JPS6363943A - Floating fine particle observing apparatus - Google Patents

Abstract

PURPOSE:To measure the behavior and density of floating fine particles in a non-contact manner, by making a laser beam irradiate an observing part scanning in a fixed direction to detect the scattered light thereof from the floating fine particles at the observing part. CONSTITUTION:This apparatus is provided with a scanner 13 which irradiates an observing part with a laser beam 4a scanning in a fixed direction and a detector 14 which detects the scattered light 6 of the beam 4a from floating fine particles at the observing part. An incident optical path for the device 13 is provided with a beam slit 11 having an opening with the shape identical to that of the section of the beam 4a and additionally an optical path of the scattered light 6 is provided with a detection slit 16 having an opening with a fixed section. The detector 14 has a camera 17, a photoelectric multiplier tube 18 and an amplifier 19 arranged in an optical path after passage through a telescopic lens 15 and a slit 16 arranged on the incidence side of scattered light of the slit 16. A pulse generated from the detector 14 is counted with a pulse counter 21, thereby enabling non-contact measurement of the behavior and the density of floating fine particles.

Description

[Detailed description of the invention]

Industrial application field 11 is related to observation equipment for fine particles suspended in the air.
In particular, it relates to a suspended particle observation device that non-contactly observes suspended particles at an observation site in a clean room. Yes, leave. In clean rooms that require a high degree of cleanliness,
It is necessary to measure and evaluate properties such as the behavior of spaceborne particles, air flow, air filter, and leakage from equipment connections on the side walls of the room. A conventional suction type suspended particulate counter 1 shown in FIG. 2 counts suspended particulates in a sample air sampled through a suction tube 2. However, with this conventional suction-type suspended particle counter, (a) the measurement space is disturbed by the suction tube and suction airflow, making it difficult to capture the state of the observation area with high precision; and (b) fine particles adhere to the inside of the suction tube. - It tends to scatter and disturb the measurement f1^, (c) T=fast suction is almost impossible, and (d) there is a time delay in particle detection. In order to avoid these drawbacks, the present inventors have proposed a laser light scattering type particle observation device shown in FIG. In the figure, a laser beam 1i is energized from a power source 3d.
Laser light 4 generated by laser beam 3 is directed toward the observed site by surface mirror 5. The laser beam 4 is scattered by the floating particles (in the target area 1111) and the scattered light 6 is captured. A camera 7 having a telephoto lens captures the scattered light 6 from the target area 111. The image formed at the position is observed by 11 viewing or recorded on a video tape recorder by a video camera 9 with a microscope adapter 8 and repeatedly observed. 11 to observe the behavior of 1γ free particles in a non-contact manner.
Problem with not being able to measure the C degree of floating M fine particles

