JPH06160032A - Fine particle measuring device - Google Patents

Abstract

PURPOSE:To detect the behavior and generation source of fine particles low in density by arranging a detection system to the outside of a reaction chamber and providing a secondary electron amplifier amplifying the weak quantity of electricity obtained by a photoelectric conversion part receiving scattered light. CONSTITUTION:Laser beam is emitted into a reaction chamber from an irradiation system. A filter 9 permitting only scattered light due to the fine particles A present in an irradiation area to transmit is fitted in the window opened to the front wall surface of the reaction chamber. The beam transmitting through the filter 9 is condensed by a condensing lens 10 to be photoelectrically converted by a fiber plate 11. A concave surface is formed to the rear surface of the plate 11 and the photon condensed by the concave surface is amplified to about 10<6> times by a secondary electron amplifier 12. A fluorescent surface 13 emits light by the output of the amplifier 12 to form an image which is, in turn, photographed by a CCD camera 14. Since only the wavelength of laser beam is allowed to be incident on a detection system by the filter 9, this device can be adapted to a light emitting device wherein multi- wavelength light is present and particles A can be accurately measured from the min. one particle by the amplifier 12.

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 for measuring the particle size or the number of particles in order to clarify the behavior and the source of particles.

[0002]

2. Description of the Related Art The number of generated fine particles is one of the indexes showing the performance of a semiconductor process device. When processing a semiconductor device such as an IC in a semiconductor process device, the presence of fine particles is not preferable because the defect rate of the semiconductor device increases due to contamination. Further, with the miniaturization of ICs in recent years, the influence of this contamination tends to increase more and more. Therefore, it is important to measure the particle size or quantity of the fine particles and clarify the behavior and the source of the fine particles.

Conventionally, a light scattering method has been used for measuring fine particles, and the light scattering method is roughly classified into two. One is a method of taking out the wafer from the apparatus and measuring fine particles on the wafer, and the other is a method of performing in-situ observation in the apparatus during the process. The former measures the particle size of fine particles by irradiating light on the wafer and analyzing the wave height of the scattered light, but it is difficult to distinguish between surface roughness and fine particles,
Also, it is a big problem that in-situ observation cannot be performed.

In the latter, for example, as disclosed in Japanese Utility Model Laid-Open No. 18669/1992, a particle sensor unit in which a light source and a detection unit are integrated is installed in the middle of an exhaust system. In this device, light is emitted from the light source to the exhaust system space, and scattered light scattered by particles (fine particles) present in the irradiation space is detected by the detection unit. In this way, a light source and a detection unit integrated with each other have been commercialized, and it is possible to install them in a portion to be measured. In this device, the light source and the detection unit are arranged in the immediate vicinity so that the scattered light from the fine particles can be efficiently detected.

Further, in recent years, it is important to measure fine particles in a plasma device in which a gas plasma is introduced into a reaction chamber and a high frequency is applied to parallel plate type electrodes to perform plasma processing on a wafer placed on one electrode. Is increasing, for example “Gary
S.Selwyn, John E.Heidenreich, and Kurt L.Haller App
57 (18), 29 Oct 1990 ”, a device for introducing a laser beam into a reaction chamber, scanning the laser beam in parallel with an electrode, and observing scattered light from fine particles with a high-resolution video camera. The results have been reported.
FIG. 3 is a schematic diagram showing an image obtained as a result of measuring fine particles using a Ne or Ar ion laser.

[0006]

In the apparatus disclosed in Japanese Utility Model Publication No. 18669/1992, in which the light source and the detection unit are integrated, the light source and the detection unit are placed in the immediate vicinity for the purpose of increasing the light-collecting solid angle as much as possible. It is impossible to separate them because they are placed in the space, and the measurement is limited to a specific place, and it is difficult to measure a wide space. Further, when the detection unit is installed in the reaction chamber to measure the reaction chamber of the process apparatus, the process conditions are different from the original conditions, and it is difficult to perform actual in-situ observation. The other device has the detection system installed outside the reaction chamber,
Since scattered light is detected from a distant place, detection sensitivity is low, and detection is difficult unless the particle density is high or the particle size is several μm or more. The results shown in FIG. 7 were obtained because the RF plasma device trapped particles in the vicinity of the electrode and had a high density. If the fine particles at this time are assumed to be 0.2 μm, it is assumed to be about 1 × 10 ⁷ particles / cm ^-3 .

