ASSEMBLY, IN PARTICULAR IN A MICROLITHOGRAPHIC PROJECTION EXPOSURE APPARATUS

Abstract

An assembly, for example in a microlithographic projection exposure apparatus, comprises an optical element and a joint arrangement for mechanically bearing the optical element. The joint arrangement comprises at least one connecting element secured on the optical element. The mass of the connecting element is distributed over its length so that the moment of inertia of the connecting element is increased in comparison with a connecting element of identical mass and length in which the mass is distributed uniformly over the length.

Claims

1. An assembly, comprising: an optical element; and a joint arrangement configured to mechanically bear the optical element, wherein: the joint arrangement comprises a connecting element secured on the optical element; the connecting element has a mass (m), a moment of inertia (l), a length (L), and a center of mass (L.sub.s); and (I) is between 50% and 150% of (L−L.sub.s)L.sub.sm.

2. The assembly of claim 1, wherein: the connecting element is mounted via a bearing at an end section of the connecting element that is distant from the optical element; and the connecting element extends beyond the bearing in a direction facing away from the optical element.

3. The assembly of claim 1, wherein (I) is between 70% and 130% of (L−L.sub.s)L.sub.sm.

4. The assembly of claim 1, wherein (I) is between 90% and 110% of (L−L.sub.s)L.sub.sm.

5. The assembly of claim 1, wherein the connecting element has a hollow portion.

6. The assembly of claim 1, wherein the connection element has hollow regions.

7. The assembly of claim 1, wherein the mass (m) of the connecting element is distributed irregularly over its length (L).

8. The assembly of claim 7, wherein the mass (m) of the connecting element is distributed over its length (L) so that the moment of inertia (I) of the connecting element is increased compared with a connecting element having an identical mass, an identical length and a mass that is uniformly distributed over its length.

9. The assembly of claim 1, wherein: the connecting element has a first section facing the optical element, a second section distant from the optical element, and a third section located between the first section and the second section; and the connecting element the third section is tapered compared with at least one section selected from the group consisting of the first section and the second section.

10. The assembly of claim 1, wherein the connecting element has a substantially pin-shaped geometry.

11. The assembly of claim 1, wherein the optical element comprises a mirror module.

12. The assembly of claim 1, wherein the optical element comprises a mirror.

13. The assembly of claim 1, wherein the optical element is configured for an operating wavelength of less than 30 nm.

14. An optical system, comprising: an assembly according to claim 1.

15. An apparatus, comprising: an assembly according to claim 1, wherein the apparatus is a microlithographic projection exposure apparatus.

16. The apparatus of claim 15, wherein the assembly comprises a mirror.

17. The apparatus of claim 15, wherein the assembly comprises a mirror module.

18. The apparatus of claim 15, wherein the assembly comprises a facet mirror.

19. The apparatus of claim 15, wherein the microlithographic projection exposure apparatus is an EUV microlithographic projection exposure apparatus.

20. An assembly, comprising: an optical element; and a joint arrangement configured to mechanically bear the optical element, wherein: the joint arrangement comprises a connecting element secured on the optical element; and a mass of the connecting element is distributed over a length of the connecting element so that a moment of inertia of the connecting element is increased compared with a connecting element having an identical mass, an identical length and a mass that is uniformly distributed over its length.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In the drawings:

[0041] FIG. 1 shows a schematic illustration for elucidating a concept of the disclosure;

[0042] FIGS. 2-5 show schematic illustrations for elucidating possible embodiments of a connecting element used in an assembly according to the disclosure;

[0043] FIG. 6 shows a schematic illustration for elucidating the possible set-up of a microlithographic projection exposure apparatus designed for operation in the EUV;

[0044] FIG. 7 shows a schematic illustration of a known hexapod structure for elucidating a possible application of the disclosure; and

[0045] FIGS. 8-9 show schematic illustrations for elucidating an issue occurring in a known assembly.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0046] FIG. 6 firstly shows a merely schematic illustration of a projection exposure apparatus 610 which is designed for operation in the EUV and in which the present disclosure can be realized in an exemplary manner.

