Currently, there is an unmet need for a seamless metal interconnect gap-filling material which not only possesses low dielectric constant and sufficient mechanical strength but can also be grown plasma-free. Nanoporous metal-organic frameworks (MOFs), particularly zeolitic imidazolate frameworks (ZIFs) are an attractive option to meet this need because of their favored reported properties and ability to be deposited using a simple thermal vapor process. Furthermore, they are a candidate to be used in the semi-damascene process because it is organic and easily etched. In this work, ZIF-8 metal-organic frameworks were converted by exposing an ALD ZnO film to the vapor of an organic linker, 2-HmIM. Experiments on planar substrates suggest a threshold for the sacrificial ZnO layer thickness in which the ZIF-8 crystal grains coalesce to form a coherent layer, before which only islands are formed, and after which crystals continue to ripen and increase roughness. The formation of a coherent layer constitutes a diffusion barrier which prevents further linker diffusion, resulting in a saturated ZIF-8 layer thickness, and excess ZnO being left unconverted at the bottom. These results are consistent with recent literature experiments.

Experiments in the deposition of ZIF-8 onto patterned trench substrates with varying aspect ratios revealed a limitation on the sacrificial ZnO thickness on the full conversion of the ZnO layer which is consistent with what is observed for films deposited on planar substrates. Full conversion of the ZnO in trenches was shown for sufficiently low sacrificial ZnO layers, which has not been explicitly displayed in literature experiments. Furthermore, the mechanism for ZIF-8 gap filling was revealed to be motivated by reflow in which surface diffusion is enhanced by capillary forces. The geometry and progression of the filling is visually similar to bottom-up superfill described previously for Cu electrodeposition. These results serve as a strong basis for low temperature, plasma-free, and seamless gap fill of high and low aspect ratio trenches.