JP3285068B2 - Standard particle generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a standard particle generator and, more particularly, to a particle counter used for controlling nm-sized ultrafine particles contained in a gas phase of a semiconductor or liquid crystal display manufacturing process. N included in the gas phase of the test and the manufacturing process of semiconductors and liquid crystal displays
The present invention relates to a technique for generating standard particles of nm size, which is indispensable for measuring the collection efficiency of a filter used for removing ultrafine particles of m size.

[0002]

2. Description of the Related Art In recent years, high integration of LSIs has progressed, and 16-Mbit integrated circuits having a pattern size of half microns have begun to be produced. As the pattern size becomes finer, it becomes necessary to more strictly control the remaining amount of stains appearing as defects in the process.

The surface contamination goal to be controlled in the current semiconductor industry is 0.05 μm for particle contamination.
is to suppress m or more of the in several levels by 8-inch wafer, with respect to the surface heavy metal impurities dirt, 10 ⁹ a
That is, it is to be suppressed to the level of toms / cm ² . As for “particle contamination”, particles having a certain “size” or more cause a failure that causes disconnection or short circuit of a device circuit. On the other hand, with regard to “surface heavy metal impurity contamination”, there is a problem in which particulate or molecular heavy metal impurities adhering to the surface penetrate into the interior from the surface due to heating, oxidation, etc. during the manufacturing process, causing malfunction of the device. Cause. Therefore, even if the “ultra” particles smaller than 0.05 μm are used, if the chemical components may cause the device to malfunction, the surface contamination cannot be overlooked.

Here, a specific example of surface contamination by "ultra" fine particles will be described. Now, ultrafine particles having a size of 3 nm mainly composed of heavy metal are deposited on a silicon wafer (10 mm).
¹⁵ Si atoms / cm ² ). Assuming that the size of the heavy metal atom is 3 angstroms, this particle contains heavy metal atoms on the order of 10 ³ . It is assumed that the adhered particles are diffused on the wafer surface in a 1 μm square area by heating during the manufacturing process.
This range is set to 10 ¹¹ atoms by heavy metal impurities.
/ Cm ² of contamination, which slightly exceeds the above-mentioned 10 ⁹ atoms / cm ² level which is a problem in current devices. Therefore, in the future semiconductor manufacturing, n mainly containing heavy metals, carbon, etc.
Ultrafine particles of m size must also be adequately controlled.

[0005] The present invention is based on such a technical standpoint, and the nm contained in the gas phase of a semiconductor manufacturing process is disclosed.
Indispensable for measuring particle counters used to control ultrafine particles and measuring the collection efficiency of filters used to remove nanometer-sized ultrafine particles contained in the gas phase of semiconductor manufacturing processes. The present invention relates to a technology for generating standard particles of a size.

It is generally considered that standard particles used for calibration of a measuring instrument are particularly important in terms of particle size uniformity (monodispersity), stability of generated concentration, ease of generation, and economy. The method of generating the standard particles is generally as follows. 1. evaporation / condensation method; Chemical reaction method, 3. It can be classified into three methods of mechanical dispersion method.

[0007] 1. Evaporation / condensation method In a supersaturated atmosphere, when nucleated fine particles and ions are present, they become nuclei and nucleated condensation occurs. Due to the spatial and temporal concentration fluctuations of
From them, stable particles grow, the so-called nuclear-free condensation. This generation method utilizes these phenomena, and there are two methods, a low melting point particle generation method and a high melting point particle generation method.

(1) Low melting point particle generation method This is a method for generating particles composed of a substance having a melting point of up to about 100 ° C., such as stearic acid and DOP (dioctyl phthalate). Sinclai, a representative example of the method of the present invention
r-Lamer type particle generator (Sinclair, D., Lamer,
VK (1949): Light scattering as a measure of partic
le size in aerosols, Chem. Revs, Vol.44, p.245-26
7) is shown in FIG.

