development of radiation hard si detectors for the slhc...

Development of Radiation Hard Si Detectors for the SLHC Experiments and the European XFEL

Ajay K. SrivastavaAjay K. SrivastavaInstitute for Experimental Physics, Institute for Experimental Physics,

University of Hamburg, University of Hamburg, GermanyGermany

Work within CERN RDWork within CERN RD--50, Central European 50, Central European Consortium CEC (within CMS) and AGIPD Consortium CEC (within CMS) and AGIPD (@XFEL) Collaboration(@XFEL) Collaboration

TIFR seminar, Mumbai, India, 22.11.2010 1 Ajay K. Srivastava, Uni-Hamburg

• Introduction

OutlineOutline

I. CMS Upgrade Project (CERN RD50 and CEC within CMS): • Work performed within RD50 collaboration• Research and development of Si strixel detector for large radii of a new CMS tracking detector for the SLHC within CEC consortium• Neutron and mixed radiation damage model for MCz-n Si sensor

II.AGIPD Project at the European XFEL• Research and development of Adaptive Gain Integrating Pixel Detector (AGIPD) for the European XFEL

�� Experimental measurements on non-irradiated and irradiated test structures

* Gated diodes* CMOS capacitors & p+n Si microstrip detectors, n+n CMS pixel sensors

�� Synopsys-TCAD device simulation *Work done�� Comparision with experimental data (test structures, p+n Si

strip sensor) + simulation of n+n Si pixel sensors �� Optimization of rad-hard p+n Si pixel sensor design for AGIPD

�Conclusion (How to design rad-hard sensors on earth- a design idea)�Outlook

TIFR seminar, Mumbai, India, 22.11.2010 Ajay K. Srivastava, Uni-Hamburg 2

The RD50 Collaboration and The CEC ConsortiumThe RD50 Collaboration and The CEC Consortium

Aachen University, Germany Deutsches Elektronen-Synchrotron DESY, GermanyInstitut für Experimentalphysik, Universität Hamburg, GermanyUCL Louvain, BelgiumInstituto de Física de Cantabria (UC-CSIC), Santander, SpainInstitut für Hochenergiephysik der Österreichischen Akademie der Wissenschaften, HEPHY, Vienna, AustriaInstitute of Materials Science and Applied Research, Vilnius University, LithuaniaInstitute of Electron Technology, Al. Lotnikow 32/46, 02-668 Warsaw, Poland

9 European institutes (52 members)

The CEC Consortium within CMS - "for an R&D project to develop materials, technologies and simulations for silicon sensor modules at intermediate to large radii of a new CMS tracker for SLHC.”

- Specially for the SLHC experiment

Ajay K. Srivastava, Uni-Hamburg TIFR seminar, Mumbai, India, 22.11.2010 3

InnovationInnovation

LAr dark matter detector,Bubble chamber detector

LAr neutrinodetector

LHeC


�LHC (2009), L = 1034cm-2s-1

(14 TeV pp collider, 25 ns bunch spacing)

Φ(r=4cm) ~ 3·1015cm-2

LHC upgrade:

�Super-LHC (2019), L = 1035cm-2s-1

Φ(r=4cm) ~ 2.5·1016cm-2

~ 500 Mrad

- ~ 400 particles/track expected , high granularity detector with short length required with low material budget technology

• A new CMS tracker detector (pixel, short, and strip for small, intermediate and large radii) required for the LHC upgrade

� Detector for the European x-Ray Free-Electron Laser (XFEL) at Hamburg (start in 2014): photon fluxes up to: 1016 γ/cm2 ≙ 109 Gy [109 J/kg] ~ 1 GGY dose (220 ns distance between the pulses)

5 years

2500 fb-1

10 years

500 fb-1

×××× 8

Main Motivations for Present R & D on Radiation Main Motivations for Present R & D on Radiation Tolerant Si DetectorsTolerant Si Detectors


•Why Si detectors for particle tracking in High-Energy Physics Experiments?

1. Fast response 2. High position resolution (~10µm) 3. Reliable operation

•Types: I. Si strip detector (single sided/double sided)II. Si pixel detectorIII.Si pad detector

Si Detector Si Detector for Different Radiifor Different Radii

Strip detector Pixel detector Pad detector


• Depletion depth and full depletion voltage

• Reverse current = generation current

• Detector capacitance

• Noise (S/N)

• Charge collection

• Interstrip resistance

� Relevant Parameters of Radiation Hard Si Sensors for SLHC

Working Principle of Si Strip DetectorWorking Principle of Si Strip Detector

� Requirement for Radiation Hard Sensors:Less full depletion voltage – choice of Si materials & thin/thick Si sensorLess reverse current - cool down to lower temperatureNo breakdown up to operational time – design should be properly optimizedSufficient charge collection – choice of materials and device design


Si Detectors: Technology DevelopmentSi Detectors: Technology Development

n in pn in p TechnologyTechnology

n in n Technologyn in n Technology Epitaxial (p in n) TechnologyEpitaxial (p in n) Technology

DSSD TechnologyDSSD Technology


� Bulk (crystal) damage due to Non Ionizing Energy Loss (NIEL)

- displacement damage, crystal defects/microscopic defect

I. Change of effective doping concentration Neff

(higher full depletion voltage Vfd)

II. Increase of leakage current (increase of shot noise, thermal runaway)

III. Increase of charge carrier trapping (reduced charge collection efficiency (CCE))

� Avalanche multiplication effect (CCE>1), Type inversion effect (DJ/SCSI)

� Surface damage due to Ionizing Energy Loss (IEL)I. Charge build-up in SiO2

(Nfixox) (shift of flatband voltage Vfb,+

II. Traps of Si-SiO2 interface

(Nit/Dit) breakdown of critical corners)

III Surface generation current (increase shot noise)

Macroscopic Radiation Damage in Silicon DetectorsMacroscopic Radiation Damage in Silicon Detectors


trapping (e and h)⇒⇒⇒⇒ CCE

shallow defects do not contribute at room temperature

due to fast detrapping

charged defects ⇒⇒⇒⇒ Neff , Vdep

e.g. donors in upper half of band gap and

acceptors close to midgap

generation⇒⇒⇒⇒ leakage current

levels close to midgap

most effective

• Influence of defects on the material and device properties

Radiation Induced Defects and Impact on Radiation Induced Defects and Impact on Device PerformanceDevice Performance� defects in the crystal� point defects and “cluster” defects� energy levels in the band gap filled


