Bruker Nano Gmbh

Veeco Instruments Inc.

Onto Innovation Inc.

4d Technology Corporation

Ad Technology Corporation

Veeco Metrology, Inc.

Erik Novak

Florin Munteanu

Dong Chen Chen

Joanna Schmit

G Lawrence Best

Bryan W Guenther

Colin T Farrell

Brad Kimbrough

James E Millerd

Neal Brock

Paul R Unruh

Der-Shen Wan

Goldie Goldstein

Sen Han

A pixelated color mask is combined with a pixelated polarization mask in dynamic interferometry. The color mask includes a wavelength-selective bandpass filter placed in front of each camera pixel such that each set of contiguous four camera pixels is covered by two green bandpass filters, a red bandpass filter, and a blue bandpass filter. The pixelated phase mask is coupled to the color filters such that one polarization filter covers one set of color filters. At least three polarization filters are used to calculate phase. In addition, the color signals can be used, for example, to encode the motion of the interferometer, to provide very high speed autofocus or tip/tilt feedback, to create a color image of the object being measured, to automatically focus the system at different positions for different measurements conducted with different color sources, and to perform heterodyne interferometry with a single, vibration-immune measurement.

Interferometry with pixelated color discriminating elements combined with pixelated polarization masks

A cycloidal diffraction waveplate is combined with a pixelated phase mask (PPM) sensor in a dynamic fringe-projection interferometer to obtain phase-shifted interferograms in a single snap-shot camera operation that provides the phase information required to measure test surfaces with micrometer precision. Such mode of operation enables a portable embodiment for use in environments subject to vibration. A shifting mechanism coupled to the cycloidal waveplate allows temporal out-of-phase measurements used to remove noise due to test-surface characteristics. Two or more pixels of each unit cell of the PPM are combined to create super-pixels where the sum of the phases of the pixels is a multiple of 180 degrees, so that fringes are eliminated to facilitate operator focusing. By assigning colors or cross-hatch patterns to different ranges of modulation measured at the detector, the areas of best focus within the field of view are identified quantitatively to ensure measurements under best-focus conditions.

Single snap-shot fringe projection system

A portion of the surface of a cylindrical part with a machined groove is mapped with an optical profilometer during the manufacturing process and the height map is fitted to a virtual cylindrical configuration that best fits the data. Two-dimensional Fourier Transfer analysis of the map data is advantageously used to find the orientation of the groove on the part. The orientation of the groove is then compared to the longitudinal axis of such virtual cylinder to calculate the groove's lead angle. If the measured lead angle is outside a predetermined design tolerance deemed acceptable for manufacturing purposes, the part is removed from the fabrication line.

Optical measurement of lead angle of groove in manufactured part

A substrate is tested with an interferometer in-line in a roll-to-roll processing operation to detect defects and exclude them from further processing. A tilt is introduced in the illumination path of the interferometer to allow detection of best fringes in a selected measurement field of view (FOV) that is smaller than the camera FOV in the direction transverse to the fringes. At each acquisition frame, the measurement FOV is shifted to track the best-fringe position within the camera field of view based on irradiance acquired at the previous step. As a result, the system is able to accommodate substrate flutter and roller runout and maintain focus on the substrate that allows precise identification of defects and their isolation for subsequent processing.

High-resolution in-line metrology for roll-to-roll processing operations

A reference surface is used to develop an empirical plot between a parameter of interest, such as roughness or modulation, and the position of the reference mirror in an interferometer by repeating measurements of the reference surface at different positions of the reference mirror so as to identify the in-focus position of the reference mirror. Serial quality-control measurements of samples of interest are carried out with the reference mirror in such in-focus position until a predetermined quality-control event triggers an automated system re-calibration by re-measuring the reference surface and, if the result does not correspond to the in-focus position of the reference mirror according to the plot, by finding a new in-focus position for the reference mirror using the same plot or, alternatively, a new similarly produced plot. Sample measurements are then resumed with the mirror placed at that new position.

