JP4404257B2 - Corona discharge ionizer - Google Patents

Description

  The present invention relates to a corona discharge ionizer that takes into account an object to be discharged that is easily affected by electric field noise.

In the manufacturing process of an electronic device such as a semiconductor (hereinafter simply referred to as an electronic device), if static electricity is generated in the electronic device, the electronic device is damaged due to high-voltage static electricity, or fine particles suspended in a gas Causes a failure (hereinafter referred to simply as an electrostatic failure) that causes a short circuit of the semiconductor circuit by attracting and adhering to the semiconductor circuit of the electronic device. Such static electricity failure is a major cause of decreasing the manufacturing yield of electronic devices.
This problem can be solved if all the floating substances in the clean room can be removed, but it is practically difficult. Therefore, the problem is solved by eliminating static electricity charged in the electronic device.

  Conventionally, corona discharge ionizers have been widely used for static elimination. The positive ions or the negative ions generated by the corona discharge are jetted so as to reach the object to be neutralized and sprayed on the electronic device being manufactured. At this time, in some cases, air may be blown toward the object to be discharged. Then, the sprayed ions combine the charges charged in the electronic device with ions of different polarity, thereby eliminating static electricity and preventing the occurrence of static electricity failure.

  In such a corona discharge ionizer, there are a method using a DC power supply voltage and a method using an AC power supply voltage. However, in the AC corona discharge ionizer, it is particularly necessary to consider the frequency setting. Specifically, the AC voltage has a frequency lower than about 10 kHz. This is to prevent recombination of positive ions and negative ions. If the frequency of the AC voltage is lower than about 10 kHz, for example, the positive ions generated during the positive voltage are accelerated by the Coulomb force and ejected sufficiently far, so that they are recombined by the negative ions generated later. There is no such situation that there is no change in the static elimination capability. However, if the frequency exceeds about 10 kHz, negative ions are generated immediately after the generation of positive ions and recombined with ions of different polarities in the vicinity, and the amount of ions ejected and thus the amount reaching the object to be removed decreases. Therefore, it is necessary to set the AC frequency to be lower than 10 kHz.

However, the low-frequency AC type corona discharge ionizer efficiently irradiates positive ions and negative ions alternately, but electric field noise is generated due to the electric field generated by the corona discharge and the electric field formed by the positive ions and the negative ions. To do.
This point will be described with reference to the drawings. FIG. 5 is an explanatory diagram of an experimental apparatus for detecting electric field noise by a corona discharge ionizer.
The experimental apparatus includes a corona discharge ionizer 10 and a noise sensor 20, and the noise sensor 20 detects electric field noise generated when ions are ejected from the corona discharge ionizer 10. As shown in FIG. 5, the corona discharge ionizer 10 includes an AC power source 1, a blower tube 2, a voltage supply line 3, a blower unit 4, an emitter 5, and a counter ring electrode 6. And the noise sensor 20 is arrange | positioned in the position where a to-be-eliminated object should be.

The AC power source 1 is a voltage supply unit, and applies a high voltage to the emitter 5.
The blower pipe 2 injects compressed air, which is pressurized and blown from the blower 4, from the blower opening 2 a. The blower pipe 2 is grounded to a zero potential, and shields the electric field generated from the emitter 5.
The voltage supply line 3 applies an AC voltage from the AC power source 1 to the emitter 5. The voltage supply line 3 is provided so as to be drawn into the tube from the outside of the blower tube 2.
The blowing means 4 is a compressor or a fan, and pressurizes the inside of the blowing pipe 2. The blower 2 and the blower 4 form a blower that blows air from the emitter 5 side toward the noise sensor 20 (object to be discharged).
The emitter 5 has a needle-like portion at the tip. The emitter 5 is disposed in the air duct 2 and is electrically connected to the voltage supply line 3 in the air duct 2. Then, the tip of the emitter 5 is provided so as to protrude from the blower opening of the blower tube 2.
The counter ring electrode 6 is a specific example of the counter electrode, and is grounded to zero potential. The counter ring electrode 6 forms a high voltage electric field with the emitter 5 to which a high voltage is applied. In addition, it is good also as a counter electrode, such as a needle shape and a net shape, not the main point limited to a ring shape.

