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Report
Silicon Preshower for the CMS:
BARC Participation
Anita Topkar
BARC
CMS Preshower Detector
End caps of CMS detector has ~4300
silicon strip detectors covering area
of~17 m2
BARC has delivered 1100 detector modules for
the CMS preshower
Production of additional detectors (~400
wafers) was carried out to meet the shortfall
The Preshower Silicon Detector
Preshower silicon strip detector is being
used for 0/ rejection in the ECAL, CMS
• Strips of 1.80 mm width with a pitch of 1.9 mm
• Area - 63mm x 63mm
Detector specifications are very stringent as they are to be
operated in a high radiation background of neutrons
( 2x10 14 /cm2) & gamma ( 10Mrad) for a long period of
ten years
Technology development and production of
detectors
• Technology developed by BARC in eight batches using BEL
facility. Knowhow for fabrication of detectors was provided to
BEL
• Detectors were designed during various phases (prototype,
preproduction, production)
• Characterization setups and probe jigs developed and quality
control facility setup at BEL during production
• Quality control of detectors was carried out (BARC and Delhi
university)
• Micromodule production facility was setup at BEL
There was lot of support from CERN Preshower Group
during production of silicon detectors and modules in India)
Strip Detectors for CMS Experiment at LHC, CERN
Wafers designed and fabricated during various stages of development
2
1
Front end hybrid developed
by CERN
Detector module
Silicon detectors produced
by BARC cover an area of
40,000 cm2 in the CMS
detector of LHC
3
Detector Specifications
Electrical
High breakdown voltage
Breakdown voltage for all strips >= 300V/500V
Low leakage:Total current of all strips <= 10 μA at 300V
Uniformity of all strips: Maximum 1 strip with leakage
current> 5 μA at 300V
Geometrical
Tight control over dimensions
Length 63.0 +- 0.1 mm
Width 63.0 +0.0, -0.1 mm
Detector Design
Design for improving breakdown voltage &
reducing the leakage current
Floating field guard
rings
Rounded corners
Field plates
Fabrication Process






High resistivity <111>, FZ wafers
Ion implanted junctions with oxide
passivation
P+ guard rings
Gettering to reduce leakage currents
Aluminum metallization
PSG passivation on the top
Fabrication process optimized in eight batches to
achieve desired specifications
Quality control of the strip detector
Leakage current of strips, capacitance of strips, full
depletion voltage, breakdown voltage, mechanical
tolerances on geometry
• Probe-jigs to make contact to the 32 strips simultaneously
• Simulaneous measurement of strip current of 32 strips ( IV)
• Simulaneous measurement of strip capacitance of 32 strips
( CV)
Probe-jigs, measurement setups required for qualification
of detectors and modules were developed. Test facility
was setup at BEL for qualification of detectors as per the
CERN specifications
Performance of detectors supplied to CERN
Total current at 300V
Breakdown voltage
800
500
No of Sensors
600
No of Sensors
1000
600
400
200
400
300
200
100
0
0
0.1
VBD (Volts)
2.1
4.1
6.1
8.1
I300 (Microamps)
10.1
Radiation hardness of sensors
Capacitance (Farads)
Change of full depletion voltage due to a neutron dose of
2x1014 n/cm2
5.0E-10
prerad
4.0E-10
postrad
3.0E-10
2.0E-10
1.0E-10
0.0E+00
0
100
200
Voltage (Volts)
300
Production of sensor micromodules
Detector
Detector aligned and glued
to ceramic tile
Ceramic tile
Aluminum tile
Complete micromodule
with readout hybrid
assembled on ladder
12
The assembled end cap with micromodules – Assembly,
Installation and Commissioning by CERN
Participation in CMS : Benefits
• Technology development for large area silicon
strip detectors was Initiated
• Capability for large scale production for
detectors using industry facilities is developed
• This also resulted in the development of a
wide range of silicon detectors for applications
in BARC and for international Experiments
Silicon detectors developed by BARC
Silicon microstrip
detectors for PHENIX
Experiment at RHIC, BNL
Large area PIN diodes Pad detectors for physics
experiments and radiation monitoring
Silicon pad detectors for
experiments at GANIL, France
PIN photodiodes
for scintillators &
X-ray imaging
Thanks you

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