AVS 47th International Symposium
    Plasma Science and Technology Friday Sessions
       Session PS-FrM

Paper PS-FrM9
A Downstream Plasma Etching Model Used to Describe the Etching Mechanisms of Low-k Polymers

Friday, October 6, 2000, 11:00 am, Room 310

Session: Dielectrics II
Presenter: R.R.A. Callahan, Arizona State University
Authors: R.R.A. Callahan, Arizona State University
G.B. Raupp, Arizona State University
S.P. Beaudoin, Arizona State University
Correspondent: Click to Email
Future integrated circuit manufacturing will require new materials to yield improved circuit performance and meet increasingly stringent environmental regulations. One novel material under current study is an organic polymer, parylene. Parylene is being investigated as an alternative low-k dielectric material because it offers both environmental and performance advantages over the current dielectric, silicon dioxide. From an environmental perspective, parylene-n is desirable because it can be etched using oxygen instead of perfluorinated compounds (PFCs) typically used for dielectric etching. This will reduce greenhouse gas emissions. From a performance point of view, parylene is a lower dielectric constant material than silicon dioxide. The use of parylene-n may ultimately reduce cross-talk and RC time delays. In lieu of reactive ion etching, downstream etching using a microwave source has been studied in order to characterize the etching mechanism without ion interactions for three different types of parylene; parylene-N, parylene-C, and fluorinated parylene. The apparent activation energy for the etching process has been observed to range from 6.41 to 7.64 kcal/mol at various pressure settings. Etch rate has been determined as a function of pressure ranging from 0.4 to 2.0 Torr and oxygen flow rate ranging from 25 to 225 sccm and applied plasma power of 250 watts. In addition to experimental work, the etching process has been modeled. The total model includes predictions of: 1) the velocity distribution in the afterglow region, 2) the oxygen atom concentration in the plasma, 3) the oxygen atom concentration in the afterglow region, and 4) the oxygen atom concentration at the surface of the sample. The model has been validated using nitrogen dioxide titration. The model validation, the model predictions, and their implications for parylene etching will be presented.