(Invited) Conductive Polymer/Metal Composite for Filling of TSV

Tuesday, 3 October 2017: 14:00
Chesapeake C (Gaylord National Resort and Convention Center)
J. Kawakita and T. Chikyow (National Institute for Materials Science)
Fast formation of through-silicon via (TSV) is an essential issue to fabricate the 3D-IC with respect to production efficiency. Currently, TSV is formed by opening a hole in silicon wafer, followed by stacking of an insulation layer and a diffusion barrier on the wall inside the hole and by filling of a conductive material such as metal copper by electroplating often after preparing a seed layer. Since it takes more than one hour to complete all these steps, the efficiency of formation process of TSV should be improved.

The purpose of this research was to shorten the time of the filling step less than 10 minutes. In order to realize that, solution chemistry was used in this research. Photo chemical reaction enabled conducting polymer/metal composites to be synthesized and took advantage of fast deposition of the composite ten times larger than electroplating metal in terms of growth rate. The composite obtained showed conductivity two orders of magnitude higher than commercial conducting polymer. Furthermore, reaction solution was penetrated deeply into narrow hole in silicon wafer because of its high wettability to silicon and silicon oxide.

Filling of polypyrrole/silver as conducting polymer/metal composite was carried out in two ways; 1) injection of reaction solution to silicon holes followed by UV irradiation for photo chemical reaction to form the composite and 2) injection of dispersion solution containing the composite prepared by photo chemical reaction. Filling of the composite was confirmed with laser microscopy and cross sectioning, and time of filling was within 10 minutes. The electrical characteristics such as an I-V curve were obtained with a measurement device in which the electric signal was applied between any two electrodes formed by filling of holes silicon wafer. In addition, the structure at the interface between the composite and silicon wafer was revealed and new diffusion barrier was found to attain both silver anti-diffusion and interfacial adhesion.

These results summarized that the solution chemistry of conducive polymer/metal composite could decrease the time and step for filling to narrow vertical hole of silicon wafer, indicating fast formation of TSV.