Xyratex Technology Limited

Beyond 3, Inc.

Ztek Corporation

Bryan Clark

Andrei Brunfeld

Gregory Toker

An optical inspection system includes a polarizing isolator that reduces error in measurements by preventing ghost light reflected or scattered from element of a detection subsystem from re-entering the illumination and detection optical paths. The polarizing isolator may include a polarizing splitter that isolates light directionally according the a linear polarization state and two quarter-wave plates for transforming linearly polarized light to circularly polarized light.

Optical inspection system with polarization isolation of detection system reflections

A scatterometer-interferometer and method for detecting and distinguishing characteristics of surface artifacts provides improved artifact detection and increased scanning speed in interferometric measurement systems. A scatterometer and interferometer are combined in a single measurement head and may have overlapping, concentric or separate measurement spots. Interferometric sampling of a surface under measurement may be initiated in response to detection of a surface artifact by the scatterometer, so that continuous scanning of the surface under measurement can be performed until further information about the size and/or height of the artifact is needed.

Scatterometer-interferometer and method for detecting and distinguishing characteristics of surface artifacts

A resonant ellipsometer and method for determining ellipsometric parameters of a surface provide an efficient and low-cost mechanism for performing ellipsometric measurements. A surface of interest is included as a reflection point of a resonance optical path within a resonator. The intersection of the resonance optical path with the surface of interest is at an angle away from normal so that the complex reflectivity of the surface alters the phase of the resonance optical path. Intensity measurements of light emitted from a partially reflective surface of the resonator for orthogonal polarizations and for at least two effective cavity lengths provide complete information for computing the ellipsoidal parameters on the surface of interest. The resonator may be a Fabry-Perot resonator or a ring resonator. The wavelength of the illumination can be swept, or the cavity length mechanically or electronically altered to change the cavity length.

Resonant ellipsometer and method for determining ellipsometric parameters of a surface

A Fabry-Perot resonator apparatus and method including an in-resonator polarizing element improves detection/measurement sensitivity of an optical system, provides both fields at a single end of the resonator, and overcomes other structural and performance limitations of particular optical systems. A polarizing element, which may be a quarter-wave plate, a 45-degree Faraday rotator or other polarizing element capable of converting between linear and circular polarizations and back, is placed in the resonance path of the Fabry-Perot resonator. The polarizing element effectively doubles the cavity length and orthogonally isolates forward from reverse reflection rays within the resonator, eliminating interference between rays and providing isolated bright and dark fields at each end of the resonator. The polarizing element is introduced in a lens-incorporating Fabry-Perot resonator to eliminate cross-talk between image points and is used in a non-normal incidence Fabry-Perot resonator to emit bright and dark resonance information at either end of the resonator.

Fabry-perot resonator apparatus and method including an in-resonator polarizing element

A three-dimensional imaging resonator and method therefor provides improved surface height measurement capability in optical measuring systems. A resonator including a surface of interest in a resonant image path is coupled to an external multi-pixel detector that detects an image of intensity of light reflected from or transmitted through the resonator. An imaging system is included in the resonator to image a region of a surface of interest on another reflector forming part of the resonator. By changing an effective cavity length of the resonator, the image is 'scanned' in a direction perpendicular to the other reflector and a processing system stores information corresponding to resonance peaks to achieve a mapping of feature height above the surface of interest. The resonator effective cavity length can be changed by sweeping the illumination wavelength or by mechanically or otherwise altering the optical length of the resonator.

Three-dimensional imaging resonator and method therefor

A resonator method and system for distinguishing characteristics of surface features or contaminants provides improved inspection or surface feature detection capability in scanning optical systems. A resonator including a surface of interest in the resonant path is coupled to a detector that detects light leaving the resonator. Changes in the resonance peak positions and peak intensities are evaluated against known changes for standard scatters in order to determine the material characteristics of an artifact at the surface of interest that causes a resonance change. The lateral size of the artifact is determined by de-convolving a known illumination spot size with the changing resonance characteristics, and the standard scatterer data is selected in conformity with the determined artifact size. The differential analysis using resonance peak shifts corresponding to phase and amplitude information provides an identification algorithm that identifies at least one artifact/material type is identified from matching known behaviors of artifacts/materials.

Resonator method and system for distinguishing characteristics of surface features or contaminants

A method and system for optical measurement via a resonator having a non-uniform phase profile provides a mechanism for measuring and/or detecting sub-micron surface features with increased resolution. A second surface forming part of a resonator is illuminated through a first partially reflective surface that has a non-uniform phase profile that transitions from negative to positive phase with respect to a resonance phase value of the resonator. As a result, a reduced spot size is produced at the second surface, which enhances the resolution of a measurement and/or detection of surface features on the second surface. Additionally, if a discontinuity is provided in the non-uniform phase profile, interaction of the discontinuity with surface features of the second surface will provide enhanced resolution of the surface features. The resolution of the system is improved over the resolution that can be attained using a Fabry-Perot resonator.

