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Abraham Gallas
V Jornadas sobre la participación española en futuros aceleradores lineales
Timepix Pixel Sensors Tracking & Timestamping for ILC
Outline
ILC environment and assumptions Detector design rationale ASIC (Timepix) Sensor thinning Low mass bump bonding Test beams with Timepix Next steps
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ILC in a nutshell
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e+ e- linear collider
Center of mass energy range 200-500 GeV
Peak luminosity 2 x 1034 cm-2 s-1
Bunch timing:• 5 pulses per second (5 Hz)• 1260, 2625, 5340 bunches per pulse separated by 180, 369, 500 ns
• power pulsing
• readout speed
14 mrad crossing angle
Background:• small bunches• create beamstrahlung → pairs
Hit density (#/mm2/BX)
Forward tracking detector
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Relevant physics processes with
particles emitted at small :
mostly e-, t, b- and c-jets
ILD's Forward Tracking Disks
The forward region 6° < < 30°: 0.1 rad < < 0.45 rad
0.9 < cos < 0.995
1.5 < | | < 3.
Detector design rationale
25x25 m pixel sensor instrumented with ROC derived from current Timepix (Timepix2-Timepix3)
Both ToT and ToA modes running simultaneously in each pixel
Time resolution of 10 ns or better ∼ (Timepix2 > 1.5ns
(25ns/16)) allowing time stamping (bunch tagging)
Full readout between pulses (5Hz) or every 100BX
Power cycling leading to a 70% reduction on the time the ROC is ON (Timepix2 45∼ W/pixel).
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The Medipix Chips
A philosophy of functionality built into the pixel matrix allows
complex behavior with a minimal inactive region
55 m square pixel matrix 256 by 256
3-side buttable
Configurable ‘shutter’ allows many different
applications
bipolar (h+ and e-)Silicon, CdZnTe, CdTe,
GaAs, Amorphous Silicon, 3D, Gas Amplification,
Microchannel Plates etc…
Timepix (2006)
sensor
Analogue amplification
Digital processing
Read-out ASIC
Timepix design requestedand funded by EUDET collaboration
Conventional Medipix2 counting mode remains.
Addition of a clock up to 100MHz allows two new modes.
Time over Threshold
Time of Arrival
Pixels can be individually programmed into one of these three modes
Time over Threshold
Threshold
Time Over Threshold counts to the falling edge of the pulse
Threshold
Time of Arrival
Time of Arrival counts to the end of the Shutter
Development history and future
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Medipix11m SCAMOS 64 by 64 pixels Photon Counting Demonstrator (1997)
Medipix2250nm IBM CMOS, 256 by 256 55m pixels Full photon counting (2002)
Analogue (ToT) and Time Stamping (ToA) (2006)Timepix
130nm IBM CMOSPhoton Counting, Spectroscopic, Charge Summing, Continuous Readout (2009)
Fast front end, Simultaneous ToT and ToA (2011)Timepix2
Medipix3
VELOpix
Timepix3CLICpix
130nm/90nm/65nmFuture LHCb readout – Data driven 40MHz ToT 12Gb/s per chip (2013)
130nm/90nm/65nmFuture Hybrid Pixel Time tagging layer for the LCD project (20??)
Timepix2 Main Requirements
Pixel size 55 µm x 55 µm
Pixel matrix array 256 x 256
Sparse readout YES
PC, TOA or TOT recorded simultaneously
YES (2 at a time)
Minimum detectable charge ≤ 500 e-
TOA resolution >1.5ns (25ns/16) 4bits (Gossipo3 style)
Peaking time < 25 ns
TOT resolution <5% channel to channel spread
Technology IBM 130nm DM 3-2-3
Power consumption <1.5W/cm2 (~45 μW/pixel) @1.2 V
Target floorplan 3 sides buttable and minimum periphery
TSVs possibility YES. Multi-dicing scheme as Medipix3
9
• Lots of different applications → Very demanding specs !
