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Overhead automated material handling systems have become the only material handling solution in semiconductor fabs to achieve zero footprint material handling in the expensive cleanroom floor. This paper provides two rectilinear layout configurations, single-spine and double-spine, for overhead track design. Given the locations of loadports and a pod from-to flow matrix, we determine the rectilinear layout of material flow systems with the objective of minimizing the total loaded travel distances. The optimal single-spine problem can be transformed to a known single-facility layout problem and solved with a linear-time algorithm. The optimal double-spine layout is obtained from the optimal single X-spine and Y-spine and is formulated as an allocation problem. We demonstrate the system designs by a numerical example. The resulting spine layouts are then compared with the Minimum Rectilinear Steiner Tree (MRST) and Shortest Rectilinear Flow Network (SRFN) layouts. MRST layout provides the shortest track length while the SRFN layout guarantees the shortest flow distances. The result shows that spine layout is a potential track layout pattern with respect to simplicity, track lengths and flow distances for overhead flow systems.

The reentrant flow type of the semiconductor wafer manufacturing process creates a large amount of overhead material flows in the interbay system. This paper proposes unidirectional circular layout for overhead multi-carrier systems. The layout configuration can potentially reduce the control complexity of heavy traffic flow, streamline the empty carrier supply, and meet the delivery requirements. The layout contains a central loop to reach every stocker at high speed and supply empty carriers, provide prompt delivery service to each loop addition in a dynamic and responsive manner. It is preferred to other track architectures, as minimal traffic control is required for the large amount of wafer flows in semiconductor fabs. The proposed construction procedure proceeds in two stages. In the first stage, four quantitative measures are provided to select good candidates of main loop layouts in order to minimize the total flow times distances, construction costs and service response time. Once the main loop i...