JPS61266940A - Measuring instrument for pulverous particles in liquid - Google Patents

Abstract

PURPOSE:To simplify an instrument constitution and to prevent stray light from being generated by providing a means which guides light source luminous flux into a cell through the 1st opening provided to a cell so as to hold a sample and reduces luminous flux transmitted through the sample liquid. CONSTITUTION:The sample liquid is admitted into the cell 40 through a tube 52. The liquid is reserved in a pressure regulating tank 48 with its liquid pressure. The laser luminous flux 12 from a laser beam source 10 is made incident one one end surface of a rod lens 50 orthogonally to enter the cell 40 through the pressure regulating tank 48 and piping 46, and a part of it is scattered by pulverous particles in the liquid in the cell 40 and light-received by a photoelectron multiplier tube 26 through a rod lens 54 and the opening 24, so that the diameter and the number of the pulverous particles in the sample liquid are measured from the light-receiving output value. The laser luminous flux transmitted through the sample liquid in the cell 40 enters a transparent plastic tube 52 and strikes on its curved tube internal surface. Then, the rays of light travel toward the upstream side of the sample liquid while reflected repeatedly and attenuated gradually to zero.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device that measures fine particles in a liquid using a light scattering method. The present invention relates to a device suitable for measuring submicron-order fine particles contained in pure water.

[Prior Art] In the process of manufacturing semiconductors such as LSI, each cleaning process such as wafer processing, mask production, film forming process, photolithography process, etching process, and cleaning of other jigs, etc.
Ultrapure water is used to remove chemicals and particles remaining on the wafer surface. If ions, fine particles, etc. are present in this ultrapure water, they may have an adverse effect on the oxide film, polycrystalline film, wiring, etc. incorporated into the wafer, and may cause defects in the electrical characteristics of the LSI. Therefore, an online water quality monitor is required to constantly monitor the quality of ultrapure cleaning water.

Conventionally, the measurement method used for monitoring online measurement of fine particles in liquid is the light transmission method (light blocking method).
There are methods that use light, such as the light scattering method.

The principle of particle measurement using the light transmission method (light blocking method) is that a sample liquid is passed between a light source and a photodetector, and the particles contained in this sample block the light beam, reducing the amount of light received by the photodetector. The particle diameter i of the particles is detected by detecting a voltage effect proportional to the maximum projected area of the particles. With this light transmission method, it is usually not possible to measure particles with a size of 1 μm or less or particles that do not absorb light.

With the light scattering method, even smaller particles can be measured. The measurement principle of this light scattering method is to detect the intensity of light irradiated onto a sample liquid from a light source and scattered by fine particles contained in the sample liquid.
For example, a device having the configuration shown in FIG. 3 is known.

FIG. 3 conceptually shows a conventional light scattering type submerged particulate monitor. A laser beam 12 generated by a laser light source 10 is converged as narrowly as possible by a converging lens 14, and is It is introduced into the measuring cell 18 via the window (inlet window) 16 . The scattered light is focused in the sample liquid at the center of the cell 18 and collides with fine particles to cause a light scattering phenomenon. Cell 1 through 20
The scattered light is taken out from the outside, passes through a condensing lens 22 and an aperture 24, and is guided to a photomultiplier tube 26 with high sensitivity and low dark current, and the intensity of the scattered light is measured. This scattered light intensity detection value is amplified by the amplifier 28 and then input to the measuring device 30,
In the figure, 32 indicates the inlet of the sample liquid, and 34 indicates the outlet of the sample liquid.On the opposite side of the through-hole window 20, a light beam that has gone straight is directed outside the cell 18. A light-transmitting window (output window) 36 is provided to take out the light, and the transmitted light passing through the light-transmitting window 36 is extinguished by a light trap 38.

In FIG. 3, the light detection unit consisting of a condenser lens 22, an aperture 24, a photomultiplier tube 26, etc. is 90 degrees with respect to the light source axis.
'Although it is installed at right angles.