Next, the operation and experiment will be outlined.
The blower 2 is pressurized by the blower 4 and blown from the blower opening 2a. The gas blown is a non-reactive gas or air. Under such circumstances, when an AC high voltage is applied to the emitter 5 from the AC power source 1 through the voltage supply line 3, the periphery of the emitter 5 becomes a plasma state by corona discharge, and air or a non-reactive gas is generated. Positive ions and electrons are generated from gas molecules, and the electrons attach to other molecules to generate negative ions (hereinafter, when positive ions or negative ions are collectively referred to as ions).

  First, if a positive high voltage is applied, the generated positive ions are ejected by the Coulomb force received from the positive electric field. Subsequently, if a negative high voltage is applied, the generated negative ions are Injected by Coulomb force received from a negative electric field. As described above, since positive ions and negative ions are alternately generated in the AC voltage, there is an advantage of balancing the ion balance.

  Now, ions are ejected from the corona discharge ionizer 10 to the noise sensor 20, and the electric field noise generated during the ejection is measured by the noise sensor 20. The noise sensor 20 is configured to form an electric field in the main body, detects electric field fluctuation in the main body affected by electric field noise, and outputs the electric field fluctuation as electric field noise voltage. The behavior of the electric field noise voltage will be described with reference to the drawings. FIG. 6 is an electric field noise voltage-AC voltage frequency characteristic diagram.

As apparent from FIG. 6, when the frequency is 1000 Hz or higher, the electric field noise voltage is hardly detected, but when the frequency is lower than that, the electric field noise gradually increases as the frequency decreases. That is, the electric field noise is large at low frequencies. This is because the lower the frequency, the longer the interval between negative ions and positive ions, so that ions are ejected without causing recombination, and the influence of the electric field generated between these large amounts of ions increases. , Etc. are considered to be a cause. Thus, it has been experimentally found that the electric field noise becomes a problem at a low frequency in the corona discharge ionizer 10.
In view of such a situation, the present inventors have conducted earnest research and experiments on the electric field noise of the corona discharge ionizer, and disclosed a paper considering this electric field noise as Non-Patent Document 1.

Atsushi Nagao, Kazuo Okano, “Effect of power frequency on noise generated by corona discharge ionizer”, September 11, 2003, Annual Meeting of the Japan Society of Electrostatics

Now, in the electronic device manufacturing line where the corona discharge ionizer 10 is most used, the electronic device manufacturing process has been intensively reviewed. For example, in order to reliably prevent the occurrence of an electrostatic failure during the inspection of the electronic device. During the inspection, there is a request to eliminate static electricity with the corona discharge ionizer 10.
However, as described above, the AC corona discharge ionizer 10 generates electric field noise, and there is a problem that the electronic device may be affected by the influence of the electric field noise to malfunction and cannot be inspected. . In particular, among various types of electronic devices, malfunctions are prominent when using FETs (particularly MOSFETs) that use electric fields.
Further, as described above with reference to FIG. 6, the occurrence of electric field noise is small at a high frequency, but there is a problem that the amount of ions generated is reduced by recombination at a high frequency.

  Therefore, there has been a need for a corona discharge ionizer that does not generate electric field noise at commercial power supply frequencies (50 Hz / 60 Hz) or suppresses generation of electric field noise as much as possible. Such a corona discharge ionizer has the advantage of eliminating the need for voltage frequency conversion and simplifying the device. For this reason, a commercial AC power supply type corona discharge type that eliminates static electricity without being affected by electric field noise. The development of ionizers has become an urgent issue.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a corona discharge ionizer that reduces the occurrence of electric field noise without being affected by the power supply frequency.

