JPH06300677A - Particle detection device - Google Patents

Abstract

PURPOSE: To provide a novel device and method used for detecting particles in vacuum at high efficiency and without any change of a detecting position. CONSTITUTION: This detection device particularly includes a device for a particle detection means designed to detect gas particles present in a vacuum line at high efficiency. Also, a suddenly converging nozzle 10 is used, and floating particles flowing via the nozzle 10 are selectively focused to a small zone positioned downstream of a nozzle outlet and at a distance smaller than the outlet on a nozzle axis 27. A focal zone 26 is extremely smaller than the nozzle outlet, and irradiated with a beam 22 of small breadth and high brightness. Thus, the particles flowing through the irradiated focal zone 26 are detected with a photo detector element exposed to scattered light from the particles.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a new apparatus and method for particle detection, and more particularly to an apparatus and method for detecting particles or separating particles in situ with high efficiency.
The present invention relates to particle measuring / counting systems, and more particularly to measuring / counting systems having improved particle sensing means with particular applicability in use in vacuum lines and semiconductor processing equipment.

[0002]

The use of particle measuring or particle separating devices is increasing. The single largest field of application is the semiconductor industry, where cleanliness is very important in semiconductor fabrication. For example, particle counting is used to monitor the number of particles in a room called a clean room where semiconductor manufacturing operations are performed. A clean room is usually one of the air
Classification is generally based on the maximum number of particles of a given size allowed per volume. In order for the product to be produced to meet specifications and maintain quality levels, it is necessary to ensure that particulate contaminants are kept to the minimum acceptable requirements.

The most basic system used for particle counting in air is to send an air stream of sample into a light beam, which results in scattering of light energy by the particles. This scattered energy is detected and measured by suitable optics and electronics. Significant improvements have been made to the optics and electronics used to detect and process scattered light signals. The advent of lasers has also greatly improved the quality and brightness of the illuminating light beam.

Despite these improvements, the accuracy of the data output from the devices has not yet reached the desired accuracy. Each test also showed other inaccuracies such as, for example, particle recirculation, discrepancies in absolute counting correlations between different devices, and the like.

Other problems associated with this particle detection are:
It has been solved by the development of a particle measurement system that includes particles to be detected or measured in a flow stream that passes through a light beam, which is typically a laser light beam. As mentioned earlier, particles that pass through the beam scatter light,
The scattered light is captured by one or more photodetectors and focused to generate electrical pulses. The intensity of the scattered light, and therefore the amplitude of the pulse produced by the photodetector, gives an indication of particle size.

In many systems it is important to detect every particle in the entrained flow stream. This requires the light beam to pass through the entire cross-sectional area of the flow stream containing the particles. When the flowing stream is a liquid stream, the conduits carrying the stream through the light beam are generally narrowed along the way, resulting in a narrow cross-sectional area so that the high intensity beam can pass through the entire cross-sectional area of the flowing stream. If the flow stream containing the particles is a gas stream of considerable density, the seeded gas stream is made thin into a sheet shape by a nozzle and the laser beam is directed, for example, by Kenneth P. et al. G
As described in US Pat. No. 4,746,215 to Ross, it is possible to pass along the long width of a sheet-shaped stream. The nozzle of this device has a gradual change in cross-sectional area that does not significantly affect the ability of suspended particles to closely follow the flow rate of the gas stream line (ie, there is a separation between particles and gas phase). Does not occur).
However, when the particles are in a vacuum like a semiconductor processing apparatus, it is difficult for the nozzle to form the stream in a sheet shape. Furthermore, in order for the vacuum line to efficiently transfer the vacuum to the work area of semiconductor processing, the vacuum line must have a considerable cross-sectional area. Thus, prior art particle detection systems have narrow conduits or nozzles, thus creating a flow stream that is unsatisfactory for particle detection in vacuum lines such as those used in semiconductor processing equipment.

Although thin film technology is used in the manufacture of semiconductors and packaging devices, a major obstacle in yield is defects due to particulate contaminants on the thin film surface. The main cause of such defects is attributed to particles of contaminants produced by the processing equipment or tools used to manufacture thin film devices by the authors Bowling, R .; This is made clear in the following article by A et al. "Status and needs
of in-situ real-timeprocess particle detection ",
J. Environ. Sci, Vol. 32 (5), pages 22-27 (198
9 years).

Many of the processing equipment used in the thin film manufacturing or semiconductor industries operate at low pressures (eg RI).
E, PECVD). These in-situ particle monitoring tools are often used to detect contaminants and control process equipment for contaminants, and in most cases,
It is attached to the discharge line of the processing chamber.

