The characteristic behavior of TMAH water solution for anisotropic etching on both silicon substrate and SiO2 layer

The present study aims at obtaining the etching rate of Si(1 0 0) surfaces as well as the silicon oxide layer when the surfaces are exposed to tetramethylammonium hydroxide (TMAH) water solution. The influence of TMAH solution concentration and solution temperature on the etching rate is also studied. In this work, the value of TMAH concentration (C-TMAH) ranges from 2 to 25 wt.% and the etching temperature ranges from 70 to 90 degreesC. Both n- and p-types silicon substrate were tested. Measured results show that etching changes little with the type of silicon substrate. In addition, the etching rate increases with the solution temperature but decreases with an increase in C-TMAH for C-TMAH greater than 8 wt.%. Among all experimental conditions, a maximum etching rate on the Si(1 0 0) surface reaches a value of 81 mum/h at a solution temperature of 90 degreesC. Similarly, higher temperature can result in a faster etching rate of the SiO2 surface; while the etching rate of SiO2 surface decreases consistently with an increase in C-TMAH. Measured results of surface roughness (Ra) on silicon substrate are reported after performing a 20 min etching at solution temperatures from 70 to 90 degreesC. Much smoother substrate surfaces can be observed for higher concentrations. (C) 2001 Elsevier Science B.V. All rights reserved.