Theoretical study of the gas-phase reaction of hexachlorodisilane by thermodynamic analysis and kinetics calculation

Abstract

Abstract We conducted thermodynamic analysis and kinetics calculations for hexachlorodisilane (Si2Cl6), which is used as source gas for the CVD of silicon nitride films. Thermodynamic analysis clarified Si2Cl6 decomposes almost completely to SiCl4 and SiCl2 in the range of 600 °C–1100 °C under equilibrium condition. Therefore, it is estimated that the main gas-phase reaction of Si2Cl6 is represented by the reaction Si2Cl6 → SiCl4 + SiCl2. Thermodynamic analysis also shows that the Si2Cl6 system has a larger equilibrium partial pressure of SiCl2 than SiHxCl4-x (x = 1 ~ 3) systems. Kinetics calculations revealed Si2Cl6 decomposes by 90% in 0.11 s at 600 °C, and 0.55 × 10−3 s at 800 °C, respectively. The time-dependent pyrolysis ratio of Si2Cl6 becomes larger as the total pressure decreases at 600 °C. On the other hand, the ratio is almost the same regardless of total pressure at 800 °C. These results will help optimize CVD process conditions using Si2Cl6.