JP5469494B2 - Charge amount identification device for charged particles - Google Patents

Description

  The present invention relates to a charged particle amount specifying device for taking in charged particles floating in the air and specifying the charge amount.

  It is known that a Coulomb force acts on charged particles formed by charging particles in an electric field, and the charged particles easily adhere to an electric field generating source. Examples of the electric field generation source include various electrostatically charged members. In particular, the adhesion of particles due to the electrostatic charge is the following production facility, that is, a process of manufacturing a transparent electrode as an FPD material (flat panel display), In production facilities such as facilities for assembling / manufacturing production equipment and facilities for producing next-generation secondary batteries, there is a problem as particle contamination.

  Products (workpieces) manufactured at the above facilities allow manufacturing with a low cleanliness (cleanness: about 1000 to 10,000), but in the various production facility spaces described above, friction, peeling, cleaning, drying, etc. There are also large particles having a size of several μm that can be generated in the manufacturing process, and the adhesion to the product is one of the main factors for the decrease in the product yield.

  In addition, a conductive material is generally applied to the interior member of the clean room, but this is charged with a potential of about ± 100 V, which generates charged particles in the room space and adheres to the product. The degree of cleanliness will be reduced.

  By the way, the behavior of particles is affected by end sedimentation due to gravity, airflow, and Coulomb force, and the adsorption of charged particles to a work or interior member is mainly related to the Coulomb force, and the charged amount of charged particles ( The adsorptive power is determined by the electric field intensity generated by the charge amount) and the surface potential of the workpiece. For this reason, as a countermeasure against static electricity, the work surface is neutralized with an ionizer or soft X-rays.

  However, in current clean rooms and the like, since the charge amount of particles that can be generated due to static electricity distribution, friction, separation, etc. in the space has not been grasped, the above-described potential removal measures are actually effective. It's hard to say. In particular, although the generation mechanism of charged particles, their properties, and the charge amount are important factors for measures against static elimination, a method for measuring or identifying particles having a size of several μm in an actual environment has not yet been established.

  A method of using a differential electrostatic classifier (DMA: Differential Mobility Analyzer) is currently used for measuring and specifying the charge amount of the charged particles.

  This method using DMA is an effective measurement method for particle classification under normal temperature and normal pressure, and its device configuration is a double concentric cylinder, applying voltage to the inner cylinder and grounding the outer cylinder Thus, a potential difference is provided between these cylinders, and the distance and potential between the inner and outer cylinders are kept constant, and the electric field is designed to be uniform. Clean air is introduced between the inner and outer cylinders in a laminar flow state (sheath airflow), while sample air containing charged particles is allowed to flow along the wall of the outer cylinder. In this DMA, the Coulomb force generated between the electric field that depends on the potential difference and the charged amount (charge amount) of the charged particles acts on the charged particles, and is drawn to the center electrode at a moving speed that has an electric mobility corresponding to the potential difference. Will be.

  Here, particles with higher electric mobility have a higher moving speed, and as a result, they tend to deposit on the upper part of the center electrode. On the other hand, particles with lower electric mobility flow out of the DMA together with the sheath airflow without being collected by the center electrode. easy. Note that a slit is provided below the center electrode, and only charged particles smaller than a certain electric mobility are taken out. In addition, by measuring the concentration using a condensation nucleus counter (CNC) or the like, the distribution of electric mobility can be obtained.

  As described above, DMA has a mechanism that allows particles to be taken out from the slit as classified particles when the particle size and electric mobility (that is, the number of charges) coincide with the set airflow and Coulomb force. Therefore, as the particle diameter increases, the moving speed due to gravity and air current acting downward increases, and the length of the DMA naturally becomes longer. In addition, if the moving speed is low and the number of charges is small, it is necessary to apply a strong electric field to classify the particles with the slit, but the distance between the electrode (inner cylinder) and ground (outer cylinder) If is small, the cross-sectional dimension of the DMA must be increased to avoid the risk of discharge.

  In addition, according to the verification by the present inventors, in an experiment using a DMA having an outer cylinder diameter of 10 cm and a length of 30 cm, a particle size of 0.5 μm and a charge number of ± 6 are the maximum measurable sizes Larger particle sizes are almost impossible to measure.

  On the other hand, in the case of particle contamination in various production facilities described above, there are many cases where adhesion of particles (or fine particles) having a particle size of several μm or more is a problem. In order to implement the above in the process area, an extremely large apparatus is required, and thus it is not practical to apply such a large-scale measuring apparatus.

