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 pr ocessing of thin metal films, the MR-100 incorporates an industrial amplifi ed femtosecond laser, third harmonic generator and built-in autocorrelator. The ultrashort duration of the femtosecond pulses enables the tool to remo ve chrome layers with negligible damage to the surrounding metal or the und erlying quartz substrate. The micropipette based near-field writing head ca n deliver power densities of hundreds of GW/cm(2) to spots of several hundr ed nanometres and below Repairs on sample masks will be presented and the r epair quality will be discussed.