Mechanisms of formation of buried-oxide in low-dose SIMOX

There is increasing interest in low-dose SIMOX as a substrate material. Circuits fabricated on such wafers need to have a high-quality buried-oxide (BOX) with flat, uniform interfaces and density of pipes and of Si islands as low as possible. Si islands have been reported to be responsible for increased electrical leakage current through the BOX, or in extreme cases, its dielectric breakdown. While the thickness of such Si islands in high-dose SIMOX spans only 3-5% of the BOX thickness, in low-dose material they may span 50%, or more, of the total BOX thickness. As a result, the reduction of the effective thickness of BOX could lead to degradation of dielectric properties. Thus, the understanding of BOX microstructural development is an important issue for low-dose SIMOX. Here we are reporting the mechanism of the development of BOX microstructure for annealed SIMOX as a function of implantation dose.