Atomic layer etching of high-k oxide thin films using hexafluoroacetylacetone and oxygen radicals

Abstract

As integrated circuit devices continue to shrink, achieving sub-3 nm technology nodes requires innovative 3D architectures along with the advent of advanced materials and processes. From an etching perspective, traditional reactive ion etching (RIE), which uses reactive ions and neutral species, becomes increasingly inadequate for atomic-scale dimensions due to surface damage from ion bombardment and the high surface-to-volume ratio. Atomic layer etching (ALE) presents a superior alternative, utilizing two complementary self-limiting steps. By alternating between surface modification and removal phases, ALE enables atomic-level control over etching, surpassing the limitations of traditional RIE methods. In this study, we utilized hexafluoroacetylacetone (Hhfac) and O radicals, generated by a hollow cathode plasma source, as the primary etching agents for various high-k including HfO2, ZrO2, Al2O3, and Y2O3 thin films. Our research focused on elucidating the adsorption dynamics of Hhfac, which contribute to significant volatilization upon interaction with O radicals, leading to self-limiting etching with atomic-scale precision. Detailed surface reactions, mass variations, and volatile etch byproducts were systematically analyzed using X-ray photoelectron spectroscopy (XPS), in-situ quartz crystal microbalance (QCM), and in-situ residual gas analyzer (RGA). These analyses provided both theoretical and experimental insights into the etching mechanisms. This work presents a layer-by-layer removal method for various high-kappa materials, enabling the creation of sharp interfaces and high aspect ratio patterns and contributes to a deeper understanding of etching pathways, particularly in the & Aring;ngstro<spacing diaeresis>m era of device scaling.