Reference numeral 101 in the figure denotes a portion for generating nuclear particles, which is made of about 1 liter of Pyrex glass.
Ions are generated by a high-voltage spark, and nuclei are generated by heating a coil impregnated with salt or the like. Next, reference numeral 102 denotes an evaporation unit made of a 2-liter Pyrex container, which is heated at a temperature of 100 to 200 ° C. depending on the boiling point of the substance to be evaporated and the particle diameter to be generated.

[0010] A pipe with a nozzle at the tip is inserted into the liquid in 102 to perform bubbling.
The air flow rate is the sum of the flow rate passing through 101 and the flow rate blown into this nozzle, and is usually 1 to 4 liters / minute.

The nucleus particles, the mist due to bubbling, and the vapor are sent to the next reheating unit 103. A 2 mm-diameter 2 mm is provided on the reheating section side of the connecting pipe between the reheating section 103 and the evaporating section 102.
There are a number of nozzles, which are blown into the reheat section via this nozzle, and by heating the reheat section to 300 ° C., mixing and complete evaporation take place. In this way, the nucleated vapor is introduced into the condensing section 104. This condensing part 104 has an inner diameter of 20 mm, an outer diameter of 30 mm, and a length of 30 cm.
In this double tube, the vapor is condensed around the core particles by being gradually cooled in this portion, and grows into uniform particles.

According to this generation method, particles in the range of about 0.1 to 20 μm can be generated, and a relatively uniform particle diameter can be obtained. However, it is difficult to generate particles of nm size, it takes several hours or more for the generation state of the particles to be stable, the stability and reproducibility of the generated particles are poor, the liquid consumption of the evaporator 102 is large, It has disadvantages such as high cost.

(2) Generation method of high melting point particles This generation method is basically the same as the above generation method of low melting point particles, except that metal particles such as lead, zinc, cadmium, manganese and tellurium, and sodium chloride And high melting point particles such as salt fume such as lead iodide.

(Kousaka, Y., Niida, T., Okuyam)
a, K., Tanaka, H. (1982): Development of a mixing t
ype condensation nucleus counter, Journal of Aeros
olSci., Vol.13, p.231-240) is, CNC (C ondensaito
n N uclei C ounter; condensation nucleus counter, as a test of details will be described later), as shown in FIG. 13, NaCl was generated in an electric furnace 105, DOP, the vapor of ZnCl _2, etc. in a way to push enclosed in Shisuea The aerosol particles were obtained by quenching with liquid nitrogen in the quenching chamber 106 while preventing loss of deposition of vapors and growing particles on the wall surface. In the illustrated example, both carrier air and sheath air use nitrogen gas,
The flow rate is kept constant at 1 liter / min. 0.01 μm particle diameter for ZnCl ₂ particles, 0.02-0.05 for DOP particles
μm, the generated concentration is 10 ⁵ to 10 ⁶ / cm ³ .

Fukushima et al. (Nobuhiko Fukushima, Kazuyoshi Sugimoto, Naoko Tajima, Tomio Hayano (1985): On the measurement and monitoring of fine particles in clean rooms, 3rd Aerosol Science and Technology Research Abstracts, pp. 75-77) ,
The same apparatus as that of Kosaka et al. Was prototyped, and the relationship between the temperature of the electric furnace at a constant flow rate and the particle size distribution of the generated NaCl particles was examined. One example is shown in FIG. The apparatus shown in FIG. 13 can be combined with a differential mobility analyzer (Differential Mobility Analyzer, which will be described in detail later) to achieve a specific mobility of 0.1.
It is used to generate arbitrary monodispersed standard particles of less than or equal to 05 μm.

Disadvantages of the high melting point particle generation method are that an electric furnace and a cooling device for heating and cooling to a high temperature are required, that the entire device is large-sized, that it is expensive, and that evaporative substances in the heating section are reduced. Normally, it is necessary to keep flowing an inert gas such as He or N ₂ to prevent oxidation.

