Decomposition of Boron Trifluoride in the RF Plasma Environment

Boron trifluoride (BF3) is the most commonly used gas for implanting ions of the N-type dopant boron. BF3 is non-flammable and does not support combustion, but is toxic when inhaled and corrosive to the skin. A radio frequency (RF) plasma system used to decompose BF3 was examined. The BF3 decomposition fractions (ηBF3) were determined in effluent gas streams of BF3/CH4/Ar, BF3/O2/Ar and BF3/O2(glass)/Ar plasma systems. The by-products detected in the BF3/CH4/Ar plasma system were CO, CO2, SiF4, HF and boron-carbon compounds. The by-products detected in the BF3/O2/Ar plasma system were B2O3(s) and SiF4. The ηBF3 in the BF3/CH4/Ar plasma system was 49.8%, higher than that in the BF3/O2/Ar and BF3/O2(glass)/Ar plasma system. However, the amount of decomposed BF3 divided by the input energy (EBF3, energy efficiency) in the BF3/O2(glass)/Ar plasma system was greater than that in the BF3/CH4/Ar and BF3/O2/Ar plasma systems. Moreover, the photo images of depositions of different reacting gases O2, H2 with BF3 were also compared. The reaction in the BF3/O2/Ar plasma system generated B2O3 fine particles and led to the deposition of a white substance on the surface of the reactor. The ηBF3 was only around 25% for mixing with O2, even when the input power exceeded 120 Watts, but the generation of fine particles in the system warrants much more investigation.