41 Introduction And Background

The 1990s brought revolutionary new technologies to computing, and one such new technology has been that of multilayer ceramic interconnecting substrates.

Handbook of Advanced Materials Edited by James K. Wessel ISBN 0-471-45475-3 Copyright © 2004 John Wiley & Sons, Inc.

We have witnessed many high-performance products transition from aluminum oxide dielectric with molybdenum or tungsten conductor materials to much higher performance glass-ceramic dielectric with copper conductor integrated wiring. In particular, cordierite glass-ceramics have enabled greater processing speeds due to their lower dielectric constants and copper's much higher electrical conductivity than traditional molybdenum, and tungsten has further aided signal speeds. And, new processing technologies have allowed greater dimensional control of the finished product, which in turn has permitted tighter tolerances and more advanced design ground rules. Additionally, the exceptional reliability of this technology has been demonstrated across many different form factors and applications.

This chapter reviews glass-ceramic/copper multilayer interconnect substrate technology. It reviews the fundamental materials properties as well as the key processing parameters. This chapter also reviews some future directions and challenges for this emerging technology in the new millennium.

The very first glass-ceramic/copper multilayer interconnect substrates were introduced by IBM in 1990. These interconnect substrates were as large as 127 x 127 mm and possessed as many as 70 distinct layers. The copper interconnect wiring was done with 90-^m pitch. The first applications for these interconnect substrates were for mainframe computers as multichip modules (MCMs). In this case, as many as 121 devices were flip-chip or C4 (controlled collapse chip connection) joined to the substrate, as well as hundreds of C4 decoupling capacitors. While these first interconnect packages were used for mainframe computers, subsequent applications have been found for single-chip, chip-scale-sized modules, and their use in high-speed and high-frequency applications has continued to grow with passing years. How did these new interconnect materials come about and why were they chosen? We hope to answer these questions and others like them in this chapter.

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