JPH0943132A - Particle measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the measurement accuracy of a particle measuring instrument without generating any signal resulting from diffused external light from a light receiving element by providing light shielding members which prevent the entrance of the diffused external light other than scattered light to the light receiving element. SOLUTION: A first douser 16 and second dousers 17a and 18b are provided as light shielding members. The douser 16 is positioned toward the entering direction of diffused external light. Consequently, the advance of the diffused external light into a housing 12 from a window section 18 is prevented by the douser 16 and photodiodes 14a and 14b do not generate signals resulting from the diffused external light. Therefore, only signals resulting from scattered light M caused by particles are generated and the measurement accuracy of the particle measuring instrument is improved. Since the dousers 17a and 17b are arranged on both sides of an inspection area so as to intercept the diffused external light entering the diodes 13a and 14b from the lateral direction, the measurement accuracy of the measuring instrument is further improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a particle measuring device, and more particularly to a particle measuring device for measuring particles by detecting scattered light generated when the particles collide with light emitted from a light emitting element.

For example, in a semiconductor manufacturing apparatus such as an ion implantation apparatus, it is known that when fine dust (particles) exists in the apparatus, the particles adhere to the wafer to reduce the yield. In particular, as semiconductor devices have become higher in density and finer as in recent years, the decrease in manufacturing yield due to the particles becomes a serious problem.

For this reason, particles existing in the apparatus are measured by using a measuring apparatus, and the manufacturing process conditions are optimized based on the measured values to prevent a decrease in manufacturing yield. . Therefore, improving the accuracy of the particle measuring device that measures particles is more important than improving the manufacturing yield of the semiconductor manufacturing device.

[0004]

2. Description of the Related Art FIG. 9 is a schematic configuration diagram showing an example of a conventional particle measuring apparatus. As shown in FIG. 1, the particle measuring apparatus 1 is roughly composed of a housing 2, a semiconductor laser element serving as a light emitting element 3, a photodiode 4 (shown by hatching) serving as a light receiving element, and a lens system 5. There is.

The laser light L generated by the semiconductor laser element 3 is condensed by the lens system 5, passes through the photodiodes 4, and is absorbed by the beam stopper 6 provided in the housing 2. Further, a window portion 7 having a long hole shape is formed in the housing 2 in the vicinity of the position where the photodiode 4 is disposed. Then, the particles enter the inside of the housing 2 through the window 7.

When the particles enter the housing 2 through the window 7 and collide with the laser light L emitted from the semiconductor laser element 3, the laser light L is scattered by the particles to generate scattered light M. This scattered light M is received by the photodiode 4, and thus the photodiode 4
Generates an electrical pulse signal. Therefore, this pulse signal generated by the photodiode 4 corresponds to the number of particles, and therefore the number of particles can be counted based on this pulse signal.

[0007]

However, in the vacuum apparatus, the laser light L emitted from the semiconductor laser element 3 is used.
There may be light of the same wavelength as the wavelength of. In addition, the conventional particle measuring device 1 is configured to simply form the window portion 7 in the housing 2 in order to take the particles into the housing 2.

Therefore, light having the same wavelength as the wavelength of the laser light L existing in the vacuum device (hereinafter referred to as disturbance light) may enter the housing 2 through the window 7. Then, when the ambient light enters the housing 2 and enters the photodiode 4, the photodiode 4 also generates a signal by the ambient light.

That is, in this case, the signal output from the photodiode 4 is a signal in which the signal generated by particles and the signal generated by ambient light are superimposed. Therefore, in the conventional particle measuring device 1,
There is a problem that it is not possible to count particles with high accuracy.

The present invention has been made in view of the above points, and an object of the present invention is to provide a particle measuring apparatus with improved measurement accuracy.

[0011]

In order to solve the above problems, the present invention takes the following means. According to the first aspect of the invention, the particle measurement is performed by detecting the scattered light generated by the light emitted from the light emitting device colliding with the particles entering through the window formed in the housing by the light receiving element. In the device,
It is characterized in that a light-shielding member for preventing disturbance light other than the scattered light from entering the light-receiving element is provided.

