This paper describes the lateral resolution enhancement of dynamic spectroscopic imaging ellipsometer, aiming to improve its inspection capabilities. Traditional imaging ellipsometers use a rotating optical elements type scheme which typically requires longer acquisition time. Moreover, for spectroscopic applications, an extra spectral scanning mechanism is needed. The proposed system based on a one-piece polarizing interferometric module, can efficiently extract spatio-spectral ellipsometric phase maps of two-dimensional (2D) materials with a spatial resolution of a few microns at a speed of hundreds of Hz.
Surface roughness(SR) of the EUV resists exposed to EUV, ArF and KrF radiation has been investigated using three tools: spectroscopic ellipsometry (SE), AFM and SEM. The purpose of this paper is to do determine whether SE can effectively monitor the change in resist SR, and also whether we can see the effect of photon shot noise in resist patterning. EUV resists were coated on three blank wafers, and on the shot basis, exposed to different dose of each radiation. After completion of resist process, the SR was measured first with SE. Then the wafer was sliced into patches of different dose before AFM and SEM measurements were made. SE used effective medium approximation to calculate the roughness-layer thickness as a parameter for fitting to experimental data. Thus obtained thicknesses showed a monotonic correlation with AFM-measured roughness, indicating SE can be a fast, precise and nondestructive tool to evaluate resist SR, once being calibrated with AFM. In order to examine the photon shot noise effect on the resist pattern, all the steps of the resist process was kept the same except the exposure wavelength and its dose. SE results for the three exposures were compared over the full range of doses in common. The three roughness values near the dose to clear, Eclear, apparently provide an evidence that the photon shot noise played a significant role in our experiment.
We present the application of ellipsometry to the phase measurement of surface plasmon resonance (SPR) in
biomolecular detection. In this work, the experimental setup for the SPR sensor was based on a custom-built rotating
analyzer ellipsometer, which was equipped with a SPR cell and a microfluidic system. We investigate the sensitivity of
SPR sensor which is dependent on the thickness and roughness of metal film, alignment of optical system, and stability
of microfluidics. In the drug discovery process, to directly monitor the interaction of small molecule-protein, it is
necessary to design a high-sensitivity SPR sensor with a sensitivity of greater than 1 pg/mm2. Our sensor demonstrates a
much better sensitivity in comparison to other SPR sensors based on reflectometry or phase measurements. The results of
calibration indicate that the phase change, δ▵, had an almost linear response to the concentration of ethanol in the
double-distilled water solutions. A quantitative analysis of refractive index variation was possible using the results of the
ellipsometric model fits for the multilayered thin film on the gold film. Thus, this method is applicable not only to sensor
applications, such as affinity biosensors, but also to highly sensitive kinetics for drug discovery. In this paper, we
demonstrate how a custom-built rotating analyzer ellipsometer in the SPR condition can be used to directly obtain the
interactions and binding kinetics of analytes (biotins, peptides) with immobilized ligand (streptavidin, antibody). We
achieved a detection limit of lower than 1.0 x10-7 RIU, which is the equivalent of 0.1 pg/mm2.
We describe a novel real time optical 3D nanoscope scheme that can be applied for both metrology and inspection in
various semiconductor fields. Since the proposed off-axis scheme based on a matched filter correlation method basically
measure the phase information of a nano object, the proposed scheme has some benefits in terms of sensitivity in both
3D geometry measurement and defect inspection capability. In this study, the feasibility of the proposed scheme has
been evaluated by combining the conical diffraction and wave propagation simulation codes.
We present the application of ellipsometry to the phase measurement of surface plasmon resonance (SPR) in biomolecular detection. In this configuration, the phase measurement gives a large enhancement of detection sensitivity in comparison to traditional SPR techniques. In this work, the experimental setup for SPR ellipsometry is based on both custom-built rotating analyzer ellipsometer and an imaging ellipsometer which are equipped with a SPR-cell and a flow system, respectively. We investigate the adequate thickness of the gold layer used for SPR cell and the resolution of the phase detection using two ellipsometric methods under the SPR condition. The rotating analyzer method yields higher sensitivity sufficient to detect changes in the effective thickness of biomolecular layers of less than 1 pm. In comparison to conventional SPR the simultaneous measurement of ellipsometric parameters, Δ and ψ, yields more information
which is useful for quantitative analysis based on fitting theoretical solutions to experimental results.
