2025/10/30 by Ballabriga, Rafael, Buschmann, Eric, Campbell, Michael +29
#FOS: Physical sciences #Instrumentation and Detectors (physics.ins-det)
paper · doi:10.48550/arxiv.2510.26741
The H2M (Hybrid-to-Monolithic) is a monolithic pixel sensor manufactured in a modified \SI65\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 \SI35\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 \SI21\micro\meter for which no degradation in MIP detection performance is observed. For all investigated samples, a MIP detection efficiency above \SI99% 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 \SI500\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.