Feasibility study on polyparylene deposition in a PECVD reactor

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 1 IEAP, Group Plasma Technology, University of Kiel 2 ITAP, University of Kiel 3 INP Greifswald 4 th Graduate Summer Institute ''Complex Plasmas'' August 5 th, 2014 Plasma Technology Erik v. Wahl Plasma Technology August 5 th, 2014 1

outline 1. Introduction to parylene 2. The setup 3. Langmuir probe measurements 4. Electrical measurements 5. REM 6. Contact angle measurements Erik v. Wahl Plasma Technology August 5 th, 2014 2

Parylene Illustrations: SCS Specialty Coating Systems crevice penetrating UV stable Group of polymers properties can be tuned by choosing substituents low permeability to moisture and corrosive gases low permeability to moisture and corrosive gases good temperature stability crevice penetrating high temperature applications long-term UV stability Erik v. Wahl Plasma Technology August 5 th, 2014 3

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 homogeneous coatings Erik v. Wahl Plasma Technology August 5 th, 2014 4

Parylene Pictures: SCS Specialty Coating Systems Erik v. Wahl Plasma Technology August 5 th, 2014 5

Parylene Group of polymers properties can be tuned by choosing substituents Erik v. Wahl Plasma Technology August 5 th, 2014 6

Conventional deposition process 1100-1300 F 600-700 C the precursor - a dimer < 194 F < 90 C highly reactive monomer parylene C - a linear polymer Erik v. Wahl Plasma Technology August 5 th, 2014 7

PECVD process 1100-1300 F 600-700 C PECVD P < 194 F < 90 C Erik v. Wahl Plasma Technology August 5 th, 2014 8

PECVD process Investigations: analyse deposited films - profilometer measurements - electron microscopy - contact angle measurements 1100-1300 F 600-700 C PECVD P < 194 F < 90 C analyse plasma process - langmuir measurements - electrical measurements Erik v. Wahl Plasma Technology August 5 th, 2014 9

ATILA capacitively coupled rf-discharge evaporator 4 vacuum gauges Erik v. Wahl Plasma Technology August 5 th, 2014 10

ATILA - substrates silicon wafer glas plates metal plates Erik v. Wahl Plasma Technology August 5 th, 2014 11

ATILA silicon wafer holder Erik v. Wahl Plasma Technology August 5 th, 2014 12

substrate positioning a b c d (outside of intense plasma glow) c b Erik v. Wahl Plasma Technology August 5 th, 2014 13

Sublimation of the precursor too cold too warm Erik v. Wahl Plasma Technology August 5 th, 2014 14

profilometer measurements too less precursor: negative step sputtering dominates too much precursor: positive step dust formation (easily removable) Erik v. Wahl Plasma Technology August 5 th, 2014 15

profilometer measurements temperature / C coating thickness / 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 Erik v. Wahl Plasma Technology August 5 th, 2014 16

langmuir probe measurements probe box pickup-probe for passive rf-compensation ceramic / glas probe tip Erik v. Wahl Plasma Technology August 5 th, 2014 17

langmuir probe measurements U fl = 14,8 V U pl = 35,3 V 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 Erik v. Wahl Plasma Technology August 5 th, 2014 18

langmuir probe measurements during deposition process 20 sccm argon, P = 10W, p = 10,5Pa Erik v. Wahl Plasma Technology August 5 th, 2014 19

langmuir probe measurements during deposition process 20 sccm argon, P = 10W, p = 10,5Pa Erik v. Wahl Plasma Technology August 5 th, 2014 20

langmuir probe measurements during deposition process 20 sccm argon, P = 10W, p = 10,5Pa 212 F 100 C Erik v. Wahl Plasma Technology August 5 th, 2014 21

langmuir probe measurements during deposition process probe tip dirty shape of drop at probe tip different kinds of coating Erik v. Wahl Plasma Technology August 5 th, 2014 22

electrical measurements 161 F 212 F 130 F Erik v. Wahl Plasma Technology August 5 th, 2014 23

electrical measurements 161 F 212 F 130 F coating of window increase in resistivity inelastic collisions decrease of n e collisions with particles Erik v. Wahl Plasma Technology August 5 th, 2014 24

electrical measurements 161 F 212 F 130 F Erik v. Wahl Plasma Technology August 5 th, 2014 25

electrical measurements 196 F periodical particle formation 210 F continous particle formaiton? emission intensity also fluctuating resistivity increasing, when V bias decreasing Erik v. Wahl Plasma Technology August 5 th, 2014 26

scanning electron microscopy Erik v. Wahl Plasma Technology August 5 th, 2014 27

Institute of Experimental and Applied Physics, University of Kiel scanning electron microscopy Erik v. Wahl Plasma Technology August 5th, 2014 28

contact angle measurements parylene coating total energy σ total = 64.54 ± 23.25 mn/m dispersive energy σ d = 7.35 ± 13.30 mn/m polar energy σ p = 57.19 ± 19.07 mn/m problem: dust changes the surface energy can be used to gain superhydrophoby or superhydropholy Erik v. Wahl Plasma Technology August 5 th, 2014 29

electrical measurements 161 F 212 F 130 F Erik v. Wahl Plasma Technology August 5 th, 2014 30

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. Erik v. Wahl Plasma Technology August 5 th, 2014 31

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. Thank you very much for your attention! Erik v. Wahl Plasma Technology August 5 th, 2014 32

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] Erik v. Wahl Plasma Technology August 5 th, 2014 33

deposition of parylene in ATILA Erik v. Wahl Plasma Technology August 5 th, 2014 34

langmuir probe measurements power dependence Argon p = 6,4Pa Erik v. Wahl Plasma Technology August 5 th, 2014 35

langmuir probe measurements pressure dependence Argon P = 10W Erik v. Wahl Plasma Technology August 5 th, 2014 36

Die Selfbias-Spannung Plasma zünden Wände werden beschichtet Precursor wird verbraucht, Druck sinkt Erik v. Wahl Plasma Technology August 5 th, 2014 37

Die Selfbias-Spannung aus [A. Keudell, Vorlesungsskript, 2012] V bias ist empfindlicher Indikator für eine Beschichtung der Wände mit einem Dielektrikum Erik v. Wahl Plasma Technology August 5 th, 2014 38