Yield and performance validation of the Monolithic Stitched Sensor (MOSS), the first wafer-scale prototype for the ALICE ITS3 upgrade

The ALICE Inner Tracking System upgrade (ITS3) will employ stitched, wafer-scale Monolithic Active Pixel Sensors (MAPS) for the first time in high-energy physics, achieving a material budget of only 0.09$$%$$X${}_0$ per layer. Its first stitched prototype, the Monolithic Stitched Sensor (MOSS), underwent serial testing confirming sensor yield compliance with ITS3 requirements. In-beam tests show the device meets the ITS3 efficiency requirement of >$$99$$% while maintaining a fake-hit rate below 0.1$$hits/pixel/s, with performance sustained up to irradiation levels of 4$$kGy and $4\times {10}^{12}$1MeV$$n${}_{\mathrm{e}\mathrm{q}}$cm${}^{-2}$. The sensor demonstrates excellent charge-collection properties and linearity between time-over-threshold and deposited energy in the 1.8 - 6.5$$keV range in response to soft X-ray emissions. This article provides an overview of the validation steps and characterisation results.