Feasibility study on polyparylene deposition in a PECVD reactor

Transcription

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 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,

2 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,

3 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,

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

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

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

7 Conventional deposition process F 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,

8 PECVD process F C PECVD P < 194 F < 90 C Erik v. Wahl Plasma Technology August 5 th,

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

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

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

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

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

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

15 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,

16 profilometer measurements temperature / C coating thickness / nm observations duration / min P / W ± 4.2 blocked by condensation ± 45.1 dust ± 188 resublimation on substrate before ignition, dust ± 10.7 dust ± 13.2 dust process pressure of 13.6 Pa Erik v. Wahl Plasma Technology August 5 th,

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

18 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 = m -3 Erik v. Wahl Plasma Technology August 5 th,

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

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

21 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,

22 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,

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

24 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,

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

26 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,

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

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

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

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

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. Erik v. Wahl Plasma Technology August 5 th,

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

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, (2009). [3] S. A. Khrapak et al., Phys. Rev. E 72, (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: , 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: , 1999 [9] H. Ketelsen, Diplomarbeit, Mie-Ellipsometrie an staubigen Plasmen, CAU 2009 [10] Erik v. Wahl Plasma Technology August 5 th,

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

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

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

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

38 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,