Teaching Old CMP Equipment A Few New Tricks · Summary Outline. Our Expertise, Our Services, Your...
Transcript of Teaching Old CMP Equipment A Few New Tricks · Summary Outline. Our Expertise, Our Services, Your...
Robert L. Rhoades, Ph.D.
CMPUG Spring Meeting
April 28, 2010
Teaching Old CMP Equipment
A Few New Tricks
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Introduction
Tricks for Process Improvements
Tricks for Increasing Efficiency or Uptime
Tricks for Reducing Cost
Summary
Outline
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Introduction
• A trademark of the semiconductor industry is relentless
drive toward better, faster, & cheaper everything
• CMP has been around for >15 years in HVM and is now
considered a mainstream process
– Most of the first generation equipment is still on line even if now
focused on different types of devices than advanced CMOS
– Cost and performance improvements are constantly pursued
• As new materials are integrated, CMP also has to be
adapted and redeveloped to meet changing demands
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Pad Conditioning
• Older generation pad conditioning hardware is
prone to many of the following:
– Very tricky alignments
– Delayed response time due to load sensor and
feedback loop integration time
– Process drift due to inconsistent applied force
– Overconditioning is the “norm” to ensure adequate
force at all times
– Parts obsolescence if/when components do fail
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Conceptual Design Phase Actual Field SteadySweep Retrofit
SteadySweep
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SteadySweep
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< Pressure control
rather than load
cell and feedback
> Swing arm panel
in rear cabinet
< Simple controls
below deck and
mostly built from
std components
> Sealed exterior
for easy cleaning
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Side by Side
Comparison
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372M with SteadySweep™
Improved Serviceabilty – Provides easy access to platen motors, gear boxes, etc.
Safety Features – SteadySweep™ is fully interlocked with polisher safety features
Simple Controls – PLC controller with ladder logic programming to monitor and activate
SteadySweep™ by using the digital I/O signals of the polisher
472 with APP-1000™
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Multiple Disks
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0
500
1000
1500
2000
2500
3000
A B C D E F G H I
Conditioning Disk
Re
mo
va
l R
ate
(A
/min
)
0
5
10
15
20
25
30
35
40
45
50
Un
ifo
rmit
y (
%)
SteadySweep™
using most major
brands of
conditioning
disks in back-to-back
trial.
All tests performed
on the SAME IC1000
pad.
Expt conditions:
4 lbs applied force
15 min breakin
10 min filler wafers
3 rate wafers
Repeat for next disk
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Characterization
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0
500
1000
1500
2000
2500
3000
0.5 1 2 3 3 4 5 5 6 7 9 11 15
DF(lbs)
Re
mo
va
l R
ate
(A
/min
)
0
5
10
15
20
25
30
Un
ifo
rmit
y (
%)
Pad stack: IC1000 on Suba IV
Slurry: Cabot SS-12
DF = 7psi, Platen speed = 40 rpm
SteadySweep™ in-situ conditioning
Multiple runs on
same pad in a
random sequence
Consistent rate
and uniformity
Very slight drop
in rate at applied
forces of 1 lb
and 0.5 lb.
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Marathon
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SteadySweep™: at 2 lbs conditioning down force
0
500
1000
1500
2000
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10 70 130 190 250
Total Conditioning Time(min)
Rem
oval R
ate
(A
/min
)
0
5
10
15
20
25
30
Un
ifo
rmit
y (
%)
SteadySweep™
APP1000™: at 8 lbs conditioning down force
0
500
1000
1500
2000
2500
3000
10 70 130 190 250
Total Conditioning Time(min)
Rem
oval R
ate
(A
/min
)
0
5
10
15
20
25
30
Un
ifo
rmit
y (
%)
APP1000™
Result: Slight Removal Rate decay through
four (4) hr run.
Result: Near zero Removal Rate decay and
improved uniformity through four (4) hr run.
