On buried oxide effects in SOI lateral bipolar transistors

We report buried oxide effects on the Silicon-On-Insulator Lateral Bipolar Transistor (SOILBT) performance by two-dimensional (2-D) numerical simulation and experiments. An early punchthrough is observed in SOILBT compared to the bulk due to the presence of buried oxide. In addition to dopant segregation into the buried oxide, the presence of buried oxide also diverts some electric field lines emanating from collector toward substrate, due to 2-D distribution of field, leaving fewer across the base region and hence increased depletion widths and punchthrough. One-dimensional (1-D) depletion approximation fails to predict this punchthrough. To establish the evidence of buried oxide induced punchthrough without dopant segregation effect, simple and yet novel measurement techniques are proposed to extract effective base width and base doping concentration near the buried oxide-silicon film interface using the parasitic MOSFET in SOILBT. Good agreement between 2-D simulation and experimental results was observed. Finally design curves are generated using 2-D numerical simulation for different base doping and buried oxide thicknesses on SOI substrates