The corona discharge ionizer according to claim 1 of the present invention is
In the corona discharge ionizer that irradiates the object to be neutralized with ions generated by corona discharge,
An emitter having a needle-like portion formed at the tip;
A voltage supply for applying an alternating voltage to the emitter;
A counter electrode that forms an electric field with an emitter to which an alternating voltage is applied;
A mesh body disposed between the counter electrode and the object to be discharged and grounded;
With
The distance from the end of the emitter to the meshwork and L _E, also when the distance from the meshwork to the neutralization product was L _P, the emitter so as to satisfy L _E> L _P, the mesh-like body and the electric charge removal Is placed,
The electric field generated when generating positive ions or negative ions by corona discharge is blocked by the network by the electrostatic shield effect of the network, and positive ions and negative ions can reach the object to be discharged from the network. Features.

The corona discharge ionizer according to claim 2 of the present invention is
In the corona discharge ionizer according to claim 1,
The net-like body is a plate-like net-like body.

A corona discharge ionizer according to claim 3 of the present invention is
In the corona discharge ionizer according to claim 1,
The mesh body, mesh body der of cylindrical or conical shape that covers the space from the emitter to the neutralization product is, the bottom surface of the mesh body is opposed to the electric charge removal, from the end of the emitter to the bottom surface of the mesh body the distance and L _E, further characterized in that the distance from the bottom surface of the mesh body to the neutralization product was L _P.

The corona discharge ionizer according to claim 4 of the present invention is
In the corona discharge ionizer according to any one of claims 1 to 3,
A blower tube in which the emitter is located in the tube and the tip of the emitter protrudes from the blower port, the blower port is opposed to the counter electrode, and has the same potential as the mesh by grounding;
A blowing means that communicates with the internal flow path of the blower pipe and blows air to the blower pipe;
With
When the inside of the air pipe is pressurized and blown by the air blowing means, the electric field is generated from the air outlet to the object to be discharged through the periphery of the emitter, and the electric field generated from the emitter to the air pipe is electrostatically shielded. The air duct is shielded by the effect .

  According to the present invention as described above, it is possible to provide a corona discharge ionizer that reduces the occurrence of electric field noise without being affected by the power supply frequency.

Next, the best mode for carrying out the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a corona discharge ionizer 10A of this embodiment.
As shown in FIG. 1, the corona discharge ionizer 10 </ b> A of this embodiment includes an AC power source 1, a blower tube 2, a voltage supply line 3, a blower unit 4, an emitter 5, a counter ring electrode 6, and a mesh body 7. The corona discharge ionizer 10 </ b> A discharges ions by spraying ions to the object 30 to be discharged.
The object to be neutralized 30 is, for example, an electronic device that flows through a production line in an electronic device manufacturing factory, and is charged with either a positive charge or a negative charge. This tendency is attributed to, for example, a machine such as a manufacturing apparatus or a manufacturing line. Here, for the sake of concrete explanation, it is assumed that the object to be neutralized 30 is charged with a lot of negative charges.

In this embodiment, in addition to the corona discharge ionizer 10 of the prior art shown in FIG. 5, a plate-like mesh body 7 is arranged between the emitter 5 and the object to be discharged 30 and grounded. is there. More preferably, the distance of the end of the emitter 5 (needle point) to net body 7 and L _E, also when the distance from the meshwork 7 until the neutralization was 30 was L _P, L _E> L _P It was made to satisfy. And as small as possible this L _P, that is, the mesh body 7 as close as possible to the object to be electric charge removal 30.

In this embodiment, the mesh body 7 functions as an electrostatic shield body, and the mesh body 7 shields the electric field existing from the end of the emitter 5 to the mesh body 7. Therefore, the electric field does not reach the object 30 to be removed.
In addition, when the object to be neutralized 30 is negatively charged, the mesh body 7 is positively charged by electrostatic induction. Therefore, of the positive ions and negative ions that have reached the mesh body 7, negative ions are present in the mesh body 7. The positive ions are preferentially attracted, and the positive ions pass through the reticulate 7 without being attracted, and the positive ions preferentially reach the object 30 to be neutralized, and the object 30 is neutralized.

