INDUCTIVELY COUPLED PLASMAS: ONE BIG PRESHEATH? Carole Maurice 1 , - - PowerPoint PPT Presentation

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14/10/2002 GEC 2002 Minneapolis 1

INDUCTIVELY COUPLED PLASMAS: ONE BIG PRESHEATH?

Carole Maurice1, Jaap Feijen1, Mark Kushner2, Gerrit Kroesen1

1 Eindhoven University of Technology 2 University of Illinois at Urbana-Champaign

http://uigelz.ece.uiuc.edu/presentations.html

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AGENDA

• Introduction
• Reactor Geometry
• Diagnostics
• Experimental and Modeling: Ion Velocity

Distributions

• Conclusions

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INTRODUCTION

• In Capacitively Coupled Plasmas:

distinctive regions

– Glow: small E-field, ions nearly at rest – Pre-sheath: acceleration of ions to Bohm velocity – Sheath: space charge region, large E-field

• How about Inductively Coupled Plasmas?

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• Pancake, spiral electrode
• 30 cm diameter
• 4 cm axial length
• 13.56 MHz

REACTOR

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REACTOR

electrode quartz plate plasma spiral antenna

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DIAGNOSTICS

• Doppler shifted LIF for ion velocity in the

plasma volume

• Langmuir probe for plasma potential, ion

density and electron density

• Energy resolved mass spectrometry for ion

energy distribution at electrode

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fluorescence 460.96 nm

metastable

laser 611.493 nm 490 263 GHz 4p’2F7/2 3d’2G9/2 4s’2D5/2

DOPPLER SHIFTED LIF

• Measure ion transport in plasma
• Argon LIF scheme
• Moving ion → Doppler shift

tr i L

f c v f ⋅ = ∆

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Model: Hybrid Plasma Equipment Model (HPEM)

• Monte Carlo Simulation for EEDs
• Kinetically derived current in Maxwell’s Eq’s.
• Ion & Neutral Continuity, Momentum, Energy
• Ion Monte Carlo Simulation to obtain velocity

distributions; energy/angle distributions to substrate.

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LANGMUIR PROBE ELECTRON DENSITY

2 4 6 8 10 12 14 16 0.0 2.0x10

11

4.0x10

11

6.0x10

11

8.0x10

11

1.0x10

12

ionic density (cm

• 3)

radius (cm) Setup2 5 mTorr 50 mTorr

• Electron density is mid

1011 cm-3. Off axis maxima at higher pressures denotes transition to collisional plasma. 400 W

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DOPLLER SHIFTED LIF

• 10
• 8
• 6
• 4
• 2

2 4 6 8 10 5x10

• 9

39.5 mm 39 mm 38 mm 35 mm 30 mm 25 mm 20 mm 15 mm 10 mm 5 mm 2 mm 1 mm 0.5 mm signal x3 signal x3 signal x3 frequency shift (GHz) LIF signal (A)

5x10

• 9
• 6098-4878-3659-2439-1220

1220 2439 3659 4878 6098

velocity (m/s)

• Ion velocity distribution is

a drifting Maxwellian. 5 mTorr, 400 W

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AVERAGE ION VELOCITY AND PLASMA POTENTIAL

40 30 20 10

• 4000
• 2000

2000 4000

vi distance to electrode (mm) mean ion velocity (m/s)

• 4
• 3
• 2
• 1

1

quartz plate metal electrode potential potential (V)

• No low E-field region

Ions are in continuous acceleration from midplane to surfaces. 5 mTorr, 400 W

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• Average ion velocity

tracks the electric potential with nearly continuous acceleration from midplane. 400 W

AVERAGE ION VELOCITY (MODEL)

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ION ENERGY DISTRIBUTIONS (r=0)

• Monotonic increase in IED

with decreasing pressure reflects: 400 W

• Increase in plasma

potential Decrease in collisionality

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ION ENERGY DISTRIBUTIONS (r=0) (MODEL)

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ION ENERGY DISTRIBUTIONS (r=0) (MODEL)

• Monotonic increase in IED

with decreasing pressure is captured 400 W

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10 20 1x10

4

35 W input Counts (cps) Energy (eV)

10 20 1x10

4

2x10

4

3x10

4

4x10

4

5x10

4

6x10

4

37 W input Counts (cps) Energy (eV)

10 20 0.0 2.0x10

5

4.0x10

5

6.0x10

5

8.0x10

5

1.0x10

6

1.2x10

6

1.4x10

6

1.6x10

6

1.8x10

6

2.0x10

6

2.2x10

6

2.4x10

6

2.6x10

6

2.8x10

6

3.0x10

6

3.2x10

6

45 W input Counts (cps) Energy (eV)

10 20 0.0 2.0x10

5

4.0x10

5

6.0x10

5

8.0x10

5

1.0x10

6

1.2x10

6

1.4x10

6

1.6x10

6

1.8x10

6

2.0x10

6

100 W inpu t Counts (cps) Energy (eV)

• 4
• 2

2 4 6 8 10 12 14 16 18 20 22 24 50000 100000 150000 200000 250000 300000 10 20 0.0 2 .0x10

