593 results about "Diffraction order" patented technology

An alignment system uses a self-referencing interferometer that produces two overlapping and relatively rotated images of an alignment markers. Detectors detect intensities in a pupil plane where Fourier transforms of the images are caused to interfere. The positional information is derived from the phase difference between diffraction orders of the two images which manifests as intensity variations in the interfered orders. Asymmetry can also be measured by measuring intensities at two positions either side of a diffraction order.

Methods and systems for performing measurements of semiconductor structures and materials based on scatterometry measurement data are presented. Scatterometry measurement data is used to generate an image of a material property of a measured structure based on the measured intensities of the detected diffraction orders. In some examples, a value of a parameter of interest is determined directly from the map of the material property of the measurement target. In some other examples, the image is compared to structural characteristics estimated by a geometric, model-based parametric inversion of the same measurement data. Discrepancies are used to update the geometric model of the measured structure and improve measurement performance. This enables a metrology system to converge on an accurate parametric measurement model when there are significant deviations between the actual shape of a manufactured structure subject to model-based measurement and the modeled shape of the structure.

A method and apparatus for microlithography. The method and apparatus include optimizing illumination modes based on characteristics of a specific mask pattern. The illumination is optimized by determining an appropriate illumination mode based on diffraction orders of the reticle, and the autocorrelation of the projection optic. By elimination of parts of the illumination pattern which have no influence on modulation, excess DC light can be reduced, thereby improving depth of focus. Optimization of mask patterns includes addition of sub-resolution features to reduce pitches and discretize the probability density function of the space width.

An optical beam combiner and a related method for its operation, in which multiple coherent input beams are directed onto a diffractive optical element (DOE) along directions corresponding to diffraction orders of the DOE, such that the DOE generates a single output beam in a direction corresponding to a desired diffraction order, and suppresses outputs in directions corresponding to unwanted diffraction orders. The phases of the input beams are actively controlled to ensure and maintain the condition that only a single diffraction mode is present in the output of the DOE.

A measuring system is disclosed with enhanced resolution for periodic structures on a substrate for semiconductor manufacture. Aperture structures of varying geometries are provided in the illumination beam path. The aperture structures differ regarding the transmission characteristics of light, and which adjust the intensity distribution of the diffraction orders in the imaging pupil of the optical system.

Disclosed are apparatus and methods for measuring a characteristic, such as overlay, of a semiconductor target. In general, order-selected imaging and/or illumination is performed while collecting an image from a target using a metrology system. In one implementation, tunable spatial modulation is provided only in the imaging path of the system. In other implementations, tunable spatial modulation is provided in both the illumination and imaging paths of the system. In a specific implementation, tunable spatial modulation is used to image side-by-side gratings with diffraction orders ±n. The side-by-side gratings may be in different layers or the same layer of a semiconductor wafer. The overlay between the structures is typically found by measuring the distance between centers symmetry of the gratings. In this embodiment, only orders ±n for a given choice of n (where n is an integer and not equal to zero) are selected, and the gratings are only imaged with these diffraction orders.

Methods and systems for characterizing dimensions and material properties of high aspect ratio, vertically manufactured devices using transmission, small-angle x-ray scattering (T-SAXS) techniques are described herein. Exemplary structures include spin transfer torque random access memory (STT-RAM), vertical NAND memory (V-NAND), dynamic random access memory (DRAM), three dimensional FLASH memory (3D-FLASH), resistive random access memory (Re-RAM), and PC-RAM. In one aspect, T-SAXS measurements are performed at a number of different orientations that are more densely concentrated near the normal incidence angle and less densely concentrated at orientations that are further from the normal incidence angle. In a further aspect, T-SAXS measurement data is used to generate an image of a measured structure based on the measured intensities of the detected diffraction orders. In another further aspect, a metrology system is configured to generate models for combined x-ray and optical measurement analysis.

