DE102016202127A1 - Damping arrangement and projection exposure system - Google Patents

Abstract

The invention relates to a damping arrangement (200) for dissipating mechanical vibration energy, wherein the damping arrangement (200) comprises a damping element (4) which contains a magnetic shape-memory alloy, and means (6, 7) which are suitable, the damping element (4) to suspend a magnetic field comprises. Furthermore, the invention relates to a projection exposure system equipped with said damping arrangement (200).

Description

The invention relates to a damping arrangement for the dissipation of mechanical vibration energy, in particular a vibration damper, for damping components exposed to vibration and a projection exposure apparatus for semiconductor lithography, which is equipped with a damping arrangement. In a large number of technical disciplines, it is necessary to prevent or effectively dampen oscillations of individual elements in higher-level systems. Thus, for example, in construction vibrations of high buildings or bridges are reduced by the fact that the structures are provided with an absorber mass, such as a heavy pendulum, which absorbs part of the resulting in a vibrational excitation of the building, for example by wind kinetic energy and thus the vibration of the Building itself reduced.

Likewise, in vehicle construction, for example in internal combustion engines, vibration absorbers are used to reduce mass forces.

The vibration damper typically has an absorber mass, which is mechanically coupled to the object to be damped via a Tilgerfeder. To dampen the vibration or to dissipate the vibration energy additional damping elements may be present. The properties of said components damper mass, Tilgerfeder and possibly damping element determine the natural frequency of the vibration. The frequency of the system to be damped which is damped particularly effectively by the vibration damper depends on the natural frequency of the vibration damper.

Damping arrangements, in particular vibration dampers, are also used in projection exposure apparatuses for semiconductor lithography, which contain highly accurately manufactured and positioned optical components. It goes without saying that any form of vibration or shock, either during the transport of such a plant or in its operation, for example by seismic events, has a very negative effect on the imaging quality of the plant and thus on its overall performance. The conventional socket technique for optical components alone is usually not sufficient to attenuate introduced vibrations sufficiently fast, as it is designed for precise and stable storage rather than vibration damping. Various approaches have been taken in the past to either effectively inhibit vibrations, particularly optical components in projection exposure equipment, or to mitigate them to an acceptable level in a reasonable amount of time, if they do occur.

In the international patent application WO 2007/006577 A1 , which goes back to the applicant, a solution is presented in which additional damping elements are positioned at appropriate locations in the system. The damping elements described in the cited document dissipate vibration energy by friction. However, the damping properties of a purely friction-based arrangement are relatively limited. In particular, the damping elements shown in the prior art can not be adapted or only with considerable effort in view of the priority to be damped frequency. However, since over time the frequency spectrum of primarily dampening vibrations at the location of a component to be damped can change, there is a risk that the effectiveness of the damping will decrease over time.

Object of the present invention is to provide damping arrangements which allow an adaptation of their damping behavior, in particular for different frequencies to be damped.

This object is achieved by a device having the features of independent claim 1. The subclaims relate to advantageous developments and variants of the invention.

The damping arrangement according to the invention for dissipating mechanical vibration energy comprises a damping element which contains a magnetic shape-memory alloy, and means which are suitable for exposing the damping element to a magnetic field.

Elements containing said magnetic shape-memory alloy have a force-displacement characteristic with pronounced hysteresis. This pronounced hysteresis means that during a compression / expansion cycle described by the respective hysteresis, a high proportion of energy dissipates, ie is usually converted into heat. This effect, which is also known from conventional shape memory materials, is also referred to as pseudoelasticity. Unlike these materials, however, the pseudo-elasticity of magnetic shape-memory alloys does not rely on a phase transition between a martensitic and an austenitic phase, but rather on a transition between two martensitic phases of different magnetic configurations. A suitably obtained damping element thus shows pronounced advantageous damping properties. The Damping properties as well as the stiffness of the damping element are influenced on the one hand by the choice of the alloy used, on the other hand, but also by an applied magnetic field. This makes it possible to make a damping arrangement, in particular with regard to the elastic properties of the damping element used adjustable, so that the damping arrangement can be flexibly adjusted to changing requirements.

The use of a magnetic shape-memory alloy also offers the advantage that resulting particles are usually ferromagnetic and thus attracted by magnets, so that in the result a significant reduction of contaminating particles can be achieved. Compared with elastomers also used for damping arrangements, the abovementioned alloys also tend to degas to a much lesser extent, thereby also resulting in a reduction of the contamination associated with the use of dampers.