2. Chemical reaction method Gas-particle conversion by a photochemical reaction represented by photochemical smog is a typical example. As a particle generation method, NH ₃
That the HCl is reacted in the vapor phase to produce a NH ₄ Cl particles is well known. Although it can be easily generated, it has a disadvantage that it is difficult to control the generated particles.

3. Mechanical dispersing method (1) Spraying and dispersing liquids Nebulizers, atomizers, etc. use the principle of atomization to generate a mist of a solution containing a soluble substance to generate relatively polydisperse particles, and a special method. The method can be roughly classified into a method of generating a monodispersed mist by mechanical dispersion. By passing the generated mist through the evaporator / condenser, the soluble substance is left in the air as fine particles after the evaporation of the solvent component.

FIG. 15 shows Liu et al. (Liu, BY
H., Lee, KW (1975): An aerosol generator for high
stability, Amer. lnd. Hyg. Assoc. J., Vol. 36, p. 86
This is a syringe pump type atomizer developed by 1-865). Liquid is supplied to the atomizer section by a fixed amount syringe pump. The usual nebulizer has the drawback that the concentration of the solution returned to the reservoir as a drain increases with the operation time and the generated particle size increases.However, according to this method, the syringe volume and the liquid supply speed are properly selected for several hours. Stable generation can be performed. By attaching a simple evaporator / condenser downstream of this device, the monodispersity of the generated mist can be increased. For example, DOP dissolved in alcohol
By changing the ratio of the stock solution, the particle size can be changed from 0.032 μm to 1.
DOP particles are obtained in the range of 3 μm.

(2) Spraying of Monodisperse Particle Suspension This is a method of obtaining standard particles by spraying a monodisperse particle suspension with a nebulizer using compressed air. As a monodisperse particle suspension, polystyrene latex is famous and widely used in many fields related to aerosols. The lower limit of the particle size that can be generated is about 0.05 μm.

(3) Dispersion of dust This is a method in which powder is dispersed in the air to form standard particles. The lower limit of the particle size that can be generated is a submicron size.

[0022]

As is apparent from the above description, among the conventional standard particle generation methods, particles of nm size can be obtained by "generation of high melting point particles based on evaporation / condensation method". Only. However, this method includes
Requires electric furnace and cooling device to heat and cool to high temperature
To it, the whole apparatus is increased in size, it is expensive, usually in order to prevent oxidation of the evaporated substance in the heating unit has a problem such that it is necessary to continuously flow the inert gas such as He or N2 and The solution was sought.

The present invention has been made in view of such technical standpoints, and has as its object to verify a particle counter used to manage ultra-fine particles contained in a gas phase of a semiconductor manufacturing process, N is indispensable for measuring the collection efficiency of a filter used to remove nm-sized ultrafine particles contained in the gas phase of a semiconductor manufacturing process.
An object of the present invention is to provide a new and improved apparatus for generating m-size standard particles, and more specifically, an electric furnace or a cooling apparatus having an expensive and complicated structure like a conventional standard particle method or apparatus. It is possible to reduce the size and cost of the entire device because it does not require a device, stabilize the particle generation state in a short time, and have excellent stability and reproducibility of the generated particles. An object of the present invention is to provide an nm-size standard particle generator.

[0024]

According to a first aspect of the present invention, there is provided a standard particle generator for dispersing nuclear particles having a substantially uniform particle diameter in a gaseous phase. And a mixed gas forming means for adding moisture and a hydrophobic organic gas to the raw material gas supplied by the raw gas supply means until a predetermined concentration is reached, and an alternating current corona discharge in the mixed gas formed by the mixed gas forming means. And discharge means for exciting the electric current.

According to a second aspect of the present invention, there is provided the standard particle generator according to the first aspect, wherein water and organic gas contained in the raw material gas supplied to the mixed gas forming means are substantially removed. A gas purifying means for purifying the gas.

The device according to claim 3 is the device according to claim 1.
Alternatively, a classification means for classifying only fine particles having a predetermined particle size range is provided downstream of the discharge means of the standard particle generation device described in 2.

