Today’s
Talk:
OutlineNext generation silicon pixel detectors:

towards picosecond timing
Giuseppe Iacobucci— Université de Genève

Precise timing measurement at HL-LHC- High Luminosity LHC (HL-LHC, starting in 2029): expect a pile-up of 150-200 events per bunch crossing- Timing and spatial resolution of standard silicon trackers not sufficient: 10-15% of vertexes composed of 2 events

Pile-up without timing:

Pile-up with precise timing – 4D tracking:

H. Sadrozinski, A. Seiden and N. Cartiglia, 2018 Rep. Prog. Phys. 81 026101

Requirements for silicon detectors for 4D tracking at the HL-LHC:- Time resolution: 30 ps- Spatial granularity: ~1 mm (timing information assigned to the track)- Radiation tolerance: ≳1015 neq·cm-2
Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 20222

Precise timing with siliconTiming resolution in silicon pixel detectors mainly determined by:
1. Sensor geometry and fields
2. Charge-collection (Landau) noise
Spatialprecision

3. Electronic noise

Low
power

4. Gain: Internal charge multiplication (except 3D)
Challenge:
Optimise these parameters for picosecond timing
while maintaining other performance requirements

Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

Radiation
tolerance

Picosecond
timing3

1. Sensor geometry and fields
Sensor geometry needs to guarantee fast and uniform time response:• High and uniform electric field (charge transport with uniform and saturated drift velocity)• High and uniform weighting field (fast and uniform signal induction)

Iind =∑i⃗qi v drift,i

⃗
⋅E

w,i

Challenge:• Small pixels introduce low and non-uniform electric and weighting field regions:inter-pixel region

pixel centre

inter-pixel region

Weighting field map for large collection electrode CMOS sensor with pitch of 100μm

Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

Red = highBlue = low

4

2. Charge-collection (Landau) noise
L. Paolozzi PhD thesis, 2014 – http://www.infn.it/thesis/thesis_dettaglio.php?tid=11828

Sensor design needs to reduce charge-collection noise:
Non uniform charge deposition along particle track induces a jitter in the current pulse

Iind =∑i⃗⃗qi v drift,i ⋅ E w,itestbeam

The statistical originof this variability of Iind makes this effectirreducible in PN-junction sensors“Landau” floor

Total current

Laser
Electron current
Hole current

H. Sadrozinski, A. Seiden and N. Cartiglia, 2018 Rep. Prog. Phys. 81 026101

Way out:

thinning of the sensor

Challenge: although thin sensors reduce charge collection noise, they are typically bad for Signal/Noise(less ionization + increased capacitive coupling to sensor backside)
Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

5

3. Electronic noise
Once the geometry has been fixed, the time resolution depends mostly on theamplifier performance:➔ Need an ultra-fast, high-gain, low-noise (low power-consumption) electronics
with fast risetime and small capacitance

Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

6

Towards ps timing: Outline
Under the impulse of the High Energy Physics community, a new generationof silicon sensors for timing is being developed:

30 ps sensors:‣ LGAD (Low-Gain Avalanche Detector)➡ TI-LGAD (Trench-Isolated LGAD)➡ AC-Coupled (Resistive) LGAD

10 ps sensors:‣ 3D sensors (TIMESPOT Project)
Giuseppe Iacobucci — Université de Genève‣ PicoAD (MONOLITH Project)

Tsukuba Global Science Week, September 27, 2022

7

Low Gain Avalanche Detectors
LGAD

Low Gain Avalanche Detectors
LGADs: developed and being produced for HL-LHC
gain layer

trise
σtime ≈
S/N

20 – 100 µm

1 mm‣ Internal charge multiplication (gain = 10 – 20)

60 µm

1 mm

S/N increases and gives better σtime‣ Hybrid silicon “pad” sensors; 1 mm pads, with ≲100µm inactive inter-pad region‣ Depleted thickness 20 – 100 µm‣ Time resolution: 25 – 35 ps (depending on the thickness)
Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

9

Low Gain Avalanche Detectors
Recent test of ultra-thin FBK LGADs :Demonstrated radiation tolerance
and time resolution for HL-LHC:

F. Carnesecchi et al., arXiv:2208.05717

25µm

50µm

35µm

35 μm thick LGADs approach 25 ps time resolution(mostly due to reduction of Landau-noise jitter)

Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

σT [ps]30
40

NIEL [neq/cm2]
15
1∙10
15
2.5∙1010

Low Gain Avalanche Detectors
LGADs now being fabricated for the HL-LHC experiments:(Courtesy of G. Paternoster)

Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

11

LGAD: from pads to pixels
Standard LGAD

TRENCH-ISOLATED LGAD

1 mm

≳ 55µmno-gain region~60µm

no-gain region< 5µm

Gain layer

Pixel isolation and termination structures are replaced by a trench that:‣ is a few µm deep and ~1 µm wide, filled with silicon oxide‣ acts as a drift/diffusion barrier for electrons and isolates adjacent pixels‣ reduces the inactive region in-between pixels from ~60 µm to few µm
Prototypes already produced with pixel pitch down to 55µm
Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

12

TI-LGAD radiation tolerance
90Sr β source

Laser
data

3.5 1015 neq/cm2

left pixel

right pixel

Pixel isolation by trenches: good before and after irradiation
Inter-pixel distance remains of few µm before and after irradiation
Time resolution degraded after irradiation, but still uniform until the edges:
NIEL level: 0
3.5∙1015 neq/cm2
with laser: 5ps → 30ps
with 90Sr: 35ps → 60ps
Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

13

Resistive AC-Coupled LGADs
Standard LGAD

AC-Coupled Resistive LGAD
Thin coupling
dielectric layer

AC pads

DC Bias Pad

Resistive n+electroden+Gain layerp+ implantEpi-silicon (p-)
Support wafer (p+)‣ AC-coupled to the resistive n+ layer via dielectric coupling‣ Gain layer NOT segmented: 100% fill factor‣ Note that it is a different way to read out the signal and segment the sensor,
since the signal spreads over adjacent pixels

Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

14

AC-Coupled LGAD: How does it work ?
Signal spreads over adjacent pixels, with amplitude inversely proportional to the hit distance

M. Tornago et al., NIMA 1003 (2021) 165319
TCT Measurements withIR Laser Setup

Channel 0

Channel 2

Laser SpotRSD2 production

Channel 1

Giuseppe Iacobucci — Université de Genève

Channel 3

Tsukuba Global Science Week, September 27, 2022

15

AC-Coupled LGAD
Pixel AC-LGAD by FBK

Pixel AC-LGAD by

N. Cartiglia

R. Heller et al., arxiv:2201.07772
S. Kita et al., arxiv:2207.07355

500 µm pitch

arXiv:2201.07772v

Time resolution: 30-35 ps, regardless of pixel pitch
Spatial resolution: ≈ 4µm + 3% of pixel pitch
Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

16

AC-Coupled Resistive LGAD
AC-Coupled LGAD is a candidate to combine in future experiments
30ps timing and few µm spatial resolution with a reduced number of readout channels
Figure from N. Cartiglia et al., arxiv:2204.06536

Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

17

The TIMESPOT Project3D sensors““(A. Lai, INFN)

3D sensors: no gain, but geometry
Original idea by Sherwood Parker (1997)

Hybrid sensor in which collection electrodes are vertical highly doped columns

1. Very short drift distance to collection electrode➡ Fast charge collection
2. Reduced distance to ohmic contacts➡ High drift field➡ High weighting field

Precise timing
Columns produced by Deep Reactive Ion Etching(Bosch technology developed for MEMS)

Challenge:
Inefficiency in region of collection electrode at perpendicular particle incidence
Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

19

3D sensors
Sensitive volume and electrode shapes designed for maximum performance:
50µm

150 µmTCAD simulation of three electrode geometries:

Columns

Giuseppe Iacobucci — Université de Genève

TrenchesThrench geometry offers the best configuration

Tsukuba Global Science Week, September 27, 2022

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Timespot: testbeam results

Time Resolution: down to ≈ 12 ps
Giuseppe Iacobucci — Université de Genève

Efficiency ~80% for particle angle = 0º,
due to trenches dead area.
Recovered for angles ≳10º
Tsukuba Global Science Week, September 27, 2022

21

Timespot: irradiated sensors

3D sensors are intrinsically radiation hard:
16
time resolution and efficiency maintained even after the extreme fluence of 2.5∙10 neq/cm2
Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

22

The

Project

Our recepy forpicosecond timingwith silicon:

