AVS 50th International Symposium
    Plasma Science and Technology Wednesday Sessions
       Session PS1-WeA

Paper PS1-WeA7
Fluorocarbon-based Plasma Etching: The Role of the Energy Distribution of Bombarding Ions

Wednesday, November 5, 2003, 4:00 pm, Room 314

Session: Mechanisms in Plasma-Surface Interactions
Presenter: A.E. Wendt, University of Wisconsin, Madison
Authors: R. Silapunt, University of Wisconsin, Madison
S. Williams, University of Wisconsin, Madison
A.E. Wendt, University of Wisconsin, Madison
K.H.R. Kirmse, Texas Instruments
L. Losey, Texas Instruments
Correspondent: Click to Email
In fluorocarbon-based plasma etching of dielectrics, an overlying thin fluorocarbon film, deposited on the substrate during etching, strongly affects etch rate and etch selectivity.@footnote 1@ Here we report on recent results that suggest that the energy distribution of bombarding ions (IED) has a significant effect on the thickness of this polymer layer, subsequently affecting etch rate and selectivity as well. Specifically, we have narrowed the IED while keeping other process conditions unchanged by tailoring the shape of the RF voltage waveform used for substrate bias. Significant improvements in etch selectivity for SiO@sub2@ over silicon, SiO@sub2@ over photoresist and organosilicate glass (OSG) over silicon nitride and silicon carbide have been obtained by using a narrow IED compared to the broad IED resulting from a sinusoidal bias waveform. X-ray photoelectron spectroscopy (XPS) has been used to determine the thickness of the overlying fluorocarbon film as a function of bias voltage for both narrow and broad IEDs. The results show a strong inverse correlation between film thickness and etch rate, suggesting that the sensitivity of this polymer film to the IED is the key to observed improvements in selectivity.@footnote 2@@FootnoteText@@footnote 1@ G. S. Oehrlein et al., JVST A 15, 1881 (1997)@footnote 2@ Supported by SRC (TI custom funding) .