JPH08247923A - Counter for particle in vacuum - Google Patents

Abstract

PURPOSE: To provide a compact and inexpensive device which stably and accurately measures the number of particles and the particle diameter in real time without sacrificing the degree of vacuum of a vacuum device, comprising a sensor and an X-Y scanner for improving maintenance property. CONSTITUTION: In a counter for particles in vacuum for detecting the number of particles and the size by detecting scattered light using a photo detector 13 by applying pulse-shaped detection light to particles collected in a vacuum device from a light source 8, a sampling glass 22 is airtightly replaceably arranged in a space which is connected to the inside of the vacuum device, a sensor 7 provided with, for example, a light source 8 and the photo detector 13, is arranged at the lower part, and at the same time the sensor 7 can be moved on X-Y plane so that detection light scans a specific range of the sampling glass 22. Based on the scattered light from particles settling on a detection surface 22a of a glass surface by applying detection light from the light source 8 via the glass 22, the number and size of particles on the detection surface 22a are detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum particle counter capable of measuring the number and size of particles generated in a vacuum device in real time.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
A so-called face plate defect measuring device (surface scanner) is known for managing particles in a vacuum device. However, the stationary surface scanner is large and expensive, and is not always close to the measurement location, which causes many problems in its handling and operation.

Further, if a sample is directly measured using such a surface scanner, there is a problem that sufficient sensitivity cannot be obtained when measuring a patterned wafer or the like. For this reason, a method has been proposed in which an optical system for particle measurement is directly set in a vacuum device for measurement, but there is still a practical limit to use.

5 to 7 show a conventional particle counter or particle monitor proposed as an alternative to the surface scanner. First, in the conventional technique shown in FIG.
Is a sensor for measuring the number of particles by a light scattering method, 10
1 is a laser diode as a light source for emitting detection light,
102 and 104 are lenses, 103 is a prism, 105 is an aperture, 106 is a photocell, 107 is a filter,
Reference numeral 108 denotes a beam stop, and 109 denotes a laser beam, and scattered light of the laser beam 109 due to particles existing in the measurement window 110 is detected by the photocell 107.
The sensor 100 is installed inside the vacuum apparatus or in an exhaust system outside the vacuum apparatus.

In the above-mentioned prior art, when the sensor 100 is installed inside a vacuum device, dirt and particle deposition (stagnation, accumulation) due to secondary products of the introduced gas are carried out.
Damage to the detection system due to the effect of. Further, the sensor 100 has poor heat resistance and may detect noise due to stray light inside the vacuum apparatus. In addition, there is a concern that the degree of vacuum may decrease due to gas leakage.

Further, since the signal cable is connected inside, it is vulnerable to electrical noise, and since the speed at which particles pass through the sensor 100 is random, there is a problem that the particle size cannot be detected. Of these drawbacks, the sensor 10 is excluded except those caused by being placed inside the vacuum device.
Almost the same drawback occurs when 0 is arranged in the external exhaust system.

FIG. 6 shows another conventional technique. Figure 6
, 200 is a sensor, 201 is a laser diode, 202 and 203 are lenses, 204 is a detection chamber,
205 is a light stop, 206 is a lens, and 207 is a photodetector, and light scattered by particles existing in the detection chamber 204 is detected by the photodetector 207. The sensor 200 is installed in an exhaust system outside the vacuum device.

Also in this prior art, there are problems such as the generation of dirt due to secondary products of exhaust gas, the influence of deposition on the detection system, the heat resistance of the sensor 200, and the inability to detect the particle size. .

FIG. 7 shows still another conventional technique. In FIG. 7, 300 is a sensor, 301 is a laser diode, 302 is a collimator, 303 is a mirror, 304 is a flow cell, 305 is a gas inlet, 306 is a gas outlet, and 30.
7 is a collector lens, 308 is a photodetector, 309 is an amplifier, 310 is a discriminator, and 311 is a display. The sensor 300 is installed in the air supply system or the exhaust system of the vacuum device.

In this prior art, when the sensor 300 is arranged in the exhaust system of the vacuum apparatus, there is the same problem as in the prior art of FIG. 6, and when the sensor 300 is arranged in the air supply system, particle size detection still remains. Impossible, flow cell 304
There is a problem such as being polluted.

The present invention solves the above-mentioned various problems, can accurately measure the number and size of particles without impairing the degree of vacuum of the vacuum apparatus, and without being influenced by the introduced gas and the like.
It is an object of the present invention to provide a particle counter in vacuum which has excellent heat resistance of a sensor, is easy to maintain, and has high measurement stability.

