Quality Control (QC) of FBK Preproduction 3D Si Sensors for ATLAS HL-LHC Upgrades

TL;DR

This paper details the quality control procedures and results for FBK's preproduction 3D silicon sensors designed for the ATLAS HL-LHC upgrade, focusing on electrical testing and parametric analysis.

Contribution

It presents a systematic QC test campaign for 3D Si sensors, including electrical and parametric characterizations, for the first time in this context.

Findings

Electrical tests confirm sensor functionality before irradiation

Parametric analyses provide insights into oxide and inter-pixel properties

QC procedures ensure sensors meet HL-LHC radiation hardness requirements

Abstract

The challenging demands of the ATLAS High Luminosity (HL-LHC) Upgrade aim for a complete swap of new generation sensors that should cope with the ultimate radiation hardness. FBK has been one of the prime foundries to develop and fabricate such radiation-hard 3D silicon (Si) sensors. These sensors are chosen to be deployed into the innermost layer of the ATLAS Inner Tracker (ITk). Recently, a pre-production batch of 3D Si sensors of 50x50 um2 pixel geometry, compatible with the full-size ITKPix (RD53B) readout chip, was fabricated. Two wafers holding temporary metal were diced at IZM, Germany, and a systematic QC test campaign was carried out at the University of Trento electronics laboratory. The paper briefly describes the 3D Si sensor design for ATLAS ITk and the required QC characterization setups. It comprises electrical tests (i.e., I-V, C-V, and I-T) of non-irradiated RD53B sensors. In addition, the study of several parametric analyses, i.e., oxide charge density, oxide thickness, inter-pixel resistance, inter-pixel capacitance, etc., are reported with the aid of Process Control Monitor (PCM) structures.