Monitoring and control of semiconductor manufacturing processes

Concerns optical measurement techniques for semiconductor manufacturing process monitoring and control. They can provide previously impossible real-time monitoring of several process variables, in-situ or ex-situ. This further enables the applications of more sophisticated real-time control algorithms, other than SPC. The SPC-based run-to-run (RtR) control, on the other hand, is still an instrumental part of the control algorithm, whenever there is a lack of real-time sensors for measuring critical process metrics. An emerging practice is to integrate RtR with the real-time control design to provide a comprehensive control design algorithm for semiconductor manufacture. The continued trend of semiconductor industry is toward an bigger wafers and smaller devices. This requires more integrated supervisory control, able to provide even tighter control, especially for photolithography, CVD, and etch processes. A unified framework needs to be established, at least for these critical processes, to facilitate and expedite systematic control design and development. In addition, as more sophisticated algorithms are being implemented, the control-related software and hardware should be user-friendly so that it can be operated by nonexpert personnel. Finally, since chip manufacturing consists of various processes, a comprehensive control algorithm on a factory-wide basis should utilize information (process-state, wafer-state, and tool-state data) from the current process as well as upstream and downstream processes.