Patterned surfaces which include semiconductor devices, optical components and other functional surfaces play important role in recent manufacturing. Optical measurements with non-destructive property is available for them but further improvement in spatial resolution and throughput are necessary. In this study, structured illumination microscopy was employed for high-resolution wide-field measurement. Structured illumination microscopy has been usually applied for fluorescent bio-imaging. For non-fluorescent imaging and industrial applications, one problem is speckle noise in structured illumination generation and another problem is vibration and thermal drift in high-precision positioning of laser-interference standing-wave illumination. In our development, the phase of the structured illumination is detected as a fringe signal with another interferometric measurement system, which is employed by structured illumination microscopy as originally developed; it uses a low-coherence light source for high-resolution and low-speckle imaging. We constructed an optical system consisting of plural Michelson interferometers, which allow the low-coherence interference fringes to be manipulated on a sample and the phase to be detected on another sensor. Feeding back the phase of structured illumination through super-resolution processing allows robust imaging despite vibrations, drifting, and environmental changes. A series of experiments were performed to verify our developed microscope system applied for measurement of patterned surfaces.
The low-coherence interferometry which is usually combined with the wide-field optical microscopy is well known technique for surface profile measurement, micro step measurement and so on. One of the problems is that its axial measurement range is typically limited by its depths of field of imaging, which is determined by the numerical aperture of their objective lens and the central wavelengths of their light source. If a low-coherence interference fringe is far outside the depth of field, the measurement accuracy inevitably decreases, regardless of how well adjusted the reference mirror is. To solve this problem and improve the axial measurement range of the low-coherence interferometry in this study, an object scanning measurement scheme involving a Linnik interferometer was developed. To calibrate the system in the proposed technique, image post-processing is performed for a well-conditioned state to ensure that a lowcoherence interference fringe is generated within the depth-of-field, so that three-dimensional objects with high-aspectratio structures can be scanned along the axial direction. During object scanning, this state is always monitored and corrected by adjusting the reference mirror. By using this scheme, the axial measurement range can be significantly improved up to the working distance of the objective lens without compromising the measurement accuracy. The working distance is typically longer than 10 mm, while the depth-of-field of the microscope is generally around 0.01 mm, although it varies depending on the imaging system. In this report, the experimental setup of an object scanning low-coherence interferometry is presented, a series of experimental verifications is described, and the results are discussed.
Digital zooming especially on microscopy image has attempted to improve their quality of measurement into a better assessment. However, since the field of view of high-resolution image are not wide despite of the fact that high-resolution image has more information detail and low-resolution image has their merits which is bring a big picture of the whole structure, we need to observe the sample in any scale. This problem was been solved by developing dual-view of high and low images resolution1 but in a single interpolated images. The goal of this research is utilize multi-resolution images to develop smooth zooming magnification of microscopy image. In order to achieve smooth zooming magnification on different condition of the images, scheme process will be needed. First, we took a several spatial images of the same sample based on the different objective lens, author was used 4 objective lens which are 10×, 20×, 50× and 150× magnification. In this synthesize phase, we interpolate lower resolution image for synthesize purpose with the next higher resolution image of the sample. Second, continue to looking for the feature point of both images with SIFT feature point method until we synthesize both images. Third, author treat this synthesized image with discrete fourier transform (DFT) with low-pass filter as the same size with numerical aperture (NA) that was input on the first phase. Then the fourth phase is looping this processes until intermediate images are generated enough to be blend with pyramid blend method. In this article we also try to make a system that can arbitrarily generate intermediate image with hierarchical system.
