AVS 51st International Symposium
    Plasma Science and Technology Monday Sessions
       Session PS1-MoM

Paper PS1-MoM4
Low-k and Porous Low-k Sidewall Roughening: Fluorocarbon Plasma and Beam Measurements

Monday, November 15, 2004, 9:20 am, Room 213A

Session: Low-k Dielectric Etching
Presenter: Y. Yin, Massachusetts Institute of Technology
Authors: Y. Yin, Massachusetts Institute of Technology
S.A. Rasgon, Massachusetts Institute of Technology
H.H. Sawin, Massachusetts Institute of Technology
Correspondent: Click to Email
For the patterning of sub 100 nm features, a clear understanding of the origin and control of line edge roughness (LER) is extremely desirable, both from a fundamental as well as a manufacturing perspective. Plasma etching processes often roughen the feature sidewalls, leading to the formation of anisotropic striations. It is this post-etch sidewall roughness which will ultimately affect device performance. The integration of organosilicate glass (OSG) and porous OSG films as low-k interlayer dielectrics presents new challenges from a roughening standpoint, particularly when using highly polymerizing fluorocarbon plasma chemistries typical of oxide etching. Under certain conditions the added carbon present in OSG films can increase localized deposition, yielding both carbon-rich and substrate-rich areas of the sample, and creating surface roughness based on the etch selectivity difference (polymer micromasking). Additionally, fluorocarbon polymer can be seeded into the pore structure of porous OSG films, magnifying the effect. We have previously examined this effect on planar samples in a conventional plasma etcher. However, the role of fluorocarbon polymerization on sidewall roughening/striation of OSG/porous OSG has not been investigated. Therefore, we have undertaken an examination of this sidewall roughening using a new, inductively coupled plasma beam source. This source allows the exposure of a sample to a realistic ion and neutral flux, of any desired plasma chemistry, while allowing independent control of the ion bombardment energy and incident angle. By rotating the sample to a near-glancing angle, a sidewall can be simulated, eliminating any effects associated with patterning. The effects of ion bombardment, impingement angle, and fluorocarbon chemistry (highly polymerizing vs. low polymerizing) on the roughening of SiO2, OSG, and porous OSG are discussed. Finally, insight into the surface roughening mechanism is obtained through modeling.