EP1688964A2 - Electrostatic deflection system for corpuscular radiation - Google Patents

Abstract

An electrostatic diffraction system for corpuscular radiation for micro- and nano-structure lithography or measurement comprises bar electrodes held axially and symmetrically in an inner hollow carrier (1) through which an electron beam is directed. The carrier comprises between two and four mutually connectible carrier elements (1.1,1.2).

Description

The invention relates to electrostatic deflection systems for corpuscular beams, which can be used in particular for microstructured and nanostructured applications in lithography systems or measuring devices (eg, SEM).

For such processes, a highly precise deflection possibility for charged corpuscles, in particular electrons with a short time constant, is desired. In addition, such a deflection system should have only a small volume requirement in order to install them at electron optically favorable positions.

Thus, DE 199 30 234 A1 discloses an electrostatic deflection device in which rod-shaped electrode elements are mounted within a holding device. In this case, the individual electrode elements should be made of a conductive ceramic material with a given specific resistance. The holding device should be designed as a hollow cylindrical tube. The individual electrode elements are then inserted in a desired axially symmetrical arrangement in the holding device and connected to the holding device cohesively.

It has been found that the required for a highly accurate deflection of a corpuscular beam alignment accuracy for an exact axisymmetric to be maintained arrangement of the individual electrode elements to each other once during assembly can not be met and the other the integral connection to deviations in the positioning of the individual electrode elements the holding device leads. The cohesive connection is formed by punctiform soldering or gluing over in the holder Openings made.

Deflection systems should also be suitable for use in the rapidly changing magnetic field, which is advantageous for low-ion electron-optical solutions.

Even in this form, reproducible deflection devices for electron beams can not readily be produced.

Furthermore, also such deflection systems are known, in which the individual electrodes are formed from tensioned wires, as described for example in EP 1 033 738 A1. Here, the acted upon by a tensile wires form weak points, in particular by the fact that they are more mechanically stressed at their cohesive connection points, so that it can lead to detachment or different bias voltages.

In addition, the individual electrodes forming wires may have deviations of electrical parameters, which lead to inhomogeneities of the usable for the deflection of electron beams electric fields.

It is therefore an object of the invention to provide an electrostatic deflection system for corpuscular radiation available, in which the individual electrodes permanently have a very accurate axial symmetric arrangement to each other and maintained.

According to the invention, this object is achieved with an electrostatic deflection system for corpuscular radiation having the features of claim 1.

Advantageous embodiments and further developments of the invention can be achieved with the features described in the subordinate claims.

The electrostatic deflection system according to the invention also uses, as is known from the prior art, a plurality of rod-shaped electrodes, which are held in axially symmetrical arrangement in an internally hollow support. By means of such a hollow support, the respective corpuscular radiation to be deflected can then be directed, so that its deflection for lithographic applications can be influenced by the correspondingly modifiable electric fields formed around the rod-shaped electrodes. The carrier according to the invention is formed from at least two and a maximum of four interconnectable carrier elements. Preferably, the carrier is formed with two carrier elements.

It can be a placement of the individual support elements with the rod-shaped electrodes prior to the actual assembly of the respective carrier elements to a single carrier, in which form the interior of the carrier when inserting the rod-shaped electrodes in an advantageous form is very accessible, so that an exact positioning and adjustment of the rod-shaped electrodes, as well as the fixation of the electrode to the support elements in advance is possible. Access for optical or tactile measuring methods is also easy.

The carrier elements forming the carrier can preferably be mechanically processed beforehand, so that they can be positioned, adjusted and then preferably materially joined together during assembly of a carrier, wherein the assembly maintains the arrangement of the individual electrodes and the axial symmetry for the Whole system is made.

For the positioning and adjustment of the rod-shaped electrodes, it is advantageous to the support elements Provide support areas for the electrodes. At the respective contact areas, the individual electrodes can then be firmly bonded, and this can be done preferably with soldering but also adhesive bonding.

In this case, the individual electrodes should each rest on two bearing areas at a distance from one another and have been fixed.

It is particularly advantageous to form the contact areas on the front side and directly on the support elements. In this case, the support regions may have been formed on in the interior of a formed from the carrier elements carrier annular flanges. In each case a support area should have been formed on the 'support elements on one end face and another support area on the opposite end side of support elements.

The support areas can preferably be formed in the form of a stair structure which can be produced in a highly precise form by mechanical processing on the respective support elements.

For accurate positioning of the electrodes, these can then be kinematically defined in each case in a step, arranged adjacent and then, as already mentioned, firmly bonded. As a result, a defined axially symmetrical arrangement of the individual electrodes of an electrostatic deflection system can be achieved, which can also be permanently maintained.

