Simulation of an Ar/Cl2 inductively coupled plasma: study of the effect of bias, power and pressure and comparison with experiments

Abstract

A hybrid model, called the hybrid plasma equipment model, was used to study Ar/Cl2 inductively coupled plasmas used for the etching of Si. The effects of substrate bias, source power and gas pressure on the plasma characteristics and on the fluxes and energies of plasma species bombarding the substrate were observed. A comparison with experimentally measured etch rates was made to investigate how the etch process is influenced and which plasma species mainly account for the etch process. First, the general plasma characteristics are investigated at the following operating conditions: 10% Ar 90% Cl2 gas mixture, 5 mTorr total gas pressure, 100 sccm gas flow rate, 250 W source power, −200 V dc bias at the substrate electrode and an operating frequency of 13.56 MHz applied to the coil and to the substrate electrode. Subsequently, the pressure is varied from 5 to 80 mTorr, the substrate bias from −100 to −300 V and the source power from 250 to 1000 W. Increasing the total gas pressure results in a decrease of the etch rate and a less anisotropic flux to the substrate due to more collisions of the ions in the sheath. Increasing the substrate bias has an effect on the energy of the ions bombarding the substrate and to a lesser extent on the magnitude of the ion flux. When source power is increased, it was found that, not the energy, but the magnitude of the ion flux is increased. The etch rate was more influenced by a variation of the substrate bias than by a variation of the source power, at these operating conditions. These results suggest that the etch process is mainly affected by the energy of the ions bombarding the substrate and the magnitude of the ion flux, and to a lesser extent by the magnitude of the radical flux.