Standard Oxide Process: Pad stack – IC1000on Suba IV; Slurry – Cabot SS-12; Polish DF = 7 psi; Platen speed = 40 rpmNOTE: Same polish head and conditioning disk was used or both sets of data shown above
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SteadySweep Specs
Force 0.5 to 20 pounds
Rotational Speed 0 to 200 rpm
Modes of operation 1. Breakin (new pad)
2. In-situ (during polish)
3. Ex-situ (between wafers)
End effector size 2 inch through 7 inch diameter
(custom sizes upon request)
Platforms supported IPEC 372, 372M, 472
Strasbaugh 6DS-SP, 6EC, etc.
Virtually any rotational polisher
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OnTrak Systems
SynergySeries II Classic or CE Synergy Integra
Load
Station
Dual Brush
Module
Spin
Station
Unload
Handler
User
Interface
97.29 inches
28.56 inches
Load
Station
Dual Brush
Module
Spin
Station
Unload
Handler
User
Interface
97.29 inches
28.56 inches
Chemical Dispense Manifold (Drip)
PVA Brush
DIW
Polyurethane Rollers
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OnTrak brush module
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• Double-sided scrubbing with
PVA brushes is the most
commonly used approach for
post-CMP cleaning
• Thousands of installed
systems worldwide (including
OnTrak, DNS, integrated
cleaners on DIDO tools, etc.)
• All systems include wafer
sensors for feedback and
control
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Clear Wafer Issues
A growing number of applications require processing of transparent or low opacity substrates, such as glass, sapphire, quartz, SiC, etc.
Typical configuration uses through beam sensing to detect the presence or passage of opaque substrates.
Clear substrates are not detected by through beam sensors nor most standard capacitive sensors. In dry environments, reflective sensors are a good solution.
Post-CMP cleaning environment involves liquid sprays, highly polished metals, wet plastics, and other reflective surfaces which generate “noise” to the typical reflective sensor.
Attempts to tune a standard reflective sensor to detect only the substrate and not the liquid overspray or materials were ineffective.
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Sensors Resolved
New sensor types employed for clear wafers
1) Sensor Type 1
• Allows detection of a surface at a specific point (+\-.02”).
• Mounted near to the product surface (1-2” preferred).
• Uses a digital amplifier to suppress “noise” generated by
background surfaces or water droplets.
2) Sensor Type 2
• Enables longer distance sensing
• Amplifies attenuation in received light even as it passes
through a clear surface.
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Sensor Locations
Multiple Sensors:
Load station
Brush box #1
Brush box #2
Transfer carriage
Spin station
Unload station
Net Result:
Enables clear
wafer processing
on OnTrak double
sided wafer
cleaning tools
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Spray Bar
• Pad rinse occurs at end of polish or between wafers
• Spray bar helps remove agglomerates, pad fragments,
and other surface debris especially from grooves
• Lowers defectivity
• Improves yield with minimal investment
• Best performance achieved with atomizer design using
both DIW and N2 to create high velocity spray
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Spray Bar Photos
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Spray bar installed on
Auriga polisher (above)
Spray bar installed on
IPEC polisher (below)
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Defect Improvement
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0
0.5
1
1.5
2
2.5
3
3.5
Ln A
dder
# D
efe
cts
POR Spray Bar
Group
All Pairs
Tukey-Kramer
0.05
Oneway Analysis of Ln Adder # Defects By Group Part=39206A
-5.5
-5
-4.5
-4
-3.5
-3
-2.5
-2
Lo
git A
dder
%D
D
POR Spray Bar
Group
All Pairs
Tukey-Kramer
0.05
Oneway Analysis of Logit Adder %DD By Group Part=39206A
Fit Y by X Group
Statistically validated reduction in defect
levels with addition of spray bar
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Polymer Pressure Canister
• In many facilities, cleaning
chemistry is fed to the
scrubbers from stainless
steel pressure canisters
• Most canisters are treated
to reduce leaching of
metals, but this can break
down or be destroyed by