Currently available vacuum line monitors are:
Lasers are commonly used to normalize the direction of flow by utilizing the scattering of light.
Detect particles in the gas passing through the section illuminated by the beam. Please refer to the following article for this. Greenstein, D.D. By "Invest
igating a Prototype In Situ ParticleMonitor on the
Exhaust Line of a CVD Reactor ", Microcontaminatio
n, Vol. 3, pages 21-26 (1991), and Stern,
J. E. Et al., "Monitoring Downstream Particles in a
Single-Wafer CVD Oxide Reactor ", Microcontaminati
on, Vol. 11, pages 17-56 (1991). The means described above uses a single focused laser beam to illuminate a narrow portion of the fluid passage cross section. Only a very narrow portion of the fluid particle population is illuminated and detected. The low detection efficiency (0.1% to 3.0%) of such particle monitors yields poor quality particle count statistics,
As a result, monitors are not used in statistical process control (SPC) applications.

Many attempts have been made to solve the low detection efficiency. In one case, multiple reflected beams were used to create a "sheet" or "net" of light that increased the illuminated area in a vacuum conduit. This is described in US Pat. No. 4,739,177 to Borden. However, Caldow, R .; The independent work described below by them et al. Only slightly improved the system efficiency described by Borden and others. "Performance of the High Y
ield Technology Inc. PM-100 In SituParticle Flux M
onitor ", Aerosol Science Technology, Vol. 12, page
s 981-991 (1990). The result is High Yield Tec, assignee of Borden US Pat. No. 4,739,177.
Using a multi-reflecting beam system manufactured by hnology, the monitor count efficiency was 4.7 percent at 6.0 micron particles and only 0.1% at 0.5 micron particles.

Recently, US Patent No. 50 to Sommer
The device described in No. 92675 is capable of detecting all particles flowing through a conduit by illuminating the entire cross-sectional area of the vacuum conduit using a sheet of laser light. this is,
Increasing the illuminated cross section, however, current state of the art requires a fairly high power laser to detect the minimum detectable particle size.

Thus, further improvements in particle detectors or particle counters are desired.

The invention described herein also detects particles by scattered light. However, the new design utilizes a light source, beam optics, a light-sensing element, and a single aerodynamic focusing of most of the suspended particles in the fluid stream into a focal zone whose cross-section is narrow compared to the nozzle exit zone. A specially designed system using the nozzle design of The focal zone is illuminated by one or more narrow, high-intensity light beams, which are preferably focused laser beams, to detect significant particles (nearly 100% predicted) of the fluid stream particles. it can. The highly efficient particle detection provided by this new invention is suitable for many industrial applications such as SPC applications.

[0014]

SUMMARY OF THE INVENTION The present invention is a new method and apparatus for detecting particles in situ in a fluid stream with high efficiency.

It is an object of the present invention to provide an apparatus and method for detecting particles in situ with high efficiency.

Another object of the present invention is to provide a particle detector that operates in a vacuum with high efficiency.

It is a further object of the present invention to provide a particle detector that works on-line in semiconductor processing.

Yet another object of the present invention is to provide a particle detector having an adjustable nozzle capable of changing the focus position of a detected particle.

Yet another object of the invention is to provide a particle detector having slidable means capable of varying the distance between the nozzle used to detect particles and the light beam.

[0020]

A feature of the invention includes an apparatus for sensing particles flowing in a fluid conduit. The fluid conduit has the following configuration. A nozzle having at least one focusing means for aerodynamically focusing the particles in a focal zone, wherein the cross sectional area of the focal zone is substantially smaller than the cross sectional area of the focusing means, and at least 1 At least one means for illuminating the focal zone with two narrow light beams and at least one means for detecting scattered light by the particles illuminated by the light beams.

Another feature of the present invention is to include a method for detecting particles flowing in a fluid conduit of the following construction. (A) Aerodynamically focus particles detected by at least one focusing means into a focal area, wherein the cross-sectional area of said focal area is smaller than the cross-sectional area of said focusing means,
(B) illuminating the focal region with at least one narrow light beam such that the light beam is scattered by the particles in the focal region; (c) scattering by the particles illuminated by the light beam. The method further comprising detecting the light and counting the number of particles in the focal zone detected in the detecting step.

[0022]

EXAMPLES When operating a sensing system to determine the number of particles in a fluid stream, such as a gas or liquid, it is assumed that the particles are suspended in the fluid. A gas or liquid generally acts as a carrier, transporting airborne particles through the focus of a light beam, such as the laser beam used by the sensing system. Since the suspended particles scatter light to be detected, it is possible to know the physical characteristics of the particles such as the size and number of particles. Particle detection is performed for various reasons. For example, knowing the number and size of particles scattered into the environment, to name but a few, can tell if the degree of contamination exceeds specified process or environmental limits.