The present invention has been made in view of the above circumstances, and has a structure in which the irradiation system and the detection system can be installed outside the process apparatus, and the weakness obtained by the photoelectric conversion member that receives scattered light. It is an object of the present invention to provide a particle measuring device capable of detecting the behavior of fine particles having a low density and the generation source by providing a secondary electron multiplier that amplifies a large amount of electricity.

[0008]

A fine particle measuring apparatus according to a first aspect of the present invention is an apparatus for irradiating light to fine particles in a space, detecting scattered light by the fine particles, and measuring the particle size or the number of the fine particles. A light source for irradiating a light beam, and a detection system installed outside the space for detecting the scattered light,
The detection system includes a filter that selectively transmits the frequency component of the light beam, a lens that collects the light that has passed through the filter, a photoelectric conversion member that receives the collected light, and photoelectrically converts the collected light. The secondary electron multiplier that amplifies the amount of electricity obtained by the above, an image forming member that forms an image by the output of the secondary electron multiplier, and a camera that captures the formed image. It is characterized by A fine particle measuring apparatus according to a second aspect of the present invention is characterized in that, in the first aspect, a plurality of the detection systems are arranged at different angles with respect to the irradiation direction of the light beam. A fine particle measuring apparatus according to a third invention is characterized in that, in the first invention, an absorber that absorbs incident light and non-scattered light such as reflected light by a wall of the space is provided in the space.

[0009]

In the first aspect of the invention, since the detection system is provided with the secondary electron multiplier, it is possible to detect even when the particle density is low and the scattered light intensity is low. Further, since a filter for selectively transmitting light is provided, only the wavelength of the light beam can be made incident on the detection system, and the invention can be applied to a light emitting device in which light of multiple wavelengths exists. Since the scattered light is not directly imaged but photoelectrically converted and the electric signal is used, signal processing such as amplification and image formation by a phosphor can be easily performed.

According to the second invention, in addition to the effect of the first invention, by measuring at a plurality of angles, information on the angular dependence of scattered light can be obtained, and more detailed and accurate measurement results can be obtained. can get. In the third invention, in addition to the effect of the first invention, it is possible to create an environment in which it is easy to detect weak scattered light by absorbing non-scattered light such as incident light and light reflected by a wall, and thus the measurement accuracy can be improved. Rises.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. 1 and 2 are schematic cross-sectional views showing a fine particle measuring apparatus according to the present invention, and FIG. 1 shows a first embodiment of an irradiation system when applied to an ECR (electron cyclotron resonance) -CVD apparatus. 2 shows the detection system of the device of the present invention.

As shown in FIG. 1, the ECR-CVD apparatus has a reaction chamber 1
A plasma generation chamber 2 is continuously provided above, and a microwave introduction tube 3 is attached above the plasma generation chamber 2. A gas introduction pipe 4 for introducing a gas to be turned into plasma is arranged in the generation chamber 2, and an exciting coil 5 is provided around the gas introduction pipe 4. Further, the reaction chamber 1 is provided with a sample table 6 facing the generation chamber 2 for mounting the wafer W thereon. Further, an entrance window (not shown) for passing a laser beam is provided on one side surface (right side surface in FIG. 1) of the reaction chamber 1. In the generation chamber 2, a magnetic field is generated by the exciting coil 5, microwaves are introduced through the microwave introduction pipe 3, and the gas introduced through the gas introduction pipe 4 is turned into plasma to generate gas plasma. Then, this gas plasma is introduced into the reaction chamber 1 to process the wafer W.

