Reactive high power impulse magnetron sputtering of CFx thin films in mixed Ar/C4F4 and Ar/C4F8 discharges
2013 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 542, 21-30 p.Article in journal (Refereed) Published
The reactive high power impulse magnetron sputtering processes of carbon in argon/tetrafluoromethane (CF4) and argon/octafluorocyclobutane (c-C4F8) have been characterized. Amorphous carbon fluoride (CFx) films were synthesized at deposition pressure and substrate temperature of 400 mPa and 110 degrees C, respectively. The CFx film composition was controlled in the range of 0.15 andlt; x andlt; 0.35 by varying the partial pressure of the F-containing gases from 0 mPa to 110 mPa. The reactive plasma was studied employing time averaged positive ion mass spectrometry and the resulting thin films were characterized regarding their composition, chemical bonding and microstructure as well as mechanical properties by elastic recoil detection analysis, X-ray photoelectron spectroscopy, transmission electron microscopy, nanoindentation, and water droplet contact angle measurements, respectively. The experimental results were compared to results obtained by first-principles calculations based on density functional theory. The modeling of the most abundant precursor fragment from the dissociation of CF4 and C4F8 provided their relative stability, abundance, and reactivity, thus permitting to evaluate the role of each precursor during film growth. Positive ion mass spectrometry of both fluorine plasmas shows an abundance of CF+, C+, CF2+, and CF3+ (in this order) as corroborated by first-principles calculations. Only CF3+ exceeded the Ar+ signal in a CF4 plasma. Two deposition regimes are found depending on the partial pressure of the fluorine-containing reactive gas, where films with fluorine contents below 24 at.% exhibit a graphitic nature, whereas a polymeric structure applies to films with fluorine contents exceeding 27 at.%. Moreover, abundant precursors in the plasma are correlated to the mechanical response of the different CFx thin films. The decreasing hardness with increasing fluorine content can be attributed to the abundance of CF3+ precursor species, weakening the carbon matrix.
Place, publisher, year, edition, pages
Elsevier , 2013. Vol. 542, 21-30 p.
c-C4F8, Tetrafluoromethane, Carbon tetrafluoride, Carbon fluoride, High power impulse magnetron sputtering, First principle calculations, X-ray photoelectron spectroscopy, Positive ion mass spectrometry
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-98146DOI: 10.1016/j.tsf.2013.05.165ISI: 000323859400005OAI: oai:DiVA.org:liu-98146DiVA: diva2:652291
Funding Agencies|Linkoping Linnaeus Initiative on Novel Functionalized Materials (VR)||Swedish Foundation for Strategic Research (SSF) Synergy Grant|RMA11-0029|Carl Trygger Foundation for Scientific Research||2013-09-302013-09-302016-08-31