastic hose 9 filled with a pressure medium. Hose 9 initiates, in dependence upon the movement of the fork 5 parallel to the direction of the beam axis, either a pressure directed upwardly or downwardly. The construction of the column 1 and the fork 5 for receiving the hose 9 is illustrated in FIG. 4.

A compensating vessel 11 having a manometer 12 is located between the

pressure vessels

8 and 9 and the pump 10. The line system 13 connects the various pressure vessels with the compensating vessel 11. In dependence upon the occurring vibrations which generate movements of the column 1, the pressure in the various pressure vessels can be adjusted by means of the valve 14, so that a proper damping or attenuation is achieved.

If required, spring bodies 15 can be added between the support surface of the support structure 2 and the floor of the room in which the microscope is located.

cap 8b is divided, in order to impede or slow down the movement, by means of a plate 8d which has a bore 8e of relatively slight diameter. The interior space of the cap 8b is connected via a lead 13 to the compensating vessel 11 (FIGS. 1 and 2). I

To those skilled in the art it will be obvious upon a study of this disclosure, that the invention permits of various modifications and hence may be given embodiments other than illustrated and described herein, without departing from the scope of the claims annexed hereto.

I claim:

1. A particle-beam device having a beam axis and being exposed to mechanical movements, comprising a column assembly for housing electro-opticai equipment needed to focus the particle beam, a support structure for supporting said column assembly, and damping means for damping the mechanical movements having a plurality of elastic pressure vessels mounted intermediate said column assembly and said support structure and communicating with said support structure and said column assembly for holding said column assembly, said damping means including fluid actuating means connected to said pressure vessels for actuating said pressure vessels in response to the mechanical movements.

2. In a particle-beam device according to claim 1,

said pressure vessels being disposed in rotationsymmetrical relation with respect to said beam axis.

3. In a particle-beam device according to claim 1,

each of said pressure vessels being a pressure cylinder.

4. A particle-beam device according to claim 1, wherein said fluid actuating means comprises a pressure generator and a compensator vessel, said compensator vessel being connected between said pressure generator and said pressure vessels, and adjusting means connected to said compensator vessel for adjusting the pressure in said pressure vessels.

5. A particle-beam device according to claim 1, wherein said column assembly has upper and lower portions and wherein said support structure includes swinging means having a fork-like member engaging said column assembly for displacing said upper portion from said lower portion and, at least one of said pressure vessels being disposed intermediate said fork-like member and said column assembly, whereby said one pressure vessel applies pressure forces to said column assembly in the vertical direction in dependence upon the movement of said fork-like member.

6. In a particle-beam device according to claim 5, said one pressure vessel being in the form of a hose surrounding said beam axis.

Claims

1. A particle-beam device having a beam axis and being exposed to mechanical movements, comprising a column assembly for housing electro-optical equipment needed to focus the particle beam, a support structure for supporting said column assembly, and damping means for damping the mechanical movements having a plurality of elastic pressure vessels mounted intermediate said column assembly and said support structure and communicating with said support structure and said column assembly for holding said column assembly, said damping means including fluid actuating means connected to said pressure vessels for actuating said pressure vessels in response to the mechanical movements.

2. In a particle-beam device according to claim 1, said pressure vessels being disposed in rotation-symmetrical relation with respect to said beam axis.

3. In a particle-beaM device according to claim 1, each of said pressure vessels being a pressure cylinder.