Enhanced selectivity of atomic layer deposited Ru thin films through the discrete feeding of aminosilane inhibitor molecules

Abstract

Area-selective atomic layer deposition has attracted considerable interest as a means for enabling versatile fabrication of selectively formed thin films in both vertical and lateral direction in extremely downscaled 3D semiconductor devices. Herein, we report a methodology for an enhanced selectivity ALD process with a discrete feeding method (DFM), capable of improving the chemisorption density of small alkylating agents onto desired substrates. Using the DFM strategy of (N, N-diethylamino)trimethylsilane as an aminosilane inhibitor to render surface alkyl groups, we explored its efficacy with regard to improving its blocking capability against subsequent Ru ALD on various substrates such as Si, SiO2, and SiN substrates to provide H-, OH-, and NHx-terminated surface groups, respectively. As a result, a denser chemisorption layer could be selectively obtained on OH-terminated SiO2 and NH-terminated SiN but not on H-terminated Si, which in turn led to significant growth retardation on both SiO2 and SiN during Ru ALD. Adding a process sequence composed of intermittent Ru etching followed by DFM retreatment on both SiO2 and SiN allowed for selective removal of Ru moieties and restoration of inhibitory alkyl groups. In this way, we finally achieved enhanced deposition selectivity with a combination of sequential DFM and Ru ALD-etch supercycles.