Effect of microgroove structures on the fluid dynamics and film conformality in spatial atomic layer deposition of Al2O3

Abstract

With the development of semiconductors, efficient ultrathin coatings on large areas is of great significance to the commercial needs for the encapsulation of materials with micro- or nano-structures. Spatial Atomic Layer Deposition (ALD) is an emerging high throughput and economic technique which can deposit nano-scale films on substrates with different topographies. However, the complex fluid dynamics and diffusion kinetics in the spatial ALD system bring great challenge to the investigation and optimization of the film conformality. In this work, a two-dimensional model coupling Computational Fluid Dynamics (CFD) coupled with chemical kinetics details is built to investigate the hydrodynamics and film growth characteristics in spatial ALD system with different substrates. The effects of the microgroove structures and the microgroove heights on the velocity flow fields and the conformality of alumina films are studied, as shown in the Figure. With numerical simulations, our results show that higher aspect ratio of groove structure leads to more vortex flow at the corner of the microstructures. The motion of the substrates exacerbates the formation of vortex, which will definitely cause the precursor intermixing. Besides, the conformality of the alumina film decreases as the aspect ratio of microgroove structures increases. In order to ensure the self-limited ALD reaction and improve the film conformality, process parameters of total gap size, separate gas flow rate, the carrier gas flow rate as well as the motion velocity of the substrate are investigated. It is found that low carrier gas flow rate can not only reduce the chemical vapor deposition (CVD) growth, but also increase precursor utilization. This work is important for the packaging of micro structure devices and is rather instructive to the further design of spatial ALD system. Figure 1