Structural Changes in Tungsten and Tantalum Wires in Catalytic Chemical Vapor Deposition Using 1,3-Disilacyclobutane

摘要

Metal wires (typically made of W or Ta) serve as catalysts to decompose the precursor gases to form reactive species in the technique of catalytic chemical vapor deposition. The reactions of these reactive species with the heated wire cause structural changes in the wire, which affect its catalytic properties and lifetime. Here, we report a systematic study on characterizing the structural changes in W and Ta wires when they are exposed to 1,3-disilacylobutane, a useful single-source precursor for SiC film deposition. We have shown that filament temperature, reaction time, and filament material are among the important factors in determining the nature of metal alloys formed. Formation of crystalline W2C, SiC, and W5Si3 (weak) was observed on W, whereas crystalline TaC, SiC, and Ta5Si3 (weak) were formed on Ta. While both filaments proved to form cubic crystalline 3C-SiC at low temperatures, alloying has taken different paths at higher temperatures. Between 1400 and 2400 degrees C, alloying in W was dominated by the formation of W2C with little contribution from WC. For Ta, the main alloy formed was TaC in the temperature range of 1400-2000 degrees C. Heating the aged Ta filament to temperatures higher than 2000 degrees C tended to recover the metal wire. This same practice does not seem to work for W wires since more W2C is formed at high temperatures. It is concluded that Ta outperforms W for SiC film growth in its resistance to forming more carbides and its ability to recover at high temperatures.