SiNx Coatings Deposited by Reactive High Power Impulse Magnetron Sputtering: Process Parameters Influencing the Nitrogen Content

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• 作者：Susann Schmidt ; Tuomas Hänninen ; Cecilia Goyenola ; Jonas Wissting ; Jens Jensen ; Lars Hultman ; Nico Goebbels ; Markus Tobler ; Hans Högberg
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2016
• 出版时间：August 10, 2016
• 年：2016
• 卷：8
• 期：31
• 页码：20385-20395
• 全文大小：597K
• 年卷期：0
• ISSN：1944-8252

文摘

Reactive high power impulse magnetron sputtering (rHiPIMS) was used to deposit silicon nitride (SiN_x) coatings for biomedical applications. The SiN_x growth and plasma characterization were conducted in an industrial coater, using Si targets and N₂ as reactive gas. The effects of different N₂-to-Ar flow ratios between 0 and 0.3, pulse frequencies, target power settings, and substrate temperatures on the discharge and the N content of SiN_x coatings were investigated. Plasma ion mass spectrometry shows high amounts of ionized isotopes during the initial part of the pulse for discharges with low N₂-to-Ar flow ratios of <0.16, while signals from ionized molecules rise with the N₂-to-Ar flow ratio at the pulse end and during pulse-off times. Langmuir probe measurements show electron temperatures of 2–3 eV for nonreactive discharges and 5.0–6.6 eV for discharges in transition mode. The SiN_x coatings were characterized with respect to their composition, chemical bond structure, density, and mechanical properties by X-ray photoelectron spectroscopy, X-ray reflectivity, X-ray diffraction, and nanoindentation, respectively. The SiN_x deposition processes and coating properties are mainly influenced by the N₂-to-Ar flow ratio and thus by the N content in the SiN_x films and to a lower extent by the HiPIMS frequencies and power settings as well as substrate temperatures. Increasing N₂-to-Ar flow ratios lead to decreasing growth rates, while the N content, coating densities, residual stresses, and the hardness increase. These experimental findings were corroborated by density functional theory calculations of precursor species present during rHiPIMS.