Tutorial on Applying the VM Technology for TFT-LCD Manufacturing

In the high-tech industries, on-line quality monitoring on each workpiece under processing is required to ensure process stability and improve yield rate. However, conducting workpiece-by-workpiece actual metrology is very expensive and time-consuming. In this case, a novel idea is to use “virtual metrology” (VM) that conjectures workpiece quality based on process data collected from production equipment with a slight supplement of actual metrology data. The purpose of this tutorial paper is to select the thin film transistor-liquid crystal display (TFT-LCD) manufacturing processes as the illustrative examples for demonstrating the methodology of fab-wide implementation of the VM technology systematically. To begin with, a survey of VM-related literature is performed. Then, the features of an effective and refined VM system are presented with the automatic VM (AVM) system developed by the authors as a case study, followed by introduction of the TFT-LCD production tools and manufacturing processes. After that, the generic deployment schemes of the VM technology for the TFT-LCD tools are proposed. Finally, illustrative examples with the AVM system as a case study are presented to show how the VM technology applies to TFT-LCD manufacturing.