The invention according to claim 2 is characterized in that, in the particle measuring device according to claim 1, the light shielding member can cover the window portion. The invention according to claim 3 is characterized in that, in the particle measuring device according to claim 2, the position of the light shielding member is adjustable along the housing.

According to a fourth aspect of the present invention, in the particle measuring device according to the second or third aspect, the light shielding member has a blind structure that allows passage of the particles and regulates transmission of the ambient light. It is characterized by that.

According to a fifth aspect of the present invention, in the particle measuring apparatus according to the first aspect, the light shielding member is arranged in the housing in the vicinity of the light receiving element.

Further, in the invention according to claim 6, in the particle measuring device according to claim 5, the light shielding member is opposed to both sides of the light receiving element in a traveling direction of light emitted from the light emitting device. It is characterized by being arranged as follows.

Each of the above means operates as follows. According to the invention described in claim 1, since the light receiving element is provided with the light shielding member for preventing the disturbance light other than the scattered light from entering, the light receiving element does not generate a signal by the disturbance light. It is possible to improve the accuracy of particle measurement.

Further, according to the second aspect of the invention, since the light shielding member covers the window portion, it is possible to prevent disturbance light from entering through the window portion with a simple structure. Incidentally, it is needless to say that when the light shielding member is arranged, the light shielding member is arranged so that particles can enter the housing through the window.

Further, according to the third aspect of the invention, since the position of the light shielding member can be adjusted along the housing, the light shielding member can be directed in the direction in which the ambient light is incident, and thus the ambient light It is possible to reliably prevent the entry of the into the housing. Further, according to the invention of claim 4, the light shielding member has a blind structure that allows the passage of particles and restricts the transmission of ambient light, so that the light shielding member prevents the particles from entering through the window portion. It is possible to prevent the entry of ambient light.

According to the fifth aspect of the invention, by disposing the light shielding member in the vicinity of the light receiving element for generating a signal, it is possible to efficiently prevent ambient light from entering the light receiving element. . Further, according to the invention as set forth in claim 6, since the light shielding members are arranged on both sides of the light receiving element so as to face each other in the traveling direction of the light emitted from the light emitting device, the light shielding member enters through the window portion and diffusely reflects in the housing. By doing so, ambient light that enters the light receiving element from the lateral position can be blocked, and the accuracy of particle measurement can be further improved.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will now be described with reference to the drawings. 1 and 2 show a particle measuring apparatus 10 which is an embodiment of the present invention, and FIG.
Shows an application example of the particle measuring apparatus 10. 1 is a partially cutaway sectional view of the particle measuring device 10, FIG.
3 is an external view of the particle measuring device 10, and FIG. 3 is a sectional view showing an example in which the particle measuring device 10 is applied to the ion implantation device 11.

The configuration of the particle measuring device 10 will be described below with reference to FIGS. 1 and 2. The particle measuring device 10 roughly includes a housing 12, a semiconductor laser element 13 that serves as a light emitting element, a pair of photodiodes 14a and 14b that serve as a light receiving element, and optical lenses 15a and 1a.
5b, and the first light-shielding plate 16 and the second light-shielding plates 17a and 17b, which are essential parts of the present invention and serve as light-shielding members.

First, the basic constituent elements of the particle measuring device 10 will be described. The housing 12 has a cylindrical shape and is made of, for example, stainless steel. The semiconductor laser element 13, the photodiodes 14a and 14b, the optical lenses 15a and 15b, and the like described above are provided in the housing 12. Further, as will be described later in detail, a long hole-shaped window portion 18 (shown by a chain line in FIG. 1) is formed at a predetermined position of the housing 12, and particles (fine dust) are generated from the window portion 18 in the housing. It is configured to be able to enter inside 12.

The semiconductor laser element 13 outputs a laser beam L having a predetermined wavelength and has a cylindrical housing 1.
2 is arranged substantially coaxially. The laser light L emitted from the semiconductor laser element 13 is condensed by the optical lenses 15a and 15b and then travels in the housing 12 in the right direction in the drawing. As described above, the semiconductor laser device 13 is arranged substantially coaxially with the housing 12, so that the laser light L travels in the axial direction at the substantially central position of the housing 12. Further, a beam stopper 19 is provided at the right end of the housing 12 in the drawing,
The laser light L is absorbed by the beam stopper 19.

