Preparation of pixel module production
for the HL-LHC ATLAS ITkKoji Nakamura (KEK)on behalf of ATLAS Japan Itk group

21 March 2022

TCHoU meeting1

High Luminosity LHC (HL-LGC) -- schedule update

1 year longer Run 3
1.5 year delay of HL-LHC• High Luminosity LHC (HL-LHC) start in 2029 to take 10 times higher integratedluminosity (3000-4000fb-1) in 10 years.
– Center of Mass Energy will be 14TeV– Instantaneous luminosity after leveling is ~5x1034cm-2s-1• Requirement : No major degradation of performance upto 7.5x1034cm-2s-1 instantaneous luminositywith 200 multiple interaction per bunch crossing.
21 March 2022

TCHoU meeting2Inner Tracker (ITk) Layout
Type of sensors
Strip Detector
Pixel Detector

strip
Pixel

Layer 0

3D type

Layer 1Thin planar(100um)

Layer 2-4

Thick planar(150um)

η=2.4

Inner 2 layers can be replaced.

Layer 1-4
Planar : Quad module (single sensor)• Larger coverage area
– Pixel : current 2.7m2 ➔upgrade 8.2m2– Strip : current 34m2 ➔upgrade 165m2• Higher Forward coverage

Readout ASIC

– Current η<2.5 ➔ upgrade η<4.0– Better Pileup removal & background rejection

40mm20mm• For Layer 1-4, constructing Quad module– Size : 40mm x 40mm
– Single sensor with 4 Front End ASIC bonded.
21 March 2022

TCHoU meeting

20mm

40mm

3

Sensor and module design• Basic principle :– Backside is negative bias and n+ is ground.
– Detect electron-hole pairs created by ionizing energy
loss from MIP particle.

• Strip detector

AlSiO2– n+ can easily ground at the end of strip.
– Readout usually via “wire bonding” strips to thereadout ASIC.

• Pixel detectore- hee- hhn+P-stop

p Bulk-V
4 chip module– Electrode placed two dimensionally.
– To ground all pixels, high resistivity biasing grid isnecessary. (important for testing sensor alone)– Readout ASIC is connected by “bump-bonding”.
Our development is together with Hamamatsu Photonics K.K (HPK)
21 March 2022

TCHoU meeting4

Flex assembly and CTE mismatch• Module - Flex assembly– To read signal from ASIC, Flex Printed Circuit (FPC) is glued tothe module by Araldite 2011.
– Cooling TPG/CFRP will attach to the backside of ASIC.
– Then wire bond ASIC pad to FPC.

• CTE mismatch issue– Coefficient of Thermal Expansion (CTE) is different forsilicon/copper/Carbon.
•E.g. Silicon 2.6ppm/oC Copper 16.7ppm/oC

Assembly tool

– Huge bump stress during thermal cycling.
• During 10 years operation, expected 400 times TC from -45oC to40oC• Qualification : 100 cycle with -55oC to 60oC Temp range
This issue could be solved by “Parylene coating” of assembled module.
21 March 2022

TCHoU meeting5

Schedule of Production
PDR : Preliminary Design Review
FDR : Final Design Review
PRR : Production Readiness Review• Production has already started.
JFY20211212

JFY2022

345Sensor
Pre-Prod

Front End ASIC
ITKpix-v1 :pre-production
Full size chip
ITKpix-v2 :production
21 March 2022

789Sensor PRR

SensorFlip-chip &Module build

6JFY2023

10 11 1212345672022.11-2023.12
Sensor Production

Hybridization PRR

Final prototype
for CTE mismatch issue

Hybrid Pre-Prod2022.12-2024.10
Hybrid Production

Module FDR
FE PRR

Module Ass.
Site
qualificationModule Assembly Pre-Prod

ITKpix-v2 Eng. run
ITKpix-v1

ITKpix-v2
TCHoU meeting

6Schedule of Production
PDR : Preliminary Design Review
FDR : Final Design Review
PRR : Production Readiness Review• Production has already started.
JFY20211212

JFY2022

345Sensor
Pre-Prod

Front End ASIC
ITKpix-v1 :pre-production
Full size chip
ITKpix-v2 :production
21 March 2022

789Sensor PRR

SensorFlip-chip &Module build

6

JFY2023

10 11 1212345672022.11-2023.12
Sensor Production

Hybridization PRR

Final prototype
for CTE mismatch issue

Hybrid Pre-Prod2022.12-2024.10
Hybrid Production

Module FDR
FE PRR

Module Ass.
Sitequalification

Module Assembly Pre-Prod

ITKpix-v2 Eng. run
ITKpix-v1

ITKpix-v2
TCHoU meeting7Delivery of HPK Pre-production sensors• Delivered 124 good sensors by the end of Feb.
– First 20 good sensors have been diced.
– Remaining 104 sensor as wafer.

