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This letter presents the first demonstration of a silicon-germanium heterojunction bipolar transistor (SiGe HBT) capable of operation above the one-half terahertz (500 GHz) frequency. An extracted peak unity gain cutoff frequency (f T ) of 510 GHz at 4.5 K was measured for a 0.12 × 1.0 µm 2 SiGe HBT (352 GHz at 300 K) at a breakdown voltage BV CEO of 1.36 V (1.47 V at 300 K), yielding an f T × BV CEO product of 693.6 GHz-V at 4.5 K (517.4 GHz-V at 300 K).

The effort to design RF circuits in CMOS is motivated by low cost and significant capacity for on-chip integration. We discuss some of the challenges of implementing RF designs in CMOS focusing on those introduced by the changing properties of FETs as technology nodes scale and devices shrink. We present methods and tools using which designers can ease these challenges and reduce the risk of implementing RF circuits in CMOS.

A record 210-GHz SiGe heterojunction bipolar transistor at a collector current density of 6-9 mA/ m 2 is fabricated with a new nonself-aligned (NSA) structure based on 0.18 m technology. This NSA structure has a low-complexity emitter and extrinsic base process which reduces overall thermal cycle and minimizes transient enhanced diffusion. A low-power performance has been achieved which requires only 1 mA collector current to reach 200-GHz . The performance is a result of narrow base width and reduced parasitics in the device. Detailed comparison is made to a 120-GHz self-aligned production device.

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