In the autumn of 1978 I attended a Motorola Integrated Circuit Division press conference. Back in those heady days it wasn't unusual for semiconductor houses like Moto to hold lavish and extravagant press events, often at far-out venues such as New York City's
Windows On The World restaurant at the top of the World Trade Center. Ice sculptures, greetings by long-legged scantily clad models at the door, champagne, and endless platters of seafood delicacies were the rule.
At this particular conference Motorola rolled out its first 64 kbit dynamic RAM. Robert Dennard's one-transistor, one-capacitor memory cell revolutionized the embryonic microcomputer industry, and Motorola was rejoicing.
I still have one of those devices sitting on my desk, encapsulated in clear plastic. The engraving on this memento from Moto reads: "64K Dynamic RAM, First Silicon, November 8, 1978, Austin, Texas."
Wow, time sure flies, especially when you're having fun, and what Editor covering this extraordinary industry isn't having fun? In 1978, I thought word processing on a Xerox Z80 computer running CP/M and Wordstar was heavenly. Today’s multi-GHz PC is every bit as exciting.
From that day to this, the ubiquitous DRAM has enabled every imaginable kind of portable computer and nomadic device – all at outrageously rock bottom bit costs, and there's no end in sight. Or is there?
Today's very low-voltage DRAMs (and all sub-micron ICs, for that matter) challenge chipmakers. Speed variability in sense amplifiers is one problem with deep-sub-100-nm memory technologies, but there are myriad others. Nonetheless, news of groundbreaking technologies crosses my desk almost daily.
New DeparturesFor example, compound III-V technology and mainstream silicon techniques are merging. Compound semiconductor-on-silicon
devices, based on the latest high-k gate dielectrics, tout feature sizes and densities that are competitive with the best of today's silicon. CSOS technology is moving rapidly out of academia and into the world of commercialization, too.
When they debut for real, enhancement-mode CSOS FETs, normally off, will be just the ticket for an entirely new breed of power-stingy battery-powered products. By the way, a few years ago, Motorola announced that it was taking steps to commercialize CSOS technology by creating a focused business unit called Thoughtbeam, but that entity seems to have gone the way of Moto’s Iridium satellite business. Gone.
Another exciting development is all-optical signal processing. The first experimental proof of all-optical processing with silicon-based devices has been announced in a collaborative release from
IMEC in Belgium, the University of Karlsruhe in Germany, Lehigh University, and
ETH Zurich in Switzerland.
IMEC, an independent research center for nanoelectronics and nanotechnology, bills the achievement as a critical step towards the development of complex silicon-based photonic ICs. All-optical signal processing is especially intriguing for telecom applications, where speed, power and cost are crucial parameters.
Ultra-Fast Optical WaveguidesA key element to enable all-optical processing is optical waveguides with highly nonlinear and ultra-fast performance. The IMEC consortium has demonstrated an optical waveguide fabricated by means of deep-ultraviolet lithography in standard CMOS, along with organic molecular beam deposition. So-called SOH (silicon-organic hybrid) enables waveguides that should pave the way towards all-optical processing, where photons no longer need to be converted to electrons.
A 4-mm long SOH waveguide proved the concept, with record values predicted by theory experimentally confirmed. Based on these waveguides, all-optical de-multiplexing of a 171 Gbit/s signal to 43 Gbit/s was performed in the lab. This milestone marks the fastest silicon photonic optical signal processing to date.
With SOH, some inherent limitations of silicon can be overcome, too. Silicon-based technology, in particular SOI (silicon-on-insulator), has proven successful for the fabrication of passive linear optical devices such as filters. But, the development of ultra-fast active Si-based functions, such as all-optical switching, remained challenging due to the slow dynamics caused by unwanted non-linear effects in silicon. The data rate using bare silicon waveguides was limited to about 40 Gbit/s.
SOH overcomes the speed limitation, fostering data rates of 100 Gbit/s, and higher. SOH combines mature CMOS (used to fabricate the waveguide) and organic molecular beam deposition. Organic molecules efficiently transfer all-optical interaction without introducing absorption.
Given today's frayed and uncertain world economy, there are no more sumptuous press conferences for Editors that I know of. But, that doesn't hold back news of leading edge technologies. I full well expect that some Editor somewhere in cyberspace will be sitting at his or her desk in the year 2050, wistfully looking at a memento of 200 Gbit/s technology, and musing about the days when 10-Gbit/s network switches costing $1000 or more were considered breathtaking.
