Near‐field optical photomask repair with a femtosecond laser

We present a high‐resolution near‐field optical tool designed for repair of opaque defects in binary photomasks. Both instrument design and near‐field imaging and patterning results will be presented. Designed for ablative processing of thin metal films, the MR‐100 incorporates an industrial amplified femtosecond laser, third harmonic generator and built‐in autocorrelator. The ultrashort duration of the femtosecond pulses enables the tool to remove chrome layers with negligible damage to the surrounding metal or the underlying quartz substrate. The micropipette based near‐field writing head can deliver power densities of hundreds of GW/cm2 to spots of several hundred nanometres and below. Repairs on sample masks will be presented and the repair quality will be discussed.