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©2016 SPTS Technologies - Confidential & Proprietary
Deep Silicon Etching
- Increasingly Relevant >20 Years On!
229th Electrochemical Society Meeting Dr Dave Thomas
Senior Director, Etch Product Management
31 May 2016
2
This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ Origins & basis of the Bosch process
■ End markets & technologies
■ Evolution of plasma sources
■ Overview of DRIE diversity
■ Examples of Si etch capability
■ High rate etching
■ Importance of polymer etch step
■ Controlling profile, bow, tilt, scallops
& notching
■ Extendibility
■ Emerging biomedical applications
■ TSV etching & plasma dicing
■ End-point detection for DRIE
■ Blanket Si etching
■ Competing technologies to Bosch etching
■ Summary
Contents
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ Awarded IEEE Jun-Ichi Nishizawa Medal in Amsterdam in 2014
■ Patented in 1994
■ Licensed to other manufacturers
■ SPTS was the first licensee & shipped the first
etch tool based on the Bosch process in 1995
■ SPTS has shipped ~1,200 modules since
Bosch Process – The ‘Foundation’ of MEMS
Franz Laermer (VP Corp Sector Research & Advanced Engineering, Bosch Stuttgart)
Andrea Urban (Senior Expert, Eng Sensor Process Technol Dept, Bosch Reutlingen)
The development of the deep reactive ion etching
process by Franz Laermer and Andrea Urban
revolutionized the micro-electro-mechanical
systems (MEMS) industry by enabling cost-
effective production and proliferation of devices
such as the tiny sensors found in automobile air
bag and anti-skidding systems, as well as in
today’s smartphones and laptop computers.
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ High mask selectivity
■ Deep etching
■ High net etch rate
■ Productive
■ Vertical ‘macro’ profile
■ Dimensional control
■ Scalloped ‘micro’ profile
■ Roughness
Bosch Process
Polymer Deposition
D = C4F8
Polymer Etch
E1 = SF6 or O2
Silicon etch
E2 = SF6
Loop
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
Si Etch Technology/Market Overlap
Adv Pack MEMS
RF & Power
Si thinning Range of
DRIE
processes
TSV
Dicing
Si etch-off
Carriers
Active &
isolation
trenches
• CIS
• Interposers
• 3D stacking
• FO-WLP
• MOSFETs
• IGBTs
• Super-junction
• GaN on Si
• Automotive
• Consumer
• Micro-fluidics
• Biomedical
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
Decoupled, Single
Sources
Process Module Evolution for DRIE
Si E
tch
ra
te
Si E
tch
qu
alit
y
(CD
, pro
file
, tilt ..)
ICP DSi Pegasus Rapier
DSi-v
Module selection
determined by
rate/quality
balance
HDPs Dual Source
1995 ~2005 Today
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
DRIE Diversity
High Aspect Ratio
1.6 x 98 µm trenches
~60:1 AR
Smooth walls
<20nm scallops
Through Wafer
Sensors
Microphones
NEMS
50nm features
High Rate
Cavities, Caps,
ink-jets High Aspect Ratio
~0.4 µm trenches
~90:1 AR
SOI
2.5 x 25µm
Low Tilt
<0.1º
Mixed isotropic/
anisotropic
processing
High Aspect Ratio
4 x 160 µm trench/TSV
40:1 AR
Complex shapes
High Aspect Ratio
8 x 180 µm trench/TSV
22:1 AR
High Aspect Ratio
1 x 40µm trench
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
High Rate ‘Non-Critical’ Etching
90
95
100
105
110
115
120
125
20
22
24
26
28
30
32
34
36
38
-1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
Pro
file
(˚)
Etc
h r
ate
(µ
m/m
in)
Run No
etch rate
ProfileRapier Mode (R7 to R14)Dual Source Results
37µm/min
±2% uniformity
~1,200 atomic layers/s
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
Microphone Acoustic Cavities
400µm deep
45% open area
11µm/min
±3% uniformity
100:1 selectivity
91.5º profile
400µm deep
26% open area
12µm/min
±3% uniformity
200:1 selectivity
93º profile
400µm deep
40% open area
17µm/min
±5% uniformity
150:1 selectivity
93º profile
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
Importance of Polymer Etch Step (E1)
Non-uniform polymer etch
affects Si etch direction
problems with tilt
Non-uniform polymer etch
affects Si etch width
problems with profile, CD & bow
Wafer position
Non-uniform ion density?
Non-uniform ion direction?
