[PPT] - Tracking and Timing with Induced Current Detectors Ronald Lipton PowerPoint Presentation

SLIDE 1

Ronald Lipton CPAD 2019

Dec. 10 2019

Tracking and Timing with Induced Current Detectors

SLIDE 2

12/10/2019

Ronald Lipton

Introduction

There has been increasing interest in fast timing as well as “intelligent” detector systems. I would like to present some ideas for alternate designs of such systems looking at how technology for silicon-based detectors might

evolve. This is a talk about the future - next generation of collider experiments.

We focus on capability enabled by new technologies that provide small pixels with low capacitance and sophisticated processing

3D integration of sensors and electronics
Monolithic active devices
Semiconductor substrate engineering

2

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Ronald Lipton

Some Basics - time resolution

The rule of thumb for the time resolution of a system dominated by jitter is:

         

slew rate (dV/dt) is related to the inverse amplifier rise time, CL is the load

capacitance td and ta are the detector and amplifier rise times and gm is the input transistor transductance - related to input current, and A is a characteristic of the amplifier.

Fast timing -> large S/N, fast amp, small load capacitance
There are tradeoffs available

3

σ t ~ σ noise ∂V ∂t ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ ~ tr Noise Signal ⎛ ⎝ ⎜ ⎞ ⎠ ⎟

σ n

2 = CL 2 4ktA

( )

gmta

Front end noise

σ t ~ CL gmta ta

2 + td 2

Signal

Jitter Time resolution

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Ronald Lipton

More Basics - Signal Development

Signal induced by moving charges

depends on work done by circuit. The charge induced on an electrode depends

n the coupling between the moving

charge and the electrode (Ramo’s theorem)

We usually work with simple parallel plate

systems

In a multi-electrode system the induced

current on an electrode depends on the velocity of the charge and the value of the effective “weighting” field

Weighting field is calculated with 1 V on

measuring elected, 0 V on others

There are fast transient induced currents
n neighbor electrodes that integrate to

zero - can we use them?

4

i = −q ! Ew × ! v Qs = idt = q ! Ew

∫ ∫

d! x Q

1→2 = q(Vw2 −Vw1)

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Ronald Lipton

3D Integration and small pixels

Fermilab has been involved the development of 3D sensor/ASIC integration for almost a decade and have demonstrated (with industrial partners):

Hybrid bonding technology
Oxide bonding with imbedded metal

through silicon vias (TSV)

Bond pitch of 4 microns
First 3-tier electronics-sensor stack
Small pixels with ADC, TDC (24 microns)
Small TSV capacitance (~7 ff)
The noise in hybrid bonded VIPIC 3D

assembly is almost a factor of two lower than the equivalent conventionally bump   bonded parts due to lower Cload

5

0" 50" 100" 150" 200" 250" 300" 350" 400" 450" 500" 25" 30" 35" 40" 45" 50" 55" 60" 65" Counts' noise'(electrons)'

Unbonded" Bump"bonded" Fusion"Bonded"

.5 mm sensor (BNL) 34 micron high 2-tier VICTR chip

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Ronald Lipton

Methodology

We explore simple systems with various pixel sizes, detector thickness and pulse shapes

Build a (Silvaco) TCAD (2D or 3D) detector

model

Inject a Qtot=4 fc pulse
Extract the capacitance and pulse shapes at

the electrodes

Inject the resulting pulse into a SPICE model
f a generic 65nm charge sensitive amplifier

including noise

Analyze the characteristics of the

resulting output pulses

For angled track studies I use simple op amp

with defined bandwidth model with adjustable bandwidth

6

3D 9 pixel model

Pulses from “x-ray” at~100μ 200μ thick detector

y = 2E-18x2 + 1E-16x + 1E-15 5E-15 1E-14 1.5E-14 2E-14 2.5E-14 3E-14 20 40 60 80 100 120

200 Micron Thick Detector Farads/micron

TCAD Simulation

Pixel Pitch (microns) Capacitance (farads)

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Ronald Lipton

Simple Example - X-Rays

Suppose an application requires fast timing on high energy x-rays

Usually we would like thin detectors for fast timing,

but thin detectors imply low efficiency - can we use induced currents to achieve time resolution in a thick detector?

