OPTIMIZATION OF COPPER PLATING PARAMETERS FOR FAST FILLING OF THROUGH SILICON VIAS (TSV)Authors: Su Wang and S. W. Ricky Lee
Company: Department of Mechanical Engineering, Hong Kong University of Science and Technology
Date Published: 1/26/2010 Conference: Pan Pacific Symposium
TSVs are typically filled with copper because of its high conductivity and wide applications in multilayer wiring. The filling is achieved with electroplating method. Even though the electroplating of copper for interconnections is well established for the copper damascene microfabrication process, it has been shown that the filling of TSVs with copper plating is a different situation due to the much larger dimensions of TSVs. Although quite a number of researchers have achieved void-free TSV filling, there still exist several technical issues to be resolved for the copper plating process. The typical issues include low throughput, high cost, heavy overburden and inconsistent void-free filling.
The plating of copper in TSVs is a very complicated electro-chemical process and has many critical factors. It is important to optimize each of these factors to achieve the desired plating results. In the present study, an electroplating process was developed to deposit copper in TSVs. The objective of this electro-plating process is to achieve a void- free copper deposited blind vias with aspect ratio 4 or higher. The ultimate goal is to achieve TSV filling with shorter plating time and better consistency. In order to achieve fully filled TSVs, chemical controlling parameters and physical parameters need to be optimized. Chemical controlling parameters typically involve copper salt, accelerator and suppressor. A series of experimental parametric studies were carried out to investigate the effects of these chemical parameters.
This paper describes the optimized plating process that results in void-free copper filling of blind via arrays. Successful plating results are demonstrated after optimizing each additive in the bath composition. The void-free copper deposition has been achieved for blind TSVs with diameters of 25 and 50 ?m within four hours of plating time. All chemical process parameters and considerations will be discussed in detail in this paper.
Key words: Copper filling, electroplating, TSV, copper plating additives, void-free filling.
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