Incoherent Optical Scatterometry (IOS) is a well-established metrology technique in the semiconductor industry to
retrieve periodic grating structures with high accuracy from the signature of the diffracted optical far field. With
shrinking dimensions in the lithography industry, finding possible improvements in wafer metrology is highly desirable.
The grating is defined in terms of a finite number of geometrical shape parameters (height, side-wall angles, midCD
etc.). In our method the illumination is a scanning focused spot from a spatially coherent source (laser) within a single
period of the grating. We present a framework to study the increment in sensitivity of Coherent Fourier Scatterometry
(CFS) with respect to the IOS. Under suitable conditions, there is a more than fourfold enhancement in sensitivity for
grating shape parameters using CFS. The dependence of scanning positions on the sensitivity analysis is also highlighted.
We further report the experimental implementation of a Coherent Fourier Scatterometer. The simulated and
experimental far fields are compared and analyzed for the real noise in the experimental configuration.
In this paper we start by presenting one recent development in the field of near field imaging where a lensless
microscope is introduced. Its operation principle is based upon wavelength encoding of the spatial information through
non periodic holes array and right after decoding the spatial information using a spectrometer. In the second part of the
paper we demonstrate a remote super sensing technique allowing monitoring, from a distance, the glucose level in the
blood stream of a patient by tracking the trajectory of secondary speckle patterns reflected from the skin of the wrist.
We present simulations and experimental results on encoding information both in the longitudinal and transverse
directions of an optical beam reflected from an asymmetric pit. The method does not require interferometric
detection but is based on intensity measurements using a simple quadrant detector. In addition, we also discuss
the implementation of this scheme in an optical recording setup and make an analysis of the crosstalk between
neighboring pits.
A new microscopy method for multi diffraction-limited spot illumination is based on extraordinary light transmission through a periodic metal grid (typical period of 600 nm) of sub-wavelength holes (150 nm). Multiple spots illuminate a fluorescently labeled sample and the emission is collected by far-field optics. Theoretical comparison with a confocal microscope reveals equivalent spot sizes and a scanning method with the advantage of multiple illumination spots. The system is used to measure the actual transmitted field with a fluorescent sample in far-field. The obtained results are consistent with the theoretical prediction and provide a proof of concept of the midfield microscope.
When light passes through a hole smaller than the wavelength of the light, the transmission is very low and the light is diffracted. This however changes if holes are arranged in a periodic array on metal. In that case the light couples to surface plasmons; this results in enhanced transmission, spectral selection and a small angular diffraction.
We develop a novel microscopic method based on a periodic hole-array, which will be used as a multiple-apertures near-field source for illuminating a biological sample while the light is collected in far-field. The measurement speed is high, due to the use of an array instead of a single source. The main advantage of this microscope originates from the low diffraction of light through a relatively thick sample with enhanced transmission. It results in the ability to measure the samples interior and 3D reconstruction can be made by semi-confocal techniques. This overcomes the major limitation of near-field methods for which only a shallow layer of the surface (~20 nm) is detectable.
For our measurements we use glass coated devices. The holes are processed with a focused ion beam. The photon-plasmon coupling process is characterized as a function of the wavelength. Our experiments aim on gaining a better understanding of the transmission process. We tested the dependence of the transmitted spectrum on angle of incidence was tested as well as far-field spectral imaging measurements of the transmission in both Koehler and collimated light illumination. The results as well as the description of the microscope that we are constructing are presented.
We report on the progress of a novel nanofluidic device for detecting and manipulating single molecules in solution. This paper discusses the development of an earlier proposed molecule separation method, where electrokinetic forces separate different molecules based on their masses and charges. Optical imaging using confocal microscopy is applied to perform the detection of the single molecules. Potential applications of this device will be assessed. This research aims for the high spatial and spectral resolutions, both in manipulation and detection, which can lead to molecular identification.
We present the latest progress on a novel technology for detecting and manipulating solution of single molecules in nanofluidic channels. This paper explains the design and fabrication of nanofluidic chip and its interface, molecule manipulation technique being used, and the optical detection method employed. Single molecule detections are performed using optical imaging as well as metal microelectrodes. The ultimate goal is to get high spatial and spectral resolutions that can lead to molecular identification.
Recently, an extraordinary transmission of light through small holes (<200 nm) in a thin metallic film has been described. This phenomenon has been shown to be the result of the photon-plasmon interaction in thin films where a periodic structure (such as a set of holes) is embedded in the film. One of the extraordinary results is that the beam that passes through a hole has a very small diffraction in extreme contrast to the wide angle predicted by diffraction theory.
Based on this effect, we propose here a new type of microscopy that we term mid-field microscopy. It combines an illumination of the sample through a metallic hole-array with far-field collection optics, a scanning mechanism and a CCD. When compared to other high resolution methods, what we suggest here is relatively simple because it is based on a thin metallic film with an array of nano-sized holes. Such a method can be widely used in high-resolution microscopy and provide a novel simple-to-use tool in many life-sciences laboratories.
When compared to near-field scanning optical microscopy (NSOM), the suggested mid-field method provides a significant improvement. This is chiefly for three reasons: 1. The penetration depth of the microscope increases from a few nanometers to a few micrometers, hence the name mid-field microscope. 2. It allows one to measure an image faster because the image is measured through many holes in parallel rather then through a single fiber tip used in conventional near-field microscopy, and 3. It enables one to perform three-dimensional reconstruction of images due to a semi-confocal effect.
We describe the physical basics of the photon-plasmon interaction that allows the coupling of light to the surface plasmons and determines the main spectral characteristics of the device. This mechanism can be ascribed due to the super-periodicity of the electron oscillations on the metallic surface engendered by the grating-like structure of the hole-array.
This paper presents a novel method for wafer-through interconnects via anisotropically etched groove in a (100)-silicon wafer. The idea is based on realization of interconnection lines on the inclined sidewalls of the anisotropically etched grooves, which are transferring the metallization to the backside of the wafer. The process itself is compatible with the standard semiconductor technology and can be applied at full wafer level, achieving in this way low packaging costs. All processes for interconnects are applied from the backside of the wafer at the packaging step, thus preserving the frontside of the wafer during processing from scratches and pollution. The key issue in the presented method is the photoresist coating of anisotropically etched grooves, which can be done by standard or electrodeposited photoresist. Further, methods to improve the photoresist uniformity over three-dimensional structures are discussed. Copper interconnects have been realized to show the feasibility of this wafer-through technique for frontside to backside electrical interconnections. Copper has been used for the metallization instead of aluminum. The thickness of the copper interconnects have been increased by copper electroplating to reduce further their electrical resistance and to increase their mechanical strength.
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