Linear approach in photo automation

If the photo engineer can´t estimate the ET value to run the wafers in a stepper, he has to guess an ET value for the test wafers to see whether the output CD will fall into the accepted area or not. It really will waste time and money. The production amount in fab is very important. The linear approach algorithm could be one of the solutions to take care of photo automation even if the algorithm in this paper might not support one hundred percent the predicted ET value or OSI overlay falling into the accepted area. Actually, this linear approach algorithm, through the implementation, has already reached some kind of level. We take more concern with this algorithm and hope to see it improve itself in the future