Measuring Contact Hole Corner Rounding Uniformity Using Optical Scatterometry

Inhalt:
Uniformity distribution of the corner rounding radius of curvature is investigated using reflectance- and transmittancebased optical scatterometry. Arrays of square contact holes are measured at multiple locations on an ACI photomask using a broadband spectrophotometer capable of collecting polarized reflectance (Rs and Rp) and polarized transmittance (Ts and Tp) spectra in 190 – 1000 nm wavelength range in one-nanometer intervals. The measured spectra are analyzed using two-dimensional Rigorous Coupled-Wave Analysis algorithm (2D RCWA) in conjunction with the Forouhi-Bloomer dispersion relations for n and k. As a result of the analysis, the values of contact hole width and the radius of curvature associated with the corner rounding are determined at every measurement location. The measurements are presented as uniformity distribution maps and correlation plots, comparing the results with the values obtained using a conventional CD-SEM.