Secondary emission of strain-induced dopant contrast in the source/drain regions of metal-oxide-semiconductor devices

Abstract

Secondary electron (SE) imaging with scanning electron microscopy has been used for two-dimensional dopant profiling. However, the mechanism of dopant contrast is still not yet understood. Here we propose another significant contribution from interface strain for the source/drain regions in p- and n-type metal-oxide-semiconductor (MOS) devices. The results show that the width of the dopant profile by SE imaging agrees well with the strain profile by dark-field technique with transmission electron microscopy. We demonstrate that the dopant contrast of the p-MOS device by SE imaging is higher than a test wafer by 45%. The enhanced SE signals for both p-MOS and n-MOS devices are caused by band bending through CoSi2-induced strain.