Universita de Firenze Hartmut Sadrozinski, Scott Ely, Vitaliy Fadeyev, Zachary Galloway, Jeffrey...

SCIPPSCIPP

Hartmut Sadrozinski, Scott Ely, Vitaliy Fadeyev, Zachary Galloway, Jeffrey Ngo, Colin Parker, Brett Petersen,

Abe Seiden SCIPP, Univ. of California Santa Cruz

Nicolo Cartiglia, Amadeo Staiano INFN Torino

Mara Bruzzi, Riccardo Mori, Monica Scaringella, Anna VinattieriUniversita de Firenze

4D Sensors: Unifying the Space and Time Domain

with Ultra-Fast Silicon Detectors

SCIPPSCIPP

Ultra-Fast Silicon Detectors (UFSD) incorporate the time-domain into the excellent position resolution of semiconductor sensors

they provide in the same detector and readout chain• ultra-fast timing resolution [10’s of ps]• precision location information [10’s of mm]

2 questions need to be addressed for UFSD:• can they work: signal, capacitance, collection time vs. thickness • will they work: required gain and E-field, fast readout

We hope that we will answer the questions within an RD50 Common Project (Giulio Pellegrini)

A crucial element for UFSD is the charge multiplication in silicon sensors investigated by RD50, which permits the use of very thin detectors without

loss of signal-to-noise.

“4D”

SCIPPSCIPP Motivation for UFSD Up to now, semiconductor sensors have supplied precision data only for the

3 space dimensions (diodes, strips, pixels, even “3D”), while the time dimension has had limited accuracy (e.g. to match the beam structure in the accelerator).

We believe that being able to resolve the time dimension with ps accuracy would open up completely new applications not limited to HEP

Proposal: Combined-function pixel detector will collect electrons from thin n-on-p pixel sensors read out with short shaping time electronics

Charge multiplication with moderate gain g ~10 increases the collected signal

Need very fast pixel readout

SCIPPSCIPP

The Alpha Magnetic Spectrometer (AMS) detector, operating in the International Space Station since 2011, performs precision measurements of cosmic ray composition and flux. The momentum of the particles is measured with high-resolution silicon sensors inside a magnetic field of about 1 m length.

Time of Flight for Particle Identification in Space.

A time resolution of 10 picoseconds, the “Holy Grail” of Cosmic Ray Physics: the distinction between anti-carbon ions and anti-protons can be achieved up to a momentum of 200 GeV/c.

SCIPPSCIPP

5

Range straggling limit for 200 MeV p

Future: 4-D Ultra-Fast Si Detectors ?

Hartmut F.-W. Sadrozinski: UFSD, Tredi 2013

Protons of 200 MeV have a range of ~ 30 cm in plastic scintillator. The straggling limits the WEPL resolution.

Replace calorimeter/range counter by TOF:Light-weight, combine tracking with WEPL determination

SCIPPSCIPP

6

A. Del Guerra, RESMDD12

Positron Emission Tomography PETStudy accumulation of radioactive tracers in specific organs. The tracer has radioactive positron decay, and the positron annihilates within a short Distance with emission of 511 keV γ pair, which are observed in coincidence.

Resolution of detector (pitch)Positron rangeA-collinearityParallax (depth)

T: true event S: Compton ScatterR: Random Coincidence

Resolution and S/N Effects:

Hartmut F.-W. Sadrozinski, UFSD, Tredi 2013

Perfect Picture:

SCIPPSCIPPReduce Accidentals & Improve Image: TOF-PET

t1

t2

Localization uncertainty:Dd = c x Dt /2

When Dt = 200 ps ➔ Dd = 3 cm

PET

TOF-PET

@ VCIK. Yamamoto 2012 IEEE NSS-MIC

Hartmut F.-W. Sadrozinski: UFSD, Tredi 2013 7

SCIPPSCIPP

8

1. For a given acquisition time and dose to the patient, TOF can provide better image quality and improved lesion detection.

OR2. with TOF the scan time and dose can be

reduced while keeping the same image quality ( better clinical workflow and added comfort for the patient).

