Conformal deposition of GeTe films with tunable Te composition by atomic layer deposition

Abstract

Atomic layer deposition (ALD) of chalcogenide amorphous films has attracted attention, thanks to its ability to deposit highly conformal and uniform thin films on three-dimensional structures; these film properties are critical for the development of ultrahigh-density integrated electronic circuits such as nanoscale 3D cross-point memory stacks. Control over the composition of chalcogenide compounds is indispensable for fabricating functional electronic devices. In this work, the authors used trichlorogermane (HGeCl3) and bis(trimethylsilyl)telluride [(Me3Si)2Te] as ALD precursors to develop conformal and uniform germanium telluride (GeTe) films at low temperature (60 °C). The growth of GeTe resulted in moderately Ge rich films independently of the ALD precursor injection time and the use of single or discrete (Me3Si)2Te doses. To achieve control over the GeTe film composition, the authors developed a unique ALD of elemental tellurium (Te) using tellurium ethoxide [Te(OEt)4] and (Me3Si)2Te as precursors. Combining GeTe and elemental Te in an ALD supercycle fashion, they obtained GeTex films with a controllable Te content showing a uniform and conformal morphology on high aspect ratio trench structures. A detailed analysis of the variations in Ge and Te contents upon exposure of GeTex films to Te(OEt)4 revealed that an interfacial replacement of Ge atoms to form volatile Ge(OEt)2 takes place and produces a decrease in Ge and an increase in Te content. The ALD studies of GeTe and Te films described in this work provide a facile route for deposition of GeTe with controllable composition. This material system is important for the development of ovonic threshold switching selectors and phase change memories.