Comprehensive simulation and design of 3D silicon sensors for enhanced timing performance

This paper presents the procedure developed and used within the TimeSPOT (for Time and Space real time Operating Tracker) project to design and characterise 3D silicon sensors with enhanced timing capabilities. Such procedure is based on the combined use of commercial (TCAD), semi-custom (GEANT4) and custom (TCoDe) software tools which allow to fully design and simulate the device, from the definition of doping profiles and concentrations to the description of the charge carriers transportation mechanisms and the calculation of the induced current signals, which are input to the front-end electronics. A very important feature of the procedure is its speed in the most time-consuming part, that is the calculation of the carriers transportation phenomena inside the sensor volume. This allows to routinely perform analyses based on several thousand of signals, thus giving a statistically significant description of the detection mechanisms and the possibility to compare simulation and experimental results. The design study has been decisive to obtain a 3D silicon sensor with time resolutions well below 30 ps. The procedure is in principle extendable to any kind of solid state sensors.