AMD to offer strained silicon chips

Following Intel, IBM

AMD has begun punching out 90nm Opterons from its Dresden fab, a company executive revealed this week. And it plans to introduce Intel-style strained silicon materials to its processors in due course.

The chip maker will ship 90nm chips to customers next quarter, but according to Thomas Sonderman, an AMD director of manufacturing technology, prototype chips are already falling off the production line - and running in test computers.

Speaking during a presentation made in Munich yesterday ahead of the Semicon Europa conference, Sonderman said the 90nm process will initially use AMD's existing silicon-on-insulator technique and Black Diamond low-k dielectric technology.

Intel already uses strained silicon in its 90nm process, which debuted with the launch of 'Prescott' Pentium 4 desktop CPUs in February. The technique works by adding a layer of silicon over a layer of silicon germanium (SiGe). The top layer's silicon atoms align themselves with those in the SiGe layer's wider-spaced crystal lattice, pulling them apart. Wider spaced silicon atoms make for a smoother flow of electrons between them, improving the material's electrical properties.

Adding that SiGe layer into an existing fabrication process is tricky - it's almost certainly one of the reasons Intel took longer than planned to roll out its 90nm chips. IBM claims to have perfected the technique by leveraging its own silicon-on-insulator technology. As it announced last September, IBM removes the SiGe layer before fabrication, after applying the strained silicon onto the insulator. The upshot: it gains benefits of strained silicon using what is essentially a standard SOI process. By removing the SiGe layer, it doesn't have to integrate that material into the chip fabrication process per se. It calls the new technique Strained Silicon Directly on Insulator (SSDOI).

IBM has said it is using SSDOI to fab its 90nm PowerPC 970FX chip, which Apple uses in its Xserve G5 server. Apple recently said during its latest quarterly results conference that the delays it had experienced shipping said server were due to difficulties IBM has had producing sufficient 90nm G5s, so IBM's SSDOI process may not be working as smoothly as anticipated.

AMD, of course, has a technology partnership with IBM, primarily at the 65nm node, and it's entirely possible that it will implement SSDOI when it makes that transition. Even if it brings the technique to its 90nm chips, it should benefit from taking its time and learning from IBM's experience. ®

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