Today a great many industries benefit from MEMS (micro-electro-mechanical systems) technologies that combine semi-conductor micro-electronics with micro-machining, thus enabling the realisation of entire complex systems on a die.
 
Since the first developments of this technology in the 1970s, the commercial application of micro electro-mechanical systems (MEMS) technology has grown at the beginning of the 90s, from implementations in products such as automotive applications (sensors for airbags,….) to a full deployment in peripherals (such as ink jet cartridges), medical applications, aerospace or defence.

In 1997, using the experience gained in other fields, MEMS was deployed into wireless  and optical communications, where MEMSCAP was one of the very first players.

The experience gained from these MEMS applications has made it an enabling technology for fiber-optic applications, frequently referred to as micro opto electro-mechanical systems (MOEMS), wireless applications and biomedical applications, often referred to as bioMEMS. Work in MEMS is going on throughout the world, and it is often referred to as microsystems technology (MST) in Europe.

MEMS, or micro-electro-mechanical systems, or micro-systems, are microscopic mechanical systems that combine mechanical, optical, electromagnetic, thermic and fluidic elements with electronics on semi-conductor substrate electronics. They act as sensors able to identify physical parameters in their environment (pressure, acceleration, etc.) and/or actuators able to act on this environment. This technology enables to improve the performance of the products, increase the systems speed, reduce the energy consumption, do mass manufacturing, miniaturise and increase the reliability and the integration.

Already delivering workhorse solutions in everyday applications, MEMS technology has proven its paradox, which is its ability to perform in challenging applications with stringent reliability requirements, while reducing costs and miniaturising. These performances can be achieved in severe conditions such as violent thermal chocks, important pressure, high-humidity, and in varied environments from the human body to space  As a result, MEMS are seen as the cost-effective candidate for today and next-generation solutions across an infinite range of markets.

A proven technology

Efficiency and Security
While one of the first MEMS applications was the simple tire pressure sensor gauge, MEMS are now integrated throughout automotive systems, serving functions ranging from the airbag accelerometer sensor to fuel sensors, engine and brake force control, and noise cancellation. Some of the latest automotive innovations on the market include "intelligent tires" that alert the driver to a flat 50 miles before it needs to be replaced.

Reliability in extreme conditions
Severe environment applications, such as life sciences, defence or aerospace, have in common extreme demands of reliability, security and miniaturisation. MEMS technology has been able to address these challenges from its beginning and those markets are now fast expanding.

Performance and miniaturisation
MEMS can encompass mechanical functions, such as motors, pivots, links, and optical and electrical components, such as switches, all on a single chip—ranging in size from a dozen microns to a dozen millimeters. These capabilities allow MEMS solutions to simplify design, cut costs, boost performance, improve battery life, and shrink device sizes as compared to other methods of design and fabrication.
By virtue of these advantages, and the fact that it is a proven technology for high volume manufacturing in demanding applications, MEMS have become a technology of choice for most industries

From Lab to Fab

One of the first applications of MEMS was a resonant gate field-effect transistor designed by Westinghouse in 1969. While this product proved to be mostly a technical curiosity, it signaled the beginning of what would become a ubiquitous technology. By the early 1970s, manufacturers were using bulk-etched silicon wafers to produce pressure sensors, and experimentation began in the early 1980s to create surface-micromachined polysilicon actuators that were used in disc drive heads. By the late 1980s, MEMS potential was being embraced and widespread design and implementation was ongoing in the microelectronics and bio-medical industries.

By the 1990s, MEMS had the full attention of the US government, and relevant agencies had large-scale MEMS support and projects underway. For instance, the Air Force Office of Scientific Research (AFOSR) was supporting basic research in materials while Defense Advanced Research Projects Agency (DARPA) initiated its foundry service in 1993. Additionally, NIST began supporting commercial foundries for complementary metal-oxide semiconductor (CMOS) and MEMS devices.

