Interface reactions during processing of chemical vapor deposited yttrium oxide high-k dielectrics

by 1971- Niu, Dong

NIU, DONG. Interface reactions during processing of chemical vapor deposited yttrium oxide high-k dielectrics. (Under the direction of Dr. Gregory N. Parsons) High dielectric constant (high-k) insulators are important for advanced MOS devices to limit gate leakage and increase gate capacitance. Reactions between high-k’s and the substrate during deposition or post-deposition processing lead to an increase in the equivalent oxide thickness, and the mechanisms that control the changes need to be well understood. We investigate yttrium-based high-k dielectrics formed by oxygen plasma assisted CVD on Si(100), using two different yttrium diketonate precursors. Characterization techniques include IR, XPS, TEM, EELS, AES, and IV and CV electrical analysis. During deposition and post-deposition anneals a thin Y-O-Si (silicate)/SiO2 structure due to intermixing of Y, O and Si and substrate oxidation is formed at the interface, between the Y2O3 and silicon. The extent of the intermixing depends on substrate surface preparation, process conditions, and annealing conditions. As-deposited Y2O3 films show evidence for O-H bond due to water absorption. With insitu deposited Si capping layers, water pickup is significantly reduced, and interfacial SiO2 layer after annealing is less than 5 Å. Analysis of reaction mechanisms suggests that Si diffusion is attributed to silicate formation, and water absorption, catalytic dissociation of residual O2, and O2 plasma may account for SiO2 formation. Nitridation of chemical vapor deposited yttrium oxide using N2 plasma during deposition and post-deposition treatments is investigated. The use of N2 instead of O2 during deposition minimizes the substrate oxidation. Similar activation energies for postdeposition anneals of O2 and N2 films indicate substrate oxidation processes are likely the same. Bulk properties including chemical bonding, concentration and distribution of N are also studied for as-deposited and annealed films.