Plasma Diagnostics for Nanomaterials: Optical Emission Spectroscopy Study

1. REU: Mechanical Engineering University of Arkansas July 20, 2009 Plasma Diagnostics for the Deposition of Nanomaterials Jay Mehta Undergraduate Student, University of Arkansas, Fayetteville, Arkansas 72701, USA Faculty Mentor: Dr. Matthew H. Gordon Associate Professor of Mechanical Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA Ph.D. Graduate Student Mentor: Sam Mensah Graduate Student, University of Arkansas, Fayetteville, Arkansas 72701, USA University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

2. Why alpha alumina? • Many desirable properties: • high melting temperature (2053 °C) • Considered best anti—oxidation coating at high temps • corrosion resistance • chemical inertness • High mechanical strength and hardness (24GPa) • Great insulating properties • Applications: • Optical coatings • Thermal coatings • Dielectric films • Cutting tools • Biomedical implants University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

3. Goals • Long term: • Connecting spectroscopy results with film quality • Better understanding of alpha alumina • Short term: • Using OES to observe and study plasma in deposition chamber under varying conditions University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

4. What is OES? • Optical Emission Spectroscopy • Spectrometer captures data from captured photons • Produces a spectrograph • Relative intensity of peaks can be used to determine ion density University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

5. Equipment Used • ICM10 • Midfrequency inverted cylinder AC magnetron sputtering system • Used for Physical Vapor Deposition • For our case depositing Alumina (Al2O3) • Target: Aluminum • Reactive Gas: Oxygen • Sputtering Gas: Argon University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

6. Equipment Used • USB 4000 • Interprets and captures an optical signal from the ICM 10 system • Compact and usb operated University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

7. Software Used • System Software: • Used to vary power and gas flow rates • Spectrasuite: • Used to with USB 4000 to collect optical data University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

8. Experiment • Created recipes: • 4 Variables: • Pressure: 2-8 mtorr with 3 mtorr increments • Power: 4-6 kW with 0.5 kW increments • Total Gas Flow: 40-70 sccm with 10 sccm increments • Oxygen Partial Pressure: 35-75% with 5% increments • Time per run: 100 seconds • Integration time: 2 seconds • Scans per run: 1 • Total scans: 540+ University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

9. Results • Peak identification: • Unable to locate Aluminum peaks • Many Argon peaks • Few Oxygen Peaks • Representative peaks: • Argon peak at 763.51nm • Oxygen peak at 777.194nm University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

10. Results • Argon Trends • Predictable • Increasing power=increasing intensity • Increasing oxygen partial pressure=decreasing intensity • Increasing pressure=slight increase in intensity • Outliers caused by pressure changes due to oxygen reactions University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

11. Results • Oxygen • Expected trends: • Linearly increasing oxygen intensity with increasing oxygen partial pressure • Increasing oxygen intensity with increasing power (graphs) • Fairly consistent results at higher pressures University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

12. Results • Oxygen • Notable: • Very low oxygen intensity at 50 sccm throughout experiments • Peak in oxygen intensity after 4.5-5 kW for 50 sccm • Unusually low intensity at 6 kW for Pr2 • At higher powers Pressure didn’t have much effect • Jumps: • Between 55%-75% Oxygen at Pr2Tg40Pw4 • Between 50%-60% Oxygen at Pr2Tg60Pw4.5 • Between 55%-60% Oxygen at Pr2Tg50Pw4 • Between 35%-55%Oxygen at Pr2Tg40 jump from Pw4 to 4.5 • Between 55%-65%Oxygen at Pr2Tg40Pw4 • Jump in intensity from 2 to 5mtorr for Tg50 all powers • Jump in intensity from 2 to 5mtorr for Tg60Pw4 University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

13. Conclusion • Study jumps in oxygen intensities • Target poisioning • Pressure and power changes • Further experiments: • Hysteresis studies • observing aluminum vs. oxygen intensities • Test theories in deposition runs • Compare with Langmuir probe data University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu

14. REU: Mechanical EngineeringUniversity of ArkansasJuly 20, 2009 Questions? • Questions? University of Arkansas Fayetteville, Arkansas 72701 www.uark.edu