some chemicals
• Preferred solution is a
canister of all polymer
construction
Polymer
Pressure
Canister
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Pad Applicator
• All pads have PSA layer
to adhere them to the
polisher platen
• Air bubbles under the
PSA can cause defects or
nonuniformity or wafer
slipout (worst case)
• Simple solution involves
training and using a tool
to apply uniform pressure
Pad Applicator
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Pad Puller
• Changing pads on IPEC 472 polishers can be awkward
and difficult for some people
• Ergonomics were not a primary factor in original design
– Requires leaning across the APP-1000
– Physical strength required depends on pad PSA
• Custom designed solution involves a cable, air cylinder,
and unique pressure clamp
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AMAT Arm Shroud
• Cover or shroud on
bottom of arm is often
splashed with slurry
• Builds up over time and
dried slurry agglomerates
can fall back onto pad
• Frequent cleaning can
actually roughen surface
and enhance buildup
• Improved approach is to
coat with smooth finish
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AMAT Arm Shroud
Standard Shroud Coated Shroud
Reducing buildup on surface above the pad
reduces risk of fall-on particles
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Slurry Level Alarm
• Most production facilities
deliver slurry through
pressurized distribution
systems … development
facilities often do not
• An empty bucket or
unfilled feed line causes
at least an excursion and
at worst a broken wafer
• Solution = Sensors and
simple alarm tower
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Idle Water Savings
(IPEC polishers)
• In idle mode, most polishers
still consume substantial DI
water
• On IPEC tools, unload tub
overflow is a major contributor
• Auxiliary timer and valve
enables control of overflow
when tool is in idle mode
• Tub dump/refill is not affectedOver 30% reduction in monthly DI water
consumption at the beta facility !!
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Idle Water Savings
(OnTrak scrubbers)
• In idle mode, OnTrak cleaners
consume substantial DI water
• Software allows only minimal
control over brush rinse and
turning down flow meters can
negatively impact process
• Auxiliary timer and valve
enables control in idle mode
and is deactivated when
running process
• Data shows at least 30 minutes
between rinse cycles is safe
Over 50% reduction in monthly DI water
consumption at the beta facility !!
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CMP Applications
CMOS New Apps Substrate/Epi
Glass (oxide) Doped Oxides GaAs
Tungsten Nitrides GaN
Copper NiFe & NiFeCo InP
Shallow Trench Noble Metals CdTe & HgCdTe
Polysilicon Al & Stainless Ge and SiGe
Low k Polymers SiC
Cap Ultra Low k Ultra Thin Wafers Diamond & DLC
Metal Gates Direct Wafer Bond Si & Reclaim
Gate Insulators Through Si Vias SOI
High k Dielectrics 3-D Packaging Quartz
Ir & Pt Electrodes MEMS Titanium
Magnetics Nanodevices
Integrated Optics
2009 - Qty ≥ 36
As CMP applications continue to multiply …
optimized consumables, processes and
methods must be developed with lowest
possible risk and cost
1995 - Qty ≤ 2
CMOS
Glass (oxide)
Tungsten
2001 - Qty ≤ 5
CMOS
Glass (oxide)
Tungsten
Copper
Shallow Trench
Polysilicon
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Topics
• SteadySweep
• Clear Wafer Sensors
• Spray Bars
• Polymer Pressure Tanks
• Pad Applicator
• Pad Puller
• AMAT Lower Arm Shroud
• Slurry Indicator Tower
• Water Saving Controllers
Upgrades & modifications
should be tailored to the
needs of each facility
Unexpectedly large
benefits can come from
some very low cost items
The best source of what
needs improving is often
from the people running
the tools every day
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Acknowledgements
• Many thanks to the following people:
– Paul Lenkersdorfer, Donna Grannis and Terry Pfau (process team)
– Roy McCoy, Josh Beckenhauer and the rest of the equipment team
– Customers who gave permission to use images and data
– Bill Easter of SEMPlastics for spray bar and arm shroud information
• For additional information, please contact:
Robert L. Rhoades
Entrepix, Inc.
Chief Technology Officer
+1.602.426.8668