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Étude et développement de procédés de gravure plasma pour l'élaboration des grilles métalliques pour les filières technologiques CMOS : Cas de l'empilement Si/TiN/HfO2

Abstract : As the dimensions of CMOS transistors shrink, parasitic effects become more significant and the
electrical device properties are perturbated. Silicon and silicon oxide materials are no more suitable for the gate module, and it is expected that metals and high-k dielectric will replace them soon. This work focuses on plasma etching of metal gate polysilicon/TiN/HfO2 for their integration in 45 nm
and 32 nm technology nodes.
Halogen-based plasmas and plasma-surface interactions have been analyzed by mass spectrometry, Xray photoelectron spectroscopy and morphological characterization techniques (SEM, TEM, AFM). This allowed to understand the TiN etching mechanisms and to develop metal gate stack etching
processes.
It is shown that TiN etching in HBr plasma is selective towards HfO2 but leads to tapered profiles, whereas TiN etching in Cl2 plasma is more isotropic and leads to roughness formation (due to micromasking) and thus selectivity issues. Hence anisotropic and selective etching of TiN must be achieved in HB/Cl2 mixture at low RF bias power.
Furthermore when etching a polySi/metal gate stack, the silicon etching process must be rethought because the introduction of a metal layer modifies the charges distribution on etch stop layer, which results in damaged silicon etched profiles. In addition TiN etch process must respect the integrity of silicon gate sidewalls. This work shows that notching of silicon at the Si/TiN interface during TiN etching is an issue that can only be overcome by controlling the passivation layers formed on the silicon gate sidewalls and the reactor walls conditions. As a matter of fact, the chemical nature of the coatings formed on the reactor walls controls the density of Cl and Br atoms in the plasma and thus its notching capability. It is thus particularly important to control the reactor wall conditions for metal gate etching applications.
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Contributor : Anne Le Gouil <>
Submitted on : Monday, May 14, 2007 - 10:55:02 PM
Last modification on : Tuesday, February 16, 2021 - 3:33:32 AM
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A. Le Gouil. Étude et développement de procédés de gravure plasma pour l'élaboration des grilles métalliques pour les filières technologiques CMOS : Cas de l'empilement Si/TiN/HfO2. Micro et nanotechnologies/Microélectronique. Université Joseph-Fourier - Grenoble I, 2006. Français. ⟨tel-00146376⟩

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