SUPPRESSION OF THE BASE-COLLECTOR LEAKAGE CURRENT IN INTEGRATED SI SIGE HETEROJUNCTION BIPOLAR-TRANSISTORS/

High leakage currents at the base-collector junction of heterojunction bipolar transistors have been mentioned by several authors. In this a rticle, we compare two pre-epitaxy cleaning procedures which both allo w smooth epitaxy without any extended defects. Using our initial clean ing procedure, we obtained leakage current values in the range of the published results. We show that our results were consistent with the p resence of defects induced by the low-energy reactive ion etching invo lved in this procedure. In contrast, we obtain a very significant redu ction of the leakage current using our new all-wet chemical cleaning. (C) 1998 American Vacuum Society.