We present imaging ellipsometry technique for kinetic measurement of bimolecular interactions with high sensitivity. When combined with surface plasmon resonance (SPR) effects, the ellipsometry becomes powerful technique for analyzing adsorption and desorption of biomolecules on gold layer based sensor chip surfaces. Because ellipsometric measurement gives ellipsometric parameters, namely Δ, that is very sensitive to surface layer changes. The SPR combined ellipsometry is realized by Kretschmann configuration SPR cell comprising with about 30-nm-thick gold film deposited on top of glass slides, SF10 glass prism, and flow injection system. We used nulling type of imagining ellipsometer to acquire two dimensional ellipsometric parameters with spatial resolution down to one micrometer. We present results of kinetic measurements of biotin-streptavidin interactions for custom-built sensor chip.
Ellipsometry is known as high precision metrology for thin film thickness measurements with sub-angstrom resolution. In ellipsometric measurements it does not measure film thickness or optical constants directly. It measures ellipsometric parameters, ψ and Δ, namely, defined as the ratio of reflection coefficients for p- and s-polarized light. Generally in rotating component ellipsometry, light intensity values at more than 256 angular positions of polarizer or analyzer with discrete Fourier transform methods are used to evaluate Fourier coefficients, which can be calculated to ellipsometric parameters explicitly. Using this scheme it is well suited in single point measuring ellipsometry, but it degrades measurement speed in imaging ellipsometry. In imaging ellipsometry due to the limitation in CCD detection speed, rotating components must move stepwisely, so more discrete positions of polarizer or analyzer takes more measurement time dramatically. So we propose four frame method which can be easily substituted for conventional discrete Fourier transform methods. Four frame method can save measurement time, but natively intensity measurements at only four angular positions can cause erroneous results in Fourier coefficients compared with that of discrete Fourier transform method. In the four frame method, many repetitive measurements for light intensity at each angular position can solve these shortcomings. That is, conceptually to reduce random noise in ellipsometric measurements, conventional discrete Fourier transform method uses spatial averaging technique, but four frame method uses temporal averaging technique. In our experiments we could get more than ten times fast measurements with four frame method.
The ellipsometry is known as high precision metrology for thin film thickness measurements and its optical properties by measuring ellipsometric parameters, ψ and Δ, defined as amplitude and phase values of the ratio of Fourier reflection coefficients for p- and s-polarized light. With conventional ellipsometers, we can get average values of ellipsometric parameters in the region of interest determined by spot size of measurement beam. However, we can expand the measurement scheme to two dimensional spectral imaging with additional imaging spectrograph compatible to the structure of ellipsometer. That is, we can simultaneously get spatial and spectroscopic ellipsometric parameters using two dimensional imaging detectors. Using this type of ellipsometers, polarization state dependent response of imaging spectrograph must be considered carefully during azimuth calibration procedures as well as ellipsometric parameters measurement. In this paper, we suggest Jones calculus model for ellipsometer with considering dichroic response in spectrograph and background signal levels in detector. And we show experimental calibration results comparison with that of simulation using suggested Jones calculus model.
We investigated the optical properties of titanium dioxide (TiO2) thin films which were deposited by ion beam assisted deposition (IAD) method on crystalline silicon and acrylic substrates. TiO2 thin films were grown by different growing conditions which are used the conditions of vacuum pressure, and deposition rate. The controlled vacuum pressure were 3 x 10-5Torr and 3 x 10-6 Torr, and the deposition rate was controlled to 0.35 nm/second, 0.20 nm/second, and 0.12 nm/second. Measurements of spectroscopic ellipsometry were performed in the spectral range between 0.76 eV and 8.7 eV with 0.02 eV steps and at the angle of incidence of 75°. We determined the complex refractive index and thickness of TiO2 thin films using the optical model which is included the Tauc-Lorentz dispersion equation and compared the relations between the optical properties and deposition rate or vacuum pressure variation. The optical band gaps of TiO2 thin films are around 3.42 eV.
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