The corners of individual steps of the staircase structure of support areas may be formed as a 90 degree V-groove.

In particular, the fact that the usable in a deflection system according to the invention rod-shaped electrodes a high aspect ratio, d. H. have a large length compared to the outer diameter or to the cross-sectional dimensions, a certain curvature of the individual electrodes manufacturing technology can not be avoided. However, such a curvature can adversely affect the defined formation of electric fields for the deflection of a corpuscular beam when using a deflection system according to the invention.

For this reason, the respective curvature of the individual electrodes should be taken into account during assembly and fixation on the support elements. Thus, for example, the arrangement and orientation of the individual electrodes which are fastened to the carrier elements can advantageously be chosen such that their respective convex curvature is directed radially outward with respect to the longitudinal axis of the deflection system. As a result, positive influence on the desired axially symmetrical arrangement of the electrodes on the carrier can again be taken.

In addition, a measurement of the individual electrodes can be carried out before assembly, in which the respective curvature of an electrode is determined.

For a deflection system, it is then possible with particular advantage to use electrodes which in each case have the same curvature but at least one curvature lying within a narrow tolerance range.

For the determination of the curvature, known optical measuring methods can be used. To ensure that the orientation of the convex curvature of electrodes is also detected and within a tolerance range of plus minus 5 ° in the radial direction during assembly of the electrodes in the Carrier elements can be maintained, the respective rod-shaped electrodes can be ground at least at one end face in an obliquely inclined angle. This obliquely inclined face can then be used for determining the orientation of the convex curvature. After determination, this or the opposite end face can then be provided with a corresponding mark, which can provide information about the orientation of the curvature of the respective rod-shaped electrode.

Thus, a quasi-barrel-shaped or waisted cage can be formed in this form by means of the electrodes arranged in the carrier and correspondingly fixed and correspondingly aligned.

In a particularly advantageous embodiment, however, at least one further contact area may be present or formed on the carrier elements and consequently also after the mounting on the carrier. Such a contact area can preferably be arranged centrally between the support areas arranged on the end side, so that the outwardly curved rod-shaped electrodes abut against this support area arranged between the two outer support areas and the curvature of the rod-shaped electrode is reduced as much as possible.

Also, this third and possibly also another support area can also, as already explained above, have a stair structure and the location and fixation of the rod-shaped electrodes also take place analogously in the corresponding grooves of a respective step.

The support members to be mounted to a support should be made of a dielectric material having high strength and dimensional stability. Furthermore If possible, it should be machinable for the desired high-precision microstructuring. For example, glass-ceramics are suitable materials for the carrier elements. As a result, for example, compared to metals eddy currents can be avoided.

Such carrier elements should be provided to avoid electrostatic charges with an electrically conductive coating, which can then be placed at ground potential when using a deflection system according to the invention.

For this purpose, the lateral surfaces of the support elements can be provided with a metallic or other electrically conductive coating.

In this case, a single layer or a layer system, which / consists of metal or metal alloys, have been formed.

Thus, it is possible to electrolessly provide the surface of carrier elements with a nickel layer and then with a gold layer. The gold layer ensures improved wetting in a cohesive bonding by soldering. However, other coating methods and layers or layer systems are also possible with which layers with very good conductivity and good wetting behavior can be produced. In addition, there is a resistance to environmental influences and the possibility of cleaning by means of plasma. Instead of gold, other metals can be used, which also have these properties.

The areas of the support areas of the support elements which can come in contact or directly with the rod-shaped electrodes, may not with each other be electrically conductive, so that there is an electrically isolated recording of each individual electrode to the next.

These surfaces can either not be coated or the layer subsequently removed again, which can be done for example by a mechanical removal by means of microfrots or chemically by a local etching.

The rod-shaped electrodes which can be used on deflection systems according to the invention can also be advantageously made of dielectric materials which are subsequently coated in an electrically conductive manner on their outer surfaces. This is also advantageous when used in rapidly changing magnetic fields.

Thus, the rod-shaped electrodes can be produced from a glass, preferably by means of a drawing process, it being possible to use, for example, borosilicate glass, preferably silica glass, for the production.

In the production of such rod-shaped electrodes should be paid to a uniform as possible roundness, cylindricity, maintaining a constant diameter, the avoidance of bending and twisting.

After production, a selection and classification with respect to certain specifications can be carried out by means of suitable measuring methods. Thus, the outer diameter and the respective deflection / curvature can be corresponding selection parameters, so that the rod-shaped electrodes used on a deflection system are at least almost identical.

Thus, a deflection / curvature should be less than 5 microns over the total length of an electrode, for example, an electrode length of 200 millimeters. The Deviations from the roundness and the deviation of the cylindricity should be smaller than 1 μm. Diameter variations should also be less than 1 micron.