2/tx c

TOFNonx

TOF SNRD

SNR

TOF – PET SNR Improvement

M. Conti, Eur. J. Nucl. Med. MoI Imaging (2011) 38:1147-1157

The improved source localization due to timing

leads to an improvement in signal-to-noise

and an increase in Noise Equivalent Count NEC x

DGainNEC

Hartmut F.-W. Sadrozinski: UFSD, Tredi 2013

SCIPPSCIPPUFSD Pixel / Strips Collected Charge

Signal = thickness*EPM (EPM = 73 e-/mmCollection time = thickness/vsat (vsat = 80 mm/ns)

For thickness > 5 um, Capacitance to the backplane Cb << Cint

For thickness = 2 um, Cb ~ ½ of Cint, and we might need bipolar (SiGe)?

Realistic gain & cap

Good time resolution

Thickness BackPlane Capacitance Signal Coll. Time[um] Pixels [fF] Strips [pF] [# of e-] [ps] for 2000 e for 12000 e0.1 2500 500 8.3 1.3 241 14461 250 50 83 12.5 24 1452 125 25 166 25.0 12 725 50 10 415 62.5 4.8 2910 25 5 830 125.0 2.4 1420 13 3 1660 250.0 1.2 7.2

100 3 1 8300 1250.0 0.2 1.4300 1 0 24900 3750.0 0.1 0.5

Gain required

Per 1 cm

SCIPPSCIPP

)/exp(* ,,, EbE hehehe

E

bE

NN

he

hehe

,

,,

0

exp*

)*exp(*)(

Impact IonizationA. Macchiolo,16th RD50 Workshop Barcelona, Spain, May 2010

Charge multiplication in path length ℓ :

At the breakdown field in Si of 270kV/cm:ae ≈ 1 pair/umah ≈ 0.1 pair/um

→ In the linear mode (gain <10), consider electrons only

Raise maximum and minimum E-field

as close to breakdown field as possible

SCIPPSCIPPNon-uniform E-Field across a pixel/strip

Non-uniform Field across the implant results in charge collection difference

Example of electric field: Ф = 1.6·1015 n/cm2, U = 900 V

Even if non-uniformity of field across the implant is only 30%, a large fraction of the center of the implant does not exhibit charge multiplication !

Gregor Kramberger, 19th RD50 Workshop, CERN, Nov 2011 A. Macchiolo, 16th RD50 Workshop Barcelona, Spain, May 2010

SCIPPSCIPP Epi, short drift on planar diode g = 6.5

Using red laser and a’s probes E-field and gainclose to the junction, where it counts. Diode gives uniform field.

J. Lange et al., Nucl.Instrum.Meth A622, 49-58, 2010.

Charge multiplication in 3D sensors: M. Koehler et al.

Need uniform field: 3D or diode-like

SCIPPSCIPPWhat about fast readout:

CERN fixed-target experiment (NA62) needs very fast pixel sensors: Gigatracker (GTK)

Prototype CFD system (INFN Torino) has ~ 100 ps resolution, predicted to be 30 ps in next iteration.

Optimized for 200mm sensors and hole collection (?), could it be re-designed for electron collection from 2 – 10mm sensors?

SCIPPSCIPP Firenze ps Laser Data: 50 um p-on-n 6kW-cm

Laser 1.2 ps pulse width & 10 ns period: pulse distortions 740 nm wavelength for red light, penetrate ~6 um.

Oscilloscope: 500 MHz bandwidth 2 BNC into 50 Ohm, 500 Ohm in scope

Charge collection of electrons moving away from laser spot Terminal velocity ~ 100um/ns, i.e. expected collection time ~500ps for high fields

SCIPPSCIPPBase line shift due to AC coupling?

SCIPPSCIPP

Pulse is convolution of electronic shaping and charge collection, Fit pulses to extract shaping time trise & 10%-90% RTFWHM is considered best measure of the convolution

FWHM becomes constant at about 150 V biasRise times RT and trise are ~ independent of bias: Bandwidth of system

Timing Properties of ps Laser signal

SCIPPSCIPP

Above 120V bias, the field > 25kV/cm, i.e. large enough to saturate the drift velocity, i.e. constant collection time.

Below 120V bias, the unsaturated drift velocity increases the charge collection time, causing the pulses to widen.

Collection of ps Laser signal

SCIPPSCIPPStudy of ’s from Thorium 230

50 um thick P-type epi diodes

IV Measurements for diode 2 & 3 during C-V

Epi Diode IV Curve: Diode 2 & 3

1.E-10

1.E-09

1.E-08

1.E-07

1.E-06

0 50 100 150 200 250 300 350

Bias (V)

Cu

rren

t (A

)

Diode 2

Diode 3

Challenge for manufacturers: For charge multiplication,

need breakdown voltage >1000V!!

