Microstructure and properties of ultrathin amorphous silicon nitride protective coating

• Published in: Journal of vacuum science & technology. A, Vacuum, surfaces, and films Vol. 21; no. 6; pp. 1895 - 1904
• Main Authors: Yen, Bing K., White, Richard L., Waltman, Robert J., Dai, Qing, Miller, Dolores C., Kellock, Andrew J., Marchon, Bruno, Kasai, Paul H., Toney, Michael F., York, Brian R., Deng, Hong, Xiao, Qi-Fan, Raman, Vedantham
• Format: Journal Article
• Language: English
• Published: 01-11-2003
• Subjects: Si3N4
• ISSN: 0734-2101; 1520-8559
• DOI: 10.1116/1.1615974

The effect of N content on the structure and properties of rf reactively sputtered amorphous silicon nitride
(a-
SiN
x
)
has been studied by Rutherford backscattering spectrometry, x-ray reflectivity, ellipsometry, and nano-indentation. The N content in the film increased with the
N
2
concentration in the sputtering gas until the
Si
3
N
4
stoichiometry was reached. The hardness of
a-
SiN
x
increased with density, which in turn increased with the N content. The maximum hardness of 25 GPa and density of
3.2 
g/cm
3
were attained at the stoichiometric
Si
3
N
4
composition. With the application of a protective overcoat for magnetic disks in mind, thin
a-
SiN
x
films were deposited on CoPtCr media to examine their coverage, pinhole density, and wear resistance. According to x-ray photoelectron spectroscopy, the minimum thickness of
a-
SiN
x
required to protect the CoPtCr alloy from oxidation was 10 Å, which was 10 Å thinner than that of the reference amorphous nitrogenated carbon
(a-
CN
x
).
A statistic model showed this lower thickness required for
a-
SiN
x
can be attributed to its high density, which corresponds to 93% bulk density of
Si
3
N
4
.
Compared with 45 Å
a-
CN
x
coated disks, 15 Å
a-
SiN
x
coated disks had lower pinhole defect density and superior wear resistance.