There are also known devices that measure the intensity of low-angle forward scattered light.

[Problems to be Solved by the Invention] In such a conventional particle measuring device using a light scattering method, when the particle diameter reaches the submicron order, the scattered light intensity also falls into the extremely weak light range. The signal to noise level ratio (S/N ratio) is extremely reduced. In addition, in the conventional light scattering type particle measuring device, the optical axis of the light source side lens system is accurately perpendicular to the entrance window 16 of the measurement cell, and the glass surfaces of the entrance window 16 and the exit window 36 of the measurement cell are perfectly aligned. The parallel surfaces prevent stray light caused by reflected light.
This is important for improving measurement accuracy. However, this requires extremely high processing accuracy and assembly accuracy, requires special technology, and significantly increases costs. Therefore, in conventional measuring equipment, the diameter is 0.3
Particles of approximately 0.51 Lm were considered to be the measurement limit.

[Means for Solving the Problems] In the liquid particle measuring device of the present invention, a first opening is provided in a cell that holds a sample liquid, and a light source beam is introduced into the cell through this first opening. , detect the intensity of the scattered light. Further, means is provided for extinguishing the luminous flux that has passed through the sample liquid.

[Function] In the present invention, since the light flux is introduced into the cell from the opening (first opening) provided at the top of the cell, the optical axis of the light source side lens system can be accurately aligned with the cell entrance light window as in the conventional case. There is no need for the glass surfaces of the entrance window and the exit window of the measurement cell to be parallel to each other. Therefore, processing accuracy,
It is possible to reduce assembly precision, simplify the device configuration, and reduce manufacturing costs. One more reflection.

Since the generation of stray light and the loss of light source intensity are reduced, it is possible to detect and measure the light scattering intensity of fine particles of, for example, 0.14 m or less.

[Example code] Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of an apparatus for measuring particles in liquid according to a first embodiment of the present invention.

First, the configuration of the cell 40 used in the device of this embodiment will be explained. This cell 40 has a first opening 42 at the top and a second opening 44 at the bottom at a position corresponding to the first opening 42, and a T-shaped pipe 46 is connected to the first opening 42. has been done. A pressure regulating tank 48 is provided vertically above the first opening 42, and a vertical branch pipe 46a of the piping 46 is connected to the bottom of the pressure regulating tank 48, and has a T-shaped opening at the bottom. One branch pipe 4 of the pipe 46
6b is used as a sample liquid outlet.

A reflecting mirror 49 is provided above the pressure regulating tank 48, and reflects the laser beam 12 emitted from the laser light source 10 so that it is perpendicularly incident on the liquid surface in the pressure regulating tank 48. The incident position of the laser beam 12 is vertically above the opening surface of the branch pipe 46a of the pipe 46. Note that a rod lens 5o is provided at the incident position of the laser beam 12 on the liquid level of the pressure regulating tank.

A curved plastic tube 52 is connected to the second opening 44 at the bottom of the cell 40 so that a sample liquid can be introduced into the cell 40.

A rod lens 54 is provided on one side of the cell 40, and the structure is such that scattered light within the cell 40 is taken out to the outside of the cell 4o through the rod lens 54. A condensing lens 22 and an aperture 24 are installed opposite the rod lens 54, and a photomultiplier tube 26. amplifier 2
8. A measuring instrument 30 is installed. A rod lens 56 is installed on the other side of the cell 4o at a position on the optical axis extension of the rod lens 54, and a light emitting diode 58, which is a standard light source, is installed on the outdoor end surface of the rod lens 56. , are connected to the light amount control circuit 6°. As shown in the figure, one end of the rod lenses 54 and 56 faces inside the cell 4o, and the other end is exposed outside the cell 40. Further, the rod lenses 50.56 and 70.76, which will be described later, have parallel end surfaces and are made of a transparent material without curvature.

