Interplay between charging and roughness on two adjacent mask holes during plasma etching

Abstract

The surface roughness of a mask surface strongly limits the perfect pattern transfer from the mask to the substrate during the plasma etching process, which results in the deformation of etched features and greatly damages the mask pattern. For the understanding and, ultimately, the control of roughness, the interplay between two adjacent mask holes with nanoscale roughness profile under charging effects was investigated based on a reliable modeling framework. This study first verified that two adjacent mask holes with same/different roughness (i.e., same/different amplitude and wavelength) as well as with various sizes can lead to obviously different distributions of electric field (E-field), etching rate, and the profile evolution. These distributions are quite unlike those of an isolated hole. This work next shows that the interaction between two holes cannot be ignored. Specifically, the E-field strength and the etching rate in the area between two holes are weaker than those in the outermost area. As a result, the profiles moved away from each other. Then, charging phenomenon on a channel hole with a common source line slit trench structure was also studied. The mechanism was systematically analyzed. This work will aid in the understanding of the physical property of the mask and might optimize the etching technology.

The modification of roughness to corner effect in plasma etching

“…Because the roughness can lead to the local imbalance of accumulated positive and negative charges on the surface of a dielectric material, thus, it could be thought of as a tightly-coupled roughness-charging system. There are two types of roughness which are surface roughness and the line edge roughness (LER) and both of which have been already investigated focusing on the relation between the charging with the roughness [4][5][6][7][8][9]. Memos et al [5] studied this issue taking the trench as a target and revealed that on the one hand, the surface charging suppresses the LER, on the other hand, decreasing the LER helps to reduce the charging potential.…”

“…b) shows the case study. The roughness here is still parameterized as in the same way used in[8,9]. The mask plane is a perfect surface only with rough opening of the hole.…”