Increased radiation tolerance of CMOS sensors with small collection electrodes through accelerated charge collection

Mini-Malta is a Monolithic Active Pixel Sensor prototype developed in the TowerJazz 180 nm CMOS imaging process, with a small collection electrode design (3µm²), and a small pixel size (36.4 µm), on high resistivity substrates and large voltage bias. It targets the outermost layer of the ATLAS ITK Pixel detector for the HL-LHC. This design addresses the pixel inefficiencies observed in previous Malta and TJ-Monopix prototypes. The implementation of a mask change in the fabrication or an additional implant allows to improve the charge collection performance at the edges of the pixel thus improving the radiation hardness properties.