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© 2013 IBM Corporation

Cross THz Imaging

Evgeny Shumakher, Dan Corcos, Noam Kaminsky, Danny Elad IBM Haifa Research Lab Thomas Morf, Bernhard Klein IBM Zurich Research Lab

IBM Research


Outline

Background and motivation

Lower terahertz band

System level considerations

RFIC Design and characterization

Interconnect and antenna design

Higher terahertz band

Main challenges

Technology and MEMS post-processing

Antenna design and characterization

Pixel optimization and initial characterization results

IBM Research


Perspective applications

Image by Millivision

Good weather photo

Good weather mm-wave image

Bad weather photo

Bad weather mm-wave image

Apparel fit Security screening Landing/Navigation aid

Image by Enea

Dental/Medical imaging

IBM Research


State of the art

Cryogenically cooled systems

Very high cost and complexity

High sensitivity

Liquid Helium/Cryocompressor cooling

IPHT Jena

Uncooled passive systems

Compact, power efficient, safe

IBM Research

Active imaging system

Requires illumination with THz sources

High image contrast

Public concern about safety risks

L3 Comm.

IBM Research


Focusing

optics

DSP (image processing)

Target Si Chip Control

interface

Ima

ge

by Q

ine

tiQ

Staring Focal Plane Array (FPA)

Readout

IBM Imaging Technologies

Lower THz band (0.1 – 0.3 THz)

Antenna and packaging

SiGe RFIC

Read-out circuitry

Image processing

IBM Research


Higher THz band (0.5 – 1.5 THz) – EU FP7 TeraTOP

Antenna and pixel design

CMOS-SOI

MEMS (LETI in TeraTOP)

Read-out circuitry (CSEM in TeraTOP)

Focusing

optics

DSP (image processing)

Target Si Chip Control

interface

Ima

ge

by Q

ine

tiQ

Staring Focal Plane Array (FPA)

Readout

IBM Imaging Technologies


Lower THz band

130 GHz Dicke radiometer in SiGe

IBM Research


Dicke-radiometer based FPA

Primary

reflector

Secondary

reflector

D

Primary

reflector

Secondary

reflectorReceiver

complex

Close-up

LNA

ANT

on

PCKG

DSPD

OUTanlg

ROI

INRF

RX

DATA + CTRL

ANT

NS

SPI

Clo

se

-up

IBM Research


Dicke-radiometer state of the art

Reference Year Technology Integration Frequency NETD

Voinigescu, U

Toronto

2012 0.13um SiGe

BiCMOS, STM

LNA+PD 160 – 170 GHz 0.35 K

Rebeiz, UC SD 2010 8HP, IBM DS+LNA+PD 84 – 99 GHz 0.83 K

Heydari, UC Irvine 2010 0.18um SiGe

BiCMOS, Jazz

DS+LNA+PD 70 – 96 GHz 0.4 K

Voinigescu, U

Toronto

2009 65 nm CMOS,

STM

DS+LNA+PD 81 – 93 GHz 0.55 K

LNA

ANT

on

PCKG

DSPD

OUTanlg

ROI

INRF

RX

DATA + CTRL

ANT

NS

SPI

IBM Research


Specifications

Standard IBM 0.13um SiGe Technology fT/fMAX ~ 180/220 GHz

5 layer metallization

MiM capacitors available

Packaging losses < 3 dB Dicke-switch

< 3 dB insertion loss

> 15 dB on-off extinction ratio

LNA Gain of 25-30 dB

Bandwidth of 15 – 20 GHz

NF < 10 dB

Power detector NEP < 5 pW/Hz1/2

General design constraints 1. Consumed power

2. Allocated area

Silicon substrate

CPWG

Transmission line

GND

Side

shielding

Auxillary routing

MoM capacitors

IBM Research


Dicke switch

RFIN

RFOUT

50

SE

S SE

SPDT topology

3 versions of Switching Element

designed

Single 120 um Triple-well NFET

Double 60 um Triple-well NFET

Triple 36 um NPN HBT

LNA

ANT

on

PCKG

DSPD

OUTanlg

ROI

INRF

RX

DATA + CTRL

ANT

NS

SPI

IBM Research


Dicke switch

SPDT topology

3 versions of Switching Element

designed

Single 120 um Triple-well NFET

Double 60 um Triple-well NFET

Triple 36 um NPN HBT

350 um

LNA

ANT

on

PCKG

DSPD

OUTanlg

ROI

INRF

RX

DATA + CTRL

ANT

NS

SPI

IBM Research


Dicke switch

80 90 100 110 120 130 140 150 160-25

-20

-15

-10

-5

0

Frequency [GHz]

|S21|

[dB

]

STW

DTW

HBT

ON

OFF

LNA

ANT

on

PCKG

DSPD

OUTanlg

ROI

INRF

RX

DATA + CTRL

ANT

NS

SPI

IBM Research


4 cascode + 2CE stage LNA

RF Match

RF C/M RF C/M RF C/M RF C/M

VCC

Vb12

Vb11

Vb21

Vb22

Vb31

Vb32

Vb41

Vb42

RF C/M

Vb51

Vb52

Current re-use

CE

LNA

ANT

on

PCKG

DSPD

OUTanlg

ROI

INRF

RX

DATA + CTRL

ANT

NS

SPI

IBM Research


4 cascode + 2CE stage LNA LNA

ANT

on

PCKG

DSPD

OUTanlg

ROI

INRF

RX

DATA + CTRL

ANT

NS

SPI

400 um

IBM Research


4 cascode + 2CE stage LNA

110 120 130 140 150 160-40

-30

-20

-10

0

10

20

30

Frequency [GHz]

|S-p

ara

mete

rs| [d

B]

S11

S21

S22

LNA

ANT

on

PCKG

DSPD

OUTanlg

ROI

INRF

RX

DATA + CTRL

ANT

NS

SPI

IBM Research


Power detector

Vb

RF Trap

RF Match

RFIN

VCCVBB VCC

Vb

RF Trap

RF Match

VBB VCC

KQ Resistor

RFIN

Vb

120 um

LNA

ANT

on

PCKG

DSPD

OUTanlg

ROI

INRF

RX

DATA + CTRL

ANT

NS

SPI

IBM Research


Power detector

10-7

10-6

10-5

10-4

103

104

105

Incident power [W]

Resp

osiv

ity [

V/W

]

meas

sim

103

104

105

10-8

10-7

Frequency [Hz]

VS

D [

V/

Hz]

HzpWNEP 5

LNA

ANT

on

PCKG

DSPD

OUTanlg

ROI

INRF

RX

DATA + CTRL

ANT

NS

SPI

IBM Research


Package design

Flip-chip

Low loss ( < 1.5 dB)

Small space – a little bigger than chip size

Pads do not have to be only on the periphery

Easy to dissipate heat in our application

10.00 40.00 70.00 100.00 130.00 160.00Freq [GHz]

-1.75

-1.50

-1.25

-1.00

-0.75

-0.50

-0.25

0.00

dB

(S(C

PW

_p

ort

,ms

trip

))

Ansoft LLC gold_stud_matchS21 ANSOFT

Curve Info

dB(S(CPW_port,mstrip))Setup1 : Sw eep1L='-2mil'

IBM Research


Antenna design

Per-pixel antenna

Wide-band horn antenna

IBM Research


-5

-4.5

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

110 115 120 125 130 135 140

Frequency [GHz]

Ins

ert

ion

lo

ss

[d

B]

Simulation

Material A

Material B

Material C

Antenna design

Microstrip to waveguide

interconnect

Simple package design

Good results at 120GHz


Upper THz band EU FP7 TeraTOP

Uncooled antenna-coupled MOSFET

bolometer in CMOS-SOI-MEMS

IBM Research


The challenge of Passive THz detection

Detect radiation at 0.5 – 1.5 THz with NETD = 1 [K]

Very low frequencies compared to optical waves (like visible and infrared)

Spontaneous emission (in the THz range) is 1/1000 with respect to the IR

Still too high for solid-state electronics (perhaps in the future ?)

THz

Wavelength

Rad

iate

d p

ow

er

Body temperature

IR

IBM Research


Goals

Sophisticated pixels are needed:

Broadband antennas – collect as much in-band signal as possible

Light-weight – low thermal time constant (required for real-time imaging)

Coupling to fast optics – overlap and spill-over efficiency through the band

High sensitivity – achieve very low noise and high responsivity

Narrow BW 500-580 GHz Broad BW 500-1000 GHz Original temperature map

Image simulations including detector NEP = 25 pW

Conflict

Virtual prototyping:

IBM Research


IBM detector technology - Overview

On-chip planar antennas with 0.6 -1.4 THz bandwidth

MOSFET bolometer with large temperature responsivity

High thermal isolation achieved by MEMS and vacuum packaging (10-2 mbar)

