EE C245 ME C218 Introduction to MEMS Design Fall 2010

Transcription

1 EE C245 ME C218 Introduction to MEMS Design Fall 2010 Prof. Clark T.-C. Nguyen Dept. of Electrical Engineering & Computer Sciences University of California at Berkeley Berkeley, CA Lecture EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 1 Lecture Outline Reading: Senturia, Chapter 1 Lecture Topics: Benefits of Miniaturization Examples GHz micromechanical resonators Chip-scale atomic clock Micro gas chromatograph EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 1

2 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 LecM 2 C. Nguyen 8/20/09 3 Vibrating RF MEMS EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 2

3 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 LecM 2 C. Nguyen 8/20/09 5 Frequency of a Stretched Wire EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 3

4 Frequency of a Clamped-Clamped Beam EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 7 Frequency of a Clamped-Clamped Beam EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 4

5 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 LecM 2 C. Nguyen 8/20/09 9 3CC 3λ/4 Bridged μmechanical Filter Performance: f o f=9mhz, o BW=20kHz, PBW=0.2% I.L.=2.79dB, Stop. Stop. Rej.=51dB 20dB 20dB S.F.=1.95, 40dB 40dB S.F.= V P In Out Transmission [db] P in =-20dBm Sharper -30 roll-off Design: L r =40μm -40 Loss Pole W r =6.5μm h r =2μm -50 L c =3.5μm L b =1.6μm [S.-S. Li, Nguyen, FCS 05] -60 V P =10.47V P=-5dBm R Frequency [MHz] Qi =R Qo =12kΩ [Li, et al., UFFCS 04] EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 5

6 1.51-GHz, Q=11,555 Nanocrystalline Diamond Disk μmechanical Resonator Impedance-mismatched stem for reduced anchor dissipation Operated in the 2 nd radial-contour mode Q ~11,555 (vacuum); Q ~10,100 (air) Below: 20 μm diameter disk Polysilicon Electrode Polysilicon Stem (Impedance Mismatched to Diamond Disk) CVD Diamond μmechanical Disk Resonator R Ground Plane EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 11 Mixed Amplitude [db] Design/Performance: R=10μm, t=2.2μm, d=800å, V P =7V f o =1.51 GHz (2 nd mode), Q=11, Frequency [MHz] f o = 1.51 GHz Q = 11,555 (vac) Q = 10,100 (air) Q = 10,100 (air) [Wang, Butler, Nguyen MEMS 04] 163-MHz Differential Disk-Array Filter Com. Array Couplers Filter Coupler v i+ Port1 Port1 λ/2 V P Port3 Port3 λ/2 v o+ λ/4 λ λ λ/4 v i- λ/2 Port2 Port2 Diff. Array Couplers V P λ/2 Port4 Port4 v o- [Li, Nguyen Trans 07] EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 6

7 Linear MEMS in Wireless Comms High High Q and and good good linearity of of micromechanical resonators Filters Filters for for front-end frequency selection Micromechanical Bandpass Filter Filter Transmission [db] Frequency [MHz] Antenna Mixer I LPF I Diplexer A/D AGC 0 Wireless o 90 o RF PLL Xstal Osc Phone RF RXRF LO LNA Q BPF A/D From TX Mixer Q AGC LPF EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 13 Miniaturization of RF Front Ends RF RF Power Power Amplifier 897.5±17.5MHz RF RF SAW SAW Filter Filter Dual-Band Zero-IF Transistor Chip Chip MHz VCO VCO Diplexer MHz RF RF SAW SAW Filter Filter MHz RF RF SAW SAW Filter Filter 26-MHz Xstal Xstal Oscillator Problem: high-q passives pose a bottleneck against miniaturization Antenna Mixer I LPF I Diplexer A/D AGC 0 Wireless o Xstal 90 o RF PLL Osc Phone RF RXRF LO LNA Q BPF A/D From TX Mixer Q AGC LPF EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 7

8 Multi-Band Wireless Handsets Duplexer I Antenna CDMA RF BPF LNA RF BPF From TX GSM o 90 o LPF AGC A/D I RF BPF RF BPF Duplexer LNA LNA PCS 1900 DCS 1800 LNA RF BPF Q I 0 o 90 o LPF RXRF LO (N+1)/N AGC RXRF Channel Select PLL A/D Xstal Osc Q CDMA-2000 Duplexer LNA From TX RF BPF Q LNA WCDMA From TX EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 15 Tank The number of off-chip high-q passives increases dramatically Need: on-chip high-q passives All High-Q Passives on a Single Chip 0.25 mm Vibrating Vibrating Resonator Resonator 1.5-GHz, 1.5-GHz, Q~12,000 Q~12,000 CDMA RF Filters ( MHz) GSM 900 RF Filter ( MHz) PCS 1900 RF Filter ( MHz) DCS 1800 RF Filter ( MHz) CDMA-2000 RF Filters ( MHz) Vibrating Vibrating Resonator Resonator 62-MHz, 62-MHz, Q~161,000 Q~161,000 WCDMA RF Filters ( MHz) EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ mm Optional RF Oscillator Ultra-High Q Tanks Low Freq. Reference Oscillator Ultra-High Q Tank 2010 Regents of the University of California 8

