A Method to Simulate the Observed Surface Properties of Proton Irradiated Silicon Strip Sensors

TL;DR

This paper presents a simulation method to accurately reproduce the surface damage effects, including charge collection efficiency loss, in proton-irradiated silicon strip sensors for high-luminosity collider upgrades.

Contribution

It introduces a defect model approach that adds surface damage properties to existing bulk models without altering their accuracy, enabling better simulation of irradiated sensors.

Findings

Successfully reproduces charge collection efficiency loss up to high fluences.

Provides a method to parameterize oxide charge accumulation as a function of dose.

Enhances the accuracy of TCAD simulations for irradiated silicon detectors.

Abstract

During the scheduled high luminosity upgrade of LHC, the world's largest particle physics accelerator at CERN, the position sensitive silicon detectors installed in the vertex and tracking part of the CMS experiment will face more intense radiation environment than the present system was designed for. To upgrade the tracker to required performance level, extensive measurements and simulations studies have already been carried out. A defect model of Synopsys Sentaurus TCAD simulation package for the bulk properties of proton irradiated devices has been producing simulations closely matching with measurements of silicon strip detectors. However, the model does not provide expected behavior due to the fluence increased surface damage. The solution requires an approach that does not affect the accurate bulk properties produced by the proton model, but only adds to it the required radiation induced properties close to the surface. These include the observed position dependency of the strip detector's charge collection efficiency (CCE). In this paper a procedure to find a defect model that reproduces the correct CCE loss, along with other surface properties of a strip detector up to a fluence $1.5\times10^{15}$ 1 MeV n$_{\textrm{eq}}$ cm$^{-2}$, will be presented. When applied with CCE loss measurements at different fluences, this method may provide means for the parametrization of the accumulation of oxide charge at the SiO2/Si interface as a function of dose.