LOW TEMPERATURE PLASMA STUDIES AND APPLICATIONS

Xiaogang Wang Dalian University of Technology

OUTLINERelationship with IndustryMajor Applications Plasma Sources Beams Pulsed Power Technology Atmospheric Pressure Discharge Plasma Etching

Dusty Plasma ApplicationsBiophysical ApplicationsDiscussions

RELATIONSHIP WITH INDUSTRY

Basic structure (USA) Basic researches (government support) Industry R & Ds (Private sectors) Industry

Sources & Beams, Processing, Films, Electronics, Computer, etc.

Current structure in China Basic researches (government support) Industry R & Ds (none) Industry applications (???)

Basic researches (in US)

Pure scientific researches What is going to happen in 20 years?

Such as: computer beyond silicon Basic physical, chemical, biological

processes

“Basic” applied researches New sources, new ways, new materials

Such as: helicon in 90s, sources & beams for “big science” , PSII in 80s, pulsed tech, OAPUGD

Computer codes

Basic researches (in China)

Pure scientific researches What is going to happen in 20 years? (??) Basic physical (Yes), chemical (?),

biological (?) processes

“Basic” applied researches New sources, new ways, new materials

(?) Computer codes (??)

Industry R & Ds (in US)New sources, new ways, new materials Overlap with basic researches, more

profit-oriented

Computer codes Overlap with basic researches, more

specific

New processes Very detail improvements

Industry R & Ds (in China)

State sectors Government R & D

Wealthy & weak, but unwilling to share resource State owned industry

In bad shape itself, no enough resource

Private sectors “Publicly traded”: strongly rely on import Privately owned: limited resource and vision

Industry in USHigh tech leaders Computer chips New materials Medical and biological applications

Government sectors Aero-space industry & Environment industry

Big sciences Reactors and Beams Sources

Industry in China

Not a leader rely on import

Not a major manufacturer in high tech Japan: at least need process improvement China: small size, low-end, no such needs

Government Separation of funding and human resources

Big sciences Limited

INDUSTRIAL APPLICATIONS OF PLASMAS

Surface Treatment:

Ion implantation, hardening, Welding, cutting, drilling

Film deposition

Volume Processing:

Flue gas treatment, Metal Recovery, Waste Treatment

Water purification, Plasma spraying

Light Sources

High Intensity, Discharge Lamps, Low Pressure Lamps, Specialty Sources,

Lasers, Field-Emitter Arrays, Plasma Displays

Switches:

Electric Power, Pulsed Power

Energy Converters:

MHD Generators, Thermionic Energy Converters, Beam Sources

Radiation Processing:

Ceramic powders, Plant growth

Medicine:

Surface treatment, Instrument Sterilization

MAJOR APPLICATIONS

Plasma SourcesBeamsPulsed Power TechnologyAtmospheric Pressure DischargePlasma Etching

PLASMA SOURCES

HeliconsECRsICPsMagnetronsGyrotronsThrustersGEC reference reactors

GEC ReactorGaseous Electronics Conference (GEC) Reference Reactor (Hargis et al, 1991)

Capacitive coupled plasmas

RF discharge (13.56 MHz, ~100 V)

Detailed computer simulation code

GEC Reactor: Basic parameters

Rc = 5 cm

Rr = Ra = 5.25 cm

RT = 10 cm

Xc = Xr = 3.5 cm

Xa = 6.25 cm

XT = 10 cm

d = Xa-Xc = 2.75 cm

BEAMS

Laser beamsIon beamsElectron beamsEnergetic particle beams

Ion beams:Plasma focusing

Off–focus of charged particle beams

Plasma focusing

Applications to microelectronics

“ Nano” microelectronics: Quantum Ge/Si dots Growth by molecular beams + electron

beam evaporators for Si and Ge deposition

Enhancement by ion implantation Low energy As+ beam (1 keV) Depositing current density 0.02 A/cm2

PULSED POWER TECH

Pulsed voltage

Pulsed beams

Experiments atMaterials Modification Lab,

DUT

C on Al surfaceBombarded by pulsed electron beamsRegular deposition thickness: msAfter a single pulse: ~ 1mmMulti-pulses: Better results

Anomalous diffusion effect ?

Experiments at MMLab:Pulsed electron beam

parameters

Width: ~ mPower: 27.8 keVEnergy density: 3.2 J/cm2

1. Cathode, 2. Anode, 3. Target, 4. Vacuum chamber, 5. Cathode plasma, 6. Anode plasma, 7. Coils, 8. Sparks

ATMOSHERIC DISCHARGESArc discharges Circuit breakers Plasma guns & furnaces for steel, auto and

environment industries Surface physical simulation of re-entry

Corona discharges Environment industry

Glow discharges Filament glow discharges OAUGD

Physical simulation of re-entry

Fluid model (electrostatic MHD)

Kink instabilities

Two stream instabilities

Numerical simulation codes

DUSTY PLASMA APPLICATIONS

Dust particles in reactors

Removal by heart-beating waves

Removal by bipolar diffusions

Other applications

Dust particles in reactors:Particle creations

Particle creation & growth phases

Cluster formation Nucleation and cluster growth Coagulation Particle growth

Particle creations :Major processes

Surface processes: Etching Sputtering

PECVD processes: Walls Chemical polymers

Dust particles in reactors:Impacts of particles

Surface contamination

Effects on sheath and electron density

Application of dust energetics

Particle size control and nanostrutrued thin films

Surface contamination

Particle emission and trapping in plasma processing reactors

ICPs

CCPs

Helicons and ECRs

Effects on sheath and electron density

Energy absorption

Electron density reduction

Dust-free processing

Dust cleaning (removal) techniques

Magnetization and E X B drift

Dust trajectory calculations

Electrical potential configurations

Application of dust energetics

Dust energetics

Heavy particle deposition

“Dust-enhanced” PECVD

Dust charging and distribution studies

Dust size control and nanostructured thin films

Opto-electronics applications of nano-structure thin films

Nano-crystallite with dusty plasma technology

BIOPHYSICAL APPLICATIONS

Electroporation Drug delivery and gene therapy Seed modification (ion & plasma beams) ?

