AVS 53rd International Symposium
    Plasma Science and Technology Friday Sessions
       Session PS1-FrM

Paper PS1-FrM3
Measurement of Etching Kinetics and Surface Roughening of SiO2 and Coral Films during Plasma Etching

Friday, November 17, 2006, 8:40 am, Room 2009

Session: Plasma-Surface Interactions III
Presenter: Y. Yin, Massachusetts Institute of Technology
Authors: Y. Yin, Massachusetts Institute of Technology
H.H. Sawin, Massachusetts Institute of Technology
Correspondent: Click to Email
Plasma etching processes often roughen the feature sidewalls, leading to the formation of anisotropic striations. The primary cause of sidewall roughening is the templating of mask roughness into the underlying film. Specifically, the inherent roughening of photoresist provides the mask for templating effect. To fully understand the sidewall roughness evolution, it is critical to understand the mechanism of the inherent roughening of photoresist as well as other materials, such as low-k dielectric film. The etching kinetics and surface roughening of thermal SiO2 and low-k dielectric Coral in Ar, C2F6/Ar, and C4F8/Ar plasma beams have been measured as a function of ion energy, ion bombardment angle, etching time and plasma composition in an inductively coupled plasma beam system. For all plasma chemistries, the etching yield at normal impingement angle scales linearly with the square root of ion energy. The angular dependence of the etching yield of both films in Ar plasma followed the typical sputtering yield curve, with a maximum around 60-75 degree off-normal angle. By adjusting the plasma etching conditions, the etching yield in fluorocarbon plasmas can follow either the ion-enhanced-etching yield curve or a sputtering-like yield curve. The surface roughening of both films showed different trends in Ar and fluorocarbon plasmas. In Ar plasma, both films stayed smooth after etching at normal angle while became rougher at grazing angles. Specifically, the striation formed at grazing angles can be either parallel or transverse to the beam impingement direction. More interestingly, the sputtering caused roughening at different off-normal angles can be qualitatively explained combining the corresponding angular dependent etching yield curve. In fluorocarbon plasmas, the films kept smooth at normal angle; while at grazing angles, the surface can be either rougher when the etching is sputtering-like or remain smooth when ion-enhanced etching is dominant.