Formation of amorphous layers by ion implantation

This study was directed toward exploring the relationship between the implant conditions and the depth and nature of the amorphous layers generated in silicon. Interest in amorphous layer morphology stems from its role in affecting crystal defects remaining after amorphous-to-crystalline transformation. High-dose implants of As, P, and B were used to generate buried and surface amorphous layers at slightly higher than room temperature. The amorphous layer depths were measured and the depth-fluence and depth-energy relationships were compared with Brice’s analysis. It was found that good fits were obtained for a threshold damage density of 2.5×1020 keV cm−3 for As and 1.0×1021 keV cm−3 for P. For B, the results could be described by a threshold damage density of 5.0×1021 keV cm−3 or greater. Lower weight ion implantations exhibit a greater tendency to generate buried amorphous layers as well as to generate amorphous layers which include a smaller fraction of the total implanted fluence than is found for heavier ion implantations. These two factors make it more likely for residual crystal defects to be associated with lower weight ion implant distributions.