Wafer Scheduling Algorithms –  Decision On The Fly with Dynamic Input Parameters

In a previous SUSS report (V2 11/2014) the basic scheduling algorithms used in automated SUSS coating and developing tools were introduced. The different strengths and drawbacks of fixed sequential handling and dynamic handling, at SUSS MicroTec named cyclic mode and decision on the fly (DOF) mode, respectively, were discussed. While the cyclic scheduling mode ensures constant handling conditions over a process sequence, it is not optimized to run different process sequences in parallel. In addition, it cannot adapt to changing conditions in a tool. The DOF mode is by its different approach always reacting to the current situation, which makes it the preferred scheduling mode when adapting to varying tool conditions. In this article, further improvements and optimizations to the DOF mode are presented and discussed. In particular, predictive measures are added to the scheduling algorithm to adapt to varying input conditions. This especially addresses e.g. overbaking issues in hotplates if manual parameters are not set correctly.