5

4 .0x10

5

6 .0x10

5

8 .0x10

5

1 .0x10

6

1 .2x10

6

1 .4x10

6

1 .6x10

6

1 .8x10

6

2 .0x10

6

200 W input Counts (cps) Energy (eV)

10 20 50 000 100 0 00 150 0 00 200 0 00 250 0 00 300 0 00 10 20 0.0 2.0x 10

5

4.0x 10

5

6.0x 10

5

8.0x 10

5

1.0x 10

6

1.2x 10

6

1.4x 10

6

1.6x 10

6

800 W input Counts (cps) Energy (eV)

10 20 5000 10000 15000 20000 25000 30000 10 20 1x10

2

2x10

2

3x10

2

4x10

2

5x10

2

6x10

2

30 W input Counts (cps) Energy (eV)

10 20 0.0 2 .0x10

5

4 .0x10

5

6 .0x10

5

8 .0x10

5

1 .0x10

6

1 .2x10

6

1 .4x10

6

1 .6x10

6

1 .8x10

6

2 .0x10

6

2 .2x10

6

50 W input Counts (cps) Energy (eV)

10 20 0.0 2.0x 10

5

4.0x 10

5

6.0x 10

5

8.0x 10

5

1.0x 10

6

1.2x 10

6

1.4x 10

6

1.6x 10

6

1.8x 10

6

2.0x 10

6

2.2x 10

6

2.4x 10

6

100 W input Counts (cps) Energy (eV)

• 4
• 2

2 4 6 8 10 12 14 16 18 20 22 24 0.0 2.0x 10

4

4.0x 10

4

Argon, 50 mTorr, Power series, 0-25 eV

30 W 100 W 50 W 45 W 40 W 35 W 150 W 300 W 200 W Black: Ar+ Green: ArH+

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10 20 30 1x10

6

2x10

6

Counts (cps) Energy (eV)

10 20 30 500 1000 1500 2000 2500 3000 3500 4000

10 W absorbed : 7.2 W

ArH

+

Ar

+

10 20 30 1x10

6

2x10

6

C ounts (cps) Energy (eV)

10 20 30 1x10

2

2x10

2

3x10

2

4x10

2

5x10

2

6x10

2

7x10

2

8x10

2

9x10

2

1x10

3

1x10

3

1x10

3

1x10

3

50 W absorb ed : 3 6.6 W

ArH

+

Ar

+

10 20 30 1x10

6

2x10

6

C ounts (cps) Energy (eV)

10 20 30 1x10

3

2x10

3

3x10

3

4x10

3

5x10

3

6x10

3

60 W absorbed : 45.7 W

ArH

+

Ar

+

10 20 30 1x10

6

2x10

6

Counts (cps) Energy (eV)

10 20 30 0.0 5.0x10

3

1.0x10

4

1.5x10

4

2.0x10

4

2.5x10

4

3.0x10

4

3.5x10

4

4.0x10

4

4.5x10

4

5.0x10

4

5.5x10

4

6.0x10

4

6.5x10

4

80 W absorbed : 63.2 W

ArH

+

Ar

+

10 20 30 1x10

6

2x10

6

3x10

6

Count s (cps) Energy (eV)

10 20 30 0.0 2.0x 10

4

4.0x 10

4

6.0x 10

4

8.0x 10

4

1.0x 10

5

1.2x 10

5

1.4x 10

5

1.6x 10

5

100 W absorb ed : 8 3.7 W

ArH

+

Ar

+

10 20 30 1x10

6

2x10

6

Count s (cps) Energy (eV)

10 20 30 0.0 2.0x 10

4

4.0x 10

4

6.0x 10

4

8.0x 10

4

1.0x 10

5

1.2x 10

5

1.4x 10

5

1.6x 10

5

1.8x 10

5

2.0x 10

5

2.2x 10

5

2.4x 10

5

130 W absorbe d : 111.4 W

ArH

+

Ar

+

10 20 30 1x10

6

2x10

6

Counts (cps) Energy (eV)

10 20 30 0.0 2.0x10

4

4.0x10

4

6.0x10

4

8.0x10

4

1.0x10

5

1.2x10

5

1.4x10

5

1.6x10

5

200 W absorbed : 178 W

ArH

+

Ar

+

10 20 30 1x10

6

2x10

6

Count s (cps) Energy (eV)

10 20 30 0.0 2.0x 10

4

400 W absorbed : 360 W

ArH

+

Ar

+

10 20 30 1x10

6

2x10

6

Count s (cps) Energy (eV)

10 20 30 0.0 5.0x 10

4

1.0x 10

5

1.5x 10

5

2.0x 10

5

2.5x 10

5

3.0x 10

5

3.5x 10

5

4.0x 10

5

5 mTorr, argon plasma, power dependence

800 W absorbed : 695 W

ArH

+

Ar

+

7 W 37 W 46 W Black: Ar+ Green: ArH+ 84 W 63 W 111 W 178 W 360 W 695 W

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CONCLUSIONS

• Acceleration starts from center of plasma, in

both (!) axial directions.

• Ions gradually accelerate to Bohm speed.
• There is no real glow, just one big, symmetric

presheath.

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• Netherlands Technology Foundation (STW)
• Netherlands Organization for Scientific Research

(NWO)

• Center for Plasma Physics and Radiation Technology

(CPS)

• National Science Foundation (NSF)
• Semiconductor Research Corp. (SRC)

Acknowledgements