Digital image correlation of SEM images for surface deformation of CMOS IC

Abstract

In this study, 0.18 um pitch processed CMOS ICs with multiple thin film layers manufactured by United Microelectronics Corporation were used for the measurement of the surface deformation from the Scanning Electron Microscopy (SEM) images and Digital Image Correlation (DIC). The features of the natural surface were directly used for image correlation. Drift distortion and noises which arise from rasterizing, and the time-dependent nature of SEM image capturing and electromagnetic lenses was considered. A series of translation tests with various magnifications were made. Two SEM images of the sample, one each for before and after translation, were processed to extract the surface displacement from tiny changes in the SEM images of a thin film using DIC. Test results obtained from various sizes of the sub-image, noise filtering process, and the correlation approach were compared. A proper scheme was established for calibration and for obtaining a more accurate result of surface deformation of the CMOS ICs.