Quality control of silicon pixel wafers for the CMS Phase-1 pixel upgrade

Abstract

The CMS detector at the CERN Large Hadron Collider features as its innermost component a silicon pixeldetector. The original pixel detector was completely replaced during the 2016–2017 winter technical stop. One of thegoals of this Phase-1 Upgrade of the pixel detector was to replace the sensors in the original CMS forward pixel detectorwith new, unirradiated sensors. The new CMS forward pixel detector must survive an integrated luminosity of 300 fb−1before being replaced again prior to the High-Luminosity LHC era. Just as in the original construction, the Phase-1forward pixel sensors were made of n+ -in-n Diffusion Oxygenated Float Zone silicon. This note documents the qualityspot-checking of the new sensors, comparing our results with those provided by the vendor. In general there was goodagreement between the results.