Through Silicon Via polymer filling for 3D-WLP applications

In this paper, polymer filling of medium density (40 µm diameter and 120 µm depth) via-last Through Silicon Via (TSV) is investigated. Firstly, a set of specifications for the polymer selection is established and discussed. Secondly, an adequate filling process and its optimization are developed. The polymer overburden thickness and planarization issues are also taken into account, since this polymer should also passivate the copper redistribution layer on the backside surface of the wafer.