Semiconductor Vertex Detectors for High
Luminosity Environments
 The Dawn of Vertexing
 e+e- colliders
 Through Tevatron, towards LHC
 The Golden Age
 some villains
 and some heroes
 Super Heroes of the future
 The Rise and Rise of pixels: MAPs, DEPFETs,
CCDs, 3d detectors, SOI…
 Rad Hard(er) Devices: Novel materials, device
engineering…
19th February, VCI 2007
Paula Collins, CERN
Paula Collins, CERN
1
Alternatively…
To Infinity and Beyond!
SLHC
Who will be the true
superhero of the SLHC
era?
19th February, VCI 2007
Paula Collins, CERN
2
Alternatively….
How do I cope with
having 10
quadrillion particles
thrown at me?*
*1016 fluence / cm2 at 4cm SLHC
19th February, VCI 2007
Paula Collins, CERN
3
The LEP era
Singapore Conference, 1990
‘The LEP experiments are beginning to reconstruct B mesons… It
will be interesting to see whether they will be able to use
these events’
Gittleman, Heavy Flavour Review
10 fun packed
years later,
heavy flavour
physics
represented
40% of LEP
publications
19th February, VCI 2007
Paula Collins, CERN
4
and more…
 semiconductor vertex detectors used for
 vertexing
 flavour tagging, lifetimes..
 help in tracking
 triggering
 even dE/dx…
 used at all current HEP collider experiments
 exploits great precision and small beampipes
Reconstructed B-mesons in the
DELPHI microvertex detector
B hadron
Vertex
Primary
Vertex
19th February, VCI 2007
Paula Collins, CERN
tB  1.6 ps l = ctg  500 mmg
5
Challenge of the LHC
ATLAS
at full luminosity L=1034 cm-2 s-1:
 ~23 overlapping interactions in each bunch
crossing every 25 ns ( = 40 MHz )
 inside tracker acceptance (|h|<2.5) 750
charged tracks per bunch crossing
 per year: ~5x1014 bb; ~1014 tt; ~20,000 higgs;
but also ~1016 inelastic collisions – impact
parameter resolution important
 Fast Hadron dose at 4 cm after 10 years/500
fb-1 is 3 x 1015 cm-2
 Fast Hadron Dose at 22 cm after 10 years/
500 fb-1 is 1.5 x 1014 cm-2
 detector requirements: speed, granularity,
radiation hardness
19th February, VCI 2007
Paula Collins, CERN
neq/cm2 per year
 severe radiation damage to detectors:
LHCb
radius [cm]
6
What of the future?
The problems pile up…..
19th February, VCI 2007
Paula Collins, CERN
7
SLHC environment
 Integrated Luminosity 2500 fb-1 = 5 x LHC
 dictates technology choice
 Peak luminosity 1035 cm-2 s-1 = 10 x LHC
 dictates detector granularity
 Scenarios dominated by 50ns or 25 ns running
Phase 1: no major change in LHC
L = 2.34 ∙1034cm-2s-1 (higher beam current)
Phase 2: major changes in LHC
L = 4.6 ∙1034 cm-2s-1 with (BL/2, qc)
L = 9.2 ∙1034 cm-2s-1 with (fill all bunches)
Phase 3: increase beam energy to 14 TeV
(9 to 17 T magnets)
 Detector R&D focused on
 short term replacement/upgrades e.g. replacement of ATLAS b layer
after 2-3 years (1015 neq), CMS Phase 1 pixel replacement, replacement
of LHCb VELO …
 SLHC upgrades (major changes expected to modules and electronics
SLHC fluences
R=75cm, 1.5 1014 cm-2
3.5 MRad, charged hadrons 20%
R=20cm, 1 1015 cm-2
30 MRad, charged hadrons 50%
R=4cm, 1.6 1016 cm-2
400 MRad, charged hadrons 100%
19th February, VCI 2007
Mika Huhtinen
Paula Collins, CERN
8
Non Ionizing Energy Loss NIEL: displacement damage
Point defects
+ clusters
Dominated by
clusters
A common language:
“1 MeV neutron equivalent”
Use the NIEL scaling
factors
19th February, VCI 2007
NIEL allows us to look into the future and
predict what will happen in complex
environments
(!) Is known to fail for neutrons/charged
hadrons in some cases
Paula Collins, CERN
9
Radiation Damage: Traditional Villains
Increased Leakage Current
10-1
I / V [A/cm3]
Noise
Hard to bias
e.g. I(-10
oC)=1/16
I(20oC)
10-3
n-type FZ - 780 cm
n-type FZ - 410 cm
n-type FZ - 130 cm
n-type FZ - 110 cm
n-type CZ - 140 cm
p-type EPI - 380 cm
10-4
10-5
10-6 11
10
 E

I  exp   g

2
k
T
B 

1012
1013
eq [cm-2]
anneals with time and
temperature
Effective Doping Changes
negative space charge builds up,
depletion voltage changes
Junction moves from p+ to n+ side
Buildup of negative space
charge worsening in time
Strongly temperature
dependent: 500 years @ -10oC
= 21 hours at 60oC!
19th February, VCI 2007
1014
1015
[M.Moll PhD Thesis]
a, the damage parameter,
very consistent for a wide
range of impurities and silicon
types
Fluence
Depletion voltage [V]
Annealing effects
I/V=a * f
Depletion voltage [V]
strong temperature
dependence – cooling
essential
n-type FZ - 7 to 25 Kcm
n-type FZ - 7 Kcm
n-type FZ - 4 Kcm
n-type FZ - 3 Kcm
p-type EPI - 2 and 4 Kcm
10-2
Paula Collins, CERN
time [years]
10
New Villain: trapping
Trapping is characterized by an effective trapping time teff
for e- and h:


