JPH05288668A - Dust detector - Google Patents

Abstract

PURPOSE:To obtain a dust detector, which has the excellent maintenability and the high measuring accuracy, at low cost without delicate adjusting work and the like. CONSTITUTION:The laser beam from an optical fiber array 30, which is formed by arranging optical fibers in a plane, is converted into a parallel laser beam 36, wherein the beams are distributed in the sheet shape, with semi-cylindrical lens 34. Scattered light 22, which is generated when the laser beam 36 crosses a dust particle 18, is detected with a scattered-light detector means 26. A laser- light absorber means 16, which absorbs the sheet-shaped laser beam 36 without leaking to the outside, is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust detector capable of detecting the number of dusts in a product manufacturing space in real time.

[0002]

2. Description of the Related Art In a semiconductor manufacturing apparatus or an electronic component manufacturing apparatus, it is necessary to minimize dust adhesion to a substrate in order to secure a product yield. For this reason,
Always monitor the dust generation situation in the product manufacturing environment,
If there is an increase in dust, research has been done to detect it and take measures to suppress the increase in dust.

FIG. 6 is a diagram for explaining an example of a conventional dust detector of this type (disclosed in Japanese Patent Laid-Open No. 62-215843). (A), (B) and (C) of the same figure respectively show the plan view, side view and perspective view of the dust detector.

Laser beam 1 emitted from laser oscillator 10
2 is a pair of parallel plane mirrors 14a and 1 that are installed to face each other.
4b repeats reflections between the two plane mirrors 14a and 14b.
A single planar laser beam net 120 is formed between b. The laser beam 12 is the laser beam absorber 1
No. 6 is entered so that it is finally absorbed and cannot be leaked to the outside.

Dust particles 18 fly into this laser beam net 120 as shown by arrow 20, and when they cross the laser beam 12, scattered light 22 is generated. This scattered light 22 is collected by scattered mirrors 24a and 24b in scattered light detectors 26a and 26b, where the number of dust particles 18 that have crossed the laser beam 12 is counted.

By increasing the number of times the laser beam 12 is repeatedly reflected, the beam density of the laser beam net 120 is increased, the gap between the nets is reduced, and the number of dust particles 18 that pass undetected is reduced to reduce the number of dust particles. The sensitivity of measurement can be improved.

FIG. 7 is a diagram showing another example of a conventional dust detector (which is disclosed in Japanese Patent Laid-Open No. 3-176641). 7A and 7B are a plan view and a side view, respectively. The reference numerals are the same as those in FIG.

In the configuration example shown in FIG. 7, a laser beam irradiation means 28 composed of a semiconductor laser array or the like irradiates a plurality of laser beams in parallel and densely to form a laser beam sheet 30. This laser beam sheet 3
When the dust particles 18 block 0, scattered light 22 is generated. The scattered light 22 is detected using a detector 26. Reference numeral 16 is a laser beam absorber. The reflectors 14a and 14b used to reflect the laser beam in FIG. 6 are not needed.

[0009]

In the conventional dust detector having the structure shown in FIG. 6, the reflecting mirrors 14a and 14b facing each other are provided.
The mirror surface of the is gradually contaminated by dust and the like, so it must be cleaned regularly. Further, the reflecting mirrors 14a and 14b must be mechanically precisely placed in parallel planes, but it is difficult to maintain this precision at all times during the manufacturing, use and cleaning processes. Further, since the beam density of the laser beam net 120 is also limited, the number of dust particles 18 passing through the gaps of the net is large. Therefore, high measurement accuracy cannot be obtained.

On the other hand, in the conventional dust detector having the structure shown in FIG. 7, since the laser beam sheet is formed by the light from the semiconductor laser array 28 or the like, no reflecting mirror is required, and therefore the structure is extremely simple. .. However, in order to convert a laser beam emitted from a large number of laser light sources forming the semiconductor laser array 28 or the like into spot-shaped beams that are parallel and evenly spaced and well aligned, a laser beam sheet that can be used practically is formed. It is necessary to equip each of the laser light sources with a fine and highly accurate correction optical lens.

However, it is not an easy task to mount a correction optical lens on each of a number of laser light sources to form a precisely parallel laser beam. Even if the operation is successful and a large number of parallel laser beams can be formed at intervals of several tens of μm, the gap between the laser beams is too wide. Since the particle size of the dust particles 18 to be measured is several μm at the maximum, the number of dust particles passing through the wide gap without being detected is inevitably large.

