MALTA: a CMOS pixel sensor with asynchronous readout for the ATLAS High-Luminosity upgrade

Radiation hard silicon sensors are required for the upgrade of the ATLAS tracking detector for the High-Luminosity Large Hadron Collider (HL-LHC) at CERN. A process modification in a standard 0.18 μm CMOS imaging technology combines small, low-capacitance electrodes (~2 fF for the sensor) with a fully depleted active sensor volume. This results in a radiation hardness promising to meet the requirements of the ATLAS ITk outer pixel layers (1.5×10$^{15

Update on the TowerJazz CMOS DMAPS development for the ATLAS ITk

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. For the development of depleted CMOS sensors for ATLAS we combined small electrodes with minimal capacitance and advanced processing for fully depleted active sensor volume to achieve radiation hard CMOS sensors in line with ATLAS ITk specifications. Based on initial studies on the prototype sensor “TowerJazz Investigator” we have now developed, produced and tested a first full-size depleted CMOS sensor based on the 180nm TowerJazz imaging process, the so-called “MALTA” sensor. The sensor combines special low-noise/low power front-end using small electrodes with a novel high-speed asynchronous readout architecture to cope with the high hit-rates expected at HL-LHC. The sensor has been produced end of 2017 and initial measurements have been carried out assessing its analog and digital performance. The poster will show efficiency studies performed with the TowerJazz Investigator chip at the CERN SPS test beam facility in 2017 and first measurement results with the new “MALTA” sensor

Development of the monolithic "MALTA" CMOS sensor for the ATLAS ITK outer pixel layer

Depleted Monolithic Active Pixel Sensors (DMAPS) are an option for the outermost layer of the upgraded ATLAS ITk Pixel Detector at the CERN LHC. Two large size DMAPS named TJ MALTA and TJ Monopix were produced in the TowerJazz 180 nm CMOS imaging process in a small collection electrode design. The MALTA chip combines a low power front end with a novel matrix readout design to achieve a low power consumption of <80 mW/cm2. Threshold values of 250 e- with a dispersion of 30 e- and an ENC of < 10e- can be achieved before irradiation which is consistent with the results from TJ Monopix. Test beam measurements indicate an average efficiency of 96% before irradiation, with the inefficiency mainly due to problems with the slow control of the chip. After neutron irradiation to 1e15 neq/cm2 the efficiency in pixel centres is retained, but it is reduced in pixel corners. A proposal to improve charge collection in the corners is backed up by TCAD simulations and promises an improved performance with small modifications