International Standards and Conformity Assessment for all electrical, electronic and related technologies

January/February 2014

 

Tiny MEMS

Huge impact on our digital future

Gabriela Ehrlich

MEMS, tiny electromechanical systems, are now an indispensable component of any piece of electronic equipment, from smart phones, to tablets, to wearable devices, cars, aeronautics and much more (see also article on CES trends in this e-tech). Often MEMS outperform their macro scale counterparts achieving feats much larger than their size. IEC work both in standardization and conformity assessment plays an important role in the further expansion of this technology.

What are MEMS

MEMS (Micro-Electro-Mechanical Systems) are miniaturized mechanical or electromechanical elements that vary in size from 1 to 100 microns, approximately the thickness of a human hair. They were invented in the 1980s and are now present in most modern electronics.

 

MEMS all look different and can be anything from relatively simple devices without moving elements to extremely complex electromechanical systems with multiple moving elements under the control of integrated microelectronics.

 

The micro sensors and actuators in MEMS are also called “transducers” as they convert energy from one form to another. In the case of micro sensors, the device typically converts a measured mechanical signal into an electrical signal.

 

To make MEMS, generally thin layers of material are deposited onto a base and then selectively etched away, leaving a microscopic three-dimensional structure. The electrical elements process data while the mechanical elements act in response to that data. An integrated circuitry provides the thinking part of the system while the MEMS components complement the system with active perception and control functions.

Micro outperforms macro

Today MEMS are used for a large number of sensing modalities, including temperature, pressure, inertia, chemical, magnetic fields, radiation, etc. Remarkably, it seems that many of these micro machined sensors have demonstrated performances that sometimes exceed those of their macro scale counterparts. Memsnet.org, the information site for the MEMS and Nanotechnology industry puts forward the example of a pressure sensor made to the most precise macro scale level machining technique that is outperformed by a micro scale pressure transducer.

High performance, small in size, cheap to produce

While the performance and size of MEMS are important arguments for the electronics industry, their production cost has been steadily decreasing. Today an average unit costs around USD 0,60, down from USD 7 in 2006.

All kinds of electronics

For all of the above mentioned reasons, MEMS are now found in an increasing number of devices, many of which are used every day by millions of people. But MEMS have also found their way into industrial applications such as for example micro valves to control gas and liquid flows; optical switches and mirrors to redirect or modulate light beams; independently controlled micro mirror arrays for displays; micro pumps to increase the pressure of fluids; micro flaps to module airstreams on air foils, and many others.

 

Often these tiny devices can perform mechanical feats far larger than their size would imply. For example, researchers have placed small micro actuators on the far edge of air foils of an aircraft and have been able to steer the aircraft using only these micro miniaturized devices.

A fast growing market

With the proliferation of smart consumer devices and especially smart phones, the MEMS market is increasing by double digit CAGR (compound annual growth rate) and it is estimated to reach USD 19.5 billion by 2016 from next to nothing in 2000, when MEMS had just begun being used in the PlayStation game console. This market acceleration in turn drives prices further down. The fastest developing MEMS categories include pressure sensors and gyroscopes.

The MEMS phone

At CES a group of industry experts discussed the advancement of the MEMS market in consumer electronics. They agreed that smart phones, while already highly dependent on MEMS will be adding a multitude of additional functions in the future with the help of further MEMS. They already incorporate accelerometers, altimeters, magnetometers (compasses), inclinometers, gyroscopes, and pressure sensors, which in combination with apps and/or hardware drive a multitude of health and well-being functionalities.

 

In the future altimeters, pressure and humidity sensors will allow the development of fully localized and tailored weather forecasts or personalized GPS. Smartphones will soon know not only where we are horizontally at street-level but also what floor of a building we are on.

 

Biochemical or radiation sensors will allow people to test food, water and their environment on the go. A gas or biosensor may be able identify alcohol levels or even certain lung diseases by identifying the breath of the person who speaks into the phone. A UV sensor may provide alerts when sun screen needs to be reapplied.

Challenges

MEMS come in many different shapes and specifications, which makes comparison increasingly difficult. The experts at CES all agreed that going forward standardized parameters for MEMS are needed. Additionally, if algorithms are not optimized for multiple sensors then it will be difficult to achieve integrated data collection. There is a clear need for harmonization to further promote the growth of this industry.

