Effect of surfactant on surface quality of silicon microstructures etched in saturated TMAHW solutions

Anisotropic etching of silicon in tetramethyl ammonium hydroxide water (TMAHW) solutions is of great interest for the fabrication of IC-compatible microstructures. Of particular interest an solutions saturated by silicon-doping as the aluminium metallization is passivated in these solutions. However. as the surfaces etched in these solutions are rather tough, the use of additives is required to improve surface quality. A new non-ionic surfactant, which is clean room compatible as well as safe and easy to handle, appears to be quite promising a surface roughness is drastically reduced, while metal passivation is still preserved. The effect of this surfactant in bath silicon-doped and undoped TMAHW solutions is investigated. Although a reduction of the etch rate is measured, a strong improvement on the surface quality of the etched microstructures as well as an abrupt decrease in the undercutting ratio of the convex corners are observed. (C) 2000 Elsevier Science S.A. All rights reserved.