JPH10288601A - Device and method for analyzing fine grain - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to analyze the particle diameter, the number of particles, components and like quannitatively by classifying the particles charged with a charging device, and measuring the components and the quantities for every classified particle. SOLUTION: The fine grains such as particles, clusters, mist and the like floating in an atmospheric space are withdrawn with a sampling device 1. The individual particle is changed by a radiation such as the corona discharge or americium isotope (<241> Am) and the like with a charging device 2. Then one charged particles are classified for every particle diameter in accordance with the electric mobility by a differentialtype electric-mobility classifier(DME) 3. Then, the components and the amounts are measured for every particle classified by a high-frequency conduction-coupling plasma mass spectrometer (ICP-MS) 4. The number of the particles is measured in a Faraday-cup ammeter (FCE) 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an analysis technique for fine particles such as dust and mist floating in an atmosphere such as the atmosphere, and more particularly, to an analysis technique having a particle diameter of about 0.00.
The present invention relates to a fine particle analyzer and a method for measuring the particle size, the number of particles, the components, and the like in the range of 1 micron (μm) to about several microns.

[0002]

2. Description of the Related Art In recent years, in relation to the suppression of particle contamination in semiconductor manufacturing processes, the elucidation of the mechanism of generation of acid rain and smog in the atmosphere, and the development of quantum nano (nano) materials, etc. Fine particles such as dust and mist floating in the water are attracting attention.

[0003] As a conventional analysis method for such fine particles, (1) fine particles floating in an atmosphere are once collected by a filter or the like, and individual collected fine particles are micro-analyzed. And (2) micro-analysis of fine particles floating in the atmosphere in a suspended state (in situ) (Reference 1 (MV Johnston and A.
S. Wexler: “MS of Individual Aerosol Particles”, An
alytical Chemistry, 1995, 67, 721A-726A).

In the analysis method (1), the fine particles floating in the atmosphere are once collected by a filter or the like, and the collected fine particles are subjected to X-ray microanalysis (EPMA: EPMA). electron probe micro
analysis) and luminescence analysis (emission spectrochemical ana
lysis), secondary ion mass spectrometry (SIMS: secondary)
y ion mass spectrometry), laser microprobe mass spectrometry (LAMMS)
micro-analysis by trometry). Of these, for example, when performing microanalysis by emission analysis, individual particles collected in a filter or the like are sequentially taken out and plasma-emitted, and the size and components are identified based on the intensity and emission wavelength, and the The number of particles is calculated from the number of extractions.

[0005] On the other hand, in the analysis method (2), microparticles that are suspended in the atmosphere are continuously micro-analyzed in a suspended state. As such an analysis method, for example, a method is known in which individual fine particles suspended in an atmosphere are collided with an ionization heating source, and a group of ions generated by the collision is introduced into a mass spectrometer for analysis.

Further, fine particles in the atmosphere are drawn into a vacuum through a capillary, a nozzle, or the like, and the drawn fine particles are excited by an excimer laser to be ionized (laser desorption ionization). Time-of-flight mass spectrometry (TOF-MS) of particle size and components of ionized fine particles
Analysis method, and decomposition of fine particles floating in the atmosphere by high-frequency inductively coupled plasma (atmospheric pressure plasma).
A method of analyzing the components of the microparticles excited and ionized and thus ionized by a quadrupole mass spectrometer (high frequency inductively coupled plasma mass spectrometry (ICP-M
S: inductively coupled plasma mass spectrometr
y)) is known (Reference 2 (T. Nomizu et al .: “Det
ermination of Femto-gram Amounts of Zinc and Lead
in Individual Airborne Particles by Inductively Co
upled Plasma Mass Spectrometry with Direct Air-Sam
ple Introduction ”, Analytical Sciences, 1993, Vol.
9,843)).

[0007]

As described above, various analysis methods for fine particles have been conventionally developed. However, all conventional analysis methods
Insufficient sensitivity to fine particles of small particle size, especially for fine particles such as nano particles and clusters having a particle size of less than nanometer (nm), quantitatively determine the particle size, number of particles, components, etc. There is a problem that can not be.

The present invention has been made in view of the above points, and provides a particle analyzer and a method thereof capable of quantitatively determining the particle size, number of particles, components, and the like of nanometer-order particles. The purpose is to:

[0009]

According to the present invention, there is provided a fine particle analyzer for analyzing fine particles floating in an atmosphere, comprising: a charging device for charging fine particles drawn from the atmosphere;
A particle analyzer comprising: a classifier for classifying fine particles charged by the charging device for each particle size; and a mass spectrometer for measuring the component and amount of each particle classified by the classifier. Provide equipment.

