In Y4 the manufactuirng process is viewed as sequence of inter-related steps. As an example the core of the manufacturing process is showed in the next figure (in the context of yield forecasting). Note that there is a feedback loop from failure analysis back to the process steps mimicking contnuous yield improvement. Thus inherently Y4 is capable of incorporating models which can dynamically alter the state of the fab based on previous state(s).   Figure 1. Manufacturing process flow.   The next figure conceptually show the process of yield improvement as modeled in Y4. There are essentially for steps leading to yield improvement. The first step is when a wafer with yield problem is sampled for analysis. Then the cause of yield loss is identified and process intervention is undertaken. The process parameters get modified when proper cleaning/repairing is applied. Finally yield change is observed when new process parameters become effective.   Figure 2. Yield improvement steps.
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