  A technique obtained by improving the structure of the above-described DMA is disclosed in Patent Document 1. The fine particle classifying device disclosed in Patent Document 1 has a plurality of center electrode portions for each particle size as a characteristic configuration, and a particle outlet slit is individually formed in each of the center electrode portions for each particle size. This makes it possible to simultaneously classify (particle size selection) fine particles having a plurality of types of particle sizes.

  However, even with this improved fine particle classifier, the above problem still remains, that is, a clean room where adhesion of charged particles (or fine particles) having a particle size of several μm or more is a problem without increasing the scale of the device. In the actual environment such as the above, the problem of precisely measuring or specifying the charged amount of the charged particles cannot be solved.

JP 2007-315817 A

  The present invention has been made in view of the above-described problems, and is capable of precisely measuring or specifying the charge amount of charged particles having a particle size of several μm or more without increasing the scale of the apparatus. An object of the present invention is to provide a device for specifying the amount of charge.

  In order to achieve the above object, an apparatus for specifying the charged amount of charged particles according to the present invention takes in a gas containing floating charged particles, and includes an introduction unit having a particle sensor for sensing charged particles, and passing through the introduction unit. A flow rate adjustment unit that adjusts the flow rate of the gas having a flow rate, and at least the detection unit stops the gas, and the detection unit into which the gas that has passed through the flow rate adjustment unit is introduced, and generates an electric field. Receiving a charged particle data transmitted from the particle sensor, a detection unit having a mechanism, an irradiation mechanism for irradiating the charged particles with laser light, and a light receiving mechanism for receiving scattered light emitted from the charged particles; A control unit that controls the operation of the flow rate adjustment unit, and the introduction unit, the flow rate adjustment unit, and the detection unit are connected to each other via a flow path. The electric field generating mechanism is actuated to generate an electric field in the detection unit. The charged electric field and gravity cause the movement of the charged particles, and the charged amount of the charged particles from the received light data of the scattered light emitted from the moving charged particles. Is specified.

  The above-mentioned DMA of the conventional structure specifies the charge amount by measuring the particles that have moved into the slit using the air flow, gravity, and Coulomb force of charged particles (this particle can also be called aerosol) as parameters. In contrast, the charge amount specifying device of the present invention is a gas containing charged particles. For example, by making the air flow stationary, the moving speed of the charged particles using only gravity and Coulomb force as parameters. Is measured by the detection unit of the optical system, and the charge amount or the number of charges is specified.

  When measuring the moving speed of the charged particles, the flow of the gas containing the charged particles is stationary. Therefore, if the Coulomb force is not considered (ignored), the moving speed of the charged particles is caused by gravity. Therefore, the moving speed of the charged particles is relatively low as compared with the case where the moving speed is determined from gravity, air flow, and Coulomb force. For this reason, the moving path of the charged particles required for measurement may be short, and the apparatus itself can be downsized.

  In the above-mentioned DMA with a conventional structure, the amount of charge is unknown because it is a device that guides charged particles to the slit by applying a voltage to the electrode (inner cylinder) and applying a Coulomb force to the charged particles. Under these conditions, it is necessary to change the voltage as a parameter in various ways to match the charge amount (charge number) of the particles. Therefore, in an environment where there are few floating particles such as in a clean room, in addition to the measurement of charged particles, the voltage is tentatively determined, and as a result, the measurement flow assumes that the number of charges is specified by the number of charges when classification is possible. If classification cannot be performed, it is necessary to change the voltage to temporarily determine the same and repeat the same operation until classification can be performed again. It is easy to understand that it takes a lot of time to specify the charge amount. In contrast, the charge amount specifying device of the present invention can measure and specify the charge amount while confirming the measured movement state of the charged particles, greatly increasing the time required for specifying the charge amount of the charged particles. Can be shortened.

  Here, regarding “at least the gas is stationary at the detection unit”, in the cell constituting the detection unit, this “stationary” does not only mean that the gas is completely stationary, but also moves at an extremely low speed. In other words, the gas flow rate may be reduced to a speed that does not need to be considered as a parameter.

  Eventually, the received light data of scattered light emitted from the moving charged particles is taken into, for example, a computer incorporating the above-described control unit or a separate computer, and the movement state of the charged particles on this computer screen. Are sequentially confirmed by the manager, the charge amount of the charged particles is specified.

  In addition, the particle sensor and the detection unit provided in the introduction unit described above measure the particle size of the charged particles, and the detection unit further specifies the moving speed of the charged particles from the received light data of the scattered light. The charge amount can be specified from the diameter and the moving speed.

