Fabrication of Si membrane for a pressure sensor using the TMAH based etching solution

Abstract

In this study, the piezoresistive pressure sensor of Si membrane was fabricated using the Si wet etching with a tetramethyl ammonium hydroxide (TMAH). Anisotropic Si etching properties of TMAH solution and sensing characteristics of the etched Si membrane were investigated. The addition of ammonium persulfate (AP) to the TMAH solution improved the flatness of etched Si surface and the undercutting compensation. The etched surface was also enhanced significantly by the decreased hillock density on the Si surface. The sensing response for the pressure sensor of Si membrane fabricated by the AP-added TMAH solution was examined by measuring the change of voltage with pressure variation. For a range of 7 bar pressure, the output voltage increased linearly with increasing the applied pressure, showing very good linearity. The sensitivity was 23.8 mV/bar and sensing response time was fast as 90 ms.