A Fully Depleted CMOS Sensor Prototype for HEP Timing Applications

The ARCADIA project at INFN is developing Fully Depleted Monolithic Active Pixel Sensors (FD-MAPS). FD-MAPSs collect the charge mainly by drift, which allows for a faster collection time, and a better time resolution. In this context, a 2 x 2 mm2 pixel array optimized for a time resolution better than 100 ps has been fabricated. The individual collection diode has a size of 50 x 50 µm^2. Eight diodes are grouped together and read out by a dedicated front-end channel composed of a charge sensitive amplifier and a discriminator with self-compensation of the offset. To maximize the uniformity of the electric field the electronics is located at the matrix periphery. The sensor is implemented in a 110 nm CMOS technology with 3.3 V and 1.2 V transistors, and 6 metal layers. The different terms that contribute to the system time resolution have been estimated with electronics computer-aided design (ECAD) tools, and optimized to target a time resolution below 100 ps