Arrangement and method for calibrating optical line shortening measurements

摘要

A semiconductor fabrication process permits for narrowing linewidths using Optical End of Line Metrology (OELM). OELM involves measuring relative line shortening effects that are inherent in many semiconductor fabrication processes using optical overlay instruments. According to one embodiment, the process involves a frame that has two adjacent sides which are constructed of lines and spaces. The frame is imaged onto a wafer, but the optical line measurements used to implement the frame over-predict actual shortening of the lines. To calibrate the optical line measurements to the physical implementation, corrections are determined to relate the optical measurements to the actual line shortening: a relationship between the narrow linewidth elements of varying line lengths using a representation and the narrow linewidth elements in a physical implementation of the representation, a pitch effect for the narrow linewidth elements when using the alignment tool, and a duty cycle effect reflecting the impact of the line-size/spacing of the lines in the grating. A processor then calibrates the optical aligning tool as a function of these factors.