Performance studies of the CE-65v2 MAPS prototype structure

TL;DR

This study evaluates the charge collection, efficiency, and spatial resolution of the CE-65v2 MAPS prototype, demonstrating high efficiency and sub-3 micron resolution suitable for future vertex detectors, through extensive beam testing and in-pixel analysis.

Contribution

It provides a detailed characterization of the CE-65v2 MAPS prototype, including in-pixel performance and effects of process variants, advancing the development of high-resolution vertex detectors.

Findings

Hit efficiencies of ≥99% achieved across variants

Spatial resolution below 3 μm for standard process

Large sensor size enables detailed in-pixel performance analysis

Abstract

With the next upgrade of the ALICE inner tracking system (ITS3) as its primary focus, a set of small MAPS test structures have been developed in the 65 nm TPSCo CMOS process. The CE-65 focuses on the characterisation of the analogue charge collection properties of this technology. The latest iteration, the CE-65v2, was produced in different processes (standard, with a low-dose n-type blanket, and blanket with gap between pixels), pixel pitches (15, 18, 22.5 $\mu$m), and pixel arrangements (square or staggered). The comparatively large pixel array size of $48\times24$ pixels in CE-65v2 allows the uniformity of the pixel response to be studied, among other benefits. The CE-65v2 chip was characterised in a test beam at the CERN SPS. A first analysis showed that hit efficiencies of $\geq 99\%$ and spatial resolution better than 5 $\mu$m can be achieved for all pitches and process variants. For the standard process, thanks to larger charge sharing, even spatial resolutions below 3 $\mu$m are reached, in line with vertex detector requirements for the FCC-ee. This contribution further investigates the data collected at the SPS test beam. Thanks to the large sensor size and efficient data collection, a large amount of statistics was collected, which allows for detailed in-pixel studies to see the efficiency and spatial resolution as a function of the hit position within the pixels. Again, different pitches and process variants are compared.