BASE CONTACT RESISTANCE LIMITS TO LATERAL SCALING OF FULLY SELF-ALIGNED DOUBLE MESA SIGE-HBTS

A significant reduction of parasitic resistances and capacitances of t he double mesa SiGe Heterojunction Bipolar Transistors (SiGe-HBT) was achieved by using self-aligned processing steps, such as planarization of transistor contacts, outside-spacer-technology for micromasking, c ontact implantation and low ohmic silicidation. This article presents and analyses the lateral optimization of the double mesa SiGe-HBT by o n-wafer measurements and demonstrates lateral scaling limitation resul ting from the increasing base metal-semiconductor contact resistance. The increase of the more important base contact resistance is proven b y two-dimensional contact simulation. This is shown experimentally by using a fully self-aligned double mesa SiGe-HBT transistor which combi nes the advantages of superior high frequency characteristics with a s imple and low cost fabrication procedure being used mainly in compound semiconductor technology. (C) 1997 Elsevier Science Ltd.