• In wafer :– 6 main quad sensor• 40mm x 40mm sensor for actual module– Test structure• Structure for quality assurance contains diodes, baby pixel, Strip andinter pixel capacitance structures.

Main sensor

P1
Test structure

1P3

2
3

56

P2
21 March 2022

4P4
TCHoU meeting8

Main sensor – Visual inspection• Visual capture

Metrology machine @ KEK– Example of a sensor with defectWith LED via micro scope

Without LED

Took pictures of all 6 sensors.
(without LED on)

21 March 2022

TCHoU meeting

9Main sensor – IV/CV measurement• CV measurement• IV measurement– 6 main sensors has been measured.
– KEK: 20oC RH<5%Requirement : Vdep<100V– 6 main sensors has been measured and comparedwith HPK measurement– KEK: 20oC RH<5% HPK : 23oC RH~40%
Requirement : Vbd>Vdep+70V
Active area :15.5 cm2

Ileak@Vdep+50V < 0.75uA/cm2

KEKHPK
Only sensor 1&2
delivered as goodAnalysis and comparison to HPK data still on going.
(but Vdep is clearly satisfied the requirement)
21 March 2022

Leakage current and Vbd agreed well

TCHoU meeting

2.8-2.9 nA/cm2
10

Test structure – Visual capture• Not required but took high resolution picture.
– Found that no-scratch mark in Test structure…
• Made feed back to HPK and will be improved in production

Baby pixel TS

Strip TS

Diode 5x5mm2

Diode 5x5mm2

Diode 5x10mm2Inter pixel TS

21 March 2022

TCHoU meeting11

Test structure – IV/CV measurement• IV measurement• CV measurement

D1 D3

D5

D2 D4

D6

Active area :D1-4 : 0.09 cm2
D5 : 0.24cm2

Leakage current is extremely low (~0.5nA)
May not be sufficient measurement…

Strange step at shoulder (probably due to edge effect?)
A bit hard to conclude Full Depletion voltage from this measurement.

3.5-4.4 nA/cm2
21 March 2022

TCHoU meeting

12Test structure – First CCE measurement• Measured one of strip TS by Alibava setup.

Wire bonded to PCB– Used 90Sr source with scintillator trigger.
– LandauMPV=47.53±0.42 ADC count ~8570±76 e– Smaller than expected. (due to inter strip capacitance?)

21 March 2022

TCHoU meeting13Bump stress during thermal cycling• CTE mismatch introduce stress to the Bump
• Checked bump connectivity after thermal cycle– Checked number of disconnected bumps as a functionof number of cycle. (subtracted initial failure)– Additional 5 modules are tested to increase statistics.
– No visible increase of bump delamination observed.

~3800pix
Additional 5 modules

Before irradiation
5 modules[-55,60]oC TC

Only one module has been tested at the time of Nov
Total 400x384 pixels (1.5e5)

Chip with Initial bump delamination

21 March 2022

TCHoU meeting

14

Irradiation test in March• CYRIC@Tohoku Univ.
– An irradiation facility with 70MeV proton beam (~1μA beam current).
• 3-5 hours for 3x1015neq/cm2 irradiation with (600nA beam)– This allows 2-3 pixel modules with Al plate at the same time(3% Eloss/module).
– Operated at -15oC temprature with dry N2 gas.
– Scanning over full pixel surface at irradiation.

• We had irradiation beginning of this month 28th Feb – 4th Mar)– Sensor Pre-production Quality assurance• Three main sensors and 4 test structures are irradiated.

Test Structure– Final module level testing before pre-production• Four modules are also irradiated– To check bump stress issue after irradiation– Especially Parylene performance after irradiation• One of 4 modules are irradiated with chip operation– We should know the radiation effect to the CMOS FET– Checked stability of regulator/reference voltage/ring oscillator
21 March 2022

TCHoU meetingMain Sensor

15

Some fresh results of module irradiation• Irradiated module with proper cooling system.

