Developing an Automatic Virtual Metrology System

Virtual Metrology (VM) is a method to conjecture manufacturing quality of a process tool based on data sensed from the process tool and without physical metrology operations. VM has now been designated by the International SEMATECH Manufacturing Initiative and International Technology Roadmap for Semiconductors as one of the focus areas for the next-generation factory realization roadmap of the semiconductor industry. This paper defines the VM automation levels, proposes the concept of automatic virtual metrology (AVM), and develops an AVM system for automatic and fab-wide VM deployment. The example of automatic VM model refreshing for chemical vapor deposition (CVD) tools is also illustrated in this paper. The AVM system has been successfully deployed in a fifth-generation thin-film-transistor-liquid-crystal-display (TFT-LCD) factory in Chi Mei Optoelectronics (CMO), Taiwan.