According to a fourth aspect of the present invention, a conductive needle electrode is coated with an insulating material as a discharging means used in the standard particle generator according to the first aspect of the present invention. It is characterized by using a device provided with a discharge electrode.

[0028]

According to the first aspect of the present invention, a raw material gas such as purified air or an inert gas is supplied by the raw gas supply means, and water (steam) and benzene are supplied to the raw material gas by the mixed gas forming means. By adding a hydrophobic organic gas such as a gas until a predetermined concentration is reached, and exciting the alternating gas corona discharge by a discharge means to the mixed gas,
Positive and negative molecular cluster ions composed of both hydrophobic organic matter and moisture are generated in the mixed gas. Since the positive and negative molecular cluster ions are immediately bound and neutralized by the action of Coulomb force, it is possible to stably generate nanometer-sized water and hydrophobic organic fine particles in a short time.

According to the second aspect of the present invention, the water and organic gas contained in the raw material gas are substantially removed by the gas purifying means, for example, to less than 10 ppb as shown in FIG. Using the raw material gas from which the moisture and the organic substance gas have been substantially removed as background, the concentration adjustment of the moisture and the hydrophobic organic substance gas by the mixed gas forming means can be performed accurately and easily with high precision.

Further, according to the third aspect of the present invention, only ultrafine particles in a certain particle size range are classified and diluted by a classification means such as an electrostatic particle size distribution measuring device, so that a known particle size can be obtained. Since ultra-fine particles having a known concentration can be supplied as standard particles, it is possible to stably generate reproducibly fine particles of nm size having excellent uniformity.

Further, as in the invention described in claim 4, it is coated with an insulating material such as ceramics disclosed in Japanese Patent Application Laid-Open Nos. 3-230499 and 3-230500 of the present applicant. By using a conductive needle-shaped discharge electrode, it is possible to suppress the deterioration and dust generation of the electrode due to the oxidation / sputtering action at the time of discharge, which may occur when using a metal electrode. It can be generated stably and with good reproducibility.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a standard particle generator constructed according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a typical apparatus configuration of a standard particle generator to which the present invention can be applied. In the figure, 1 is an air purification device, 2 is a hydrophobic organic gas generation unit, 3 is a moisture generation unit, 4 is an AC corona discharge generation device, and 5 is a classification device. Air purification device 1 (for example, Air Purifier, Model
N-9, manufactured by Liquid Gas Co., Ltd.)
Alternatively, a raw material gas such as an inert gas such as argon or nitrogen is substantially removed therefrom with moisture and a hydrophobic organic gas. Here, the term “substantially removed” refers to a state in which water (H ₂ O), SO _X, and NO _X have been removed to about 10 ppb or less, for example, as shown in FIG. Further, all the concentrations of the gas components in the air in the present embodiment are indicated by volume fraction.

According to the present invention, the clean air generated by the air refining device 1 is used as a background gas through two separately constructed pipelines, each of which has a separately constructed hydrophobic line. It is sent to the organic matter gas generator 2 and the water generator 3. The hydrophobic organic gas generation unit 2 for generating a hydrophobic organic gas such as benzene gas includes, for example, a standard moisture generator (MG-10,
Hitachi Tokyo Electronics Co., Ltd.) can be used. This apparatus can generate benzene by controlling 0 to 20 ppm of benzene per 1 liter / minute of clean air. On the other hand, a bottle filled with ultrapure water is interposed in the water generating section 3, and by changing the opening degree of the bottle to change the contact area between the clean air and the water surface, the water concentration is reduced. Adjustments can be made.
Further, it is preferable to attach an eliminator on the downstream side in order to remove water mist generated in the water generating section 3. The water concentration at this time can be measured by a dew point meter (MBW electronically cooled dew point meter, DP3-DK1806, manufactured by Nippon Yakin Chemical Industry Co., Ltd.).

