JPS59160744A - Foreign matter detecting device - Google Patents

Abstract

PURPOSE:To increase the quantity of incident light into liquid in measuring foreign matter in liquid by scattered light by projecting light to a transmitting part at Brewster's angle. CONSTITUTION:Liquid 1 in which foreign matter 2 to be measured is mixed is lased 7 from a light transmitting part 4. The transmitting part 4 of incidence side is so constituted that angle of incidence theta1 when the laser light 7 enters inside of the transmitting part 4 from air becomes Brewster's angle when the laser light 7 enters a medium forming the transmitting part 4, such as quartz, glass etc. from air, and angle of incidence theta2 when the laser light 7 enter the liquid 1 from inside of the transmitting part becomes Brewster's angle when the laser light enters the liquid 1 from quartz, glass etc. Similar constitution can be adopted for the transmitting part of out-going side.

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 Art] Ultra-fine processing is performed in the manufacturing process of semiconductor devices, so foreign substances such as dust and microorganisms may get mixed into liquids such as purified water for cleaning and processing/notching fluids. I don't like 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, in this technique, the laser beam is incident on the transparent window at right angles, and the amount of reflected light at the point of incidence increases, which reduces the amount of light incident on the liquid and reduces measurement accuracy. The inventor of the present invention has found that this problem arises.

[Object of the Invention] An object of the present invention is to provide a foreign matter measurement technique that can increase the amount of light incident on a fluid.

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, by making the light beam incident on the transparent part at Brewster's angle, the amount of reflected light at the point of incidence is controlled, and the amount of light incident on the fluid is increased, thereby achieving the objective.

[Example] The present invention will be described below according to an example shown in the drawings.

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

In this embodiment, a pair of light-transmitting parts 4.5 are provided in a tube 3, which serves as a flow path through which liquid 1, which is a fluid to be measured for mixed foreign matter 2, flows at a constant speed and in a laminar flow state. is set at an angle of 180 degrees. A laser light source 6 is provided outside one of the transparent parts 4 of the tube 3, and a laser beam 7 from this laser light source 6 is irradiated to the opposite transparent part 4 through a lens 8. The light passes through the liquid 1 in the 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 7 enters the medium forming the transparent part 4, such as quartz or glass, from air, and the laser beam 7 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.

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 enters a certain boundary, and the Brewster angle θ varies depending on the physical properties on both sides of the boundary surface. .

A third light-transmitting portion 9 is provided at a position perpendicular to the pair of light-transmitting portions 4.5 of the tube 2, and a third light-transmitting portion 9 is provided outside the light-transmitting portion 9 to detect scattered light through a lens 10. Light receiver 1 as a means to
1 is provided. A counter 13 is provided at the output end of the light receiver 11 via an amplifier 12.

Next, the effect will be explained.

The laser beam 7 from the laser light source 6 is irradiated onto the transparent part 4 through the lens 8, and is transmitted through the transparent part 4 to the liquid 1 in the tube 3.
It passes through the inside and exits from the transparent section 5 on the opposite side. When the laser beam 7 passes through the liquid and irradiates the foreign object 2, scattered light 14 is generated.
occurs. This scattered light 14 passes through the third transparent section 9 and is detected by the light receiver 11, and the number of times of detection is counted by a counter 13. If the flow rate of the liquid 1 is constant and the scattered light detection width of the light receiver 11 is constant, the number of foreign objects 2 per unit area can be determined by counting by the counter 13, and thereby,
The amount of foreign matter 2 mixed into liquid 1 is determined.

Here, if the amount of incident light of the laser beam 7 into the liquid 1 increases, scattered light can be generated even by the foreign matter 2 with a small particle size (1), and the amount of scattered light is also increased. Sensitivity can be improved.

In the incident-side transparent section 4, when the laser beam enters the inside 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 bi, the laser beam has a polarization energy of 50 in the plane of incidence and a polarization energy of 50 parallel to the angle of incidence,
The reflected light has a polarized energy of 0 in the plane of incidence and 10 polarized energy parallel to the plane of incidence, and the transmitted light has a polarized energy of 50 in the plane of incidence and 40 polarized energy parallel to the plane of incidence. .

When the laser beam 7 enters the liquid 1 from within the light-transmitting portion 4 on the incident side, it also enters at the Brieux-Scoo angle θ2, so that the amount of incident light similarly increases.

[Effect] In this way, the amount of reflected light at the light-transmitting part on the incident side is suppressed, so the amount of light incident on the liquid is increased, so the scattered light becomes stronger when a foreign object is irradiated with a laser beam. , the sensitivity is improved, and the generation of scattered light from fine foreign matter is enhanced, resulting in improved measurement ability.

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 above-mentioned examples and can be modified in various ways without departing from the gist thereof. Nor.

For example, in the light-transmitting part 5 on the emission side, the incident angle when the laser beam enters the inside of the light-transmitting part 5 from the liquid 1 is
From the liquid to the medium (quartz or glass, etc.) of the transparent part 5, the Brewster angle is set when the laser beam is incident, and when the laser beam is incident from the inside of the transparent part 5 into the air. It is desirable that the angles be set so as to correspond to the Brieuxkoo angle when the in-air laser beam enters from the medium of the light-transmitting part 5. This is because the reflected light beam from the light-transmitting part 5 on the output side returns to the liquid and irradiates the foreign object 2 to generate scattered light, which reduces the accuracy of foreign object measurement by the incident laser beam 7. This is because it is necessary to suppress the amount of reflected light at the portion 5 as much as possible.

[Field of Application 1 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 drawings]

FIG. 1 is a perspective view showing an embodiment of the foreign matter measuring device of the present invention, and FIG. 2 is an enlarged sectional view of a main part of the embodiment shown in FIG. DESCRIPTION OF SYMBOLS 1...Fluid (liquid), 2...Foreign object, 3...Flow path (pipe), 4...Transparent part on the incident side, 5...Transparent part on the output side, 6
...Laser light source, 7...Laser beam, 8...Lens, 9...Transparent part for extracting scattered light, 10...Lens,
11... Light receiver, 13... Counter. Figure 1 Figure 2

Claims (1)

[Claims] 1. A light beam is made to enter a channel through which fluid flows at a constant speed through a transparent part formed on the channel wall, and the scattered light of this incident light beam from foreign objects in the fluid is detected. In a foreign object measuring device that measures foreign objects, the angle of incidence when the light beam enters the inside of the transparent section is the Brewster angle when the light beam enters the medium of the transparent section from the medium outside the transparent section. and the angle of incidence at which the light beam enters the flow path from inside the light-transmitting portion is set to the Brewster angle at which the light beam enters the fluid medium from the medium of the light-transmitting portion. A foreign object measuring device featuring: