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MEMS, what do you see in the future?

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In recent years, MEMS technology has become a dazzling star in the field of science and technology with its amazing innovation potential.

The full name of MEMS is Micro Electromechanical System, which is micro-electromechanical system. MEMS products are made of micro-sensors, micro-actuators, micro-structures, signal processing and control circuits, and communication/interface units with different functions on silicon wafers. They are micro-machines. Products that combine processing technology and semiconductor technology.

Simply put, MEMS is a tiny device that combines mechanical and electronic technologies.

Because MEMS has the characteristics of miniaturization, low power consumption, integration, and intelligence, it is widely used in consumer electronics, automobiles, industrial control, medical and other fields to sense motion, sound, temperature, pressure, etc., and MEMS devices are used in almost Growing adoption in all markets.

MEMS is an important technical branch of sensors and even the entire semiconductor industry. It is currently in the outbreak period of the third industrial wave and is still in the ascendant. In the future, as emerging technologies such as the Internet of Things, artificial intelligence, and autonomous driving mature, new MEMS products, new functions, and new applications will continue to emerge, thus driving the continued growth of the MEMS industry.

According to the recently released MEMS annual report “Status of the MEMS Industry 2023” released by Yole Group, the MEMS market will grow at a compound annual growth rate of 5%, from US$14.5 billion in 2022 to US$20 billion in 2028.

Amid this growth, the consumer market remains the largest segment in the MEMS market. Within this segment, emerging wearable applications will offset the recent decline in smartphone demand, growing at a 4% CAGR from $7.6 billion to $9.4 billion;

The automotive industry continues to benefit from the increasing number of autonomous driving features in cars and will maintain its position as the second largest market. MEMS penetration continues to grow, driven by the integration of autonomous driving and ADAS functions, helping to cushion the overall somewhat flat or slow growth of the automotive market. GNSS positioning requires the use of MEMS inertial sensors, lidar requires the use of MEMS micromirrors, and achieving in-car comfort requires the use of MEMS environmental sensors. These demands will help the market reach a compound annual growth rate of 7%. By 2028, the market size can be Increased to $4.1 billion;

The industrial and medical markets will register a compound annual growth rate of at least 5% during the forecast period. The industrial market is driven by industrial automation and Industry 4.0 implementation. Inertial sensors, oscillators and pressure sensors used in robots or AGVs in factories will be key to this market. The continued miniaturization of diagnostic and monitoring equipment and the introduction of wearable devices will increase the demand for MEMS components in the medical field. The Future of MEMS

During the forecast period, the telecommunications market is expected to exhibit the highest compound annual growth rate of 28%, with optical MEMS and MEMS oscillators for switches playing an increasingly important role in meeting the exponential growth in data demand.

In addition, the trend of intelligence in application fields such as artificial intelligence, Internet of Things, and smart cities is obvious. With the rise of emerging fields in the information age, the application scope of MEMS sensors will continue to expand, with huge development potential.

As global demand for sensorized and data-driven applications continues to grow, Yole looks back at the past 20 years, in which the MEMS industry has shown continued innovation and even opened up new product perspectives. Over the years, various market drivers, successive crises and ecosystem changes have shaped today’s MEMS industry, which is worth more than $14 billion.

01 MEMS Industry Review

In 1959, the famous physicist Richard Feynman delivered a famous speech entitled “There’s Plenty of Room at the Bottom”, first proposing the concept of micromachines. In 1987, scientists at the University of California, Berkeley, used integrated circuit (IC) technology to produce a silicon microelectrostatic micromotor with a diameter of only about 100 μm, which is about the same thickness as a human hair. This is considered to be a sign of the MEMS era.

Since then, MEMS technology has entered an era of rapid development, with various MEMS products emerging one after another and being used in various cutting-edge technology fields.

The first wave of commercialization of MEMS sensors began in the 1980s and 1990s, when MEMS pressure and inertial sensors began to be used in automobiles. In 2003, automotive became a major driver as more advanced safety features began to be incorporated into vehicles, such as accelerometers used in airbags, gyroscopes for ESP systems, and early adoption of pressure sensors for tire pressure monitoring were MEMS. One of the first automotive applications.

Nowadays, benefiting from the safety regulations of the automotive industry and the wave of informatization and intelligence, MEMS sensors have been developing rapidly in the automotive field. According to relevant research data, each car currently contains an average of 10-30 MEMS sensors, and about 30 or even hundreds of MEMS sensors are used in high-end cars.

The second wave emerged from the rise of PCs. MEMS technology was widely used in projectors and inkjet print heads. HP’s MEMS inkjet print heads and Texas Instruments’ DLP for projection applications created huge demand at this time. , gradually surpassing the automotive industry in terms of volume and sales, and Texas Instruments became an early market leader along with HP.

Later, the popularity of smartphones further promoted the rapid development of this wave. The introduction of the iPhone in 2007 and subsequent widespread adoption of smartphones led to a surge in demand for MEMS in the consumer sector. Automatic screen rotation created early demand for accelerometers, which was further driven by the introduction of more advanced features such as navigation assistance, step counting and gaming. meet the demand for inertial sensors in smartphones. MEMS microphones also began to be used in smartphones and eventually became one of the largest shipped MEMS devices in the industry.

According to statistics from Yole Development, the total number of MEMS sensors in a single smartphone will increase from 12 in 2014 to 20 in 2021. It mainly includes sensors such as accelerometers, gyroscopes, pressure sensors, MEMS microphones, and radio frequency devices. With the technological innovation of smartphones and the trend of differentiated competition among mobile phone manufacturers, the number of sensors will continue to grow.

Currently, MEMS is embarking on its third wave of development due to the development of AIoT. The core of the Internet of Everything era is sensing, interconnection and computing. MEMS sensor products are also widely used in emerging application fields such as wearable devices and smart homes that have emerged with the implementation of AIoT.

In recent years, the increasing adoption of wearable devices such as smart watches, TWS headsets, and VR/AR has also promoted the development of the MEMS industry. The second wave of consumption and the subsequent surge in demand for inertial MEMS sensors allowed STMicroelectronics and Bosch to seize market leadership from early leaders such as TI and HP.

In summary, the development history of the MEMS industry can be roughly divided into three stages: the automotive electronics wave from 1990 to 2000, which ignited the demand for MEMS sensors; the consumer electronics wave from 2000 to 2010, which promoted MEMS sensors to present multiple categories and multiple applications. The development trend of functional integration; the wave of Internet of Things and artificial intelligence from 2010 to the present has driven the large-scale development of MEMS sensor single products and the collaborative development of software and hardware.

Pierre Delbos, technology and market analyst at Yole Intelligence, said: “As wearable technology matures and more end products enter the market, new wearable device features can mitigate the impact of declining smartphone purchases. , especially in the Chinese market.”

For example, products such as wireless headsets, smart watches, and AR/VR headsets have new functions such as navigation assistance, altitude measurement, spatial audio and even sleep monitoring. OEM manufacturers are integrating more MEMS components to further improve performance and enhance functionality. This has led to increased MEMS penetration.

According to IDC data, the total number of IoT connections is expected to reach 10.27 billion by 2025, and the demand for IoT will drive the MEMS market to continue to grow. The incremental MEMS market generated by the Internet of Things is 11 billion yuan, accounting for about 10% of the total market, and is expected to increase to 20% in 2025.

During the above-mentioned process, China and the global MEMS industry have undergone rapid changes over the past few decades, with old and new companies rising and falling, MEMS overlords changing hands several times, and numerous industry mergers and acquisitions.

Judging from the current Top 30 list of global MEMS companies, Bosch is still the world’s largest MEMS company and has a strong growth of 12% compared with 2021. Broadcom still ranks second but has weak growth, while Qualcomm benefits from 5G communications’ impact on MEMS RF filtering. The demand for machines has achieved a rapid growth of 21%, successfully ranking among the top three in the world. STMicroelectronics entered the Top 4 due to the growth of MEMS sensors in the automotive market.

In terms of Chinese companies, Goertek Microelectronics is still the Chinese company with the highest ranking in the global MEMS industry, ranking 9th this year. It is mainly due to the sluggish demand for consumer electronics, which has led to a decline in shipments. Knowles Electronics, also a global MEMS microphone giant, has also experienced sales. Close down the situation.

A total of 6 Chinese MEMS companies have entered the global Top 30. In addition to Goertek Microelectronics, there are also AAC Technologies (ranked 23rd), Silex Microsystems, a wholly-owned subsidiary of Silex Microelectronics (ranked 26th), TSMC (ranked 27th), Hainan Microelectronics Co., Ltd. Kangweishi (ranked 29th), Ruichuang Microna (ranked 30th).

It can be seen that two domestic MEMS companies, Hikvision and Ruichuang Microna, appear on this list.

02 What is the future development trend of MEMS technology?

MEMS technology is already relatively mature in the target market. But as innovation is happening, OEMs hope to continue to optimize cost, size and performance, which will further drive the MEMS market and technology demand.

In order to remain competitive, the MEMS industry is always pursuing innovation.

