Surface profile detection with nanostructures using a Mueller matrix polarimeter

Abstract

Recently, the surface profiles of nanostructures have been reduced in size in order to develop microfabrication techniques, such as lithography and nanoimprinting. In particular, feature sizes of a few tens of nanometers are common in the semiconductor industry. This study uses a Mueller matrix polarimeter, which is based on a scatterometry technique, to evaluate the surface profiles of nanostructures. In this technique, a nanostructure profile is determined from the Mueller matrix which expresses all the polarization properties of the sample by experimental measurements and calculated values using rigorous coupled-wave analysis (RCWA). This technique is more useful than conventional scatterometry based on ellipsometry since it is able to determine the total polarization properties of a sample. This is because, the Mueller matrix is able to estimate the surface profile of a nanostructure to greater precision. The grating period of a Cr/Cr₂O₃ structure on a SiO₂ substrate was measured using a dual-rotating retarder polarimeter. The experimental results agree well with the values obtained by numerical analysis. We measured the characteristic of non-diagonal elements in the Mueller matrix by varying the incidence azimuth of the sample. We have demonstrated the possibility of evaluating a nanostructure profile from the Mueller matrix.