Characterization of embedded phase shift masks by reflectance-transmittance measurement
Cui Z., Prewett PD.
A simple and inexpensive method has been applied to the determination of transmission and phase shifting of fully embedded phase shift masks. The method is based on the measurement of reflectance and transmittance (R-T) of the embedded layer. A 3-mirror reflection system has been developed to carry out the R-T measurement and a computer program has been written to calculate the real and imaginary components of refractive index (n, k), and hence the phase shifting and attenuating properties, of an embedded layer. The effectiveness and accuracy of the R-T method has been confirmed by experiment.