Study on Potassium Contamination in SOI Wafer Fabrication Using Dynamic SIMS

In this paper, a case study of BIST failure in SOI wafer fabrication was presented. With optimized charge neutralization using a well-controlled normal incident electron beam, a reliable depth distribution of K in the ILD was obtained which is helpful to understand the source of K contamination. From the SIMS and EDX results, the root cause was concluded to be K contamination introduced by the CMP slurry. The yield has been improved greatly by depositing a layer of high density oxide on the top of ILD to block the K contamination