In this embodiment, a photodiode 62 is installed adjacent to the transparent plastic tube 52, and this photodiode 62 is connected to an alarm 64.

In the embodiment device configured in this manner, the sample liquid is introduced into the cell 40 through the tube 52 and is discharged from the first opening 42 through the branch pipe 46b of the piping 46. Moreover, the liquid is stored in the pressure regulating tank 48 due to this liquid pressure. The pressure regulating tank 48 serves to stabilize the liquid level against pressure fluctuations of the sample liquid introduced into the cell.

Therefore, the laser beam 1 irradiated by the laser light source 10
2 is reflected by a reflecting mirror 49 and is perpendicularly incident on one end surface of a rod lens 50 installed near the liquid level in the pressure regulating tank 48 . After passing through the rod lens 50, the liquid passes through the pressure regulating tank 4B and the piping 46 and enters the cell 40, where part of it is scattered by fine particles contained in the liquid in the cell 40. The scattered light is transmitted through the rod lens 54 and the condensing lens 2.
2. The light is incident on the photomultiplier tube 26 through the aperture 24, and its intensity is detected. The output value of the photomultiplier tube 26 is amplified by an amplifier 28 and then processed in a measurement n30 to measure the diameter and number of particles in the sample liquid.

Note that the laser beam that has passed through the sample liquid in the cell 40 enters a transparent plastic tube 52 placed at the irradiation position of the laser beam, and hits the curved inner surface of the tube. Then, it travels upstream from where the sample liquid is introduced while repeating reflections, and gradually attenuates its energy and disappears. Note that the photodiode 62 detects the brightness of the laser beam passing through the tube 52. If the optical axis position of the laser beam 12 irradiated from the laser light source 10 deviates from the normal position, or if the sample liquid in the cell 40 contains air bubbles, causing the laser beam to deflect, etc. Since the light intensity of the laser beam introduced into the tube 52 made of aluminum is lower than the normal intensity, the illuminance on the tube wall surface changes. The alarm device 64 to which this illuminance detection value is input automatically issues an alarm when an abnormality occurs in the operating status of the device and a change in illuminance is brought about.

Note that the light emitting diode 58, which is a standard light source, is used in the configuration of the scattered light detection system, and is preliminarily connected to the light amount control circuit 60.
The regulated electrical current is arranged to emit a weak standard intensity light pulse for the configuration.

FIG. 2 is a diagram showing the configuration of a particle measuring device in liquid according to a different embodiment of the present invention. First, the configuration of the cell 66 used in this example device will be explained. This cell 66 is cylindrical and installed diagonally,
A first opening 68 is opened in the upper part, and a rod lens 70 is attached to this first opening 68. Further, a drain lower 2 is provided in the upper part of the cell 66, and this drain lower 2
A vent lower 3 for venting gas is provided at a level above. At the lower part of the cell 66 and at a position where the optical axis of the rod lens 68 is extended, a second opening lower 4 for introducing a sample liquid is provided, and a curved transparent plastic tube 52 is connected thereto. Further, a rod lens 76 is provided in the middle of the cell 66 to take out the scattered light to the outside of the cell 66.
On the outdoor side of the rod lens 76, there are a condenser lens 22, an aperture 24, a photomultiplier tube 26, an amplifier 28, and a measuring instrument 3.
0 is set for each.

In the embodiment of FIG. 2, the sample liquid introduced into the cell 66 from the second open lower lower part 4 through the transparent plastic tube 52 is discharged from the drain lower part 2 to the outside of the cell 66. On the other hand, a laser beam 12 irradiated from a laser light source 10
is reflected by the reflecting mirror 49 and then introduced into the cell 66 through the rod lens 70. The scattered light is taken out of the cell through the rod lens 76 and its intensity is detected, while the transmitted light enters the tube 52 from the open lower 4 at the irradiation position of the transmitted light and flows upstream into the sample liquid. It travels through repeated reflections, gradually diminishing its energy and disappearing.