Target Noise Equivalent Temp. Difference (NETD) < 1 K in real-time

Cloverleaf

antenna

Transistor

and termination

Legs

Example: suspended “cloverleaf” antenna

SEM

picture of

a MEMS

antenna

array

FPA cross-section

IBM Research


Antenna design

Absorption simulations New methodology for simulating accurately antenna-coupled sensors

– Based on modal reflection coefficients

– Patent filed

Maximize the absorption of THz signal

Ab

so

rpti

on

eff

icie

nc

y

Frequency (THz)

Octagonal skirt antenna

IBM Research


Antenna design

Transmission simulations

Evaluate radiation pattern across the band

Cloverleaf antenna

0.6THz 1THz 1.4THz

IBM Research


Technology

Standard IBM 0.18 μm CMOS-SOI process BOX thickness 1μm

4 metal layers as built-in masks

MEMS post-CMOS process Front side dry etch

Metal mask wet etch

Back side wet etch

b) RIE

c) Wet etch

a) CMOS Fab

d) DRIE

IBM Research


MEMS post-processing in IBM Zurich facility

Fully released 13x9 array

High functional “survival rate”

The antennas are still planar

after release

Some holding arms are bent

upwards

This is fine as long as they

don’t touch

IBM Research


MEMS post-processing

IBM Research


Detector optimization involves best

MOSFET sizing and operating point to

yield

We aim to achieve the lowest NEP

Responsivity is increased by using large

currents, but so is noise

A noise reduction method was developed for

filtering the 1/f noise

We expect to achieve NEP≈13 pW with

ROIC bandwidth of 100 Hz

Detector optimization

NEP=13 pW

Legend

• Non-optimized sizing, ideal voltage ROIC

• Optimized sizing, ideal voltage ROIC

• Optimized sizing, ROIC with 1/f reduction

IBM Research


Antenna characterization

Measurement of the radiation patterns in air at 0.65 THz

THz source based on chain of frequency multipliers

Pixels outside of Dewar for avoiding reflections on the walls

But results in lower responsivity

Test board

THz

source

Rotation stage

Measurement setup at Univ. of Wuppertal

IBM Research


Antenna characterization

Measurement of the normalized responsivity at 0.65 THz

Several types of antenna were tested

Half-power beamwidth in good agreement with HFSS

Normalized radiation pattern of a

log-spiral antenna

The beams are broad by design (±40° typical)

for best coupling with fn<1 lenses

Current responsivity

(symbols = types of antennas)

Measurements match with the design.

Responsivity is 400x lower in air vs. vacuum

IBM Research


1/f noise is dominant for bandwidths < 1kHz

Noise of un-processed devices fits BSIMSOI

model parameters from the PDK

2x increase in 1/f power due to plasma

induced damage (MEMS) ~1.4x in NEP

PSD of HV NFET vs. gate bias

Measurement setup

Noise simulations vs. measurements

Pixel Noise

DUT

1/f noise dominates the

total pixel noise

Measurement of pixel type “spiral3”

Excellent fit with simulation

IBM Research


Summary – Lower band

Key components of a 130 GHz Dicke-radiometer

Realized in standard 0.12 μm SiGe process

Designed for incorporation into very large FPA

Dicke-switch (SPDT)

< 3 dB insertion loss

> 12 dB extinction ratio

LNA

4 cascode + 2 CE stage : > 24 dB gain in 20 GHz bandwidth

Noise figure characterization pending

PD

Demonstrated with NEP ≈ 5pW/Hz1/2

Packaging

Coupling losses < 3 dB

IBM Research


Summary – Higher band

THz pixels based on antenna-coupled MOSFET

bolometers

IBM 0.18 μm CMOS-SOI process with MEMS post-processing

THz antennas

Several new antennas for exploring the bandwidth vs. speed tradeoff

Measured HPBW (±40° typical) matching with the design

MOSFET sensors

High thermal sensitivity with MOSFET bolometers and MEMS

Simulated sensor NEP=13 pW for ROIC bandwidth of 100 Hz

Responsivity

Initial measurements (1 mA/W in air) in good agreement with simulation in

corresponding conditions

Upcoming measurements in vacuum with blackbody source

IBM Research


Acknowledgements

Dr. Eran Socher, Tel Aviv University

D-band measurement facility

IBM Tokyo Research Lab

D-band flip-chip interconnect mechanical and thermal design

Prof. Ullrich Pfeiffer, University of Wuppertal

THz antenna characterization

The European Union 7th Framework Program

TeraTOP Project

cross thz imaging - israel institutes of technologyworkshop.ee.technion.ac.il/upload/files/dan...

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