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Monolithic Active Pixel Sensors (MAPS) Maria Elisabetta Giglio February 3, 2017 Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 1 / 39 Table of contents Introduction 1 Pixel sensors: key to solve complex

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Monolithic Active Pixel Sensors (MAPS)

Maria Elisabetta Giglio February 3, 2017

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 1 / 39

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Table of contents

1

Introduction Pixel sensors: key to solve complex events Pixel sensors in High Energy Physics (HEP) experiments

2

ALICE Monolithic Pixel Sensor The experiment Upgrade of the Inner Tracking System (ITS) Pixel Chip Technology Read Out Focus on ALPIDE architecture

3

pALPIDE prototype - Test Beam Results π− irradiation Neutron irradiation

4

Conclusions

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 2 / 39

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Introduction

Outline

1

Introduction Pixel sensors: key to solve complex events Pixel sensors in High Energy Physics (HEP) experiments

2

ALICE Monolithic Pixel Sensor The experiment Upgrade of the Inner Tracking System (ITS) Pixel Chip Technology Read Out Focus on ALPIDE architecture

3

pALPIDE prototype - Test Beam Results π− irradiation Neutron irradiation

4

Conclusions

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 2 / 39

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Introduction Pixel sensors: key to solve complex events

Silicon sensors

Solid state detectors High resolution for particle tracking Principle of operation analogous to gas ionization devices Low ionization energy (3.6eV to create an electron-hole pair)

  • gas detectors 15-40 eV per electron-ion pair
  • scintillators 400-1000 eV per photon

→ Better energy resolution and high signal High density and atomic number

  • Large energy loss in a short distance

→ Thinner detectors → Diffusion effect smaller than in gas detectors → Higher spatial resolution

High carrier mobility → Fast! High intrinsic radiation hardness

Figure: Scheme explaining the working principle

  • f a semiconductor as detector.

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 3 / 39

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Introduction Pixel sensors: key to solve complex events

Silicon Pixel Sensors

2D-matrix → unambiguous hits High granularity - Small pixel area

  • Low detector capacitance (≈ 1fF/Pixel)
  • Large signal-to-noise ratio (e.g. 150:1)

Small pixel volume → low leakage current (≈ 1pA/Pixel) High cost per surface unit (Large number of readout channels)

  • Large number of electrical connections
  • Large power consumption

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 4 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

Pixel detectors - Key to solve complex events

  • L. Musa - CERN (EMMI, GSI 11June, 2015)

Si Pixel detectors are high granularity detectors in a harsh environment close to the Interaction Point (IP) Position resolution down to few µm High track density region → Unambiguous hit info is necessary! High resolution for determination of primary and secondary vertex High interaction rate → fast readout High level of radiation

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 5 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

Pixel sensors - At the heart of the LHC Experiments

  • L. Musa - CERN (Schloss Waldthausen, Germany, August 2016)

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 6 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

The variety of pixel technology

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 7 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

The CMOS Technology

What is a CMOS?

Complementary Metal Oxide Semiconductors n-channel MOSFET (NMOS) p-channel MOSFET (PMOS) MOSFET= Metal Oxide Semiconductor Field Effect Transistor

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 8 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

The CMOS Technology

What is a MOSFET?

(Metal Oxide Semiconductor Field Effect Transistor)

Figure: Physical structure of the n-channel enhancement-type transistor.

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 9 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

The CMOS Technology

What is a MOSFET?

(Metal Oxide Semiconductor Field Effect Transistor)

Figure: The enhancement-type NMOS transistor with positive voltage applied to the gate.

pn-junctions between substrate and D and S, kept reversed biased VDS is always positive (3-terminal device by connecting B and S) VGS controls the current flow from D to S in the channel region The device is symmetrical respect with S and D

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 10 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

The CMOS Technology

What is a MOSFET?

(Metal Oxide Semiconductor Field Effect Transistor)

Figure: The enhancement-type NMOS transistor with positive voltage applied to the gate.

VGS = 0 2 back-to-back diodes in series between D and S No current conduction from D to S when a VDS is applied (very high resistance ∼ 1012Ω)

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 11 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

The CMOS Technology

What is a MOSFET?

(Metal Oxide Semiconductor Field Effect Transistor)

Figure: The enhancement-type NMOS transistor with positive voltage applied to the gate.