In the liquid particle measuring device of FIGS. 1 and 2 configured in this way, there is no need for a light source side lens system and an entrance window for the measurement cell, which would cause troublesome optical axis alignment, so the optical system and measurement It is possible to reduce cell assembly accuracy and processing accuracy and reduce manufacturing costs. At the same time, stray light due to light reflection in the light source side lens system is reduced. Furthermore, since the light that has passed through the sample liquid in the cell is gradually attenuated and annihilated by the tube 52, which is the annihilation means, it is not reflected into the cell, and this has no effect on the scattered light detection system.

In this way, the loss of light source intensity is reduced, and the generation of stray light due to reflection is also reduced, so that, for example, 0. IIL
It is now possible to easily and accurately detect even very small particles in a liquid, such as particles of about 500 yen or less.

In the embodiment shown in FIG. 1, the rod lens 50 provided in the pressure regulating tank 48 is unnecessary if the liquid level in the pressure regulating tank 48 does not change. However, the pressure regulating tank 48
If a wave phenomenon occurs in the liquid due to vibrations being applied to the liquid, providing the rod lens 50 can avoid diffuse reflection of the beam due to water surface waves, making it possible to always perform accurate particulate measurement. It is said that

In the embodiments shown in FIGS. 1 and 2, the sample liquid is introduced from the bottom of the cell and extracted from the top of the cell, but in the present invention, the sample liquid is introduced into the cell from the upper opening. may be introduced and taken out from the cell through the lower opening.

Furthermore, in the embodiment shown in FIG. 2, since the cells 66 are installed diagonally, even if air bubbles are generated within the cells 66, these air bubbles will rise along the upper inner surface of the cells 66, and the vent lower 2 taken from.

Therefore, air bubbles do not enter the portion through which the laser beam 12 passes, and the occurrence of measurement errors due to air bubbles is suppressed.

1 Effect] As described in detail above, according to the present invention, it is possible to reduce the precision of the device configuration, and it is possible to significantly reduce the device manufacturing cost. In addition, it is possible to prevent stray light due to reflection, and it is possible to accurately measure particles with extremely small diameters.

[Brief explanation of the drawing]

FIGS. 1 and 2 are partial cross-sectional views showing the configuration of a device for measuring particles in liquid according to an embodiment of the present invention, and FIG. 3 is a perspective view showing the configuration of a conventional device for measuring particles in liquid. 10... Laser light source, 12... Laser light flux, 2
2... Condenser lens, 26... Photomultiplier tube, 2
8... Amplifier, 30... Measuring instrument, 40.
66...Cell, 42.68...First opening, 44.74...Second opening, 52...Transparent plastic tube, 58...Light emitting diode, 60...Light amount control Circuit, 73... Ventro. Representative Patent Attorney Tsuyoshi Shigeno Figure 2, Figure 3, Sample liquid

Claims (5)

[Claims] (1) In a device that measures fine particles in the liquid by introducing a light flux into a cell holding a sample liquid and detecting the scattered light intensity of the sample liquid with a light intensity detection means, the cell has a first opening. death,
A device for measuring particles in a liquid, characterized in that the light flux is introduced into the cell through the first opening, and a light flux extinguisher is provided at a position where the light flux transmitted through the sample liquid is irradiated. (2) A piping for flowing the sample liquid is connected to the first opening, and the sample liquid is passed through the first opening to flow. A device for measuring particles in liquid. (3) A second opening is opened in the cell at the irradiation position of the luminous flux, a tube is connected to the second opening, and the tube is curved to serve as a luminous flux extinguishing means. A device for measuring particles in liquid according to claim 1 or 2. (4) Fine particles in a liquid according to any one of claims 1 to 3, wherein the first opening is provided with a rod lens whose end surfaces are parallel to each other. Measuring device. (5) Any one of claims 1 to 4, wherein the light flux is a light flux of a laser beam.
The device for measuring particulates in liquid as described in Section 1.