Study on high performance and productivity of TSV's 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. 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 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, miniature via using RIE dry etching on a Si wafer. Filling is performed by melting alloy in a vacuum, and removing the melted alloy residue with pressurization. For this purpose, we have developed a new Bi-Sn-Ag filler material that expands when solidifying, and can withstand temperatures >;250C. Our landmark method makes it possible to increase the speed of filling a TSV by several minutes for a 12 inch wafer, as well as make it possible to fill a TSV with super high aspect ratio(>;40), super fine via(about 0.2μm) and no Keep Out Zone (KOZ) using this material.