As technology advances, the density of circuitry increases in integrated circuit (IC) chips. Meanwhile the IC chip costs are reduced. These trends require tighter specifications and higher yields. The conflict of tighter specifications and higher yields creates challenges to the wafer fabrication process control. The exposure is one key step in the wafer fabrication process. Minimizing the photomask-to-wafer alignment drifts at the exposure step is a major concern and challenge to the wafer manufacturing management. A real-time feedback control system is being developed in a wafer fabrication line at IBM's San Jose plant. The goal of the system is to minimize the alignment drifts, and hence to increase wafer yields and chip quality, by automatically adjusting the set points of the exposure machines.The major challenges of implementing the feedback control system are: 1) no modification on the existing equipment, 2) mini" interruptions to the production operation, 3) asynchronous operations and communications of multiple computers, 4) computational algorithm of new set points, 5) large volume of data, 6) data grouping, and 7) data filtering. In this paper we will discuss these challenges and the methods taken to tackle them.
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