TEM study of the origin of the surface microroughness in DSL photoetched Si-implanted GaAs wafers

TEM has been used to study the origin of the surface microroughness that formed in both 29Si as-implanted and rapid thermal annealed LEC undoped GaAs wafers after DSL photoetching. The degree of microroughness increased as the implant dose increased from 3x1012 to 3x1014 atoms/cm2. It has been found that such a microroughness is due to the fine-scale damage induced by the implantation in the as-implanted wafers and to interstitial dislocation loops in the implanted and then annealed wafers. Microroughness appears during DSL etching because such defects are effective recombination centres for the holes involved in the dissolution of the GaAs surface so that the wafers etch slower at the point-defect clusters and dislocation loops.