Effect of Microscopic Defects on Macroscopic Effect of Microscopic Defects on Macroscopic ParametersParameters


CERN RD50: Strategies to Develop Radiation Hard CERN RD50: Strategies to Develop Radiation Hard Si Detector Si Detector

I. Material/Defect engineering

� Understanding of radiation damage

• Irradiation with different particles and energies• Thermal treatment to understand kinetics• Macroscopic effects to understand detector performance• Microscopic defects and TCAD simulation

� Improved sensor performance with oxygen rich material

� Study different materials (FZ) : DOFZ, Cz, MCz, EPI-Si

II. Device Engineering

� TCAD Simulation and study of prototype detectors• n+- in- p*

• 3D detectors**

• Thin detectors*** ..

TIFR seminar, Mumbai, India, 22.11.2010

* No type inversion, sufficient CCE (e collected), less trapping

** Less Vfd (<10 V), less charge collection time (<5 ns) ..

*** higher charge collection (higher multiplication effect, less Vfd, less leakage current!..)Ajay K. Srivastava, Uni-Hamburg 13

� experiments will be exposed to both charged hadrons and neutrons

� small radii: pion dominated� large radii: neutron dominated

� will damage simply add up?� will Vfd, CCE and leakage current behave the same?

Mixed Irradiations:Mixed Irradiations: neutrons and protonsneutrons and protons

� What happens after mixed irradiation in MCz-n Si? – space charges, electric field, and charge carrier trapping inside Si sensor? Can we understand the result from TCAD commercial device simulation program?

For the RD50 collaboration


Φeq

=κpΦ

p+κ

nΦ

n

G. K

ramberger et al., N

IM A609 (2

009), 14

2-14

8

� leakage current increases in accordance with received Φeq

� FZ: damage accumulated

� MCz-n: damage compensated � MCz-p: damage not compensated

� donors introduced in p irradiation (E(30K)) compensated by acceptors introduced in n

irradiation (H(152K))� ηeff E(30K)? in MCz-n Si

� Exposure of FZ & MCz silicon PAD sensors to:• First step: Irradiation with protons or pions

• Second step: Irradiation with neutrons

Irradiations: Change of NIrradiations: Change of Neffeff



Ajay K. Srivastava, Uni-Hamburg 15

Collection in MCzCollection in MCz--n and MCzn and MCz--p Si Sensorsp Si Sensors

� CCE anneal for MCz-n Si with sufficient charge collection, a promising candidate for SLHC tracking detector� CCE do not anneal for MCz-p Si and sufficient collected most probable charge (e collected, no type inversion) MCz-p Si as a viable option under study within RD50 collaboration

G. K

ramberger et al., N

IM A609 (2

009), 14

2-14

8

A. Affolder, et al., Nucl. Instr. and Meth. A, in press, doi: 10.1016/ j.nima.2009.08.005, 2009.

G. Casse, et al.,” Nucl. Instr. and Meth. A 581, pp. 318-321, 2007.




[J.Lange et al., 14th RD50 Workshop, June 2009]•Epi diodes, 75 and 100µm thick•Trapping probability:

• proportional to fluence• consistent with FZ material

•Multiplication effect:• stronger for thinner diodes• stronger for smaller penetration

depth

� Charge multiplicationCharge multiplication in high field region at p-n-junction (epi, 3D, ..)� No evidence reported for charge multiplication in MCz-n Si Interesting candidate for SLHC-MCz-n as a material

Charge Multiplication in Epitaxial DiodeCharge Multiplication in Epitaxial Diode




I.I. CMS Upgrade Project within CEC CMS Upgrade Project within CEC Consortium:Consortium: HPK Sensor submissionHPK Sensor submission

substrate type FZ

200um

MCZ 200

um

FZ

100um

epi

100um

epi 50um FZ

300um

Total

& Active Thickness carrier no

carrier

carrier carrier carrier no

carrier

P-in-N Production 6 6 6 6 6 6 36

N-in-P Production p-spray 6 6 6 6 6 6 36

N-in-P Production p-stop 6 6 6 6 6 6 36

2'nd metal production P-on-N 6 6

2'nd metal production N-on-P

p-stop

6 6

2'nd metal production N-on-P

p-spray

6 6

Total 36 18 18 18 18 18 126

Many different • technologies• thicknesses• geometries and structures with different objectives

�� Choice of technology

All 6”

German ParticipationAachenDESYKITUH


F. Hartmann, Allianz Detector Meeting 2010 Heidelberg


CEC consortium R & D work of Si strixel sensor CEC consortium R & D work of Si strixel sensor for the upgrade of the CMS tracker for SLHCfor the upgrade of the CMS tracker for SLHC: Structure objective: Structure objective

� Pixel

� Multi-geometry strips

� Multi-geometry pixel

� Baby_std

� Baby_PA

� Baby_Strixel

� Diodes

� Test-structures

� Add_Baby aka Lorentz angle sensor

�� 30 pieces per wafer �� 3800 piecesSeveral dedicated measurement programs

Geometry/thickness

Irradiation/annealing

Routing/designIrradiation/annealing/material

Design/process/surface

Lorentz angle

more rad. hard planar pixel

Objectives:Structures

pT style

strip style




•TS-CAP:–Coupling capacitance CAC to determine oxide thickness–IV-Curve: breakthrough voltage of oxide

•Sheet:–Aluminium resistivity–p+-impant resistivity–Polysilicon resistivity

•GCD:–Gate Controlled Diode–IV-Curve to determine surface current Isurface–Characterize Si-SiO2 interface

•CAP-TS-AC:–Inter-strip capacitance Cint

•Baby-Sensor:–IV-Curve for dark current–Breakthrough

•CAP-TS-DC:–Inter-strip Resistance Rint

•Diode:–CV-Curve to determine depletion voltage Vdepletion

–Calculate resistivity of silicon bulk

•MOS:–CV-Curve to extract flatband voltage Vflatband to characterize fixed oxide charges–For thick interstrip oxide (MOS1)–For thin readout oxide (MOS2)

