Correlation of angle-resolved light scattering with the microfacet orientation of rough silicon surfaces

Abstract

The angle-resolved light scattering of several microrough silicon surfaces was measured with a laser reflectometer and presented in terms of the bidirectional reflectance distribution function (BRDF). The BRDF shows strong anisotropy and prominent subsidiary peaks for some surfaces, while it is nearly isotropic with a dominant peak for other surfaces. Similar characteristics can be observed in the microfacet orientation by analyzing the atomic force microscope (AFM) topographic data in the form of the two-dimensional (2-D) slope distribution function. A correlation has been constructed between the BRDF and the 2-D slope distribution. The salient features in the BRDF and the 2-D slope distribution are attributed to the modification of the surface of microfacets during chemical etching. This work shows that the angle-resolved light scattering measurements and the AFM topography measurement complement each other and provide important information about the microfacet orientation resulting from the wafer processing. The procedures described here can be used to obtain the slope distribution for a variety of microrough surfaces. This work will help the advancement of metrology in semiconductor wafer manufacturing.