MEMS
Micro-Electro-Mechanical Systems
An industry-leading process technology
STMicroelectronics has a long history and proven expertise in MEMS sensors and actuators. As the first major manufacturer to start high-volume MEMS production on 200 mm wafers in 2006, ST launched the consumer MEMS revolution by making motion sensors small, accurate, and affordable through the combination of innovative product design, deep application expertise, and industry-leading process and packaging technology.
Since then, ST has continued to grow and diversify its portfolio into new types of devices and application segments. Today, in addition to its successes in motion sensors for consumer markets, the company features products dedicated to automotive, industrial and medical markets with a dedicated manufacturing flow guaranteeing high quality and reliability.
MEMS sensors
In addition to using the well-understood and valuable electrical properties of silicon, MEMS (Micro-Electro-Mechanical systems) sensors leverage silicon’s unique mechanical properties to integrate mechanical structures able to sense acceleration, rotation, angular rate, vibration, displacement, heading, and other physical and environmental properties.
ST manufactures its MEMS using proprietary micromachining processes that share processing steps derived from basic integrated circuit techniques. These steps produce a circuit that combines electrical circuits and 3-dimensional mechanical structures.
MEMS sensors
In addition to using the well-understood and valuable electrical properties of silicon, MEMS (Micro-Electro-Mechanical systems) sensors leverage silicon’s unique mechanical properties to integrate mechanical structures able to sense acceleration, rotation, angular rate, vibration, displacement, heading, and other physical and environmental properties.
ST manufactures its MEMS using proprietary micromachining processes that share processing steps derived from basic integrated circuit techniques. These steps produce a circuit that combines electrical circuits and 3-dimensional mechanical structures.
ThELMA manufacturing process
ST’s long-term success using MEMS technology has drawn upon the Company-developed, industry-leading Thick Epitaxial Layer for Micro-gyroscopes and Accelerometers (ThELMA) manufacturing process. This is a surface micro-machining process that combines variably thick and thin poly-silicon layers for structures and interconnections, enabling the integration of accelerometer and gyroscope mechanical elements in a single chip.
ST’s ThELMA technology enables the creation of tiny mechanical structures that, in combination with our strong packaging expertise in creating high-vacuum cavity and controlling the hermetic sealing of the mechanical structure, assures high reliability and great performance while offering significant cost and size benefits to customers.
ST qualified and started the production of ThELMA60, an enhanced version of ThELMA technology, implementing a 60 μm surface-micromachining epitaxial layer, 3 times thicker than the standard ThELMA process.
This thicker layer brings the superior performance required by high-end inertial sensors, while keeping the cost effectiveness and flexibility of the ThELMA technology. With this step ST is bridging the gap between surface-micromachining and bulk-micromachining traditionally used to manufacture high-end sensors.
An efficient integration
ST uses a dual-chip system-in-package approach assembling separate MEMS and ASIC dice in the same package.
ST is the world’s first manufacturer to have implemented innovative solutions such as Through-Silicon Via technology (TSV) in high-volume MEMS production. Deployed in volume production since 2011, the ST-patented TSV technology replaces traditional wiring with short vertical interconnects in ST’s multi-chip MEMS devices, such as smart sensors and multi-axis inertial modules.
TSV offers greater space efficiency and higher interconnect density compared with wire bonding or flip-chip stacking, enabling a higher level of functional integration and performance in a smaller form factor.
From technology to product: iNEMO IMU
Building upon its strong experience in mobile applications, ST continues to develop its highly integrated iNEMO™ Inertial Measurement Units (IMUs) to serve all market needs.
The modules combine motion sensors and an ultra-low power processing circuit in a System-in-Package solution to offer a lower power consumption and smaller package size versus discrete solution, while providing the high accuracy and reliability required for wearable, portable devices, mobile, handset, industrial, and positioning devices.
Managing
the full design and
manufacturing chain
Managing the full design and manufacturing chain
Unlike conventional microelectronics development, MEMS compels companies to apply a unique blend of multi-disciplinary skills that combine electrical, semiconductor, and mechanical design expertise.
ST is one of the few silicon companies with the capability and experience to address and optimize the full manufacturing and testing chain: from chip specification, though architecture and design, advanced CMOS processes for ASICs, MEMS-specific front-end process, advanced packaging design and manufacturing.
This unrivaled knowledge of, and capability to control, each stage of the process uniquely qualifies ST to completely optimise the MEMS device in performance, quality, value, and reliability. It brings also to the customer enormous flexibility in its product design, as well as improved time to market.
Main types of MEMS sensors
ST has shipped more than 20 billion-micro-electro-mechanical sensors and has one of the industry’s most extensive portfolio.
A dedicated portfolio for automotive and industrial markets
A dedicated portfolio for automotive and industrial markets
Automotive and industrial markets have particularly stringent quality and reliability requirements. For them, ST offers a dedicated supply chain from design and manufacturing up to testing and qualification for the MEMS devices dedicated to those segments.
ST’s broad portfolio of automotive-grade MEMS sensors is qualified according to the AEC-Q100 standard and includes both low-g and high-g digital accelerometers, digital 3-axis gyroscopes, and 6-axis system-in-packages that combine a 3D digital accelerometer and a 3D digital gyroscope.
ST’s automotive-grade MEMS offering covers all the key applications, including sensors for non-safety applications, such as navigation and telematics, sensors for passive safety applications such as airbags, and sensors for the most demanding active-safety applications such as electronic stability control (ESC) and other applications related to vehicle dynamics.
Sensors for automotive and industrial applications are subjected to ST’s “golden flow”, which implies specific material codification, rigorous monitoring of front-end equipment, dedicated defect-detection control plan and extensive final test versus temperature. This flow includes cold and hot analysis as well as extended quality control and reliability monitoring that ensure pieces meet the required DPPM (defect parts per million) level.
For automotive devices, ST performs a specific electrical wafer sorting (EWS) based on automotive standards and an additional qualification step in compliance with the AEC-Q100 standards. All products are provided with PPAP (production parts approval program) level-3 documentation as additional guarantee of quality.
In addition, MEMS devices targeting automotive and industrial markets use two types of packages: leadframe and ceramic. Leadframe packages provide superior thermal conductivity to assure the appropriate heat dissipation properties required by specific applications.
Ceramic packages, with their lower coefficients of thermal expansion, ensure high dimensional stability of the package when exposed to high temperatures. This stability minimizes the stresses to the sensing die, which helps improve reliability and performance. These ceramic packages allow exposure to even higher operating temperatures than the ones permitted by the organic FR4 packages.
