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Remembering what front-end gate stacks, neuroscience, and poetry have in common |
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Aug 22, 2007 at 10:35 AM |
In the world of semiconductor process technology, the physical limitations of one of the longest-running games in town---the silicon dioxide gate dielectric---have spawned the creative ingenuity of strain engineering.
But strain is reaching its own end-game, so new nonsilicon materials have to be integrated into the gate stack to allow chipmakers to continue scaling down the Moore's Law curve.
Sematech has been making great progress on dealing with these front-end/transistor performance conundrums, with several recent papers and presentations detailing breakthroughs in high-k metal gates. In a press release put out over the wires earlier this week, the consortium trumpeted its successes in bringing ternary metals, silicon germanium, hafnium silicon oxynitride, and other travelers from the periodic table closer to the fab.
While the 45-nm process node will see the introduction of some of these new heterogeneous materials, Sematech believes that their integration will become widespread in the 32-nm regime. But as Raj Jammy, one of the organization's front-end gurus, notes, there are challenges aplenty in the integrating these exotics and making them function properly: leakage and resistance must be reduced, mobility enhanced, and reliability improved.
In one of Raj's comments, he uses the image of the human brain, the ultimate 10-quadrillion synapse processing and storage unit, to make a point:
"If you look at the gate as the brain of the transistor, then changing any of its components is like brain surgery. Change one material, and all the others are affected. Somehow, we need to integrate these novel materials so that they work well together and retain desirable characteristics."
While the chip scientists and engineers struggle with the laws of physics to cram more functionality into a few atoms worth of nanoscale real estate, the neuroscientists are moving closer to explaining another quadrant of the nano realm: the biochemical processes underpinning memory and forgetfulness. "Chasing Memory," a four-part series on the work of U.C. Irvine's Gary Lynch, concludes in today's Los Angeles Times. Written by Terry McDermott, this is one of the best pieces of science journalism I've seen this year.
The basis of Lynch's work is his theory of "long-term potentiation," or LTP. (No, not laser thermal processing, the other LTP familiar to Raj and the ultrashallow junction transistor formation crowd.) McDermott summarizes the brain's LTP process as follows:
"The outline of Lynch's LTP hypothesis was this: When you experienced a sensation in the outside world---seeing, smelling or touching something---the sensation was translated by the sensory organs into an electrical signal that was routed to the brain, where it caused the brain cells, or neurons, that received the stimulus to release chemicals to neighboring neurons. A cascade of chemical events inside those neighboring neurons resulted in their interior reorganization. That reorganization strengthened the connection between cells at the points where they meet, called the synapses. Networks of those neurons with strengthened connections constituted the underpinning of memory."
Outside the labs and fabs, poets continue to probe memory's mysteries as they have for eons. One of the more insightful lyrical explorers still living among us is W.S. Merwin. Here's an excerpt from his poem "The View," found in his 1996 collection, The Vixen:
"No wonder there are those lights of suspicion moving
endlessly over memory and its faces
over the way of memory itself the way
of remembering which is the way of forgetting
the way of horizons the way beyond the reach the way
of another which appears at times to be the only way
when not one thing not one moment with its heavenly
bodies flying through unrepeated places not one
sound or shining is what it was the one time before
it was remembered when I was in the midst of it
looking out thinking about something far from there
bodies and death and taxes and what I did not want
and have forgotten...."
Will poets' creative neural pathways be mapped one day by brain engineers using analytical tools employing the awesome googaflop power of future-gen nanochips? Those memories can wait---I like a bit of mystery.
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