Materials Science in Semiconductor Processing 7 (2004) 203–208 Ultrathin HfO 2 gate dielectrics on partially strain compensated SiGeC/Si heterostructure S.K. Ray a,Ã , R. Mahapatra a , S. Maikap b,1 , A. Dhar a , D. Bhattacharya c , Je-Hun Lee b a Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur 721 302, India b Center for Microstructure Science of Materials, School of Materials Science and Engineering, Seoul National University, Seoul 151-742, Republic of Korea c Materials Science Center, Indian Institute of Technology, Kharagpur 721 302, India Available online 12 October 2004 Abstract Ultrathin HfO 2 gate dielectrics have been deposited on strain-compensated Si 0.69 Ge 0.3 C 0.01 layers by rf magnetron sputtering. X-ray diffraction spectra show the films to be polycrystalline having both monoclinic and tetragonal phases. The formation of an interfacial layer has been observed by high-resolution transmission electron microscopy. Secondary ion mass spectroscopy and Auger electron spectroscopy analyses show the formation of an amorphous Hf- silicate interfacial layer between the deposited oxide and SiGeC films. The average concentration of Ge at the interfacial layer is found to be 2–3 at%. The leakage current density of HfO 2 gate dielectrics is found to be several orders of magnitude lower than that reported for thermal SiO 2 with the same equivalent thickness. r 2004 Elsevier Ltd. All rights reserved. Keywords: H f O 2 ; SiGeC; High-k oxide 1. Introduction The continuous scaling of semiconductor devices to achieve higher speed, density, and computational ability at lower power consumption and cost has been maintained for more than 30 years. One critical component, the gate dielectric, is now less than 2nm thick in state-of-the-art complementary metal–oxide–se- miconductor devices, but it cannot be indefinitely scaled with current materials [1]. The uses of SiO 2 and SiO x N y as gate dielectrics are reaching fundamental limits primarily due to high tunneling currents across the dielectric [2,3]. A physically thicker high-pemittivity (high-k) layer can be used to maintain low leakage current levels while attaining the desired value of capacitance. Considerable attention has been given to HfO 2 due to its relatively high dielectric constant (16–45), wide band gap (5.8eV) and its compatibility with n 7 polysilicon gate electrode material [4–6]. Furthermore, as the Gibbs energy formation of HfO 2 is more negative than ZrO 2 (1088 vs 1040kJ/mol) [7], it appears to be thermally stable at temperatures of upto 1000 1C. In recent years, partially strain compensated SiGeC alloy layers are being utilized in Si-based band gap engineered heterostructure devices [8–10]. These alloy ARTICLE IN PRESS 1369-8001/$-see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.mssp.2004.09.015 Ã Corresponding author. Tel.: +913222283838; fax: +913222255303. E-mail address: physkr@phy.iitkgp.ernet.in (S.K. Ray). 1 Present address: Electronics Research and Service Organiza- tion (ERSO), ITRI, Hsinchu, Taiwan, ROC.