Please cite this article in press as: M. Sochacki, et al., Mater. Sci. Eng. B (2010), doi:10.1016/j.mseb.2010.08.012 ARTICLE IN PRESS G Model MSB-12637; No. of Pages 4 Materials Science and Engineering B xxx (2010) xxx–xxx Contents lists available at ScienceDirect Materials Science and Engineering B journal homepage: www.elsevier.com/locate/mseb Electronic properties of BaTiO 3 /4H-SiC interface M. Sochacki a,∗ , P. Firek a , N. Kwietniewski a , J. Szmidt a , W. Rzodkiewicz b a Institute of Microelectronics and Optoelectronics, Warsaw University of Technology, Koszykowa 75, 00-662 Warsaw, Poland b Institute of Electron Technology, Al. Lotnikow 32/46, 02-668 Warsaw, Poland article info Article history: Received 1 October 2009 Received in revised form 25 August 2010 Accepted 26 August 2010 Keywords: Silicon carbide Barium titanate Electrical measurements Electron states abstract The possibility of barium titanate (BaTiO 3 ) application in silicon carbide (SiC) technology has been elaborated in terms of the dielectric film quality and properties of the BaTiO 3 /4H-SiC interface. High resistivity, high-k thin films containing La 2 O 3 admixture were applied as gate insulator of metal- insulator-semiconductor (MIS) structure. The thin films were deposited by means of radio frequency plasma sputtering (RF PS) of sintered BaTiO 3 + La 2 O 3 (2 wt.%) target on 8 ◦ off-axis 4H-SiC (0001) epitaxial layers doped with nitrogen. The results of current-voltage and capacitance-voltage measurements are presented for MIS capacitors. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The ability of silicon carbide to form thermal silicon dioxide (SiO 2 ) layers in high temperature oxidation process has been con- sidered as a perfect method of experience transfer from silicon technology to silicon carbide industry. It appears that the full poten- tial of silicon carbide MIS devices is still restrained by unsatisfying quality of interface in thermal SiO 2 –SiC system which has been studied for more than 10 years. Neither the oxidation process mod- ifications (e.g. dry [1] or wet [2] oxidation, N 2 O [3] or NO [4] oxidation, NH 3 pretreatment [5], reoxidation [6], annealing in dif- ferent gases [7], chlorine [8] or sodium [9] addition) nor substrates quality improvement has solved a high interface state density and reliability problems yet. The carriers are trapped and scattered by the interface defects. As a consequence of these phenomena the channel mobility and the output current capability of inversion mode SiC MOSFETs is still far from the theoretical one [10]. Addi- tionally, the reliability of silicon dioxide layers decreases rapidly at elevated temperature and premature breakdown often occurs around 250 ◦ C. An alternative high-k dielectric layers on SiC substrates have been extensively investigated for use in the field of silicon carbide MIS devices as a replacement of thermal SiO 2 gate films [11–13]. In this work, BaTiO 3 films were chosen for characterization and properties of BaTiO 3 /4H-SiC interface have been studied. Heart- ened by the most promising properties observed during silicon MISFETs characterization with barium titanate thin film as a gate insulator [14], we decided to investigate the interface between ∗ Corresponding author. E-mail address: msochack@filuts.waw.pl (M. Sochacki). 4H-SiC and BaTiO 3 . The substantial improvement was expected due to higher dielectric constant comparing to the one for silicon dioxide. 2. Experimental details MIS capacitors were fabricated on Si-faced n-type epitaxial layers grown on highly doped 8 ◦ -off 4H-SiC commercial wafers supplied by SiCrystal. Nitrogen concentration in n-type epi- layers was 1 × 10 16 cm -3 . The wafers were cleaned using the conventional RCA method followed in 3-min dip in buffered HF. The samples were sequentially boiled in organic solvents (trichloroethylene, acetone, isopropanole) and then dipped in hot solution of NH 4 OH:H 2 O 2 :H 2 O (1:1:5) for 10 min and etched in hot HCl:H 2 O 2 :H 2 O (1:1:5) for 10 min. Finally, the samples were dipped in buffered HF for 3 min and rinsed in deionized water. Then, the barium titanate films were deposited by means of radio frequency plasma sputtering (RF PS) of sintered BaTiO 3 + La 2 O 3 (2 wt.%) target. The schematic diagram of the RF PS setup was presented in our previous work [14]. All films were obtained at argon flow rate of 10 sccm. The film thickness was determined by spectroscopic ellipsometry (HORIBA Jobin Yvon UVISEL) and verified on etched pattern by profilometry (VEECO DekTak 150). 200 nm-thick nickel film was sputtered and annealed at 960 ◦ C in argon to reduce the specific resistance of backside ohmic con- tact to highly doped wafer by creation of silicon silicides at the metal-semiconductor interface. Then 30 nm-thick nickel film was sputtered and patterned as the circle gate electrode of MIS capac- itor with a diameter of 200 m. As-deposited MIS capacitors were electrically characterized at probe station integrated with Keith- ley SMU 236/237/238 and Hewlett-Packard 4061A semiconductor 0921-5107/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.mseb.2010.08.012