Evaluation of Si ₃ N ₄ /Si interface by UV Raman spectroscopy

The stresses at Si ₃ N ₄ /Si (1 0 0), (1 1 1) and (1 1 0) interfaces were measured by UV Raman spectroscopy with a 364 nm excitation laser whose penetration depth into the Si substrate was estimated to be 5 nm. The Si ₃ N ₄ films were formed on Si (1 0 0), (1 1 1) and (1 1 0) using nitrogen-hydrogen (NH) radicals produced in microwave-excited high-density Xe/NH ₃ mixture plasma. The localized stress detected from Raman peak shift was compressive at the (1 0 0) interface, and tensile at the (1 1 1) and (1 1 0) interfaces. The results showed that stress had strong correlation with the total density of subnitrides at the Si ₃ N ₄ /Si interface, and also with the full-width at half-maximum (FWHM) of Si the 2p _3/2 photoemission spectrum arising from the substrate. We believe that the localized stress affected subnitride formation because the amount of subnitride and the FWHM of Si 2p _3/2 decreased while the interface stress shifted in the tensile direction.