An Ultralow EOT Ge MOS Device With Tetragonal HfO2 and High Quality HfxGeyO Interfacial Layer.

A Ge MOS device with an ultralow equivalent oxide thickness of \(\sim 0.5\) nm and acceptable leakage current of 0.5 A/cm \(^{{2}}\) is presented in this paper. The superior characteristics can be attributed to a tetragonal HfO2 with a higher \(k\) value ( \(k\sim 31\) ) and comparable bandgap. In addition, a Ge MOS device with tetragonal phase HfO2 ( \(t\) -HfO2) also shows a lower leakage current and better thermal stability. The mechanisms for \(t\) -HfO2 formation may be explained by the little Ge diffusion from Ge substrate and oxygen deficiency, which are obtained by \({\boldsymbol { {in~situ}}}\) interfacial layer (IL) formation and high- \(k\) processes. The IL with \(k\sim 13\) can be formed by in situ H2O plasma treatment. Moreover, a Ge MOS device with the IL grown by H2O plasma shows smaller interface trap density and hysteresis effects due to a high composition of Ge \(^{{+4}}\) . [ABSTRACT FROM AUTHOR]