In 1965—even before Intel had been founded—Gordon Moore made his now-famous observation that the number of electronic devices on an integrated circuit appeared to be doubling every year, a trend that he expected to continue and that has subsequently become known as "Moore's Law." Since then, the 64-transistor "state-of-the-art" microchip that Moore was working with in his lab at Fairchild Semiconductor has evolved into today's sophisticated microprocessors, such as the Intel Pentium III that contains 28 million transistors.
While many technological breakthroughs have been instrumental in the development of today's most advanced integrated circuits, one key optoelectronic technology—photolithography—has been fundamental. Notes the International Technology Roadmap for Semiconductors 1999 Edition (www.itrs.net/ntrs/publntrs.nsf), "Lithography continues to be the key enabler and driver for the semiconductor industry. The growth of the industry has been the direct result of improved lithographic resolution and overlay across increasingly larger field sizes."
Commercial production of microchips with 180-nm design rules is currently in place and is based on 193-nm optical lithography (using an argon fluoride excimer laser). Next-generation systems will need to support even smaller design rules, and the most likely approach being pursued by key industry players is 157-nm-based lithography using a fluorine excimer laser source. This wavelength brings with it a host of new challenges, not least of which is an optical system based on calcium fluoride instead of the conventional fused silica (see cover photo and p. 87).
Meanwhile, the use of ultraviolet (UV) laser light to create very small patterns and structures is being explored in other industries as well. Direct writing with pulsed UV lasers can be used to produce mesoscale (~10 µm to 1 mm) passive devices, and in one experiment a fractal antenna has been written onto the abdomen of a worker bee for a potential application detecting low levels of dangerous chemicals (see p. 113).
Materials engineering is another important aspect of optoelectronics.
The technologies that will allow high-speed telecommunications to evolve beyond 40 Gbit/s will be based on faster, more efficient devices than are currently available. Specifically engineered materials are likely to present new opportunities for controlling light—one approach is based on using nanotechnology to produce novel photonic-bandgap materials. A device fabricated at the Massachusetts Institute of Technology, for example, contains an air-bridge microcavity with the smallest modal volume ever demonstrated—its finest feature size is on the order of 0.2 µm (see p. 133).