It is also possible to use said material advantageously for the sensing of vibrations. In this case, a vibration-induced change in the magnetization of the damping element can be measured and evaluated, for example, with a Hall sensor.

In an advantageous variant of the invention, the damping arrangement is designed as a vibration absorber, wherein the vibration damper has at least one absorber mass and a Tilgerfeder as a damping element. However, since the natural frequency of the vibration absorber depends inter alia on the damping of the Tilgerfeder used, it is possible by the arrangement according to the invention to change the natural frequency of the vibration and thus the preferred damped frequency of the component to be damped and thus adapted to the respective requirements. Furthermore, it allows the invention to integrate the damper directly into the Tilgerfeder and thus to create a very compact and simple design of - adjustable beyond - vibration damper.

As a magnetic shape-memory alloy is particularly an alloy in question, which contains nickel, manganese and gallium. Elements of such alloys are available in the meantime in reproducible quality and can thus be easily used in a corresponding arrangement.

Furthermore, a simple and cost-effective implementation of the invention can be achieved in that the means for exposing the damping element, in particular the absorber spring, to a magnetic field is at least one permanent magnet. The fact that a permanent magnet is used eliminates the need for an electrical contact, which is otherwise required in particular in the case of an electromagnet, and the wiring of the arrangement required thereby.

An advantageous possibility for changing the magnetic field in the region of the damping element is that the at least one permanent magnet is movable relative thereto. By reducing or increasing the distance between the permanent magnet and the damping element can be achieved that the magnetic flux in the region of the damping element and thus its pseudoelastic properties, in particular its damping, change. In this way, the natural frequency of a vibration absorber and thus the range of its greatest damping effect can be changed relatively simply, for example.

An advantageous possibility for changing the distance between the damping element and the permanent magnet is, for example, to arrange the permanent magnet on a lockable linear guide, such as a dovetail guide.

An amplification of the magnetic influence on the pseudoelastic properties of the damping element can be achieved in that the damping element is arranged between two permanent magnets. In particular, unlike poles of the permanent magnets may face each other.

In a variant of the invention, in which a mechanical relative movement between the damping element and the means for generating a magnetic field can be dispensed with, the means are designed as at least one electromagnet. The magnetic field can be adjusted in this case by the choice of the current through the electromagnet. Conversely, the coil of the electromagnet can be used to sense the change in the magnetic field in the case of external vibration excitation.

In a further advantageous embodiment of the invention, the damping element, in particular the Tilgerfeder be designed such that it or in the operation of the damping arrangement is subject to a compression.

If in the case of a vibration absorber, the means for generating the magnetic field at least partially as part of the absorber mass are formed, a particularly simple design of the invention can be realized. Thus, for example, the Tilgerfeder be formed in the manner of a threaded rod or having threaded portions. Screwed onto the thread is at least one provided with a matching internal thread permanent magnet as absorber mass. By a relative rotation of permanent magnet and Tilgerfeder two effects are achieved. On the one hand changes the geometry of the vibration damper and on the other hand the magnetic field in the area of the Tilgerfeder. Of course, even the change in the geometry of the vibration absorber would be sufficient to change the natural frequency of the vibration absorber. However, there are definitely cases conceivable in which it is desirable to further enhance this effect by changing the magnetic field at the location of the Tilgerfeder. In this case, with a suitable choice of the geometry and the material parameters, an increase of the adjustable addressable frequency range of the vibration absorber can be achieved.

In an advantageous embodiment of the invention, the arrangement has a plurality of absorber masses arranged on a common carrier body, which are mechanically connected to the carrier body via at least one Tilgerfeder. At least two Tilgerfedern are arranged in such a way that they develop their damping effect in a deformation in different directions in space. In this way, a damping arrangement can be realized, which is able to damp vibrations in all 6 mechanical degrees of freedom with a suitable design.

In particular for the application for vibration damping of components of projection exposure apparatuses for semiconductor lithography, the arrangement according to the invention offers considerable advantages. Such systems are subject to significant changes during their lifetime. For example, as part of maintenance or upgrades optical or mechanical components are modified, resulting in a change in the dynamic properties of the overall system and thus to a change in the spectrum of mechanical vibrations occurring. Likewise, there are changes in the environment of the corresponding facilities, such as the installation of other facilities, which also vibrational excitations go out.

