2nd Institute Of Physics, Georg-August-Universität Göttingen The Planar Pixel Sensor project Introduction IBL sensor candidates Selected R&D areas Dr. Jens Weingarten 2nd Institute Of Physics, Georg-August-Universität Göttingen 20/03/2017 5th "Trento" Workshop, University of Manchester

Planar Pixel Sensor Proposal R & D within the planar pixel proposal: slim edge sensors to reduce inactive area radiation damage in planar sensors bulk materials (n-in-n, n-in-p, DOFZ, MCz) simulation of sensor design and detector layout low threshold operation of FE readout low cost, large scale pixel production (interconnect technology) Participating institutes: CERN AS, Prague LAL Orsay LPNHE Paris Bonn University HU Berlin DESY TU Dortmund Goettingen University MPP and HLL Munich Udine University and INFN KEK IFAE-CNM Barcelona Liverpool University UC Berkeley and LBNL UNM Albuquerque UC Santa Cruz 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Planar Pixel Sensors Advantages Challenges mature technology standard processing (implantation and metallization) many qualified vendors of sensor-grade silicon high yield relatively low cost lots of research done experience with sensor design and optimization radiation hardness models Challenges trapping lowers signal charge after irradiation  increase bias voltage  need small-signal readout electronics increasing leakage current with fluence  need serious cooling  annealing reduces leakage current sensor edge usually conductive  need guardrings  significant inactive area Sensor specifications for IBL maximum bias voltage: 1000 V sensor thickness: 225 ± 25 mm coolant temperature: -30 C sensor temperature: -15 C sensor max. power dissipation: 200 mW/cm2 at -15 C edge width: 450 mm 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Charge Collection Efficiency Charge multiplication observe charge multiplication in highly irradiated strips and diodes (RD50) CCEs frequently exceeds 100% (especially thin sensors)  over a wide region, CCE is nearly linear function of bias voltage At projected IBL end-of-lifetime fluence (5x1015 neq/cm2) and 1 kV bias: 9ke- for 300mm sensor thickness 12ke- for 140mm sensor thickness  above 2x threshold  thin sensors: superior charge collection at high fluence less material 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Leakage Current Power dissipation can be reduced significantly through annealing ‘all annealing is beneficial annealing’  leakage current expected to be under control at -15 C 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Slim Edges Requirement: inactive width ≤ 450 mm reduce number of guard rings reduce guard ring width shift guard rings closer to (underneath) pixel implants reduced space allows for 10 – 14 guard rings  Vbr > 200 V after irradiation, even fewer guard rings necessary (~5)  200 – 100 mm seem feasible  trials underway to go to 100 – 50 mm using picosecond laser dicing 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

