Adaptive optic with discrete actuators for continuous deformation of a deformable mirror system

摘要

Adaptive optical elements for use in high precision lithography exposure are provided with an array of discrete actuators to provide highly stable and repeatable correction of the shape of an optical element to an accuracy of a small fraction of a very short wavelength of light in the EUV range of 1 to 50 nanometers, responsive to a metrology source and sensor arrangement. The actuators are matched to the deformation characteristics of the adaptive optical elements. Preferably, the actuators provide both positive and negative force for outward and/or inward deflection continuously over the surface of the mirror. The surface of the optical element may thus be accurately, controllably and repeatably deformed to within an allowable deformation limit to optimize optical performance of an optical system for high precision lithography exposure.