Hydrophobic organic gas generator 2 and water generator 3
Are supplied with clean air at a rate of 1 liter / minute, respectively, and the resulting gas containing a desired concentration of a hydrophobic organic substance and the gas containing a desired concentration of a water are flow metered with a flow meter 6, 7 respectively. Mixing while controlling the flow rate by a total of 2
A mixed gas of liter / min is formed. This mixed gas is led to an AC corona discharge device 4 shown in FIGS. 2 and 3 to excite an AC corona discharge, whereby positive and negative molecular clusters composed of both a hydrophobic organic substance and moisture are included in the mixed gas. Generate ions. Since the positive and negative molecular cluster ions are immediately bound and neutralized by the action of Coulomb force, it is possible to stably generate nanometer-sized water and hydrophobic organic fine particles in a short time.

As the AC corona discharge device 4, for example, a nozzle type ionizer as described in Japanese Patent Application Laid-Open No. 4-37097 can be used. This nozzle-type ionizer has a needle-shaped discharge electrode 12 disposed at substantially the center of a nozzle 11 branched in a direction substantially perpendicular to a pipe 10 into which a mixed gas flows, and is provided so as to surround the outer periphery of the nozzle 11. And a ring-shaped discharge counter electrode 13 arranged. The needle-shaped discharge electrode is configured by covering an electrode made of a conductive metal such as tungsten with an insulating material such as quartz glass. More specifically, as shown in FIG. 3, the needle-shaped discharge electrode 12 is concentrically mounted with the needle-shaped electrode 17 in a quartz glass tube 16 having one end fixed to a holder 15 having a screw 14. ing. The sealed end of the quartz glass tube 16 is formed to be pointed, and a needle-shaped electrode 17 is provided inside the end.
Is in contact.

Further, the holder 15 is detachably attached to the Teflon tube 19 of the lead wire 18 via the screw 14. The metal electrode 17 inside the discharge electrode penetrates through the Teflon tube 19 and the metal conductor inside the lead wire. 20. The metal conductor 20 is connected to an AC power supply 21 as shown in FIG.
By applying an AC voltage of kV, 60 Hz, an AC corona discharge can be generated in the nozzle, and positive and negative molecular cluster ions composed of both hydrophobic organic matter and moisture can be generated in the mixed gas. It is.

Then, the mixed gas ionized by the nozzle type ionizer at a flow rate of 2 liter / min is sent to a classifier 5 further downstream to classify and dilute only ultrafine particles in a certain particle size range, Ultrafine particles of a known concentration can be supplied as standard particles to a particle counter or a filter to be tested.

As the classifying device 5, for example, a DMA (Differential Mobility Analyzer) shown in FIG. 4 can be used. The mobility analyzer (DMA) 20 shown in FIG. 4 charges particles, guides them into a constant electric field, and classifies the particles using the electric mobility (mobility) of the particles. To
This is a classification method in which a thin slit 22 is provided below the center rod 21 of the analysis unit, and only particles having a certain mobility are extracted through this slit. In order to increase the classification accuracy, a diffusion field of both ions is created using a radiation source 23, for example, americium or krypton, and the equilibrium charge distribution of Fuchs-Boltzmann shown in FIG. 5 (Mikiji Takahashi (1984): Application) Aerosolology,
Yokendo Co., p. 270), and has a resolution capable of measuring the particle size spectrum. In the Fuchs-Boltzmann distribution (with image power), approximately 1 out of 100 particles of 3 nm (0.003 μm) is positively and negatively charged. That is, when an aerosol consisting of only 3 nm (0.003 μm) particles is passed through the DMA shown in FIG. 4, about 1% of the original total number of aerosols becomes positive or negative depending on the polarity of the DC voltage V. Charged particles are obtained at the DMA exit side. The number of charged particles sieved in this way is measured with an electrometer EM (a type of microammeter). In addition, in FIG. 4, F is a membrane filter,
P is a pump and M is a flow meter.