The projection exposure apparatus may, for example, be an EUV projection exposure apparatus.

The component to be damped may in particular be a part of the support structure of the system or else a socket of an optical element, for example a lens or a mirror.

The invention will be explained by way of example with reference to the drawing. It shows:

1 a first embodiment of the invention;

2 a second embodiment of the invention, in which an electromagnet is used;

3 a variant of the invention, wherein permanent magnets are used simultaneously as absorber masses;

4 an embodiment of the invention in which two damping elements are used,

5 a damping arrangement which is suitable for damping vibrations in three spatial directions,

6 a variant of the in 5 shown arrangement; and

7 a schematic representation of an EUV projection exposure system in which a vibration damper according to the invention is used.

1 shows a first embodiment of a vibration damper 200 formed damping arrangement in which a component to be damped as a in the figure fragmentary version 1 an optical element 2 is trained. The detail also shown optical element 2 is by means of support feet 3 in the version 1 arranged, for example with the support feet 3 soldered. The version 1 and the optical element 2 may be part of a higher-level system, in particular a projection exposure apparatus for semiconductor lithography. With the version 1 over a Tilgerfeder 4 connected is an absorber mass 5 , which can be made in particular as a metallic body suitable mass, for example stainless steel. The rod-shaped absorber spring 4 contains a magnetic shape-memory alloy and shows pseudoelastic behavior under compression. The vibrations of the socket 1 and the associated compression of the Tilgerfeder 4 are indicated in the figure by the non-designated double arrows or by the dashed representation. In the example shown is the Tilgerfeder 4 between two permanent magnets 6 and 7 arranged, whose unlike poles face each other. The permanent magnets 6 and 7 are with the version 1 via a schematically illustrated linear guide 13 connected so that the distance of the permanent magnets 6 and 7 from the absorber spring 4 can be changed in the direction indicated by the arrows. As a result, by changing the distance of the permanent magnets 6 and 7 from the absorber spring 4 an adaptation of the natural frequency of the vibration absorber 200 and thus a vote of the arrangement are made to the frequency of the damped socket oscillation.

Instead of the displaceable permanent magnets shown in the figure 6 and 7 can - as shown schematically in 2 shown - also fixed and appropriately contacted electromagnets 8th and 9 be used; the requirement of linear guides would then be eliminated. In the in 2 The arrangement shown are the electromagnets 8th and 9 stuck with the socket 1.2 a mirror 2.2 - For example, connected to an EUV projection exposure system. The polarity of the electromagnets 8th and 9 and the Tilgerfeder 4 passing magnetic flux can be modified without mechanical intervention only by adjusting the electrical parameters.

3 shows a variant of the invention, in which the means for generating a magnetic field - in the example shown permanent magnets 10 and 11 - perform the additional function of an absorber mass. In the example shown in the figure is the Tilgerfeder 4.3 on a schematically shown to be damped element 1.3 arranged and with an external thread 12 provided on which the two equipped with a matching internal thread permanent magnets 10 and 11 are screwed on. This eliminates the need for additional guidance of the permanent magnets 10 and 11 as well as a separate absorber mass. By the arrangement of the two permanent magnets 10 and 11 on the Tilgerfeder formed in the example shown as a threaded rod 4.3 the possibility is created, both the distance between the two permanent magnets 10 and 11 to each other as well as the absolute position of the permanent magnets 10 and 11 in a wide range, so that a wide frequency range of vibrations to be damped can be addressed.

4 shows a schematic representation of an embodiment of the invention, in which two damping elements are used. In the example shown is a structure to be damped 25 , For example, a socket of an optical element in a projection exposure system, in a support structure 24 the associated projection exposure system arranged. Here is the structure to be damped 25 over two damping elements 18 and 19 , which are made using a magnetic shape-memory alloy, with the support structure 24 connected.

Also easy to see in the 4 are the four permanent magnets 14 . 15 . 16 and 17 , which on linear guides 20 . 21 . 22 and 23 , similar to in 1 shown, are mounted so that they on the damping elements 18 respectively. 19 or can be moved away from them. As a result, as already stated above, the magnetic field strength at the location of the damping elements 18 respectively. 19 be changed, thereby increasing the mechanical properties of the damping elements 18 respectively. 19 to change. This opens up the parallel use of two damping elements 18 and 19 and the associated higher variability with regard to the choice of the respective combinations of magnetic field intensities extended possibilities to set the desired attenuation. Unlike the ones in the 1 to 3 Structures shown are in the 4 The arrangement shown not to a vibration absorber, but rather to a damping arrangement, which depends to a much lesser extent than a vibration damper in terms of its effectiveness on the frequency of the vibration to be damped.

