Numerical and experimental studies for the anisotropic etching of silicon with the AFM oxide lines as masks

A time-dependent numerical scheme is developed to predict the anisotropic etching of silicon formed between two adjacent silicon oxide lines. These oxide lines were prepared by the AFM (atomic force microscope) oxidations under different conditions. The present method developed on the basis of the finite difference method is used to solve the one-dimensional problem considering both the etchant diffusion and the movement of the etched boundary at the bottom surface of a groove. This numerical method is effective to predict the etching rate and etching depth of a groove under the conditions of different etching parameters. Experiments were also carried out in order to check the numerical model. Good agreements can be obtained between the experimental and predicted results. The etching rate of the silicon wafer is lowered by increasing the etching time, and significantly raised by elevating the etching temperature. Apart from the etching parameters, the difference between the aspect ratios exhibited in the fabricated gratings under the conditions of stirring and without stirring is quite significant.