Integrated fully solid-state capacitor based on carbon nanofibers and dielectrics

Com­plete on-chip fully sol­id-state 3D integ­rated capa­cit­ors using ver­tic­ally aligned car­bon nan­ofibers as elec­trodes to provide a large 3D sur­face in a MIM con­fig­ur­a­tion have been man­u­fac­tured and char­ac­ter­ized in terms of capa­cit­ance per device foot­print area. The fibers are grown dir­ectly on the bot­tom elec­trode sur­face and then con­form­ally coated with a dielec­tric mater­i­al using atom­ic lay­er depos­ition. Two dif­fer­ent dielec­tric mater­i­als, Al₂O₃ and HfO₂ , of dif­fer­ent thick­nesses have been invest­ig­ated, and dif­fer­ent con­struc­tions for the top elec­trode have been tested. The entire man­u­fac­tur­ing pro­cess is com­pletely CMOS com­pat­ible, which along with the low device pro­file of about 4 μm makes the devices read­ily avail­able for integ­ra­tion on a CMOS-chip, in 3D stack­ing, or in a 2.5D inter­poser tech­no­logy. Capa­cit­ance val­ues of up to 18.2 nF/​mm² (per device foot­print area) are achieved reproducibly.