Orthogonal Spatial Material Flow structures with application to 300mm semiconductor fab automation

To achieve higher utilization of production floor, reduce traffic congestion, and improve travel time efficiency and layout flexibility, material handling system is extended to move loads through every spatial paths to perform factory-wide handling tasks. We designate this material flow structure the Orthogonal Spatial Material Flow (OSMF) structure. Instead of planar (2-D) moves, OSMF structure outlines a three-dimensional material flow network with feasible orthogonal paths between the spatial points which may be spread over factory floor, ceiling, overhead, underground, or multifloor spaces. The OSMF paths can possess multiple flow layers that are laid in the space virtually or physically, vertically or horizontally, disjointedly or connectedly. The OSMF problem is studied within the context of automated wafer handling systems in semiconductor fabs. As all the goals are set on 300mm. or larger wafer manufacturing for the 21st century, fab automation becomes the current trend in semiconductor fabrication facilities due to the heavy wafer pod (16–20 lbs) and the large flow times distances (360 miles per day). In this dissertation, a two-layer single-floor OSMF structure is adapted to existing fab layouts. Our approach to the OSMF problem confronts the issues of flow path design and transport service level. We focus on the following developments: (1) overhead interbay track layout design by constructing circular layout for multi-carrier heavy traffic system in interbay zones, (2) overhead intrabay track layout design by developing optimal single and double spine layouts, and (3) mixed model fleet sizing capacity model by M/G/1 queue with server vacations. To our knowledge, this is the first study of OSMF analysis of material handling systems. The study aims at the development of a generic design framework for OSMF systems and to assist planar material flow systems to expand to OSMF analysis. We demonstrate the static analysis procedures by generating a two-layer mixed model system for semiconductor fabs. The procedures introduced are efficient, requiring only minor computation time, and are applicable to many real-world scenarios. The problem is significant in that, with an OSMF system all the movement activities in the shop floor can be done with less space, cost, and time