Basic 2
Anisotropic Wet-etching
of Silicon: Characterization and
Modeling of Changeable
py
Anisotropy
Prof K.
Prof.
K Sato
Dept. of Micro/Nano Systems Engineering
Nagoya University
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Orientation Dependent Etching
(Conventional Products)
〈110〉
〈111〉
〈112〉
〈100〉
SiO2
〈111〉
Si
Diaphragm
Deep grooves on a (110) wafer
Diaphragm on a (100) wafer
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Variation in etching profile on (100) silicon wafer
Groove Wall Orientations
(111)
(100)
(110)
KOH
TMAH
EDP
KOH
TMAH
KOH/IPA
TMAH/ f t t
TMAH/surfactant
EDP
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Variation in etching profile on (110) silicon wafer
(111)
KOH
TMAH
EDP
Groove Wall Orientations
(111)
(100)
KOH
TMAH
EDP
KOH
TMAH
(110)
KOH/IPA
TMAH/surfactant
EDP
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Non-conventional 3-D microstructures
using KOH anisotropic etching
Etching from both sides of a wafer
Two step etching using two mask layers
Two-step
K. Sato, et al, Proc. IFToMM Intl. Micromechanism Symp. (Tokyo, 1993.6) 155-160
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Densely Arrayed Silicon Needles with a Pitch Distance of
200 microns Aiming at Transdermal Drug Delivery
M Shikida et al.:Proc.
M.
al :Proc MEMS-03
MEMS 03 (Kyoto
(Kyoto, 2003)
2003), 562
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
New types of anisotropically etched 3-D structures: Curved,
Sharp-cornered, 45-degree-angled V-grooves
Prem Pal: Jpn. J. Appl. Phys. 49 (2010)056702
[
[110]
]
[100]
[
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
110
]
Anisotropic chemical etching of Si
from MEMS Point of View
• Etching Solutions
KOH, “TMAH”, “EDP”, N2H4, NaOH, CsOH, etc.
• Chemical
Ch i l reaction
ti
Si + 2OH- + 2H2O
2 + 2H
→ Si(OH)4 + H2 → SiO2(OH)222
• What are known;
Si (111) shows an extremely low etch rate
rate.
Etch-stop techniques: B-dope, Electro-chemical,
etc.
• Applications
Diaphragms, V-grooves,
V grooves, Cantilevers
---Limitations in fabricated shapes
Many mysteries
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Sequential reactions of Si etching
in alkaline solution
Si + 2OH- + 2H2O
→ SiO2(OH)22- + 2H2
This is the results off the following
f
steps.
(R. A. Wind, M.A. Hines, Surface Science 460 (2000) 21-38)
＝SiH2 + OH- + H2O → ＝SiHOH+ H2 + OH＝SiHOH + OH- + H2O → ＝Si(OH)2+ H2 + OH( Si)2＝Si(OH)
(≡Si)
Si(OH)2 + ２H2O → ２(＝Si-H)＋Si(OH)
２( Si H) Si(OH)4
Si(OH)
(
)4 + ２OH- → ＝SiO2 ((OH))22-+ ２H2 O
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Contents
Characterization of Anisotropic Etching
in macroscopic domains
“Dangling-Bond Model” does not tell the truth,
because no dynamics
y
included.
“Step Flow Model” explains anisotropy in the
vicinity of Si (111)
*Reversed
*R
d anisotropy
i t
between
b t
KOH and
d TMAH
*Etched shape
p clearly
y reflects atomic-step
p
behavior in the vicinity of Si (111)
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Contents
Characterization of Anisotropic Etching
in macroscopic domains
“D
“Dangling-Bond
li
B dM
Model”
d l” does
d
nott tell
t ll the
th truth,
t th
because no dynamics included.
