JPH0222534A - Particle measuring instrument - Google Patents

Abstract

PURPOSE:To measure particles such as dust with high detection efficiency by providing a light projection system which forms a sheet-shaped beam as a probe beam. CONSTITUTION:The light projection system 10 and a reflecting mirror 2a are arranged outside a glass tube 2a opposite each other. Further, the light projection system 10 uniforms the light intensity distribution of the projection light from a semiconductor laser LD by a beam expander 14. Further, a photodetection optical system is constituted by arraying and connecting semiconductor photodetectors D... in series at the outer periphery of the glass tube 2a. Then an amplifier 17 is connected to the output sides of the detectors D... and obtains a detection output by current-voltage conversion. Further, a plane mirror 12a is used as the reflecting mirror and laser light is guided reciprocally by the reflecting mirror 12a to improve the light density in a measurement area. Consequently, when a particle 7 passes in the sheet-shaped beam 11, the series-connected photodetection system detects the quantity of light corresponding to scatter area to accurately decide the diameter of the particle.

Description

[Detailed Description of the Invention] [Summary] Regarding a particle measuring device that can observe in-process the generation of particles such as dust inside semiconductor manufacturing equipment, the area of the probe beam can be widened and the light receiving area can also be increased. By making it expandable, we aim to capture dust passing through the exhaust pipe with a high probability and reliably measure the number and size of particles. In order to perform in-process measurements using a laser beam, an exhaust system-installed particle measuring device is equipped with a light emitting system and a light receiving system that detects scattered light. A light receiving optical system is configured by providing a sheet beam projection system that irradiates sheet-like light and connecting a plurality of semiconductor photodetectors in series.

A particle measuring device is required.

[Industrial application field]

The present invention relates to a particle and particle measuring device capable of in-process observation of the generation of particles such as dust inside semiconductor manufacturing equipment.

In order to improve the manufacturing yield of semiconductor devices such as LSIs, it is necessary to constantly monitor the generation of dust that adheres to wafers and damages circuit patterns. However, semiconductor manufacturing equipment that manufactures LSI etc. (for example, C
(VD, sputtering equipment, etching equipment, etc.),
-S, since the process is carried out inside the vacuum chamber, it is impossible to sample the atmospheric gas from the outside and investigate the state of dust generation. Therefore, a measuring device is needed to observe the internal situation from the outside.

In addition, as circuit patterns such as LSI become finer, the particles that must be monitored become smaller, and it is necessary to detect particles of about 1 μm or less, which increases detection efficiency.
In addition, the minimum detectable particle size is small [Conventional technology] Conventionally, as a method for detecting particle generation inside semiconductor manufacturing equipment, a dummy wafer is fed into the equipment at the beginning of the manufacturing loft, and the number of dust particles attached to the surface of the dummy wafer is measured. We investigate and measure the dust to estimate the dust situation inside the equipment. however,
If a substrate to be processed is damaged within the apparatus after particle measurement, it is not possible to immediately detect the generation of particles, so all products processed after the breakage become defective, resulting in a decrease in yield.

Therefore, there is a need for an in-process device that can constantly and immediately monitor the particle generation status within the processing device. In recent years, with the increasing desire to observe the dust generation inside the equipment, in-process particle measuring equipment (formerly CROCON
TAMINATION Oct, 1987p30-3
4) is sold by HYT (High Yield Technology). However, this device
Since the sensor section is inserted into the vacuum device, it is not completely non-invasive and causes problems such as disrupting the flow within the processing device.

In response, the applicant of the present invention submitted a patent application filed in 1983-907.
As No. 1, a device as shown in FIGS. 6 to 8 has been proposed. In FIG. 6, reference numeral 1 denotes a semiconductor manufacturing apparatus, and by creating a vacuum state with a vacuum pump P, processes such as CVD, sputtering, etching, etc. are performed in a vacuum. A sensor system 3 is provided in a pipe 2 between a semiconductor manufacturing apparatus 1 and an intake side of a vacuum pump P. 4 is an exhaust port.

As shown in FIG. 7, the sensor system 3 converts the laser light emitted from the semiconductor laser LD into parallel light using a lens 5, so that the laser light 6 having a circular cross section crosses the pipe 2. Particles such as dust in the semiconductor manufacturing equipment 1 are removed from the exhaust pipe 2.
When the particles 7 pass through the laser beam 6 in the sensor system 3, the light is scattered. When this scattered light is received by the photoelectric conversion device 9 via the light receiving lens 8, a detection signal as shown in FIG. 8 is obtained. In this waveform diagram, the point at which the output becomes steeply high indicates that the particle passes through the laser beam 6 and scattered light is generated. Therefore, by counting the number of steep waveforms, The number of particles can be measured, and the size of the particles can be determined by the height of the waveform.

