Low-Frequency Noise Assessment of Silicon Passivated Ge pMOSFETs With TiN/TaN/ HfO₂ Gate Stack

The low-frequency noise of pMOSFETs fabricated in epitaxial germanium-on-silicon substrates is studied. The gate stack consists of a TiN/TaN metal gate on top of a 1.3-nm equivalent oxide thickness HfO₂/SiO₂ gate dielectric bilayer. The latter is grown by chemical oxidation of a thin epitaxial silicon film deposited to passivate the germanium surface. It is shown that the spectrum is of the 1/f^gamma type, which obeys number fluctuations for intermediate gate voltage overdrives. A correlation between the low-field mobility and the oxide trap density derived from the 1/f noise magnitude and the interface trap density obtained from charge pumping is reported and explained by considering remote Coulomb scattering