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Vertex05, 8/11/05 Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: XEUS WIMS ILC ILC Testbeam results Summary & Outlook Univ. of Bonn: M.Karagounis, R.Kohrs, H.Krüger, M. Mathes, L.Reuen, C.Sandow, E.von Törne, M.Trimpl, J.Velthuis, N.Wermes Univ. of Mannheim: P.Fischer, F.Giesen, I.Peric Politecnico di Milano: M. Porro MPI Halbleiterlabor Munich: O Hälker, S. Herrmann, L.Andricek, G.Lutz, H.G. Moser, R.H.Richter, M.Schnecke, L.Strüder, J.Treis, P.Lechner, S. Wölfel THCA of Tsinghua Univ.: C. Zhang, S.N. Zhang

Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

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Page 1: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

DEPFET Status• DEPFET Principle• Readout modes• Projects:

– XEUS– WIMS– ILC

• ILC Testbeam results• Summary & Outlook

Univ. of Bonn: M.Karagounis, R.Kohrs, H.Krüger, M. Mathes, L.Reuen, C.Sandow, E.von Törne, M.Trimpl, J.Velthuis, N.Wermes

Univ. of Mannheim: P.Fischer, F.Giesen, I.Peric

Politecnico di Milano:M. Porro

MPI Halbleiterlabor Munich:O Hälker, S. Herrmann, L.Andricek, G.Lutz, H.G. Moser, R.H.Richter, M.Schnecke, L.Strüder, J.Treis, P.Lechner, S. Wölfel

THCA of Tsinghua Univ.:C. Zhang, S.N. Zhang

Page 2: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

DEPFET Principle

• A p-FET transistor is integrated in every pixel.• By sidewards depletion potential minimum created below

internal gate.• Electrons, collected at internal gate, modulate transistor current

~1µm

p+

p+ n+

rear contact

drain bulksource

p

sym

met

ry a

xis

n+

ninternal gate

top gate clear

n -

n+p+

--

++

++

- 50

µm

------

MIP

Page 3: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

DEPFET Principle

• Advantages:– Fast signal collection due to fully depleted bulk– Low noise due to small capacitance and amplification in

pixel– Transistor can be switched off by external gate – charge

collection is then still active !– Non-destructive readout

• Disadvantages:– Need to clear internal gate. This still requires high

voltages.

• 2 readout modes:– Source follower mode readout. Signal is voltage (XEUS)– Drain readout. Signal is current (WIMS&ILC)

required

Page 4: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

SOURCE FOLLOWER

• Constant bias current IBias provided• Charge at internal gate translates into source voltage node change• Speed depends on overall load capacitance• Slow (t≈CL/gm≈3µs), but excellent noise

Clear

Clear-gate

Drain Source

GateDEPMOSdevice

Ibias

Buffer /amplifierIbias

Page 5: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

DRAIN readout

• Measure Idrain directly• Fast response: limited by RC time of input resistance CURO and

Cload (~ns)

Clear

Clear-gate

Source Drain

GateDEPMOSdevice

Vout

CURO: currentamplifier

transimpedenceamplifier

Page 6: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

DEPFET Applications

• DEPFET under study for:– XEUS

• Exploring the early universe by imaging spectroscopy in the X-ray band

• Need noise < 4e-

• Source follower mode

– WIMS• Wide-band Imaging and Multi-band Spectrometer, part of

China’s spacelab mission• Drain readout

– ILC• Need row rates of 20MHz• Drain readout

Page 7: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

XEUS

• Exploring the early universe by imaging spectroscopy in the X-ray band

• Detector:– Device active area 7.68 x 7.68

cm2

– Monolithic sensor integrated onto a single 6“ wafer

– Device thickness 450 µm– Pixel size 75 x 75 µm2

– Position resolution ca. 30 µm– Total 1024 x 1024 pixel cells– Total readout time / frame

1.25 ms– Processing time per detector

row 2.5 µs

Page 8: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Excellent noise

• Single pixel device • 10 µs shaping• Room

temperature (22° C)

Page 9: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Excellent noise

• Large structure (64x64):– 75 x 75 µm2 pixel size – 45 µm gate circumference

/ 5 µm gate length– Drain in center of pixel– Cut gate geometry– Curved edge– Double metal

• Operated at:– Pixel current 30 µA– Line processing time 25 µs

0 1 2 3 4 5 6 71

10

100

1000

10000

Si-KAl-K

Mn-KMn-K

Cou

nts

Energy (keV)

