Experimental investigation for performance assessment of scheduling policies in semiconductor wafer fabrication-a simulation approach

This paper is concerned with assessing the impact of 15 existing release policies in combination with three dispatching rules (together called as scheduling policy) on the performance of semiconductor fabrication facilities using a simulation model of a representative but fictitious semiconductor wafer fab. The performance criteria employed includes average cycle time, standard deviation of cycle time, work in process (WIP) level, and throughput. Arena simulation software is used to build the simulation model and conduct the experimental study. The experimental results indicate that workload regulating (WR), constant work in process (CONWIP), and constant load (CONLOAD) policies are superior among tested release policies and shortest remaining processing time (SRPT) is the best dispatching rule. This paper present a new release policy called as constant workload (CONSTWL), which is a modified version of CONWIP policy to overcome the limitations of traditional release policies. CONSTWL policy triggers the release of job into the system based on the overall workload of shop floor. Results on computational experiments indicate that CONSTWL outperforms traditional release policies in terms of the average cycle time, the standard deviation of cycle time and work in process under a prescribed throughput level. The positive impact of CONSTWL policy on system performance appears to be reliable with the increase of system congestion level. CONSTWL policy may prove useful in practical contexts of make to stock manufacturing environment whose orders are met usually from finished inventory