Overview of MEMS and Microsystems- uNIT1

WHAT IS MEMS? MEMS = Micro Electro Mechanical System Any engineering system that performs electrical and mechanical functions with components in micrometers is a MEMS. (1 μm = 1/10 of human hair) Available MEMS products include: ● Micro sensors (acoustic wave, biomedical, chemical, inertia, optical,pressure, radiation, thermal, etc.) ● Micro actuators (valves, pumps and microfluidics; electrical and optical relays and switches; grippers, tweezers and tongs; linear and rotary motors, etc.) ● Read/write heads in computer storage systems, Inkjet printer heads. ● Micro device components (e.g., palm-top aircrafts, minirobots and toys, micro surgical and mobile telecom equipment, etc.)

HOW SMALL ARE MEMS DEVICES? They can be of the size of a rice grain, or smaller! Two examples: - Inertia sensors for air bag deployment systems in automobiles - Microcars

Inertia Sensor for Automobile “Air Bag” Deployment System Courtesy of Analog Devices, Inc)

Micro Cars Rice grain (Courtesy of Denso Research Laboratories, Denso Corporation, Aichi)

There has been increasing strong market demand for: “Intelligent,” MINIATURIAZATION – The Principal Driving Force for the 21st Century Industrial Technology There has been increasing strong market demand for: “Intelligent,” “Robust,” “Multi-functional,” and “Low-cost” industrial products. Miniaturization is the only viable solution to satisfy such market demand

Miniaturization is ideal for precision movements and for rapid actuation. Miniaturized systems encounter less thermal distortion and mechanical vibration due to low mass. Miniaturized devices are particularly suited for biomedical and aerospace applications due to their minute sizes and weight. Small systems have higher dimensional stability at high temperature due to low thermal expansion. Smaller size of the systems means less space requirements. This allows the packaging of more functional components in a single device. Less material requirements mean low cost of production and transportation. Ready mass production in batches

Micro pressure sensors MEMS as a Microsensor Power Supply Micro Input Signal Sensing Transduction Unit Output Signal Element Micro pressure sensors

MEMS as a Microactuator- motor Power Supply Output Micro Actuating Transduction Element Unit Action Rotor Torque Transmission Gear Stators Micro motor produced by a LIGA Process

Components of Microsystems Microsystem Power Supply Signal Transduction & Processing Unit Sensor Actuator Microsystem

Unique Features of MEMS and Microsystems • Components are in micrometers with complex geometry using silicon, si-compounds and polymers: A micro gear-train by Sandia National Laboratories 25 µm

SignalConditioner& Processor Microsystems - Micromechatronics systems Intelligent Package on a single “Chip” Sensing /actuating Mems INPUT: Desired Measurements or functions SignalConditioner& Processor Transduction unit OUTPUT: Measurements or Actions Controller Actuator Signal Processor Comparator Measurements

Micro Sensors Vs MicroActuators Acoustic wave sensors Biomedical and biosensors Chemical sensors Optical sensors Pressure sensors Stress sensors Thermal sensors Micro Actuators: Grippers, tweezers and tongs Motors - linear and rotary Relays and switches Valves and pumps Optical equipment (switches, lenses, mirrors, shutters, phase modulators, filters, waveguide splitters, latching & fiber alignment mechanisms)

Microsystems Microsystems = sensors + actuators+ signal transduction Microfluidics, e.g. Capillary Electrophoresis (CE) Microaccelerometers (inertia sensors)

