Microwave MIM Capacitors Enabled by an iCVD N-type Parylene Dielectric for Flexible MMIC

In this paper, microwave metal-insulator-metal (MIM) capacitors with high mechanical flexibility are presented by utilizing N-type parylene dielectric. The N-parylene copolymer dielectric is deposited atom by atom at room temperature via a solvent-free process called initiated chemical vapor deposition (iCVD), which is fully compatible with low-temperature fabrication request for plastic substrates. By employing the N-parylene dielectric, microwave flexible MIM capacitors based on a 150 µm polyethylene terephthalate (PET) substrate are designed and fabricated. Experimental results show that negligible deterioration in capacitor's value (C) and quality factor (Q) are observed under high strain levels (1.5% and 2%), which indicates that our MIM capacitors based on N-parylene dielectric are mechanical stable and robust at high tensile strain (at least 2 %). The mechanical failure mechanism of flexible MIM capacitors is also studied, which indicates that the capacitors could be transferred to microwave inductors over strain level of 3%. These high tensile strain microwave devices would be helpful for flexible/wearable high-frequency wearable circuits and systems in the future.