Optical devices with versatile spectral attributes are provided that are implemented with one or more modulated and homogeneous layers to realize leaky-mode resonance operation and corresponding versatile spectral-band design. The first and/or higher multiple evanescent diffraction orders are applied to excite one or more leaky modes. The one- or two-dimensional periodic structure, fashioned by proper distribution of materials within each period, can have a resulting symmetric or asymmetric profile to permit a broadened variety of resonant leaky-mode devices to be realized. Thus, the attributes of the optical device permit, among other things, adjacent, distinct resonance frequencies or wavelengths to be produced, convenient shaping of the reflection and transmission spectra for such optical device to be accomplished, and the wavelength resonance locations to be precisely controlled so as to affect the extent to which the leaky modes interact with each other. Further, the profile asymmetry allows for the precise spectral spacing of interactive leaky modes so as to provide greater flexibility in optical device design.

According to the present invention, the method for designing a diffraction grating structure (1), the grating period (d) of the structure comprising at least two grating lines each consisting of a pair of adjacent pillars (2) and grooves (3), comprises the steps of—determining desired diffraction efficiencies η_d of the diffraction orders, and—dimensioning the pillars (2) and grooves (3) so that when calculating for each pillar, on the basis of the effective refractive index n_eff for the fundamental wave mode propagating along that pillar, the phase shift Φ experienced by light propagated through the grating structure, the differences in the calculated phase shifts between adjacent pillars corresponds to the phase profile Φ_r required by the desired diffraction efficiencies.

A three-dimensional image display apparatus includes a light source and an optical system including a light modulation unit having pixels for generating a two-dimensional image by modulating light from the light source by the respective pixels and emitting a spatial frequency in the generated two-dimensional image along a diffraction angle corresponding to diffraction orders generated from the respective pixels, a Fourier transform image formation unit for performing Fourier transform on the spatial frequency in the two-dimensional image to generate Fourier transform images corresponding to the diffraction orders, a Fourier transform image selection unit for selecting a Fourier transform image corresponding to a desired diffraction order among the Fourier transform images, and a conjugate image formation unit for forming a conjugate image of the selected Fourier transform image, and further includes a semi-transmissive mirror for changing a light ray travelling direction emitted from the optical system.

A method of qualifying a diffraction grating comprises performing plural measurements by illuminating a region of the grating with a beam of measuring light and detecting an intensity of measuring light diffracted by the grating into a 0th diffraction order. A wavelength of the measuring light or a polarization of the measuring light or an angle of incidence of the measuring light onto the diffraction grating is varied between subsequent measurements. A shape parameter of diffracting elements forming the grating comprises a pitch, height or width of structural features of the diffracting elements. The shape parameter is advantageously used in analyzing interferometric measurements performed on optical surfaces during manufacture of optical elements of a high accuracy.

Disclosed herein is a three-dimensional image display apparatus includes a light source, a light modulation section modulates light from the light source by means of pixels to produce two-dimensional images and emits a spatial frequency of the produced two-dimensional images along diffraction angles corresponding to a plurality of diffraction orders produced from each pixel, a Fourier transform image formation section Fourier transforms the spatial frequency of the two-dimensional images emitted from the light modulation section to produce Fourier transform images whose number corresponds to the number of diffraction orders, a Fourier transform image selection section selects one of the Fourier transform images produced by the Fourier transform section which corresponds to a desired diffraction order, a conjugate image formation section forms a conjugate image of the Fourier transform image selected by the Fourier transform image selection section.

An ophthalmic endoilluminator is provided. The ophthalmic endoilluminator includes a light source, a first optical assembly, an optical coupling element, and an optical fiber having an optical grating located distally on the optical fiber, the optical fiber optically coupled to the optical coupling element. The first optical assembly receives and substantially collimates the white light. The optical coupling element receives the substantially collimated white light from the first optical assembly and directs the light to an optical fiber. The optical grating couples to the distal end of the optical fiber, the optical grating having a surface relief grating, and an overlayer optically coupled to the surface relief grating. The optical grating is operable to substantially diffract incident light into N diffraction orders, the N diffraction orders having a substantially uniform intensity.

