Study of poly-Si/TaSiN/Pt structure for stacked capacitors
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U1.6.1
Study of poly-Si/TaSiN/Pt structure for stacked capacitors F. Letendu, M.C. Hugon, O. Voldoire, B. Agius LPGP, Universite Paris sud, Orsay, France. I. Vickridge GPS, Universite Paris 6 et 7, Paris, France. C. Berthier, J. M. Lameille CEA Saclay, DEN/DPC/SCPA/LALES, Gif sur Yvette, France. ABSTRACT Due to its high oxidation resistance, TaSiN is a promising candidate as an electrically conductive barrier layer for integration of high permittivity oxides in advanced memory devices. In this work, we report on the properties of TaSiN thin films deposited by reactive magnetron sputtering of a TaSi2 target. We have mainly studied the influence of deposition pressure and power density on film properties (composition, density, resistivity). The oxidation resistance of TaSiN films has been investigated at typical conditions for crystallization of perovskite dielectrics. The as-deposited and annealed samples were characterized using Rutherford backscattering spectroscopy and nuclear reaction analysis for atomic composition and XPS for chemical bonding. To study oxidation resistance, films have been processed in 18O2. The concentration depth profiles of 18O was measured after thermal treatments via the narrow resonances of 18O(p,α)15N at 151 keV (fwhm=100eV). The different results suggest that a pressure of 0.5 Pa, a power density of 2.63W/cm2 and a gas flow ratio N2/Ar of 5% allow to perform TaSiN films with high density, low resistivity and good oxidation resistance. INTRODUCTION The use of high dielectric constant oxides in high-density memory devices (Dynamic Random Access Memory (DRAM) and Ferroelectric Random Access Memory (FRAM)) requires the presence of a diffusion barrier between the capacitor's bottom electrode layer and the poly-Si plug. This barrier must prevent electrode/plug interactions such as plug oxidation - due to the out diffusion of oxygen from the oxide dielectric layer - and must remain conductive after annealing [1]. RuTiN [2], IrAl-Ni [3], IrSiN [4], TiN, TiAlN [5], TaN, TaSiN [6-8] have all been proposed as oxygen diffusion barriers. Amorphous TaSiN alloy films are of great interest for both O and Cu diffusion barrier properties. These films have been extensively studied for the diffusion barrier application in Cu interconnection. They have shown good barrier properties against Cu diffusion due to their lack of fast diffusion paths and high crystallization temperature. But their diffusion barrier properties for oxygen have only been reported in a few papers [1]. In this work, we study the influence of deposition parameters on the properties of TaSiN thin films deposited by reactive magnetron sputtering of a TaSi2 target, in particular with regard to their ability to act as oxygen diffusion barriers in stacked ferroelectric capacitors. EXPERIMENTAL PROCEDURE TaSiN films, with thickness ranging from 80 to 120 nm, were deposited without additional heating by reactive rf magnetron sputtering using a TaSi2 target (dsubstrate-target=7cm).
U1.6.2
Thin film properties were studied as a function of r
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