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Title: Silicon and silicon oxide etching rate enhancement by nitrogen containing gas addition in remote perfluorocarbon plasmas

Abstract

The addition of 3% nitrogen to a mixture of perfluorocarbon/oxygen/argon in a remote toroidal plasma source was shown to double the etching rate of both silicon dioxide and silicon in a downstream process. It is believed that the nitrogen blocks the surface recombination sites for COF{sub 2} formation on the wall of the transfer tube, thereby transporting more fluorine atoms to the downstream process chamber and increasing the etching rate.

Authors:
; ;  [1];  [2]
  1. Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States)
  2. (United States)
Publication Date:
OSTI Identifier:
20778778
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 88; Journal Issue: 10; Other Information: DOI: 10.1063/1.2185254; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ARGON; ATOMS; ETCHING; FLUORIDES; FLUORINE; MIXTURES; NITROGEN; OXYGEN; PLASMA; RECOMBINATION; SEMICONDUCTOR MATERIALS; SILICON; SILICON OXIDES; SPUTTERING; TUBES; WALL EFFECTS

Citation Formats

Bai Bo, An Jujin, Sawin, Herbert H., and Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139. Silicon and silicon oxide etching rate enhancement by nitrogen containing gas addition in remote perfluorocarbon plasmas. United States: N. p., 2006. Web. doi:10.1063/1.2185254.
Bai Bo, An Jujin, Sawin, Herbert H., & Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139. Silicon and silicon oxide etching rate enhancement by nitrogen containing gas addition in remote perfluorocarbon plasmas. United States. doi:10.1063/1.2185254.
Bai Bo, An Jujin, Sawin, Herbert H., and Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139. Mon . "Silicon and silicon oxide etching rate enhancement by nitrogen containing gas addition in remote perfluorocarbon plasmas". United States. doi:10.1063/1.2185254.
@article{osti_20778778,
title = {Silicon and silicon oxide etching rate enhancement by nitrogen containing gas addition in remote perfluorocarbon plasmas},
author = {Bai Bo and An Jujin and Sawin, Herbert H. and Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139},
abstractNote = {The addition of 3% nitrogen to a mixture of perfluorocarbon/oxygen/argon in a remote toroidal plasma source was shown to double the etching rate of both silicon dioxide and silicon in a downstream process. It is believed that the nitrogen blocks the surface recombination sites for COF{sub 2} formation on the wall of the transfer tube, thereby transporting more fluorine atoms to the downstream process chamber and increasing the etching rate.},
doi = {10.1063/1.2185254},
journal = {Applied Physics Letters},
number = 10,
volume = 88,
place = {United States},
year = {Mon Mar 06 00:00:00 EST 2006},
month = {Mon Mar 06 00:00:00 EST 2006}
}
  • In this study, chemical dry etching characteristics of silicon oxide layers were investigated in the F{sub 2}/N{sub 2}/Ar remote plasmas. A toroidal-type remote plasma source was used for the generation of remote plasmas. The effects of additive N{sub 2} gas on the etch rates of various silicon oxide layers deposited using different deposition techniques and precursors were investigated by varying the various process parameters, such as the F{sub 2} flow rate, the additive N{sub 2} flow rate, and the substrate temperature. The etch rates of the various silicon oxide layers at room temperature were initially increased and then decreased withmore » the N{sub 2} flow increased, which indicates an existence of the maximum etch rates. Increase in the oxide etch rates under the decreased optical emission intensity of the F radicals with the N{sub 2} flow increased implies that the chemical etching reaction is in the chemical reaction-limited regime, where the etch rate is governed by the surface chemical reaction rather than the F radical density. The etch rates of the silicon oxide layers were also significantly increased with the substrate temperature increased. In the present experiments, the F{sub 2} gas flow, the additive N{sub 2} flow rate, and the substrate temperature were found to be the critical parameters in determining the etch rate of the silicon oxide layers.« less
  • The authors investigated the effects of various additive gases and different injection methods on the chemical dry etching of silicon nitride, silicon oxynitride, and silicon oxide layers in F{sub 2} remote plasmas. N{sub 2} and N{sub 2}+O{sub 2} gases in the F{sub 2}/Ar/N{sub 2} and F{sub 2}/Ar/N{sub 2}/O{sub 2} remote plasmas effectively increased the etch rate of the layers. The addition of direct-injected NO gas increased the etch rates most significantly. NO radicals generated by the addition of N{sub 2} and N{sub 2}+O{sub 2} or direct-injected NO molecules contributed to the effective removal of nitrogen and oxygen in the siliconmore » nitride and oxide layers, by forming N{sub 2}O and NO{sub 2} by-products, respectively, and thereby enhancing SiF{sub 4} formation. As a result of the effective removal of the oxygen, nitrogen, and silicon atoms in the layers, the chemical dry etch rates were enhanced significantly. The process regime for the etch rate enhancement of the layers was extended at elevated temperature.« less
  • Silicon oxide etching processes in C{sub 2}F{sub 6} and C{sub 4}F{sub 8}+80% Ar plasmas were investigated. Neutral and ion compositions in the plasma were measured using quadrupole mass spectrometry and etching yield was measured by a quartz-crystal microbalance. In C{sub 2}F{sub 6} plasma, the concentration of atomic fluorine in the neutral flux was 5%-25%, whereas there was less than 0.5% of atomic fluorine in C{sub 4}F{sub 8}+80% Ar plasma. A surface plot representing the etching yield as a function of neutral and ion fluxes was constructed and used to qualitatively explain the etching characteristics of silicon oxide in fluorocarbon plasmas.more » In C{sub 2}F{sub 6} chemistry, etching yield decreases slightly with increasing rf coil power. This is attributed to the decrease in both F/ion and CF{sub x}/ion, which is caused by an increase in ion flux, with a more significant effect due to a decrease in F/ion. In C{sub 4}F{sub 8}+80% Ar chemistry, however, etching yield increases with increasing rf coil power. This is attributed to the decrease in CF{sub x}, without the effect of F/ion due to the low atomic fluorine concentration. With increased operating pressure, etching yield decreases for both chemistries because as the pressure increases, ion current decreases, and CF{sub x} neutral concentration increases to have more deposition and less etching.« less
  • A fast flow reactor-quadrupole mass spectrometer coupled with a laser vaporization source is used to study the gas-phase reactions of nickel and nickel oxide cluster anions (Ni{sub x}O{sub y}{sup {minus}}, where x = 1--12 and y = 0, 1, or 2) with nitric oxide. The results indicate that three processes are occurring in the presence of the nickel cluster anions. First, nickel and nickel oxide clusters are oxidized by the reaction with nitric oxide. Second, addition products with these oxides are also formed. Third, nitrogen dioxide and nitrogen trioxide are formed on nickel oxide clusters and subsequently released as anions.more » Rate constants are reported for the initial reaction occurring between the nickel cluster anions and the nitric oxide, and the reaction rates are compared with reaction rates of the same nickel anion clusters with molecular oxygen. Finally, a comparison of the reaction rates for nickel oxides formed both in the flow tube and in the laser vaporization source are reported. These reactions (previously reported on Part 1) to help to provide a better understanding of the formation of free nitrogen oxide anions observed in the current experiments.« less