9 Chip-Scale Atomic Clocks (CSAC) EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 17 NIST F1 Fountain Atomic Clock Vol: ~3.7 m 3 Power: ~500 W Acc: Stab: 3.3x10-15 /hr After 1 sec Error: sec Loses 1 sec every million years! Physics Package EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 9

10 Benefits of Accurate Portable Timing Better Timing Networked Sensors Secure Communications More efficient spectrum utilization Longer autonomy periods Larger networks with with longer autonomy GPS Faster frequency hop hop rates Faster acquire of of pseudorandom signals Superior resilience against jamming or or interception Fewer satellites needed Higher jamming margin Faster GPS acquire EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 19 NIST F1 Fountain Atomic Clock Vol: ~3.7 m 3 Power: ~500 W Acc: Stab: 3.3x10-15 /hr After 1 sec Error: sec Loses 1 sec every million years! Physics Package EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 10

11 1 st Chip-Scale Atomic Physics Package NIST s NIST s Chip- Chip- Scale Scale Atomic Atomic Physics Physics Package Package 1.5 mm Photodiode Cell 4.2 mm Optics ND Quartz Si ND Glass Alumina Lens VCSEL 1.5 mm Laser Total Total Volume: mm mm 3 3 Cell Cell Interior Vol: Vol: mm mm mm Stability: x s 1s Power Power Cons: Cons: mw mw EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 21 Tiny Physics Package Performance NIST s NIST s Chip-Scale Chip-Scale Atomic Atomic Physics Physics Package Package Drift 10-9 Cs Drift Cs (D (D 2 ) Drift Drift to to Be 2 ) Issue Issue Be Q Removed Removed 5.67 =1.3x106 6 in in Phase Phase Sufficient 7.1 khz Sufficient to to meet meet 5.66 CSAC CSAC program Contrast: 0.91% program 2.4e e-10 Allan goals Rb Allan goals deviation Rb (D (D 1 ) deviation 1 1 s 1 hour 1 day Frequency Detuning, Δ [khz] from 9,192,631,770 Hz Integration Time, τ [s] EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 22 PD Signal [V] Dime Dime Open Loop Resonance: Experimental Conditions: Cs D2 Excitation External (large) Magnetic Shielding External Electronics & LO Cell Temperature: ~80 ºC Cell Heater Power: 69 mw Laser Current/Voltage: 2mA / 2V RF Laser Mod Power: 70μW Allan Deviation, σ y Stability Measurement: CSAC Goal 2010 Regents of the University of California 11

12 Atomic Clock Fundamentals Frequency determined by an atomic transition energy Energy Band Diagram ΔE = 1.46 ev Excite e- e-to to the the next next orbital m = Cs ν = ΔE/h = 352 THz nm ΔE = ev ν = ΔE/ħ = Hz m = 0 f = 4 Opposite e- e-spins m = 0 f = 3 EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 23 Miniature Atomic Clock Design Sidebands Carrier (852 nm) Modulated Laser 9.2GHz 4.6GHz λ 133 Cs vapor at 10 7 torr Atoms become transparent to to light at at nm nm Photo Detector ν = ΔE/ħ = Hz Hyperfine Hyperfine Splitting Splitting Freq. Freq. v VCXO o 4.6 GHz μwave osc Mod f Close feedback loop to to lock lock EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 12

13 Chip-Scale Atomic Clock Laser 133 Cs vapor at 10 7 torr v o VCXO 4.6 GHz μwave osc Atomic Clock Concept MEMS and Photonic Technologies Mod f Photo Detector GHz Resonator in Vacuum VCSEL Cs or Rb Glass Detector Substrate Key Challenges: thermal isolation for low power cell design for maximum Q low power μwave oscillator Chip-Scale Atomic Clock Vol: 1 cm 3 Power: 30 mw Stab: EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Challenge: Miniature Atomic Cell Large Vapor Cell 1,000X Volume Scaling Tiny Vapor Cell Wall Wall collision dephases atoms lose lose coherent state Surface Volume EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 26 Intensity lower Q Atomic Resonance More wall wall collisions stability gets gets worse 9.2 GHz lowest Q Mod f 2010 Regents of the University of California 13

