Modeling of Radiation Damage Effects at HighLuminosity LHC Expected Fluences: Measurements and Simulations

Abstract

A practical, yet physically grounded, TCAD modeling approach to study the radiation damage effects on silicon detectors exposedto the very high fluences expected at High Luminosity LHC (greater than 2.2 ×1016 1MeV n eq/cm2) is presented in this work. The modeling strategyis based on combined bulk and surface damage effects accountingfor alimited number of measurable parameters. Starting from standardtest structure measurements (i.e. MOS capacitors, gated diodes and MOSFETs), the most relevant parameters able to describe the complex phenomena related to the damage effects at these very high fluences have been extracted and therefore fed as input to the simulation tools. In particular the properties of the SiO 2 layer and of the SiO 2 /Si interface have been deeplyinvestigated on high-resistivity n-type and p-type silicon test structures, before and after irradiation with X-rays in the range from 50 krad(SiO 2 ) to 20 Mrad(SiO 2 ). Thus the extrapolated dose-dependent parameters (e.g. interface trap density and oxide chargedensity) have been straight included in the TCAD modeling scheme.The adopted numerical approach has been validated by means of the comparison between simulation results and experimental data. To this purpose, steady-state and small signal analysis have been selected as reference analyses to assess the model suitability along with the charge collection efficiency. Different technology and design options/detector geometries can be therefore evaluated, from conventional planar pixelated(strip/pixel) detectors to active-edges or 3D (columnar electrodes) detectors, as well different principle of operation such as charge multiplication in Low Gain Avalanche Detector. This would support technology independence of the model and its use as a predictive tool for the design and the optimization of new classes of silicon sensors for the next generation High-Energy Physics experiments.