AVS 51st International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS1-TuM

Paper PS1-TuM6
Surface Kinetics Modeling for Silicon Oxide and OSG Etching in Fluorocarbon Plasmas

Tuesday, November 16, 2004, 10:00 am, Room 213A

Session: Dielectric Etching
Presenter: O. Kwon, Massachusetts Institute of Technology
Authors: O. Kwon, Massachusetts Institute of Technology
B. Bai, Massachusetts Institute of Technology
H.H. Sawin, Massachusetts Institute of Technology
Correspondent: Click to Email
Fluorocarbon plasma for silicon oxide or OSG etching is a complicated system involving many ion and neutral species. Depending on the plasma condition, many difficulties arise such as RIE lag, etch stop, and low selectivity to photoresist. For a better understanding of the process it is necessary to have an appropriate surface kinetics model which includes simultaneous etching and deposition. We have developed a novel surface kinetics modeling approach, Translating Mixed Layer (TML) model that is based on the assumption that the surface layer is a well-mixed region due to energetic ion bombardments. The mixed layer thickness is given the depth associated with ion bombardment, i.e. ~2.5 nm. The etching and deposition reactions are modeled based on the elemental composition of this layer using a lumped kinetic model. The lumped kinetic model was constructed and verified using measured oxide etching yield data determined by quartz crystal microbalance (QCM) in conjunction with plasma neutral and ion concentrations/fluxes determined by mass spectrometry of C2F6 and C4F8 discharges over broad ranges of process conditions. Etching chemistries with low atomic fluorine concentration (e.g. C4F8 chemistry) exhibit etching yields that are sensitive to compositional change in the plasma. In chemistries with high atomic fluorine concentration (e.g. C2F6 chemistry); however, the etching yield is less sensitive to compositional change in the plasma. Based on the measurements and the simulation, a lumped oxide etching surface kinetics model was constructed. In this model, adsorbed fluorocarbon species act as the etchant and the etching yield is determined by the composition of the surface layer. Atomic fluorine acts as a fluorocarbon etchant to control the etching yield. The model was also applied to OSG etching with fluorocarbon chemistry. The model successfully predicts the etching characteristics of OSG film.