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Timepix Pixel Sensors Tracking & Timestamping for ILC. V Jornadas sobre la participación española en futuros aceleradores lineales. Abraham Gallas. Outline. ILC environment and assumptions Detector design rationale ASIC (Timepix) Sensor thinning Low mass bump bonding

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Abraham gallas

Timepix Pixel Sensors

Tracking & Timestamping for ILC

V Jornadas sobre la participación española en futuros aceleradores lineales

Abraham Gallas


  • ILC environment and assumptions

  • Detector design rationale

  • ASIC (Timepix)

  • Sensor thinning

  • Low mass bump bonding

  • Test beams with Timepix

  • Next steps

Abraham Gallas

Ilc in a nutshell
ILC in a nutshell

  • 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)

Abraham Gallas

Forward tracking detector
Forward tracking detector

  • Relevant physics processes with

    particles emitted at small :

    mostly e-, m, 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.

Abraham Gallas

Detector design rationale
Detector design rationale

  • 25x25 mm 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 ∼45mW/pixel).

Abraham Gallas

The medipix chips
The Medipix Chips

bipolar (h+ and e-)

Silicon, CdZnTe, CdTe, GaAs, Amorphous Silicon, 3D, Gas Amplification, Microchannel Plates etc…

A philosophy of functionality built into the pixel matrix allows complex behavior with a minimal inactive region

Configurable ‘shutter’ allows many different applications

55 mm square pixel matrix

256 by 256

3-side buttable

Timepix 2006
Timepix (2006)

Timepix design requestedand funded by EUDET collaboration

Time over Threshold

Time of Arrival

Conventional Medipix2 counting mode remains.



Addition of a clock up to 100MHz allows two new modes.

Time over Threshold

Time of Arrival


Analogue amplification

Digital processing

Pixels can be individually programmed into one of these three modes

Time of Arrival counts to the end of the Shutter

Time Over Threshold counts to the falling edge of the pulse

Read-out ASIC

Development history and future
Development history and future

1mm SCAMOS 64 by 64 pixels

Photon Counting Demonstrator (1997)


250nm IBM CMOS, 256 by 256 55mm pixels

Full photon counting (2002)

Analogue (ToT) and Time Stamping (ToA) (2006)




130nm IBM CMOS

Photon Counting, Spectroscopic, Charge Summing, Continuous Readout (2009)

Fast front end, Simultaneous ToT and ToA (2011)




Future LHCb readout – Data driven 40MHz ToT 12Gb/s per chip (2013)




Future Hybrid Pixel Time tagging layer for the LCD project (20??)

Abraham Gallas

Timepix2 main requirements
Timepix2 Main Requirements

  • Lots of different applications → Very demanding specs !


Sensor thinning
Sensor thinning

  • 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

Timepix on SOI 150mm


Abraham Gallas

Low mass bump bonding
Low mass bump bonding

  • 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

Abraham Gallas

Solid liquid inter diffusion slid soldering

  • In SLID tin, indium or other metals with low melting point (MP) are capped on high melting point (MP) pads, because:

    • Creation of intermetallic compounds (IMC) with the pad metal.

    • 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.

  • 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.

Solid-Liquid-Inter-Diffusion (SLID) Soldering

  • Step 1

  • Sn reacts with Cu and creates IMC’s.

  • Cu6Sn5 phase grows in big scallops.

  • Beginning:

  • Thick Cu pads and < 5 µm of Sn.

  • Bonding at 270 – 300 ̊C.


Carbon nano fiber interconnections
Carbon Nano Fiber Interconnections (MP) are capped on high melting point (MP) pads, because:

  • 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.


