Nanoscratch Testing of Thin Films Prepared by Plasma Polymerization from the Vapour Phase of Tetravinylsilane Monomer

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One of the most important properties that determined application possibilities of thin films is their adhesion to the substrate. Value of the critical load obtained by nanoscratch test is the normal force which is evaluated from the measured load curves and corresponding to the first significant lateral force component fluctuation which correlates with the adhesion failure of the film. In addition, this critical load is load at which the adhesive failure occurs in the scratch track observed by atomic force microscopy. Thin films of hydrogenated amorphous carbon-silicon (a-SiC:H) alloy were deposited on silicon wafers from tetravinylsilane (TVS) monomer by plasma-enhanced chemical vapor deposition (PECVD). The pretreatment of silicon wafers was carried out with argon or oxygen plasmas (10 sccm, 5.7 Pa, 5-200 W) using continuous wave for 10 min to clean the surface from adsorbed gases and reach reproducible adhesion of films. A mass flow rate of TVS used for film deposition was 3.8 sccm at a pressure of 2.7 Pa. Pulsed plasma was employed to deposit thin films at an effective power ranging from 2 to 150 W. Thin films of 0.1 μm thickness were tested by scratch test using a conical (90o) diamond tip (radius of 1 µm) with the peak load of 6 mN at a loading rate of 12 mN/min and using a scratch length of 10 μm. Measurements demonstrated that the scratch test resulted in the same values of the critical load over the entire surface of the samples regardless of the exact position on the sample. Good reproducibility of the film adhesion was found for the individual depositions. It was discovered that the critical load also does not depend on the loading rate. Different powers (5-200 W) applied for wafer pretreatment with argon or oxygen plasmas did not affect the film adhesion. We revealed that the critical load for a-SiC:H films increased with enhanced power from 1.6 mN (2 W) up to 4.6 mN (75 W) and was invariable for higher power 4.4 mN (150 W). No aging effects were observed in the first 850 days after film deposition.

PECVD, thin films, adhesion, nanoscratch test.

PLICHTA, T.; ČECH, V.

23. 3. 2017

Vysoké učení technické v Brně, Fakulta chemická

Purkyňova 464/118, 612 00 Brno

978-80-214-5488-0

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