D. Scott

Submicron scaling of HBTs

The variation of heterojunction bipolar transistor (HBT) bandwidth with scaling is reviewed. High bandwidths are obtained by thinning the base and collector layers, increasing emitter current density, decreasing emitter contact resistivity, and reducing the emitter and collector junction widths. In mesa HBTs, minimum dimensions required for the base contact impose a minimum width for the collector junction, frustrating device scaling. Narrow collector junctions can be obtained by using substrate transfer or collector-undercut processes or, if contact resistivity is greatly reduced, by reducing the width of the base ohmic contacts in a mesa structure. HBTs with submicron collector junctions exhibit extremely high f/sub max/ and high gains in mm-wave ICs. Transferred-substrate HBTs have obtained 21 dB unilateral power gain at 100 GHz. If extrapolated at -20 dB/decade, the power gain cutoff frequency f/sub max/ is 1.1 THz. f/sub max/ will be less than 1 THz if unmodeled electron transport physics produce a >20 dB/decade variation in power gain at frequencies above 110 GHz. Transferred-substrate HBTs have obtained 295 GHz f/sub T/. The substrate transfer process provides microstrip interconnects on a low-/spl epsiv//sub r/ polymer dielectric with a electroplated gold ground plane. Important wiring parasitics, including wiring capacitance, and ground via inductance are substantially reduced. Demonstrated ICs include lumped and distributed amplifiers with bandwidths to 85 GHz and per-stage gain-bandwidth products over 400 GHz, and master-slave latches operating at 75 GHz.

SCALING OF InGaAs/InAlAsHBTs FOR HIGH SPEED MIXED-SIGNAL AND mm-WAVE ICs

High bandwidths are obtained with heterojunction bipolar transistors by thinning the base and collector layers, increasing emitter current density, decreasing emitter contact resistivity, and reducing the emitter and collector junction widths. In mesa HBTs, minimum dimensions required for the base contact impose a minimum width for the collector junction, frustrating device scaling. Narrow collector junctions can be obtained by using substrate transfer processes, or -if contact resistivity is greatly reduced -by reducing the width of the base Ohmic contacts in a mesa structure. HBTs with submicron collector junctions exhibit extremely high fmax and high gains in mm-wave ICs. Logic gate delays are primarily set by depletion-layer charging times, and neither fτ nor fmax is indicative of logic speed. For high speed logic, epitaxial layers must be thinned, emitter and collector junction widths reduced, current density increased, and emitter parasitic resistance decreased. Transferred-substrate HBTs have obtained 21 dB unilateral power gain at 100 GHz. If extrapolated at -20 dB/decade, the power gain cutoff frequency fmax is 1.1 THz. Transferred-substrate HBTs have obtained 295 GHz fτ. Demonstrated ICs include lumped and distributed amplifiers with bandwidths to 85 GHz, 66 GHz master-slave flip-flops, and 18 GHz clock rate Δ-Σ ADCs.

Demonstration of a 311-GHz Fundamental Oscillator Using InP HBT Technology

In this paper, a sub-millimeter-wave HBT oscillator is reported. The oscillator uses a single-emitter 0.3 m15 m InP HBT device with maximum frequency of oscillation greater than 500 GHz. The passive components of the oscillator are realized in a two metal process with benzocyclobutene used as the primary transmission line dielectric. The oscillator is implemented in a common base topology due to its inherent instability. The design includes an on-chip resonator, output matching circuitry, and injection locking port. A free-running frequency of 311.6 GHz has been measured by down-converting the signal. Additionally, injection locking has been successfully demonstrated with up to 17.8 dB of injection-locking gain. This is the first fundamental HBT oscillator operating above 300 GHz.

