Investigation of the tantalum chlorination with hydrogen chloride for LPCVD tantalum elaboration

Abstract
A chlorination process is presented in order to produce tantalum chloride. Solid tantalum is used as started material whereas the reducing agent is hydrogen chloride. Previous thermodynamic calculations allow to determine that the more convenient chlorination reaction temperature is 670°C. Hydrogen chloride flow rate is varied from 10 to 40 sccm whereas the chlorination chamber is maintained at a total pressure ranging from 10 to 40 mbar. This process has been evaluated for depositing tantalum films by LPCVD through hydrogen reduction of the just formed tantalum chloride. Chlorination parameters such as HCl residence time, HCl partial pressure and chlorination chamber total pressure are investigated with respect to the tantalum weight deposited by LPCVD. By using the optimum set of parameters : HCl flow rate of 10 sccm and total pressure of the chlorination chamber of 36 mbar, tantalum films are deposited at 800°C and under a total pressure of 3.3 mbar at a deposition rate of 32.6 ± 2.9 mg/h that corresponds to 1.42 ± 0.09 µm/h.