5 shows in the subfigures 5a to 5f a damping arrangement which is suitable for damping vibrations in six degrees of freedom. In the 5 shown damping arrangement shows a carrier body 26 , via which it can be attached to a virtually any element to be damped. The carrier body 26 is cuboid and formed on its side surfaces with four absorber masses 5.5 provided, which about Tilgerfedern 4.5 with the carrier body 26 are connected. It is according to the arrangement in 5 provided that the Tilgerfedern 4.5 develop their damping effect when shearing. 5a now shows the conditions at a translational vibration in the x-direction, as shown by the also in 5a indicated to coordinate system. The mentioned translational oscillation in the x-direction results in an oscillation of the two laterally mounted absorber masses 5.5 as evidenced by the unmarked double arrows, causing the swinging absorber masses 5.5 associated Tilgerfedern 4.5 be sheared and thus dissipate vibration energy through the effects described earlier. The co-movement of the front and rear absorber masses 5.5 does not lead to a deformation of their associated Tilgerfedern.

In contrast to this is in 5b the case of a translatory vibration in the y-direction shown, in which the front or rear (not visible) Tilgermasse 5.5 is translated into corresponding translational vibrations and their associated Tilgerfedern 4.5 undergoes a shear, so that in the manner described a damping of the translational vibration in the y-direction is achieved.

Analog shows 5c a translational vibration in the z-direction, in which case all absorber masses 5.5 be translated in translational vibrations in the z-direction and in this way all Tilgerfedern 4.5 be sheared, whereby an efficient damping can be achieved.

In 5d the case of a rotational vibration about the x-axis is shown, in which the two laterally located Tilgerfedern 4.5 , as also indicated by the arrows, are put into a translational oscillation. Analogously, the in 5e and 5f To see cases that are practically self-explanatory and should not be further elaborated.

6 shows in the subfigures 6a to 6c a modification of in 5 shown arrangement in which the Tilgerfedern 4.6 not to shearing, but to be stressed on compression. These are also in a carrier body 27 , which in the example shown in 5 is executed cuboid, absorber masses 5.6 arranged. It shows each side surface of the cuboid carrier body 27 a cuboidal recess in the example shown, in which the likewise cuboid absorber mass 5.6 over the four Tilgerfedern 4.6 is suspended, wherein the Tilgerfedern each opposing absorber masses extend in the same direction and overall covers the course of the longitudinal extent of the Tilgerfedern all three spatial directions. In 6a Now the case is shown in which a rotation about the z-axis and a translational vibration takes place along the x-direction. In this case, the front absorber mass as well as the viewer facing away (not visible) oscillates, as indicated by the double arrow, and causes in this way by compression or expansion of the associated Tilgerfedern 4.6 a damping of the corresponding vibration.

In contrast to this is in the 6b the case is shown in which a rotational vibration about the x-axis and a translational vibration along the y-axis takes place; In this case, the upper and lower absorber masses get 5.6 , as also indicated by the double arrow, in vibration and compress in this way their assigned Tilgerfedern 4.6 , which causes a damping in a known manner.

In 6c Now the case is shown in which a translational vibration along the z-axis and a rotational vibration about the y-axis. In this case, swing the laterally arranged absorber masses 5.6 and dampen over their assigned Tilgerfedern 4.6 in a known manner.

Not shown in the 5 and 6 are means which are suitable, the Tilgerfedern 4.5 or 4.6 subject to a magnetic field. Such means - ie, for example, if necessary, movable permanent magnets or electromagnets, can advantageously in the interior of the carrier body 26 respectively. 27 to be ordered. However, they can also act from the outside or be omitted.

7 shows an example of the basic structure of an EUV projection exposure system 100 for microlithography, in which the invention can be applied. A lighting system 102 the projection exposure system 100 points next to a light source 103 an illumination optics 104 for illuminating an object field 105 in an object plane 106 on. One is illuminated in the object plane 106 arranged reticle 107 that of a schematically represented Retikelhalter 108 is held. A merely schematically illustrated projection optics 109 which are the mirrors 122 . 123 . 124 . 125 . 126 and 127 includes, serves to image the object field 105 in a picture field 110 into an image plane 111 , A structure is shown on the reticle 107 on a photosensitive layer in the area of the image field 110 in the picture plane 111 arranged wafers 112 , by a wafer holder also shown in detail 113 is held. The light source 103 can emit useful radiation, in particular in the range between 5 nm and 30 nm.

