A closed form analytic model for separation by implantation of oxygen oxide growth using a joined-Gaussian approximation

Abstract

A closed form analytic solution to the growth characteristics of the separation by implantation of oxygen (SIMOX) buried oxide and silicon film, based on a two-sided Gaussian approximation to the oxygen implant profile in the SIMOX process, is presented. The model used includes the effects of substrate swelling and sputtering due to the implanted oxygen, as well as the effects of saturation of the oxygen density at the stoichiometric SiO2 level in the implanted region. The results of this investigation show that for typical SIMOX implant conditions currently used in high-current implanters, the total dose of oxygen required to first reach the saturation level is only slightly dependent on the swelling and sputtering effects associated with the oxygen implantation, and that the deviation of the location of the first saturation point from the commonly used implant range can be significantly affected by the implant profile. In addition, it is shown that a ‘‘natural parameter’’ GNsat, where G is the net growth of the substrate per implanted oxygen atom and Nsat is the saturation level of oxygen atoms in the buried oxide, can be used to characterize the magnitude of the effects of the implant parameters on the final SIMOX material. It is also shown that the parameter GNsat can be easily obtained from the slope of a Tox vs Tsi plot.