Microelectronics Comparison of Microelectronics and Microsystems Microsystems (silicon based) Primarily 2-dimensional structures Complex 3-dimensional structure Stationary structures May involve moving components Transmit electricity for specific electrical functions Perform a great variety of specific biological, chemical, electromechanical and optical functions IC die is protected from contacting media Delicate components are interfaced with working media Use single crystal silicon dies, silicon compounds, ceramics and plastic materials Use single crystal silicon dies and few other materials, e.g. GaAs, quartz, polymers, ceramics and metals Fewer components to be assembled Many more components to be assembled Mature IC design methodologies Lack of engineering design methodology and standards Complex patterns with high density of electrical circuitry over substrates Simpler patterns over substrates with simpler electrical circuitry Large number of electrical feed-through and leads Fewer electrical feed-through and leads Industrial standards available No industrial standard to follow in design, material selections, fabrication processes and packaging Mass production Batch production, or on customer-need basis Fabrication techniques are proven and well documented Many microfabrication techniques are used for production, but with no standard procedures Manufacturing techniques are proven and well documented Distinct manufacturing techniques Packaging technology is relatively well established Packaging technology is at the infant stage Primarily involves electrical and chemical engineering Involves all disciplines of science and engineering

Physics & Biochemistry The Multi-disciplinary Nature of Microsystems Natural Science: Physics & Biochemistry Engineering Electrochemical Quantum physics Solid-state physics Scaling laws Material Science Processes Mechanical Engineering • Machine components design • Precision machine design • Mechanisms & linkages • Thermomechanicas: (solid & fluid mechanics, heat transfer, fracture mechanics) • Intelligent control • Micro process equipment design and manufacturing • Packaging and assembly design Materials Engineering • Materials for substrates & package • Materials for signal mapping and transduction • Materials for fabrication processes Electrical Engineering • Electric systems for dynamics and • Electric circuit design •Integration of MEMS and CMOS • Power supply electrohydro- signal transduction Chemical Engineering • Micro fabrication processes • Thin film technology Industrial Engineering • Production control • Process design • Micro assembly

MEMS in Automotive Industry (6)(1) (4) (3) (2) (10) (5) (9) (8) (1) Manifold or Temperature manifold absolute pressure sensor (2) Exhaust gas differential pressure sensor (3) Fuel rail pressure sensor (4) Barometric absolute pressure sensor (5) Combustion sensor (6) Gasoline direct injection pressure sensor (7) Fuel tank evaporative fuel pressure sensor (8) Engine oil sensor (9) Transmission sensor (10) Tire pressure sensor

Silicon Capacitive Manifold Absolute Pressure Sensor

Application of MEMS and Microsystems in Aerospace Industry Cockpit instrumentation. Wind tunnel instrumentation Microsattellites • Sensors and actuators for safety – e.g. seat ejection • Sensors for fuel efficiency and safety Command and control systems with MEMtronics Inertial guidance systems with microgyroscopes, accelerometers and fiber optic gyroscope. Attitude determination and control systems with micro sun and Earth sensors. Power systems with MEMtronic switches for active solar cell array reconfiguration, and electric generators Propulsion systems with micro pressure sensors, chemical sensors for leak detection, arrays of single-shot thrustors, continuous microthrusters and pulsed microthrousters Thermal control systems with micro heat pipes, radiators and thermal switches Communications and radar systems with very high bandwidth, low-resistance radio-frequency switches, micromirrors and optics for laser communications, and micro variable capacitors, inductors and oscillators.

Application of MEMS and Microsystems in Biomedical Industry Disposable blood pressure transducers: Lifetime 24 to 72 hours; annual production 20 million units/year, unit price $10 Catheter tip pressure sensors Sphygmomanomet ers Respirato rs Lung capacity meters Barometric correction instrumentation Medical process monitoring Kidney dialysis equipment Micro bio-analytic systems: bio-chips, capillary electrophoresis, etc.

Application of MEMS and Microsystems in Consumer Products Scuba diving watches and computers Bicycle computers Sensors for fitness gears Washers with water level controls Sport shoes with automatic cushioning control Digital tire pressure gages Vacuum cleaning with automatic adjustment of brush beaters Smart toys

Telecommunication Industry Application of MEMS and Microsystems in the Telecommunication Industry • Optical switching and fiber optic couplings • RF relays and switches • Tunable resonators Microlenses: Microswitches:

Micro Optical Switches 2- Dimensional 3- Dimensional