By the end of the 1990s and the turn of the 21st century, MEMS devices were in full-scale production around the globe. Commercial semiconductor fabs dedicated to MEMS production were built or planned by companies such as Bosch and Philips Semiconductors. Government interest in MEMS continues, with significant ongoing funding through agencies such as DARPA. In fact, recently a series of miniaturized navigation and control, sensing, propulsion, computation and thermal control devices were sent into space for performance testing on a US Space Shuttle mission.Today, high-volume MEMS can be found in diverse systems ranging across defence, medical, electronic, communications, and automotive applications (see chart). They can function individually or as part of an array in matrices to sense the need for and then control and trigger actions or events.

Defence	Medical	Electronics	Communications	Automotive
Munitions Guidance	Blood Pressure Sensor	Disk drive heads	Optical or Photonic Switches and cross-connects in Broadband networks	Embarked Navigation sensors
Surveillance	Muscle stimulators & drug delivery systems	Inkjet Printer heads	RF Relays, Switches, and Filters	Air conditioning compressor sensor
Arming Systems	Implanted Pressure sensors	Projection Screen Televisions	Projection displays in portable communications devices and instrumentation	Brake force sensors & Suspension control accelerometers
Embedded Sensors	Prosthetics	Earthquake Sensors	Voltage controlled oscillators (VCOs)	Fuel level and vapor pressure sensors
Data Storage	Miniature analytical instruments	Avionics Pressure sensors	Splitters and couplers	Airbag sensors
Aircraft Control	Pacemakers	Mass Data Storage Systems	Tunable lasers	"Intelligent" Tires

Making MEMS
Today's MEMS manufacturing uses high volume, integrated-circuit (IC)-style batch processing. Because the technology encompasses several different approaches, there are multiple ways to manufacture MEMS, including surface micromachining, bulk micromachining, electro-discharge micromachining (EDM), and high-aspect-ratio micromachining (HARM) technologies such as LIGA (a German acronym for lithography, electroplating, and molding).

Silicon surface micromachining uses the same equipment and processes as the semiconductor manufacturing industry, so it was one of the first techniques widely adopted for MEMS fabrication. Typical applications for this method include actuators and electrostatic motors. In silicon bulk micromachining, the device structures are created using etch techniques on bulk silicon. Applications using this technology range from mirrors to accelerometers such as the ones used in airbag deployment, or complex pressure sensors such as the ones used in aerospace applications.

EDM is a relatively new approach that uses machine shop production techniques and offers the capability to make parts out of most conductive materials. In the LIGA process, polymethyl methacrylate (PMMA) plastic is exposed to radiation through a mask. This washes away some of the PMMA, leaving structures that are then electroplated with metal. These metallized structures can act as the final MEMS device, or can be used as molds for parts made out of other plastics. Devices manufactured using the LIGA technique include electrostatic motors and gears.

MEMS in Action

MEMS have a unique ability to collect information, process it, determine a course of action, and then act as a trigger by communicating through an electronic interface. These capabilities allow MEMS to provide the "nuts and bolts" of advanced applications known as "smart devices," such as collision avoidance systems and wireless handsets. MEMS devices do not work in isolation; they are embedded systems that make it possible for a component to perform higher level functions, such as controlling the fuel to air mixture in a car's engine.

A singular feature of this technology is the ability to integrate both MEMS and CMOS devices on a single chip, often referred to as integrated MEMS (IMEMS).  Why a single chip ? The integration of electro-mechanical, optical, and electronic circuits all on the same chip simplifies design and manufacturing, and improves reliability because of fewer interconnects and components. As a result, this approach can offer a lower cost than alternative technologies such as multi-chip modules (MCM). This advanced integration also improves overall system performance, because fewer interconnects reduces circuit parasitics.

MEMS Momentum

Published studies forecast that the overall MEMS market, considered to be 5.1 billion dollars today, will grow with an annual growth rate of 15 to 19% , to reach more than 9 billion dollars.
This market can be divided in two segments:

Establisehd markets such as automotive, peripherals, medical
and aerospace, representing most of the MEMS market size

Emerging markets, such as consumer applications,
communications and biomedical, representing today most of
the growth of the MEMS market

MEMS have proven that they are able to fulfill each and any function in all kind of environments. The only limit to their growth today is man imagination.