A method for assuring a blazed condition in a DMD device used in telecommunications applications. By meeting certain conditions in the fabrication and operation of the DMD, the device can achieve a blazed condition and be very effective in switching near monochromatic spatially coherent light, thereby opening up a whole new application field for such devices. This method determines the optimal pixel pitch and mirror tilt angle for a given incident angle and wavelength of near monochromatic spatially coherent light to assure blazed operating conditions. The Fraunhofer envelope is determined by convolving the Fourier transforms of the mirror aperture and the delta function at the center of each mirror and then aligning the center of this envelope with a diffraction order to provide a blazed condition. The method of the present invention presents a formula for precisely determining the mirror pitch and tilt angle to assure that a blazed condition exists for a given incident angle and wavelength of near monochromatic spatially coherent light. Considerations for the special case, know as Littrow conditions, where the incident and the reflected light transverse the same path, are also given. This case is particularly attractive for fiber optic/telecommunication applications since the same optics can be used for incoming and outgoing (reflected) light.

The optical assembly of a GDI instrument is configured to deviate or steer stray beams away from the pupil of the instrument's imaging device and/or to suppress stray beams. Stray beam deviation is optimized by selecting particular wedge and/or tilt configurations that achieve the desired stray beam deviation while avoiding or at least minimizing phase offset at the optimum metrology plane. Stray beam suppression can be achieved by providing the diffractive groove profile of the instrument's optical assembly with smooth edges. The resultant profile facilitates effective diffraction order management as well as a reduction in back reflection. The invention is particularly well-suited for use with a GDI instrument in which the optical assembly comprises first and second diffraction gratings. In this case, any average phase offset that remains after setting wedge and/or tilt can be eliminated by inserting a suitable compensating plate between the first and second diffraction gratings or between the second diffraction grating and the object.

An Interferometer for off-axis digital holographic microscopy includes a recording plane, and a grating located in a plane optically conjugated with the recording plane. The grating defining a first and a second optical path, the optical path corresponding to different diffraction order.

By steering wanted diffraction orders within a concentrated angular region and steering all unwanted diffraction orders outside that region, a wavelength selective switch achieves high port isolation and densely spaced ports. N inputs receive an optical signal. Optics spatially separate and direct wavelength channels from the signal. A phased array switching engine comprising cells steers a wanted diffraction order of each spatially separated wavelength channel from each cell at an angle within a concentrated angular region relative to the PASE, and steers all unwanted diffraction orders of spatially separated wavelength channels from cells outside the concentrated angular region. Optics direct each wanted diffraction order to one of N outputs in accordance with the steering of the wanted diffraction orders by the PASE. The concentrated angular region is defined by a largest and smallest steering angle wherein the largest steering angle is a margin less than the smallest steering angle.

Methods and apparatus for measuring an optical azimuth angle φ_O of a substrate relative to a plane of detection in scatterometry tools are disclosed. A grating target on a stage of a scatterometry tool may be illuminated and positions of the resulting diffraction orders may be observed. The optical azimuth angle may be determined from the positions of the diffraction orders. Alternatively, polarization-dependent signals of radiation scattered from a line grating may be measured for equal and opposite polarization angles +A and −A. A combination signal may be computed from the polarization-dependent signals obtained at +A and −A and a property of the combination signal may be calculated for several mechanical Azimuth angles φ_M. A relationship between the optical azimuth angle φ_O and the mechanical azimuth angle φ_M may be determined from a behavior of the property as a function of mechanical azimuth angle φ_M.

Methods and systems for evaluating the performance of multiple patterning processes are presented. Patterned structures are measured and one or more parameter values characterizing geometric errors induced by the multiple patterning process are determined. In some examples, a single patterned target and a multiple patterned target are measured, the collected data fit to a combined measurement model, and the value of a structural parameter indicative of a geometric error induced by the multiple patterning process is determined based on the fit. In some other examples, light having a diffraction order different from zero is collected and analyzed to determine the value of a structural parameter that is indicative of a geometric error induced by a multiple patterning process. In some embodiments, a single diffraction order different from zero is collected. In some examples, a metrology target is designed to enhance light diffracted at an order different from zero.