The simulation analysis of the scatterfield microscopy for the critical dimensions measurement

Critical dimension measurement based on scatterometry is expected to be the key technology in current and future semiconductor manufacturing processes. Scatterometry has strong dependence on modeling. The paper compares the Integral Equation Solver and the Rigorous Coupled Waveguide Analysis (RCWA) technique from convergence, and chooses the RCWA method to simulate the critical dimension measurement. The paper introduces an angle resolved scatterometry technology constructed on microscope. The back focal plane of a bright field reflection microscope contains diffraction information about the sample, and positions in the back focal plane map to diffraction angles from the sample. With suitable control of the angle of the incident illumination, back focal plane imaging can provide information similar to that obtained from angle resolved scatterometry. The paper simulates the reflectance of the rectangular grating at a fixed wavelength (λ =532nm) versus angle of incidence, measured for both s polarization and p polarization. The silicon gratings are 10nm difference with line width, pitch, line height and sidewall angle. The simulations reveal that the p polarization light is more sensitive than the s polarization light to the changes of the grating size, and the scatterfield microscopy has nanometer level sensitivity to the line width variations.