pressure sensors

The automotive industry is changing. Our vehicles are getting electrified, connected and automated. As this trend is accelerating, it’s having an impact on how semiconductor devices, including MEMS sensors, are designed and qualified for automotive. As automotive semiconductor designers carefully consider product definition, product validation, and long-term reliability, MEMS sensor suppliers are responding to new opportunities created by electrified and automated vehicles by developing inertial measurement units (IMUs) for automated driving as well as battery pressure monitoring sensors for Li-ion EV batteries. The most complex MEMS device of all The automotive MEMS IMU is probably the most complex MEMS device that will be used inside a vehicle. This type of IMU is a System-in-Package (SiP) comprised of multiple gyroscope and accelerometer sensing elements plus a signal processing ASIC, integrated into one package that creates an inertial sensor able to measure up to six degrees of freedom (6DoF): yaw, roll and pitch for rotational movements, and lateral, longitudinal and vertical acceleration for linear movements. Degrees of freedom in a vehicle For vehicles with Level 3 autonomy and above (per SAE definition), the IMU is mandatory for taking over the trajectory control of the vehicle in case other sensors, such as the camera, radar or LiDAR, become impaired. Should such a failure occur, the IMU will function as a guidance sensor to bring the car to a safe stop within a short period of time and distance. The IMU is also used to control the regular movement of the car while driving in automated mode. While IMU technology already exists for aerospace applications, there are significant challenges to adapting it for automotive. The automotive IMU requires high performance at costs that are compatible with the automotive industry. Because automotive life cycles are long, MEMS sensor suppliers must produce the device in high volume for an extended period of time. They must also guarantee the sensor’s performance and reliability over a 10- to 15-year lifetime with no maintenance or recalibration of the sensor required. Only a few MEMS suppliers have the capability and willingness to embark on this kind of journey. Electrification is creating new applications for MEMS sensors The conversion from internal combustion engines to electrified propulsion is going to affect the powertrain MEMS market. For example, pressure sensors used in engine management for air pressure and fuel pressure will simply go away with electrification. However, the use of large Li-ion batteries in electrified vehicles has created a new application for MEMS sensors. One of the known risks of Li-ion batteries is the small probability for a battery cell to go into a thermal runaway situation that will lead to a fire. The press has reported multiple cases of EV batteries catching fire. Thermal runway effects When it comes to thermal runaway events, every second counts. Detecting the event as early as possible enables the vehicle safety system to take all necessary measures to warn occupants of an imminent fire and activate timely countermeasures (e.g., trigger fire extinguisher and call fire brigade) to mitigate the impact of the fire. Published studies have shown that measuring the pressure inside the battery pack is a good indication that a thermal runaway is starting. The outgassing of a battery cell, plus a sudden rise in temperature, will increase pressure inside the battery pack, which will generate a pressure pulse. To detect such a pressure pulse, a MEMS pressure sensor must permanently measure the pressure inside the pack. It must also report to the battery management system any suspicious change in pressure, independent of atmospheric pressure changes. It’s important to keep this kind of sensor on all the time to detect any pressure anomaly in the system, even when the vehicle is completely off. NXP has developed a pressure sensor to specifically address this new safety application in EVs, and several automotive manufacturers are already using this solution. NXP battery pressure management sensor The quest for zero defects While the automotive industry is targeting zero fatalities as its ultimate goal, the semiconductor industry and module suppliers are targeting zero defects for each and every semiconductor device. For safety-critical automotive MEMS sensors complying with the Automotive Electronics Council (AEC) Q100 qualification for semiconductors, it’s necessary but clearly not sufficient to guarantee a zero defects production launch and long-term reliability of the device. To boost the reliability and robustness of automotive sensors, NXP has developed Above and Beyond (AaB), a new methodology that studies advanced reliability and robustness well ahead of the device’s qualification and production release. Based on risk-mitigation analysis, AaB consist of extensive testing, such as test-to-fail, corner lot testing, and new use-case testing combined with advanced statistics, all of which help NXP understand how these different parameters interact with each other. As sensor suppliers must integrate AaB into their project planning, it does add time and cost to the project. The upside is that this early investment pays off as long as weaknesses in the device can be detected and corrected before a production launch. Field failures, on the other hand, can lead to unplanned redesign and requalification of a device. Worst-case, they can lead to a recall campaign that costs a huge amount of money. We’re systematically using the AaB methodology at NXP for safety-critical MEMS sensors because its potential benefits far outweigh its costs. For more information about NXP MEMS sensors, register for the upcoming webinar series, MEMS to Market: Ingredients for Success, where NXP will discuss The Growing Importance of MEMS Reliability (May 5, 2021). Register by March 10 to watch all the webinars LIVE. Each webinar will also be available to watch on-demand at your convenience. Contact the author via LinkedIn or learn more about NXP sensors. About the Author With nearly 30 years of experience in the field of automotive and MEMS sensors, Marc Osajda is responsible for European automotive MEMS sensors business development activities at NXP Semiconductors. Osajda holds an engineering degree in mechanics and electronics from the French Ecole Nationale Superieure d’Arts et Métiers (ENSAM). NXP Semiconductors is an active member of MEMS Sensors Industry Group®(MSIG), a SEMI technology community that connects the MEMS and sensors supply network in established and emerging markets to enable members to grow and prosper. Visit us today.

