Arrangement for actuating an element in a microlithographic projection exposure apparatus

Abstract

The invention relates to arrangements for actuating an element in a microlithographic projection exposure apparatus. In accordance with one aspect, an arrangement for actuating an element in a microlithographic projection exposure apparatus comprises a first number (nR) of degrees of freedom, wherein an adjustable force can be transmitted to the optical element in each of the degrees of freedom, and a second number (nA) of actuators, which are coupled to the optical element in each case via a mechanical coupling for the purpose of transmitting force to the optical element, wherein the second number (nA) is greater than the first number (nR). In accordance with one aspect, at least one of the actuators is arranged in a node of at least one natural vibration mode of the optical element.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The invention relates to arrangements for actuating an element in a microlithographic projection exposure apparatus.[0003]2. Prior Art[0004]Microlithography is used for producing microstructured components such as, for example, integrated circuits or LCDs. The microlithography process is carried out in a so-called projection exposure apparatus having an illumination device and a projection lens. The image of a mask (=reticle) illuminated via the illumination device is in this case projected via the projection lens onto a substrate (e.g. a silicon wafer) coated with a light-sensitive layer (photoresist) and arranged in the image plane of the projection lens, in order to transfer the mask structure to the light-sensitive coating of the substrate.[0005]In a projection exposure apparatus designed for EUV (i.e. for electromagnetic radiation having a wavelength of less than 15 nm), for lack of light-transmissive materials bei...

AI Technical Summary

Benefits of technology

The present invention provides arrangements for actuating an element in a microlithographic projection exposure apparatus which enable active positional control of the element with higher control quality. This is achieved by performing an "over-actuation" in which the number of actuators exceeds the number of degrees of freedom. This additional freedom can be used to reduce or mask out the excitation of natural vibrations of the mechanical structures and achieve a better distribution of forces. Furthermore, a surplus of sensors can also be provided to choose an arrangement of sensors in such a way that specific natural frequencies or modes are not even detected, which avoids unwanted deformations of the optical element or mirror.

Problems solved by technology

In this case, however, the problem occurs in practice that the mirrors are not ideally rigid bodies, but rather each have specific natural frequencies of the mechanical structures (e.g. of a typical order of magnitude in the range of 2-3 kHz), wherein the corresponding natural frequency spectra for the dimensions of the mirrors and of the carrying and measuring structures, the dimensions increasing with increasing numerical apertures, are shifted further and further toward lower frequencies.

An excitation of the natural frequencies via the actuators can have the effect, however, that on account of the relatively low damping in the control loop comparatively large amplitudes are detected by the respective position sensors, as a result of which the stability of the control loop can be jeopardized and active positional control can no longer be operated stably or can be operated only with low control quality.

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