Room temperature synthesis of HfO2/HfOx heterostructures by ion-implantation

摘要

Implantation of Hf films with oxygen ions is shown to be an effective means of fabricating high-quality HfO2/HfOx heterostructures at room temperature, with the layer composition and thicknesses determined by the ion energy and fluence. Implantation with 3 keV O+ ions to a fluence of 1 x 10(17) ions cm(-2) produces a polycrystalline (monoclinic-) HfO2 layer extending from the surface to a depth of similar to 12 nm, and an underlying graded HfOx layer extending an additional similar to 7 nm, while implantation with 6 keV O to a similar fluence produces a near-stoichiometric surface layer of 7 nm thickness and a graded substoichiometric layer extending to depth of similar to 30 nm. These structures are shown to be broadly consistent with oxygen range data but more detailed comparison with dynamic Monte Carlo simulations suggests that the near-surface region contains more oxygen than expected from collisional processes alone. The bandgap and dielectric strength of the HfO2 layer produced by 3 keV; 1 x 10(17) ions cm(-2) implant is shown to be indistinguishable from those of an amorphous film deposited by atomic layer deposition at 200 degrees C. The utility of these layers is demonstrated by studying the resistive switching properties of metal-oxide-metal test structures fabricated by depositing a top metal contact on the implanted film. These results demonstrate the suitability of ion-implantation for the synthesis of functional oxide layers at room temperature.