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/​mm² have been achieved at a pro­file height of only 7 μm, when employ­ing medium‑k field dielec­tric mater­i­als such as HfO₂ and Al₂O₃ , 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 mΩ 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.