Dual etch processes of via and metal paste filling for through silicon via process

Abstract

We investigated the etched slope control of silicon via and the filling of the through silicon via (TSV) with nano-scale Ag paste. Patterns for a 10 μm-diameter hole and line were etched using the Bosch process in a deep reactive ion etching system (the first etching process). The diameter of via (Top) and the depth of the via were about 10.6 μm and 80 μm, respectively, with a nearly vertical profile. In sequence, the tapered via and the removal of the scallops were obtained using an inductively-coupled etching system (the second etching process). We investigated the effects of gas pressure and input power on the slope of the TSV during the second etching process. In the second etching process, as the process pressure increased from 10 to 80 mTorr, the diameter of via (Top) decreased from 13 to 12.2 μm. Meanwhile, the expansion of via (Top) increased with increasing source power from 200 to 600 W. We found that the expansions of the via (Top) size were related to the desorption of by-product and the arrival of ion flux. We achieved a smooth surface and a slope angle of about 86° using the dual etch process. Finally, the depth of the 80 μm via was filled with nano-scale Ag paste using a vacuum-assisted filling method.