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1999 IEEE Symposium on Indium Phosphide & Related Materials. Transferred-Substrate Heterojunction Bipolar Transistor Integrated Circuit Technology. M Rodwell , Q Lee, D Mensa, J Guthrie, Y Betser, S Jaganathan, T Mathew, P Krishnan, S Long University of California, Santa Barbara

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Transferred-Substrate Heterojunction Bipolar Transistor Integrated Circuit Technology


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transferred substrate heterojunction bipolar transistor integrated circuit technology

1999 IEEE Symposium on Indium Phosphide & Related Materials

Transferred-Substrate Heterojunction Bipolar Transistor Integrated Circuit Technology

M Rodwell , Q Lee, D Mensa, J Guthrie, Y Betser, S Jaganathan, T Mathew, P Krishnan, S LongUniversity of California, Santa Barbara

SC Martin, RP Smith, NASA Jet Propulsion Labs

Supported by ONR (M Yoder, J Zolper, D Van Vechten), AFOSR ( H Schlossberg )

why are hemts smaller faster than hbts
Why are HEMTs smaller & faster than HBTs ?

FETs have deep submicron dimensions.

0.1 µm HEMTs with 400 GHz bandwidths (satellites).

5 million 1/4-µm MOSFETs on a 200 MHz, $500 CPU.

FET lateral scaling decreases transit times.

FET bandwidths then increase.

HBTs have ~1 µm junctions.

vertical scaling decreases electron transit times.

vertical scaling increases RC charging times.

lateral scaling should decrease RC charging times.

HBT & RTD bandwidths should then increase.

But, HBTs must first be modified . . .

current gain cutoff frequency in hbts
Current-gain cutoff frequency in HBTs

Collector velocities can be high: velocity overshoot in InGaAsBase bandgap grading reduces transit time substantiallyRC terms quite important for > 200 GHz ft devices

excess collector base capacitance in mesa hbts
Excess Collector-Base Capacitance in Mesa HBTs
  • base contacts: must be > 1 transfer length (0.3 mm)® sets minimum collector width® sets minimum collector capacitance Ccb
  • base resistance spreading resistance scales with emitter scaling contact resistance independent of emitter scaling® sets minimum base resistance® sets minimum RbbCcb time constant
  • fmax does not improve with submicron scaling
transferred substrate hbts a scalable hbt technology
Transferred-Substrate HBTs: A Scalable HBT Technology
  • Collector capacitance reduces with scaling:
  • Bandwidth increases rapidly with scaling:
slide9

Thinning base, collector epitaxial layers improves ft, degrades fmax

Lateral scaling provides moderate improvements in fmax

Regrowth (similar to Si BJT !) should help considerably

Transferred-substrate helps dramatically

slide13

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• 400 Å 5E19 graded base (

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slide14

Transferred-Substrate Heterojunction Bipolar Transistor

Device with 0.6 µm emitter & 1.8 µm collector

extrapolated fmax at instrument limits, >400 GHz

(?)

0.25 µm devices should obtain >1000 GHz fmax

submicron transferred substrate hbt
Submicron Transferred-Substrate HBT

0.4 mm x 6 mm emitter, 0.4 mm x 10 mm collector

emitter profile stepper device
Emitter Profile: Stepper Device

0.5 mm emitter stripe

0.15 mm e/b junction

transferred substrate hbt stepper lithography
Transferred-Substrate HBT: Stepper Lithography

0.4 mm emitter, ~0.7 mm collector

transit times hbt with 2kt base grading
Transit times: HBT with 2kT base grading

2000 Å InGaAs collector400 Å InGaAs base, 2kT bandgap grading

why would you want a 1 thz transistor
Why would you want a 1 THz transistor ?

Digital microwave / RF transmitters (DC-20 GHz)

direct digital synthesis at microwave bandwidths

microwave digital-analog converters

Digital microwave / RF receivers

delta-sigma ADCs with 10-30 GHz sample rates

16 effective bits at 100 MHz signal bandwidth ?

