Page 314 - Introduction to Information Optics

Chapter 6 Interconnection with Optics

Ray T. Chen and Bipin Bihari
MICROELECTRONICS RESEARCH CENTER,
THE UNIVERSITY OF TEXAS, AUSTIN

6.1. INTRODUCTION

Extraordinary developments during the last decade in microelectronics
fabrication technologies have provided the means to achieve submicron feature
size and accommodate millions of logic gates in a small volume. This shrinking
feature size in Si VLSI circuits manifests into short transit time and switching
speeds within the processor chip, allowing extremely fast intrinsic signal speeds.
However, preserving the integrity of the signals generated by these novel
devices while communicating among other chips on a system or PC board level
is becoming extremely difficult by electrical means (i.e., using conventional
metallic transmission lines and interconnects), and requires employment of
bulky, expensive terminated coaxial interconnections. High packaging density
and long on-board communication distances (> 10 cm) make even state-of-the-
art electrical interconnects unrealistic in some cases [1]. Several critical
problems exist for electrical interconnects in high-speed, large-area, massive
signal transmission. These include:

1. Impedance mismatch caused by multistage electrical fanouts.
2. Transmission reflection (noise) at each fanout junction as well as at the
end of each transmission line.
3. Electromagnetic interference with other interconnection lines and other
interconnection layers.
4. High transmission loss resulting in a large driving power [2,3].
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