AVS 53rd International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuM

Paper PS2-TuM4
Plasma-Surface Reaction Mechanisms for Si Etching Profiles in UHF-ECR Cl@sub 2@/O@sub 2@, Cl@sub 2@/O@sub 2@/HBr Plasmas

Tuesday, November 14, 2006, 9:00 am, Room 2011

Session: Plasma Surface Interactions I: Joint AVS-AIChE Session
Presenter: M. Mori, Hitachi, Ltd., Japan
Authors: M. Mori, Hitachi, Ltd., Japan
N. Itabashi, Hitachi, Ltd., Japan
K. Eriguchi, Kyoto University, Japan
K. Ono, Kyoto University, Japan
Correspondent: Click to Email
For fabricating beyond 45 nm-node ULSI devices, the nanometer-scale control of etching profiles is indispensable in Si etching processes, which in turn requires a better understanding of the mechanisms responsible for the feature profile evolution during etching. In this study, we analyze the mechanisms for Si etching by comparing the etched profiles with the profile simulation using an atomic-scale phenomenological model, which includes the effects of passivation layer formation, ion and neutral reflection on sidewalls, and chemical etching in addition to ion-enhanced etching.@footnote 1@ Experiments were performed by using an UHF-ECR plasma reactor in Cl@sub 2@/O@sub 2@/HBr mixtures, as a function of O@sub 2@ flow rate, Cl@sub 2@/HBr gas flow ratio, RF bias power, pressure, wafer temperature, and so on. The SEM and TEM results showed that the sidewall profiles became more tapered with increasing O@sub 2@ flow rate. The micro-trenching and footing (or sidewall bowing near the feature bottom) were found to be significant in Cl@sub 2@/O@sub 2@ plasmas, being suppressed with increasing O@sub 2@ flow rate; however, the sharp micro-trenching and footing disappeared in HBr/O@sub 2@ and Cl@sub 2@/O@sub 2@/HBr, and a weak lateral etch was observed on sidewalls in Cl@sub 2@/O@sub 2@/HBr plasmas. A comparison with the profile simulation indicated that the tapered profiles were enhanced by oxidization of re-incident etch products/by-products deposited on feature sidewalls. On the other hand, the micro-trenching was found to be attributed to the ion reflection on feature sidewalls; the footing was caused also by re-deposition of etch products on sidewalls from the feature surfaces being etched. Competition between etching reactions of chlorine and bromine and also between etching and passivation would be responsible for nanometer-scale control of the Si etching profiles. @FootnoteText@ @footnote 1@ Y. Osano, K. Ono, Jpn. J. Appl. Phys. 44, 8650 (2005).