CONTINUITY IN PLASMA PROCESSING: YESTERDAY’S ... · (APP) have had tremendous technological...
Transcript of CONTINUITY IN PLASMA PROCESSING: YESTERDAY’S ... · (APP) have had tremendous technological...
AVS03_01
CONTINUITY IN PLASMA PROCESSING: YESTERDAY’S ACCOMPLISHMENTS, TODAY’S INNOVATIONS, TOMORROW’S CHALLENGES*
Mark J. KushnerUniversity of Illinois
Dept. of Electrical and Computer EngineeringUrbana, IL 61801
[email protected] http://uigelz.ece.uiuc.edu
November 2003
* Work supported by SRC, NSF, Sematech, GE and EPRI
University of IllinoisOptical and Discharge PhysicsAVS03_02
ACKNOWLEDGEMENTS
• Andre Anders• Eray Aydil• Kurt Becker• Ned Birdsall• Matt Blain• Nick Braithwaitte• Jane Chang• Frank Chen• Joel Cook• J. Gary Eden• Brett Cruden• Ashok Das• Rajesh Dorai
• Pietro Favia• Bish Ganguly• Valery Godyak• Matt Goeckner• Martin Gundersen• Bill Holber• Alan Howling• Fred Huang• Ulrich Kogelschatz• Uwe Kortshagen• Toshiaki Makabe• Joelle Margot• Dennis Manos
• Tom Mantei• Jim Olthoff• Larry Overzet• Ajit Pranjpe• Zoran Petrovic• Louis Rosocha• Karen Seward• Phillipe Schoeborn• Tim Sommerer• L. Tsendin• Peter Ventzek• David Wharmby• Gerald Yin
University of IllinoisOptical and Discharge PhysicsAVS03_03
AGENDA
• What is our legacy in plasma processing?
• How have we leveraged that legacy to innovate plasma based technology?
• What challenges and opportunities lie ahead for plasma technologies? (50th Anniversary PSTD Talks)
•Materials Processing and Sources (R. Gottscho, F. Chen, T. Dalton, J. Schmitt, H. Sawin)
•Diagnostics (V. Donnelly)• Lighting•Nanoscience•Bioscience
• Concluding remarks
University of IllinoisOptical and Discharge PhysicsAVS03_
WORKING DEFINITION OF PLASMA PROCESSING
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University of IllinoisOptical and Discharge Physics
• Technological plasmas are a power transfer media.
• Electrons transfer power from the "wall plug" to internal modes of atoms / molecules to make “benign” species into “reactive” species.
• Once activated, their physical or chemical potential may be used to make products (add or remove materials, photons…)
• Plasma processing is the use of partially ionized gases in technology to create "products."
WALL PLUG
POWER CONDITIONING
ELECTRIC FIELDS
ENERGETIC ELECTRONS
COLLISIONS WITHATOMS/MOLECULES
EXCITATION, IONIZATION, DISSOCIAITON (CHEMISTRY)
LAMPS LASERS ETCHING DEPOSITIONE
eA
PHOTONS RADICALS
IONS
• Displays
• Materials Processing
COLLISIONAL LOW TEMPERATURE PLASMAS
• Lighting
• Thrusters
• Spray Coatings
UTA_1102_05
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CONTINUITY IN PLASMA TECHNOLOGY
• Our striking record of innovation in developing plasma based
technologies has relied on leveraging a continuity of progress
through generations of these technologies.
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(a very incomplete) TIME LINE: OUR ROOTS IN SCIENCE
→→→→→Breakdown
Crooke W.s1880'
DBDsSiemens W.
s1850'
SputteringGrove R. W.
s1850'
DischargesGlow Faraday M.
s1830'
DischargesGlow First Hawsbee F.
s1790'
• R. Powell, S. Rossnagel, “PVD for Microelectronics”• J. Hopwood and T. Mantei, JVSTA, 2003• Y. P. Raiser, “Gas Discharge Physics”• J. R. Roth, “Industrial Plasmas Part I”• Joel Cook, private communication.
