Electrochemical Grafting Of Polyacrylic Acid In Aqueous Solution And Its Application On 3D Copper Interconnection

In recent years,the semiconductor industry has developed greatly with the reform of information technology.Microelectronic manufacture is increasingly pursuing microminiaturization,multifunction and low cost.Due to its high integration density and low manufacturing cost,threedimensional(3D)through-silicon-via technology is attracting increasing people’s attention.In TSV technology,stacked packaging through copperfilled semiconductor vias is an important means of electronic packaging in the future.However,it is difficult to achieve defect-free copper plating for large aspect ratio vias.The problems of voids and seams appearing in the late stage of copper filling can reduce the reliability of the chips in the subsequent packaging process and seriously affect the industrial application of the technology.In this paper,the technique of filling organic polymers into partially copper-filled vias was studied.In this paper,the technique of filling organic polymers into partially copper-filled vias was studied.On one hand,TSV is partially filled with copper to ensure the electronic interconnection of chips.On the other,filling organic polymers into TSV can avoid the voids and seams appearing in the late stage of copper plating,which reduces the process requirements of copper filling.In addition,filling vias with the flexible organics can also buffer the stress in the subsequent packaging process,ensuring the reliability of the chip.Firstly,the basic rules of grafting organic layer onto copper surface in aqueous solution was studied systematacially.The effects of grafting time and solution components on the thickness of organic layer were investigated and the mechanism of electrochemical graft was illustrated.The results showed that the thickness of organic layer increased with the increasement of time and the NBD concentration when the concentration of AA was suitable;on the contrary,the thickness of organic layer decreased at the late stage of grafting when the concentration of AA was high,which was because that the bond of organic layer and copper surface was not strong enough to resist the external force and then part of the layer was peeled.We found that when the concentration of NBD was 16.88 mM and the concentration of AA was 0.82 M,the organic layer was the thickest,which suggested that the solution at this condition was suitable for planar copper.Secondly,the technique of electrochemical grafting of organic polymers in aqueous solution was applied to 3D copper interconnection.By adjusting the concentration of AA and the grafting time,we studied the filling effect on TSV and the growth trend of the organic layer with different reaction parameter.The results showed that the organic layer realized a certain degree of filling of the TSV when the solution concentration was appropriate and the grafting time was relatively long.The organic layer had a higher degree of regularity and better filling effect on TSV with the increasement of AA concentration when the grafting time was the same.What is more,the organic layer filled the bottom of vias first and then gradually thicken the side-wall organic layer to achieve the final filling of the TSV with the extension of grafting time at the sufficient solution concentration.In the research process,we also found that the organic layer at the bottom of TSV can achieve rapid and substantial thickening at a sufficient concentration of solution.We define this as "spatial aggregation effect" and propose a reasonable explanation and theoretical model.