University of ArkansasFayetteville, Arkansas 72701

www.uark.edu

Plasma Diagnostics for the Deposition of Nanomaterials

Jay MehtaUndergraduate Student, University of Arkansas, Fayetteville, Arkansas 72701, USA

Faculty Mentor: Dr. Matthew H. GordonAssociate Professor of Mechanical Engineering, University of Arkansas, Fayetteville, Arkansas 72701,

USA

Ph.D. Graduate Student Mentor: Sam MensahGraduate Student, University of Arkansas, Fayetteville, Arkansas 72701, USA

REU: Mechanical EngineeringUniversity of Arkansas

July 20, 2009

University of ArkansasFayetteville, Arkansas 72701

www.uark.edu

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 ArkansasFayetteville, Arkansas 72701

www.uark.edu

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 ArkansasFayetteville, Arkansas 72701

www.uark.edu

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 ArkansasFayetteville, Arkansas 72701

www.uark.edu

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 ArkansasFayetteville, Arkansas 72701

www.uark.edu

Equipment Used

• USB 4000» Interprets and captures an optical signal from the ICM 10 system» Compact and usb operated

University of ArkansasFayetteville, Arkansas 72701

www.uark.edu

Software Used

• System Software:» Used to vary power and gas flow rates

• Spectrasuite:» Used to with USB 4000 to collect optical data

University of ArkansasFayetteville, Arkansas 72701

www.uark.edu

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 ArkansasFayetteville, Arkansas 72701

www.uark.edu

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

25% 45% 65%0

0.5

1

1.5

Varying Argon Partial Pressure

Ar 750.95 Ar 752.08

Ar 764.1 Ar 801.95

Ar 843.04

4 4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 60

0.5

1

1.5

Varying PowerAr 750.95

Ar 752.08

Ar 764.1

Ar 801.95

Ar 843.03

1 2 3 4 5 6 7 8 90

0.5

1

1.5

Varying PressureAr 750.95

Ar 752.08

Ar 764.1

Ar 801.95

Ar 843.03

40 45 50 55 60 65 700

0.5

1

1.5

Varying Total Gas FlowAr 750.95

Ar 752.08

Ar 764.1

Ar 801.95

Ar 843.03

University of ArkansasFayetteville, Arkansas 72701

www.uark.edu

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 ArkansasFayetteville, Arkansas 72701

www.uark.edu

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 ArkansasFayetteville, Arkansas 72701

www.uark.edu

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 ArkansasFayetteville, Arkansas 72701

www.uark.edu

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 ArkansasFayetteville, Arkansas 72701

www.uark.edu

REU: Mechanical EngineeringUniversity of Arkansas

July 20, 2009

Questions?» Questions?