Improved process of fabricating AC-coupled silicon micro-strip sensors

A single-sided silicon sensor with capacitors coupling and polysilicon bias resistors has been designed and fabricated. A proposed process with ONO (Oxide-Nitride-Oxide) replacing the usual SiO2 layer as the dielectric of coupling capacitor, in conjunction with a reordering of sequence for layer formations, is to produce sensors with self-moisture-protection and free from the effect of pin holes. A comparison of presented data of IV, CV and RV measurements for the sensors with ONO and with SiO2 dielectrics revealed that the ONO processes could lead to an excellent voltage-handling capability of the coupling capacitor. One sensor has been successfully tested twice in the beam at CERN in the past two years, yielding an S/N ratio of 20 and an efficiency above 95%, also demonstrating its excellent stability with respect to lengthy exposure to atmosphere.