CERN & LAL contribution to AIDA2020 WP4 on interconnections: Pixel module integration using TSVs and direct laser soldering Malte Backhaus, Michael Campbell, Karola Dette, Heinz Pernegger, CERN PH Department Aboud Fallou, Maurice Cohen Solal, Evangelos Gkoukgoussis, Abdenour Lounis, Clara Nellist, Laboratoire de l’Accélérateur Linéaire, Orsay H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015

The standard pixel modules LHC Hybrid pixel modules are integrated like: Wire bonds are the weak link Oscillation in magnetic field Protection required or desired “To pot or not to pot” Limit on envelopes Require flex to be glued very precisely Access to bond area on FEIx limits the sensor active area (not 4-side buttable) FEIx Sensor Flex Wire-bond Stave surface H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015

Modules without wire-bonds Reverse sensor and FEIx order Flex to FEIx connection by TSV-last and re-distribution layer (RDL) Better controlled envelopes Flex to chip connection by direct laser soldering Sensor can be larger than FEIx size and is 4-side buttable No fragile wire bonds needed Sensor cooled directly by stave FEIx Sensor Flex Wire-bond Stave surface FEIx Sensor Flex Wire-bond Stave surface H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015

Enabling Technologies CERN plans to contribute to the development of new inter-connection and integration methods in WP4: TSV-last + RDL Connect chip M1 from front to back of chip RDL distributes all FEIx connections over full chip surface Do not need fine-pitch connections Power can be brought to chip at several places , not just on the edge Direct laser soldering for flex to FEIx connection Thin 2-layer Al flex No glue layer needed Connections are solder 1-by-1, module stays at RT Reworkable leti FEIx Sensor Flex Wire-bond Stave surface CEA-LETI H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015

Industrializing module assembly Die-to-Die assembly is tedious and expensive ~50% of module costs TSV and RDL allow to potentially explore the benefits of industrialized integration with cost & technical benefit Wafer-Die assembly High-yield sensor wafer paired with high-functionality ROC Wafer-Wafer assembly Thin ROC wafer is “fused” to sensor wafer H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015

Direct laser soldering Developed within the ALICS ITS project – is demonstrated & functional and now baseline for 10m2 of ITS assembly Flex is thin 2-layer Al on Kapton flex with Solder ball (200mm) inside which is melted by laser No module heat up & No thermal stress on module No glue is needed between flex and bare module Solder holds flex mechanically well in place P. Riedler, A. Di Mauro, A. Junique (PH-AID ALICE) 27 cm long 9 MAPS solder to flex (50 µm thick chips, 15x30mm2 each chip) H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015

AIDA2020 kick-off meeting 4/6/2015 LETI TSV+RDL Medipix & LETI developed TSV on Medipix IBM chip to allow for BGA assembly for buttable X-ray/particle detectors M.Campbell /CERN-PH – G.Pares / CEA-LETI Medipix specifications Design Test structures Wafer diameter: 200mm Wafer thickness: ~725um IC Technology: 130 nm / IBM Top Surface: Al + Nitride Chip size : 14100 x 17300 µm TSV per chip: ~100 TSV aspect ratio : 120:60 µm (MEDIPIX RX) 50: 40 µm (timepix3) Process Flow Wafer view Single chip H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015

AIDA2020 kick-off meeting 4/6/2015 TSV with LETI Second run processed 6 wafers of Medipix3rx : TSV yield ~ 70% to 80% Jerome Alozy / CERN and Gabriel Pares / LETI Before TSV After TSV TSV edge limit H. Pernegger AIDA2020 kick-off meeting 4/6/2015

LETI TSV-last process example H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015

LAL Orsay Contribution to WP4 TEAM :Aboud Fallou, Maurice Cohen Solal, Evangelos Gkoukgoussis, Abdenour LOUNIS, Clara Nellist, Laboratoire de l’Accélérateur Linéaire, Orsay History of relationships with LETI (# 2 years) Flip chipping at LETI FEI4 B + Sensor, Satisfactory results (prototype irradiated and Beam tests ..) Project LAL-LETI for 3D Tezzaron-Chip+ VTT Edgless Planar Pixel Sensor on going : It is a feasability study : Die-to-Die procedure. Results expected soon. Reasonable cost for instance, Good technical interactions and feed-back from LETI Now :Start With FEI4 , TSV + RDL The Ultimate Goal The Future: Build a demonstrator: 100 μm 150 μm or less TSVs module Bonding … front end chip (65 nm) back side front side sensor HV New (LETI Proprietary) Bump Bonding H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015

FEI4 Front and back metal options H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015

FEI4+TSV module project We plan to build over the project time a demonstrator based on FEI4 with TSV+RDL together direct laser soldering to thin Al-flex circuits This is done in tight collaboration between CERN, Glasgow, LAL and MPI to investigate this module concept and its technologies on TSV+RDL and laser soldering Developments for Alice ITS and MEDIPIX have laid the foundation for future developments in this direction by ATLAS ITK phase-2 module RD H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015

FEI4+TSV module project Main technologies development path with FEI4 as demonstrator Step-by-Step TSV+RDL Test wafer processing with TSV only (2 sacrificial wafers to allow LETI gain FEI4-TSV experience) Processing of 4 wafers with goal of ≥40 FEI with TSV+RDL Wafer test of FEI4+TSV followed by dicing Flip chip assembly to single-chip FEI4+planar sensor Step-by-step Flex + laser soldering Design of RDL + Flex Dummy RDL + Flex production and laser soldering tests Assembly of Flex+Dummy RDL to normal FEI4 to test flex design Assembly first FEI4+TSV to flex and electrical test Assembly and test of FEI4+TSV+sensor with flex If successful try on quad assemblies H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015

AIDA2020 kick-off meeting 4/6/2015 Summary We plan to devise a module integration concept without wire-bonds as technology driver for development of TSV on FEI4 with LETI and direct laser soldering for RDL to flex There is an excellent starting point for both technologies through the development of ALICE on laser soldering and of MEDIPIX for TSV with LETI The work will be carried out in tight collaboration between CERN, Glasgow, LAL & MPI We plan to design the specific TSV+RDL together with LETI for processing on present ATLAS Pixel chip FEI4b The goal are FEI4b based demonstrator modules with Sensor+FEI4 with TSV+ Laser soldered Flex H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015

AIDA2020 kick-off meeting 4/6/2015 TSV design on FEI4 Latest 72 wafers have exclusion zone for poly-si to ease contacts to M1 Cross-checking possible TSV design with LETI Exclude zone in the poly-silicon layer 50x50 mm2 designed for the new production of FE-I4 chips it excludes the filling structures but not the large 10x10 um2 poly squares A. Macchiolo / MPI H. Pernegger, A. Lounis AIDA2020 kick-off meeting 4/6/2015