Next, the particles generated by the standard particle generator configured as described above are converted to CNC (Condensation N).
The results measured by a uclei counter (condensation nucleus counting device) will be described with reference to FIGS. Note that the CNC (condensation nucleus counting device) used here counts fine particles (having a size of sub-micron or less) in air having a high degree of cleanliness, and an outline thereof is shown in Fig. 9. A cylindrical saturated tube 3 in which aerosol (clean air containing fine particles) is saturated with n-butyl alcohol (butanol)
0, and further cooled to 10 ° C. in a condensation tube (cooling tube), thereby forming a supersaturated state of butanol. In the chamber 32, the alcohol vapor condenses the fine particles as condensation nuclei and grows as particles. Then, the enlarged particles are converted into lamps 33, lenses 34,
The counting is performed by an optical device including a condenser lens 35 and a photodetector 36.

First, the vertical axis of the particle size distribution measured by DMA shown in FIGS. 6 to 8 is expressed as dN / d (lnDp) [number / cm
The meaning of [ ³ ] will be briefly described. As described above, the DMA measures the charged particles in a certain size range section. FIG. 10 shows the relationship between the center point Dp of the section of the particle size range of the charged particles measured by the DMA 20 of FIG. 4 and the section width ΔDp. For example, Dp = 4.
Since ΔDp = 0.66 nm at 84 nm, (4.
84-0.66 / 2) nm to (4.84 + 0.66 /
2) Range up to nm, ie 4.51 nm to 5.17.
The number of charged particles in the range up to nm is counted, and this is indicated by ΔN. The center points of the particle size ranges before and after Dp = 4.84 nm are 4.23 nm and 5.54 nm, and their natural logarithms are In4.23 = 1.442 and In4.84.
= 1.577, ln5.54 = 1.712,
The step width ΔlnDp of lnDp is 1.712 to 1.577.
= 1.577-1.4442 = 0.135. That is, in the DMA 20 of FIG. 4, dN / d (lnDp) = ΔN / Δ (lnDp) around Dp = 4.84 nm.
= ΔN / 0.135. Each particle size range division center point Dp
Count of charged particles ΔN measured every
6 , 7 and 8 are obtained by plotting d (lnDp).

As described above, FIG.
While maintaining a constant value of 1 ppm, the water concentration was 3.2 × 1
0 ppm, 4.8 × 10 ² ppm, 6.7 × 10 ³ ppm
5 shows the measurement results of the particle size distribution of positively charged particles sieved by DMA in place of FIG. It can be seen that the generated particles become larger as the water concentration increases. The total number of generated particles including uncharged particles measured by CNC is 1.
9 × 10 ³ cells /cc,2.4×10 ³ pieces /cc,1.0×
It was 10 ⁴ / cc, and it became clear that the number of generated particles increased as the generated particles increased as the water concentration increased.

FIG. 7 shows that the benzene concentration was 14.1 p.
pm while keeping the water concentration at 3.2 × 10p
It is the measurement result of the particle size distribution of the positively charged particles sieved by DMA while changing to pm, 4.8 × 10 ² ppm, and 6.7 × 10 ³ ppm. It can be seen that the generated particles become larger as the water concentration increases. The total number of generated particles including uncharged particles measured by CNC was 5.4 × in order of decreasing water concentration.
10 ^{2 /} cc, 6.7 × 10 ^{3 /} cc, 3.0 × 10
^It became ⁴ particles / cc, and it became clear that the number of generated particles increased as the water concentration increased, while the generated particles increased.

FIG. 8 shows that the water concentration was 6.7 × 10 ^3.
while maintaining the benzene concentration at 6.1 p
10 shows the measurement results of the particle size distribution of negatively-charged particles sieved with DMA at pm and 14.1 ppm. It can be seen that the size of the generated particles increases as the benzene concentration increases. C
The total number of generated particles including uncharged particles measured by NC is
1.0 × 10 ⁴ particles / cc in ascending order of benzene concentration,
3.0 × 10 ⁴ particles / cc, and it became clear that as the benzene concentration increased, the number of generated particles increased while the generated particles increased.

