MEMS stands for Microelectromechanical Systems. These are miniature devices or systems that integrate microsensors, microactuators, micromechanical mechanisms, signal processing and control circuits, high-performance electronic integrated devices, interfaces, communication, and power supplies using traditional semiconductor processes and materials. They are characterized by small size, low cost, and high integration.
MEMS working principle diagram
I. Application Areas of MEMS Sensors
In addition to smartphones, MEMS sensors will be widely used in consumer electronics such as AR/VR and wearables, as well as in IoT fields such as intelligent driving, smart factories, smart logistics, smart homes, environmental monitoring, and smart healthcare.
1. Wearable device applications
Taking the Xiaomi Mi Band as an example, it uses ADI's MEMS accelerometer and heart rate sensors to monitor movement and heart rate. In addition to MEMS accelerometers, gyroscopes, and MEMS microphones, the Apple Watch also uses a pulse sensor.
2. VR Applications
VR devices need to accurately measure the speed, angle, and distance of head rotation. Using MEMS accelerometers, gyroscopes, and magnetometers for measurement is a crucial solution and has almost become standard in VR devices. Oculus Rift, HTC Vive, and PlayStation VR all use MEMS accelerometers and gyroscopes, and future VR devices may also use MEMS eye-tracking technology.
3. Applications of drones
MEMS sensors have found new applications in drone flight attitude control technology. Combined with accelerometers and gyroscopes, angle changes can be calculated, and position and flight attitude can be determined. MEMS sensors can operate normally under various harsh conditions while obtaining high-precision output. The application of MEMS accelerometers and gyroscopes in drones has truly shone.
4. Vehicle-to-Everything (V2X) Applications
The Internet of Vehicles (IoV) is a major area of IoT development, and intelligent vehicles are the core of IoV, currently experiencing rapid growth. In the era of intelligent vehicles, active safety technology has become a highly anticipated emerging field, requiring improvements to existing active safety systems, such as rollover and ESC. This necessitates MEMS accelerometers and angular velocity sensors to sense vehicle attitude.
Voice will become an important way for people to interact with smart cars, and MEMS microphones will usher in new development opportunities. MEMS sensors also have many other applications in the automotive field, including airbags (high-g accelerometers used in frontal airbags and pressure sensors used in side airbags) and automotive engines (absolute pressure sensors and flow sensors used to detect the amount of air entering the intake manifold).
5. Autonomous driving applications
The rise of autonomous driving technology has further propelled the integration of MEMS sensors into automobiles. While GPS receivers can calculate their own position and speed, navigation is affected in areas with poor GPS signal (underground parking garages, tunnels) and when signals are interfered with, a fatal flaw for autonomous driving. By utilizing MEMS gyroscopes and accelerometers to acquire speed and position (angular velocity and angular position), even the slightest movements and tilts of the vehicle are converted into digital signals and transmitted to the vehicle's computer via a bus. Even at the highest speeds, the accuracy and response speed of MEMS remain adaptable. Thanks to advancements in silicon micromachining and wafer bonding technologies, accuracy has reached 0.01.
6. Industrial Applications
MEMS enables the miniaturization and intelligentization of sensors, and MEMS sensors will play a significant role in the era of smart industry. MEMS temperature and humidity sensors can be used to detect environmental conditions, while MEMS accelerometers can be used to monitor the vibration and rotation speed of industrial equipment. High-precision MEMS accelerometers and gyroscopes can provide accurate position information for the navigation and rotation of industrial robots.
II. Major MEMS Sensor Types and Suppliers
MEMS sensors come in many varieties, with the main types including motion sensors, pressure sensors, microphones, environmental sensors, and light sensors. Among these, motion sensors can be further divided into gyroscopes, accelerometers, and magnetometers.
1. MEMS motion sensor
MEMS motion sensors mainly fall into three categories: accelerometers, gyroscopes, and magnetometers. Accelerometers and gyroscopes can be integrated into a six-axis inertial sensor; magnetometers and accelerometers can be integrated into an electronic compass (e-compass); and accelerometers, gyroscopes, and magnetometers can be integrated into a nine-axis sensor.
Inertial sensor (accelerometer + gyroscope) manufacturers include: STMicroelectronics, Asahi Kasei Microelectronics (AKM), InvenSense, Robert, Bosch, etc.
