JP2017003385A - Particle measuring device and particle measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particle measuring device and a particle measuring method using a condensation nucleus method capable of detecting microscopic particles in sampling gas with a high detection rate even when the sampling gas flows at a large flow rate.SOLUTION: A particle measuring device comprises: a condensation section 1 where sampling gas including microscopic particles is introduced thereinto, saturated vapor is produced therein and condensation particles are generated in a manner that allows vapor molecules in the saturated vapor to be condensed with the microscopic particles in the sampling gas as nuclei; and a particle measuring section 3 which measures the number of the microscopic particles by measuring the number of condensation particles generated in the condensation section 1. The condensation section 1 has: a plurality of condensation pipes 11 which generate the condensation particles; and a vapor production section 12 which produces the vapor in the plurality of condensation pipes 11. The condensation particles generated in the plurality of condensation pipes 11 are introduced into the particle measuring section 3 to count the number thereof.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a particle measuring apparatus and a particle measuring method using a condensation nucleus method that grows particles by condensing vapor molecules using microparticles as nuclei and measures the number of particles.

  When manufacturing a semiconductor device, there are various processes such as film formation, photolithography, and etching. In these processes, if particles adhere to the semiconductor substrate, the performance of the formed device deteriorates. Therefore, it is necessary to install the processing apparatus in a clean room and perform processing in a clean atmosphere with very few particles.

  For this reason, it is required to quickly detect dust by measuring the number of particles in the processing apparatus or clean room with a measuring instrument. Condensed nucleus counters (CNC or CPC) that can measure nano-sized airborne particles are used as measuring instruments because particles affect the device performance even if they are nano-sized. .

  The condensation nucleus counter is used to pass particles through supersaturated vapors such as alcohol and water, and to condense the vapor molecules using the particles as nuclei, thereby growing the particles and detecting the grown particles at the detection unit. . The particle size at the detection limit of the detector due to light scattering is usually about 100 nm. However, since the condensed nucleus counter grows particles, it can detect particles of several nm.

  As such a condensation nucleus counter, Non-Patent Document 1 describes that the saturation in the condensation tube is adjusted by heat transfer and humidification from the tube wall of the condensation tube along the inner wall of a wet porous sheet. What controls the particle size is described. Such a condensed nucleus counter is also described in Patent Document 1.

Japanese Patent No. 4832473

Catalog TSI model 3781

  By the way, recently, it is required to measure minute air particles having a low concentration of 100 nm or less, and in order to accurately measure such particles, it is necessary to increase the sampling flow rate.

  However, in the measuring instruments described in Non-Patent Document 1 and Patent Document 1, when the flow rate of the sampling gas is increased, the condensing tube is a thin tube, so the ejection speed of the sampling gas becomes extremely high. For this reason, the sampling gas becomes a turbulent flow, the condensed particles formed by condensing vapor molecules with the particles as nuclei adhere to the wall portion, and the detection rate becomes low. Increasing the diameter of the condensing tube reduces the flow velocity and makes it possible to suppress turbulent flow, but a region with low saturation occurs due to insufficient heat transfer and humidification from the wall. For this reason, there are not a few particles that do not grow to a size that can be detected, and the detection rate is still low.

  Therefore, an object of the present invention is to provide a particle measuring apparatus and a particle measuring method by a condensation nucleus method that can detect fine particles in a sampling gas at a high detection rate even when the sampling gas is increased in flow rate. .

  In order to solve the above-described problem, a first aspect of the present invention is that a sampling gas containing fine particles is introduced and saturated vapor is generated, and vapor molecules in the saturated vapor are formed using the fine particles in the sampling gas as nuclei. A condensing unit that generates condensed condensed particles, and a particle measuring unit that measures the number of minute particles by measuring the number of condensed particles formed in the condensing unit, the condensing unit, A plurality of condensing pipes for generating condensed particles; and a steam generating section for generating steam inside the plurality of condensing pipes, and guiding the condensed particles generated in the plurality of condensing pipes to the particle measuring section. And providing a particle measuring apparatus characterized by measuring the number of particles.

