JPH07134094A - Particle sensor head - Google Patents

Abstract

(57) [Abstract] [Objective] In a scattered light type particle detection means, even if the intensity of scattered light / reflected light of the beam increases due to contamination of the beam stopper that receives the beam, particle detection by stray light caused by the It is intended to provide a particle sensor head capable of suppressing a decrease in reliability. [Structure] A light source, an optical system for shaping the light emitted from the light source into a beam shape, and a light source for the beam light in a cylindrical casing having a long inlet in the axial direction through which particles enter A filter that faces a virtual surface that is formed in the advancing direction and the particle entering direction, and a photodetector that detects scattered light generated when the beam light collides with the particle entering from the inlet through the filter. A particle sensor head in which a beam stopper that receives a beam of light is arranged, and an interference film filter is used as the filter. Alternatively, a spacer or aperture is inserted in the front part of the beam stopper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor head for a particle detecting device for detecting particles in a vacuum processing device.

[0002]

2. Description of the Related Art In recent years, semiconductor devices represented by LSI have been highly integrated, and for example, in 4M DRAM, the pattern line width is 0.8 μm, which is already submicron.
Under these circumstances, 80
% Or more is attributed to particles. As a particle measuring method for a vacuum processing apparatus related to the manufacture of a semiconductor device, a light scattering type particle detecting apparatus capable of detecting “in-situ” particles generated during an actual process in an actual manufacturing process is used. . As this particle detecting device, for example, a particle measuring system disclosed in Japanese Patent Application Laid-Open No. 3-311604, specifically, a particle trend monitor PM-150 manufactured by Ushio Inc.
XS and its sensors M-20, M-25, M-20
S, M-25S and the like are known.

A conventional sensor head used in a light scattering type particle detecting device will be described with reference to FIG.
As shown in FIG. 8, the sensor head uses a light source 1 and a light beam emitted from the light source 1 as a beam in a cylindrical casing 20 having an inlet 10 on the side which is long in the axial direction and through which particles enter. An optical system including lenses 2 and 5, prisms 3 and 4, and a diaphragm 6 that are shaped into a shape, and a filter 7 that faces an imaginary surface formed in a direction in which the beam light L travels and a direction in which particles enter, Beam light L
Is composed of photodetectors 8a, 8b, 8c and 8d for detecting scattered light generated by colliding with particles entering from the inlet 10 and a beam stopper 9 for receiving the beam light L. .

Particle information is obtained as follows. The scattered light generated by the collision of the beam light L with the particles that have entered the intake port 10 exists for the time when the particles exist, and the intensity thereof is stronger as the particles are larger. Therefore, the scattered light is processed as a pulse signal. The number of particles is measured by the number of pulses, and the size of the pulse identifies the size of the particles. Since scattering by such particles has various scattering angles, it is advantageous to detect scattered light with a wide solid angle in order to detect particles with high sensitivity. In the example shown in FIG. 8 above, a colored glass filter having no dependence on the incident angle is used as the filter 7 so that scattered light with a large incident angle can be detected.

Normally, it is difficult to completely absorb the beam L by the beam stopper 9, even if the shape, material, coating technology of the light receiving surface, etc. of the beam stopper 9 are sufficiently taken into consideration. The reflected light / scattered light of L enters the photodetectors 8a, 8b, 8c, 8d. Also, it is difficult to construct an optical system that realizes perfect beam shape shaping, and a part of the shaped beam light is directly
Alternatively, the light is reflected by each part of the sensor head and indirectly enters the photodetectors 8a, 8b, 8c, 8d. Such background light is called stray light,
Its intensity is also monitored by the photodetectors 8a, 8b, 8c, 8d. Therefore, the scattered light signal is obtained as shown in FIG. 9, for example.

[0006]

By the way, for example, when a sensor head is installed in the exhaust line of a certain type of etcher or a CVD apparatus, the gas containing the reaction product generated during the process flows through the particle intake port 10. pass. Therefore, the light-receiving surfaces of the filter 7 and the beam stopper 9 facing the inlet 10 are contaminated by the attachment and deposition of reaction products. Such contamination is caused by the decrease in the sensitivity of the photodetectors 8a, 8b, 8c and 8d due to the decrease in the transmittance of the filter 7 and the reflected light of the beam at the beam stopper 9.
It induces phenomena such as increased stray light due to scattered light.

