Non-Contact Electrical Critical Dimensions Metrology Sensor for Chrome Photomasks

摘要

This paper describes a novel non-contact capacitive-sensor metrology tool developed for chrome photomasks. This work further describes suitable types of test structures printed on photomasks appropriate for linewidth metrology. The Critical Dimension (CD) metrology sensor is developed using a Low Temperature Co-Fired Ceramic (LTCC) technology to reduce the effects of parasitic capacitances. The sensor is based on non-contact micro-capacitance measurements of features on chrome-on-glass reticles. The CD-extraction algorithms based on the capacitance measurements are formulated from extensive evaluation with a Maxwell simulator. The purpose of the non-contact micro-capacitive sensor is to measure chrome-feature linewidths in the range of 0.4 μm - 0.5 μm. These dimensions correspond to a 0.18-μm process on a 4X mask.