Study on TSV with new filling method and alloy for advanced 3D-SiP

We focus on 3D-SiP using TSV´s as one possible breakthrough method that can overcome semiconductor scaling limits. To this point, despite numerous investigations, this method has not reached mass production due to many problems in processing, structure, mass production, reliability, etc... In particular, typical filling methods used in the current TSV such as Cu electro-plating, W-CVD and the like have poor manufacturability and are limited to holes with small aspect ratios making practical adoption a problematic. To overcome this obstacle, we have developed a new Bi-Sn liquid metal filling method that is completely different from previous methods. In this method, we first form a high aspect ratio (>;25) miniature via (about 1μm) using RIE dry etching on a Si wafer. Filling is performed by melting metal in a vacuum, and then applying pressure. For this purpose, we have developed a new Bi-Sn filler material that expands when it congeals, and can withstand temperatures >;250C. Our landmark method makes it possible to increase the speed of filling a TSV by over 10 times, i.e., several minutes for a 12 inch wafer, as well as make it possible to fill a TSV with super high aspect ratio. In this work we provide an overview of the method and report on the characteristics of the new filler material. As a result Compared with the Cu-TSV, there is almost no Keep Out Zone using this material. It was clearly shown that this contributes to increased gate density.