As described above, according to the standard particle generator constructed in accordance with the present invention, the mixed gas containing water and the hydrophobic organic gas adjusted to a predetermined concentration is subjected to the alternating current by the ionizer. When the corona discharge is excited, positive and negative molecular cluster ions composed of both a hydrophobic organic substance and moisture are generated in the mixed gas. Since the positive and negative molecular cluster ions are immediately bound and neutralized by the action of Coulomb force, it is possible to stably generate nanometer-sized water and hydrophobic organic fine particles in a short time. Furthermore, by classifying and diluting only ultrafine particles of a certain particle size range by a classification means such as DMA, it becomes possible to supply ultrafine particles of a known particle size and a known concentration as standard particles. Fine particles of excellent nm size can be generated stably and with good reproducibility.

In the above embodiment, the moisture (steam) and the hydrophobic organic gas are injected into the pipe through which purified air from which the organic gas and the moisture (steam) have been substantially removed so as to have a predetermined concentration. Although the present invention is not limited to this example, the present invention is not limited to this. Water (water vapor) and a hydrophobic organic gas are supplied to a pipe in which an inert gas such as argon or nitrogen from which the organic gas and water (water vapor) have been removed flows. Can be stably and reproducibly generated by injecting and mixing so as to have a concentration of 0.1 nm.

Further, in the above embodiment, FIGS.
Although only one needle-like ceramic-coated electrode 12 was provided in the nozzle 11 as shown in FIG.
Alternatively, it is possible to increase the number of generated particles by adopting a configuration in which a plurality of electrodes are provided by increasing the cross-sectional area of the pipeline of the nozzle 11.

Further, in the above embodiment, benzene was used as the hydrophobic organic substance gas. However, the present invention is not limited to such a gas, and other hydrophobic organic substance gases such as octane and toluene have the same effect as benzene. It is possible to get.

The corona discharge is a direct current, the raw material gas contains only one of moisture (water vapor) and a hydrophobic organic gas, or the water (water vapor)
And both hydrophobic organic gases are not included.
In any case, unlike the device of the present invention, it was not possible to generate nm-sized particles.

Further, the water generator and the hydrophobic organic substance generator are not limited to the apparatus shown in FIG. 1, and as shown in FIG. 11, a container 42 having a liquid reservoir 41 of water or a hydrophobic organic substance (liquid) is provided. Purified air or an inert gas is blown, and the flow rate of the blown air can be controlled to control the concentrations of moisture and hydrophobic organic substances. Further, a part or the whole of the container having the liquid reservoir is heated by a heating means 43 such as a winding electric heater, and the heating temperature is controlled in combination with a thermocouple 44 so that water or a hydrophobic organic substance (liquid) is formed. Evaporation amount of
Also, the concentration of those contained in purified air or inert gas can be controlled. In short, the flow rate of purified air and inert gas and the concentration of water and hydrophobic organic matter contained therein are freely controlled to achieve excellent particle diameter uniformity (monodispersity) and stable generation concentration. It suffices if ultra-fine particles of nm size can be generated.

[0051]

As described above, according to the standard particle generator constructed on the basis of the present invention, it is possible to generate ultra-fine particles of nm size having a uniform particle diameter and excellent stability of generated concentration. Is possible. That is, according to the first aspect of the present invention, a raw material gas such as purified air or an inert gas is supplied by the raw material gas supply means, and water (steam) or benzene or the like is supplied to the raw material gas by the mixed gas forming means. A hydrophobic organic substance gas is added until a predetermined concentration is reached, and the mixed gas is excited by an alternating current corona discharge by a discharge means, so that the positive and negative constituents composed of both the hydrophobic organic substance and moisture are included in the mixed gas. Negative molecular cluster ions are generated. The positive and negative molecular cluster ions are immediately bound and neutralized by the action of Coulomb force.
It is possible to stably generate m-size water and hydrophobic organic fine particles in a short time.

