87 GHz Static Frequency Divider in an InPbased Mesa DHBT Technology

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87 GHz Static Frequency Divider in an InP-based
Mesa DHBT Technology

• S. Krishnan, Z. Griffith, M. Urteaga, Y. Wei,
• D. Scott, M. Dahlstrom, N. Parthasarathy and M.
  Rodwell
• Department of Electrical and Computer
  Engineering,
• University of California, Santa Barbara

griffith_at_ece.ucsb.edu 805-893-8044
GaAsIC, October 2002Monterey, CA
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Why Static Frequency Dividers (SFD)?
MS flip-flops are very widely-used high speed
digital circuits Master-Slave Flip-Flop with
inverting feedback Connection as 21
frequency divider provides simple test method
Standard benchmark of logic speed
Performance comparisons across
technologies Dynamic, super-dynamic, frequency
dividers Higher maximum frequency than
true static dividers Narrow-band operation
? more limited applications High Speed
technology performance HRL gt 100 GHz
dividerthis conference with E2CL UCSB 75 GHz
static dividers using InAlAs/InGaAs TS-HBTs HRL
72.8 GHz static dividers using InAlAs/InGaAs HBTs
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Why Static Dividers, and what makes them fast
MS latch key digital element resynchronizes
data to clock often sets system maximum clock

• f? does not predict logic speed
• fmax does not predict logic speed
• Large signal operation involves switching time
  constants ??

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Mesa DHBT Epitaxial Layer Structure
InP Emitter n doped
P InGaAs Base 52 meV Band gap grading
2000 Å n- InP Collector
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mesaIC Process Key Features
Slide 1

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mesaIC Process Key Features
Slide 2

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mesaIC Process Key Features
Slide 3

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mesaIC Process Key Features
Slide 4

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mesaIC Process Key Features
Slide 5

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mesaIC Process Key Features
Slide 6

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mesaIC Process Key Features
Slide 7

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mesaIC Process Key Features
Slide 8

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mesaIC Process Key Features
Slide 9

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mesaIC Process Key Features
Slide complete

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mesaIC Process overview

• Both junctions defined by selective wet-etch
  chemistry
• Narrow base mesa allows for low
• AC to AE ratio
• Low base contact resistance
• Pd based ohmics with ?C lt 10-7 ?cm2
• Collector contact metal and metal 1 used as
  interconnect metal
• NiCr thin film resistors 40 ? / ?
• MIM capacitor, with SiN dielectric -- used
  only for bypass capacitors
• Low loss, low ?r 2.7 microstrip wiring
  environment

• Microstrip wiring environment.
• has predictable characteristic impedance
• controlled-impedance interconnects within
  dense mixed signal ICs
• ground plane eliminates signal coupling that
  occurs through on-wafer gnd-return inductance

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DC and RF measurements

• Common emitter characteristics
• Device geometry emitter metal 0.7 ? 8.0
  ?m2, real device 0.6 7.0 ?m2
• Collector to emitter area ratio, AC / AE 4.5

• IB 50 ?A per step
• DC beta ? 20
• Self heating presentnot observed
• in previous runs with same material

• f? 205 GHz, fmax 210 GHz
• Measurement condition
• VCE 1.2 Volts, Jc 2.5 mA/?m2

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Circuit diagram Static Frequency Divider

• Circuit Details.
• ECL topology
• JEF 2.0 mA / ?m2
• Jsteering 2.5 mA / ?m2
• VEE - 4.5 Volts
• Microstrip interconnects
• Output voltage for acquire and hold
  components, ?V 300mV
• Output buffer used for measurement isolation,
  Vout ? 300 mV

Hold ckt
Acquire ckt
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Chip Photograph 87 GHz Divider
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Measurements DC 40 GHz setup
? 0 d?m
Sampling oscilloscope
DC - 40 GHz Synthesizer
Clk
Out
VEE

• Clock input ? 0 d?m
• Divider Operation from 4 GHz to 40 GHz
• Measurement establishes fully static nature of
  divider

Output waveform _at_ 2 GHz fclk 4 GHz
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Measurements 50 75 GHz setup

• Clock input ? 0 d?m
• Divider Operation from 50 GHz to 75 GHz

Output waveform _at_ 37.5 GHz fclk 75 GHz
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Measurements 75 110 GHz setup
Sampling oscilloscope
? 9.7 d?m
Out
Clk
VEE

• Clock input ? 9.7 d?m
• Divider Operation from 75 GHz to 87 GHz

Output waveform _at_ 43.5 GHz fclk 87 GHz
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Conclusions

• Accomplishments
• Demonstrated a fully static, static frequency
  divider in a narrow triple-mesa DHBT processup
  to 87 GHz
• Future Direction
• Reduce device parasitics (rex, rbb) and wiring
  capacitance
• Increased current density (JE) reduces
• Continued lateral scaling of base contact to
  decrease
• AE / AC ratio lower CCB
• Acknowledgements
• This work was support by the Office of Naval
  Research (ONR--N00014-01-1-0024) and by Walsin
  Lihwa / UC Core