This technology is software containing an algorithm used for computerized scheduling in wafer fabrication plants that manufacture multiple products. It efficiently schedules the wafer lots and reduces the mean cycle time as well as its variance. This is done by more efficient prioritization of competing lots for processing by available tools at workstations.
How It Works
One of the common methods of mass production used in the semiconductor industry is a process called re-entrant line processing. In this method, each incomplete product, in the form of numerous wafers, is conveyed through a series of workstations while undergoing several cycles of cleaning, oxidation, deposition, metallization, etching, ion implantation, stripping, etc., before completion. At any particular time in the process, the buffers for the various workstations may contain many incomplete products in varying stages of completion, vying for the same finite resources. This new technology uses a new policy to generate a priority variable for each waiting lot. In addition, this method adapts itself to actual changes in production system performance. It does not require a model of the plant; rather, all it requires is the sequence of stations visited by various lot types.
Why It Is Better
This technology provides a scheduling method that can be used in multiple-product production or fabrication. It does not require fabrication plant modeling before application. Existing methods also are particularly sensitive to discrepancies between simulation models and actual systems and cannot be easily adapted to change. This new technology is more robust, stable, and adaptable via its use of a normalized slack policy method to determine the priority of each lot waiting the queue.