ALTERNATIVE ROUTES TO ATOMIC LAYER DEPOSITION: REACTOR DESIGN AND PROCESS DEVELOPMENT
Atomic layer deposition (ALD) is a powerful technique capable of depositing a variety of thin films with conformality and atomic-level control over film thickness. As a gas-phase deposition technique that has low processing temperature and applicability on substrates with high aspect ratios, ALD has been widely applied in semiconductor industry. Recently two emerging applications of ALD to manufacturing processes have drawn considerable attention. Those ALD chemistries possessing area selectivity are viewed as an alternative approach to existing patterning techniques; spatial ALD also holds promise as high-throughput, roll-to-roll processing by virtue of spatial separation of reactants. Novel applications of ALD, like those mentioned above, involves development of new reactor design, process conditions, and most importantly, surface chemistries. The focus of the work presented here is the development of alternative approaches to selective area ALD by exploring all three aspects. The new reactor design provides us with abilities to produce industrially-relevant process conditions, to generate complex dosing sequences beyond conventional ALD, and to probe surface chemistry of the resulting ALD film in situ, without any air break. All these capabilities are exploited in a single chamber system. We begin with the design and characterization of a micro-reactor for spatially-confined ALD that is integrated to our ultra-high vacuum (UHV) surface analysis chamber. The new reactor design allows deposition of ALD films at a reactor pressure in Torr range and in situ UHV surface analysis, including X-ray photoelectron spectroscopy (XPS) and low-energy ion scattering spectroscopy (LEISS). The micro-reactor design, which exhibits strong similarities to spatial ALD print head design, gives rise to spatial confinement of ALD films, as predicted by the computational fluid dynamics (CFD) models. We investigate how an additional, third species in conventional ALD process affects the precursor-substrate interaction on dielectric and metal surfaces via competitive adsorption in our unique apparatus. Effects of a thiol, a phosphine and four amines as co-adsorbates on zirconia ALD (with a focus on the first half-cycle) are examined, and possible reaction mechanisms are discussed. Among the six co-adsorbates examined, triethylamine and 1,2 – ethanedithiol hold promise for selective deposition of continuous ALD zirconia films.
Atomic Layer Deposition; Chemical engineering; Materials Science; computational fluid dynamics; in situ surface analysis; Selective deposition; X-ray photoelectron spectroscopy; Reactor design
Engstrom, James R.
Wise, Frank William; Hanrath, Tobias
PHD of Chemical Engineering
Doctor of Philosophy
dissertation or thesis