Excursion detection and source isolation in defect inspection and classification [VLSI manufacture]

In-line monitoring of defects in VLSI manufacturing has become an indispensable tool in SPC (Statistical Process Control) and Yield Management. Wafer inspection for defects has two stages: optical wafer scanning to detect the presence of defects; and review/classification performed at the coordinates of the scanned defect to determine the defect type (for instance, shorts or opens). Typically, fabs use standard control charts, based on total defect count monitoring. However, many fabs have found this aggregate tracking of defects to be inadequate for efficient excursion or drift detection. In this paper, we demonstrate how defect type information can be utilized to optimize the excursion detection procedure. In addition, we also demonstrate how the defect type information can be useful for source identification