Escape Peak

Energy resolution: 126 eV FWHM @ Mn-Ka Line

corresponding to 4.9 e- ENC

-60 -40 -20 0 20

10

20

30

40

50

60

70

2.78

5.56

8.33

11.11

13.89

16.67

19.44

Normal cycles (tInt

= 3 ms)

Reference cycles (tInt

= 5 s)

Pix

el r

ea

do

ut n

ois

e (

e-

EN

C)

Pix

el r

ea

do

ut n

ois

e (

eV

)

Temperature (°C)

Noise dependence

Pixel readout noise: 63 – 14eV (17 – 3.6 e- ENC)

Page 10: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

WIMS

• Wide-band Imaging and Multi-band Spectrometer (WIMS) is part of China’s spacelab mission .

• Observe high-energy bursts, transients and fast-varying sources over a broad spectral range simultaneously

• Using Macro pixels– Pixel size 0.5x0.5 mm2

– “Si-drift chamber readout using DEPFET”

0 1000 2000 3000 4000 5000 6000 70000

100

200

300

400

500

600

700

800

FWHM = 209 eV

ENC = 19.1 el r.m.s

Room temperatureBack side illuminates, fast drain readoutShaping time: 3μsClear pulse period 1 ms with width 3 μs

Page 11: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

DEPFET for ILC

• Basic system • Clearing• ILC requirements• Ladder proposal• Power consumption• Thinning• Radiation hardness• Testbeam results

Page 12: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Basic system

• Select and Clear signals provided by SWITCHER – 64 x 2 outputs– Max ΔV = 25V

• Read out row-wise: CURO– current based read out– 128 channels– CDS – real time hit finding

& zero-suppression– row rate up to 24 MHz

n x mpixel

IDRAIN

DEPFET- matrix

VGATE, OFF

off

off

on

off

VGATE, ON

gate

drain VCLEAR, OFF

off

off

reset

off

VCLEAR, ON

reset

output

0 suppression

VCLEAR-Control

Gate Switche

r

ClearSwitche

r

Current Readout CUROII

DEPFET Matrix64x128 pixels, 36 x

28.5µm2

Page 13: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

HighE vs non-HighE

• HighE extra n-type implant– Moves internal gate

deeper into bulk– Clearing takes places

deeper in the bulk– Lower signals, but

easier clearing

clear

Internal gate

channel

Optional HighE implant

Page 14: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Clearing

• CURO measures: Isig,i+Iped,i & Iped,i+1

• Need to remove all charge such that Iped,i+1=Iped,i

• COMPLETE CLEAR possible for HighE with low voltages (~7V)⇒ possible to make radhard SWITCHER in standard CMOS

HighE

Page 15: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

ILC requirements

• Time structure: 1 train of 2820 crossings in ~1 ms every ~200ms– Hit density: for r = 15 mm: ~ 100 tracks / mm2 / train– Row readout rate: > 20 MHz – Occupany < 0.5 %

• Radiation length: ~0.1% X0 per layer– thinned sensors (50 μm) – low power consumption

• Radiation tolerance: 200 krad (for 5 years operation)

• Resolution: few µm ( pixel size ≤ 25 x 25 µm2)

950 µs 199 ms 950 µs

2820 bunches

Page 16: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Ladder proposal

• Modules have active area ~13 x 100 mm2

• Read out on both sides.

• Detectors 50µm thick, with 300µm thick frame yields 0.11% X0

• SWITCHER & CURO chips connected by bump bonding

SWITCHER

CURO

Page 17: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

ILC Power

• Measured Power Dissipation:– Switcher: 6.3 mW per active channel at 50MHz– CURO: 2.8 mW / channel

• Assumed Power Dissipation of DEPFET Sensor:– 0.5 mW per active pixel– duty cycle: 1/200

• Only active pixel dissipate power– 1024 active pixels per module– 8 modules in Layer 1 => 8192 active pixels

• Expected Power Dissipation in Layer 1– Sensor: 8192 x 0.5 mW / 200 = 20 mW– Switcher: 16 x 6.3 mW / 200 = 0.5 mW– Curo: 8192 x 2.8 mW / 200 = 114 mW

• For Layer 1 Sum: 135 mW

For 5 Layer DEPFET Vertex Detector: Total ~ 3.6 W no active cooling

Page 18: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Thinning

sensor wafer

handle wafer

1. implant backside on sensor wafer

2. bond wafers with SiO2 in between

3. thin sensor side to desired thick.

