Comparative study of surface roughness measured on polysilicon using spectroscopic ellipsometry and atomic force microscopy

Abstract

Polysilicon layers prepared by low-pressure chemical vapor deposition at 560°C, 620°C, 660°C, and 700°C were measured by Atomic Force Microscopy (AFM) and Spectroscopic Ellipsometry (SE). Morphology, cross-sectional profile, roughness spectral density, and roughness of the surfaces were investigated by AFM using window sizes of 1×1 μm 2, 10×10 μm 2, and 50×50 μm 2. The layer structure and the surface roughness were determined by SE using the Bruggemann-Effective Medium Approximation (B-EMA). The Root Mean Square (RMS) and mean square ( R a) roughness values measured by AFM were compared to the thickness of the top layer of the SE model describing the surface roughness. Although AFM results depend on the used window size, good correlation was found between the roughness values determined by AFM and SE for each window sizes. The results show that SE calibrated with AFM could be used for quantitative surface roughness determination.