Stefano Zanella, Head of Automotive, Industrial and Location Businesses, TDK InvenSense will present at next month’s SEMICON Taiwan (September 18-20, 2019 in Taipei City, Taiwan). SEMI Taiwan’s Emmy Yi spoke with Stefano for a preview of his talk.SEMI: What macro market trends are driving automotive manufacturers to increase the variety and volume of MEMS sensors in cars?Zanella: The car world is changing. Consumers increasingly view car ownership as less desirable, yet the number of miles traveled and of hours spent in a car are rising steadily. At the same time, cars are changing profoundly, and the pace of change is rapid. To thrive in this new world, automakers are becoming transportation enablers and providers.Many vehicles today autonomously interact with humans and the world around them, operate with less or no human control, and are powered by electric batteries. MEMS sensors – which mimic and augment the five human senses – are front and center in these advancements.Unlike other types of sensors – such as cameras, radar and GNSS/GPSS – MEMS gyroscopes are functional in every environment. Gyroscopes, as well as accelerometers, can supplement those other sensors when they are not available and boost the accuracy of their outputs when they are available. Both camera stabilization and dead reckoning when GNSS is unavailable are good examples of the latter. Other prevalent sensors include MEMS microphones, used to capture voice commands, ultrasonic sensors, which can be leveraged for parking and gesture recognition, and fingerprint sensors, which can improve car security.SEMI: How can automakers stay competitive in this changing landscape?Zanella: Automakers can future-proof their relevance in the transportation market in several ways. By embracing consumer migration toward ride-sharing over car ownership, many are transforming from manufacturers to mobility providers. Carmakers that invest in ride-sharing and other modes of transportation (e.g., scooters) can sustain their profitability, even if the number of vehicles sold eventually shrinks or simply doesn’t grow as much as anticipated.Automakers will need to pursue new avenues of product differentiation. Traditionally, automakers have kept performance and aesthetics to themselves by owning the engine and the body design of the car, leaving nearly everything else to suppliers. Autonomous driving and electrification, however, are pushing automakers to own the battery pack and the autonomous driving software stack.While we are just beginning to see standardization in battery packs, automakers are likely to own the autonomous driving stack for many years to come. Automakers that offer cars with highly functional and efficient batteries and driving stacks stand to gain market share.Automotive infotainment systems will become increasingly crucial as autonomous driving turns everyone into a passenger. Audio subsystem providers such as Harman Kardon, Bose, and Bang Olufsen, for example, jockeyed for attention at the most recent Geneva Motor Show, demonstrating sophisticated surround-sound systems that rival premium-quality home audio setups.With more and more consumers using voice interfaces to interact with devices in the home, drivers are less willing to accept spotty accuracy in the car. Hence, automakers are using more higher-performing MEMS microphones to accurately capture voice commands. This will come as a relief to those of us who routinely yell at our steering wheels while using voice command to try to call home. Demand for higher quality infotainment systems has prompted some automotive OEMs to own the entire infotainment system and work directly with sensor and chipmakers, a level of intimacy that gives automakers a chance to tune sensor and chip development to their own needs. This tighter relationship also positions device suppliers to forge more direct links with drivers.SEMI: Which MEMS sensors are particularly important to tomorrow’s automobiles and why?Zanella: For many years the automotive industry has been integrating more electronics into cars to improve safety, advance the driver and passenger experience, and, more recently, power the car. As vehicles rely less on human control, automakers must replace the senses of the driver with something else. That something else is a bunch of sensors, microphones, cameras, radar and LIDAR to replace vision and hearing.Since MEMS sensors such as accelerometers, gyroscopes and pressure sensors are much more robust than other types of sensors to operate in snow, rain and darkness and other imperfect environments, automakers use them to ensure that the vehicle never gets lost when other sensors and/or the GPS/GNSS signal become unavailable in tunnels or urban canyons. Gyros help determine direction, accelerometers velocity and distance driven, and pressure sensors height, such as when taking a fork on a multi-level highway. At the same time, fingerprint sensors, ultrasonic parking sensors, and temperature sensors are improving convenience, safety and security for the car’s occupants. Automakers increasingly use inertial and environmental sensors, MEMS microphones, fingerprint sensors, and vision/imaging sensors to augment or replace the five human senses on which car drivers have relied for over 100 years. Source: TDK InvenSense SEMI: To what degree can MEMS sensors enable automotive security?Zanella: MEMS sensors are used widely to enhance security today. Some of their mechanisms are easy to understand while some are unexpected. For instance, ultrasonic fingerprint sensors can authenticate the driver of