TS-CAP

sheet

GCD

CAP-TS-AC CAP-TS-AC

baby diode

MOS 1

MOS 2

CEC consortium R & D work of Si strixel sensor CEC consortium R & D work of Si strixel sensor for the upgrade of the CMS tracker for SLHC: for the upgrade of the CMS tracker for SLHC: Structure objectiveStructure objective

Ajay K. Srivastava, Uni-Hamburg 20TIFR seminar, Mumbai, India, 22.11.2010

Test Structures Description (as per CMS)

� HPK quality is excellent

� Pre-qualification ongoing/starting

C Coupling Strip current Rpoly

IV IV

CVCV

S/N (ALIBAVA)

Cint

TCT

CEC consortium R & D work of Si strixel sensorCEC consortium R & D work of Si strixel sensor--Initial measurementsInitial measurements




MESH GENERATOR (SDE)

DEVICE PHYSICS SIMULATOR

(DESSIS, SDEVICE)

Description of boundaries with suitable boundary conditions (Neumann, Dirchilet,

and GBC , doping and mesh

SIMULATION RESULTS

VISUALISATION TOOLS (Techplot, Inspect)

Physical models and

parameters

An Overview of Synopsys TCAD Simulation (Process An Overview of Synopsys TCAD Simulation (Process and Device) as a Tool for Technology Developmentand Device) as a Tool for Technology Development

Detector Design


Physical models: SRH recombinationDoping dependent mobilityHurkx TAT tunneling Exp temp dependenceImpact Ionization, Si-SiO2 Interface, bulk deep trap model ..

CPU time � Grid points

p-

x

y


Aim: Detailed simulation of sensor (p+ PAD Si with one guard ring with all useful physical and geometrical parameters taken from measurements) including bulk radiation damage effects (deep trap parameters; Et, Nt, σn,p)

��Link between microscopic defects and macroscopic paramatersSoftware: 2-D device simulation with synopsys T-CAD

Cut X=160

List of Physical parameters

I.I. CMS Upgrade Project within CERN RD50: CMS Upgrade Project within CERN RD50: Modelling of Four Level Trap Radiation Damage Model Modelling of Four Level Trap Radiation Damage Model for Neutron Irradiated MCzfor Neutron Irradiated MCz--n Si PAD Sensorn Si PAD Sensor

Aja

y K. S

ri,eta

l., Pos(R

D0

9)1

9.


Rectangular cell of 0.25 cm2 x 280 µm


Modelling of Four Level Trap Radiation Damage Model for Modelling of Four Level Trap Radiation Damage Model for Neutron Irradiated MCzNeutron Irradiated MCz--n Si PAD Sensorn Si PAD Sensor

Defect/type Effects Energy level [eV]

σn[cm2] σp[cm

2] η[cm-1]

E5 / Increase ofleakagecurrent

Ec- 0.46 eV 3.0×10-15 4.1×10-15 12.4

H(152K) / -ve spacecharge

EV+ 0.42 3.05×10-13 1.0×10-13 0.06

CiOi/ +vespacecharge

EV+ 0.36 1.64×10-14 2.24×10-14 1.10

E(30K)/ +ve spacecharge

Ec- 0.10 2.77×10-15 2.0×10-15 0.017

Parameters of the ‘four trap level model’ for MCz –n Si

�� Cluster effect taken into account by increasing one order magnitude of cluster related defect center E5 (“M. Petasecca et al”; IEEE TNS VOL. 53, NO. 5,2006 etc.)

�� σn,p finally tune for deep traps in order to get agreement in SRH theoretical calculation for Neff and experimental leakage current@ VFD

Acceptor

Acceptor

Donor

Donor


(as-irradiated)


pn

pn,

TT e+e

eN=(T)n

)Tk

E(T)E(±(T)(T)Nc=(T)e

b

VC,a

VC,pn,pn,

−exp

)(acceptorsn((donors)n(+N∆NTT

Deff ∑∑ −=

The leakage current at full depletion (VFD) and effective doping concentration can be calculated by first order approximation;

effg,

ni

T

nT

pfdτ

AWqn=

))(acceptorsΣne+(donors)ΣnqAW(e=)(T)I(V

��

(i) ��

(ii) ��

SRH Theoretical CalculationsSRH Theoretical Calculations


Comparision of Simulation with Experiment: (I/V) and Comparision of Simulation with Experiment: (I/V) and (C/V) Characterstics(C/V) Characterstics

� Good agreement in simulated current and experimental result @ VFD of

RT=293K (200C) (as expected, α=5.9x10-17 A/cm) [Moll]� Little estimation of SRH theoretical current than simulated and experimental current (293K)

�� Good agreement in simulation, experimental and model (ii) for VFD


Impact on Electric Field DistributionImpact on Electric Field Distribution--Important ObservationsImportant Observations

For a fluence of 1x 1014 n eq. /cm2 at 100V (450 ns)

� Double junction observed due to occupation of deep traps for fluence of1 x1014 neq./cm

2

� Generation life time (deep traps) affects the E-field


Rectangular cell of 0.0625 cm2 x 300 µm

Before irradiation,� Full depletion voltage, VFD=200 V � Geometrical capacitance, Cgeom= 2.16 pF at 10 kHz frequency

ND=2.87x1012 cm-3 ~ 1.5 kohm-cm

Device uses for TCAD simulation- MCz-n Silicon PAD Detector

I. CMS Upgrade Project within CEC Consortium : I. CMS Upgrade Project within CEC Consortium : Modelling of Four Level Trap Radiation Damage Model Modelling of Four Level Trap Radiation Damage Model for Mixed Irradiated MCzfor Mixed Irradiated MCz--n Si PAD Sensorn Si PAD Sensor


Aja

y K. S

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l., RE

SM

DD

2010

accepte

d (o

ral p

resenta

tion)


Mixed Irradiation Four Level Trap Model for Mixed Irradiation Four Level Trap Model for MCzMCz--n Si and Effective Introduction Rate of E(30K)n Si and Effective Introduction Rate of E(30K)