MONOLITHIC

SiGe BiCMOS

PicoAD:
Picosecond
Avalanche
Detector

The UniGe Silicon Team
Giuseppe Iacobucci

Lorenzo Paolozzi

Didier Ferrere• Sensor design• Analog electronics• System integration• Laboratory test

Thanushan Kugathasan

Magdalena Munker

Yannick Favre

Roberto Cardella

Stefano Zambito• project P.I.
• System design• Lead chip design• Digital electronics• Sensor design• Laboratory test

Mateus Vicente• System integration• Laboratory test

Matteo Milanesio• Laboratory test
• Data analysis

Antonio Picardi• Chip design• Firmware

Jihad Saidi• Laboratory test
• Data analysis

Carlo Alberto Fenoglio• Chip design• Firmware

Giuseppe Iacobucci — Université de Genève• Sensor design• Laboratory test

• Laboratory test
• Data analysis

Fulvio Martinelli• Chip design• Firmware

Théo Moretti• Laboratory test
• Data analysis• Board design• RO system

Sergio Gonzalez-Sevilla• System integration• Laboratory test

Stéphane Débieux• Board design• RO system

Main research partners:
Roberto Cardarelli

INFN Rome2 & UNIGE

Marzio Nessi

CERN & UNIGE

Holger RückerIHP Mikroelektronik

Bernd Heinemann
IHP Mikroelektronik

Chiara Magliocca• Laboratory test
• Data analysis

Funded by:

Rafaella Kotitsa• Sensor simulation

Luca Iodice• Chip design• Firmware
Tsukuba Global Science Week, September 27, 2022

UNITEC24

SiGe BiCMOS Front-End Electronics
SiGe HBT = BJT with Germanium as base material.
Grading of Ge doping in base:• charge-transport in base via drift‣ reduced charge-transit-time in base‣ high current gain 𝜷• Higher doping in base is possible:‣ thinner base‣ reduced base resistance 𝑹𝒃
𝑬𝑵𝑪𝒔𝒆𝒓𝒊𝒆𝒔 𝒏𝒐𝒊𝒔𝒆 ∝

𝒌𝟏

𝟐
𝑪𝒕𝒐𝒕

𝜷

𝟐
+ 𝒌𝟐𝑹𝒃𝑪𝒕𝒐𝒕

Leading-edge IHP SG13G2 technology, 130 nm process featuring SiGe HBTGiuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

25

Monolithic SiGe BiCMOS for timing
Monolithic prototypes with SiGe BiCMOS (without internal gain layer)
2016

2017

2018

2019

Test beam results of 2019 prototype
JINST P02019 2022

200ps
• 1 and 0.5 mm2 pixels• Discriminator output

110ps

50ps

• 30 pixels 500x500µm2• 100ps TDC +I/O logic• Hexagonal pixels 65µm
and 130µm side
• Discriminator output

Giuseppe Iacobucci — Université de Genève

36 ps• Hexagonal pixels 65µm side
• 30ps TDC +I/O logic• Analog channels

Tsukuba Global Science Week, September 27, 2022

26

PicoAD Sensor Concept© G. Iacobucci, L. Paolozzi and P. Valerio. Multi-junction pico-avalanche detector;
European Patent EP3654376A1, US Patent US2021280734A1, Nov 2018

PicoAD:
Multi-Junction Picosecond-Avalanche Detector©
with continuous and deep gain layer:• De-correlation from implant size/geometry

m

μ
0
10

➙ high pixel granularity and full fill factor(high spatial resolution)gain• Only small fraction of charge gets amplified➙ reduced charge-collection noise

Giuseppe Iacobucci — Université de Genève

Step 2

Step 3

laye

1
r

m
μ
5

(enhance timing resolution)

Step 1m
μ0Step 4

Tsukuba Global Science Week, September 27, 2022

Step 5

Step 627

PicoAD monolithic proof-of-concept prototype
The proof-of-concept monolithic ASIC was produced by
IHP in their SG13G2 SiGe BiCMOS process.
The ASIC contains:• Four matrices of hexagonal pixels with ≈ 100µm pitch‣ with different electronics configurations

PicoAD Proof-Of-Concept Prototype (2021)• Four analog pixels

55Fe source and in testbeam
tested
with
‣

65µm

IHP also produced PicoAD special wafers
with four different gain-layer implant doses
Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

28

55
Gain Measurement with Fe source
55Fe X-ray Source+HV

X-rays from 55Fe radioactive source:N‣ mainly ~5.9 keV photons‣ point-like charge deposition