One by means of the light source 103 generated EUV radiation 114 is by means of one in the light source 103 integrated collector aligned so that they are in the area of a Zwischenfokusebene 115 undergoes an intermediate focus before moving to a field facet mirror 116 meets. After the field facet mirror 116 becomes the EUV radiation 114 from a pupil facet mirror 117 reflected. With the aid of the pupil facet mirror 117 and an optical assembly 118 with mirrors 119 . 2.2 and 121 become field facets of the field facet mirror 116 in the object field 105 displayed.

Exemplary is in 7 the mirror 2.2 with a vibration damper shown only schematically 200 shown equipped according to the present invention. It goes without saying that each component of the system shown could be equipped with the vibration damper.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2007/006577 A1 [0005]

Claims (14)

Damping arrangement ( 200 ) for the dissipation of mechanical vibration energy, characterized in that the damping arrangement ( 200 ) - a damping element ( 4 . 4.3 . 18 . 19 . 4.5 . 4.6 ), which contains a magnetic shape-memory alloy, as well as means ( 6 . 7 . 8th . 9 . 10 . 11 ), which are suitable, the damping element ( 4 . 4.3 . 18 . 19 . 4.5 . 4.6 ) to a magnetic field. Damping arrangement ( 200 ) according to claim 1, characterized in that the damping arrangement as a vibration damper ( 200 ) is formed, wherein the vibration damper ( 200 ) at least one absorber mass ( 5 . 5.5 . 5.6 ) and a Tilgerfeder ( 4 . 4.3 . 4.5 . 4.6 ) has as a damping element. Damping arrangement ( 200 ) according to claim 1 or 2, characterized in that that the magnetic shape memory alloy contains nickel, manganese and gallium. Damping arrangement ( 200 ) according to one of the preceding claims, characterized in that the means are at least one permanent magnet ( 6 . 7 . 10 . 11 . 14 . 15 . 16 . 17 ). Damping arrangement ( 200 ) according to claim 4, characterized in that the at least one permanent magnet ( 6 . 7 . 10 . 11 . 14 . 15 . 16 . 17 ) relative to the damping element ( 4 . 4.3 . 18 . 19 ) is movable. Damping arrangement ( 200 ) according to claim 5, characterized in that the damping element ( 4 . 18 . 19 ) between two permanent magnets ( 6 . 7 . 14 . 15 . 16 . 17 ) is arranged. Damping arrangement ( 200 ) according to claim 6, characterized in that unlike poles of the permanent magnet ( 6 . 7 . 14 . 15 . 16 . 17 ) are opposite each other. Damping arrangement ( 200.2 ) according to one of claims 1 to 3, characterized in that the means are at least one electromagnet ( 8th . 9 ). Damping arrangement ( 200 . 200.2 ) according to one of the preceding claims, characterized in that the damping element ( 4 . 4.3 . 4.6 ) is arranged such that it is subject to a compression during operation of the damping arrangement. Damping arrangement according to claim 2, characterized in that the means ( 10 . 11 ) are at least partially formed as part of the absorber mass. Damping arrangement according to claim 2, characterized in that the arrangement more on a common carrier body ( 26 . 27 ) arranged absorber masses ( 5.5 . 5.6 ), which with the carrier body via in each case at least one Tilgerfeder ( 4.5 . 4.6 ) are mechanically connected, wherein at least two Tilgerfedern ( 4.5 . 4.6 ) are arranged in such a way that they develop their damping effect in a deformation in different directions in space. Projection exposure apparatus ( 100 ) for semiconductor lithography, characterized in that at least one component ( 2.2 ) of the projection exposure apparatus, a damping arrangement ( 200 . 200.2 ) according to one of the preceding claims. Projection exposure apparatus according to claim 12, characterized in that the projection exposure apparatus is an EUV projection exposure apparatus ( 100 ) Projection exposure apparatus according to claim 12 or 13, characterized in that the component is a socket ( 1 ) of an optical element ( 2 . 2.2 ).

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