Post on 05-Feb-2016
description
karl.gill@cern.ch
High statistics testing of radiation High statistics testing of radiation hardness and reliability of lasers and hardness and reliability of lasers and
photodiodes for CMS optical linksphotodiodes for CMS optical links
Karl Gill
CERN, Geneva
karl.gill@cern.ch LECC 2004
OverviewOverview
• Optical links in CMS• Environment• Advance validation test (AVT)• Results, lasers then photodiodes:
– Radiation damage– Annealing– Ageing
• Summary and Conclusions
karl.gill@cern.ch LECC 2004
CMS optical link projects at CERNCMS optical link projects at CERN
3 optical link systems developed at CERN, with Univ. Minnesota, HEPHY Vienna, INFN Perugia
• Tracker analogue readout
• Control links for Tracker, ECAL, Preshower, Pixels, RPC
• ECAL readout
60000 fibre channels
Aim to share as many components as possible
Focus here on tests on lasers and photodiodes pre-production
karl.gill@cern.ch LECC 2004
Lasers under testLasers under test
1310nm InGaAsP/InP multi-quantum-well edge-emitting lasers
Based on commercial off-the-shelf (COTS) Mitsubishi laser die, ML7CP8 Packaged by STMicroelectronics
Custom mini-pill package for CERN
Typical starting L-I characteristics:
Initial Threshold: 6mA at 20C Output efficiency (out of fibre): 40W/mA
600
500
400
300
200
100
0
pow
er, P
(uW
)
20161284current, I (mA)
L-I data 20 lasers
karl.gill@cern.ch LECC 2004
Photodiodes under testPhotodiodes under test
InGaAs/InP p-i-n photodiodes
Based on commercial off-the-shelf (COTS)
Fermionics FD80S8F
Package includes CERN qualified fibre pigtail and connector
Initial characteristics:
Leakage current <100pA at –5V Responsivity 0.85A/W Capacitance ~1pF at –2V
2photodiodes and 2 lasers on a digital optohybrid (DOH)
karl.gill@cern.ch LECC 2004
Operating environmentOperating environment• Temperature: Tracker -10C, ECAL 20C• Magnetic field 4T• Radiation environment
– 21014/cm2 (E ~ 200MeV)– 100kGy
• Inaccessible over 10 year lifetime
Charged hadron fluence (/cm2) over first 10yrs
r (cm
)
z (cm)
• LHC p p at 14TeV– 150 tracks per pp collision– ~10 collisions every 25ns
karl.gill@cern.ch LECC 2004
Quality Assurance programmeQuality Assurance programme
AVT is essential for COTS parts
Prototype sample validation
Pre-production Qualification
Pre-productionAdvance validation test (AVT)
Lot acceptance
FunctionalityRadiation hardness
FunctionalityRadiation hardnessReliability
Radiation hardnessReliability
Functionality
1996-2000
2000-2002
2003-2004
2003-2005
karl.gill@cern.ch LECC 2004
Advance validation testAdvance validation test
10 devices80C
20 devices(same as test A & B)80C
20 devices100kGy and 51014n/cm2
20-30C
Sampling
Radiationdamage
Tests A & B
Annealing
AcceleratedageingTest C
AcceleratedageingTest D
Success?
Success?
Failureanalysis
Interact withmanufacturer
Procure newwafer
Repeat test
Finalclearance
Advanceclearance
unirr
adia
ted
sam
ples
Yes
No
Yes
No
30 samples
AVT is a unique opportunity to gather and study a large amount of data on radiation damage and reliability
karl.gill@cern.ch LECC 2004
Failure criteriaFailure criteria
Current
Ligh
t pow
er
Laseroutput
Opticalsignal
Inputmodulation
signal
Max
imum
curr
ent
Current
Ligh
t pow
erLaseroutput
Opticalsignal
Inputmodulation
signalM
axim
umcu
rren
t
(a)
(b)
Ligh
t pow
er
Laseroutput
Opticalsignal
Inputmodulation
signal
(c)
• Normal working device
• Device failure due to threshold increase
• Device failure due to efficiency loss
e.g. lasers
karl.gill@cern.ch LECC 2004
Ageing and ReliabilityAgeing and Reliability
• Accelerated ageing examining wearout degradation– Burn in should eliminate early failures and random failures difficult to test
• Thermally activated
early failureperiod
random failure period wear-out failure period
wear-outfailure rate
total failure rate
random failure rate
TIME, t
FAIL
UR
E R
ATE
212
1 11exp)()(
TTkE
TMTTFTMTTF
b
a
karl.gill@cern.ch LECC 2004
Gamma irradiation at SCK-CENGamma irradiation at SCK-CENUp to 60 parts in each AVT
100kGy in 48 hours
30C
In-situ measurements of device characterictics
e.g. laser measurements
