Absolute Fluorine Atom Densities in Fluorocarbon High-Density Plasmas Measured by Appearance Mass Spectrometry
- 1 April 1997
- journal article
- Published by IOP Publishing in Japanese Journal of Applied Physics
- Vol. 36 (4A) , L439-442
- https://doi.org/10.1143/jjap.36.l439
Abstract
We report absolute fluorine atom (F) density measurements based on appearance mass spectrometry (AMS). A liquid nitrogen cold trap installed in a mass spectrometer dramatically reduces background noise at m/e=19 (F+), enabling reliable AMS measurement of F density. The F density reaches ∼1019 m-3 in high-density inductively coupled plasmas in 100 % CF4 or C4F8 while addition of 50 % hydrogen decreases the F density by one order of magnitude. A conventional actinometry technique results in a factor of ∼4 greater reduction of F density in comparison with the AMS result. High etch selectivity of SiO2 to Si is achieved for the radical density ratio CFxF larger than 25 (x=1–3).Keywords
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