Surface micromachining
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Surface micromachining builds microstructures by deposition and etching structural layers over a substrate.[1] This is different from Bulk micromachining, in which a silicon substrate wafer is selectively etched to produce structures.
Layers
Generally,
As the structures are built on top of the substrate and not inside it, the substrate's properties are not as important as in bulk micro-machining. Expensive
Fabrication process
Micro-machining starts with a silicon wafer or other substrate upon which new layers are grown. These layers are selectively etched by
Sacrificial layers
A sacrificial layer is used to build complicated components, such as movable parts. For example, a suspended cantilever can be built by depositing and structuring a sacrificial layer, which is then selectively removed at the locations where the future beams must be attached to the substrate (i.e. the anchor points). A structural layer is then deposited on top of the polymer and structured to define the beams. Finally, the sacrificial layer is removed to release the beams, using a selective etch process that does not damage the structural layer.
Many combinations of structural and sacrificial layers are possible. The combination chosen depends on the process. For example, it is important for the structural layer not to be damaged by the process used to remove the sacrificial layer.
Examples
Surface Micro-machining can be seen in action in the following MEMS (Microelectromechanical) products:
- Surface Micro-machined Accelerometers[2]
- 3D Flexible Multichannel Neural Probe Array[3]
- Nanoelectromechanical relays
See also
References
- doi:10.1109/5.704260.
- doi:10.1109/4.494198.
- ^ Takeuchi, Shoji; Takafumi Suzuki; Kunihiko Mabuchi; Hiroyuki Fujita (October 2003). "3D Flexible Multi-channel Neural Probe Array". Journal of Micro-machines and Micro-engineering.