Ultra-Thin Capacitors based on Carbon nanofibers with Ultra-High Capacitance Density

In this paper, we present the current state-of-the-art technology of solid-state capacitors based on carbon nanofibers (CNFs). Taking advantage of the large 3D surface featured by vertically aligned and tightly spaced carbon nanofibers directly grown on the capacitor's electrode, capacitance densities in excess of 650 nF/mm
²
have been achieved at a profile height of only 7 μm, when employing medium-k field dielectric materials such as HfO
₂
and Al
₂
O
₃
, to form the MIM-like capacitors. The integrated capacitors were fabricated on high-resistive Si substrate, while employing fully CMOS compatible processes. For the devices with highest capacitance density, the leakage currents are typically below 0.01 nA/nF at 1V, while sustaining voltages up to 6 V as well as very good temperature and voltage stability. For the largest devices, the equivalent series resistance (ESR) and inductance (ESL) are as low as 60 mOhm and 6 pH, respectively, as well as very good temperature and voltage stability. The results of the extensive DC and RF characterizations strongly support the potential for CNF-based solid-state capacitors to compete with established high capacitance density technologies and are suitable both in integrated on-chip solutions as well as in discrete electronic applications at a minimal component volume.