The rod-shaped electrodes produced from the dielectric material can then subsequently be provided with an electrically conductive coating which has good electrical conductivity, high adhesive strength and suitability for use in a vacuum. In addition, they should be solderable and free of hydrocarbons.

It has been found that these properties can be achieved particularly advantageously with a layer system of several layers of different metals, wherein such a layer system can be formed with a multistage sputtering process. However, individual layers can also be used.

Thus, an adhesion-promoting layer of titanium may be formed directly on the outer surface of the electrodes made of the dielectric material. Onto this titanium layer, a diffusion barrier layer of platinum and, in turn, a solderable gold layer can be applied to this platinum layer, wherein such a layer system can have a total thickness of approximately 300 nm.

The number of electrodes used in a deflection system according to the invention should be at least eight, if possible, but for many applications a larger number of electrodes is to be preferred. For example, twelve or twenty such electrodes can readily be used on a deflection system. For some simple applications, however, four electrodes may be sufficient.

It is also convenient to arrange electrodes of different diameters in relation to the longitudinal axis. Thus, the electrodes can be arranged on a deflection system at least two, but preferably at least three different diameters with respect to the longitudinal axis of the deflection system, wherein in such an arrangement, the axial symmetry should be considered. As a result, a homogeneous homogeneous electric field is formed in the interior of the system, the higher-order disturbances such. As the three- and fünfzählige field, particularly well suppressed. This can also be achieved by other arrangements of electrodes of the same or different diameters.

As already mentioned, areas which are not electrically conductively coated are present on the support areas. For this reason, it is advantageous to arrange shielding flanges in the area of the support areas.

Thus, two Abschirmflansche frontally form outer statements. These can then be materially connected to the support elements that have already been mounted to a carrier. However, these end-side terminations should be designed such that openings are provided through which a particle beam can be directed through the deflection system.

If a third support region is formed on a carrier for a deflection system, a shielding flange should also be arranged there. This may have been produced as an annular structure, wherein the outer contour may be formed on the staircase contour of the support area, taking into account the arrangement of the electrodes with corresponding recesses for the electrodes. The latter aspect should also lead to the fact that the electrodes are not subjected to forces leading to deformations and tension.

In particular, the electrodes can be connected to the carrier elements at the contact areas arranged on the front side, wherein this can be carried out by means of a laser soldering process with suitable solders and possibly by adding a flux.

However, the cohesive connection of the electrodes to the carrier elements can also be effected by gluing, wherein preferably UV-curable adhesives should be used which are suitable for use under vacuum conditions.

The electrodes mounted and fixed to the carrier elements are then contacted electrically conductively at one of their end faces. This can be done for example by soldering thin gold wires with a diameter of about 100 microns. These gold wires can then be electronically connected again with correspondingly provided contact surfaces of a contact plate, so that each individual electrode for the targeted deflection of a corpuscular beam can be acted upon with a correspondingly suitable potential. But it may also be possible that certain electrodes form groups, which are each acted upon by the same potential or placed at ground potential.

Such contact plate provided with contact surfaces may be attached to an end face of the deflection system, which may be done on a Abschirmflansch or also a contact plate may be an integral part of such Abschirmflansches.

The invention will be explained in more detail by way of example in the following.

Figur 1

eine Draufsicht auf ein Trägerelement für ein Beispiel eines erfindungsgemäßen Ablenksystems;

Figur 2

eine Seitenansicht eines Trägerelementes mit Elektroden und

Figur 3

zwei Trägerelemente nach Figur 1, die zu einem gemeinsamen Träger miteinander verbunden sind, in einer Seitenansicht.

Showing:

FIG. 1

a plan view of a support member for an example of a deflection system according to the invention;

FIG. 2

a side view of a support element with electrodes and

FIG. 3

two support elements according to Figure 1, which are connected together to form a common carrier, in a side view.

In Figure 1 is a plan view of a support member 1.1, that with a further support member 1.2 (not shown here) mounted to a common carrier 1 and then preferably cohesively, z. B. can be interconnected by laser soldering.

At the two outer end faces and centrally in between the bearing areas 3.1, 3.2 and 3.3 are formed.

The carrier element 1.1, like the carrier element 1.2 made of a glass ceramic, not shown here, can be produced by a mechanical micromachining, wherein in particular the step structure of the bearing areas 3.1, 3.2 and 3.3 can be mechanically formed and they have the desired high precision.

The support element 1.1 has been coated with a layer system, as has been explained in the general part of the description. As a result, a base layer of nickel provided with an overcoat of gold was prepared as a layer system. The coating between the individual surface areas the support areas 3.1, 3.2 and 3.3 was subsequently separated again to achieve electrical isolation of the individual areas with each other.

