Atomic layer chemical vapor deposition of ZrO2-based dielectric films:: Nanostructure and nanochemistry

A 4 nm layer of ZrOx (targeted xsimilar to2) was deposited on an interfacial layer (IL) of native oxide (SiO, tsimilar to1.2 nm) surface on 200 mm Si wafers by a manufacturable atomic layer chemical vapor deposition technique at 300 degreesC. Some as-deposited layers were subjected to a postdeposition, rapid thermal annealing at 700 degreesC for 5 min in flowing oxygen at atmospheric pressure. The experimental x-ray diffraction, x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and high-resolution parallel electron energy loss spectroscopy results showed that a multiphase and heterogeneous structure evolved, which we call the Zr-O/IL/Si stack. The as-deposited Zr-O layer was amorphous ZrO2-rich Zr silicate containing about 15% by volume of embedded ZrO2 nanocrystals, which transformed to a glass nanoceramic (with over 90% by volume of predominantly tetragonal-ZrO2 (t-ZrO2) and monoclinic-ZrO2 (m-ZrO2) nanocrystals) upon annealing. The formation of disordered amorphous regions within some of the nanocrystals, as well as crystalline regions with defects, probably gave rise to lattice strains and deformations. The interfacial layer (IL) was partitioned into an upper SiO2-rich Zr silicate and the lower SiOx. The latter was substoichiometric and the average oxidation state increased from Si0.86+ in SiO0.43 (as-deposited) to Si1.32+ in SiO0.66 (annealed). This high oxygen deficiency in SiOx was indicative of the low mobility of oxidizing specie in the Zr-O layer. The stacks were characterized for their dielectric properties in the Pt/{Zr-O/IL}/Si metal oxide-semiconductor capacitor (MOSCAP) configuration. The measured equivalent oxide thickness (EOT) was not consistent with the calculated EOT using a bilayer model of ZrO2 and SiO2, and the capacitance in accumulation (and therefore, EOT and k(Zr-O)) was frequency dispersive, trends well documented in literature. This behavior is qualitatively explained in terms of the multilayer nanostructure and nanochemistry that evolves. (C) 2003 American Institute of Physics.