Elmer: As others have pointed out before, your claims about F30 production utilization are flawed. Let me try to explain.
First off, you appear to be using a defect density of 0.25/cm2 for all production. This is a naive assumption. As you stated, that defect density is considered excellent yield. However, what you don't consider is that there are several concurrent production processes at any time at F30 each of which is in a different state of maturity. As with most production processes, yields start off lower and increase as the process matures, yet you are assigning a mature yield figure to all processes. I am certain that the overall weighted average yield for the fab is quite a bit lower than the figure you use. It is completely unreasonable to assume that all concurrent processes are producing excellent yields.
Second, at any given time, some process are ramping up, others are winding down, and others are preparing for production.
Each of these affects capacity to some unquantifiable degree. You tend to spin the numbers in a way that makes it appear that half of the fab is collecting dust. However, if some reasonable assumptions are made for the impact of the above, it is a simple matter to calculate that the fab is running at near capacity. For that matter, one can calculate utilization for any number of reasonable scenarios and come up with anywhere from 25% to 150% utilization. You seem to be fixated on 50%, but that position makes no sense from a business perspective. I suspect that the number is closer to about 80%, and that it varies significantly as processes begin, mature and end.But that's my guess, and it is every bit as good as yours. I can certainly come up with a product mix and yield scenario that would be reasonable and support my guess.
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