Institute of Experimental and Applied Physics Kiel Combination of calorimetric and Langmuir probe measurements as a plasma diagnostic tool F. Haase 1 , D. Lundin 2 , S. Bornholdt 1 , H. Kersten 1 1 Institute of Experimental and Applied Physics Kiel 2 IFM, Linköping University SFB Summer School 2014 Fabian Haase 1 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel Overview 1. Motivation 2. Diagnostic methods 1. Langmuir probe 2. Calorimetric probe 3. Experimental Setup 4. Results and discussion 5. Summary/Outlook Fabian Haase 2 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 1. Motivation Fabian Haase 3 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 1. Motivation PVD: thin film deposition using magnetron sputtering: • established for industrial purposes • wide range of materials that can be sputtered • knowledge of energy influx and internal plasma parameters to customize coating process crucial: J. A. Thornton, J. Vac. Sci. Technol. Vol. 11, No. 4, 1974 – quality of film, physical and chemical properties – in contrast to CVD: treatment of heat sensible materials Fabian Haase 4 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 1. Motivation doing it old school: thermal probe measurement: Langmuir measurement: Fabian Haase 5 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 1. Motivation • Combination: enables splitting up the energy influx into single contributions of the plasma species • before: long measurement time goal: improvement of deposited film quality Fabian Haase 6 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 2. Diagnostic methods Fabian Haase 7 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 2. Diagnostic methods 2.1 Langmuir probe (Irving Langmuir 1926) Fabian Haase 8 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 2. Diagnostic methods - Langmuir probe • widely used type of probe • determination of: – floating potential – plasma potential – electron temperature – electron density – (ion temperature, ion density, EEDF) Fabian Haase 9 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 2. Diagnostic methods - Langmuir probe principle: • metal surface is exposed into plasma • log probe current with respect to probe voltage Fabian Haase 10 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 2. Diagnostic methods - Langmuir probe Langmuir probe characteristics Fabian Haase 11 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 2. Diagnostic methods - Langmuir probe • floating potential: zero crossing • plasma potential: inflection point Fabian Haase 12 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 2. Diagnostic methods - Langmuir probe • electron temperature: from slope • plot ln(current) vs. probe voltage: • calculation of electron density: Fabian Haase 13 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 2. Diagnostic methods 2.2 Calorimetric probe Fabian Haase 14 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 2. Diagnostic methods – calorimetric probe setup: • metal plate (Cu) with high heat capacity • Type-K thermo couple connected to backside Fabian Haase 15 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 2. Diagnostic methods – calorimetric probe energy flux: Fabian Haase 16 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 2. Diagnostic methods – calorimetric probe • record cooling and heating phase • calculate incoming power via: heating: cooling: energy balance: energy influx: assume: P out is equal for heating and cooling phase! Fabian Haase 17 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 2. Diagnostic methods – calorimetric probe transient method: Bornholdt et al., The European Physical Journal D, 67(8), 2013 Fabian Haase 18 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 3. Setup Fabian Haase 19 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 3. Setup Magnetron: Fabian Haase 20 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 3. Setup LA 250 pressure gauge DC magnetron probe turbo pump gas flow control booster pump RF electrode Fabian Haase 21 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 3. Setup calorimetric probe DC magnetron RF electrode typical pressures: 0.1…10 Pa P mag = 10…150 W Fabian Haase 22 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 4. Discussion Fabian Haase 23 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 5. Discussion manual sweep: Ag target Fabian Haase 24 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 5. Discussion manual sweep: Ag target Fabian Haase 25 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 5. Discussion manual sweep: automatic sweep: Ag target Fabian Haase 26 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 5. Discussion Gas: Kr p= 4.0 Pa P mag = 100 W Ti target Fabian Haase 27 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 5. Discussion energy influx contributions: Gas: Kr p= 4.0 Pa P mag = 100 W Ti target Fabian Haase 28 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 5. Discussion • improving the film properties by a higher degree of ionization: mean free path of ionization (for a neutral): • mainly determined through the process gas: Ionization potentials: Fabian Haase 29 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 5. Discussion electron temperature and density: P= 100 w Ti target Fabian Haase 30 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 5. Discussion mean free path for ionization (normalized to Ar): Fabian Haase 31 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 5. Discussion deposition rates: Fabian Haase 32 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 5. Summary/Outlook Fabian Haase 33 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel 5. Summary/Outlook • Combination of those two methods is working • Langmuir data in good agreement with calorimetric data • with Ne: T e is a factor 3 higher compared to Ar and Kr Outlook: • investigate for Ag target • other contributions for better agreement? Fabian Haase 34 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel Thank you for lending me your ear Fabian Haase 35 Calorimetric Langmuir probe measurements
Institute of Experimental and Applied Physics Kiel Appendix sheath model Fabian Haase 36 Calorimetric Langmuir probe measurements
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