In Situ Measurements of Etching Species in SF6 Microwave Downstream Plasma by Ion Attachment Mass Spectroscopy

Abstract

In situ measurements of etching species in a SF6 downstream plasma are performed by employing a new type of mass spectrometer, the Li ion attachment mass spectrometer. Since the problem of fragment ion generation is less important in this type of mass spectrometer, the etching species can be directly detected. In particular, the etching product SiF4 is detected with the addition of Li+, not in the form of SiF3+ which is usually detected using a conventional mass spectrometer employing electron impact ionization. Another new finding is that the F radical is the only etching species measured with the same level under two conditions, with and without a silicon substrate.