Combining HRTEM–EELS nano-analysis with capacitance–voltage measurements to evaluate high-j thin films deposited on Si and Ge as candidate for future gate dielectrics S. Schamm-Chardon a,⇑ , P.E. Coulon a , L. Lamagna b , C. Wiemer b , S. Baldovino b,c , M. Fanciulli b,c a CEMES-CNRS and Univ. de Toulouse, nMat group, BP 94347, 31055 Toulouse Cedex 4, France b Laboratorio MDM, IMM-CNR , via C. Olivetti 2, 20041 Agrate Brianza (MB), Italy c Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, Milano, Italy article info Article history: Available online 19 October 2010 Keywords: Dielectric constant Permittivity High-k dielectric stacks on Si and Ge La-doped ZrO2 Erdoped HfO2 Nanoanalytical electron microscopy Aberration corrected high resolution transmission electron microscopy (HRTEM) Electron energy loss spectroscopy (EELS) Capacitance-voltage measurements abstract Aberration corrected transmission electron microscopy and electron spectroscopy are combined with electrical measurements for the quantitative description of the structural, chemical and dielectric param- eters of rare earth/transition metal oxides thin films. Atomic structure near the interface and elemental profiles across the interface up to the surface of La-doped ZrO 2 and Er-doped HfO 2 films prepared by atomic layer deposition on Si(100) and Ge(100) are determined. Interfacial layers unavoidably form between the semiconductor substrate and the dielectric oxide after deposition and annealing. They are evidenced from a structural and chemical point of view. From the knowledge of the chemical extent of the interfacial layer and of the accumulation capacitance of the stack, it is possible to recover the dielec- tric constant of both the interfacial layer and the high-j oxide layer constituting the stack using a multi- layers capacitor model approach. Oxides with permittivities higher than 30 are stabilized. Interfacial lay- ers, silicate/germanate in composition, with permittivites, respectively, tripled/doubled compared to the one of SiO 2 are evidenced. Ó 2010 Elsevier B.V. All rights reserved. 1. Introduction Downscaling in microelectronics raises big challenges particu- larly concerning the choice of new materials and their integration in metal-oxide-semiconductor (MOS) structures for logic applica- tions [1]. Research is now focused on gate oxides and semiconduc- tor substrates with high permittivity (j) and high mobility, respectively. A lot of effort is devoted today to the engineering of the interface between the high-j oxide and the semiconductor substrate. An interfacial layer might form during deposition and transform due to post-annealing treatments. Associated to a low dielectric constant, this additional layer is detrimental for the total equivalent oxide thickness of the stack. Our purpose here is to pro- vide a way to describe at the nanometer level the structural and chemical states of each layer constituting the stack and also to try to estimate their dielectric contribution. Ternary compounds based on transition metal oxides (TM: HfO 2 , ZrO 2 ) doped with rare earth elements (RE: La, Er) are considered here. Indeed doping of transition metal oxides have been reported to stabilize metastable phases, cubic and tetragonal ones, with higher dielectric constant than the monoclinic polymorph [2–6]. Moreover, particularly for the case of the high-mobility semiconductor Ge, rare earth-based doping has also proved to be an efficient way of passivating inter- face defects [7–9]. In this work, we address the case of La-doped ZrO 2 (La–ZrO 2 ) and Er-doped HfO 2 (Er–HfO 2 ) films prepared by atomic layer deposition (ALD) on Si(100) and Ge(100). The atomic structure and the elemental profiles across the stacks are investigated at the nanometric level and the thickness of each layer constituting the stack measured. In parallel, the dielectric constant of the stack is determined by capacitance–voltage measurements. By introduc- ing these structural, chemical and dielectric parameters in a mul- tiple-layers capacitor model describing the succession of the layers in the stack, the dielectric constant of each layer is esti- mated and the values obtained discussed taking into account the elemental composition and the stabilized crystallographic phase [10]. 2. Experimental La–ZrO 2 and Er–HfO 2 films with variable precursors pulse ratio were grown in a Savannah 200 (Cambridge Nanotech Inc.) ALD reactor at 300 °C using ( i PrCp) 3 La(or Er), (MeCp) 2 Zr(or Hf)Me(OMe), 0167-9317/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.mee.2010.10.012 ⇑ Corresponding author. E-mail address: sylvie.schammchardon@cemes.fr (S. Schamm-Chardon). Microelectronic Engineering 88 (2011) 419–422 Contents lists available at ScienceDirect Microelectronic Engineering journal homepage: www.elsevier.com/locate/mee