Structural modification of a trench by hydrogen annealing

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.