An Ultralow EOT Ge MOS Device With Tetragonal HfO<sub>2</sub> and High Quality Hf<sub><italic>x</italic></sub>Ge<sub><italic>y</italic></sub>O Interfacial Layer

Abstract

A Ge MOS device with an ultralow equivalent oxide thickness of ~0.5 nm and acceptable leakage current of 0.5 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is presented in this paper. The superior characteristics can be attributed to a tetragonal HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> with a higher k value (k ~ 31) and comparable bandgap. In addition, a Ge MOS device with tetragonal phase HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (t-HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) also shows a lower leakage current and better thermal stability. The mechanisms for t-HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> formation may be explained by the little Ge diffusion from Ge substrate and oxygen deficiency, which are obtained by in situ interfacial layer (IL) formation and high-k processes. The IL with k ~ 13 can be formed by in situ H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O plasma treatment. Moreover, a Ge MOS device with the IL grown by H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O plasma shows smaller interface trap density and hysteresis effects due to a high composition of Ge <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+4</sup> .