“RF-on” polysilicon etch defectivity monitor for manufacturing and process development

Decreasing gate length and increasing chip size are resulting in higher kill ratios from blocked edge defects at polysilicon gate etch. As a result etcher defectivity needs to be closely monitored and tightly controlled. In this work the usefulness of blanket etch-back of an poly-Si/SiO₂/Si wafer to monitor the particle performance of the etcher is presented. This monitoring method predicts the particle impact on product wafers and offers information about the particle generation event. In this study two sources of defects were seen-Si/O etch by-product flakes and Al/O/F/Si particles. Applicability of this monitor to guide process improvement is discussed