JP2867718B2 - Suspended particle counter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fine particles floating in space.
The present invention relates to a suspended particle counter for counting suspended particles (hereinafter, referred to as “suspended particles”), and particularly to a suspended particle counter capable of accurately counting suspended particles. In order to manufacture a semiconductor device having a fine wiring pattern with good yield, it is important to reduce the number of floating particles in a clean room for manufacturing the semiconductor device to the limit. For this purpose, a floating particle counter capable of accurately counting floating particles is indispensable.

[0002]

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

As shown in FIG. 2, a conventional floating particle counter employs a laser on one of a first plane mirror 21 and a second plane mirror 22 whose reflection surfaces 21a and 22a are opposed to each other and parallel and separated from each other. The laser beam 12 generated by the light beam generator 11 is irradiated obliquely, and the zigzag (Zigzag; zigzag) laser beam 12 that is repeatedly reflected between the reflection surfaces 21a and 22a is irradiated to the floating fine particles 10 to radiate the laser beam 12. A pulse counter counts the number of pulse-like electrical signals output each time the photodiode array 16 that forms the scattered light 13 and faces the light receiving surface 16a in the direction in which the laser beam 12 travels is desired to receive the scattered light 13. (Not shown).

[0004]

However, suspended particulates
Since the scattered light 13 from the light source 10 is radial and travels in all directions, the scattered light 13
Becomes extremely weak, and the S / N ratio (photodiode array
As a result, the ratio of the peak value of the pulse-like electric signal input to the pulse counter to the internal noise voltage between the photodiode array 16 and the pulse counter decreases. For this reason, the conventional suspended particle counter has a problem that the suspended particles 10 cannot be accurately counted.

The present invention has been made in order to solve such a problem, and an object of the present invention is to improve a S / N ratio and accurately count floating particles floating in space. Is to provide.

[0006]

The object of the present invention is to provide a floating particle counter for irradiating a floating particle with a laser beam as shown in FIG. 1 and detecting the scattered light of the laser beam scattered by the particle to count the floating particle. A laser beam generator 11 for irradiating a floating particle 10 with the generated laser beam 12
A cylindrical concave mirror 14, which is arranged with the reflecting surface 14 a facing the direction of travel of the laser beam 12 and whose linearly continuous center of curvature 14 b coincides with the optical axis 12 a of the laser beam 12,
With the incident surface 15a facing the reflecting surface 14a of the cylindrical concave mirror 14, and a linearly-focused focal position 15b on the incident surface 15a side coinciding with the optical axis 12a of the laser beam 12. The scattered light 13 of the laser beam 12 scattered by the floating fine particles 10 scattered from the light exit surface 15c of the cylindrical lens 15 with the light receiving surface 16a aligned with the focal position 15d on the exit surface 15c side of the cylindrical lens 15 is formed. This is achieved by a floating particle counter characterized by comprising a plurality of light receiving elements 16 which are incident on a light receiving surface 16a and convert the electric signals into electric signals.

[0007]

The floating particle counter according to the present invention uses the scattered light 13 scattered by the floating particles 10 as shown in FIG.
The scattered light 13 traveling in this direction is reflected by the reflecting surface 14a and then passes through the cylindrical lens 15 to enter the light receiving element 16. Further, the scattered light 13 directly traveling in the direction of the cylindrical lens 15 passes through the cylindrical lens 15 and enters the light receiving element 16.

Accordingly, in the floating particle counter according to the present invention, the floating particle 10 has a laser beam reflected radially.
The scattered light 13 of 12 is incident on the light receiving element 16 at the same time, and the peak value of the pulse-like electric signal output from the light receiving element 16 at the same time as the incidence of the scattered light 13 is increased, the S / N ratio is improved, and the floating Fine particles can be accurately counted.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A floating particle counter according to one embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a view for explaining a suspended particle counter according to one embodiment of the present invention. FIG. 1 (a) is a perspective view schematically showing a configuration of a main part of the apparatus, and FIG. Is a sectional view of a main part.