a vehicle to prevent car theft or something less onerous, like a teenage driver taking the car out without permission.Accelerometers and gyroscopes can prevent a new type of spoof on keyless entry systems. Imagine that you are very close to your vehicle. Your car senses the remote control in your pocket and automatically opens the doors when you pull the handle. Now suppose that your car is parked on the street, not far from your house. You leave the remote control home, and the car doesn’t sense the proximity of the remote control. Great! No one can enter your car, unless ... a thief has a big signal amplifier that makes your car think that the keyless entry device is next to the car. In this case, what can an automaker do? Add an accelerometer that restricts the keyless device from broadcasting the entry signal unless you are walking to the car with the device on your person.SEMI: What would you like SEMICON Taiwan attendees to take away from your presentation?Zanella: I would like them to embrace the transformations afoot in the automotive market as well as their associated design challenges since, by overcoming these hurdles, they can offer significant societal benefits such as safer and cleaner transportation. At the same time, these transformations mean significant opportunities for semiconductor industry revenue growth. And while design-to-delivery cycles in automotive are longer than in consumer and mobile, the automotive market supports higher-value devices as well as the chance to fold dozens of MEMS sensors into a single model.To paraphrase Lord Kelvin: If you can’t sense it, you can’t manage it. As suppliers of many key technologies that make intelligent transportation possible, the MEMS sensors industry is in an excellent position to help automakers manage the many challenges ahead.Stefano Zanella, Ph.D., is Head of Automotive, Industrial and Location Businesses at TDK InvenSense, where he brings MEMS sensors (including accelerometers, gyroscopes and microphones) and location solutions to the automotive and industrial markets. Zanella holds an MS and a Ph.D. in Electrical Engineering from the University of Padova, Padova, Italy as well as MBAs from both the UC Berkeley Haas School of Business and from Columbia University.He will present MEMS Sensors Enabling the Smart Car Revolution on Wednesday, September 18, 2019, at SEMICON Taiwan at 1F 4F, Taipei Nangang Exhibition Center, Taipei City, Taiwan. Register today and save 20% to learn how MEMS sensors are transforming the human experience with cars.Connect with Stefano Zanella at SEMICON Taiwan or via LinkedIn. You can also get more information on TDK’s automotive solutions and application guides online.Interested in engaging with the MEMS sensors supply chain? SEMI MEMS Sensors Industry Group is a technology community that enables professionals in the MEMS and sensors industry to innovate, address common challenges and accelerate business results.Emmy Yi is a marketing specialist at SEMI Taiwan.

New MEMS-based products are constantly emerging, fueled by the Internet of Things (IoT), autonomous driving, smart manufacturing and healthcare applications. The MEMS pressure sensor market is no exception to this trend1. Its growth has been driven mainly by automotive applications such as tire pressure management system (TPMS) regulations in China, fuel and ignition systems, thermal systems, oil-pressure monitoring, and indoor and outdoor navigation systems. Easy to customize and integrate, miniature, sensitive, accurate and low-power MEMS devices are especially well-suited to the accuracy, power consumption, sensitivity and miniaturization that pressure sensors require.Yet MEMS design also presents some specialized challenges, such as a strong coupling between fabrication technology and design. Complex physical structures that exhibit non-linear behavior, custom packaging requirements, and a final product that requires integration with surrounding CMOS circuitry are just a few examples. What’s more, there is a lack of standardized processes and process validation in MEMS design ecosystems. Pressure Sensor (Courtesy: X-FAB) As with other products based on MEMS technology, designers must increasingly customize pressure sensors for higher performance – sensitivity and linearity, in this case – while decreasing their package size. Designers can accomplish the task by studying sensor performance and manufacturability using computer models prior to fabrication. This can ensure that the sensor meets its required specifications while simultaneously reducing manufacturing cycles and cost.The Power of CollaborationThis is where strong collaboration among EDA providers, MEMS technologists and designers delivers tangible benefits. EDA providers and MEMS foundries can collectively help MEMS designers to incorporate foundry process constraints into their designs.In the semiconductor industry, first-pass successful silicon relies on standardized manufacturing processes, thorough technology characterization, accurate model generation, established simulation and verification, and extensive reuse of proven design blocks. In the MEMS world, where processes and products are developed concurrently, and processes change with every product, is it possible to adopt standardized processes, design methodologies, and tools that enable efficient reuse of existing technology and design knowledge? The challenge lies in maintaining the flexibility to optimize products for a diverse array of requirements. The ideal design platform should ease sharing of technology and design data between