Inside AMD - Touring Fab 30

Fab 30 – First to Copper, Now first to SOI

As you may remember, Fab 30 migrated to Copper interconnects very early on, even before Intel. The first CPUs to use the new Copper interconnects were actually engineering sample K6-2 processors, but they never made it onto the market. Just two months later, AMD began producing Thunderbird cores using Copper interconnects. It wasn’t until the Pentium 4 that Intel shifted to Copper interconnects, but truthfully it wasn’t necessary until the Pentium 4 for Intel. For AMD, Copper interconnects became an absolute requirement after their transition to the 0.13-micron Thoroughbred core although there were measurable improvements on previous processors.

The reason behind moving to Copper is often quoted as being the lower resistivity of Copper in comparison to Aluminum, but there are also other driving factors behind the move. With the move to Copper AMD was able to move to Inlaid Interconnects, which made lithography easier and avoided metal etching. Going deeper into the benefits of inlaid interconnects is beyond the scope of this article but the point to take away is that there are more drivers behind the move to Copper interconnects than lowering the inherent resistances of the wires.

Once again we find AMD breaking new ground at Fab 30 with their Hammer line of processors slated to be the first x86 CPUs to be manufactured using Partially Depleted Silicon on Insulator transistors. While both AMD and Intel are working towards introducing Fully Depleted SOI in a matter of years, only AMD is introducing PD-SOI. We’ve outlined the benefits of PD-SOI before but to recap, the end result are transistors that are much more efficient with current resulting in cooler running chips and the ability to scale to higher clock speeds.

We asked some of the AMD fab engineers how the move to SOI impacted yields and development time on Hammer. According to the AMD engineers, the move to SOI simply impacted the initial design stages but once that was taken care of the manufacturing was just like any other CPU to come out of Fab 30 – but obviously on SOI wafers.

With our questions about SOI’s impact on Hammer’s production we led into a series of questions about the highly anticipated processor release from AMD…