+
+h +

h h

e–

h+ multiplication-HV 1st peake– multiplication
2nd peakP+‣ photon absorbed in absorption region➡ electrons through gain layer & multiplied➡ second peak in the spectrum

P
P+

Entries➡ holes drift through gain layer & multiplied➡ first peak in the spectrum“Absorption”
region

h+

2500

2000

55

Fe data

Dose 41500

1000

HV = -100 V
T = 20°C500

00Giuseppe Iacobucci — Université de Genèveh+e–e–e–

N+

Characteristic double-peak spectrum‣ photon absorbed in drift region“Drift”
region–ee– –e–ee––e–
e–e–e–e– – –ee e–ee–e
– –ee
–

e–

P

Tsukuba Global Science Week, September 27, 2022

10

20

30

40

50

60

70

80

90

Amplitude [mV]29

55
Gain Measurement with Fe source

55

Fe data

Dose 4
1500

1000

500

0
0

10

20

30

40

50

60

70

-

-

HV = -100 V
T = 20°C

MPV charge - h+ initiated avalanche [e ]

2000

80

90

Amplitude [mV]Assumption of no gain multiplication when:• photon absorbed in drift region• lowest voltage (85 V)
normalization• lowest dose (dose 1)

12000

Fe data

10000
8000

h+ multiplication
1st peak

6000

Dose 2T = -20°C
T = -10°C
T = +20°C
Dose 4
T = -20°C
T = -10°C
T = +20°C

4000
2000
0
4000080

35000

PicoAD proof-of-concept prototype (2022)
90
100
110
120
130

140
150
160
Dose 1 High Voltage
Dose 2 [V]T = -20°C
T = -20°C
T = -10°C
T = -10°C
T = +20°C
T = +20°C
Dose 3T = -20°C
T = -10°C
T = +20°C
Dose 4
T = -20°C
T = -10°C
T = +20°C

e55– multiplication
Fe data
2nd peak

30000
25000
20000
15000
10000
5000
0
80

value

Giuseppe Iacobucci — Université de Genève

Dose 1
T = -20°C
T = -10°C
T = +20°C
Dose 3T = -20°C
T = -10°C
T = +20°C

55

-

2500

PicoAD proof-of-concept prototype (2022)

MPV charge - e initiated avalanche [e ]Entries

Average amplitudes of h+ and e- gains
extracted via gaussian fit around local maxima

PicoAD proof-of-concept prototype (2022)

Tsukuba Global Science Week, September 27, 2022

90

100

110

120

130

140
150
160
High Voltage [V]30

55
Gain Measurement with Fe source
R. J. McIntyre, IEEE Trans. Electr. Dev.,
Vol. 46, no. 8, 1623-1631, Aug. 1999

25

Dose 1
T = -20°C
T = -10°C
T = +20°C

55

Fe data20

arXiv:2206.07952

15
10
5

Dose 2T = -20°C
T = -10°C
T = +20°C
Dose 3T = -20°C
T = -10°C
T = +20°C
Dose 4
T = -20°C
T = -10°C
T = +20°C

e- gainh+ gaine- gain for 55Fe X-rays

PicoAD proof-of-concept prototype (2022)

8
7
6

PicoAD proof-of-concept prototype (2022)
55

Fe dataarXiv:2206.07952

5
4
3
2
1

0
80

90

100

110

120

130

140
150
160
High Voltage [V]A gain up to ≈ 20 for 55Fe X-rays
obtained at HV = 120 V and T = -20 ℃
Giuseppe Iacobucci — Université de Genève002Dose 1
T = -20°C
T = -10°C
T = +20°C

Dose 2T = -20°C
T = -10°C
T = +20°C

Dose 3T = -20°C
T = -10°C
T = +20°C

4

10

16

6

8

12

14

Dose 4
T = -20°C
T = -10°C
T = +20°C

18 20 22 24 26
e- gain for 55Fe X-rays

Evidence for gain suppression
due to space-charge effects
in the case of 55Fe X-rays

Tsukuba Global Science Week, September 27, 2022

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PicoAD: laser measurements

Time jitter [ps]PicoAD proof-of-concept prototype:
Laser data

Charge [e–]Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

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Testbeam results: Detection Efficiency
99.9% for all power consumptions

