An Introduction to mems (Micro-electromechanical Systems)
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| An Introduction to MEMS
Prime Faraday Technology Watch – January 2002 17
3. MEMS Fabrication Methods
MEMS fall into three general classifications; bulk micromachining, surface micromachining and high-aspect-ratio micromachining (HARM), which includes technology such as LIGA (a German acronym from Lithographie, Galvanoformung, Abformung translated as lithography, electroforming and moulding).
Conventional macroscale manufacturing techniques e.g. injection moulding, turning, drilling etc, are good for producing three dimensional (3D) shapes and objects, but can be limited in terms of low complexity for small size applications. MEMS fabrication, by comparison, uses high volume IC style batch processing that involves the addition or subtraction of two dimensional layers on a substrate (usually silicon) based on photolithography and chemical etching. As a result, the 3D aspect of MEMS devices is due to patterning and interaction of the 2D layers. Additional layers can be added using a variety of thin-film and bonding techniques as well as by etching through sacrificial ‘spacer layers’. Figure 16 shows the potential complexity of a MEMS system by the addition of independent structural layers.
Figure 16. MEMS device complexity by structural layers [2].
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