An example of a suitable nozzle is shown in FIG. The abrupt convergent nozzle 10 has a nozzle housing 12 and is covered by one or more upper fixed or moveable nozzle plates 14 and one or more lower fixed or moveable nozzle plates 16. It is being appreciated. The nozzle housing 12 is preferably tubular, but can be any shape. The nozzle housing 12 is preferably circular and has a nozzle opening or nozzle outlet 15 for outflowing the fluidized particles 11 and 13. For purposes of illustration, only fluid particles 11 are sometimes referred to as carrier fluids or gases, and fluid particles 13 are referred to as detected particles or unwanted particles or contaminants.

The top plate 14 generally has an angle 4 shown in FIG. This angle 4 is 90 depending on the process conditions.
It can be changed in the range of degrees to 135 degrees. Similarly, the lower plate 16 has an angle 6. This angle 6 can also be changed in the range of 90 to 135 degrees depending on the process conditions. It has been found that for typical operation, the preferred angle between angles 4 and 6 in the figure is 90 degrees.

The plates 14 and 16 may be the same size or different sizes. Similarly, the plates 14 and 16 may be rectangular or semi-circular or other shapes. Nozzle 10
A single plate 17 instead of the plates 14 and 16 of
Which is preferably circular for the passage of the flowing particles 11 and 13 and which is the outlet or opening 15.
Have. Similarly, the plate 17 has an iris-like variable opening 15 to allow modification of fluid flow characteristics. The angle between the angles 4 and 6 of the plate 17 is preferably 90 degrees, but it is better to change the angle depending on the application.

The fluid flow in a typical situation has one or more carrier fluids 11 containing one or more undesired particles 13 which must be detected or counted.
In semiconductor processes, the carrier fluid 11 is generally a gas, for example nitrogen, helium, hydrogen, argon, oxygen or a mixture of gases, to name a few,
And the flow particles 13 are some contaminant particles that commonly enter during the semiconductor manufacturing process. Generally fluidized particles 13
Has a much larger mass than the carrier gas molecule 11.

As the fluid containing gas and contaminant particles passes through the focusing nozzle 10, the heavy particles 13 are replaced by the light gas particles 1.
1, resulting in a fluid or particle gas jet. As shown in more detail in FIG. 1, the fluidized particles 11 converge as they approach the nozzle opening or outlet 15 and diverge immediately after passing through the opening 15 without being significantly compressed. On the other hand, the suspended pollutant particles 13 are also
It converges as it approaches the nozzle outlet or opening 15, but due to its large momentum, ie inertia, its converging movement tends to stay downstream of the nozzle opening or outlet and if its weight is sufficient. , And finally intersects the jet axes at a common focus or focal zone 26. Unlike the flowing particles 11, the pollutant particles 13 have a focal area 26
The result is a highly concentrated local particle concentration in the region. The fluid flow downstream of the nozzle is thus separated into a region 23 enriched in particles 13 and a region 21 depleted in particles 13 and divided by an imaginary plane or region 20. In summary, the focusing nozzle 10 concentrates the heavy particles 13 mainly and narrows the focus area 26.
However, it also plays a role of not restricting the light gas particles 11.

The following references are recent theoretical and experimental studies, and refer to the detailed description of the phenomenon of selective particle focusing described above. Fernandez de la Mora,
J. Rossell-Llompart, J .; And Riesco-Chueca, P.M.
(1989) "Aerodynamic Focusing of Particles an
d Molecules in Seeded Supersonic jets ", fromRarefi
ed Gas Dynamics: Physical Phenomena, Muntz, E.
P. , Weaver, D. P. , And Campbell, D.M. H. , Eds. Vo
l. 117 of Progress in Astronautics and Aeronautic
s, AlAA, Washington D.S. C. For example, Fernandez de la
FIG. 2 on page 252 of the aforementioned article by Mora et al. Shows the trajectories of heavy particles seeded in a light gas as it flows through a nozzle that causes the gas to rapidly converge. Heavy phase particles tend to concentrate along the nozzle axis downstream of the nozzle. Particles with sufficient inertia intersect the nozzle axis at a common intersection point or focal point, the location of the intersection depending on flow rate, nozzle geometry, particle inertia, and to some extent upstream of the nozzle where the particles are seeded. Involved. Aside from the inertia of large particles, the location of the focal point is theoretically independent of the flow and particle parameters, but the "geometrical aberrations" seen in particles from substantially different locations upstream of the nozzle Affects as well as optical systems. However, in a constant nozzle operating over a wide range of flow conditions, most of the particles orbit through a focal zone that is much narrower (a few percent) than the outlet of the nozzle. The focal zone 26 is generally located at a distance downstream from the opening or outlet 15 which is smaller than the outlet dimension of the nozzle, and the particle phase is up to 1000 times thicker in this area.

