RESEARCH OF TEMPERATURE AND CONCENTRATION ON ANISOTROPIC WET ETCHING OF MONOCRYSTALLINE SILICON
Abstract
The main material of most mechanical sensors is silicon. For the formation of silicon structures, the methods of bulk micromachining - deep etching of the substrate – are used. Anisotropic wet etching is traditionally used to form structures that are subject to high requirements for dimensional accuracy and reproducibility. In this case, an aqueous solution of alkali is used as an etchant. Determining the optimal mode by the concentration and temperature of the solution will allow you to obtain a relatively uniform, smooth surface at a high etching rate. An experimental study of the influence of concentration (20-40%) and temperature (60-80°C) was carried an aqueous KOH solution on the etching rate of monocrystalline silicon, as well as the surface morphology under conditions of a long etching process. The etching rates in 20%, 30%, and 40% solution for the selected temperature range were 0.68–2.0 μm/min, 0.77–2.4 μm/min, and 0.7–1.9 μm/min, respectively. The morphology of the silicon surface at a depth of 270 microns was analyzed. It was found that at a solution concentration of 20% KOH and 80°C, a developed surface morphology with a roughness of ~ 400 nm is formed; a decrease in the solution temperature makes it possible to obtain a more even surface with a residual roughness of ~ 340 nm. At a concentration of 30% KOH solution, the surface is more uniform with a roughness of ~ 100 nm; a change in temperature from 60 to 80 °C has almost no effect on its morphology. At a concentration of KOH solution of40% and 80°The initial relief of the etching surface is sufficiently developed ~ 340 nm, and a decrease in the temperature of the solution to 60°C allows it to be reduced to a state characteristic of the etching condition at 30% and a temperature of 80°C.
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