Forty-Five Degree Micromirror Fabrication Using Silicon Anisotropic Etching with Surfactant-Added Tetramethylammonium Hydroxide Solution

Flat and smooth 45° micromirrors were successfully fabricated on a 4-in. silicon wafer by means of wet anisotropic etching at the industrially practical temperature of 80 °C using tetramethylammonium hydroxide (TMAH) solution with added NCW-1002, a nonionic surfactant with little environmental load. The effects of the TMAH concentration and the amount of NCW-1002 added were extensively investigated, and it was found that a high TMAH concentration (25 wt %) and a very low amount of NCW-1002, approximately 10 vol ppm, are the optimum conditions to fabricate optically smooth and geometrically flat micromirrors. The mechanism underlying the effects of the concentration of the surfactant is discussed in relation to the clouding point of the surfactant-added TMAH solution.