The phenomenon in which particles are concentrated by an inertia greater than the inertial force of the carrier fluid is technically called "aerodynamic focusing" in the technical literature. As an example, the above-mentioned Fernandez de
See la Mora et al.

FIG. 2 is a schematic diagram of the preferred embodiment of the present invention. The device 25 of the invention in a general application is inserted between two fluid conduit sections 32 and 34 of a flow conduit carrying a particle-containing gas and secured by suitable coupling or securing means 31 and 33. Fluid conduit 32 is the inlet of the flow conduit, while fluid conduit 34 is the outlet of the flow conduit.

The openings or outlets 15 are preferably circular in order to ensure focusing of contaminated or unwanted fluid particles 13. The diameter of the opening 15 depends on the nozzle 1
It must be at least 1/2 less than the 0 entry. Particles 13 approaching the nozzle 10 are optionally dispersed in a carrier gas and pass through the nozzle 10 to create the appropriate conditions, all particles 13 being focused and positioned on the nozzle axis 27. Narrow focal range 2
Flowing through 6. By varying the shape parameters of the nozzle appropriately, for example, by varying the diameter of the nozzle opening or nozzle outlet 15 with respect to the diameter of the inlet, the focal zone 26 will be at different distances from the outlet or opening 15. Can be located in. The optimum design of the nozzle 10 depends, of course, on the physical properties of the particles being detected, the characteristics of the carrier fluid flow, the number of particles being detected, etc.

In most applications, the focal zone 26 is located downstream from the nozzle opening or outlet, and a distance of 0.5 to 3 times the diameter of the nozzle opening or outlet is typical. know. The focal zone 26, which has a small cross-sectional area compared to the cross-sectional area of the nozzle exit or opening 15, is illuminated by a high intensity light beam 22 that is narrower focused than the particle stream in the focal zone 26. The intersection of the two focal points (ie the light beam 22
And the stream of particles 13)
Will be detected and can be counted. It is believed that by using this device of the present invention, much higher particle detection efficiencies approaching 100% can be obtained than currently available similar means without focusing nozzles.

A narrow beam of light 22, such as a laser beam, is source 18 which is preferably a laser diode.
To focus the light beam 22 on the focal zone 26 using a suitable collimator 28. The scattered light is received by the light receiving unit 29.
Is collected by a photodetector 19, which is preferably a solid-state photodetector or a photomultiplier tube.
The incident light beam ends at the light stop 24 in the forward scattering configuration shown in FIG. This light stop 24 prevents the incident light beam 22 from reaching the detector 19, so that the detector 19 only detects scattered light from the particles. The particles 11 and 13 passing through the device 25 are generally discharged through the outlet of the flow conduit 34 using a pump.

As can be seen from FIGS. 1 and 2, the maximum concentration of counted particles 13 is in the focal zone 26. Therefore,
In order to obtain the maximum density count, the nozzle axis 27 and the optical axis 37
Must intersect at an angle of 90 degrees so that the focus of the light beam can optimally intersect the focus of the particle stream.

Aperture 15 of nozzle 10 for abrupt convergence
Is generally smaller than the conduit, but larger for the thickness of the focused light beam 22. This allows the vacuum to be effectively delivered through the nozzle without experiencing extreme resistance.

In most applications, the sensing optics and the flowable particles are preferably contained within housing 30. The housing 30 also protects the focal zone 26 from external influences such as ambient air vibrations and light from unwanted sources.

Another preferred embodiment of the device of the present invention is shown in FIG. The device 35 of the present invention is very similar to the device 25, but the light source 18 is aligned substantially coaxially with the nozzle 10. If the angle of the intersection 7 between the nozzle axis 27 and the light beam axis 37 is small, the long part of the nozzle axis will be illuminated. Light beam 2 in extreme cases
2 may be coaxial with the nozzle 10. In this example, the effect of geometrical aberrations is less so that the particles 13 at the nozzle 10 will cross the axis at a slightly modified distance from the nozzle exit 15.

As shown in FIG. 3, the nozzle outlet, that is, the distance between the opening 15 and the axis of the light beam 37 is adjustable. To change this distance, for example, the nozzle 10 is mounted on an appropriate movable means 39 such as a bearing,
Can be moved axially or the housing 30 of the optical device can be moved axially. Similarly, the nozzle 10, the optical system, or both can be moved using a telescoping method to achieve the desired result.

