2-DIMENSIONAL SIMULATION OF POLYSILICON ETCHING WITH CHLORINE IN A HIGH-DENSITY PLASMA REACTOR

A two-dimensional fluid simulation of polysilicon etching with chlorine in an inductively-coupled high density plasma source is presented. A modular approach was used to couple in a self-consistent manner the disparate time scales of plasma and neutral species transport. This way, complex plasma chemical reactions (involving electrons, ions and neutrals) as well as surface chemistry can be included in the simulation. The power deposited into the plasma was calculated by an electromagnetics module which solves Maxwell's equations. The power deposition was used in the electron energy module to find the electron temperature and the rate coefficients of electron-impact reactions. These were in turn used as source terms in separate neutral and charged species transport modules. By iterating among the modules, a self-consistent solution was obtained, Quantities of interest, such as power deposition, species density and flux, and etch rate and uniformity were thus calculated. As power deposition was increased, the electron density increased linearly, the plasma became less electronegative, the degree of gas dissociation increased, and the plasma potential remained constant. The radial uniformity of the Cl atom flux was better than that of the ion flux The reactivity of the wafer as compared to that of the surrounding electrode surface significantly affected the etch uniformity, despite the low pressure of 10 mtorr.