Abstract
To ensure wafer quality, engineers have to impose wafer residency time constraints and chamber cleaning operations on cluster tools; this has been widely used in semiconductor manufacturing. Wafer residency time constraints and chamber cleaning operations make the scheduling problem of cluster tools more challenging. This work aims to solve such a scheduling problem for single-arm cluster tools and presents a novel method based on the use of virtual wafers. Under a one-cyclic schedule obtained for single-arm cluster tools without chamber cleaning requirements, virtual wafers are loaded into the tool such that when a process module (PM) processes virtual wafers, a chamber cleaning operation is performed in practice. The key to solve this scheduling problem is to find a wafer loading sequence with the highest performance in terms of cycle time. With this idea, this work constructs a genetic algorithm to search for such a solution. Since the obtained solution is a periodical wafer loading sequence based on a one-wafer cyclic schedule, it can be easily implemented. Therefore, this work has high practical value to numerous semiconductor manufacturers. Experiments were performed to show the efficiency and effectiveness of the proposed method.
Highlights
In semiconductor manufacturing, cluster tools are important for wafer fabrication.A modern semiconductor fabrication plant is equipped with hundreds of cluster tools
In order to select a better group of parameters for the genetic algorithm (GA), experiments were performed with different parameter settings for 20 cases
This work deals with a scheduling problem for single-arm cluster tool (SACT) with wafer residency time constraints (WRTCs) and chamber cleaning operations which are commonly seen requirements in real semiconductor manufacturing
Summary
Cluster tools are important for wafer fabrication. A modern semiconductor fabrication plant (fab) is equipped with hundreds of cluster tools. A cluster tool is very expensive, and the cost for equipment accounts for more than a half of the total investment for a fab. Maximizing the productivity of cluster tools is an important means for manufacturers to ensure the return on their investment. The single-wafer processing technology is adopted for processing large-size wafers in cluster tools. By such a technology, a PM in a tool can process only one wafer at a time. A PM in a tool can process only one wafer at a time In this way, precision processing requirements can be satisfied such that the quality of processed wafers can be guaranteed
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