Research On Scheduling Of Batch Processing Machines In Semiconductor Wafer Fabrication System

The batch processing machine（BPM）of semiconductor wafer fabrication system（SWFS）has lots of complex characteristics,such as multi-re-entrant processing flow,high uncertainties.It belongs to a bottleneck machine in SWFS.There are two kinds of BPM types:one is that a single processing machine is followed by a BPM（i.e.,it is denoted asδ→β）,the other is that one BPM is followed by another BPM（i.e.,it is denoted asβ₁→β₂）.It is obvious that a good scheduling decision of BPM is beneficial to improve performance of the whole SWFS.The major contents of this thesis consist of batch sequencing of theδ→βtype,batch regrouping and sequencing of theβ₁→β₂ type,batch assigning of parallel BPMs.The research methods and results are listed as follows.（1）Re-entrant family-orientedβsequencing in theδ→βtypeIn order to use the re-entrant characteristic of BPM in SWFS,this thesis proposes a method of re-entrant family-orientedβscheduling in theδ→βtype.On one hand,this method can solve the serious disadvantage of batch-orientedβscheduling method.On the other hand,different re-entrant families can be given different priority weights.It is suitable for the real requirement of SWFS.As for high uncertainties and real production control of releasing on wafer and delivering on week in SWFS,this thesis proposes a method ofβbatch sequencing with due window in theδ→βtype.This method can avoid the serious disadvantage that the high uncertainties affectβbatch sequencing with due date point.The products always can’t be delivered on-time at the due point.Moreover,it is suitable for the real requirement of SWFS,too.For theβscheduling algorithms in theδ→βtype,the research results include re-entrant family-oriented batch sequencing through both slack-based mixed integer linear programming model with due date point and the model with distinct due window.（2）Unifyingβ₂ batch regrouping and sequencing in theβ₁→β₂ type by a unified modelThe batch regrouping is a special procedure forβ₂ scheduling in theβ₁→β₂ type.This thesis proposes aβ₂ scheduling method to unify batch regrouping and sequencing in one model.Not only it meets the conditions of model complexity,but also it does not pass data between batch regrouping and batch sequencing,which can improve efficiency.The research result is the batch regrouping and sequencing through a combined slack-based mixed integer linear programming model for theβ₂ scheduling.（3）Re-entrant family-oriented batch assigning of parallel BPMsIn the parallel BPMs area,the number of identical machines maybe more than one,this thesis studies batch assigning of parallel BPMs,which is based on pull and push strategies.As different job families of the batch regrouping of theβ₁→β₂ type are compatible,different regrouping batches are regarded as single re-entrant family.Theβ₂ batch assigning problem in theβ₁→β₂ type is an exception of theβbatch assigning problem in theδ→βtype with single re-entrant family.The research result is the re-entrant family-oriented closed loop control batch assigning algorithm for the parallel BPMs.The above scheduling models and algorithms have been executed by the real-time scheduling simulation platform of SWFS,the standard commercial solver ILOG CPLEX and the program developed by ourselves.It can be found that our proposed methods can balance computation time and solution quality.