Electron-beam direct writing system employing character projection exposure with production dispatching rule

摘要

An electron-beam direct writing (EBDW) system with a character projection (CP) aperture is a promising candidate as an effective maskless lithography tool to realize a system on a chip fabrication process at low cost with quick turn-around time. We have proposed an approach to enhance the throughput of an EBDW system by using a production dispatching rule. Through an event-driven simulation analysis in the backend of the line, the effect of production dispatching rules on the throughput and the cost in an EBDW system is evaluated. We considered four kinds of dispatching rules, FIFO, APA, LWKR, and SLACK. FIFO is a usually used dispatching rule and gives the highest priority to the waiting lot that came in first at the EB lithography process. In APA, the highest priority is given to the waiting lot that does not require the CP aperture exchange. In LWKR, the highest priority is given to the waiting lot associated with the job having the least amount of total processing time remaining to be done. In SLACK, the highest priority is given to the waiting lot with the shortest slack. Simulated result shows that the EBDW system with APA enhances the throughput more than 1.2 times as compared to that with FIFO, LWKR, or SLACK, and has a throughput of 5 wafers/h or more. Furthermore, compared with the cost per chip for FIFO, the APA rule reduces the cost/chip by more than 30% at the cost minimum lot arrival rate point.