Research On Wet Anisotropic Etching Of Silicon In MEMS

The complexity and the diversity of the silicon anisotropic etching process rendering the difficulty in selecting the etching parameters often lead to the windage between the results and the structures designed before. Therefore, the know-how of the discipline and the mechanism of anisotropic etching process is pressed, so as to shorten the periods of the production of MEMS and improve the quality of MEMS products.The research of the paper is aimed to understand the characteristic and the mechanism of the etching process. Such factors as crystallography, temperature and concentration influencing the etching results are dissectedly studied. The related calculation using Guassian internet applications are carried out. The model of the etching process with high concentration etchant is proposed. The results are detailed as follows.Such factors as geometry structure, temperature and concentration ,based on literature on the subject ,are systematically investigated in the paper.Potential contour map of Si(n)-OH- simulating OH- chemically adsorbed on Si low-index crystal planes are acquired by using Hatree Fock method of Guassian internet applications. The theoretical results suggest that the best adsorption sites are all top position of all rearched Si planes. Thereafer, the calculations of systematic energy of Si(n)-OH- have been performed while one OH- draw the silicon atoms of the best adsorption sites away. All of the work done above accords with the results of the literatures.Based the preconditions of the solution viscosity increase and the etching rates decrease of low-index crystal planes with higher concentration, a diffused control mechanism model is proposed. The factors influencing the diffusion coefficient (D) are studied. According to the Einstein-Stokes equation, D-C and D-T are ploted. The diffused control mechanism model is validated in comparison D-C and D-T maps with the preconditions which the proposed model are based.The research on the silicon anisotropic etching characteristic and the primary exploration of the etching mechanism are of practically guiding importance for MEMS manufacture.