FIG. 5 illustrates another embodiment of the present invention, showing a dust collection or removal means 50 for removing particles 13 from a fluid stream. The removal means 50 is placed in or near the focal zone 26. Therefore, the high concentration region 2 of the fluid flow
3 is removed by the removal means 50, while the lean region 21 of the fluid stream substantially bypasses the removal means 50. For removal near the focal zone 26, the removal means 50 define a limit for removing the high concentration zone 23 of the fluid stream. The closer the removal means 50 is to the focal zone 26, the higher concentration zone 23 of the fluid flow
Are further removed. The removal means can be used in conjunction with the light beam 22 and associated equipment, as shown in FIG. 5, to count particles prior to removal. Instead, light beam 2
There is also a method in which 2 and related devices are removed, and particles are simply removed and counted later. The removal device 50 can have a tube 56 into which the flow in the high concentration zone 23 enters. Since the tube 56 intersects the fluid flow at or near the focal region, the cross-sectional area (or diameter) of the tube 50 is the cross-sectional area (or diameter) of the nozzle 15.
Smaller than. Pump 52 is added if necessary. Tube 56 removes particles 13 from the fluid conduit and through via conduit 54 for further processing. After passing through the conduit 56 and through the fluid conduit 34, the particles can be counted at a location if desired.

FIG. 4 is a schematic diagram illustrating a practical process utilizing the present invention. Processing device 40 having processing chamber 45
Has a flow process inlet 42 and a flow process outlet 44.
As shown in FIG. 4, the apparatus according to the present invention has a flow treatment inlet 4
It can be located at the two or the flow treatment outlets 44 or both. As a result of the work in the processing chamber 45, in order to obtain an accurate count of the particles introduced into the flow stream,
The sensing system of the present invention may be located at both flow process inlet 42 and flow process outlet 44. Also, care must be taken that the particle detectors of the present invention are sufficiently separated from the process chamber 45 so that these particle detectors are not adversely affected by any of the processing that occurs within the process chamber 45.

The present invention also includes apparatus and methods for highly efficient and in-situ particle detection and particle separation. The present invention provides highly efficient separation and measurement of particles, especially particles in a gas. The invention is required in many industrial applications. Such industries include, for example, the semiconductor industry, the pharmaceutical industry, the environment-related industry, and the like. Perhaps the most used field of the invention is the semiconductor industry, where cleanliness in semiconductor fabrication is very important. The present invention not only allows measurement of particles, but can separate useful and useless particles. Similarly, in the pharmaceutical industry, separation of microparticles is desired so that certain drugs are processed into a finely divided state. Environmental applications provide sampling for detailed analysis and enrichment of diluted environmental fumes. Of course, there are numerous devices currently in use, such as filters and impactors, to separate particles from the gas stream. These devices generally collect particles on the surface of the element that obstruct the flow.
However, the present invention not only measures flowing particles in situ, but also separates particles of the same type with high efficiency.

The present invention relates to a nozzle 1 as shown in FIG.
A nozzle 10 is used which is aligned with a removing means 50 which is a probe or collector downstream from 0. Generally, the flow through nozzle 10 is subsonic, so nozzle 1
It is not necessary to discharge the stream exiting 0 into the vacuum. Under properly selected flow conditions, the nozzle 10 aerodynamically focuses, i.e., focuses, the particles 13 in the fluid into a focal zone 26 that is smaller in size than the nozzle outlet. The probe or removal means 50 used typically has an inlet section that is smaller than the size of the outlet section of the nozzle 10. The probe or removal means 50 is preferably aligned with the nozzle axis and is located close to or overlapping the focal zone 26 of the particle. A small central portion of the gas stream exiting the nozzle 10 is very rich in particles due to focusing and is drawn through the probe or removal means 50. That is, it is extracted, while the rest, which is generally a "clean" carrier gas 60, is discharged along the outer wall of the removal means 50. The flow through the removal means 50, which is a probe, is preferably constant velocity. That is, the velocity of the gas or particles passing through the probe inlet is equal to the velocity of the flow upstream of the probe. Constant velocity sampling is generally useful in reducing particle loss on the probe wall. This was not possible with prior art means which generally have a larger collection opening diameter than the outlet of the nozzle.

