Design and Development of Depleted Monolithic Active Pixel Sensors with Small Collection Electrode for High-Radiation Applications

Abstract

Depleted monolithic active pixel sensors (DMAPS) have emerged as a low material and low cost alternative to the established hybrid technology. In this thesis, two large scale prototype chips that feature a fast column-drain readout architecture have been developed in order to demonstrate the feasibility of a small collection electrode DMAPS implementation for high rate and high radiation environments such as the High Luminosity Large Hadron Collider (HL-LHC) upgrade of the ATLAS (A Toroidal LHC Apparatus) experiment Inner Tracker (ITk). They have been fabricated using a novel modification of the TowerJazz 180 nm imaging process that enhances the charge collection properties and allows for full depletion of the sensitive volume. High radiation tolerance is combined with high analog performance and low power consumption as a result of the low sensor capacitance. The first prototype, called TJ-Monopix1, has demonstrated the proof of concept yielding a low Equivalent Noise Charge (ENC) of approximately 10 electrons and up to 97 % detection efficiency after irradiation to 10¹⁵n_eq/cm² Non Ionizing Energy Loss (NIEL) fluence. A full scale successor chip, called TJ-Monopix2, has been designed in order to further improve performance and enable easier system integration. Apart from LHC type applications, the TJ-Monopix DMAPS are ideally suited to other experiments such as lepton colliders and can also benefit the development of imaging devices.