• Blended Learning & Flipped Classroom

The course aims at introducing the basic concepts of different microelectronic devices that allow acquiring information from the physical world around us (microsensors), and performing actions on it (microactuators) at the microscopic and nanoscopic level. The focus is centered on MEMS (Micro-Electro-Mechanical-Systems) transducers, on optical CMOS (complementary-metal-oxide-semiconductor) pixel image sensors, on related driving/readout electronics, and on system-level considerations (e.g. noise-consumption-area trade-off, bounded/unbounded performance optimization, definition of the specifications for the different applications...). The course is thaught with a balanced mix of theoretical classes (with realistic numerical examples), project-oriented exercises, and software-assisted exercises. Through the teaching of these technologies, sensors, and circuits, the course provides consistent examples of electronic sensing systems applied in several fields of the modern and future society (Internet of Things, Autonomous Driving, Smart City, Industry 4.0...).

Exploting the new didactic methods learned during the Pandemic, several theoretical classes will be pre-recorded with high quality videos, so that students will enjoy an optimal equilibrium between remote teaching (theory) and live classes (laboratories, exercises and Q&A sessions). At the end of each week, some time will be used to review topics of the recorded classes and to take students questions and properly answer (Q&A sessions).

This is an innovative and stimulating didactic approach, aimed at maximizing the teaching effectiveness, minimizing the passive didactics, and maximizing the active participation of students during the live classes.

At the end of the course:

- the student will be aware of the increasing needs for sensors that the society is having in this era, their benefits and their prospected evolution;

- according to DdD1 for Master Level courses, the student will have a comprehensive knowledge, both from a top view (system-level) and in details (subsystems design), about the design strategies of sensing and transduction systems based on microelectronic sensors (MEMS and CMOS technologies, in particular) and on electronic circuits;

- according to DdD1 for Master Level courses, the student will know the theoretical basis and equations that lie behind the design of a sensing system, the trade-off between the electronic domain (power, noise) and the sensor domain (area, dynamic range, linearity, bandwidth...); he/she will know if, when and why the aid of CAD simulations is needed; and he/she will know how to use the approriate softwares to develop such simulations;

- according to DdD1 for Master Level courses, the student will also be able to discuss the physical principles at the basis of the discussed variety of sensors (in particular, MEMS and CMOS), and to identify the pros and cons of the different approaches;

- according to DdD2 for Master Level courses, the student will be able to tackle the design of a sensing system (e.g. accelerometer, clock, magnetometer, gyroscope, light sensor...) starting from the specifications given by the target application (consumer, automotive, medical, industrial...); to co-develop then the sub-specifications for the sensor part and for the electronic part; and finally to design the sensor and the electronics according to the technologies discussed in the course;

- acciording to DdD 2 for Master Level courses, the student wil be able to choose among different technologies to solve a specific problem related to a sensing system similar to those discussed in the course;

- according again to DdD2 for Master Level courses, the student will know the basics of advanced software used in the design of sensing systems (e.g. use of multiphysics finite element modeling for sensors design, use of Cadence for electronic design);

- according to DdD2 for Master Level courses, the student will know the most significant parameters that characterize the sensing system behavior (scale-factor and its drift, linearity, full-scale range, offset and its drift, noise, power consumption, bandwidth, area and - last but not least - cost). She/he will also know how to practically measure them;

- according to DdD3 for Master Level courses, the student will be able to extend the concept studied on the categories of sensors discussed in the course to other categories, not discussed in the course which share the same set of problems (e.g. to microphones, pressure sensors, ultrasonic transducers, IR sensors...). To this purpose, specific exercise will be given, where the student is request to design sensing systems not discussed in the course. To stimulate this ability, the students will be left time for autonomous solving before the exercise is solved by the lecturer.

The course discusses topics related mostly to MEMS and CMOS microsensors, and the related driving/readout electronics.

- MEMS sensors and transducers 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, rotational 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 for sensors, 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. Time sensors (resonators, oscillators, clocks). 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). HDR (High Dynamic Range) architecture. Backside illumination technologies.

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. The software is licensed to PoliMi students. 2-3 seminars will be given by invited indusrial members about hot topics for the sensors community.

Knowledge in electronics fundamentals is recommended, in particular on:

- basic working principle of MOS transistors;

- concept of negative and positive feedback in electronic/control systems;

- working principle of an operational amplifier in the basic active configurations for amplification (inverting/non inverting) and filtering (high- and low-pass);

- basics of electronic noise and its representation.

Background in control automation is also partially recommended.

Background in optics fundamentals is also partially recommended.

Evaluation will be carried on so to understand whether the student has achieved the expected results, listed above. To this aim, the exam is formed by:

1 - a written exam, split into three parts

a) one theoretical question, whose aim is to verify the student comprehension of the physical principles behind the sensors and/or to verify her/his capability in making choices among different system topologies and/or to verify his capability in taking decisions and being convincing, and/or to verify her/his knowledge of the industrial state of the art and need (according to DdD1, DdD4 and DdD5);

b) one numerical exercises on design of sensing systems, whose aim is to verify how the student practically turns design considerations into a quantitative, optimized, system design, accounting for the trade offs and the boundary conditions (according to DdD2);

c) a second numerical exercises on design of sensing systems, whose aim is to stimulate the applications of the concept studied in the course to similar domains, e.g. other sensing systems, or systems for the same physical quantity but based on other technologies (according to DdD3);

The written exam duration will be 3 hours, and the maximum grade that can be achieved with the written exam is 30/30 (no cum laude).

2 - the discussion of the exam, and facultative oral exam

Students will be given the possibility to discuss the exam correction together with the lecturers. This will allow to understand more in depth the student awareness of the topics discussed in the written exam, and thus to deepen its evaluation. This procedure also aims at identifying possible misunderstandings, and thus may give rise to partial amendment of the grade.

There is then the possibility to take a facultative oral exam (approximate duration is 10-15 minutes) only for students with a grade equal or larger than 26. The oral exam can increase or decrease the grade, typically by 1 to 3 points. Oral questions often deal with problems that go beyond the course content, but that can be discussed by the students that have a comprehensive knoledge of the course topics.

The aim of the additional oral exam is to verify more in depth the knowledge acquired by the top-10% of the class, and gives the possibility to grant 30 cum laude for the students that really demonstrate advanced system design capabilities.

No intermediate (in itinere) exam sessions are foreseen. However, the new didactic approach stimulates a continuous self-judgment of the student preparation.

Chapter 13 of the book: "Smart Sensors and Mems"