Fabrication of 3-Dimensional Structure of Metal Oxide Semiconductor Field Effect Transistor Embodied in the Convex Corner of the Silicon Micro-Fluidic Channel

Abstract

As micro-fluidic systems and biochemical detection systems are scaled to smaller dimensions, the realization of small and portable biochemical detection systems has become increasingly important. In this paper, we propose a 3-dimensional structure of a metal oxide semiconductor field-effect transistor(3-D MOSFET) using tetramethyl ammonium hydroxide (TMAH) anisotropic etching, which is a suitable device for combining with a micro-fluidic system. After fabricating a trapezoidal micro-fluidic channel, the 3-D MOSFET embodied in the convex corner of the micro-fluidic channel was fabricated. The length of the gate is about 20 µm and the width is about 9 µm. The depth and top width of the trapezoidal micro-fluidic channel are about 8 µm and 60 µm, respectively. The measured drain saturation current of the 3-D MOSFET was about -22 µA at VGS=-5 V and VDS=-5 V, and the device characteristics exhibit a typical MOSFET behavior. Moreover, a gold layer was used for the MOSFET's gate metal to detect charged biochemical samples using the affinity between gold and thiol.