Berlin 2005 – scientific programme
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DF: Dielektrische Festkörper
DF 6: Dielektrische und ferroelektrische dünne Schichten und Nanostrukturen II
DF 6.5: Talk
Monday, March 7, 2005, 15:20–15:40, TU TC6
Ti-doping of Pr silicate layers for high-k dielectrics applications — •Grzegorz Lupina1, Thomas Schroeder1, Jarek Dabrowski1, Dieter Schmeißer2, and Hans-Joachim Muessig1 — 1IHP, Im Technologiepark 25, D-15236 Frankfurt (Oder) — 2BTU Cottbus, PF 101344, D-03013 Cottbus
Near-term downscaling of the metal-oxide-semiconductor field-effect transistors (MOSFETs) requires the replacement of the SiO2 gate oxide with a material having a higher dielectric constant. Recent studies indicate that silicate materials are the most promising candidates; among them are Pr silicates. Applying a combination of x-ray photoelectron spectroscopy (XPS), electrical measurements (C-V), and ab initio calculations, we investigated the effect of thin Ti doping on the structural and electrical properties of the gate stacks composed of a Pr silicate film and a SiO2-based interfacial buffer layer. Metallic Ti was deposited at room temperature after the formation of the Pr silicate dielectric. The resulting layered structures were annealed under ultra-high vacuum (UHV) at various temperatures between 70∘C and 880∘C. XPS indicates that the evaporated layer preserves its metallic character over the whole range of UHV annealing temperatures. Synchrotron radiation XPS at BESSY II shows that large amounts of Ti atoms incorporated into the Pr silicate remain metallic even after air exposure at room temperature. Annealing in nitrogen ambient at 300∘C leads to the oxidation of these atoms so that a mixed Pr:Ti silicate is formed. We show that the so formed dielectrics exhibit an improved equivalent oxide thickness and a reduced density of interface states.