Abraham Gallas

Timepix testbeams
Timepix Testbeams (MP) are capped on high melting point (MP) pads, because:

Six Testbeams with Timepix

in 2009 and 2010

Abraham Gallas

2009 testbeam proving timepix
2009 Testbeam - Proving Timepix (MP) are capped on high melting point (MP) pads, because:

Main Measurements:

Resolution vs. Angle

Resolution vs. Threshold

Resolution vs. Silicon Bias

Efficiency vs. Threshold

Efficiency vs. Bias


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 mm standard silicon Timepix assembly and a DS3D assembly

Abraham Gallas

Three testbeams in 2009
Three Testbeams in 2009 (MP) are capped on high melting point (MP) pads, because:

June 2009 : Medipix Testbeam

3 days to demonstrate tracking

July 2009 : CMS SiBit beam period

Two weeks – parasitic Timepix Telescope

2 Timepix

4 Medipix


300μm and 3D DUTs

Manual angle adjustment

2 Timepix

2 Medipix



August 2009 timepix telescope
August 2009 Timepix Telescope (MP) are capped on high melting point (MP) pads, because:

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

2.3mm Track Reconstruction Error

~100Hz track rate

1 frame per second

~100,000 tracks per measurement point

~1.5 hours per point in SPS North Area

Angled planes to boost resolution
Angled Planes to Boost Resolution (MP) are capped on high melting point (MP) pads, because:

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 resolution

9o ~4.2μm resolution

Indicative Timepix events

2009 results resolution vs track angle
2009 Results – Resolution Vs Track Angle (MP) are capped on high melting point (MP) pads, because:

Operating point of Telescope planes

Resolution result from 2009 testbeam demonstrating resolution of a Timepix assembly and the performance of the telescope

Eta distributions
Eta distributions (MP) are capped on high melting point (MP) pads, because:











1 pixel wide clusters

3 pixel wide clusters

2 pixel wide clusters

Abraham Gallas

2010 testbeam activity
2010 Testbeam Activity (MP) are capped on high melting point (MP) pads, because:

  • 3 beam periods as main user

  • Added Time Tagging System

  • May

    • USB2 readout

    • 300mm Timepix and PR01 fine pitch microstrip sensor (40μm)

  • June

    • USB2 readout

    • 150mm Timepix and PR01 Strip

  • August

    • RELAXD readout

    • 3D irradiated Timepix, FZ, MCZ, BCB strip, 150mm Timepix and 300mm Timepix

  • Not all data analysed yet so not too many results to show

2010 timepix telescope
2010 Timepix Telescope (MP) are capped on high melting point (MP) pads, because:

6 pixel telescope planes angled in 2 dimensions to optimise resolution

Fine pitch strip detector

with fast electronics LHC readout

Device Under Test

moved and rotated via

remote controlled stepper motor

2010 telescope in timepix dut configuration
2010 Telescope in Timepix DUT Configuration (MP) are capped on high melting point (MP) pads, because:

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

Timepix DUT


Timepix ToT Tracking

Timepix ToT Tracking

Scintillators to set shutter length to e.g. 100 tracks

Shutter Generator

Time resolution for lhc readouts
Time Resolution for LHC readouts (MP) are capped on high melting point (MP) pads, because:

  • 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

Telescope in Time Tagging configuration for LHCb Sensor Readout

Timepix ToA Track Time Tagging Plane ~100ns



Timepix ToT Tracking

Timepix ToT Tracking

Scintillator Coincidence and TDC ~1ns

Logic + TDC

Synchronized Trigger

150 m sensor results
150 (MP) are capped on high melting point (MP) pads, because: μm 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
RELAXD Readout (MP) are capped on high melting point (MP) pads, because:

  • High Resolution Large Area X-Ray Detector

  • RELAXD readout from NIKHEF

  • 50 frames per second over gigabit Ethernet

August 2010 telescope timepix dut
August 2010 Telescope – Timepix DUT (MP) are capped on high melting point (MP) pads, because:

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

RELAXD interface

RELAXD interface

RELAXD interface

Cooled DUT

Timepix ToT Tracking

Timepix ToT Tracking

Cooling system
Cooling system (MP) are capped on high melting point (MP) pads, because:

Water Block

To operate irradiated assemblies its necessary to cool the sensor to below 0oC

This system achieved a steady temperature of ~-5oC

Sensor+ROC and Pyrolytic Graphite

80W Peltier

Abraham Gallas

Telescope comparisons
Telescope Comparisons (MP) are capped on high melting point (MP) pads, because:

EUDET. Telescope

Abraham Gallas

Next steps
Next steps (MP) are capped on high melting point (MP) pads, because:

  • 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)

Abraham Gallas