Modelling of sacrificial aluminium etching in complex geometries

In this paper, the modelling of sacrificial aluminium etching in complex network geometries is presented. The structures for the etching experiments are arrays of membranes for a capacitive tactile sensor for medical applications. The modelling is based on the two-dimensional diffusion equation. A one-dimensional model for correlating etch rate and diffusion coefficient in silicon dioxide etching is extended to cover two-dimensional geometries. The etch front progression can be derived from the modelled concentration of the etchant within the etch network. This allows for the extraction of numerical values of diffusion coefficients D from the data. The values of D for the three sections of the geometry in both networks studied reflect the differences in the boundary conditions of the etching process.