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
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
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
Pixel Cell Description One super-pixel (500um * 500um) = 8 mini-pixels (62.5um * 500um) 62.5um 500um Firenze RD03, 30th September 2003
Silicon Sensor Optimised for photoelectron detection (Canberra, Belgium) Diode side: p-on-n pixel diodes Ohmic side: X-section Firenze RD03, 30th September 2003
Electronics performance 1 Analog & digital performance meet LHC speed requirements Shaper output 25ns 100ns shaper output 5000e- input Firenze RD03, 30th September 2003
Electronics performance 2 Using calibration test pulse Mean ~ 970e- RMS ~ 90e- Mean ~ 130e- (Without individual threshold adjustment) Firenze RD03, 30th September 2003
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
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
Encapsulation in HPD From DEP, Holland Firenze RD03, 30th September 2003
… and finally Cherenkov rings! LHCb UK RICH1 prototype Cherenkov rings (air radiator) One trigger Accumulated triggers Firenze RD03, 30th September 2003
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