Computer simulation of inductively coupled plasma using chlorine gas etching of polysilicon

An inductively coupled plasma (ICP) operated at low chlorine pressures has been modeled. in order to save computational time, a global, steady state model incorporating mass balances for chlorine ionic and neutral chemical species and energy balances for the electrons is used to determine specie densities and electron energy. Also, a gas energy balance and a self-consistent relation for ion temperature are used to predict the gas and ion temperatures. The model incorporated a gas-phase model and a phenomenological surface model to characterize the Cl₂ plasma etching of polysilicon and predict etch rates, surface coverage, atomic chlorine concentration, and ion flux as affected by reactor pressure, flow rate, and chamber height and radius of the ICP. In addition, sensitivity analysis has been used to determine which parameter uncertainties have the largest effects on the modeling results.; When the reactor height and radius are increased, the electron energy decreases to keep the electron ionization and loss rates balanced. Even fairly large changes (a factor of 3) in the height and radius give relatively small changes (less than 40%) in the total ion density and electron density. When pressure increases, neutral temperature increases due to an increased probability of electron-gas inelastic collisions. Ion temperature decreases when the pressure increases due to a decrease in electron energy. Also, etch rate increases as power is increased due to the increase in total ion flux. The effects of reactor height and reactor radius on etch rate are relatively small, with less than 20% change in total etch rate from 3–15 cm. The recombination rate coefficient of Cl with the walls has a significant effect on etching rate.; Results from this work contribute to understanding the characteristics of Cl₂ plasma etching of polysilicon and provide valuable insights on the chemistry in low pressure inductively coupled plasmas. The model developed here should be a useful tool to help predict how reaction parameters should be adjusted to scale processes for larger diameter wafers.