7

Initial Current Spike Central pixel Corner neighbor 0 collected charge Edge neighbor (diffusion collected charge)

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Ronald Lipton

Pulse Shapes - 200 micron detector Χ-ray 2D Simulation

8

2ns 2ns 2ns 2ns z=10 z=190 z=100 Central Electrode z=10 z=100 z=190

Central = n n+1 n+2 n+3

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Ronald Lipton

h Entries 25 Mean 104.5 Std Dev 0.0204 / ndf

2

χ 0.4421 / 2 Constant 2.457 ± 9.179 Mean 0.0 ± 104.5 Sigma 0.00445 ± 0.02177

104 104.2 104.4 104.6 104.8 105 2 4 6 8 10

h Entries 25 Mean 104.5 Std Dev 0.0204 / ndf

2

χ 0.4421 / 2 Constant 2.457 ± 9.179 Mean 0.0 ± 104.5 Sigma 0.00445 ± 0.02177

Timing histogram

E1

X-Ray With Noise at 185/200 micron depth

Apply a constant threshold of E1~10 mV, E4~130 mV
Tabulate time at threshold crossing including noise
Edge pixel can provide a “start” time stamp if needed

9

Edge pixel Edge pixel σ~ 30ps Central pixel Central pixel σ~ 22ps

730 mV 850 mV 720 mV

10 ns

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Ronald Lipton

Example - MIP in a 50 micron Detector

10

h Entries 26 Mean 102.3 Std Dev 0.01593 / ndf

2

c 0.6285 / 1 Constant 3.24 ± 12.34 Mean 0.0 ± 102.3 Sigma 0.00311 ± 0.01657

102 102.1 102.2 102.3 102.4 102.5 102.6 102.7 2 4 6 8 10 12

h Entries 26 Mean 102.3 Std Dev 0.01593 / ndf

2

c 0.6285 / 1 Constant 3.24 ± 12.34 Mean 0.0 ± 102.3 Sigma 0.00311 ± 0.01657

Timing histogram

σ~16ps σ~25 micron pitch, 50 microns thick 200 V, sensor potential distribution Pulse on central pixel

2ns

Amplifier output with noise, 20ff load Threshold

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Ronald Lipton

Comments

The 20-30 ps resolution will be degraded in a real system However:

All pixels with spacing small compared to depth will have similar signals ~ 16

pixels for a 25x200 micron sensor x 4 in (uncorrelated) time resolution

The central pixel will see a large signal within a few ns of the leading edge -

initial thresholds can be set low and signals latched only if a central pixel fires at a higher threshold

The pattern of pixels will provide depth and slope information
Multiple thresholds or more sophisticated processing can give a time walk

correction

These results are for n-on-p with maximum field at the top. n-on-n sensors

have a maximum field at the bottom. The field profiles can be adjusted to suit the application by varying the applied bias

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Ronald Lipton

Pattern Recognition

Collider based experiments have to   deal with increasingly complex events

HL LHC with ~200 interactions per

crossing

The CMS experiment is addressing this with stacked sensor arrays to

distinguish low from moderate momentum tracks

Can we do this in a single sensor?
Muon collider experiments with huge decay backgrounds
Muon collider studies use timing - fall x 100 short
Backgrounds are from various absorber surfaces/angles
We can use the pattern of electrode signals to distinguish between

signal and background tracks signatures To get a feeling for this we use a 25 micron pitch electrode geometry in a ~300 micron thick sensor.

12

CMS “Pt module”

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Ronald Lipton

Charge Motion Visualization

13

.1 ns 2 ns 1.5 ns 1.0 ns .5 ns 2.5 ns

electrons holes

30 degree track, n on n, maximum field at bottom.