People in the industry should understand that MEMS is inherently capable of innovation, which begins with its highly innovative design, innovative structure, and innovative packaging technology. For example, after Bosch introduced through silicon vias (TSVs) in application-specific integrated circuit ASICs for the first time and adopted wafer-level chip-scale packaging technology on 3-axis accelerators, Bosch MEMS products compared with its competitors ST and mCube The package size is reduced to 55%. This technological breakthrough helped them reduce the size of silicon chips and thus reduce product costs.

This innovation race never stops. mCube later overtook Bosch again with its innovative MC3600 series accelerator solutions and regained its leading position.

Today, innovation in the MEMS field continues, not only from new technologies, but also from new applications of mature MEMS technologies.

03 Advanced packaging: miniaturization and integration trends

As a technology trend, MEMS sensors and actuators are constantly committed to reducing size, reducing cost and improving performance, and are turning to systemization with integration of heterogeneous functions as the key.

First of all, miniaturization is irreversible, and MEMS is evolving towards NEMS (nano-electromechanical systems). Similar to MEMS, NEMS is a micro-nano system technology focusing on the nanoscale field, but it is smaller in size. With the miniaturization and diversification of terminal equipment, the evolution of MEMS to smaller sizes is the general trend.

In addition, the entire MEMS supply chain is moving towards hybrid capabilities, from front-end manufacturing to packaging, modules and system integration.

With the advancement of MEMS processing technology and the integration of CMOS technology and MEMS technology, MEMS sensors can integrate more powerful computing and storage capabilities on smaller-area chips to better meet the low-cost, small-volume, and high-performance requirements of system applications. comprehensive performance requirements.

04 Multi-sensor fusion

As the “perception center” of electronic products, modern sensors can also undertake functions such as automatic zeroing, calibration and calibration by adding micro-control units and corresponding signal processing algorithms to realize the intelligence of terminal equipment.

At the same time, the sensor market is also showing a high degree of integration and combination of multiple functions. As design space, cost and power consumption budgets become increasingly tight, integrating multiple sensitive components on the same substrate to create a multi-functional combination MEMS sensor that can detect multiple parameters has become an important solution.

Multi-sensor fusion technology helps increase the amount of data available and significantly improves the redundancy and fault tolerance of the system, thereby ensuring the speed and accuracy of decision-making. As the intelligence of devices increases, the number of sensors mounted on a single device continues to increase. The fusion and collaboration of multiple sensors improve the signal recognition and collection effects.

Taken together, advanced packaging technologies, such as multi-chip modules that can package multiple chips together, especially 3D stacked packaging technology, represent the continuous development trend of MEMS products towards miniaturization and high integration, indicating that they can be used in Integrate more components into a limited volume to achieve more complex and powerful functions. With the development of MEMS sensor technology, the size of the sensor will continue to shrink, which will be beneficial to more application fields, such as consumer electronics, automotive industry and other fields, and will be easier to integrate into different types of products.

Based on this, many new technologies have emerged in the industry:

05 Sealed dual-mold technology

Currently, hearables and audio-centric wearables have high expectations for sound quality and battery life. Therefore, engineers must leverage advanced MEMS technology and innovative circuit designs to keep pace.

For example, Infineon uses sealed double-membrane technology in the MEMS microphone in Apple Airpods Pro, taking its proprietary MEMS technology and clever ASIC design to the extreme. This design can reduce power consumption by two times and reduce high Audio quality and low noise combined in a tiny microphone device also achieves ultra-high SNR (signal-to-noise ratio), extremely low distortion, and prevents water and dust from becoming trapped between the membrane and backplate, resulting in virtually noise-free audio Signal capture.

It is reported that Infineon MEMS microphones have developed from the earliest single backplane technology and double backplane design to the current sealed double membrane structure, which has taken nearly 20 years.

The single back plate structure is a back plate with a diaphragm. When the diaphragm is affected by sound pressure, it will vibrate above the back plate, and the change in the capacitance signal is transmitted by using the distance change relationship between the diaphragm and the back plate. , this is the basic sensing principle of MEMS microphones that convert the mechanical energy of air vibration into electrical energy.

Since the single-backplane MEMS microphone outputs a single-ended signal, in order to enhance the anti-interference ability of the MEMS microphone, reduce the background noise, and improve the signal-to-noise ratio of the MEMS microphone, Infineon successfully mass-produced a dual-backplane MEMS microphone in 2017. MEMS microphone products with technological differential output increase the signal-to-noise ratio of MEMS microphones to 69dB.

