Temperature Excursions Due to the Reaction Heat Produced by Atomic Layer Deposition on Nanostructured Substrates

摘要

Many atomic layer deposition (ALD) reactions are highly exothermic, with some likely releasing hundreds of kJ/mol per cycle. In ALD on conventional substrates (e.g., wafers), this exothermicity is typically ignored, because the deposited mass is small compared to the substrate mass. However, in the case of high-surface-area substrates such as metal–organic frameworks (MOFs) or nanopowders, the mass deposited per cycle can be a substantial fraction of the substrate mass, raising the possibility of nonnegligible reaction heat. To understand the potential impact of this heat on nanostructured substrates and ALD processes, we measure via pyrometry the surface temperature of a ceramic nanopowder bed undergoing particle ALD (pALD). Depositing Al_(2)O_(3) from trimethylaluminum (TMA) and water on Y_(2)O_(3)-stabilized ZrO_(2) (YSZ) nanopowder with an average nanoparticle (NP) diameter of 8 nm, we observe temperature gains, ΔT , around 20 °C above the baseline. Under certain conditions, the maximum local ΔT may be significantly greater than 20 °C, according to an estimate of the temperature of a hypothetical isolated NP based on standard formation enthalpies and sticking coefficients from the literature. Examining the dependence of ΔT (t ) curves on the precursor, cycle number, and NP size, we find that the pyrometry dataset also provides insights into pALD kinetics and the evolution of deposition chemistry and substrate morphology.