Stress evaluation induced by wiggling silicon nitride fine pattern using Raman spectroscopy

Abstract

We evaluated the residual stress of the silicon nitride (SiN) fine pattern structure in order to quantitatively predict the occurrence of wiggling, which causes device failure. UV Raman spectroscopy showed an increase of tensile stress in Si substrate with increasing etching time, and the tensile stress in Si substrate was caused by the enhancement at the very edge of the fine pattern and the increase in the amount of over-etching. It was also confirmed that the edge enhanced effect can be obtained by using a UV laser for fine patterns, so that the Raman intensity from Si (amorphous and crystal) increased significantly with the etching time of the pattern. Furthermore, using water-immersion Raman spectroscopy, we evaluated the anisotropic biaxial stress applied to the fine patterns and showed occurrence of strain relaxation. The wiggling, therefore, occurs due to the huge anisotropic stresses induced in the Si substrates.