The pair of photodiodes 14a and 14b are arranged so as to face the inner wall of the housing 12 and generate a pulsed electric signal (hereinafter referred to as a detection signal) when irradiated with light. . In addition, a filter 20 is provided above the photodiodes 14a and 14b.
a and 20b are provided. This filter 20a,
20b is configured to transmit only light having the same wavelength as the laser light L output from the semiconductor laser element 13 and block light having different wavelengths. Therefore, only the light having the same wavelength as the laser light L output from the semiconductor laser element 13 is incident on the photodiodes 14a and 14b.

Further, the window 18 formed in the housing 12 has a formation position selected near the arrangement position of the photodiodes 14a and 14b. Therefore, the particles pass between the pair of photodiodes 14a and 14b through the window 18 (the pair of photodiodes 14a and 14b).
The area between a and 14b is called a detection area). Reference numeral 21 in the drawing is a preamplifier for driving the semiconductor laser device 13 (not shown in FIG. 2).

Subsequently, the above-mentioned particle measuring device 1
The operation of each basic component of 0 will be described. As described above, the laser light L generated by the semiconductor laser device 13 is condensed by the optical lenses 15a and 15b and then absorbed by the beam stopper 19 through the detection region between the photodiodes 14a and 14b. At this time, when the particles enter the detection region in the housing 12 through the window 17 and collide with the laser light L emitted from the semiconductor laser element 13, the laser light L is scattered by the particles to generate scattered light M. .

This scattered light M is filtered by the filters 20a, 20
The light is received by the photodiodes 14a and 14b via b, and the photodiodes 14a and 14b generate electric pulse signals. As described above, the filter 20
Each of a and 20b has a characteristic of transmitting only light having the same wavelength as the laser light L output from the semiconductor laser element 13. Therefore, the light that is incident on the photodiodes 14a and 14b and is optoelectrically converted should be only the scattered light M scattered by the particles.

However, separately from the scattered light M, the window 18
When light (hereinafter, referred to as disturbance light) having the same wavelength as the laser light L output from the semiconductor laser element 13 is incident on the disturbance light, the disturbance light passes through the filters 20a and 20b and is incident on the photodiodes 14a and 14b. Therefore, as described above, the photodiodes 14a and 14b generate the detection signal not only by the scattered light M caused by the particles but also by the disturbance light, and thus the measurement accuracy of the particles is deteriorated.

Therefore, the present invention is characterized in that the first light-shielding plate 16 and the second light-shielding plates 17a and 17b serving as light-shielding members are provided in order to prevent ambient light from entering the detection area. To do. Hereinafter, the first light shield plate 16 and the second light shield plates 17a and 17b will be described.

First, the first light shielding plate 16 will be described. The first light shielding plate 16 is a plate-shaped member made of stainless steel, like the housing 12, for example. The first light shielding plate 16 has an area larger than at least the area of the window portion 18 described above, and has a shape capable of covering the window portion 18. The first light shield plate 16 is fixed to the mounting plate 22 with screws 23a and 23b.
Is fixed to the housing 12 by a bracket 24.

The bracket 24 is provided integrally with the mounting plate 22, and by loosening the adjusting screw 25, the first light shielding plate 16 is movable along the housing 12. That is, the mounting plate 22, the bracket 24, and the adjusting screw 25 also function as a mounting position adjusting mechanism that allows the mounting position of the first light shielding plate 16 to be adjusted along the housing 12. By providing this mounting position adjusting mechanism, the first light shielding plate 16 can be linearly moved in the direction of arrow X in FIG. 2, and can also be rotated about the housing 12 as shown by arrow M. Becomes

The first light-shielding plate 16 having the above-described structure is arranged in the direction in which ambient light is incident. Therefore, the entry of ambient light from the window portion 18 into the housing 12 is prevented by the first light shielding plate 16, and thus the photodiode 1 is prevented.
4a and 14b will not generate a signal due to ambient light. Therefore, the signals generated by the photodiodes 14a and 14b are only signals caused by the scattered light M generated due to the presence of particles, and the accuracy of particle measurement can be improved.

