Depth-sensitive thin film reflectometer

Abstract

Quality control of microchemical products is based on the inspection of surface topography, film thickness and other optical constants. Especially for lab-on-chip applications, there is a strong demand for concurrent metrology and passive layer thickness observation. Chromatic confocal microscopy is a common method to reconstruct surface topographies, while thin film reflectometry is a technique for measuring film thicknesses. In this work, we present a combination of these two established techniques, simultaneously determining topography and film thickness. The proposed spectrometric measuring system captures confocal and thin film signals from a given sample. The extracted signals are analyzed according to a given model by a least-squares estimator in order to extract the parameters of interest. Finally, the sample's film thickness and topography are locally determined at the same time and with high precision. By scanning the sample surface laterally, both the surface topography and its film thickness can be reconstructed. The presented measurements performed at a test object exhibit excellent performance of the method.

On-Line Thickness Measurement for Two-Layer Systems on Polymer Electronic Devices

“…Figure 2a illustrates our measurement setup. A complete description of this measurement system is presented in [ 21 , 22 ]. In this setup, light from a spectrally broad source is coupled to a multimode fiber (Y-branch) and guided by two focusing lenses to the layer system at normal incidence.…”

“…The chromatic effect can be described through a function, c ( z ,λ), of the wavelength, λ, and the axial position, z , considering all system apertures. Figure 2b shows a set of chromatic functions for different values of z [ 22 ]. The chromatic effect on the reflectance can be described by multiplying both signals R (λ) · c ( z ,λ).…”

“…In the same way, we analyze the influence of the chromatic effect [ 21 , 22 ] introduced by the setup on the captured signal. This effect should be considered to avoid distortions in the measured results.…”

Spatially Multiplexed Micro-Spectrophotometry in Bright Field Mode for Thin Film Characterization

“…Optical techniques, such as imaging ellipsometry [ 6 , 7 , 8 ], white light interferometry [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ] and micro-spectrophotometry [ 17 , 18 , 19 , 20 , 21 , 22 ] are widely used experimental methods for thin film thickness characterization. These are nondestructive methods, they do not require any previous sample preparation and can easily achieve spatial lateral resolution in the micrometer range.…”

Infrared transmissometer to measure the thickness of NbN thin films

“…For example, Hirth et al [5] combine reflectometry and confocal microscopy to determine both film thickness and topography. Jafarfard et al [6] use dual--wavelength diffraction phase microscopy to determine the refractive index and the thickness spatial distribution of a sample, which requires the use of a laser, a transmission grating, a spatial filter and collimating and focusing optics.…”