Comparision of Simulation with Experiment: (I/V) and Comparision of Simulation with Experiment: (I/V) and (C/V) Characterstics(C/V) Characterstics

� Good agreement observed in simulated leakage current and experimental current @ VFD of RT=293K, α=3.75x10-17 A/cm� Good agreement observed in VFD measured from experiment and simulation


+ve space charges

-ve space charges

Space Charges for the Applied Bias of 185VSpace Charges for the Applied Bias of 185V

3.13 x 1014 /cm2

� +ve and – ve space charges observed in mixed irradiated sensors


+ve space charges in 5x 1013 neq./cm2 MCz-n Si

+ve spacecharges -ve space

charges

+ve/-ve space charges (mixed)

Distribution of the Space Charges (Neutron Distribution of the Space Charges (Neutron Irradiated MCzIrradiated MCz--n Si and Mixed Irradiated)n Si and Mixed Irradiated)

3.13 x 1014 /cm2

applied bias of 185Vapplied bias of 185Vapplied bias of 100Vapplied bias of 100V

(for detailed on neutron irradiated (for detailed on neutron irradiated MCzMCz--n model see 14n model see 14ThTh RD50 RD50 Freiburg workshop and POS Freiburg workshop and POS (RD09)19).(RD09)19).

�+ve space charges observed in neutron irradiated sensors (not type inverted for the fluence of 5x1013 n eq. /cm

2)

�+ve and – ve space charges observed in mixed irradiated sensors

+ve space charges -ve space

charges


Space Charges and Electric Field Distribution (Mixed Space Charges and Electric Field Distribution (Mixed Irradiated) for the Applied Bias of 600 VIrradiated) for the Applied Bias of 600 V

� Distribution of space charges (+ve /-ve) changes in the bulk of MCz-n Si and depend upon the applied bias

�+ve space charges shift left with increasing fluence � E-field at front side higher than back-side as expected for over-depletedvoltage (600V) whereas for higher mixed fluence, Eback-side> Efrontside due to applied bias closed to VFD

Front sideBack-side

Base region


Trap Occupancy (Mixed Irradiated) for the Applied Trap Occupancy (Mixed Irradiated) for the Applied Bias of 600 VBias of 600 V

Front side

Back-side

� The occupancy for e-trapped increases from front to back side of the sensor� Uniform occupancy observed for h-trapped in the bulk of MCz-n Si


Important Observations on Mixed Irradiated Si PAD Important Observations on Mixed Irradiated Si PAD Sensors using synopsys TCAD device simulationSensors using synopsys TCAD device simulation

� Mixed irradiation four level trap model for MCz-n Si proposed for the bulk damage study

�ηmixedeff E(30K) obtained�Good agreement in simulated and experimental leakage current and VFD (I/V) obtained (α=3.75x10-17A/cm)

��Space charges distribution (homogeneous/non-homogeneous) depend upon the applied bias and the occupancy of the deep traps (inverted/not type inverted)� E-field distribution depends upon the occupancy of deep traps that will have macroscopic effect and also on space charges distribution� Sufficient E-field (~ 25 kV/cm) in the base region that is giving higher charger collection in MCz-n Si


I.I. CMS Upgrade Project within CEC ConsortiumCMS Upgrade Project within CEC ConsortiumSi Strixel Sensor Design for the Upgrade of Si Strixel Sensor Design for the Upgrade of a New CMS Tracker Detector for the SLHCa New CMS Tracker Detector for the SLHCTest structures proposed for TCAD simulation of Si strixel sensor design (p in n, n in p (Ist , and II metal layer, epi etc.)

Near-far-strixel sensor design PA integrated into I/II metal layer Si strixel sensor

IInd metal layer Si strixel sensor: TCAD design and plan to obtained low interconnection capacitance (mixed radiation damage)


Si Strixel Sensor Design for the Upgrade of Si Strixel Sensor Design for the Upgrade of a New CMS Tracker Detector for the SLHCa New CMS Tracker Detector for the SLHC

Double metal layer AC coupled Si strixel sensor design: 2-D view

Aja

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2009


� Simulated neutron fluences of

2x1014-8x1014 n eq. /cm2

using MCz-n radiation damage model


� No change in Cint (for Nox= 0 shown) and similar leakage current for Si strixel sensors with Ist and IInd metal layer observed for every Nox as expected

Irradiation results for n-type MCz Si strixel sensors with Ist metal layer:VFD and leakage current increases with fluence(2x1014-8x1014 n eq. /cm2)� Double junction observed for every fluence � 200 µm MCz Si strixel sensor seems to be good candidate

*VFD= 844 V@ 8x1014 n eq. /cm2 still acceptable� Si strixel sensor with 2nd metal layer viable option for SLHC

� Taken in HPK sensors submission.

Important Observations on Si Strixel SensorImportant Observations on Si Strixel SensorDesign for the Upgrade of a New CMS Tracker Design for the Upgrade of a New CMS Tracker Detector for the SLHC Detector for the SLHC (simulated results not shown here)


Introduction: Requirements XFEL:� planned to be operational in 2014, unprecedented peak brilliance� High dynamic range(100 fs x-ray coherent pulse 1 � 104 12 keV photons per pixel per pulse)and bunch spacing- 220ns (3000 bunches), � Flux of 12 keV photons: 1016 γ /pixel � 1 GGy [109 J/kg]

Radiation damage and its impact on sensor performance-Bulk damage not expected (threshold is 300 keV)-Only damage in SiO2 and Si-SiO2 interface important � surface damage-Charge build-up in oxide i.e. Nfix

ox (oxide trapped charge density and build –up of interface trap density (Nit) � shift of flatband voltage (Vfb) -High field (breakdown regions) at critical corners-Dark current (surface recombination current Iox) � increases shot noise in readout ASIC -Change of interstrip capacitance (noise) and interpixel resistance (spatial resolution)

II. AGIPD Project @XFEL: The Adaptive Gain The Adaptive Gain Integrating Hybrid Pixel Detector (AGIPD): A Integrating Hybrid Pixel Detector (AGIPD): A Detector for the European XFELDetector for the European XFEL


