Silicon microgripper for microassembly realized by photolithography and fast anisotropic silicon etching

In this paper we present a new silicon microgripper for microassembly realized by photolithography and fast anisotropic silicon etching. Technological and manufacturing problems of the silicon microgripper will be described. The optimized etch process results in a high silicon etch rate of up to 6.2 mu m/min, a good selectivity silicon/photoresist of up to 100:1, a high anisotropy, a nearly vertical etch profile, and a smooth surface topography. Excellent profile control for trench etching with a depth of about 250 mu m and an anisotropy of better than 0.98 at a mean etch rate of 4 mu m/min was obtained. Higher etch rates of up to 6.2 mu m/min have been achieved resulting, however, in lower anisotropy. The developed microgripper is driven by a differential-type shape memory alloy (SMA) actuator. SMA actuators exhibit the best power-to-volume ratio of all actuators, do not release any particles, and can perform various movements like bending, elongation or twisting. Heating can easily be achieved by direct electrical current. Therefore SMA actuators are well suited for microgripper applications.