fbk ufsd3.2 & hpk2 lgad productionsfbk + hpk non-irradiated hpk irradiated comparison of fbk...

Siviero F., Arcidiacono R., Cartiglia N., Costa M., Ferrero M., Mandurrino M., Milanesio M., Sola V. Staiano A., Tornago M.Borghi G., Boscardin M., Dalla Betta G-F., Ficorella F., Pancheri L., Paternoster G., Centis Vignali M.

Characterization with a β-source setup of the FBK UFSD3.2 & HPK2 LGAD productions

37th RD50 Online Workshop, 11.20.2020

Outline

Siviero F. 37th RD50 Online Workshop , 20.11.2020 2

➢ The FBK UFSD3.2 & HPK2 productions

➢ Torino β-source setup

➢ Measurements of sensors for the CMS Encap Timing Layer:

○ FBK + HPK non-irradiated

○ HPK irradiated

➢ Comparison of FBK sensors with different active thicknesses: 35, 45, 55 μm

Outline






○ HPK irradiated


FBK UFSD3.2

Siviero F. 37th RD50 Online Workshop , 20.11.20204

● 5 wafers for ETL measured so far:○ 2 thicknesses○ 3 carbon doses○ Shallow and deep gain layer (GL)

Latest R&D production of LGADs for CMS ETLWafer thickness GL depth Carbon

4 45 μm shallow 0.4*A

7 55 μm shallow A

10 45 μm deep 0.6*A

12 45 μm deep A

14 45 μm deep A

FBK UFSD3.2





7 55 μm shallow A

10 45 μm deep 0.6*A

12 45 μm deep A

14 45 μm deep A

FBK UFSD3.2





7 55 μm shallow A

10 45 μm deep 0.6*A

12 45 μm deep A

14 45 μm deep A

Explore different doses around the optimal “A” dose defined with the previous UFSD3 production

FBK UFSD3.2





7 55 μm shallow A

10 45 μm deep 0.6*A

12 45 μm deep A

14 45 μm deep A

Introduce deep gain layer implant to improve radiation resistance → interesting to compare performances with the standard shallow GL

FBK UFSD3.2



● All sensors are 2x2 arrays with “safe” interpad design strategy → interpad gap = 65 / 70 μm



7 55 μm shallow A

10 45 μm deep 0.6*A

12 45 μm deep A

14 45 μm deep A


FBK UFSD3.2

Wafer VBD

4 250

7 300

10 375

12 385

14 300

● charge [fC] = Area [pWb] / 4700○ 4700 = board transimpedance

● All sensors deliver 15 fC ○ target charge for electronics

deep GL

No significant differences between deep and shallow GL

preliminary

HPK2


● 4 gain split:○ split 1,2 highly doped ○ split 3,4 less doped

● All splits feature deep GL, no carbon, 45μm active thickness

● All measured devices are 2x2 arrays with interpad design strategy “IP5” or “IP7” → interpad gap = 100 / 120 μm

Gain split thickness GL depth Carbon

1 45 μm deep NO

2 45 μm deep NO

3 45 μm deep NO

4 45 μm deep NO


HPK2

Split VBD

1 160

2 180

3 220

4 240

● Splits 1,2 heavily doped → operate at very low V

○ Particularly interesting for ATLAS as they are the most rad-hard

● Splits 3,4 are less rad-hard but with better performances when new

preliminary


HPK2

Split VBD

1 160

2 180

3 220

4 240

We focused in particular on split 4, since it has the best performance when new (it might be the most suited for ETL) → remaining splits will be measured soon

● Splits 1,2 heavily doped → operate at very low V

○ Particularly interesting for ATLAS as they are the most rad-hard

● Splits 3,4 are less rad-hard but with better performances when new

preliminary

Outline






○ HPK irradiated


Torino β-source setup - 1


● DAQ and Analysis are fully automated○ Based on UCSC DAQ software○ works with pyVISA

● Compact, easy-to-use○ can be mounted in < 1h

● Dark box for measurements at room temp● Fridge + dry air for cold measurements

Lecroy 9404HD 40 Gs/s

Dark box

CAEN HV

LV



● Sr90 source, can work down to -40°C○ 3.6 kBq → max activity allowed in our lab

● Telescope formed by DUT + Trigger

● Trigger placed below the DUT ensures that we trigger only on MIPs

○ Trigger: HPK1 1x3 mm^2 single pad DUT

Trigger

Beta trajectory

3D-printed structure for sensors alignment



● Sr90 source, can work down to -40°C○ 3.6 kBq → max activity allowed in our lab

● Telescope formed by DUT + Trigger

● Trigger placed below the DUT ensures that we trigger only on MIPs

○ Trigger: HPK1 1x3 mm^2 single pad

● “Santa Cruz” Read-out board made by Artel○ single channel○ x10 amplification (+ 20dB Cividec

broadband external amplifier)

