New Application of High Pressure/Environmental Microscopy to Semiconductor Inspection and Metrology
Michael T. Postek, Andras Vladar
High-pressure/environmental scanning electron microscopy has been used to successfully investigate binary and phase-shifting chromium on quartz optical photomasks. This methodology was also applied to patterned193 nm photoresist structures. The application of this methodology to semiconductor metrology is new because of the recent availability of high-pressure SEM instrumentation equipped with high-resolution, high-signal, thermally-assisted field emission technology in conjunction with large chamber and sample transfer capabilities. The high-pressure SEM methodology employs a gaseous environment around the sample to help diminish the charge build-up that occurs under irradiation with the electron beam. Although very desirable for the charge reduction in many biological, pharmaceutical and food applications, this methodology has not been employed for semiconductor photomask or wafer metrology until now. This is a new application of this technology to this area, and it shows great promise in inspection, imaging and metrology in a charge-free operational mode. For accurate metrology, high-pressure SEM methodology also affords a path that minimizes, if not eliminates, the need for charge modeling. This paper presents some of the early results in the high-pressure SEM metrology of photomask and photoresist structures.
critical dimension, environmental microscopy, high-pressure, metrology, scanning electron microscopy, SEM