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Patras,June 2007 Gerhard Lutz, PNSensor GmbH 1
Semiconductor Photon DetectorsSemiconductor Photon DetectorsPart 1Part 1
Gerhard Lutz
PNSensor GmbH, München
for the
MPI Semiconductor Laboratory, Otto Hahn Ring 6, D 81739 München
3rd Joint ILIAS-CERN-DESY Axion-WIMPs training-workshop
Patras, GreeceJune 19-25, 2007
Patras,June 2007 Gerhard Lutz, PNSensor GmbH 2
IntroductionIntroduction
Development of position sensitive silicon detectors initiated by developments in particle physics attracted interest of X-ray astronomers at MPE
MPE activities in X-ray astronomy based on X-ray mirror imagingFocal gas proportional detector (ROSAT) replaced withsilicon detector (pn-CCD) in XMM/Newton
Development of these detectors required new technology not available in industry
Semiconductor Laboratory founded 1992 by two Max-Planck institutesAim: Development of novel detectors for institute experiments in particle physics and astrophysicsComplete high-tech production lineDevelopments based on new (own) detector concepts
Attention initially concentrated on X-rays, now expanded to include optical region and may extend further to near infrared
Talk will describeo Principles and properties of semiconductor detectorso Capabilities of the laboratory
o Institute projects requiring photon detectorso Further developments
•
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ContentContent
• Basic Semiconductor Properties and Structures (diode, drift detector)• Photon detection in semiconductor detectors
• PN-CCDs for X-ray astronomy (XMM/Newton, e-Rosita)• DEPFET
Function PrincipleProperties
• DEPFET detectors for X-ray spectroscopic imagingPixel detectors for XEUSMacro-pixel detectors for SIMBOL-X and BEPI-COLOMBO
• RNDR (Repetitive Non Destructive Readout) detectors with sub-electron noise• DEPFET Ping-Pong structure• CCDs with RNDR readout
• Avalanche Detectors• Avalanche drift diode• CCDs with avalanche readout
• Low background photon detectors
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Why semiconductor detectorsWhy semiconductor detectors
• Excellent properties for measuring ionization:small band gap (Si 1.12eV) ⇒ low e-h pair generation energy (Si 3.6 eV) (ionisation energy for gases ≈ 30 eV) ⇒precise energy measurementprecise energy measurementHigh density (Si 2.33 g/cm2) ⇒ large energy loss/length for ionising particles ⇒ thin detectors; small range δ-electrons;precise position measurementprecise position measurementAlmost free movement of electrons and holesMechanical rigidity; self supporting structureDoping creates fixed space charges; building of sophisticated field structuresintegration of detector and electronics in single detector and electronics in single devicdevicee
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Basic Detector: Semiconductor DiodeBasic Detector: Semiconductor Diode
• Most basic: reversely based diodeElectron-hole pairs generated by ionizing radiation (photons or charged particles) are separated by electric field and collected at electrodesTypical structure:p+ n- n+
Patras,June 2007 Gerhard Lutz, PNSensor GmbH 6
(Diode) Strip Detectors(Diode) Strip Detectors
• Divide diode into strips and measure charge arriving at individual strips ⇒ position measurement• Further developments:
charge division readoutdouble sided readoutcapacitive coupled readoutbiasing methodsbreakdown protectionradiation hardening
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A simple processing sequence: strip detectorA simple processing sequence: strip detector
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TheThe MPI MPI SemiconductorSemiconductor LaboratoryLaboratory
Capabilities:•Everything from wafer to tested detector•Design and Simulation•Complete detector technology•Sophisticated test and analysis equipment and tools
Separation, mounting, bonding
Quality assurance and control
System test equipment
photo resist deposition
photo lithography
visual inspection
wet chemistry
sputter
oxidation
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• Why own technology:Use of ultra-pure silicon: properties not to deteriorate during processingwafer size defect free processingdouble sided processingsophisticated detectors require complete and detailed control over process
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(Historical)(Historical) Detectors for particle physicsDetectors for particle physics
• Particle tracking: position measurementFirst strip detectors (NA11/NA32)
First double sided Capacitive coupled, simple biasingRadiation hardPixel sensors(First drift detectors)Readout electronics
Na11 strip detector: charmed particles
Aleph strip detectors: e+e- collider
HERAB or ATLAS?
