Silicon pad detector for an electromagnetic calorimeter at future linear collider experiments: characterisation and test beam results Antonio Bulgheroni University of Milan – Italy on behalf of LCCAL: Official INFN R&D project, official DESY R&D project PRC R&D 00/02 Contributors (Como, LNF, Padova, Trieste): M. Alemi, M.Bettini, S. Bertolucci, E. Borsato, M. Caccia, P.Checchia, C. Fanin, G. Fedel, J. Marczewski, S. Miscetti, M. Nicoletto, M. Prest, R. Peghin, L. Ramina, E. Vallazza.

8 th ICATPP – Villa Erba (Como), 6 th October ‘03 Calorimeter Layout Absorber Scintillator Silicon pad detectors 25 x 25 x 0.3 cm 3 25 Cells 5 x 5 cm 2 3 layers 725 Pads ~ 1 x 1 cm 2 2, 6 and 12 X 0 Total of 50 layers 27 X 0

8 th ICATPP – Villa Erba (Como), 6 th October ‘03 Sensor details Guard ring pad Bias pad 7 cm 6 cm ~0.9 cm Main characteristics: Sensor thickness: 300  m Resistivity: 4-6k  AC coupling (2 ways) Silicon dioxide thickness: 265 nm SMD capacitors Bias grid and guard ring 3M  poly-Si bias resistors Symmetric structure

8 th ICATPP – Villa Erba (Como), 6 th October ‘03 Hybridisation details Hybridisation through conductive glue Analogue Readout Chip: VA-HDR9c (IdeAs) VA  Viking family HDR  High dynamic range 9c  Four selectable gains Gain* [mv/fC] DR [mip] 3.3± ± ± ± 300 *Measured value SMD caps

8 th ICATPP – Villa Erba (Como), 6 th October ‘03 Motherboard design 6 sensors per motherboard with serial readout. Status of production: 24 sensors available 3 motherboards fully and 2 partially equipped Signal routing through Erni connectors

8 th ICATPP – Villa Erba (Como), 6 th October ‘03 How we get there… step by step 3 technological runs First batch of 11 sensors (spring ’02) Second batch of 9 sensors (summer ’02) Third batch of 9 sensors (summer ’03) Next batch will be ready next months Soft Breakdown “Leaky” pads GOOD!

8 th ICATPP – Villa Erba (Como), 6 th October ‘03 Soft breakdown Bias current reasonable (few  A) Strange shape with a “soft” breakdown n+ or metal shallow impurities on the backplane Metal n n+ Impurities Depletion region Solution 1: replace the implanted backside contact with a diffused one, but it does not work! Solution 2: replace the mash backplane contact with a uniform one, it works!

8 th ICATPP – Villa Erba (Como), 6 th October ‘03 “Leaky” pads: a surface effect Polysilicon residua Readout metal Al bridge ResistorBias grid n p+ No pin holes in SiO 2 Surface leakage  residua of polysilicon after the etching of the polysilicon layer Equivalent circuit with two opposite diodes. Solution: remove the integrated capacitors

8 th ICATPP – Villa Erba (Como), 6 th October ‘03 Yield Quite uniform behaviour of the depletion voltage YIELD 1 st Batch 2 nd Batch 3 rd Batch CouplingAC DC Wafer Rejected 1/112/90/9 Depletion Voltage 32V27V28 V depletion 2.1  A0.8  A0.6  A Not depleted pads 0/4208/2490/378

8 th ICATPP – Villa Erba (Como), 6 th October ‘03 Test beam: Signal to Noise ratio Theory: 3 rd batch: ~ 18 2 nd batch: ~ 15 1 st batch: ~ = Theoretical* SNR ~ 20 *Value obtained for detector of the 3 rd batch

8 th ICATPP – Villa Erba (Como), 6 th October ‘03 Test beam: shower reconstruction / 2X 6X 12X 0 20 GeV e - Forward tracker

8 th ICATPP – Villa Erba (Como), 6 th October ‘03 Test beam: shower reconstruction / 2X 6X 12X 0 20 GeV e - Forward tracker

8 th ICATPP – Villa Erba (Como), 6 th October ‘03 Test beam: energy linearity Silicon wafers rearranged in 5 planes ant tested alone Pb of 2.5 cm Electrons beam Error bars = sigma distribution

8 th ICATPP – Villa Erba (Como), 6 th October ‘03 Summary Some technological problems fixed with the last batch Detector performances very close to the design rules and hopefully will improve with the next and last batch Shower reconstruction capability and energy linearity are shown in the first test beam … we keep going …