Particle Measuring Systems, Inc.

Other

Dennis J Knowlton

Todd A Cerni

Scott Waisanen

Edward R Green

A sensitive particle distribution probe uses special processing including a modified Twomey/Chahine iterative convergence technique and a specially constructed sample cell to obtain particle size distribution measurements from optically dense slurries, such as the slurries used in the semiconductor industry for chemical mechanical planarization. Spectral transmission data is taken over the spectral range of 0.20-2.5 microns, utilizing specially constructed, chemically resistant sample cells of 50-2000 microns thickness, and miniature, fixed grating, linear detector array spectrometers. At wavelengths greater than one micron, the preferred design utilizes InGaAs linear detector arrays. An ultrasonic disrupter can be employed to breakup harmless soft agglomerates. In addition to direct particle size distribution measurement, the invention described here could be used to detect other fundamental causes of slurry degradation, such as foaming and jelling. The probe accomplishes continuous, real time sampling of undiluted slurry. A three-position chopper allows automated operation in an industrial environment without the need for frequent reference spectra, which would require taking the probe off-line. In other embodiments, the invention provides a quality control and/or particle size measuring system for CMP slurries using transmission data through an as-used CMP slurry flow. The process of the invention detects transmission through the flow, at select wavelengths, and determines changes in the logarithmic slope of transmission versus wavelength to detect acceptable or unacceptable CMP slurries. The process can further determine CMP slurry particle size through empirical extinction data stored in memory.

Chemical mechanical planarization (CMP) slurry quality control process and particle size distribution measuring systems

A particle detection system in which a beam of light is incident upon an inviscid jet of fluid. A sample fluid containing particles is passed through an inviscid flow producing nozzle. An inviscid flow jet is output from the nozzle. The entire inviscid flow jet moves with uniform velocity and can therefore be contained within the sample region for the detection system. A volumetric measurement is thereby achieved where all of the sample fluid moves with uniform velocity. Sample fluid is decelerated in a deceleration chamber to a velocity significantly less than the nozzle velocity. The nozzle has a length and a width where the ratio of length to width is less than about 1. Sample fluid flows from the deceleration chamber through the nozzle and is output from the nozzle in an inviscid flow jet into a collection chamber. An optical collector system collects light scattered by particles in the inviscid flow jet and images the scattered light on a detector. The shape of the inviscid flow jet can be circular or non circular. An inviscid flow jet having a high aspect ratio can be fully illuminated by a relatively focussed beam of light providing a highly sensitive measurement.

Particle detection system utilizing an inviscid flow-producing nozzle

Noise reduction is effected by multiplying together electrical signals that include pulses embedded in noise, with the pulses being indicative of the same event, such as light scattered by particles, occurring at a viewing area, and with the signals being processed prior to multiplication so that the pulses and the variance of the noise in the electrical signals are multiplied by one another. A detector in each of a plurality of channels detects the events occurring at the common viewing area and provides pulses indicative thereof, and the output from each detector is amplified, passed through matched low-pass filters to enhance pulse detection, and then passed through a baseline restorer to remove DC components from the noise then present in the signal, prior to coupling of the signals to a multiplier. At the multiplier, peak values of the pulses included in the signals from each of the channels multiply, as do the variances of the uncorrelated noise included in the signals from each of the channels, resulting in multiplication of the signal-to-noise ratio, and hence improvement in signal-to-noise.

Noise reduction utilizing signal multiplication

Device and method are disclosed for optically detecting particles in a free (i.e., unenclosed) stream of liquid. The free liquid stream is produced by ejecting liquid under pressure from a nozzle so that the stream has a smooth round surface. A laser beam intersects the free liquid stream and light scattered by particles in the free liquid stream is collected and processed to provide an output indicative of size and/or number of particles causing the light to be scattered. The free liquid stream is preferably directed vertically downward, and the laser beam and light collector are angularly positioned with respect to the free liquid stream and one another with the light collector collecting scattered light at the intersection of the light beam and the free liquid stream. Embodiments are also disclosed wherein scattered light is collected at a collecting position spaced along the free liquid stream from an illuminating position where the laser beam intersects the free liquid stream with the scattered light traveling along the liquid free stream between the illuminating and collecting positions.

Device and method for optically detecting particles in a free liquid

A pulse code modulation communication system adapted in a preferred embodiment to the remote control of a flying model aircraft. The positions of the various control sticks are represented by a digital code which is multiplexed and then transmitted via pulse code modulation of a unique subcarrier signal. The unique subcarrier signal is locked onto by the receiver which, through correlation detection, detects and demultiplexes the digital code for use by the servo motors to position the flight control surfaces of the aircraft.

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Boulder, CO, United States of America

Dennis J Knowlton