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
Firenze RD03, 30th September 2003

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
Firenze RD03, 30th September 2003

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
Firenze RD03, 30th September 2003

4. Pixel Cell Description
One super-pixel (500um * 500um) = 8 mini-pixels (62.5um * 500um)
62.5um
500um
Firenze RD03, 30th September 2003

5. Silicon Sensor
Optimised for photoelectron detection (Canberra, Belgium)
Diode side: p-on-n pixel diodes
Ohmic side:
X-section
Firenze RD03, 30th September 2003

6. Electronics performance 1
Analog & digital performance meet LHC speed requirements
Shaper output
25ns
100ns
shaper output
5000e- input
Firenze RD03, 30th September 2003

7. Electronics performance 2
Using calibration test pulse
Mean ~ 970e-
RMS ~ 90e-
Mean ~ 130e-
(Without individual threshold adjustment)
Firenze RD03, 30th September 2003

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
Firenze RD03, 30th September 2003

9. Packaging of chip+sensor assembly
Custom ceramic PGA carrier
Test with Sr90 beta-source
Si sensor
Si bias
connection
Wire-bonds
to chip
Pin grid
array
Firenze RD03, 30th September 2003

10. Encapsulation in HPD From DEP, Holland
Firenze RD03, 30th September 2003

11. … and finally Cherenkov rings!
LHCb UK RICH1 prototype
Cherenkov rings (air radiator)
One trigger
Accumulated triggers
Firenze RD03, 30th September 2003

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 => Cherenkov photon detection
Pre-production run of chip wafers tested => more HPDs
Ageing tests of assemblies & HPDs underway
Measure aerogel Cherenkov rings
Firenze RD03, 30th September 2003