Drops to 99% for HV=105 V

100

99.8

99.2

99
0

100

99

98

99.6

99.4

PicoAD proof-of-concept prototype (2022)

Efficiency [%]Efficiency [%]PicoAD proof-of-concept prototype (2022)

arXiv:2208.11019

97

arXiv:2208.11019

CERN SPS Testbeam: 180 GeV/c pions

CERN SPS Testbeam: 180 GeV/c pions

Vth = 4 mV ; HV = 125 V

Vth = 4 mV ; Power = 2.7 W/cm2

0.5

1

Giuseppe Iacobucci — Université de Genève

1.5

96

2
2.5
3
Power [W/cm2]

95
100

Tsukuba Global Science Week, September 27, 2022

105

110

115

120
125
130
High Voltage [V]33

Testbeam results:

PicoAD proof-of-concept prototype (2022)

40
35
30
25
20

PicoAD proof-of-concept prototype (2022)

40
35
30
25
20

arXiv:2208.11019

15
10

Timing resolution of 30 ps evenat power consumption of 0.4 W/cm2
Time resolution [ps]Time resolution [ps]Best performance: (17.3±0.4) ps
for HV=125 V and Power = 2.7 W/cm2[6]Time Resolution

CERN SPS Testbeam: 180 GeV/c pions

102

Vth = 4 mV ; Power = 2.7 W/cm

5

5

0
100

0
0

105

110

Giuseppe Iacobucci — Université de Genève

115

arXiv:2208.11019

15

120
125
130
High Voltage [V]CERN SPS Testbeam: 180 GeV/c pions

GOAL

Vth = 4 mV ; HV = 125 V

Tsukuba Global Science Week, September 27, 2022

0.5

1

1.5

2
2.5
3
Power [W/cm2]
34

Testbeam results: dependence on position
Signal MPV amplitude

arXiv:2208.11019

Time resolution

Efficiency

arXiv:2208.11019

m

56µm

65µm

µ
65

arXiv:2208.11019

56µm(𝟏𝟑.𝟐 ± 𝟎.𝟖) ps at the pixel center
Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 202235

Sub-picosecond TDC
We are developing a sub-picosecond TDC based on a novel design (our patent© & more):© R. Cardarelli, L. Paolozzi, P. Valerio and G. Iacobucci, European Patent Application /Filing - UGKP-P-001-EP, Europe Patent EP 18181123.3. 2 July 2018.

MONOLITH TDC prototype(very preliminary)Standalone prototype still under test at UNIGE.
Integrated in MONOLITH 2022 monolithic ASIC.

Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

36

Summary
Triggered by the needs of the HL-LHC and beyond, the HEP community is
working on precise timing with silicon to produce 4D trackers.
Hybrid LGAD pads will be used in ATLAS & CMS, with 30 ps time capabilities
Evolving towards : - TI-LGAD to obtain small-pitch pixels- resistive AC-Coupled LGAD to reduce the number of channels
Two projects are producing results at the level of 10 ps (below the Landau limit):- TIMESPOT, featuring the intrinsically rad-hard hybrid 3D sensors- MONOLITH, featuring monolithic implementation of SiGe BiCMOS electronics
on the novel PicoAD sensor

Production of full systems with 10µm and 10ps resolutions is a long way ahead of us
Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

37

ExtraMaterial

3D trench sensors

Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

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Timespot: timing tilted sensors

Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

40

Test Beam: Experimental Setup
CERN SPS Testbeam with 180 GeV/c pions to measure efficiency and time resolution

UNIGE FE-I4 telescope to provide spatial information (σx,y ≈10 μm)
Two LGADs (σt ≈35 ps) to provide the timing reference (and two SPADs with σt ≈20 ps)
Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

41

30
25

PicoAD proof-of-concept prototype (2022)
CERN SPS Testbeam: 180 GeV/c pions
2

HV = 125 V ; Power = 2.7 W/cm

20
15

Amplitude [mV]

Amplitude [mV]

Waveform Example

30
25
20
15
10

10

5
0
−5
320

325

330

335

340

5

345
350
Time [ns]Vth = 4 mV0
−50
Giuseppe Iacobucci — Université de Genève

100

200

300

Tsukuba Global Science Week, September 27, 2022

400

500
Time [ns]42Testbeam results: Time Resolution

PicoAD proof-of-concept prototype (2022)
CERN SPS Testbeam: 180 TOF
GeV/c
DUTpions- LGAD3 for OA0