The decrease in the transmittance of the filter 7 does not cause a problem in use unless the filter 7 itself is significantly contaminated. On the other hand, since the beam L incident on the beam stopper 9 formed by the optical system has high light intensity, even slight contamination of the beam stopper 9 causes scattered light or reflected light having high light intensity. Therefore, stray light having a high light intensity is incident on the photodetectors 8a, 8b, 8c, 8d, which causes erroneous counting and the like, which causes a problem in the characteristics and reliability of the sensor. Therefore, there is a drawback that the cleaning frequency of the beam stopper increases and the practicality becomes poor.

Therefore, the present invention has been made in view of the above circumstances. Even if the intensity of scattered light and reflected light of the beam is increased due to the contamination of the light receiving surface of the beam stopper, the particle detection due to stray light caused by the contamination can be performed. It is to provide a sensor head capable of suppressing a decrease in reliability.

[0009]

In order to achieve the above object, the present invention provides a light source and a light source in a cylindrical casing having an inlet, which is long in the axial direction and into which particles newly enter, in a side portion. An optical system that shapes the emitted light into a beam shape, a filter that faces a virtual surface that is formed in the direction in which the beam light travels and the direction in which the particles enter, and the beam light that collides with the particles that enter from the intake. An interference film filter is added to the filter in a particle sensor head in which a photodetector that detects scattered light generated by passing through the filter is detected and a beam stopper that receives the beam is arranged. Alternatively, a spacer or aperture is inserted in the front part of the beam stopper.

[0010]

Since the beam stopper is present at the end portion in the longitudinal direction of the inlet, the incident angle at which the scattered light / reflected light from the beam stopper enters the photodetector is larger than that of the scattered light from particles. On the other hand, the interference film filter controls the transmittance of light having a predetermined wavelength according to the incident angle. Therefore, in the wavelength range of the light emitted by the light source, the incident angle of stray light due to the beam stopper is used as a reference,
By adding an interference film filter that has a low transmittance for light with an incident angle greater than that and a high transmittance for light with an incident angle less than that, the incidence of stray light due to the beam stopper on the detector is suppressed. As a result, deterioration in reliability of particle detection due to stray light is suppressed.

Since the incident angle of the stray light due to the beam stopper on the photodetector is about 70 ° or more, the transmittance of the interference film filter is 50% at the incident angle of 60 ° or more at the wavelength of the light source used. The following is desirable.

On the other hand, with respect to the operation when the spacer or the aperture is inserted in the front portion of the beam stopper, the incident angle of stray light due to the beam stopper becomes larger than that when the spacer or the aperture is not inserted. Therefore, the incident angle range where stray light is incident on the detector is narrowed, and as a result, the amount of stray light incident on the detector is reduced. Also, the insertion of the spacers or apertures suppresses the contamination of the beam stopper due to the attachment and deposition of reaction products. Therefore, it is possible to prevent a decrease in reliability of particle detection due to stray light caused by the beam stopper. The term “incident angle” as used herein means an acute angle formed by the incident light ray with respect to the normal line of the boundary surface.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the embodiments shown in the drawings. As shown in FIG. 1, the casing 20
Is a cylindrical body, and an inlet 10 which is a long hole elongated in the axial direction of the casing 20 is formed on a side portion thereof. The light source 1 has a wavelength of 780 at one end of the casing 20.
A semiconductor laser that emits nm light is arranged.
In front of the light source 1, lenses 2 and 5, prisms 3 and 4,
An optical system including a diaphragm 6 is arranged, and the laser light from the light source 1 is converted into a beam light L by the optical system. The beam light L travels along the axis of the casing 20.

A pair of filters 7 corresponding to the inlet 10 and a photodetector 8 which is a large area Si photodiode.
Although a, 8b, 8c, and 8d are arranged, as described above, the filter 7 and the photodetector 8a are arranged so as to face a virtual surface formed in the direction in which the light beam L advances and the direction in which particles enter. , 8b, 8c, 8d are arranged,
The area between the filters 7 and 7 is the detection area. A beam stopper 9 that receives the beam light L that has passed through the detection area is arranged downstream of the filter 7 and the photodetectors 8a, 8b, 8c, and 8d.

The filter 7 is a colored glass filter 7a.
It is an interference film filter in which a vapor-deposited film 7b made of silicon oxide or titanium oxide is formed using the substrate as a substrate. For example, in the case of a filter in which 31 layers of silicon oxide and titanium oxide are alternately deposited by a vacuum deposition method with a colored glass filter RG9 manufactured by Schott Glass Co., Ltd. as a substrate, a wavelength of 7
The transmittance of 80 nm light has an incident angle dependency as shown in FIG.

In order to confirm the effect of the present invention, various beam stoppers 9 having different stains are attached to the particle sensor head M-20S manufactured by Ushio Inc., with or without an interference film filter. The intensity of stray light in each case was compared. The interference film filter was constructed by alternately depositing 31 layers of silicon oxide and titanium oxide by a vacuum deposition method using a colored glass filter RG9 manufactured by Shot Glass Co., Ltd. as a substrate. FIG. 5 is an explanatory diagram of data showing a comparison of stray light when the above-mentioned interference film filter is used and when only the colored glass filter RG manufactured by Schott glass is used. The degree of contamination of the beam stopper 9 on the horizontal axis is defined as follows. When the beam stopper 9 having a certain dirt is irradiated with a laser beam, the intensity of scattered light scattered by the dirt on the beam stopper 9 is proportional to the degree of the dirt on the beam stopper 9. Therefore, in a preliminary experiment, the wavelength of 78 that was formed into a beam shape by an optical system on the beam stopper 9 having various stains in advance.
The semiconductor laser light of 0 nm was irradiated, and the scattered light intensity was measured with a condensing optical system installed at a position of 45 degrees in front of the beam stopper 9 and a Si photodiode as a detector. Then, among the beam stoppers 9 having various stains described above, the scattered light intensity of the above-mentioned preliminary experiment for the stray light intensity which becomes the maximum value of the allowable limit of the stray light level when the beam stopper 9 is used in the conventional sensor head, Beam stopper 9
Was set as 1 unit.

The vertical axis represents the light intensity of stray light. Here, the stray light intensity of 500 (AU) is the allowable limit of the stray light level. This limit depends on the type of sensor. In the particle sensor head M-20S, when the stray light intensity exceeds 500 (AU), the probability of miscounting by 1 count or more in any 5 minutes during particle measurement exceeds 0. The allowable limit of the stray light level here is that the output signal due to the stray light has a particle size of 2 μm.
It is the stray light intensity when it corresponds to the peak value of the output pulse when measuring m particles. As shown in FIG. 9, the stray light is a DC component. On the other hand, the scattered light output pulse when measuring particles is an AC component. Therefore, the scattered light output pulse is not affected even if the stray light level changes to a certain level, and the detection sensitivity of the sensor does not change. However, if it exceeds a certain level, it becomes easy to make a false count as described above. In FIG. 5, black circles are data when the interference filter is used, and white circles are data when the interference filter is not used. By using the interference filter, the particle sensor head can handle up to 2.8 times more dirt than when not used.

FIG. 2 shows another embodiment. The structure is the same as that of FIG. 1, 7 is a filter, 8 is a photodetector, 9 is a beam stopper, 10 is an inlet, and a spacer 1
1 is arranged in front of the beam stopper 9. Here, L1 is an optical path of a conventional beam, and L2 is an optical path when a spacer is used, and the incident angle of stray light due to the beam stopper is larger than that when the spacer 11 is not inserted. As described above, the incident angle range where stray light is incident on the detector is narrowed, and as a result, the amount of stray light incident on the detector is reduced. Further, since the distance between the detection region between the filters 7 and 7 and the beam stopper 9 is lengthened by inserting the spacer 11, the contamination of the beam stopper due to the attachment or deposition of reaction products is suppressed. Therefore, the decrease in reliability of particle detection due to stray light caused by the beam stopper is suppressed.

FIG. 3 shows still another embodiment. Figure 1
7 is a filter, 8 is a photodetector,
Reference numeral 9 is a beam stopper, 10 is an inlet, and an aperture 12 is arranged in front of the beam stopper 9. Here, L1 is stray light of the conventional beam, and L3 is stray light when the aperture 12 is used, and the incident angle of the stray light due to the beam stopper is larger than that when the aperture 13 is not inserted. As in the case of FIG. 2, the amount of stray light incident on the detector is reduced. Further, the insertion of the aperture 12 suppresses the contamination of the beam stopper due to the attachment and deposition of reaction products. Therefore, the decrease in reliability of particle detection due to stray light caused by the beam stopper is suppressed. In the present embodiment, the structure of the sensor head can be made more compact than when the spacer 11 of the embodiment shown in FIG. 2 is used.

FIG. 6 shows an example of the embodiment described with reference to FIG.
For various beam stoppers 9 with different dirt, without spacers, and 10 mm, 2
It is explanatory drawing of the data which shows the comparison of the stray light at the time of installing a 0 mm spacer. The horizontal axis represents the degree of contamination of the beam stopper 9 defined as described above. The vertical axis represents the light intensity of stray light. As described above, the stray light intensity 500 (A.
U. ) Is the allowable limit of stray light level. The white squares are the data when the spacer is not used, the black circles are the data when the spacer with a length of 10 mm is used,
White circles are data when a spacer having a length of 20 mm is used. The particle sensor head using the spacer having a length of 10 mm can cope with up to 1.8 times as much dirt as when the spacer is not used. The particle sensor head using the spacer having a length of 20 mm can cope with up to 2.8 times as much dirt as when the spacer is not used.

