Integrating metal-organic frameworks (MOFs) in microelectronics has disruptive potential because of the unique properties of these microporous crystalline materials, e.g. as active sensor coatings, low-k dielectrics and tuneable conductors. Suitable film deposition methods are crucial to leverage MOFs in these fields. Conventional solvent-based procedures, typically adapted from powder preparation routes, are incompatible with nanofabrication because of corrosion and contamination risks. We demonstrate a chemical vapour deposition (CVD) process that enables nanoscopic films of zeolitic imidazolate frameworks, with a uniform and controlled thickness, even on high-aspect ratio features. The ‘MOF-CVD’ method consists of two steps: a metal oxide deposition step and a vapour-solid reaction step. For the first step, well-established methods such as atomic-layer deposition or reactive sputtering are used. Complete vapour-solid reaction conversion of these metal oxide films to highly crystalline and microporous ZIF films is observed using techniques such as SAXS/WAXS, AFM, HAADF-STEM, TOF-SIMS and ATR-FTIR. Moreover, the BET surface area of the MOF-CVD films is directly measured by Kr physisorption and is consistent with the calculated surface area of the crystallographic reference structures. We demonstrate how MOF-CVD enables previously inaccessible routes such as lift-off patterning and depositing MOF films on fragile features. The compatibility of MOF-CVD with existing infrastructure, both in research and production facilities, will dramatically facilitate MOF integration in microelectronics. MOF-CVD is the first vapour-phase deposition method for any type of microporous crystalline network solid and marks a milestone in processing such materials.

Chemical vapour deposition of zeolitic imidazolate framework thin films

251st National Meeting (2016)

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