In order to achieve a studio-level audio user experience in consumer electronics products, while further improving the reliability of MEMS microphone products and enhancing anti-pollution and waterproof capabilities, Infineon has successfully mass-produced sealed dual-diaphragms in 2021. With the new product technology, the signal-to-noise ratio has been further improved, and the MEMS microphone alone can have IP57 level dustproof and waterproof capabilities.

With the advantages of high performance and low power consumption brought by sealed double-membrane technology, this type of MEMS products are suitable for TWS, earphones and hearing enhancement products, and can also be used in other space-critical applications, such as wearable devices, Smartphones and IoT devices, etc.

06 Laser resealing process

For example, from 2015 to 2018, Bosch’s pressure sensor in Apple’s iPhone switched from LGA packaging to O-ring waterproof packaging, allowing Apple to improve its durability. During this period, Bosch reduced the size of MEMS chips by more than half, from 0.8mm² to 0.35mm², following the industry’s pattern of miniaturization.

Bosch has also introduced new manufacturing technology, with a new laser resealing process that significantly reduces pressure changes to maximize the performance of the inertial sensors inside iPhone 14 Pro. Although the process is three times more expensive than previous processes, it allows MEMS gyroscopes and accelerometers to be integrated on the same chip, allowing for further miniaturization of the sensor and better control of vacuum levels within the cavity.

07 MEMS device vacuum packaging structure

The manufacturing process of vacuum packaging of MEMS devices mainly includes steps such as substrate processing, film deposition, vacuum chamber formation and sealing structure preparation. This structure is to protect its microstructure from external environmental influences, such as temperature, humidity, gas, etc., which can effectively reduce the air resistance of the device and improve its sensitivity and performance stability.

MEMS device vacuum packaging structure and its manufacturing process are crucial to ensure the performance and stability of the device. High-quality vacuum packaging can be achieved through precise process steps such as substrate processing, film deposition, vacuum chamber formation, and sealing structure preparation.

However, as the size and complexity of MEMS devices continue to increase, their vacuum packaging manufacturing processes also face many challenges. In the future, with the continuous innovation and optimization of packaging technology, it is expected to further improve the performance and reliability of vacuum packaging of MEMS devices.

To sum up, with the continuous development of MEMS technology, the requirements for packaging technology will also continue to increase. Future packaging technology needs to make more breakthroughs in reducing costs, improving production efficiency, and reducing packaging volume. For example, by integrating multiple functional packaging technologies, connections between devices can be reduced and overall performance improved. In addition, the development and application of new materials will also bring more possibilities for vacuum packaging of MEMS devices.

In practical applications, in order to meet the needs of different MEMS devices, packaging technology should have a certain degree of flexibility and customizability. To achieve this goal, future research should focus on the integration and innovation of multiple packaging technologies, such as combining micro- and macro-scale packaging technologies, and combining traditional and emerging packaging technologies.

In short, the MEMS device vacuum packaging structure and its manufacturing process play a vital role in ensuring device performance and stability. Future research and development will continue to focus on improving the performance, reliability and production efficiency of packaging technology to meet the changing needs of MEMS devices. Through continuous innovation and optimization, it is expected to provide more efficient, stable and reliable MEMS device solutions for various industries.

08 MEMS wafer: moving towards 12 inches

Another trend worth noting is the shift from 6-inch, 8-inch to 12-inch MEMS manufacturing. While this requires significant investment for MEMS vendors, it allows for better integration with 12-inch CMOS wafers and supports optimal device performance.

The world’s undoubted MEMS sensor king, Bosch is promoting the construction of a 12-inch MEMS wafer production line in Dresden, a city in eastern Germany. The project has invested 1 billion euros.

The domestic MEMS industry is also making great strides forward. In January last year, Sai Microelectronics announced that it would build a 12-inch MEMS production line in Hefei High-tech Zone. The total investment is expected to be 5.1 billion yuan, and the monthly production capacity will be 20,000 pieces after completion.

In addition, earlier in December 2020, Silan Micro’s 12-inch production line was officially put into production in Haicang, Xiamen. The project has a total investment of 17 billion yuan and plans to build two lines with power semiconductor chips and MEMS sensor chips as its main products. 12-inch specialty process power semiconductor chip production line.

In addition, SMIC, currently the largest MEMS foundry in mainland China, announced at the end of May this year that it will invest in the construction of SMIC Shaoxing Phase III 12-inch specialty process wafer manufacturing pilot line project in Binhai New Area, Shaoxing.

