An Overview of Micro-Electro-Mechanical Systems
(MEMS)
Hiroshi Toshiyoshi
E.E. UCLA
on leave from
Institute of Industrial Science, Univ. of Tokyo, Japan
H. Toshiyoshi Hiroshi@ee.ucla.edu
Acknowledgement
Prof. Ming C. Wu (UCLA)
Prof. Hiroyuki Fujita (IIS, Univ. of Tokyo)
Prof. Takahisa Masuzawa (IIS, Univ. of Tokyo)
Prof. Hideki Kawakatsu (IIS, Univ. of Tokyo)
Prof. Dominique Collard (IEMN, CNRS, France)
Prof. Hannes Bleuler (EPFL, Swiss)
and their colleagues
H. Toshiyoshi Hiroshi@ee.ucla.edu
Question: Which is most precisely made ?
(A) Bridge
(B) Stepper
(C) Micro Motor
Civil Engineering
Precision Engineering
Micromachining
Akashi Channel Bridge, Japan
Nikon
Hirano, UTIIS
Micro Electro Mechanical Systems (MEMS)
H. Toshiyoshi Hiroshi@ee.ucla.edu
Answer: Depends on your interest
(A) Bridge
(B) Stepper
1991 m
(C) Micro Motor
100 m
300 m
http://www.nikon.co.jp
Size of
object
~4m
< 0.25 m
(car)
(photoresist)
Scale
300 m
1m
Design Rule
(tower)
???
1 mm
(stators)
0.1 mm
1 m
0.1 m
(tower)
(stage)
(gap)
10-6~7
10-6
10-3
Precision
=
Design Rule
Scale
H. Toshiyoshi Hiroshi@ee.ucla.edu
Contents
To answer your questions:
Q1. What is MEMS ?
Q2. What is the difference from the precision machining ?
Q3. What is the precision of MEMS (or micromachining) ?
Q4. What is the advantage of using MEMS technology ?
Q5. What is the application of MEMS ?
H. Toshiyoshi Hiroshi@ee.ucla.edu
What is MEMS ?
On the extension of conventional machining
Micro Robot "Monsieur"
Seiko Epson
1cc, 98 parts,
~ $500
Watch Movement
Miniaturizing
http://www.epson.co.jp/epson/mm/emros/5.htm
Cutting, Slicing, Drilling, Milling, Grinding,
Embossing, Blasting, Electro Discharge,
Assembling
H. Toshiyoshi Hiroshi@ee.ucla.edu
What is MEMS ?
On the extension of IC Fabrication Techniques
Motorola Power PC
UCLA Micro Optical Bench
Electric Circuits
Mechanical Devices
http://www.ee.ucla.edu/labs/laser/
http://www.mot.com/
Thin Film Deposition
Photolithography
Etching
H. Toshiyoshi Hiroshi@ee.ucla.edu
Fundamental Four Techniques of Micromachining
1. Thin Film Deposition
Structural Layer
t 0.1 ~ 3 m
Chemical-Vapor-Deposition
Sputtering
Vacuum Evaporation
Electroplating etc
Sacrificial Layer
Etching Selectivity
Photoresist
Movable
2. Photolithography
Photoresist
UV exposure
Development
3. Selective Etching
Wet Chemical Etching
Dry Plasma Etching
4. Releasing
H. Toshiyoshi Hiroshi@ee.ucla.edu
Selective Etching
Anisotropic
Isotropic
SiN
54.7
Silicon
WET
Mirror Surface
{111}
{100}
Si / KOH, EDP, TMAH
Side Etch
Etch Depth
Orientation Dependent
Photoresist
R
SiO2
Photoresist
SiO2 / HF
DRY
Silicon
Si / SF6 + Sidewall Protective Gas
Independent of Crystallographic Axis
H. Toshiyoshi Hiroshi@ee.ucla.edu
Precision of IC-compatible Micromachining
Isotropic
Anisotropic
rms
Side Etch
Etch Depth
~ 10 nm
Photoresist
R
WET
rms
~3 m
SiO2
SiO2 / HF
HF wet-etched Quartz
0.1 ~ 1 m / min
2 m
10 m
rms
~ 0.5 m
DRY
rms ~ 10 nm
(SiO2 etch stop)
rms
rms
~ 0.5 m
~ 0.5 m
0.1 ~ 1 m / min
SF6 dry-etched Silicon
H. Toshiyoshi Hiroshi@ee.ucla.edu
SF6 + Freon dry-etched Silicon
Bulk & Surface Micromachinings
Bulk Micromachining
Surface Micromachining
Photoresist
Photoresist
Si
Sacrificial silicon oxide
Si
Thin Film Deposition and Etching
Structural polysilicon
Deep RIE (ICP-RIE)
Si
KOH, EDP, TMAH, ...
H. Toshiyoshi Hiroshi@ee.ucla.edu
Releasing