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

Abstract

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 structure changes in the wire, which affects 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 W 2 C, SiC, and W 5 Si 3 (weak) was observed on W, whereas crystalline TaC, SiC, and Ta 5 Si 3 (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 -2400 °C, alloying in W was dominated by the formation of W 2 C with little contribution from WC. For Ta, the main alloy formed was TaC in the temperature range of 1400 -2000 °C. Heating the aged Ta filament to temperatures higher than 2000 ºC tended to recover the metal wire. This same practice does not seem to work for W wires since more W 2 C are 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.

Hot metal wires as sinks and sources of B atoms

“…W, one of the most widely used wire materials, can easily be carburized when exposed to organic material gases [1][2][3][4][5]. Silicidation is a problem when we use SiH 4 or organosilicon compounds, although the silicidation by SiH 4 is rather minor at high temperatures, i.e., over 1.810 3 K [3][4][5][6][7][8][9][10][11]. Metal contamination is another problem.…”