[0012]

In order to achieve the above-mentioned object, the present invention irradiates particles generated in a vacuum device with pulsed detection light from a light source and detects the scattered light by a photodetector. In a particle counter in vacuum for detecting the number and size of particles, a sampling glass is replaceably and hermetically arranged in a space communicating with the inside of a vacuum device, and a light source, a photodetector and a lens are arranged below the sampling glass. While arranging a sensor having an optical system such as
The sensor and the sampling glass are configured to be relatively movable on the XY plane so that the detection light scans a predetermined range of the sampling glass, and the detection light is emitted from the light source through the sampling glass to thereby make the front side of the sampling glass. The number and size of particles on the detection surface are detected based on the scattered light from the particles settled on the detection surface.

[0013]

In the present invention, the backscattered light is received by the photodetector by irradiating the particles settled on the front detection surface of the sampling glass with pulsed detection light through the sampling glass, This is converted into a pulse signal. From the number and amplitude of this pulse signal, the number and size of particles on the detection surface are detected. The number of particles in the vacuum apparatus and other particle management are performed by making the sensor or sampling glass relatively movable on the XY plane and scanning a predetermined range on the sampling glass.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing an embodiment of the present invention. In this figure, 1 is a base, and a Y-axis stage 3 that is movable in the front-back direction of the paper surface of FIG. 1 by a mechanism such as a Y-axis pulse motor 2 (see FIG. 2) and a feed screw is provided on the base 1. It is installed.

A support base 4 is integrally fixed to the upper surface of the Y-axis stage 3, and the upper surface of the support base 4 can be moved in the left-right direction in FIG. 1 by a mechanism such as an X-axis pulse motor 6 and a feed screw. An X-axis stage 5 is attached. The X-Y scanner is configured by the X-axis pulse motor 6, the X-axis stage 5, the Y-axis pulse motor 2, the Y-axis stage 3 and the like.

A sensor 7 is integrally attached to the upper surface of the X-axis stage 5. This sensor 7 includes a semiconductor laser 8 as a pulse light source, a pickup lens 9, a lens 10, a condenser lens 11, an aspherical lens 12, a photodetector 13, and a preamplifier (circuit elements are not shown).
14 and the like, which are tubular casings 15,
16 are arranged coaxially. If an interference filter is provided in the optical system, it will be less likely to be affected by plasma light or the like. The end surface of the upper casing 16 on the lens 10 side is open, and the top plate 1 bolted to the base 1 is mounted.
The sensor 7 is arranged immediately below the sensor 7.

A square tube-shaped detection tube 19 is erected on the top plate 17 through a through hole 18, and the sampling glass 22 is held between the detection tube 19 and the upper detection tube 20. ing. In addition, 21 is a clamp that sandwiches the flanges 19a and 20a of the detection cylinders 19 and 20, and 23 is O.
It is a ring, and the sampling glass 22 can be replaced with one touch by removing the clamp 21.
Needless to say, the airtightness is maintained above and below the sampling glass 22.

The upper end of the detection tube 20 communicates with the lower part of the reaction furnace of a vacuum device (not shown) or the exhaust system, and in any case, particles generated in the vacuum device settle on the surface of the sampling glass 22. The detection cylinder 20, the sampling glass 22 and the like are arranged at such positions.

FIG. 3 is an explanatory view of the mounting position of this embodiment. FIG. 7A shows the case where the sensor 7 is attached to the lower part of the reaction furnace of the vacuum device 30, and the controller 50 controls the drive of the semiconductor laser 8, the processing of the light reception signal of the photodetector 13, and the X, Y respective. The drive control of the pulse motors 6 and 2 of the shaft is performed, and the number and size (particle size) of the detected particles are calculated by the personal computer 60. In addition, 40 shows a pump. FIG. 2B shows an example in which the sensor 7 is attached to the exhaust system outside the vacuum device 30.

Next, the operation of this embodiment will be described. First, the light detected by the semiconductor laser 8 is pulsed light of about 200 Hz, and the laser beam passing through the lenses 9 and 10 is 0.5 mm on the detection surface 22a on the surface of the sampling glass 22.
Sampling glass 2 focused on a spot of × 50 μm
Irradiate from below 2. In this state, X-axis pulse motor 6
Drive the X-axis stage 5 and the sensor 7 to 10 mm / s.
The laser beam scans the detection surface 22a on the sampling glass 22 in the X-axis direction by moving it in either the left or right direction in FIG. 1 at a speed of ec.

