ABSTRACT

Wet bulk micromachining is employed for the fabrication of a wide range of microelectromechanical system structures, from simple cavities to complex structures. The fabrication of square/rectangular freestanding diaphragms requires only one lithography step. In the time-controlled etching method, a suspended structure can be fabricated using moderately doped silicon, but it requires a stable etch rate during etching. The same fabrication methodology can be employed for the formation of silicon gratings with triangular profiles on silicon wafers with different orientations. Silicon bulk micromachining is a promising method for the fabrication of silicon-based microvalves and micropumps. It is well known that wet silicon anisotropic etching cannot be used for forming an arbitrary-shaped mesa/cavity/groove in a silicon wafer as the crystallographic properties restrict the size and shape of the silicon microstructures. The deep reactive ion etching (DRIE) process can be used for the fabrication of these types of structures because the etching rate of DRIE is almost crystallographic direction independent.