Silicon nitride/silicon oxynitrid/silicon dioxide thin film multilayer characterized by variable angle spectroscopic ellipsometry

Authors

Yi-Ming Xiong, University of Nebraska-Lincoln
Paul G. Snyder, University of Nebraska-LincolnFollow
John A. Woollam, University of Nebraska-LincolnFollow

Document Type

Article

Date of this Version

7-1-1992

Comments

Published in J. Vac. Sci. Technol. A 10(4), Jul/Aug 1992. Copyright 1992 American Vacuum Society. Used by permission.

Abstract

Variable angle spectroscopic ellipsometry (VASE) was used to nondestructively characterize a silicon nitride (Si₃N₄)/silicon oxynitride (SiO_xN_y)/silicon dioxide (SiO₂) thin film multilayer structure, in which Si₃N₃ and SiO_xN_y layers were deposited by plasma enhanced chemical vapor deposition and low-pressure chemical vapor deposition, respectively. The measured VASE spectra (3500-8200 Å) were analyzed with an appropriate multilayer fitting model, in which the SiO_xN_y layer was modeled. in the Bruggeman effective medium approximation (EMA), to be a physical mixture of two distinct phases, SiO₂ and Si₃N₄. Remarkably good agreement between the measured spectra and the model calculations was obtained, indicating that the EMA and the fitting model were appropriate for the data analysis. As a result, the three layer thicknesses, compositions, and the optical constants of SiO_xN_y layer at several spots across the sample were determined. The thickness values obtained by VASE were in very good agreement with those measured by cross-sectional transmission electron microscopy.