FBK UFSD3.2 & HPK2 LGAD productionsFBK + HPK non-irradiated HPK irradiated Comparison of FBK sensors with different active thicknesses: 35, 45, 55 μm Outline Siviero F. 37th RD50

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


Documents

FBK UFSD3.2 & HPK2 LGAD productionsFBK + HPK non-irradiated HPK irradiated Comparison of FBK sensors with different active thicknesses: 35, 45, 55 μm Outline Siviero F. 37th RD50