Thin-layer SIMOX for future applications

Abstract

Separation by implantation of oxygen (SIMOX) substrates implanted with stoichiometric doses of oxygen (1.8/spl times/10/sup 18/O/sup +//cm/sup 2/) at high energy (180-200 keV) and annealed at high temperatures have been accepted in silicon technology. Four times lower doses and extended annealing schemes were shown to form 100 nm thick buried oxides (Nakashima et al. 1993; Izumi, 1997) with application in commercial processes. The need for lower cost SOI wafers and thinner layers in future fully-depleted circuits continuously stimulates efforts to develop lower dose, thin buried oxide processes (Giles et al. 1994; Meyyappan et al. 1995; Holland et al. 1996). This work aims to demonstrate the formation of SIMOX layers in large area wafers with further reduced oxygen doses at energies below 100 keV. At the low energy peak of oxygen, the distribution is shallower and the full width at half maximum of this distribution is smaller than that for high energy implantation. Implantation at 65 keV generates near factor of 2 lower lattice damage per ion compared to 200 keV implantation. This allows more favorable conditions for formation of a stoichiometric buried oxide at low energy rather than at high energy. In addition, the manufacturability is improved due to the direct tailoring of the layer thickness for the criteria of fully depleted circuits at the basic process.