Thin-film metrology of silicon-on-insulator materials

摘要

Spectroscopic rotating-analyzer ellipsometry employing a compensator was used to measure the ellipsometric angles and depolarization from 0.73 to 5.4 eV of commercial separation by implantation of oxygen wafers. The data were analyzed to find the thicknesses of the native oxide cap, the top Si layer, and the buried oxide (BOX). From the depolarization in the spectral region of interference fringes, we determine layer thickness nonuniformities. Although a reasonable agreement between the data can be found by describing the BOX with the optical constants of thermal oxide, it can be improved by modeling the BOX as an effective medium consisting of thermal oxide and amorphous Si. The physical justification for this model is the presence of Si islands near the BOX/substrate interface. We compare our ellipsometry results with a destructive analysis using electron microscopy and secondary ion mass spectrometry.