Method and system for optical measurement via a resonator having a non-uniform phase profile

A method and system for determining surface feature characteristics (including position and dimensions) using slit detectors provides a low-cost and high-speed measurement system for inspecting a surface. The system includes multiple slit detectors positioned so that a feature on a surface scanned by the system is detected by at least two detectors that are rotationally offset from each other and from the direction of scanning, a scanning control system for providing motion to the surface of interest in relation to the detectors, and an electronic analyzer for computing characteristics (including position and dimensions) of surface features. The location of surface features along an axis perpendicular to the direction of motion of the surface is determined from the relative timing between the presence of surface feature within the slit detector fields and the dimension of surface features in a direction crossing the short axis of a slit detector field is determined from the relative length of time the features remain in the slit detector field.

Method and system for determining surface feature characteristics using slit detectors

A method and apparatus including in-resonator imaging lens for improving resolution of a resonator-enhanced optical system provides resolution improvements for optical inspection and measurement systems, optical storage and retrieval systems as well as other optical systems. An imaging lens is incorporated in the resonator to image a point or area of one of the reflective surfaces of the resonator on a point or area of another reflective surface of the resonator. Resonance may be supported between the two surfaces, or with respect to only one surface with the other surface acting as an intermediary reflector. The partially reflective surface or a totally reflective surface may also be incorporated on a planar outside surface of the imaging lens.

Method and apparatus including in-resonator imaging lens for improving resolution of a resonator-enhanced optical system

A method and system for determining dimensions of optically recognizable features provides a low-cost and efficient high speed/high resolution measurement system for determining surface feature dimensions. Multiple imaging subsystems are arranged at predetermined differing angles above a surface under test. A scanning subsystem moves either the imaging subsystems or the surface under test and a processor coupled to the imaging subsystems determines the height of a surface feature by determining the deviations between the outputs of the imaging systems as an edge of the surface feature passes within the optical paths of the imaging subsystems.

Method and system for determining dimensions of optically recognizable features

A method and system for performing swept-wavelength measurements within an optical system incorporating a reference resonator provides improved operation in resonator-enhanced optical measurement and data storage and retrieval systems. The system includes an illumination subsystem, an illumination coupler for producing a measurement beam and a reference beam from an output of the optical illumination source, a reference resonator for receiving the reference beam, a measurement resonator for receiving the measurement beam, at least two detectors, one optically coupled to the reference resonator and one optically coupled to the measurement resonator, and a time-domain measurement system coupled to the detectors for comparing detected optical signals received from the resonators. The detected signal from the reference resonator is used to compensate or detect variations in the wavelength of the illumination system, improving the resolution and accuracy of the measurement provided by the measurement resonator.

Method and system for performing swept-wavelength measurements within an optical system incorporating a reference resonator

A method and system for performing swept-wavelength measurements within an optical system provides improved operation in resonator-enhanced optical measurement and data storage and retrieval systems. The system includes an illumination subsystem having a swept-wavelength mode, a detection subsystem, an interferometer or an optical resonator interposed in an optical path between the illumination subsystem and the detection subsystem and a time domain analysis subsystem. Multiple resonance points of the optical resonator are detected by the time-domain subsystem when the illumination subsystem is in the swept-wavelength mode in order to determine resonator or interferometer characteristic changes. The resulting information can be used directly as a measurement output, or cavity length information may also be used to adjust the operating wavelength of a constant wavelength mode of the illumination subsystem.

Method and system for performing swept-wavelength measurements within an optical system

A method and system for controlling resonance within a resonator-enhanced optical system provides improved tracking performance in resonator-enhanced optical measurement and data storage and retrieval systems. The system includes an illumination subsystem and a detection subsystem with an optical resonator interposed in an optical path between the illumination subsystem and the detection subsystem. The resonance of the optical resonator is tuned, either by changing the wavelength of the illumination subsystem or the geometric path length within the resonator. Closed-loop feedback control signals can thereby maintain resonance at a desired operating point. The feedback control signal components can be further used to provide measurement data if the resonance of the optical resonator is a function of a measured surface, such as when a reflective surface of the resonator is a surface under measurement.

Method and system for controlling resonance within a resonator-enhanced optical system

An optical inspection method and apparatus having an enhanced height sensitivity region and roughness filtering uses a Fabry-Perot cavity to increase the phase detection sensitivity for light reflected from surface defects having a height above a predetermined level. A partially reflective surface is inserted between an illumination subsystem and a surface under inspection. The position of the partially reflective surface with respect to the surface under inspection is adjusted to provide both filtering of defects below the predetermined level and enhance sensitivity for a region of defect heights above the predetermined level. The angular resolution of the inspection system is improved, providing far-field inspection that can detect small-profile defects having unacceptable heights. Media storage, semiconductor wafer and other precision surface manufacture may be improved by use of the techniques of the present invention.

Optical inspection method and apparatus having an enhanced height sensitivity region and roughness filtering

An optical storage method and apparatus having enhanced resolution uses a Fabry-Perot cavity to narrow a beam used for reading data stored on media. The method and apparatus achieve an enhanced resolution due to the reduction of beam size and the increased slope of the beam profile in a beam used to illuminate physical changes in the media corresponding to data encoded in the media. The Fabry-Perot cavity may be included in a media for use with standard optical storage devices or may be external to the media, as part of an optical storage head for use with standard media.

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Mountain View, CA, United States of America

Bryan Clark