XAVIER LLOPART– CERN PH-ESE
Sensor thinning
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Timepix on SOI 150m
Collaboration with CNM to thin 2D-pixel (55x55 μm) sensor from 300 μm down to 200, 150, 100 μm, p-on-n & n-on-p
Read out with TimePix ASIC
Goal:• Measure resolution, efficiency, … thin sensor•Minimal guard ring design.•Production of module/ladder with 3 ASICs
55Fe
Low mass bump bonding
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Pixel detectors consist of a sensor chip and ROC which are connected with flip chip bumps. One of the current technologies (FC µ-bump):
20-30μm (SnPb, SnAgCu, SnAg, … )
40-… μm pixel pitch
For 55(25) μm pixel size adds 0.019(0.091) % Xo
Other technologies that can reduce considerably the material budget:
Solid-Liquid-Inter-Diffusion (SLID) Soldering:
55 μm pixel sensor: 0.0027 % Xo
25 μm pixel sensor: 0.013 % Xo
Carbon Nano Fiber (CNF) Interconnections (R&D stage):
55 μm pixel sensor: 0.00087 % Xo
25 μm pixel sensor: 0.0042 % Xo
• In SLID tin, indium or other metals with low melting point (MP) are capped on high melting point (MP) pads, because: 1. Creation of intermetallic compounds (IMC) with the pad metal.2. High planarity requirements of metal-metal bonding (e.g., Cu-Cu) are
compensated. • Solid-Liquid-Inter-Diffusion (SLID) soldering, AKA Transient-Liquid-Phase (TLP).
• Thin layer of solder turns completely into IMC ultra thin metallic joints!• After the first reflow the MP increases significantly and becomes thermally
very stable.• Cu-Sn-Cu structure is the most commonly used, and with an optimized
process Sn transforms to Cu3Sn in some minutes.
Solid-Liquid-Inter-Diffusion (SLID) Soldering
Beginning:
•Thick Cu pads and < 5 µm of Sn.•Bonding at 270 –
300 ̊C.
Step 1
•Sn reacts with Cu and creates IMC’s.•Cu6Sn5 phase grows in big scallops.
Step 2:•Cross-hatched Cu6Sn5 phase consumes the Sn aggressively.• Cu3Sn phase grows on at Cu
interfaces.
Step 3:•All Sn has been transformed to IMC’s. •Cu3Sn is taking over Cu6Sn5 and grows at the expense of Cu6Sn5 and Cu.
Step 4:•After long heating, the ductile Cu3Sn expands over the whole area and forms the a thin joint.
SAMI VAEHAENEN – CERN PH-ESE
Carbon Nano Fiber Interconnections
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• CERN has started a small project with Smoltek (Gothenburg, Sweden) to develop fine-pitch CNF interconnection technique for pixel chips.
• Goal is set at growing 5 µm – 10 µm long fibres on chips and joining them together.
• Electrical contacts will be tested with/without metal contacts.
• CNF’s would be ultra-low mass interconnections.
• Technology has prospects to be ultra-fine pitch capable.
• High planarity of ROC and sensor is required.
• First CNF forests have been deposited on CERN test vehicle chips.• Development plan has been made to improve the patterning resolution and to develop suitable
flip chip processes.
