JPS6011145A - Measuring device of foreign matter - Google Patents

Abstract

PURPOSE:To measure a foreign matter in a fluid with a high precision by projecting a pipe into a flow passage and making light incident along the axis of this pipe and detecting scattered light of this incident light due to the foreign matter in the liquid. CONSTITUTION:Laser light 9 from a laser light source 8 is transmitted through a light-transmissive part 4 and passes a liquid 1 in pipes 6 and 7 and a duct (flow passage) 3 and is discharged from a light-transmissive part 5 in the opposite side. When the laser light 9 is irradiated to a foreign matter 2, scattered light 15 is generated. This scattered light 15 is detected through the third light-transmissive part 10 by a photodetector 12, and the mixture quantity of the foreign matter 2 in the liquid 1 is obtained by counting of a counter 14. When the laser light 9 is diffused radially, stray light 16 and 18 is not generated because diffused light 17 and refleced light 19 are totally reflected repeatedly on inside circumferential faces of pipes 6 and 7.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a technology for measuring foreign matter, and in particular, it can be effectively used to measure the density of foreign matter in various liquids used in the field of manufacturing semiconductor devices. This is related to foreign matter measurement technology, which is a major technology.

[Background technology] In the manufacturing process of semiconductor devices, ultrafine processing is performed, so foreign substances such as dust and microorganisms are mixed into liquids such as pure water for cleaning and etching liquid. I hate it. Therefore, it is possible to measure the density of foreign matter in such a liquid.

The present inventor has developed a device for measuring foreign substances in liquid as described below.

In other words, a laser beam is made to enter a flow path through which liquid flows at a constant speed through a light-transmitting part formed in the flow path, and by detecting the scattered light of this incident light beam from foreign objects in the liquid, foreign objects in the liquid can be detected. The purpose is to measure the

However, the inventor of the present invention has found that in this technique, there is a problem in that the laser beam is diffused at the point of incidence on the liquid, producing a stray beam, which causes noise in the detection signal.

In addition, in this technology, when the flow channel is formed into a cylindrical shape, the scattered light is totally reflected on the flow channel wall in the axial direction, and the amount of output light of the scattered scattered light decreases, so that the amount of detected light is insufficient. The inventors of the present invention have found that a problem arises in that it is not possible to obtain the desired results.

[Object of the Invention] An object of the present invention is to provide a foreign object measurement technique that can measure foreign objects in a fluid with high precision.

Another object of the present invention is to provide a foreign matter measurement technique that can suppress stray light rays in a fluid.

Another object of the present invention is to provide a foreign object measurement technique that can increase the amount of detected light scattered by foreign objects.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the Invention] A brief overview of typical inventions disclosed in this application is as follows.

That is, a pipe is provided protruding from the flow path, and by making light rays incident along the axis of the pipe, stray light rays are attenuated by total reflection within the pipe.

In addition, by forming the transparent part that detects scattered light to form a part of the hollow sphere, total internal reflection in the axial direction as in a cylinder is avoided, and the amount of detected light is increased accordingly. It is something.

[Embodiment 1] FIG. 1 is a perspective view showing a foreign matter measuring device according to an embodiment of the present invention, and FIG. 2 is an enlarged sectional view of the main parts.

In this embodiment, a tube 3 serving as a flow path through which liquid 1 as a fluid to be measured for mixed foreign matter 2 flows at a constant speed and in a laminar flow state has one end blocked by a light-transmitting portion 4.5. A pair of thin vibros 7 each having an inner diameter of about several hundred μm are provided at an angle of 180 degrees in the circumferential direction. A laser light source 8 is provided outside one transparent part 4 of the tube 3, and a laser beam 9 from this laser light source 8 is irradiated to the opposite transparent part 4 through a lens (not shown). It passes through part 4, passes through liquid 1 in tube 3, passes through the other transparent part 5, and exits to the outside.

As shown in FIG.
The angle of incidence θ when the light enters the inside of the transparent part 4 from the air
1 is the Brewster angle (polarization angle) at which the laser beam 9 enters the medium forming the transparent part 4, such as quartz or glass, from air, and the laser beam 9 enters the liquid 1 from inside the transparent part. The incident angle θ2 at this time corresponds to the Brewster angle at which the liquid laser beam enters from quartz, glass, or the like.

The Brewster angle is the angle of incidence when a certain component of the incident light is completely transmitted without reflection loss when a laser beam is incident on a certain boundary, and the Brewster angle θ is determined by the physical properties on both sides of the boundary. different.

