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.