7 December 1994 High-resolution UV laser repair of phase-shifting photomasks
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Abstract
Processes for repairing defects on phase shifting masks have been developed at Excel/Quantronix. The processes are based on DUV (248 nm) laser ablation and DUV laser- assisted chemical vapor deposition. The light source of the repair system consists of a gain- switched Ti:Sapphire laser system. The 248 nm wavelength is obtained by frequency tripling. The all-solid-state laser provides high stability, short pulse duration, and good beam quality required by the repair processes. By significantly improving the optical system, we are capable of repairing features with a diameter of approximately 0.2 micrometers . The repair of programmed defects such as 0.5 X 0.5 micrometers 2 extra quartz phase shifter (with or without chrome on top) and 1 X 1 micrometers 2 phase divots have been successfully demonstrated and examined by the aerial image measurement system (AIMS) developed by IBM. After opaque defect repair, the repaired area exhibits a transmission greater than 95% for both I-line and 248 nm. Clear defects are repaired in an open-air environment with controlled transmission. The deposited films show good uniformity and sharp edges. Extra quartz phase shifter defects are reliably repaired in an open-air environment with the technique of laser ablation by surface enhancement (LASE), which was developed at Excel/Quantronix. Phase divots have been successfully repaired by photolytic deposition of SiO2 in a vacuum system using a single precursor, without the need of an oxidizing co-reactant. The repair techniques developed by Excel/Quantronix have broad applicability to a wide variety of conventional and phase shifting photomasks.
© (1994) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Baorui Yang, Yung-Ho Chuang, Kuo-Ching Liu, "High-resolution UV laser repair of phase-shifting photomasks", Proc. SPIE 2322, 14th Annual BACUS Symposium on Photomask Technology and Management, (7 December 1994); doi: 10.1117/12.195841; https://doi.org/10.1117/12.195841
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