VGS > 0 Free holes are repelled from the channel, a carrier-depletion region is formed e− from n+ regions accumulate under the gate, an n-region is created An electric field develop from G and the channel, it controls the amount of charge in the channel (”filed-effect transistor”) VDS makes the current to flow, forming the n-channel

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 12 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

The CMOS Technology

What is a MOSFET?

(Metal Oxide Semiconductor Field Effect Transistor)

Figure: The enhancement-type NMOS transistor with positive voltage applied to the gate.

Threshold voltage Vt: VGS such that a sufficient number of e− accumulate to form a conducting channel Overdrive voltage: VOV = VGS − Vt →V across the oxide must exceed Vt for a channel to form!

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 13 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

The CMOS Technology

What is a MOSFET?

VGS > Vt enhances the channel (MOSFET conducts) small VDS: MOSFET as a resistance whose value is controlled by VGS

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 14 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

The CMOS Technology

What is a CMOS?

Fast switching characteristics → CPUs no ohmic resistors needed → low power easy to implement capacitors

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 15 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

Hybrid Pixel Technology

Hybrid Pixel Detector (currently used at LHC) Sensor based on silicon junction detectors Readout chip: ASIC - CMOS sub-micron technology (limited number of producers ∼ 10 world-wide) Sensor and front-end electronics in two separate Si chips and connected by bump bonds (complex and costly) Bump bonds limited to pitches of 30 − 50µm (input capacitance, power consumption)

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 16 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

Beyond Hybrid Pixel Detectors... How to design a CMOS particle detector?

Monolithic Active Pixel Sensors (MAPS)

Monolithic=single process Sensing part incorporated inside the ASIC! (signal processing inside the pixel) → high granularity typical dimensions 20 × 20µm2 Motivation to reduce cost, power, material budget, assembly and integration complexity

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 17 / 39

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Introduction Pixel sensors in High Energy Physics (HEP) experiments

Monolithic Pixel Sensors in Heavy Ion (HI) experiments

  • L. Musa - CERN (Schloss Waldthausen, Germany, August 2016)

Industrial development of CMOS imaging sensors and intensive R&D work within the HEP community! Several HI experiments have selected CMOS pixel sensors for their inner trackers!

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 18 / 39

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ALICE Monolithic Pixel Sensor

Outline

1

Introduction Pixel sensors: key to solve complex events Pixel sensors in High Energy Physics (HEP) experiments

2

ALICE Monolithic Pixel Sensor The experiment Upgrade of the Inner Tracking System (ITS) Pixel Chip Technology Read Out Focus on ALPIDE architecture

3

pALPIDE prototype - Test Beam Results π− irradiation Neutron irradiation

4

Conclusions

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 18 / 39

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ALICE Monolithic Pixel Sensor The experiment

The current ALICE detector

  • L. Musa - CERN (EMMI, GSI 11June, 2015)

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 19 / 39

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ALICE Monolithic Pixel Sensor The experiment

The current ALICE Inner Tracking System (ITS)

  • L. Musa - CERN (EMMI, GSI 11June, 2015)

6 concentric barrels, 3 different technologies 2 layers of silicon pixels (SPD) 2 layers of silicon drift (SDD) 2 layers of silicon strips (SSD)

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 20 / 39

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ALICE Monolithic Pixel Sensor Upgrade of the Inner Tracking System (ITS)

Physics motivation for upgrade

  • L. Musa - CERN (EMMI, GSI 11June, 2015)

Provide a characterization of QGP properties for a better understanding of QCD measurements of rare probes → High statistics (luminosity) required! → deal with the challenge of expected Pb-Pb interaction rates of up to 50kHz new high precision measurements → Coverage in pT as complete as possible (down to very low momenta) → Very accurate identification of secondary vertices from decaying charm and beauty → High standalone tracking efficiency Improve the resolution and the readout rate capabilities is fundamental!

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 21 / 39

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ALICE Monolithic Pixel Sensor Upgrade of the Inner Tracking System (ITS)

Upgrade objectives

  • 1. Improve impact parameter resolution by a factor of 3

Get closer to IP (position of the first layer): 39mm → 22mm Reduce x/X0/layer: ∼ 1.14%→∼ 0.3% (for inner layers) Reduce pixel size: 50µmX425µm → 28µmX28µm

  • 2. Improve tracking efficiency and pT resolution at low pT (Increase granularity)

6 layers → 7 layers silicon drift and strips → pixels

  • 3. Fast readout (study of new readout architectures): 1kHz→ 50kHz

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 22 / 39

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ALICE Monolithic Pixel Sensor Upgrade of the Inner Tracking System (ITS)

The new ITS Layout

  • L. Musa - CERN (EMMI, GSI 11June, 2015)

7-layer geometry based in CMOS Sensors r coverage: 23-400mm pseudorapidity: |η| ≤ 1.22 (90% most luminous region) 3 Inner Barrel Layers 4 Outer Barrel Layers Material/Layer: 0.3%X0 (IB), 1%X0 (OB)

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 23 / 39

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ALICE Monolithic Pixel Sensor Upgrade of the Inner Tracking System (ITS)

PIXEL Chip - General Requirements

  • L. Musa - CERN (EMMI, GSI 11June, 2015)

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 24 / 39

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ALICE Monolithic Pixel Sensor Pixel Chip Technology

A novel Pixel Chip Technology

CMOS Pixel Sensor using TowerJazz 0.18µm CMOS Imaging Process High Resistivity (> 1kΩcm) p-type epitaxial layer (18µm to 30µm) on p-type substrate Small N-well diode (2µm diameter) → minimize spread of charge over many pixels → minimize capacitance (∼ fF) (decisive for large S/N at low power) → large depletion volume Application of reverse bias voltage (−6V < Vbb < 0V ) to substrate to increase depletion zone around NWELL collection diode Deep PWELL shields NWELL of PMOS transistors to allow for full CMOS circuitry within active area

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 25 / 39

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ALICE Monolithic Pixel Sensor Read Out

Different Architectures

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 26 / 39

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ALICE Monolithic Pixel Sensor Read Out

Different Architectures

Pixel pitch: 28µmx28µm Event time resolution: < 2µs Power consumption: 39mW /cm2 Dead Area: 1.1mmx30mm Pixel pitch: 36µmx64µm Event time resolution: ∼ 20µs Power consumption: 97mW /cm2 Dead Area: 1.7mmx30mm ALPIDE and MISTRAL-O have the same dimensions (15mmx30mm), identical physical and electrical interfaces

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 27 / 39

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ALICE Monolithic Pixel Sensor Focus on ALPIDE architecture

ALPIDE-Principle of Operation

  • L. Musa - CERN (EMMI, GSI 11June, 2015)

Architecture In-pixel amplification In-pixel discrimination In-pixel (multi-) hit buffer In-matrix sparsification (less data to send, shorter time, lower power)

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 28 / 39

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ALICE Monolithic Pixel Sensor Focus on ALPIDE architecture

pALPIDE-1 - First full scale prototype

ALPIDE Full Scale prototype dimensions: 30mmx15mm Pixel Matrix: 1024 cols x 512 rows Final pixel pitch: 28µmx28µm Power consumption: ∼ 30mW /cm2 Interface pads over matrix Global shutter: triggered acquisition (200kHz) or continuous (int time < 10µs)

Figure: Picture of pALPIDE-1

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 29 / 39

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ALICE Monolithic Pixel Sensor Focus on ALPIDE architecture

Projected Performance of new ITS

  • L. Musa - CERN (EMMI, GSI 11June, 2015)

∼ 40µm at pT = 500MeV /c

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 30 / 39

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pALPIDE prototype - Test Beam Results

Outline

1

Introduction Pixel sensors: key to solve complex events Pixel sensors in High Energy Physics (HEP) experiments

2

ALICE Monolithic Pixel Sensor The experiment Upgrade of the Inner Tracking System (ITS) Pixel Chip Technology Read Out Focus on ALPIDE architecture

3

pALPIDE prototype - Test Beam Results π− irradiation Neutron irradiation

4

Conclusions

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 30 / 39

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pALPIDE prototype - Test Beam Results

Experimental setup-CERN PS, September 2015

  • M. Mager, ”ALPIDE, the Monolithic Active Pixel Sensor for the ALICE ITS upgrade”, Nucl. Instrum. Meth., A 824 (2016) 434-438

Telescope made of 6-7 planes of pALPIDE-1 sensors 3 reference planes DUT (Device Under Test) 2/3 reference planes

Figure: Photograph of the pALPIDE-1 indicating its splits. Figure: The pALPIDE-1 test beam telescope

set-up.

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 31 / 39

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pALPIDE prototype - Test Beam Results π− irradiation

Detection efficiency and Noise occupancy

  • P. Yang et al., ”MAPS development for the ALICE ITS upgrade”, JINST 10 (2015) no.03,C03030

Figure: Noise occupancy and detection efficiency of sectors of 1 to 3, beam test results by using a 6GeV π− source.

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 32 / 39

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pALPIDE prototype - Test Beam Results π− irradiation

Detection efficiency and Noise occupancy

  • P. Yang et al., ”MAPS development for the ALICE ITS upgrade”, JINST 10 (2015) no.03,C03030

Figure: Detection efficiency as a function of the hit position within the pixel of sector 1, beam test results by using a 6GeV π−

source.

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 33 / 39

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pALPIDE prototype - Test Beam Results π− irradiation

Residual and Cluster size

  • P. Yang et al., ”MAPS development for the ALICE ITS upgrade”, JINST 10 (2015) no.03,C03030

Figure: Residual and average cluster size of sectors of 1 to 3, beam test results by using a 6GeV π− source.

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 34 / 39

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pALPIDE prototype - Test Beam Results π− irradiation

Residual and Cluster size

  • P. Yang et al., ”MAPS development for the ALICE ITS upgrade”, JINST 10 (2015) no.03,C03030

Figure: Cluster size as a function of the hit position within the pixel of sector 1, beam test results by using a 6GeV π− source.

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 35 / 39

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pALPIDE prototype - Test Beam Results Neutron irradiation

Detection efficiency and Fake Hit Rate

Large operational margin with detection efficiencies well above 99% at fake hit rate significantly below 10−5 for several sensors!

  • M. Mager, ”ALPIDE, the Monolithic Active Pixel Sensor for the ALICE ITS upgrade”, Nucl. Instrum. Meth., A 824 (2016) 434-438

Figure: Detection efficiencies and fake hit rates of pALPIDE-1 (50µm thick chips) shown for different dies as well as before and

after neutron irradiation. Data is for sector 2 with a reverse bias voltage of −3V .

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 36 / 39

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pALPIDE prototype - Test Beam Results Neutron irradiation

Cluster size and spatial resolution

  • M. Mager, ”ALPIDE, the Monolithic Active Pixel Sensor for the ALICE ITS upgrade”, Nucl. Instrum. Meth., A 824 (2016) 434-438

Figure: On the left, cluster sizes and spatial resolution of pALPIDE-1 shown for different dies as well as before and after

neutron irradiation. On the right, cluster sizes dependent on impact point within 2x2 pixels (elementary layout cell). When particles hit the sensor at the center, the average size is below 2, rising to 3,5 in cases where the particle impinges the sensor at the corner of a pixel. Data is for sector 2 with a reverse bias voltage of −3V .

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 37 / 39

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Conclusions

Outline

1

Introduction Pixel sensors: key to solve complex events Pixel sensors in High Energy Physics (HEP) experiments

2

ALICE Monolithic Pixel Sensor The experiment Upgrade of the Inner Tracking System (ITS) Pixel Chip Technology Read Out Focus on ALPIDE architecture

3

pALPIDE prototype - Test Beam Results π− irradiation Neutron irradiation

4

Conclusions

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 37 / 39

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Conclusions

Conclusions

MAPS provides:

Very thin sensors and small pixels Reduced power consumption and integration time by an order of magnitude

Tests results of pALPIDE prototype are very promising!

DE above 99% and FHR much better than 10−5 Spatial Resolution ∼ 5µm

MAPS are used and considered for many upgrade projects Further optimisation is foreseen on

The collection electrode to reduce power and achieve lower charge detection threshold The pixel array readout circuit (AERD) to increase readout speed

→ Clearly the way to go in future!

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 38 / 39

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Conclusions

Thank you for your attention!

Maria Elisabetta Giglio Monolithic Active Pixel Sensors (MAPS) February 3, 2017 39 / 39