Extending Moore's Law

New chip technologies keep getting smaller and faster

Intel Corp. co-founder Gordon Moore observed in 1965 that the number of transistors on a semiconductor chip doubled every 18 to 24 months. A corollary to Moore's Law is that the speed of microprocessors, at a constant cost, increases at the same rate. For some three decades, the name of the game in semiconductors has been to make their circuits ever smaller.

But just making things smaller isn't enough anymore, says Bernard Myerson, chief technology officer at IBM's Technology Group. "There has been a sea change that people perhaps have not noticed in how progress is being made in semiconductor design," he says. "Scaling has reached the point of diminishing returns. You are making spectacular dollar investments for minimal technical advance. We are now in a region where as much or more progress will be made by changes in the fundamentals of [chip] materials."

Indeed, IBM has recently developed or is developing these fundamental new ways of building chips:

  • Copper interconnects: PowerPC chips use copper wiring instead of the poorer performing, but easier to manufacture aluminum wires used for years in most processors. Copper is a better electrical conductor, and as circuits shrink, the performance and cost advantages of copper grow (see story).
  • Silicon on insulator (SOI): SOI technology can speed transistor switching by 20% to 35% by putting an insulating layer of silicon dioxide between the transistor and its silicon substrate. The technology reduces distortion and current drain and allows circuits to be made smaller (see story).
  • Silicon germanium: These hybrid chips have faster transistor speeds and low power consumption. The recently announced 210-GHz SiGe transistor is optimized for communications functions and draws 50% less power.
  • System on a chip: Integrating processor, memory and communications functions onto a single chip offers a tenfold cost improvement and a fivefold power reduction, IBM says.
  • Strained silicon: Silicon is placed atop a substrate of silicon and germanium, and that allows the silicon atoms to be "strained" farther apart. Electrons move through strained silicon 30% faster than through conventional silicon.
  • Carbon nanotube transistor: This radical new device draws its name from its material (pure carbon), its size (1 to 3 nanometers in diameter) and its shape (a tube composed of hexagonal structures). Nanotubes are light yet strong, conduct heat well and are better electrical conductors than copper. "Carbon nanotubes are already the top candidate to replace silicon when current chip features just can't be made any smaller, a physical barrier expected to occur in about 10 to 15 years," says Phaedon Avouris, manager of nanoscale science at IBM Research.

Copyright © 2002 IDG Communications, Inc.

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