Novel retaining ring to reduce CMP edge exclusion

This study presents a new approach to edge profile control during air back carrier Chemical Mechanical Polishing (CMP). Control of wafer edge profile proves to be difficult as different factors are reported to influence polishing characteristics. To evaluate a CMP on the wafer's edge it needs to look at polish characteristics of leading and trailing edges separately. To understand polish performance on both leading and trailing edges, and their impact on resulting wafer's edge profile a non-rotating carrier experiment had been conducted. Based on the results of the nonrotating carrier experiment a novel retaining ring design has been proposed. In the course of this study CMP of the wafer's edge evaluation for a novel retaining ring has been performed on blanket PETEOS 200 mm wafers for different retaining pressures. Edge profile evaluation provided a proof for the Pad Wave Hypothesis and helped to significantly enhance the CMP performance by increasing process stability and achieving wider process window for retaining ring pressure.