Pressure sensor
Surface Micromachining
Deposit sacrificial layer
PSG
By HF
Si
Poly
by
XeF2
Deposit/pattern structural layer
2.008-spring-2003
Pattern anchors
Etch sacrificial layer
2.008-spring-2003
Residual stress gradients
Surface micromachining
Structure
sacrificial
„ Polysilicon
Silicon dioxide
„ SiNx
PSG
„ Silicon dioxide polysilicon
„ SiNx
polysilicon
„ Aluminum
photoresist
More tensile on top
etchant
HF
HF
XeF2
XeF2
oxygen plasma
More compressive on top
Just right!
2.008-spring-2003
Clean Room
„
„
Gowning with
bunny suit
Class 1, 10, 100
2.008-spring-2003
Class of clean rooms
„
„
„
Class 1 means
one speckle of 0.5 µ
partical in one ft3.
Class 10, 100, 1000
HEPA filter, AHU
A salt grain on a chip
2.008-spring-2003
2.008-spring-2003
6
Air Filters
„
„
„
„
Class of clean rooms
HEPA (High Efficiency Particulate Air)
filters
High efficiency, low ∆p, good loading
characteristics
Glass fibers in a paper like medium
97% retainment of incident particles of
0.3 µm or larger
2.008-spring-2003
0.5 µ Temp
RH
$/ft2
particle tolerance tolerance
Class
10,000
10,000
+/-
3oF
+/-
5%
$250-300
1,000
1,000
+/-
2oF
+/-
5%
$350-400
100
100
+/-
10
1
1oF
+/-
5%
$1200
10
+/-
0.5oF
+/-
3%
$3500
1
+/-
0.3oF
+/-
2%
$10,000
2.008-spring-2003
Toxicity
Particles
„
class 0.1µ 0.2µ 0.3µ 0.5µ 5.0µ
1
35
7.5
3
1
N/A
10
350
75
30
10
N/A
100
N/A
1000 N/A
750
N/A
300
100
N/A 1000
TLV (Threshold Limit Value)
„
„
N/A
7
Upper limit material concentration that an average healthy
person can be exposed without adverse effects, ppm or
mg/m3
Notorious Poisons
„
CO (100 ppm), CO2 (5000 ppm), HCN (110 ppm), H2S (10 ppm)
„
SO2 (5 ppm), NH3 (50 ppm)
„
Arsenic trioxide AS2O3 (0.1g fatal)
„
Hg (0.1 ppm via skin contact)
„
All material are toxic in sufficient quantity, 5g caffein is fatal.
Federal Standard 209; Number of particles per cubic foot
2.008-spring-2003
MEMS Applications
2.008-spring-2003
Display Technologies
Market
Leader
CRT
Flat
CRT
LCD
PDP
CRT
R-TV
HT Poly
LCD
LCD
R-TV
DLP
OLED
20
R.& D. FED
Issues
z
z
z
2.008-spring-2003
40
60
80
100
Screen
Size
300 inch
TMA
LT Poly
LCD
HDTV for 60” ~ 80” Home Theater
Digital Presentation for 100 ” ~ 300” Projector
Key Factor : Brightness
2.008-spring-2003
7
Brightness of Projection
Displays
1st Optical MEMS device
TM
& DLP PROJECTOR
1995
CRT
lmlm
CRT: ~300
: ~300
LCD
lmlm
LCD: ~600
: ~600
? : :~2000
~2000lmlm
AMA
lux = lumen / m2
2.008-spring-2003
DMD Optical Switching Principle
DMD Cell Structure
2
DMD Mirror on/off ± 10o
Texas Instruments’s Technical Journal: Vol. 15, No. 3, July-Sept. 1998.
Texas Instruments’s Technical Journal: Vol. 15, No. 3, July-Sept. 1998.
2.008-spring-2003
2.008-spring-2003
Light Modulation of TMA
TMA
Thinfilm Micromirror Array
Projection Lens
Black
Light
Increase of tilting angle
µm
50
No
NoTilting
Tilting
Light Source
Modulation Stop Max. Tilting
Max. Tilting
Source Stop
White
TMA
Mirror
2.008-spring-2003
2.008-spring-2003
8
Pixel Architecture
TMA vs DMD
Post contact
to actuator
Mirror
Actuation
DMDTM
(Texas
Instrument)
Electrostatic
Tilting
Angle
-10o, 0o, +10o
Mirror
Via contact to MOS
Top Electrode
PZT
Actuator
Bottom Electrode
Supporting Layer
Common Electrode
MOS
Anchor
Drain Pad
Gate Line
Gray Scale
Control
0o ~ 3o
(continuous)
On/Off
Complex
Linear
Simple
• Fatigue
• Sticking
• High Cost
Drawbacks
Source Line
2.008-spring-2003
TMATM
(Daewoo
Electronics)
Piezoelectric
• Uniformity
2.008-spring-2003
Mirror Flatness (VGA)
Micromirror Arrays
• MLE = Module Light
= εf × εr × εm
= 0.81 × εm
Efficiency
MLE
XGA
1024 X 768
786,432 pixels
•εf = Fill Factor = 90%
•εr = Reflectvity = 90%
•εm= Mirror Flatness
εm = 50%
MLE = 43%
Human Hair
VGA
640 X 480
307,200 pixels
εm = 83%
MLE = 70%
50
µm
2.008-spring-2003
(97µm × 97µm TMA mirror)
2.008-spring-2003
Coupled Natures of Thin Film
Processes
Forward coupling
„
„
Step coverage, confromality
Backward coupling
„
„
„
Temperature dependent microstructural degradation
Over/under etch, etch stop control
Side attack, Passivation breakage
Optical Efficiency(%)
„
Evolution of TMA Pixels
24
3rd
3rd
20
16
2nd
2nd
1st
1st
12
8
4
95
96
97
98
99
Year
2.008-spring-2003
2.008-spring-2003
9
MIT Bow-actuator
Piezoelectric
Amplifiers
Design of nanopipette (2):
In-line array of nanopipettes
Nick Conway, MS 2003
End effector
„
Released
„
Bottom
PZT
Top
„
Massive Parallel Nanopipette Array by Inplane Scanning Probe Systems
Integration with Microfluidic channels
Integration of nanopipettes in AFM in an
100 x 100 array
4-bar linkage design
Fixed substrate
Single nanopipette
2.008-spring-2003
2.008-spring-2003
Photonic band gap microcavity waveguide processing
Photonic crystal modeling
Microcavity waveguide finite-difference time-domain 1 mesh
SiO2
Si
max
Ex,r
a
ƒ Nanofabrication:
ƒ SiNx mask1 /w electron-beam
ƒ Proximity pattern transfer to resist
ƒ 130 nm minimum features
100 µm
0
w
input
pulse
ƒ design matrix of various geometries:
defect lengths, waveguide width, d/a, number of holes
ƒ
ad
ƒ
Q = 180
Hard mask from Cr lift-off 2
Optimized Si RIE
PMMA on Si
a
d
min
Cr lift-off mask
J. Ferrera, NanoStructures Laboratory, MIT.
2.008-spring-2003
1
2.008-spring-2003
200 nm
300 nm
2
J. Foresi, Kimerling group, MIT.
Design Domains
„
„
„
Design is a mapping process
From “What” to “How”
Small scale systems design
What
2.008-spring-2002
How
N. P. Suh, Axiomatic Design, Oxford
10