The silicon mold fabrication of a kind of micro-optical resonator and coupler

We present the fabrication of a kind of hexagonal and triangular cavity mold, which can cast Polymethyl Methacrylate (PMMA) resonators and couplers. The mold is designed on (I 11) silicon wafer according to its crystal structure and anisotropic etching properties in the etchant of ethylene diamine, pyrocatechol, and water (EDP/EPW), forming sidewalls by six {110} crystal surfaces, which are perpendicular to the (111) plane and constitute precise hexagons and triangles. The RlE-lCP etching is used to define the depth of the triangle and hexagonal cavities, and the following EDP etching smoothes the sidewalls of cavities. Only high temperature EDP etching is proved to be able to get smooth sidewalls. Before etching, the wafer is aligned to the right crystal orientation by pre-etched marks. The etched results of different geometrical cavities are analyzed and discussed based on the crystal structure.