Analytical Instrumentation

Introduction to MEMS, MEMS pressure sensor

Micro-Electro-Mechanical Systems, or MEMS, are technologies that are in the most common form that can be defined as miniature mechanical and electro-mechanical elements (i.e. devices and structures) made using microfabrication techniques.

the types of MEMS devices can vary from relatively simple structures having no moving elements, electromechanical systems to very complex with multiple moving elements under the control of integrated microelectronics. One of the main criteria of MEMS is that there are at least some elements that have some kind of mechanical function or whether the elements can move.

In the most common form, MEMS consists of mechanical microstructure, microsensors, microactuators, and microelectronics, all of which are integrated on the same silicon chip.

Working of MEMS:

Overview of a MEMS system is shown below:

A MEMS is developed by combining conventional complementary metal oxide semiconductor (CMOS) with a pre-CMOS or post-CMOS MST.

MEMS made using films are deposited on wafers such as CMOS.

Example: Working principle of MEMS Pressure sensor: 

There are examples of a bulk micro-machined piezoresistive pressure sensor. Resistors can be diffused on a membrane or deposited on a membrane with an intermediate isolation layer (usually SiO2). The etching membrane from behind the wafer usually has tens of micrometres thickness. Time-based etching has several advantages, the membrane does not require boron doping. However the ability to produce with low membrane thickness. Etching by involving boron provides good control over controlling membrane thickness, however high doping levels prohibit the use of diffusion of gauges strains.

Therefore electrochemical etching often uses lighter doping membranes. Because the membrane in the etching of the back of the wafer is very possible with standard IC fabrication processes.

Application from MEMS device:

  • Automotive: In the car several types of pressure sensors are used, which have the same working principle, which functions to monitor pressure.
  • Medical: Technology is needed to make pressure sensors that are used for medical purposes that require expertise in making devices that have low-pressure accuracy.
  • Industry: In the technology industry used are switches, barometer pressure sensors, and smart road
  • Military: In military activities, the technology used is GPS, gyroscope, accelerometers, micro-propulsion systems

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