Simultaneous thickness and surface profiling of blank mask and its experimental verification using robust harmonic fringe-iterative algorithm and Fizeau interferometer

Abstract

The quality of blank masks should be assessed with nano-scale accuracy to achieve the efficiency improvement of semiconductor devices. In this study, we proposed a harmonic fringe-iterative method that uses seven-frame interferograms for simultaneous thickness and surface assessment of blank masks. The incorporation of the noble convergence formula and pixel array into the proposed method was found to eliminate harmonics-related errors and significantly increase the computational ability. For verification, the numerical simulation and simultaneous assessment of a blank mask using a multi-surface Fizeau interferometer with wavelength scanning were performed using a seven-frame harmonic fringe-iterative method. The results of the simulations and experiments verify that the harmonic fringe-iterative method has a better phase-extraction ability than the conventional fringe-iterative and Fourier window methods in terms of computational ability and suppression of non-target harmonic signals and nonlinearity of phase-modulation errors.