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Department Seminar – Majeda Al Hareri, Thursday, February 16, 1:30pm
	
 Feb 16, 2023 
 1:30PM to 2:30PM





Event Categories  Grad Events and  Seminars






























Date/Time

Date(s) - 16/02/2023
1:30 pm - 2:30 pm





Title: Precursor and Reactivity Design for Atomic Layer Deposition of Nonmetals and Group 4 Metal Oxides


Date: Thursday, February 16, 2023


Time: 1:30-2:30


Room: ABB 165


Zoom: please contact chemgrad@mcmaster.ca for Zoom details


Host: David Emslie


Abstract: Atomic layer deposition (ALD) is a techniqueby which surface-based reactions between a precursor molecule (oftenmetal-containing) and coreactant (e.g. H2O, O2 or H2)yield highly uniform and conformal (ultra-)thin films. The precursor and coreactantare each delivered in the gas phase, separated from one another by inert gaspurge steps, and each ‘precursor–purge–coreactant–purge’ cycle represents 1 ALDcycle. These surface-based reactions are self-limiting, meaning that once theprecursor or coreactant has reacted with all available reactive surface sites,reactivity ceases, and as a consequence, the thickness of the film iscontrolled solely by the number of ALD cycles.[1,2] This nano-scale controlof film thickness allows for a large number of applications for ALD, such as forfabrication of flat panel displays, fuel and solar cells, and microelectronicdevices.[3,4]


In order to be suitable for ALD studies, apotential precursor molecule must have the following characteristics: (i) sufficientvolatility to allow delivery to the reaction chamber in the gas phase, (ii) long-and short-term thermal stability at the temperatures of delivery anddeposition, respectively, and (iii) high reactivity towards the chosen coreactant,forming only volatile by-products.[2] 


The first goal of this project was the pursuitof new low-temperature processes for nonmetal elemental ALD by exploiting thethermodynamically favourable formation of Si-X bonds from the reaction of an E(SiR3)3precursor with an EX3 coreactant (E = Sb, B; X = Br, Cl, F).[4]The second goal of the project was the development of unique methods for ALD ofgroup 4 (M = Hf or Zr) oxides that would encourage effective (ie. void-free)filling of narrow (<20 nm) trenches in high aspect-ratio (HAR) substrates.[5]­These approaches focused on deposition of non-surface-tethered molecularor oligomeric species with sufficient surface mobility to allow them to “flow”into trenches on the surface prior to decomposition to form the desired metaloxide (occurring via ligand decomposition during ALD, on a longer timescalethan migration on the surface, or by post-deposition annealing).


This work describes the development of newprecursor molecules, determination of precursor structures, evaluation ofthermal stability and volatility, investigation of ALD-relevant solutionreaction pathways, ALD reactor studies, and characterization of the resultingthin films.


 


[1] S. M. George, Chem. Rev. 2010, 110, 111-131. [2] D. J. H. Emslie, P.Chadha, J. S. Price, Coord. Chem. Rev.2013, 257, 3282-3296. [3] A. C. Jones, M. L. Hitchman, Chemical Vapor Deposition: Precursors, andProcesses and Applications, ACS Publishing, Cambridge, 2009. [4] H. Kim, H. B. R. Lee, W. J. Maeng, Thin Solid Films 2009, 517, 2563-2580. [4] M. Al Hareri, D. J.H. Emslie, Chem. Mater. 2022, 34, 2400-2409. [5] M. AlHareri, D. J. H. Emslie, Eur. J. Inorg. Chem. 2022, e202200594.