1

Qe ,h (t )  Q0 e ,h exp 
t
 t

 eff e ,h 
1
where
t eff e,h
0.5
24 GeV/c proton irradiation
0.4
data for electrons
data for holes
1/t changes with annealing
Inverse trapping time 1/t [ns-1]
Inverse trapping time 1/t [ns-1]
Increase of 1/t with fluence
0.3
0.2
0.1
[M.Moll; Data: O.Krasel, PhD thesis 2004, Uni Dortmund]
0
0
2.1014 4.1014 6.1014 8.1014
 N defects  fluence
1015
0.25
24 GeV/c proton irradiation
eq = 4.5.1014 cm-2
0.2
0.15
data for holes
data for electrons
[M.Moll; Data: O.Krasel, PhD thesis 2004, Uni Dortmund]
0.1
particle fluence - eq [cm-2]


 10 cm / s  2  10
1
5 10
5 102
annealing time at 60oC [min]
t eff (1015 )  2ns
w  vsatt eff  10 7 cm / s  2  10 9 s  200 mm
t (1016 )  0.2ns
w  vsatt eff
19theff
February, VCI 2007
7
Paula Collins, CERN
5 103
10
s  20 mm
Huge
Decrease
in CCE?
11
Radiation Damage: Is Neff really so bad?
V. Chiochia et.al.
IEEE Trans. Nucl. Sci 52 (2005) 1067
Charge collection measured
using cluster profiles in a row
of pixels illuminated by a 15º
beam and no magnetic field
after type inversion
-
 = 6x1014 n/cm2
Neff=NDNA<0
19th February, VCI 2007
Model with constant space charge density
does not describe the measured charge collection
Paula Collins, CERN
12
Two trap model
EA/D = trap energy level fixed
NA/D = trap densities from fit
se/h = trapping cross sections
from fit
1=6x1014 n/cm2,
NA/ND=0.40, sh/se=0.25
 Data
--- Simulation
n+-p junction
n-p+ junction
E
19th February, VCI 2007
Paula Collins, CERN V.Chiochia, Vertex 05
13
Radiation damage as experienced in running
HEP experiments
NA60 first use of pixels in high multiplicity experiment dimuon
production by 158 gev indium ions
16 planes of silicon pixel detectors
12.8 x 13.6 mm2 active area
32 x 256 cell matrix
50 x 425 um2 cell size
ALICE 1LHCb readout chips
ATLAS faster pixels
radiation damage
type inversion
after 4 weeks
running 4x1012 ions on
target
~1013 neutrons equivalent
19th February, VCI 2007
Paula Collins, CERN
14
Irradiation at CDF/D0
 2 fb-1 data collected (goal = 5-8fb1)
 L00 (1.4cm) SVXII (2.5-10.6cm),
ISL
 Ionising dose measured with TLDs




3cm z<45cm: 300 +- 60 kRad/fb-1
scales as 1/ra (1.5 < a < 2.1)
L00 2 MRad, SVX layer 0 800 kRad
Measured depletion voltages both
with signal and noise methods
Ignacio Redondo, CMS workshop, 20th October 2006
L0 depletion Voltage
19th February, VCI 2007
Paula Collins, CERN
15
tackling the villains
Defect Engineering
 Oxygen enriched silicon
Cz silicon
…
New Sensor Materials
Silicon Carbide
Amorphous silicon
Compound semiconductors
Diamond
Device Engineering
 p-type silicon detectors
Operational conditions
thin detectors
 Cryogenic operation
3D See talk of S. Eckert
3D silicon stacks
Monolithic devices -> see talk of J. Mnich
DEPFETS
-> see talk of W. Dulinkski
MAPS
CCDs with on situ storage
SOI … -> see talk of Toru Tsuboyama
+ posters of Bamberger, Traversi, Gabrielli, Servoli, Luuka,
19th February, VCI 2007
Paula Collins, CERN
16
new kid on the block: p-type substrate



n-on-n already preferred option for
ATLAS, CMS, and LHCb
Faster charge collection
underdepleted operation an option
After type inversion n-on-n
effectively becomes p-on-n: Why not
start with step p type substrates
p side
n side
Efficiency

ATLAS
ATLAS
Vbias
NIM A 450 (2000) 297
Reminder: figure shown at
VCI 2001 – silicon experts
p side
learn about weighting field!!
n side
Resolution [mm]
19th February, VCI 2007
Paula Collins, CERN
Vbias
LHCb
LHC
b
Vbias
Vbias
NIM A 440 (2000) 17
17
p type continued

Advantages of p-type
 high field region always on the strip side –
no need for (expensive) double sided
processing
 easier handling
 proven radiation hardness
 collect electrons – slightly less susceptible
to trapping after neutron irradiation
 indication of good annealing behaviour (as
measured with CCE) cooling, handling
 Effort going into characterising strip
isolation methods (as for n-in-n)
S2
high-field regions
RD50 collaboration with CNM, Micron
 FZ, DOFZ, MCz silicon
 pads, strips, pixels
 p-stop, p-spray
 Many groups: Liverpool,
IFIC, KEK, INFN..
p-stop
p-spray
S1

