Normal-incidence spectroscopic ellipsometry for optical CD metrology

摘要

Normal-incidence polarized reflectance spectra of line-space patterns provide the same type of CD information as more complex scatterometry, ellipsometry, and reflectometry methods. Over the past year, optical critical dimension (OCD) metrology has seen rapid growth in both interest and use in the semiconductor industry as engineers and scientists push the boundaries of current technologies for measuring critical dimensions at the sub-0.1 μm level. The current ITRS predicts a 0.9nm precision requirement in 2003 to control a final gate length of 45nm in microprocessors. As the new technology nodes come on-line, traditional CD-SEM measurements will no longer be capable of measuring these dimensions reliably. OCD metrology has shown the ability to measure very small features (down to ～40nm) with the high level of precision necessary for IC fabrication. Additionally, OCD metrology is a noninvasive, nondestructive, ambient pressure measurement that can be carried out on product wafers and, like optical thin film metrology, can be integrated into the process tool for in-line monitoring or advanced process control.