On the other hand, the laser beam also passes through the liquid l in the light-transmitting part 5 on the emission side.
The angle of incidence θ3 when entering the inside of the transparent part 5 from inside is
The angle of incidence θ4 is set so that the laser beam enters the medium (quartz or glass, etc.) of the light-transmitting part 5 from the liquid at the Brieux-Scoo angle, and the angle of incidence θ4 is set so that the laser beam enters the air from inside the light-transmitting part 5. is set to be the Brewster angle when the in-air laser beam is incident from the medium of the light-transmitting part 5.

At a position perpendicular to the pair of light transmitting parts 4.5 of the tube 3, a light transmitting part 10 shown in FIG. A light receiver 12 is provided as a detection means.

A counter 14 is provided at the output end of the light receiver 12 via an amplifier 13.

Next, the effect will be explained.

A laser beam 9 from a laser light source 8 is irradiated onto the transparent part 4 through a lens, passes through the transparent part 4, passes through the vibro, 7 and the liquid 1 in the tube 3, and exits from the transparent part 5 on the opposite side. To go. When the laser beam 9 irradiates the foreign object 2 while passing through the liquid, scattered light I5 is generated. This scattered light 15 is detected by the light receiver 12 after passing through the third light transmitting section 1o, and the number of detections is counted by the counter 14. If the flow rate of the liquid 1 is constant and the scattered light detection ψm of the light receiver I2 is constant, the number of foreign objects 2 per unit area is calculated by the count of the counter 14, and thereby the contamination of the foreign objects 2 that falls into the liquid 1 is determined. The amount is full.

Here, if the amount of incident light of the laser beam 9 into the liquid 1 increases, it is possible to generate ft & scattered light even for the foreign matter 2 with a small particle size, and the amount of scattered light increases (because 1. Sensor sensitivity can be improved.

In the incident-side transparent section 4, when the laser beam 9 enters the interior of the transparent section 4 from the air, the Brewster angle θ
1, a certain component of the reflected light at this point of incidence becomes zero, and the amount of reflected light is smaller than when the incident angle is not θ1, so the amount of incident light is large. For example, if a laser beam has a polarization energy of 50 perpendicular to the plane of incidence and a polarization energy of 50 parallel to the plane of incidence, the reflected light has a polarization energy of 0 perpendicular to the plane of incidence and an energy of polarization parallel to the plane of incidence. 10. The transmitted light has a polarization energy of 50 perpendicular to the plane of incidence and a polarization energy of 40 parallel to the plane of incidence.
It is as follows.

When the laser beam 9 enters the liquid 1 from inside the light-transmitting portion 4 on the incident side, it also enters at the Brewster angle θ2, so that the amount of incident light similarly increases.

In this way, the amount of reflected light at the light-transmitting part on the incident side is suppressed, which increases the amount of light incident on the liquid, which increases the intensity of scattered light when a foreign object is irradiated with a laser beam, which increases sensor sensitivity. The effect is that the measurement performance is improved, and the generation of scattered light from fine foreign matter is enhanced, thereby improving the measurement ability.

When the laser beam 9 is radially diffused at the point of incidence into the tube 3, a stray beam 1 is formed as shown by phantom lines in FIG.
6 is generated. When this stray ray 1G passes through the light transmitting part IO and is detected by the light receiver 12, light other than the light scattered by the foreign object 2 is detected, and noise is generated. Due to the need to eliminate this noise, the minimum particle size of measurable foreign substances increases, resulting in a decrease in measurement performance.

In the foreign matter measuring device having the above configuration, the laser beam 9 that enters the liquid 1 from the transparent portion 4 first enters the vibro. When the laser beam 9 is radially diffused at this point of incidence, the diffused light 17 is attenuated by being totally reflected countless times at the inner periphery of the vibro, as shown by the imaginary line in FIG. Therefore, the diffused light 17 is not emitted from the exit of the vibro to the tube 3, and the stray light 16 as described above is not generated.

On the other hand, when the reflected light ray at the light-transmitting part 5 on the output side returns to the tube 3, it becomes a stray ray 18 as shown by the imaginary line in FIG. This causes a decrease in

In the foreign matter measuring device having the above configuration, since the incident angle θ3 from the liquid 1 into the transparent portion 5 in the output side transparent portion 5 is set to a predetermined Brewster angle, the amount of reflected light here is suppressed to an extremely low level.

