Effects of lateral scaling on power gain of multifinger SiGe power HBTs

The lateral scaling issues of high-power SiGe HBTs are analytically studied and verified using industry SiGe HBTs. It is found that due to increased parasitics in large-area power SiGe HBTs, f_max cannot be readily improved by only downscaling the emitter finger width. It is further found that without proper downscaling of the base stripe width, the maximum stable power gain (MSG) of power SiGe HBTs may be degraded by only shrinking the emitter finger width. It is thus proposed that both emitter finger width and the base stripe width ought to be downscaled properly in order to optimize the RF performance of SiGe power HBTs that are configured in a multiple subcell structure