DUT

Trigger

Beta trajectory

3D-printed structure for sensors alignment



● Analysis code partially based on UCSC one and adapted to our setup

● Important parameters for time resolution: signal amplitude, area (charge), ToA○ Signal amplitude: gaussian fit around sampled point with maximum V○ Signal area: take 10% and 20% on both rising / falling edge → linear interpolation to find

start and end time of the signal → Integral of the signal using Simpson's rule○ Time of Arrival: once time corresponding to signal maximum (Tmax) has been determined,

take the two sampled points closest to the xx% of the signal → linear interpolation to find the time corresponding to xx%

● Temporal resolution defined as σDUT = √(σ 2measured - σ

2Trigger)

○ σ measured is the std. deviation of ToA DUT - ToA Trigger

○ 20% CFD usually provides the best result

https://en.wikipedia.org/wiki/Simpson%27s_rule


Dry & Cold β setup● Commissioning of a cold setup started in September in

Torino● Commercial freezer that can work in the -10°C / -30°C range● Old setup:

○ Dry air provided by a commercial compressor → main issue: 30-50% humidity

○ Sensors can be measured, although it is not ideal○ Performed several measurements with no issue○ But, metal support of our beta source eventually rusted

because of the ice forming on it → we had to stop measurements and look for a better compressor

● New setup○ Same freezer but better compressor → <10% humidity

● Future setup○ Climate chamber (next year)

Outline






○ HPK irradiated


Resolution vs Bias


● All FBK sensors reached ~30ps● HPK split 1 and 2 cannot reach 30ps since bias voltage is too low: electrons drift velocity not yet saturated ● Noise is low for all sensors: 1.2 / 1.5 mV

All sensors are non irradiated and measured at room T (23°C)

deep GL

preliminary preliminary

Resolution vs Gain


deep GL

High gain in both productions


Resolution vs Gain


● HPK needs higher gain to reach 30ps as they are operated at lower V


deep GL

Resolution vs Gain


● HPK needs higher gain to reach 30ps as they are operated at lower V● Effect well visible comparing HPK split1 and split4: the gain required to reach a given resolution is higher

in sensors operated at lower V ( = lower E field → worse dV/dt )

increasing electric field


deep GL

Resolution vs Gain


● HPK needs higher gain to reach 30ps as they are operated at lower V● Effect well visible comparing HPK split1 and split4: the gain required to reach a given resolution is higher

in sensors operated at lower V ( = lower E field → worse dV/dt )

increasing electric field

A good time resolution is given by the interplay of high gain and high electric field → GL doping must be chosen

to optimize these two aspects


deep GL

Jitter


total resolution

● Estimated jitter = noise / (dV/dt)○ noise : RMS of the baseline○ dV/dt (slew rate): derivative of the signal rising edge, taken from 20% to 80%

jitter only


Jitter


● Total resolution vs Gain flattens around 30ps because of the Landau term ( σLandau )

total resolution

jitter only



Temperature scan

● We performed a temperature scan on both productions● For deep implants, the bias shift to reach 30ps is ~ 1V/1°C : ΔT = 55°C → ΔV = 55-60 V● We will measure a sensor with shallow GL soon

-10°C

- 30°C

23°C 23°C

- 30°C -10°C

ΔV = 55


Outline






○ HPK irradiated


HPK2 split 4 irradiated


● Tested sensors (all 2x2 arrays):○ split4 IP5 non-irr

○ split4 IP7 1.5e15 neq/cm2 → max nominal fluence foreseen for the inner part of ETL

○ split4 IP7 2.5e15 neq/cm2 → max fluence considering a x1.5 safety margin

● Measurements performed at -30°C, relative humidity ~40%

Expected radiation levels @ ETL

HPK2 split4 irradiated


● 12fC delivered @ 1.5e15 neq/cm2

● 7fC @ 2.5e15 neq/cm2

non-irr

1.5e15

2.5e15

preliminary



● Time resolution in the 30-40ps range up to a fluence of 2.5e15 neq/cm2

● Most irradiated device operated for many hours at 775V with no issues → good check of sensors stability

non-irr

1.5e15

2.5e15

non-irr1.5e15

2.5e15

preliminarypreliminary





non-irr

1.5e15

2.5e15

non-irr1.5e15

2.5e15

best CFD non-irr, 1.5e15 : 20%

2.5e15 : 40%






HPK2 split4 meets the ETL requirements!

non-irr

1.5e15

2.5e15

non-irr1.5e15

2.5e15


Outline






○ HPK irradiated


FBK UFSD3.2 → Thin sensors


● 2 additional wafers (not ETL) have been produced at FBK:

○ 25 / 35 μm active thickness○ only 35 μm considered here

Wafer thickness GL depth Carbon


6 35 μm shallow A

7 55 μm shallow A





● Tested sensors:○ W4 & W7 2x2 arrays



6 35 μm shallow A

7 55 μm shallow A





● Tested sensors:○ W4 & W7 2x2 arrays○ W6 single pad



6 35 μm shallow A

7 55 μm shallow A





● Tested sensors:○ W4 & W7 2x2 arrays○ W6 single pad

● Comparison performed only on pre-rad devices at room T



6 35 μm shallow A

7 55 μm shallow A

Performance of thin sensors


35um

55um45um

W6 is the 1st wafer comprising thin sensors manufactured at FBK→ designed for tracking at extreme fluences (see V.Sola’s talk), not optimized for timing

35um

45um

55um




35um

55um45um 35um

45um

55um

Wafer VBD

4 (45um) 250

6 (35um) 230

7 (55um) 300



Lower collected charge and VBD because of the smaller volume



35um

55um45um


35um

45um

55um

low noise and good gain, regardless the active thickness



FBK thin sensors: time resolution

W6 (35μm) reaches 28ps:

● Smaller σLandau because it is thin

● but, worse dV/dt:○ risetime similar to thicker device○ smaller V because capacitance is

higher (approx. 4.5pF instead of 3pF) → worse jitter

35um 55um45um

preliminary


FBK thin sensors: jitter

35um

55um

45um

total resolution

jitter only

● Estimated jitter = noise / (dV/dt)preliminary

Measurements of gain on thin sensors are still very preliminary → need further studies for a precise determination


FBK thin sensors: jitter

35um

55um

45um

total resolution

jitter only

● Estimated jitter = noise / (dV/dt)

● Compare total resolution and jitter and get the Landau term:

○ σLandau (35μm) = 25 ps

○ σLandau (45μm) = 28.5 ps


preliminary


FBK thin sensors: the Landau term

35um

55um

45um

● Estimated jitter = noise / (dV/dt)

● Compare total resolution and jitter and get the Landau term:


○ σLandau (45μm) = 28.5 ps


→ go thin to minimize Landau fluctuations25um

Summary & outlook


● The FBK UFSD3.2 & HPK2 productions have been extensively measured in Torino with a β-source setup:

Summary & outlook


● The FBK UFSD3.2 & HPK2 productions have been extensively measured in Torino with a β-source setup:○ FBK UFSD3.2 features different level of carbon and either shallow and deep GL → all sensors have good gain and

low noise, reaching 30ps time resolution

Summary & outlook



low noise, reaching 30ps time resolution ○ HPK2 features only deep-GL and no carbon: splits 3,4 work well when new, whereas splits 1 and 2 (heavily doped)

operate at too low V → GL doping must be carefully chosen to provide both high gain and high electric field

Summary & outlook





● UFSD3.2 & HPK2 have been measured at different temperatures:○ In sensors with deep GL, the bias shift to reach 30ps is ~ 1V/1°C

Summary & outlook






● HPK2 split4 irradiated up to a fluence of 2.5e15 neq/cm2 has been measured at -30°C○ It reached 40ps even at the largest fluence

Summary & outlook







● We measured 3 UFSD3.2 with different thicknesses (45, 35, 25 μm):○ First production of thin sensors by FBK → optimized for tracking, not for timing○ thin sensors reached 28ps, comparable with resolution of thicker sensors

Summary & outlook







● We measured 3 UFSD3.2 with different thicknesses (45, 35, 25 μm):○ First production of thin sensors by FBK → optimized for tracking, not for timing○ thin sensors reached 28ps, comparable with resolution of thicker sensors

● Measurement campaign will continue in the next months: irradiated FBK, remaining splits of irradiated HPK2, irradiated thin sensors

Thank You!

BACKUP



FBK + HPK Temperature scans: jitter

solid: total res

dashed: jitter only

23°C

23°C

-10°C

-10°C

- 30°C - 30°C



FBK + HPK Temperature scans

● Tested sensors:○ FBK UFSD3.2 W12, W10 (deep GL, carbon, 45μm active thickness)○ HPK2 split4

-10°C

- 30°C

23°C

23°C

-10°C - 30°C



FBK + HPK Temperature scans - 2

● Gain needed to reach 30ps is smaller at cold since the mobility is higher

-10°C

- 30°C

23°C

-10°C

- 30°C

23°C



HPK2 split4 irradiated - 2

low noise even in the most irradiated sensor, between 1.2 and 1.7 mV


fbk ufsd3.2 & hpk2 lgad productionsfbk + hpk non-irradiated hpk irradiated comparison of fbk...

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