Micro Electro-Mechanical Systems
Micro Electro-Mechanical Systems (MEMS) is the integration of mechanical elements, sensors, actuators and electronics on a common silicon substrate using microfabrication techniques. MEMS are a hot area of research because they integrate sensing, analyzing and responding on the same silicon substrate hence promising realization of complete systems-on-a-chip. As MEMS are manufactured using batch fabrication techniques similar to IC technology, MEMS are expected to deliver high functionality at low prices.
Current systems are limited by the capability of sensors and actuators, as these are bulkier and less reliable than the microelectronic circuit. In a ...view middle of the document...
1. Deposition Processes: One of the basic building blocks in MEMS processing is the ability to deposit thin films of material. This is achieved either through the processes like PVD or CVD.
2. Lithography: Lithography in the MEMS context is typically the transfer of a pattern to a photosensitive material by selective exposure to a radiation source such as light. In lithography for micromachining, the photosensitive material used is typically a photoresist. When resist is exposed to a radiation source of a specific a wavelength, the chemical resistance of the resist to developer solution changes.
3. Etching: If the resist is placed in a developer solution after selective exposure to a light source, it will etch away one of the two regions (exposed or unexposed). Then another layer of material is deposited and the first layer selectively etched away as shown in the figure resulting in the required MEMS.
Comb drives actuators and electrostatic motors can be fabricated using this technique.
Fig: The processes involved in Silicon Micromachining technique.
The LIGA process is used to make MEMS with a higher accuracy. Actuators in MEMS are made using either piezoelectric effect or shape memory alloys.
Fig: Actuator using piezoelectric effect
Application of MEMS:
As MEMS are smart the applications one can conjure for them is limitless. On one hand scientist in University of California, Berkeley are developing dust particles which gather information about the weather while on the other MEMS are already being used in the automotive industry as accelerometers for triggering airbags. Some of the applications of MEMS in the industry are as follows.
1. Pressure, temperature and Chemical Sensors: MEMS pressure sensors are made using piezoelectric strain gauges placed on a silicon substrate. Biomedical uses of these sensors are to measure the blood pressure inside arteries while aerospace uses the same for measuring airspeed and altitude information.