Carbon and Silicon Related Surface Compounds of Palladium Ultrathin Films on SiC After Different Annealing Temperatures
- PDF / 930,740 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 74 Downloads / 200 Views
INTRODUCTION SiC-based device developments require that the metal contacts and interconnects are physically, chemically, and electrically stable under severe conditions, such as at high temperatures. Metal contact studies on SiC have resulted in commercially available SiC devices which can be operated at high temperatures [1,2]. The diffusions and reactions between metal thin films and the SiC substrate result in the formation of various interfacial compounds, and alter the electrical properties. Therefore, it is one of the most critical issues to investigate the interfacial compositions of metal/SiC at elevated temperatures in SiC based device research. Pd/SiC Schottky diodes have been successfully demonstrated as a chemical sensor for hydrogen and hydrocarbon [3,4], which can be operated at high temperatures. The heat treatment significantly promotes interfacial diffusion and chemical reactions, and broadens the interface region. The two-dimensional surface diffusion and surface segregation of Si from dissociated SiC result in a thin silicon oxide layer on the top of the Pd film [3]. The Pd chemical states are various co-existing palladium silicides (Pd•Si, x = 1,2,3,4) for the Pd thickness of about 400A [4] after annealing at 425°C. Lu et al. [5] found the Pd exists as PdSi and Pd 2Si for the ultra-thin Pd film (-30A thickness) at the elevated temperatures. To the best of our knowledge, the formations of the silicon and carbon related compounds in Pd/SiC after annealing at high temperatures have not been systematically 87 Mat. Res. Soc. Symp. Proc. Vol. 572 © 1999 Materials Research Society
investigated. In this study, the interfacial composition and the morphological features of Pd ultra-thin films on 6H-SiC and 4H-SiC at different annealing temperatures were investigated using XPS and AFM. The Pd ultra-thin films were prepared by the RF sputtering method, and the thickness was about 30A. The silicon and carbon related compounds in Pd/SiC were determined by XPS after annealing.
EXPERIMENTAL 1. Samples and Pd Ultra-thin Film Fabrication n-type, Si-face 6H-SiC and 4H-SiC wafers with 3.50 off-axis on Si (0001) substrates were purchased from Cree Research Inc. The doping concentration was 2.6 x 1018 cm3. An RF sputtering system (Kurt J. Lesker Company) was used for the Pd ultra-thin film preparation. The SiC wafer
cleaning procedure and the Pd ultra-thin preparation procedure are in Ref [5]. The thickness of Pd thin film on SiC was about 30 A, so that XPS can effectively detect the Pd/SiC interfacial compositions. The Pd/SiC samples were analyzed and annealed consecutively from 100IC to 600 0C in 100IC increments in air for 30 minutes each time. The Pd/6H-SiC and Pd/4H-SiC samples were prepared and annealed at the same time. 2. Characterization The XPS experiments were performed on a Kratos X-SAM 800 spectrometer with an energy resolution of 0.1 eV. The base pressure was at 10-9 Torr. The Mg Ka (hl,= 1253.6 eV) radiation was used. The energy scale of the analyzer was calibrated by the Cu (2p3/ 2) XPS peak at 93
Data Loading...
