We already covered here 3-D chips in last July. (Check "Chipmakers are running out of room. The answer might lie in 3-D" for details.) But it's time to revisit the subject with the announcement of a new technology from IBM.
The Economist tells us how IBM will build its 3-D chips.
The plan is to stack high-performance circuit layers so intimately that they can be thought of as a single chip built on many circuit layers. This has been tried before, by growing a layer of silicon on top of a standard chip and then using it to create another layer of circuitry. But the high-temperature processes used to make the circuits in the second layer then degrade the performance of those in the first.
According to IBM, such problems may be overcome by making each complete layer of circuitry on a separate wafer, and only then sticking them together at low temperatures. First, a thin piece of glass is stuck to the face of the upper layer of the wafer. The back of this wafer is then ground and etched in a process that stops when a buried layer of silicon oxide is exposed. The result is a transparent wafer that is as thin as 200 millionths of a millimetre. The bottom of this very thin wafer is then aligned, and bonded, with the exposed silicon of the surface of the lower circuit layer.
The Economist sees several potential benefits with this new technology.
- It may cut the amount of power that a system uses.
- It may solve the usual trade-off between creating very fast chips and keeping them busy.
- it could be used to connect different types of circuit layers into one very dense block, like associating high-frequency radio and digital computing parts of a mobile phone onto a single chip.
For more details, please read the full article.
And for additional material from IBM, you can read "Microchip Fabrication," a presentation by Kathryn Guarini (from IBM's T.J. Watson Research Center in Yorktown Heights, New York, March 9, 2002) or "IBM Creates New Dimension for High-Performance Chips," an IBM press release from November 11, 2002.
Source: The Economist print edition, November 28, 2002; IBM documents, March and November 2002
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