plasma diagnostics for the deposition of nanomaterials

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?