  In addition, the flow rate adjusting unit described above is an actuator valve whose opening degree is adjusted by the control unit interposed in the above-described flow path, or provides a fluid such as pressure air to the gas to provide a gas velocity. It is also possible to use any one of a combination of a fluid providing mechanism for lowering the pressure and the actuator valve.

  Adjust the opening of the actuator valve according to the flow rate of the incoming gas, or close the valve completely to stop the flow with respect to the incoming gas, and gradually adjust the opening. However, it is possible to reduce the flow rate of the gas to a static or close speed. Further, in the embodiment having the fluid providing mechanism, in addition to adjusting the opening degree of the valve, by providing pressure air or the like in a direction to reduce the flow velocity of the inflowing gas, the gas flow velocity is more effectively stopped or close to it. It is possible to drop to speed.

  The irradiation mechanism described above includes a laser oscillator, a condensing lens that condenses the laser light emitted from the laser oscillator, a focusing lens that focuses the laser light that has passed through the condensing lens on the charged particles, The light receiving mechanism may include a condensing lens that condenses scattered light emitted from the charged particles, and a focusing lens that focuses the scattered light that has passed through the condensing lens.

  More specifically, for example, received light data regarding scattered light focused on an imaging mechanism such as a CCD camera is transmitted to a computer via a focusing lens. Both the focusing of the laser beam on the charged particles and the focusing of the scattered light on a CCD camera or the like (computer screen) combine to make precise measurement of the charged particles and the precise identification of the charge amount based on this measurement. Can be realized.

  As can be understood from the above description, according to the charged particle amount specifying device of the present invention, the flow of the gas containing charged particles introduced into the detection unit of the optical system is stopped, so that the DMA having the conventional structure is used. In comparison with the moving speed of the charged particles in the detector, the charged amount of the charged particles can be specified based on the moving speed. For this reason, the moving path of the charged particles required for measurement can be shortened, and the apparatus itself can be downsized. Further, it is possible to measure and identify the measured moving state of the charged particles, and the time required for specifying the charged amount of the charged particles can be greatly shortened. From these facts, it can be said that the charge amount specifying device of the present invention is suitable for a clean room or the like where the charge amount of charged particles is to be specified precisely and quickly with a small-scale device.

It is explanatory drawing explaining the apparatus structure of the charge amount specific apparatus of this invention. It is sectional drawing of the detection part which comprises a charge amount specific device. It is a figure which shows one Embodiment of the operation | movement flow of a charge amount specific apparatus.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is an explanatory diagram for explaining a device configuration of a charge amount specifying device according to the present invention, and FIG. 2 is a cross-sectional view for explaining in detail a detection unit constituting the charge amount specifying device.

  The charge amount specifying device 100 shown in the drawing includes an air A including charged particles p,... Floating in a room such as a clean room, and includes a particle sensor (not shown) that senses the particle size and the like of the introduced charged particles p. The introduction unit 10, the flow rate adjustment unit 30 that adjusts the flow rate of the air A that passes through the introduction unit 10, the detection cell 1 that includes an electric field generation mechanism (not shown), the laser oscillator 4 that irradiates the laser light LZ 1, The detection unit 20a including the optical system unit 2 and the light receiving system unit 3 and a control unit 40 that receives data on charged particles transmitted from the particle sensor and controls the operation of the flow velocity adjustment unit 30 are roughly configured. Yes.

  The introduction unit 10, the flow rate adjustment unit 30, and the detection unit 20 a are connected in series via a flow path L through which air A flows, and include charged particles p (...) Taken into the introduction unit 10 (X1 direction). The air A circulates through the flow path L (X2 direction), the flow velocity is reduced in the process of passing through the flow velocity adjusting unit 30, and is further introduced into the detection unit 20a through the flow path L (X3 direction). At this time, the flow rate control by the flow rate adjustment unit 30 is executed so that the flow rate becomes zero or a speed approximate thereto.

  In addition to the actuator valve 31, the flow rate adjusting unit 30 provides a fluid supply mechanism 32 including a compressor that provides high-pressure fluid or the like to the air A to reduce the speed of the air A, and a control device that performs valve opening / closing control. The actuator valve 31 is closed before the air A is taken into the introduction part 10.

  When the air A is taken in, the actuator valve 31 is controlled to be opened by a control unit 40 built in a computer (not shown), and when the actuator valve 31 is opened, the air A is taken into the introduction unit 10.