“Step Flow Model” explains anisotropy in the
c ty o
of S
Si ((111))
vicinity
*Reversed anisotropy between KOH and TMAH
*Etched shape clearly reflects atomic-step
behavior in the vicinity of Si (111)
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Etching rate measurement
K. Sato et al.: Sensors and Actuators A-64 (1998) 87-93.
(110)
contact probe
R = 22 mm
R
probing network
( )
(001)
(110)
Hemispherical specimen of single-crystal silicon
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Hemispherical specimen
Before
After
• Maximum etching depth: 100 - 150 µm
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Etching rate contour map for a KOH solution
K. Sato et al.: Sensors and Actuators A-64 (1998) 87-93.
(100)
90゜
(111)
(110)
60゜
0゜
30゜
30
(110)
90゜
0゜
0゜
30゜
(100)
60゜
90゜
min
max
NAGOYA UNIVERSITY
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Effects of a surfactant added to TMAH solution
K. Sato et al.: Sensors and Materials 13-5 (2001) 285-291.
(010)
(010)
90°
(111)
90°
(110)
(110)
60°
60°
30°
30°
(100)
0°
(001)
00°
30°
30
60°
60
90°
90
(100)
0°
(001)
0°
0
30°
30
60°
60
min
25%TMAH + NCW
25%TMAH
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
90°
90
max
Poly-oxiethylene-alkyl-phenyl-ether
C9H19
Hydrophobic
O(CH2CH2O)nH
Hydrophilic
• Liquid easy to operate with little foaming
• Stable
S bl both
b h in
i acid
id andd alkaline
lk li solutions
l i
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Etch ratte ratio oof {i j kk}/{100}}
Orientation-dependent effects of surfactant
decreasing etch rates of silicon
2.500
25%TMAH (without surfactant)
2.000
1.500
1.000
25%TMAH+2%NCW
0.500
0.000
{100} {310} {210} {530} {320} {540} {110} {331} {221} {111} {211} {311} {100}
Orientations
K. Sato, et al., Sensors and Materials 13-5 (2001) 285-291.
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Mask-corner undercut suppression
K. Sato, et al., Sensors and Materials 13-5 (2001) 285-291.
Effects of the surfactant NCW
Orientations appearing on a vertex:
(111) - ( j j 1 ) - (110)
25 wt.% TMAH, 80 ºC
Etching depth: 50 µm
{111}
without NCW
{100}
{110}
{110}
with
ih
2 wt.% NCW
300 µm
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Comparison of Structure Shape Etched
from Same Mask Apertures
Prem Pal, J. Micromech. Microeng. 17 (2007) 2299–2307
<110>
<110>
Etch depth = 35 μm
( )
(a)
( )
(c)
(b)
(d)
Pure 25 wt% TMAH
(a)
(b)
(d)
(c)
25 wt% TMAH + NC-200
T-Shaped
cantilever
Circular
island
Cross
island
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Cross
aperture
Etching rate
database
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Anisotropic etching
simulation system
MICROCAD
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Simulation results using MICROCAD
K Sato
K.
Sato, et al
al., Electronics and Communications in Japan,
Japan Part2
Part2, 83
83-4
4 (2000)
(2000).
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Simulation results using MICROCAD
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Simulation results using MICROCAD
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Densely Arrayed Silicon Needles with a Pitch Distance of
200 microns for Transdermal Drug Delivery
M. Shikida et al. Sensors and Actuators A 116 (2004) 264–271
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Arrayed Needle Fabrication Process:
Combination of mechanical dicing and wet etching
M. Shikida et al. J. Micromech. Microeng. 14 (2004) 1462–1467
Etching time: (a) 0 min.
(b) 10 min.
(d) 30 min.
i
(c) 20 min.
( ) 40 min.
(e)
i
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
MICROCAD Simulation Results.
Etching time: (a) 0 min., (b) 5 min., (c) 10 min.,
(d) 15 min., (e) 20 min., (f) 25 min.
Et hi conditions:
Etching
diti
34
34.0
0 wt.%
t % KOH
KOH, 80oC
(a)
(d)
(b)
(c)
(e)
(f)
M Shikida,
M.
Shikida et al,
al JJ. Micromech.
