Sensitivity of the silicon layer thickness in SOI process in the UV regime

Abstract

In measuring films deposited on SOI structures, it was found that both spectroscopic ellipsometer (SE) and reflectance data are insensitive to the Si and O thickness in the UV regime. This can be attributed to the high absorption of the silicon film in this wavelength range. In this regime, both reflectance and SE are sensitive only to layers above Si, and to the optical constants of the Si film. The full thickness information concerning the SOI structure itself is contained in the visible region of the spectrum. In the current work, several SOI structures, with and without surface oxide films, were analyzed and are discussed. The thickness of the layer above the silicon layer varied between 1.1 nm to 700 nm. These thicknesses were obtained by modeling the reflectance and ellipsometric data in the UV-regime.