Predicted Propagation Delay of Si/Si1-xGex Heterojunction Bipolar Circuits

A comparison is made between silicon homojunction and Si/SiGe heterojunction technology by means of ECL gate delay calculations. The calculations are based on state of the art 1¿m technology and basewidths of initially 0.1¿m and then scaled basewidths of 0.025 ¿m. Results of 42.5 ps for silicon homojunction circuits and 35.4 ps for HLBT circuts demonstrate improvement in gate delays for HBT silicon heterojunction technology at 0.1 ¿m basewidths. Furtlher improvements are predicted for basewidths scaled to 0.025 ¿m, with delays of 33.7 ps for homojunction and 28.3 ps for HBT circuits. In addition, sub 20 ps delays are predicted for appropriately designed devices.