LMS IPRO: enabling accurate registration metrology on SiN-based phase-shift masks

SiN-based absorber materials are considered to be the new work horse for cutting-edge patterning using 193-nm immersion lithography. The high robustness against cleaning procedures and the low susceptibility for haze makes SiN an ideal material for phase-shift masks. Reliable metrology with high precision, on target as well as on feature, is enabled by the LMS IPRO^TM metrology tool. This is achieved by taking into account the optical properties of the novel materials and utilisation of the high-accuracy die-to-database algorithm. Simulation as well as actual measurement results are presented. Cost effectiveness of the LMS IPRO is demonstrated by comparison of high-performance mode results versus high-throughput results, confirming suitable metrology performance for high-volume manufacturing.