[Problem to be solved by the invention]

The device is completely non-invasive and can detect particles during the process. The intensity of light scattered by dust particles is inversely proportional to the square of the distance from the scattering point to the detection point, so if the light receiving area is limited and the light receiving area is small, it is difficult to accurately detect the scattered light from any point. Difficult to detect. Therefore, in the conventional technology, as described above, the probe beam for detecting particles is made into a single round beam 6, and measurement performance is obtained by limiting the measurable area. However, since the area occupied by the laser beam 6 in the pipe 2 is small, the probability that particles will encounter the laser beam 6 is low, resulting in low particle detection efficiency and insufficient reliability. In addition, although the measurable area can be expanded, the behavior of dust in the entire device and in the device cannot be known, which is a problem.

The present invention aims to solve the problems of the prior art, and it is possible to widen the area of the probe beam,
Moreover, by making it possible to expand the light-receiving area, it is possible to capture dust passing through the exhaust pipe with a high probability, thereby making it possible to reliably measure the number and size of particles.

(Means for Solving the Problems) Fig. 1 is a diagram explaining the basic principle of the particle measuring device according to the present invention. 2 is an exhaust pipe that connects the semiconductor manufacturing equipment and the vacuum pump, and It is made of a material that is transparent to the light used.

It has a light projecting system 11) for inputting light into the exhaust pipe 2, and this projecting system 10 has a function of forming a thin sheet-like light 11, and the sheet-like surface is It is arranged perpendicular to the exhaust flow.

A plurality of semiconductor photodetectors D... are arranged around the outer periphery of the exhaust pipe 2. These photodetectors D... are connected in series.

[Effect]

In this way, if the light beam for detection is made into a thin sheet with a wide area and the light beam is irradiated onto a wider area in the exhaust pipe 2, most of the particles passing through the exhaust pipe 2 will be absorbed by the light beam. will cross.

Furthermore, when dust particles are detected using the sheet-shaped light beam 11 with a uniform intensity distribution, the scattered light intensity when the particle crosses the light beam is independent of the position of the scattering point. Determined only by the size of the dust particles.

Therefore, by providing a large number of semiconductor photodetectors D and detecting all the scattered light from each position, it becomes possible to reliably capture and detect all the dust particles passing across the beam.

In addition, by providing the reflecting mirror 12 and passing the light back through the two measurement regions, it is also possible to prevent measurement errors based on the intensity distribution of scattered light that occurs when the particle diameter is larger than the wavelength.

In reality, it is impossible to capture all of the scattered light, and the usual approach is to expand the light-receiving area of the light receiver as much as possible. However, as shown in the equivalent circuit shown in Figure 9, a semiconductor photodetector has a junction capacitance proportional to the pn junction area, and simply expanding the light receiving area will result in a decrease in response speed and reduce the amount of light scattered from particles. Waveform(
In particular, since the wave height value changes, it becomes difficult to distinguish the particle size.

Therefore, the inventors realized that the combined capacitance of the capacitors connected in series is one-fold of the original value, and measured the frequency characteristics by connecting multiple photodetectors in series. As a result, we confirmed that the characteristics could be improved several times compared to when operated as a Sakae detector. It is clear that by using this method, the light receiving area can be expanded and more scattered light can be detected without significantly lowering the detection performance.

[First Example] Next, how the particle measuring device according to the present invention is actually implemented will be explained using an example. FIGS. 2(a) and 2(b) are a longitudinal sectional view and a transverse sectional view showing a first embodiment of the present invention.

2a is a glass tube with the same inner diameter as the exhaust pipe 2, and an O-ring 13 is attached to the exhaust pipe 2 between the semiconductor manufacturing equipment and the vacuum pump.
The connection is made airtight through a sealing material such as

A light projecting system 10 and a reflecting mirror 12a are arranged facing each other on the outside of the glass tube 2a. The light projection system 10 is a semiconductor laser LD.
This device expands the beam spot of the emitted light with a beam expander 14, then shapes it into a wide sheet with a cylindrical lens 15, and makes the light intensity distribution uniform by means such as a density filter 16. . This lighting system 1
As a sheet-like beam formed by 0, the width is 20 to 30 mm.
A material having a thickness of about 0.1 to 0.21 mm can be obtained.

The light receiving optical system for detecting scattered light includes nine semiconductor photodetectors D arranged around the outer periphery of the glass tube 2a and connected in series.
...uses a glass tube 2a with one side of about 10 mm.
Arrange several or more pieces at equal intervals around the outer circumference.

do.

Then, an amplifier 17 is connected to the output side of the semiconductor photodetector D to perform current-to-voltage conversion to obtain a detection output.

Furthermore, in this embodiment, a plane mirror 12a is used as a reflecting mirror, and the laser beam is reciprocated by the plane reflecting mirror 12a to improve the light density within the measurement area. When the particles pass, the amount of light corresponding to the scattering cross section is detected by a series-connected semiconductor light receiving system, and particle diameters can be accurately determined and counted. In this case, forward scattering and backward scattering can be made uniform, so it is suitable for measuring particles whose particle size is larger than the wavelength of the laser beam.