[
-There are people. ``Moxibustion''``Moxibustion'' [Yo a = ta + r υ surface force Therefore, while the uninvented is trying to solve the problem, γ is the behavior of fine particles and the actual contact observation of C degree and AI is constant. r-1 for determining anal kneeling position A. Referring to FIG.
#The device 1v1 scans the laser beams 1 and 4a in a fixed direction and scans 3 + 11 parts (11
3, and a detector 14 for detecting the scattered light 6 of Zaheem 4a from the floating particles at the observation site. In a preferred embodiment of the invention, a beam slit 11 having an aperture 11 of the same cross-sectional shape as the beam 4a is provided in the optical path of incidence to the bipedal scanning device 13, and furthermore! - In the optical path of the laser beam scattered light 6, there is provided a detection triplet 1G having an aperture 11 of a constant cross section. The laser beam 4a is formed by converting the laser light 4 from the laser light source 3, which is preferably a He-N e 1y- laser light source, into a beam by the two-head beam throat 11. In Figure 1, the example detector 14 includes 1 - star detection three 2 16
The telephoto lens 15 is placed on the scattered light incident side, and the detection slit IB through iIiSg? A camera 17 is placed in the optical path of the camera 17, and a photomultiplier I8 and an amplifier 19 are connected to the output of the camera 17. However, the float I of the present invention
! ! 2. The detector 14 used in the particle observation device is not limited to the configuration shown in the illustrated example. In this case, the detector 14 detects the HN! from the incidence frequency of the laser beam scattered light 6 and the aperture of the beam slit 11 and l-, the 1 method of the aperture of the star detection slit 16. The 1γ'M fine particle C degree at one site is calculated. The mo-convex lens 12 in the illustrated example can be omitted when the laser beam exiting the beam three 7 is a mole beam. Referring to Fig. 4, when the laser beam 4 from the laser light source 3 is converted into a laser beam 4d by the beam slit 11 and is scanned by the scanning device 13 and irradiated to a part of the observation AI, the laser beam 4d from the laser light source 3 is scanned by the scanning device 13. Light scattering theory of suspended particles (G
, Mie, Beitrage zur 0ptik
triiber Medien, 5peziell
kolloidaler Metallilisung
en. Ann, Physik, Vol 25 (1908
) is known to generate scattered light according to 377). Therefore, if the optical axis of the detector 14 is arranged so as to intersect the traveling direction of the laser beam 4a at the acceptance angle 0 determined by the scattering theory, the scattered light 6 can be captured by the detector 14. The detector 14 of the 1A small example generates a pulse from the amplifier 19 every time it detects one wave of scattered light 6. By counting the pulses with the pulse counter 21 and counting the number of times the scattered light 6 is generated, the number of floating particles can be counted based on the number of collisions between the laser beam 4a and the particles at the measurement site. By making the opening L of the beam slit ll circular with a diameter W, the cross section of the laser beam 4a is made circular with the same diameter, and when the opening [1 of the detection slit 1G is set to a shape with a horizontal width and an M1 shape with a vertical width, , the floating 'ML particle concentration n is given by the following (1
) is given by the formula. n=(Ntasinθ)/(2f*m2ish*v
*t) ・Fist e (1) Here, t: l11 constant time interval (s) Particle count value (number) within Nt・time f: Frequency of scanning device (Hz) θ: Detector optical axis Receiving angle (degrees) m・Detector imaging magnification coefficient W: Laser beam diameter (am) p: Width of rectangular slit (am) h: Vertical width of rectangular slit (C1) Calculation using equation (1) above is as follows: , for example, by computer 22 in FIG. Display unit 20 in the same figure
is, for example, a cathode tube display for visually observing the output pulses of the amplifier 19. - As is clear from the above equation (1), the measurement target space at the observation site is limited by the aperture size of the beam slit 11 and the aperture size of the detection slit 16. In the L equation, w+5.18xlO-2cm, ? 0.20c
m. b-0.05 am, this measurement space is 83 cIr per minute! becomes. Only the scattered light 6 of the particles contained within the measurement target space is captured by the detector 14, and converted into a pulse signal by the photomultiplier 18. In this way, it is possible to observe and measure suspended particles at the observation site without contact. The present invention will now be described in more detail with reference to experimental examples. [Experimental Example 1] The characteristics of the suspended particle observation device according to the present invention are shown in Fig. 5 (
-III was determined using an experimental system. That is, air was flowed into a double normal laminar flow clean booth at a flow rate of 60 ci/s as shown by white arrow F, and standard particles (PS) with a particle size of 0.79 Sμ were
LJ>R) was supplied to the upstream side of the airflow through the particle supply pipe 24 to generate suspended particles 25. The concentration of suspended particles 25 was measured at the observation site 26 at a diameter of 185 mm.
