Effects of adsorbed moisture in SiO₂ substrates on the formation of a Mn oxide layer by chemical vapor deposition

Manganese oxide formed by a chemical vapor deposition (CVD) method is a promising candidate for an ultrathin diffusion barrier layer in the interconnect structure of advanced semiconductor devices. This study placed emphasis on the adsorbed moisture in a hydrophilic SiO₂ substrate and investigated the effects of the adsorbed moisture on the formation behavior, structure and composition of the CVD Mn oxide layer. The SiO₂ substrates were preannealed at 150 to 500 °C for 1 h to control the type and amount of the residual adsorbed moisture. A Mn oxide layer was subsequently deposited by thermal CVD of bis(ethylcyclopentadienyl)Mn at 200 °C for 30 min. The Mn oxide layer deposited on an as-received substrate was composed of the bilayer of crystalline MnO_x and amorphous MnSi_xO_y. The Mn oxide layer deposited on a preannealed substrate was composed of the single layer of amorphous MnSi_xO_y. The crystalline MnO _x layer was formed by the reaction of the Mn precursor with physisorbed moisture on the as-received SiO₂. The amorphous MnSi _xO_y was due to the reaction with chemisorbed moisture on both the as-received and the preannealed SiO₂. Results of the present work indicate the importance of controlling the adsorbed moisture of the substrates in order to obtain a Mn oxide layer with desired structure and thickness as a diffusion barrier layer.