This work presents the micro-machined 2-D switch array for use on free-space optical interconnect platform integrated with a digital 1x8 de-multiplexer control circuit together. Moreover, this device employs electrostatic actuation for light beam directions control. The CMOS-MEMS array-based optical platform contains 10x10 circular micromirrors switching spots, the diameter of each mirror is about 50 μm and the overall chip size is around 2 mm by 2 mm. The commercialized simulation softwares were used to validate the micromirror design and elucidate the behavior of the micromirror before fabrication. The post-process simply employs HF based solution to etch silicon dioxide layer to release the suspended mirror structures. The micromirror array is actuated using an electrostatic force. The results reveal that the micromirror has a tilting angle of around 8° according to the triangular relation with a driving voltage of 18V at pull down state. Also described herein are the general principles of the light-beam switching method used, the detailed of device design, the post-CMOS fabrication process flow, the result of simulations and preliminary experimental results are discussed.
This study presents a novel method based on the surface acoustic wave (SAW) sensor, for monitoring the thickness of a silicon membrane in real time during wet etching. Similar to accelerometers and pressure sensors, some micro-electro-mechanical systems (MEMS) devices require the thickness of silicon membranes to be known precisely. Precisely controlling the thickness of a silicon membrane during wet etching is important, because the thickness strongly affects post-processing and device performance. Moreover, the proposed surface acoustic wave sensor allows the thickness of a silicon membrane to be monitored from a few μm to hundreds of μm in situ, which depends on the periodicity of interdigital transducers (IDT). A novel method, which differs from any in previous work on etch-stop techniques, is developed in-situ for monitoring the thickness of a silicon membrane during wet etching. In summary, the proposed method for measuring the thickness of a silicon membrane in real time, is highly accurate; is simple to implement, and can be mass-produced. This work also describes the principles of the method used, detailed process flows, the method of taking measurements and the simulated and experimental results. The theoretical and measured values differ by an error of less than 2.50μm, so the results closely agree with each other.