Modification of porous SiOCH by first contact with water vapor after plasma process

Abstract

Porous low-k dielectrics used in integrated circuits interconnects are sensitive to plasma processes and exposure to moist ambient. In this paper, the authors use a vacuum and dry N2 sample transportation in conjunction with controlled atmosphere infrared spectroscopy (in transmission and in multiple internal reflections mode) to investigate the role of the first exposure to humidity on plasma-damaged porous low-k. They show that a porous low-k exposed to a N2/H2 or O2 plasma is irreversibly modified by the first exposure to water molecules. In the former case, Si-NHx and Si-H groups are converted into Si-OH while C=O and/or CH=NH groups are formed. In the latter case, irreversible water uptake as icelike water leads to a decrease of the density of isolated silanol groups. In both cases, no additional modifications are observed after a second cycle of water adsorption/desorption, meaning that subsequent water adsorption is reversible.