IBL Production Candidates Three candidate designs were sent to IBL management: conservative design (ATLAS-like), n-in-n: CiS slim edge design (~100 mm inactive edge), n-in-n: CiS thin sensors (~150 mm thickness), n-in-p: HLL Munich Additional productions: thin (~150 mm) n-in-p sensors: HPK thin (~200 mm) n-in-p sensors: Micron finish sensor production in August bump bonding until end of September testbeams and irradiation until Xmas 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Official Design A Conservative design goal is to resemble current ATLAS design as far as possible 13 (out of 16) guard rings, to stay within 450 mm  proven to be sufficient ATLAS Pixel sensor, outer guard rings cut off, before (top) and after (bottom) irradiation 450 um 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Official Design B Slim edge design minimize inactive edge by shifting guard rings underneath active pixel region  200 – 100 mm inactive edge achievable simulation shows uniform depletion of edge pixels first IV curves show standard behavior 100 um 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Production I PPS/RD50 production @ CiS dedicated IBL production @ CiS production finished, UBM being applied ~10 FE-I4 SC sensors each of conservative and slim edge design available ~6 4x1 FE-I4 MCM sensors available dedicated IBL production @ CiS 2x1 MCMs adopted as IBL baseline after previous submission new submission soon: 1 conservative, 1 slim edge MCM/wafer 2 conservative, 2 slim edge SC/wafer FE-I3 SCs, diodes and test structures expect production to be finished in september 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Official Design C Thin design Production II utilize advantages of thin sensors at limited bias voltage edge width 450 mm design validated with CiS n-in-p production of FE-I3 sensors thinning done using handle wafer  stable frame around thinned area additional passivation layer for improved HV protection of FE Production II 6” FZ n-in-p wafers, active thickness ~150 mm 5 wafers a 6 FE-I4 MCMs, 6 FE-I4 SCs, 2 FE-I3 SCs available for bump bonding early september 450 um SC FE-I4 SC FE-I4 SC FE-I4 SC FE-I4 2x2 FE-I4 2x1 FE-I4 SC FE-I4 SC FE-I4 2x1 FE-I4 2x1 FE-I4 2x1 FE-I4 2x1 FE-I4 2x1 FE-I4 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Additional Productions KEK with HPK: edge space in the longitudinal pixel direction of 0.450 mm 3 types (of 2x1 FE-I4 sensors) x 2 sensors/type/wafer 3 types of FE-I4 SCs x 2 sensors/type/wafer 6 types of FE-I3 SCs per wafer 320 μm and thinned (150 μm) wafers Delivery due in June (320 mm) and July (150 mm) Micron: 40 FE-I4 n-in-p SCs and 70 FE-I3 n-in-p SCs available for UBM 300 mm thick 2x1 MCM production with reduced edges planned later. 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Selected non-IBL activities 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Slim Edge II: Trench Idea Reduce leakage current by shielding cut-edge from high-field region produce trench using Deep Reactive Ion Etching thermally oxidize trench (anneal possible damage) fill trench with poly-silicon (mechanical stability) continue sensor processing cut very close to trench DRIE cut vary width vary width Trench p-stop Guard ring courtesy of IFAE/CNM Barcelona 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Slim Edge II: Trench Initial pixel production: Plan 6 different layouts produced 13 sensors were tested (≥1 of each type)  all types show high leakage current, but Vbd > 100 V  suspect low p-stop dose  no correlation of leakage current with distance cut – guard ring  trench effectively isolates active area from diced edge Plan Repeat production changing p-stop dose and punch-through bias structure. Start FE-I4 design. 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Device Simulation Charge multiplication Assumptions: Can reproduce trap-assisted band-to-band tunneling impact ionization Can reproduce ‘soft breakdown’ (‘escalation’) of leakage current CCE exceeding 100% at high bias voltages 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Low-Cost Production Handling Flip chip process no test steps before bare module assembly  less FE/module  good yield for rework less chips per module  bigger Fes (FE-I4 ≈ 4x FE-I3) Flip chip process reduce pick-and-place machine time use less precise flip-chip machine (DataCon) much faster, ~5 sec per die instead of 2 min minimum specs: 80 µm pitch, 40 µm bump diameter needs staggered bump pads to achieve 50 µm effective pitch bigger alignment marks, placed diagonally across FE area  test impact on sensor performance  evaluating usability of this machine 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

resistance measurement Low-Cost Production Bump bonding larger pitch would reduce cost significantly  try to increase pitch by staggering bump pads wafers with FE-I4 sized structures, both chip- and sensor-dummies are produced to explore possibilities with IZM resistance measurement Traces 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen

Thank you for your attention Further Activities Quite a few PPS institutes are here and will present their own work. Preview: Munich thin sensor production SLID interconnects on thin sensors through-silicon vias  more details in Annas talk KEK n-in-p strip and pixel sensors  more details in Nobus talk Liverpool charge collection in highly irradiated silicon  more details in Gianluigis and Tonys talks LAL device simulation  more details in Mathieus talk and many more Thank you for your attention 20/03/2017 Jens Weingarten, II. Institute of Physics, University of Goettingen