AVS 45th International Symposium
    Plasma Science and Technology Division Thursday Sessions
       Session PS-ThP

Paper PS-ThP8
Rare Gas Dilution of Fluorocarbon Plasmas: Te Measurements using TRG-OES and Processing Implications

Thursday, November 5, 1998, 5:30 pm, Room Hall A

Session: Plasma Science and Technology Division Poster Session
Presenter: H.L. Maynard, Bell Laboratories, Lucent Technologies
Authors: H.L. Maynard, Bell Laboratories, Lucent Technologies
M.V. Malyshev, Bell Laboratories (Also at Princeton University)
W.W. Tai, Bell Laboratories, Lucent Technologies
V.M. Donnelly, Bell Laboratories, Lucent Technologies
Correspondent: Click to Email
In the etching of sub-250 nm oxide contacts and vias with high-densityplasmas, rare gas dilution of the fluorocarbon etchant gas has several benefits, including the suppression of etch stop. The addition of a small amount of Ar to a C@sub 2@F@sub 6@ plasma in an Applied Materials' High Density Plasma etcher increases the oxide etching rate (as measured in features > 350 nm). Further addition of Ar does not decrease the oxide etching rate until the diluent concentration exceeds ~80%. For Ar dilution between 20-80%, sufficient fluoropolymer deposits on the oxide surface to provide reactant, and the energy required to drive the etching reaction can apparently be provided equally well by either an Ar or a CF@sub x@ ion. For [Ar] > 80%, insufficient fluoropolymer is deposited to provide sufficient reactant for the oxide etching or to protect the photoresist. For relatively dilute mixtures (50 < [Ar] <80%), one can control the fluoropolymer deposition such that small features are not plugged with excess polymer -- (i.e. suppress etch stop). To better understand plasmas used in this processing regime, we have measured electron temperatures using Trace Rare Gas Optical Emission Spectroscopy.@footnote 1@ Previous attempts to measure T@sub e@ using Langmuir probes in fluorocarbon plasmas have encountered many experimental difficulties, including the deposition of polymer films on the probe surface, oscillating plasma potentials, and inadequate plasma ground reference - often resulting in the reporting of elevated values of T@sub e@. With TRG-OES, one can measure T@sub e@ in the plasma chemistry of interest, non-intrusively and irrespective of the etching or depositing nature of the gas phase chemistry. For a range of processing conditions, we find T@sub e@ to be approximately 3 eV when the primary diluent is Ar. T@sub e@ is substantially higher in Ne/C@sub 2@F@sub 6@ mixtures. In addition, F, C and O concentrations were measured using actinometry and will be presented. @FootnoteText@ @footnote 1@M. V. Malyshev and V. M. Donnelly, J. Vac. Sci. and Technol. 15, 550 (1997)