S1
p-spray/p-stop
S2
high-field regions
Cint, VBR improve with radiation Cint, VBR degrade with radiation
19th February, VCI 2007
Paulainitially
Collins, CERN
(Oox), worse initially
(Oox), better
S1
S2
high-field region
depends on Qox
compromise
18
p type; irradiation of short strip devices
Detector geometry: Thickness=300 mm, strip pitch=80 mm, implant width= 18 mm,
LHC speed readout (SCT128A-HC), beta source measurements
n-in-p : annealing
n-in-p : standard FZ
 ~40% charge loss after 3x1015 p/cm2 (23 GeV)
 ~7000 e after 7.5x1015 p/cm2 (23 GeV)
 3 x 1015 n/cm2
 Vdep ~ 1200 V
Vfd~1200 V
0.7x1015
Vfd>2500 V
1.9x1015
4.7x1015
10x1015
P.P. Allport et al.,
IEEE Trans. NS
52(5) (2005)
1903.
Performance superior to p-on-n
(n-on-n unknown at these fluences)
19th February, VCI 2007
Collected Charge (ke)
14
Vfd
12
10
8
6
600 V
4
400 V
2
900 V
G. Casse, this conference
0
M Lozano,
this conference
1
10
100
1000
10000
Eq. days @ 20 oC
Annealing behaviour w.r.t. CCE spectacular
Paula Collins, CERN
19
p type continued
 Full scale sensors
manufactured for LHCb and
placed in final detector layout
in test beam
 8.4 cm diameter sensors
 strip pitch 40-100 mm
 excellent leakage currents
 fraction of bad strips < 1%
 preliminary results show preirradiation performance very
comparable to n-in-n –
technology feasibility
demonstrated
p-type IV characteristics
2433-07A
Current (uA)
2433-08C
1000.00
2433-10A
100.00
2433-12A
2433-12B
10.00
2433-01D
1.00
0.10
0
100
200
300
400
2433-06D
2433-05D
0.01
0.00
19th February, VCI 2007
2433-01E
Volts
T. Bowcock
2433-05E
2488-01D
2488-01E
Paula Collins,
CERN
20
Oxygen lessons from LHC
10
8
Carbon-enriched (P503)
Standard (P51)
O-diffusion 24 hours (P52)
O-diffusion 48 hours (P54)
O-diffusion 72 hours (P56)
Carbonated
500
6
Standard
2
0
0
400
300
4
Oxygenated
However, note that neutron irradiation is
3xmore damaging and constant for all materials…
600
200
Vdep [V] (300 mm)
|Neff| [1012cm-3]
Based on RD48 discovery
that Vfd varies more slowly
for oxygenated sensors, DOFZ
chosen for detectors in most
irradiated regions of ATLAS,CMS,LHCb
100
1
2
3
4
24 GeV/c proton [1014 cm-2]
5
try materials naturally rich in Oxygen
Czochralski silicon
Pull Si-crystal from a Si-melt
contained in a silica crucible while
rotating.
Silica crucible is dissolving
oxygen into the melt  high
concentration of O in CZ
Material used by IC industry
(cheap), now available in high
purity for use as particle
detector (MCz)
19th February, VCI 2007
Epitaxial silicon
Chemical-Vapor Deposition (CVD) of Silicon
CZ silicon substrate used  diffusion of
oxygen
Growth rate about 1mm/min
Excellent homogeneity of resistivity
150 mm thick layers produced (thicker is
possible)
price depending on thickness of epi-layer
but not extending ~ 3 x price of FZ wafer
Paula Collins, CERN
21
Oxygen concentration in FZ, Cz, and EPI
Epitaxial silicon
1018
5
Cz as grown
1017
5
1016
5
0
1017
5
DOFZ 72h/1150oC
DOFZ 48h/1150oC
DOFZ 24h/1150oC
50
100
[G.Lindstroem et al.]
150
depth [mm]
200
250
1016
5
75 mu
50 mu
5
5
1018
5
CZ substrate
25 mu
5
EPI
layer
O-concentration [1/cm3]
O-concentration [cm-3]
Cz: high homogeneous
concentration and formation of
Thermal Donors (reducing
acceptors due to radiation)
1018
5
1017
5
1016
5
0
SIMS 25 mm
SIMS 50 mm
SIMS 75 mm
simulation 25 mm
simulation 50 mm
simulation 75mm
10 20 30 40 50[G.Lindström
60 70
80European
90 Symposium
100 on
et al.,10
Semiconductor
Detectors,
12-16
June
2005]
Depth [mm]
th
EPI: inhomogeneous O
DOFZ: inhomogeneous oxygen
concentration due to diffusion
distribution, increasing with time
from substrate into epi-layer
at high
temperature
19th February,
VCI 2007
during production
Paula Collins, CERN
22
MCz silicon
irradiation with charged hadrons
8
Carbonated
600
PN std irradiated 3E13 p/cm2
PN oxg irradiated 3E13 p/cm2
PN std irradiated 2E14 p/cm2
PN oxg irradiated 2E14 p/cm2
PN std irradiated 3E14 p/cm2
PN oxg irradiated 3E14 p/cm2
NP std. irradiated 3E14 p/cm2
MCZ irradiated 3E13 p/cm2
MCZ irradiated 2E14 p/cm2
MCZ irradiated 3E14 p/cm2
140
120
500
MCz-n Helsinki
6
Standard
-3
400
300
4
Oxygenated
2
Vdep [V] (300 mm)
Carbon-enriched (P503)
Standard (P51)
O-diffusion 24 hours (P52)
O-diffusion 48 hours (P54)
O-diffusion 72 hours (P56)
Neff (x 1E11 cm )
|Neff| [1012cm-3]
10
200
100
100
80
T=80ºC
FZ
60
DOFZ
40
p-type
20
0
n-type
-20
Cz
-40
0
0
1
1
2
3
4
24 GeV/c proton [1014 cm-2]
5
E. Tuovinen
et. al.
4th RD50 workshop
10
100
Time (min)
Annealing behaviour
1000G. Pellegrini et. al “Annealing Studies
of magnetic Czochralski silicon
radiation detectors”
 Gradient of slope after minimum (b) is smaller for MCz than for FZ for 10
MeV, 50 MeV and 24 GeV proton irradiation
 The effective trap introduction rate for both electrons and holes is similar
for MCz, FZ, and DOFZ silicon
 Leakage current behaviour is also similar
19th February, VCI 2007
Paula Collins, CERN
Many groups studying Cz, MCz:
INFN, Glasgow, BNL, HIP,
Purdue, Liverpool,
Rochester…
23
MCz TCT measurements
300

