Improved Silicon on Insulator (SOI) Manufacturing Technology for Low Power, High Speed, Radiation Hard Devices

SOI technology offers the potential for creating radiation hard integrated circuits which can operate at low power and high speed. These advances are important for DoD and space applications and for battery operated devices. SOI is excellent for rad-hard applications because dielectric isolation of active circuitry from the supporting substrate by the Buried OXygen (BOX) layer enhances resistance to transient radiation effects by limiting charge collection volumes. Thin BOX (TBOX) layer material is particularly effective because the small dielectric region minimizes charge accumulation even further. An important technology for the production of SOI wafers is Separation by Implarltation of OXygen (SIMOX) developed by the Ibis Technology Corporation (Ibis). Research has shown that hardening processes developed for thermal oxides in bulk silicon technology (thermal oxide or fused silica) can be successfully applied to harden the SIMOX BOX if the BOX material properties (particularly density) can be made similar to those of thermal oxide. Also shown was that this matching of densities can be accomplished through the use of a supplemental oxygen implant. There are significant opportunities to speed rad-hard TBOX development, accelerate yield learning, improve quality, reduce scrap, lower costs, improve fabrication tool efficiency, reduce time to optimize fabrication tool operating parameters, reduce time to identify and correct faults, and reduce personnel, by the use of in-situ and in-line analysis of SIMOX wafers during processing. A number of recent developments suggest that Fourier Transform Infrared (FT-IR) spectroscopy can be an excellent analysis tool for monitoring and control of SIMOX fabrication. It is sensitive to thickness and composition of the layers (including the BOX layer density), it can be employed off-line for mapping and it can be employed in-line or in-situ in the ion implanter and the annealing oven. Measurements are made in seconds, and can be applied for in-situ diagnostics to guarantee product quality at each process step. Advanced Fuel Research, Inc., On-Line Technologies, Inc., and Ibis will develop FT-IR tools for in-situ control technology for SIMOX. Phase I will develop the F