Mechanisms of porous dielectric film modification induced by reducing and oxidizing ash plasmas

This work focuses on the impact of oxidizing and reducing ash chemistries on the modifications of two porous SiOCH films with varied porosities (8% [low porosity (lp)-SiOCH] and 45% [high porosity (hp)-SiOCH]). The ash processes have been performed on SiOCH blanket wafers in either reactive ion etching (RIE) or downstream (DS) reactors. The modifications of the remaining film after plasma exposures have been investigated using different analysis techniques such as x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy (FTIR), x-ray reflectometry, mercury probe capacitance measurement (C‐V), and spectroscopic ellipsometry (SE). FTIR analyses show that the lp-SiOCH film is not significantly altered by any of the ash processes investigated (DS‐H2∕He, RIE‐O2, and RIE‐NH3), except by downstream oxidizing plasmas (DS‐O2 or DS‐N2∕O2) which induce some carbon depletion and moisture uptake, resulting in a slight increase of the k value. The porosity amplifies the sensitivity of the material to p...