The particles were measured using a particle observation device and a suction type particle counter 1 at a distance of 200 mm directly below the generation. At this time, the suction type particle counter 1 has achieved uniform suction, and the suction pipe 2 is also short with a length of 600 m, so the measured value of the suction type particle counter 1 is the true suspended particulate concentration. It was thought that this indicates that FIG. 6 shows a comparison between the values measured by the suction type particulate counter 1 and the Jll constant 1 by the suspended particulate observation device of the present invention when the concentration of standard particles generated is varied. Good agreement was observed between both measurements. [Experimental example? ] As shown in Fig. 7, a silicon wafer 29 with a diameter of 3 inches is placed horizontally in a vertical laminar flow clean booth, and standard particles are generated at a constant velocity from upstream using a glass tube.
Cross section along the diameter of 9” 80 am on the upstream side of the second airflow!
80! Assuming a measurement surface 30 of 1 m, the suspended particle concentration at 81 measurement points at 10 cm intervals on the measurement surface 30 was measured using the suspended particle observation device according to the present invention. Figure 8 shows the coordinate axes used in the measurements. When the speed of the airflow indicated by the white arrow F in FIG. The measurement results are shown in Figure 9. However, the concentration at each point is shown as a relative value with the suspended particulate concentration measured at a position 10 Wml directly below particle generation as 1. As the particles approach the surface of the wafer 29, they gradually become
spreads in the diametrical direction of the wafer and is almost uniformly distributed at the position of the L flow 10 rm layer of the wafer, and its concentration is 10-3-10-2
It becomes. In this case, it is considered that wafer contamination is very likely to occur. As explained in detail above, the floating particle observation device according to the present invention includes a scanning device that irradiates the observation area with a laser beam while scanning it in a fixed direction, and - Since a configuration including a detector for detecting the scattered light of the beam is used, the following remarkable effects are achieved. (B) View 3: The behavior of floating M fine particles at one location can be observed non-contact. (B) The concentration of floating M particles at the observation location can be measured non-contact. (C) It is possible to accurately measure the concentration distribution of suspended particles on the measurement surface at intervals of about 10 am. (d) If the relationship between the particle size of floating M particles and the brightness of scattered light is given, 4. Determining the concentration of suspended particulates in 4 points becomes the "T run." (E) Measurement of the degree of suspended particulates at the observation site can be carried out without affecting the particulate distribution at the site.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the suspended particle observation device according to the present invention, Fig. 2 and Fig. 3 are explanatory diagrams of the conventional technology, Fig. 4 is an explanatory diagram of the operation, and Fig. 5 to Fig. 59 are experimental examples. It is an explanatory diagram. l...suction type 7γjft fine particles 5.1 attack 2;, 2
... Suction saving, 3... Laser light source, 4... Laser light, 4a... Laser beam, 5... Surface mirror, 6... Scattered light, 7.17... Camera,
8...Microscope adapter, 9...Video camera, 10...Video chip recorder, +1...Heemsuri, I., 12...Ze convex lens. 13... Scanning device, 14... Detector, 15...
・Telephoto lens, 16...Detection slit 18...Photoelectric f-multiplier tube, 19...Amplifier, 20...Table device, 21...Pulse meter ¥! Device 22...computer, 24...particle (jj picture 'Otsu, 25 ・
・・Floating fL particle-126 viewing side part, 2 tons・・Licon wafer, 30・・all fixed surface. 4ν 1 piece Out Rabbit 1 well
Osamu 〕°. Patent Applicant 1.1 Kawa-・Tun #-Kaide U Agent Jr. Riju Shandong Reiji Department Figure 4, 254! Figure 7 Figure 9J8 Figure 9

Claims (2)

[Claims] (1) A floating particle observation device comprising: a scanning device that scans a laser beam in a fixed direction and irradiates the observation region; and a detector that detects scattered light of the laser beam from floating particles in the observation region. (2) In the suspended particle observation device according to claim 1, a beam slit having an aperture having the same shape as the cross-sectional shape of the laser beam to be scanned, which is disposed on the optical path of incidence to the scanning device, and the laser beam A detection slit arranged in the optical path of the scattered light and having an aperture of a constant cross section is provided, and the detector calculates the suspended particulate concentration at the observation site from the incident laser beam, the dimensions of the aperture of the beam slit, and the aperture of the detection slit. A floating particle observation device.