[0010] The present invention also provides the above-described particle analyzer, further comprising a counter for counting the number of particles for each of the particles classified by the classifier, wherein the number of particles introduced into the mass spectrometer is determined. There is provided a fine particle analyzer characterized in that the calculation is performed.

Further, the present invention provides a fine particle analysis method for analyzing fine particles floating in an atmosphere, wherein a step of drawing the fine particles from the atmosphere, a step of charging each of the drawn fine particles, And a method for measuring the component and amount of each of the classified fine particles.

According to the present invention, the fine particles of a specific particle size classified by the classifier are introduced into the mass spectrometer to perform mass spectrometry. Can be introduced. Therefore, the component and amount of the fine particles corresponding to the specific particle size can be accurately obtained based on the measured value of the mass spectrometer.

Further, since the number of fine particles introduced into the mass spectrometer is calibrated by the counter, the number of fine particles can be measured simultaneously with the mass spectrometry. Can be quantitatively performed based on the absolute amount.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 to FIG. 4 are views showing one embodiment of a particle analyzer according to the present invention.

As shown in FIG. 1, the fine particle analyzer comprises a sampling device 1 for drawing fine particles such as particles, clusters, and mist floating in the air atmosphere, and a corona discharge or americium isotope ( ²⁴¹ ) for each of the fine particles. Charge device 2 charged by a radiation source such as Am)
And a differential electric mobility classifier (DMA: differential m classifier) that classifies charged fine particles for each particle size according to the electric mobility.
Mobility analyzer) 3, a high-frequency inductively coupled plasma mass spectrometer (ICP-MS) 4 for measuring the component and amount of each classified fine particle, and a Faraday cup ammeter (FCE) for counting the number of classified fine particles. : Faraday cu
p electrometer, counter) 5.

Here, the high-frequency inductively coupled plasma mass spectrometer 4 and the Faraday cup ammeter 5 are connected in parallel to the differential-type electric mobility classifier 3 via a branch 6.
The branch 6 selectively switches the traveling direction of the fine particles by a mechanical, electrical or magnetic method. The fine particles classified by the differential electric mobility classifier 3 pass through the branch 6. Thus, it is selectively introduced into either the high frequency inductively coupled plasma mass spectrometer 4 or the Faraday cup ammeter 5.

Next, the details of the differential electric mobility classifier 3, high-frequency inductively coupled plasma mass spectrometer 4, and Faraday cup ammeter 5 constituting the particle analyzer shown in FIG. 1 will be described with reference to FIGS. I do.

First, the differential electric mobility classifier 3 will be described with reference to FIG. The differential-type electric mobility classifier classifies charged microparticles for each particle size by utilizing the difference in electric mobility (for details, see, for example, Reference 3 (EOKnutson and KT Whitby: “Aerosol Cl
assification by Electric Mobility: Apparatus, Theo
ry, and Applications ”, J. Aerosol Sci., 1975, Vol. 6,
pp.443-451)). As shown in FIG. 2, the differential type electric mobility classifier 3 includes a base 1 made of an insulator such as Teflon material.
0 and a central rod 11 having an annular slit 13 connected to the base 10 and for discharging fine particles after classification.
And an enclosure 12 connected to the base 10 and having an annular slit 14 for introducing fine particles.

Here, the center rod 11 and the enclosure 12
Consists of a conductor, the center rod 11 is connected to a high voltage source 17, and the enclosure 12 is grounded. In addition, the enclosure 12
A discharge port 15 for sheath air circulating in the enclosure 12 is provided at the upper part of the housing 12, and a filter 16 for removing impurities contained in the sheath air is attached.

In FIG. 2, fine particles charged by the charging device 2 are introduced from a slit 14 provided in the enclosure 12. The fine particles introduced from the slit 14 move axially downward together with the sheath air discharged from the discharge port 15 of the enclosure 12, and form between the outer peripheral surface of the center rod 11 and the inner peripheral surface of the enclosure 12. Under the influence of the applied electric field, the fine particles are attracted in the direction of the central axis at a speed corresponding to the electric mobility of the fine particles. Then, only the fine particles that reach the slit 13 of the center rod 11 along a predetermined trajectory are taken out.