Further, as described above, the first light shielding plate 16 has a mounting position adjusting mechanism so that the mounting position can be adjusted along the housing 12. Therefore,
The position of the first light shielding plate 16 can be adjusted in the direction in which the ambient light is incident, and thus the ambient light can be reliably prevented from entering the housing 12.

In addition, ambient light is transmitted from the window portion 18 to the housing 12
By disposing the first light shielding plate 16 so as not to enter the inside, it may be considered that the first light shielding plate 16 also prevents particles from entering the housing 12 through the window portion 18. However, in the present embodiment, as shown in each drawing, the first light shielding plate 16 is arranged apart from the outer periphery of the housing 12 by a distance indicated by an arrow H in the drawing. Therefore,
It is possible to prevent the disturbance light from entering the housing 12 while allowing the particles to enter the housing 12.

Further, as shown in FIG. 2B, in this embodiment, the shape of the first light shielding plate 16 is a rectangular main body portion 16.
The shape and the area of the first light shielding plate 16 are not limited to this, but the shape and the area of the first light shielding plate 16 are not limited to this. Of course, it may be appropriately changed depending on the space of the semiconductor manufacturing apparatus to which the particle measuring apparatus 10 is attached.

Next, the second light shielding plates 17a and 17b will be described. The second light-shielding plates 17a and 17b are formed inside the housing 12, and have a disk shape with passing holes 26a and 26b for passing the laser light L formed in the center. This pair of second shading plates 17
Reference numerals a and 17b are in the vicinity of the photodiodes 14a and 14b in the housing 12, specifically, on both sides of the photodiodes 14a and 14b (on both sides of the inspection area), the traveling direction of the laser light L. Are arranged so as to face each other.

Considering the behavior of the ambient light that has entered the housing 12 through the window 18, the ambient light may be directly reflected by the photodiodes 14a, 1 depending on the incident direction.
There is a case where the light does not enter the photodiodes 4b, but diffusely reflects inside the housing 12 (reflection occurs because the housing 12 is made of stainless steel), so that the photodiodes 14a and 14b may enter from the lateral positions.

However, by disposing the second light-shielding plates 17a and 17b with the inspection region sandwiched therebetween as described above, the disturbance light incident from the lateral positions toward the photodiodes 14a and 14b is prevented by the second light-shielding plate. Light can be shielded by 17a and 17b. Therefore, the second light shielding plates 17a and 17b
By providing, it is possible to further improve the accuracy of particle measurement. This will be described in detail with reference to FIGS. 4 and 5.

FIGS. 4 and 5 show the second light shielding plates 17a, 1a.
7B shows the change of the incident range of the disturbance light incident on the photodiodes 14a and 14b depending on the presence or absence of 7b. As shown in FIG. 5, when the second light shielding plates 17a and 17b are not provided, the photodiodes 14a and 14b may output an erroneous signal when disturbance light enters from the range shown by the arrow W2 in the figure. There is. On the other hand, in the configuration in which the second light-shielding plates 17a and 17b shown in FIG. 4 are provided, the range in which the photodiodes 14a and 14b may output an erroneous signal is the range indicated by the arrow W1 in the figure, and the erroneous signal The range in which there is a possibility of output can be made narrower than in the configuration shown in FIG. That is, the second light shielding plates 17a and 17b can reduce the disturbance light incident from the lateral positions toward the photodiodes 14a and 14b. The second light shielding plates 17a and 17b are used for the photodiode 14
The closer to the photodiodes a and 14b, the more efficiently ambient light can be prevented from entering the photodiodes 14a and 14b.

FIG. 3 shows the particle measuring device 10 described above.
2 is a cross-sectional view showing an example in which the above is applied to an ion implantation apparatus 11, which shows an end station of the ion implantation apparatus 11. The end station of the ion implantation apparatus 11 is roughly configured such that a disk 31, an electro flat gun 32, an exhaust line 33, and a particle measuring apparatus 10 are provided in a cover 30.