[http://hasylab.desy.de/instrumentation/detectors/projects/agipd/presentations/]

AGIPD Collaboration @XFEL - A collaboration in between DESY, PSI, Uni-Hamburg, and Uni-Bonn


Experimental MeasurementExperimental MeasurementSurface Damage due to 10 keV XSurface Damage due to 10 keV X--RaysRays

Test structure Gate controlled diodeTest structure gate controlled diode


Strategy: Irradiation of test structures: CMOS capacitors + gated diodes�� relevant microscopic parameters for SYNOPSYS-TCAD sensor simulations�� predict (explain) properties of irradiated sensors �� optimize sensor design


�� Test structures: Gated diode with 5 gate rings, CMOS capacitors (fabricated at CiS) for surface damage analysis

•Circuit for I/V ( Iox, S0) and C/V (Vfb, Cox,Cinv and Cfb) measurement & TSC (TDRC) (Nit, σn/p, Ec-Eit energy level, σ

rmsit)

of CMOS gated diode

�� CMOS gated

diode shown

Experimental MeasurementExperimental MeasurementSurface Damage due to 10 keV XSurface Damage due to 10 keV X--RaysRays


�� Results from gated diode measurements for 5MGy dose:Nfix

ox=2 x1012 cm-2,

Acceptor @Ec-E=0.35eV,σrms

it=0.05 eV, Dit=4x1012 cm-2 eV-1

Acceptor @Ec-E=0.60 eV,σrms

it=0.05 eV, Dit=4x1013 cm-2 eV-1

Experimental Measurement: Experimental Measurement: Surface Damage due to 10 keV XSurface Damage due to 10 keV X--RaysRays


Radiation damage and its impact on sensorRadiation damage and its impact on sensorperformanceperformance


�� Radiation effects in oxides depend on a lot of parameters like kind of radiation, energy, dose rate, applied field during irradiation

• frequency dependence C/V �� Nit(shallow) – close to band edge

• shift of flatband voltage*) from C/V �� Nox+Nit

• surface current �� Nit(deep) – centre band gap

CMOS capacitor:

Gated diode:*) complicated due to injection of “mobile oxide states” in deep inversion

(confirmed from TCAD simulation)

Important observations:


TCAD Simulation of Test StructuresTCAD Simulation of Test Structures

Schematic of CMOS capacitor


High frequency model used for C/V and G/V

characterization (non-uniform doping profile)


� Capacitance well described qualitaveley at 10, 100 kHz

� VShift @10 to 100 kHz = 0.50 V� Conductance well described qualitaveley in The accumulation, depletion and inversion and the peak range problem@10 kHz Reason possibly due to the measurements

TCAD Simulation :TCAD Simulation : Comparison with Comparison with Experiments (CMOS capacitor): Experiments (CMOS capacitor): I (NonI (Non--Irradiated)Irradiated)


Input microscopic parameters for simulation: Nfixox =1.5 x1011 cm-2, Dit=

2.66 x1011 cm-2eV-1,acceptor type, EC-Eit:0.4 eV, Gaussian distribution, σ rms

it= 0.1 eV Frequency shift due to Nit (shallow) for

Gacc

Gp

Ginv

Gp depend upon the distribution ofcharge carrier at Si-SiO2 interface Gacc/Cox/Cinv depend upon the doping profile �� RSD, RSB


Input microscopic parameters for simulation (60min 800C annealing):Acceptor, Ec- Eit: 0.35 eV, Gaussian distribution σ rms

it: 0.06791 eVDonor, Ec- Eit : 0.60 eV Gaussian distribution σ rms

it : 0.0065 eVNfix

ox=2.3 x 1012 cm-2, Acceptor, Dit=1x1013 cm-2eV-1 , and Donor, Dit=4x1013 cm-2 eV-1

� Capacitance well described qualitaveley at 10, 100 kHz

� Conductance well described in the peak range @10 kHz, 100 kHz Problem in inversion Reason possibly due to the measurements (“mobile oxide charges” causing irreproducible results) Results cross-checked by analytical formulations

TCAD Simulation :TCAD Simulation : Comparison with Comparison with Experiments (CMOS capacitor): Experiments (CMOS capacitor): I (Irradiated with I (Irradiated with 5 MGy)5 MGy)


• Input parameters for simulations:

tcp (SiO2+Si3N4)= 100nm+50nmtox (SiO2+Si3N4)= 300nm+50nmWMO= 1 µmND= 8.1x10

11 cm-3

Biasing scheme:I/V- 0V on implant ohmic contact (both)C/V- AC signal on implant ohmic contact (both)

x

y

0V0V

+V0

TCAD Simulation : TCAD Simulation : pp++n FZ Si Strip Sensorsn FZ Si Strip Sensors


Schematic of <100> 98 AC coupled Si strip sensor (CiS, Erfurt, Germany): (0.643 cm2x 282 µm) irradiated with 1, 10 MGy doses by 10 keV X-rays

Von Neumann boundary condition (NBC) applied


TCAD Simulation : TCAD Simulation : pp++n FZ Si Strip Sensors n FZ Si Strip Sensors

� Surface current (9 µA/cm2 for 1 MGy) & non-implanted depleted surface area linearly increases with bias voltage (x-ray radiation damage result)

- Von Neumann boundary condition exist

Input microscopic parameters for simulation (60min 800C annealing):1 MGy [(Nfix

ox=2.08 x 1012 cm-2), 10 MGy (Nfixox=2.0 x 1012 cm-2)]

1 MGy [Dit, A= 4.2x 1012cm-2], 10 MGy [D it, A= 3.2x 1012cm-2](Acceptor@Ec-Eit: 0.35 eV, Gaussian distribution, σσσσrms

it= 0.06791 eV)1 MGy [Dit, A= 1x1013cm-2 ], 10 MGy [D it, A= 8x 1012cm-2](Acceptor@Ec-Eit: 0.60 eV , Gaussian distribution, σσσσrms

it= 0.0065 eV)(The capture cross-sections of both interface trap finally tune for agreement in experiment and simulation (for shallower and deeper interface trap), σeff= 2.75x 10

-15 cm2)


Increase of Idark- Idark ~ Sdep x Nit(deep)Tentative conclusion: �� increase of dark current due to in-

crease of Nit(deep) for irradiation




Simulation describes data*):- ∆Vdep by ~ 10V due to surface charges- change of 1/C2-slope- at ~ 6V jump in C: depletion regions from adjacent strips join- effect of Nox saturates at few·10

11cm-2

- Good agreement in Cback-plane (shown here for 0 Gy), and Nfixox extracted.

