Enhanced Lateral Drift (ELAD) sensors Charge sharing and resolution - - PowerPoint PPT Presentation

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Enhanced Lateral Drift (ELAD) sensors Charge sharing and resolution - - PowerPoint PPT Presentation

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Enhanced Lateral Drift (ELAD) sensors Charge sharing and resolution studies Anastasiia Velyka, Hendrik Jansen Pixel 2018 Taipei 13.12.2018 DESY-Strategy-Fund Position resolution Improving position resolution: Down-sizing the pitch

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Enhanced Lateral Drift (ELAD) sensors

Charge sharing and resolution studies Anastasiia Velyka, Hendrik Jansen Pixel 2018 Taipei 13.12.2018 DESY-Strategy-Fund

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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Improving position resolution:

  • Down-sizing the pitch
  • Disadvantages:
  • Increases number of readout channels
  • Potentially higher band width from detectors
  • Less area/logic on-chip per channel
  • Higher power dissipation
  • Charge sharing
  • Lorentz angle or tilted sensor

Position resolution

Silicon (p-type) electrons holes

n+ - pixel implants p+ - implant

ionizing particle track

2

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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Improving position resolution:

  • Down-sizing the pitch
  • Disadvantages:
  • Increases number of readout channels
  • Potentially higher band width from detectors
  • Less area/logic on-chip per channel
  • Higher power dissipation
  • Charge sharing
  • Lorentz angle or tilted sensor
  • Disadvantages:
  • Doesn’t work for thin sensors
  • Tilting increases material budget

Position resolution

Silicon (p-type) electrons holes

n+ - pixel implants p+ - implant

ionizing particle track

3

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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Improving position resolution:

  • Down-sizing the pitch
  • Disadvantages:
  • Increases number of readout channels
  • Potentially higher band width from detectors
  • Less area/logic on-chip per channel
  • Higher power dissipation
  • Charge sharing
  • Lorentz angle or tilted sensor
  • Disadvantages:
  • Doesn’t work for thin sensors
  • Tilting increases material budget
  • What else can be done?

Position resolution

Silicon (p-type) electrons holes

n+ - pixel implants p+ - implant

ionizing particle track

4

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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  • Charge collection between 2 strips in a standard planar sensor
  • Standard sensor design:
  • charge in the left part of pitch collected by 1st strip,
  • charge in the right part of pitch collected by 2nd strip.

Charge sharing

Towards the theoretical optimum of position resolution

x

Q1 Q2

x0 xn MIP position

n+ - pixel implants

Q

x x0 xn 100% 50% 0%

Q1 Q2

MIP position x

diffusion area

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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  • Charge collection between 2 strips
  • Standard sensor design:
  • charge in the left part of pitch collected by 1st strip,
  • charge in the right part of pitch collected by 2nd strip.
  • In an ideal case:
  • charge distribution between 1st and 2nd strip is linear → best charge sharing.

Charge sharing

Towards the theoretical optimum of position resolution

x

Q1 Q2

x0 xn MIP position

n+ - pixel implants

Q

x x0 xn 100% 50% 0%

Q1 Q2

MIP position x

Theoretical optimum

diffusion area

6

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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  • Charge carriers follow the electric field

lines.

  • Achieve improved position resolution of charged particle sensors
  • Induce lateral drift by locally engineering the electric field
  • Introduce a lateral electric field inside

the bulk.

Concept of an Enhanced Lateral Drift Sensor

Manipulating the electric field

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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  • Charge guiding areas created by adding higher doping concentration.

p-ELAD sensor

  • Lateral electric field is introduced by adding repulsive areas inside the bulk.
  • Implants constitute volumes with different values of doping concentration.
  • This allows for a modification of the drift path of the charge carriers by

adding p-n-p structure.

Enhanced Lateral Drift Sensor

Manipulating the electric field

MIP

Q1 Q2

n+ - deep implants p+ - deep implants

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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  • Parameters for simulation:
  • Width, depth of implants
  • Distance within/to next layer
  • Position/shift to neighbouring layer
  • Number of layers
  • Optimal doping concentrations for deep implants
  • Quasi stationary:
  • Solve electric field
  • Ramp voltage to the set value
  • Transient:
  • Poisson’s equation
  • Carrier continuity equations
  • Traversing particles or arbitrary charge distribution

TCAD simulations

Static and transient simulations in TCAD SYNOPSYS

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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TCAD simulations

ELAD geometry

  • deep p and n implants are located

in the sensor bulk

  • first and second layer are

located in the epitaxial part

  • f the sensor with a thickness 40 µm
  • TimePix3 geometry
  • pitch 55×55 µm
  • pixel implant size 20 µm
  • p-substrate, p-EPI, p-n-p structure→p-ELAD
  • n-substrate, n-EPI, n-p-n structure→n-ELAD

55 µm 150 µm 40 µm

p-spray readout electrode epi-zone deep n-implants deep p-implants p-bulk backplane

10 µm

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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  • Deep p+- and n+-implants create the lateral electric field in the bulk.

Electric field lines move to the centre. Standard Standard planar planar sensor p-ELAD sensor p-ELAD Repulsive areas for charge carriers. U = 400 V In the blue zones electrons move in the right direction, in the red - left.

