Parallel spectroscopic ellipsometry for ultra-fast thin film characterization

Spectroscopic ellipsometer (SE) is an essential optical metrology tool commonly used to characterize thin films and monitor fabrication processes. However, it relies on mechanical rotation of a polarizer or a photo-elastic phase modulator which are limited in speed and prone to errors when handling dynamic processes. The constant trend of micro-electronics dimensions shrinkage and increase of the wafer area necessitates faster and more accurate tools. A fast SE design based on parallel snapshot detection of three signals at different polarizations is proposed and demonstrated. Not relying on mechanical rotation nor serial phase modulation, it is more accurate and can reach acquisition rates of hundreds of measurements per second.