tpw2010_session1talk4

8th Technological Plasma Workshop

Thurs. 6th Jan. '11, 14:35

The effect of 'reflux' (ions from etch products) in a

microwave source Ar/HBr silicon-etch process.

Dr. James Munro

Prof. Jonathan Tennyson,

Mr. Stephen Harrison

Dr. Song-Yun Kang

Global Model

Electron Chemistry

Reactor Model

Process and Tool

Development

Measurement,

Experimentation

Data Data

Informs Informs Validates Validates

Modeling polyatomic electron-molecule interactionsWhat does Quantemol-N do?

Elastic cross sections Electronic excitation cross sections Electron impact dissociation Rates Resonance parameters Ionisation cross sections Dissociative electron attachment Differential cross sections Momentum transfer cross sections Vibrational excitation cross sections

Tennyson et. al., J. Phys. Conf. Ser. 86, 012001 (2007)‏

Recent Additions v3.8:

o Atomic cross-sections

o High energy excitation cross-sections

Methane

The R-Matrix Method• The sphere, of radius a, has

the centre of mass of the molecule as its origin;

• the sphere contains the electron cloud of the molecule;

• equations of motion are solved in the body-fixed frame (fixed nuclei approximation)‏

r

e-

How does Quantemol-N work?

Tennyson, Phys. Rep. 491 (2010) 29-76

CF2 C6H6 C5H12 SiH4

Cl2 C3H4 NO2 C2H6

O2 C2 NO C3H8

H2O C3H6 O3 HCN

H3+ CaF+ PH3 HNC

CH4 CaF BF3 SiO

C3N CF N2 CS

Cl2O CO2 CO F2

CONH3 BF3 H2 HBr

Progress...

... and more.

CF4/O2 CCP etch

0-D plasma simulation CCP etching chamberSCCM

Simulation

0.0E+00

2.0E+11

4.0E+11

6.0E+11

8.0E+11

1.0E+12

1.2E+12

1.4E+12

1.6E+12

1.8E+12

2.0E+12

0 500 1000 1500 2000

Power (W)

CF2 (

#/cm

3)

Original

CF2*

0.0E+00

1.0E+11

2.0E+11

3.0E+11

4.0E+11

5.0E+11

6.0E+11

7.0E+11

8.0E+11

9.0E+11

0 500 1000 1500 2000

Power (W)

CF (

#/cm

3)

Original

CF2*

0.0E+00

2.0E+13

4.0E+13

6.0E+13

8.0E+13

1.0E+14

1.2E+14

1.4E+14

0 500 1000 1500 2000

Power (W)

F (

#/cm

3)

Original

CF2*

CF2

CF

F

T. Mori, M.Sasaki, T Nishizuka and T. Nozawa, 55th AVS, PS-TuM10

13Reaction model

-Charged species: e-, Br-, Ar+, HBr+, Br+, Br2+, SiBr2

+, and SiBr+

-Neutral species: Ar, Ar*, HBr, Br, Br2, H2, H, SiBr2, SiBr, and Si

-Electron impact reactions: Ionization, excitation, dissociation,

attachment, and recombination

-Ion – neutral reactions

-Ion – ion reactions

-Molecule – molecule reactions

SiBr2+, SiBr+, SiBr, and Si are omitted in case

without SiBrx reactions.

14

Ar/Cl2 = 90/10 sccm

500 W ICP

15mTorr

Re-flux of SiCl2+ was

important but was not

dominant at this lower

pressure.

Agarwal A. & Kushner M.

JVSTA 26 (2008) 498

15

SiBr49 Electrons

Bond length: 2.641 Ang.

0.1

1

10

100

1000

0 2 4 6 8 10 12 14 16 18 20

Cross -

secti

on

(an

g.

sq

rd

.)

Energy (eV)

Ionisation Elastic

Dissociative impact Dissociative Attachment

e + SiBr >

SiBr284 Electrons

Bond length: 2.039 Ang.

Bond Angle: 122.8 Deg.

