Power optimisation system for optical projection objective - uses test phase in which processor evaluates focus measurements to determine objective position

摘要

The power optimisation system uses a test phase to establish the optimum spatial position between the object (1) and the image plane (5) relative to the objective (4) using selective optoelectronic image focus measurements within the image field. The measured values are fed to a programme-controlled processor which determines the optimum image sharpness plane. An adjustment optical system (11) coupled to the objective (4) is used to provide the focus position by dufference evaluation of the sharpness signals, each obtained value being stored for use during the subsequent image projection phase. USE/ADVANTAGE - For micro-lithography in LSI IC mfr. Ensures optimum image quality.