Transcript Document 7321291

1st Coordination Meeting of the CBM Experiment at the future GSI facility
GSI, Nov. 15-16, 2002
Silicon Pixel and Strip Detectors
for LHC Experiments
P. Riedler
ALICE Silicon Pixel Team
CERN
Acknowledgements:
M. Campbell, P. Collins, H. Dijkstra, F. Faccio, H.
Pernegger, G. Stefanini and the ALICE SPD
Team
GSI - 15/11/2002
P.Riedler - CERN
2
Outline
- The LHC and its experiments
- Radiation damage in silicon
- Electronics
- Detectors
- A closer look at the ALICE SPD
ALICE Silicon Pixel Telescope
Reconstructed event: Testbeam 2002
GSI
GSI -- 15/11/2002
15/11/2002
P.Riedler
P.Riedler -- CERN
CERN
3
3
GSI - 15/11/2002
P.Riedler - CERN
4
The LHC and its Experiments
• head-on collisions of protons (7TeV on 7 TeV)
• and heavy ions
Lmax~1034cm-2 s-1
f(4cm)~3 1015 (neq) cm-2 in 10 years
(>85% charged hadrons)
! RADIATION DAMAGE !
Detectors for LHC under full construction now
Installation: 2006, First Beam: 2007
=> RD groups (e.g. RD48, now RD50) already work on solutions for
next generation of detectors
GSI - 15/11/2002
P.Riedler - CERN
5
GSI - 15/11/2002
P.Riedler - CERN
6
2 general purpose detectors:
Higgs in SM and in MSSM, supersymmetric Particles, B physics (CP violation, ...),…
CMS
ATLAS
Strips: 61m2, 6.3 x 106 channels
210m2, 9.6 x 106 channels
Pixels: ~2m2, 80 x 106 channels
~2m2,
GSI - 15/11/2002
P.Riedler - CERN
33 x 106 channels
7
Heavy ion physics
CP violation and rare decays
ALICE
LHCb
Strips: 4.9m2, 2.6 x 106 channels
VELO: 0.32m2, 2 x 105 channels
Drifts: 1.3m2, 1.33 x 105 channels
Tracker: 14m2, ~8 x 105 channels
Pixels: 0.2m2, 9.83 x 106 channels
HPD: ~ 0.02m2, ~1 x 106 channels
GSI - 15/11/2002
P.Riedler - CERN
8
Silicon Strip Detectors
Silicon Pixel Detectors
amplifier
Detector
p+
+ +
- +n bulk
+-
Chip
• 2-dim matrix of cells
• Each cell is connected to its own
processing electronics
• high granularity
GSI - 15/11/2002
P.Riedler - CERN
Al strip
SiO2/Si3N4
n+
+ Vbias
Each strip is connected to one
readout channel
•
•
•
•
N-in-n detectors
Double sided detectors
Floating intermediate strips
…
9
Radiation Damage in Silicon
Surface Damage
Bulk Damage
Electronics
Detectors
Full bulk is
sensitive to
passing
charged
particles
Sensitive
components
are located
close to the
surface
e.g. ATLAS Pixel Detector
GSI - 15/11/2002
P.Riedler - CERN
10
Electronics
Single Event Effects (SEE)
Cumulative Effects
Total Ionizing Dose (TID)
Ionisation in the SiO2 and SiO2Si interface creating fixed
charges
(all devices can be affected)
Permanent (e.g. single
event gate rupture
SEGR)
Static (e.g. single
event upset SEU)
Transient SEEs
Displacement Defects
(bipolar devices, optocomponents)
In the following the effects of TID only will be discussed :
GSI - 15/11/2002
P.Riedler - CERN
11
Total Ionizing Dose
Ionization due to charged hadrons, g, electrons,… in the SiO2 layer and
SiO2-Si interface
• Fixed positive oxide charge
• Accumulation of electrons at the interface
• Additional interface states are created at the SiO2-Si border
R. Wunstorf, PhD thesis 1992
GSI - 15/11/2002
P.Riedler - CERN
12
Effects of TID in CMOS devices
Threshold voltage shift, transconductance and noise degradation, source drain
leakage, leakage between devices
E.g.: transistor level leakage and threshold voltage shift
Parasitic channel between source and drain
GSI - 15/11/2002
P.Riedler - CERN
F. Faccio, ELEC2002
13
Radiation Levels in some LHC experiments
ATLAS Pixels
ATLAS Strips
CMS Pixels
CMS Strips
ALICE Pixel
LHCb VELO
total dose
fluence
50 Mrad
7.9 Mrad
~24Mrad
7.5Mrad
500krad
-
1.5 x 1015
~2 x 1014
~6 x 1014 *
1.6 x 1014
~2 x 1013
1.3 x 1014/year**
1MeV n eq. [cm-2] after 10 years
A radiation tolerant design is important to ensure the functionality
of the read out over the full life-time!
