Depth Profile Analysis of Ultrathin Silicon Oxynitride Films by ToF‐SIMS

Abstract

A new method to depth profile N and O concentrations through sub‐30 Å silicon oxynitride films by time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) is examined. Using secondary matrix ions to cationize neutral molecular and elemental species, quantitative N and O concentration (concn) data are obtained through sub‐30 Å films with N concns of 12 atom % or less. Concentration depth profiles through 10 Å thick silicon oxide films are achieved. Isobaric mass interference with the peak at unit atomic mass resolution elevates the N background concn to 0.25 atom % at a 5 Å depth. At higher mass resolution (m/Δm = 5,500 full width at half‐maximum), the N background is less than 0.1 atom % at 1 Å, achieving a baseline level of 0.015 atom % after 10 Å. Using a reference sample, variation in O and N depths and concentrations over several months is less than 2% relative standard deviation. © 2000 The Electrochemical Society. All rights reserved.