1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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 : x 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

8. 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

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

10. 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

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

12. 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

13. 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

14. 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

15. 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