Plasma etch profiles modeling of silicon dioxide contact holes with etching and deposition

An etch profile evolution model for SiO₂ contact holes etched in a MERIE system by using fluorocarbon gases is developed with a semi-analytic approach. The model includes both etching and deposition based on the chemistry mechanisms. The effective etch rate at each individual point of the etching surface is the linear combination of etching and deposition rate. Etching by the combination effects of ions and neutrals is modeled by Langmuir kinetics, and deposition is dominated by neutrals.; The etch rate due to ions is assumed proportional to the ion energy flux as suggested by experimental evidence. The geometrical shadowing of the contact hole and the mask is included in the derivation of the ion energy flux in cylindrical velocity coordinates for a drifting Maxwellian distribution. Neutrals with varying sticking coefficients are modeled by interpolation between the etch rate for shadowed neutrals with unity sticking coefficients and isotropic neutrals with zero sticking coefficients. The etch profiles are determined by the method of characteristics from the nonlinear etching surface evolution equation.; Scanning electron microscopy (SEM) images for SiO₂ contact holes etched in CF₄/CHF₃/Ar plasmas are compared with etch profiles calculated from the model. The simulated results of etched profiles reasonably well reproduced the characteristic features of experimental contact hole configurations with a radius of about 1 gym. These results show that this model includes the important factors in the etching process. The plasma characteristics in the experiment are studied with both statistical analysis of a 25-1 fractional factorial design and a homogeneous model for MERLE reactors. The ion energy fluxes on a flat surface and the average ion energy in the sheath region are estimated from the parameters used in the simulations, and show consistency with the plasma characteristics.; Main contributions of this study are the derivation and use of explicit analytic expressions for the contact hole etch rates and the explicit inclusion of deposition in the etch profile evolution. The computation of etch profiles is efficient, and the model can be used together with experiments for investigation of SiO₂ contact hole etching and to illuminate the parameter dependence of etch profiles.