Area-Selective Atomic Layer Deposition using Aminosilane Precursors to Confer Oxide versus Nitride Selectivity

Area-selective atomic layer deposition (AS-ALD) offers tremendous advantages in comparison with conventional top-down patterning processes in that atomic-level selective deposition can achieve in a bottom-up fashion on pre-defined areas in multi-dimensional structures. Inherent AS-ALD of oxide thin films on SiO₂ versus SiN surfaces is highly relevant to manufacturing of 3D-structured memory devices, but little is known about inherent AS-ALD on such surfaces. For example, in accordance with the continuous demand for higher memory density, the number of stacked SiO₂/SiN layers in 3D V-NANDs is increasing, resulting in an increased aspect ratio and decreased SiO₂/SiN tier size in the vertical direction. Accordingly, when NAND cells with an information storage layer are formed by a conventional top-down lithography/etching process, inter-cell non-uniformity and interference problems inevitably occur. This suggests that AS-ALD of SiO₂ thin film as an interlayer dielectric is required only on SiO₂, not on SiN, for NAND cell formation with discontinuous SiN CTL to prevent crosstalk between adjacent cells. For this purpose, AS-ALD of SiO₂ thin films on SiO₂ versus SiN substrates are investigated. Theoretical screening based on density functional theory (DFT) calculation is performed to identify Si precursors which maximize adsorption selectivity, results indicate that an aminosilane has the potential to function as a highly chemo-selective precursor as compared with a halosilane. Application of the aminosilane precursor to SiN and SiO₂ substrates result in inherent deposition selectivity of ≈4 nm without the aid of surface inhibitors. Furthermore, deposition selectivity is enhanced using an ALD-etch supercycle in which an etching step inserts periodically after a certain number of ALD SiO₂ cycles. Thereby, enlarged deposition selectivity greater than ≈10 nm is successfully achieved on both blanket-and SiO₂/SiN-patterned substrates. Therefore, this approach for performing inherent AS-ALD expands the potential utility of bottom-up nanofabrication techniques for next-generation nanoelectronic applications.