re: "The key to the K7 is the 0.18 micron process. I doubt if AMD can yield any reasonable volumes with the die size at 180mm2."
Not necessarily.
There appear to be 3 problems with AMD yield.
(i) Yield loss due to speed binning.
A major problem with AMD at the moment is that they cannot yield high-speed parts. In process terms, this is primarily a question of siting the average channel length low enough to achieve high speeds (while avoiding yield loss due to sub-threshold leakage), and then controlling the channel length (primarily through excellent control of the polysilicon gate lithography/etch step).
(ii) Yield loss due to the tungsten local interconnect used on the SRAM cell. This was news to me, but not a surprise. W processing is always very dirty. The effect will be die-size dependant (actually, more dependant on the SRAM area if this is where the problem is), and I can't see why it would affect the availability of high-speed parts
(iii) Design fault(s)
Yield loss due to speed binning won't be much affected by die size (yes, I can come up with cases where it will affect it, but in general it won't). The primary yield loss related to die size is the random defects on the wafers - primarily due to particles (include here the local interconnect issue).
Dresden is a brand new fab - very clean equipment etc. I wouldn't worry about random defectivity too much (I presume the local interconnect problem is fixed by now, and it should be). Sure the K7 yield will be worse because of it, but that's not the key issue IMHO.
No, far more important is how they plan to ramp Dresden, and on which process. Are they transferring a process running in volume elsewhere? If so, is the part they are making (K7) also running in volume on this process.
If the answers to the above questions is no, then AMD will be ramping a fab with an untested design on a new process - asking for trouble. When things go wrong (and many things will) you have no 'baseline' to fall back on. It's hard to tell if a yield problem is a fab or design problem (and the worst ones are an interaction between the two).
So what process will the K7 be run on initially, and what is the process roadmap? |
