Removing (Sub)Surface Defects Induced by Si Wafer Thinning Processes Enables High-Performance Backscattered Electron Detector

High-performance backscattered electron detectors (BSDs) with high sensitivity and low dark current require a high-quality wafer substrate surface. Currently, chemical-mechanical polishing (CMP) has become an essential method to obtain a polished flat wafer surface. However, during a CMP process, wafers are subjected to various defect sources attributed to slurries, polishing pads, and polishing machines. Therefore, post-CMP cleaning of a wafer is crucial in fabricating high-performance BSD detectors. In this work, four post-CMP cleaning experiments were taken to identify different (sub) surface defects and to develop proper approaches for such defects' removal. Minority carrier lifetimes of Si wafer before and after various surface-defect removal treatments were measured and found to increase significantly, especially after the surface passivation using amorphous silicon, with an increase from
$26\ \mu\mathrm{s}$
to
$202\ \mu\mathrm{s}$
, indicating the successful recovery of Si wafer (sub) surface that was previously damaged by conventional wafer thinning processes.