Unformatted text preview: es a straightforward method for assisting the largely intuitive decision of how to accommodate product-mix uncertainty. If a similarly simple method could be developed of dividing the universe of possible product mixes into constant-tool-set regions and assigning probabilities to these regions, this method’s power would be augmented significantly. SUMMARY: ACTING ON THE FINDINGS OF THIS METHOD A major benefit of this method is that it tells one what tools not to worry about in regard to mix-driven capacity constraints. Headway has found that this method weeds out about 95% of its tool groups, leaving a manageable 5% as mix-driven capacity constraints. These tool groups then are the only ones that need be kept in mind when looking at signs of product-mix change and how they will affect fab capacity. Large fabs can expect a larger percentage of their tool groups to qualify as mix-driven capacity constraints. This is because large fabs have more of each type of tool and can therefore purchase capacity in smaller increments and have more tool groups close to 85% loading at any one time . In such cases, analysis can be simplified by limiting considera...
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- Spring '11
- Semiconductor device fabrication, Headway, tool group