Planar sensor R&D activity in Liverpool
Liverpool pixel R&D mask Designed for investigating several issues of general relevance to any pixel system for future Vertex detectors in high luminosity experiments. Important issue are obviously charge sharing, thickness, dimensions of the non-sensitive area between the active region and the cut line (usually called “edge”).
GR structure 5: every guard structure has 4 variances to study the cut edges
With CNM Barcelona Edgeless detectors with trenches Possible layout n-p 80um 80 um 32 um 10um 10u SiO 2 (DRIE or Diamond saw) Si 3 N 4 m p+ p+ p+ n+ n+ n+ 200um poly Side cut p-stop p guard strips 100um p+ (epitaxy) Al Giulio Pellegrini, CNM • High resistivity polysilicon used to fill the trenches to assure mechanical strength • Thermal oxide inside trenches to assure insulation. • No guard ring
Detector 3 trench DRIE cut line Floating ring Bias ring P-stops Guard rings
Detector type (6 sensors each on a 4” mask) ● Detector 1, no floating ring, small bias ring. ● Detector 2, large bias ring. ● Detector 3: one bias ring + one floating ring (best conditions from simulation). ● Distance between last strip and cut line (DRIE) and Diamond Saw: ● Detector 1 80um 325um ● Detector 2 258um 325um ● Detector 3 258um 325um
Many measurements to be performed: Strip readout for studying the charge sharing as a function of fluence (best done in test beam, preliminary measurements in lab with source). Study of thin edge sensors with the options above. CCE and edge as a function of wafer thickness. Studying the pixel sensors with the various readout (more specific to VELO is Medipix, but anything that can be learned with available readout to the various institutes is welcome). Other aspects: operating conditions (annealing and bias voltage), n-in- n, investigation. Need to start rather regular meeting among the “planar sensor institutes’ to distribute tasks and to envisage next steps (first VELO specific mask? .....).
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