Surface sterilization Anti-bioterrorism application Medical and other industry applications

Surface modification To artificial organs etc.

High power, low duty circle pulses Applications to biological systems

Electroporation:Basic processes

Applying short electrical pulsesCharging of lipid bilayer membranesFast local structure rearrangementTransition to “pore” stageTremendous enhancement of ionic and molecular transport

Possible candidate for seed modification?

Electroporation:Basic parameters

Pulse width: ~ s – msPore creation period: ~ s Pore relaxation time: > 1 sPore radii: ~ nmBilayer thickness: ~ mMembrane voltage: > 1 VElectrical field: ~ kV/cm

Surface sterilization: Anti-bioterrorism application

Large scale anthrax outbreak Soviet Union, 1979 (Science 266, 1994) USA, 2001

Plasma sterilization for large areas No damage to the surface Fast cleanup: > 10cm/s In-place agent destruction, no hazard waste

Tools Montec steam plasma torch TTU arc-jet thruster

Surface sterilization: Plasma parameters

Power: 60 – 100 kWWork plasma: Water steam &Temperature: > 1500 KThreshold: > 3000 KRate > 10 cm/sKill rate: > 80 %

DISCUSSIONS

Plasma cloaking Drag-reduction and EM waves

absorption Plasma shock formation and its effect

Plasma etching

Plasma chemistry

University Research Centers in US

UW-UM Center for Plasma Aided Manufacturing

Research Areas:

Thin Film Deposition Thick Film Deposition Plasma Etching Surface Modification

Thin Film Deposition

Plasma-mediated, surface modification of organic and inorganic polymeric substrates for generating controlled etching reactions, creating specific surface topographies, and implanting specific functionalities onto various substrate surfaces.

Deposition of novel and conventional macromolecular layers (e.g. Teflon-like thin layers and IR transparent films) on inorganic and organic surfaces by involving plasma-state and plasma-induced reaction mechanisms, including template polymerization reaction mechanisms initiated from surfaces with plasma-enhanced crystallynity.

Investigation of the influence of plasma parameters (electron energy distribution, power, frequency, pressure, etc.) on the discharge-induced gas phase molecular fragmentation and surface-mediated plasma-chemistry mechanisms

•Kinetic modeling of plasma-induced gas phase fragmentation and gas phase and surface-mediated recombination processes (e.g. Kinetic modeling of ammonia and hydrazine-RF plasma environments).

•Generation of intelligent substrates for molecular recognition and molecular machining processes by immobilizing and synthesizing active biomolecules (e.g. enzymes, oligonucleotides) on plasma-functionalized substrate surfaces

•Evaluation of the influence of the amorphous and stereoregular nature of the polymeric substrates and the chemical nature and length of spacer molecules on the activities of the immobilized biomolecules.

•Development of novel plasma installations for specific plasma treatments, and for scaling up laboratory technologies to industrial applications

Thick Film Deposition

A) Plasma spraying:

* Nozzle and shroud development and evaluation for increased plasma jet stability, and improved deposition efficiency and consistency of coating quality.

* Development of sensors and control algorithms for detecting and avoiding variations in plasma jet behavior and coating quality. 

B) Wire arc spraying:

•* Spray pattern control through different nozzle and shroud designs.

•* Development of fundamental process correlations using process models andadvanced diagnostics with a novel torch.

•* Application of novel control algorithm based on computer analysis of arcvoltage traces.

•C) Thermal plasma CVD:

•* Texture control during high rate diamond film deposition through detailed understanding of the boundary layer chemistry based on modeling and diagnostics using gas chromatography.

•* Arcjet deposition at high rates of hard, boron containing films.

Plasma Etching

Etch Tool Development

Helicon plasma etching

Magnetically enhanced inductively coupled plasmas (ICP)

Large area substrates

Modeling

Semiconductor Processing:

* Fluorocarbon-based SiO2 etching - chemical characterization of gas phase using infrared spectroscopy, endpoint detection, etch selectivity/ion energy control at the wafer surface

* Plasma-Induced Damage - surface charging effects in device damage and feature profile evolution, discharge modulation for reduction of charging-induced damage, vacuum ultraviolet radiation damage

* Real-time Control of Plasma Etching - efforts includes development of sensors (e.g., wall deposition monitor), and control strategies

Advanced Plasma Etch Diagnostics

Diagnostics currently under development:

Langmuir probe theory in magnetized plasmas

Infrared absorption spectroscopy

Electro-optical probe

Recent collaborations with industrial partners

•Process development for polymer etching

•Surface charging reduction during plasma etching

•Process development for etching of magnetic materials

•Chemical characterization of plasmas for fluorocarbon-based etching of SiO2

Thank you!