  According to a second aspect of the present invention, sampling gas containing microparticles is introduced into a plurality of condensing tubes, steam is generated in the plurality of condensing tubes, and the minute particles in the sampling gas are used as nuclei in saturated steam. There is provided a particle measuring method characterized in that condensed particles in which vapor molecules are condensed are generated, and the number of particles is measured by guiding the condensed particles generated in the plurality of condensing tubes to a particle measuring unit.

  As the vapor generating part, a member having a porous sheet provided on the inner wall of the condensing tube and a liquid tank for storing a liquid for holding the liquid in the porous sheet can be used.

  The plurality of condensing pipes include a saturated portion that generates saturated vapor, and a condensation / nuclear growth portion that condenses the vapor to minute particles in the sampling gas to form condensed particles and grows condensed particles. can do. In this case, you may have a heating part which heats the said condensation and nucleus growth part of the said condensation tube, and may have a heating part which heats the said condensation and nucleus growth part of the said condensation tube.

  The condensing unit includes a main body container that accommodates the plurality of condensing tubes. The main body container is reduced in diameter toward the introduction unit into which the sample gas is introduced and the particle measuring unit, and the condensation is performed. A supply unit for supplying particles to the measurement unit, and the plurality of condensing pipes correspond to the previous stage unit that is the saturation unit, the middle unit unit that is the condensation / nuclear growth unit, and the supply unit. It can be set as the structure which has the back | latter stage part diameter-reduced. In this case, it can be set as the structure which has a heating part which heats the said middle stage part of the said condensation pipe | tube. Moreover, it is preferable that the said back | latter stage part of the said condensation pipe | tube is hold | maintained at the same temperature as the said middle stage part at this time, and it is preferable that the supersaturation degree of the saturated steam in the said middle stage part and the said back | latter stage part is 1-2. .

  According to the present invention, since a plurality of condensing tubes are provided, even if the diameter of one condensing tube is about the same as the conventional one, it is possible to cope with an increase in the sampling gas flow rate without increasing the sampling gas flow rate. In addition, unlike the case where the condensing tube is thickened, there is no occurrence of a region with low saturation due to insufficient heat transfer and humidification from the wall. For this reason, even if the sampling gas is increased in flow rate, fine particles in the sampling gas can be detected with a high detection rate.

It is sectional drawing which shows the particle measuring device which concerns on one Embodiment of this invention. It is sectional drawing by the AA 'line of FIG. It is sectional drawing which shows a part of condensation tube used for the condensation part of the particle | grain measuring apparatus of FIG. It is sectional drawing which shows the steam generation part used for the condensation part of the particle | grain measuring apparatus of FIG. It is a schematic diagram which shows the condensing tube applied to the particle measuring device which concerns on other embodiment of this invention. It is a schematic diagram which shows the condensing tube applied to the particle measuring device which concerns on further another embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
<Configuration of particle measuring device>
FIG. 1 is a sectional view showing a particle measuring apparatus according to an embodiment of the present invention.

  The particle measuring apparatus 100 is configured as a condensation nucleus counter, and a sampling gas (aerosol) is introduced, the condensation unit 1 that generates condensed particles in which vapor is condensed into minute particles, and the condensation unit 1 are heated. A heater 2 which is a heating unit and a particle measuring unit 3 are provided.

  The condensing unit 1 includes a cylindrical main body container 10, a plurality of condensing tubes 11 inserted therein, and a steam generating unit 12 that generates steam inside the condensing tubes 11. The main body container 10 is provided with an introduction unit 13 for introducing sampling gas (aerosol) into the plurality of condensation tubes 11 and a supply unit 14 for supplying condensed particles from the plurality of condensation tubes 11 to the particle measurement unit 3. ing.

  As shown in FIG. 2, which is a cross-sectional view taken along the line AA ′ in FIG. 1, the plurality of condensing tubes 11 are arranged in a bundled state in the main body container 10. In this example, the plurality of condensing tubes 11 are arranged in a lattice pattern. However, the arrangement method is not limited to the lattice shape, and may be another arrangement such as a hexagonal close-packed shape. Further, the condensing tubes 11 may be arranged concentrically instead of being bundled.

