Atmospheric Pressure Plasma Jet

1. Atmospheric Pressure Plasma Jet Abstract authors: H.W. Herrmann, L. Rosacha Los Alamos National Laboratory Los Alamos, NW 87544 Presented by Zhenwei Hou

2. What is Atmospheric Pressure Plasma Jet(APPJ) •APPJ: a non-thermal, glow-discharge plasma operating at atmospheric pressure. •The non-thermal plasma (NTP) generates highly reactive ions, electrons and free radicals. •The reactive species are directed onto a surface where the desired chemistry occurs. •The electrons are quite “hot”, however the overall gas temperature remains quite “cold”, typically 50-300 °C. Source: Louis Rosocha, “Non-Thermal Reactor Technology for Control of Atmospheric Emissions,”

3. APPJ Advantage • Non expensive vacuum equipment is required. • Non constraint is related to a chamber based process. • Thin film processes with high rate is possible. • The rectangular box in the lower right corner represents the domain for vacuum processing. • The larger box represents the domain constraints for atmospheric pressure plasma processing. • The larger box also contains much of the process domain represented for vacuum-based plasma processing. Source: http://www.lanl.gov/partnerships/pdf/license/appj_2.pdf

4. APPJ Applications • Clean steel draw roll used to produce nylon. • Remove Photoresist from silicon wafer. • Etch polyimide, tungsten, tantalum, silicon and SiO2. • Make Teflon wettable so that it can bond with other materials. • Remove graffiti. • Decontaminated surface exposed to chemical or biological warefare agents or surfaces containing radioactive materials. Source: http://www.lanl.gov/partnerships/pdf/license/appj_2.pdf

5. APPJ Devices • Feed gas • Inert carrier gas: He • reactive gas: O2, H2O, CF4. • Frequency: 13.56 MHz • Power: 300 W The low temperature plasma is generated by the electrical field between the electrodes. The plasma boosters other atoms or molecules into the their metastable states. Unlike the plasma, the metastables can survive in the air for a few tenths of a second. The long-life metastables have enough time to reach and react with their targets. Source: www.emtd.lanl.gov/TD/Treatment/NonthermalPlasmaTreatment.html

6. APPJ Process Feed gas Closely spaced electrodes powered 300W at 13.56MHz Be activated electron temp: 2eV electron density: 1011 cm-3 Plasma feed gas becomes excited, dissociated and ionized Metastable Species & radicals Temp: 50-300 C Onto the surface Source: http://www-p24.lanl.gov/

7. Cleaning with APPJ • APPJ Plasma excites the air or oxygen feed gas and generates reactive oxygen species. The reactive oxygen species burn many organic materials with a release of H2O and CO2. Source: http://www.lanl.gov/p/pdfs/papp_appj.pdf

8. Deposition of SiO2 with an APPJ • PROCESS PARAMETERS: • Carrier gas: He, 757.2 Torr • Reactive materials: • O2 2.8 Torr • TEOS (Tetraethoxysilane), 7.1 mTorr • Substrate: Si(100), 115 C (at the • back surface) • Total flow rate: 49.4 l/min • (at 25 C and 760 Torr) • Distance: 1.7cm • Power: 280 W RF • QUALITY & PERFORMANCE • OF SILICON DIOXIDE FILM • The refractive index: 1.43 to 1.47 • (measured by ellipsometry) • The dielectric constant: 3.8073 Source: S.E. Babayan, R.F.Hicks et al, Deposition of silicon dioxide with an atmospheric-pressure plasma jet, Plasma Sources Sci, Technol. 7(1998) 286-288

9. APPJ SiO2 Deposition • The deposition rate increases with the power from 180 to 500W. • The process is limited by the flux of reactive species in the plasma. • The highest recorded deposition rate is 3020 A/min at TEOS partial pressure of 0.2 Torr and RF power of 400 W. • The deposition rate decreases with increasing sample temperature (Arrhenius relationship). •The transmission infrared absorption spectra of the SiO2 film is indistinguishable from the that of SiO2 produced by the thermal oxidation of a silicon wafer at 900 C. •The dielectric constants are varied from 5.2 for films grown below 150 C to 3.8 for films grown at 350 C.

10. Sterilization with APPJ • The feed gas (air) is pumped into the chamber and ionized by the metastable Helium. • The plasma power density: 50 – 100 mW/cm3. • The kinetic temperature of electron: 1- 5 eV. • The bacterium sample: 3 x 107/ml of E. coli bacteria. • The outer membrane of the cells is punctured during its exposure to the plasma. • The punctured cells become very vulnerable to the surrounding plasma environment. E. coli bacterium in the untreated control sample E. coli bacterium subjected to 30 seconds exposure to the plasma. Source: M. Laroussi, M. Chad et al., Images of Biological Samples undergoing sterilization by a glow discharge at atmospheric pressure, IEEE Transactions on Plasma Science v27. N1 1999, P34-35.

11. Decontamination of Chemical & Biological Warfare (CBW) Agents with APPJ • • The use of CBW agents in either a • domestic terrorist attack or military • conflict is a growing threat. • • Biological warefare agents consist of • Spore forming bacteria (Anthrax) • Vegetative bacteria (Plague, E. coli) • Viruses (Small Pox, Yellow Fever) • Biotoxins (Ricin, Botox) • •Toxic chemical warfare agents consist of • Blister agents (Mustards, Lewisite) • Nerve agents [V agents(VX), G agents • (Tabun, Sarin, Soman)] • Choking agents (phosgene) • Blood agents (Hydrogen Cyanide) • A U. S. Air Force Armstrong Laboratory report on BW countermeasures concluded that “the pulsed corona discharge reactor may have potential as a countermeasure, but its ability to destroy appropriate agents remains to be demonstrated.” • APPJ has greater potential and less risk than corona plasma discharge. Source: H.W. Herrmann, I. Henins, J. Park et al., “Decontamination of Chemical and Biological Warefare (CBW) Agents Using an Atmospheric Pressure Plasma Jet,” Physics of Plasmas 6, 2284-2289 (1999)

12. CBW Decon with APPJ Biological Decon Chemical Decom PROCESS PARAMETERS Sample temp: 175 C Exposure time: 30 s Hot gas power: 200 W Plasma power: 300 W Distance: 0.5 cm He flow: 92 slpm O2 flow:0.72 slpm Electrode gap:0.16cm Hot gas is used as a control. Mustard simulant Dried BG spores Dried BG spores VX simulant