the foundry and its customers, enabling two-way collaborative development and allowing foundry technologists to easily perform a feasibility assessment of a customer’s project. This approach offers important benefits, allowing designers to explore and evaluate the suitability of a foundry’s process technology in their unique application. It also supports accurate prediction of device performance prior to fabrication and reduces costly build-and-test cycles. Combining standardized manufacturing processes, MEMS process design kits (PDKs), and a proven design flow are the starting point for development of manufacturing-ready designs.A Real-Life Example using Pressure SensorsAn EDA company, Coventor (a Lam Research company), along with MEMS foundry partner X-FAB, collaborated to develop a PDK that would ensure that manufacturing constraints are automatically considered early in their design process. The design flow is based upon an X-FAB fabrication platform that supports multiple process options for the manufacturing of absolute and relative MEMS pressure sensors. The PDK is a “golden container” for all the process and material characteristics of the silicon membrane and substrate, glass, passivation layers, and piezoresistive components. It enforces material properties and guarantees their correct implementation during the simulation. It also includes a component library containing ready-to-use, 3D parameterized devices (such as membranes and resistors), all pre-designed with foundry-supported materials to support their respective design rules. The components are readily partitioned for optimized meshing and simulation, saving design and simulation time. Figure 1: The elements and design flow of the PDK designed by Coventor and X-FAB. (Courtesy: Coventor)Designers can use components from the library to create a custom design — which might include different membrane shapes and sizes, and resistors of varying shape, size and position — to simulate the impact of different technology variants (such as resistor doping profiles, membrane and substrate thickness, glass material properties, and passivation schemes). This allows them to anticipate the effect of these design changes on sensor sensitivity for varying pressure and temperature regimes.Extensive validation of the pressure sensor design platform is currently underway. So far, the simulations have exhibited very good correlation to actual device measurements across a range of pressure and temperature conditions, including predictions of non-linear behavior for various pressure sensor designs. At the same time, the simulation accounts for mechanical membrane properties and piezoresistivity. With this type of design platform, a foundry can provide guidelines to help customers select both the fab technology and design features that lead to an optimal design solution. Figure 2: Simulation results depicting mechanical displacement in a pressure sensor design (Courtesy: X-FAB) Let’s Face the Next Challenges…A complete design platform for MEMS must eventually include not only MEMS device design, but system integration functions, such as the application-specific integrated circuit (ASIC) design and packaging/assembly of the product. In addition to the design verification that the PDK provides, additional partnerships among foundries, integrated device manufacturers (IDMs), research centers, equipment suppliers, and EDA vendors will help to define requirements and solutions that address every level of design and production. These might include tasks such as describing standardized material properties and process specifications, creating accurate foundry-proven design models, and defining requirements for system-level simulation. In the future, PDK simulations might even include up to tape-out and physical verification. To learn more about this collaborative PDK development work, please click here for the whitepaper.Christine Dufour, MEMS PDK Program Manager, CoventorChristine Dufour is the MEMS PDK program manager at Coventor. She has more than 20 years of experience in the semiconductor industry, leading process design kit development for BiCMOS and CMOS processes at several major semiconductor companies. Ms. Dufour has also worked as a product manager in the RF design environment area. In addition to her extensive experience in MEMS PDK development, she is an expert in all aspects of MEMS design flow and design tool development. Ms. Dufour received an engineering degree at Technological University of Compiegne.For more information on Coventor, a Lam Research Company, visit: https://www.coventor.com/ Viraja Sharma, Development Engineer, MEMS Simulation Design, X-FABViraja Sharma is a development engineer for MEMS Simulation Design at X-FAB. Her work involves the design and simulation of MEMS inertial and pressure sensors. Prior to her tenure at X-FAB, Ms. Sharma performed similar duties for other semiconductor companies. She received her Master of Science degree in Micro and Nano Systems from TU Chemnitz, where she studied MEMS and micro technologies.For more information on X-FAB, visit: https://www.xfab.comCoventor and X-FAB are members of SEMI-MEMS Sensors Industry Group that connects the MEMS and sensors supply network, enabling members to address common industry challenges and explore new markets. 1 Market research firm Yole Développement predicts that MEMS pressure sensors alone will become a $2 billion market by 2023. See: https://yole-i-micronews-com.osu.eu-west 2.outscale.com/uploads/2019/01/YD18018_MEMS_Pressure_Sensor_Market_Yole_Developpement_2018_Sample.pdf