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

摘要

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 ( (ksim 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 (ksim 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}}) .