Study on the Distribution Control of Etching Rate and Critical Dimensions in Microwave Electron Cyclotron Resonance Plasmas for the Next Generation 450 mm Wafer Processing

摘要

A newly designed microwave electron cyclotron resonance (ECR) plasma etching reactor has been developed for 450 mm wafer processing. The etching rates of polycrystalline silicon (poly-Si) and SiO_2 across the wafer were evaluated as a function of ECR position. Two-dimensional (radial and vertical) distributions of the ion flux in the reactor were also investigated using a movable single probe system. A ring-shaped region of high-density plasma along the ECR plane was observed. This reveals the mechanism that the etching-rate distribution could be controlled by the ECR position. As a result, a polycrystalline silicon etching rate uniformity of 1.5% across a wafer was successfully obtained. Furthermore, the uniformity control of critical dimensions (CDs) based on wafer temperature was also investigated, and CD uniformity below 3nm across the wafer was obtained in the optimum temperature distribution.