[0047] According to FIG. 6, an illumination device of the projection exposure apparatus 610 comprises a field facet mirror 613 and a pupil facet mirror 614. The light from a light source unit comprising a plasma light source 611 and a collector mirror 612 is directed at the field facet mirror 613. A first telescope mirror 615 and a second telescope mirror 616 are arranged in the light path downstream of the pupil facet mirror 614. A deflection mirror 617 operated with grazing incidence is arranged downstream in the light path and directs the radiation incident thereon at an object field in the object plane of a projection lens with mirrors 631-636, which is merely indicated in FIG. 6. At the location of the object field, a reflective structure-bearing mask 631 is arranged on a mask stage 630, the mask being imaged with the aid of a projection lens into an image plane in which a substrate 641 coated with a light-sensitive layer (photoresist) is situated on a wafer stage 640.

[0048] The assembly according to the disclosure serves for mechanical bearing and/or actuation of an optical element, which might be, purely by way of example, a mirror or a mirror module of a microlithographic projection exposure apparatus (e.g., the projection exposure apparatus 610 in FIG. 6).

[0049] FIG. 1 shows a merely schematic and much simplified illustration for elucidating a concept of the present disclosure.

[0050] According to FIG. 1, “110” indicates a connecting element in the form of a pin, as is able to be used, for example, in a hexapod arrangement as per FIG. 7. In further embodiments, the arrangement can also be a bearing (also referred to as “3-2-1 bearing”), in which three connecting elements extending parallel to a first spatial direction (e.g., x-direction) bring about securing in three degrees of freedom (e.g., x, R.sub.y, R.sub.z), two further connecting elements extend parallel to a spatial direction perpendicular thereto (e.g., y-direction) and bring about securing in two further degrees of freedom (e.g., y and R.sub.x), and a further connecting element in the remaining, in turn perpendicular spatial direction (z-direction) brings about securing in one degree of freedom (z). In this context, reference is made to the publication Paul R. Yoda: “Opto-Mechanical Systems Design”, Third Edition, ISBN 081946091-5, with respect to known technology.

[0051] “105” indicates, purely schematically, a section of the supporting structure (e.g., a support frame of an illumination device), whereas “120” denotes an optical element or mirror module.

[0052] Using a model-like description of the structure as per FIG. 1 on the basis of a mechanical model and an existing force equilibrium, the following relationship (1) can be derived between a deflection y.sub.MM resulting at one end section of the connecting element 110 and a (bearing) force F.sub.FF acting at the opposite end section of the connecting element 110 on account of a frequency-dependent parasitic stiffness of the connecting element 110:

[00001]$\begin{array}{cc}.Math.F_{\mathrm{FF}}.Math.=.Math.\frac{I-\left(L-L_s\right)L_s{m}_{\mathrm{pin}}}{L^2}\cos \beta {\stackrel{.Math.}{y}}_{\mathrm{MM}}.Math.& \left(1\right)\end{array}$

[0053] Equation (1) has been linearized. In this case, I denotes the moment of inertia of the connecting element 110, denotes the mass of the connecting element 110, L denotes the length of the connecting element 110, L.sub.s denotes the path between the end section of the connecting element 110 distant from the optical element 120 and the centre of mass of the connecting element 110, and β denotes the deflection of the connecting element 110 or of the pin in the fundamental state (i.e., without movement). Depending on the combination of the degrees of freedom of deflection y.sub.MM and force F.sub.FF (e.g., deflection in the x-direction in the case of a force in the z-direction or deflection in the z-direction in the case of a force in the y-direction), the relationship between deflection y.sub.MM and force F.sub.FF may possibly deviate slightly from the aforementioned specific relationship. In FIG. 1, m.sub.vcm denotes the moving part of the motor. φ denotes the deflection relative to the “zero-position” of the optical element 120 (i.e. φ will be zero for y.sub.MM=0). Accordingly, β+φ will be the deflection of the connecting element 110 resulting from a general movement or deflection y.sub.MM in any arbitrary position.

[0054] Even if the deflection y.sub.MM in FIG. 1 is considered at the end section of the connecting element 110 facing the optical element 120 and the force F.sub.FF is considered at the opposite end section of the connecting element 110 thereto (i.e., at the end section facing the support frame 105), reference is made to the fact that the relationship (1) also exists in the “reverse direction”, i.e., for the relationship between a deflection present on the side of the support frame 105 and a force resulting at the optical element 120 as a consequence of a frequency-dependent parasitic stiffness of the connecting element 110.

