JPH04254741A - Suspended particulate counter - Google Patents

Abstract

PURPOSE:To obtain a suspended particulate counter which can count suspended particulates exactly. CONSTITUTION:A suspended particulate counter is constructed in such a manner that it comprises a laser beam generator 11 which applies a laser beam 12 to a suspended particulate 10, a cylindrical concave mirror 14 which makes centers 14b of curvatures ranging in a straight line coincide with the optical axis 12a of the laser beam 12, a cylindrical lens 15 which makes focal positions 15b ranging in a straight line on the incident surface 15a side coincide with the optical axis 12a of the laser beam 12, and a plurality of light-sensing elements 16 which sense a scattered light 13 of the laser beam 12 scattered by the suspended particulate 10, as an incident light, and converts it into an electric signal.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspended particle counter that counts particles floating in space (hereinafter referred to as "suspended particles"), and more particularly to a suspended particle counter that can accurately count suspended particles. In order to manufacture semiconductor devices having fine wiring patterns with a high yield, it is important to reduce the number of floating particles in a clean room for manufacturing semiconductor devices to the utmost. For this purpose, a suspended particle counter that can accurately count suspended particles is essential.

0002

2. Description of the Related Art Next, a conventional suspended particle counter will be explained with reference to FIG. FIG. 2 is a perspective view of a main part schematically showing a conventional suspended particle counter. In this specification, the same parts, the same materials, etc. are given the same reference numerals throughout the drawings.

[0003] As shown in FIG. 2, a conventional suspended particle counter uses a laser beam on either a first plane mirror 21 or a second plane mirror 22, which have reflecting surfaces 21a and 22a facing each other, parallel to each other, and separated from each other. A laser beam 12 generated by a light beam generator 11 is irradiated obliquely, and the laser beam 12 is repeatedly reflected between the reflecting surfaces 21a and 22a to form a zigzag shape (zigzag). A pulse counter measures the number of pulsed electrical signals output each time the photodiode array 16, which forms the scattered light 13 and faces the light-receiving surface 16a in the desired direction of the traveling direction of the laser beam 12, receives the scattered light 13. (
(not shown).

0004

However, since the scattered light 13 from the suspended particles 10 travels in a radial manner in all directions, the scattered light 13 that enters the photodiode array 16 becomes extremely weak, causing a problem with the S/N ratio. (The ratio of the peak value of the pulsed electrical signal input from the photodiode array 16 to the pulse counter and the internal noise voltage value of the photodiode array 16 and the pulse counter) will decrease. For this reason, the conventional suspended particulate counter has a problem in that it cannot accurately count the suspended particulates 10.

The present invention has been made to solve these problems, and its purpose is to provide a suspended particle counter that can improve the S/N ratio and accurately count suspended particles floating in space. Our goal is to provide the following.

[0006]

[Means for Solving the Problems] The object is to provide a suspended particle counter that counts the suspended particles by irradiating the suspended particles with a laser beam and detecting the scattered light of the laser beam scattered by the particles, as shown in FIG. , a laser beam generator 11 that irradiates the floating particles 10 with a generated beam-shaped laser beam 12, and a reflecting surface 14a in the traveling direction of the laser beam 12.
The centers of curvature 14b are arranged in a straight line with
A cylindrical concave mirror 14 with the laser beam 12 aligned with the optical axis 12a of the laser beam 12, and an incident surface 15a facing the reflective surface 14a of the cylindrical concave mirror 14 with the laser beam 12 interposed at an intermediate position. The cylindrical lens 15 has a linearly connected focal point 15b aligned with the optical axis 12a of the laser beam 12, and the light receiving surface 16a is the focal point 15 on the side of the output surface 15c of the cylindrical lens 15.
d, and a plurality of light receiving elements 16 which input the scattered light 13 of the laser beam 12 scattered by the floating particles 10 emitted from the output surface 15c of the cylindrical lens 15 into the light receiving surface 16a and convert it into an electric signal. This is achieved by a suspended particle counter characterized by comprising:

[0007]

[Operation] As shown in FIG. 1, in the floating particle counter of the present invention, the scattered light 13 scattered by the floating particles 10 and the scattered light 13 directed toward the cylindrical concave mirror 14 are reflected by the reflecting surface 14a.
After being reflected, the light passes through the cylindrical lens 15 and enters the light receiving element 16 . Further, the scattered light 13 directly directed toward the cylindrical lens 15 passes through the cylindrical lens 15 and enters the light receiving element 16 .

