Photomask etch: addressing the resist challenges for advanced phase-shift and binary photomask

摘要

As lithography requirements mandate ever-thinner resist thickness, the need for in-situ monitoring has become more urgent. In this paper we present an in-situ optical methodology-based system to determine residual photoresist thickness during advanced photomask etch with < 1000 ? photoresist. Several types of phase-shift masks and photoresists were examined. A series of masks were etched to demonstrate the performance of the system. Results show an average accuracy of better than 2%, with a maximum absolute range of all tests within 8%.