Arbitrary 3D linewidth form measurement simulations for the next-generation semiconductor circuits by scatterometry using the FDTD method

This paper shows basic numerical data for measuring the double periodic linewidths in the complicated LSI circuits using lightwaves. The double periodic areas, containing contact holes, memory arrays, and the mazy and arbitrary line structures are hard to analyze by the RCWA(rigorous coupled wave analysis). Therefore we analyze them using the finite-difference time-domain (FDTD) method. The 3D FDTD analysis is explained in this paper. The reflected electromagnetic waves in the near fields are obtained by the vertical plane wave incidences. The far field solutions are calculated using the numerical integration of the near field currents and the magnetic currents. Then, the scatterometry characteristics can be calculated as a far field by superimposing the scattering electromagnetic fields in a periodic reference surface (a square or rectangular region). Finally, we confirm the FDTD analysis is effective to obtain the reflected light characteristics close to the complicated real photolithographic models.