Lecture 3: Semi-conductors - Generalities - Material and ...
Transcript of Lecture 3: Semi-conductors - Generalities - Material and ...
Jean-Marie Brom (IPHC) – [email protected]
DETECTOR TECHNOLOGIESLecture 3: Semi-conductors
- Generalities- Material and types- Evolution
Jean-Marie Brom (IPHC) – [email protected] 2
Semiconductors : generalities
Solid‐States band structures :Valence band : e– bond atoms togetherConduction band : e– can freely jump from an atom to another
At T ≠ 0 KElectrons mayacquireenough energyto pass the band gap… Thermal condution
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Semiconductors : generalities
Not the same !(Thermal excitation + phonons)
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Semiconductors : generalities
Energy loss by a charged particle : Bethe‐Bloch
Standard :Energy loss :
electrons – holes pairs created(NOT electrons – ions…)
If Field (even natural)electrons migrationElectrical pulseInformation
Too simple !
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Semiconductors : generalities
One MIP in Silicon at 300°K
Energy loss : dE / dx ≈ 388 Ev/µm
Ionisation Energy : 3.62 eV
e – holes pairs created : 107/µm
For 300 µm : 3.2 10 4 pairs created
Free charge carriers in the same volume :≈ 4.5 10 9
Signal is lost !Solution : Depletion of the detector
‐ Doping‐ Blocking contacts
Depletion : removing the maximum possible thermally excitable electrons
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Semiconductors : generalities : the Fano factor
Number of e – h pairs is a statistical process :
Number of e‐h pairs : N = E loss / E ionization
If excitations are independants , they obey to a Poisson statisticwith a standard deviation
σ
variance : σ
Fano factor : variance / mean of the process (should be 1 for a perfect Poisson distribution)
Si 0.115
Ge 0.13
GaAs 0.10
Diamond 0.08
Fano factor related to energy resolution :A Fano factor < 1 means that the energy resolution would be better thantheoretically expected…
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Semiconductors : generalities : p and n types
dopants :Arsenic, Phosphorous
dopants :Boron, Gallium, Indium
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Semiconductors : generalities : p and n types
Typically : doping level for a Silicon Detector : 10 12 atoms / cm 3Doping us usually done by ion implantation.
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Semiconductors : generalities : junction detectors
A p‐n junction is formed when asingle crystal of semiconductor is doped with acceptors on one side and donors on the other
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Semiconductors : generalities : junction detectors
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Semiconductors : generalities : reverse biasing scheme
The p – n zones will be used for contactand to block (Blocking Contacts) the undesired noise
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Semiconductors : generalities : building
DC Coupling Silicon detector
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Semiconductors : generalities : building
AC Coupling Silicon detector
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Semiconductors : generalities : building
AC coupled Si detectors create 2 electrical circuits :
‐ Read‐out circuit to the amplifier (AC current)
‐ Biasing circuit (DC current)
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AC Coupling Silicon detector : bias voltage system
Semiconductors : generalities : building
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Most commonly scheme AC + poly S‐bias resistor
Semiconductors : Si detectors designs
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Semiconductors : Si detectors designs
CMS design ATLAS design
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Semiconductors : Si detectors designs
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Semiconductors : Radiation Damage
Two types of radiation damage :
Bulk (Crystal) damage due to Non Ionizing Energy Loss (NIEL)‐ displacement damage, built up of crystal defects –
Change of effective doping concentration (higher depletion voltage, under‐ depletion)
Increase of leakage current (increase of noise, thermal runaway)Increase of charge carrier trapping (loss of charge)
Surface damage due to Ionizing Energy Loss (IEL)‐ accumulation of positive in the oxide (SiO2) and the Si/SiO2 interface –
affects: interstrip capacitance (noise factor), breakdown behavior, …
Impact on detector performance(depending on detector type and geometry and readout electronics!)
Signal/noise ratio is the quantity to watch Sensors can fail from radiation damage !
