Particle Measuring Systems, Inc.

Other

Robert G Knollenberg

Albury John Dascher

Robert E Luehr

Clinton E Utter

Scott C Knollenberg

Kenneth R Sample

Vaughn C Hoxie

Ramin Lalezari

System and method are disclosed for inspecting objects, such as sheets of flat panel glass, to detect flaws or contamination at a surface. The surface to be inspected is illuminated with 253.7 nm ultraviolet (UV) radiation to assure detection of defects only at the front surface subjected to the radiation. UV radiation reaching the front surface is scattered by defects at the front surface, and scattered UV radiation is collected by a UV dark field imaging system and directed by the imaging system to a detecting unit, preferably including a charge coupled device (CCD). The detecting unit senses UV radiation scattered at the surface due to defects within a selected size range and provides an output to a processing unit providing an output indicative of the defects sensed within the selected size range. The illumination system preferably illuminates the entire surface to be inspected, an enclosed dark field chamber having shielding houses the illuminating source and radiation collecting system, an anti-reflecting UV coating is preferably used, as is a bandpass filter, and the detecting unit is preferably cooled, accompanied by heating of the imaging system. The system is capable of detecting defects at least as small as five microns using a ten second sampling period.

Surface defect inspection system and method

A modular particle detecting device is disclosed for nonintrusive in-situ detection of particles passing through a sensing region. The device is particularly useful for microcontamination control in semiconductor processing environments, and includes, as separate components, a viewing unit and a sensing unit. The viewing unit has a detecting window and heated illuminating and discharge windows for condensation control. A fluid passage connectable to a flow line enables particle-carrying fluid to pass through a sensing region within the passage. The sensing unit has illuminating circuitry for providing light through the illuminating window to the sensing region, and has detecting circuitry to receive, through the detecting window, light scattered at the sensing region to thereby detect particles in fluid then at the sensing region without physical intrusion of the sensing unit into the sensing region. The sensing unit is mounted on the viewing unit when operationally positioned, and is readily removable to allow servicing and/or alternate use without interupting fluid flow through a flow line having the viewing unit connected therewith.

Nonintrusive modular particle detecting device

Submicron diameter particle detection utilizing a high density array is disclosed. The high density array, such as a charge coupled device, is utilized to detect light scattered at a sensing region by particles illuminated by a light source, such as a laser source. Charge storage is utilized to buffer each data frame transferred from the high density array and the multiple serial outputs are processed by parallel processing that includes threshold detection and analog-to-digital converting. A micro-computer and associated digital storage receives the digital outputs and provides outputs indicative of submicron particle sizing. Further improvement in minimum detectable particle sizing of particles carried by a fluid is realized by use of beam shaping optics to shape the illumination beam passed through the sensing region to form either an astigmatic (highly elliptical) beam cross-section, with the fluid being directed towards the imaging system orthogonal to the object plane, or a circular beam cross-section with the flow directed parallel to object plane, and with the focal point of the beam being substantially centrally positioned within the sensing region in either case.

Submicron diameter particle detection utilizing high density array

A detection device is disclosed for determining particle size from particle effected light scattering in a sensing region illuminated by a laser beam and receiving the particles in a medium, such as air. Background light from molecular scattering is reduced to a level that enables light scattered by particles having a size of at least as low as about 0.1 micron to be sensed in a high background of molecular scattering such as, for example, where molecular scattering can exceed the 0.1 micron particle's scattering by one hundred times. High sensitivity at high molecular scattering background is achieved through use of a linear array of detectors positioned, with respect to an imaging system, so that each detector monitors a different portion of the sensing region and provides an electrical output signal indicative of sensed particle presence within that portion monitored, with the output signals from the detectors being parallel processed and with the output signals from detectors monitoring non-adjacent portions of the sensing region being combined at noise cancellation units.

Highly sensitive particle size detection device having noise cancellation

A surface analysis system and method are disclosed for determining particle contamination and/or defects on or below a surface of material. Laser beams having different polarizations are directed to the surface to be analyzed and light scattered from particle contamination and/or defects on or below the surface is collected and detected to provide electrical signals representative thereof. The electrical signals are then processed to provide an output indicative of sensed contamination and/or defects. In the embodiment particularly shown and described, a pair of polarized laser beams, one of which is a 'P' polarized laser beam and the other of which is a 'S' polarized laser beam, are separately directed to a monitoring region so that the beams impinge at a common point on the surface to be analyzed. The scattered light is then collected and split into two components depending upon whether scattered from the 'P' polarized laser beam or the 'S' polarized laser beam and each component is separately detected, after which the electrical outputs are processed to provide the desired indication.