• D. Manos, D. Flamm, “Plasma Etching: An Introduction”• J. Waymouth “Electric Discharge Lamps”• J. Hecht, “Laser Pioneer Interviews”• J. Schmitt, AVS 50th Symposium• www.siemens.com
→→→Plasmas Microwave
Brown C. S.s1940'
Functions onDistributi AllisW.
s1930'
ICPsBabat I. G. Thomson, J. J.
s1920'
sElectronic Gaseous ModernPhelps A.
s1960'
Transport ModernHolstein & Bernsteins1950'
ECRBrown Allis,Lax,s1950'
→→
→→→→→Shielding
Debye P.s1920'
Plasma Sheaths,Langmuir I. Tonks, L.
s1920'
Transport Townsend S. J.
s1900'
Discharges RFTesla N.
s1890'
ICPsHittroff W.
s1880'
University of IllinoisOptical and Discharge PhysicsAVS03_07
PLASMA MATERIALS PROCESSING:WHAT DO WE DO WELL?
• The fabrication of conventional microelectronics has met and bested extreme challenges as the nm scale is approached and exceeded.
• Plasma science has played a critical role in virtually all aspects of meeting these challenges
• Physical Vapor Deposition• Plasma Enhanced Chemical Vapor Deposition• Etching• Cleaning• Passivation• Plasma sources of UV radiation for lithography (Hg lamps
to EUV)
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→→→→→ySelectivit
Heinecke A.R.s1970'
Etcher DiodeReinberg R. A.
s1970'
Stripping t Photoresis
Irving S.s1970'
PECVDSwann & Sterlings1960'
↓ECR-Brown Allis,Lax,
s1950'
ICP PlanarKeller Ogle,
s1990'
ECRs1990'
TegalWaferSingle
s1980'
Labs BellProcessing Batch
s1970'
n ActivatioIonWinters&Coburn
s1970'→→→→
(very incomplete) TIME LINE: MATERIAL PROCESSING
PVD Metal IonizedRossnagel S.
s1990'
RIE encyMultifrequs1990'
THelicon/PMs1990'
→→→
HeliconBoswellChen, −↑
↓
↑ICPs-Hittrof-s1880'
SputteringGroves1850' −−↑
Ref: J. P. Chang
Ref: J. P. Chang
University of IllinoisOptical and Discharge PhysicsAVS03_09
ADVANCES IN EQUIPMENT DESIGN ENABLES ADVANCED DEVICE FABRICATION
• Perhaps our most challenging accomplishments have been the design of reliable plasma sources for these processes.
• The continuity of progress through generations of advances in plasma fundamentals, diagnostics, modeling and empiricism have been leveraged to produce reliable manufacturing tools.
University of IllinoisOptical and Discharge PhysicsAVS03_10
SOPHISTICATED PLASMA TOOLS
• Ref: Ashok Das• AMAT Ionized Metal PVD
• AMAT-Komatsu PECVD
Ref: W. Holber
Ref: R. Dorai
University of IllinoisOptical and Discharge PhysicsAVS03_11
PLASMA DIAGNOSTICS HAVE PLAYED A CRITICAL ROLE AND ARE MOVING CLOSER TO THE PRODUCT
• Plasma process and equipment design have and will continue to critically rely on advanced plasma diagnostics.
• Real time control strategies, a requirement for sub-100 nm processing, will also rely on robust, cost-effective diagnostics.
• The most mature plasma diagnostics are typically too far removed from critical measurements of activation of surface processes.
• Non-intrusive diagnostics which provide the state of activating species impinging on surfaces are required for a complete picture.
University of IllinoisOptical and Discharge PhysicsAVS03_12
LANGMUIR PROBES IN HARSH ENVIRONMENTS
• Development of basic diagnostics, such as Langmuir probes, for use in harsh rf environments improved our knowledgebase and provided stringent test of models.
• Ref: V. Godyak
• RF CCP in Argon
Ref: E. Aydil
80 mTorr SF6, 200 W
• New materials (metal gates, low-k dielectrics, high-k dielectrics, SiGe/SOI substrates, porous materials).
• Increasing demands on etch selectivity.• Shorter development cycle.• Lower thermal budgets.• More controllable knobs.• Use of plasmas as processing tools (e.g., self assembly) as
opposed to pattern replication.• Reduced cost of ownership through plasma tools which are
used for multiple processes.• Improved and more relevant contributions from modeling.
MATERIALS PROCESSING: CHALLENGES
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• Ref: J. Cook, T. Mantei, P. Schenborn, P. Ventzek, D. Manos
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University of IllinoisOptical and Discharge PhysicsAVS03_14
CHALLENGES IN TAILORING PLASMAS FOR SELECTIVE ACTIVATION
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• As in most relationships, it’s all about control.
