Research And Application Of Copper Filling For High Aspect Ratio Via In Printed Circuit Board

Copper electroplating for via filling is widely used in high density interconnection printed circuit board,IC substrate and advanced package,which is attributed to small size,high reliability and flexible design of via interconnection.In the industrial application,defects and efficiency of via filling are the most concerned topics.This work focuses on the filling problem electroplating and filling process for high aspect ratio blind vias with about 110 μm diameter and about 180 μm depth.To achieve void-free filling of highaspect-ratio blind vias,the main results in this dissertation include.（1）Electrochemical behavior of additives for high aspect ratio via.The electrochemical behavior of organic additives was studied,the results shows that the monomolecular EO/PO（Poly（Ethylene Glycol）-Block-Poly（Propylene Glycol）Copolymer）can adsorbed on electrode surface reveal suppression on copper deposition.The saturated concentration of the EO/PO adsorption on copper surface is obtained.The suppressor is supersaturated in the electroplating solution,and the consumption of the suppressor during via electroplating filling can be ignored.The SPS（Bis-（Sodium Sulfopropyl）-Disulfide）shows an accelerating effect on copper deposition.The relationship between the accelerator concentration and the electrode surface coverage,the exchange current density,and the cathode Tafel slope was obtained.The nitrogen-containing heterocyclic compounds which is added in solution as a leveler presents suppression effect on copper deposition.the suppression of leveler is related to convection intensity and concentration.（2）Model and mechanism of electroplating filling for high aspect ratio via.Based on the electrochemical data off additives,the electroplating filling of via with an aspect ratio of 1.8:1.1 was simulated by Multiphysics Coupling.The risk of filling void for this high aspect ratio via was predicted.The copper ion concentration was further studied.It is found that the greater the copper concentration in solution,the greater the copper concentration at via bottom.The influence of cathode air agitation was investigated.With the increase of convection intensity in solution,the mass transfer in via is enhanced.The copper ion distribution in different aspect ratio via was studied,which shows that greater distribution gradient is obtained in higher aspect ratio via.The direct current electroplating filling of via with different aspect ratio was studied by Harring cell.The results show that via with aspect ratio of 1:1.1 or 1.4:1.1 is void-free filled,but the via with aspect ratio of 1.8: 1.1 is filled with void.The filling of via with 1.8:1.1 aspect ratio is improved by increasing the copper ion concentration,air agitation and temperature of solution.As a result,the void ratio of via is reduced to 8%.（3）Research on the technology of Localized Pre-adsorption of accelerators for electroplating and via filling.An accelerator local pre-adsorption technology is employed to realize the void-free filling of high-aspect ratio via.The void-free filling of high-aspect ratio via is obtained by adjusting the copper ion concentration,air agitation,and solution temperature.The accelerator local pre-adsorption process not only shorten the via filling time,but also reduce the risk of filling voids.It is necessary for void-free filling of via with high aspect ratio that enhancing the copper mass transfer to via bottom by increasing cathode air agitation,solution temperature and copper ion concentration.In condition of high solution temperature,such as 28 ?C and 31 ?C,the void-free filling of via with 110μm diameter and 180 μm depth is achieved.