Transcript Introduction to MEMS Design and Fabrication MEMS Design & Fab ksjp, 7/01 Kristofer S.J.

Introduction to MEMS Design and
Fabrication
MEMS Design & Fab
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Kristofer S.J. Pister
Berkeley Sensor and Actuator Center
UC Berkeley
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1750s first electrostatic motors (Benjamin Franklin, Andrew Gordon)
1824 Silicon discovered (Berzelius)
1927 Field effect transistor patented (Lilienfield)
1947 invention of the transistor (made from germanium)
1954 Smith, C.S., "Piezoresistive effect in Germanium and Silicon, Physical Review, 94.1,
April 1954.
1958 silicon strain gauges commercially available
1961 first silicon pressure sensor demonstrated (Kulite)
1967 Invention of surface micromachining (Nathanson, Resonant Gate Transistor)
1970 first silicon accelerometer demonstrated (Kulite)
1977 first capacitive pressure sensor (Stanford)
1980 Petersen, K.E., "Silicon Torsional Scanning Mirror", IBM J. R&D, v24, p631, 1980.
1982 disposable blood pressure transducer (Foxboro/ICT, Honeywell, $40)
1982 active on-chip signal conditioning
1984? First polysilicon MEMS device (Howe, Muller )
1988 Rotary electrostatic side drive motors (Fan, Tai, Muller)
1989 Lateral comb drive (Tang, Nguyen, Howe)
1991 polysilicon hinge (Pister, Judy, Burgett, Fearing)
1992 Grating light modulator (Solgaard, Sandejas, Bloom)
1992 MCNC starts MUMPS
1993? first surface micromachined accelerometer sold (Analog Devices, ADXL50)
1994 XeF2 used for MEMS (OK, so this one isn’t as important as the others)
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A brief history of MEMS
References
Books
• Elwenspoek and Jansen, Silicon Micromachining,
Cambridge
• Keller, Microfabricated High Aspect Ratio Silicon Flexures,
MEMS Precision Instruments
• Kovacs, Micromachined Transducers Sourcebook, McGrawHill
• Madou, Fundamentals of Microfabrication, CRC
• Maluf, An Introduction to Microelectromechanical Systems
Engineering, Artech House
• Ristic, Sensor Technology and Devices, Artec House
• Senturia, Microsystem Design, Kluwer
• Sze, Semiconductor Sensors, Wiley
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References
Conferences
• Sensors and Actuators Workshop (Hilton Head), even years,
Hilton Head Island, SC. N. America only
• IEEE MEMS workshop, annual, 00 Japan, 01 Europe, 02
U.S.
• Intl. Conf. Solid State Sensors and Actuators (Transducers),
odd years, 99 Japan, 01 Europe, 03 U.S.
• MOEMS, 97 Japan, 98 U.S. (LEOS), 99 Germany
• SPIE, annual, San Jose, CA. (formerly Austin, TX)
• LEOS, OSA, CLEO
• ASME
• …
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• Periodicals
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References
IEEE/ASME, JMEMS
Sensors and Actuators A/B
J. Micromechanics and Microengineering
Sensors and Materials
• Petersen, Silicon as a Mechanical Material, Proc.
IEEE, V70 pp.420-457, 1982.
• Proc. IEEE V86N8, 1998 Special issue on MEMS
• Wu, Micromachining for Optical and
Optoelectronic Systems, Proc. IEEE V85N11
pp.1833-1856, 1997.
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• Articles
Http://www.memsnet.org - probably the best overall MEMS site on the
web. Materials database, bibliography are great.
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References
J. Bardeen, W.H. Brattain, “The first transistor, a semiconductor
triode”, Phys. Rev., 74, 230 (1948).
