Integrated and Discrete Ultra-Thin Capacitors Based on Carbon Nanofibers with High Capacitance Density

Vertically aligned carbon nanofibers (CNFs) have been used to enhance the electrodes of the classical metal - insulator - metal (MIM) capacitor concept to form fully solid-state CNF-MIM capacitors with a large 3D surface area. The manufactured devices are characterized with regards to the capacitance density, the equivalent series resistance (ESR) and inductance (ESL), and leakage current. The process flow allows for the devices to be either integrated or discrete components, and the low height profile of about 7 μm makes the devices readily available for integration on a chip, in 3D stacking, or onto an interposer. A test vehicle is designed and used to demonstrate the simultaneous values of 420 nF/mm
²
(per footprint area) capacitance density, an ESR of 35 moΩ, and an ESL of 3.4 pH. Furthermore, the leakage current is found to be below 0.01 nA/nF.