4
250
3
200
150
2
100
hole
collection
1013
5
1014
24 GeV/c protons [ cm-2 ]
High
field
5
5x1014
p/cm2
electron
collection
High
field
Low
field
Low
field
19th February, VCI 2007
1
MCZ (n320) - Vfd from IV
MCZ (n320) - Vfd from CV
50
| Neff | [ 1012 cm-3 ]

TCT measurements confirm that
after irradiation with charged
hadrons the material does not type
invert
the trap introduction rate for holes
and electrons is similar for FZ, DOFZ
and MCz silicon
This behaviour can be understood
qualitatively as a build up of donors,
which overcompensates the
(classical) introduction of acceptors
Vfd [V]

Paula Collins, CERN
Time [ns] 1
4
A. Bates, VERTEX 04
24
MCz TCT measurements continued
[D. Menichelli, RD50 Workshop, Nov..2005]
1 MeV, = 5 ×1014 cm-2 CZ n-Si,
p+
n+
Φ (1014n*cm-2)
 Irradiation with neutrons shows a more complex picture
 High field region on n+ side implies type inversion
 In this respect MCz and FZ behave similarly
p+
E(x) is non-uniform in these sensors (as in other,
n+
E2
2
non MCz, heavily irradiated structures)
E1 1
hn
Consider 3 regions: Neff>0, electrically neutral, Neff<0
reverse current flow induces electric field in electrically
B
Eb
neutral base
For detector performance, Vdep is an “abstract concept”
W2
W1 W
More important to consider CCE, charge collection time etc.
b
19th February, VCI 2007
25
Verbitskya et.al. NIM A 557 (2006) 528
Paula Collins, CERN
MCz CCE
MCz Si microstrip detectors
p-type MCz Si MG diodes
1,0
1,0
0,8
0,8
13
0,4
CCE
CCE
0,6
2
4.0x10 n/cm SMG1
13
2
6.8x10 n/cm SMG2
14
2
1.4x10 n/cm SMG4
14
2
2.7x10 n/cm SMG7
14
2
6.8x10 n/cm SMG16
0,2
0,0
0
200 400 600
Voltage [Volt]
800
0,4
1000
p type MCz Si diodes, proton irradiated
AC coupled r/o shaping time 2.4us
At overdepletion 90% CCE for 6.8 x 1014 neq
Sadrozinski
STD07
19th February, VCI 2007
m bruzzi et al, hiroshima
symposium 2006
0,6
0,2
non-irradiated
14
2
3.3x10 n/cm
0
200
400
600
800
Voltage [Volt]
p-on-n MCz microstrip device, 200 ns shaping time
proton irradiated
90% CCE achieved at 500V for 3.3 x 1014 neq
Simulation predicts for 300 and 200 um thick
a S/N of 10 at 3 x 1015 which would be adequate
for operation of a detector
Paula Collins, CERN
26
EPI silicon
G. Lindström et al.
neutron irradiation
Kramberger et al 8th RD50 workshop June 2006
G. Kramberger et al., 8th RD50 workshop
SMART coll., 8th RD50 workshop
Neutron irradiation: excellent peformance of
Neff evolution; no SCSI for 50 mm sample
CCE measured with mips : 3200 electrons
after 8 x 1014 neq / cm2
Superrad hard : Fledermaus-man? (performs
best in superhero mode…)
19th February, VCI 2007
Paula Collins, CERN
27
EPI silicon : annealing behaviour
Kramberger et al 8th RD50
workshop June 2006

Annealing behaviour shows drop of Vdep in time
Using the LHC operation model:


With cooling when not operated
600
Operation without cooling is beneficial!!!
S-LHC scenario
Vfd [V]

