EE C245 ME C218 Introduction to MEMS Design

Transcription

1 EE C245 ME C218 Introduction to MEMS Design Fall 2008 Prof. Clark T.-C. Nguyen Dept. of Electrical Engineering & Computer Sciences University of California at Berkeley Berkeley, CA Lecture 2: Benefits of Scaling EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 1

2 Lecture Outline Reading: Senturia, Chapter 1 Lecture Topics: Benefits of Miniaturization Examples GHz micromechanical resonators Chip-scale p atomic clock Micro gas chromatograph EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 2

3 Technology Trend and Roadmap for MEMS inc creasing ab bility to co ompute Num mber of Trans sistors s 10 9 Pentium Distributed Structural 10 7 CPU s Digital Micromirror Terabit/cm 2 Control Device (DMD) Data Storage 6 ADXL Inertial Phased-Array Displays 10 5 Navigation Antenna OMM 32x32 On a Chip Integrated Fluidic Systems i-stat Weapons, Caliper Adaptive Safing, Arming, Optics and Fusing 10 3 ADXL ADXRS ADXL Optical Switches & Aligners Future MEMS Integration Levels Enabled Applications Majority of Early MEMS Devices (mostly sensors) Number of Mechanical Components increasing ability to sense and act EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 3

4 Example: Micromechanical Accelerometer The MEMS Advantage: >30X size reduction for accelerometer mechanical element allows integration with IC s Basic Operation Principle Tiny mass means small output need integrated transistor circuits to compensate 400 μm m 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 2 C. Nguyen 9/2/08 4

5 Technology Trend and Roadmap for MEMS inc creasing ab bility to co ompute Num mber of Trans sistors s 10 9 Pentium Distributed Structural 10 7 CPU s Digital Micromirror Terabit/cm OMM 2 8x8 Optical Control Device (DMD) Data Storage Cross-Connect Switch 6 ADXL-50 Analog 10 Devices ADXRS Adv.: faster Phased-Array switching, low Integrated Gyroscope Inertial Displays Antenna 10 5 Navigation loss, larger networks OMM 32x32 Adv.: small size On a Chip Integrated Fluidic Systems i-stat Weapons, Caliper Adaptive Safing, Arming, Optics and Fusing 10 3 ADXL Caliper 2 Microfluidic ADXRS Chip ADXL Majority of Early MEMS Optical Switches & Aligners Future MEMS Integration Levels Enabled Applications TI Digital Micromirror Device Adv.: low loss, fast switching, high fill factor Devices (mostly sensors) Adv.: small size, small sample, fast analysis speed Number of Mechanical Components increasing ability to sense and act EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 5

6 Technology Trend and Roadmap for MEMS incr easing po ower cons umption inc creasing ab bility to co ompute Num mber of Trans sistors s 10 9 Pentium Distributed Structural 10 7 CPU s Digital Micromirror Terabit/cm 2 Control Device (DMD) Data Storage 6 ADXL Inertial Phased-Array Displays 10 5 Navigation Antenna OMM 32x32 On a Chip Integrated Fluidic Systems i-stat Weapons, Caliper Adaptive Safing, Arming, Optics and Fusing 10 3 ADXL ADXRS ADXL Optical Switches & Aligners Future MEMS Integration Levels Enabled Applications Lucrative Ultra-Low Power Territory (e.g, mechanically powered devices) Majority of Early MEMS Devices (mostly sensors) Number of Mechanical Components increasing ability to sense and act EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 6

7 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 Power Consumption n Complexity Economy Robustness Frequency, Thermal Time Const. Actuation ti Energy, Heating Power Integration Density, Functionality Batch Fab. Pot. (esp. for packaging) g-force Resilience EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 7

8 Vibrating RF MEMS EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 8

9 Basic Concept: Scaling Guitar Strings Guitar String μmechanical h l Resonator Vib. Am mplitude Low Q High Q Guitar Freq. 110 Hz Freq. Vibrating A String (110 Hz) Stiffness Freq. Equation: 1 kr f o = 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 air, P EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 9

10 Frequency of a Stretched Wire EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 10

11 Frequency of a Clamped-Clamped Beam EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 11

12 Frequency of a Clamped-Clamped Beam EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 12

13 Basic Concept: Scaling Guitar Strings Guitar String μmechanical h l Resonator Vib. Am mplitude Low Q High Q Guitar Freq. 110 Hz Freq. Vibrating A String (110 Hz) Stiffness Freq. Equation: 1 kr f o = 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 air, P EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 13

