1. Summary of Introduction MEMS (U.S.) Sometimes Microsystems in Europe. MEMS=MicroElectroMechanical Systems Very broad definition in practice: Mechanical, Electrical, Optical, Thermal, Fluidic, Chemical, Magnetic. Generally systems created using microfabrication that are not integrated circuits. Many (but not all) of the microfabrication techniques were borrowed from the IC industry. Market is smaller than IC market, but more diverse and growing faster.

2. Some Examples Accelerometer –Electrical/Mechanical  TAS or Micro Total Analysis System –Purifies, amplifies, and detects DNA, for example. –Fluids/Biochemistry/Optical/Electrical TI DLP –Optical/Mechanical/Electrical/Surface Science Microrelay –Mechanical/Electrical/Surface Science Microplasma Source –Electrical/Electromagnetic/Plasma What do you need to know for MEMS? Everything!!!??? Truly an interdisciplinary field.

3. What are we going to do? Learn a useful subset of techniques needed for designing MEMS devices. Not all!! We will design MEMS devices. –Project teaming survey is due Monday – see web site. –Project assignment to be posted on the web site. We will discuss examples of MEMS devices and use the techniques we have developed. First we will look at microfabrication and process integration. Other notes: –First homework is due Thursday. We will try to have all students consolidated to one section to make the discussion board and the electronic turn-in (for video streaming students) in one place by Thursday. –Second homework is due Thursday, Sept. 23 (but you will have everything you need to do the work over the weekend). Homework 3 will probably be due on Monday, Sept. 27. The homework load will decrease as the project load increases (generally).

4. Microfabrication: Types of Micromachining for MEMS Bulk Micromachining –Etch away large parts of the silicon wafer. –Traditionally, KOH or other chemical etch. –Recently DRIE (Deep Reactive Ion Etch), an anisotropic plasma etch.

5. Microfabrication: Types of Micromachining for MEMS Surface micromachining –On surface of wafer/substrate –Sometimes can be a post-process on top of CMOS wafer for process integration with electronics. –Typically much thinner structures than bulk micromachining, but metal structures can be fairly thick.

6. Microfabrication: Types of Micromachining for MEMS LIGA –X-ray lithographie, galvanoformung, abformtechnik (or lithography, electrodeposition, and molding). –A special type of surface micromachining, not much used in its original form. –Now sometimes refers to using very thick photoresist to make thick electroplated structures.

7. Packaging Ideally, part of fabrication process, then just use a cheap plastic package. Often, a surface micromachined device is bonded to a bulk micromachined package (the cavity to contain the device is etched from the wafer using bulk micromachining). Sometimes the package is the most expensive part of the device (pressure sensors, microfluidics). Especially true when the device interacts with the outside environment.

8. References: Text (brief), Campbell or other IC fabrication text (generally good, but incomplete for MEMS), Madou (specific to MEMS).

10. Silicon wafer fabrication Taken from www.egg.or.jp/MSIL/english/index-e.html

11. Silicon wafer fabrication – slicing and polishing Taken from www.egg.or.jp/MSIL/english/index-e.html

16. LPCVD Systems Taken from http://www-bsac.EECS.Berkeley.EDU/~pister/245/

38. Electrodeposition/Electroplating SEM of NEU microswitch Drain Source Gate Beam Drain Gate Source Beam Drain Gate Source Surface Micromachined Post-Process Integration with CMOS 20-100 V Electrostatic Actuation ~100 Micron Size

39. IBM 7-Level Cu Metallization (Electroplated)

42. Packaging Ideally, part of fabrication process, then just use a cheap plastic package. Often, a surface micromachined device is bonded to a bulk micromachined package (the cavity to contain the device is etched from the wafer using bulk micromachining). Sometimes the package is the most expensive part of the device (pressure sensors, microfluidics). Especially true when the device interacts with the outside environment.

45. Adhesives Organics Glass (Glass Frit) Metals (~Solders, Metal/Semiconductor Eutectics) Thermal Compression Bonding Au-Au/Clean/300 C Why?

