High mobility Ge pMOSFETs with ∼ 1nm thin EOT using Al2O3/GeOx/Ge gate stacks fabricated by plasma post oxidation

A novel plasma post oxidation method has been proposed to form an Al₂O₃/GeO_x/Ge gate stack by using oxygen plasma through a thin ALD Al₂O₃ layer. This Ge gate stack is shown to simultaneously realize both thin EOT of ~1 nm and low D_it of <;60;10¹¹ cm^-2eV^-1. Ge pMOSFETs, fabricated by employing this method, have demonstrated superior device operation with high hole mobilities of 437, 526 and 345 cm²/Vs on (100), (110) and (111) Ge substrates, respectively. These mobilities on (100) and (110) are the highest under ~1 nm EOT among the results reported so far. Also, this is the first demonstration of (110) and (111) Ge pMOSFET operations in this ultrathin EOT range.