Ptychographical Iterative Engine Profilometry (PIEP) for Wafer Surface Profile Measurement

The surface profiles of wafers affect the performance of produced integrated circuit devices. Problems arising during wafer manufacturing, including imperfections in surface flatness, step height variations, curvature, warping, and surface defects, directly compromise the quality of subsequent chip manufacturing processes. Point-scanning methods, such as step profiler, confocal microscope, atomic force microscope (AFM), and scanning electron microscope (SEM), offer high accuracy in measuring wafer surface profiles but are often limited by slow measurement speeds. Interferometry achieves wavelength-scale accuracy and operates at fast speeds, yet it necessitates an expensive, large reference plate comparable in size to the wafer. To address these issues, we developed the Ptychographical Iterative Engine Profilometry (PIEP), which attains wavelength-scale accuracy without relying on costly optical components or devices. The experimental results demonstrated that PIEP was effective in profiling the surface of 4-inch wafers. We anticipate that PIEP is a promising tool for inspection in wafer manufacturing.