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Early Semiconductor Fabrication
Intel
133 MHz
Pentium
Processor
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3.3 million transistors
0.35 micron lithography
4 layer metalization
First silicon: May 1995
• IC Fabrication
Fabrication
• Deposition
• Lithography
• Removal
• Bulk micromachining
• Crystal planes
• Anisotropic etching
• Deep Reactive Ion Etching
• Sacrificial etching
• Molding
• Bonding
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• Surface micromachining
Process Flow
• Integrated Circuits and MEMS identical
• Process comlexity/yield related to # trips
through central loop
Wafers
Lithography
Etch
Chips
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Deposition
• Metals
Materials
• Al, Au, Cu, W, Ni, TiNi, NiFe,
• Insulators
• SiO2 - thermally grown or vapor deposited (CVD)
• Si3N4 - CVD
• Polymers
• The King of Semiconductors: Silicon
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• stronger than steel, lighter than aluminum
• single crystal or polycrystalline
• 10nm to 10mm
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Pressure sensors
• Automotive, Medical, Industrial, …
Accelerometers
• Automotive, Medical, Industrial
Gyros
• Automotive
Displays
• TI DMD, SLM GLV
Fiber optics
• Switches, attenuators, alignment
RF components
• Relays, filters, tunable passive elements
Biomedicine
• Drug delivery, DNA sequencing, chemical analysis
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Applications
• Fabrication
Course content
• Materials, geometry
• Compatibility, integration
• Physics
• Beam theory, electrostatics, thermal, fluidic, …
• Design
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• Combs, springs, hinges
• Resonators, accelerometers, gyros
• Scanning mirrors
Design
• To conceive; invent; contrive
• MEMS Design
Process
Device
System
Application
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(American Heritage Dictionary)
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IntelliSuite
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IntelliSuite
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IntelliSuite
SUGAR: Spice-like environment
Simulation Engine
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Analyses: Static,Transient,
Steady-state,Sensitivity,Modal
Input Netlist
n1
a1
v1
b1
n2
a2 n4
g1
n3
n5
a3
uses mumps.net
v1 Vsrc
* [n1 g] [V=10]
e1 eground * [g]
[]
a1 anchor p1 [n1]
[l=5e-6 w=10e-6 oz=180 R=100]
b1 beam2de p1 [n1 n2] [l=1e-4 w=2e-6 oz=0 R=1000]
g1 gap2de p1 [n2 n3 n4 n5] [l=1e-4 w1=1e-5 w2=2e-6 …
gap=2e-6 R1=100 R2=100 oz=0]
a2 anchor p1 [n4]
[l=5e-6 w=1e-5 oz=-90 R=100]
e2 eground * [n4]
[]
a3 anchor p1 [n5]
[l=5e-6 w=1e-5 oz=-90 R=100]
e3 eground * [n5]
[]
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g
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Y-axis Accelerometer
Netlist of Y-axis Accelerometer
XSusp p1 [c(1)] [susp_len=200u angle=0]
for k=1:10 [
mass(k) XMass p1 [c(k) c(k+1)] [finger_len=100u]
]
XSusp p1 [c(11)] [susp_len=200u angle=180]
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uses mumps.net
subnet XSusp [B] [susp_len=* angle=*][
a1 anchor parent [A] [l=10u w=10u h=6u oz=90+angle]
b1 beam3d parent [A a1] [l=susp_len w=2u h=6u oz=0+angle]
b2 beam3d parent [a1 a2] [l=10u w=2u h=6u oz=-90+angle]
b3 beam3d parent [a2 B] [l=susp_len w=2u h=6u oz=180+angle]
b4 beam3d parent [A a3] [l=susp_len w=2u h=6u oz=180+angle]
b5 beam3d parent [a3 a4] [l=10u w=2u h=6u oz=-90+angle]
b6 beam3d parent [a4 B] [l=susp_len w=2u h=6u oz=0+angle]
]
subnet XMass [A B] [finger_len=*][
b1 beam3d parent [A b1] [l=25u w=50u h=6u oz=-90]
b2 beam3d parent [b1 B] [l=25u w=50u h=6u oz=-90]
b3 beam3d parent [b1 b2] [l=finger_len w=2u h=6u oz=0]
b4 beam3d parent [b1 b3] [l=finger_len w=2u h=6u oz=180]
]
Static Simulation Example
• Test structures are fabricated by MCNC;
• Beam: Nominal Lb=100um, w=2um, h=2um. Measured :
L=100um, w=1.74um, h=2.003um
Lb
6
• Gap plate: Lg=100um, w=10um, h=2.003um.
• Young’s Modulus: assume 165GPa.