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Ronald Lipton

MIPs at various angles

14

0 Deg 30 Deg 20 Deg 10 Deg 10ns 10ns 10ns 10ns Current (Arb. Units) Current (Arb. Units) Current (Arb. Units) Current (Arb. Units) Transient time. Transient time.

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Ronald Lipton

Time resolution and Pattern Recognition

15

E2

0.00E+00 2.00E-06 4.00E-06 6.00E-06 8.00E-06 1.00E-05 1.20E-05 1.40E-05 0.00E+00 2.00E-09 4.00E-09 6.00E-09 8.00E-09 1.00E-08 1.20E-08 1.40E-08

E4

1ns Iin 2ns

0.00E+00 2.00E-07 4.00E-07 6.00E-07 8.00E-07 1.00E-06 1.20E-06 1.40E-06 1.60E-06 1.80E-06 2.00E-06 0.00E+00 2.00E-09 4.00E-09 6.00E-09 8.00E-09 1.00E-08 1.20E-08 1.40E-08

Electrode 6

Iin 2ns 1ns

Long drift

some collected charge
dominated by induced current
difficult to measure secondary peak

Medium drift

Dominated by collected charge

Short drift

collected charge similar

to induced current

Induced and collected

signals merge

E4 E6

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Ronald Lipton

A look at angular resolution

To try to get a feeling for what time and pulse

height resolution is needed we look at 10 and 20 degree tracks

1 nanosecond rise time is assumed
Lowest threshold defines time resolution and

provides induced   current t0

Other thresholds provide time structure and shape
f secondary peak

16

1.00E-06

0.00E+00 1.00E-06 2.00E-06 3.00E-06 4.00E-06 5.00E-06 6.00E-06 0.00E+00 5.00E-09 1.00E-08 1.50E-08 2.00E-08 Sig (Arb Units) Time (sec)

20 Deg Track

E2 E3 E4 E5 E6

1.00E-06

0.00E+00 1.00E-06 2.00E-06 3.00E-06 4.00E-06 5.00E-06 6.00E-06 0.00E+00 5.00E-09 1.00E-08 1.50E-08 2.00E-08 Signal (Arb Units) Time (Sec)

10 Degree Track

E2 E3 E4 E5 E6

0.00E+00 2.00E-07 4.00E-07 6.00E-07 8.00E-07 1.00E-06 0.00E+00 5.00E-09 1.00E-08 1.50E-08 2.00E-08 Sig (Arb Units) Time (sec)

20 Degree Track

E2 E3 E4 E5 E6

ToT end Threshold ToT start Threshold

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Ronald Lipton

Time over Threshold

This simple case seems to work, time stamps reflect pulse shape
Slope indicates difference in charge drift among electrodes
Clear cutoff in signal for 10 degree track
Consistent start times (particle impact at 1 ns)

17

300ps error bars to

guide the eye 1E-09 2E-09 3E-09 4E-09 5E-09 6E-09 7E-09 8E-09 9E-09

60
40
20

20 40 60 Time (Sec) Electrode Position (microns)

Time over threshold

20 Deg Tend 20 Deg, Tstart 10 Deg, Tstart 10 Deg Tend

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Ronald Lipton

Comments

Patterns of hits on pixels in “thick” detectors can provide a wealth of information - but the devil is in the details

S/N and bandwidth are crucial
Information is in the first 10 ns
This means power
The more information about the waveforms the better
Time over Threshold (TOT) with multiple threshold points
Requires transresistance amplifier
Simple diode arrays are more radiation hard than LGADs, but radiation will

affect internal fields and charge collection

We also need to process and transmit that information - this implies

“intelligent” pixels where the information in a field of pixels can be processed and decisions made

18

σ t ~ CL gmta ta

2 + td 2

Signal f ~ gm gm ∼ Id

SLIDE 19

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Ronald Lipton

More Work (for someone …)

This work is very much at a conceptual stage Details will need to be understood to validate the concept and understand it’s range of application To Do:

Define an overall toy->serious algorithm
What is the angular resolution as a function of bandwidth?
How do Landau fluctuations affect the reconstruction?
What is the overall time resolution?
Implement a realistic transimpedance amplifier in 65 nm and access power

requirements

Re-acquire hybrid bonding technology for sensor/readout integration
Access optimal detector thickness and depletion fields

Build something

19

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Ronald Lipton

Prospects

Fast timing in small pixels and thin detectors - most technologies have been demonstrated

Thin sensors (8” wafers)
Time of arrival (demonstrated with LGADs)
fine pitch bonding (3D hybrid bonding)
Chip to wafer bonding (dead regions?)

The use of induced currents

Small signal/noise, large bandwidth
Power consumption
Assembly geometry and size
Data processing - intelligent pixels to

select hits around a central core

Data bandwidth

Vendors - The basic hybrid bonding technology is now licensed to several foundries (inc MIT-LL, Sandia, IZM), used in cell phone cameras many

20

VICTR& VIP& VIP& VIPIC& VIPIC&

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Ronald Lipton

Conclusions

I have discussed some possible applications of small pixels enabled by emerging technologies.

It is one way of addressing some of the extreme challenges of future

experiments (FCC, Muon Collider, EIC …)

Fast timing
Radiation hard
Complex event topologies
I have presented toy models without engineering detail

To do more, a specific application and real engineering is needed

What power is needed? Cooling mass? Support geometry
Amplifier/discriminator design
Design of the digital tiers
Area to be deployed? Coverage? Cost? - What Experiment?

21

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Ronald Lipton

Chip to Wafer

22

DBI bonding of ROICs (VICTR, VIPIC, VIP) to BNL sensor wafer

Expose TSVs, pattern Top aluminum Wafer-wafer 3D Bond Oxide bond Handle wafer Expose sensor side TSVs, pattern DBI structures DBI bond ROIC chips to sensor wafer (RT pick+Place) Grind and etch to expose top connections

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Ronald Lipton

Integrator Circuit

23

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Ronald Lipton

Implementation

24

25µ Digital tier processes a field of pixels

Analog electronics tier with discriminators timing and memory

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Ronald Lipton

Time resolution of a thick detector

We use the TCAD/SPICE simulation chain to model an x-ray in the thicker

detector going into a 65nm charge sensitive amplifier

25

Electrode 1 – small pulse, but fast rise Deposit at Z=185 – note scales are not equal Electrode 3 – Deposit at Z=25

Edge pixel peak at 25 mV, 2 ns 0 total charge collected Central pixel   peak at 1V, 12 ns 100ns 110ns

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Ronald Lipton

Pixel Capacitance

A detector with low capacitance can provide excellent time resolution:      Before this improvement is realized other effects will dominate including charge deposition

variations. Power considerations will limit front-

end current which will reduce transistor transductance        However with “spare” margin we can become more adventurous

26

y = 2E-18x2 + 1E-16x + 1E-15 5E-15 1E-14 1.5E-14 2E-14 2.5E-14 3E-14 20 40 60 80 100 120

200 Micron Thick Detector Farads/micron

σ t,pixel σ t,LGAD ∼ Cpixel CLGAD × 1 GainLGAD ≥102 × 1 20 ∼ 5

σ t ∼ 1 gm , gm ∼ Id

α

(α ~ 1)

TCAD Simulation TSV Test Structure

Pixel Pitch (microns) Capacitance (farads)

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Ronald Lipton

Hybrid Bonding Vendors (2019)

27

Vendor Wafer Diam Wafer-Wafer Die-Wafer TSV Sony

NHanced

8” ✓ ✓ ~1 um? Teledyne Dalsa 6”, 8” ✓ ~5 um Sandia 6”->8” developing ✓ no IZM 12” ✓ no ~5 um Raytheon 8” ✓

Tracking and Timing with Induced Current Detectors

Introduction

There has been increasing interest in fast timing as well as “intelligent” detector systems. I would like to present some ideas for alternate designs of such systems looking at how technology for silicon-based detectors might

We focus on capability enabled by new technologies that provide small pixels with low capacitance and sophisticated processing

Some Basics - time resolution

capacitance td and ta are the detector and amplifier rise times and gm is the input transistor transductance - related to input current, and A is a characteristic of the amplifier.

σ t ~ σ noise ∂V ∂t ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ ~ tr Noise Signal ⎛ ⎝ ⎜ ⎞ ⎠ ⎟

σ n

( )

gmta

σ t ~ CL gmta ta

Signal

More Basics - Signal Development

depends on work done by circuit. The charge induced on an electrode depends

charge and the electrode (Ramo’s theorem)

systems

current on an electrode depends on the velocity of the charge and the value of the effective “weighting” field

measuring elected, 0 V on others

zero - can we use them?

i = −q ! Ew × ! v Qs = idt = q ! Ew

∫ ∫

d! x Q

3D Integration and small pixels

Fermilab has been involved the development of 3D sensor/ASIC integration for almost a decade and have demonstrated (with industrial partners):

through silicon vias (TSV)

assembly is almost a factor of two lower than the equivalent conventionally bump bonded parts due to lower Cload

Methodology

We explore simple systems with various pixel sizes, detector thickness and pulse shapes

model

the electrodes

including noise

resulting output pulses

with defined bandwidth model with adjustable bandwidth

3D 9 pixel model

Simple Example - X-Rays

Suppose an application requires fast timing on high energy x-rays

but thin detectors imply low efficiency - can we use induced currents to achieve time resolution in a thick detector?

Pulse Shapes - 200 micron detector Χ-ray 2D Simulation

X-Ray With Noise at 185/200 micron depth

730 mV 850 mV 720 mV

Example - MIP in a 50 micron Detector

Comments

The 20-30 ps resolution will be degraded in a real system However:

pixels for a 25x200 micron sensor x 4 in (uncorrelated) time resolution

initial thresholds can be set low and signals latched only if a central pixel fires at a higher threshold

correction

have a maximum field at the bottom. The field profiles can be adjusted to suit the application by varying the applied bias

Pattern Recognition

Collider based experiments have to deal with increasingly complex events

crossing

distinguish low from moderate momentum tracks

signal and background tracks signatures To get a feeling for this we use a 25 micron pitch electrode geometry in a ~300 micron thick sensor.

Charge Motion Visualization

MIPs at various angles

Time resolution and Pattern Recognition

A look at angular resolution

Time over Threshold

Comments

Patterns of hits on pixels in “thick” detectors can provide a wealth of information - but the devil is in the details

affect internal fields and charge collection

“intelligent” pixels where the information in a field of pixels can be processed and decisions made

σ t ~ CL gmta ta

Signal f ~ gm gm ∼ Id

More Work (for someone …)

This work is very much at a conceptual stage Details will need to be understood to validate the concept and understand it’s range of application To Do:

requirements

Build something

Prospects

Fast timing in small pixels and thin detectors - most technologies have been demonstrated

The use of induced currents

select hits around a central core

Vendors - The basic hybrid bonding technology is now licensed to several foundries (inc MIT-LL, Sandia, IZM), used in cell phone cameras many

Conclusions

I have discussed some possible applications of small pixels enabled by emerging technologies.

experiments (FCC, Muon Collider, EIC …)

To do more, a specific application and real engineering is needed

Chip to Wafer

DBI bonding of ROICs (VICTR, VIPIC, VIP) to BNL sensor wafer

Integrator Circuit

Implementation

assembly is almost a factor of two lower than the equivalent conventionally bump   bonded parts due to lower Cload

Collider based experiments have to   deal with increasingly complex events

A detector with low capacitance can provide excellent time resolution:      Before this improvement is realized other effects will dominate including charge deposition

end current which will reduce transistor transductance        However with “spare” margin we can become more adventurous