karl.gill@cern.ch LECC 2004
Neutron irradiation at UCLNeutron irradiation at UCL
deut
eron
sneutro
ns
Up to 60 parts (3 x 20) in each AVT
51014n/cm2 in 7 hoursEneutron ~ 20MeV
25C
In-situ measurements
karl.gill@cern.ch
Laser resultsLaser results
karl.gill@cern.ch LECC 2004
Radiation Damage in lasers – Radiation Damage in lasers – 6060Co gammaCo gamma
• No significant change after 100kGy
7
6
5
4
Thre
shol
d (m
A)
605040302010Laser sample number
before after 100kGy
H I L
50
45
40
35
30
Effi
cien
cy (
W/m
A)
605040302010
Laser sample number
before after 100kGy
H I L
Threshold currents
Efficiency
Data for 60 lasers from 3 wafers in AVT 3
karl.gill@cern.ch LECC 2004
Radiation Damage in lasers – 20MeV neutronsRadiation Damage in lasers – 20MeV neutrons
• A lot of damage from neutrons
– Increase in laser threshold current
– Decrease of laser efficiency
Typical L-I characteristics before and after 5x1014n/cm2
1000
800
600
400
200
0
Out
put l
ight
pow
er, L
(W
)
50403020100Current, I (mA)
before irrad after 5x1014n/cm2
karl.gill@cern.ch LECC 2004
Neutron damage effects in lasersNeutron damage effects in lasers
• Damage proportional to fluence
– Degradation of carrier lifetime
• After 4.5x1014n/cm2
– Threshold increase ~20mA– Efficiency loss ~20%
25
20
15
10
5
0
thre
shol
d in
crea
se (m
A)
1.0 2.0 3.0 4.0
~20MeV neutron fluence (1014n/cm2)
1.00
0.95
0.90
0.85
0.80
0.75
0.70
relative efficiency, E/E
(0)
efficiency
threshold
Data for 20 lasers from 1 wafer
00 1
knr
karl.gill@cern.ch LECC 2004
Laser wafer comparison: thresholdsLaser wafer comparison: thresholds
• 5 AVTs = 4 to 61014n/cm2
time 6 – 7.5 hrs• To compare wafers, normalized results
51014n/cm2 using only first 6 hr of data
30
20
10
0thre
shol
d in
crea
se (m
A)
6420
time, t (hrs)
5
05
0
Num
ber o
f las
ers
5
0
threshold increase after 5x1014neutrons/cm2 (mA)
5
05
05
05
05
05
05
05
05
05
020
10
0343230282624222018
A
B
C
D
E
F
G
H
I
L
M
N
O
All wafers
• Similar damage in lasers from a given wafer• Some variation across wafers• Average damage 24mA
– 400% of initial threshold value
karl.gill@cern.ch LECC 2004
Laser wafer comparison: efficiencyLaser wafer comparison: efficiency
• Larger spread across a wafer• Similar results from wafer to wafer• Average damage 23%
1.0
0.9
0.8
0.7
0.6Effi
cien
cy c
hang
e, u
W/m
A
6420
time, hours
420420
Num
ber o
f las
ers
420
relative efficiency loss (/E0) after 5x1014n/cm2
420420420420420420420420420420
2010
00.400.350.300.250.200.150.10
A
B
C
D
E
F
G
H
I
L
M
N
O
All wafers
karl.gill@cern.ch LECC 2004
Annealing in lasersAnnealing in lasers• Significant amount of annealing
– Proportional to log(tanneal)• distribution of activation energies
for annealing
• Similar rate for efficiency
– damage mechanism same as Ithr
• Expect at least 70% annealing after 10 years
102 105103 104
1.0
0.8
0.6
0.4
fract
ion
of d
amag
e re
mai
ning
1.0
0.8
0.6
0.40.1 1 10 100
annealing time (hrs)
wafer E
threshold damage
efficiency damage
0.4
0.2
karl.gill@cern.ch LECC 2004
Thermally accelerated ageing of unirradiated Thermally accelerated ageing of unirradiated laserslasers
• Most wafers (11 out of 13) very little wearout degradation observed• Wafer M is one of 2 wafers with lower reliability• 1000 hours at 80ºC corresponds to 4x106 hours at –10ºC (CMS Tracker)
– assuming Ea=0.7eV
10
9
8
7
6
thre
shol
d cu
rren
t at 2
0ºC
(mA
)
6.0
5.5
5.0
4.5
4.0
6.0
5.5
5.0
4.5
4.01400120010008006004002000
ageing time at 80ºC (hrs)
M
N
O
50
45
40
35
30
effic
ienc
y at
20º
C (
W/m
A)
50
45
40
35
30
50
45
40
35
30120010008006004002000
ageing time at 80ºC(hrs)
M
N
O
karl.gill@cern.ch LECC 2004
Distribution of device lifetimes in unirradiated Distribution of device lifetimes in unirradiated laserslasers• Wearout data extrapolated to failure criteria
• Log-normal distribution of failures– Typical of semiconductor devices
• Long lifetimes compared to project timescale– Especially at CMS operating temperatures– Estimate failure rates after 10 years
• 20FITs in CMS Tracker• 1000FITs in CMS ECAL
• Few devices will wear out. – Probably will be dominated by random failures.