• Simulation was done by considering fringing-field effects;
V +
-
• Contact force model was used to get pull-in voltage;
1.8
20
1.6
18
1.4
16
Pull-in Voltages (V)
1.2
1
0.8
0.6
0.4
Simulation results
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12
10
8
6
4
0.2
0
O Experimental results
6
6.5
7
7.5
8
Voltage V (v)
8.5
9
9.5
10
2
40
60
80
100
120
140
160
180
Length of the beam L (um)
200
220
240
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Gap distance at node 6 (um)
22
Steady State Simulation Examples
• Simulation of a linear multiple
mode resonator by Reid
Brennen. Sugar results match
his measurements within 5%.
The response of vertical displacement of mass
The response of induced current in lower comb
log10(magnitude)
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-8
-9
10
3
4
10
Frequency (Hz)
10
5
10
-12
-13
-14
-15
2
10
6
200
100
100
50
0
-100
-200
2
10
10
3
4
10
Frequency (Hz)
10
5
10
6
10
3
4
10
Frequency (Hz)
10
5
10
6
0
-50
-100
2
10
10
3
4
10
Frequency (Hz)
10
5
10
6
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-6
-10
2
10
phase(degree)
-11
phase(degree)
log10(magnitude)
-5
TA / Gap-Closing Actuator
A)
B)
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Transient response of a gap-closing actuator. A) shows a plot of displacement as a function of time. The
voltage ramps from 5V at t=5usec to 12V at t=500usec, and then releases. As the voltage increases
linearly during this time interval, the space between the gap decreases at a nonlinear rate due to
electrostatic forces; likewise, the period of oscillation decreases. The amplitude of oscillations decrease
exponentially due to the viscous layer of air between the device and substrate. MEMS Design & Fab
What is MEMS?
• MEMS is Micro ElectroMechanical Systems
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• Integrated circuit processing + micromachining
• = Sensors, Motors, Structures, Electronics
•  Systems on a micron to centimeter scale
Foundry Services and Standard
Processes
• MUMPS
• 3 level poly, no electronics
• started in 1992, now 6? runs per year
• LIGAMUMPS
• single level metal, no electronics
• Sandia
• 5 level poly, no electronics
• 1 level poly w/ quality CMOS
• EDP, TMAH, XeF2 (Parameswaran)
• Plasma (Fedder)
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• CMOS + post-processing
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MUMPS process flow
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MUMPS process flow
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MUMPS process flow
Sandia National Lab 5 layer polysilicon
5-Level Polysilicon surface Micromachine Technology: Application to Complex Mechanical Systems
Solid-State Sensor and Actuator Workshop
Hilton Head 1998
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M. Steven Rodgers and Jeffry J. Sniegowski
Planarized, translating gear trains
Solid-State Sensor and Actuator Workshop
Hilton Head 1998
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Sandia National Lab
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Most complex mechanical system to date in MEMS?
2D beam scanning
AR coated dome
lens
Steering Mirror
laser
CMOS ASIC
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0.5mm
~8mm3 laser scanner
Two 4-bit mechanical DACs
control mirror scan angles.
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~6 degrees azimuth, 3 elevation
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MicroOptical Bench (Ming Wu, UCLA)
LIGA: synchrotron lithography,
electroplated metal
Closed Loop Controlled, Large
Throw, Magnetic Linear
Microactuator with 1000 mm
Structural Height
H. Guckel, K. Fischer, and E. Stiers
Micro Electro Mechanical Systems
Jan., 1998 Heidelberg, Germany
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U. Wisconsin
Spectacular assembly!
Fig. 2 shows a detailed view of an assembled actuator.
Micro Electro Mechanical Systems
Jan., 1998 Heidelberg, Germany
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U. Wisconsin
Magnetic Actuation in LIGA
Micro Electro Mechanical Systems
Jan., 1998 Heidelberg, Germany
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U. Wisconsin
Tuneable RF components
Inductors and Variable Capacitors
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UCLA
Fiber Attenuator
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Bell Labs
Residual stress gradients
More tensile on top
Just right! The bottom line: anneal
poly between oxides with similar
phosphorous content. ~1000C for
~60 seconds is enough.
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More compressive on top
A bad day at MCNC (1996).
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Residual stress gradients
MEMS Gyroscope Chip
Proof
Mass
Sense
Circuit
Electrostatic
Drive Circuit
J. Seeger, X. Jiang, and B. Boser
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Rotation
induces
Coriolis
acceleration
Digital
Output
J. Seeger, X. Jiang, and B. Boser
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MEMS Gyroscope Chip
Digital Light Processor
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(Texas Instruments)