SCIPPSCIPP NIST Range

0.00E+00

5.00E+00

1.00E+01

1.50E+01

2.00E+01

2.50E+01

3.00E+01

3.50E+01

4.00E+01

4.50E+01

5.00E+01

0 200 400 600 800 1000 1200

Alpha Energy [MeV]

Ran

ge

[g/c

m^

2]

SILICON

AIR (dry,

SILICON

0.00E+00

1.00E-03

2.00E-03

3.00E-03

4.00E-03

5.00E-03

6.00E-03

7.00E-03

8.00E-03

9.00E-03

1.00E-02

0 2 4 6 8 10

Alpha Energy [MeV]

Ran

ge

[cm

]

SILICON

Thorium 230: 4.7 MeV

SCIPPSCIPP

Do NOT expect: Charge multiplication

Pulses from Th 230 alpha’s

Expect collection time of ~ 500ps for over-depleted bias (drift velocity is saturated)large rise time dispersion for low bias voltage

SCIPPSCIPP Bias dependence of pulse(mean values vs bias voltage)

SCIPPSCIPPExpected Performance from 50um epi Diode

SCIPPSCIPP

Thin Sensor Simulations Preliminary Results

Colin Parker

UCSC / UNITN

1/18/13

SCIPPSCIPPFinite Element Mesh

SCIPPSCIPPElectric FieldWidth = 2um Depth = 2um

SCIPPSCIPP

2um deep * width (um) Vbd

2 190

10 250

20 340

39 >500

5um deep * width (um) Vbd

2 350

10 450

20 >500

39 >500

Breakdown Voltage vs. Implant Dimension

SCIPPSCIPP Doping Profiles & Biasing Assume doping distributions with maximum 2 doping

distributions, uniform in depth,“pad fields”

Explore two basic conditions: Emax = 270 kV/cm, adjust bias -> maximum gain Common Bias for pairs of distributions: all 100 W-cm vs. 100 W-cm

with p+ implants of 5, 10, 20 W-cm (4um deep in 20 um, 2 um 5 um) Thickness 20, 5 um Resistivity 10, 50, 100, 1000 Ohm-cm

p+ substr.

p- epi

+ n

SCIPPSCIPP Emax = 270 kV/cm, (Bias adjusted), 5 mm

Electric Field 5um, Emax = 270 kV/cm

0

50

100

150

200

250

300

0 1 2 3 4 5Depth [um]

Fie

ld [

kV

/cm

]

5 Ohm-cm10 Ohm-cm15 Ohm-cm10 Ohm-cm only100 Ohm-cm only1 kOhm-cm only

[3um 100 W-cm + 2um of p+ implants (5, 10, 15 W-cm)] vs. [5um 100W-cm]

Multiplication Factor 5um, Emax = 270 kV/cm

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 1 2 3 4 5Depth [um]

Mu

ltip

lica

tio

n F

ac

tor


SCIPPSCIPPEmax = 270 kV/cm, (Bias adjusted), 5 mm

Charge vs. Depth 5um, Emax = 270 kV/cm

10

100

1000

10000

0 1 2 3 4 5Depth [um]

Ch

arg

e [

e]


[3um 100 W-cm + 2um of p+ implants (5, 10, 15 W-cm)] vs. [5um 100WW-cm]

Charge vs. time 5um, Emax = 270 kV/cm

1.E+01

1.E+02

1.E+03

0 10 20 30 40 50Time [ps]

Ch

arg

e p

er

2 p

s [

e]

5 Ohm-cm

10 Ohm-cm

15 Ohm-cm

10 Ohm-cm only

50 kOhm-cm only

100 Ohm-cm only

1 kOhm-cm only

Shower development in Space Shower development in Time


Gain 5um, Emax = 270 kV/cm

0

2

4

6

8

10

12

14

16

18

20

1 10 100 1000Resistivity

ga

in

P+ Implant, 100 Ohm-cm

No P-implant


Gain vs. Resistivity

Collected Charge 5um, Emax = 270 kV/cm

1.E+02

1.E+03

1.E+04


Co

llec

ted

Ch

arg

e [

e]


