Trenches in SiO2 Substrate for Relaxation of SiGe Films on SOI Wafers
Original Publication Date: 2003-Nov-14
Included in the Prior Art Database: 2003-Nov-14
Research and development to achieve fully relaxed SiGe buffer layer for strained Si technology has been very active in the past several decades. Utilization of SiGe mesa islands to further relax the SiGe films on silicon on insulator (SOI) has recently been proposed and demonstrated. In this publication, we describe an improved method by creating trenches in the SiO2 substrate surrounding the SiGe mesa islands to induce an augmented-relaxation of both substrate and SiGe. The trenches create open space (recesses) in the substrate so that SiO2 can undergo a viscous reflow during high temperature anneal, especially during the Ge condensation anneal. Relaxation of SiO2 substrate will, in turn, further relax SiGe mesa islands on the top by releasing the stress across the SiO2/SiGe interface. Results of continuum stress simulations confirmed the desired improvement: Trenches in the SiO2 substrate, sufficiently close to the mesa islands, accelerate indeed the relaxation process and at a given time during anneal more relaxation is achieved with trenches in SiO2 compared to the cases without trenches.