Fine Cone-shaped Bumps for Three-dimensional LSI Package—An Optimization of Thermocompression Bonding Process

Shunsuke Nemoto,Hiroshi Nakagawa,Masahiro Aoyagi,Ying Ying Lim,Katsuya Kikuchi

doi:10.18494/sam.2018.2009

Abstract

Fine Cone-shaped Bumps for Three-dimensional LSI Package—An Optimization of Thermocompression Bonding Process

Highlights

Multifunctional LSI chips with small footprints are desirable for consumer applications in the area of mobile, medical, and AI sensors
The effect of temperature on the bump compression process was investigated, with the goal of optimizing the load and bonding strength in flip-chip connections targeted for 3D LSI packages
1) From the results of the bump compression test and the temperature dependence of the resistivity of the nanoparticle deposition (NPD) film, the crystal grain size was found to have a significant effect on the compressive stress

Summary

Introduction

Multifunctional LSI chips with small footprints are desirable for consumer applications in the area of mobile, medical, and AI sensors. Three-dimensional (3D) LSI packaging is a promising approach to obtaining smaller footprints and higher densities, where the LSI chips are stacked in the vertical direction. A typical 3D LSI package is composed of stacked chips, which are connected using through silicon vias and microbumps. Work has been ongoing in the development of microbumps using a nanoparticle deposition (NPD) method.[1,2] A key advantage of NPD bumps is their compliance during compression, as the bumps are coneshaped. Compared with copper pillar bumps, which may be noncoplanar owing to process tolerances, chip-to-chip connection during flip-chip bonding could be improved with NPD bumps. From our previous work,(1) 10 μm NPD bumps were flip-chip-bonded and the signal transmission was demonstrated between LSI chips. In an extension of the work done previously,(2) the effect of heat on the compressive stress is investigated in this work to understand the effects of heating on the bump strength and ISSN 0914-4935 © MYU K.K. https://myukk.org/

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Conclusion