EE C245 ME C218 Introduction to MEMS Design Fall 2007

Transcription

1 EE C245 ME C218 Introduction to MEMS Design Fall 2007 Prof. Clark T.-C. Nguyen Dept. of Electrical Engineering & Computer Sciences University of California at Berkeley Berkeley, CA Lecture 1: Definition and Incentives for MEMS EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/07 1 Instructor: Prof. Clark T.-C. Nguyen Education: Ph.D., University of California at Berkeley, : joined the faculty of the Dept. of EECS at the University of Michigan 2006: (came back) joined the faculty of the Dept. of EECS at UC Berkeley Research: exactly the topic of this course, with a heavy emphasis on vibrating RF MEMS Teaching: (at the UofM) mainly transistor circuit design courses, from undergraduate to graduate 2001: founded Discera, the first company to commercialize vibrating RF MEMS technology Mid-2002 to 2005: DARPA MEMS program manager ran 10 different MEMS-based programs topics: power generation, chip-scale atomic clock, gas analyzers, nuclear power sources, navigation-grade gyros, on-chip cooling, micro environmental control EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/07 2 1

2 Course Overview Goals of the course: Accessible to a broad audience (minimal prerequisites) Design emphasis Exposure to the techniques useful in analytical design of structures, transducers, and process flows Perspective on MEMS research and commercialization circa 2007 Related courses at UC Berkeley: EE 143: Microfabrication Technology ME 119: Introduction to MEMS (mainly fabrication) BioEng 121: Introduction to Micro and Nano Biotechnology and BioMEMS ME C219 EE C246: MEMS Design Assumed background for EE C245: graduate standing in engineering or physical/bio sciences EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/07 3 Course Overview The mechanics of the course are summarized in the course handouts, given out in lecture today Course Information Sheet Course description Course mechanics Textbooks Grading policy Syllabus Lecture by lecture timeline w/ associated reading sections Midterm Exam: tentatively set for Thursday, Oct. 25 Final Exam: Saturday, Dec. 15, 8-11 a.m. Project due date TBD (but near semester s end) EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/07 4 2

3 Lecture Outline Reading: Senturia, Chapter 1 Lecture Topics: Definitions for MEMS MEMS roadmap Benefits of Miniaturization Examples GHz micromechanical resonators Chip-scale atomic clock Micro gas chromatograph EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/07 5 MEMS: Micro Electro Mechanical System A device constructed using micromachining (MEMS) tech. A micro-scale or smaller device/system that operates mainly via a mechanical or electromechanical means At least some of the signals flowing through a MEMS device are best described in terms of mechanical variables, e.g., displacement, velocity, acceleration, temperature, flow Input: voltage, current acceleration, velocity light, heat Transducer Transducer to to Convert Convert Control Control to to a Mechanical Mechanical Variable Variable (e.g., (e.g., displacement, displacement, velocity, velocity, stress, stress, heat, heat, ) ) Control: voltage, current acceleration velocity light, heat, MEMS Output: voltage, current acceleration, velocity light, heat, [Wu, UCLA] Angle set by mechanical means to control the path of light EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/07 6 3

4 Other Common Attributes of MEMS Feature sizes measured in microns or less [Najafi, Michigan] 80 mm Gimballed, Spinning Micromechanical Macro-Gyroscope Vibrating Ring Gyroscope MEMS Technology (for 80X size Reduction) Merges computation with sensing and actuation to change the way we perceive and control the physical world Planar lithographic technology often used for fabrication can use fab equipment identical to those needed for IC s however, some fabrication steps transcend those of conventional IC processing 1 mm Signal Conditioning Circuits EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/07 7 Bulk Micromachining and Bonding Use the wafer itself as the structural material Adv: very large aspect ratios, thick structures Example: deep etching and wafer bonding 1 mm [Najafi, Michigan] Micromechanical Vibrating Ring Gyroscope [Pisano, UC Berkeley] Movable Silicon Substrate Structure Silicon Substrate Electrode Glass Substrate Metal Interconnect Anchor Microrotor (for a microengine) EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/07 8 4

5 Surface Micromachining Fabrication steps compatible with planar IC processing EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/07 9 Single-Chip Ckt/MEMS Integration Completely monolithic, low phase noise, high-q oscillator (effectively, an integrated crystal oscillator) Oscilloscope Output Waveform [Nguyen, Howe 1993] To allow the use of >600 o C processing temperatures, tungsten (instead of aluminum) is used for metallization EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/

