Relationship between edge roughness in mask pattern and charging in plasma etching

Abstract

AbstractThe edge roughness (ER) developed in the mask pattern during the plasma etching process harms the perfect pattern transformation from mask to substrate. To understand and ultimately manipulate plasma‐induced ER, this study investigated the interplay between charging and nanoscale roughness of an isolated rough mask hole in the plasma etching process using a modeling framework, which consisted of a surface etching module, a surface charging module, and a profile evolution module. Specifically, on the one hand, the distributions of the spatial electric field (E‐field) and etching rate were simulated for the rough mask surface being etched. It is revealed that the distribution of the etching rate is similar with that of E‐field clinging to the mask surface, and both of them reach their maximum strength around the mask hole edge and gradually becomes uniform/nonuniform with the decrease of the value of the dominant amplitude/wavelength of roughness; on the other hand, a string algorithm was used to simulate the evolution rule for a rough profile of a mask hole with etching time under various values of roughness parameters. The simulated evolution of the profile has good agreement with experimental observation. The charging effect contributes to the enhancement of the root mean square roughness. Additionally, the influence of roughness parameters on the charging time versus root mean square was also examined. The mechanism behind these results was analyzed systematically. This study will greatly contribute toward improving the physical and chemical properties of the mask or optimizing the etching technique.