Manufacturers of electronic compasses (magnetometer + accelerometer) include: Asahi Kasei Microelectronics (AKM), Yamaha, Alps Electric, MEMSIC Semiconductor (acquired by HC SemiTek in July 2016), etc.
2. MEMS microphone manufacturers
3. MEMS pressure sensor manufacturers
4. MEMS environmental sensors
Environmental sensors can be further categorized into gas, temperature, and humidity sensors, among others. MEMS temperature sensors can be used anywhere temperature needs to be detected.
MEMS humidity sensors have been widely used in industries such as industrial control, meteorology, agriculture, and mining inspection.
MEMS gas sensors are mainly used to detect the composition and concentration of target gases.
5. MEMS biosensors
MEMS biosensors are currently in the early stages of development. MEMS biosensors are devices that utilize biomolecules to detect biological responses and are listed as one of the five major medical testing technologies of the new century. They are a product of the interdisciplinary integration of modern biotechnology with microelectronics, chemistry, and other disciplines. In the future, MEMS biosensors have broad development prospects in fields such as medicine, food industry, and environmental monitoring.
III. MEMS Industry Chain
MEMS is a complex system that integrates multiple disciplines, and the entire industry chain involves design, manufacturing, packaging and testing, software and application solutions. The upstream of the MEMS industry chain is responsible for MEMS device design, material and production equipment supply, the midstream manufactures MEMS devices, and the downstream uses MEMS devices to manufacture end electronic products.
The MEMS industry chain is complex and involves numerous manufacturers; Chinese design, manufacturing, packaging and testing companies are actively developing MEMS, and a complete MEMS industry chain has been formed.
1. Global MEMS manufacturers
The world's top ten MEMS manufacturers include Bosch, STMicroelectronics, HP, Texas Instruments, Canon, InvenSense, Avago, Qorvo, Knowles Electronics, Panasonic, and others. Among them, Bosch firmly holds the top position in the industry due to its dual focus on automotive and consumer electronics, with its revenue accounting for approximately one-third of the combined revenue of the top five companies.
Most major manufacturers in the MEMS industry are fabless companies, such as Knowles, HP, and Canon. At the same time, there are also IDM (Integrated Device Manufacturer) companies that are vertically involved in various parts of the entire industry chain, such as Bosch and ST, which have built their own wafer foundry production lines.
2. MEMS foundry
MEMS foundry services mainly fall into two categories: MEMS foundry services provided by IDM (Integrated Device Manufacturer) companies and MEMS foundry services provided by independent foundries. Independent foundries include integrated circuit foundries and pure MEMS foundries. In recent years, fabless MEMS device manufacturers have developed rapidly. Independent MEMS foundries are striving to standardize processes to improve economies of scale, reduce manufacturing time, and lower costs, leading to their rapid growth. However, IDM foundries currently still hold a leading market position.
Currently, the main IDM manufacturers providing MEMS foundry services include STMicroelectronics, Sony, and Texas Instruments. TSMC is currently the world's largest independent MEMS foundry. Other leading pure MEMS foundries in the world include Silex Microsystems, Teledyne DALSA, Asia Pacific Microsystems, X-FAB, and Innovative MicroTechnology. In China, SMIC, Huahong Hongli, and Shanghai Advanced Semiconductor also have the capability to produce MEMS.
3. MEMS packaging testing
Currently, major international manufacturers with MEMS packaging and testing capabilities include ASE, Amkor, SPIL, and Powertech, while domestic manufacturers include Huatian Technology, JCET, and ChipMOS Technologies. Although China's MEMS front-end manufacturing lags behind international giants, its packaging technology started earlier, resulting in a relatively complete back-end packaging system in the domestic MEMS industry chain.
Packaging technology differs significantly from IC packaging and places high demands on companies. As is well known, the price of MEMS devices is decreasing very rapidly; currently, packaging costs account for 40% to 60% of the total price of some MEMS devices. Achieving low-cost packaging is a major challenge for packaging and testing companies.
After more than forty years of development, Microelectromechanical Systems (MEMS) has become one of the world's most prominent scientific and technological fields. It involves multiple disciplines and technologies such as electronics, mechanics, materials, physics, chemistry, biology, and medicine, and has broad application prospects.
