Browsing by Author "Chien, CS"

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Downgrade decision for control/dummy wafers in a fab
(2005-09-01)
Wu, MC
;
Chien, CS
;
Lu, KS
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Control and dummy (C/D) wafers are indispensable materials used in a semiconductor fab. C/D wafers stored in a high-grade buffer can be downgraded to several low-grade buffers. The downgrade decision is to determine the amount to downgrade for each of these low-grade buffers. Previous literature solves the downgrade decision by considering only the instantaneous WIP information, which is a short-term approach and may not yield the optimum solution in the long run. This paper presents an LP model to solve the downgrade decision problem, which aims to minimize the long-term daily usage of brand-new C/D wafers in a fab. The formulated problem assumes that the storage cost of C/D wafers is much less than the usage cost. This assumption has been justified by analyzing the cost structure of C/D wafers in a typical fab site.
Planning yields in recycling test wafers
(2004)
Wu, MC
;
Chien, CS
;
Lu, KS
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This paper formulates a decision problem and proposes two solution methods for selecting the yield improvement alternatives in the test wafer recycle processes. The decision problem is to determine the yield improvement target for each recycle process in order to minimize the use of test wafers.
Yield improvement planning for the recycle processes of test wafers
(2006-02-01)
Wu, MC
;
Chien, CS
;
Lu, KS
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Test wafers are used to measure the process quality in semiconductor manufacturing. Test wafers are reusable by recycle cleaning and can be downgraded to the downstream processes. Most previous studies on test wafers aimed to reduce the use of test wafers by making appropriate operational decisions. Yet, the effective improvement of yield in the recycle process of test wafers is seldom explored. This paper formulates a decision problem and proposes two solution methods for selecting the yield improvement alternatives in the test wafer recycle processes. The decision problem is to determine the yield improvement target for each recycle process in order to minimize the use of test wafers, under a given budget for yield improvement. The two solution methods involve a genetic algorithm and a marginal allocation algorithm. The two methods yield very close solutions, but the marginal allocation method is better because it requires less computation time.