Jean-Marie Brom (IPHC) – [email protected] 20
Semiconductors : Effect of radiations
Charge > 200 V above Vfd
12000
14000
16000
18000
20000
22000
24000
26000
0 2E+14 4E+14 6E+14 8E+14 1E+15 1.2E+15
eq [cm-2]
mos
t pro
babl
e ch
arge
[e]
Fz n-p (2551-7)Fz n-n (2535-11)MCz n-p (2552-7)MCz n-n (2553-11)MCz n-p (W184)MCz n-pFz n-psimulation neutrons - low limitssimulation protons - low limitssimulation protos - nominal"simulation neutrons - nominal"bh=2.5, be=2.1
Loss of collected charges(new 300 µm Silicon ≈ 24 000 e‐ for 1 MIP)
tQtQ
heeffhehe
,,0,
1exp)(
Trapping is characterized by an effective trapping time eff for electrons and holes:
where
defectsheeff
N,
1
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Semiconductors : Effect of radiations
Increase of Leakage current
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Semiconductors : Effect of radiations
Change in depletion voltage and type inversion
before inversion
after inversion
n+ p+ n+p+
Innermost layersshould still work afterΦ 10
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Semiconductors : 2‐dimensional detectors
Double Sided Silicon Detectors (DSSD) Not much in use…
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Semiconductors : 2‐dimensional detectors
Stereo Modules
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Semiconductors : Performance
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Semiconductors : Pixels Detectors
Pixel sizes :ATLAS : 50 µm x 400 µmCMS : 100 µm x 150 µmALICE : 50 µm x 425 µm
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Semiconductors : Pixels Detectors
CONNECTION BY BUMP BONDING
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Semiconductors : Pixels Detectors
Pitch : 50 µm
(wire bonding typically 200µm)
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CMS ≈ 215 m2
ATLAS ≈ 61 m2
LHCb ≈ 12.5 m2
ALICE ≈ 1.5 m2
CDF ≈ 3.5 m2
NA 11 DELPHI
Semiconductors : Silicon history
CDF
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Semiconductors : CMS Silicon Detector
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Semiconductors : CMS Silicon Detector
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Semiconductors : ATLAS Silicon Detector
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Semiconductors : ATLAS Silicon Detector
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Semiconductors : CMS and ATLAS Silicon Detector
ATLAS : Si Pixels + Si Strips + Gas TRDCMS : Si Pixels + Si Strips
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Semiconductors : Challenges and Evolutions
Main Challenge : The LHC at High Luminosity (2024 ?)
More tracks : Occupancy increases ‐ Less resolutionMore Flux : Radiation (bulk) damage
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Reduce the Occupancy : Increase the granularityMini‐strips sensors (reduce lenght from 10 cm to 5 cm)
‐ Increases the number of channels‐ Increases the cost‐ Increases the power to be dissipated(already3kW in CMS, at ‐10°C)
Reduce the material : Thin Si sensors‐ Reduce the Charges Collected
Reduce the number of layers‐ Reduce the overall Tracker efficiency
300 µm 150 µm
Semiconductors : Challenges and Evolutions
Jean-Marie Brom (IPHC) – [email protected] 37
Change the material : Oxygenated Silicon
HE detectrors : FZ (Float Zone) Crystal ‐ High resistivity > 3‐4 kΩcm‐ O2 contens < 50 10 16
New Materials : DOFZ : O2 doped FZ Silicon (Oxydation of wafer at high temperature)
MCZ (Magnetic Czochralki) ‐ Less resistivity ≈ 1.5 kΩcm‐ O2 contens > 5 10 17
EPITAXIAL growth : Chemical Vapor Deposition on CZ substrate
0 50 100 150 200 250depth [m]
51016
51017
51018
5
O-c
once
ntra
tion
[cm
-3]
51016
51017
51018
5
Cz as grown
DOFZ 72h/1150oCDOFZ 48h/1150oCDOFZ 24h/1150oC [G.Lindstroem et al.]