14 Challenge: Miniature Atomic Cell Large Vapor Cell 1,000X Volume Scaling Tiny Vapor Cell Buffer Gas Soln: Add Add a buffer gas gas Intensity Lower the the mean free free path of of the the atomic vapor Atomic Resonance Return to to higher Q 9.2 GHz Mod f EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 27 Chip-Scale Atomic Clock Laser 133 Cs vapor at 10 7 torr v o VCXO 4.6 GHz μwave osc Atomic Clock Concept MEMS and Photonic Technologies Mod f Photo Detector GHz Resonator in Vacuum VCSEL Cs or Rb Glass Detector Substrate Key Challenges: thermal isolation for low power cell design for maximum Q low power μwave oscillator Chip-Scale Atomic Clock Vol: 1 cm 3 Power: 30 mw Stab: EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 14

15 Micro-Scale Oven-Control Advantages Macro-Scale Atomic 80 o C 3 cm Macro-Oven (containing heater and T sensor) Insulation Laser 25 o C 300x300x300 μm 3 Atomic 80 o C Micro-Scale Heater Laser Thermally Isolating Feet R th = th K/W K/W C th = th J/K J/K P (@ (@ o o C) C) = W Warm Up, Up, τ = min. min. T = P x R th P R th C th support length R th ~ X-section area C th ~ volume 550x lower power 7,300x faster warm up T Sensor (underneath) Long, Thin Polysilicon Tethers R = th 83,000 K/W th K/W C th = th 6.3x J/K J/K P (@ (@ o o C) C) = mw mw Warm Up, Up, τ = s EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 29 Physics Package Power Diss. < 10 mw Achieved via MEMS-based thermal isolation Cesium cell VCSEL / Photodiode Heater/Sensor Suspension Frame Spacer VCSEL Suspension Symmetricom Symmetricom // Draper Draper Physics Physics Package Package Assembly Assembly 7 mm 20 pin LCC Temperature [ o C] EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 30 Power [mw] Only Only ~5 ~5 mw mw heating power power needed to to achieve o o C cell cell temperature Measured Model 2010 Regents of the University of California 15

16 Thermal Circuit Modeling Macro-Scale Atomic 80 o C 3 cm Macro-Oven (containing heater and T sensor) Insulation Laser 25 o C Thermally Isolating Feet EE C245: Introduction to MEMS Design Lecture 3 C. Nguyen 9/4/08 31 Thermal Circuit Modeling Atomic 80 o C 3 cm Insulation Laser 25 o C Thermally Isolating Feet EE C245: Introduction to MEMS Design Lecture 3 C. Nguyen 9/4/ Regents of the University of California 16

17 Thermal Circuit Modeling EE C245: Introduction to MEMS Design Lecture 3 C. Nguyen 9/4/08 33 Thermal Circuit Modeling EE C245: Introduction to MEMS Design Lecture 3 C. Nguyen 9/4/ Regents of the University of California 17

18 MEMS Thermal Circuit Modeling 300x300x300 μm 3 Atomic 80 o C Heater Laser 25 o C T Sensor (underneath) Long, Thin Polysilicon Tethers EE C245: Introduction to MEMS Design Lecture 3 C. Nguyen 9/4/08 35 Micro Gas Analyzers (MGA) EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 18

19 EE 245: Introduction to MEMS Micro Gas Analyzers Objective: enable remote detection of chemical agents via tiny, ultra-low power, fast, chip-scale gas analyzers that greatly reduce the incidence of false positives Approach: use micromachining technologies to implement separation-based analyzers (e.g., gas chromatographs, mass spectrometers) at the micro-scale to enhance gas selectivity Conventional Sensor B Separation Analyzer Capacitor Plates Gas Sensitive Polymer Species A Species B Species A ΔC ~gas conc. Result Problem : :species too big, A & toob slow, now A Problem: polymer has finite power hungry separated Ö can identify and analyze individually B sensitivity to both A & B EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 37 Advantages of Miniaturization Portable Gas Chromatograph 19 Preconcentrator Detector Array 5 mm Depth = 10 Chip-Scale Gas Chromatograph cm Reduction ReductionFactors Factors Size 40,500 cm3 20,000X 20,000X 1 ppb 1,000X 1,000X 15 min. 225X 225X 10,000 J 10,000X 10,000X Sensitivity Analysis Time Energy Per Analysis EE C245: Introduction to MEMS Design LecM 2 Separation Micropump Column Size 2 cm3 Sensitivity 1 ppt Analysis Time 4 sec Energy Per Analysis C. Nguyen 2010 Regents of the University of California 8/20/09 1J 38 19

