Dependency of the Underlying Surface Condition on Dielectric Film Removal at Wafer Edge

Abstract

Tight control of a bevel wrap of a dielectric film stack is required to prevent issues in subsequent film deposition and defectivity excursions. In this report, a structure of dielectric films consisting of a plasma SiO 2 (P-SiO 2 : cap layer), a low dielectric constant (low-k film: middle layer), and P-SiO 2 (base layer) was examined. We investigated the dependency of underlying surface wettability as well as geometric shape on dielectric film removal at the wafer edge. The hydrophobic surface on a single crystal Si (s-Si) substrate gave a smaller etching distance with a larger variation in edge etching, in contrast to that of the hydrophilic surface (silicon nitride; SiN layer), which gave a larger etching distance with smaller variation. An Si sidewall (Si step) formed on s-Si through an etching process of shallow trench isolation (STI) prevented the over-etching.