  The condenser tube 11 is a pre-stage unit 11a that is a saturated unit that generates saturated vapor in a state cooled to about 20 ° C., condenses the vapor into fine particles in the sampling gas, and condenses the vapor (condensed particles). It has a middle part 11b which is a condensation / nuclear growth part to be grown, and a rear part 11c corresponding to the supply part 14. As shown in FIG. 3, a wick 21, which is a porous sheet having water absorption, is provided on the inner walls of the front stage part 11 a and the middle stage part 11 b of the condensing tube 11. As shown in FIG. 4, the wick 21 is immersed in a liquid L such as water or alcohol stored in the liquid tank 22 and is in a state of being wetted by the liquid in the liquid tank 22. Steam is generated from the surface. The wick 21 and the liquid tank 22 form the steam generation unit 12.

  The introduction part 13 is provided at one end of the main body container 10 and is connected to a pipe 15 for supplying a sampling gas (aerosol). The introduction part 13 is provided so as to spread from the connection part of the pipe 15 toward the condensation pipe arrangement region of the main body container 10. The sampling gas is a gas containing fine particles of about 100 nm or less sampled from a clean room or the like.

  From the pipe 15, a sampling gas having a larger flow rate than the conventional one is supplied. The flow rate of the sampling gas is 10 to 100 L / min.

  Saturated steam is generated from the wick 21, which is a porous sheet having water absorption, in the front part 11 a of the condenser tube 11, and in the middle part 11 b, the vapor molecules are condensed with minute particles of about 100 nm or less in the sampling flow as nuclei. Condensed particles are formed, and the condensed particles grow to a size of about a submicron size that can be measured by the particle measuring unit 3.

  The supply unit 14 is reduced in diameter toward the particle measurement unit 3, and the rear stage part 11 c of the condensing tube 11 inside the supply unit 14 is also reduced in diameter toward the particle measurement unit 3 in the same manner as the supply unit 14. Then, the gas containing the condensed particles discharged from the condensing tube 11 joins at the tip end portion 14a of the supply unit 14 and is supplied to the detection unit of the particle measurement unit 3. Thereby, the gas containing condensed particles can be supplied to the particle measurement unit 3 without causing convection in the supply unit 14. The diameter of the distal end portion 14 a is a value corresponding to the maximum detection area of the particle measuring unit 3. The residence time of the particles in the condenser tube 11 corresponding to the supply unit 14 is preferably about 0.2 sec.

  The diameter of the front stage part 11a and the middle stage part 11b of the condensing tube 11 is preferably about 4 to 10 mm. Moreover, although the preferable number of the condenser tubes 1 is determined by the flow rate of the sampling gas, about 10 to 100 are preferable. Further, the diameter of the main body container 10 may be appropriately set depending on the number of the condenser tubes 1.

  The heater 2 is provided so as to surround the main body container 10 in a portion corresponding to the middle stage portion 11 b of the condenser tube 11. The heater 2 heats the wall surface of the middle portion 11b of the condenser tube 11 to form a saturated vapor having a preferable supersaturation degree. The vapor is condensed into particles to form condensed particles, and the condensed particles grow. At this time, the supersaturation degree of the steam is preferably 1 to 2, and the temperature of the wall surface of the middle portion 11b is preferably 40 to 80 ° C.

  The rear stage portion 11c of the condenser tube 11 is maintained at the same temperature as the middle stage portion 11b by forming the wall portion of the supply portion 14 with a heat insulating material or by providing a heater around the supply portion 14. Is preferred.

  The particle measuring unit 3 determines the number of particles in the gas by measuring the number of condensed particles formed in the condensing tube 11, and can use a commonly used optical particle measuring instrument. . Among these, an optical system capable of measuring a wide range of particles is preferable. The particle measuring unit 3 includes a housing 31, a laser oscillator 32 that irradiates laser light into the housing 31, and a detector 33 that receives scattering holes generated by the particles when condensed particles pass through the laser light. The number of particles is measured by converting the received scattered light into an electrical signal.