Nfixox (0 Gy) = 2.1x1010 cm-2 (<100> oriented Silicon)

*) accumulation layer depends on environment, etc.!

e-accumulation



Results from model calculationResults from TDRC measurements


http://hasylab.desy.de/instrumentation/detectors/projects/agipd/presentations/e97045/ASrivastavaDevelopmentofRadiationHardSiPixel.pdf

� Good qualitatively agreement obtained in Cback-plane and interstripcapacitance, and Nfix

ox extracted (1MGy:1.9x1012 cm-2, 10MGy:1.55x1012 cm-2)for annealed segmented detectors (60 min 800C)

5 MGY, MOS, 60 min 800C annealed

60 min 800C annealed

Small increase of Cint due to increase of width of accumulation layer �� decrease of width of depleted area

between strips (Sdep)


• Input parameters for simulations :Simulation of 2 dim cell of 600x500 µm2

n+-pixel of 200x200µm2

tox(SiO2+Si3N4)= 400nm+100nmWMO= 5 µmXj= 1 µmn+-pixel implant depth= 5 µmND= 1x10

12 cm-3

NBC applied on top of oxide (dry)

TCAD Simulation : TCAD Simulation : Design ofDesign of nn++n FZ Si Pixel Sensors n FZ Si Pixel Sensors

Schematic of cut edge of DC coupled n+n-p+ Si pixel x-ray sensor and its rear-side layout (x-ray entrance)

(V0: bias voltage, V1 = -0.85xV0, V2 = -0.7xV0 and V3 = -0.5xV0, V4= -0.27xV0), CTR: Current terminating ring, CR: Current ring and GR: Guard ring.

Why choosen n+n-p+ Si pixel sensor for AGIPD detector as first design idea?� Photons incident on rear side of sensor (if high electric field on rear side-++)� Bump bonding with read out ASIC electronics- ++

y

x 0V 0V

Layout of sensor model 1


Microscopic paramaters for 5 MGy (60min 800C annealing) – from CMOS capacitor

�Rad-hard n+n-p+ Si sensors design (VFD:197 V for 500 µm thick sensor) proposed for 1000 V operation (in order to avoid plasma effect)

� no VBD observed

Input parameters for simulation from experiment: 5 MGy: Nfixox=2.82 x 1012 cm-2

Dit, A= 1x 1013cm-2 eV-1(Acceptor@Ec-Eit: 0.35 eV, Gaussian distribution, σrmsit=

0.06791 eV)Dit, A= 4x1013cm-2 eV-1 (Acceptor@Ec-Eit: 0.6 eV, Gaussian distribution, σrms

it= 0.0065 eV)

TCAD Simulation :TCAD Simulation : Design of nn++nn--pp++ FZ Si Pixel XFZ Si Pixel X--ray ray SensorSensor


TCAD Simulation : TCAD Simulation : Design ofDesign of nn++n FZ Si Pixel Sensors n FZ Si Pixel Sensors

Layout of sensor model 2

�VBD improve in the presence of acceptor interface trap, VBD=995 V� Orientation not important <100> or <111> (p-spray compensates Nox

fix)

(on slide 42, from 5 MGy gated diode)


Specification of AGIPD sensor with an aim for 1 GGy radiation tolerance:

Specification of Prototype AGIPD pSpecification of Prototype AGIPD p++n Si Pixel Sensorn Si Pixel Sensor


� Sensor fabrication• single sided p+n is “standard” �� costs and number of vendors (but not yet demonstrated that

1000 V (500 V sufficient for ASIC electronics to protect HV sparking at cut edge and also in order to avoid plasma effect in Si sensors*) operating voltage for irradiated sensors can be achieved !)

• usually dead edges (0.5 mm to 1 mm)

* jinst.sissa.it/jinst/theses/2010_JINST_TH_003.pdfAjay K. Srivastava, Uni-Hamburg 54

Work performed:1. Optimize Cinter-pixel, dark current and breakdown voltage2. Understand uniformity of charge collection3. Guard ring and minimum dead space4. Radiation tolerance of existing sensors (n+n)5. Sensor design and prototype fabrication

TCAD Simulation: DTCAD Simulation: Design ofesign of pp++n FZ Si Pixel Sensorsn FZ Si Pixel Sensors(Optimize Optimize CCinterinter--pixelpixel, Dark current and Breakdown , Dark current and Breakdown VoltageVoltage


NBCx x

y

3 x 3 pixel array

Total capacitance of a pixel array ,CT=4C1+4 Cdiag+Cback-plane


Pixel gaps optimization from TCAD simulation*:

gap dose Cinter-pixel

Ileakage Vdep Cdep

20 µm 0 MGy 140 fF 2.6 pA 189 V 8.7 fF

5 MGy 340 fF 5.3 pA 190 V

40 µm 0 MGy 90 fF 2.6 pA 187 V

5 MGy 230 fF 36 pA 190 V

80 µm 0 MGy 50 fF 2.6 pA 194 V

5 MGy 110 fF 100 pA

198 V

Synopsys TCAD device model:

• Pixel size: 200x 200μm2

• Thickness: 500 μm• Doping: 1.0 x 1012 /cm2

(~ 5 kΩ·cm)• Orientation: <100>• Isolation: SiO2 (no Si3N4 –for simulation only)• Design parameters tox, Xj, WMO chosen to work pixel up to 1000V (as a first simulation result for the design idea)

TCAD Simulation: 1.Optimize TCAD Simulation: 1.Optimize CCinterinter--pixelpixel

� Expected load at input of preamp@ 5 MGy= 110+200 fF (bump-bond+preampload)=310 fF ~ 250-280 e- noise (calculation performed from electronics peoples)


