Thermal Stability of Ru Gate Electrode on HfSiO Dielectric
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0917-E05-02
Thermal Stability of Ru Gate Electrode on HfSiO Dielectric Karol Frohlich1, Juan Pedro Espinos2, Andrej Vincze3, Milan Tapajna1,4, and Kristina Husekova1 1 Institute of Electrical Engineering, SAS, Dubravska 9, Bratislava, Slovakia, 841 04, Slovakia 2 Instituto de Ciencia de Materiales de Sevilla, CSIC, Avda. Americo Vespucio, Sevilla, Spain, 410 92, Spain 3 International Laser Centre, Ilkovicova 3, Bratislava, Slovakia, 812 19, Slovakia 4 Department of Microelectronics, Slovak University of Technology, Ilkovicova 3, Bratislava, Slovakia, 812 19, Slovakia
ABSTRACT We have investigated advanced metal-oxide-semiconductor (MOS) structures containing Ru gate electrode, HfxSi1-xOy dielectric film and Si substrate. The Ru gate electrode was grown by atomic layer deposition at 290 oC. The MOS structures were annealed for 30 min in forming gas and nitrogen at temperatures up to 550 oC. Capacitance-voltage measurements showed important shift of the flat band voltage of the Ru/ HfxSi1-xOy/Si gate stack after treatment at 550 oC. X-ray photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS), reflection electron energy loss spectroscopy (REELS) and secondary ion mass spectroscopy (SIMS) were used to analyze interface between ruthenium and high-κ dielectric film. Based on the analysis we were able to build up energy-band alignement for the Ru/ HfxSi1xOy interface. We observed that the energy-band structure of the Ru/HfxSi1-xOy interface remains stable upon annealing in forming gas up to 550 oC. Presence of hydrogen revealed by SIMS can account for compensation of negative charges in HfxSi1-xOy during thermal treatment.
INTRODUCTION Ruthenium is promising gate electrode material for advanced pMOSFET applications. It exhibits high work-function value, low resistivity and good stability on various high-κ dielectric films. Unfortunately, there is important spread of effective work function values for the Ru gate electrode in the literature, ranging from 4.55 to 5.3 eV [1-4]. The effective metal work function value can be modified during thermal treatment of metal-oxide-semiconductor structure. The electrode material can react during heat treatment with the underlying dielectric film, giving rise to an interface layer. The presence of the interface layer can subsequently modify the work function. Metal work function on high-κ dielectric can also differ appreciably from their values on SiO2 or in vacuum due to pinning of the Fermi level [5]. In this paper we investigated stability of the Ru gate electrode on high-κ HfxSi1-xOy dielectric film. The Ru/HfxSi1-xOy/Si structures were annealed in forming gas and nitrogen at temperatures up to 550 oC. We analysed Ru/HfxSi1-xOy interface using capacitance-voltage measurements, (C-V), X-ray photoelectron spectroscopy, (XPS), ultraviolet photoelectron
spectroscopy, (UPS), reflection electron energy spectroscopy, (REELS) and by means of secondary ion mass spectroscopy, (SIMS). EXPERIMENTAL The HfxSi1-xOy layers were grown by a MOCVD based technique - AVD®
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