As shown by the imaginary line in FIG. 2, a very small amount of reflected light 19 is repeatedly totally reflected on the inner circumferential surface of the pipe 7, so that it is attenuated. Therefore, the reflected light 19 is not irradiated backward into the pipe 3 from the entrance of the pipe 7, and no stray light rays 18 are generated.

In this way, in the foreign matter measuring device according to the above configuration, since stray light rays are hardly generated, noise is reduced by the stray light rays and the S/N ratio is improved, and as a result, the measurable foreign matter A reduction in the minimum particle size is achieved and the measurement capability is improved.

Note that it is desirable that the vibro be configured so that the attenuation due to the total reflection is effectively achieved.

For example, it is preferable to form the vibro to be as long and thin as possible, and to form its inner peripheral surface to have a highly light-absorbing surface.

[Embodiment 2] FIG. 3 is a perspective view showing a foreign matter measuring device according to another embodiment of the present invention, FIG. 4 is a cross-sectional view, and FIG. 5 is a longitudinal cross-sectional view.

In this embodiment, this foreign matter measuring device is equipped with a main body 21 formed into a substantially hollow spherical shape, a navel 22 is formed at the top of this main body 21, and a discharge pipe 23 having a stop valve 24 is formed at the bottom. has been done.

An introduction pipe 25 is inserted into the top surface of the header 22 for introducing liquid 1 as a fluid to be measured for mixed foreign matter 2 into the main body 21, and this introduction pipe 25 is formed to have a small diameter. The outlet is approximately aligned with the spherical center of the main body 21. A lead-out pipe 26 for leading out the liquid 1 from inside the main body 21 is connected to the body of the header 22, and a differential pressure between the lead-out pipe 26 and the introduction pipe 25 is detected. A differential pressure sensor 27 is provided. The measured flow rate is determined based on the differential pressure value obtained by the differential pressure sensor 27.

At a position perpendicular to the header 22 and the discharge pipe 23 of the main body 21, a pair of vibros 7 protrude at an angle of 180 degrees from each other in the circumferential direction, and their axial extensions pass through the spherical center of the main body 21. One end of each vibro 7 is closed by each transparent portion 4.5. A laser light source 8 is provided outside one of the transparent parts 4, and a laser beam 9 from this laser light source 8 is irradiated to the opposite transparent part 4 through a lens (not shown). The light passes through the liquid 1 of the main body 21, passes through the other transparent part 5, and exits to the outside.

As shown in FIG.
When entering the inside of the transparent part 4 from the air, each incident 0
1 is the Brewster angle (polarization angle) at which the laser beam 9 enters the medium forming the transparent part 4, such as quartz or glass, from air, and the laser beam 9 enters the liquid 1 from inside the transparent part. The incident angle θ2 at this time corresponds to the Brewster angle at which the liquid 1 laser beam enters from quartz, glass, or the like.

As explained in the first embodiment, the Brewster angle is the angle of incidence when a certain component of the incident light is completely transmitted without reflection loss when a laser beam is incident on a certain boundary. θ varies depending on the physical properties on both sides of the interface.

On the other hand, the laser beam also passes through the liquid l in the light-transmitting part 5 on the emission side.
The angle of incidence θ3 when entering the inside of the transparent part 5 from inside is
The angle of incidence is set so that the laser beam enters the medium (quartz or glass, etc.) from the liquid into the transparent part 5 at the Brewster's angle, and the incident angle is adjusted so that the laser beam enters the air from inside the transparent part 5. θ4 is set to be the Brewster angle when the in-air laser beam enters from the medium of the light-transmitting portion 5.

At a position perpendicular to the pair of transparent parts 4.5 of the main body 21, a third
A light transmitting section 28 is provided, and a light receiver 12 serving as a means for detecting scattered light through a lens 11 is provided outside the light transmitting section 28 . A counter 14 is connected to the output end of the light receiver 12 via an amplifier 13.

Since the light-transmitting portion 28 is formed to form a part of the wall of the main body 21, it substantially has a shape formed by cutting out a part of a hollow sphere having a radius of curvature from the center of the main body 21. It consists of

At a position 180 degrees opposite to the transparent part 28 of the main body 21, a concave mirror 29 whose spherical center coincides with that of the main body 21 is formed on the outer surface of the transparent main body 21. This concave mirror 29 is set to have an area corresponding to the solid angle θ6 (described later) of the lenses 11 facing each other with the transparent portion 2B in between.

