Passivation and Nucleation of Ge(100) via H2O and HOOH Dosing

Abstract

Germanium is a promising candidate for potential channel materials due to its higher hole and electron mobility. To minimize the oxide-semiconductor interfacial defect density, a proper passivation layer must be used before the oxide layer is deposited <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> . The passivation layer must be very thin, ideally one monolayer, to allow for increased scaling of the equivalent oxide thickness (EOT). H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O provides a well-ordered chemisorption monolayer (ML) at room temperature without disrupting surface Ge atoms <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . In this study, a monolayer of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O chemisorbates is shown to activate TMA chemisorption due to the Ge-OH bonds catalyzing the formation of an ultrathin passivation layer which can serve as an ideal ALD nucleation template on a Ge surface <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . However, since H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O chemisorption results in equal density of Ge-H and Ge-OH sites on the Ge(100), H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O can only provide a maximum of 0.5 monolayer of Ge-OH sites, limiting the TMA nucleation density. By using HOOH dosing, the density of Ge-OH sites can be doubled thereby increasing the potential TMA nucleation density. This study compares the passivation of the Ge(100) surface via H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O and HOOH, for the application of nucleating ALD growth on the surface, using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). This study will also look into similar H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O/HOOH passivation and TMA nucleation techniques on SiGe.