Mini-MALTA: Radiation hard pixel designs for small-electrode monolithic CMOS sensors for the High Luminosity LHC

TL;DR

This paper presents the Mini-MALTA DMAPS prototype with small electrodes and pixel size, demonstrating radiation hardness up to 1x10^15 n_eq/cm^2, suitable for HL-LHC upgrades.

Contribution

It introduces a radiation-hard DMAPS design with innovative edge efficiency improvements for high-energy physics applications.

Findings

Full efficiency maintained after high radiation dose

Successful characterization in particle beam tests

Design improvements address pixel edge inefficiencies

Abstract

Depleted Monolithic Active Pixel Sensor (DMAPS) prototypes developed in the TowerJazz 180 nm CMOS imaging process have been designed in the context of the ATLAS upgrade Phase-II at the HL-LHC. The pixel sensors are characterized by a small collection electrode (3 $\mu$m) to minimize capacitance, a small pixel size ($36.4\times 36.4$ $\mu$m), and are produced on high resistivity epitaxial p-type silicon. The design targets a radiation hardness of $1\times10^{15}$ 1 MeV n$_{eq}$/cm$^{2}$, compatible with the outermost layer of the ATLAS ITK Pixel detector. This paper presents the results from characterization in particle beam tests of the Mini-MALTA prototype that implements a mask change or an additional implant to address the inefficiencies on the pixel edges. Results show full efficiency after a dose of $1\times10^{15}$ 1 MeV n$_{eq}$/cm$^{2}$.