Femtosecond laser ablation and deposition of metal films on transparent substrates with applications in photomask repair

Abstract

We describe experiments using ultrashort pulses of laser light to ablatively remove opaque and partially transmitting materials from transparent substrates. Pulses of 100 femtosecond duration at a wavelength of 266 nm were used to repair defects on photomasks used in lithographic printing of integrated circuits, with better than 100 nm spatial resolution. Details of the development and implementation of a photomask repair tool, presently operating in manufacturing, which exploits the advantages of ablation with femtosecond pulses, are presented. We further describe experiments where pulses of 400 nm light were used to photolytically deposit Cr metal with better than 200 nm resolution. Finally we describe a gas phase 35 femtosecond laser source used to extend this approach to ablative mask repair at 193 nm.