Trade-offs inRFPerformance andElectrothermal Ruggedness ofMultifinger SiGePowerCells

Inthis contribution weanalyze thetrade-offs existing II. LAYOUTPARASITIC between theRFperformances andthethermal ruggedness ofSiGe power multifinger HBTs.Sixstructures withconstant emitter area Fig. 1showsasimplified drawing oftheparasitics ofasingle anddifferent emitter geometry areconsidered. Smallsignal s- emitter bipolar cell. Fromthis wecanderive somequalitative parameters aswellaslarge signal load-pull measurements are considerations ontheeffect ofthelayout variations onthe performed toevaluate theeffect ofemitter geometry onthedevice RFperformances. Moreover, thestructures areanalyzed throughparameters: RE,RBandCBC. aninhouse developed electrothermal simulator inorder todefine First we candescribe therelation betweentheemitter thelayout influence onthesafe operating area (SOA). Finally, some resistance andtheemitter width; itisevident that decreasing the guidelines aredrawntohelpthedesigner intrading electrical emitter width (e.g., increasing thenumber ofemitter fingers for performances forthermal ruggedness. afixed area), results inanincreased RE.Thisinturn affects the de-biasing effect along thefinger, reducing thehighfrequency presented. ~~~~~~~~~~~~~~~~~~~~~~Fig. 1. Cross-section viewofthebasic cell.