Surface Chemistry and Development of Group 11 and 13 Thin Film Vapour Deposition Precursors

Abstract

Techniques for depositing thin films of metals or ceramics, such as atomic layer deposition (ALD) and chemical vapour deposition (CVD), are well established and used in a wide variety of industries and applications, such as for dielectric layers, passivation coatings, surface functionalization, conductive layers, catalysis, anti-reflection coatings, optical property modification, etc. These techniques make use of a series of vapourous precursor/solid substrate interactions, typically at elevated temperatures and low pressures, to ultimately deposit a thin, conformal, uniform film of desired material. The nature of this vapour/solid surface chemistry is paramount to determining the what material is deposited as well as its properties. Determining the specific chemistry occurring at the vapour/solid interface is not a trivial task and typically requires expensive and potentially complicated characterization techniques. ALD and CVD processes of novel materials typically suffer from purity and uniformity issues that prevents them from being widely adopted by industry. By experimentally determining the surface chemistry of these processes it is possible to logically assess and modify existing processes to address these issues. This work examined the surface chemistry of several group 11 and group 13 vapour deposition precursors using a variety of characterization techniques, primarily solid-state nuclear magnetic resonance spectroscopy (SS-NMR). In group 11, several novel Cu ALD precursors were studied, including a copper(I)-tert-butyl-iminopyrrolidinate and several copper(I)-hexamethyldisilazide-N-heterocyclic carbene complexes, as well as a novel Au ALD precursor; a Me3AuPMe3 complex. Using ex situ characterization techniques such as SS-NMR (13C and 29Si), HR-NMR, EDX, and elemental analysis, the initial chemisorption of these precursors on high surface area silica (HSAS) was determined. In group 13, a gallium complex (acetamidinatediethylgallium(III)) was exposed to HSAS and the initial chemisorption mechanism was quantitatively determined by using 29Si SS-NMR and the techniques used to study group 11 complexes. This work demonstrates the novelty of using SS-NMR to examine the chemisorption mechanism of ALD precursors on high surface area substrates quantitatively. The nature of precursor chemisorption can be used to develop new precursors and new deposition processes with more efficient deposition (no impurities, higher growth rates, better uniformity) with the results gathered in this work.