• Advanced applications will depend on selectively promoting desired plasma chemical reactions and preventing undesirable reactions.
• The ability to tailor the energy distributions of plasma particles is key to this selectivity.
• Tailored electron energy distributions: Control formation of radicals and ions; best if also spatially segregated.
• Tailored Ion energy distributions: Determine activation of surface processes; must be narrow to differentiate thresholds.
• Tailored synergy between ions and neutrals: Necessary for monolayer control of selectivity, deposition, end-point.
Model results from HPEMRef: K. Seaward, S. Samakawa
University of IllinoisOptical and Discharge PhysicsAVS03_15
TAILORING f(ε) BY FREQUENCY
University of IllinoisOptical and Discharge Physics
• Plasma tools for multiple processes or recipes (different chemistries) require control of electron energy distribution for optimum generation of precursors.
• [e], ICP, 10 mTorr, Ar/Cl2 = 70/30.
• f(ε) 50 MHz
• f(ε) 5 MHz
• Model results from GLOBAL_KINRef: K. Seaward
University of IllinoisOptical and Discharge PhysicsAVS03_16
TAILORING FLUXES THROUGH PULSING
University of IllinoisOptical and Discharge Physics
• Processing of thin films depends on the synergy between energetic ions and radical fluxes. Pulsed plasmas which control these contributions produce unique films not otherwise attainable.
• Pulsed ICP Ar/C4F8=70/30, 15 mTorr • Deposition of low-k fluorocarbon film from perfluoroallyl benzene [L. Han, JVSTB 18, 799 (2000)]
• Self assembling nanostructures
• Non-invasive MEMs based plasma sensors with L < λD.
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ROLE OF PLASMA SCIENCE TO MEET CHALLENGES
• Multi-process plasma tools with frequency and pulse power agility to selectively activate species
• On wafer and plasma diagnostics which enable real-time-control to sub-monolayer accuracy.
University of IllinoisOptical and Discharge Physics
University of IllinoisOptical and Discharge PhysicsAVS03_18
PLASMA LIGHTING TECHNOLOGIES
• Annual US energy use for lighting is 750 TWH (8.2 quads)
• 8.3 % of total energy consumption• 22% of total electrical energy consumption.
• Plasmas are 59% of lighting energy use (13% of total). There are 2.6 billion plasma lighting sources in the US.
• Replacing incandescent lamps with plasma sources will decrease US electrical energy use 5% [20 nuclear power plants or 1.2 Million barrels of oil/day (10% of imports)].
• Improving efficiencies and utilization of plasma lighting will enormously impact our economy, environment, foreign policy.
• Ref: U.S. Lighting Market Characterization, Navigant Consulting, 2002
• DOE Annual Energy Outlook 2003
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(very incomplete) TIME LINE: LIGHTING TECHNOLOGIES
→→→→Excimers
Goldstein F. Curtis, W.s1910'
Hg PressureLow P.C.Hewitt
s1900'
Ozonizers DBDs,Siemens W.
s1850'
radiation Line PlasmaGiessler H.
s1850'
Lamps Excimer DBDKogelshatz & Elliason
s1980'
Displays PlasmaSlottow & Blitzer
s1960'
Trapping RadiationHolstein T.
s1940'
Lampst Fluorescens1930'
→→→
Lighting PanelFlat ExcimerHitzschke and Vollkommer
s2000'
PDPs Commercials1990'
→→
University of IllinoisOptical and Discharge PhysicsAVS03_20
LIGHTING: ACCOMPLISHMENTS AND CHALLENGES
• Efficient white sources based on Hg plasmas in fluorescent and arc lamps; and non-white metal vapor lamps. Environmental impacts are debatable but not ignorable.
• Challenges:
• Highly efficient non-Hg plasma white-light sources (rare gases, excimers, metal halides, molecular radiators)
• Improving understanding of plasma-surface interactions to extend lifetimes (cathodes)
• Quantum splitting phosphors to improve utilization of UV (2 visible photons from 1 UV reduces US energy use 5-10%).
• Leverage advances plasma lighting to other applications (and vice-versa)
• Solid State Lighting? (next talk…M.G. Craford, Lumileds Lighting)
University of IllinoisOptical and Discharge PhysicsAVS03_21
ATMOSPHERIC PRESSURE PLASMAS
• Atmospheric Pressure Plasmas (APP) have had tremendous technological impact
• High power lasers (e.g., Excimer lasers)
• Lighting Sources (e.g., HID lamps)
• Ozone generators
• Modification of surfaces
• Toxic gas abatement
• The potential for APPs to perform “high value” manufacturing is literally untapped.
