[PPT] - Combination of calorimetric and Langmuir probe measurements as a PowerPoint Presentation

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Institute of Experimental and Applied Physics Kiel

Fabian Haase Calorimetric Langmuir probe measurements

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Combination of calorimetric and Langmuir probe measurements as a plasma diagnostic tool

F. Haase1, D. Lundin2, S. Bornholdt1, H. Kersten1

1Institute of Experimental and Applied Physics Kiel 2IFM, Linköping University

SFB Summer School 2014

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Institute of Experimental and Applied Physics Kiel

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Overview

1. Motivation 2. Diagnostic methods

1. Langmuir probe 2. Calorimetric probe

3. Experimental Setup 4. Results and discussion 5. Summary/Outlook

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1. Motivation

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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:

– quality of film, physical and chemical properties – in contrast to CVD: treatment

f heat sensible materials
1. Motivation
J. A. Thornton, J. Vac. Sci. Technol. Vol. 11, No. 4, 1974

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doing it old school:

thermal probe measurement: Langmuir measurement:

1. Motivation

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Combination: enables splitting up the energy

influx into single contributions of the plasma species

before: long measurement time

goal: improvement of deposited film quality

1. Motivation

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2. Diagnostic methods

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2.1 Langmuir probe (Irving Langmuir 1926)

2. Diagnostic methods

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widely used type of probe
determination of:

– floating potential – plasma potential – electron temperature – electron density – (ion temperature, ion density, EEDF)

2. Diagnostic methods - Langmuir probe

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principle:

metal surface is

exposed into plasma

log probe current with

respect to probe voltage

2. Diagnostic methods - Langmuir probe

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Langmuir probe characteristics

2. Diagnostic methods - Langmuir probe

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floating potential: zero

crossing

plasma potential: inflection

point

2. Diagnostic methods - Langmuir probe

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electron temperature:

from slope

plot ln(current) vs.

probe voltage:

calculation of electron

density:

2. Diagnostic methods - Langmuir probe

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2.2 Calorimetric probe

2. Diagnostic methods

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2. Diagnostic methods – calorimetric probe

setup:

metal plate (Cu) with high heat capacity
Type-K thermo couple connected to backside

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2. Diagnostic methods – calorimetric probe

energy flux:

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2. Diagnostic methods – calorimetric probe
record cooling and heating phase
calculate incoming power via:

assume: Pout is equal for heating and cooling phase!

heating: cooling: energy balance: energy influx:

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2. Diagnostic methods – calorimetric probe

transient method:

Bornholdt et al., The European Physical Journal D, 67(8), 2013

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3. Setup

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Magnetron:

3. Setup

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3. Setup

RF electrode pressure gauge gas flow control

LA 250

booster pump turbo pump DC magnetron probe

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3. Setup

RF electrode calorimetric probe DC magnetron typical pressures: 0.1…10 Pa Pmag= 10…150 W

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4. Discussion

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5. Discussion

manual sweep:

Ag target

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5. Discussion

manual sweep:

Ag target

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5. Discussion

manual sweep: automatic sweep:

Ag target

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5. Discussion

Gas: Kr p= 4.0 Pa Pmag= 100 W Ti target

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5. Discussion

energy influx contributions:

Gas: Kr p= 4.0 Pa Pmag= 100 W Ti target

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improving the film properties by a higher degree
f ionization:

mean free path of ionization (for a neutral):

mainly determined through the process gas:

Ionization potentials:

5. Discussion

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5. Discussion

electron temperature and density:

P= 100 w Ti target

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mean free path for ionization (normalized to Ar):

5. Discussion

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deposition rates:

5. Discussion

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5. Summary/Outlook

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5. Summary/Outlook
Combination of those two methods is working
Langmuir data in good agreement with

calorimetric data

with Ne: Te is a factor 3 higher compared to Ar

and Kr Outlook:

investigate for Ag target
other contributions for better agreement?

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Thank you for lending me your ear

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sheath model

Appendix