  In the introduction unit 10, the particle size and the number of particles of the charged particles p mixed in the air A, and the flow velocity of the air A are sensed by the built-in particle sensor, and the charged particle data and flow velocity data are detected. It is transmitted to the control unit 40. For example, a probe directly connected to an OPC (Optical Particle Counter) can be applied to the introduction unit 10.

  In the control unit 40, the flow rate of the air A is reduced by the flow rate adjusting unit 30, and at least when the air A is introduced into the detection unit 20a on the downstream side, the speed becomes zero or a speed approximate thereto. In addition, adjustment of the opening degree of the actuator valve 31 of the flow velocity adjusting unit 30, adjustment of the flow rate and fluid pressure of the pressure fluid from the fluid providing mechanism 32, and the like are performed.

  The detection unit 20a introduces the charged particles p and includes a detection cell 1 having an electric field generation mechanism such as an internal electrode therein, a laser oscillator 4 that irradiates laser light LZ1, a light transmission system unit 2, and light reception The system unit 3 is generally configured.

  The light transmission system unit 2 includes a condenser lens 2a that condenses the irradiated laser light LZ1, and a focusing lens 2b that focuses the laser light LZ1 that has passed through the condenser lens 2a onto the charged particles p. These are integrated with the frame 2c. On the other hand, the light receiving system unit 3 includes a condenser lens 3a that condenses the scattered light LZ2 emitted from the charged particles p, and a focusing lens 3b that focuses the scattered light LZ2 that has passed through the condenser lens 3a. They are integrated with a frame 3c. Each of the condenser lenses 2a and 3a and the focusing lenses 2b and 3b is preferably mounted so as to be movable along the frames 2c and 3c, and is focused by automatic control. The illustrated example includes an optical system unit adjustment unit 20b that controls the position adjustment of the various lenses.

  In the focusing lens 3b of the light receiving system unit 3, the focusing is executed and focused so that the image focus of the charged particles p is focused by the imaging unit 5 such as a CCD camera disposed in front of the focusing lens 3b. The image related to the charged particles p is transmitted to a computer having the control unit 40 or a separate computer, and the administrator checks the image on the computer screen and calculates the charge amount of the charged particles p using the image. It can be executed.

  The detection unit 2 is a power source for the detection unit 20a, the optical system unit adjustment unit 20b, and the laser oscillator 4 described above, and is also a power source applied to the electrodes constituting the electric field generation mechanism in the detection cell 1. And a power source 20c.

  When the stationary state of the charged particles p introduced into the detection cell 1 is confirmed, a voltage is applied to the electric field generating mechanism to move the charged particles p by gravity and Coulomb force acting on the charged particles p. The laser beam LZ1 is irradiated before and after the movement is confirmed, and the scattered light LZ2 from the charged particles p moving at an arbitrary moving speed is confirmed on the computer screen. The information to be confirmed includes not only the moving speed of the charged particles p but also the number of charged particles p existing in the detection cell 1.

  Here, an embodiment of the operation flow of the charge amount specifying device 100 will be outlined with reference to FIG.

  In the control unit 40, image processing software and actuator valve control software are installed as measurement software. First, the measurement software is activated (step S1).

  Here, as the image processing software, multi-functional TV software, mAgicTV, can be applied. Moreover, MX-8085T-W manufactured by Enomoto Micropump Mfg. Co., Ltd. can be applied as the actuator valve 31. As this actuator valve control software, USB-6251 manufactured by Japan National Instruments Co., Ltd. CHM-AIR can be applied.

  Next, the actuator valve 31 is controlled to open, and the air A including the charged particles p,... Is taken into the introduction unit 10 (step S2).

  When the air A is taken into the introduction unit 10, the actuator valve control software is activated and the flow rate of the air A is reduced by adjusting the opening degree of the valve or closing control, and the value is adjusted to zero or extremely low speed. (Step S3).

  Next, air A is introduced into the detection cell 1 of the detection unit 20a. In the detection cell 1, it is confirmed that the charged particles p are stationary, and the focusing lens 2b for the charged particles p is used. And the focus adjustment of the focusing lens 3b with respect to the imaging unit 5 is executed (step S4).

  Next, the power supply 20c is turned on to generate an electric field in the detection cell 1 and to irradiate a laser beam to capture the scattered light reflected by the charged particles p that move at a relatively low speed due to gravity and Coulomb force. While confirming on the computer screen via the unit 5, the number and particle size of the charged particles p in the detection cell 1 and the moving speed thereof are measured (step S5).