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ O2 plasma blanket removal of etch polymer
■ Measure of ion density variation at the wafer level
Polymer Removal Uniformity
Single Source Dual Source ICP
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ Example of 3.5 x 70µm (20:1 AR) trench
Impact on Profile Control
Dual Source
Profile range = 0.11°
Single source
Profile range = 0.18°
Parameter Single Source Dual source
Etch Rate (µm/min) 3.46 3.52
Profile (°) 89.54-89.72 89.93-90.04
Sidewall Roughness (nm) <130 <140
Solid symbols: W→E
Open symbols: S→N
S = notch
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ Example of 8 x 180µm (22:1 AR) trench TSV
Impact on Profile & Bow Control
Profile ranges
Rapier = ~0.14°
Rapier-cd (avg) = ~0.07°
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
Impact on Tilt
Fine tilt ~±0.15º
Single source Dual source
Fine tilt ~±0.6º
Gyro electrical data
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
Scallop Control = Smoother Walls
Faster gas switching Polymer in E2 step
2.7 x 55µm trench
<20nm Sc
10 x 70µm TSV
<30nm Sc
Base
Top
5 x 50µm TSV
~5nm ‘waves’
<10nm Sc
80 x 500nm trenches
~5nm ‘waves’
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
Control of Notching at SOI Layers
750 x 500µm
cavity
12µm/min
No notch
3 x 50µm trenches
~3µm/min
<120 nm notch
No Notch in 30µm trench
>50% overetch 1.4µm trench open Notches in the range 0-120nm
Continuous bias
15% over-etch Pulsed bias
25% over-etch
SPTS IP on
bias pulsing for
notch control
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ Ability to cope with future device dimensions
Extendibility to Sub-Micron Features
1µm
spacing
150nm
50nm
10µm spacing
■ … and all with a single hardware set
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ Driving the demand for flexible Si etch technologies
Emerging Biomedical Applications
Micro-needles
(drug delivery)
Pillar arrays
(mixing & reactions)
Neural probe
Cell sorter
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ Required Via shape depends on subsequent deposition technology
TSV Etching Evolution
Top ~85µm
Base ~47µm
Profile ~77°
Top ~89µm
Base ~49µm
Profile ~63°
10 x 100µm
Sc ~100nm
Profile 90°
5 x 50µm
Sc ~70nm
Profile 90°
8 x 180µm
Sc <200nm
4 x 160µm
Sc <50nm
Continuous process
SF6 + passivant
Switched (Bosch) process
SF6/C4F8 cycling
CIS MEMS
50 x 130µm
Sc ~500nm
Profile ≤92°
75 x 150µm
Sc ~200nm
Profile ≤91°
MEMS Semi
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ Higher throughput
■ Parallel process
■ Higher die density
■ Die shape/location can be varied
■ Narrower dicing lanes (<10µm)
■ Lower damage
■ Bosch etch creates clean scallops
■ No vibrations, debris, water
■ Increased die strength
Plasma Dicing
20 x 100µm
10 x 100µm
7 x 120µm
Die back face
(>15µm notch)
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ Large operating envelope
■ Applicable to all DRIE etches to a stop layer
■ Detection limit <0.05%
Claritas™ End-point Detection
Etch Chamber
Rapid fluorination
of SiF to SiF4
Unable to ‘see’
SiF*
Claritas Unit
High concentration
of SiF4 cracked to
re-form SiF*
Easily detected
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ Via Reveal
■ For stacking TSV wafers
■ 5-10µm to reveal TSV tips
■ Si etch-off
■ For FO-WLP
■ 50-65µm to dielectrics/metals
■ Extreme thinning for Via-Last
■ For low cost TSVs
■ ~50µm to leave 5µm
Blanket Si Etching
Etch rate ~9µm/min
Uniformity ~±2%
3mm EE on 300mm wafer
Etc
h d
ep
th (
µm
)
Wafer position (mm)
End-point detection:
• ReVia for Via Reveal
• OES for Si etch-off
• NIR interferometry
for Si thinning
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ Wet etching
■ Preferential etching along crystal planes
■ OK only for large non-critical devices
■ Non-Bosch etching
■ Depth limit 20-50µm
■ Limited mask selectivity of ~20:1
■ Grass in larger features
■ Cryogenic etching
■ Interesting to academics
■ Smooth sidewalls
■ Max etch rate 2-3µm/min
■ Not manufacturable (-110°C, PR cracking etc)
■ LASER drilling
■ Crude features
■ No selectivity to under-layers
■ New materials
■ Glasses, polymers ….
Competing Technologies for Si Etching
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ Bosch etching has greater relevance today than it did >20yrs ago when it was invented
■ Applicable to growing range of markets/technologies
■ MEMS, Advanced Packaging, Power, RF & Biomed
■ Plasma reactors have evolved to address key needs
■ Higher etch rates higher productivity
■ Higher quality CD, profile, bow & tilt control
■ High rate processes in production at 37µm/min
■ Polymer etch step (E1) controls etch quality
■ By improving polymer etch uniformity from ~±20% to 1% ....
■ Profile variation 0.35º 0.07º in a 22:1 AR TSV
■ Bow 250nm 0nm
■ Tilt ±0.6º ±0.15º
■ Scallops controlled through gas switching & chemistry
■ Notching control using bias pulsing & end-point detection
■ Scalable to 50nm feature size
■ Used for Plasma Dicing for increased die per wafer & die strength
■ Optimized Si etch step for Via Reveal, Si etch-off & extreme thinning
■ 9µm/min, ±2% on 300mm wafers
■ Still competitive vs wet, non-Bosch, Cryo & LASER drilling
Summary
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This presentation and the information contained within it is the property of SPTS Technologies and is confidential. Any duplication, disclosure, distribution, dissemination or copying
of this presentation or its contents or use for any purpose other than that for which it is supplied is strictly prohibited, without the prior written consent of SPTS Technologies. © 2016 SPTS Technologies
■ Matt Muggeridge, Janet Hopkins, Nicolas Launay,
Huma Ashraf & Tony Barrass
Acknowledgements
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