The disk 31 is configured to rotate by a driving device (not shown), and a plurality of wafers 34 are mounted on the surface thereof. Further, the electro flat gun 32 includes a beam gate 36 and the like in the Faraday 35, and is configured to irradiate the wafer 34 with an ion beam IB emitted from an ion source and accelerated by an accelerator or the like to implant ions. There is. Furthermore, the exhaust line 3
Reference numeral 3 is connected to a vacuum device (not shown), so that the inside of the ion implantation device 11 is configured to have a predetermined degree of vacuum.

The particle measuring device 10 is arranged in the exhaust line 33. Since the exhaust line 33 is a part for sucking the gas existing in the device, when particles are present in the device, the part where the particles are most likely to be collected is also the exhaust line 33. Therefore, by providing the particle measuring device 10 in the exhaust line 33 and measuring the particles, the number of particles existing in the device can be reliably detected, and the particle measuring accuracy can be improved.

In the ion implanter 11 having the above structure,
Light emission may occur in the beam line by the ion beam IB and the electro flat gun 32 during the ion implantation operation. This light emission includes light having the same wavelength as the laser light L output from the semiconductor laser element 13 (that is, disturbance light). Therefore, when the disturbance light enters the particle measuring apparatus 10, the light of the particles is generated. Measurement accuracy is greatly reduced.

However, as described above, since the particle measuring device 10 according to the present embodiment is provided with the first light shielding plate 16 and the second light shielding plates 17a and 17b, the disturbance light enters the housing 12. Can be prevented. Here, FIG. 6 and FIG. 7 show the results of actual particle measurement processing using the ion implantation apparatus 11 having the above-described configuration while the electro flat gun 32 was activated.

FIG. 6 shows the first and second light shielding plates 16 and 17.
FIG. 7 shows a measurement result when the particle measurement processing is performed using the particle measurement apparatus 10 including a and 17b. FIG. 7 shows a particle measurement processing performed using a conventional particle measurement apparatus that does not have a light shielding plate. The measurement result when it is performed is shown. In each figure, the horizontal axis represents time, and the vertical axis represents the number of pulses output by the photodiodes 14a and 14b per second (therefore, when there is no ambient light, this becomes the number of particles). Shows.

First, looking at the results of particle measurement processing using the conventional particle measuring device shown in FIG. 7, which does not have a light-shielding plate, a count of about 350 particles per second (particle size of 0.27 μm or more) is continuously observed. Was given. On the other hand, the first and second light blocking plates 16, 17a, 17b
Looking at the particle measurement processing result using the particle measuring apparatus 10 having the above, it is considered that an appropriate count number was measured without the count of about 350 particles per second as shown in FIG. 7.

From this measurement result, the excessive count value of about 350 per second observed when using the conventional particle measuring device without the light shielding plate shown in FIG. 7 is that the ambient light enters the particle measuring device. It is presumed that this is caused by the photodiode counting the ambient light.

On the other hand, the first and second light shielding plates 16,
In the particle measuring device 10 configured so that the ambient light does not enter the housing 12 by providing 17a and 17b, an excessive count value of about 350 per second which is considered to be influenced by the ambient light does not appear, and is generated by the particles. The count value of only the scattered light M is counted. Therefore, the first and second shading plates 16, 17a,
It was proved that the accuracy of counting particles can be improved by providing 17b.

In the above embodiment, as shown in FIG. 2B, the first light shielding plate 16 is formed by using a simple plate member.
Was configured. However, instead of this, as shown in FIG. 8, a plurality of fins 38 are obliquely combined so as to partially overlap with each other, and passage of particles is permitted, but a light shielding plate 39 having a blind structure for restricting transmission of ambient light is also used. Good. With this configuration, it is possible to prevent the light-shielding plate 39 from hindering the progress of particles into the housing 12, and it is possible to prevent ambient light from entering the housing 12, so that the particle measurement accuracy is further improved. Can be made.

