Structural modification of a trench by hydrogen annealing

Abstract

The structural change of a trench by hydrogen ambient thermal annealing was investigated from the viewpoint of crystallographic orientation change and stress relaxation. By short-time hydrogen ambient annealing, structural stresses within sharp corner regions were relaxed, and new crystal planes were formed by surface energy minimization. The thermal oxide thickness difference at the corner region diminished mainly with the annealing temperature. Surface migration of silicon atoms was confirmed by the reduction in the surface roughness on the sidewall after the hydrogen annealing and by the crystalline reorientation of the silicon surface at the concave corner region. Migrated atoms on the crystal surfaces formed specific crystal planes, such as the (111) and the (113) low-index planes. On surfaces where atomic migration occurred, steps were mainly formed on (111) plane groups. By applying hydrogen annealing to the trench process, we were able to achieve stress relaxation and reliable oxide growth because of silicon atomic migration.