Inspection planning based on excursion risk management
Inspection Planner 1.0 (IP1.0) is the first inspection planning software offered to the semiconductor industry. Using process, defect, and economic data, IP1.0 allows fabs to identify the defect inspection capacity that minimizes excursion risk and maximizes fab profitability.
Analysis with fab data estimated up to 2% fab yield increase due to sample plan optimization*. There was no increase in tool cost, utilization, false alarm risk, or cycle time.
The key to identifying the optimal inspection capacity is to calculate and balance the competing inspection and excursion costs.
IP1.0 captures inspection costs with a cost-of-ownership model and the excursion costs by calculating excursion detection delays. The delays are calculated with state of the art stochastic formulations based on process tools’ in-&-out-of-control cycles.
The excursion detection model
Process tools are modeled to experience out-of-control (OOC) states at random points in time. In the OOC state, a defect count of some type has increased. These events, also knows as defect excursions, need to be detected quickly to minimize yield impact.
The below figure depicts a single process tools’ in-&-out-of control cycle. Root cause analysis (RCA) commences after detection, followed by the fixing of the problem. After the fix, the cycle starts over.