Electrochemical deep etching technology for silicon-based MEMS fabrications

Photo-assisted electrochemical etching is investigated, especially for the case called the boundary effect between the array and silicon substrate. The structure collapse is observed in the boundary area, which is due to the inhomogeneous current distribution and the vacancy injection from the sidewall of the hole. Such an effect can be inhibited when the illumination intensity is modulated with a poriodic signal. The electrochemical polish effect in case of high etching current is also observed. It has been demonstrated that the obtained square grid structure shows the typical behavior as the photon crystal with its forbidden band near 6 μm.