Generation and extinction characteristics of negative ions in pulse-time-modulated electron cyclotron resonance chlorine plasma

The time dependence of plasma parameters in a pulse-time-modulated electron cyclotron resonance plasma of Cl₂ and Ar source gases is measured. It is found that Cl₂ plasma produces a large quantity of negative ions during afterglow and decay times of electron density, electron temperature and sheath potential of Cl₂ plasma are much smaller than those of Ar plasma. The negative ions in Cl₂ plasma stay for a long time in the afterglow and they quickly become extinct when the microwave power is turned on. These characteristics suggest that the pulse modulation of Cl₂ plasma produces a large amount of negative ions and changes the flow of charged particles through the sheath region to the substrate surface, which enables us to improve highly anisotropic and charge-free poly-Si etching.