6 3D Direct-Assembled Tunable L [Ming Wu, UCLA] EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/07 11 Technology Trend and Roadmap for MEMS increasing ability to compute Number of Transistors Majority of Early MEMS Devices (mostly sensors) CPU s Pentium 4 ADXL-50 Inertial Navigation On a Chip i-stat 1 Weapons, Caliper Safing, Arming, and Fusing ADXL-278 ADXRS ADXL-78 Terabit/cm 2 Data Storage Phased-Array Antenna OMM 32x32 Adaptive Optics Optical Switches & Aligners Distributed Structural Control Displays Integrated Fluidic Systems Number of Mechanical Components increasing ability to sense and act Digital Micromirror Device (DMD) Future MEMS Integration Levels Enabled Applications EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/

7 Benefits of Size Reduction: IC s Numerous benefits attained by scaling of transistors: Lower Power Higher Current Drive Lower Capacitance Higher Integration Density Lower Supply Voltage Faster Speed Higher Circuit Complexity & Economy of Scale But some drawbacks: poorer reliability (e.g., hot e- effects) lower dynamic range (analog ckts suffer) EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/07 13 Example: Micromechanical Accelerometer The MEMS Advantage: >30X size reduction for accelerometer mechanical element allows integration with IC s Basic Operation Principle Tiny Tiny mass mass means means small small output output need need integrated integrated transistor transistor circuits circuits to to compensate compensate 400 μm x o x Fi = ma x Displacement Spring a Inertial Force Proof Mass Acceleration Analog Devices ADXL 78 EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/

8 Technology Trend and Roadmap for MEMS increasing ability to compute Number of Transistors ADXL-50 Analog 10 Devices 6 ADXRS Integrated Gyroscope Inertial 10 5 Navigation Adv.: On a Chip Adv.: small small size size i-stat Weapons, Caliper Safing, Arming, and Fusing 10 3 ADXL Caliper 2 Microfluidic ADXRS Chip ADXL-78 Distributed Structural Terabit/cm OMM 2 8x8 Optical Control Data Storage Cross-Connect Switch Adv.: Adv.: faster faster Phased-Array switching, low Displays low loss, Antenna OMM loss, larger 32x32larger networks Integrated Fluidic Systems Adaptive Optics Optical Switches & Aligners 10 1 TI Digital Micromirror Device 10 0 Adv.: Adv.: low low loss, loss, fast fast switching, 10 6 high 10high 7 fill fill factor 10 8 factor 10 9 Number of Mechanical Components Majority of Early MEMS Devices (mostly sensors) CPU s Pentium 4 Adv.: Adv.: small small size, size, small small sample, fast fast analysis speed speed increasing ability to sense and act Digital Micromirror Device (DMD) Future MEMS Integration Levels Enabled Applications EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/07 15 Technology Trend and Roadmap for MEMS increasing power consumption increasing ability to compute Number of Transistors Majority of Early MEMS Devices (mostly sensors) CPU s Pentium 4 ADXL-50 Inertial Navigation On a Chip i-stat 1 Weapons, Caliper Safing, Arming, and Fusing ADXL-278 ADXRS ADXL-78 Terabit/cm 2 Data Storage Phased-Array Antenna OMM 32x32 Adaptive Optics Optical Switches & Aligners Distributed Structural Control Displays Integrated Fluidic Systems increasing ability to sense and act Digital Micromirror Device (DMD) Future MEMS Integration Levels Enabled Applications 10 1 Lucrative Ultra-Low Power Territory (e.g, mechanically powered devices) Number of Mechanical Components EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/

9 Benefits of Size Reduction: MEMS Benefits of size reduction clear for IC s in elect. domain size reduction speed, low power, complexity, economy MEMS: enables a similar concept, but MEMS extends the benefits of size reduction beyond the electrical domain Performance enhancements for application domains beyond those satisfied by electronics in the same general categories Speed Frequency, Thermal Time Const. Power Consumption Actuation Energy, Heating Power Complexity Integration Density, Functionality Economy Batch Fab. Pot. (esp. for packaging) Robustness g-force Resilience EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/07 17 Vibrating RF MEMS EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/

10 Basic Concept: Scaling Guitar Strings Guitar String μmechanical Resonator Vib. Amplitude Low Q High Q Guitar Freq. 110 Hz Freq. Vibrating Vibrating A A String String (110 (110 Hz) Hz) Stiffness Freq. Equation: 1 kr fo = 2π m r Mass [Bannon 1996] f o =8.5MHz Q vac =8,000 Q air ~50 Performance: L r =40.8μm m r ~ kg W r =8μm, h r =2μm d=1000å, V P =5V Press.=70mTorr EE C245: Introduction to MEMS Design Lecture 1 C. Nguyen 8/28/