MALTA-Cz: A radiation hard full-size monolithic CMOS sensor with small electrodes on high-resistivity Czochralski substrate

TL;DR

MALTA-Cz is a radiation-hard, high-resolution, full-size monolithic CMOS sensor designed for collider experiments, featuring small electrodes, fast asynchronous readout, and excellent performance after high radiation doses.

Contribution

This work introduces a novel radiation-hard CMOS sensor with optimized process and implant design on high-resistivity Czochralski substrate, achieving high efficiency and fast response.

Findings

Maintains high detection efficiency after $2\times10^{15}$ n$_{eq}$/cm$^{2}$ radiation dose

Achieves a time resolution of 2 ns

Demonstrates suitability for high-rate, triggered, and trigger-less applications

Abstract

Depleted Monolithic Active Pixel Sensor (DMAPS) sensors developed in the Tower Semiconductor 180 nm CMOS imaging process have been designed in the context of the ATLAS ITk upgrade Phase-II at the HL-LHC and for future collider experiments. The "MALTA-Czochralski (MALTA-Cz)" full size DMAPS sensor has been developed with the goal to demonstrate a radiation hard, thin CMOS sensor with high granularity, high hit-rate capability, fast response time and superior radiation tolerance. The small pixel size ($36.4\times 36.4$~$\mu$m$^2$) provides high spatial resolution. Its asynchronous readout architecture is designed for high hit-rates and fast time response in triggered and trigger-less detector applications. The readout architecture is designed to stream all hit data to the multi-channel output which allows an off-sensor trigger formation and the use of hit-time information for event tagging. The sensor manufacturing has been optimised through process adaptation and special implant designs to allow the manufacturing of small electrode DMAPS on thick high-resistivity p-type Czochralski substrate. The special processing ensures excellent charge collection and charge particle detection efficiency even after a high level of radiation. Furthermore the special implant design and use of a Czochralski substrate improves the sensor's time resolution. This paper presents a summary of sensor design optimisation through process and implant choices and TCAD simulation to model the signal response. Beam and laboratory test results on unirradiated and irradiated sensors have shown excellent detection efficiency after a dose of $2\times10^{15}$ 1 MeV n$_{eq}$/cm$^{2}$. The time resolution of the sensor is measured to be $\sigma=2$~ns.