Feasibility study on polyparylene deposition in a PECVD reactor

(1)

Institute of Experimental and Applied Physics

Feasibility study on polyparylene

deposition in a PECVD reactor

E. v. Wahl

1

_{, C Kirchberg}

2

_{, M. Fröhlich}

3

_{, H. Kersten}

1

4

th

_{Graduate Summer Institute ''Complex Plasmas''}

August 5

th

_{, 2014}

1_{IEAP, Group Plasma Technology, University of Kiel} 2_{ITAP, University of Kiel}

(2)

Erik v. Wahl _{Plasma Technology} August 5th_{, 2014 2}

outline

1. Introduction to parylene

2. The setup

3. Langmuir probe measurements

4. Electrical measurements

5. REM

(3)

Parylene

Group of polymers

properties can be tuned by

choosing substituents

Illustrations: SCS Specialty Coating Systems

crevice penetrating

UV stable

low permeability to

moisture and corrosive

gases

crevice penetrating

high temperature applications

low permeability to moisture and

corrosive gases

(4)

Parylene properties

Illustrations: SCS Specialty Coating Systems

transparent

hydrophobic

low friction coefficient

low gas permeability

biostable

biocompatible

high chemical resistivity

oxidation resistant up to 350

°

C / 662

°

F

(5)

Parylene

(6)

Parylene

Group of polymers

properties can be tuned

by choosing substituents

(7)

Conventional deposition process

1100 - 1300

°

F

600 -700

°

C

< 194

°

F

< 90

°

C

the precursor -

a dimer

highly reactive

monomer

parylene C -

a linear polymer

(8)

PECVD process

P

PECVD

1100 - 1300

°

F

600 -700

°

C

< 194

°

F

< 90

°

C

(9)

PECVD process

P

PECVD

Investigations:

analyse deposited films

- profilometer measurements

- electron microscopy

- contact angle measurements

analyse plasma process

- langmuir measurements

- electrical measurements

1100 - 1300

°

F

600 -700

°

C

< 194

°

F

< 90

°

C

(10)

ATILA

capacitively coupled

rf-discharge

evaporator

4 vacuum gauges

(11)

ATILA - substrates

silicon wafer

glas plates

metal plates

(12)

(13)

substrate positioning

a

b

c

d

(outside of intense

plasma glow)

b

c

(14)

Sublimation of the precursor

too

cold

too

warm

(15)

profilometer measurements

too less precursor:

• negative step



sputtering dominates

too much precursor:

• positive step

• dust formation (easily

removable)

(16)

profilometer measurements

temperature /

°

C

coating thick-

ness / nm

observations

duration

/ min

P / W

148…150

- 43.3

±

4.2 blocked by condensation

30

10 200…220

- 162.6

±

45.1 dust

15

30 185…190

6430

±

188 resublimation on substrate

before ignition, dust

10

20 130…157

72.3 ±

10.7 dust

20

20 120…155

388.8 ±

13.2 dust

110

30 process

pressure of

13.6 Pa

(17)

langmuir probe measurements

pickup-probe for passive

rf-compensation

probe tip

ceramic / glas

probe box

(18)

langmuir probe measurements

argon

p

_Baratron

= 6.4 Pa

P

= 10 W

V

_bias

= 273 V

T

_e

= 2.63 eV

n

_e

= 9.6∙10

15 _m

-3

U

_fl

= 14,8 V U

_pl

= 35,3 V

(19)

langmuir probe measurements during deposition process

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langmuir probe measurements during deposition process

(21)

20 sccm argon, P = 10W, p = 10,5Pa

langmuir probe measurements during deposition process

212 °

F

100 °

C

(22)

langmuir probe measurements during deposition process

probe tip dirty

shape of drop at probe tip

different kinds of coating

(23)

electrical measurements

(24)

electrical measurements

coating of window

increase in resistivity

→ inelastic collisions

→

decrease of n

_e

→

collisions with particles

(25)

electrical measurements

(26)

electrical measurements

continous

particle formaiton?

periodical particle formation

emission intensity also fluctuating

resistivity increasing, when V

_bias

decreasing

210 °F

(27)

(28)

(29)

contact angle measurements

problem:

dust changes the surface

energy

can be used to gain

superhydrophoby or

superhydropholy

parylene coating

total energy σ

total

= 64.54

±

23.25 mN/m

dispersive energy σ

d

= 7.35

±

13.30 mN/m

(30)

electrical measurements

(31)

summary

The properties of depositing parylene are strongly

dependent on the temperature at which sublimation

occurs.

Polymerisation took place.

Low discharge power is enough to initialize

polymerisation.

No undesired byproducts / chemical decompounds

could be found.

(32)

outlook

More deposition trials are needed in order to obtain a

clean thin film deposition.

Contact angle measurements have to be done on

samples without dust.

Mass spectrometry could give an insight into the chemical

reactions.

(33)

literature

[1] Phil Morten Hundt, Diplomarbeit,

Spektroskopische Diagnostik an Prozessplasmen

,

CAU 2009

[2] J. Berndt, E. Kovacevic, I. Stefanovic, O. Stepanovic, S. H. Hong, L. Boufendi and J.

Winter,

Some Aspects of Reactive Complex Plasmas

. Contrib. Plasma Phys., vol.

49,

107–133 (2009).

[3] S. A. Khrapak et al., Phys. Rev. E 72, 016406 (2005)

[4] Hollenstein, Ch.:

The physics and chemistry of dusty plasmas

. Plasma Physics and

Controlled Fusion, 42:R93–R104, 2000

[5] Bouchoule, A. (Herausgeber):

Dusty Plasmas - Physics, Chemistry and Technological

Impacts in Plasma Processing

. Wiley-VCH Verlag, 1999

[6] Cui, C. und J. Goree:

Fluctuations of the charge on a dust grain in a plasma

. IEEE

Transactions on Plasma Science, 22:151–158, 1994

[7] Patrick Sadler, Diplomarbeit,

Partikelbildung in reaktiven Plasmen unter Verwendung

kohlenwasserstoffhaltiger bzw. siliziumorganischer Precursoren,

CAU

2010

[8] Kortshagen, U. und U. Bhandarkar:

Modeling of particulate coagulation in low

pressure plasmas

. Physical Review E, 60:887–898, 1999

[9] H. Ketelsen, Diplomarbeit,

Mie-Ellipsometrie an staubigen Plasmen,

CAU 2009

[10]

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(35)

langmuir probe measurements – power dependence

(36)

Argon P = 10W

(37)

Die Selfbias-Spannung

Precursor wird „verbraucht“, Druck sinkt

(38)

Die Selfbias-Spannung

aus [A. Keudell, Vorlesungsskript, 2012]

V

_bias

ist empfindlicher Indikator für eine Beschichtung der

Wände mit einem Dielektrikum