Various modifications can be made in this embodiment. For example, in FIG. 1, air is blown by a blower unit including the blower pipe 2 and the blower unit 4. The emitter 5 may be removed to simply surround the emitter 5 with a tube.
Further, since the electric field is surely shielded by sufficiently widening the mesh body 7, the structure in which the blower pipe 2 that also functions as a shield is removed and the blower means is disposed above the emitter is adopted. However, you may make it blow toward the to-be-eliminated object 30. FIG. These configurations are selected as appropriate. However, if the mesh body 7 having a sufficiently large area covers the object to be neutralized 30, the electric field noise can be cut off and the effects of the present invention can be achieved.

  In the corona discharge ionizer 10A of the present embodiment described above, even if ions are generated with a low-frequency AC voltage of a commercial power supply, electric field noise does not reach the object 30, and for example, a charge removal that is easily affected by an electric field such as a MOSFET. The object 30 can be inspected simultaneously with static elimination, and the range of use has been widened.

Next, another embodiment for carrying out the present invention will be described with reference to the drawings. FIG. 2 is a configuration diagram of another embodiment of the corona discharge ionizer 10B.
As shown in FIG. 2, the corona discharge ionizer 10 </ b> B of this embodiment includes an AC power source 1, a blower tube 2, a voltage supply line 3, a blower unit 4, an emitter 5, a counter ring electrode 6, and a frustoconical mesh body 8. Yes. Then, the corona discharge ionizer 10 </ b> B discharges ions by spraying ions on the object to be removed 30. Although the object to be neutralized 30 is charged with either a positive charge or a negative charge, for the sake of concrete explanation, it is assumed that the object to be neutralized 30 is charged with a lot of negative charges.

  This embodiment is novel in that a frustoconical mesh body 8 having a frustoconical shape is arranged in place of the plate-like mesh body 7 of the corona discharge ionizer 10A described above with reference to FIG. The counter ring electrode 6 is fixed to the upper opening of the frustoconical mesh body 8, the frustoconical mesh body 8 and the counter ring electrode 6 are electrically connected, and the counter ring electrode is grounded. The frustoconical mesh body 8 is also grounded. If the position of the upper opening of the frustoconical mesh body 8 is arranged at a position sufficiently higher than the air outlet 2 a of the air duct 2, the emitter 5 is shielded by the electrostatic shielding function of the air duct 2 and the frustoconical mesh body 8. The electric field does not reach the outside.

More preferably, the distance of the end of the emitter 5 (needle point) to the bottom surface of the frustoconical mesh body 8 (the surface facing the object of electric charge removal 30) and L _E, also be from the bottom of the frustoconical mesh body 8 When the distance to the static elimination object 30 is L _P , L _E > L _P is satisfied. And as small as possible this L _P, i.e., the distance between the bottom and the electric charge removal 30 of frustoconical meshwork 8 is intended that as short as possible, the electrostatic In such corona discharge type ionizers 10B The shielding effect is enhanced, and the ability to remove electric field noise can be enhanced.

When the corona discharge ionizer 10B of this embodiment is operated to irradiate the object 30 with the ions, the truncated cone network 8 functions as an electrostatic shield, and the truncated cone network from the end of the emitter 5 is used. Since the frustoconical mesh body 8 shields the electric field existing in the electric field 8, the electric field does not reach the object 30 to be neutralized.
In addition, when the object to be neutralized 30 is negatively charged, the bottom surface of the frustoconical mesh body 8 is positively charged by electrostatic induction, so negative ions are preferentially attracted to the frustoconical mesh body 8, The positive ions pass through the frustoconical mesh body 8 without being attracted, and the object to be neutralized 30 is neutralized.

