Stability of Nitrogen and Hydrogen in High-k Dielectrics
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Stability of Nitrogen and Hydrogen in High-k Dielectrics K.P. Bastos, R.P. Pezzi, L. Miotti, G.V. Soares, C. Driemeier, J. Morais and I.J.R. Baumvol1 Instituto de Física - UFRGS, CP 15051 Porto Alegre 91501-970, Brazil 1 Centro de Ciencias Exatas e Tecnologicas - UCS Av. Francisco G. Vargas 1130, 95070-560 Caxias do Sul, Brazil
ABSTRACT We report here on atomic transport, thermal stability, and chemical evolution of HfSiO, HfSiN, and AlON films on Si(001), aiming at investigating the atomic scale behaviour of the involved chemical species, N and H in particular, when the films are submitted to usual thermal processing steps in inert and oxidizing atmospheres. The films were characterized by nuclear reaction analyses in resonant and non-resonant regions of the cross-section curves, X-ray photoelectron spectroscopy, and low energy ion scattering. The HfSiN/Si structure was shown to be more resistant to oxygen diffusion than HfSiO/Si, although the amounts of O incorporated in HfSiN/Si are larger than in HfSiO/Si. The main channel of oxygen incorporation is atomic exchange with nitrogen or oxygen atoms. HfSiN film on Si incorporate more hydrogen (or deuterium) and in more stable configurations than HfSiO/Si. Nitrogen incorporation into AlON films on Si renders this structure more stable against thermal annealing in vacuum and/or oxidizing atmospheres than Al2O3/Si. INTRODUCTION The implementation of high-k materials as gate dielectrics in the coming CMOS technology generations is currently a subject of intensive research. Replacement of the well studied and controlled silicon oxide or oxynitride ultrathin layers by alternative materials having a much higher dielectric constant became eminent owing to the exponential increase of the gate current with the thinning of the gate dielectric [1,2]. There are however several challenges to be faced before high-k materials can be incorporated in the MOSFET fabrication process flow. Among these challenges, it appears that introducing nitrogen into the so far considered metal oxides and silicates films on Si is mandatory, because the incorporation of N provides substantial improvement in many of the required electrical, structural, and thermodynamical stability characteristics [3]. Indeed, the nitridation of aluminum, zirconium, and hafnium oxide and silicate films, either during or after deposition by plasma or during thermal processing [4-7] was seen to: i) reduce boron and oxygen migration across the films toward the substrate, as well as migration of substrate Si atoms into the films; ii) inhibit the crystallization of the amorphous high-k films; and iii) reduce gate leakage current. Another important requirement is hydrogen (1H ) or deuterium (2H) passivation of the high-k/Si interface. The stability of incorporated 1H or 2H must also be controlled because it is determinant of device reliability [8,9]. We report here on the thermal stability of HfSiO, HfSiN, and AlON films deposited on Si(001) by different deposition methods aiming at understanding the role of nitroge
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