Modeling Thermal Effects in Atomic Layer Deposition for Trench-Shaped Structures

An atomic layer deposition (ALD) simulation approach is presented for transient diffusion of heat and mass at low Knudsen numbers ($Kn<0.1$), focusing on thermal effects in trench-shaped structures. Two boundary conditions (BCs) are analyzed: the ‘thin wall’ BC incorporates exothermic reactions with a derived wall heat flux term, and the ‘thick wall’ BC maintains constant wall temperature ranging between 500 K and 800 K. For both BCs, we examine aspect ratios from 1 to 100. The chosen BC significantly impacts reaction kinetics/peak temperatures, with local temperature variations up to 200 K under ‘thin wall’ conditions. The coating time ratio between ‘thin wall’ and ‘thick wall’ ranges from 0.9 to 1.7. Two ‘universal’ functional forms are proposed to explain how surface coverage depends on time and how coating time relates to aspect ratio and diffusion timescale. Results emphasize the crucial role of temperature distribution in ALD, impacting growth per cycle, reactant decomposition/desorption, and potential substrate damage.