Simulation modeling and visualization of start-up transient processes of dual-arm cluster tools with wafer revisiting

The trends of increasing wafer diameter and smaller lot sizes from 25 wafers to a few wafers have led to more transient periods in wafer fabrication, thereby requiring more research on the optimal execution of transient processes. For some wafer fabrication processes, such as atomic layer deposition (ALD), wafers need to visit some process modules for a number of times, instead of once, thus leading to a so-called revisiting process. Research on transient processes of dual-arm cluster tools with wafer revisit processes becomes urgently needed for high-performance wafer fabrication. A cluster tool has no buffer except its robot, which makes its scheduling difficult. Thus, in order to study a cluster tool with revisiting process, a simulation system is helpful. This work develops a simulation model and system for a dual-arm cluster tool with a wafer revisit by using eM-Plant as a simulation platform. The resultant simulation system can be used for analysis and optimization of transient processes. An illustrative example is given to show its applications.