Therefore, in the floating particle counter of the present invention, the scattered light 13 of the laser beam 12 reflected radially by the floating particles 10 simultaneously enters the light receiving element 16, and the light receiving element 16 detects the incident scattered light 13. At the same time, the peak value of the pulsed electrical signal that is output increases and becomes S/
The N ratio is improved, and suspended particles can be counted accurately.

[0009]

Embodiment A suspended particle counter according to an embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a diagram for explaining a suspended particle counter according to an embodiment of the present invention, in which FIG. 1 (a) is a perspective view schematically showing the configuration of the main part of the device, and FIG. is a sectional view of the main part.

[0010] A floating particle counter according to an embodiment of the present invention shown in Figs. The generator 11 and the reflective surface 14a, which is formed by dividing a cylinder in half and using the inner surface of the cylinder, are arranged in the traveling direction of the laser beam 12, and the centers of curvature 14b, which are connected in a straight line, are aligned with the optical axis of the laser beam 12. A cylindrical concave mirror 14 aligned with the angle 12a, and a linearly connected focal point on the side of the incident surface 15a, with the laser beam 12 interposed at an intermediate position and a flat incident surface 15a facing the reflective surface 14a of the cylindrical concave mirror 14. The position 15b is the optical axis 1 of the laser beam 12.
2a, and the light receiving surface 16a is aligned with the focal position 15d on the exit surface 15c side of the cylindrical lens 15, which has a cylindrical peripheral wall shape. A plurality of light-receiving elements, for example, a photodiode array 16, convert the scattered light 13 of the laser beam 12 scattered by the laser beam 10 into an electric signal by entering the light-receiving surface 16a.
It is composed of:

The suspended particle counter according to one embodiment of the present invention constructed as described above uses the scattered light 13 of the laser beam 12 scattered by the suspended particles 10 to detect the cylindrical concave mirror 14 as shown in FIG. Scattered light 13 heading in the direction
After being reflected by 4a, the light passes through the cylindrical lens 15 and enters the light receiving element 16. Further, the scattered light 13 directly directed toward the cylindrical lens 15 passes through the cylindrical lens 15 and enters the light receiving element 16 .

Therefore, in the floating particle counter of the present invention, the scattered light 13 of the laser beam 12 reflected radially by the floating particles 10 simultaneously enters the light receiving element 16, and the light receiving element 16 detects the incident scattered light 13. At the same time, the peak value of the pulsed electrical signal that is output increases and becomes S/
The N ratio is improved, and suspended particles can be counted accurately.

[0013]

As described above, the present invention makes it possible to provide a suspended particle counter that can accurately count suspended particles. Therefore, when the floating particle counter of the present invention is employed, floating particles in a clean room or the like can be managed accurately, thereby improving the manufacturing yield of semiconductor devices or the like.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining a suspended particle counter according to an embodiment of the present invention;

FIG. 2 is a perspective view of a main part schematically showing a conventional suspended particle counter.

[Explanation of symbols]

10 is floating particulate; 11 is a laser beam generator; 12 is a laser beam; 12a is an optical axis of the laser beam; 13 is scattered light; 14 is a cylindrical concave mirror; 14a is reflection of the cylindrical concave mirror 14b is the center of curvature, 15 is the cylindrical lens, 15a is the incident surface of the cylindrical lens, 15b
and 15d is the focal position of the cylindrical lens, 15
c is the output surface of the cylindrical lens; 16 is the light receiving element (photodiode array); 16a is the light receiving surface; 21 is the first plane mirror; 21a is the reflection surface of the first plane mirror; 22 is the second plane mirror. The plane mirrors 22a each represent a reflective surface of a second plane mirror.

Claims (1)

[Claims] 1. In a floating particle counter that counts particles by irradiating particles floating in space with a laser beam and detecting the scattered light of the laser beam scattered by the particles, the beam-shaped laser beam (12 ) for irradiating the floating particles (10) with a laser beam generator (11); )
a cylindrical concave mirror (14) with the laser beam (12) aligned with the optical axis (12a) of the laser beam (12); A linear series of focal positions (1
5b) aligned with the optical axis (12a) of the laser beam (12), and a cylindrical lens (15) with the light receiving surface (1
6a) is aligned with the focal position (15d) on the exit surface (15c) side of the cylindrical lens (15), and the exit surface (15c) of the cylindrical lens (15) is
) The scattered light (13) of the laser beam (12) scattered by the suspended particles (10) emitted from the light receiving surface (16
a) A plurality of light receiving elements (
16) A suspended particle counter comprising: