Oxidation of high area ratio silicon microchannels fabricated by electrochemical etching

Silicon microchannel structures exhibit numerous possible applications. In this report, the oxidation of high area ratio silicon microchannels used in weak light detection and night vision is studied. High area ratio microchannels are fabricated by electrochemical etching, and the influences of oxidation time and environments on the microstructures are investigated and analyzed combined with computer simulation. Damages and distortion are found after the oxidation process. It is found that after oxidation at high temperature, surface morphology becomes rough and followed polishing step is recommended to smooth the silicon microchannels' surfaces.

I. Introduction

Microchannel structures exhibit numerous possible applications on microchannel plates, micro-total analysis systems, microheat exchange device, and microchemical reactors etc, especially for silicon microchannels. Silicon microchannels technology based on electrochemical etching process comes from macroporous silicon technology, and has the advantage of high aspect ratio achievement by employing simple and low cost equipments. Therefore, this method has been explored widely for the fabrication of silicon photonic crystal, micromachined devices and through wafer interconnection for 3D integration [1]~[5]. In these applications, the formation of an insulator layer on the sidewall of the channels is necessary for electrical isolation or passivation of the surface. Silicon dioxide (SiO₂) is one of the preferred options because it is a good electric insulator with high electrical breakdown field, and has good passivation properties. Further, SiO₂ also has good mechanical stability, low thermal conductivity and chemical inertness [6].