Transparent Thin Film Layers Research Articles

Surface and thickness measurement of transparent thin-film layers utilizing modulation-based structured-illumination microscopy.

In this research, an approach called modulation-based structured-illumination microscopy (MSIM) is proposed to measure the surface and thickness profile of thin film layers. With this method, a sinusoidal fringe pattern generated by digital micro-mirror devices (DMD) is projected on the sample. The modulation estimation of the reflected patterns is implemented for characterizing the surface and thickness profile of the sample. The measurement system is relatively simple and only an ordinary objective is enough to achieve imaging of the sample. In addition, the reflected signals come from the back surface of the film create less disturbance to the front surface compared with white-light interferometry. Consequently, they can be easily distinguished and achieve a successful measurement precisely. Both simulation and experiments are carried out to demonstrate the availability of this MISM method. The results are in excellent agreement with commercial stage profiler and the relative uncertainty is less than 10 nm.

Fabrication of unilateral conductive and transparent polymer thin films decorated with nanomaterials for flexible electrodes

Recently, electrically conductive, flexible, and transparent nanocomposite thin films consisting of nanomaterials on insulating polymer layers are of particular interest to scientific and industrial experts and have promising applications in energy, electronic, and environment areas, due to their remarkable properties. In this study, nanomaterials including silver nanowires, reduced graphene oxide, and carbon nanotubes, and also, conducting polymer poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate were embedded onto insulating polyamide 6‐based polymer layer to form unilateral (one‐sided) conductive nanocomposite thin film with advanced optical, electrical, and mechanical properties. Spin coating technique was used to fabricate these flexible, conductive, and transparent thin film layers. Thin conductive films decorated with silver nanowires exhibited sufficiently low sheet resistance of 105 Ω/sq with a transparency of ∼85%. The maximum measured stress and elongation was obtained as 2.24 N/mm2 and 12.5%, respectively. POLYM. COMPOS., 39:1771–1778, 2018. © 2016 Society of Plastics Engineers

Thickness and Surface Measurement of Transparent Thin-Film Layers using White Light Scanning Interferometry Combined with Reflectometry

Surface profiling and film thickness measurement play an important role for inspection. White light interferometry is widely used for engineering surfaces profiling, but its applications are limited primarily to opaque surfaces with relatively simple optical reflection behavior. The conventional bucket algorithm had given inaccurate surface profiles because of the phase error that occurs when a thin-film exists on the top of the surface. Recently, reflectometry and white light scanning interferometry were combined to measure the film thickness and surface profile. These techniques, however, have found that many local minima exist, so it is necessary to make proper initial guesses to reach the global minimum quickly. In this paper we propose combing reflectometry and white light scanning interferometry to measure the thin-film thickness and surface profile. The key idea is to divide the measurement into two states; reflectometry mode and interferometry mode to obtain the thickness and profile separately. Interferogram modeling, which considers transparent thin-film, was proposed to determine parameters such as height and thickness. With the proposed method, the ambiguity in determining the thickness and the surface has been eliminated. Standard thickness specimens were measured using the proposed method. Multi-layered film measurement results were compared with AFM measurement results. The comparison showed that surface profile and thin-film thickness can be measured successfully through the proposed method.

Internal profile measurement of GaAs microstructures based on near-infrared light phase-stepping interferometry

Internal profile nondestructive measurement of MEMS microstructures based on semiconductor materials is urgently demanded with the dramatic development of MEMS industry. A new attempt was made to extend the interferometric method and the thickness-profile measurement theory of transparent thin film layers from the visible light region (400–800 nm) to near-infrared light region (900–1700 nm). The measurement system based on Linnik interferometer using a near-infrared halogen light source with 1127 nm center wavelength was established for internal profile measurement. The measurement method for internal profile of GaAs microstructures was realized. From a comparison of reflection interferometry and transmission interferometry, it can be concluded that the latter measurement results were consistent with those of the former and internal profile was determined within an error range of 8%.

Spectrally resolved phase-shifting interferometry of transparent thin films: sensitivity of thickness measurements

Spectrally resolved white-light phase-shifting interference microscopy can be used for rapid and accurate measurements of the thickness profile of transparent thin-film layers deposited upon patterned structures exhibiting steps and discontinuities. We examine the sensitivity of this technique and show that it depends on the thickness of the thin-film layer as well as its refractive index. The results of this analysis are also valid for any other method based on measurements of the spectral phase such as wavelength scanning or white-light interferometry.

Spectrally resolved white–light phase–shifting interference microscopy for thickness–profile measurements of transparent thin film layers on patterned substrates

We describe how spectrally-resolved white-light phase-shifting interference microscopy with a windowed 8-step algorithm can be used for rapid and accurate measurements of the thickness profile of transparent thin film layers with a wide range of thicknesses deposited upon patterned structures exhibiting steps and discontinuities. An advantage of this technique is that it can be implemented with readily available hardware.

Thickness-profile measurement of transparent thin-film layers by white-light scanning interferometry

White-light scanning interferometry is increasingly used for precision profile metrology of engineering surfaces, but its current applications are limited primarily to opaque surfaces with relatively simple optical reflection behavior. A new attempt is made to extend the interferometric method to the thickness-profile measurement of transparent thin-film layers. An extensive frequency-domain analysis of multiple reflection is performed to allow both the top and the bottom interfaces of a thin-film layer to be measured independently at the same time by the nonlinear least-squares technique. This rigorous approach provides not only point-by-point thickness probing but also complete volumetric film profiles digitized in three dimensions.