1. Silicon Preshower for the CMS: BARC Participation
Anita Topkar
BARC

2. CMS Preshower Detector
End caps of CMS detector has ~4300 silicon strip detectors covering area of~17 m2
BARC has delivered detector modules for
the CMS preshower
Production of additional detectors (~400 wafers) was carried out to meet the shortfall

3. 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

4. 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)

5. Front end hybrid developed by CERN
Strip Detectors for CMS Experiment at LHC, CERN
Wafers designed and fabricated during various stages of development 1 2 3
Front end hybrid developed
by CERN
Silicon detectors produced
by BARC cover an area of
40,000 cm2 in the CMS
detector of LHC
Detector module

6. 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 mm
Width , -0.1 mm

7. Detector Design Design for improving breakdown voltage &
reducing the leakage current
Floating field guard
rings
Rounded corners
Field plates

8. 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

9. 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

10. Performance of detectors supplied to CERN
Total current at 300V
Breakdown voltage

11. Radiation hardness of sensors
Change of full depletion voltage due to a neutron dose of 2x1014 n/cm2

12. Production of sensor micromodules
Detector
Ceramic tile
Detector aligned and glued
to ceramic tile
Aluminum tile
Complete micromodule
with readout hybrid
assembled on ladder

13. The assembled end cap with micromodules – Assembly, Installation and Commissioning by CERN
Fully assembled Preshower
Dee plane

14. 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

15. 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

16. Thanks you