FT-IR reflectance spectroscopy control of SIMOX structures

The technique of implanting silicon wafers with sufficient oxygen to form a continuous underlying buried oxide (BOX) layer is known as SIMOX (separation by implantation of oxygen). On-line process control for SIMOX wafer fabrication would provide an avenue for tighter process control, especially for ultra thin BOX development. The fabrication of 80 nm to 200 nm BOX is a key development for improved device performance and cost reduction. At present, the Faraday measurement of charged ions ultimately controls the thickness of the BOX layer. Accurate in-situ control of the amount of implanted ions would enable the manufacturer to fine tune the dose to produce wafers with optimal and consistent BOX thickness. An achievement of the BOX thickness within the specified dose is predicted to enhance SIMOX performance for high speed, radiation hard devices based upon ultra-thin BOX structures. This work reports on a successful ex-situ FTIR demonstration of unannealed SIMOX analysis with predicted BOX thicknesses to within 1% for ultimate in-situ analysis of dosimetry in SIMOX manufacturing.