CD-SEM distortion quantification for EPE metrology and contour analysis

Given the potential impact of distortions within the Field Of View (FOV) of the SEM, we need a method to quantify and describe them. We will show a method to find the magnitude and directions of the distortions. This description will enable assessment of impact on local distance measurements like edge placement errors (EPE) analysis and contour measurements. Knowing the distortions with sufficient resolution and stability can also enable corrections for this phenomenon. We will show that applying this correction in post processing, we can bring back the absolute measurement error from 1.5 nm to 0.3 nm.