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.