Sunday, 2 December 2012


Nanoprocessors: Scaling Beyond CMOS Limits Using Nanotechnology

By Will Soutter

Introduction: Moore's Law

Moore's Law states that the density of transistors on a chip will increase exponentially - doubling in performance every two years. The computing industry has managed to adhere to this law since it was first proposed by Gordon Moore in 1965. However, this prediction only considers silicon-based CMOS (complementary metal-oxide semiconductor) technology.
This technology has limits which will must eventually break the exponential trend. This article explores some of the ways in which the lifetime of CMOS microprocessors can be extended, and some of the technologies which are being suggested as replacements.

Limits to CMOS Scaling

There are three main limits to the continued down-scaling of CMOS feature size:
  • Capabilities of the fabrication method
  • Decreasing switching performance
  • Increasing leakage (spontaneous switching of states, leading to errors and data corruption)
There have been multiple points in the history of computing where CMOS technology has been predicted to hit a limit.
Engineers in the microchip industry have an excellent track record for getting around seemingly unbreakable performance limits. Because of this, CMOS technology and Moore's Law will probably continue for much longer than many commentators currently claim.
However, as quantum effects begin to have a much stronger effect on the behaviour of the electronic components in microprocessors, silicon will become unworkable, and new materials and designs must be employed to continue to meet the demand for increasing performance in microelectronics.

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