Development of 28 nm CMOS Front-End Channels for the Readout of Hybrid Pixel Sensors in Future Colliders and Photon Science Applications

This paper describes two front-end architectures developed in a 28 nm CMOS process for the readout of pixel detectors in future high-energy physics (HEP) colliders and advanced X-ray imaging instrumentation. The front-end channels have been developed in the framework of the PiHEX project, funded by the Italian Ministry of University and Research. PiHEX aims to improve the state of the art of pixel readout chip technology in high-luminosity colliders and X-ray imagers in the next generation of free electron lasers (FELs) by developing, in 28 nm CMOS technology, the fundamental microelectronic building blocks for pixel readout chips. Such blocks, also implementing innovative circuit ideas, will enable, in future applications, the integration of large-scale readout chips, meeting a set of challenging requirements, such as high spatial resolution, high signal-to-noise ratio, very wide dynamic range and the capability to withstand unprecedented radiation levels. Two different front-end channels were designed, integrated into two prototype chips, and tested. One architecture, featuring a pixel size of 25 µm × 100 µm, was optimized for tracking applications in high-energy physics experiments, like the ones that take place at CERN in the high-luminosity upgrade of the Large Hadron Collider (LHC), while the second one, featuring a pixel size of 110 µm × 55 µm, was devised for X-ray imaging applications in FELs.