14 3CC 3λ/4 Bridged μmechanical Filter Performance: f o =9MHz, BW=20kHz, PBW=0.2% IL=2 I.L.=2.79dB, Stop. Rej.=51dB 20dB S.F.=1.95, 40dB S.F.=6.45 V P In Out 0 Transmis ssion [db B] P in =-20dBm [S.-S. Li, Nguyen, FCS 05] Sharper roll-off Loss Pole [Li, et al., UFFCS 04] Frequency [MHz] Design: L r =40μm W r =6.5μm h r =2μm L c =3.5μm 35 L b =1.6μm V P =10.47V P=-5dBm R Qi =R Qo =12kΩ EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 14

15 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 M h i l Disk Resonator R Ground Plane Mixed Amplitu ude [db] Design/Performance: R=10μm, t=2.2μm, 22 d=800å, V P =7V f o =1.51 GHz (2 nd mode), Q=11, f o = 1.51 GHz Q = 11,555 (vac) Q = 10,100 (air) Q = 10,100 (air) Frequency [MHz] [Wang, Butler, Nguyen MEMS 04] EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 15

16 163-MHz Differential Disk-Array Filter Com. Array Couplers Filter Coupler v i+ Port1 V P Port3 v o+ λ/2 λ/2 λ/4 λ λ λ/4 λ/2 λ/2 v i- Port2 Diff. Array Couplers V P Port4 v o- [Li, Nguyen Trans 07] EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 16

17 Linear MEMS in Wireless Comms High Q and good linearity of micromechanical resonators Filters for front-end frequency selection Micromechanical Bandpass Filter Tra ansmission n [db] Wireless Phone Antenna Diplexer RF LNA Mixer I LPF AGC 0 o RF PLL 90 o RXRF LO Q From TX BPF Mixer Q LPF AGC Frequency [MHz] I A/D Xstal Osc EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 17 A/D

18 Miniaturization of RF Front Ends RF Power Amplifier 897.5±17.5MHz RF SAW Filter Dual-Band Zero-IF Transistor Chip MHz VCO Diplexer MHz RF SAW Filter MHz RF SAW Filter 26-MHz Xstal Oscillator Problem: high-q passives pose a bottleneck against miniaturization Wireless Phone Antenna Diplexer RF LNA Mixer I LPF AGC 0 o RF PLL 90 o RXRF LO Q From TX BPF Mixer Q LPF AGC I A/D Xstal Osc EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 18 A/D

19 Multi-Band Wireless Handsets Duplexer I Antenna CDMA RF BPF LNA From TX RF BPF GSM o 90 o LPF AGC A/D I RF BPF RF BPF Duplexer LNA LNA LNA PCS 1900 DCS 1800 RF BPF LPF Q I RXRF LO 0 o 90 o AGC A/D (N+1)/N Xstal Osc RXRF Channel Select PLL Q CDMA-2000 Duplexer WCDMA Q Tank LNA From TX RF BPF LNA From TX The number of off-chip high-q passives increases dramatically Need: on-chip high-q passives EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 19

20 All High-Q Passives on a Single Chip 0.25 mm Vibrating Resonator 1.5-GHz, Q~12,000 Vibrating Resonator 62-MHz, Q~161,000 CDMA RF Filters ( MHz) Optional RF Oscillator Ultra-High Q Tanks GSM 900 RF Filter ( MHz) PCS 1900 RF Filter ( MHz) Low Freq. Reference Oscillator Ultra-High Q Tank DCS 1800 RF Filter ( MHz) CDMA-2000 CDMA 2000 RF Filters ( MHz) WCDMA RF Filters ( MHz) EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 20

21 Chip-Scale Atomic Clocks (CSAC) EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 21

22 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 30 million years! Physics Package EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 22

23 Benefits of Accurate Portable Timing Better Timing Networked Sensors Secure Communications More efficient spectrum utilization Longer autonomy periods Larger networks with longer autonomy GPS Faster frequency hop rates Faster acquire of pseudorandom signals Fewer satellites needed Superior resilience against jamming or interception Higher jamming margin Faster GPS acquire EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 23

24 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 30 million years! Physics Package EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/08 24

25 [V] PD Signal Tiny Physics Package Performance Dime Open Loop Resonance: khz Contrast: 0.91% NIST s Chip-Scale Atomic Physics Package Q =1.3x10 6 Sufficient to meet CSAC program goals 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 σ y Allan Deviation, Stability Measurement: Cs (D 2 ) Drift Issue Rb 2.4e-10 (D Allan deviation 1 1 s1 hour Drift to Be Removed in Phase 3 1day Frequency Detuning, Δ [khz] from 9,192,631,770 Hz Integration Time, τ [s] EE C245: Introduction to MEMS Design Lecture 2 C. Nguyen 9/2/