1. ¿Quien soy y por qué estoy aquí? Thomas Adams, PhD En el mundo hispano: Tomás McDaniel Adams McDaniel Soy profesor de ingeniería mecánica en Rose-Hulman Institute of Technology Mis estudiantes me llaman “Doctor Tom”. Más cabello

2. Terre Haute, Indiana, USA Private university with ~ 2000 students, mostly undergraduate (pregrado) Ciencias, ingeniería, y matemáticas

3. Introduction to MEMS (micro-tecnología)

4. Movie of a motor Motor and gear train movies from Sandia National Laboratory

5. Movie of a motor Motor and gear train movies from Sandia National Laboratory

6. Still pictures of motor A still picture of the motor… with a spider mite on it! Another view of the engine

7. Movie of a motor Motor and gear train movies from Sandia National Laboratory

8. Movie of a motor Motor and gear train movies from Sandia National Laboratory

9. Movie of a motor Motor and gear train movies from Sandia National Laboratory

10. Course overview and objectives Overview: This course gives an introductory treatment of MEMS, also known as microsystems and micro-technology (MST). Fabrication, device functionality, and modeling strategies are explored. Objectives (Objetivos): Through the student work in the course program, the student will be able to:  Identify the relative importance of different physical phenomena based on length scale  Identify and describe the most commonly used fabrication processes in making MEMS devices  For a simple MEMS device, identify the major required fabrication steps and put them in the appropriate order (create a process flow)  Use the principles of elastic theory in predicting the stress/strain state of MEMS devices

11. Course overview and objectives Objectives (Objetivos) continued: Through the student work in the course program, the student will be able to:  List a number of common MEMS transducers and explain their operating principles  Explain in detail the operating principles of a piezoresistive MEMS pressure sensor, and predict the performance of such a device  Give a well-formed argument considering a microtechnology-based solution for a given problem  Gain experience using English in spoken and written forms as a means of expressing technical ideas

12. Topics Specific topics 1. Introduction to MEMS: Scaling and basic fabrication 2. The Substrate 3. Additive Techniques 4. Creating Patterns – Lithography 5. Bulk Micromachining 6. Surface Micromachining 7. Process flow 8. Solid mechanics 9. Overview of MEMS operating principles 10. Modeling case study: piezoresistive sensors

13. References Required Introductory MEMS: Fabrication and Applications by Thomas Adams and Richard Layton, Springer Disponible (¡gratis! ) en los bases de datos de PUCP: http://biblioteca.pucp.edu.pe/colbasd.html Suggested (sugerencias) Fundamentals of Microfabrication by Marc J. Madou, CRC Press. Microsystem Design by Stephen Senturia, Springer Foundations of MEMS by Chang Liu, Prentice Hall.

14. ¿Cómo va a ser el curso? Notas: Problems/reading summaries10% Midterm exam30% Final Exam35% Report15% Attendance/participation10% 100% En y fuera de clase Puntos fáciles No quiero que este curso sea una dictación sino un diálogo. Por eso creo que es importante que nos charlemos en una manera relajada para entender mejor y practicar nuestros idiomas. (Ustedes, inglés y yo, español.) I will correct your English, but it will not affect your grade. The reading summaries will be based on effort.

15. ¿Cómo va a ser el curso? Report: Can be about any aspect of MEMS you would like—a new or advanced fabrication technique not covered in the book/lectures, a particular MEMS device, a particular class of MEMS technology, modeling strategies, etc. Some examples: Focused ion beam instruments Micro fuel cell technology Dyanamic systems modeling in MEMS Advanced photolithography techniques Digital microfluidics MEMS gyroscopes MEMS packaging Reading summaries: One each week on assigned reading Inlcude a brief summary of the major points (¡No me den otro libro!) Describe the thing you feel you understand the best (Algo que entiendes bien) Describe the thing you feel you understand the least (Algo que no entiendes para nada)

16. What are MEMS? Acronym (acrónimo) for micro-electro-mechanical systems. Micro: Small size. The basic unit of measure is the micrometer or micron (μm) 1 μm = 10 -6 m Electro: MEMS have electrical components (quizás) Mechanical: MEMS have moving parts (quizás) Systems: Refers to integration of components. (Funcionan juntos.)

