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This study investigates the impact of rubber residuals on Vbias and proposes a reliable method for ingot pre-qualification. Additionally, interstrip capacitance measurements for HPK sensors are provided.
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Simulated LHC conditions with respect to surface damage! Vbias The second row will prevent the former problem of rubber residuals! (Thanks to Anna, Laura, Alberto, Ettore)
Second row to avoid bad contact Due to residuals of rubber on the Biasing AC row!
Ingot pre-qualification • All measuremens on diode or minisensor Save large sensors as spares! • INGOT: IV & CV on diode (with guard on GND) • To determine Vdepletion, fluence estimate and a-factor. • PROCESS:Cint, Rint, leakage current, Rpoly vs. Vbias upto Vdepletion + 50V (for ~10 strips) • 10 strips only to ensure fast turnaround and no „RED Flag“ cause of one strange value on a single strip! If sensors comes non-diced we propose to use the FS!
Possible additional measurements-no standard procedure-- not in the standard protocol- • IV & CV on full sensor (FS) • Complete FS (or baby) characterization • Leakage current, Rpoly, CaC, Cint • GCD & MOS measurements for x-ray irradiated sensors
Concerns • Rint measurement is quite complicated and gives only reasonable results at low voltages, for FD we can only give a lower limit! Conclusion • We think we found a fast and reliable way to qualify an ingot, and also the belonging process!
Interstrip capacitance of HPK sensor (1 neighbour) 100 fF 3.2 pF