In this study we examined properties of SURMOF HKUST-1 material which are essential from the viewpoint of its application as ultra low-k dielectric. The films under test demonstrated Young’s modulus above 10 GPa in combination with microporosity imposed by crystalline structure of the HKUST-1 layer. Contributions to the static dielectric constant were investigated using both experimental and theoretical approaches. Ellipsometry was used for evaluation of the high-frequency electronic contribution while the static dielectric constant was extracted from capacitance measured with a mercury probe. These values were compared to results of ab-initio DFT calculations which were employed for assessment of electronic and ionic contributions. The experimentally determined electronic contribution is found to be about 1.9, while the measured static dielectric constant is equal to 6.7. The difference is largely attributed to the dipolar contribution originating from environmental moisture adsorbed on open copper sites of HKUST-1 framework. The computed ionic term accounts only for 2% of the measured static dielectric constant. Analysis of ionic dielectric constants calculated for dehydrated HKUST-1 and MOF-5 shows that low frequency oscillations of metal-oxide bonds build up the largest part of the ionic term. Based on these findings one can suggest that hydrophobic metal-organic frameworks with lower density than HKUST-1 and minimal concentration of metal oxide bonds can be considered as favorable candidates for replacement of porous organosilica low-k films in advanced on-chip interconnects.