  An exhaust port 34 is formed in the housing 31, and a pipe 35 is connected to the exhaust port 34. The pipe 35 is provided with a pump 36. Then, the inside of the particle measuring unit 3 is exhausted by the pump 36.

<Operation of particle measuring device>
In the particle measuring apparatus 100 configured as described above, the pump 36 is operated, and the sampling gas (aerosol) is introduced from the introduction unit 13 into the plurality of condensing tubes 11 via the pipe 15. The sampling gas flow rate at this time is preferably 10 to 100 L / min from the viewpoint of accurately measuring minute air particles of 100 nm or less.

  The sampling gas introduced into the condensing tube 11 is cooled to about 20 ° C., passes through the front stage part 11a for generating steam, and reaches the middle stage part 11b whose wall surface is heated by the heater 2, where there are minute particles in the sampling gas. The vapor is condensed to form condensed particles, and the condensed particles are grown to a submicron size or more that can be measured by the particle measuring unit 3. From the viewpoint of appropriately growing the condensed particles, the supersaturation degree of the vapor is preferably 1 to 2, and the heating temperature of the wall surface of the middle part 11b is preferably 40 to 80 ° C.

  The sampling gas containing the condensed particles reaches the rear-stage part 11a having a reduced diameter corresponding to the supply part 14 of the condensation tube 11, joins at the front end part 14a of the supply part 14, and is sent to the particle measuring part 3, where the condensed particles , That is, the number of particles.

  In such particle measurement, when measuring particles using only one thin condensing tube as in the past, the sampling gas flow rate is set to accurately measure minute airborne particles with low concentration of 100 nm or less. When increased, the flow rate of the sampling gas becomes extremely high, so that the sampling gas becomes a turbulent flow and the condensed particles adhere to the wall portion, and the detection rate becomes low. On the other hand, by increasing the thickness of the condensing tube, the flow velocity can be reduced and turbulent flow can be suppressed. However, since heat transfer from the wall and humidification are insufficient, a region with low saturation occurs. For this reason, there are particles that do not grow to a size that can be detected, and the detection rate is still low.

  On the other hand, in the present embodiment, since the plurality of condensing tubes 11 are provided, the flow rate of the sampling gas is increased without increasing the sampling gas flow rate even if the diameter of the single condensing tube 11 is approximately the same as the conventional one. In addition, unlike the case where the condensing tube is thickened, there is no occurrence of a region with low saturation due to insufficient heat transfer and humidification from the wall. For this reason, even if the sampling gas is increased in flow rate, fine particles in the sampling gas can be detected with a high detection rate.

  From the viewpoint of suppressing the occurrence of turbulent flow in the condensing tube 11 at a desired sampling gas flow rate, the diameter of the front stage portion 11a and the middle stage portion 11b of the condensing tube 11 is preferably about 4 to 10 mm.

  It is possible to grow the diameter of the condensed particles to a desired value in the middle stage portion 11b of the condensation tube 11, but when the sampling gases from the plurality of condensation tubes 11 are merged in the supply portion 14 having a reduced diameter, the condensation tube Since the merging is performed in a state where the gap between the 11 flow paths is large, convection easily occurs. As a result, the residence time at the junction becomes longer than 0.2 sec, which is a preferred residence time. In addition, the condensed particles may adhere to the wall and the particle detection rate may be low.

  On the other hand, in the present embodiment, the rear stage portion 11c of the condensing tube 11 is arranged in the supply portion 14 that is reduced in diameter to the introduction diameter to the particle measuring portion, and the gap between the flow paths of the condensing tube 11 is reduced. After becoming small, the sampling gases from the plurality of condensing tubes 11 are merged. For this reason, the convection at the time of merging can be suppressed, the residence time can be lengthened, and the adhesion of the condensed particles to the wall portion can be suppressed.

