Effect of Low Temperature on the Fabrication of Microring Resonator by Wet Etching

Research related to semiconductor devices often relies on wafer fabrication. The fabrication of Silicon (Si) based devices by anisotropic wet etching can be affected by many etching parameters such as etching temperature, crystal orientation and percent of composition. Most of the anisotropic wet etchings by KOH solution done before were conducted at temperature over 70°C. We found that the temperatures are not suitable to fabricate ring waveguide as the waveguide wall will collapse at such high temperature. This study reports the etching characteristics of Si <100> in KOH solution with 35% concentration at the temperature below 70°C. The etched wafer is targeted to be the basic structure for Microring Resonators (MRRs) based devices. This technique provides not only lower cost as compared to other etching technique, but also simple preparation. We found that low temperature manage to mold a good ring waveguide with low tendency to form rectangular structure due to crystal orientation. At 40°C, the best waveguide formation was obtained with a smooth waveguide surface, experiencing an etching rate of 0.066 µ min^-1 and an appreciable ring waveguide structure. The effect of the low temperature on the fabrication of the MRRs devices has been investigated and studied.