The embodiments shown here may be combined. FIG. 7 shows the interference film filter and the length of 20 mm for various beam stoppers 9 with different stains.
With both spacers, and with no spacer installed, shot glass company colored glass filter RG9
It is explanatory drawing of the data which shows the comparison of the stray light at the time of installing only. The horizontal axis represents the degree of contamination of the beam stopper 9 defined as described above. The vertical axis represents the light intensity of stray light. As described above, the stray light intensity of 500 (AU) is the allowable limit of the stray light level. The black circles are the data when both the interference film filter and the spacer having a length of 20 mm are installed, and the white circles are the data when the interference film filter and the spacer are not installed. The particle sensor head in which both the interference film filter and the spacer having a length of 20 mm are installed can deal with up to about 100 times as much dirt as when the interference film filter and the spacer are not installed.

[0022]

As described above, since the incident angle of scattered light / reflected light from the beam stopper to the photodetector is larger than that of scattered light from particles, stray light caused by the beam stopper is incident. Incident of stray light to the detector by adding an interference film filter with low transmittance of light with an incident angle larger than that of the angle and high transmittance of light with an incident angle smaller than that Can be suppressed, and the decrease in reliability of particle detection can be suppressed. Also, if a spacer or aperture is inserted in the front part of the beam stopper, the incident angle of stray light due to the beam stopper will be large and stray light with an incident angle smaller than that will not enter the detector. The amount of incident light on the beam stopper is reduced, and the contamination of the beam stopper due to the attachment and deposition of reaction products is suppressed as a result of the insertion of the spacer or aperture. Therefore, the reduction in the reliability of particle detection due to stray light due to the beam stopper is suppressed. You can

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment of a particle sensor head of the present invention.

FIG. 2 is an explanatory view of another embodiment of the particle sensor head of the present invention.

FIG. 3 is an explanatory view of another embodiment of the particle sensor head of the present invention.

FIG. 4 is an explanatory diagram of data of incident angle dependency of transmittance of the interference filter.

FIG. 5 is an explanatory diagram of data showing an effect when an interference filter is used.

FIG. 6 is an explanatory diagram of data showing an effect when a spacer is used.

FIG. 7 is an explanatory diagram of data showing an effect when an interference filter and a spacer are used at the same time.

FIG. 8 is an explanatory diagram of a conventional particle sensor head.

FIG. 9 is an explanatory diagram of a scattered light signal and a backland light signal by particles.

[Brief description of symbols] 1 light source 2 lens 3 prism 4 prism 5 lens 6 diaphragm 7 filter 7a colored glass filter 7b vapor deposition film 8a, 8b, 8c, 8d photodetector 9 beam stopper 10 inlet 12 spacer 13 aperture 20 casing L beam light L1, L2, L3 stray light

Claims (4)

[Claims] 1. A light source, an optical system for shaping the light emitted from the light source into a beam shape, and a beam in a cylindrical casing having an intake port on the side, which is long in the axial direction and through which particles enter. A filter that faces a virtual surface that is formed in the direction in which the light travels and the direction in which the particles enter, and light detection in which scattered light generated when the beam light collides with the particles that enter from the inlet passes through the filter and is detected. A particle sensor head having a container and a beam stopper for receiving a beam, wherein an interference film filter is used as the filter. 2. A light source, an optical system for shaping the light emitted from the light source into a beam shape, and a beam in a cylindrical casing having an inlet on a side portion which is long in the axial direction and through which particles enter. A filter that faces a virtual surface that is formed in the direction in which the light travels and the direction in which the particles enter, and light detection in which scattered light generated when the beam light collides with the particles that enter from the inlet passes through the filter and is detected. A particle sensor head in which a container and a beam stopper for receiving a beam are arranged, wherein a spacer is arranged in front of the beam stopper. 3. A light source, an optical system for shaping the light emitted from the light source into a beam shape, and a beam in a cylindrical casing having an intake port on the side which is long in the axial direction and through which particles enter. A filter that faces a virtual surface that is formed in the direction in which the light travels and the direction in which the particles enter, and light detection in which scattered light generated when the beam light collides with the particles that enter from the inlet passes through the filter and is detected. A particle sensor head in which a container and a beam stopper for receiving a beam are arranged, and an aperture is arranged in front of the beam stopper. 4. The particle sensor head according to claim 1, wherein the transmittance of the interference film filter is 50% or less at an incident angle of 60 ° or more at a wavelength of light emitted from the light source.