Here, the electric mobility Z _p of the fine particles reaching the slit 13 provided in the center rod 11 is calculated by the following equation (1). Z _p = q · ln (r ₂ / r ₁ ) / (2 · π · V · L) (1)

In the above equation (1), q is the flow rate of the sheath air introduced into the differential electric mobility classifier 3, and r ₁ and r ₂
Are the radius of the outer peripheral surface of the center rod 11 and the enclosure 12
Is the radius of the inner peripheral surface. V is a voltage applied between the outer peripheral surface of the center rod 11 and the inner peripheral surface of the enclosure 12, L
Is the distance between the slit 13 and the slit 14.

The electric mobility Z _{p of} the fine particles and the particle diameter D _p
Has a relationship represented by the following equation (2). Z _p = ne · C _m / (3 · π · D _p ) (2)

In the above formula (2), n is the charge amount of the fine particles, e is the elementary charge (1.6 × 10 ⁻¹⁹ coulomb), C _m
Is the correction coefficient of Cunningham, and μ is the viscosity coefficient of the introduced sheath air.

It should be noted, from the above equation (1) (2), the particle diameter D _p of the particles is taken out from the differential mobility classifier 3 is determined based on the flow rate q and the applied voltage V of Shisuea.

Next, the high frequency inductively coupled plasma mass spectrometer 4 will be described with reference to FIG. As shown in FIG.
The high-frequency inductively coupled plasma mass spectrometer 4 includes a high-frequency inductively coupled plasma unit 20 for decomposing and ionizing the fine particles classified by the differential electric mobility classifier 3 (see FIGS. 1 and 2), and a finely divided and ionized fine particle. Unit 21 and a lens unit 22 for drawing in a quadrupole mass filter 23 described later, and a quadrupole mass filter 2 having electrodes to which a DC voltage and a high-frequency voltage are applied.
3 and a detector 24 that detects fine particles that have passed through the quadrupole mass filter 23.

Here, the interface unit 21, the lens unit 22, and the quadrupole mass filter 23 are connected to a vacuum pump 25, whereby the inside of the interface unit 21, the lens unit 22, and the quadrupole mass filter 23 are measured. It is always kept under vacuum. Further, the high frequency inductively coupled plasma section 20 and the quadrupole mass filter 23
Are connected to RF oscillators 27 and 28, respectively, so that a predetermined high-frequency voltage is applied to a high-frequency coil in the high-frequency inductively coupled plasma unit 20 and an electrode in the quadrupole mass filter 23, respectively. The RF oscillators 27 and 28 and the vacuum pump 25 are connected to a computer 29.
Is controlled by a system controller 26 connected to the

In FIG. 3, the differential type electric mobility classifier 3
The fine particles classified by (see FIGS. 1 and 2) and introduced through the branch portion 6 are drawn into the high frequency inductively coupled plasma portion 20, and are decomposed and ionized by the high frequency inductively coupled plasma portion 20. The decomposed and ionized fine particles are supplied to the interface unit 21 and the lens unit 2.
2, and is incident along the central axis of the quadrupole mass filter 23. At this time, a DC voltage and a high-frequency voltage are applied to the electrodes of the quadrupole mass filter 23, and an electric field is formed in the quadrupole mass filter 23 by applying the voltages. The applied voltage is controlled by the system controller 26.
And only particles having a specific mass (mass number / charge amount) pass through the quadrupole mass filter 23 under the conditions determined by the applied voltage, the distance between the quadrupole electrodes, the frequency, and the like. At the detector 24. Then, data analysis is performed by a computer 29 connected to the system controller 26 based on the detected result, the mass analysis of the particles having a predetermined particle diameter D _p which is introduced during a predetermined period of time T is performed.

Next, the Faraday cup ammeter 5 will be described with reference to FIG. As shown in FIG. 4, the Faraday cup ammeter 5 includes a Faraday cup 30 for collecting fine particles, and an electrometer 40 for measuring a charge amount of the fine particles collected in the Faraday cup 30.

Here, the Faraday cup 30 is configured as a double metal container composed of an outer container 31 and an inner container 32. In the outer container 31 and the inner container 32,
An introduction portion 33 for introducing fine particles from the outside is provided, and a filter 34 for depositing the fine particles introduced from the introduction portion 33 is attached to the inner container 32. Note that the filter 34 is connected to an electrometer 40 provided outside the Faraday cup 30 via a lead wire 35.

