A novel through-hole filling technology for next generation organic interposer applications

We report an approach to full fill the laser drilled through-hole by DC electroplating. A hydrodynamics-sensitive organic compound with selective inhibition being used to Cu electrodeposition is required as an additive of plating bath. Void-free Cu column can be fabricated as the interconnects in the organic substrate of 2.5D IC interposer. The residual dimples were almost eliminated with thin overburden at low current density and high agitation speed. The following Cu thickness thinning by Chemical Mechanical polish (CMP) can be reduced further. 3D X-ray inspection indicates that the filled through-hole of aspect ratio of 2 to 2.5 can be completely filled within 75 minutes, which is the highest speed among the reported interposer metallization. It is also compatible with most of PCB plating equipment. Compare with recent TSV process using semiconductor tool, this novel technology is beneficial to reduce the cost and process of manufacturing. Through-hole filling will have potential applications in 3D IC packaging.