Modeling two-dimensional diffusion-controlled wet chemical etching using a total concentration approach

A total concentration fixed-grid approach analogous to the enthalpy method for melting/solidification is presented in this article to model two-dimensional diffusion-controlled wet chemical etching. A total concentration, which is the sum of the unreacted and the reacted concentrations is defined. Using this newly defined total concentration, the governing equation also contains the interface condition. For demonstration purposes, the finite-volume method is used to solve the resulting set of governing equation, initial condition and boundary conditions. The results obtained using the total concentration method are compared with solutions from the asymptotic solution and the finite element method. The effects of mask thickness and initial concentration on evolution of etchfront during etching are examined. High initial etchant concentration leads to faster etching and hence the speed of etchfront. It is seen that when mask thickness increases, the bulging effect near the mask corner is less pronounced.