Basic Science:

0.1 µm Ebeam device: 1000 GHz transistor (?)

transistor electronics in the far-infrared

Fast fiber optics, fast digital communications:

200 GHz ft, 500 GHz fmax device: ~ 75-90 Gb/s

160 Gb/s needs ~350 GHz ft, 500 GHz fmax

transferred substrate hbt ics key features

Transferred-Substrate HBT ICs: Key Features

100 GHz clock-rate ICs will need:

very fast transistors

short wires –> high IC density –> high thermal conductivity

low capacitance wiring

low ground inductance –> microstrip wiring environment

Transferred Substrate HBT ICs offer:

800 GHz fmax now , > 1000 GHz with further scaling250 GHz ft now, >300 GHz with improved emitter Ohmics

copper substrates / thermal vias for heatsinking

low capacitance (= 2.5) wiring

thz bandwidth hbts
THz-Bandwidth HBTs ???

deep submicron

transferred-substrate

regrown-base HBT

2

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1) regrown P+++ InGaAs extrinsic base --> ultra-low-resistance

2) 0.05 µm wide emitter --> ultra low base spreading resistance

3) 0.05 µm wide collector --> ultra low collector capacitance

4) 100 Å, carbon-doped graded base --> 0.05 ps transit time

5) 1kÅ thick InP collector --> 0.1 ps transit time.

Projected Performance:

Transistor with 500 GHz ft, 1500 GHz fmax

slide25

Why is Improved Wiring Essential?

Wire bond creates

ground bounce between

IC & package

ground return

loops create

inductance

30 GHz M/S D-FF in UCSB - mesa HBT technology

Ground loops & wire bonds:

degrade circuit & packaged IC performance

slide26

digital

ADC

sections

input

buffer

L

ground

ground return

ground

currents

D

V

bounce

in

noise

Ground Bound Noise in ADCs

Ground bounce noise must be ~100 dB below full-scale input

Differential input will partly suppress ground noise coupling

~ 30 to 40 dB common-mode rejection feasible

CMRR insufficient to obtain 100 dB SNR

Eliminate ground bounce noise by good IC grounding

microstrip ic wiring to eliminate ground bounce noise
Microstrip IC wiring to Eliminate Ground Bounce Noise

Transferred-substrate HBT process provides vias & ground plane.

power density in 100 ghz logic
Power Density in 100 GHz logic

Transistors tightly packed to minimize delays 105 W/cm2 HBT junction power density. ~103 W/cm2 power density on-chip ® 75 C temperature rise in 500 mm substrate.

Solutions: Thin substrate to < 100 mm Replace semiconductor with metal® copper substrate

transferred substrate hbt integrated circuits
Transferred-Substrate HBT Integrated Circuits

11 dB, 50+ GHz AGC / limiting amplifier

47 GHz master-slave flip-flop

10 dB, 50+ GHz feedback amplifier

7 dB, 5-80 GHz distributed amplifier

transferred substrate hbt integrated circuits30
Transferred-Substrate HBT Integrated Circuits

multiplexer

16 dB, DC-60 GHz amplifier

W-band VCO

2:1 demultiplexer (120 HBTs)

6.7 dB, DC-85 GHz amplifier

Clock recovery PLL

slide31

Darlington Amplifier - 360 GHz GBW

  • 15.6 dB DC gain
  • Interpolated 3dB bandwidth of 60 GHz
  • 360 GHz gain-bandwidth product
6 7 db 85 ghz mirror darlington amplifier
6.7 dB, 85 GHz Mirror Darlington Amplifier
  • 6.7 dB DC gain
  • 3 dB bandwidth of 85 GHz
  • ft-doubler (mirror Darlington) configuration
slide33

Master-Slave Flip-Flops

CML: 47 GHz

ECL: 48 GHz

66 ghz static frequency divider in transferred substrate hbt technology

66 GHz Static Frequency Divider in Transferred-substrate HBT Technology

Q. Lee, D. Mensa, J. Guthrie, S. Jaganathan, T. Mathew, Y. Betser, S. Krishnan, S. Ceran, M.J.W. RodwellUniversity of California, Santa Barbara

IEEE RFIC’99, Anaheim, California

slide35

Fiber Optic

ICs

(not yet working !)

PIN / transimpedance amplifier

CML decision circuit

AGC / limiting amplifier

transferred substrate hbts
Transferred Substrate HBTs
  • An ultrafast bipolar integrated circuit technology
  • Ultrahigh fmax HBTs
    • Low capacitance interconnects
    • Superior heat sinking, low parasitic packaging
  • Demonstrated:
  • HBTs with fmax > 800 GHz
  • fast flip-flops, 85 GHz amplifiers, ...
  • Future:
  • 0.1 mm HBTs with fmax > 1000 GHz
  • 100 GHz digital logic ICs --> DACs, DDS, ADCs, fiber