1.8
1.6 DUT - LGAD1

Entries65399

r2 /Ndf

44/31

mGauss [ps]1.4

49.5 ± 0.2

Outside fit [%]

1.2

3.90

FWHM/2.355 [ps] 48.1 ± 1

10.8Power = 2.7 W/cm

0.6

HV = 125V

2

0.4
0.2
0
<300 <200 <1000
100 200 300
TOAOA0-TOALGAD1 [ps]Giuseppe Iacobucci — Université de Genève

×103

PicoAD proof-of-concept prototype (2022)
CERN SPS Testbeam: 180 TOF
GeV/c
DUTpions- LGAD0 for OA0

2.2
Entries63935
2
r /Ndf
23/24
DUT - LGAD0m[ps]39.7 ± 0.3
1.8
Outside fit [%]4.28
1.6
FWHM/2.355 [ps] 38.2 ± 1
1.4
1.2
1
Power = 2.7 W/cm2
0.8
HV = 125V
0.6
0.4
0.2
0
<300 <200 <1000
100 200 300
TOAOA0-TOALGAD0 [ps]
2

Gauss

Tsukuba Global Science Week, September 27, 2022

Entries

×103

Entries

Entries• Time Of Arrival (TOA) as a time at constant fraction• Distributions after time-walk correction• Distributions are Gaussian: only ≈2-4 % of entries in non-gaussian tails• Simultaneous fit to extract time resolutions of the DUT, LGAD0, LGAD1
×103
18
16

PicoAD proof-of-concept prototype (2022)
CERN SPS Testbeam: 180 GeV/cpions
TOF LGAD0- LGAD3 for OA0

LGAD0 - LGAD1

14
12

Entries

738173

r2/Ndf47/37

mGauss [ps]Outside fit [%]58.1 ± 0.1
2.02

FWHM/2.355 [ps] 56.6 ± 1

108
6Power = 2.7 W/cm2
HV = 125V

420<300 <200 <1000
100 200 300
TOALGAD0-TOALGAD1 [ps]43TCAD: transient space-charge effectTransient 3D TCAD simulation of point like 55-Fe charge deposition in absorption layer:

Space charge:
10ps after charge generation – before charge generation:

Accumulated
multiplied
electron
population

DriftregionElectric field:
10ps after charge generation – before charge generation

Significant
reduction offield in gain
layer

Drift
regionGain layer
Absorption
regionInitial point-like
55-Fe charge

Giuseppe Iacobucci — Université de Genève

Accumulated
multiplied hole
population

Absorption
regionInitial point-like
55-Fe charge

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TCAD: transient space-charge effectGain as function of sensor depth fordifferent primary charge carrier densities:• For high charge carrier densities (Fe55) the gain issuppressed compared to lower charge carrier densities(MIPs).
• Simulated suppression factor of Fe55 w.r.t. MIP charge
compatible to calculation of compression factor fromtest-beam and Fe55 measurements.
àMeasured gain for Fe55 significantly supressed bytransient space charge effect.
àNeed of fully self consistent transient TCAD simulations.

Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

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PicoAD simulation - 3D TCAD setup
3D TCAD pixel matrix:
Highly p-doped p-stops (floating)Highly n-doped pixel implants
Lowly p-doped drift region
Highly doped n-type gain layer implant
Highly doped p-type gain layer implant
Lowly p-doped absorption region
Highly p-doped substrate wafer
Critical TCAD aspects:

Giuseppe Iacobucci — Université de Genève• Gain layer: meshing & modelling (Okuto, vanOverstreaten etc…)• Si/Ox interface in inter pixel region (top layer oxidestack
not shown here)
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27, 2022

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PicoAD 3D TCAD - electrostatic potential
Electrostatic potential – 2D map:
Electrostatic potential – cuts C1, C2:
DriftregionSubstrate

Gain layer

Absorbtion
region• Highest potential drop in gain layer (as expected)• Significant potential drop in drift region, less compared to absorbtion region due
to increased thickness• In inter-pixel region:• Potential maximum close to surface
region• Reduced potential drop in drift & gain layer
Tsukuba Global Science Week, September 27, 2022
Giuseppe Iacobucci — Université de Genève

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PicoAD 3D TCAD - Electric field
Electric field – 2D map:

Electric field – cuts C1, C2:

Substrate

Drift region

Gain layer

Absorbtion
region• Highest elecric field in gain layer (as expected)• Significant E field in drift region, less compared to absorbtion region due to increased thickness• In inter-pixel region:• Field minimum close to surface• Reduced field in drift & gain layer region à
Giuseppe Iacobucci — Université de Genève

lower gain in inter pixel region

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Electron drift velocity
Electron drift velocity – 2D map:

à Electron drift velocity very close to saturation in full pixel volume (note the scale!)à Important for precise timing
Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

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Weighting potential & field
Weighting potential – 2D map:

Active region:
Drift & absorbtion
regionSubstrate
Single pixel• No impact of gain layer onweighting potential & field• High weighting field over full
active thickenessà

Weighting field – 2D map:

Active region:
Drift & absorbtion
regionImportant for precise timing• Highest weighting field in pixel
implant corners due to largest
potential drop

Substrate
Giuseppe Iacobucci — Université de Genève

Single pixel

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Next submission – optimisation of drift region
First proof of concept prototype with non-optimal drift region thickness:
Thickness of epi-layer limited by production processà Significant gain variations in inter-pixel region:
At high voltage, small variations of
the electric field in the gain layer
result in large gain variations:Electric Field [V/cm]

Efield, 1st prototype, 10µm drift region:

!

0

5

10

nd

Electric Field [V/cm]

Efield, 2

15

prototype, 25µm drift region:!

J. McIntyre. A new look at impact ionization-Part I: A
theory of gain, noise, breakdown probability, andfrequency response. IEEE Transactions on Electron
Devices, vol. 46, no. 8, pp. 1623-1631, Aug. 1999

Sensor Depth [µm]Sensor Depth [µm]Giuseppe Iacobucci — Université de Genève

à Next production (withexternal company): thicker
epitaxial layer for drift region

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Detection Efficiency
PicoAD proof-of-concept prototype (2022)

3.05

0.7
0.6

3

0.5

Track position y [mm]0.8

Efficiency

Track position y [mm]1
Apparent degradation at the external edgesof the four pixels is due to the telescope
0.9
3.1
pointing
resolution of ≈10 μm
3.1

0.99
3.05
0.98
3

0.4
2.95
0.3
0.2

2.9

1

Efficiency

CERN SPS Testbeam: 180 GeV/c pions
2
Vth = 4 mV ; HV = 125 V ; Power = 2.7 W/cm

0.97
2.95
0.96

2.9

0.1
2.85

−4

−3.95

−3.9

−3.85

−3.8 −3.75 −3.7 −3.65
Track position x [mm]

0

2.85

−4

−3.95

−3.9

−3.85

−3.8 −3.75 −3.7 −3.65
Track position x [mm]0.95

Selection of two triangles:• representative of a whole pixel• unbiased by telescope resolution
Giuseppe Iacobucci — Université de Genève

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Time Resolution

180 GeV/c pions

Results were also verified using two SPADs (but with much smaller statistics)

Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

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Time-walk Correction• Shift at 200 ps of the waveform to subtract low-frequency noise• Time at constant fraction: 25% of max amplitude• Amplitude-based time-walk correction for residual time walk

Giuseppe Iacobucci — Université de Genève

Tsukuba Global Science Week, September 27, 2022

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MONOLITH: First PicoAD Prototype
PicoAD Proof-Of-Concept Prototype

Prototypes without internal gain layer
2016

2017

2018

200ps

110ps

50ps

• 30 pixels 500x500µm2• 100ps TDC +I/O logic• Hexagonal pixels 65µm
and 130µm side
• Discriminator output• 1 and 0.5 mm2 pixels• Discriminator output

2019

2021

36 ps
• Hexagonal pixels 65µm side
• 30ps TDC +I/O logic• Analog channels

Sensor with no gain test beam results: JINST P02019 2022

17 ps
• Same electronics as 2019 prototype• Epitaxial layers + gain layer• 4 different gain-layer doses

Gain measurements: arXiv:2206.07952, June 2022
PicoAD proof-of-concept prototype
Testbeam results: arXiv:2208.11019, August 2022
Giuseppe Iacobucci — Université de Genève

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The MONOLITH ERC Project• Funded by the H2020 ERC Advanced grant 884447 ,[1]

