Fabrication And Performance Of 3D Dielectric Capacitors For Embedded Packaging

The rapid development of consumer electronics has driven the development demand of electronic systems with multi-function,miniaturization and low cost,especially in the new era of mobile interconnection.Capacitor is one of the most important and basic components of electronic equipment.The key to meet the development of new systems is to optimize the capacitor's high capacity,miniaturization and integration.In order to meet the demand of miniaturization of future devices,improving capacitance could start with?_r,S and d respectively according to the formula of parallel-plate capacitor:C=?₀?_rS/d??₀ is vacuum dielectric constant,?_r is relative dielectric constant,S is electrode area and d is electrode distance?.At present,the giant dielectric materials such as CaCu₃Ti₄O₁₂?CCTO?,NiO,?Pb,La?TiO₃ still have some defects in temperature/frequency dependence and dielectric loss,which hinder their commercial application.Traditional multilayer ceramic capacitors?MLCC?increase capacitance by reducing the thickness of the dielectric layer and increasing the number of stacks.But the thickness of MLCC is approaching to the limit of thick film technology.At present,the new 3D capacitors based on silicon etching and ALD/CVD technology are too expensive to be commercialized.Therefore,disordered porous ceramics and AAO templates were selected to prepare high capacity and low-cost 3D capacitors for embedded packaging in this work.The properties of materials and capacitors were studied.1.The stable slurry of sliver-barium titanate composite with uniform dispersion was obtained by optimizing the process,and the green tapes with different silver content were prepared.3D capacitors with disordered porous structure were fabricated using sliver-barium titanate composite green tapes and AgPd alloy electrodes.Increased effective area of electrodes is obtained by optimizing the composition of capacitors,sintering temperature and time.And the space charge polarization of the dielectric layer is reduced at low frequency.Finally,a BTO/Ag 3D capacitor with excellent performance is obtained at 940°C with the capacitance density up to 3.4 nF/mm³.Its capacitance density is 10 times higher than that of the pure barium titanate capacitor.The loss value of 3D capacitor is less than 0.04 and the change rate of capacitance density of 3D capacitor shows a good stability with the variation of temperature?30-180°C/10 KHz?.2.Disordered porous barium titanate materials were prepared by different sintering parameters.Then the nano-silver conductive ink was dripped on the top and bottom of the porous barium titanate as electrodes to build 3D capacitors.The 3D capacitors showed higher capacitance density than that of parallel plate capacitors with same size.More detailed work will be carried out in future.3.The electrode materials and dielectric layers of capacitors were prepared by the electrochemical method using the AAO as a template.The effects of solution composition and electrodeposition parameters on the morphology of capacitor electrodes were investigated.The deposition rate of the electrode increases with the increasing of voltage.But it is difficult to control the growth of the nanotubes when the voltage is too high.When the pH is about 4,the growth of the nanotubes is facilitated with the increasing of the main salt and boric acid concentration.As time goes on,the product changes from nanotube to nanorod.The metal preferentially deposits along the channel due to the existence of gold particles at the bottom of the AAO channel and the surface adsorption energy of the pore wall in the early growth stage.However,with the prolongation of time,the above two effects gradually weaken.In this case,the electric field plays a major role in the deposition,and finally the nanorod structure is obtained.Abnormal co-precipitation exists during the preparation of alloy nanotubes.Binary and ternary alloy nanotubes were prepared by adjusting the voltage to change the deposition rate of each element and adding sodium citrate to adjust the deposition potential of each element in a similar range.Eventually,uniform and ordered nanotube array electrodes were obtained,and the electrochemical properties of nanotubes?CV,Tafel curves,etc.?were systematically tested.Titanium dioxide dielectric layer was prepared by electrochemically induced sol-gel method.