Numerical simulation of the TSV-Cu filling by electroplating process with the accelerator and suppressor

Abstract

Through silicon via (TSV) technology is the key enabling technology of high density, high performance three dimensional packaging such as System-in-Package (SiP) and System-on-Chip (SoC). In TSV technology, to obtain high-aspect-ratio vias with good electrical and mechanical properties, filling the material (copper mostly) without voids or seams in the vias is vitally important. The filling properties of the copper is influenced significantly by the additives in the electrolyte, especially the accelerator and suppressor. In this simulation work, the electroplating process was described by a mathematical model, in which the fluid flow of electrolyte, the mass transport of the charged and neutral species and electrochemical reactions on the electrode surface were involved. Based on the mathematical model, the surface coverage of the additives and the local current density distribution at the electrode/electrolyte interface were calculated. The results show that the kinetics and mechanism of the copper deposition reaction are dependent on the fractional surface coverage of the additives. The results show that the suppressor is prior to adsorb at the electrode surface than the accelerator, due to the competitive adsorption of the suppressor and accelerator, by following the Langmiur isotherm adsorption model. Moreover, the coverage of the accelerator (SPS, Na 2 (S(CH 2 ) 3 SO 3 )) is high at the TSV bottom and relatively low at the TSV top. The local current density at the TSV bottom is larger than that at the TSV top and surface due to the influence of the surface coverage of the accelerator and suppressor, which contribute to the superfilling of TSV.