ABSTRACT
This chapter discusses the importance of precise mask alignment in wet anisotropic etching–based silicon bulk micromachining. The role of precise alignment of mask edges along crystallographic directions during the lithography process is described by taking three examples of the most widely used structures in Microelectromechanical systems, namely microchannels, cantilever beams, and diaphragms. Alignment of the mask edges along the precise crystallographic directions is necessary to obtain dimensionally accurate cantilever beams. The basic method to align mask patterns along crystallographic directions is to use the wafer flat (WF) as a reference direction. Since the WF is not precisely aligned with the exact crystallographic directions, the use of pre-etched patterns aids in aligning the mask precisely along the crystallographic directions in order to obtain dimensionally accurate structures. The prefabricated reference line at the wafer end on the mask can be aligned with the notches of four circles along their diagonals.