Transistor and circuit design for 100-200 GHz ICs

Compared to SiGe, InP HBTs offer superior electron transport properties but inferior scaling and parasitic reduction. Figures of merit for mixed-signal ICs are developed and HBT scaling laws introduced. Device and circuit results are summarized, including a simultaneous 450 GHz f/sub /spl tau// and 490 GHz f/sub max/ DHBT, 172-GHz amplifiers with 8.3-dBm output power and 4.5-dB associated power gain, and 150-GHz static frequency dividers (a digital circuit figure-of-merit for a device technology). To compete with advanced 100-nm SiGe processes, InP HBTs must be similarly scaled and high process yields are imperative. Described are several process modules in development: these include an emitter-base dielectric sidewall spacer for increased yield, a collector pedestal implant for reduced extrinsic C/sub cb/, and emitter junction regrowth for reduced base and emitter resistances.

Demonstration of 184 and 255-GHz Amplifiers Using InP HBT Technology

In this letter, 184 and 255 GHz single-stage heterojunction bipolar transistor (HBT) amplifiers are reported. Each amplifier uses a single-emitter 0.4 ¿m 15 ¿m InP HBT device with maximum frequency of oscillation (fmax) greater than 500 GHz and of 200 GHz. The 183 GHz single-stage amplifier has demonstrated gain of 4.3 ± 0.4 dB for all sites on the wafer. The 255 GHz amplifier has measured gain of 3.5d B and demonstrates the highest frequency measured HBT amplifier gain reported to date. Both amplifiers show excellent agreement with original simulation.

G-band (140-220-GHz) InP-based HBT amplifiers

We report tuned amplifiers designed for the 140-220-GHz frequency band. The amplifiers were designed in a transferred-substrate InP-based heterojunction bipolar transistor technology that enables efficient scaling of the parasitic collector-base junction capacitance. A single-stage amplifier exhibited 6.3-dB small-signal gain at 175 GHz. Three-stage amplifiers were subsequently fabricated with one design demonstrating 12.0-dB gain at 170 GHz and a second design exhibiting 8.5-dB gain at 195 GHz.

Advanced Heterogeneous Integration of InP HBT and CMOS Si Technologies

Northrop Grumman Aerospace Systems (NGAS) is developing an Advanced Heterogeneous Integration (AHI) process to integrate III-V semiconductor chiplets on CMOS wafers under the Compound Semiconductor Materials on Silicon (COSMOS) DARPA program. The objective of the program is to have a heterogeneous interconnect pitch and length less than 5 um to enable intimate transistor scale integration. This integration will enable significant improvement in dynamic range and bandwidth of high performance mixed signal circuits.

An 8-GHz continuous-time /spl Sigma/-/spl Delta/ analog-digital converter in an InP-based HBT technology

We report an 8-GHz clock-rate, second-order continuous-time /spl Sigma/-/spl Delta/ analog-digital converter (ADC) that achieves 57.4-, 51.7-, and 40.2-dB SNR at signal sampling rates of 125, 250, and 500 Ms/s, respectively. The integrated circuit occupied 1.45-mm/sup 2/ die area, contains 76 transistors, is fabricated in an InP-based HBT technology, and dissipates /spl sim/1.8 W. We also study the effect of excess delay on modulator performance, and show that excess delay does not affect performance as long as the centroid-in-time of the digital-analog converter pulse remains stationary.

Advanced heterogeneous integration of InP HBT and CMOS Si technologies for high performance mixed signal applications

Northrop Grumman Space Technology (NGST) is developing an Advanced Heterogeneous Integration (AHI) process to integrate III-V semiconductor chiplets on CMOS wafers under the Compound Semiconductor Materials on Silicon (COSMOS) DARPA program. The objective of the program is to have a heterogeneous interconnect pitch and length less than 5 um to enable intimate transistor scale integration. This integration will enable significant improvement in ADC dynamic range and bandwidth

87 GHz static frequency divider in an InP-based mesa DHBT technology

Reports on a static frequency divider with a maximum clock frequency of 87 GHz in a mesa InP/InGaAs/InP DHBT technology. The divider is operational at all tested frequencies between 4 and 87 GHz and dissipated 700 mW of power from a -4.5V supply.