Micromech Microeng.
Microeng 14 (2004) 1462
1462–1467
1467
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Etched deep grooves on (110) Si
using a KOH water solution
Groove depth:
90 microns
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
KOH and TMAH show different types of anisotropy
K. Sato, et al.: Sensors and Actuators A-73 (1999) 131-137.
TMAH: 25%, 90°C
(010)
90°
KOH: 40%, 90°C
90゜
(110)
(430)
60°
60゜
(011)
30°
0
0°
(001) 0°
30゜
30° (101) 60°
( 00)
(100)
90°
00゜
0゜
30゜
60゜
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
90゜
Relation between the etching rate distribution
and etched profile
Etching rate distribution
1.0
Etch rate (µm
m/min)
Etch rate (µm
m/min)
1.5
10
1.0
0.5
0
-90°
(111)
0°
(110)
90°
(111)
0.5
0
-90°
(111)
(311)
0° (311)
(110)
90°
(111)
Etched profile analyzed using Wulff-Jaccodine method
Etch rate vector
(111)
(110)
Si
25% TMAH (86°C)
40% KOH (70°C)
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Contents
Characterization of Anisotropic Etching
in macroscopic domains
“D
“Dangling-Bond
li
B dM
Model”
d l” does
d
nott tell
t ll the
th truth,
t th
because no dynamics included.
“Step Flow Model” explains anisotropy in the
c ty o
of S
Si ((111))
vicinity
*Reversed anisotropy between KOH and TMAH
*Etched shape clearly reflects atomic-step
behavior in the vicinity of Si (111)
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Conventional Explanation of Anisotropy in Etching
Hypothesis: Number of dangling bond appearing on the
silicon surface determines the etching rate
z
z
y
x
y
x
z
(110)面
(100)面
Dangling bond：2
Back bond：2
y
x
Dangling bond：1
Back bond：3
Dangling bond：1 +(2)
（
（Exposed
d back
b k bbond：2）
d ）
Back bond：3
(111)面
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Step Flow Model for (111) Silicon
M. Elwenspoek, J. Electrochem. Soc. 140-7 (1993) 2075-80
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Two types of stable steps on Si (111) surface
(Mono-hydride and Di-hydride steps)
M A Gosalvez
M.A.
Gosalvez, et al.
al J.
J Micromech.
Micromech Microeng
Microeng. 17 (2007) S1
S1–S26
S26
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Step movements determine profiles of
pits and mesa on (111) silicon surface
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Atomic level etching simulation
in the vicinity of Si (111)
M.A. Gosalvez, et al. J. Micromech. Microeng. 17 (2007) S1–S26
(110)
←
(111)
→
(001)
Pit-nucleation and Step-propagation
100 nm
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Our concern
• IIs the
th atomic
t i scale
l step
t flow
fl
model
d l
applicable
pp
to macroscopic
p etching?
g
Etching solutions: KOH, TMAH
Et hi depth:
Etching
d th tens
t
off micrometers
i
t
• Does the number of dangling bonds
determine the activeness of the surfaces or
steps?
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Contents
Characterization of Anisotropic
p Etching
g
in macroscopic domains
Dangling-Bond
Bond Model
Model” does not tell the truth,
truth
“Dangling
because no dynamics included.
“Step Flow Model” explains anisotropy in the
y of Si ((111))
vicinity
*Reversed
Reversed anisotropy between KOH and TMAH
*Etched shape clearly reflects atomic-step
b h i in
behavior
i the
th vicinity
i i it off Si (111)
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Etch Pit Growth on (111) Silicon.
K. Sato, et al.: Sensors and Materials 15-2 (2003) 93-99.
Growth of individual pit traced during TMAH etching
etching.
10分後
Optical microscope
images with time
increments
・Wafer p
preparation…
p
Oxidization
for 20 hours (3μm thick oxide)
followed by oxide removal using HF.
