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Through Silicon Vias and Holes Metallization using CoWP and Cu Nanoparticles as Barrier and Seed Layers
Keywords: Through Silicon Via, Copper Nanoparticles, Copper Electroplating
More recently, 3D chip stacking technology has been feasible and desirable. The structural concept of 3D stacking for fabricating MEMS and multi-chip is similar to that of the fabrication of multi-layers PCB. Therefore, through holes, which are used in the multi-layers PCB for a period of history, are employed to construct the connecting lines of multi-chip in z-direction. However, through hole filling by Cu electroplating without using a conducting template is difficult. Alternatively, deep blind vias (i.e., through silicon vias, TSVs) that are formed by dry etching are easily filled using Cu electroplating, serving as z-direction interconnects between the stacked chips. Since the TSVs are blind vias before CMP treatment, a big challenge that is to fill the deep microvias arises. So far, many approaches are proposed to fill the TSVs by Cu plating. Herein, we develop three new technologies for Cu nanoparticle coating and deposition in TSVs and through silicon holes (TSHs). One is to synthesize Cu nanoparticles (CNPs) with a particle size of 3-5 nm and then coat the CNPs onto the sidewall of TSVs by a wet process to act as a seed layer. The wet process for Cu seed layer formation can make sure of conformal coating and reduce the process cost of TSV. Second, we develop a new Cu electroplating formula that can make selective Cu fill (SCF) in TSVs, which leads to no increase in Cu thickness on the top surface after electroplating. The plating technique, SCF, can greatly reduce the loading of Cu CMP and the process coat of TSV. Finally, we develop a novel Cu plating technique for direct through hole filling, meaning that the conducting template assembled on one side of the TSH in advance is unnecessary. Cu can fill the TSH directly in a center-up mode. This filling mode can make sure of no void after electroplating.
Wei-Ping Dow, Professor
National Chung Hsing University
Taichung 40227,

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