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That information is generally guarded by fabs. We know IBM had difficulty ramping up their new 300mm factory in Fishkill and those problems have largely been corrected. Process technologies and product technologies must both be debugged and optimized, which takes time. Once you've worked out most of the systematic yield-loss factors (Ys), you're still impacted by various random yield killers (Yr). How quickly a fab is able to solve its most pressing Ys/Yr problems provides an indication of the skill and maturity of its employees and design prowess. Actual yield information is provided to people who need to know, and in general, actual yield numbers are considered confidential.
 
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