Further, in the above-described embodiment, the configuration in which both the first light shielding plate 16 and the second light shielding plates 17a and 17b are provided in the particle measuring device 10 has been described as an example, but the first light shielding plate is used. Since the 16 and the second light shielding plates 17a and 17b prevent the entry of ambient light by their respective different actions, it goes without saying that they may be independently provided.

Further, in the above-described embodiment, the example in which the particle measuring device 10 is applied to the ion implantation device 11 has been described. However, the particle measuring device 10 according to the present invention is described.
The present invention can be widely applied to devices other than ion implantation devices in which the presence of particles poses a problem.

[0052]

According to the present invention as described above, the following various effects can be realized. According to the invention described in claim 1, the light receiving element does not generate a signal due to the ambient light, so that the accuracy of particle measurement can be improved.

According to the second aspect of the invention, it is possible to prevent disturbance light from entering through the window with a simple structure. Further, according to the third aspect of the invention, the light shielding member can be oriented in the direction in which the ambient light is incident, so that the ambient light can be reliably prevented from entering the housing.

According to the fourth aspect of the invention, it is possible to prevent the entry of ambient light without the particles blocking the entry of the particles through the window portion. Also,
According to the invention described in claim 5, it is possible to efficiently prevent the ambient light from entering the light receiving element.

Further, according to the invention described in claim 6, it is possible to block the ambient light entering the light receiving element from the lateral position, and further improve the accuracy of particle measurement.

[Brief description of drawings]

FIG. 1 is a partially cutaway cross-sectional view of a particle measuring device according to an embodiment of the present invention.

FIG. 2 is an external view of a particle measuring device according to an embodiment of the present invention, (A) is a plan view, and (B) is a side view.

FIG. 3 is a diagram showing an example in which a particle measuring device according to an embodiment of the present invention is applied to an ion implantation device.

FIG. 4 is a diagram showing an entry range of stray light when a second light shielding plate is provided.

FIG. 5 is a diagram showing a range in which stray light enters when a second light shielding plate is not provided.

FIG. 6 is a diagram showing a result of particle measurement by a particle measuring apparatus according to an embodiment of the present invention.

FIG. 7 is a diagram showing a result of particle measurement by a conventional particle measuring device.

FIG. 8 is a diagram showing a modified example of the first light shielding plate, (A)
Is a plan view and (B) is a sectional view taken along the line AA.

FIG. 9 is a schematic configuration diagram showing an example of a conventional particle measuring device.

[Explanation of symbols]

 10 Particle Measuring Device 11 Ion Implanting Device 12 Housing 13 Semiconductor Laser Element 14a, 14b Photodiode 16 First Light-shielding Plate 17a, 17b Second Light-shielding Plate 18 Window 19 Beam Stopper 20a, 20b Filter 24 Bracket 25 Adjusting Screw 32 Electro Flat gun 33 Exhaust line 34 Wafer 38 Fin 39 Light shield

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Minor Yoshida Minoru Yoshida 1844-2, Kozoji-cho, Kasugai-shi, Aichi Prefecture Fujitsu Vielle SII Co., Ltd. (72) Minor Inoue 1844-2 Kozoji-cho, Kasugai-shi, Aichi Prefecture Fujitsu Within VIS Co., Ltd.

Claims (6)

[Claims] 1. A particle measuring device for measuring particles by detecting scattered light generated by light emitted from a light-emitting device colliding with particles entering through a window formed in a housing by a light receiving element, A particle measuring device comprising a light blocking member for preventing disturbance light other than the scattered light from entering the light receiving element. 2. The particle measuring device according to claim 1, wherein the light shielding member can cover the window portion. 3. The particle measuring device according to claim 2, wherein the position of the light shielding member is adjustable along the housing. 4. The particle measuring device according to claim 2 or 3, wherein the light shielding member has a blind structure that allows passage of the particles and restricts transmission of the ambient light. 5. The particle measuring device according to claim 1, wherein the light shielding member is arranged in a position near the light receiving element in the housing. 6. The particle measuring device according to claim 5, wherein the light shielding member is arranged at both sides of the light receiving element so as to face each other in a traveling direction of light emitted from the light emitting device. Measuring device.