From the side view of the carrier element 1.1 shown in FIG. 2, the formation of the staircase structures at the contact areas 3.1, 3.2 and 3.3 becomes particularly clear.

In each 90-degree V-groove of a step, an electrode 2 is positioned positioned in a defined form and, as also mentioned in the general part of the description, have been materially connected.

It is also clear from FIG. 2 that electrodes 2 are arranged at different diameters in relation to the longitudinal axis of the carrier 1 or the deflection system according to the invention, and the electrodes 2 can also have different outer diameters. In this case, the arranged on a common diameter with respect to the longitudinal axis electrodes 2 should each have the same outer diameter.

FIG. 3 then shows the carrier elements 1.1 and 1.2 assembled and joined to a carrier 1 with the respective electrodes 2 attached thereto, the arrangement of electrodes 2 having different diameters with respect to the longitudinal axis again being made clear.

The electrodes 2 were obtained in a fusing process of silica glass and provided with a layer system, as has been explained in the general part of the description with an adhesive layer of titanium, a diffusion barrier layer of platinum and a gold layer.

Claims (21)

Electrostatic deflection system for corpuscular beams, in which rod-shaped electrodes are held in axially symmetrical arrangement in an internally hollow support, through which an electron beam is directed,
characterized in that the carrier (1) from at least two and a maximum of four interconnectable carrier elements (1.1, 1.2) is formed. Deflection system according to claim 1, characterized in that on the support elements (1.1, 1.2) support areas (3.1, 3.2) for electrodes (2) are provided, on which the electrodes (2) are fixed cohesively. Deflection system according to claim 1 or 2, characterized in that the support areas (3.1, 3.2) are formed on the front side of the support elements (1.1, 1.2). Deflection system according to one of the preceding claims, characterized in that the contact areas (3.1, 3.2) in the form of a stair structure formed and the electrodes (2) in each case a groove of a stair step adjacent in a defined form of an axially symmetric arrangement. Deflection system according to one of the preceding claims, characterized in that the grooves of stair structures form a 90-degree V-groove. Deflection system according to one of the preceding claims, characterized in that the electrodes (2) in the support elements (1.1, 1.2) are aligned so that their respective convex curvature is directed radially outwards with respect to the longitudinal axis of the deflection system. Deflection system according to one of the preceding claims, characterized in that at least one further contact area (3.3) is arranged / formed between the bearing areas (3.1, 3.2) arranged at the end. Deflection system according to one of the preceding claims, characterized in that the carrier elements (1.1, 1.2) and the electrodes (2) formed from a dielectric material and the carrier elements (1.1, 1.2) in its interior and the electrodes (2) electrically conductively coated outside are. Deflection system according to one of the preceding claims, characterized in that the electrodes (2) at the bearing areas (3.1, 3.2) are materially connected, electrically isolated with the support elements (1.1, 1.2) are connected. Deflection system according to one of the preceding claims, characterized in that the electrodes (2) are arranged on at least two different diameters with respect to the longitudinal axis of the deflection system. Deflection system according to one of the preceding claims, characterized in that electrodes (2) are held with different outer diameters in the carrier. Deflection system according to one of the preceding claims, characterized in that shielding flanges are arranged in the region of the support regions (3.1, 3.2, 3.3). Deflection system according to one of the preceding claims, characterized in that two Abschirmflansche form the front side outer statements, with the interconnected support elements (1.1, 1.2) are connected cohesively. Deflection system according to one of the preceding claims, characterized in that in / on one of the Abschirmflansche an electrical contact for the individual electrodes (2) is integrated or arranged thereon. Deflection system according to one of the preceding claims, characterized in that the electrodes (2) are made of a glass by a drawing process. Deflection system according to one of the preceding claims, characterized in that the electrically conductive coating of the electrodes (2) is formed from a layer system formed from a plurality of layers of different metals formed one above the other. Deflection system according to one of the preceding claims, characterized in that the layer system of titanium, platinum and gold is formed. Deflection system according to one of the preceding claims, characterized in that the carrier elements (1.1, 1.2) are formed from a glass ceramic which is internally provided with an electrically conductive coating of a nickel layer on which a layer of gold is provided. Deflection system according to one of the preceding claims, characterized in that at the bearing areas (3.1, 3.2, 3.3) areas are present on which no electrically conductive coating is present, so that the electrodes (2) electrically insulating on the support elements (1.1, 1.2 ) are fastened. Deflection system according to one of the preceding claims, characterized in that the electrodes (2) are ground on at least one end face at an obliquely inclined angle. Deflection system according to one of the preceding claims, characterized in that a marking indicating the orientation of the curvature of the electrodes (2) is present on the electrodes (2).

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