Finally, the charge amount of the charged particle p is specified from the particle size and moving speed of the charged particle p.
Here, an outline of an algorithm for specifying the charge amount from the particle diameter and the moving speed will be described.

When charged particles are introduced into an electric field having an electric field strength E (V / m), the charge amount n _p e (C) of the particles is expressed by the following formula 1.

Where D _p is the particle size (m), v _et is the particle moving speed (m / s), C _c is the Cunningham correction factor, e = 1.602 17733 × 10 ^-19 (C), and the derivation formula is It is shown by the following formula 2. Further, μ is the viscosity of air and is 0.018110 ⁻³ (Pa · s).

Here, K _n in the Knudsen number, when the mean free path of the air and lambda, may be represented by the formula 3 below.

  From the above formulas 1 to 3, it can be seen that the charge amount of the charged particles depends on the particle size and the moving speed of the particles in the electric field. Therefore, the charge amount of the charged particles can be specified by measuring these precisely. can do.

  The above calculation formula is also incorporated in the computer constituting the control unit 40, for example, and after the moving speed and particle size of the charged particles are confirmed on the screen, these read values are substituted into the calculation formula. Thus, the charge amount of the charged particles is specified.

  The number of charged particles sensed by the particle sensor of the introduction unit 10 is compared with the number of charged particles confirmed in the detection cell 1, and the detection rate of the charged particles in the detection cell falls below a certain threshold. In this case, the setting and adjustment of each device described above can be performed again, and the charge amount can be specified again in the same operation flow.

  According to the charge amount specifying device 100 described above, the flow of the gas A containing the charged particles p introduced into the detection unit 20a of the optical system is stopped, and therefore the moving speed of the charged particles p in the detection unit 20a is set. Since the charge amount of the charged particles p can be specified based on the moving speed while being slow, the moving path of the charged particles p required for measurement can be shortened, and the miniaturization thereof can be realized. Become. In addition, since the measurement and identification can be performed while confirming the movement state of the measured charged particles p, the time required for specifying the charge amount of the charged particles p can be greatly shortened.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

DESCRIPTION OF SYMBOLS 10 ... Introduction part, 20 ... Detection unit, 20a ... Detection part, 20b ... Optical system unit adjustment part, 20c ... Power supply, 30 ... Flow rate adjustment part, 31 ... Actuator valve, 32 ... Pressure air supply unit, 40 ... Control part, DESCRIPTION OF SYMBOLS 100 ... Charge amount identification apparatus, L ... Flow path, A ... Air (gas), p ... Charged particle

Claims (4)

Introducing a gas containing floating charged particles, and an introduction unit equipped with a particle sensor for sensing charged particles;
A flow rate adjusting unit that adjusts the flow rate of the gas having a flow rate through the introduction unit, and at least the detection unit stops the gas;
The detection unit into which the gas that has passed through the flow rate adjustment unit is introduced, and an electric field generation mechanism, an irradiation mechanism that irradiates the charged particles with laser light, and a light receiving mechanism that receives scattered light emitted from the charged particles And a detection unit having
A control unit that receives charged particle data transmitted from the particle sensor and controls the operation of the flow rate adjustment unit, and the introduction unit, the flow rate adjustment unit, and the detection unit mutually pass through a flow path. Connected,
In the detection unit, the electric field generation mechanism is activated to generate an electric field in the detection unit, and the movement of the charged particles is caused by the applied electric field and gravity, and the received light data of the scattered light emitted from the moving charged particles Charge amount identifying device for identifying charged particles from a charged particle. In the particle sensor, at least the particle size of the charged particles is measured,
In the detection unit, the moving speed of the charged particles is specified from the received light data of the scattered light,
The charged particle amount specifying device for charged particles according to claim 1, wherein the charged amount is specified from the particle diameter of the charged particles and the moving speed.   The flow rate adjusting unit is an actuator valve whose opening degree is adjusted by the control unit interposed in the flow path, or a fluid providing mechanism that provides fluid to the gas and reduces its speed, and The charged particle amount specifying device for charged particles according to claim 1 or 2, comprising any one of a combination with an actuator valve. The irradiation mechanism includes a laser oscillator, a condensing lens that condenses the laser light emitted from the laser oscillator, and a focusing lens that focuses the laser light that has passed through the condensing lens on the charged particles.
The said light receiving mechanism consists of a condensing lens which condenses the scattered light emitted by a charged particle, and a focusing lens which focuses the scattered light which passed the condensing lens in any one of Claims 1-3. The charge amount specifying device for charged particles as described.

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