Overview of MEMS fabrication

Microelectromechanical systems (MEMS) fabrication developed out of the thin-film processes first used for semiconductor fabrication. To understand the unique features of the MEMS fabrication process it is helpful to consider the semiconductor fabrication process.

The typical thin films that are deposited include semiconductors (e.g., polysilicon), insulators (e.g., silicon nitride), and metals (e.g., aluminum). In addition, some layers are grown (oxide), diffused, or implanted (dopants) rather than deposited using thin-film techniques. A cross section of a complementary metal oxide semiconductor (CMOS) process that includes six levels of metal is shown in Figure 1.2 [1]. A schematic diagram of one of the first MEMS devices, which used semiconductor processing for fabrication, the resonant gate transistor, is shown in Figure 1.3 [2].