Defect monitoring system

A method of determining a cost effective number of corrective tests to perform on a process experiencing process excursions, the method comprising the steps of:

• determining a test cost for each corrective test,
• calculating a total test cost for each of an incremental number of corrective tests,
• determining an effect of each corrective test on a reduction in the process excursions,
• determining lost revenue for each process excursion,
• calculating a reduction in the lost revenue for each of the incremental number of corrective tests, based at least in part on the effect of each corrective test on the reduction in process excursions and the revenue lost for each process excursion,
• calculating an overall cost for each of the incremental number of corrective tests based at least in part on a sum of the total test cost and the reduction in the lost revenue for each of the incremental number of corrective tests,
• graphing on a chart,
• the total test cost for each of the incremental number of corrective tests,
• the reduction in the lost revenue for each of the incremental number of corrective tests, and
• the overall cost for each of the incremental number of corrective tests,
• graphically finding a minimum value of the overall costs, and
• selecting as the cost effective number of corrective tests to perform that incremental number of corrective tests that is associated with the minimum value of the overall costs.

A method of determining a cost effective number of corrective tests to perform on a process experiencing process excursions, the method comprising the steps of:

• determining a test cost for each corrective test, calculating a total test cost for each of an incremental number of corrective tests, wherein the total test cost for each of the incremental number of corrective tests includes a cost of materials for each corrective test, a cost to perform each corrective test, and a cost to analyze each corrective test,
• determining an effect of each corrective test on a reduction in the process excursions,
• determining lost revenue for each process excursion, wherein the lost revenue for each process excursion includes a selling price of product lost in the process excursion reduced by a fabrication cost of the product lost in the process excursion,
• calculating a reduction in the lost revenue for each of the incremental number of corrective tests, based at least in part on the effect of each corrective test on the reduction in process excursions and the revenue lost for each process excursion,
• calculating an overall cost for each of the incremental number of corrective tests based at least in part on a sum of the total test cost and the reduction in the lost revenue for each of the incremental number of corrective tests,
• finding a minimum value of the overall costs, and
• selecting as the cost effective number of corrective tests to perform that incremental number of corrective tests that is associated with the minimum value of the overall costs.