Further, the semiconductor laser array that radiates a plurality of laser beam lights all at once may become unstable in operation due to heat generated by a large number of semiconductor lasers. In order to solve this heat generation problem, it is necessary to limit the electric power supplied to the semiconductor laser or to add a cooling mechanism to the semiconductor laser array. Then, there is a drawback that the detection sensitivity of dust particles is lowered, or the number of components of the dust detector is increased to complicate the structure and increase the cost.

An object of the present invention is to provide a dust detector which does not require delicate adjustment work, is inexpensive, and has excellent maintainability and high measurement accuracy.

[0014]

SUMMARY OF THE INVENTION According to the present invention, an optical fiber array composed of a plurality of optical fibers whose light emission side portions are arranged in a plane, and a laser beam from the optical fiber array are distributed in a sheet form. A conversion means for converting into a parallel laser beam, a detection means for detecting scattered light generated when dust particles cross the parallel laser beam, and a beam stopper means for absorbing the parallel laser beam and not leaking it to the outside are provided. The object is achieved by the dust detector.

The conversion means for converting the laser beam from the optical fiber array into a parallel laser beam is an optical lens means for narrowing down the laser beam in a direction orthogonal to the arrangement direction of the optical fiber array, and the optical lens means is used. The accuracy of dust particle detection can be further improved by providing the optical fiber array close to the light emitting end face.

In the optical fiber array, the incident side portion of the light is bundled into a cylindrical shape, and the end portion of the cylindrical shape is irradiated with a laser beam from a laser light source. The part can be constructed inexpensively.

[0017]

According to the above-mentioned structure of the present invention, the laser beam emitted from the optical fiber array is controlled by the beam converting means so as to suppress the spread of the beam in the direction perpendicular to the array, and the laser beam is distributed parallel to the sheet. Get the laser beam. In the optical fiber array, a large number of single optical fibers are arranged adjacent to each other in a plane, so that the parallel laser beam obtained is a uniform sheet-like laser beam without a gap. Therefore, when the dust particles enter the area of the sheet-shaped laser beam and interrupt the laser beam, scattered light is generated. The scattered light detector detects the scattered light and counts the number of dust particles. Therefore, all the dust particles that have entered the sheet-shaped laser beam region can be completely detected by the detector, so that the dust particles can be accurately counted without the conventional adjustment. Further, the laser beam is completely absorbed by the beam stopper means, which is safe.

[0018]

Embodiments of the dust detector of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining the configuration of an embodiment of the dust detector of the present invention, and FIG.
Shows a perspective view and (B) shows a side view.

The dust detector of the present invention comprises an optical fiber array 30, a converting means 34 for converting a laser beam into a parallel laser beam 36, a scattered light detecting means 26, and a beam stopper means 16. ((A) and (B) in FIG. 1). In this embodiment, the optical fiber array 30 is composed of a large number of optical fibers, and one end of the optical fibers on which the laser beam is incident is formed as a cylindrical end portion 30a. An appropriate optical system, for example, a concave lens 32 is passed through the end portion 30a so that the laser oscillator 1
A laser beam (laser light) from 0 is made incident. The other end portions 30b of these optical fibers are arranged adjacent to each other in a planar shape, and the laser beam is emitted from the emission end faces arranged in a straight line. Preferably, optical lens means such as a cylindrical lens or a semi-cylindrical lens 34 is provided for narrowing the laser beam emitted from the optical fiber array 30 only in the thickness direction orthogonal to the array of the optical fiber array. The laser light that has passed through the lens 34 forms a parallel laser beam 36 in which a laser beam without a gap is distributed in a sheet shape. This parallel laser beam 36 is called a laser beam sheet.

When the dust particles 18 cross the laser beam sheet 36, the laser beam is scattered by the dust particles 18,
The scattered light 22 is detected by the scattered light detector 26. Each time the detector 26 detects the scattered light 22, the number of times of detection is counted, and as a result, the number of dust particles 18 is counted.