According to the second aspect of the present invention, since the water and the organic gas contained in the raw material gas are substantially removed by the gas purifying means, the water and the organic gas are substantially removed. With the source gas as the background, the concentration adjustment of the water and the hydrophobic organic gas by the mixed gas forming means can be performed accurately and easily with high precision.

Further, according to the third aspect of the present invention, only ultrafine particles in a certain particle size range are classified and diluted by a classification means such as an electrostatic particle size distribution measuring device, thereby obtaining a known particle size. Since ultra-fine particles having a known concentration can be supplied as standard particles, it is possible to stably generate reproducibly fine particles of nm size having excellent uniformity.

Furthermore, by using a conductive needle-shaped discharge electrode covered with an insulating material such as ceramics as in the invention according to the fourth aspect, a discharge which occurs when a metal electrode is used. Since deterioration and dust generation of the electrode due to the oxidation / sputtering action at the time can be suppressed, fine particles of nm size can be generated stably and with good reproducibility.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a standard particle generator configured based on the present invention.

FIG. 2 is an explanatory diagram schematically showing an AC corona discharge device of a standard particle generator configured according to the present invention.

FIG. 3 is a schematic sectional view showing an electrode portion of the AC corona discharge device shown in FIG.

FIG. 4 is an explanatory diagram showing a DMA (differential mobility analyzer) applicable to a standard particle generator configured based on the present invention.

FIG. 5 is a table showing a distribution of an average charge amount in an equilibrium charge state due to diffusion of both positive and negative ions.

FIG. 6 is an explanatory diagram showing a particle size distribution (benzene concentration: 6.1 ppm, moisture concentration change) of positively charged particles sieved by DMA based on the present invention.

FIG. 7 is an explanatory diagram showing a particle size distribution (benzene concentration change: 14.1 ppm, water concentration change) of positively charged particles sieved by DMA based on the present invention.

Particle size distribution of negatively charged particles sieved through a DMA based on the present invention; FIG (water concentration 6.7 × ¹⁰ 3 pp
m, benzene concentration change ).

FIG. 9 is an explanatory diagram showing a CNC (condensation nucleus counting device) applicable to a standard particle generator configured according to the present invention.

FIG. 10 is a table showing the relationship between the division center point Dp of the particle size range of the charged particles measured by DMA and the division width ΔDp.

FIG. 11 is an explanatory view showing another embodiment of the water or hydrophobic organic matter generator applicable to the standard particle generator constructed according to the present invention.

FIG. 12 is an explanatory diagram of a conventional Sinclair-Lamer particle generator.

FIG. 13 is a schematic explanatory view of a conventional NaCl fine particle generator.

FIG. 14 is a table showing a particle size distribution of NaCl particles by a heating and quenching method.

FIG. 15 is an explanatory diagram showing a structure of a constant output atomizer by Liu et al.

FIG. 16 is a table showing impurity gas concentrations in clean air.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Air purification apparatus 2 Hydrophobic organic gas generation part 3 Water generation part 4 AC corona discharge device 5 Classification device 6 Flow meter 7 Flow meter 11 Nozzle 12 Discharge electrode 13 Discharge counter electrode

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/02 B01J 19/00

Claims (4)

(57) [Claims] 1. A standard particle generator for dispersing nuclear particles having a substantially uniform particle diameter in a gaseous phase, comprising: a raw material gas supply means; and a raw material gas supplied by the raw material gas supply means; A mixed gas forming means for adding an organic gas until a predetermined concentration is reached, and discharge means for exciting an AC corona discharge in the mixed gas formed by the mixed gas forming means,
Standard particle generator. 2. A gas purifying means according to claim 1, further comprising a gas purifying means for substantially removing moisture and organic gas contained in the raw material gas supplied to said mixed gas forming means. Standard particle generator. 3. The standard particle generator according to claim 1, further comprising a classification unit provided downstream of the discharge unit for classifying only particles having a predetermined particle size range. 4. The discharge means includes a discharge electrode in which a conductive needle-like electrode is covered with an insulating material.
The standard particle generator according to claim 1, 2 or 3.