[0055] In order now to minimize the force resulting on the side of the optical element 120 from a frequency-dependent parasitic stiffness contribution of the connecting element 110 in the case of a deflection occurring on the part of the support frame 105 (e.g., due to vibration), it is desirable according to Equation (1) for the term

[00002]$\frac{I-\left(L-L_s\right)L_s{m}_{\mathrm{pin}}}{L^2}$

and hence also for the deviation of the value of the moment of inertia I from the value of the term (L−L.sub.s)L.sub.sm.sub.pin to have a value that is as small as possible (ideally equal to zero).

[0056] Proceeding from this idea, the disclosure now contains the principle of achieving the minimization of the aforementioned term by way of a suitable design of the connecting element 110 in view of the parameters occurring in this term. According to the disclosure, the moment of inertia I of the connecting element 110 has a value ranging between 50% and 150%, for example ranging between 70% and 130%, such as ranging between 90% and 110%, of the value of the term (L−L.sub.s)L.sub.sm.sub.pin.

[0057] In the process, according to the disclosure, it is possible for example to exploit the circumstances that in the aforementioned mathematical expression that is decisive for the frequency-dependent stiffness contribution the term or summand proportional to the moment of inertia of the connecting element has an opposite sign to the term or summand proportional to the mass m.sub.pin of the connecting element. Since the quantity L−L.sub.s always has a positive value, suitably adjusting the moment of inertia I for a given mass m.sub.pin of the connecting element 110 specifically makes it possible to achieve that the summands I and (L−L.sub.s)L.sub.sm.sub.pin are (at least approximately) the same size in terms of absolute magnitude and hence the term relevant to the frequency-dependent stiffness contribution becomes (at least approximately) zero.

[0058] According to the disclosure, the aforementioned suitable adjustment of the parameters (for example of the moment of inertia I) of the connecting element 110 can be achieved by various measures, as will be elucidated below with reference to the purely schematic and much simplified illustrations of FIG. 2-5. In this case, attention is drawn to the fact that the relevant measures can also be realized in combination depending on the specific application situation. F denotes a bearing force (or constraint force), while x denotes the deflection occurring at the opposite end section of the connecting element.

[0059] According to FIG. 2, a connecting element 210 according to the disclosure (which is mounted on a support structure 205 at its one end section in the schematic illustration) can have a hollow embodiment, for example at least in regions. This reduces, for example, the mass m.sub.pin of the connecting element 210 in comparison with a connecting element 210 that does not have a hollow configuration, with the flexural and axial stiffness remaining unchanged (and hence with the functionality of the connecting element 210 being maintained). A reduction in the mass m.sub.pin (without violating existing desired properties for stiffness) can additionally also be obtained by using a suitable material during the production of the connecting element 210, for example by using a ceramic material instead of a metallic material.

[0060] According to FIG. 3 and FIG. 4, the connecting element 310 and 410, respectively, can also have a mass m.sub.pin that is distributed irregularly over the respective length L in further embodiments. For example, the connecting element 310 or 410 can have a lower mass in a region situated between its outer end sections, which can be obtained, in turn, by reducing the diameter in this region and/or attaching additional mass(es) to the respective outer regions or end sections (as indicated in FIG. 3 and FIG. 4 by the reference signs “311” and “312”, and “411”, respectively). “305” or “405” denote the support structure in FIG. 3 and FIG. 4, respectively.

[0061] Moreover, as per FIG. 5, a connecting element 510 can also be configured in such a way that it extends beyond a bearing 505 at its end section distant from the optical element, with the length of the corresponding projecting section being denoted by “d” in FIG. 5. Since the projecting section contributes to the relevant moment of inertia I in Equation (1) but not to the relevant mass m.sub.pin, this allows an increase in the moment of inertia I to be obtained in comparison with a configuration of the connecting element with the same mass m.sub.pin but without a projecting section.

[0062] Even though the disclosure has been described on the basis of specific embodiments, numerous variations and alternative embodiments will be apparent to a person skilled in the art, for example through combination and/or exchange of features of individual embodiments. Accordingly, it goes without saying for a person skilled in the art that such variations and alternative embodiments are encompassed by the present disclosure, and the scope of the disclosure is only restricted as provided by the appended patent claims and the equivalents thereof.