Semiconductor fabrication is one of the most complex manufactur-ing processes. From raw silica to packaged integrated circuits (IC), semiconductor fabrication involves hundreds of steps performed on a variety of types of equipment, many taking place in a clean-room environment. Yields—the percentage of product that passes all tests and makes it into the field—strongly depend on sevearl factors, most of which are extremely difficult to control. With all of these complexities, isolating and reducing variables is a monstrous task—one that is perfect for Six Sigma.Increasingly, Six Sigma tools are used in the semiconductor industry to ensure consistency, predictability and, ultimately, optimality of process out-puts. Coupled with improved control, optimal performance and increased throughput, many semiconductor companies have enjoyed substantial savings by applying Six Sigma. In this case study, we present the results of the application of Six Sigma in a semiconductor manufacturing company interested in increasing throughput and yield of its wafer-sawing (dicing) process. This step at the end of wafer fabrication is the most critical in determining the throughput and overall yield of the process.

Optimal approach

A manufacturing company had established that among many serial processes, the wafer-sawing process was a yield-limiting process with typical batch process yields of about 65%. A batch is 25 wafers of 6-inch diameter, with each wafer having about 10,000 semiconductor dies. This yield-limiting process presented an excellent opportunity for a Six Sigma define, measure, analyze, improve and control (DMAIC) approach for optimizing the process, as well as the yield of this operation.

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