TCAD simulations

Electric field simulations

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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TCAD simulations

Drift with MIP MIP MIP MIP MIP

  • In comparison to the usual design, with the same MIP position and applied voltage,

in the ELAD sensor the charge is shared between two strips. t = 0 ns t = 0.1 ns t = 1.2 ns t = 1.8 ns

  • The part of the charge created beneath the deep implants area changes the drift

path

  • It is collected by two electrodes

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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TCAD simulations

Drift with MIP: Standard planar sensor vs ELAD

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Standard planar sensor ELAD sensor

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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  • The collected charge as a function of the MIP incident position.
  • ELAD design gives an opportunity to tune the η - function close to the theoretical
  • ptimum.

TCAD simulations

η - function

400 V p-ELAD Standard Sensor Design

MIP MIP MIP MIP MIP

S T R I P

  • p-ELAD;
  • sum from 1st and 2nd

strip in p-ELAD.

  • standard sensor;
  • sum from 1st and 2nd

strip in a standard sensor.

  • theoretical optimum;

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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p-ELAD n-ELAD

  • The optimal voltage for the p-ELAD is in a range between 350V and 400V.
  • The optimal voltage for the n-ELAD is in a range between 300V and 350V.
  • High depletion voltage is an artefact of available background concentration of EPI.

TCAD simulations

η - function, Voltage scan

Vdep=240 V Vdep=260 V

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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Allpix2 simulations

Resolution studies

  • To To estimate the position resolution → AllPix2 simulations.
  • Allpix2 - generic simulation framework for silicon tracker and vertex detectors
  • Simulations with MC particles
  • Based on Geant4 and ROOT
  • Possibility to use TCAD electric field

y x 55 µm

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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Allpix2 simulations

Results for n-ELAD Deep implant concentration 3e15 cm^-3, V=300V

m] µ x%pitch [

10 20 30 40 50

m] µ y%pitch [

10 20 30 40 50 1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9

Cluster size in X as function of in-pixel impact position for dut

m] µ x%pitch [

10 20 30 40 50

m] µ y%pitch [

10 20 30 40 50 1.2 1.4 1.6 1.8 2 2.2

Cluster size in Y as function of in-pixel impact position for dut

cluster size x [px]

2 4 6 8 10

clusters

50 100 150 200 250 3 10 ×

Cluster size X for dut

cluster size y [px]

2 4 6 8 10

clusters

50 100 150 200 3 10 ×

Cluster size Y for dut

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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Deep implant concentration 3e15 cm^-3, V=280V, 290V, 300V 280V 290V 300V Residual 8.2 um 7.7 um 7.6 um

Allpix2 simulations

Residuals for n-ELAD

m] µ [

cluster
  • y
track

y

100 − 50 − 50 100

events

1000 2000 3000 4000

Residual in Y for dut

m] µ [

cluster
  • y
track

y

100 − 50 − 50 100

events

1000 2000 3000 4000

Residual in Y for dut

W

  • r

k i n p r

  • g

r e s s

m] µ [

cluster
  • y
track

y

100 − 50 − 50 100

events

1000 2000 3000 4000

Residual in Y for dut

W

  • r

k i n p r

  • g

r e s s W

  • r

k i n p r

  • g

r e s s

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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  • Ion beam implantation on to the wafer

surface (ISE, Freiburg).

  • Epitaxial growth process, a thin silicon

layer is grown on the wafer surface. Process temperature is approximately 1150°C (ISE, Freiburg).

  • Combination of implantation and

epitaxial growth is repeated three times. After the last epitaxial growth, the implantation for the readout electrodes is performed (CiS, Erfurt).

Production

New method

Wafer Deep implants Epitaxial layer Readout implants Back plane

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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  • Simulation of the effect from the epitaxial growth process.
  • The difference in sizes (less than 1 µm) of deep implants has a negligible effect on

a charge sharing between strips.

Production

Process simulations in TCAD

Boron implant, 1st temperature cycle Boron implant, 2nd temperature cycle Boron implant, 3rd temperature cycle Active Boron concentration after 1st, 2nd and 3rd temperature cycle as a function of depth

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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  • Ph implant in n-type silicon
  • n-type epi on the implanted silicon
  • Epitaxial process replaced the annealing process
  • Possible to reach the necessary deep implant concentration

Production

Epi process on implantation [um]

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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GDS

Pixel readout 1st deep implants layer 2nd deep implants layer 3rd deep implants layer Pixel readout ELAD design

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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Production

Wafer layout TimePix3 readout Strip readout Diode Small diode Test structure

  • Three types of sensors:
  • TimePix3 pixel sensor
  • strip sensor
  • diode
  • Sensors with different values of deep

implant concentrations are foreseen.

  • Wafers including the epitaxial layers but

excluding the deep implants will be produced.

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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  • Implementation of the 3D TCAD simulation

to the AllPix2

  • AllPix2 simulation
  • Creation of wafer layout files for

production (DESY + CiS)

  • Production of the prototypes
  • Flip chipping with TimePix3 sensor
  • Tests at DESY/CERN
  • Lab: IV, CV, TCT
  • Test beam

Summary & Outlook

Summary

  • Technologically challenging project (no one tried this before in HEP)
  • Try to reach theoretical optimum of position resolution
  • Interesting technology for future HEP detectors

Outlook

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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Thank you for attention!

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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Backup!

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| ELAD sensors | Pixel2018, Taipei | 13.12.2018 | Anastasiia Velyka

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TCAD simulations

Drift with MIP: Standard planar sensor vs p-ELAD

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Standard planar sensor p-ELAD sensor