As shown in FIG. 1, a galvanometer 7 which vibrates so as to change the reflection direction up and down at 800 Hz, for example, is installed in the vicinity of the entrance window, and laser light emitted from a light source (not shown) is fed into the reaction chamber 1. Is incident from the right-hand side to the left-hand side. Further, a beam stopper 8 for attenuating the non-scattered light is provided on one side surface (left side surface in FIG. 1) of the reaction chamber 1 where the incident laser light reaches. When one galvanometer 7 is used, a planar irradiation area can be formed in the reaction chamber 1, and a vertical irradiation plane can be obtained when vibrating vertically as described above. Further, it is possible to measure fine particles existing in this irradiation area, and it is possible to measure a three-dimensional space by using two galvanometers 7.

Next, the detection system shown in FIG. 2 will be described.
This detection system is installed outside the reaction chamber 1 on the front side in FIG. A window (not shown) is opened on the front wall surface of the reaction chamber 1, and a filter 9 for transmitting only the scattered light scattered by the fine particles A existing in the irradiation area is fitted into this window. It's complicated. The detection system is the filter 9 and an optical lens that collects the light that has passed through the filter 9.
10, a photoelectric conversion member 11 including a fiber plate for photoelectrically converting the collected light, the photoelectric conversion member 11 including a photoelectric surface having a flat surface on the optical lens 10 side and a concave surface on the other surface side, and a photoelectric conversion member.
A secondary electron multiplier 12 capable of amplifying the photoelectrons emitted from 11 and focused by the concave surface up to 10 ⁶ times at maximum;
The secondary electron multiplier 12 is provided on the back surface of the secondary electron multiplier 12.
It is composed of a phosphor screen 13 which emits light by the output of 1 to form an image and a CCD camera 14 which captures the image.
Note that the window may be configured such that ordinary glass is fitted instead of the filter 9 and the filter 9 is separately provided.

FIG. 3 is a schematic view showing a state in which a plurality of such detection systems are installed. When the irradiation angle of the laser light emitted from the light source B on the horizontal plane is 0 °, the angle θ with respect to this irradiation direction is varied as shown in FIG.
A plurality of detection systems C are installed within a range of up to 160 ° so that scattered light can be detected from a plurality of angles. When it is installed at a right angle to the irradiation direction (C ₂ ), θ = 90 °, and when it is installed on the emission side from this position (C ₃ ), θ <90 °.

Fine particles were actually measured using the apparatus of the present invention having the above-described structure. The condition of ECR plasma is O ₂
The flow rate is 100 sccm, the pressure is 1 mTorr, the microwave power is 500 W, and the laser used is a 488 nm Ar ion laser. FIG. 4 shows the CCD camera 14 according to the first embodiment.
It is a photograph by. In Fig. 4 (a), the installation position of the detection system is θ =
The case of 20 ° is shown, and FIG. 4 (b) shows the case of θ = 90 °.
As is clear from FIG. 4, more fine particles were measured at θ = 20 °, and it was found that at least 0.3 μm or more fine particles were measured. This is
Although the scattered light in the ie scattering region is measured, the intensity of the forward scattered light (θ <90 °) in the Mie scattering region is the backward scattered light (θ> 90).
It is much larger than the intensity of °). Therefore, in order to perform high sensitivity measurement, it is desirable to install at the position of θ ≦ 45 °. When the wavelength of light is constant, the particle size of the particles affects the intensity of the forward scattered light and the intensity of the back scattered light, so the detectors are placed at the positions of θ ≦ 45 ° and θ ≧ 90 °. It is possible to measure with higher accuracy by simultaneously performing the measurement.

FIG. 5 is a schematic sectional view showing a second embodiment of the irradiation system of the apparatus of the present invention applied to the ECR-CVD apparatus. In this second embodiment, an optical fiber 15 for irradiating a laser beam is introduced into the reaction chamber 1 in the same ECR-CVD apparatus as in FIG. Further, as in FIG. 1, a beam stopper 8 for attenuating non-scattered light is installed in the reaction chamber 1. By using the optical fiber 15 in this way, the installation position can be freely selected, and therefore, in the present embodiment, the emission end of the optical fiber 15 is installed near the gas introduction position. If the optical fiber 15 with sufficient fine particles removed is used, the light emitted from the optical fiber 15 becomes incoherent, and it is possible to utilize the effect of expanding and emitting in three dimensions, enabling three-dimensional space irradiation. Become.

