A 1-μW Radiation-Hard Front-End in a 0.18-μm CMOS Process for the MALTA2 Monolithic Sensor

In this article, a low-power, radiation-hard front-end circuit for monolithic pixel sensors, designed to meet the requirements of low noise and low pixel-to-pixel variability, the key features to achieve high detection efficiencies, is presented. The sensor features a small collection electrode to achieve a small capacitance (<5 fF) and allows full CMOS in-pixel circuitry. The circuit is implemented in the 180-nm CMOS imaging technology from the TowerJazz foundry and integrated into the MALTA2 chip, which is part of a development that targets the specifications of the outer pixel layer of the ATLAS Inner Tracker upgrade at the LHC. One of the main challenges for monolithic sensors is a radiation hardness up to 10¹⁵ 1-MeV $\text {n}_{\text {eq}}/\text {cm}^{{2}}$ non-ionizing energy loss (NIEL) and 80 Mrad total ionizing dose (TID) required for this application. Tests up to ${3} \cdot {10}^{15}$ 1-MeV $\text {n}_{\text {eq}}/\text {cm}^{{2}}$ and 100 Mrad were performed on the MALTA2 sensor and front-end circuit, which still show good performance even after these levels of irradiation, promising for even more demanding applications such as the future experiments at the high-luminosity large hadron collider (HL-LHC).