Scheduling semiconductor in-line steppers in new product/process introduction scenarios

Muh-Cherng Wu*, Chie W. Chiou

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


This paper presents a scheduling method for an in-line stepper operating in a new process/production introduction (NPI) scenario. An in-line stepper is a bottleneck machine in a semiconductor fab. Its interior is comprised of a series of chambers, while its exterior is a dock equipped with a limited number of ports. The transportation unit for each chamber is a piece of wafer, while that for each port is a job that can contain up to 25 wafers. This transportation incompatibility may lead to an unexpected capacity loss for an in-line stepper-in particular in an NPI scenario that, by nature, includes a substantial number of small-sized jobs. Such a capacity loss can be alleviated by effective scheduling. A genetic algorithm (GA) scheduling method is proposed to enhance the productivity of in-line steppers. Four other sequencing methods are compared with the GA method. Numeric experiments indicate that the GA method outperforms the four benchmarks. The higher the percentage of small-sized jobs, the better the performance of the GA.

Original languageEnglish
Pages (from-to)1835-1852
Number of pages18
JournalInternational Journal of Production Research
Issue number6
StatePublished - 1 Jan 2010


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