Radiation @ 4cm: eq(year) = 3.5  1015 cm-2
SLHC-scenario:
 1 year = 100 days beam (-7C)
 30 days maintenance (20C)
 235 days no beam (-7C or 20C)
500
50 mm cold
50 mm warm
400
25 mm cold
25 mm warm
300
Without cooling when
not operated
200
100
19th February, VCI 2007
0
0
365
Paula Collins,
CERN
730
1095
time [days]
G.Lindström et al.,10th European
Symposium on Semiconductor Detectors,
12-16 June 2005 (Damage projection:28
M.Moll)
1460
1825
Diamond
Polycrystalline Diamonds
traditionally grown by CVD
large band gap and strong atomic
bonds give fantastic radiation
hardness
low leakage current and low
capacitance both give low noise
3 (1.5) times better mobility and 2x
better saturation velocity give fast
signal collection
Ionization energy is high: MIP 2x
less signal for same X0 (w.r.t. SI)
Diamond: 13.9ke- in 361 mm
SI: 26.800 ke- in 282 mm
In Polycrystalline Diamond grainboundaries, dislocations, and defects:
limits carrier lifetime, mobility and
charge collection distance and
position resolution
19th February, VCI 2007
Grain size: ~100-150μm
growth
substrate
Diamond as detector material now well
established with BCM as first large scale
(HEP) application
Detector application (pixel, strip, pad) 29
Paula Collins, CERN
demonstrated
Radiation Hardness of pCVD diamond
 pCVD charge collection distances of
250-300 mm now routinely achieved
 charge collection distance saturates
at 1V/mm
 pCVD detectors have been built as
pixel,
pad, strip detectors
 Proton irradiation of strip
detectors to 2.2x1015/cm2:
 15% loss of S/N at 2.2x1015/cm2
 Decrease of leakage current (~
pA)
 Improvement of resolution by
~35% - irradiated material is
more “uniform”
 Proton irradiation to 1.8 x
1016/cm2
 75% loss of signal
 S/N performance > 10
19th February, VCI 2007
Paula Collins, CERN
30
Single Crystal Diamond
• Single crystal diamond has been fabricated with
Element six ≈ 10 mm × 10mm, >1 mm thickness.
• Largest scCVD diamond ≈ 14 mm × 14 mm.
Most probable charge versus thickness
 High quality scCVD diamond can
collect full charge at 0.2 V/um
 Width of Landau distribution is ≈ 1/2
that of silicon, ≈ 1/3 that of pCVD
diamond
 radiation hardness under study
d=320 μm

Excellent mobility. For this sample:
 µ0h = 1714 cm2/Vs, µ0e = 2064 cm2/Vs
High drift velocity  better lifetimes 
charge trapping might not be an issue
19th February, VCI 2007
Paula Collins, CERN
QMP=9500e-
31
Irradiation: 3d detectors
Proposed
by
Parker,
Kenney
1995
Planar Device
3D Device
 Maximum drift and depletion
distance governed by electrode
spacing
Lower depletion voltages
Radiation hardness
Fast response
same technology: dope edges of sensor for
edgeless detection efficiency
 At the price of more complex processing
19th February,
VCI 2007
 Narrow
dead regions at wells Paula Collins, CERN




Unit cell defined by
e.g. hexagonal
array of electrodes
32
How do we make the holes?
p
n
p
n
(not like this)
19th February, VCI 2007
Paula Collins, CERN
33
3d detector processing
Non Standard Processing: Wafer bonding, Deep reactive ion etching ,
Low pressure chemical vapor deposition, Metal deposition  Mass
production expensive
1) ETCHING THE ELECTRODES
2) FILLING THE ELECTRODES
Aspect ratio:
D:d = 11:1
IR picture of 2 bonded wafers
290 mm
WAFER BONDING
(mechanical
stability)
Si-OH + HO-Si ->
Si-O-Si + H2O
d
DEEP REACTIVE
ION ETCHING
(electrodes
definition)
Bosh process
SiF4 (gas) +C4F8
(teflon)
C shaped test structure
~1VCI
mm2007
difference between top and bottom
19th February,
Paula Collins, CERN
D
LOW PRESSURE
CHEMICAL VAPOR
DEPOSITION
(Electrodes filling with
conformal doped
polysilicon)
2P2O5 +5 Si-> 4P + 5 SiO2
2B2O3 +3Si -> 4 B +3 SiO2
METAL
DEPOSITION
Shorting electrodes
of the same type
with Al for strip
electronics readout
or deposit metal for
bump-bonding
34
3d detectors: characteristics
Efficiency measured in testbeam 98%
rise time seen on oscilloscope
Aug 2006, H8 CERN beam line
100 GeV/c pions
Institutes:
Stanford
Brunel/Manchester
Hawaii/LBL
New Mexico
Glasgow
Freiburg
Bonn
Praha
Genova
Oslo
+++
19th February, VCI 2007
Paula Collins, CERN
4000 e
threshold
40V depletion
v
35
3d detectors: radiation hardness




electrode spacing 71 mm
n type before irradiation
Irradiated with reactor neutrons
signal height measured on scope
Compilation plot from C. da Via
M Lozano, n-on-p
this conference
19th February, VCI 2007
EPI
Paula Collins, CERN
36
Different Geometry: 3D devices
1um
0.4um
Passivation
Oxide
50mm
Metal
5mm
n+ doped
P-stop
p+
10mm
TEOS 2um
300mm
Poly 3mm
p- type
substrate
p+ doped
50mm
p+ doped
Oxide
Metal
55um pitch
19th February, VCI 2007
Paula Collins, CERN
Design proposed by RD50
collaboration (IRST, CNM,
Glasgow)
•much simplified process – no
need for support wafer during
production
•single sided processing with
additional step of etching and
B diffusion
See S. Eckert talk for
beautiful results
37
What about the ILC?
At LC:
“x sections are tiny”
“No radiation issues”
“Triggerless operation possible”
“Modest rates”
30% E
Why not use a LEP detector?
we need to trim the X0!
LC physics demands
Excellent
Vertexing (b,c,t)
and Tracking
 in a high B field
 with energy flow
19th February, VCI 2007
t t event at 350 GeV
Paula Collins, CERN
38
Silicon for vertexing @ the ILC
Required Vertexing performance
Flavour tagging: beauty + charm
discriminate b
e  e   tt  bq qb q q
Vertex detector characteristics
point resolution 1-5 mm
from background
discriminate b from c
disentangle complex
events
Thickness ~ 0.1 % X0
H  bb , cc , gg ,tt

