MEMS and Microsensors
The Course aims at introducing the basic concepts of different microelectronic devices that allow acquiring information from the physical world around us, and performing actions on it at the microscopic and nanoscopic level. The focus is centered this year on MEMS (Micro-Electro-Mechanical-Systems), on optical image sensors, and on related driving/readout electronics.
- MEMS sensors are probably the most disruptive technology of the 21st century. They are rapidly changing our everyday life and they are at the basis of the Internet-of-Things forthcoming revolution. MEMS allow acquiring - in ultra-compact dimensions and high-performance - several physical quantities like acceleration, rotation speed, magnetic field direction and pressure. These devices are nowadays widely applied in automotive, avionics, health care instrumentation and consumer applications (mobile phones, tablets, portable devices). Other kinds of MEMS allow generating and detecting ultrasound waves or producing video images by deflecting light beams.
- Optical and infrared image sensors, mostly CMOS Active Pixel Sensors, allow getting color and multispectral digital images both in still and video cameras. The applications of these devices range from consumer to scientific, surveillance, medical and technical fields. They pervade our everyday life in cameras and mobile phones, with a so far neverending performance improvement.
The target audience of the Course is represented by students oriented towards either:
(i) advanced design of innovative micro-sensors, or
(ii) advanced design of their low-noise, low-power integrated electronics, or finally
(iii) advanced design of electronic systems embedding these sensors.
The Course is split into 3 main sections, whose main topics are summarized in the following.
– MEMS sensors (about 40% of the Course).
Building technologies of MEMS and NEMS (Nano Electro Mechanical Systems). Sensing and actuation elements based on capacitive, piezoelectric and piezoresistive effects. Inertial sensors: accelerometers, gyroscopes. Springs configurations. MEMS resonators and resonant mass sensors. Magnetic field sensors: MEMS, Hall and AMR magnetometers. MEMS based on membranes: ultrasonic transducers (CMUT and PMUT) and microphones. Optical MEMS (micromirrors, microbolometers). Aspects of MEMS relaibility (fracture, adhesion, fatigue).
– Electronics for MEMS driving and signal acquisition (about 25% of the Course).
Low noise–low power front-end electronics for accelerometers. Oscillators and sensing electronics for gyroscopes. Amplitude-gain-control in oscillators. Resonant and off-resonance circuit operation. High-performance characterization setups (rate tables, shakers, ...) and electronics for MEMS. Driving and sensing electronics for ultrasonic devices.
– Digital image sensors (about 35% of the Course).
Basics about the interaction of light with the semiconductors. CMOS-APS pixel detectors. General architecture and sensor performances: noise, dynamic range, nonlinearities, frame rate. Main acquisition technques: 4T circuits and CDS (Correlated Double Sampling), rolling and global shutter. HDR (High Dynamic Range) architecture. Backside illumination technologies. Multi-spectral imaging. Infrared detectors.
For each sensor topology, realistic case studies will be discussed through numerical exercises and comparisons to existing cutting-edge products. Some activities are also foreseen concerning the application of CAD software to the design of high-performance MEMS sensors. 3-4 seminars will be given about hot topics for the sensors community.