Achieving Uniform and Conformal ALD Coatings on Sub-10nm Pores Using Dual-Stage Exposure/Purge at Optimized Growth Temperatures

Nanopore tuning via atomic layer deposition (ALD) is promising but its conformality on sub-10nm pores and its homogeneity over the whole porous network is still challenging, primarily due to the slow transport within the porous network. Conventional ALD process oftentimes falls into a dilemma: higher temperature and prolonged exposure/purge time are required to overcome the slow transport issue, but higher temperature will cause the instability of surface-OH groups and prolonged exposure/purge time will result in over purge at the surface vicinity, leading to another type of non-homogeneity. To resolve this issue, a new dual-stage exposure/purge ALD process was developed. Each exposure/purge step contains a longer exposure/purge stage and a shorter exposure/purge stage, where the longer stage ensures ideal exposure/purge for inner pores, and the shorter stage makes up the surface depletion for the outer pores. By doing so, we've been able to extend the ALD nanopore tuning to sub-10nm pores with excellent coating homogeneity and conformality.