ILLUMINATION SYSTEM AND METHOD EMPLOYING A DEFORMABLE MIRROR AND DIFFRACTIVE OPTICAL ELEMENTS

摘要

An illumination system for use in photolithography using a laser or radiation beam source. A deformable mirror is used to shape the beam of laser radiation to obtain global uniformity. A profile sensing means is used to detect any global nonuniformities. The output of this sensing means is fed to a controller for calculating a mirror contour and controlling actuators that shape the deformable mirror to obtain a globally uniform intensity. A diffractive or diffusive optical element, such as a microlens array, eliminates local non-uniformities. Movement of this element eliminates speckle caused by interference due to the coherent beam source. A uniform intensity profile and appropriate angular spread is achieved with very little transmission loss and is automatically compensated for degraded or changing source performance. The illumination system is particularly applicable to a scanning photolithography process as used in the manufacture of semiconductor substrates.