Mass spectrometric and ion energy diagnostics in the study of plasma etching and polymerization

Abstract

Mass spectrometric sampling of ions and neutrals from water, hydrogen, and styrene plasmas sustained by 13.56-MHz radio frequency excitation have been studied using a reactor equipped with a small (80–200 μm) sampling orifice leading to a quadrupole mass spectrometer. The apparatus is described, including a discussion of the use of retarding grids to measure ion energy distributions in the sheaths of these plasmas. For both etching and polymer deposition in the pressure regime of 1–50 mTorr, evidence is provided from the mass spectra and ion energy spectra suggesting that the sheath is not collisionless. The data indicate that collisionally activated dissociation and high-energy ion–molecule reactions occur in the sheath, while collisional stabilization occurs in the bulk of the discharge.