A Study of 65nm Silicon Etch

Abstract

During the process development and mass production of 65nm technology node, the role of silicon etch is essential to meet more stringent device requirements. The control of shallow trench isolation (STI) depth uniformity and poly gate profile necessitate the combination of more advanced silicon etch methodology, in-situ measurement and integration scheme. This paper presents a study of the difficulties and corresponding solutions in 65nm silicon etch from the point view of process development and mass production. In development phase, the STI trench profile and the depth uniformity of STI depth can be well controlled by etch recipe tuning. In mass production phase, we focused on the impact of different products on the inter-field variation of STI depth. Results show a good correlation of depth to pattern density variation. Such relationship has been utilized in feed-forward mode to fulfill the tightening and robust process control. Besides, we also address the influence of oxide amount variation in STI fabrication and STI step height difference on poly gate profile and pits defect.