Implementation And Application Of Rigorous Coupled-Wave Analysis In Optical Scatterometry

The optical critical dimension (OCD) metrology, also called scatterometry, is one ofthe well-known optical techniques that has gained considerable interest in the industrialenvironment because it is fast, noncontact, nondestructive, and of low-cost, compared toother techniques. Currently, the rigorous coupled-wave analysis (RCWA) method has beenwidely used in OCD metrology for the optical modeling of periodic structures. This thesisinvestigates the implementation of RCWA, as well as its application in OCD metrology.The principle and implementation of RCWA is introduced for one-dimensional andtwo-dimensional periodic structures. In order to evaluate the validity and modelingaccuracy, the comparison between home-made RCWA program and commercial software,i.e. GSolver and RSoft, has been carried out.Performances of RCWA, such as stability, convergence, computational efficiency andaccuracy, are studied through simulations. The convergence order associated with thestructural and optical parameters has been estimated. The results indicate that theconvergence order is linear with the period of the sample when fixing the other parameters,both for planar diffraction and conical diffraction. With further investigations concentratedon the ratio of illuminated wavelength to period, it is discovered that the convergenceorder decreases with the growth of the ratio, and when the ratio is fixed, convergenceorder jumps slightly, especially in a specific range of wavelength. This characteristic couldbe applied to estimate the optimum convergence order of given samples to obtain highcomputational efficiency.The applications of RCWA in reflectometry, ellipsometry and Mueller matrixpolarimetry are illustrated, based on the calculation of reflectivity, ellipsometricparameters, and Mueller matrix elements from the normalized amplitudes of reflectedwave. By varying each structural parameter and overlay, respectively, the sensitivities ofthose simulations can be observed qualitatively, which demonstrates the feasibility ofextensive applications of RCWA in optical scatterometry.