4. process DEPFETs on top side

5. etch backside up to oxide/implant

first ‘dummy’ samples:50µm silicon with 350µm frame

thinned diode structures:leakage current: <1nA /cm2

Thinning technology for active area established

Page 19: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Radiation hardness

• Irradiations with 60Co and X-rays (~17keV) up to ~1Mrad (SiO2)

• Threshold shift of the MOSFET (~4V) can be compensated by bias voltage shift

60Co

Page 20: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Testbeam

• DESY test beam with 6 GeV e- • Bonn ATLAS telescope system:

– double sided strip detectors– pitch 50 µm (no intermediate strips)– readout rate 4.5 kHz (telescope only)

• DEPFET:– 128x64 (28.5x36 µm2)– 450 µm thick– Frame time 1.8 ms

DEPFET

beam

1 2 3 4Scintillator Scintillator3 x 3 mm²

Page 21: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Pedestal & Noise

• Pedestal: average signal after hit removal• Noise: standard deviation after pedestal,

common mode and hit removal

Page 22: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Clustering

• Look for clusters:– Seed

• pixel largest signal • seed cut >5σ

– Neighbours• Neighbour cut >2σ

• Combine signals seed & neighbors

• S/N3x3=125.9±0.2– Noise higher than

expected– Next generation expect to

reduce noise by factor 2

Page 23: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Position resolution

• Hit positions reconstructed using the CoG algorithm• Note: pixelsize X=36µm Y=28.5µm• Terrible, but … due to multiple scattering

Page 24: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Multiple scattering

• Eelectron only 6GeV

• Telescope planes 10cm apart

• Minimize effect scattering by selecting hard tracks using 2 cut

• Price: lose statistics

Page 25: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Multiple scattering (II)

• Performed simulation.• Using Fraction remaining

tracks, telescope uncertainty can be estimated.

• From CERN testbeam know that σintrinsic~5-6µm, but not compared S/Ntel

• σX=9.71±0.02µm, σY=9.31±0.02µmσ intrinsic X Y

5µm 5.9 5.2

6µm 3.9 2.7

Page 26: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

HighE matrix

• HighE implant moves internal gate into bulk– Lower signal– Easier clearing

• Results:– S/N3x3=99.5±0.1

– σX=9.11±0.03µm, σY=8.80±0.03µm

– Somewhat larger clusters yield better position resolution

Poor stats& fit

σ intrinsic X Y

5µm 4.8 4.3

6µm 1.9 --

Page 27: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Summary

• DEPFET integrates MOSFET in fully depleted bulk. Developed towards: – XEUS mission:

• Slow readout (source follower mode)• Excellent noise (~2.2e-)

– WIMS mission• Very large pixels (0.5x0.5mm2) • Si-drift chamber readout by DEPFET• Fast(er) readout (noise=19e-)

Page 28: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Summary (II)

• Developed towards ILC. Meets already demands on– Radiation length (0.11 X0)

– Radiation hardness (ΔVth shift~4V@1Mrad)– Power consumption (<5W full detector)– Position resolution (≲5µm)

• Excellent S/N:– S/N=126 without HighE– S/N=100 with HighE– ⇒can thin detector to 50µm with still good S/N

Page 29: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Outlook

• Improving the system to increase readout speed.– Individual parts already function well at ILC

speed

• Testbeam at DESY (6GeV electrons) with better mechanics and at CERN. Goals:– Improve S/N– Test zero suppression

• Build 512x512 matrix

Page 30: Vertex05, 8/11/05Jaap Velthuis, Bonn University DEPFET Status DEPFET Principle Readout modes Projects: –XEUS –WIMS –ILC ILC Testbeam results Summary &

Vertex05, 8/11/05 Jaap Velthuis, Bonn University

Author list

Univ. of Bonn: M.Karagounis, R.Kohrs, H.Krüger, M. Mathes, L.Reuen, C.Sandow, E.von Törne, M.Trimpl,

J.Velthuis, N.Wermes

Univ. of Mannheim: P.Fischer, F.Giesen, I.Peric

Politecnico di Milano:M. Porro

MPI Halbleiterlabor Munich:O Hälker, S. Herrmann, L.Andricek, G.Lutz, H.G. Moser, R.H.Richter, M.Schnecke, L.Strüder,

J.Treis, P.Lechner, S. Wölfel

THCA of Tsinghua Univ.:C. Zhang, S.N. Zhang