Silicon pixel detectors and electronics for hybrid photon detectors

1
Silicon pixel detectors and electronics for
hybrid photon detectors
Ken Wyllie, CERN on behalf of the LHCb pixel HPD
group OUTLINE

• Principle and requirements
• LHCBPIX1 General chip description
• Pixel cell description
• Silicon sensor
• Electronics performance
• Bump-bonding packaging
• Integration in hybrid photon detector
• Conclusion and future plans

2
Principle of the hybrid photon detector (HPD)
Designed to meet specs of LHCb Ring-Imaging
Cherenkov Detector

• Low noise pattern recognition
• Low detection threshold 2000e-
• 25ns time precision (LHC)
• 2.5mm x 2.5mm channel size (focus x 5)
• 8 maximum time occupancy
• Compatible with HPD manufacturing

3
LHCBPIX1 General Chip Description

• Commercial 0.25um CMOS process
• 6 metal layers
• Radiation-tolerant layout
• 13 million transistors
• 1.8W total power (40MHz clk, 1MHz trig)
• Current-starved logic
• 2nd generation of ALICE1LHCB chip
• see talk by G Stefanini

21mm
DACs
16mm
4
Pixel Cell Description
One super-pixel (500um 500um) 8 mini-pixels
(62.5um 500um)
62.5um
500um
5
Silicon Sensor
Optimised for photoelectron detection (Canberra,
Belgium)
Ohmic side
Diode side p-on-n pixel diodes
X-section
6
Electronics performance 1
Analog digital performance meet LHC speed
requirements
Shaper output
100ns
25ns
shaper output 5000e- input
7
Electronics performance 2
Using calibration test pulse
Mean 130e-
Mean 970e- RMS 90e-
(Without individual threshold adjustment)
8
Bump-bonding

• VTT, Finland bump-bonding recipe using solder
  with high melting-point.
• Compatible with
• high temp curing of glue used for packaging
• high temp processing of HPD (bake-out)

25um
9
Packaging of chipsensor assembly
Custom ceramic PGA carrier
Test with Sr90 beta-source
Si sensor
Si bias connection
Wire-bonds to chip
Pin grid array
10
Encapsulation in HPD
From DEP, Holland
11
and finally Cherenkov rings!
LHCb UK RICH1 prototype
Cherenkov rings (air radiator)
One trigger
Accumulated triggers
12
Conclusions and Future Plans

• Silicon pixel sensor electronics chip
  designed for HPD application
• Electrical requirements of chip fulfilled
• New bump-bonding process used
• Packaged encapsulated in HPD gt Cherenkov
  photon detection

• Pre-production run of chip wafers tested gt
  more HPDs
• Ageing tests of assemblies HPDs underway
• Measure aerogel Cherenkov rings