As illustrated in detail in FIG. 5, a removal means 50 is shown which is a collector or probe for removing particles 13 from the fluid stream. The removal means 50 is located at or near the focal zone 26. The fluid in the particle high-concentration region 23, which is the fluid flow, is removed by the removing means 50 by such a method. On the other hand, the fluid in the particle-lean zone 21, which is the fluid stream, substantially bypasses the removal means 50 and exits as a "clean" carrier gas 60. The degree of proximity of the removal means 50 to the focal zone 26 determines the extent to which fluid in the high concentration zone 23 of the fluid stream is removed.
The closer the removal means 50 is to the focal zone 26, the more fluid in the dense zone 23 in the fluid stream is removed. Removing means 50
Can be used in conjunction with the light beam 22 and associated equipment as shown in FIG. 5 and can be counted prior to particle removal.
Another method is to disconnect the light beam 22 and associated devices and simply remove the particles before counting. The removing device 50 has a pipe 56 into which the fluid in the high concentration region 23 flows.
The cross-sectional area (or diameter) of the tube or pipe 50 is smaller than the cross-sectional area (or diameter) of the nozzle opening or outlet portion 15 in order to intersect the fluid flow at or near the focal zone 26. Pump 52 is added if needed to remove particulates. Tube 56
Particles 13 are removed from the fluid conduit for processing in via conduit 54. After the particles have exited fluid conduit 34 by tube 56, the particles can be counted at a point if desired. Similarly, the removed particulate can be delivered for further processing. This treatment may be a fine particle treatment of the drug, or removal of these fine particles from a closed loop system.

Of course, the present invention also includes aerodynamically focusing to separate heavy particles from lighter particles, or to separate particles that have already separated, or to selectively focus particles to selectively particle. Can be used for separation, etc.

Furthermore, it is generally better to detect the forward scattered light from the particles 13. The device of the present invention is not limited in its configuration, and angular freedom sensing can be used as well.

In some applications it may be advantageous to use a rectangular nozzle opening 15. In this case, a large aspect ratio is created in the opening 15, and the suspended particles 13 are converged when flowing through, for example, a rectangular slit whose vertical width is longer than its horizontal width. The focal zone 26 in this case has a length transverse to the fluid flow, which corresponds to the length of the slit. The light beam 22 illuminates the particles across the wall of the flow conduit along the length of the particles that it passes through.

Another configuration of nozzle 10 has an adjustable outlet or opening 15 which expands the application of the device of the present invention over a wide range of pressures and flow rates. Instead of the iris diaphragm 17 due to the configuration of the axisymmetric shape, for example,
Plates 14 and 16 may be substituted to provide variable shapes used in camera apertures and the like. In the rectangular shape, a slit opening 15 can be used which is variable using two coplanar plates 14 and 16 moving in opposite directions.

The device of the present invention can operate under subsonic and supersonic flow velocity conditions. Particle focusing is observed at subsonic and supersonic flow rates through the nozzles described above, but in many intended applications of the device it is generally advantageous to operate under subsonic conditions. Because of the constant pump capacity, the subsonic flow is generally operated with large diameter nozzles, resulting in a correspondingly small pressure drop across the nozzle. In the case where the flow velocity is subsonic and the pressure range is 0.1 torr to 10 torr, most of the nozzles are 3m.
While having an exit diameter greater than m, in such applications, the focused laser beam preferably has a thickness of about 1 mm or greater. If the flow velocity is supersonic, nozzles smaller than 1 mm are needed.

Although the present specification has been described with reference to particular preferred embodiments, it will be apparent to those skilled in the art that many alternatives, modifications and variations are possible within the scope of the foregoing. Accordingly, the appended claims encompass any alternatives, modifications and variations within the spirit and scope of the invention.

