ee c247b –me c218 introduction to mems design

EE C247B/ME C218: Introduction to MEMSLecture 2m1: Benefits of Scaling I

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Copyright @ 2021 Regents of the University of California 1

EE C245: Introduction to MEMS Design LecM 2 C. Nguyen 8/20/09 1

EE C247B – ME C218Introduction to MEMS Design

Spring 2021

Prof. Clark T.-C. Nguyen

Dept. of Electrical Engineering & Computer SciencesUniversity of California at Berkeley

Berkeley, CA 94720

Lecture Module 2: Benefits of Scaling


Lecture Outline

• Reading: Senturia, Chapter 1

• Lecture Topics:Benefits of MiniaturizationExamples

GHz micromechanical resonatorsChip-scale atomic clockMicro gas chromatograph


Benefits of Size Reduction: MEMS

MEMS extends the benefits of size reductionbeyond the electrical domain

Performance enhancements for applicationdomains beyond those satisfied by electronics

in the same general categories

Speed

Power Consumption

Complexity

Economy

Frequency , Thermal Time Const.

Actuation Energy , Heating Power

Integration Density , Functionality

Batch Fab. Pot. (esp. for packaging)

Robustness g-Force Resilience

• Benefits of size reduction clear for IC’s in elect. domain size reduction speed, low power, complexity, economy

•MEMS: enables a similar concept, but …


Vibrating RF MEMS

1 2

3 4


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Basic Concept: Scaling Guitar Strings

Guitar String

Guitar

Vibrating “A”String (110 Hz)

High Q

110 Hz Freq.

Vib

. A

mp

litu

de

Low Q

r

ro

m

kf

2

1

Freq. Equation:

Freq.

Stiffness

Mass

fo=8.5MHzQvac =8,000

Qair ~50

mMechanical Resonator

Performance:Lr=40.8mm

mr ~ 10-13 kgWr=8mm, hr=2mmd=1000Å, VP=5VPress.=70mTorr

[Bannon 1996]


-60

-50

-40

-30

-20

-10

0

8.7 8.9 9.1 9.3Frequency [MHz]

Tra

nsm

issio

n [

dB

]

Pin=-20dBm

In Out

VP

Sharper roll-off

Loss Pole

Performance:fo=9MHz, BW=20kHz, PBW=0.2%

I.L.=2.79dB, Stop. Rej.=51dB20dB S.F.=1.95, 40dB S.F.=6.45

Design:Lr=40mm

Wr=6.5mm hr=2mm

Lc=3.5mmLb=1.6mm VP=10.47VP=-5dBm

RQi=RQo=12k

[S.-S. Li, Nguyen, FCS’05]

3CC 3l/4 Bridged mMechanical Filter

[Li, et al., UFFCS’04]


w

vovi

Micromechanical Filter Circuit

1/krmr cr 1/krmr cr 1/krmr cr-1/ks -1/ks

1/ks

-1/ks -1/ks

1/ks

1/kb 1/kb

-1/kb

Co Co

1:he he:1

1:hc 1:hchc:1 hc:1

1:hb hb:1

l/4

l/4

3l/4Input

Outputvi

RQ

RQ

vo

VP

Bridging Beam

Coupling Beam

Resonator


-100

-98

-96

-94

-92

-90

-88

-86

-84

1507.4 1507.6 1507.8 1508 1508.2

1.51-GHz, Q=11,555 Nanocrystalline Diamond Disk mMechanical Resonator

• Impedance-mismatched stem for reduced anchor dissipation

•Operated in the 2nd radial-contour mode

•Q ~11,555 (vacuum); Q ~10,100 (air)

• Below: 20 mm diameter disk

PolysiliconElectrode R

Polysilicon Stem(Impedance Mismatched

to Diamond Disk)

GroundPlane

CVD DiamondmMechanical Disk

Resonator Frequency [MHz]

Mix

ed

Am

plitu

de [

dB

]

Design/Performance:R=10mm, t=2.2mm, d=800Å, VP=7V

fo=1.51 GHz (2nd mode), Q=11,555

fo = 1.51 GHzQ = 11,555 (vac)Q = 10,100 (air)

[Wang, Butler, Nguyen MEMS’04]

Q = 10,100 (air)

§

9 10

11 12


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vi+

vi-

vo+

vo-

VP

VP

l

l/2

l/4

l/2

l/4

Port1

Port2

Port3

Port4

l

l/2

l/2

Filter CouplerCom. Array Couplers

Diff. Array Couplers

[Li, Nguyen Trans’07]

163-MHz Differential Disk-Array Filter


Wireless Phone

90o

0o

A/D

A/D

RF PLL

Diplexer

From TX

RF BPF

Mixer I

Mixer Q

LPF

LPF

RXRF LO

Xstal Osc

I

Q

AGC

AGC

LNA

Antenna

Frequency [MHz]

Tra

ns

mis

sio

n [

dB

]

Micromechanical Bandpass Filter

High Q and good linearity of micromechanical resonators

Filters for front-end frequency selection

Linear MEMS in Wireless Comms

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ee c247b –me c218 introduction to mems design

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