Barrier-free process for fluorinated silicon glass film in Cu interconnects

Highlights: • Barrier-free fluorinated silicon glass (FSG) dielectric process is evaluated. • FSG films provide better hardness, O₂ plasma resistance, Cu barrier, and breakdown strength. • Post-annealing or in-situ two-step FSG deposition solves Cu/FSG thermal instability. • Barrier-free FSG process is promising for back-end-of-line interconnects integrity. -- Abstract: A dielectric barrier is required for a porous low-dielectric-constant (low-k) film used in Cu interconnects, however, resulting in an increased effective dielectric constant. In this study, a barrier-free fluorinated silicon glass (FSG) dielectric process is proposed and evaluated. Experimental results indicated that FSG films, although had a higher capacitance than p-SiCOH/SiCN stacked films, provide a higher hardness, better O₂ plasma resistance, supper Cu barrier, and enhanced dielectric breakdown strength. Therefore, a barrier-free FSG dielectric process is feasible and promising strategy for back-end-of-line interconnects integrity. Moreover, the issue of Cu/FSG peeling under a thermal stress can be solved by providing a post-annealing after FSG deposition or using an in-situ two-step FSG deposition process. The mechanism is also proposed in this study.