Oxygen concentration in DOFZ0 10 20 30 40 50 60 70 80 90 100
Depth [m]
51016
51017
51018
5
O-c
once
ntra
tion
[1/c
m3 ]
SIMS 25 m SIMS 25 m
25 m
u25
mu
SIMS 50 mSIMS 50 m
50 m
u50
mu
SIMS 75 mSIMS 75 m
75 m
u75
mu
simulation 25 msimulation 25 msimulation 50 msimulation 50 msimulation 75msimulation 75m
EPIlayer CZ substrate
Oxygen concentration in Epitaxial
Semiconductors : Challenges and Evolutions
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24 GeV/c proton irradiation
0 2 4 6 8 10proton fluence [1014 cm-2]
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Vde
p [V
]
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Nef
f [10
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m-3
]
CZ <100>, TD killedCZ <100>, TD killedMCZ <100>, HelsinkiMCZ <100>, HelsinkiSTFZ <111>STFZ <111>DOFZ <111>, 72 h 11500CDOFZ <111>, 72 h 11500C Standard FZ silicon
• type inversion at ~ 21013 p/cm2
• strong Neff increase at high fluence
Oxygenated FZ (DOFZ)• type inversion at ~ 21013 p/cm2
• reduced Neff increase at high fluence
CZ silicon and MCZ silicon no type inversion in the overall fluence range (verified by TCT measurements)
(verified for CZ silicon by TCT measurements, preliminary result for MCZ silicon) donor generation overcompensates acceptor generation in high fluence range
Common to all materials (after hadron irradiation): reverse current increase increase of trapping (electrons and holes) within ~ 20%
Semiconductors : Challenges and Evolutions
Jean-Marie Brom (IPHC) – [email protected] 39
Semiconductors : Challenges and Evolutions
MAPS (Monolithic Active Sensor) or CMOS (Complementary Metal Oxide Semiconductor)
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Semiconductors : Challenges and Evolutions
3D Silicon Detectors
Manufacturing challenge Electrodes : dead zones
Efficiency vs fluence
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Semiconductors : diamonds
Diamond detectors
CVD Diamond
Si
Z 6 14
Energy Gap 5,5 eV 1,21 to 1,1eV
Resistivity 1013 – 1016Ωcm
105 – 106Ωcm
Breakdown 107 V/cm 3.105 V/cm
Mobility (electrons) 2000 cm2/V/s
1350 cm2/V/s
Mobility (holes) 1600 cm2/V/s
480 cm2/V/s
Displacement Energy (e‐) 43 eV/atom
13 à 20 eV/atom
Pairs Creation 13 eV 3.6 eV
Charge Collection Distance 250 m 100 m ?
Mean signal (MIP) 3600 e‐ / m
8900 e‐ / m
Dielectric Constant 5.5 10 à 12
Thermal Conductivity (W/m∙K)
1600 ‐2000
150
Diamond is better than SiliconDoes not need any dopingBetter radiation hardnessBetter thermal conductivityBetter speed (1psec vs 1 nsec)Light insensitiveMulti‐metalization possible
(test and physics) But :
3 times less signal for MIPs (3.6 / 13)Difficult to manufactureExpensiveDiamond is not understood (at the moment)
2 forms :PolycristallineWafer max.6 inches
Monocrystallinemax : 4 x 4 mm 2
Jean-Marie Brom (IPHC) – [email protected] 42
Semiconductors : Diamonds
CCD : CHARGE COLLECTION DISTANCE
Energy loss (Bethe‐Bloch 1932)
Charge transportation (Hecht 1932)
= e + h = (e e +h h ) E : mean drift distance (mean free path of the carrier) : mobility : lifetimeE : applied electric field
CHARGE COLLECTION DISTANCE :
Si (mono) = 100m
Si (amorphe) =10 µm
Diam = 0(100µm)
Jean-Marie Brom (IPHC) – [email protected] 43
Semiconductors : Diamonds
CCD : MEASUREMENT
Collected charge: QQ 0Ld
E)...(d hhee Charge Collection Distance :
Pairs / MIP : 3600 / 100 µ diamant)
36d Nélectrons
CCD : Measurement of diamond quality (pCVD ou sCVD)
For particle detection :Nélectrons (MIP) ~ 10 000Thickness (Xo…) ~ 300 µm
CCD ~ 280 µm
CCD OK, but different shapes ?
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Semiconductors : Diamonds
Diamant ?
Natural diamond: Lots of impuritiesLots of defects
Diamant HPHT (High Pressure – High Temperature) 1940P > 50 000 barsT > 2000 °C
MonocrystalDimension (few mm2) Impurities
Diamant CVD (Carbon Vapor Deposition) 1980Plasma CH4 – H2 (+X…)
P 0,1 barT 1000 °K
Slow deposition on substrate1 – 50 µm / heure
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Semiconductors : Diamonds
Polycristalline CVD (pCVD)Grows on any substrate (Si)Slow process (around 1µm / h)Cristal bigger along the processIndustrial well controlled process
Substrate
Gowth zoneBig cristalsCCD OK
1 mm = 1000 h !!
Nucleation zoneSmall cristalsLots of boundaries
300 µm
Jean-Marie Brom (IPHC) – [email protected] 46
Semiconductors : Diamonds
Monocrystalline CVD (sCVD)Grows only on another monocrystal (HPTHT seed)small dimensions (typical 4 x 4 mm2)faster processus : 25 µm /h)Very few industrial manufacturers
Cristal
Seed
Jean-Marie Brom (IPHC) – [email protected] 47
Semiconductors : Diamonds
JM Brom LAPP
Finishing :
pCVD : Nucleation (small grains) supppression)
sCVD : Seed suppression
Métalisation (cf bonding)
charactérisation (CCD…)
CleaningRe‐métalisation
Monocristal CVD
seed HPHT
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Semiconductors : Diamonds
JM Brom LAPP
APPLICATIONS IN HEP EXPERIMENTS
Beam Conditions MonitorsBeam Loss Monitors
BaBarCDFATLAS – CMS ‐ LHCb
MAPS vertical integration(Heat Dissipation)Since 2007
Principe :Continuous current measurementwith field E ~ 1 V / µ
Jean-Marie Brom (IPHC) – [email protected] 49
Semiconductors : Diamonds
CDF at FermilabConclusion : Diamond is OK for beam condition monitor
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Semiconductors : Diamonds
Idea in 1995 : Diamond is more resistant than Siliconcan it be used for tracking in very difficult conditions ?
at 4 cm ~1.4 ÷ 1.6 1016 neq/cm2 mainly charged at r> 60cm ~1 ÷ 3 1014 neq/cm2 mainly neutral
LHC Phase II :
2/22/2017 A.Messineo / conveners CERN June 3rd SUWG meeting
High fluence regimeCharged particlespredominant
Low fluence regimeNeutral particlespredominant
Medium fluence regimeCombined Charged and neutral particles
Dat
a an
d si
mul
atio
ns a
gree N
ot a
cle
ar p
ictu
re
Mix
ed ir
radi
atio
nne
w o
ptio
ns/s
cena
rio
Present TrackerLayers radii
L= 8 x 1034
r (cm) X 1013 cm-2 % charged % neutral
4,30 1509,97 84,5 15,57,10 622,76 82,0 18,011,00 297,74 78,7 21,322,00 117,71 69,2 30,832,00 72,39 63,6 36,441,00 54,55 59,1 40,949,00 43,40 55,8 44,258,00 35,47 51,8 48,274,50 19,35 26,0 74,082,50 17,27 21,9 78,190,50 15,78 18,5 81,598,50 14,33 13,9 86,1114,50 12,79 8,4 91,6
Jean-Marie Brom (IPHC) – [email protected] 51
Semiconductors : Diamonds
CVD diamond already tested as pixel sensorsBy ATLAS (pCVD) By CMS (sCVD)
Correct…
But onlyonce…
Jean-Marie Brom (IPHC) – [email protected] 53
Semiconductors : Diamonds
Why ? ‐ Industrial manufacturers (industrial secrets)‐ Characterisation test : CCD measuremen t for a short time.‐ lack of information within the community.‐ Particle physicists are NOT solid state physicists.
The fundamental problems is : Understanding what makes a ’’good’’ diamond
MONODIAM‐HE Project (ANR‐12‐BS05‐0014)
Work with a laboratory expert in growing diamonds (LSPM – Paris)‐ growing sCVD and comparison with industrial sCVDs‐ Understanding the important parameters‐ Improving the quality (for tracking at HE)
Jean-Marie Brom (IPHC) – [email protected] 54
Semiconductors : Diamonds
Answering some questions :
‐ Important parameters for growing diamond (the recipe)‐ Important parameters for preparing the diamond‐ Important parameters to watch
‐ Nitrogen contens‐ Surface finishing‐ Metallisation‐ Long term
JM Brom LPSC‐Grenoble 9 juin 2015
1. Growing conditions : Nitrogen impurities
Adding Nitrogen :Strong effect on growth rates (up to 100 µ/h )
Twinning at the edgesLimitation of twinning at the surfaceEffect on CCD
(incorporation of N2 in the crystal)
Increasing N2 impurities
Industrial sCVD(no N2 ?)
Laboratory sCVD(2 ppm N2 )
Prototypes made at LSPM with variable N2 contents
JM Brom LPSC‐Grenoble 9 juin 2015
thickness N2 cont. CCD max.
CCDNorm.
HT Lim
518 0 512 99 500
582 0 499 86 500
500 0,5 530 106 500
430 1 412 103 400
452 1 550 122 500
571 2 410 72 500
518 4 130 25 1500
20
40
60
80
100
120
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1
AT1502 ‐0ppmAT1503‐ 0ppmAT1319‐0,5ppmAT1355 ‐1ppmAT1514‐1ppmAT1515‐2ppmAT1401‐4ppm
CCD (µ) vs field ‐ variable N2 concentration
0
0,5
1
1,5
0 1 2 3 4
Normalized CCD vs N2 contens at max field
Optimal : 0 to 1 ppm
Study made on several prototypes‐ same laboratory (LSPM)‐ same growing protocol‐ same finishing‐ same metallisation‐ variable N2 contents
2. Surface finishing
Evaluation of the quality of a diamond detector :Measurement of the CCD using MIP (90 Sr)Need : 10 000 e‐ : CCD ≈ 280 – 300µ
≈ 100% for a 300µ sCVD
Example :Industrial sCVDThickness : 635 µCCD about 600 µ
Observation :2 possible problems :
‐ CCD not correct (less than 10000 e‐ )‐ High voltage limitation (less than 1V/µ )
Possibility ?CCD related to defects (traps) in the bulkHV limitation due to surface problems
Use 4 LSPM prototypes sCVD (MM7‐ 1 to 4)grown under the same conditionsin the same reactorat the same timeprepared the same way (same company)
laser cut to separate the HPHT seedprecise polishing
Cleanedmetallised (Cr‐Au) in laboratoryMeasured (CCD and HV limts)
Use 1 industrial (good) sCVD (IND‐1)
JM Brom LPSC‐Grenoble 9 juin 2015
Reprocessing :MM7‐1 : precise re‐polishing by another company (specialized in pCVD)MM7‐ 2 : re‐etched by RIE at laboratoryMM7‐ 3 : Terminated by VUV (172nm) in O2 flux MM7‐ 4 : untouched . For calibration IND ‐ 1 : badly re‐polished (on purpose)
And metallisation Cr‐Au
Before reprocessing After reprocessing ObservationsCVD Side 1 Side 2 Side 1 Side 2
IND ‐ 1 500V 600V 500V 300V degradationMM7‐1 600V 400V 600V 400V sameMM7‐2 200V 400V 400V 500V ImprovementMM7‐3 100V 100V 300V 100V Little improvementMM7‐4 500V 350V 500V 400V same
On HV Limits
As good as it is , polishing may not be enough…Reactive Ion etchingOzonization(and probably very agressive cleaning)
Seems to be having an effect on the HV limitation
JM Brom LPSC‐Grenoble 9 juin 2015
050100150200250300
0 100 200 300 400 500 600 700
CCD (M
icrons)
HV (V)
CCD after Reprocessing
MM7‐1 S1MM7‐1 S2MM7‐2 S1MM7‐2 S2MM7‐3 S1MM7‐3 S2MM7‐4 S1MM7‐4 S2
050
100150200250300
0 100 200 300 400 500 600
CCD (m
icrons)
CCD before Reprocessing
MM7‐1 S1
MM7‐1 S2
MM7‐2 S1
MM7‐2 S2
MM7‐3 S1
MM7‐3 S2
Reprocessinghas a little effect on CCD(given the measuerment
uncertainties)
Conclusion :‐ CCD is related to Bulk quality‐ HV limitation is related to surface quality
and may be improved.
JM Brom LPSC‐Grenoble 9 juin 2015
3. Metallisation Metallisation needed for contacts (wire bonding or bump‐bonding)Early prototypes showed a Schottky Diode BehaviourExtensive researches on diamond contacts
see, for example «
Use Two (industrial) reference detectorsmetalised Cr‐AuTested on different benches
CleanedMetallisation (pulverisation)Tests : Cr‐ Au
WCuAlIn (Cu‐In)
At LSPC‐Grenoble Metal deposition byby microwave plasma‐assisted sputteringCleaning by 2 steps of plasma‐assisted cleaning
At Icube ‐ StrasbourgMetal deposition byVacuum evaporation Cleaning by Hot H2S04 – KNO3
JM Brom LPSC‐Grenoble 9 juin 2015
Cr‐Au : HT limits 500V / 400VCCD 440 µm / 420 µm
W : HT limits 500V / 450VCCD 440 µm / 420 µm
Al : HT limits 500V / 500VCCD 440 µm / 440 µm
Cu : HT limits 500V / 500VCCD 425 µm / 425 µm
Cu‐In : HT limits 500V / 500VCCD 410 µm / 410 µm
Cr‐Au W Al
Cu Cu‐In
JM Brom LPSC‐Grenoble 9 juin 2015
Ti‐Au AlW
Cu Cu‐In
Ti‐Au : HT limit 500V / 500VCCD 380 µm / 380 µm
W : HT limit 500V / 500VCCD 425 µm / 425 µm
Al : HT limit 500V / 500VCCD 460 µm / 460 µm
Cu : HT limit 500V / 500VCCD 410 µm / 410 µm
Cu‐In : HT limit 500V / 450VCCD 410 µm / 420 µm
Various metallisations have very little effect on CCD (Schottky element already stabilized by cleaning ?)
HT limit related to surface quality
JM Brom LPSC‐Grenoble 9 juin 2015
4. Bulk Studies By Cathodo‐luminescence at low temperature(electron beam 10kV, 7nA – T=110°K)
0
2 000
4 000
6 000
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14 000
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18 000
Inte
nsité
(cou
ps)
200 250 300 350 400 450 500 550 600 650 700 750 800Longueur d’onde (nm)
Pic excitonique Réplique 2 du Pic excitonique
SiLarge defects
Réplique 3 du Pic excitonique
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Réplique 2 du Pic excitonique
Réplique 3 du Pic excitonique
Possibly nitrogen relatedcenter (533nm) – low doping
200
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Inte
nsité
(cou
ps)
250 300 350 400 450 500 550 600 650 700 750 800Longueur d’onde (nm)
Lab – 0.5 ppm N2
Industrial
Lab – 2 ppm N2
Lab – 0.5 ppm N2 : Limit HT, limited CCDLab – 2 ppm N2 : HT OK, CCD OKInd ‐ ? : HT OK, CCD OK
Radiation damage
One can see clearly the presence of NitrogenThere are extended defects in all diamondsTest under source (74 MBq ) induces damages: Radiation hardness ?
250 300 400 500 700600 800 nm
JM Brom LPSC‐Grenoble 9 juin 2015
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200 250 300 350 400 450 500 550 600 650 700 750 800Longueur d’onde (nm)
Lab – 0.5 ppm N2Growth Side – CCD 530 µm
Lab – 0.5 ppm N2Nucleation Side – CCD 420 µm
Lab – 0.5 ppm N2Growth Side – CCD 390 µm
Lab – 0.5 ppm N2Nucleation Side – CCD 210 µm
HPHT seed
sCVD
Growth Side
Nucleation Side
More extended defects on the nucleation side (HPHT mirror effect)Even the sCVD are asymetrics (known for the pCVDs)
(with consequences on the CCD)
500400250 600 800 nm300 700
JM Brom LPSC‐Grenoble 9 juin 2015
5. Bulk and surface Studies By Images (Fluorescence / polarised light / X‐ray Tomography)
LSPM – 0 ppm N2results on CCD OK
LSPM – 1 ppm N2results on CCD OK
Industryresults on CCD very good
All sCVD show defects‐ deep dislocations‐ bad polishing‐ N2 incorporation‐ …
JM Brom LPSC‐Grenoble 9 juin 2015
6. Long term effects – ‘’Polarisation’’ ?
Long term measurement leakage current at max field ( ≈1 V/µm)
Total time : 3mins
Back to normal after 20 mins
Slow and continuous increase over 100 hours (about 15%)
Total time : 3 hours
74 MBq sourceClear source effect‘’ slow ‘’ discharges (charging – discharging of traps)
JM Brom LPSC‐Grenoble 9 juin 2015
Total time : 100 h
Total time : 100 h
0
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0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0,9 1,0
C‐SideS‐Side
CCD vs Field E6‐1 Cu
Difference between sidesLower CCD on the nucleation sideMore defects (traps) on the nucleation side
For a ‘’good’’ (industrial) sCVD
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AT1319 ‐ Cr‐Au ‐ Nucleation side 500V Total time : 150 h
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5000
10000
15000
AT1319 ‐ Cr‐Au ‐ Nucleation side 500V Total time : 3 h
pA
pA
pA pA
Strong difference between sidesMore defects (traps) on the nucleation sideCould be a way to evaluate the defects rate ??
JM Brom ‐ VCI feb 2016
Conclusion and prospectives (?)
We have started to adress fundamental problems :
Diamond bulk effectsimpurities (Nitrogen – Boron)bulk defects importance
defects rate have to be understood, and under controlsome ideas exist :
differential growing, immediate anealing, disorientation)
Diamond surface effectssurface finishingmetallisation
problem considered as solved (?)
The main lesson :True :
Developpements in the Research Community may lead to Industrial Developpements.
Wrong : Objects developped in the Industrial World can be easily used in the
Research Community.