•For fixed metal-overhang width =5 µm, junction depth=5µm, oxide thickness=1µm, and Cdiag=2 fF for all pixel gaps• C3-D=(4C1+4Cdiag)x25% (error implication in 2-D and 3-D TCAD simulation result)+Cback-planeAjay K. Srivastava, Uni-Hamburg 56

Breakdown voltage

�1000 Volts (p+n structures – not guard rings)

500 V

bulk current

20 µµµµm gap

40 µµµµm gap

80 µµµµm gap

2-D simulation for 5 MGy parameters

SiO

2a

rea

with

field

[arb

. un

its]

TCAD Simulation: 1.Dark CurrentTCAD Simulation: 1.Dark Current

~ 9 µA/cm2


Accumulation layer below oxide �� field free region �� if E = 100V/cm �∆t =

10 ns for ∆x = 15 µm (electrons)

� small volume where charge is stored and slowly released

Simulation for: 80 µm gap, 500 V, 5 MGy

EEEE----field field field field 0 0 0 0 �� 20 kV/cm20 kV/cm20 kV/cm20 kV/cm

TCAD Simulation: 2.ETCAD Simulation: 2.E--field and Uniformity Charge field and Uniformity Charge CollectionCollection

check exper. by light injection in between pixels

660 nm Laser light used → absorption length = 3 µm

(for soft XFEL 1 keV , and hard XFEL 12 keV → 230 µm)

Holes lost in accumulation region:→ signals on neighbor pixel reduced by ~ 25%→ signals on next neighbor pixel ~ 5%Try to avoid/reduce electron accumulation layer (EAL)→ small gap between p+ implantation→ high operation voltage + low Cint-pixel and dark current+ high Rint


TCAD Simulation:3. TCAD Simulation:3. Technology for Guard ring and Technology for Guard ring and Minimum Dead Space I. MGR (no nMinimum Dead Space I. MGR (no n++ at Cut Edge)at Cut Edge)


NBC


TCAD Simulation:3. TCAD Simulation:3. Guard Ring and Minimum Guard Ring and Minimum Dead Space: II. MGR (nDead Space: II. MGR (n++ at cut edge)at cut edge)

(V0: bias voltage=-1000V, V1 = -0.85xV0, V2 = -0.7xV0 and V3 = -0.5xV0, V4= -0.27xV0), CR: Current ring and GR: Guard ring.


� No breakdown observed for 0 Gy dose� Breakdown observed for 633 V for 5 MGy dose (curvature of junction)

VBD

((symmetric overhang )

NBC

p+ SiO2GR1

(ongoing work to achieve 1000V for 5 MGy, technological parameters)Ajay K. Srivastava, Uni-Hamburg 60

TCAD Simulation:3. TCAD Simulation:3. Guard Ring and Minimum Guard Ring and Minimum Dead Space: III. HPK technology (nDead Space: III. HPK technology (n++ at cut edge)at cut edge)


� No breakdown observed for 0 Gy dose� Breakdown observed for 217 V for 5 MGy dose (below overhang of GR1)

VBD

(symmetric big overhang, V0=-1000V)NBC

(ongoing work for different dead edges (< 0.5 mm), technological parameters)

30 micron towards cut edge160 micron from cut edge to the oxide

Red- 5 MGyBlack-0 GY

p+ SiO2

GR1SiO2

n+


CMS n+n test pixel sensor’s performance up to 1 MGy:

No change of full depletion voltage due to irradiation (no accumulation layer)*

� Jump of capacitance around full depletion voltage

→ merge of bulk depletion and p-spray depletion

� Step of leakage current → depleted Si-SiO2 interface (p-spray isolation)

� Increase of leakage current with bias voltage → increase of depleted area Sdep

Decrease of inter-pixel capacitance*

*) advantages compared to p+n sensors!

~6.70 μA/cm2

100 kHz

< 20% decreases

In capacitance

4.Characterization of Segmented n4.Characterization of Segmented n++n Si Detectorn Si Detector


- By J. Jhang at UH.


Implications for the design of 200x200 µm2 p+n pixel for AGIPD:� Small width of electron accumulation layer (WEAL)

(gap should be in between 20 and 40 µm) � XDAC report on 21.10.2010

� Low interpixel capacitance (within specs)� Low dark current (within specs)� High interstrip resistance� High bias voltage (500V (++for ASIC electronics))

TCAD Simulation: Optimal DTCAD Simulation: Optimal Design ofesign of pp++n FZ Si Pixel n FZ Si Pixel SensorsSensors


Segmented detector: 30 micron gap@ 500VPixel implant – 170 µm2

Xj=1 micron, tox=350 nm (300nm oxide+50 nm nitride), Wn+ =1 micronNBC applied on top of oxide+nitride surfaceStudy of radiation damage in oxide• 0 Gy- Nox

fix=2.1x1010 cm-2

• 5 MGy dose (see paramaters on slide 65)

Normal


TCAD Simulation: Optimal DTCAD Simulation: Optimal Design ofesign of pp++n FZ Si Pixel n FZ Si Pixel Sensors: Sensors: Strategy to improve radiation hardnessStrategy to improve radiation hardness

Surface rad-hard design- method I Surface rad-hard design- method II


Effect of bias voltage on WEAL for 0Gy, 5 MGy (WMO=0 µm)

� The influence of bias voltage on WEAL in non-irradiated (0 Gy ) sensors clearly visible whereas in irradiated sensors (5 MGY), no change in WEAL

10 micronP-stop dose=1.125x1015 cm-2

2 micron



Effect of metal-overhang (0, 2.5, 12.5 µm) on WEAL for 5 MGy

Effect of metal-overhang (0, 2.5, 12.5 µm) on dark current for 5 MGy

� The influence of larger WMO=12.5 µm on WEAL clearly visible in irradiated sensors whereas for small overhang width, no change in WEAL� Dark current increases with metal overhang width (flattening in I/V curve observed for higher WMO) whereas in case of WMO=0, Iox increases with voltage



Effect of intra p+ on WEALfor 5 MGy as a function of applied voltage,WMO=12.5µm)

Surface rad-hard design I

Effect of metal on WEAL for 5 MGyas a function of applied voltage, WMO=12.5µm)

