Production of microstrip silicon sensors
for HL-LHC ATLAS ITk
22 March 2022, TCHoU Workshop
Shigeki Hirose (U. Tsukuba)
K. Kuramochi (Tsukuba), K. Hara (Tsukuba), Y. Hiemori (Tsukuba),
T. Ishii (Tsukuba), K. Nakamura (KEK), K. Saito (Tsukuba), K. Sato (Tsukuba)
and the ATLAS ITk Strip Sensor team

■ ATLAS experiment at LHC
44 m

25 m

Large Hadron Collider (LHC)• Circumference = 27 km• 𝑝𝑝 collision at 𝑠 = 13 TeV• Bunch per 25 ns• ATLAS detector– Targets high-𝑝T objects from decays of heavy particles– Severe environment of 𝑝𝑝 collisions due to QCD→ Track finding performance of ID is essential for any physics analyses

Shigeki Hirose, University of Tsukuba TCHoU Workshop 2022

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■ Upgrades for HL-LHC
Latest LHC scheduleToday• High-luminosity LHC starting in 2029

HL-LHC– Collect ~10x more data with ~3x higher instantaneous luminosity– The schedule was delayed by two years to allow all LHC experiments toabsorb delays in upgrade projects (largely due to COVID-19)
New muon chambers inthe inner barrel region
Our contributionsAll-silicon inner tracker(pixel + strip)

High Granularity Timing
Detector with LGAD
(𝜎𝑡 ~50 ps)

My talk
Next talk by K. Nakamura
Shigeki Hirose, University of Tsukuba TCHoU Workshop 2022

Better performancetrigger DAQ &electronics systems

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■ ATLAS ITk Strip
Short-strips(Inner two barrel layers)
20x ABCstar

Strip

2x HCCstar

AMACstar

DC-DC converter

Current microstrip detector (SCT)
volume in ATLAS~10 cm (1280 strips)

Surface# modules# channels

SCT
63 m2
4,088
(8,196 sensors)
6.3M

ITk Strip
165 m2
17,88860.2M• Huge silicon detector system!
Shigeki Hirose, University of Tsukuba TCHoU Workshop 2022

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■ Strip sensor production• 20,800 sensors are produced with 6-inch wafers– All strip sensors are produced by Hamamatsu Photonics K.K.
Main sensors
QC sites
14,450sensors

HPK

CERN
QA pieces

Cambridge
QMUL
PragueCarleton
Vancouver

QA sites
QA pieces KEK/Tsukuba

6,350
sensors

KEK

Birmingham
Ljubljana
PragueBarcelona

KEK/Tsukuba
Main sensors
UCSC

ModuleProduction
Sites

ModuleLoading
Sites

19 sites in total

8 sites in total• Sensors must pass all quality checks– Quality control (QC): basic inspection for all sensors– Quality assurance (QA): monitoring of radiation hardness• Tsukuba is in charge of both QC and QA in collab. with KEK
Shigeki Hirose, University of Tsukuba TCHoU Workshop 2022

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■ Strip sensor QC• Items to be measured in QC tests
KEKTsukuba

UCSC– Visual inspection (taking high-reso. photos)– Metrology (height measurement)– Electrical tests on strips– IV stability– Sensor thickness• QC procedures established during
Saito, JPS Fall 2020 (14pSF-7)
pre-production in 2020 K.T. Ishii,
JPS Spring 2021 (13aT3-3)– Our measurements are done at HPK→Sensors are delivered to UCSC for further tests• Sensor production has started in July 2021
– About 30% of the sensors have been measured / delivered• Measurements are done at the rate of ~20 sensors per day– Establishing stable "routine flow" was a key in the first year
Shigeki Hirose, University of Tsukuba TCHoU Workshop 2022

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■ QC machine at HPK• VI / metrology machine located at HPKCamera (Nikon D5600)

Auto-focus(for metrology)••Lens2x for VC
10x for metrology

XY stage

Shigeki Hirose, University of Tsukuba TCHoU Workshop 2022

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■ Results from pre-production

0.03mmScratch pad
AC pad98 mm

98 mm

Poly-Si resistors• Sensor photo for visual inspection– Possible to catch images of very fine structures• Metrology– Bowing is at most ~100 μm while < 200 μm is required

Shigeki Hirose, University of Tsukuba TCHoU Workshop 2022

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■ Electrical performance tests
Al short
Strip short

Pinhole(meaningless value)• Electrical performance checks for every strips– DC test: measure interstrip currents– AC test: measure coupling capacitance→ Tests are done by HPK• Good performance in general: defect rate is ~0.01%
Shigeki Hirose, University of Tsukuba TCHoU Workshop 2022

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■ Strip sensor QA
Test chip• Bias resistance• Interstrip
characteristics• Coupling capacitance• Punch-throughprotection• Oxide thickness

Main sensor

8×8 mm2 diode• I-V and C-Vcharacteristics
Mini sensor (1×1 cm2)
• Charge collection• Inspection for basic silicon properties after irradiation– Several structures (QA pieces) are formed on the wafer– Three structures are used for sensor production QA• We are in charge of proton irradiation– Irrad. up to 1.6×1015 neq/cm2  1.5×[total fluence at HL-LHC]
Shigeki Hirose, University of Tsukuba TCHoU Workshop 2022

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■ Irradiation @ CYRIC
Samples(attached ona G10 plate)Box containing
samplesProtonbeam

Protonbeam• Irradiation at CYRIC, Tohoku U.
– 70 MeV proton beam up to ~1000 nA– 10-20 QA pieces every ~6 months• Procedures well established– Hold samples on a G10 plate → Put them in the box (movable XY)– After irradiation, attach a sample onto the PCB with wire-bonding→ Measure basic parameters at KEK
Shigeki Hirose, University of Tsukuba TCHoU Workshop 2022

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■ Irradiation tests
Leakage current @ 8.4×1014 neq/cm2

Non-irrad.

-20℃-20℃Threshold(6250 e-@500 V)

Charge collection @ 1.6×1015 neq/cm2• 13 samples were irradiated at CYRIC in 2021
• Overall good performance was confirmed

T. Ishii, JPS Fall 2021 (17aT3-6)– All parameters are very stable (same for results from other QA sites)– Occasional issues such as early breakdowns are attributed to ourhandling and measurements→ Accumulating experiences to achieve more stable "routine"
Shigeki Hirose, University of Tsukuba TCHoU Workshop 2022

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■ Summary• ITk Strip is a key for successful physics programs atHL-LHC ATLAS– Huge silicon tracker with 165 m2– Production for >20,000 sensors has been launched in July2021!
– U. Tsukuba is strongly contributing to sensor QC/QA• Strip module production is also progressing– Many module sites have been qualified → Starting preproduction modules• The entire ITk will be ready by the middle of 2027
Shigeki Hirose, University of Tsukuba TCHoU Workshop 2022

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