20分後
30分後
・etching condition…25%TMAH,
80°30min
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
AFM image at the center of a pit
etched with TMAH solution
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Comparison in the shape of etch pits between
KOH and TMAH
K. Sato, et al.: Sensors and Materials 15-2 (2003)
40%KOH 70℃30分
25%TMAH 80℃30分
[ 1 1 2]
[-1-1
[1 11-2]
2]
[-1-1 2]
[1 1-2]
Top
View
100μm
0.50
0.6
0.4
0.25
0.2
0.00
-0.2
-0.25
Etching time: 10 min
Etching time: 20 min
Etching time: 30 min
-0.50
-0.75
0 75
-1.00
Etch pit depth (ｵm
E
m)
CrossSection
Ettch pit depth (ｵm
m)
0.0
-0
0.4
4
-0.6
-0.8
-1.0
-1.2
Etching time: 10 min
-1.4
-1.6
Etching time: 20 min
-1.8
Etching time: 30 min
-2.0
-2.2
-1.25
0.00
0.05
0.10
0.15
Distance (mm)
0.20
0.25
-2.4
0.0
0.1
0.2
Distance (mm)
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
0.3
0.4
Step movements determine profiles of
pits and mesa on (111) silicon surface
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Differently oriented etch pit growth governed
by the difference in activated step
KOH
TMAH
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Difference in Etching Rate Contour Map
between KOH and TMAH
(010)
90゜
(111)
(010)
90゜
(111)
(110)
60゜
(110)
60゜
(011)
30゜
30゜
(001)
(100)
0゜
0゜
30゜
60゜
(101)
KOH40%70℃
90゜
(001)
(100)
0゜
0゜
30゜
60゜
(101)
90゜
TMAH25%80℃
KOH: Etch rate sharply increases by misorientation toward [1 1-2]
TMAH: Etch rate sharply increases by misorientation toward [-1-1 2]
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
min
max
Contents
Characterization of Anisotropic Etching
in macroscopic domains
Dangling Bond Model
Model” does not tell the truth,
truth
“Dangling-Bond
because no dynamics included.
“St Fl
“Step
Flow M
Model”
d l” explains
l i anisotropy
i t
in
i the
th
vicinity of Si (111)
*Reversed
Reversed anisotropy between KOH and TMAH
*Etched shape clearly reflects atomic-step
behavior in the vicinity of Si (111)
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Step Flow Model for (111) Silicon
M. Elwenspoek, J. Electrochem. Soc. 140-7 (1993) 2075-80
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Difference in surface structure depending
on a direction of deviation from silicon (111)
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Etched deep grooves on (110) Si
using a KOH water solution
Groove depth:
90 microns
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Asymmetric increase in etching rate by
angular deviation from (111) orientation
(110)
(-11-1)
(-112)
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Step movements determine profiles of
pits and mesa on (111) silicon surface
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Answers to the questions
• Is the atomic scale step flow model applicable
to macroscopic etching?
YES, in the vicinity of (111)
• Does the number of dangling bond determine
the activeness of the surfaces or steps?
NO
(neither of the surface
surface, nor of steps)
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
Contents
Characterization of Anisotropic Etching
in macroscopic domains
“D
“Dangling-Bond
li
B dM
Model”
d l” does
d
nott tell
t ll the
th truth,
t th
because no dynamics included.
“Step Flow Model” explains anisotropy in the
c ty o
of S
Si ((111))
vicinity
*Reversed anisotropy between KOH and TMAH
*Etched shape clearly reflects atomic-step
behavior in the vicinity of Si (111)
Basic 2 Anisotropic Wet-etching of Silicon:
Prof. K. Sato
Characterization and Modeling of Changeable Anisotropy
COE for Education and Research of Micro-Nano Mechatronics, Nagoya University
References
Etch mechanisms and characterization
R.A. Wind and M.A. Hines, Surface Science 460 (2000) 21-38.
p
, J. Electrochem. Soc. 140-7 ((1993)) 2075-80.
M. Elwenspoek,
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COE for Education and Research of Micro-Nano Mechatronics, Nagoya University