[Second example]

FIG. 3 is a cross-sectional view showing a second embodiment of the invention, in which two prisms 121 and 122 are used as reflecting mirrors. That is, the two prisms 121 and 122 are arranged so that the surface of the sheet-like beam 11 is perpendicular to the reflecting surface of the prism 121 and 122 and is reflected at 45 degrees. Therefore, the sheet-like beam becomes prism 121.12
2 and reciprocating, the width of the sheet beam is doubled, making it possible to capture particles more reliably and further improve detection efficiency. Moreover, this case is suitable for measuring particles whose particle size is larger than the wavelength of the laser beam.

[Third Example]

In this embodiment, as shown in FIG. 4, a concave mirror 12b is used as a reflecting mirror to prevent the sheet beam from expanding. Further, the concave mirror 12b is connected to the optical trap 1.
It is located in 8.

As described above, by folding the sheet beam 11 with a reflecting mirror and passing it through the measurement area, it is possible to prevent measurement errors based on the intensity distribution of scattered light that occur when the particle diameter is larger than the wavelength. can.

However, in order to increase the light density and improve the particle detection efficiency, the laser light is thinned (narrowed down) in the thickness direction of the sheet-like beam within the measurement region.

Therefore, when it reaches the reflecting mirror surface, it becomes a diverging light, and the reflected light diffuses and enters the light receiver as stray light, which actually reduces the detection efficiency.

Therefore, if the probe beam is again focused on the detection region using an optical element with a focusing function, such as a concave mirror, the amount of laser light irradiated onto the particles can be doubled.

However, since the size of the concave mirror is limited due to the dimensions of the device, if light that cannot enter the concave mirror occurs, it becomes stray light and reduces detection efficiency.

Therefore, the concave mirror 12b is installed inside the optical trap 18. As a result, the light that cannot enter the concave mirror 12b is transmitted to the optical trap 18 side, so that these stray light components are removed and the detection efficiency is further improved.

Note that the concave mirror 12b is focused on the center of the glass tube 2a.

Instead of the concave surface m12b, a plane mirror or the aforementioned prisms 121, 122 may be arranged in the optical trap 18. Moreover, if the light projecting optical system 11) is also installed within the optical trap, it is more effective.

[Fourth embodiment]

FIG. 5 is a diagram showing a fourth embodiment, in which a concave mirror 19 with a slit-shaped opening in the center is installed as the final stage of the light emitting part of the light projection system 10, so that the probe beam can be multiplexed. It is configured to reflect back and forth. This further increases the light density in the measurement region and further increases the intensity of the scattered light.

[Effects of the Invention] As described above, according to the present invention, particles such as dust can be measured with high detection efficiency because the projection system IO that forms a sheet-like beam as a probe beam is used. In addition, since a plurality of semiconductor photodetectors D... are arranged and connected in series around the outer circumference of the exhaust pipe of the detection section, the number and size of particles can be determined from the scattered light intensity when the particles pass through the sheet beam. can be measured with high precision.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a diagram explaining the basic principle of the particle measuring device according to the present invention, FIGS. 2 to 5 are diagrams showing various embodiments of the present invention,
Fig. 6 is a diagram showing the entire structure of a conventional particle measuring device, Fig. 7 is a diagram explaining the principle of a conventional particle measuring device, Fig. 8 is a diagram showing the output waveform of the particle measuring device, and Fig. 9 is a diagram showing the semiconductor FIG. 3 is a diagram showing an equivalent circuit of a photodetector. In the figure, l is semiconductor manufacturing equipment, P is a vacuum pump, and 2
is an exhaust pipe, 2a is a glass tube provided in the middle of the exhaust pipe, 7 is a particle, 10 is a floodlight system, 11 is a sheet-shaped beam, 12 is a reflecting mirror, 12a is a plane mirror, 121.122 is a prism, D
...indicates a semiconductor photodetector, respectively. Patent Applicant: Fujitsu Limited Sub-Agent Patent Attorney: Yasushi Fukushima Basics of Unreleased Date/Month -) Liri Figure 1 Figure 2 Fig. 6. Conventional stand-up device Fig. 7

Claims (1)

[Claims] 1. Installation of an exhaust system that includes a light projecting system and a light receiving system that detects scattered light in order to measure dust particles generated inside the processing equipment in-process using light scattering. In this type of particle measuring device, a sheet beam projection system (10) that transforms the laser emission pattern and irradiates a sheet of light (11) with a uniform intensity distribution is used.
A particle measuring device characterized in that a light receiving optical system is configured by providing a plurality of semiconductor photodetectors (D...) and connecting a plurality of semiconductor photodetectors (D...) in series. 2. In the optical system, a sheet beam projection system (10)
By installing a reflecting mirror (12) in a position facing the
Claim 1 characterized in that the beam is reflected and folded back.
The particle measuring device described. 3. The particle measuring device according to claim 1, wherein the reflecting mirror is composed of a prism and is arranged so that a deviation occurs between an incident optical axis and an output optical axis. 4. The particle measuring device according to claim 1, wherein the reflecting mirror is composed of a concave mirror and is adjusted to refocus the incident light beam at a predetermined position.