CONTOURING OF SIMOX PROFILES BY OXYGEN ION ENERGY CHANGE

The objective of this work was to determine if, by changing the ion energy during the implant, depth distribution profiles could be contoured to produce improved SIMOX material. In the SIMOX process, oxygen ions are implanted into bare silicon or into silicon through a silicon dioxide capping layer. During the course of the implant, the incoming fast ions sputter silicon atoms from the surface. Through this mechanism, by the end of the implant, the apparent depth of penetration with respect to the original surface will have increased. However, a competing action is at work: oxygen ions retained by the formation of the buried oxide layer will cause swelling. Detailed calculations have been performed, which show that the sputtering effect is approximately compensated by the swelling. Experimentally, by increasing the oxygen beam energy during the implant, improved SIMOX material was formed without the silicon islands normally observed.