PROCESS-CONTROL SYSTEM FOR VLSI FABRICATION

A modular framework for the implementation of process control in VLSI fabrication is described. The system integrates existing approaches to process control with new methodologies in order to achieve on-line optimization and control of unit processes with consideration of preceding and following process steps. The process control system is based on three core modules. The flexible recipe generator determines an initial operating point in response to a new product design. The run by run controller tunes the recipe between runs based on feedback from post-process and in situ measurements. The real time controller further modifies the equipment settings during a process step based on in situ measurements. The algorithmic bases of these modules are described. The flexible recipe generator was used to optimize the LPCVD of polysilicon. The run by run controller was used to locally optimize and control a simulation of the LPCVD of polysilicon.