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 st
resses within sharp corner regions were relaxed, and new crystal planes wer
e formed by surface energy minimization. The thermal oxide thickness differ
ence at the corner region diminished mainly with the annealing temperature.
Surface migration of silicon atoms was confirmed by the reduction in the s
urface roughness on the sidewall after the hydrogen annealing and by the cr
ystalline reorientation of the silicon surface at the concave corner region
. Migrated atoms on the crystal surfaces formed specific crystal planes, su
ch as the (111) and the (113) low-index planes. On surfaces where atomic mi
gration occurred, steps were mainly formed on (111) plane groups. By applyi
ng hydrogen annealing to the trench process, we were able to achieve stress
relaxation and reliable oxide growth because of silicon atomic migration.