Multi-Stacked Flip Chips with Copper Plated Through Silicon Vias and Re-distribution for 3D System-in-Package Integratio
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0970-Y05-04
Multi-Stacked Flip Chips with Copper Plated Through Silicon Vias and Re-Distribution for 3D System-in-Package Integration Shi-Wei Ricky Lee1,2 and Ronald Hon2 1
Department of Mechanical Engineering, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, 00000, Hong Kong
2
Electronic Packaging Laboratory, Center for Advanced Microsystems Packaging, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, 00000, Hong Kong
ABSTRACT The study is a prototype design and fabrication of multi-stacked flip chip three dimensional packaging (3DP) with TSVs for interconnection. Three chips are stacked together to make a 3DP with solder bumped flip chips. TSVs are fabricated and distributed along the periphery of the middle chip. The TSVs are formed by dry etching, deep reactive ions etching (DRIE), with dimensions of 150 x 100 microns. The TSVs are plugged by copper plating. The filled TSVs are connected to the solder pads by extended pad patterns surrounding the top and the bottom of TSVs on both sides of the wafer for the middle chip. After pad patterning passivation and solder bumping, the wafer is sawed into chips for subsequent 3D stacked die assembly. Because the TSVs are located at the periphery of the middle chips and stretch across the saw street between adjacent chips, they will be sawed through their center to form two open TSVs (with half of the original size) for electrical interconnection between the front side and the back side of the middle chip. The top chip is made by the conventional solder bumped flip chip processes and the bottom chip is a carrier with routing patterns. The three middle chips and top chip are stacked by a flip chip bonder and the solder balls are reflowed to form the 3DP structure. Lead-free soldering and wafer thinning are implemented in this prototype. In addition to the conceptual design, all wafer level fabrication processes are described and the die stacking assembly is also presented. INTRODUCTION Due to the explosive growth in the electronics industry in past decades, the general trends for microelectronic devices are smaller, shorter, thinner, and lighter. Traditional wire bonding technology is not sufficient to provide enough functionality and performance of the chips. In order to fulfill this requirement, three dimensional packaging (3DP) has to be implemented.
3D integrated systems can reduce chip areas and optimize component partitioning, both of which decrease the fabrication cost of a system. In addition, three dimensional packaging systems enables minimal interconnection lengths and eliminates the speed-limiting inter-chip interconnects. Without 3DP technologies, compact hand-held devices such as mobile phones and PDAs would never have materialized. There are various methods for implementing 3DP structures [1-7] other than wire bonding die stacking. One of the major technologies is microvias for vertical interconnection. In the past, microvias were mainly made on printed circuit boards (PCBs) or substrates. Recently, the
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