Automated re-focusing of interferometric reference mirror

The rough bottom surface of a recessed feature partially obscured by an overlying structure is profiled interferometrically with acceptable precision using an objective with sufficiently large numerical aperture to illuminate the bottom under the obscuring structure. The light scattering produced by the roughness of the surface causes diffused light to return to the objective and yield reliable data fringes. Under such appropriate numerical-aperture and surface roughness conditions, the bottom surface of such recessed features can be profiled correctly simply by segmenting the correlograms produced by the scan and processing all fringes that correspond to the bottom surface elevation.

Signal sectioning for profiling printed-circuit-bord vias with vertical scanning interferometry

The bottom surface of a via drilled in a fiber-reinforced PCB is profiled interferometrically with acceptable precision using an objective with sufficiently large numerical aperture to illuminate the bottom under the fibers. The light scattering produced by the inherent roughness of the surface of the via bottom causes diffused light to return to the objective and yield reliable data fringes. Under such appropriate numerical-aperture and surface roughness conditions, the bottom surface of vias can be profiled correctly simply by segmenting the correlograms produced by the scan and processing all fringes that correspond to the bottom surface elevation.

Signal sectioning for profiling printed-circuit-board vias with vertical scanning interferometry

Correction factors for the ALR and PTR parameters of magnetic-head sliders are determined by calculating an effective reflectivity and a corresponding PCOR at each pixel of the air-bearing surface. The absolute value of reflectivity at each pixel of the AlTiC air-bearing surface is obtained from an empirical equation relating it to modulation. The ratio of AlOand TiC in the AlTiC surface is then calculated at every pixel assuming a linear relationship between the absolute value of AlTiC reflectivity and the theoretical reflectivity of each constituent. The linear relationship is then also used to calculate the effective (complex) reflectivity for the AlTiC material from the relative concentrations of AlOand TiC at each pixel.

Interferometric measurement of non-homogeneous multi-material surfaces

An explicit relationship is developed between the ratio of average interferometric modulation produced by diamond-like carbon (DLC)-coated magnetic-head surfaces and the thickness of the DLC layer. Accordingly, the thickness of the DLC layer is calculated in various manners from modulation data acquired for the system using object surfaces of known optical parameters.

Interferometric measurement of DLC layer on magnetic head

An illumination system for an interferometer combines a white-light source and a green source with a reflective green dichroic filter. When the green source alone is energized for PSI measurements, the output of the illumination system is green only. When a white-light output is desired for VSI measurements, both sources are energized and the intensity of the green light is judiciously calibrated to match the spectral band filtered out by the dichroic mirror. Therefore, the system can switch between green and white light simply by changing the selection of energized sources, without any mechanical switching and attendant delays and vibrations. Multiple narrowband sources may be combined with white light in a similar manner.

Variable-wavelength illumination system for interferometry

A collimated light is used in combination with a compensation element and an aberration-corrected objective with a long working distance to produce a greatly improved fringe contrast in the measurement of a sample surface through a dispersive element. When the dispersive element consists of a fixed cover with substantially consistent characteristics from sample to sample, the compensation element is a plate that matches the optical characteristics of the dispersive element. When the dispersive element varies, the compensation element consists of a variable-thickness transmissive element embodied in a pair of half-cube prisms is adapted to slide along the beam-splitting plane, thereby permitting the adjustment of the optical path-length through the splitter in the reference-beam direction while retaining unchanged the optical path-length in the test-beam direction.

Profilometry through dispersive medium using collimated light with compensating optics

An interferometric profiler is used to measure object motion by modifying the motion of the scanner so that the phase variation at each scanning step is kept within the acceptable limits of the algorithm used to calculate phase changes. The scanner motion is so manipulated on the basis of prior knowledge about the nature of the object motion, or knowledge obtained by pre-calibration, or by real-time feedback based on current measurements. The object motion is recovered from the scanning information by subtracting the scanner position from the object position as it evolves during the scan.

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Tucson, AZ, United States of America

Erik Novak