Speaker
Description
The upgrade of the ATLAS tracking detector for the HL-LHC requires radiation hard silicon sensor technologies. For the development of depleted CMOS sensor for ATLAS we combined small electrodes with minimal capacitance and advanced processing to achieve radiation hard CMOS for the ITK. We developed and tested a first full-size depleted CMOS sensor based on a 180nm imaging process. The ''MALTA'' sensor combines special low-noise/low power front-end using small electrodes with a novel high-speed/asynchronous readout architecture for high hit-rates. The presentation will summarize design and initial measurements on analog and digital performance as obtained in lab and beam tests.
Summary
The upgrade of the ATLAS tracking detector for the High-Luminosity Large Hadron Collider at CERN requires the development of novel radiation hard silicon sensor technologies. Latest developments in CMOS sensor processing offer the possibility of combining small electrodes with minimal capacitance and advanced processing for fully depleted active sensor volume. This achievement allows to realize monolithic CMOS sensors with radiation hardness promising to meet the requirements of the ATLAS ITK outer pixel layers (1.5x10^15 1 MeV neq/cm2), and simultaneously achieve high signal-to-noise and fast signal response as required by the HL-LHC 25ns bunch structure. We developed radiation hard depleted CMOS sensors with the front-end being optimised for low capacitance in order to achieve low noise (ENC<20 e-) and low power operation (1uW/pixel) while meeting the 25ns bunch spacing requirement. Separating the collection well from digital area in the 36.4x36.4um2 pixel allows to decouple analog and digital electronics to further minimize capacitance and prevent cross-talk. The radiation hardness of the charge collection to Non Ionizing Energy Loss (NIEL) has been previously characterized on prototypes for the different pixel sensor cell designs, which will be summarised together with key elements of the pixel design chosen for the full-size pixel matrix. These results enabled the design of full-size monolithic CMOS sensors for the ATLAS ITk outermost pixel layer, which comprises ~1.8m2 of pixel sensor active area. With the development of the MALTA" sensor, we implemented this front-end in a novel high-speed matrix readout architecture capable of meeting the challenging hit-rate requirements of up to 2 MHz/mm2 in the outer layers of the ITk pixel tracker. TheMALTA" sensor features a 512x512 pixel matrix with fully asynchronous readout without clock distribution over the matrix. The design was chosen to combine low digital power consumption which fast signal response and high hit-rate capability. The development of this novel depleted monolithic sensors based on a low capacitance analog design with asynchronous readout architectures will be presented together with first test results from manufactured ``MALTA" sensors, as obtained in lab tests, radio-active source tests and X-ray measurements.
