Effect of single-step, high-oxygen-concentration annealing on buried oxide layer microstructure in post-implant-amorphized, low-dose SIMOX material

Fabrication of high-dose SIMOX (typically 1.8/spl times/10/sup 18/ cm/sup 2/ at 200 keV) is a maturing materials technology with increasing commercial usage. However, lower-dose SIMOX (2 to 4/spl times/10/sup 17/ cm/sup 2/) has the potential to be more economical, as well as allow device designers a choice of oxide thickness, but film uniformity and quality must be as good or better than standard high-dose material. A variety of approaches to produce low-dose SIMOX have been used which include: low dose implant plus ITOX (internal thermal oxidation), which uses a second high temperature anneal with high oxygen concentration (Nakashima et al. 1996; Mrstik et al. 1995); multiple energy implants (Alles, 1997); lower energy implantation (Anc et al. 1998); rapid ramping to the high temperature anneal range (Ogura, 1998); N pre-implantation (Meyappan et al. 1995); and very-low dose, post-implant amorphization prior to high temperature annealing (Holland et al. 1996; Bagchi et al. 1997). For the last technique, it was reported there were changes in the precipitation mechanisms that control BOX development. The first was elimination of multiply-faulted defects as sites for preferred nucleation and growth of oxides which form a discontinuous upper layer of precipitates in untreated material. The second was enhanced diffusion of oxygen along defects and phase boundaries in the amorphized region to the single BOX layer that was developing. In this research, we extend the work on post-implant-amorphized low-dose SIMOX by reporting effects of a single-step high oxygen concentration anneal on its BOX microstructure.