Title: Evaluating the performance of look-ahead policies for upstream serial processor with downstream batch processor serving incompatible job families and finite buffer sizes

Authors: John Benedict C. Tajan; Appa Iyer Sivakumar; Stanley B. Gershwin

Addresses: Singapore-MIT Alliance, N3.2-01-36, 65 Nanyang Drive, Singapore 637460, Singapore ' Singapore-MIT Alliance, N3.2-01-36, 65 Nanyang Drive, Singapore 637460, Singapore; School of Mechanical and Aerospace Engineering, Nanyang Technological University, N3-02a-01, 50 Nanyang Avenue, Singapore 639798, Singapore ' Singapore-MIT Alliance, N3.2-01-36, 65 Nanyang Drive, Singapore 637460, Singapore; Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 35-210, Cambridge, MA 02139-4307, USA

Abstract: Batch processors can concurrently process more than one job. In wafer fabrication, the processing time of a batch is independent of batch size, and only jobs from the same job family can be batched together. We consider a two-stage subsystem of a wafer fabrication facility (wafer fab), comprised of the diffusion furnace (a batch processor) and its upstream serial processor, with random job arrivals. We hypothesise that allowing the serial processor to anticipate the job family preference of the batch processor will reduce the overall cycle time of jobs passing through this system. To evaluate this hypothesis, we model the performance of the two-stage system under different system parameters and processor control policies as discrete state continuous time Markov chains. We characterise the system performance and show that the concept of constraining the production of the upstream processor according to the anticipated needs of the batch processor can reduce the mean cycle time of jobs being processed. We also perform simulation experiments to show that a simple heuristic based on this insight can translate to substantial cycle time reductions for systems with assumptions closer to those found in wafer fabs.

Keywords: batch processing; cycle time; semiconductor manufacturing; heuristics; look-ahead policies; job families; buffer sizes; wafer fabrication; serial processing.

DOI: 10.1504/IJOR.2012.049482

International Journal of Operational Research, 2012 Vol.15 No.3, pp.260 - 289

Published online: 11 Jan 2015 *

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