PHASE-STEPPING MICROSCOPY FOR LAYER THICKNESS MEASUREMENT IN SILICON-ON-INSULATOR STRUCTURES

The thickness of the top Si and buried SiO2 layers from Silicon-On-Ins ulator structures obtained by ion implantation are measured by Phase S tepping Microscopy (PSM). The strong difference in optical transmissio n between the Si and SiO2 layers gives different interference patterns , and allows the measurement of the thickness of both layers from the PSM image of small angle bevelled surfaces. Unlike previously reported optical techniques, where assumptions on the values of the optical co nstants of the layers have to be made, no theoretical simulation is ne eded. Fairly good agreement was found between the experimental and cal culated data. (C) 1997 Elsevier Science S.A.