Analysis of thin high-k and silicide films by means of heavy ion time-of-flight forward-scattering spectrometry

The use of forward scattered heavy incident ions in combination with a time-of-flight-energy telescope provides a powerful tool for the analysis of very thin (5-30 nm) films. This is because of greater stopping powers and better detector energy resolution for heavier ions than in conventional He-RBS. Because of the forward scattering angle, the sensitivity is greatly enhanced, thus reducing the ion beam induced desorption during the analysis of very thin films. The drawback of forward scattering angle is the limited mass separation for target elements. We demonstrate the performance of the technique with the analysis of 25 nm thick NiSi films and atomic layer deposited 6 nm thick HfxSiyOz films on silicon using 3-8 MeV 16O ions as projectiles. In these measurements, a depth resolution of 2 nm was obtained at the surface, while deeper in the film the resolution was limited by multiple scattering. A full composition with detailed impurity analysis can be obtained by combining time-of-flight forward-scattering spectrometry (TOF-FS) and low energy TOF-ERDA measurements.