Paper TF-ThP31
Development of the Synchrotron-based Capabilities for Direct, In-situ XANES/XAFS Measurements of Thermal ALD: Initial Proof-of-Concept Study Exploring ZrO₂ ALD

Thursday, October 25, 2018, 6:00 pm, Room Hall B

Atomic layer deposition (ALD) has become an essential tool for the design and fabrication of electronic materials key for a wide range of applications from semiconductor processing to advanced power electronics and photovoltaics. The resulting materials are characterized by thicknesses in the nm scale, they are typically amorphous and yet they exhibit unique properties that depend on growth conditions in ways that are not yet understood. As an example, ferroelectric hafnium oxide has been recently reported, achieved through the stabilization at the nanoscale of a non-centrosymmetric orthorhombic phase that is not stable at ambient pressure for bulk materials. Another example is the development of nanolaminate (NL) materials, composite thin films comprised of alternating layers of metal oxides (eg. HfO₂ and ZrO₂ in the case of ferroelectric HfO₂)that demonstrate unique optical, mechanical, and electrical properties. To this end, the stable monoclinic phase found for HfO2 has Hf-O bonds with 7-fold coordination at room temperature whereas the tetragonal phase, which is favoured for ZrO₂ at room temperature, has Zr-O bonds with an 8-fold coordination environment. The intermixing of these phases by tuning the number of ALD sub-cycles of each component ─ thereby changing the NL composition ─ can lead to non-trivial phase transformations in their local structure that deviate from their bulk composition. In this work we explore the genesis and evolution of ZrO₂ films in the first 10 ALD cycles using a custom conflat cube reactor design for in-situ (fluorescence mode) XANES/XAFS measurements at the Advanced Photon Source. We will present results of the direct XANES/XAFS measurement of single TDMAZr and H₂O exposures during the ZrO₂ ALD process, results of initial proof-of-principle experiments using the in-situ XAFS/XANESchamber and ex-situ XAFS/XANES results of (HfO₂)_x(ZrO₂)_y NLs.