SILICON ETCHED-GROOVE PERMEABLE BASE TRANSISTORS WITH 90-NM FINGER WIDTH

Silicon etched-groove permeable base transistors (PBT's) with finger sizes down to 90 nm have been fabricated. In order to eliminate surface depletion effects, a new structure was used. Tbe fingers are n+ -doped and the channel region is buried below tbe bottom of the grooves. Doping and thickness of the active layer were optimized according to two-dimensional computer simulations. The maximum measured transconductance of 155 mS/mm is the highest reported for Si PBT's and demonstrates the potential of silicon as substrate material. The measured transit frequency was 12 GHz; fmax reached 13 GHz. It has been recognized that for improved high-frequency performance a reduction of the gate capacitance is necessary, demanding a more precise control of groove depth and geometry. © 1990 IEEE