Near-Infrared Detector Arrays- The State of the Art -

Klaus W. Hodapp

Institute for Astronomy

University of Hawaii

Historic Milestones

• 1800: Infrared radiation discovered

• 1960s and 70s: Single detectors (PbS, InSb …)

• 1980s: First infrared arrays (322, 5862, 642, 1282)

• 1990: NICMOS-3 (2.5m PACE-1 HgCdTe)

• 1991: SBRC 2562 (InSb)

• 1994: HAWAII-1 (2.5m PACE-1 HgCdTe)

• 1995: Aladdin (InSb)

• 2000: HAWAII-2 (2.5m PACE-1 HgCdTe)

• 2002: HAWAII-1RG (5.0μm MBE HgCdTe)

• 2002: HAWAII-2RG (5.0μm MBE HgCdTe)

• 2002: RIO 2K×2K NGST InSb

• 2002: RIO 2K×2K Orion

Hawaii-2RG Heritage

1.05 million pixels>3.4 million FETs

CDS: <10e-

16,384 pixels70,000 FETsCDS: <50e-

65,536 pixels250,000 FETsCDS: <30e-

1987 1994 19981990

65,536 pixels250,000 FETsCDS: <20e-

1994

All Successfully Developed on 1st Design PassAll Successfully Developed on 1st Design Pass

4.2 million pixels>13 million FETs

Expect CDS <10e-

Exploiting Many LessonsLearned to Minimize Development Risk

And Enable Next Generation Performance Transition to 0.25µm CMOSWith Full Wafer Stitching and

Low-Power System-on-Chip ASIC

CDS: <TBD e-

2000

-1-2

-1R

Infrared Arrays

•Diode Array

•Multiplexer

•Readout Electronics

Electric Field in a CCD 1.

The n-type layer contains an excess of electrons that diffuse into the p-layer. The p-layer contains an excess of holes that diffuse into the n-layer. This structure is identical to that of a diode junction. The diffusion creates a charge imbalance and induces an internal electric field. The electric potential reaches a maximum just inside the n-layer, and it is here that any photo-generated electrons will collect. All science CCDs have this junction structure, known as a ‘Buried Channel’. It has the advantage of keeping the photo-electrons confined away from the surface of the CCD where they could become trapped. It also reduces the amount of thermally generated noise (dark current).

n p

Ele

ctri

c po

tent

ial

Potential along this line shownin graph above.

Ele

ctri

c po

tent

ial

Cross section through the thickness of the CCD

pixe

l bo

unda

ry

Charge packetp-type silicon

n-type silicon

SiO2 Insulating layer

Electrode Structure

pixe

l bo

unda

ry

inco

min

gph

oton

s

Charge Collection in a CCD.

Photons entering the CCD create electron-hole pairs. The electrons are then attracted towards the most positive potential in the device where they create ‘charge packets’. Each packet corresponds to one pixel

NIR Photodiode Array Technologies

•LPE HgCdTe on Sapphire (PACE-1): Rockwell, CdTe buffer

•MBE HgCdTe on CdZnTe: Rockwell, thin or substrate removed, AR coated

•InSb (Raytheon): Bulk material, p-on-n, thinned, AR coated

•LPE HgCdTe on CdZnTe: Raytheon, thick

•MBE HgCdTe on Si: Raytheon, ZnTe and CdTe buffer, thick, thin in future

Problems:

•Substrate availability

•Thermal expansion match to Si

•Lattice match to detector material

Time

Dio

de B

ias

Vol

tage

0.5 V

0 V

Res

et

Open Shutter Close Shutter

Readout

Re

se

t

kTC Noise

Reset-Read Sampling

Recharge Noise in Capacitors

Energy stored in a capacitor: E = ½ Q²/C

Noise Energy must be: E_n = ½kT

Noise Charge: ½ (Q_n)²/C = ½kT

(Q_n)² = kTC

Q_n = √ kTC

Example:

