Partial-SOI Isolation Structure for Reduced Bipolar Transistor Parasitics

A novel bipolar isolation structure with capability of significantly reducing collector-base capacitance and base resistance is presented. Partial SOI, with SOI surrounding the collector opening, can be used to reduce the collector window width in combination with any emitter-base self-aligned bipolar device structure, and in particular for device structures that feature sublithographic emitter width. Near-ideal transistor Gummel characteristics and a minimum ECL gate delay of 24 ps have been achieved with a nonoptimized lateral device layout, and simulations suggest that sub-20-ps delay at reduced switch current will be possible by using the optimized partial-SOI isolation structure. © 1992 IEEE