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

TL;DR

This paper reports on the validation and performance testing of the Monolithic Stitched Sensor (MOSS), a wafer-scale prototype for the ALICE ITS3 upgrade, demonstrating high efficiency, low fake-hit rate, and robustness under irradiation.

Contribution

It introduces the first wafer-scale stitched MAPS prototype for high-energy physics, validating its yield, efficiency, and radiation hardness for the ITS3 upgrade.

Findings

Sensor achieves >99% efficiency

Fake-hit rate below 0.1 hits/pixel/s

Maintains performance after irradiation up to 4 kGy

Abstract

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$\mathrm{_{0}}$ 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\times10^{12}$1MeV$\,$n$\mathrm{_{eq}}\,$cm$\mathrm{^{-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.