Synthesis of Chromium Oxycarbide Thin Films by Reactive DC Sputtering with Carbon Dioxide Gas

The synthesis of chromium oxycarbide thin films by reactive sputtering with carbon dioxide gas was examined in order to investigate the effects of such processing parameters on the formation of the chromium oxycarbide. The deposition of Cr-C-O films onto silicon substrates was carried out in the gas mixture of argon and carbon dioxide at the pressure of 0.5Pa by reactive DC sputtering of a chromium target with DC power of 250W. The gas flow rate of the Ar/CO2 was 7 sccm (standard cubic centimeter per minute)/ 3 sccm. For the investigation on the effects of substrate temperature, the reactive sputtering was performed with the substrates heated at various temperatures ranging from 370 to 450 degree Celsius. Under visual observation, the obtained Cr-C-O films appeared to be uniform and adhesive, and their color tone was metallic black. According to electron probe microanalysis (EPMA), it was found that the films were of oxygen-rich composition comparing with the stoichiometric chromium oxycarbide. Based on XRD, it was found that the crystallinity of chromium oxycarbide [Cr(C,O)] phase in the films depended on the substrate temperature, and assumed that the optimum temperature for the formation of the phase was about 400 degree Celsius in the examined range. Furthermore, the lowest electrical resistivity was also obtained for the film deposited at 400 degree Celsius, finding that it was approximately 10mΩcm.