20 Basic Approach: Separation Analyzer Three Analytes Compacted Slice of Analytes Separated Analytes Electronic Processor Pump Input Gas Mixture Pre-Concentrator Separator Detector Miniaturization Tiny Tiny Dimensions fast fast time time constants 10,000X gain gain factor factor via via multi-staging enhanced sensitivity lower lower power power Tiny Tiny Dimensions faster faster separation lower lower power power EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 39 Scaling Leads to Faster Separation Example: gas chromatograph separation column unique analyte interactions with the column walls different analyte velocities result: separation after a finite distance Wide Channel Carrier Gas (Mobile Phase) Conc. Stationary Phase Miniaturize Peak Broadens Conc. 240 μm Peak Stays Thin 150 μm Thin Channel Less Separation Needed to Resolve x EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 40 x 2010 Regents of the University of California 20

21 Scaling Leads to Faster Separation Example: gas chromatograph separation column unique analyte interactions with the column walls different analyte velocities result: separation after a finite distance Wide Channel Carrier Gas (Mobile Phase) Column Width Surface-to- Volume Ratio Stationary Phase Miniaturize Peak Spreading 240 μm 150 μm Separation Distance Thin Channel Result of Scaling: shorter column length; faster analysis time EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 41 Gas Chromatography in Less Than 4s! Relative Intensity Design/Measurement Data: 0.75m x 100μ column 0.1μ 0.1μDB-5 stationary phase Heart-cut msec peak injection Temperature: ~30 ~30 deg deg C/sec H 2 carrier: psi psi at at 1 psi/sec Solvent 3-methylhexane Toluene DMMP Peak capacity >40, >40, in in 4 sec sec DEMP DIMP Sandia s micro-gc Column 1,6-dichlorohexane n-dodecane Green Green = Analyte Blue Blue = Inteferent 1-decanol Elution time [s] EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 21

22 Basic Approach: Separation Analyzer Three Analytes Compacted Slice of Analytes Separated Analytes Electronic Processor Pump Input Gas Mixture Pre-Concentrator Separator Detector Miniaturization Tiny Tiny Dimensions fast fast time time constants 10,000X gain gain factor factor via via multi-staging enhanced sensitivity lower lower power power Tiny Tiny Dimensions faster faster separation lower lower power power Tiny Tiny Dimensions higher higher sensitivity faster faster refresh rate rate lower lower power power arrays arrays for for specificity EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 43 Zeptogram Mass Sensors Nanomechanical Resonator Shutter Nanomechanical Resonator Au Nozzle Measurement noise level indicates ~7 ~7 zg zg of of resolution Frequency Shift (Hz) ~100 zg zg zg Au Au atom clumps resolved! Frequency Shift (Hz) Time (sec) Mass (zeptograms) EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ δ m (zg) 133 MHz 190 MHz ~7 zg Time (s) >1Hz/zg 2010 Regents of the University of California 22

23 Gas Analyzer Technology Progression Agilent 6852A Vol: 60,000 cm 3 Power: 20 W small small enough enough for for Energy/Analysis: 18 kj LLNL projectile projectile delivery delivery Analysis Time: 15 min. Vol: 40,500 cm 3 1 ppt ppt det. det. limit limit Power: 11.5 W Gas Gas Chromatograph/Mass very very fast fast Energy/Analysis: 10 kj Spectrometer Spectrometer (GC/MS) (GC/MS) is battery battery operable operable is Analysis Time: 15 min. a gold gold standard standard in in chemical chemical gas gas detection detection Sandia μchem Lab with with excellent excellent immunity immunity Vol: 1,050 cm 3 to to false false alarms alarms Power: 4.5 W Energy/Analysis: 540 J Problems: Analysis Time: 2 min. Problems: too too big, big, too too slow, slow, power power hungry hungry Solution: MGA Objective Solution: use use MEMS MEMS technology Vol: 2 cm 3 technology to to miniaturize miniaturize the Power: <200 mw the GC/MS, GC/MS, which which in in turn turn makes Energy/Analysis: 1 J makes it it faster faster and and more more energy energy efficient efficient Analysis Time: 4 s EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 45 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 LecM 2 C. Nguyen 8/20/ Regents of the University of California 23

24 Messages Going Forward MEMS are micro-scale or smaller devices/systems that operate mainly via a mechanical or electromechanical means MEMS NEMS offer the same scaling advantages that IC technology offers (e.g., speed, low power, complexity, cost), but they do so for domains beyond electronics: Size resonant frequency (faster speed) actuation force (lower power) # mechanical elements (higher complexity) integration level (lower cost) Micro nano it s all good Just as important: MEMS or NEMS have brought together people from diverse disciplines this is the key to growth! What s next? Nano-nuclear fusion? Chip-scale atomic sensors? limitless possibilities EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/ Regents of the University of California 24