# Simulations of CMOS pixel sensors with a small collection electrode, improved for a faster charge collection and increased radiation tolerance

## TL;DR

This paper uses 3D simulations to develop CMOS pixel sensors with small collection electrodes, aiming for faster charge collection and better radiation tolerance, addressing limitations in charge collection time and timing resolution.

## Contribution

It introduces new design concepts for CMOS sensors with small collection electrodes, improving charge collection speed and radiation tolerance through advanced simulations.

## Key findings

- Enhanced charge collection speed in small electrode CMOS sensors.
- Improved radiation tolerance demonstrated in simulations.
- Potential for better timing resolution in high-radiation environments.

## Abstract

CMOS pixel sensors with a small collection electrode combine the advantages of a small sensor capacitance with the advantages of a fully monolithic design. The small sensor capacitance results in a large ratio of signal-to-noise and a low analogue power consumption, while the monolithic design reduces the material budget, cost and production effort. However, the low electric field in the pixel corners of such sensors results in an increased charge collection time, that makes a fully efficient operation after irradiation and a timing resolution in the order of nanoseconds challenging for pixel sizes larger than approximately forty micrometers. This paper presents the development of concepts of CMOS sensors with a small collection electrode to overcome these limitations, using three-dimensional Technology Computer Aided Design simulations. The studied design uses a 0.18 micrometer process implemented on a high-resistivity epitaxial layer.