On the Oxide Trap Density and Profiles of 1-nm EOT Metal-Gate Last CMOS Transistors Assessed by Low-Frequency Noise

摘要

The low-frequency noise behavior of replacement metal gate high-$k$ /metal-gate MOSFETs with an equivalent oxide thickness of the ${rm SiO}_{2}/{rm HfO}_{2}$ bilayer in the range ${sim}{rm 1}~{rm nm}$ has been investigated. It will be shown that both the average trap density and its profile derived from the frequency exponent $gamma$ of the flicker noise spectra are mainly determined by the interfacial layer (IL) oxide processing, with a higher trap density corresponding with a thinner chemical oxide, compared with a ${leq}{rm 1}{hbox{-}}{rm nm}$ thermal ${rm SiO}_{2}$ IL. The thickness of the ${rm HfO}_{2}$ layer and the metal gate fill has only a marginal impact on the noise power spectral density. It will also be shown that for the extraction of the trap density profiles from the $1/f^{gamma}$ noise spectra accurate values for the tunneling effective mass and barrier height are required.