Performance of CMOS pixel sensor prototypes in ams H35 and aH18 technology for the ATLAS ITk upgrade

TL;DR

This paper evaluates the performance of CMOS pixel sensor prototypes in ams H35 and aH18 technologies, demonstrating their suitability for the ATLAS ITk upgrade with high radiation tolerance and detection efficiency.

Contribution

It presents large-area CMOS sensor prototypes in H35 and aH18 technologies, showcasing their potential for high-energy physics applications and integration capabilities.

Findings

H35DEMO achieves high detection efficiency with external readout.

ATLASPix1 shows promising initial performance as a monolithic sensor.

Both prototypes demonstrate radiation tolerance suitable for HL-LHC conditions.

Abstract

Pixel sensors based on commercial high-voltage CMOS processes are an exciting technology that is considered as an option for the outer layer of the ATLAS inner tracker upgrade at the High Luminosity LHC. Here, charged particles are detected using deep n-wells as sensor diodes with the depleted region extending into the silicon bulk. Both analog and digital readout electronics can be added to achieve different levels of integration up to a fully monolithic sensor. Small scale prototypes using the ams CMOS technology have previously demonstrated that it can achieve the required radiation tolerance of $10^{15}~\text{n}_\text{eq}/\text{cm}^2$ and detection efficiencies above $99.5~\%$. Recently, large area prototypes, comparable in size to a full sensor, have been produced that include most features required towards a final design: the H35demo prototype produced in ams H35 technology that supports both external and integrated readout and the monolithic ATLASPix1 pre-production design produced in ams aH18 technology. Both chips are based on large fill-factor pixel designs, but differ in readout structure. Performance results for H35DEMO with capacitively-coupled external readout and first results for the monolithic ATLASPix1 are shown.