Next, the effect will be explained.

The radar beam 9 from the laser light source 8 is irradiated onto the transparent part 4 through the lens, passes through the transparent part 4, passes through the vibro, 7, and the liquid 1 in the main body 21, and exits from the transparent part 5 on the opposite side. To go. When the laser beam 9 irradiates the foreign object 2 while passing through the liquid, scattered light 31 is generated. This scattered light 31 passes through the third transparent section 28 and is detected by the light receiver 12, and the number of detections is counted by the counter 14. If the flow rate of the liquid I is constant and the scattered light detection width of the light receiver 12 is constant, the number of foreign substances 2 per unit area is calculated by the count of the counter 14, and thereby the amount of foreign substances 2 mixed in the liquid 1 is circle.

Here, in this embodiment as well, as in the previous embodiment, since the vibro 7 is provided which is closed in the transparent part 4.5 set at Brewster's angle, the effect of increasing the amount of incident light and reducing the stray rays is achieved. is obtained.

By the way, when the flow path is formed in a cylindrical shape, for example, as shown by the imaginary line in FIG. If the defined critical angle θ5 is exceeded, total reflection will occur. Due to this total reflection phenomenon of the oblique light 30 in the axial direction, the light that passes through the transparent portion 1° of the tube 3 is limited within the range of the critical angle θ5 in the axial direction. That is, the transparent part l
.

It is not possible to increase the solid angle of the lens 11 corresponding to this. Therefore, the amount of scattered light that can be detected by the light receiver 12 becomes insufficient, the sensor sensitivity decreases, and it becomes impossible to measure minute foreign objects.

In the case of the foreign matter measuring device having the above configuration, since no total reflection phenomenon of oblique light occurs in the axial direction, all of the scattered light from the foreign matter 2 can be transmitted through the light-transmitting portion 28.

That is, since the tip of the introduction tube 25 for the liquid 1 substantially coincides with the spherical center of the main body 21, the foreign object 2 passes through the spherical center. Since the optical path of the laser beam 9 passes through the spherical center of the main body 21, the foreign object 2 on the spherical center is irradiated with the laser beam, and scattered light is generated. All of this scattered light 31 travels toward the spherical surface of the main body 2 as if radiated from the spherical center and enters the spherical surface of the transparent portion 28 .

Since the center of curvature of the light-transmitting portion 28 coincides with the spherical center of the main body 21, the normal line at the point of incidence of the light-transmitting portion 28 all passes through the spherical center. Therefore, all the scattered light emitted from the spherical center will be incident along the normal line. According to the general laws of optics, incident light that coincides with the normal passes through a transparent medium without being reflected, so the light that is scattered by the foreign object 2 on the center of the sphere and reaches the transparent part 28 is All of the light passes through the light-transmitting portion 28.

In this way, all of the foreign object scattered light 31 enters the transparent part 28 along the normal line, so the total internal reflection phenomenon that occurs when the incident angle exceeds the critical angle is caused by how far from the center of the transparent part 28 can't happen either. Therefore, the solid angle θ6 of the lens 11 corresponding to the transparent portion 28 can be set as large as desired without being restricted.

By setting the solid angle θ6 of the lens 11 as large as possible, the light collecting ability is increased, so much of the light scattered by the foreign object 2 is collected, and the amount detected by the light receiver 12 is increased. When a sufficient amount of light is detected by the light receiver 12, the sensor sensitivity is improved and even minute foreign objects can be measured.

The light 31 scattered by the foreign object 2 on the center of the sphere passes through the transparent part 28
The light also enters the concave mirror 29, which is exactly opposite to the above. According to the optical law of concave mirrors, the incident light from the spherical center is reflected toward the spherical center, so the scattered light that reaches the concave mirror 29 returns to the spherical center, and then passes through the normal line of the transparent part 28 to the transparent part. 28. That is, the concave mirror 29 enhances the light gathering ability of the lens 11. As a result, the amount of light detected by the light receiver 12 is further improved.

Since the introduction tube 25 that introduces the liquid 1 mixed with the foreign matter 2 into the spherical center of the main body 21 is formed to have a small diameter, the amount of liquid 1 used as a sample used for foreign matter measurement can be reduced. Also,
Since the introduction pipe 25 is formed to have a small diameter, the flow rate of the liquid 1 being measured can be adjusted by detecting the pressure difference lost here with the differential pressure sensor 27.

