Optimization of UHV-CVD Thin Films for Gate Dielectric Applications

Abstract

In-situ and ex-situ spectroscopic ellipsometry (SE), atomic force microscopy (AFM), transmission electron microscopy (TEM), and time of flight medium energy backscattering (ToF MEBS), are used to investigate the properties of 30 and 60 Å ZrO2 films deposited at different temperatures on hydrogen terminated silicon (H-Si) and native silicon oxide surfaces. Results show that the initial-stage deposition of ZrO2 on H-Si and native silicon oxide surfaces are different. A 3-dimesional (3D) type nucleation process of ZrO2 on H-Si leads to high surface roughness films, while layer-by-layer deposition on native silicon oxide surfaces leads to smooth, uniform ZrO2 films. An interfacial layer, between the substrate and the metal oxide, is formed through two independent mechanisms: reaction between the starting surfaces and ZTB or its decomposition intermediates, and diffusion of reactive oxidants through the forming ZrO2 interfacial stack layer to react with the substrate.