Evaluation of Strain in Si-on-Insulator Substrate Induced by Si3N4 Capping Film

Strain introduced to Si-on-insulator (SOI) substrates by Si3N4 capping film was evaluated by UV-Raman spectroscopy. The induced strain became larger with increasing Si3N4 film thickness. SOI substrates originally had tensile strain and the Si3N4 cap shifted the strain toward the compressive direction. The induced strain was larger in thinner SOI substrates with the same thickness of the Si3N4 capping film. In the SOI substrates with patterned Si3N4 film, the strain was in different directions between the regions with and without Si3N4 film; i.e., if the strain was compressive in the region beneath the Si3N4 film, it was tensile beneath the space between the Si3N4 lines. We also evaluated substrates after Si3N4 patterning with a high spatial resolution of 200 nm, and observed strain enhancement near the pattern edge on both sides.