  Further, since it is not necessary for the rear stage part 11c of the condensing tube 11 to grow condensed particles, it is not necessary to increase the temperature from that point. However, if the rear stage part 11c is lower than the temperature during the nucleus growth, the inner wall Condensation is likely to occur and the detection rate may decrease. In addition, there is a possibility that the supersaturation level rapidly increases in the rear stage portion 11c, and the false count increases due to non-nuclear condensation. For this reason, the rear-stage part 11c of the condensation pipe 11 is maintained at the same temperature as the middle-stage part 11b by forming the wall part of the supply part 14 with a heat insulating material or by providing a heater around the supply part 14. Is preferred.

<Other applications>
The present invention can be variously modified without being limited to the above embodiment. For example, in the above-described embodiment, in the condenser tube 11, the pre-stage portion 11 a that is a saturated portion that generates saturated vapor is cooled, and then a condensation / nuclear growth portion that condenses the vapor using particles as nuclei and grows condensed particles. However, the present invention is not limited to this, and can be applied to any type of condensation nucleus counter used conventionally. For example, as shown in FIG. 5, the front stage part 11a that is a saturation part may be heated and the middle stage part 11b that is a condensation / nuclear growth part may be cooled. In addition, when the front stage portion 11a is heated and the middle stage portion 11b is cooled, as shown in FIG. 6, a porous sheet (wick 21) having water absorption, which is a steam generation section, may be provided only on the front stage portion 11a. Good.

DESCRIPTION OF SYMBOLS 1; Condensing part 2; Heater 3; Particle measuring part 10; Main body container 11; Condensation pipe 11a; Pre-stage part 11b; Middle stage part 11c; Rear stage part 12; Steam generation part 13; Introducing part 14; Wick (porous sheet)
22; Liquid tank 31; Housing 32; Laser oscillator 33; Detector 34; Exhaust port 35; Piping 36; Pump 100;

Claims (10)

A condensing unit for generating a condensed gas in which a sampling gas containing fine particles is introduced and saturated vapor is generated, and vapor molecules in the saturated vapor are condensed with the fine particles in the sampling gas as a nucleus,
A particle measuring unit that measures the number of fine particles by measuring the number of condensed particles formed in the condensing unit;
The condensing part is
A plurality of condensing tubes for producing the condensed particles;
A steam generating section for generating steam inside the plurality of condensing tubes,
A particle measuring apparatus characterized in that the condensed particles generated in the plurality of condensing tubes are guided to the particle measuring unit to measure the number of particles.   The said steam generation part has a porous sheet provided in the inner wall of the said condensation pipe | tube, and a liquid tank which stores the liquid for hold | maintaining a liquid in the said porous sheet. Particle measuring device.   The plurality of condensing pipes include a saturation portion that generates saturated vapor, and a condensation / nuclear growth portion that condenses the vapor to minute particles in the sampling gas to form condensed particles and grows condensed particles. The particle measuring device according to claim 2.   The particle measuring apparatus according to claim 3, further comprising a heating unit that heats the condensation / nuclear growth unit of the condensation tube.   The particle measuring apparatus according to claim 3, further comprising a heating unit that heats the saturated portion of the condensing tube. The condensing unit has a main body container that houses the plurality of condensing tubes,
The main body container has an introduction part into which the sample gas is introduced,
Having a diameter that is reduced toward the particle measuring unit and supplying the condensed particles to the measuring unit;
The plurality of condensing pipes include a front-stage part that is the saturation part, a middle-stage part that is the condensation / nuclear growth part, and a rear-stage part that is reduced in diameter corresponding to the supply part. Item 4. The particle measuring apparatus according to Item 3.   The particle measuring apparatus according to claim 6, further comprising a heating unit that heats the middle stage of the condensing tube.   The particle measuring apparatus according to claim 7, wherein the rear stage part of the condensing tube is maintained at the same temperature as the middle stage part.   The particle measurement apparatus according to claim 8, wherein a supersaturation degree of saturated steam in the middle stage part and the rear stage part is 1 to 2. Sampling gas containing minute particles is introduced into a plurality of condensing tubes, vapor is generated in the plural condensing tubes, and condensed particles in which vapor molecules in saturated vapor are condensed with the minute particles in the sampling gas as nuclei. Generate
A particle measuring method comprising: measuring the number of particles by guiding the condensed particles generated in the plurality of condensing tubes to a particle measuring unit.

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