Next, the operation of the cylindrical lens or the semi-cylindrical lens 34 will be described with reference to FIGS. Since the laser light emitted from each optical fiber has a divergence angle of about several tens of degrees, the laser light emitted from the emission end face of the optical fiber array 30 arranged in a straight line has a cylindrical lens shape or a semi-cylindrical shape. When the lens 34 is not provided, a divergent light beam 38 that is formed by overlapping circular spots that gradually expand and becomes thicker toward the end (FIG. 2A). However, when the cylindrical lens or the semi-cylindrical lens as described above is arranged as the converting means 34 which is a constituent feature of the present invention in close proximity to the emitting end face of the optical fiber array 30, the emitted laser beam is emitted from the array 30. The thickness is narrowed in the direction orthogonal to. Therefore, this laser beam forms an ideal sheet-shaped parallel laser beam 36 having no gap in the width direction and being thin in the thickness direction ((B) in FIG. 2). Therefore, the detection omission of the dust particles 18 can be prevented, and the counting accuracy can be extremely improved.

Since the technique for constructing the optical fiber array 30 as shown in FIG. 1 is a technique which has already been put into practical use and is mature, the device of the present invention does not require any special device. Since the optical lens is simple as a single unit, the dust detector of FIG. 1 is more cost effective, easier to manufacture, and easier to adjust than the conventional dust detector described with reference to FIGS. 6 and 7. Far superior.

FIG. 3A shows an optical fiber 4 having a core diameter of 5 μm when a semi-cylindrical lens 34 having a diameter of 2 mm is used.
The diameter of the light emitted from 1 is the light exit 4 of the optical fiber 41.
6 is a graph showing how the distance α changes between 0 and (the plane side of) the semi-cylindrical lens 34 when changing. The abscissa of FIG. 3A shows the optical fiber-lens distance α (in mm), and the ordinate shows the distance L from the apex of the semi-cylindrical lens 34 (L = 30 mm).
The beam diameter D (in mm) at the measurement point P spaced apart is shown.

FIG. 3B is a diagram schematically showing the measurement state at this time. Here, the output angle of the light emitted from the optical fiber is 17 degrees, and the refractive index n of the lens is 1.51.

The spot diameter D of the focused beam largely depends on the distance α, and when α is about 0.3 mm, a substantially parallel beam is obtained, and the beam diameter D at that time is about 0.5 mm. I understand. The graph of (A) of this FIG.
It has been shown that even a lens having a simple structure such as the semi-cylindrical lens 34 can be effectively used in the dust detector 26 (FIGS. 1A and 1B) of the present invention.
Although not described, the same effect can be obtained with a cylindrical lens.

In the present invention, it is preferable that the end portion 30a of the optical fibers bundled in a cylindrical shape be efficiently irradiated with the laser beam through the concave lens 32. ((A) and (B) of FIG. 1). Therefore, the shape of the dust particle detector 26 can be made small regardless of the size of the laser oscillator as the light source 10. On the other hand, it is possible to use a laser oscillator 10 as a light source, which is sufficiently large and has a high output, and therefore strong light greatly improves the detection sensitivity of the scattered light detector 26 to the dust particles 18. Can be made

FIG. 4 is a view of the dust detector of FIG. 1 in which the whole dust detecting portion is housed in a container 42 and compacted, and FIG. 4A is a plan view excluding the upper cover and ( 7B is a side sectional view taken along line I-I of FIG. Incidentally, FIG.
The same reference numerals are given to the same components as those shown in FIG.

Here, a semi-cylindrical lens 34 is arranged at the light exit of an optical fiber array 30 in which 160 optical fibers having a cladding diameter of 250 μm are arranged adjacent to each other in a plane.
A sheet beam 36 having a width of 40 mm is produced. As the semi-cylindrical lens, a 2 mm diameter microcylinder lens (trade name) manufactured by Natsume Optical Co., Ltd. was used.

Of the laser beam emitted from the optical fiber, all the light other than the light scattered by the dust particles is absorbed by the laser beam absorber 16. The laser beam absorber 16 includes two or more absorption filters 15 and 17 such as a glass filter and a gelatin filter having sufficient absorption characteristics for the laser light used, as shown in FIG. 4 (B). It is used in combination to ensure absorption and prevent light from leaking to the outside. If it leaks and enters the scattered light detector 26, the measurement accuracy of dust particle detection is reduced. The scattered light detector 26 also preferably has an elongated shape, and is a PIN manufactured by Hamamatsu Photonics KK
Silicon photodiode S2551-01, S358
8 (brand name) was selected and used.