Surface rad-hard design II

Comparision of dark current: method I and method II


� Increase of bias voltage from 500V to 1000V influence the •WEAL and no change in dark current (rad-hard design II and without metal) whereas increases with voltage for rad-hard design I and saturate for high bias


TCAD Simulation: Optimal DTCAD Simulation: Optimal Design ofesign of pp++n FZ Si Pixel n FZ Si Pixel Sensors: Sensors:

Impact of WMO =12.5µm on interstrip and interpixel capacitances@1MHz,Vfd

Surface radSurface rad--hard designhard design


4.06x10-174.18x10-174.18x10-174.06x10-174.18x10-174.18x10-17Cback-plane

4.89x10-174.79x10-17Cimplant-metal

1.13x10-163.2x10-161.47x10-161.13x10-163.46x10-161.36x10-16Cimplant-implant

Rad-hard method II

Rad-hard method I

NormalRad-hard method II

Rad-hard methodI

Normal

5 MGy0 Gy

Irradiation DosesCapacitances(F/µm)

101

8.12

101

8.12

267

8.36

288

8.36

129

8.36

120

8.36

Interpixel capacitances(4C1+4Cdiag)

* (fF)

Back-planeCapacitances (fF)

5 MGy0 Gy5 MGy0 Gy5 MGy0 GyIrradiation doses

Rad-hard method IIRad-hard method INormalS.No.

*Equivalent to 3-D interpixel capacitance without an error implication in 2-D and 3-D TCAD simulation•Cdiag for 30 micron gap= 2.52 fF – Ideal case, no overhang (IEEE TNS vol.44 no.1, 1997), Cdiag=2.73fF for 12.5 µm overhang


TCAD Simulation: Optimal DTCAD Simulation: Optimal Design ofesign of pp++n FZ Si Pixel n FZ Si Pixel Sensors: Sensors: Surface radSurface rad--hard designhard design


� Cint increases with overhang width (already known technological effects, not shown here) whereas for method II, low Cint and low cross-talk (additional metal on top) obtained

� similar Cint obtained for 0 Gy and 5 MGy dose• Negligible WEAL (in general, Cint increases with oxide charges Nox

fix+Nit)• No chance to hole trapped � Cint (5 MGy) for 200x200 µm2 = 101 fF, and Cback-plane=8.12 fF� 3-D equivalent, total capacitance, Ct (5MGy) =109.12 fF

Important observations for the optimal design of AGIPD sensorDark current, capacitance (within specs) independent of bias voltage (from 500V to 1000V) for large WMO

The following things suggested to reduce the WEAL (concentration of e)• Large WMO , high bias voltage and rad-hard method II• Results at 5 MGy@1000V, WEAL=1.05 µm, depth from X=98.5 µm, 0.115 µm/pixel for 12.5 µm overhang, Ct (5 MGy) =109.12 fF, and Idark-current=0.2nA (depleted area=2.15 µm2)

- Simulation for guard ring design underway for 1000V operation and reduced dead space < 0.5 mm (input from first simulation available)Ajay K. Srivastava, Uni-Hamburg 68

Summary and OutlookSummary and Outlook

I. New CMS Tracking Detectors @SLHC� Strixel sensor design simulation performed for a new CMS tracking detector within CEC� Four level trap neutron as-irradiated and mixed irradiated MCz-n Si model developed for the

radiation damage study of MCz-n Si sensor� Precharacterization of HPK sensors shown excellent results � MCz-n Si as a promising candidate for the tracking systems at SLHC� Avalanche multiplication effects observed in epi, strip, 3-D sensors� n in p Si thin sensor represent promising sensor candidates for the inner layers of the tracking

systems at SLHC thanks to their reduced material budget and n in p pixels may be replace the n in n Si pixels sensor

� Technologies and materials for a silicon tracker at SLHC available. We will further investigate which solution would be the optimum for the operation of the experiment

OutlookCEC consortium:� Radiation damage study on new structures (PA integrated into double metal layer p in n and n in p structure)� Precharacterization of HPK sensors still ongoing within CEC, Irradiation (n, p, mixed), final characterization (I/V, C/V,

TCT, DLTS, TSC, S/N test) of the strixel sensors and diodes planned

RD50 Collaboration:� Mixed irradiated study for detailed characterization of different composition of protons and neutrons in different

thin/thick sensors (p in n, n in p MCz Si)�� Avalanche multiplication study in MCz-n/p Si sensors�� Detailed characterization of n in p thin Si sensors (different materials) for different radii�� Microscopic characterization of n in p MCz Si�� Determination of Physical structure of microscopic defects in new Si materials

Summary and OutlookSummary and OutlookCCoonncclluussiioon n andand Outlook (within CEC Outlook (within CEC , and RD50) , and RD50)


Summary and OutlookSummary and Outlook

II. AGIPD @ XFEL� Detailed comparison of experimental result and TCAD simulation of test structures and

strip sensors performed � good qualitatively agreement observed� the measured radiation behaviour of the dark current, depletion voltage and inter-strip capacitances of segmented sensors can be understood via simulations on the basis of the parameters derived from irradiated test structures� x-ray radiation damage results produced

� Simulation of n in n pixel design with GR performed to work up to 1000V� Detailed simulation for the rad-hard design of p+n pixel sensor for AGIPD performed

with and without guard ring with different technology Two major Si sensor design challenge:a) 1000 V operating voltage b) reduce dead edges < 0.5 mmwith aim: reduce WEAL for negligible hole charge loss, low Cint, low dark current (within specs)..� Pixel sensor design idea proposed

• No breakdown obtained up to 1000V (p+n structures – not guard rings)

� Input from TCAD simulation available for sensor design

Outlook:� Guard ring design simulation ongoing to achieve a) and b), finalization of pixel design layout (Cadence Virtuoso

layout editor available)� Aim to be ready for tendering end Jan ’11 and order end March ’11(discussion with vendors soon (HPK, CiS))

Summary and OutlookSummary and OutlookCCoonncclluussiioon n andand Outlook (within Outlook (within AGIPD) AGIPD)


Efforts ongoing!Not to the End!

Till commissioning.


CCoonncclluussiioonn

Questions please!


development of radiation hard si detectors for the slhc...

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