Copper metallization has become the primary means of reducing on-chip interconnection delays and allowing the integration of hundreds of millions of transistors on a single chip. But systems often contain more than one chip. And when moving signals from chip to chip, metallization systems and I/O buffers add significant delays to the signals—typically 2 to 4 ns for each I/O pin. Depending on the distance that the signal travels on the circuit board or substrate, a delay might even be a few hundred picoseconds. To shorten this transit time, researchers at the DigitalDNA Laboratories of Motorola Inc., Tempe, Ariz., are developing an optical-interconnect scheme that uses the free space above the chips to transport the optical signals.
展开▼
