Bipolar transistor fabrication in low-temperature (745°C) ultra-low-pressure chemical-vapor-deposited epitaxial silicon

In this letter we report for the first time the successful fabrication of bipolar transistors in low-temperature (T
dep
= 745°C) epitaxial silicon deposited by a chemical-vapor-deposition (CVD) technology. The epitaxial layers were deposited by an ultra-low-pressure CVD (U-LPCVD) technique utilizing an optimized in-situ predeposition argon sputter clean. The critical parameter during the sputter clean has been identified as the substrate bias. Bias voltages of -200 or -300 V create dislocations that form emitter-collector shunts during the bipolar transistor fabrication process; a bias voltage of -100 V, however, permits the deposition of essentially defect-free (<10 dislocations cm
^-2
by defect etching) epitaxial films suitable for bipolar transistor fabrication.