AVS 46th International Symposium
    Manufacturing Science and Technology Group Thursday Sessions
       Session MS+PS-ThM

Paper MS+PS-ThM10
Study of NF@sub 3@-Based High Density Plasma Oxide Etch Processes for Reduced Global Warming Emissions

Thursday, October 28, 1999, 11:20 am, Room 611

Session: Environmentally Benign Manufacturing
Presenter: L.C. Pruette, Massachusetts Institute of Technology
Authors: L.C. Pruette, Massachusetts Institute of Technology
S.M. Karecki, Massachusetts Institute of Technology
R. Chatterjee, Massachusetts Institute of Technology
R. Reif, Massachusetts Institute of Technology
Correspondent: Click to Email
Current oxide etch processes in the semiconductor industry rely on fluorocarbon chemistries, particularly perfluorocarbons (PFCs). The emission of PFCs from these processes has become a cause of concern to the industry because of the long atmospheric lifetimes and the suspected global warming properties of these molecules. Whereas it has been seen that the use of some fluorocarbon molecules in place of PFCs does lead to measurable emissions reductions, stemming typically from a more efficient breakdown in the plasma that that seen with PFCs, it is also known that any process based on a fluorocarbon source material, whether a PFC or not, is likely to emit significant quantities of CF@sub 4@, an extremely long-lived molecule possessing an appreciable global warming potential. The goal of the research presented here is to minimize the amount of CF@sub 4@ and other PFC by-products produced in high density plasma (HDP) oxide etch processes by replacing the fluorocarbon etch gas with an inorganic molecule, namely NF@sub 3@. The NF@sub 3@ gas acts as a fluorine source for the plasma, and is mixed with a rare gas diluent to enhance plasma stability. Experiments illustrating the etch behavior of this dilute NF@sub 3@ plasma with the addition of several different hydrocarbon additives meant to enhance photoresist selectivity and sidewall passivation, and scavenge free fluorine, will be discussed. Scanning electron micrographs (SEMs) will be shown to demonstrate process feasibility. In-situ optical emission spectroscopy data will be used to characterize the plasma, and quadrupole mass spectrometry (QMS) and Fourier-transform infrared (FTIR) spectroscopy data will be used to identify the global warming compounds and hazardous air pollutants (HAPs) found in the process effluent.