*Set as limit, inner layer reaches this value after ~2 years
**inner part of detector (inhomogeneous irradiation )
GSI - 15/11/2002
P.Riedler - CERN
14
Solution - Technology Hardening
Flatband-voltage shift as function of the oxide thickness
Tunneling of trapped charge
in thin oxides
•
•
D VT ~ 1/tox2 for tox > 10nm
A
•
D VT ~ 1/tox3 for tox < 10nm
B
D
C
After N.S. Saks, M.G. Ancona, and J.A. Modolo,
IEEE Trans.Nucl.Sci., Vol. NS-31 (1984) 1249
GSI - 15/11/2002
P.Riedler - CERN
15
Using a 0.25µm CMOS process reduces th-shift significantly
GSI - 15/11/2002
P.Riedler - CERN
16
Enclosed geometrie to avoid leakage
Enclosed Geometry
Standard Geometry
Leakage path
Gate
S
D
D
S
Gate
Enclosed gate (S-D leakage)
Guard ring (leakage between devices)
GSI - 15/11/2002
P.Riedler - CERN
17
F. Faccio, ELEC2002
GSI - 15/11/2002
P.Riedler - CERN
18
Front end technology choices of the different experiments
ALICE Pixel
ALICE Strips
ALICE Drift
ATLAS Strips
ATLAS Pixel
CMS Pixel
CMS Strips
LHCb VELO
LHCb Tracker
Technology
Chip
0.25µm CMOS
0.25µm CMOS
0.25µm CMOS
DMILL
DMILL->0.25µm CMOS
DMILL->0.25µm CMOS
0.25µm CMOS
DMILL/0.25µm CMOS
0.25µm CMOS
ALICE1
HAL25
PASCAL
ABCD
FE-D25
PSI
APV25
SCTA/Beetle
Beetle
Deep sub-µm means also: speed, low power, low yield, high cost
GSI - 15/11/2002
P.Riedler - CERN
19
Radiation Damage in Detectors
Bulk Damage
Surface Damage
Displacement of an Si atom
and creation of a vacancy and
interstitial
• Creation of positive
charges in the oxide and
additional interface
states.
• Electron accumulation
layer.
• Point like defects (g, electrons)
• Cluster Defects (hadrons, ions)
GSI - 15/11/2002
P.Riedler - CERN
20
Macroscopic Effects
Bulk Damage
Surface Damage
• Increase of leakage current
• Increase of depletion voltage
• Charge trapping
• Increase of interstrip
capacitance (strips!)
• Pin-holes (strips!)
Effects signal, noise, stability (thermal run-away!)
• Annealing effects will not be discussed here.
But: Do not neglect these effects, esp. for long term running!
All experiments have set up annealing scenarios to simulate the
damage after 10 years.
GSI - 15/11/2002
P.Riedler - CERN
21
Leakage current
But:
I prop. Exp(-Eg/2kT)
ATLAS Strip detector
M. Moll - Vertex 2002
Linear increase of leakage current
with fluence:
DIvol=a fne (a=4-6 x 10-17 A/cm)
GSI - 15/11/2002
P.Riedler - CERN
P. Riedler Phd-thesis
Cooling will help!
e.g:
ATLAS Strips: -7°C
CMS Pixel: -8°C
22
Depletion Voltage
Before Inversion
p+
V
depletion
n+
After Inversion
M. Moll - Vertex 2002
Type-Inversion:
n-type bulk starts to behave like p-type bulk ->
depletion from the backside of the diode!
Vdep increases with fluence
(after inversion)
GSI - 15/11/2002
P.Riedler - CERN
V
depletion
If depletion voltage has increased too
so much that underdepleted operation
is necessary-> charge loss and charge
spread!
23
Possible Solutions
Efficiency
1. n-in-n detectors
Underdepleted operation is
possible!
p-in-n
n-in-n
ATLAS
ATLAS
Vbias
NIM A 450 (2000) 297
At LHC:
ATLAS pixel
CMS pixel
Fluences close to 1015 cm-2
LHCb VELO (special case)
GSI - 15/11/2002
P.Riedler - CERN
24
2. Oxygenated Silicon
Defect engineering (RD48) - to reduce reverse annealing
=> Lower depletion voltage can be expected after several years
sunning (including warm-up times)
But: improvement only for
charged hadrons and g. No
effect for neutrons observed.
