Selective deposition of AlOx for Fully Aligned Via in nano Cu interconnects

Abstract

AlOx was selectively deposited on top of SiCOH in 32 nm pitch Cu-SiCOH pattern to form a Fully Aligned Via (FAV) test structure. Selective deposition process performance and its integration into the 5nm BEOL FAV structure were evaluated. The selective AlOx deposition involves multistep process including surface treatment, selective Self-Aligned Molecules (SAM) bonding to inhibit Cu metal surface, and the selective growth of AlOx on top of SiCOH dielectric using Chemical vapor deposition process with various precursors and process conditions below 300°C. Thin selective AlOx of 4-6 nm thickness show excellent selectivity on SiCOH over Co capped Cu-SiCOH patterned structures with various spacing. The Via Chain electrical yields were measured on 32 nm pitch structures by AlOx selective deposition and are comparable to the established FAV process by Cu wet recess. This indicates that the Selective AlOx deposition process is highly selective on SiCOH dielectric surface without defect formation in the Co Capped Cu surfaces.