5 layers

e e  AH  tt tt
Inner radius ~ 1.5 cm
h
12 jets
background: mainly e+/e- pair production
due to beamstrahlung
radiation tolerance ~ 360 kRad /
year
d(IP) < 5 mm  10 mm/(p sin3/2 q)
best SLD 8 mm  33 mm/(p sin3/2 q))
[C.Büssser, DESY]
19th February, VCI 2007
 Use a silicon based pixel detector
 Confine the background with a big
solenoidal field
Paula Collins, CERN
39
Timing @ the ILC
Time
Train/rf pulse
LEP
0.2 TeV
NLC/JLC
Superconducting
Linac
0.5 TeV
Train length, ms
0.750
0.265
950
Number of bunches/Train
4
190
2820
Bunch separation, ns
200
1.4
337
Repetition rate, Hz
45500
100
5
 at ILC, keep occupancy reasonable by reading out innermost layer in 50 msec
19th February, VCI 2007
Paula Collins, CERN
40
Silicon Trends
p+
+ +
- +n bulk
+-
chip
chip
amplifier
Al strip
SiO2/Si3N4
n+
+ Vbias
Start with high resistivity silicon
More elaborate ideas:
•n+ side strips – 2d readout
•Integrate routing lines on detector
•Floating strips for precision
•Stripixels: 2d readout
Hybrid Pixel sensors
Chip (low resistivity silicon)
bump bonded to sensor
Floating pixels for precision
n+
n+
p
chip
Basic idea
DEPFET:
Fully depleted sensor
with integrated preamp
chip
CCD: charge collected in thin layer
19th February, VCI 2007
and transferred through silicon
MAPS: standard CMOS wafer
Integrates
Paula Collins,
CERN all functions
41
DEPFET sensors
Kemmer, Lutz, 1987
R&D for tracking ~ 2000
15 V
0V
0V
+
+
+
+
•Amplifying transistor integrated into high resistivity
silicon detector
Image of DEPFET team
•Low noise operation possible at room temperature
•Thinning possible to 50 mm
R&D: pixel size, power, thinning, speed,
radiation tolerance
2005: 128x64 36mmx29mm prototypes
Paula
Collins, CERN
512 x 512, and 128 x 2048 array under
development
19th February, VCI 2007
42
Testbeam setup: 5 DEPFET planes
Switcher chip
provides gate
voltages
PCB ‘hybrid’ with
DEPFET matrix,
2 x SWITCHER, 1 x CURO
DEPFET Matrix
64x128 pixels
36 x 28.5µm2
row clear
Sources
~
Switcher chip
provides clear
voltages
19th February, VCI 2007
Sources
Drain 2
Drain 1
Sources
row gate
double pixel
Paula matrix
Collins, CERN
double metal
43
DEPFET
 S/N for 450 mm thick sensor 110
 upper limit on position resolution ~8 mm
(contains an estimated 7 um contribution
from low energy tracks – data from CERN
testbeam will improve this)
 cluster sizes for inclined tracks comparable
to simulation
FE 55 spectrum from irradiated pixel
measured at room temperature
 Ionising dose to ~1MRad without
degradation in performance of pixel
 HV switcher does not survive this
dose
 New switcher layout with rad hard
technology and “stacked transistors”
submitted and will be tested soon
19th February, VCI 2007
Paula Collins, CERN
noise of 3.5 e
(was 1.6 before irradiation)
44
P Fisher et. al. Vertex 06
Thinning
sensor wafer
handle wafer
1. implant backside
on sensor wafer
2. bond wafers with
SiO2 in between
3. thin sensor side
4. process DEPFETs
on top side
to desired thickness.
5. etch backside up
to oxide/implant
active DEPFET area
(~ 50µm thick)
Estimated material budget for first layer 0.11% X0:
pixels, 50 mm thick, 0.05% X0
chips, 50 mm thick, 0.008% X0
perforated frame, 300 mm thick, 0.05% X0
leakage
current
Thinned diode structures:
leakage current: < 1 nA/cm2
19th February, VCI 2007
CURO Readout chips
SWITCHER Steering chips
100pA / cm2
Paula Collins, CERN
Possible ILC
implementation
45
Monolithic Active Pixel Sensors (MAPS)
1999 – R&D on CMOS MAPS
1999 – small scale prototypes
1999-2000 first beam tests
2001 – large prototypes
2005 – dedicated application specific chips
Same unique substrate for detector and
electronics
No connections(e.g. bumps)
Radiation hardness (no bulk charge
transfer)
Advantages of CMOS process: Easy
Design/good yield/low power/Rad hard
Very small pixel sizes achieveable
Mimosa
I
……..
IV
V …….
VIII …….. IX
Process
0.6 mm AMS
0.35 mm AMS
0.6 mm AMS
0.25 TSMC
0.35 mm AMS
Epi layer 14 mm
0 (!!!)
14 mm
8 mm
14 mm
19th February, VCI 2007
64x64x4 1Mx7
# pixels 64x64x4
Paula7k
Collins, CERN7k
……
X
……..
0.25 mm TSMC
XIV ..
0.35 mm AMS
8 mm
0
16k
16k
46
MAPS Beam Test Results
MIMOSA I
MIMOSA II
MIMOSA V
Resolution
1.4 mm
2.2 mm
1.7 mm
Efficiency at S/N > 5
99.5 %
98.5 %
99.3%
Signal to Noise
Resolution [mm]
MIMOSA V
MIMOSA I
Two track separation 30 mm
thinning possible to 50 mm
R&D for high temperature operation (STAR upgrade)
19th February, VCI 2007
Paula Collins, CERN
47
MAPS: Radiation Hardness
Expectations at ILC (for 3 years of nominal running):
-
“non-ionizing” radiation: 3.1010 neq/cm2
MIMOSA I, II, V irradiated with 1013 n/cm2 




