Surface Characterization of Silicon Carbide Following Shallow Implantation of Palladium Ions
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0900-O12-15.1
Surface Characterization of Silicon Carbide Following Shallow Implantation of Palladium Ions C. I. Muntele∗, S. Sarkisov, I. Muntele, D. ILA Center for Irradiation Materials, Alabama A & M University, Normal, AL, 35762
ABSTRACT Silicon carbide is a promising wide-bandgap semiconductor intended for use in fabrication of high temperature, high power, and fast switching microelectronics components running without cooling. For hydrogen sensing applications, silicon carbide is generally used in conjunction with either palladium or platinum, both of them being good catalysts for hydrogen. Here we are reporting on the temperature-dependent surface morphology and depth profile modifications of Au electrical contacts deposited on silicon carbide substrates implanted with 20 keV Pd ions. INTRODUCTION Palladium and platinum are known as good catalysts for hydrogen, which makes them good active materials in designing hydrogen sensors. They are absorbing hydrogen from the surrounding environment and then release it back in a continuous process, since they do not form stable hydrides. A typical hydrogen sensor design would consist of an electrically insulating substrate on which a thin Pd or Pt layer is deposited along with electrical contacts for monitoring changes in its resistivity due to hydrogen absorption. This concept is rather crude and not very sensitive, therefore the insulating substrate is typically replaced by a semiconductor and a nonlinear (p-n, Schottky, or MOSFET) electronic device is then devised. This kind of device, while having a tremendous increase in sensitivity, becomes much more fragile and structurally unstable, especially in environments where high temperatures associated with corrosive or oxidizing gases are expected to be monitored. Our past work dealt with both palladium-coated and palladium-implanted SiC sensors. In this work we are investigating the effects of temperature on the structure of devices built using very shallow (~ 13 nm) palladium ion implantation into semi-insulating silicon carbide. Literature [1] mentions that Au, Ti, Ta, and W layer deposition for electrical contacts. Since the sensors are supposed to work at 800 °C, we used various annealing steps up to this temperature level. We used atomic force microscopy (AFM) for monitoring the silicon carbide surface morphology before and after implantation, Rutherford Backscattering Spectrometry (RBS) for measuring the amount and depth profile of the platinum and tungsten distribution, and Optical Absorption Spectrometry (OAS) to determine the irradiation defects evolution of the SiC crystalline lattice. EXPERIMENTAL DETAILS Based on the previous experience, for this work we used 6H semi-insulating SiC, with a dopant level below 1e14 atoms/cm3 and therefore an electrical resistivity greater than 1e4 Ω·cm, as we are attempting to measure the electrical behavior at 800 °C. We were also able of ∗
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implanting 8×1015 cm-2 Pd
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