1E-06

1E-05

0.0001

0.001

0.01

0.1

1

10

100

1000

10000

0 2 4 6 8 10 12 14 16 18 20

Cro

ss

-secti

on

(an

g.

sq

rd.)

Energy (eV)

Elastic Dissociative impact

Dissociative Attachment Ionisation

e + SiBr2 >

19

Open

H

Br

H

H

Br

H

Br

Br

H2

HBr

HBr

Br2

Surface reactions with Walls

20

Si

SiBrSiBr2

SiBr

Br

H HBr

Ion SiBrIon SiBr2

SiBr2

Br2

SiH

SiBr

Br

Br2 Br

H HBr

SiBr SiBr2

Si SiBr

HH H2

Br HBr

Surface reactions with wafer

SiBrSiBrSiSiSiBrSiBrSiSiBrSiBriisER 22

/

21 Simulation model

• Comsol• Incompressible Navier-Stokes (INSM)

• Convection and diffusion transport (CDTM)

• Convection and conduction heat transport (CCHT)

• Transverse electromagnetic wave propagation (TEM)

• Gas flow

• Electron temperature

• Charged particles

• Neutral particles

Same model for Si2H6 & NH3 PECVD:

Jozef Brcka, Song-Yun Kang,

Plasma Process. Polym. 2009, 6, S776–S783

22

Microwave

Wafer

Stage with rf bias

Gases

inlet

Pumping

out

Gas flow

23e- Br- SiBr2

With

SiBrx

reactions

Without

SiBrx

reactions

Electron distributions are localized near top, because microwave heat comes from top.

Br negative ion produced both inlet and near wafer because of attachment reaction of SiBrx.

SiBr2 in case with SiBrx reactions is localized near wafer because there are reactions of SiBr2.

5.0e11

Number is

maximum

[#/cm3]

1.6e13

4.6e111.5e13

1.9e13

6.6e13

100 mTorr

24 SiBr Si

SiBr2+ SiBr+

SiBr2

SiBr and Si are produced from SiBr2 and SiBr respectively.

Ions produced from byproducts are localized near wafer which is dominant ions attack to

wafer.

1.8e13

Number is

maximum

[#/cm3]

1.9e13

2.3e11

5.7e12

4.7e11

100 mTorr

25

0.0E+00

1.0E+15

2.0E+15

3.0E+15

4.0E+15

5.0E+15

Ar+ Br+ HBr+ SiBr+ Br2+ SiBr2+

Flu

x (#

/cm

2 s

)

40

70

80

100

0.0E+00

5.0E+15

1.0E+16

1.5E+16

2.0E+16

2.5E+16

Ar+ Br+ HBr+ SiBr+ Br2+ SiBr2+

Flu

x (#

/cm

2 s

)

40

70

80

100

Ion fluxes on wafer

Including SiBrx

reactions

Without SiBrx

reactions

26

o Ion mass gets heavier as pressure

increases

o Ion fluxes and energies will change

significantly with pressure in this

collisional sheath.

0

30

60

90

120

150

180

0 50 100 150

Pressure (mTorr)

Ave

rage

mas

s of

ions

with SiBr2 reaction

without SiBr2reactions

27

Specific conclusions:

o SiBr1,2 molecular data is critical in the correct understanding

of this etch process.

o SiBr1,2 ions are important in determining the etch profile and

have pressure dependant concentrations (and therefore

fluxes and energies).

o Cross-sections with SiBr4 and SiBr3 could be included.

o SiBr3,4 are not expected to be important etch products

o Ions of SiBr3,4 could be important however.

General conclusions:

o The availability of molecular data is critical to understanding

the gas-phase.

o ...and therefore what arrives at the surface.

o Cross-sections can and have been calculated on demand for

these applications.

Thank you for listening

With thanks also to:

Dr. Josef Brcka & Dr. Song-Yun Kang (for 2D Comsol model)

T. Mori, M.Sasaki, T Nishizuka & T. Nozawa (for experiment)

Brought to you by:

Dr. James Munro

Prof. Jonathan Tennyson,

Mr. Stephen Harrison

Dr. Song-Yun Kang

tpw2010_session1talk4

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