No P-implant

Collected Charge vs. Resistivity


Electric Field 20 um, Emax = 270 kV/cm

0

50

100

150

200

250

300

0 5 10 15 20Depth [um]

E F

ield

[k

V/c

m]

5 Ohm-cm10 Ohm-cm15 Ohm-cm10 Ohm-cm only50 Ohm-cm only100 Ohm-cm only1 kOhm-cm only

[16um 100 W-cm + 4um of p+ implants (5, 10, 15 W-cm)] vs. [20um 10, 50, 100, 1000 W-cm]

Multiplication 20 um, Emax = 270 kV/cm

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 5 10 15 20Depth [um]

Mu

ltip

lica

tio

n F

ac

tor

alp

ha

[1

/um

]



Charge vs. Depth 20 um, Emax = 270 kV/cm

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

0 5 10 15 20

Depth [um]

Co

llec

ted

Ch

arg

e [

e]



Shower development in Space Shower development in TimeCharge vs. Time 20 um, Emax = 270 kV/cm

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

0 50 100 150 200

Time [ps]

Co

llec

ted

Ch

arg

e in

2 p

s [

e/2

ps

]


SCIPPSCIPP Emax = 270 kV/cm, (Bias adjusted), 20 mm

Gain 20um, Emax = 270 kV/cm

1.E+00

1.E+01

1.E+02

1.E+03

1.E+04

1.E+05

1.E+06


ga

in


No P-implant


Gain vs. Resistivity Collected Charge vs. Resistivity

Collected Charge 20 um, Emax = 270 kV/cm

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09


Co

llec

ted

ch

arg

e in

20

20

0 p

s


No P-implant

SCIPPSCIPPCommon Bias of 100 W-cm Bulk and Implant, 5 mm

Electric Field 5um, Bias = 103 V

0

50

100

150

200

250

300

0 1 2 3 4 5

Depth [um]

Fie

ld [k

V/c

m]

5 Ohm-cm g = 2.4

100 Ohm-cm only g = 1.8


0

50

100

150

200

250

300

0 1 2 3 4 5

Depth [um]

Fie

ld [k

V/c

m]

10 Ohm-cm g = 4.3




0

50

100

150

200

250

300

0 1 2 3 4 5

Depth [um]

Fie

ld [k

V/c

m]

15 Ohm-cm g = 5.7



Gain 5um, Emax(Implant) = 270 kV/cm

0

2

4

6

8

10

1 10 100

Resistivity

ga

in

P+5 Ohm-cm, 100 Ohm-cm, 103 VP+10 Ohm-cm, 100 Ohm-cm 119VP+15 Ohm-cm, 100 Ohm-cm 124 V


Collected Charge 5um, Emax(Implant) = 270 kV/cm

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

1 10 100

Resistivity

Co

llect

ed

Ch

arg

e [e

]

P+5 Ohm-cm, 100 Ohm-cm, 103 VP+10 Ohm-cm, 100 Ohm-cm 119VP+15 Ohm-cm, 100 Ohm-cm 124 V


Electric Field 20 um, Bias = 212 V

0

50

100

150

200

250

300

0 5 10 15 20Depth [um]

E F

ield

[k

V/c

m]

5 Ohm-cm g = 2.3


Electric Field 20 um, Bias =364 V

0

50

100

150

200

250

300

0 5 10 15 20Depth [um]

E F

ield

[k

V/c

m]

10 Ohm-cm g = 7.1



Electric Field 20 um, Bias = 415 V

0

50

100

150

200

250

300

0 5 10 15 20Depth [um]

E F

ield

[k

V/c

m]

15 Ohm-cm g = 27.6


SCIPPSCIPPCommon Bias of 100 W-cm Bulk and Implant, 20 mm[16um 100 W-cm + 4um of p+ implants (5, 10, 15 W-cm)] vs. [20um 100W-

cm]

SCIPPSCIPP Collected Charge in 5 & 20 um[16um 100 W-cm + 4um of p+ implants (5, 10, 15 W-cm)] vs. [20um 100W-

cm][3um 100 W-cm + 2um of p+ implants (5, 10, 15 W-cm)] vs. [5um 10, 100, 1000W-cm]

Universita de Firenze Hartmut Sadrozinski, Scott Ely, Vitaliy Fadeyev, Zachary Galloway, Jeffrey...

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