Double-crystal x-ray topographic determination of local strain in metal-oxide-semiconductor device structures

A double-crystal x-ray topograph was used to determine local strain in metal-oxide-semiconductor (MOS) transistor test chips. The double-crystal machine could sense strains as small as 10−6, with a spatial resolution of a few micrometers. Results indicate that two types of strain are present: local surface strain as well as the more familiar strain due to bulk deformation of the crystal. Both types of strain have been correlated with surface mobility changes in n-channel metal-oxide-semiconductor (nMOS) transistors.