Test beam measurement of ams H35 HV-CMOS capacitively coupled pixel sensor prototypes with high-resistivity substrate

TL;DR

This study evaluates the performance of ams H35 HV-CMOS pixel sensor prototypes with varying substrate resistivities through beam tests, demonstrating their suitability for high-luminosity collider environments.

Contribution

It presents the first beam test results of capacitively coupled HV-CMOS sensors with different substrate resistivities for ATLAS upgrades.

Findings

Sensors meet ATLAS ITk efficiency requirements.

Capacitive coupling with epoxy glue is effective.

Higher resistivity substrates show improved performance.

Abstract

In the context of the studies of the ATLAS High Luminosity LHC programme, radiation tolerant pixel detectors in CMOS technologies are investigated. To evaluate the effects of substrate resistivity on CMOS sensor performance, the H35DEMO demonstrator, containing different diode and amplifier designs, was produced in ams H35 HV-CMOS technology using four different substrate resistivities spanning from $\mathrm{80}$ to $\mathrm{1000~\Omega \cdot cm}$. A glueing process using a high-precision flip-chip machine was developed in order to capacitively couple the sensors to FE-I4 Readout ASIC using a thin layer of epoxy glue with good uniformity over a large surface. The resulting assemblies were measured in beam test at the Fermilab Test Beam Facilities with 120 GeV protons and CERN SPS H8 beamline using 80 GeV pions. The in-time efficiency and tracking properties measured for the different sensor types are shown to be compatible with the ATLAS ITk requirements for its pixel sensors.