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/​mm² (per foot­print area) capac­i­tance den­si­ty, an ESR of 35 mΩ, and an ESL of 3.4 pH. Fur­ther­more, the leak­age cur­rent is found to be below 0.01 nA/​nF.