46. NUMEM Microrelay Process

48. Residual stress gradients More tensile on top More compressive on top Just right! The bottom line: anneal poly between oxides with similar phosphorous content. ~1000C for ~60 seconds is enough. Taken from http://www-bsac.EECS.Berkeley.EDU/~pister/245/

49. Residual stress gradients A bad day at MCNC (1996). Taken from http://www-bsac.EECS.Berkeley.EDU/~pister/245/

50. DRIE structures Increased capacitance for actuation and sensing Low-stress structures –single-crystal Si only structural material Highly stiff in vertical direction –isolation of motion to wafer plane –flat, robust structures 2DoF Electrostatic actuator Thermal Actuator Comb-drive Actuator Taken from http://www-bsac.EECS.Berkeley.EDU/~pister/245/

52. 1 µm Scalloping and Footing issues of DRIE 10 micron gap microgrid Footing at the bottom of device layer Milanovic et al, IEEE TED, Jan. 2001.

53. Taken from: http://www.imm-mainz.de/english/sk_a_tec/basic_te/liga.html

54. Sub-Micron Stereo Lithography Micro Electro Mechanical Systems Jan., 1998 Heidelberg, Germany New Micro Stereo Lithography for Freely Movable 3D Micro Structure -Super IH Process with Submicron Resolution- Koji Ikuta, Shoji Maruo, and Syunsuke Kojima Department of Micro System Engineering, school of Engineering, Nagoya University Furocho, Chikusa-ku, Nagonya 464-01, Japan Tel: +81 52 789 5024, Fax: +81 52 789 5027 E-mail: ikuta@mech.nagoya-u.ac.jpikuta@mech.nagoya-u.ac.jp Fig. 1 Schematic diagram of IH Process Fig. 5 Process to make movable gear and shaft (a) conventional micro stereo lithography needs base layer (b) new super IH process needs no base Fig. 6 Schematic diagram of the super IH process

55. Sub-Micron Stereo Lithography Micro Electro Mechanical Systems Jan., 1998 Heidelberg, Germany New Micro Stereo Lithography for Freely Movable 3D Micro Structure -Super IH Process with Submicron Resolution- Koji Ikuta, Shoji Maruo, and Syunsuke Kojima Department of Micro System Engineering, school of Engineering, Nagoya University Furocho, Chikusa-ku, Nagonya 464-01, Japan Tel: +81 52 789 5024, Fax: +81 52 789 5027 E-mail: ikuta@mech.nagoya-u.ac.jpikuta@mech.nagoya-u.ac.jp Fig. 10 Micro gear and shaft make of solidified polymer (b) side view of the gear of four teeth (d) side view of the gear of eight teeth

56. Simple Carbon Nanotube Switch Diameter: 1.2 nm Elastic Modulus: 1 TPa Electrostatic Gap: 2 nm Binding Energy to Substrate: 8.7x10 -20 J/nm Length at which adhesion = restoring force: 16 nm Actuation Voltage at 16 nm = 2 V Resonant frequency at 16 nm = 25 GHz Electric Field = 10 9 V/m or 10 7 V/cm + Geom. (F-N tunneling at > 10 7 V/cm) Stored Mechanical Energy (1/2 k x 2 ) = 4 x 10 -19 J = 2.5 eV

59. Extras

60. Micromachining Ink Jet Nozzles Microtechnology group, TU Berlin

61. Bulk micromachined cavities Anisotropic KOH etch (Upperleft) Isotropic plasma etch (upper right) Isotropic BrF3 etch with compressive oxide still showing (lower right) Taken from http://www-bsac.EECS.Berkeley.EDU/~pister/245/

62. Surface Micromachining Deposit sacrificial layer Pattern contacts Deposit/pattern structural layerEtch sacrificial layer Taken from http://www-bsac.EECS.Berkeley.EDU/~pister/245/

63. Packaged Plasma Source Top View Side View Die in Hybrid Package

64. Fabrication SEM of Interdigitated Capacitor Structure