Silicon bulk micromachining in MEMS packaging and optical applications

This dissertation explores the applications in MEMS packaging and optics by using silicon bulk micromachining. Various techniques for anisotropic etch of bulk micromachining are described that reduce the misoriented undercut, increase structure precision, and improve the etched surface smoothness. Bulk-micromachined silicon substrates can also provide a platform for micro device packaging, which serves for electrical interconnection and precise pre-aligned microstructures. In addition, high manufacture precision and unique etched profiles of bulk-micromachined silicon offer many opportunities in optical applications.; The flats of typical silicon wafers cannot be relied on as good references since they can be as much as around 1° off from the crystal directions. The alignment techniques described in the dissertation have improved the accuracy up to 0.1°. Previous alignment techniques are reviewed and a new, practical approach is designed for both Si (100) and Si (110) wafers by using asymmetry effect for effective inspection. All of the applications discussed in this dissertation used the pre-processed alignment marks instead of wafer flats.; A new MEMS packaging based on the hybrid integration of a silicon submount and an optical MEMS device is demonstrated. The two-silicon substrate submount with pre-aligned microstructures accommodates all the optical elements of fiber-optic switches, providing a greater integration flexibility and making the assembly procedure much more efficient. In order to meet fiber-optic switch specifications, the required distance in which the switching mirror is inserted is within around 1 mm for the fiber-lens-lens-fiber configuration, and within around 175 μm for the fiber-to-fiber configuration.; As for opto-mechanical applications, the translational microslider that can carry optical elements is fabricated by the electroplated microriveting and sacrificial layer etching techniques, which eliminates the high-temperature wafer bonding and manual assembly. The coefficient of the static friction was measured to be 0.42–0.78.; We have also studied feasibility of silicon vertical mirrors on a glass substrate. The results of the optical testing show promising characteristics of the mirror, such as verticality (<0.03°) and surface curvature. An assembly-transfer process is developed to transfer silicon vertical mirrors to another substrate, which opens new possibilities in constructing optical devices.