Monolithic active pixel sensors based on the TPSCo 65 nm imaging CMOS technology: an overview of results and future challenges

Monolithic active pixel sensors (MAPS) are a key enabling technology for the next generation of detectors in High-Energy Physics experiments due to their low material budget, fine spatial resolution, and scalability to large areas at low cost. Building on the success of ALPIDE in the ALICE ITS2 detector, the CERN EP R&D program in synergy with the ALICE experiment have adopted the TPSCo 65 nm imaging CMOS process to address the demands of future detectors. This technology node enables smaller pixel pitches, increased output data rates and radiation hardness compared to the 180 nm technology adopted for ALPIDE, and allows the design of wafer-scale sensors through the stitching technique. This paper presents the evolution of the R&D program from initial technology qualification with small-area prototypes to the development of the wafer-scale stitched sensor prototypes MOSS and MOST, and the full-size, full-functionality wafer-scale MOSAIX prototype for the ALICE ITS3 vertex detector. Building on the results obtained for MOSS and MOST, MOSAIX integrates 9.97 million pixels with on-chip high-speed data links and advanced power segmentation, resulting in an unprecedented level of integration and complexity in the high energy physics community. In parallel, the Hybrid-to-Monolithic (H2M) ASIC demonstrates the feasibility of embedding hybrid pixel detector functionalities in a monolithic sensor. The paper also outlines future challenges for upcoming detectors such as ALICE3 and FCC-ee, including further pixel pitch reduction, increased speed of the front-end for the same power consumption, further minimization of the inactive area, and enhanced radiation tolerance.