NSF Award
9560259
This Small Business Innovative Research Phase I project will produce a MM-wave sensor that remotely measures sheet resistivity in real time of Molecular Beam Epitaxy (MBE) grown wafers. Manufacturing high performance semiconductor epitaxial wafers by MBE requires precision doping and layer thickness control to obtain optimum device and circuit performance. High reproducibility requires the precise doping and layer thickness to be the same every time. The u wafer sheet resistivity is a key calibration parameter that indicates these variables are correct in the final wafer structure. The current approach used for monitoring this parameter is to measure the sheet resistivity on special calibration wafers outside the ultra high vacuum (UHV) chamber of the MBE machine. If the sheet resistivity is out of specification a new calibration run with adjusted growth conditions must be performed before the actual product wafers may be further processed. This entails extra loading and unloading of wafers through the load locks and generally results in production delays and lower MBE throughput. This innovative wave sensor approach eliminates all of this waste. The overall objective for the Phase I effort is to demonstrate the feasibility of in situ monitoring of sheet resistivity of GaAs or InP epitaxial wafers (typically used for MMICs) inside an MBE machine with an instrument located completely outside the UHV chamber. This capability will streamline the production process while providing superior performance and precise reproducibility of the epi-wafers at a reduced cost and higher throughput. This will allow consistent and reliable optimum devices and circuits (e.g. microwave and mm-wave integrated circuits) for various military and commercial system applications. The development of a sheet resistivity sensor for in situ MBE measurements will result in product improvement and reduction of manufacturing costs for high volume production of GaAs and InP epitaxial wafers. The instrument's application, however, is not restricted to any one semiconductor material. It has potential use for any moderately to highly conducting epitaxial material grown on a host substrate including silicon.
