Ultra High Vacuum Physical Vapor Deposition of Yttrium Aluminate and Hafnium Aluminate High-k Dielectrics on Silicon

Abstract

Ultra high vacuum physical vapor deposition is used to deposit thin films of varying yttrium:aluminum and hafnium:aluminum concentrations on H-terminated silicon(100) and oxidized ex-situ at several temperatures. X-ray Photoelectron Spectroscopy is used to analyze the surface composition of the films and electrical properties were evaluated using capacitance-voltages measurements with aluminum electrodes. The diffusion of silicon into the dielectric films is decreased with high concentrations (>78%) of aluminum. However, at high concentrations of aluminum a relatively thick interfacial oxide layer is formed. The flatband voltage shifted from –0.18V to –0.78V for the hafnium oxide films and –1.22V to –1.18V for yttrium oxide films. The flatband voltage shifted from –0.55V to –0.61V for 70% Hf:Al mixture and –0.78V to –0.76V for 42%Y:Al mixture. These flatband voltage shifts indicate that hafnium based mixtures are more sensitive to thermal treatments than yttrium based mixtures. Also, capacitance-voltage measurements show the ability to tune the flatband voltage and possibly vary the rate of silicon oxidation (tune equivalent oxide thickness) by aluminum alloying.