• Atmospheric pressure DBD ozone generator
Ref: U. Kogelshatz
University of IllinoisOptical and Discharge Physics
PLASMA SURFACE MODIFICATION OF POLYMERS• To improve wetting and adhesion of
polymers atmospheric plasmas are used to generate gas-phase radicals to functionalize their surfaces.
Untreated PP
Plasma Treated PP
• M. Strobel, 3M
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Hydrophobic
Hydrophilic
• Polyethylene, Humid-air• Akishev, Plasmas Polym. 7, 261 (2002).
University of IllinoisOptical and Discharge Physics
POLYMER TREATMENTPLASMA TOOL
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• Web based corona plasmas treated sheet polymers for improved surface functionality.
Tantec Inc.
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FUNCTIONALIZATION OF POLYPROPYLENE
• Air, 300 K, 1 atmAVS03_24
• Control of surface energy by plasma treatment results from functionalization with hydrophilic groups.
• Carbonyl (-C=O) • Alcohols (C-OH)• Peroxy (-C-O-O) • Acids ((OH)C=O)
• Functionalization depends on process parameters such as gas mix, energy deposition and relative humidity (RH).
University of IllinoisOptical and Discharge PhysicsAVS03_25
OPPORTUNITIES: ATMOSPHERIC PRESSURE PLASMASTHE CHALLENGE
• APP’s provide the potential to selectively generate activated species (radicals, ions and photons) for modification and cleaning of surfaces.
• Most (many) industrial processes performed with liquid solvents could in principle be performed with APP generated radicals.
• The environmental impact of eliminating liquid solvents for cleaning of parts, removal of paint, functionalizing or sterilizing surfaces would be immense.
• Advanced concepts include improvement of combustion processes, homeland defense (chemical and biological remediation), and microplasma devices.
Ref: B. Ganguly
Ref: L. Rosocha
Ref: M. Gundersen
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In-situ H2 Generation for Small Scale (i.e. Low Power) Fuel Cells Using a Microhollow Cathode Discharge
0 20 40 60 80 100 120 1400
10
20
30
40
50
60
Plasma offPlasma on
N2
H2
NH3
Part
ial P
ress
ure
(Tor
r)Time (min)
• High throughput is facilitated by microplasma arrays
• Ref: Kurt Becker
University of IllinoisOptical and Discharge PhysicsAVS03_26
THE ROLE OF PLASMAS IN BIOSCIENCE
• Plasmas, to date, have played important but limited roles in bioscience.
• Plasma sterilization
• Plasma source ion implantation for hardening hip and knee replacements.
• Modification of surfaces for biocompatibility (in vitro and in vivo)
• Artificial skin
• The potential for commodity use of plasmas for biocompatibility is untapped.
• Low pressure rf H2O2 plasma (www.sterrad.com)
PE-CVD -COOH functional coatingsPLASMA TREATMENT N-grafted polymer surfaces
cell growth covalent binding of molecules
-COOH
-COOH
-COOH
-COOH
>C=O
-OH
>C=O
-OH
C CO
CH2=CCOOHH
-NH
2
-CN
>C=O
--OH
--NH
2
=NH
-NH
2
-CN
NH3
KEY ISSUESretention of monomer structurelow power, modulated discharges
process controldensity of groups
stability
cell adhesive surfaces
-CN
Ref: P. Favia
University of IllinoisOptical and Discharge PhysicsAVS03_27
ATMOSPHERIC PRESSURE PLASMAS:THE CHALLENGE
• Controlling functional groups on polymers through fundamental understanding of plasma-solid interactions will enable engineering large area biocompatible surfaces.
• 10,000 square miles of polymer sheets are treated annually with atmospheric pressure plasmas to achieve specific functionality.
• Cost: < $0.05 /m2
• Low pressure plasma processing technologies produce biocompatible polymers having similar functionalities.
• Cost: up to $100’s /cm2 ($1000’s/cm2 for artificial skin)
• Can commodity, atmospheric pressure processing technology be leveraged to produce high value biocompatible films at low cost? The impact on health care would be immeasurable.
