Very High Aspect Ratio (AR>10) through Glass Hole (TGH) Filling in Stagnant Condition By Using DC Plating for Advanced Interposer Applications

High aspect ratio (AR) through glass interposer filling has been widely investigated and developed in the recent years. Most efforts put on blind via filling by using the agitation (i.e., air agitation, cathode rotation, paddle agitation, etc.) or periodic pulse reverse (PPR) plating technique to help improvement of filling performance and enhancement of mass transfer of each component in plating electrolyte. However, high aspect ratio through hole filling has been less addressed because the void or seam defects are easily formed in the through hole. In this study, the AR>10 (AR~12) through glass hole filling with defect-free has been successfully demonstrated under stagnant condition, as shown in Figure 1 by using DC mode of fixed current density plating. Based on the operation condition, the equipment design is simple and the lifetime of additives could be long. Furthermore, the thickness difference between Cu overburden (3.51 μm) and dimple (2.88 μm) is around 0.7 μm, implying that the Cu surface is nearly flat, as shown in Figure 2. This achievement is because the additive of leveler could effectively inhibit the Cu deposition on the Cu seed layer surface, but it does not inhibit Cu deposition in the through hole center. Therefore, the butterfly pattern could be formed in the early stage of Cu filling. Besides, the relatively flat Cu surface is beneficial to post Cu removal process, such as expensive CMP process. Figure 1