Capacitance: 50 fF, T=37 K

k = 1.38 e-23 J/K

Q_n = √ kTC

Q_n = 5 e-18 C

With q_e = 1.6 e-19 C

Q_n = 32 electrons rms

Time

Dio

de B

ias

Vol

tage

0.5 V

0 V

Re

se

t

Open Shutter Close Shutter

Readout

Re

se

t

Readout

kTC noise

CD

S S

ign

al

Double Correlated Sampling

Time

Dio

de B

ias

Vol

tage

0.5 V

0 V

Res

et

Open Shutter Close Shutter

Readout

Re

se

t

Readout

kTC noise

MC

S S

ign

al

Fowler (multi) Sampling

Time

Dio

de B

ias

Vol

tage

0.5 V

0 V

Res

et

Open Shutter Close Shutter

Re

se

t

Up-the-ramp Readout

kTC noise

MC

S S

ign

al

Up-the-Ramp Sampling

NASA CDR 05-08-01 Rockwell Proprietary Information

HAWAII-2: Photolithographically Abut 4 CMOS Reticles to Produce Each 20482 ROIC

Twelve 20482 ROICs per 8” Wafer

20482 Readout Provides Low Read Noise for Visible and MWIR

Canon 16mm x 14 mm

GCA 20mm x 20 mm

ASML 22mm x 27.4 mm

Reticle-Stitching: 2048x2048 ROIC

Submicron Stepper Options

External JFETs

optimized

HAWAII-1Rockwell Science Center

• 10241024 2.5m HgCdTe detector array

• 4 Quadrant architecture

• 4 Output amplifiers

• 18.5 m pixels

• LPE HgCdTe on sapphire (PACE-1)

• Use of external JFETs possible

• Available for purchase

HAWAII-1 Focal Plane Array

HAWAII-1

• Quantum efficiency (50% - 60%)

• Dark current 0.01 e-/s (65K)

• Read noise about 10 - 15 e- rms CDS

• Residual image effect

• Some multiplexer glow

• Fringing

3600 s

128 samp

T= 65K

Internal FETs

External JFETs

optimized

Fringing in PACE-1 material

1997 1998

Residual Images in PACE-1 HAWAII-1 Arrays

AladdinRaytheon Center for Infrared Excellence

• 10241024 InSb detector array

• 4 Quadrant architecture

• 32 Output amplifiers

• 27 m pixels

• Thinned, AR coated InSb

• Three generations of multiplexers

• “Foundry Run” distribution mode

Aladdin

• Quantum efficiency high (80% - 90%)

• Dark current 0.2 - 1.0 e-/s

• Read noise about 40 e- rms CDS

• Charge capacity 200,000 e-

• Residual image effect

• No amplifier glow

Aladdin frame taken with SPEX (J. Rayner)

NIRI Aladdin Image of AFGL2591

HAWAII-2Rockwell Science Center

• 20482048 2.5m HgCdTe detector array

• 4 Quadrant architecture

• 32 Output amplifiers

• 3 Output modes available

• 18.0 m pixels

• Use of external JFETs possible

• Reference signal channel

HAWAII-2: Photolithographically Abut 4 CMOS Reticles to Produce Each 20482 ROIC

Twelve 20482 ROICs per 8” Wafer

20482 Readout Provides Low Read Noise for Visible and MWIR

Canon 16mm x 14 mm

GCA 20mm x 20 mm

ASML 22mm x 27.4 mm

Reticle-Stitching: 2048x2048 ROIC

Submicron Stepper Options

HAWAII-2 Reference Signal

New Developments

• Multiplexers:• HAWAII-1R

• HAWAII-1RG

• HAWAII-2RG

• Abuttable 2K2K

• RIO developments

• Detector Materials:• MBE HgCdTe on CdZnTe

• MBE HgCdTe on Si

• Cutoff wavelength

• Thinning

• Substrate removal

• AR coating

NGST H-2RG & H-1R Packaging Critical

Design ReviewMay 8th, 2001

Rockwell Science Center Thousand Oaks, CA

HAWAII Heritage

1024 x 1024 pixels3.4 million FETs

0.8 µm CMOS3-4 e- (8/8 Fowler)

10 e- (CDS)

HAWAII - 1HAWAII - 11994

2048 x 2048 pixels13 million FETs0.8 µm CMOS

3-4 e- (8/8 Fowler)10 e- (CDS)

1998HAWAII - 2HAWAII - 2 HAWAII - 1RHAWAII - 1R

2000

2048 x 2048 pixels25 million FETs0.25 µm CMOS

HAWAII - 2RGHAWAII - 2RG

1024 x 1024 pixels3.4 million FETs

0.5 µm CMOSno noise data

Stitching(four independ.Quadrants)

Guide mode& additional

read/reset opt.