University of IllinoisOptical and Discharge PhysicsAVS03_28
THE ROLE OF PLASMAS IN NANOSCIENCE
• Plasma science has been absolutely critical to the development of conventional microelectronics structures.
• What will the role of plasma science be in facilitating these advances in truly nanoscale science and technology?
• Atomic layer processing (etch and deposition)• Plasma aided lithography (trimming)• Selective activation or functionalization of materials on
molecular scales (inanimate and living)• Self- and directed-assembly• Commodity production of nanostructures
Cruden et al., J Appl Phys, 12, 363 (2001).
SELECTIVE, ALIGNED PLASMA GROWTH OF CARBON NANOTUBES
DC Plasma CVD
DC Plasma (C2H2/NH3)
RF Plasma (C2H4/NH3)
Ref: B. Cruden
• Aligned CNT growth can be obtained in a low pressure rf and dc plasmas using different feedstocks.
• Catalyst choice and configuration may dominate.
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PLASMA BASED SELF- AND DIRECTED ASSEMBLY
J. Appenzeller et al, Trans. Nanotech. 1, 184 (2002)W. Choi, Appl. Phys. Lett. 79, 3697 (2001)J. Zou et al, Trans. Microw Theory Tech. 51, 1067 (2003)M. Meyyappan et al, PSST 12, 205 (2003)
University of IllinoisOptical and Discharge Physics
• As plasma tools become more sophisticated and reproducibility more critical, mastery of the fundamentals becomes essential.
University of IllinoisOptical and Discharge Physics
MODELING IMPROVES FUNDAMENTAL UNDERSTANDING:ANAMOLOUS SKIN DEPTH EFFECTS IN ICPS
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• Ref: V. Godyak, “Electron Kinetics of Glow Discharges” • Ar, 10 mTorr, 7 MHz, 100 W
ANIMATION SLIDE
Ref: V. Kolobov
Ref: F. Huang, P. Ventzek, P. Stout
University of IllinoisOptical and Discharge PhysicsAVS03_30
CHALLENGE FOR MODELING AND SIMULATIONChallenge…..Become a tool for design and optimization of
equipment and processes as reliable as Computational Fluid Dynamics.
Requirements
• Knowledge bases (cross sections, sticking coefficients):
The time required to generate knowledge bases for new materials must be weeks-to-months, not months-to-years.
• Manufacturing friendliness:
Autocad → Prediction/Recommendation → Autocad
• Acceptance:
Realistic expectations and critical assessment of ROI (one scrapped 300 mm wafer funds a modeling activity for a year).
University of IllinoisOptical and Discharge PhysicsAVS03_31
THE CONTINUUM OF PLASMA TECHNOLOGIES
Werner von Siemens, 1872
Ozone Tube of W. Siemens
Annalen der Physik und Chemie (1857)
Ref: U. Kogelschatz,www.siemens.com, www.samsung.com
• The road to PDPs began in a lab in Germany in 1857
University of IllinoisOptical and Discharge PhysicsAVS03_32
STATUS OF OUR DISCIPLINE• The diversity of technological plasmas is its strength.
• Interdisciplinary• Wide range of applications• Entry point from many educational backgrounds• Extraordinary economic and social impact
• The weakness of this diversity is there is no recognized “discipline” of plasma processing (as for fusion plasmas).
• No home in funding agencies• Lack of formal programs in universities resulting in lack
of hiring priorities.• Excessive reliance on supporting disciplines• Often indirect path from academic innovation to
commercialization
• Ref: Frank Chen
University of IllinoisOptical and Discharge PhysicsAVS03_33
NURTURING OUR DISCIPLINEOur greatest challenge: Create a self-sustaining, self identified discipline of plasma processing. The result will
• Attract the best-and-the-brightest• Provide educational and professional opportunities for
young scientist and engineers (and replace rapidly graying university faculty)
• Insure critical funding to improve core competencies and motivate relevant work in supporting sciences
• Recognize and advertise social and economic benefits• Provide a lobbying base for proactiveness by academics
and industry• Establish paths for innovation to be commercialized• Create and benefit from unrealized synergies
University of IllinoisOptical and Discharge PhysicsAVS03_34
OUR GREATEST CHALLENGE: NURTURING OUR DISCIPLINE
Recommend Executive Summary from:
"The Impact of Academic Research on Industrial Performance"(National Academies Press, Washington DC, 2003, www.nap.edu)