Also: spread of depletion
voltage of detectors from
different suppliers can reduce
the beneficial effect
ATLAS pixel uses oxygenated Si
GSI - 15/11/2002
P.Riedler - CERN
25
Further solutions to allow a reasonable operating voltages even after high
fluences and annealing:
•
•
•
•
Low resistive silicon
Thin detectors (also intersting for material budget reasons)
CZ starting material (under investigation)
<100> to reduce interstrip capacitance
Choice of LHC experiments:
ALICE pixel
ATLAS pixel
ATLAS strips
CMS pixel
CMS strips
LHCb VELO
GSI - 15/11/2002
p-in-n
n-in-n
p-in-n
n-in-n
p-in-n
n-in-n
standard FZ
oxygenated
standard FZ
standard FZ
standard FZ
standard FZ
P.Riedler - CERN
<100>
26
A closer look at the ALICE Silicon Pixel Detector (SPD)
2 barrel layers
D z= 28.3 cm
r= 3.9 cm & 7.6 cm
INFN Padova
GSI - 15/11/2002
P.Riedler - CERN
27
The two barrels will be built of 10 sectors, each equipped with 6
staves:
Sector - Carbon Fibre Support
stave
INFN Padova
INFN Padova
Material budget(each layer)
≈ 0.9% X0 (Si ≈ 0.37, cooling ≈ 0.3,
bus 0.17, support ≈ 0.1)
(lowest material budget of all pixel detectors!)
GSI - 15/11/2002
P.Riedler - CERN
28
Each Stave is built of two HALF-STAVES, read out on
the two sides of the barrel, respectively.
Bus
Ladder: 5 chips+1 sensor
MCM
ALICE1LHCb chip
Silicon sensor
Grounding foil
Cooling tube
193 mm long
GSI - 15/11/2002
Carbon-fibre sector
P.Riedler - CERN
29
Bus:
• 7 layer Al-Kapton flex
• Wire bonds to the ALICE1LHCb chip
2mm
11mm
7
SMD component
7
7
6
5
4
3
2
goal:150µm
240µm
2
1
1
200µm
7
6
5
PIXEL DETECTOR
Aluminum
Polyimide
Glue
READOUT CHIP
COOLING TUBE
M.Morel
GSI - 15/11/2002
P.Riedler - CERN
30
ALICE1LHCb chip
Multi Chip Module (MCM)
AP
DP
GOL
Analog Pilot:
• Reference bias
• ADC (T, V and I monitor)
Laser and pin diode
Data out
JTAG
Clock
Digital Pilot:
• Timing, Control and Readout
GSI - 15/11/2002
P.Riedler - CERN
31
ALICE1LHCb chip
• Mixed signal
13.5 mm
(analogue, digital)
15.8 mm
• Produced in a commercial
0.25µm CMOS process
• Radiation tolerant design
(enclosed gates, guard rings)
• 8192 pixel cells
• 50 µm x 425 µm pixel cell
• ~100 µW/channel
GSI - 15/11/2002
P.Riedler - CERN
32
Low minimum threshold: ~1000 electrons
Low individual pixel noise:~100 electrons
GSI - 15/11/2002
P.Riedler - CERN
33
Fully developed test system for wafers:
Class I - Mean Threshold
Class I: 42-75%
Class II: 6-12%
Class III: 17-42%
(sample: 4 wafer, 750µm)
Production testing will start this autumn
GSI - 15/11/2002
P.Riedler - CERN
34
Ladders and Assemblies
Detector
Chip
Bump-bonding:
• VTT/Finland
Pb-Sn solder bumps
• AMS/Italy
In bumps
GSI - 15/11/2002
Detectors:
• single chip detectors
• 5 chip detectors for ladders
• p-in-n
• 300 µm thick(tests) final thickness: 200µm
Chips:
• single chips
• 750 µm thick (tests) - 150µm final
P.Riedler - CERN
35
First testbeam with full size ladder - July 2002
chip0
chip1
chip2
chip3
chip4
Chip 2
250
250
200
200
150
150
100
100
50
50
5
10
15
20 25
GSI - 15/11/2002
200
150
100
50
P.Riedler - CERN
36
Detector
Chips
GSI - 15/11/2002
P.Riedler - CERN
37
GSI - 15/11/2002
P.Riedler - CERN
38
Sr-source measurement of thin ladder (300µm chip, 200µm detector)
Missing Pixels
% missing
% working
63
28
0.34
99.66
53
21
0.26
99.74
50
44
0.53
99.47
43
3
0.04
99.96
33
61
0.74
99.26
Chip 63
Chip 53
Chip 50
Chip 43
Chip 33
matrices
GSI - 15/11/2002
P.Riedler - CERN
39
Summary
• All LHC experiments use silicon detectors to improve their tracking
capabilities (up to >200m2!).
• Installation foreseen in 2006.
• The high radiation environment demands radiation tolerant
technologies for front end chips and detectors.
• Almost all silicon detectors use 0.25µm CMOS chips (future?).
• P-in-n and n-in-n detectors are used depending on the expected
fluences and the annealing damage.
• The current challenges are the actual construction and integration of
the detectors.
GSI - 15/11/2002
P.Riedler - CERN
40