Active pixel sensors in AMS H18/H35 HV-CMOS technology for the ATLAS HL-LHC upgrade

Abstract

Deep sub micron HV-CMOS processes offer the opportunity for sensors built by industry standard techniques while being HV tolerant, making them good candidates for drift-based, fast collecting, thus radiation-hard pixel detectors. For the upgrade of the ATLAS Pixel Detector towards the HL-LHC requirements, active pixel sensors in HV-CMOS technology were investigated. These implement signal processing electronics in deep n-wells, which also act as collecting electrodes. The deep n-wells allow for bias voltages up to 150V leading to a depletion depth of several 10μm.Prototype sensors in the AMS H18 180nm and H35 350nm HV-CMOS processes were thoroughly tested in lab measurements as well as in testbeam experiments. Irradiations with X-rays and protons revealed a tolerance to ionizing doses of 1Grad while Edge-TCT studies assessed the effects of radiation on the charge collection. The sensors showed high detection efficiencies after neutron irradiation to 1015neqcm−2 in testbeam experiments.A full reticle size demonstrator chip, implemented in the H35 process is being submitted to prove the large scale feasibility of the HV-CMOS concept.