The laser beam irradiates the particles settled on the detection surface 22a due to dust generated in the vacuum device 30 through the sampling glass 22, and the backscattered light is emitted through the through hole 1.
The light is received by the photodetector 13 from 8 through the condenser lens 11 and the aspherical lens 12, and is converted into a pulsed electric signal.

This pulse signal is amplified by the preamplifier 14 and input to the personal computer 60 via the controller 50. In the case of the personal computer 60, from the number of pulse signals, the above 1
The number of particles on the scan line and the particle size (particle diameter) are calculated from the amplitude of the pulse signal.

Next, the Y-axis pulse motor 2 is driven, and the Y-axis stage 3 is moved at a speed of 0.5 mm / sec in either of the front and back directions of FIG. The surface 22a is moved in the Y-axis direction. After that, the X-axis pulse motor 6 is driven to move the X-axis stage 5 and the sensor 7 in the opposite direction to 10 mm /
It is moved at a speed of sec, and the detection surface 22a is scanned in the opposite direction.

By repeating this operation, for example, 1
Detection surface 2 of sampling glass 22 of 0 mm x 10 mm
The entire area of 2a can be scanned in about 30 seconds,
The count value of particles at this time is 4000 at maximum. Note that FIG. 4 is an explanatory diagram of the scanning operation on the XY plane on the sampling glass 22 (detection surface 22a) described above. Further, the measurement area can be arbitrarily changed by changing the strokes of the X axis and the Y axis.

By feeding back the data concerning the number and size of the sedimented particles on the detection surface 22a thus detected to the manufacturing process or the like through the personal computer 60,
Particles inside the vacuum device 30 can be managed in real time. In the above embodiment, the sensor 7 is moved on the XY plane, but the sensor 7 may be fixed and the sampling glass 22 may be moved.

[0026]

As described above, according to the present invention, the sensor and the X-
The Y scanner is integrated and attached to the outside of the vacuum device, and the scattered light from the particles settled on the detection surface of the Y scanner is detected through the airtightly installed sampling glass. Therefore, there is no concern about gas leakage that impairs the degree of vacuum of the vacuum device, and stable real-time measurement can be performed without being affected by the introduced gas.

Further, since the particles are stationary and fixed on the sampling glass, it is possible to measure the number of particles with high accuracy, and it is difficult to be affected by stray light or electric noise inside the vacuum apparatus. At the same time, since the particles that move at random speed are not measured, the particle size can be reliably measured. Further, it is easy to take heat resistance measures for the sensor arranged outside the vacuum device.

Since the sampling glass can be replaced with one touch, it is excellent in maintainability, and the sampling glass, the sensor and the like can be attached by utilizing the existing empty port of the vacuum device. Further, the sensor and the XY scanner have a relatively simple structure and can be miniaturized, and can be provided at low cost. If the thin film level deposition on the glass is not detected, a more stable measurement operation becomes possible.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a plan view showing an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a mounting position according to the embodiment of this invention.

FIG. 4 is an explanatory diagram of a scan operation according to the embodiment of this invention.

FIG. 5 is a diagram showing a conventional technique.

FIG. 6 is a diagram showing a conventional technique.

FIG. 7 is a diagram showing a conventional technique.

[Explanation of symbols]

 1 base 2 Y-axis pulse motor 3 Y-axis stage 4 support 5 X-axis stage 6 X-axis pulse motor 7 sensor 8 semiconductor laser 9 pickup lens 10 lens 11 condenser lens 12 aspherical lens 13 photodetector 14 preamplifier 15, 16 Casing 17 Top plate 18 Through hole 19,20 Detection tube 21 Clamp 22 Sampling glass 22a Detection surface 23 O-ring 30 Vacuum device 40 Pump 50 Controller 60 PC

Claims (1)

[Claims] 1. A particle counter in vacuum, wherein particles generated in a vacuum device are irradiated with pulsed detection light from a light source, and the scattered light is detected by a photodetector to detect the number and size of the particles. In the above, the sampling glass is replaceably and airtightly arranged in a space communicating with the inside of the vacuum device, and a sensor having an optical system such as a light source, a photodetector and a lens is arranged below the sampling glass, and The sensor and the sampling glass are configured to be relatively movable on the XY plane so as to scan a predetermined range of the sampling glass, and the detection light is irradiated from the light source through the sampling glass to detect the front surface of the sampling glass. A party in a vacuum characterized by detecting the number and size of particles on a detection surface based on the scattered light from the particles settled on top. Rukaunta.