• Failure distributions similar for most wafers– Except A and M, will try to avoid using these
10
20
30
40
50
60
70
80
90
Cum
ulat
ive
failu
res
105 106 107 108
Time to failure at 80ºC (hours)
threshold failure (I=55mA)
10
20
30
40
50
60
70
80
90
Cum
ulat
ive
failu
res
103 104 105 106 107
Time to failure at 80ºC (hours)
efficiency failure(
A M
AM
karl.gill@cern.ch LECC 2004
Thermally accelerated ageing of irradiated lasersThermally accelerated ageing of irradiated lasers
• Measurements made at 20ºC at periodic intervals
– (no lasing at 80ºC)
• No wearout observable
• Only annealing– Perhaps this masks the wearout
30
20
10
0
thre
shol
d cu
rren
t mea
sure
d at
20º
C (m
A)
30
20
10
0
30
20
10
010008006004002000
ageing time at 80ºC (hours)
H
I
L
karl.gill@cern.ch
Photodiode resultsPhotodiode results
karl.gill@cern.ch LECC 2004
Radiation Damage in photodiodes – leakage Radiation Damage in photodiodes – leakage currentscurrents
• Increase in leakage current after neutron irradiation– Similar level across all 60 devices– Expect maximum 10A after 10 years at LHC (2x1014/cm2 equivalent to 5x1014n/cm2 at CRC)
• Damage not a problem • dc optical levels generate greater currents in photodiode
– Small amount of annealing just after irradiation
• [No damage from 100kGy gammas]
0.01
0.1
1
10
100
leak
age
curr
ent,
I dar
k (1
0-6A
)
0.1 1 10
neutron fluence, (1014/cm2)
5V
1.00
0.95
0.90
0.85
0.80
0.75
0.70
un-a
nnea
led
dam
age
fract
ion
4003002001000
annealing time, tanneal (hrs)
karl.gill@cern.ch LECC 2004
Radiation Damage in photodiodes – Radiation Damage in photodiodes – photocurrentsphotocurrents
• Complicated evolution of photocurrent [responsivity] with fluence– Not understood but fairly consistent from device to device– No more than 32% loss over fluence range tested– Again, only small amount of annealing just after irradiation
• Not same rate as for leakage current so probably different defects responsible for the two effects
• [Again, no damage from 100kGy gammas]
1.0
0.9
0.8
0.7
0.6
rela
tive
phot
ocur
rent
, Iph
oto/
I pho
to(0
)
121086420
neutron fluence, (1014/cm2)
1.0
0.9
0.8
0.7
0.6
1.0
0.9
0.8
0.7
0.6
wafer 1
wafer 2
wafer 3
1.00
0.95
0.90
0.85
0.80
0.75
0.70
un-a
nnea
led
dam
age
fract
ion
4003002001000
annealing time, tanneal (hrs)
karl.gill@cern.ch LECC 2004
Thermally accelerated ageing of photodiodesThermally accelerated ageing of photodiodes
• No wearout degradation observed in any of the 60 devices• Only annealing of leakage current (but not photocurrent)• 800 hours at 80ºC corresponds to ~107 hours at –10ºC (CMS Tracker)
– assuming Ea=1eV
500
400
300
200
100
0
Leak
age
curr
ent,
I leak
(10-6
A)
8006004002000
time, t (hours)
5V
Unirradiated samples
200
180
160
140
120
100
80
60
Pho
tocu
rren
t, I p
hoto
(10-6
A)
8006004002000
time, t (hours)
5V
karl.gill@cern.ch LECC 2004
Summary and ConclusionsSummary and Conclusions• AVT procedure established as part of ongoing QA Programme
– Aim to reject unsuitable parts before mass production• 390 Lasers tested out of 60000 from 13 wafers in 5 AVTs• 90 Photodiodes tested out of >4000 from 3 wafers in 1 AVT
• Radiation damage very well characterised, great statistics:– No damage from 100kGy gammas but significant damage from 5x1014n/cm2
– Equivalent to worst case in CMS (first 10 years)• Lasers
– Average 24mA increase of threshold current, 23% efficiency loss, significant annealing– Final damage in CMS will be limited to ~6mA threshold increase, 6% efficiency loss
• Photodiodes– Increase of leakage current up to 10A, and up to 30% signal loss expected in CMS
• Very little wearout degradation under thermally accelerated ageing– Lasers
• Device lifetimes >106 hours under CMS conditions.• Two wafers are 10x less reliable than others, will try to avoid using them
– Photodiodes• No wearout. Device lifetimes extraordinarily large.
• Program of tests started in 1996 almost finished!