We developed a self-aligned low-temperature process for the production of SiGe hetero bipolar transistors (HBTs) using a new metallization scheme with Ni/Ag taking advantage of the low specific resistivity of Ag and good contact resistance and low silicon consumption of the Ni silicide. Gummel plots of fabricated HBTs show sufficiently good behaviour. The formation of Ni silicide over temperature (325-500 • C) in a rapid thermal process system is studied. At temperatures above 425 • C a rather smooth film of monosilicide NiSi is formed. The resistivity of the thin (110 nm) NiSi was found to be excellent (11 µ cm) compared with bulk values. The contact resistance to n-and p-type silicon of 5 × 10 19 cm −3 is determined. Formation of self-aligned Ni silicide/Ag contacts is investigated and compared to non-self-aligned contacts.

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This paper present the design of a f T =200GHz SiGe Hetero Bipolar Transistor (HBT). A simple set of analytical equations describe the high frequency characteristics guaranteeing at the same time an easy understanding of the physics behind them . In detail the transit or delay times are analysed and the transistor design is optimized. Limitations and validity problems are pointed out.