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Semiconductor Drift ChamberSemiconductor Drift Chamber• Sideward depletion
Diodes on both surfacesPotential maximum in middle plane
• Drift chamber(Gatti and Rehak 1984)Sideward depletion + graded potential on outer surfacesignal charge collected in centre valley, moves parallel to surface towards collecting anodePosition (from drift time) and/or energy measurement (from signal charge)small capacitive load gives good energy resolution
• Basis for spectroscopic imaging detectors to be described
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Noise in semiconductor detectorsNoise in semiconductor detectors
• Noise created in electronics:• - Serial noise with 2 components
Thermal (white) noiseLow frequency (1/f) noise
• represented by noise voltage at amplifier input
• Noise created in detector- Parallel noise
represented by noise current source parallel to the detector
•
Charge sensitive amplifierCharge sensitive amplifier
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DetectorsDetectors notnot coveredcovered in in presentationpresentation
• Strip detectors and standard drift detectors used for charge particle tracking• Drift diode used for X-ray spectroscopy
• Drift detector principle is basis for several spectroscopic imaging detectors to be described:PN-CCDsDEPFETs
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PN-CCDs
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PNPN--CCD (CCCD (Chargeharge CCoupledoupled DDeviceevice) principle) principle
•Pn-CCD:Based on drift chamber principleCharge transfer in bulk (~10µm depth)Spectroscopic imaging
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pnpn--CCDCCD forfor ESAESA‘‘ss XMMXMM--NewtonNewton satellitesatellite
Detectors for X-ray astronomy
• XMM: three X-ray telescopes• one dedicated to imaging (with pn-CCD) • two with additional reflecting gratings
(andMOS CCDs) • one optical telescope• all pointing on same object
• Wolter I type mirror telescopes• 58 nested mirror shells • Wall thickness 0.5 to 1mm Ni
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MOS-CCD (´video CCD´)
• MOS transfer gates
• buried channel
• partial depletion
• frontside illumination
• serial readout
MOS-CCD (´video CCD´)
• MOS transfer gatesimplanted pn-junctions
• buried channel
deep transfer
• partial depletion
full depletion
• frontside illumination
back entrance window
• serial readout
1 preamp / channel
pn-CCD
pnpn--CCDCCD principleprinciple
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Simulation of Simulation of pnpn--CCDCCD chargecharge transfertransfer
Device simulation
Charge transfer in pn-CCD
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pnpn--CCDCCD performanceperformance
• largest monolithic CCD
6 x 6 cm²
384 x 400 pixel
150 µm pixel
• fast, parallel readout
5 msec full frame
• low noise
4 el. rms
• high quantum efficiency
90 %
• radiation hard
400 Mp/cm²
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Wafer size detectorWafer size detector
• XMM 6x6 cm2 CCDswere produced on 4 inch wafer
• CAST uses one segment prototype of 1x3cm2
4 inch wafer(Ø = 100 mm)(d = 280 µm)
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New 6 inch technologyNew 6 inch technology
• Frame store pn-CCDs for e-ROSITA produced in6 inch technology
wafer size:6 inch,Ø = 150 mmd = 450 µm
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High High speedspeed frameframe storestore pnCCDs pnCCDs forfor XX--raysraysthethe eROSITA eROSITA conceptconcept
FS pn-CCD for the eROSITA mission (MPE, IAAT, ROSKOSMOS)
• format 384 x 384 x 2, geom.: 19.25 cm2 per chip, • pixel size 75 µm □ image, 48 µm □ in frame store• eROSITA sensitive chip area: 2.9 x 2.9 cm2 = 8.4 cm2 (7 x)• eROSITA has 1.03 Mega Pixel on 60 cm2
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eROSITA typepnCCDs:384x384x275x75 µm2
This picture:256x256x2 pixel75x75 µm2
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image area384 x 384 Pixel
75μm x 75μm
frame store area384 x 384 Pixel
75μm x 51μm
37 mm
5
6 m
m
X-rayexposure
fast transfer of image
readout of image (shielded against X-rays)
28.8 mm
2
8.8
mm
CAMEX128 channels
CAMEX128 channels
ADC
CAMEX128 channels
ADC ADC
25 x 39 mm
Chip size:35 x 55 mm2,i.e. 19.25 cm2
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Energy Energy resolutionresolution @ C_K of a pnCCD@ C_K of a pnCCD
110 eV
277 eV
525 eV
Trigger Threshold: 22 eV
50 eV
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5151µµm pnCCD m pnCCD withwith a a doubledouble--sidedsided readoutreadout,,mountedmounted ontoonto a a ceramicceramic substratesubstrate
detector size = 27×13.5 mm2
51 µm pixel size528×264 pixel in total,264×264 in each image & storage
areareadout transfer to both sidesimage transfer time = 20 µsOOT probability = 2% @ 1000 fpscharge transfer loss CTI ≈ 10-6
i.e. total charge loss < 0.05 %charge handling capability > 106 e-
100% fill factorreadout noise vs. frame rate:
1.8 e- @ 10 .. 400 fps2.3 e- @ 400 .. 1.100 fps
With binning: 2.3 e- @ 2.200 .. 4.400 fps
All measurements were performed@ - 40 o C
this pnCCD system is used in:adaptive optics, high time resolution astrophysics,synchrotron radiation, transmission electron microscopy, channeling radiation, X-ray microscopy, etc . . & CFEL
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Low Low energyenergy responseresponse of of pnCCDpnCCD
• Measured at FLASH (DESY)
E = 90 eV ± 0.1 eV# e-h pairs: 25 ± 1.6ENC: 2.3 el. (rms)
pile up events
Triggerthreshold@ 25 eV(4 σ cut,i.e. 2 e-)