Examples will be summarized and described below. (1) A device for detecting particles flowing in a fluid conduit, the nozzle having at least one focusing means for aerodynamically focusing the particles in a focal zone, wherein: A cross-sectional area is substantially smaller than the cross-sectional area of the focusing means, and at least one for illuminating the focal zone with at least one narrow light beam.
The device comprises one means and at least one means for detecting scattered light of the particles irradiated by the light beam. (2) The device according to (1), wherein the focusing means is a nozzle that rapidly converges. (3) The device according to (2), wherein the nozzle is substantially axisymmetric. (4) The device according to (2), wherein the nozzle has a substantially rectangular shape. (5) The device according to (2), wherein at least a part of the cross-sectional area of the nozzle is adjustable. (6) The velocity of the fluid flow through the nozzle is subsonic.
(2) The device described in the above. (7) The apparatus according to (1), wherein the light beam traverses the focal region substantially in the lateral direction. (8) The device according to (1), wherein the light beam traverses the focal region from a substantially coaxial direction. (9) The device according to (1), wherein the focusing unit has a unit capable of changing a distance between the focal region and the focusing unit. (10) The distance between the nozzle and the focal area irradiated by the light beam is at least 3 of the nozzle width.
It is the device according to (2), which is one-tenth. (11) At least one for moving the focusing means
The device according to (1), which has two means. (12) The device of (1), wherein the detected particles are carried by at least one carrier fluid. (13) The device according to (12), wherein the at least one fluid is at least one gas. (14) The apparatus according to (1), wherein the at least one light beam is laser light. (15) At least one means for detecting the scattered light is at least one for electrically calculating the scattered light.
The device according to (1), which has two means. (16) further comprising at least one means for removing at least a portion of the particles from the focal zone and the fluid conduit in and near the focal zone.
The device described. (17) The apparatus according to (16), wherein the removing means is a tube. (18) A method for detecting particles flowing in a fluid conduit, comprising: (a) aerodynamically focusing particles detected by at least one focusing means into a focal zone, wherein: The cross-sectional area is smaller than the cross-sectional area of the focusing means, (b) illuminating the focal zone with at least one narrow light beam such that the light beam is scattered by the particles in the focal zone; The method further comprising detecting the scattered light by the particles illuminated by a light beam and counting the number of particles in the focal region detected in the detecting step. (19) The method according to (18), wherein the focusing means is a nozzle that rapidly converges. (20) The nozzle is substantially axisymmetric, (19)
This is the method described. (21) The nozzle is substantially rectangular, (19)
This is the method described. (22) The method according to (19), wherein at least a part of the cross-sectional area of the nozzle can be changed. (23) The method according to (19), wherein the velocity of the fluid flow passing through the nozzle is subsonic. (24) The method according to (18), wherein the light beam traverses the focal region substantially in the lateral direction. (25) The method according to (18), wherein the light beam traverses the focal region in a substantially coaxial direction. (26) The method according to (18), wherein the focusing means has means for changing a distance between the focal region and the focusing means. (27) The distance between the nozzle and the focal area irradiated by the light beam is at least 3 of the nozzle width.
It is the method according to (19), which is one-third. (28) The method according to (18), further including at least one means for moving the focusing means. (29) The method according to (18), wherein the detected particles are carried by at least one carrier fluid. (30) The method according to (29), wherein the at least one fluid is at least one gas. (31) The method according to (18), wherein the at least one light beam is laser light. (32) The method according to (18), wherein at least one means for detecting the scattered light has at least one means for electrically calculating the scattered light. (33) The method of (18), further comprising the step of removing at least a portion of the particles from the focal zone and the fluid conduit at or near the focal zone. (34) The method according to (33), wherein the removing means is a tube. (35) A device for separating particles flowing in a fluid conduit, the nozzle having at least one focusing means for aerodynamically focusing the particles to a focal zone, wherein the nozzle of the focal zone is An apparatus having a cross-sectional area substantially smaller than the cross-sectional area of the focusing means and comprising the focal zone and at least one means for removing the focused particles from the fluid conduit. (36) A method for separating particles flowing in a fluid conduit, comprising: (a) aerodynamically focusing particles separated by at least one focusing means into a focal zone, wherein the focal zone is cut off. The area is smaller than the cross-sectional area of the focusing means, and (b) is a method of removing the separated particles from the focal zone and the fluid conduit. (37) The apparatus according to (16), further including at least one means for counting the particles in the focal region. (38) further comprising counting the particles in the focal zone using at least one particle counting means, (3
3) The method described.

[0051]

The highly efficient particle detection provided by this new invention is suitable for many industrial applications such as SPC applications.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a preferred flow nozzle of the present invention.

FIG. 2 is a schematic diagram of a preferred embodiment of the invention in which the direction of travel of the light beam is substantially transverse to the fluid flow through the nozzle.

FIG. 3 is a schematic view of another embodiment of the invention in which the direction of travel of the light beam is substantially coaxial to the fluid flow through the nozzle.

FIG. 4 is a schematic diagram of another embodiment of the present invention showing an industrial process utilizing the present invention.

FIG. 5 is a schematic view of another embodiment of the present invention showing a dust collector for removing particles from a flowing stream.

[Explanation of symbols]

 10 Nozzle 12, 30 Housing 14, 16 Nozzle Plate 11, 13 Flowing Particle 15 Opening or Outlet 18 Light Source 17 Iris Diaphragm 19 Photodetector 21 Dilute Region 22 Light Beam 23 High Concentration Region 24 Light Stopper 26 Focal Region 27 Nozzle Axis 28 Collimator 29 Light Receiving Section 32, 34 Fluid Conduit 37 Light Beam Axis 40 Processing Device 45 Processing Chamber 50 Removal Means 52 Pump 54 Via Conduit 56 Tube 60 “Clean” Carrier Gas

Front Page Continuation (72) Inventor Keanush Bayzavi P-O Box 4751, Carly, NC 27519, USA

