Robustness of carbon nanofiber-based MIM capacitors with ultra-high capacitance density to electrical and thermal stress

In this paper, we present car­bon nanofiber (CNF)-based capac­i­tors in a MIM con­fig­u­ra­tion, a CNF-MIM, with a small foot­print, low pro­file height, and high capac­i­tance den­si­ty that can be used both as inte­grat­ed and as dis­crete com­po­nent. Being pro­duced in a ful­ly CMOS com­pat­i­ble process it is like­ly to play a major role as fur­ther minia­tur­iza­tion of future elec­tron­ics moves on. The devices were char­ac­ter­ized from 25 °C to 150 °C and from 0 V to 5 V. It was demon­strat­ed that a CNF-MIM with a total CNF height of 6 μm achieved a capac­i­tance den­si­ty of about 400 nF/​mm². Also shown was an ESR of about 45 mΩ. It was found that the capac­i­tance increased slight­ly with tem­per­a­ture by 0.03−0.06 %/​K and that the capac­i­tance was sta­ble for bias­ing volt­age with an increase between 0.5−4 %/​V. Hence, it meets well with the X7R spec­i­fi­ca­tions. This behav­ior makes it a good com­peti­tor com­pared to MLCCs whose capac­i­tance decreas­es with tem­per­a­ture and applied volt­age and the CNF-MIM does this at the frac­tion of the device thick­ness of the MLCC.