It is desirable that the flow of the liquid 1 introduced from the introduction tube 25 be controlled so as to have a constant flow rate and a laminar flow state.

During the measurement, the interior of the body 21 is filled with liquid 1, and the liquid 1 is led out from the outlet tube 26 at the top of the body 21. Outlet pipe 2
6 is connected to the top, even if bubbles should occur, they will not remain in the main body 21 and will be immediately discharged.

After the measurement is completed, all of the liquid 1 in the main body 21 can be discharged by opening the valve 24 of the discharge pipe 23.

[Effect (l)] By causing the measurement light beam to travel along the axis of the pipe, stray light beams can be reduced by attenuated total reflection in the pipe, so the S/N ratio in the measurement signal can be improved.

(2) By setting the angle of the light-transmitting part to the light beam at the Brieuscoe angle, the amount of reflected light can be suppressed, so the amount of scattered light can be increased, and measurement accuracy and performance can be improved.

(3) By forming the transparent part for extracting scattered light in the shape of a cutout of a hollow sphere, total internal reflection phenomenon can be avoided, so the light gathering ability can be improved by utilizing the entire solid angle of the lens, and the measurement Accuracy and ability can be improved.

(4) By providing a concave mirror on the opposite side of the one spherical light-transmitting part, the reflected light of the concave mirror is focused on the light-transmitting part, so that the light-gathering ability is further enhanced.

(5) By directly introducing the measurement fluid into the spherical center of the transparent part in the flow channel using the introduction tube, it is possible to align foreign objects with the measurement optical path passing through one point of the spherical center, thereby reducing scattered light. It can be reliably generated at the center of the ball.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, a pipe should be provided at least on the input side (,
The setting of the Brillou-Scoot angle in the transparent part may be omitted.

The flow path does not have to be formed entirely into a hollow sphere, but may be formed so that at least a light-transmitting part for extracting scattered light constitutes a part of the hollow sphere. Further, it is not necessary to form the lens into a truly hollow sphere, but it may be any shape that can sufficiently obtain transmitted light commensurate with the solid angle of the lens. It is not necessary to form the entire flow path so that it can transmit light.

The inlet pipe, outlet pipe, discharge pipe, differential pressure sensor, etc. can be omitted.

[Field of Application] The present invention is not limited to the field of manufacturing semiconductor devices, but can be applied to devices for measuring particles in fluids in all fields.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the present invention, and FIG. 2 is a perspective view showing one embodiment of the present invention.
FIG. 3 is a perspective view showing another embodiment of the present invention; FIGS. 4 and 5 are a cross-sectional view and a longitudinal section of the embodiment shown in FIG. It is a front view. ■...Fluid (liquid), 2...Foreign matter, 3...Flow path (
tube), 4... Incidence side transparent part, 5... Output side transparent part,
6, 7... Pipe, 8... Laser beam, 9... Laser beam, 10... Transparent part for extracting scattered light, 11...
...Lens, 12...Receiver, 14...Counter,
21... Main body, 22... Header, 23... Discharge pipe, 24... Stop valve, 25... Inlet pipe, 26... Outlet pipe, 27... Differential pressure sensor, 28... ... Translucent part for extracting scattered light, 29... Concave mirror.

Claims (1)

[Claims] 1. A pipe is provided protrudingly in a channel through which a fluid flows, and this pipe is closed with a light-transmitting part, and a light beam is made to enter the flow channel through this light-transmitting part, and the fluid of this incident light is A foreign object measuring device that measures foreign objects in a fluid by detecting light scattered by the foreign objects inside. 2. The angle of incidence when the light ray enters the transparent part is set to the Brewster angle when the light ray enters the medium of the transparent part from the medium outside the transparent part, and the angle of incidence when the light ray enters the transparent part Claim 1, characterized in that the angle of incidence when the light beam enters the flow path from inside is set to the Brewster angle when the light beam enters the medium of the fluid from the medium of the transparent part. Foreign matter measuring device as described in section. 3. A light beam is made to enter the channel through which the fluid flows through the transparent part, and the scattered light of the incident light beam by foreign matter in the fluid is made to form a part of a substantially hollow sphere on at least a part of the channel wall. A foreign object measuring device that measures foreign objects in a fluid by detecting them through a formed non-transparent part. 4. The foreign matter measuring device according to claim 3, wherein the channel wall is formed into a substantially hollow sphere whose center is at one point of the incident optical path.