Gain -> constant
Noise -> constant
Leakage current a moderate rise
collected charge a 50-70% of initial value
(smooth decrease after 1012 or few x 1011 )
MIMOSA9 chip irradiated with 1011n/cm2 

test beam: S/N ~ 25, e > 99.9%

dose increased to 1012n/cm2 with good results
- “ionizing” radiation: 5.4.1012e(10MeV)/cm2
MIMOSA5 and MIMOSA9 chips irradiated
at Darmstadt with 1013e(9.4MeV)/cm2
 test beam (MIMOSA9):
S/N ~ 23, e > 99% - slight deterioration but
still excellent performance
19th February, VCI 2007
Paula Collins, CERN
michael deveaux
48
Charged Coupled Devices - CCDs
CCDs invented in 1970 – widely used in cameras,
telescopes etc.
Tracking applications for HEP:
1980-1985
NA32
120 kpixels
1992-1995
SLD
120 Mpixels
1996-1998
SLD upgrade
307 Mpixels
ILC
799 Mpixels
10V
2V
~1000 signal electrons are
collected by a combination
of drift and diffusion over a
~20mm region just below
surface
• Small pixel size – 20 x
20 mm
• Possibility of very thin
detectors
•Column parallel readout:
serial register -> direct
bump bonding to chip
19th February, VCI 2007
Paula Collins, CERN
49
CCD R&D for ILC requirements
 Speed up readout
 5 MHz readout -> 50 MHz
 Reduce clock amplitudes 10V->2V
 Build with high resistivity epitaxial material
 distributed busline over entire image area
•
Study radiation resistance to
LC doses of 100Krad ionising
radiation + 5 x 109 neutrons
Temperature dependence
CCD 55Fe spectrum:
1MHz 2V clocks
noise ~ 60 e-
Layer
Radius (mm)
CCD lxw
(mm x mm)
CCD
Size (Mpix)
Clock / readout time
Background
(Hits/mm2)
Integrated
background
(kHits/train)
1
15
100 x 13
3.3
50 MHz/50 ms
4.3
761
5
60
125 x 22
6.9
25 MHz/250 ms
0.1
28
19th February, VCI 2007
Paula Collins, CERN
50
CCDs: Thinning
 CCD community have come up with incredible
ways to lose weight!
Unsupported silicon with tensioning
- lateral instabilities
Silicon thinned to epitaxial layer and
glued to substrate
- can reach 0.15% X0
Carbon fibre substrates
- good CTE match but instabilities
Silicon on foam substrate or sandwich
core - < 0.1% Xo should be possible!!!
silicon carbide foam
19th February, VCI 2007
RVC foam
Paula Collins, CERN
51
ISIS
– In-Situ Storage Image Sensor
ISIS1 “proof of principle”
constructed at e2V
Beam-related RF pickup is a concern for all sensors converting charge into voltage during the
bunch train;
 The In-situ Storage Image Sensor (ISIS) eliminates this source of EMI:
 Charge collected under a photogate;
 Charge is transferred to 20-pixel storage CCD in situ, 20 times during the 1 ms-long train;
 Conversion to voltage and readout in the 200 ms-long quiet period after the train, RF pickup
is avoided;
 1 MHz column-parallel readout is sufficient
19th February, VCI 2007
Paula Collins, CERN

