193 nm Angle-Resolved Scatterfield Microscope for Semiconductor Metrology

摘要

An angle-resolved scatterfield microscope (ARSM) featuring 193 nm excimer laser light was developed for measuring critical dimension (CD) and overlay of nanoscale targets as used in semiconductor metrology. The microscope is designed to have a wide and telecentric conjugate back focal plane (CBFP) and a scan module for resolving Kohler illumination in the sample plane. Angular scanning of the sample plane was achieved by linearly scanning an aperture across the 12 mm diameter CBFP, with aperture size as small as 0.4 mm for some scans. For each aperture, the sample was illuminated over a range of angles from 12° to 48°, corresponding to a numerical aperture of 0.2 to 0.74. Angle-resolved measurement results are presented for grating targets with nominal linewidths down to 50 nm.