Evaluation of etching performance of single etching gases for high-κ films

The continuous advancement of CMOS technology has put forward higher requirements for dielectric etching processes. However, conventional mixed etching gases fail to elucidate the contribution of each gas. The role of single etching gas in the etching process remains elusive. In this work, we investigated the etching characteristics of high-κ thin films using a variety of single fluorine-based or chlorine-based gases. We further analyzed the underlying reasons for the observed differences in etching behaviors with different gases. Our findings demonstrate that BCl3 is the optimal single etching gas for HfO2 and Al2O3 films with a fast and stable etching rate, while the films etched by Cl2, BCl3, CF4, CHF3, and C4F8 exhibited varying degrees of etching residuals. The outstanding etching performance of BCl3 is attributed to the interaction between physical bombardment and chemical reactions. Furthermore, we propose a set of evaluation methods for etching residues and mechanisms. These results provide valuable insights into the etching process and facilitate the selection of appropriate etching gases for high-κ films in advanced semiconductor process nodes.