| AVS 56th International Symposium & Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS1-MoM |
| Session: | Advanced Interconnect Etch |
| Presenter: | J. Kelber, University of North Texas |
| Authors: | J. Kelber, University of North Texas S. Behera, University of North Texas S. Manandhar, University of North Texas S. Gaddam, University of North Texas |
| Correspondent: | Click to Email |
Exposure of ultralow-k organosilicate (“SiCOH”) materials to oxygen plasma induces methyl group abstraction and other changes leading to significant increases in k value. We present ex situ FTIR and in situ XPS data for O2 plasma and thermal (Ekinetic < ~ 0.1 eV) electronic ground state atomic O (thermal O(3P)) interactions with SiCOH films. The data yield new insight concerning the fundamental mechanisms and kinetics of oxygen plasma-induced CH3 abstraction, and how these are affected by organosilicate pore structure. FTIR measurements indicate that methyl group abstraction kinetics in the presence of a direct O2 plasma are diffusion-dominated, and that this diffusion is directly related to SiCOH diffusivity (pore interconnectedness) rather than total pore volume. Pre-treatment of a high porosity/high diffusivity material with He plasma prior to O2 plasma exposure sharply limits CH3 abstraction in a manner similar to that exhibited by a vicinal high porosity/low diffusivity material—evidence that He pretreatment results in closure of pore channels. Exposure to O(3P) from a thermal source (1300 K) results in changes in FTIR spectra similar to exposure to O2 plasma, indicating that thermal O(3P) is a major reactant in the diffusion-dominated CH3 abstraction mechanism. In situ XPS analysis of thermal O(3P)/organosilicate interactions indicate that carbon loss and O/OH incorporation in the organosilicate surface region occur concurrently; i.e., Si-C bond scission and Si-O formation are related processes resulting from interaction with O(3P). This conclusion is supported by recent ab initio DFT-based molecular simulation (AIMDS) results recently reported by Jincheng Du and co-workers (Chaudhari, et al., submitted) that also indicate energy barriers to O/SiCOH interactions are extremely trajectory-sensitive, thus providing a rationale for the experimentally indicated O diffusion mechanism. The experimental and theoretical data also provide insight concerning O interactions with other Si/C based materials, such as SiC, and the implications of this work for processing of SiC will be discussed.
Acknowledgments: This work was supported by the Semiconductor Research Corporation under task ID 1862.001 and by the Robert Welch Foundation under grant B-1356. The authors thank Dr. G. A. Antonelli for providing samples and for useful discussions.