The dust detector of FIG. 4 has a flat shape with an outer shape of about 6 cm square, but when the number of optical fibers is reduced and a small photodetector is used, it should be made into a smaller device. You can

Incidentally, the dust detector of the present invention can sufficiently measure not only the measurement of dust particles in the atmosphere but also the detection of dust particles in a vacuum device. FIG. 5 is a cross-sectional view of the essential parts of an embodiment of the present invention when a dust detection unit is installed in the exhaust pipe of a vacuum device to detect dust.

According to the structure of this embodiment, the dust detecting section 50 is provided in the middle of the exhaust pipe 46. When the flanges at both ends of the exhaust pipe 46 are attached to a vacuum device and the vacuum device is evacuated through the exhaust pipe 46, the dust particles contained in the exhausted atmospheric gas pass through the laser beam when passing through the sheet-like light beam. Diffuse the beam. By detecting this diffusely reflected light by the scattered light detector 26 as described above,
The number of dust particles contained in the atmospheric gas is measured, and the number of dust particles in the vacuum device can be grasped.

It can be easily understood that the dust detector of the present invention can be used not only in the vacuum exhaust pipe but also in the load lock chamber, the film forming chamber and the like of the semiconductor manufacturing apparatus.

Although the present invention has been described with reference to the embodiments, the present invention can be variously modified other than the embodiments.

[0035]

According to the apparatus of the present invention, it is possible to form a laser beam sheet without a gap, and it is possible to detect and count dust particles without omission of detection or measurement error. Moreover, the structure is simple, does not require fine adjustment, and does not require expensive parts.

[Brief description of drawings]

FIG. 1 is a view showing the principle of a dust detector according to an embodiment of the present invention, (A) is a plan view, (B) is a side view, and (C) is a perspective view.

FIG. 2 is a diagram showing the shape of light emitted from an optical fiber and the effect of a cylindrical or semi-cylindrical lens. FIG. 2 (A) shows laser light in the absence of a cylindrical lens or a semi-cylindrical lens and ( B) is a diagram of the laser light when they are arranged.

FIG. 3 is a diagram showing a diameter of a laser beam with respect to an arrangement position of a semi-cylindrical lens, (A) is a graph and (B) is a diagram showing an arrangement position.

4A and 4B are views showing an example of a dust detection portion of the dust detector of the embodiment of the present invention, FIG. 4A is a plan view without an upper cover, and FIG.

FIG. 5 is a cross-sectional view of the dust detector according to the embodiment of the present invention when attached to an exhaust pipe of a vacuum device.

6A is a plan view, FIG. 6B is a side view, and FIG. 6C is a perspective view of a conventional dust detector.

FIG. 7A is a plan view and FIG. 7B is a side view of a conventional dust detector.

[Explanation of symbols]

10: Laser oscillator 12: Laser beam 14a, 14b: Parallel plane mirror 120: Laser beam net 16: Laser beam absorber 18: Dust particle 20: Moving direction of dust particle 22: Scattered light 24a, 24b: Condensing mirror 26, 26a , 26
b: scattered light detector 30: optical fiber array 32: concave lens 34: cylindrical lens or semi-cylindrical lens 36: laser beam sheet 40: optical fiber light outlet 42: container 46: exhaust pipe 48: flange 50: dust Detection unit

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[Procedure amendment]

[Submission date] February 26, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

1A and 1B are diagrams showing the principle of a dust detector according to an embodiment of the present invention, in which FIG. 1A is a perspective view and FIG. 1B is a plan view.

Claims (3)

[Claims] 1. An optical fiber array comprising a plurality of optical fibers whose light emission side portions are arranged in a plane, and a conversion means for converting a laser beam from the optical fiber array into a parallel laser beam distributed in a sheet shape. And a dust stopper that detects scattered light generated when dust particles cross the parallel laser beam, and beam stopper means that absorbs the parallel laser beam and does not leak it to the outside. .. 2. A conversion means for converting a laser beam from an optical fiber array into a parallel laser beam is an optical lens means for narrowing down the laser beam in a direction orthogonal to the arrangement direction of the optical fiber array, and the optical lens. 2. The dust detector according to claim 1, wherein the means is provided close to the light emitting end face of the optical fiber array. 3. The dust detection device according to claim 1, wherein the optical fiber array is formed by bundling the light incident side portions into a cylindrical shape, and irradiating a laser beam from a laser light source to the end portion of the cylindrical shape. vessel.