Previously, projects planned to use raised funds include “MEMS and power device chip manufacturing and packaging and testing survival base technology transformation project”, “Phase II wafer manufacturing project” and “supplementary working capital”. After subsequent adjustments, the “SMIC Shaoxing Phase III 12-inch specialty process wafer manufacturing pilot line project” was added.

In December last year, the 12-inch advanced smart sensor and specialty process wafer manufacturing line project, the first phase of the Guangzhou Zengxin Phase I project, officially started construction. Zengxin is a 12-inch advanced smart sensor and specialty process wafer manufacturing line. MEMS manufacturing production line project. It is planned to open the line in the first half of 2024 and reach full production by the end of 2025. A mass production line for 12-inch wafer manufacturing will be built to process 20,000 pieces per month.

It is obvious that the global MEMS wafer production capacity is transitioning to 12 inches, and China Semiconductor is also working hard in this direction. 12-inch MEMS manufacturing is increasingly becoming a reality, and in addition to the additional capacity it brings, other key advantages of 12-inch manufacturing are seen in miniaturization and overall device availability and quality.

In addition, MEMS sensor manufacturers are trying to escape the commoditization cycle and move up the value chain by adding software, processing and computing capabilities to MEMS sensors to give them additional functionality. Applications combining MEMS sensors with AI/ML/DL at the edge or in the cloud are blazing a trail.

09 Behind the opportunities, MEMS challenges still exist

In recent years, with the continuous advancement of MEMS technology and the continuous expansion of application fields, the global MEMS industry continues to show a good development trend.

Although MEMS technology has made significant progress, there are still some challenges that need to be overcome.

First, the manufacturing process requirements of MEMS technology are very high, including nano-level processing and control, which increases production costs and manufacturing difficulty. In order to promote the development of MEMS technology, it is necessary to continuously improve the manufacturing process and improve production efficiency and scalability. Secondly, the reliability and stability of MEMS devices are also issues that need attention. Due to the tiny size and complex structure of MEMS devices, they are easily affected by environmental factors and vibration, which may lead to unstable performance or shortened lifespan. Therefore, it is necessary to strengthen the reliability testing and sustainable design of MEMS devices to ensure that they can work stably in various application environments. In addition, MEMS technology also needs to be deeply integrated with other technical fields to achieve wider applications. For example, combined with technologies such as artificial intelligence, big data and cloud computing, intelligent analysis and application of MEMS sensor data can be achieved. Through data mining and machine learning algorithms, valuable information can be extracted and support decision-making in various fields.

MEMS also has challenges in packaging. Most of the current MEMS packaging technologies are developed and evolved from integrated circuit packaging technology. However, due to the complexity of its application environment, it has great particularities compared with integrated circuit packaging. , you cannot simply package integrated circuits directly to package MEMS devices.

Similar to IC packaging, MEMS packaging differs in three aspects: mechanical support, environmental protection and electrical connection. In addition, in actual MEMS packaging, the following factors must also be considered: First, the stress that the package must bring to the sensor should be as small as possible, and the coefficient of thermal expansion (CTE) of the material must be similar to or slightly higher than that of silicon. Large, due to material mismatch, it is easy to cause interface stress, causing chip cracks or delamination. For stress sensors, the impact of stress caused by packaging on device performance must be considered during design. Secondly, for general MEMS structures and circuit packaging, heat dissipation must be given full attention. The possibility of device failure at high temperatures will greatly increase. , and for thermal flow meters and infrared sensors, proper thermal isolation will increase the sensitivity of the sensor.

In short, MEMS technology has become a powerful force in the field of science and technology with its unique characteristics and broad application prospects. As an important direction and breakthrough for “More than Moore”, and catalyzed by hot application trends such as artificial intelligence and the Internet of Things, the MEMS industry has ushered in a period of huge strategic opportunities.

Although it faces some challenges, through continuous research and development and innovation, it is believed that MEMS technology will continue to reach greater heights.

As industry expert Lin Xueping said in the article: “MEMS sensors are still a kind of prophecy. Everything has eyes and spoils the future. Every move of MEMS manufacturers is like a reference book about future products, foreshadowing various The path to possible intelligence.”

In the future, where will the market be that will change today’s MEMS landscape?

Reference content

MEMS Industry: Looking back at innovation and growth over the past 20 years, YOLE

MEMS: The future is promising, Runze Fund

[Technology Frontier] Exploring MEMS technology: Leading the trend driven by innovation, Zhongke Feilong

In the past 10 years, the MEMS overlord has changed hands! Lin Xueping

“Technological innovation + quality management” achieves Infineon’s leading position in MEMS, Memes Consulting

Entering the microscopic world: Exploring the vacuum packaging structure and manufacturing process of MEMS devices


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