UV Activated Surface Preparation of Silicon for High-k Dielectric Deposition

Casey C. Finstad; Anthony J. Muscat

doi:10.4028/www.scientific.net/SSP.103-104.7

Paper Titles

Preface, Committees

High-k Gate Dielectrics on Silicon and Germanium: Impact of Surface Preparation
p.3

UV Activated Surface Preparation of Silicon for High-k Dielectric Deposition
p.7

Enhanced Surface Preparation Techniques for the Si/High-k Interface
p.11

Uniform Ultrathin Oxide Growth for High-k Preclean
p.15

On the Application of a Thin Ozone Based Wet Chemical Oxide as an Interface for ALD High-k Deposition
p.19

Interface State Densities and Surface Charge on Wet-Chemically Prepared Si(100) Surfaces
p.23

A Study of the Influence of Typical Wet Chemical Treatments on the Germanium Wafer Surface
p.27

Surface Preparation Techniques for High-k Deposition on Ge Substrates
p.31

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UV Activated Surface Preparation of Silicon for High-k Dielectric Deposition

Abstract:

High-k gate materials, such as HfO2, are unstable on silicon and form low permittivity interfacial oxides when heated. A single layer of silicon nitride grown prior to gate dielectric deposition could serve as a diffusion barrier to prevent oxide formation. A monolayer film of surface amine groups will be chemically similar to surface hydroxyl groups, and could also serve as a seed layer to promote the nucleation of a high-k film. The deposition of amines (≡Si-NH2 or ≡Si-NH-Si≡) on chlorine and hydrogen terminated Si(100) at low temperature (<100°C) was investigated using x-ray photoelectron spectroscopy (XPS). UV-Cl2 exposures (0.1-10 Torr Cl2 at 25-150°C, 10-600 s, 1000 W Xe lamp) were used to terminate Si(100) with Cl atoms. Exposure to NH3 (0.1-1000 Torr, 75°C, 5-60 min) replaced Cl atoms with up to 0.3 ML of amine groups, as measured by XPS. Cl atoms served as reactive leaving groups, lowering the overall activation energy barrier for nitridation. Alternatively, UV photons with energy greater than 5.7 eV were used to photodissociate NH3 molecules, yielding NH2 photofragments that reacted with the H-terminated Si(100) surface. At a UV photon flux of 19 mW/cm2, the N coverage increased with time and saturated at ~1 ML. Significant oxygen was observed on the surface due to H2O contamination in the source gas.