In FIG. 4, the differential type electric mobility classifier 3
The fine particles classified by (see FIGS. 1 and 2) and introduced through the analysis section 6 are introduced into the introduction section 3 of the Faraday cup 30.
The fine particles thus introduced are deposited on a filter 34 mounted in an inner container 32. Then, the charge amount of the fine particles deposited on the filter 34 is measured by the electrometer 40 as a current value flowing through the lead wire 35.

Here, there is a relationship expressed by the following equation (3) between the measured current value i and the number concentration N of fine particles. N = i / (n · eq) (3)

In the above equation (3), n is the charge amount of the fine particles, e is the elementary charge (1.6 × 10 ⁻¹⁹ coulomb), and q is the flow rate of the gas to be introduced.

[0034] Incidentally, from the above equation (3) is determined based on the flow rate q of a gas particle number of the fine particles of the introduced predetermined diameter D _p between the predetermined time T is introduced together with the particles after classification .

Next, the operation of the present embodiment having such a configuration will be described with reference to FIGS.

First, as shown in FIG. 1, fine particles such as particles, clusters, and mist floating in the air atmosphere are drawn in by the sampling device 1, and then the drawn fine particles are transferred to the charging device 2 and transferred to the charging device 2. Are charged by the charging device 2.

Next, the charged individual fine particles are charged into the charging device 2.
Transferred to differential mobility classifier 3, a differential mobility classifier 3, take out only particles having a predetermined particle diameter D _p. That is, the particles are classified under a predetermined sheath air flow rate q and an applied voltage V, and the above equations (1) and (2)
Only the fine particles having the particle diameter D _p determined according to the above are taken out of the slit 13 of the central rod 11 to the outside.

As shown in FIG. 1, the classified fine particles taken out of the differential type electric mobility classifier 3 are passed through a branch 6 to a high frequency inductively coupled plasma mass spectrometer 4 or a Faraday cup current. A total of 5 are alternately introduced at predetermined time intervals. In other words, during a certain predetermined time T, the high-frequency inductively coupled plasma mass spectrometer 4 performs mass analysis on the classified fine particles, and the subsequent time T
During (the same time as the time when the fine particles are introduced into the high frequency inductively coupled plasma mass spectrometer 4), the number of the classified fine particles is measured by the Faraday cup ammeter 5.

Since the same amount of fine particles classified by the differential mobility classifier 3 is introduced into the high frequency inductively coupled plasma mass spectrometer 4 and the Faraday cup ammeter 5, the Faraday cup current The result of the high-frequency inductively coupled plasma mass spectrometer 4 can be calibrated based on the number of particles measured by the total 5, so that the mass analysis of the fine particles introduced into the high-frequency induction plasma mass spectrometer 4 can be performed based on the absolute amount. Quantitatively.

[0040] According to the present embodiment, performing mass spectrometry by introducing fine particles of a specific particle diameter D _p which is classified by differential mobility classifier 3 to the high-frequency inductively coupled plasma mass spectrometer 4 As a result, a large amount of fine particles having a uniform particle diameter can be introduced into the high-frequency inductively coupled plasma mass spectrometer 4. Therefore, the component and amount of the fine particles corresponding to the specific particle size can be accurately obtained based on the measurement value of the high frequency inductively coupled plasma mass spectrometer 4.

In this case, the component and the amount of the fine particles corresponding to the specific particle size are predicted in advance, and the component and the amount of the fine particles corresponding to the specific particle size are obtained by the high frequency inductively coupled plasma mass spectrometer 4. Based on the predicted value, it is possible to eliminate a clearly wrong value among the measurement results of the high frequency inductively coupled plasma mass spectrometer 4. As a result, it is possible to improve the lower limit of the particle size range of the fine particles for which mass spectrometry can be performed by about an order of magnitude (specifically, the particle size is about 0.0
Mass spectrometry is possible for fine particles ranging from 01 micron to several microns).

Since the number of fine particles introduced into the high frequency inductively coupled plasma mass spectrometer 4 is calibrated by the Faraday cup ammeter 5, the number of fine particles can be measured simultaneously with the mass analysis. The mass analysis of the fine particles in the high frequency inductively coupled plasma mass spectrometer 4 can be quantitatively performed based on the absolute amount.

Further, since the high frequency inductively coupled plasma is used to ionize the fine particles, the ionization efficiency can be improved and the apparatus can be simplified.

