Energy-Resolved Quadrupole Mass Spectrometry in IIB-VIA … · 2016-10-24 · Title: Use of...
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Sputtered II B -VI A Materials Used in Thin Film PV Identification of ZnS Mass Spectra • Do particles sputter atomically or in clusters? • RF magnetron sputtered ZnS in pure Ar ambient • Atomic ions more prevalent than clusters • Ion fluxes: Ar > Zn > S > ZnAr > ZnS Acknowledgements This work was supported by the DOE SunShot Program funding of the NREL Core Science and Technologies activities under Contract No. DE-AC36-08-GO28308 with the National Renewable Energy Laboratory. Energy-Resolved Quadrupole Mass Spectrometry in II B -VI A Sputtering Investigations Daniel M. Meysing a , Matthew O. Reese b , James M. Burst b , Hasitha Mahabaduge b , Timothy A. Gessert b , Colin A. Wolden a , Teresa M. Barnes b Colorado School of Mines a , National Renewable Energy Laboratory b Sputtering Studies Useful but not Common • Sputtering is often treated as a black box o Control inputs: power, pressure, ambient composition, etc. o Observe film properties: crystallinity, transmittance, conductivity, etc. • This approach does not consider complex sputtering phenomena o Ion/electron energy o Particle aggregation/film nucleation Use mass spectrometry to advance understanding • Chemistry/composition of sputtered particles • Critical energetics/potentials Equipment: QMS Mounted to Sputtering Chamber • The Sputter-Plasma Diagnostic (SPD) multi-source UHV chamber • Hiden EQP 500 Quadrupole Mass Spectrometer o Mounted via rotating flange with 2-axis motion o Line of sight access to sputtering plasma o Capable of analyzing neutrals and plasma-generated ions ZnS Ion Energy Distribution (IED) Scans • Plot of Intensity vs. arrival energy of plasma-generated ions • Peak position equal to plasma potential 1 • Electron temperature from V p – V f = T e 2e 1 + ln m i 2πm e • Experimental design o Sputter ZnS in Ar ambient o Investigate reproducibility, effects of flight distance, pressure, and power o Baseline conditions: 26 cm displacement, 5 mTorr, 30 W • Scans show good reproducibility; plasma potential is highly variable o Uncertainty in peak position ~0.5 eV o Bimodal IED for Ar, single mode for Zn and S o Near-linear decrease in potential with increasing distance from target o Exponential drop in potential with increasing pressure o Increasing potential with increasing power Conclusions • Under baseline conditions, atomic sputtering dominates • Processing conditions greatly affect arrival energy of sputtered ions Future work • Investigate oxygen incorporation in CdS and ZnS films • Identify process conditions for atomic vs. cluster sputtering References 1 K. Ellmer, T. Welzel, Reactive magnetron sputtering of transparent conductive oxide thin films: Role of energetic particle (ion) bombardment, J. Mater. Res. 27 (2012), 765. Potential (V) z Target Substrate Plasma V t ~ –400 V V p ~ +5 V V s ~ –15 V Reflected Ar Sputtered neutrals Negative ions Ar + Ar + Glass superstrate Glass substrate SnO 2 :F SnO 2 CdS CdTe ZnTe:Cu Ti Mo Cu(In,Ga)Se 2 Zn(O,S) ZnO ZnO:Al CdTe solar cell CIGS solar cell Turbo pump Turbo pump Detector Orifice Rotating flange Sputter gun SPD Tool Orifice Ion source Quadrupole lens Energy filter Mass filter Detector Differential pump port Hiden EQP 500 Isotopic abundances of Zn, S, and Ar 36 38 40 64 66 67 68 70 Zn S 32 33 34 36 Ar
Transcript of Energy-Resolved Quadrupole Mass Spectrometry in IIB-VIA … · 2016-10-24 · Title: Use of...
Sputtered IIB-VIA Materials Used in Thin Film PV
Identification of ZnS Mass Spectra • Do particles sputter atomically or in clusters? • RF magnetron sputtered ZnS in pure Ar ambient
• Atomic ions more prevalent than clusters • Ion fluxes: Ar > Zn > S > ZnAr > ZnS
Acknowledgements This work was supported by the DOE SunShot Program funding of the NREL Core Science and Technologies activities under Contract No. DE-AC36-08-GO28308 with the National Renewable Energy Laboratory.
Energy-Resolved Quadrupole Mass Spectrometry in IIB-VIA Sputtering Investigations
Daniel M. Meysinga, Matthew O. Reeseb, James M. Burstb, Hasitha Mahabadugeb, Timothy A. Gessertb, Colin A. Woldena, Teresa M. Barnesb
Colorado School of Minesa, National Renewable Energy Laboratoryb
Sputtering Studies Useful but not Common • Sputtering is often treated as a black box
o Control inputs: power, pressure, ambient composition, etc. o Observe film properties: crystallinity, transmittance, conductivity, etc.
• This approach does not consider complex sputtering phenomena o Ion/electron energy o Particle aggregation/film nucleation
Use mass spectrometry to advance understanding • Chemistry/composition of sputtered particles • Critical energetics/potentials
Equipment: QMS Mounted to Sputtering Chamber • The Sputter-Plasma Diagnostic (SPD) multi-source UHV chamber • Hiden EQP 500 Quadrupole Mass Spectrometer
o Mounted via rotating flange with 2-axis motion o Line of sight access to sputtering plasma o Capable of analyzing neutrals and plasma-generated ions
ZnS Ion Energy Distribution (IED) Scans • Plot of Intensity vs. arrival energy of plasma-generated ions • Peak position equal to plasma potential1
• Electron temperature from Vp – Vf = Te2e
1 + lnmi
2πme
• Experimental design o Sputter ZnS in Ar ambient o Investigate reproducibility, effects of flight distance, pressure, and power o Baseline conditions: 26 cm displacement, 5 mTorr, 30 W
• Scans show good reproducibility; plasma potential is highly variable o Uncertainty in peak position ~0.5 eV o Bimodal IED for Ar, single mode for Zn and S o Near-linear decrease in potential with increasing distance from target o Exponential drop in potential with increasing pressure o Increasing potential with increasing power
Conclusions • Under baseline conditions, atomic sputtering dominates • Processing conditions greatly affect arrival energy of sputtered ions
Future work
• Investigate oxygen incorporation in CdS and ZnS films • Identify process conditions for atomic vs. cluster sputtering
References 1K. Ellmer, T. Welzel, Reactive magnetron sputtering of transparent conductive oxide thin
films: Role of energetic particle (ion) bombardment, J. Mater. Res. 27 (2012), 765.
Pote
nti
al (
V)
z
Target Substrate
Plasma
Vt ~ –400 V Vp ~ +5 V Vs ~ –15 V
Reflected Ar
Sputtered neutrals
Negative ions
Ar+
Ar+
Glass superstrate
Glass substrate
SnO2:F
SnO2
CdS
CdTe
ZnTe:Cu
Ti
Mo
Cu(In,Ga)Se2
Zn(O,S)
ZnO
ZnO:Al
CdTe solar cell CIGS solar cell
Turbo pump
Turbo pump
Detector
Orifice
Rotating flange
Sputter gun
SPD Tool
Orifice Ion
source
Quadrupole lens
Energy filter
Mass filter
Detector
Differential pump port
Hiden EQP 500
Isotopic abundances of Zn, S, and Ar
36
38
40
64
66
67 68
70
Zn S
32
33
34
36
Ar
