Defect Dynamics in Simox Structures as a Function of the Annealing Parameters

Abstract

Advanced semiconductor devices on the SIMOX (Separation by IMplanted OXygen) substrate have many advantages including high-speed, large packing density and low power consumption. SIMOX consists of a layer structure generated by oxygen ion implantation into silicon wafers. The implantation process introduces a high density of defects that can be reduced by post-implantation annealing. Decreasing the oxygen dose not only reduces the cost but also decreases the damage to the top Si layers. Low-dose implantation results in thinner buried oxide (BOX) layer, in contrast to traditional high-dose SIMOX. The BOX layer formation mechanism is different for low-dose SIMOX from that of high-dose. For a high-dose SIMOX, the BOX layer is already formed by implantation. However, for a low-dose, a number of oxide precipitates are formed during implantation. The larger precipitates grow at the expense of smaller ones until they coalesce to the BOX layer during annealing. This step is known as Ostwald ripening, which is responsible for the thin BOX formation.