ISO 23216:2021 pdf free download – Carbon based films一Determination of optical properties of amorphous carbon films by spectroscopic ellipsometry.
This document provides a determination method and a classification for optical properties of amorphous carbon films by spectroscopic ellipsometry.
Amorphous carbon films have a structure, containing both sp2 and sp3 bonded carbon atoms and in several cases also hydrogen. There are graphite-like, polymer-like, glass-like and diamond-like carbon films. Because of their outstanding mechanical properties, amorphous carbon films are used in various hard coating applications on hard metals, e.g. as protective coatings against wear and corrosion in automotive parts. Biomedical and optical applications on alternative substrate materials such as silicon and glass have become more and more important. Currently, amorphous carbon films are classified into several types with regard to their chemical structures, and each type is selectively used according to its appropriate application. For an easy classification of amorphous carbon films, an optically quantified phase fingerprint with high accuracy is provided as a result of an international interlaboratory comparison.
The optical properties of refractive index n and extinction coefficient k determined by spectroscopic ellipsometry are the key quantities for the proposed classification of amorphous carbon films. The interlaboratory comparison demonstrated that a classification within the n-k plane is feasible for all types of amorphous carbon films. This will be beneficial for the identification of the coating type on alternative substrate materials (such as silicon and glass) and additional industrial applications. Spectroscopic ellipsometry as a fast and non-destructive analytical method can also be applied to quality control and development in industrial applications, given that smooth and well-defined substrate materials are used and appropriate modelling is applied.
This document is intended to implement recommended ellipsometric test conditions and the n-k plane classification scheme of amorphous carbon films on silicon wafers.
This document is useful for the complementary optical property classification and quality control of amorphous carbon films.
As amorphous carbon films show a huge diversity of structure and properties, it is crucial to select the appropriate type of amorphous carbon film to exploit their excellent properties in practical use. Therefore, carbon films are characterized by spectroscopic ellipsometry under reasonable conditions. This enables the classification of amorphous carbon films on silicon wafers within the n-k plane acting as a process fingerprint.
6.1 Treatment of specimen before test
Wash the specimens ultrasonically in a high purity organic solvent for 10 mm or longer, with the testing surface downward in the case of the disc specimen. Without allowing them to dry, the specimens should be rinsed with high purity organic solvent and then dried for 30 mm or longer in an oven set at 120 °C. Organic solvent can be replaced with other solvents or deionized water as long as clean specimen surfaces are produced at the end of the procedure. The specimens shall be stored, in the same atmosphere as that used for the testing apparatus, until required.
6.2 Preparation for test
Place the specimen for measurement on the stand and set it in place to be irradiated with the light. Adjust the stand height to allow the signal to be as strong as possible for detection.
6.3 Testing conditions for test
Recommended test conditions are listed below, but these may be changed to suit the particular needs of the measuring process. All test conditions shall be described in the test report.
a) Wavelength in measurement: 450 nm to 950 nm.
b) Angle of incidence: 70°.
c) Spot size: over 500 urn x 500 urn.
d) Duration of measurement: 5 s.
The test provides data for the angle of the ratio for the amplitudes of reflected p and s polarized lights, and the phase difference.
From the refractive index and extinction coefficient spectra, the values at or as close as possible to 550 nm should be used for amorphous carbon classification.