Light field microscope (LFM) is an optical microscope capable of obtaining images having large depth of field with different viewpoints. By using the parallax of these multi-view images, it is possible to reconstruct the 3D sample. However, the sampling interval of this multi-viewpoint image depends on the pitch interval of the microlens array, so the spatial resolution is low, and the accuracy of the 3D sample to be reconstructed is also low. Conventional research has a method of increasing the spatial resolution by subpixel-shifted multiple images. However, this method has problems such as the necessity of mechanical operation and high cost. Therefore, we propose applying Fourier ptychography to the LFM. Fourier ptychography is a technique to obtain high spatial resolution images by joining images obtained by irradiating samples from different angles using LED arrays in Fourier space. Fourier ptychography does not require mechanical scanning and is high throughput and low cost. In addition, Fourier ptycoography is possible to obtain phase information on a sample, and it is also possible to obtain a fine 3D sample. We propose a method to generate high spatial resolution multiview images using Fourier ptychography and reconstruct highly accurate 3D sample from those images. In this research, we experiment with the original LFM and verify the effect.
The resolving power in optical imaging is limited not only by optical diffraction but also by the sampling size, which in
turn is determined by the optical magnification and pixel size of the imaging devices such as CCD or CMOS. In order to
exceed these limits, we propose a method for improving the optical resolving power by using structured illumination
shift and multiple image reconstruction. Theoretical and experimental verifications reveal that the use of structured light
illumination together with successive approximation (which provides the extrapolation effect) causes the resolving
power of the proposed method to exceed the optical diffraction limit. Furthermore, we focused on subpixel sampling
using the structured illumination shift method. Subpixel image processing can improve the resolving power without
narrowing the visual field of the imaging optics. In addition, the proposed method can provide subpixel resolving power
without necessitating the mechanical displacement of the CCD camera. We investigated the relationship between the
CCD pixel size and the resolving power provided by the proposed method. We found that the subpixel spatial shift of the
structured illumination not only improves the optical resolving power but also enables sub-pixel sampling for optical
Semiconductor design rules and process windows continue to shrink, so we face many challenges in developing new
processes such as 300mm wafer, copper line and low-k dielectrics. The challenges have become more difficult because
we must solve problems on patterned and un-patterned wafers. The problems include physical defects, electrical defects,
and even macro defects, which can ruin an entire wafer rather than just a die. The optics and electron beam have been
mainly used for detecting of the critical defects, but both technologies have disadvantages. The optical inspection is
generally not enough sensitive for defects at 100nm geometries and below, while the SEM inspection has low throughput
because it takes long time in preparing a vacuum and scanning 300mm. In order to find a solution to these problems, we
propose the novel optical inspecting method for the critical defects on the semiconductor wafer. It is expected that the
inspection system's resolution exceed the Rayleigh limit by the method. Additionally the method is optical one, so we
can expect to develop high throughput inspection system. In the research, we developed the experimental equipment for
the super-resolution optical inspection system. The system includes standing wave illumination shift with the
piezoelectric actuator, dark-field imaging and super-resolution-post-processing of images. And then, as the fundamental
verification of the super-resolution method, we performed basic experiments for scattered light detection from standard
Semiconductor design rules and process windows continue to shrink, so we face many challenges in developing new processes such as 300mm wafer, copper line and low-k dielectrics. The challenges have become more difficult because we must solve problems on patterned and un-patterned wafers. The problems include physical defects, electrical defects, and even macro defects, which can ruin an entire wafer rather than just a die. The optics and electron beam have been
mainly used for detecting of the critical defects, but both technologies have disadvantages. The optical inspection is generally not enough sensitive for defects at 100nm geometries and below, while the SEM inspection has low throughput because it takes long time in preparing a vacuum and scanning 300mm. In order to find a solution to these problems, we propose the novel optical inspecting method for the critical defects using standing wave shift. This method is based on a super-resolution algorism in which the inspection system's resolution exceeds the diffraction limit by shifting standing wave with the piezoelectric actuator. Additionally this method is optical one, so we can expect to develop high throughput inspection system. In this report, we performed theoretical discussions and computer
simulations the defect detection on a patterned wafer. As a result, we succeeded in detecting the critical defects in the sub-90nm line and space interconnections.