July 2020 - June 2025

• Monolithic silicon sensor able to:‣ precisely measure 3D spatial position‣ provide picosecond-level time resolution• Implements:‣ Fast and low-noise SiGe BiCMOS electronics‣ Novel sensor concept:
the Picosecond Avalanche Detector (PicoAD)[1] MONOLITH H2020 ERC Advanced Project Web Page - https://www.unige.ch/dpnc/en/groups/giuseppe-iacobucci/research/monolith-erc-advanced-project/

Giuseppe Iacobucci — Université de Genève

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Other UNIGE projects that use
monolithic SiGe BiCMOS
1. 100µPET SNSF SINERGIA
2. FASER W-Si pre-shower

The 100µPET SNSF SINERGIA project

Giuseppe Iacobucci• P.I.

Mateus Vicente• System integration• Laboratory test

Jihad Saidi

Michäel Unser

Martin Walter• P. I.

• P. I.

Pol del Aguila Pla

Pablo Jané

• Statistical signal
processing• Nuclear Medicine• PET imaging• Translational imaging

Aleix Boquet-Pujadas

Xiaoying Xu• Signal/image processing• Physical modeling• System simulation• Laboratory test

• Molecular Biology• In vivo studies• Bioinformatics

Didier Ferrere• System integration• Laboratory test

Lorenzo Paolozzi• Sensor design• Analog electronics

Yannick Favre• Board design• RO system

Giuseppe Iacobucci — Université de Genève

Franck Cadoux• Mechanics• FEA calculations
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The 100µPET SNSF SINERGIA project
Simplified and improved scanner design, avoiding acceptance holes from cooling blocks
Monolithic 100µPET detector ASIC: 2.5 x 3 cm2 active pixel matrix; 100 µm pixel pitch; 250 µm thick active silicon sensor
Single silicon detection layer composed by 2x2 chips assembled, covering 30 cm2
4 “towers” compose the scanner. 60 detection layers on each tower = 960 chips!

¤
¤
¤
■

Large number of services and interconnections, requiring innovative design. Two possible designs under study■

5 silicon detector layers (20 chips) stacked on a PCB, staggered for wire-bonding. 12 modules are stacked in a tower■

1 detection layer (2x2 chips) are interfaced to a FPC via ACF bonding. 60 FPC/ASIC layers are stacked in a tower

4 Tower
assembly

Silicon/flex layer (4 chips)

a
Dat

HV

Tow
er

34mm

w/

60

flex

/sil

ico

n la
yer
s

ID

4 Tower
assembly59

The 100µPET Performance

100µPET

Fully Active
No absorber

Fully Active+
Bi absorber(Compilation of digital PET/MRI for Preclinical Applications from the doctoral thesis of B. Weißler, 2016)

20
60

FLAREHigh granularity FASER W-Si pre-shower
A. Sfyrla and G. Iacobucci groups

Current FASER pre-shower:
2 layers of tungsten + scintillating detectors⟹ no XY granularity
To have access to two-photon final states:• High granularity andhigh dinamic range
pre-shower based on
six planes of monolithic pixels• Discriminate TeV-scale EM showers• Targeting data taking in 2024-2026
and during HL-LHC

Giuseppe Iacobucci — Université de Genève

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FLAREHigh granularity FASER W-Si pre-shower

FASER preshower pre-production chip:• First engineering run produced by UNIGE in SiGe BiCMOS• Three large ASIC (15x7.5 mm2) with alternative designs• pixels with 65µm side (~100µm pitch)• Delivered in July; presently under test

ADC output before calibration

Five pixels
with largely varying response

After test-pulse calibration

Giuseppe Iacobucci — Université de Genève

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Summary & Outlook
The PicoAD© Monolithic proof-of-concept prototype works:• Gain ≈ 20 for 55Fe X-rays (space-charge effects, for X-rays, measured)• Efficiency = 99.9 % at full sensor-bias voltage• Time resolution σt = (17.3 ± 0.4) ps (although sensor not yet optimized for timing)
Ongoing activities include:• Optimization for timing of the PicoAD sensor design with TCAD to achieve ≲10 ps(smaller pixel pitch; thicker drift layer; improved inter-pixel region)• Development of picosecond TDC for fully monolithic chip
Deliverable of MONOLITH project:• Full-reticle chip with 50µm pitch and sub-10ps timing in Summer 2025
Giuseppe Iacobucci — Université de Genève

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