Claims (38)

[Claims] 1. A device for detecting particles flowing in a fluid conduit, said nozzle having at least one focusing means for aerodynamically focusing said particles in a focal zone, wherein said focus is provided. At least one means for illuminating the focal zone with at least one narrow light beam, the particle having a cross-sectional area substantially smaller than the cross-sectional area of the focusing means, and the particles illuminated by the light beam And at least one means for detecting scattered light of. 2. The apparatus according to claim 1, wherein the focusing means is a nozzle that rapidly converges. 3. The apparatus of claim 2, wherein the nozzle is substantially axisymmetric. 4. The device of claim 2, wherein the nozzle is substantially rectangular. 5. The apparatus of claim 2 wherein at least a portion of the nozzle cross-sectional area is adjustable. 6. The apparatus of claim 2, wherein the velocity of the fluid flow through the nozzle is subsonic. 7. The apparatus of claim 1, wherein the light beam traverses the focal zone from a substantially lateral direction. 8. The apparatus of claim 1, wherein the light beam traverses the focal zone from a substantially coaxial direction. 9. The apparatus according to claim 1, wherein the focusing means includes means capable of changing a distance between the focal zone and the focusing means. 10. The apparatus according to claim 2, wherein a distance between the nozzle and the focal area irradiated by the light beam is at least one third of the nozzle width. 11. The apparatus of claim 1 having at least one means for moving said focusing means. 12. The apparatus of claim 1, wherein the particles to be detected are carried by at least one carrier fluid. 13. The device of claim 12, wherein the at least one fluid is at least one gas. 14. The apparatus of claim 1, wherein the at least one light beam is laser light. 15. The apparatus of claim 1, wherein the at least one means for detecting scattered light comprises at least one means for electrically calculating the scattered light. 16. Further comprising at least one means for removing at least a portion of the particles from the focal zone and the fluid conduit in and near the focal zone.
The device according to claim 1. 17. The apparatus of claim 16 wherein said removing means is a tube. 18. A method for detecting particles flowing in a fluid conduit, comprising: (a) aerodynamically focusing particles detected by at least one focusing means into a focal zone, wherein the focus is (B) illuminating the focal zone with at least one narrow light beam such that the light beam is scattered by the particles in the focal zone; D) detecting the scattered light by the particles illuminated by the light beam, and counting the number of particles in the focal zone detected in the detecting step. 19. The method according to claim 18, wherein said focusing means is a nozzle for rapidly focusing. 20. The method of claim 19, wherein the nozzle is substantially axisymmetric. 21. The method of claim 19, wherein the nozzle is substantially rectangular. 22. The method of claim 19, wherein at least a portion of the cross-sectional area of the nozzle is variable. 23. The method of claim 19, wherein the velocity of the fluid flow through the nozzle is subsonic. 24. The method of claim 18, wherein the light beam traverses the focal zone from a substantially lateral direction. 25. The method of claim 18, wherein the light beam traverses the focal zone from a substantially coaxial direction. 26. The method of claim 18, wherein said focusing means comprises means for varying the distance between said focal zone and said focusing means. 27. The method of claim 19, wherein the distance between the nozzle and the focal area illuminated by the light beam is at least one third of the nozzle width. 28. At least one for moving said focusing means.
19. The method according to claim 18, comprising one means. 29. The method of claim 18, wherein the particles to be detected are carried by at least one carrier fluid. 30. The method of claim 29, wherein the at least one fluid is at least one gas. 31. The method of claim 18, wherein the at least one light beam is laser light. 32. The method of claim 18, wherein the at least one means for detecting scattered light comprises at least one means for electrically calculating on the scattered light. 33. The method of claim 18, further comprising the step of removing at least a portion of the particles from the focal zone and the fluid conduit at and near the focal zone. 34. The method of claim 33, wherein the removing means is a tube. 35. A device for separating particles flowing in a fluid conduit, said nozzle having at least one focusing means for aerodynamically focusing said particles in a focal zone, wherein said focusing point. An apparatus having a cross-sectional area substantially smaller than the cross-sectional area of the focusing means, and comprising the focal area and at least one means for removing the focused particles from the fluid conduit. 36. A method for separating particles flowing in a fluid conduit comprising: (a) aerodynamically focusing particles separated by at least one focusing means into a focal zone, wherein said focal zone. The cross-sectional area of is smaller than the cross-sectional area of the focusing means, and (b) removing the separated particles from the focal zone and the fluid conduit. 37. The apparatus of claim 16 further comprising at least one means for counting the particles in the focal zone. 38. The method of claim 33, further comprising counting the particles in the focal zone using at least one particle counting means.