Surface analysis system and method

A detection device is disclosed for determining particle size from particle effected light scattering in a sensing region receiving the particles in a gas carrier, such as air, and a laser beam to illuminate the sensing region. Background light from molecular scattering is reduced to a level that enables light scattered by particles having a size of at least as low as about 0.1 micron to be sensed in a high background of molecular scattering such as, for example, where molecular scattering can exceed the 0.1 micron particle's scattering by one hundred times. High molecular scattering is generated whenever the gas volume being viewed is large as is required for high flow rates, high molecular density (high pressures), or large gas molecules. This high sensitivity at high molecular scattering background is achieved through use of a linear array of detectors positioned, with respect to an imaging system, so that each detector monitors a different portion of the sensing region and provides an electrical output signal indicative of sensed particle presence within that portion monitored. The output signals from the detectors are parallel processed and coupled to a converter which provides an output indicative of the particles sensed in the entire sensing region.

Particle size detection device having high sensitivity in high molecular

A laser device is disclosed having mirror heating to enhance performance of the device by minimizing induced light absorption to thereby improve mirror quality. The mirrors of a laser device are commonly made of a substrate having a coating thereon formed by alternating layers of high and low refractive index materials, normally classified as refractory oxide materials, which materials are susceptible to formation therein of color centers, such as formation of F-centers when exposed to ultraviolet light, which color centers reduce mirror quality due to induced light absorption losses. By heating the mirror, the F-centers are substantially eliminated to thereby improve mirror quality and enhance the longevity of the laser device.

Laser device having mirror heating

A device and method are disclosed for optically detecting particles in a fluid. A fluid passage with transparent walls defining a monitoring volume, or region, is provided, and particles in the fluid are optically detected by directing a laser beam through the fluid in the monitoring region and collecting light scattered by the particles. A capillary is utilized as the fluid passage, and reflections from the walls of the capillary are effectively precluded. The laser beam is directed through the capillary by means of a window at the entrance side and a lens at the collecting side with the air-glass interfaces being outside the depth of view of particle monitoring within the monitoring region. As a result of this arrangement, the amount of scattered light is greatly reduced and a more uniform light signal is achieved which results in better size resolution of particles than has heretofore been achieved.

Device and method for optically detecting particles in a fluid

Particle measurement is disclosed utilizing orthogonally polarized components of a laser beam. A laser beam is split into orthogonally polarized components and at least one of the components is thereafter beam shaped to have a modified dimension. The components are then recombined and focused to provide a beam combination that is directed through a particle containing volume where scattering of the components occurs by the particles. With the components superimposed upon one another, a localized volume is created with one beam being contracted to a smaller volume than the other beam with the illumination intensity ratios thereat being either greater or less than unity depending upon the optics selected. Particle scattering events are observed within the localized volume in order to define those particles transitting through its central uniform intensity region (sample volume) independent of viewing circumstance by comparing scattered intensity ratios of the orthogonally polarized beam components using a polarizing analyzer and a pair of detectors. The scattering intensities measured of those particles transitting through the preferred sample volume are retained as valid size measurements. With the components in juxtaposition with respect to one another, flow velocity measurement is enabled by measurement of the transit times between the juxtapositioned components.

Particle measurement utilizing orthogonally polarized components of a

A laser having a stabilized external passive cavity is disclosed, with stabilization being effected by modulation of an external mirror positioned along the laser axis. The laser system includes first, second and third spaced mirrors with the second mirror being an output coupler positioned between the first and third mirrors so that an active cavity is defined between the first and second mirrors and a passive cavity is defined between the second and third mirrors. The active cavity feeds, or pumps, the passive cavity which is stabilized by modulation of the third mirror by movement along the laser axis by linear oscillation to Doppler shift the reflected waves within the passive cavity and thereby produce frequencies that do not interfere with the stable modes of the active cavity. By stabilization of the passive cavity, advantages of an intercavity laser device can be realized without incurring the practical disadvantages of such devices, and results in a laser device that is particularly well suited for particle size measurement.

