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We have developed a plasma etching simulator to investigate the evolution of pattern profiles in SiO2 material under different plasma conditions. This model focuses on energy and angular dependent etching yield (physical sputtering in this paper), neutral and ion angular distributions, and reflection of ions or neutrals on the surface of a photoresist or SiO2. The effect of positive charge accumulation on the surface of insulated mask or SiO2 is studied and the charge accumulation contributes to a deflection of ion trajectory. The wafer profile evolution has been simulated using a cellular-automata-like method under radio-frequency (RF) bias and direct-current (DC) bias, respectively. On the basis of the critical role of angular distribution of ions or neutrals, the wafer profile evolution has been simulated for different variances of angles. Observed microtrenching has been well reproduced in the simulator. The ratio of neutrals to ions has been considered and the result shows that because the neutrals are not accelerated by an electric field, their energy is much lower compared with ions, so they are easily reflected on the surface of SiO2, which makes the trench shallower.

Using a combination of the Monte Carlo models of fast electrons, of molecular ions (N+2) and of atomic species (N+, Nf), the influence of the discharge pressure (P) and voltage (Vc) on the energy distributions of fast atomic species (N+, Nf) produced by e−-N2s and N2+-N2s dissociation reactions at the cathode in a nitrogen dc glow discharge was investigated. Both the angular distributions and the density distributions along the radius of the species (N+, Nf) produced by the two dissociations at the cathode were calculated. The results show that: (1) there is an optimum discharge condition for P and Vc in order to obtain the species (N+, Nf) at the cathode with high a density and energy, (2) when the voltage is above 800 V, the species (N+, Nf) bombarding the cathode are mainly produced by the N+2-N2s dissociation, whereas when the voltage is below 300 V, they are mainly produced by the e−-N2s dissociation, and (3) at high voltages the incident angles of a considerable number of Nf into the cathode are quite small. The density of the species (N+, Nf) at the cathode increases with the voltage, and when the pressure goes up to about 133 Pa, it decreases with the increasing pressure.