In the above embodiment, the fine particles are charged by the corona discharge or the radiation source in the charging device 2, but the charging method in the charging device 2 is not limited to this. Instead, various existing methods for charging the fine particles can be employed.

In the above-described embodiment, the fine particles classified by the differential-type electric mobility classifier 3 are supplied to the high-frequency inductively coupled plasma mass spectrometer 4 or the Faraday cup ammeter 5 via the branch 6. However, in addition to this, for example, the classified fine particles may be supplied to both the high frequency inductively coupled plasma mass spectrometer 4 and the Faraday cup ammeter 5 at a predetermined ratio ( For example, they may be distributed in a ratio of 1: 1). Here, the ratio of the fine particles distributed to the high-frequency inductively coupled plasma mass spectrometer 4 and the Faraday cup ammeter 5 is not limited to 1: 1 but may be, for example, an arbitrary ratio such as 2: 1 or 3: 1. Things can be adopted. In this case, the number of particles introduced into the high-frequency inductively coupled plasma mass spectrometer 4 is calculated from the number of particles counted by the Faraday cup ammeter 5 in consideration of the distribution ratio.

Further, in the above-described embodiment,
Although the mass spectrometry of the fine particles is performed by the high frequency inductively coupled plasma mass spectrometer 4, various other mass spectrometry methods well known in the art as described above can be used as needed.

[0047]

As described above, according to the present invention, fine particles having a specific particle size classified by a classifier are introduced into a mass spectrometer and mass analysis is performed. Can be introduced into a mass spectrometer in large quantities. Therefore, the component and amount of the fine particles corresponding to the specific particle size can be accurately obtained based on the measured value of the mass spectrometer.

Further, since the number of fine particles introduced into the mass spectrometer is calibrated by the counter, the number of fine particles can be measured simultaneously with the mass spectrometry. Can be quantitatively performed based on the absolute amount.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a particle analyzer according to the present invention.

FIG. 2 is a differential electric mobility classifier (DMA) shown in FIG.
It is a figure which shows the detail of.

FIG. 3 is a diagram showing details of the high-frequency inductively coupled plasma mass spectrometer (ICP-MS) shown in FIG. 1;

FIG. 4 is a Faraday cup ammeter (FCE) shown in FIG.
It is a figure which shows the detail of.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Sampling device 2 Charging device 3 Differential type electric mobility classifier (DMA) 4 High frequency inductively coupled plasma mass spectrometer (ICP-M)
S) 5 Faraday cup ammeter (FCE) 6 Branch

Continued on the front page (72) Inventor Kenichi Sakata 2-2-5 Fujimidai, Kunitachi-shi, Tokyo Sanfore National 302

Claims (9)

[Claims] 1. A fine particle analyzer for analyzing fine particles floating in an atmosphere, a charging device for charging fine particles drawn from the atmosphere, and a classifier for classifying the fine particles charged by the charging device for each particle size. And a mass spectrometer for measuring a component and an amount of each of the fine particles classified by the classifier. 2. The apparatus according to claim 1, further comprising a counter for counting the number of particles for each of the fine particles classified by said classifier, wherein the number of fine particles introduced into said mass spectrometer is calculated. The particle analyzer according to claim 1. 3. The fine particle analyzer according to claim 2, wherein the fine particles classified by the classifier are time-switched and introduced into the mass spectrometer or the counter. 4. The particle analyzer according to claim 2, wherein the fine particles classified by said classifier are distributed to said mass spectrometer and said counter at a predetermined ratio. 5. The classifier according to claim 1, wherein the classifier is a differential-type electric mobility classifier that classifies charged fine particles for each particle size according to electric mobility. Particle analyzer. 6. The mass spectrometer according to claim 1, wherein said mass spectrometer is a high-frequency inductively coupled plasma mass spectrometer for decomposing and ionizing the classified fine particles by plasma to measure the component and amount of the fine particles. A particle analyzer according to any one of the above. 7. The particle analyzer according to claim 2, wherein said counter is a Faraday cup ammeter for counting the number of classified particles. 8. A fine particle analysis method for analyzing fine particles floating in an atmosphere, a step of drawing fine particles from the atmosphere, a step of charging each of the drawn fine particles, and a step of converting the charged fine particles according to electric mobility. A method for analyzing fine particles, comprising: a step of classifying each particle size; and a step of measuring a component and an amount of each classified fine particle. 9. The method for analyzing fine particles according to claim 8, further comprising the step of counting the number of particles for each classified fine particle.