Regulator output voltage Beam off– Kept module temp ~-15oC• During irradiation chip was operated andmeasured various parameters.
– Ring Oscillator Frequency went down (15%)– Reference voltage going up (5%)

Regulator input voltage

Ring Oscillator Frequency
Reference voltage

Module oncooling plateTemperature [oC]

Module and box temperature

Time [dd:mm:hh]

21 March 2022

TCHoU meeting16Conclusion
Conclusion in November last year

• Pre-Production has started already– Production needs several parts to construct modules.
– 7% of Sensor production as first important parts haveavailable for quality check.
– Pre-production for the other parts and assembly startsoon.
Like engine of a car

JFY2022 will be busy year for full pre-production and assembly
21 March 2022

TCHoU meeting17

backup

21 March 2022

TCHoU meeting18

Thermal Cycle after irradiation• Only one module has performed
thermal cycle after irradiation so far.
– The number of disconnected bump havenot increased after TC– The result confirmed Parylene coating
effect is not changed even after irradiation.
– Need to increase statistics of the test.

21 March 2022

TCHoU meeting

After irradiation
1 module

19

Irradiation at CYRIC (28th Feb-)• Irradiation samples– Test structure (2x 2e15 and 2x 5e15)• 2x1015 : w5-TS-P2, w7-TS-P2• 5x1015 : w1-TS-P2, w3-TS-P2

Test Structure– 3D Test structure (2x 1e16 and 2x1.7e16)• 1x1015 : w9-PCM117, w13-PCM117• 1.7x1015 : w9-PCM634, w13-PCM634– 3D Single sensor (2x 1.7e16)– Main Quad sensor (3x 5e15)• 1x1016 : w9-I34, w13-S22• 1.7x1016 : w9-P43, w13-U42• 5x1015 : w7-P1, w7-P2 and w7-P3
No way to handle
without touching surface soft UBM…
Glued to PCB.
Main Sensor

Irradiated successfully except 2x1015 Test structure➔ Irradiation box broken and couldn’t continue irradiations.
Samples will be ready to pickup around 22nd March

21 March 2022

TCHoU meeting20

Itkpix-v1.1 irradiation with chip operation
Last time• Cooling– In previous irradiation we observed rapid temperature ramp
when chip LV turned on. →LV off after measurement.
– Better cooling system has been developed and successfully
operated with [-15,-10]oC temperature range!

21 March 2022

TCHoU meeting

21

MUX monitoring and Ring Oscillator frequency• VDDD/A rising due to Vref change.
• RO frequency going down. (50MHz/500Mrad)– C.f. in Xray irrad (about twice reduction..)– Quite consistent to what Maria saw in Birmingham
irradiation.

21 March 2022

TCHoU meeting22

Pick up
• Picked up all Test structures from w1, 3 ,5 and 7.
• Picked up all Quad sensors from w7.
• All are stored to gel-packs
Package send to institutew7

P3
P1w51 32 456P3

P3
P1

P1

P4

P4
P3

P4P2

w1
21 March 2022

P2

w3

TCHoU meeting

P2
w5P2
w7

w1

P1

P3
P1

P4P4w3w7
23

Shipment TS to testing institutes• each gel-pack contain P1,P3,P4– To Goettingen : w5-P1,P3,P4– To Dortmund : w1-P1, P3, P4– To IJC lab : w7-P1, P3, P4– Keep one at KEK : w3-P1, P3, P4

21 March 2022

TCHoU meeting24

Main sensor – Thickness and bow• Bow• Thickness– Hight measurement with Vacuumed
chuck on– Take average of height for points
scanned with 2mm steps (2D)

– Hight measurement without
Vacuumed chuck on
Graph2D

15105180

15170

10160

20180

170

5-15130-20120-15-10-50

51015170

160

0150

150-5140

180105150-515160
00-10-5140-10140-10-15

130-15130-20120-20120-15-10-50

51015-15-10sensor 2sensor
Graph2D 1
190

15180-50

51015sensor
3
Graph2D

Graph2D

20

Average ~157.5um

Graph2D

Graph2D
20

20

20

190

15180

20

190

15180

All sensors havequite similar shape10170

1010170

170
5160

55150
-50

0150

-5150
-5

140-10-10

140-15130-15120-20140-10130-15-20

160

160

0-15-10-50

5sensor 4

1015120-20-15-10-50

510sensor 515

130-15-10-50

51015120

sensor 6

Height differences are 20-35um after slope correction
Not within <25um specification(?) → may be ok since FC by HPKMatching to Specification : 150±15um
21 March 2022

TCHoU meeting25bow measurement results (height diff in um)
Q1

Q3

Q2

Q4

Q5

Q6

Max – top right

22.1

34.1

31.4

31.3

27.3

32.7

Max – bottom right

18.2

26.4

23.3

22.5

28.2

22.4

Max – top left

28.7

31.9

33.8

32.8

39.5

33.9

Max – bottom left

29.2

31.7

27.1

26.8

28.425.5

21 March 2022

TCHoU meeting26