Mechanistic study of surface contamination of dielectric oxides using isotope labeling

Surface molecular contamination of gate dielectrics in metal oxide semiconductor structures is a problem affecting the performance of integrated circuits. The impact depends strongly on the nature of the interactions between the contaminants and the dielectric surfaces. The mechanism of interactions of moisture and isopropyl alcohol (IPA) with SiO₂ and ZrO₂ films was studied using isotope labeling with deuterium oxide (D₂O). The results revealed that H₂O adsorbs in a random multilayer configuration with three distinct types of interactions (hydroxylation of oxide in the first layer, MOH-H₂O interactions in the second layer, and nondissociative H₂O-H₂O interactions in the higher layers). On the basis of these findings, a multilayer multicomponent adsorption/desorption model was developed that agrees well with the experimental data. The adsorption of IPA also follows multilayer dynamics. The interaction with the bare dielectric surface is nondissociative and relatively weak. However, IPA chemisorbs on a hydroxylated oxide. The isotope labeling studies revealed an exchange mechanism in which IPA undergoes an esterification reaction with chemisorbed H₂O.