Control of differential etch rates in heterogeneous poly-silicon and oxide etch environments

This article primarily focuses on the research of flash gate dry etching technology in a plasma environment. The challenge lies in the need to etch multiple film layers and different layer structures. It elaborates on a step-etching strategy tailored for multilayer structures and explores the use of CF4 and He gas combination gas as a method to improve the etch rate uniformity between polysilicon and oxide layers. This method can effectively improve etch uniformity, reduce etch steps, mitigate the loading effect during the etching process, and does not require any additional process steps. While adjusting the etch rate differences between different thin film layers, this study also explored the impact of oxygen atoms on the etch rate of polysilicon during the etching process. A reduction in oxygen content helps to decrease etch height variations and improve etch precision. These research findings have not only greatly enriched our understanding of the etching mechanisms of complex film layers, providing a strong basis for revealing the complex processes involved in etching multilayer structures at the microscale, but also offered solid theoretical support for achieving nanoscale precision etching in semiconductors.