17. Examples of MEMS You can find MEMS in Automobiles (Air bag sensors) Computer printers (Ink jet print heads) Cell phones (RF devices) Lab-on-a-chip (Microfluidics) Optical devices (Micromirrors) Lots of other things

18. MEMS accelerometer MEMS accelerometers are used widely to deploy airbags. (Casi todos los coches los tienen.)

19. MEMS accelerometer Most accelerometers use electrical capacitance to sense acceleration. Se llama “comb structure (estructura de peine) Adapted from Microsystem Design by Stephen Senturia, Springer

20. Movie of a motor Can be used in reverse as an actuator. With alienating current (corriente alterna) it becomes a motor. In MEMS this type of motor is called a comb drive. Comb drive

21. Ink jet print heads Ink dots are tiny (10-30 per mm) and so are the nozzles that fire them.

22. Ink jet print heads Ink-filled chambers are heated by tiny resistive heating element By heating the liquid ink a bubble is generated

23. Ink jet print heads The vaporized part of the ink is propelled towards the paper in a tiny droplet Chambers are filled again by the ink through microscopic channels

24. Micromirrors Micromirrors are used as optical switches and even computer displays

25. Micromirrors An array of micromirrors

26. Micromirrors Video of micromirror actuation from Sandia National Labs

27. More examples Labs-on-a-chip can replace entire chemical and biological analysis laboratories.

28. More examples There are many other MEMS devices in development…

29. More examples …some more useful than others.

30. Why go micro? Smaller devices require less material to make. (Earth has limited resources.) Smaller devices require less energy to run. Redundancy can lead to increased safety. (You can use an array of sensors instead of just one.) Micro devices are inexpensive (?)  Less material  Can be fabricated in batch processes What are some reasons that you would want to make micro-sized devices? Más cabello

31. Why go micro? Micro devices are minimally invasive and can be treated as disposable. (Especially good for chemical and medical applications.) Many physical phenomena are favored at small scales. What are some reasons that you would want to make micro-sized devices?

32. Examples of small scale effects Hot arm actuator A poly-silicon hot-arm actuator fabricated using surface micromachining

33. Examples of small scale effects Hot arm actuator A poly-silicon hot-arm actuator fabricated using surface micromachining I +V-+V-

34. Examples of small scale effects Electro-osmotic flow Electricity can move fluids! junction separation column entry port + V -

35. Scaling laws Water spills out of key ring, but it stays in the smaller holes of the key (llave). Why? Activity – Demo with key and key ring Gravity (weight) pulls water down. Surface tension holds water up. Which one wins? (¿Quien gana?) Weight depends on volume/area/length Surface tension depends on volume/area/length Entonces,

36. Scaling laws Te toca a ti – La musaraña (shrew) es el animal más pequeño que es de sangre caliente. Si no come constantemente, se muere. Usa “scale analysis” para explicar.

37. Scaling laws Te toca a ti – Use scale analysis to show that every animal on the planet can jump approximately the same height. Es decir, que la habilidad de saltar no cambia con la dimensión.

38. Scaling laws Heat transfer (tranferencia del calor) is faster Frequency response is faster Electrostatic forces are more prominent (más fuertes) Surface tension can move fluids And more Favorable scalings at the microscale

39. How are MEMS made? Many techniques borrowed from integrated circuit (IC) fabrication -Silicon wafers are commonly used -Bulk micromachining Surface micromachining Other techniques

40. How are MEMS made? Bulk micromachining example - A diaphragm for a pressure sensor Adapted from MEMS: A Practical Guide to Design, Analysis, and Applications, Ed. Jan G. Korvink and Oliver Paul, Springer, 2006 Membrane is piezoresistive; i.e., the electrical resistance changes with deformation.

41. Bulk micromachining Bulk micromachining example - A diaphragm for a pressure sensor Silicon wafer Grow SiO 2 Spin on photoresist Glass plate Opaque region Unexposed photoresist removed by developer SiO 2 chemically etched with HFl Unexposed resist removed Silicon anisotropically etched with KOH Mask

42. Bulk micromachining Depending on the chemical/structure combinations, etching can be… isotropic or anisotropic 001 silicon wafer011 silicon wafer Anisotropic etches

43. Surface micromachining = Surface micromachining + The Si wafer functions like the big green flat plate. Some Jenga pieces are removed. The ones that remain form the MEMS structure.

44. Surface micromachining Surface micromachining example – Creating a cantilever Silicon wafer (Green Lego ® plate) Deposit aluminum (structural layer—the Jenga pieces that remain) Remove sacrificial layer (release) Deposit polyimide (sacrificial layer— the Jenga pieces that are removed) Etch part of the layer.

45. Micromachining Complicated structures can be made by combining these techniques and repeating

46. Micromachining Everything has to be very clean! (¡Ojala estén limpias todas cosas!)

47. Surface micromachining Te toca a ti —Come up with the process steps needed to make the cantilever in the last example. (Deposition, photolithography, etc.) Side viewTop view Hint: You will need two masks and two photolithography steps.