SAMI VAEHAENEN – CERN PH-ESE
Timepix Testbeams
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Six Testbeams with Timepix in 2009 and 2010
2009 Testbeam - Proving Timepix
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Timepix had not been used at all in a particle tracking application
We took the opportunity to run parasitically in three beam periods
Tested a 300 m standard silicon Timepix assembly and a DS3D assembly
Main Measurements:
Resolution vs. Angle
Resolution vs. Threshold
Resolution vs. Silicon Bias
Efficiency vs. Threshold
Efficiency vs. Bias
Timewalk
Three Testbeams in 2009
June 2009 : Medipix Testbeam3 days to demonstrate tracking
July 2009 : CMS SiBit beam periodTwo weeks – parasitic Timepix Telescope
2 Timepix2 Medipix~perpendicularNo DUT
2 Timepix4 Medipix~perpendicular300μm and 3D DUTsManual angle adjustment
August 2009 Timepix TelescopeAugust 2009 Timepix Telescope
4 Timepix, 2 Medipix planes in telescope
Symmetric positioning of planes around DUT
Telescope planes mounted at 9° around x & y to boost resolution
DUT position and angle controlled remotely by stepper motors
2.3m Track Reconstruction Error~100Hz track rate1 frame per second~100,000 tracks per measurement point~1.5 hours per point in SPS North Area
55μm
300μm
0o
Angled Planes to Boost Resolution
Hits that only affect one pixel have limited resolution (30μm region in 55μm pixel)
Tilting the sensor means all tracks charge share and use the ToT information in centroid, CoG calculations
0o ~10μm resolution9o ~4.2μm resolution
Indicative Timepix events
55μm
300μ
m
9o
2009 Results – Resolution Vs Track Angle
Resolution result from 2009 testbeam demonstrating resolution of a Timepix assembly and the performance of the telescope
Operating point of Telescope planes
Eta distributions
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Uncorrected
0o
incidence5o
incidence8o
incidence18o
incidence
1 pixel wide clusters2 pixel wide clusters 3 pixel wide clusters
Corrected
2010 Testbeam Activity
3 beam periods as main user Added Time Tagging System May
USB2 readout 300m Timepix and PR01 fine
pitch microstrip sensor (40μm) June
USB2 readout 150m Timepix and PR01 Strip
August RELAXD readout 3D irradiated Timepix, FZ, MCZ,
BCB strip, 150m Timepix and 300m Timepix
Not all data analysed yet so not too many results to show
2010 Timepix Telescope
6 pixel telescope planes angled in 2 dimensions to optimise resolution
Device Under Testmoved and rotated viaremote controlled stepper motor
Fine pitch strip detectorwith fast electronics LHC readout
2010 Telescope in Timepix DUT Configuration
Timepix ToT Tracking
Timepix ToT Tracking
Timepix DUT
Scintillators to set shutter length to e.g. 100 tracks
beam
Shutter Generator
In this configuration the telescope was optimized for running with a Timepix DUT
The USB2 readout allowed a 7 frame per second readout rate (700Hz track rate)
The all angled six Timepix telescope gives a ~2.0μm Track Extrapolation Error
Time Resolution for LHC readouts Asynchronous SPS beam not suited to LHC systems designed for 25ns bunch structure Implemented a TDC which with Timepix ToA mode gives us ~1ns per track time stamping Able to provide and record synchronised triggers to 40MHz readout systems (TELL1) Allows software reconstruction and analysis of asynchronous tracks
PR01 DUT Timepix ToT
Tracking
Timepix ToT Tracking
Timepix ToA Track Time Tagging Plane ~100ns
Scintillator Coincidence and TDC ~1nsLogic +
TDCSynchronized
Trigger
Telescope in Time Tagging configuration for LHCb Sensor Readout
beam
150μm Sensor Results
With a 150μm sensor the optimum resolution point is at twice the angle of a 300μm
The higher data rate allows a significant number of measurements to be taken
RELAXD Readout
High Resolution Large Area X-Ray Detector RELAXD readout from NIKHEF 50 frames per second over gigabit Ethernet
August 2010 Telescope – Timepix DUT
Cooled DUT Timepix ToT
TrackingTimepix ToT Tracking
RELAXD interface
RELAXD interface
RELAXD interface
RELAXD system allowed 55 frames per second readout (~2,500 tracks per second)Each 100,000 point measurement now takes 4 minutes
Eight angled Timepix tracking planes gives a ~1.67um Track Extrapolation Error
Closer tacking planes reduce multiple scattering effects
Cooling system
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To operate irradiated assemblies its necessary to cool the sensor to below 0oC
This system achieved a steady temperature of ~-5oC
Water Block
Sensor+ROC and Pyrolytic Graphite80W Peltier
Telescope Comparisons
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Telescope Pixel Resolution Time Tag Rate
Timepix 2009 55m 2.3m 100ns 100Hz
Timepix 2010 (May) 55m 2.0m ~1ns 350Hz
Timepix 2010 (Aug) 55m 1.7m ~1ns 2.8kHz
EUDET (Low res) 18m ~2m 100us 990Hz
EUDET (High res) 10m ~1m - 300Hz?
EUDET. Telescope
Next steps
Module0 construction (3-4 ROC) Minimal guard ring design Thinning of ROC (50μm) Thinning of sensor to 80 μm Bump bonding thin sensor on thin ROC Support structures (CVD)
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