Modeling and performance analysis of cluster tools using Petri nets
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abstract
The performance of cluster tools is gaining ever-increasing importance as the semiconductor industry migrates to larger wafer sizes, and smaller device geometries. Customers demand higher throughput-to-footprint ratios for semiconductor equipment. Cluster tool throughput is the outcome of complex interactions of various subsystems, and there is a critical need for appropriate tools that aid in understanding these inter actions, and their effects on throughput. Current methods for throughput analysis are not very well oriented toward understanding the dynamics in cluster tool processing. In this paper we present a procedure to model cluster tools using Petri nets. These models help designers to comprehend the flow of wafers during processing. While Petri nets have been used extensively in the modeling and analysis of diverse manufacturing processes/systems, this to the best of our knowledge is the first attempt to specifically model cluster tools. A state cycle analysis is discussed next; this method enables equipment designers to extract steady state throughput information, as well as understand the interplay of subsystems during the wafer flow. Two example configurations are used to illustrate Petri net-based model building and analysis. These two examples encompass a variety of design features found in the industry today, e.g., sequential and parallel processing, single and dual end effector robots, anticipatory and simple scheduling.
