Process driven oxygen redistribution and control in Si_0.7Ge _0.3/HfO₂/TaN gate stack film systems

Bulk and surface sensitive photoemission core line spectra have been acquired for Si and Ge following each step in the process sequence of Si _0.7Ge_0.3/2 nm HfO₂/2.5 nm TaN/950 C gate stack film systems. Extended x-ray absorption fine structure measurements have confirmed Ge segregation and pileup to form a Ge-rich layer at the SiGe surface during Si oxidation. Transmission electron micrograph cross-sections with electron energy loss element profiles have verified the effectiveness of plasma nitridation for restricting SiGe oxidation and achieving <1 nm equivalent oxide thickness with gate leakage current density equivalent to that of Si substrates without the necessity of a Si cap for oxidation control.