The H2M (Hybrid-to-Monolithic) is a monolithic pixel sensor manufactured in a modified \SI{65}{\nano\meter}~CMOS imaging process with a small collection electrode. Its design addresses the challenges of porting an existing hybrid pixel detector architecture into a monolithic chip, using a digital-on-top design methodology, and developing a compact digital cell library. Each square pixel integrates an analog front-end and digital pulse processing with an 8-bit counter within a \SI{35}{\micro\meter}~pitch. This contribution presents the performance of H2M based on laboratory and test beam measurements, including a comparison with analog front-end simulations in terms of gain and noise. A particular emphasis is placed on backside thinning in order to reduce material budget, down to a total chip thickness of \SI{21}{\micro\meter} for which no degradation in MIP detection performance is observed. For all investigated samples, a MIP detection efficiency above \SI{99}{\%} is achieved below a threshold of approximately 205 electrons. At this threshold, the fake-hit rate corresponds to a matrix occupancy of fewer than one pixel per the \SI{500}{\nano\second}~frame. Measurements reveal a non-uniform in-pixel response, attributed to the formation of local potential wells in regions with low electric field. A simulation flow combining technology computer-aided design, Monte Carlo, and circuit simulations is used to investigate and describe this behavior, and is applied to develop mitigation strategies for future chip submissions with similar features.
@article{arxiv.2510.26741,
title = {Characterization of the H2M Monolithic CMOS Sensor},
author = {Rafael Ballabriga and Eric Buschmann and Michael Campbell and Raimon Casanova Mohr and Dominik Dannheim and Jona Dilg and Ana Dorda and Ono Feyens and Finn King and Philipp Gadow and Ingrid-Maria Gregor and Karsten Hansen and Yajun He and Lennart Huth and Iraklis Kremastiotis and Stephan Lachnit and Corentin Lemoine and Stefano Maffessanti and Larissa Mendes and Younes Otarid and Christian Reckleben and Sébastien Rettie and Manuel Alejandro del Rio Viera and Sara Ruiz Daza and Judith Schlaadt and Adriana Simancas and Walter Snoeys and Simon Spannagel and Tomas Vanat and Anastasiia Velyka and Gianpiero Vignola and Håkan Wennlöf},
journal= {arXiv preprint arXiv:2510.26741},
year = {2026}
}