Vapor-Deposited MOF for Low-k Dielectric Seamless High-Aspect-Ratio Interconnect Gap Fill

Abstract

A vapor-phase ZIF-8 MOF deposition procedure for seamless high-aspect-ratio interconnect gap fill has been developed with a short process time (15 min) at a 160 °C process temperature. This is the most rapid documented vapor technique to produce a MOF film and is made possible by a higher process temperature and a low background H₂O environment. The process consists of ALD of a thin (<5 nm) ZnO film followed by conversion to ZIF-8 in an organic linker (ALD + soak cycle). This method exhibited complete ZnO to MOF conversion, as well as MOFs with low-k (k ∼ 2.6). Dielectric gap fill was investigated utilizing patterned samples with widths ranging from 40 to 400 nm. Both high aspect ratio gap fill and multiple aspect ratio gap fills were shown with no residual ZnO. The MOF gap-fill process could be attributed to the reflow behavior of 2-methylimidazole-ZnO reaction intermediates or nascent product. The MOF was found to be stable at 400 °C under vacuum (1 × 10^-2 Torr), which is comparable to other low-k dielectrics. Fluorine plasma etch resistance was tested for the ZIF-8 MOF in comparison to bare Si, SiCOH, and SiO₂; the MOF was proven to be the best in resisting plasma etch. This work demonstrated that ALD + soak cycle conversion low-k ZIF-8 MOF films have the potential to be a plasma-free vapor-phase seamless gap fill for high aspect ratio features to be employed in logic and memory device fabrication, as well as three-dimensional heterogeneous integration (3DHI).

Keywords: ALD; MOF; high-aspect-ratio gap fill; interconnects; low-k dielectric.