Buried bump and AC coupled interconnection technology

A novel physical structure, buried solder bumps, is introduced that solves the compliance problems that exist in scaling present area array technologies to ever-higher densities. In this technique, buried bumps provide dc connections between integrated circuits and substrates and ac coupled interconnections provide paths for ac signals across the same interface. This approach requires co-design of packaging and circuits and meets the growing demands for both interconnect density and bandwidth. AC coupled interconnection arrays can be built with pitches for ac signals below 100 μm and data rates of 6 Gb/s per I/O. This paper presents the physical and circuit aspects of this work as well as measured results from capacitively-coupled circuits fabricated in Taiwan semiconductor manufacturing Company (TSMC) 0.35-μm technology. Simulated results from capacitively-coupled circuits in TSMC 0.18 μm are also presented.