52
Conclusions I
 Silicon is not the only solution to your vertexing requirements:
1996: scintillating liquid capillaries for LHCb
liquid: 1-methylnaphtalen
Capture light in borosilicate capillaries
self cooling system
read out with APDs or HPDs
SLAC expts workshop 1982
19th February, VCI 2007
thanks: P.
Koppenburg
But remains the dominant
player
Paula Collins, CERN
53
Conclusions II
 Devices are being tested which give
excellent CCE and can be operated at room
temperature after high fluences – we are
almost there!
 n strip technology looks very promising for
all but the most inner layer
 For which diamond and 3D look very good
 Major developments underway for ILC
 Electronics/services not touched on (see
Spieler and Mnich talks)
19th February, VCI 2007
Paula Collins, CERN
54
Conclusions III
Neff used to be THE bad
guy
For heavily irradiated
detectors other villains
come into play, Neff
becomes almost benign
19th February, VCI 2007
Paula Collins, CERN
55
Conclusions IV
We also have to see what LHC brings…
19th February, VCI 2007
Paula Collins, CERN
56
Conclusions V
Thank you for your attention
Thanks for material to:
MCz Alison Bates MAPS Marc Winter, Grzegorz Deptuch, Wojtek
Dulinski, p type Gianluigi Casse, Marina Artuso CCD Steve Worm,
Andrei Nomorotski DEPFET Marcel Trimpl Johannes Ulrici SDD Rene
Bellweid, Vladimir Rykov Irradiation Sherwood Parker, Ulrich
Parzefall, Richard Bates, Cinzia da Via, Angela Kok, Michael Moll, Mika
Huhtinen, William Trischuk, Zheng Li Tevatron Alan Sill Overview Guy
Wilkinson, Daniela Bortoletto
19th February, VCI 2007
Paula Collins, CERN
57
backup slides
19th February, VCI 2007
Paula Collins, CERN
58
depfets
https://wiki.lepp.cornell.edu/ilc/bin/v
iew/Public/WWS/VtxProjects
19th February, VCI 2007
Paula Collins, CERN
59
Properties of Diamond
Si
diamond
Band gap [eV]
1.12
5.45
Electron mobility [cm2/Vs]
1450
2200
Hole mobility [cm2/Vs]
500
1600
Saturation velocity [cm/s]
0.8x107
2x107
Breakdown field [V/m]
3x105
2.2x107
Resistivity [Ω cm]
2x105
>1013
Dielectric constant
11.9
5.7
Low capacitance, noise
Displacement energy [eV]
13-20
43
High radiation hardness
e-h creation energy [eV]
3.6
13
Ave e-h pairs per MIP per μm
89
36
Charge coll. dist. [μm]
full
~250
CERN RD42 Collaboration:
- Development of detector grade diamond
- Industrial partner: Element Six, Ltd.
19th February, VCI 2007
Paula Collins, CERN
Low Ileakage, shot noise
Fast signal collection
Smaller signals
+ high thermal conductivity:
Room temperature operation
60
ILC vtx comparison
19th February, VCI 2007
Paula Collins, CERN
61
n+
p+
Active edge 4 mm
19th February, VCI 2007
n+
p+
n+
p+
n+
p+
n+
50 mm
Paula Collins, CERN
62
MAPS
MIMOSA 9
promising technology for star vtx upgrade
 Main features:
 Self Bias / Standard
 Pitch 20/30/40 mm
 Small/large diodes (3/6 mm)
 With/without epi
 intended to withstand high temperatures
Noise vs temperature
(Noise2∝Ileak=a+b.T2exp(-Egap/2kT)) –
signal independent of T
1.2 mm
0.96 mm
6 x 6 mm
3.4 x 4.3 mm
5 x 5 mm
3.4 x 4.3 mm
19th February, VCI 2007
Paula Collins, CERN
3.4 x 4.3 mm
3.4 x 4.3 mm
6 x 6 mm
6 x 6 mm
63
p+
500 mm
n+
19th February, VCI 2007
Paula Collins, CERN
64
Silicon for tracking: Silicon Drift Detectors
 Principle of sideways depletion – as
for DEPFET sensors
 p+ segmentation on both sides of
silicon
 Complete depletion of wafer from
segmented n+ anodes on one side
!! Drift velocity must be predictable
x
y
 Temperature control
 resistivity control
 Calibration techniques
 SDD fully functioning in STAR SVT
since 2001
 216 wafers, 0.7 m2
 10 mm in anode direction
 20 mm in drift direction
 Particle ID
19th February, VCI 2007
Paula Collins, CERN
65
Silicon for tracking: Drift detectors
 SDD are a mature technology – attractive for LC
 5 precise silicon layers to
replace TPC
 56 m2 silicon
 R&D needed:
 Improve resolution to 5 mm
 Improve radiation length
 Improve rad hardness
 Track stamping possible at
nanosecond level
c2 separation for out-of-time
tracks for different drift
direction configurations
19th February, VCI 2007
Paula Collins, CERN
66
particle
Sis
Frenkel pair
Vacancy + Interstitial
EK > 25 eV
Point Defects (V-V, V-O .. )
V
I
EK > 5 keV
clusters
Influence of defects on the material and device properties
charged defects
 Neff , Vdep
e.g. donors in upper
and acceptors in
lower half of band
gap
19th February, VCI 2007
Trapping (e and h)
 CCE
shallow defects do not
contribute at room
temperature due to fast
detrapping
Paula Collins, CERN
generation
 leakage current
Levels close to
midgap
most effective
67
New Materials: Diamond, SiC, GaN
Property
Eg [eV]
Ebreakdown [V/cm]
me [cm2/Vs]
mh [cm2/Vs]
vsat [cm/s]
Z
er
e-h energy [eV]
Density [g/cm3]
Displacem. [eV]
Diamond
5.5
107
1800
1200
2.2·107
6
5.7
13
3.515
43
GaN
3.39
4·106
1000
30
31/7
9.6
8.9
6.15
20
4H SiC
3.26
2.2·106
800
115
2·107
14/6
9.7
7.6-8.4
3.22
25
Si
1.12
3·105
1450
450
0.8·107
14
11.9
3.6
2.33
13-20
 Wide band gap
(3.3eV)
 lower leakage
current
than silicon
 Signal:
Diamond
SiC
R&D on diamond detectors: RD42 – Collaboration
http://cern.ch/rd42/
CCE at high fluences degrades even
more in SiC and GaN than in Si.
19th February, VCI 2007
Paula Collins, CERN
36
e/mm
51 e/mm
Si
80
e/mm
 more charge than
diamond
 Higher displacement
threshold than
68
silicon
19th February, VCI 2007
Paula Collins, CERN
69