IEC work for MEMS

IEC TC (Technical Committee) 47: Semiconductor devices and SC (Subcommittee) 47F: Micro-electromechanical systems prepare a multitude of International Standards that enable manufacturers to build better, more resistant, efficient and reliable sensors and MEMS. They cover terms and mechanical properties, basic characteristics, essential and optimal operating ratings, as well as a multitude of testing methods for materials such as bonding strengths in composites, resistance to stress, bending or thermal expansion. Together they facilitate the design, manufacture and use and reuse of micro electromechanical systems.

 

IECQ (IEC Quality Assessment System for Electronic Components) allows electronic component manufacturers to test and measure the safety, reliability of MEMS and ensure that they meet set requirements.

Huge and growing market

The market for MEMS will grow from about USD 12 billion in 2012 to over USD 22 billion by 2018, according to market analysis published at the 12th annual meeting of the MIG (MEMS Industry Group), held in November 2013.

 

Laurent Robin, activity leader for Inertial MEMS Devices and Technologies at Yole Development in France, told the meeting that the MEMS sector could grow at a 13% CAGR (compound annual growth rate) for the next five years. He claimed that MEMS for mobile devices was the driver for future growth, noting that smartphones have as many as 12 MEMS chips today, growing to as many as 20 in the near future, including 9-axis sensors. IEC SC 47F standardization work will be central to that expansion.

 

More on MEMS

 

Processing motion

MEMS motion sensors detect the orientation of any device, where it is heading and its absolute location in three-dimensional space. By fusing the data streams from different MEMS (accelerometers, altimeters, inclinometers, etc.) they are for example used to control the hardware of game consoles or inform software such as security protocols or location-based services.

 

Sharper images in millions of shades

The MEMS micro mirror chip (DMD) is frequently used in consumer electronics and particularly in video projectors and televisions. This chip uses microscopic moving mirrors to improve the image quality and reliability of these products. The mirrors are mounted on tiny hinges that allow them to tilt either towards the light source to reflect the light or away from it to block the light. The length of time the mirror faces the light determines the brightness of each dot. They are able to produce over 16 million shades of colour and an image quality that enables them now to replace film projectors in movie theatres.

 

More storage and better sound

MEMS are revolutionizing mass data storage in the computer industry by miniaturizing components for disk drives, servers and peripherals.

 

Acoustic MEMS chips are changing the way sound reaches the human ear. They provide less distortion and higher clarity and quality of sound. For this reason they are built into cell phones, music devices but also hearing aids.

 

Increasing safety

In the automotive industry MEMS accelerometers are a key element of modern airbag systems. These MEMS contain a central mass that moves in response to the vehicle’s acceleration. The mass is mounted on a hinge that allows it to move during driving, returning it to its original position when the car stops. Sensitive electronic circuitry read the mass’s movement and relates its data to a connected micro-processor. When the mass’s movement changes at an unsafe speed, the airbags are deployed protecting passengers from impact.

 

Opening the way for new applications

In medical applications, in addition to improving speed and reliability, MEMS open the way for novel innovations: MEMS chips inserted under the skin of patients are able to release an exact amount of drug over time; built into a scalpel they measure the length and depth of incisions during delicate operations. Environmental sensors (for temperature, humidity and air quality), medical sensors (such as in blood-pressure monitors, glucose meters, weight scales and pulse oximeters) and wearable sensors that can invoke a personal emergency response system, all use MEMS often connected wirelessly to the Internet.

 

Sensing danger

MEMS low-power nano sensors are also used to detect gas leaks or saturation levels. They are so small that they can be sewn into clothing to be worn by soldiers in the field or by the elderly at home. Increasingly these MEMS sensors are placed along pipelines, around factory perimeters and in workspaces where they help increase safety and enable early warning systems.

 

This text includes extracts of technical explanations courtesy of www.memsnet.org

 

  • MEMSMEMS are tiny electromechanical systems that vary in size from 1 to 100 microns.
  • MEMS sensors, embedded in a variety of objects can send their readings over the internet to a user’s smartphone (Photo: Bosch)
  • Some MEMS sensors, such as this one by Bosch, combine pressure, humidity and temperature measurement (Photo: Bosch)

 

 

Find out more