Fine particles were actually measured by using the apparatus of the present invention having the above-mentioned structure. ECR plasma condition is the first
As in the example, the O ₂ flow rate was 100 sccm, the pressure was 1 mTorr, the microwave power was 500 W, and the laser used was 488 nm.
It is an Ar ion laser. FIG. 6 is a photograph of an image taken by the CCD camera 14 in the second embodiment.

It is known that the scattering efficiency of laser light by fine particles is inversely proportional to the fourth power of the wavelength when the particle size is the same (Milton Kerker "The Scattering of Light" ACADE).
MICPRESS, 1969). Therefore, for fine particles having a small particle diameter, the scattering efficiency can be increased by using a laser beam having a shorter wavelength. If the wavelength of the semiconductor laser used in the conventional device is 700 nm, the scattering efficiency is
Assuming the same power density, Ar ion laser (488n
m) about 4 times that of a semiconductor laser, KrF excimer laser
Approximately 60 times at (248nm), Approximately at KrF excimer laser (193nm)
170 times. Further, in the device of the present invention, since the sensitivity is high, the detection system is saturated in the presence of light due to, for example, plasma emission. In order to avoid this saturation, that is, to prevent light having a different wavelength from the light used for measurement from entering the detection system, a filter is provided. Thus, in order to separate the light emitted by plasma emission from the light used for measurement, it is necessary to use a wavelength other than the wavelength of plasma used in the plasma device for measurement.

The apparatus of the present invention is not limited to the plasma apparatus such as the ECR-CVD apparatus but can be applied to any apparatus.

[0021]

As described above, in the fine particle measuring apparatus according to the present invention, since the detection system is provided with the secondary electron multiplier, at least one fine particle can be accurately measured. Moreover, since it is easy to irradiate the laser beam spatially, it is possible to easily measure the behavior of the fine particles and the source. Further, since the detection system is not installed in the space, the conditions of the space are hardly changed, and the in-situ observation can be accurately performed. The present invention has excellent effects.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of an irradiation system of a particle measuring device according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a detection system of the particle measuring device according to the present invention.

FIG. 3 is a schematic diagram showing an installation state of a plurality of detection systems in the device of the present invention.

FIG. 4 is a photograph showing an image obtained by the device of the present invention.

FIG. 5 is a schematic sectional view showing a second embodiment of the irradiation system of the particle measuring device according to the present invention.

6 is a photograph showing an image obtained by using the irradiation system of the device of the present invention shown in FIG.

FIG. 7 is a schematic diagram showing an image obtained by a conventional RF plasma device.

[Explanation of symbols]

 7 Galvanometer 8 Beam stopper 9 Filter 10 Optical lens 11 Photoelectric conversion member 12 Secondary electron multiplier 13 Fluorescent screen 14 CCD camera 15 Optical fiber A Fine particles B Light source C Detection system

Claims (3)

[Claims] 1. An apparatus for irradiating light to fine particles in a space, detecting scattered light by the fine particles, and measuring the particle size or number of the fine particles, the light source for irradiating a light beam, and the outside of the space. A detection system that is installed and detects the scattered light is provided, and the detection system includes a filter that selectively transmits the frequency component of the light beam, a lens that condenses the light that has passed through the filter, and a condenser. A photoelectric conversion member that receives light and performs photoelectric conversion, and amplifies the amount of electricity obtained by photoelectric conversion 2
A fine particle measuring device comprising a secondary electron multiplier, an image forming member that forms an image by the output of the secondary electron multiplier, and a camera that captures the formed image. 2. The particle measuring apparatus according to claim 1, wherein a plurality of the detection systems are arranged at different angles with respect to the irradiation direction of the light beam. 3. The particle measuring apparatus according to claim 1, further comprising an absorber that absorbs incident light and non-scattered light such as reflected light from a wall of the space, in the space.