Results from CHIPIX-FE0, a small-scale prototype of a new generation pixel readout ASIC in 65 nm CMOS for HL-LHC

A prototype of a new-generation readout ASIC targeting High-Luminosity (HL) LHC pixel detector upgrades has been designed and fabricated as part of the Italian INFN CHIPIX65 project using a commercial 65 nm CMOS technology. This demonstrator, hereinafter referred to as CHIPIX-FE0, is composed of a matrix of 64 x 64 pixels with 50 $\mu$m x 50 $\mu$m pixel size embedding two different architectures of analog front-ends working in parallel. The final layout of the chip was submitted and accepted for fabrication on July 2016. Chips were received back from the foundry on October 2016 and successfully characterized before irradiation. Several irradiation campaigns with X-rays have been accomplished during 2017 at Padova INFN and CERN EP/ESE facilities under different uniformity and temperature conditions up to 630 Mrad Total Ionizing Dose (TID). These studies corfirmed negligible degradation of analog front-ends performance after irradiation. First sample chips have been also bump-bonded to 50 $\mu$m x 50 $\mu$m and 25 $\mu$m x 100 $\mu$m 3D sensors provided by Trento FBK. This represented a major milestone for the entire CHIPIX65 project, offering to the pixel community the first example of a complete readout chip in 65 nm CMOS technology coupled to such a kind of silicon detectors. Extensive characterizations with laser and radioactive sources have started.This paper briefly summarizes most important pre- and post-irradiation results, along with preliminary results obtained from chips bump-bonded to 3D sensors. Selected components of the CHIPIX65 demonstrator have been finally integrated into the large-scale RD53A prototype submitted at the end of summer 2017 by the CERN RD53 international collaboration on 65 nm CMOS technology.