Laser with stabilized external passive cavity

An aerosol sampling device and method are disclosed having improved sample flow characteristics. Sample flowing through an inlet nozzle is heated prior to discharge from the nozzle toward a measurement area to maintain sample flow more nearly laminar by compensating for the adiabatic cooling that occurs due to acceleration of flow through the nozzle. In addition, heating of the sample flow prevents condensation which can result with ambient air having a relative humidity of fifty percent. An optical particle measuring apparatus is shown having a generator for providing a laser beam, the path of which is through a measurement area, and an inlet nozzle through which aerosol sample is injected into the measurement area, after heating in accordance with this invention, to allow operation of the laser at a relatively high Q by reducing non-laminar flow characteristics.

Aerosol sampling device and method with improved sample flow

Method and apparatus for orienting and measuring fibrous particles by conducting longitudinally oriented fibrous particles through a beam of radiation and measuring the radiation scattered in a direction aligned with the length of such particle and, independently, also measuring the amount of radiation scattered transverse to the length of the particle. Preferably, the measurements are accomplished utilizing a sensor having an inactive center portion substantially corresponding to the area of undisturbed beam of radiation, a first photosensitive area in a portion of the sensor aligned with the length of the particles, and a second, independent photosensitive area transverse to the length of the particle. Signals generated by the two photosensitive areas are added to determine the size of the particles, and the ratio between the signals is established to determine the aspect ratio of the particle. Preferably, the particles are aligned by conducting the particles entrained in a compressible fluid through a conduit of decreasing cross section whereby the varying flow rates across the cross section influence particles not aligned with the direction of flow. When the particles are aligned with the direction of flow, the particle is stably oriented.

Method and apparatus for orienting and measuring fibrous particles

Method and apparatus for establishing a valid sample volume in a beam of radiation, wherein a sample stream is introduced substantially transversely to the radiation beam, an optical system is configured to produce images on first and second image planes, the two planes preferably being perpendicular to one another and established by means of a beam splitter, first and second photosensors being positioned in the image planes, the first photosensor having greater optical and an electronic gain and a masked portion, and the second photosensor being either unmasked or having masked portions corresponding generally to the unmasked portions of the first photosensor, the first photosensor being connected to comparator means and the second photosensor also being connected to the comparator means which accepts data only when the signal from second photosensor is of a greater magnitude than the signal from the first photosensor, whereby images on the photosensors from points outside the selected sample volume will be oriented with a sufficient portion of the image on the unmasked section of the first photosensor to produce a signal greater than that produced by the second photosensor thus rejecting data from that event.

Method and apparatus for determining valid sample volume

Method and apparatus for selecting data wherein the acceptability of the data is a function of a measurable quality, such as duration, of a specific event relative to the current average, or other statistical threshold, of such quality of a number of events. The magnitude of event characteristic is measured and provided as a signal. Deviations from the threshold are provided to an up-down counter in which the threshold is stored and, accordingly, updated. If the event magnitude, as registered in an up-counter, exceeds the updated threshold stored in the up-down counter, a digital comparator indicates this and up counts the up-down counter to the extent the event exceeds the threshold. If the event magnitude is less than the stored threshold, the up-down counter is down-counted an amount corresponding to the difference between the event magnitude and the stored threshold. A currently updated threshold is thus maintained in the up-down counter. Weighting can be provided by, for instance, varying the clock frequency of the up-count, and the clock frequency of the down-count, to the up-down counter.

Method and apparatus for generating a statistical basis

Two-dimensional data may be acquired at extremely high rates by means of a linear sensor array, and ganged shift registers with each sensor associated with at least one shift register. The state of each sensor is sampled periodically in accord with a selected, relatively high clock frequency and each sampling is sequentially recorded in the shift register associated with a specific sensor. A first dimension is provided by the linear nature of the sensor array and the second dimension is supplied by the sampling clock frequency as a subject moves past the sensor array. In a more advanced embodiment, the sampling operates only during the occurrence of an event and data is cyclically recorded in one group of shift registers at a rapid rate while previous data is unloaded from an alternative group of shift registers at a conventional rate.

Growing community of inventors

Boulder, CO, United States of America

Robert G Knollenberg