Sequential Use of Orthogonal Self-Assembled Monolayers for Area-Selective Atomic Layer Deposition of Dielectric on Metal

Abstract

Although there have been several demonstrations of area-selective atomic layer deposition (AS-ALD) of dielectric on dielectric in metal/dielectric patterns, the reverse process of selective dielectric on metal (DoM) is not as well developed due to the challenge of inhibiting only the dielectrics. Unavoidable native oxide formation on metals tends to lead to similar surface chemical properties between metal and dielectric substrates, decreasing the selectivity in inhibitor adsorption. Hence, to achieve DoM, preventing unwanted inhibitor adsorption on metals is critical. This study demonstrates a two-step strategy of first applying a dodecanethiol (DDT) self-assembled monolayer (SAM) on a Cu/SiO2 pattern to protect the Cu surfaces from subsequent deposition of an octadecyltrimethoxysilane (OTMS) inhibitor, which then selectively forms an OTMS SAM on SiO2. It is further shown that by removing the DDT protector with thermal treatment before AS-ALD, subsequent ALD growth on Cu is not affected while ALD remains blocked on the OTMS-covered SiO2 regions. Using this strategy, DoM is demonstrated with selectivity above 0.9 after 5.6 nm of ZnO and 1.5 nm of Al2O3 ALD. This work presents a new approach to expand the material systems available to AS-ALD which may help enable more applications in microelectronics, optoelectronics, and energy.