A floating particle counter according to one embodiment of the present invention shown in FIGS. 1A and 1B is a laser beam for irradiating a generated laser beam 12 to particles 10 floating in space. The generator 11 and the laser beam 12 are arranged in such a manner that a cylinder is halved in the direction of travel of the laser beam 12 and a reflecting surface 14a formed by using the inner surface thereof faces the laser beam.
A cylindrical concave mirror 14 aligned with the optical axis 12a of the laser 12 and a laser beam 12 interposed at an intermediate position so that the flat incident surface 15a faces the reflecting surface 14a of the cylindrical concave mirror 14, and a straight line on the incident surface 15a side is formed. The cylindrical lens 15 whose focal point 15b is aligned with the optical axis 12a of the laser beam 12, and the light receiving surface 16a is aligned with the focal point 15d of the cylindrical lens 15 on the side of the exit surface 15c having a cylindrical peripheral wall shape. A plurality of light receiving elements, such as a photodiode array 16, for converting the scattered light 13 of the laser beam 12 scattered by the floating fine particles 10 emitted from the emission surface 15c of the cylindrical lens 15 into a light receiving surface 16a and converting the scattered light 13 into an electric signal. It was done.

The floating particle counter according to one embodiment of the present invention having the above-described structure is configured as shown in FIG.
Scattered light 13 of the laser beam 12 scattered by the cylindrical concave mirror 14
The scattered light 13 traveling in this direction is reflected by the reflecting surface 14a and then passes through the cylindrical lens 15 to enter the light receiving element 16. Further, the scattered light 13 directly traveling in the direction of 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 floating particle 10 is a laser beam reflected radially.
The scattered light 13 of 12 is incident on the light receiving element 16 at the same time, and the peak value of the pulse-like electric signal output from the light receiving element 16 at the same time as the incidence of the scattered light 13 is increased, the S / N ratio is improved, and the floating Fine particles can be accurately counted.

[0013]

As described above, the present invention makes it possible to provide a floating particle counter capable of accurately counting floating particles. Therefore, when the floating particle counter of the present invention is employed, the management of floating particles in a clean room or the like becomes more accurate, so that the production yield of semiconductor devices and the like can be improved.

[Brief description of the drawings]

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

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

[Explanation of symbols]

 10 is a floating particle, 11 is a laser beam generator, 12 is a laser beam, 12a is an optical axis of a laser beam, 13 is scattered light, 14 is a cylindrical concave mirror, and 14a is a reflection of a cylindrical concave mirror. Surface, 14b is the center of curvature, 15 is the cylindrical lens, 15a is the entrance surface of the cylindrical lens, 15b and 15d are the focal positions of the cylindrical lens, 15c is the exit surface of the cylindrical lens, and 16 is the light receiving element (photodiode Array 16a is a light receiving surface, 21 is a first plane mirror, 21a is a reflection plane of the first plane mirror, 22 is a second plane mirror, and 22a is a reflection plane of the second plane mirror.

Claims (1)

(57) [Claims] A floating particle counter for irradiating a laser beam to fine particles floating in a space and detecting the scattered light of the laser beam scattered by the fine particles to count the fine particles. A laser beam generator (11) for irradiating the suspended fine particles (10) with the laser beam (12)
The reflection center (14a) is oriented in the direction of travel of the laser beam (12a).
A cylindrical concave mirror (14) matched with the laser beam (12)
The incident surface (15a) is positioned at an intermediate position so that the incident surface (15a) faces the reflecting surface (14a) of the cylindrical concave mirror (14).
A cylindrical lens (15) in which the focal position (15b) connected linearly on the side coincides with the optical axis (12a) of the laser beam (12);
The light receiving surface (16a) is connected to the emission surface of the cylindrical lens (15).
The scattered light (12) of the laser beam (12) which is scattered by the floating particulate 1
A floating particle counter characterized by comprising a plurality of light receiving elements (16) for converting 3) into a light receiving surface (16a) and converting the light into electric signals.