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To: TimF who wrote (73745)	3/6/2002 6:33:26 PM
From: semiconeng	Read Replies (3) \| Respond to of 275872

Which brings to mind the question - Is the capacity reduction from more layers greater then or less then the capacity reduction for the slightly larger die if more layers where not used? Tim They're 2 different issues.... Suppose you want your fab to run 5000 wafer starts per week. In order to keep the line balanced, in theory you need to ship 5000 wafers per week from end of line. In order to figure out how many tools of each type you need, you take the throughput of the tool (How Many Wafers processed per hour) and calculate how many tools you need for each area to keep the line moving at a rate that will theoretically give you 5000 wafers per week at end of line. If the die size changes, you still are shipping the same number of wafers per week, although less die out. The speed of the line doesn't change. On the other hand, if a certain product has additional 3 Layers to run on those same tools, then those tools can't be used to process the first 6 layers while they're processing the additional 3. So in order to keep the line moving at the same relative speed, you need to buy additional tools to give you the same number of wafers out per week. Otherwise, wafers that would have run on those tools will sit while the additional layers are processed, slowing down the line, and reducing the number of wafers per week at end of line, or worse, jamming up the line at the back end. Of course you could reduce the wafer starts to compensate, thereby reducing the overall fab output.... Semi