True stitching

Referencepixels

WFC 3

RSC Approach

H A W A I I - H A W A I I - 2 R G2 R G

H A W A I I - H A W A I I - 2 R G2 R G

• HgCdTe detector – substrate removed to achieve 0.6 µm sensitivity

HgCdTe Astronomy Wide Area Infrared Imager with 2k2 Resolution, Reference pixels and Guide Mode

• Specifically designed multiplexer– highly flexible reset and readout options – optimized for low power and low glow operation– three-side close buttable

• Two-chip imaging system: MUX + ASIC– convenient operation with small number of clocks/signals– lower power, less noise

HAWAII-2RG: UMC 0.25µm CMOS

• 3.3/2.5V Process on Epi Wafers

• 1 Poly/4- or 5-Metal

• 65/33Å Oxide

• Low, Normal and High Threshold Voltage Options

• MIM (Analog) Capacitor

• 22 mm by 22 mm Stepper Field

• Full Intra-Reticle Stitching

• One Mask Set Comprising Modular Blocks to Photocompose Each CMOS Multiplexer on 200 mm Wafers

• 2048 x 2048 resolution with 18 µm square pixels

• True stitched design (electrical connections across stitching lines)

• Close buttable die : - 2.5 mm mux overlap on top (pad) side - 1 mm mux overlap on each side gap 2 mm)

• 1, 4, or 32 output mode selectable

• Slow mode (100 kHz) and fast mode (5 MHz with additional column buffers) selectable, both usable with internal and external buffers

NGST Multiplexer Overview

Number ofoutputs

Frame time in slowmode

Frame time infast mode

1 42 s 840 ms

4 10.5 s 210 ms

32 1.3 s 26 msNGSTNGST

Output Options

Slo

w s

can

dire

ctio

n se

lect

able

Single output for all2048 x 2048 pixels

(guide mode always uses single output)

Fast scan direction selectable

Single Output ModeSingle Output Mode

default scan directions

Fast scan direction individuallyselectable for each subblock

Separate output for each subblock of 512 x 2048 pixels

S

low

sca

n di

rect

ion

sele

ctab

le

4 Output Mode4 Output Mode

default scan directions

Output Options (2)Sl

ow s

can

dire

ctio

n se

lect

able

32 Output Mode32 Output Mode

Separate output for each subblock of 64 x 2048 pixels

Four different patterns for fast scan direction selectable

default scan directions

Interleaved readout of full field and guide window

Guide windowGuide window

Full fieldFull field

FPAFPA• Switching between full field and guide window is possible at any time

any desired interleaved readout pattern can be realized• Three examples for interleaved readout:

1. Read guide window after reading part of the full field row

2. Read guide window after reading one full field row

3. Read guide window after reading two or more full field rows

Pixel by pixel reset Line by line reset Global reset

Full field

Guidewindow

Pixel by pixel reset Line by line reset Global reset

Full field

Guidewindow

Reset Schemes

3-D Barrier to Prevent Glow from Reaching the Detector

Metal 1

Metal 2

Metal 3

Poly 1

Analog Capacitor

Lo

w-N

ois

e C

MO

S M

ult

iple

xer

p-type

n+

HgCdTeDetector

IndiumInterconnect

Overglass

CMOS (LOCOS)

HAWAII-1RG Comes First

• In order to decrease risk and to get testable devices earlier, a smaller version of the HAWAII-2RG will be produced first.

H A W A I I - H A W A I I - 1 R G1 R G

H A W A I I - H A W A I I - 1 R G1 R G• 1024 x 1024 pixels (upper left quadrant of HAWAII-2RG)

• Full functionality of HAWAII-2RG

• 16 / 2 / 1 Outputs

• Some Pads folded along the right mux side

• Fits in one reticle no stitching required

CCD Mosaic Building Blocks-A Mature Packaging Technology

8K x 8K Mosaic CCD Array

•Constructed from 2Kx4K building block arrays

Prototype 2×2 Mosaic for NGST

Ground-Based Camera Projects

•IfA ULB

•UKIRT WFC

•CFHT WIRCAM

•Gemini GSAOI

•ESO VISTA

•Keck KIRMOS

Continuing to Aggressively Use CMOS• 5 Designs in 0.25µm

• 3.3/1.8V 0.18µm CMOS underway for ProCam-2

• Also migrating to 0.13µm on newest programs to boost performance via Cu and low-k interlayer dielectrics

Year of Introduction1965 1970 1975 1980 1985 1990 1995 2000 2005

Min

imu

m F

eatu

re (

µm

)

0.1

1

10

DRAM CMOSRSC FPA

After Isaac (1999)