Various modifications can be made in this embodiment. For example, in FIG. 2, air is blown by the blower pipe 2 and the blower 4, but the blower 4 is removed and the emitter 5 is removed as in the embodiment of FIG. It may be simply surrounded by a tube.
In addition, since the electric field is reliably shielded by being covered with the truncated cone-shaped mesh body 8, a configuration is adopted in which the blower pipe 2 that also functions as a shield is removed, and a blower is disposed above the emitter. You may make it blow toward the to-be-eliminated object 30. FIG.
Furthermore, the shape of the frustoconical mesh body 8 is not limited to the frustoconical shape, but may be a cylindrical or cone-shaped net that covers the space from the emitter 5 to the object to be discharged. The cylinder can be a cylinder or a polygonal cylinder. The cone can be a cone or polygonal cone.
Further, since the upper opening of the frustoconical mesh body 8 has the same shape as the counter ring electrode 6, the counter ring electrode 6 may be omitted and the frustoconical mesh body 8 may be grounded.
These configurations are appropriately selected. However, if a net is used so as to cover the emitter 5 reliably, electric field noise can be cut off and the effects of the present invention can be achieved.

The corona discharge ionizer 10B of the present embodiment described above also prevents the electric field noise from reaching the target object 30 even if ions are generated with a low frequency AC voltage of a commercial power supply, and for example, the static elimination that is easily influenced by the electric field such as a MOSFET. The object 30 can be inspected simultaneously with static elimination, and the range of use has been widened.
The frustoconical mesh body 8 is basically shielded so that the electric field generated by the emitter 5 does not leak to the outside, so that the electric field does not reach the outside of the frustoconical mesh body 8. What is necessary is that the size can be reduced as compared with the plate-like mesh body 7 shown in FIG.

Next, a corona discharge ionizer which is an embodiment for configuring the present invention more specifically and verifying the effect with specific numerical values will be described with reference to the drawings. FIG. 3 is a configuration diagram of the corona discharge ionizer according to the first embodiment, and FIG. 4 is an electric field noise voltage-power frequency characteristic diagram according to the first embodiment. The present embodiment is assembled in order to specifically verify the best mode described above.
As shown in FIG. 3, the corona discharge ionizer 10 </ b> A includes an AC power source 1, a blower tube 2, a voltage supply line 3, a blower unit 4, an emitter 5, a counter ring electrode 6, and a plate-like net member 7. (It is the same structure as FIG. 1). And the noise sensor 20 is arrange | positioned in the position where a to-be-eliminated object should be.
With such a corona discharge ionizer 10A, the frequency of the AC voltage applied to the emitter 5 was changed, and the electric field noise voltage output by the noise sensor 20 was compared based on the presence or absence of the mesh 7.

  As is apparent from FIG. 4, in the case of the conventional technique (that is, in the state where the mesh body 7 is not present), the electric field noise voltage is detected below a certain specific frequency. It has been found that an AC type corona discharge ionizer 10A using a commercial power supply frequency (50 Hz / 60 Hz) applied voltage can be used without detecting the voltage.

  The corona discharge ionizers 10A and 10B of the present invention have been described above. In this embodiment, the generation of electric field noise is suppressed without depending on the frequency of the AC voltage applied to the emitter, and for example, even if the object to be discharged is susceptible to electric field noise such as a MOSFET, it can be discharged. .

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the corona discharge type ionizer of the best form for implementing this invention. It is a block diagram of the corona discharge type ionizer of another form. 1 is a configuration diagram of a corona discharge ionizer of Example 1. FIG. It is an electric field noise voltage-AC voltage frequency characteristic figure by Example 1. FIG. It is explanatory drawing of the experimental apparatus which detects the electric field noise by a corona discharge type | mold ionizer. It is an electric field noise voltage-AC voltage frequency characteristic figure.

Explanation of symbols

10A, 10B: Corona discharge type ionizer 1: AC power supply 2: Blower tube 2a: Blower port 3: Voltage supply line 4: Blowing means 5: Emitter 6: Counter ring electrode 7: Mesh body 8: frustoconical mesh body 20: Noise Sensor 30: Charged object

Claims (4)

In the corona discharge ionizer that irradiates the object to be neutralized with ions generated by corona discharge,
An emitter having a needle-like portion formed at the tip;
A voltage supply for applying an alternating voltage to the emitter;
A counter electrode that forms an electric field with an emitter to which an alternating voltage is applied;
A mesh body disposed between the counter electrode and the object to be discharged and grounded;
With
The distance from the end of the emitter to the meshwork and L _E, also when the distance from the meshwork to the neutralization product was L _P, the emitter so as to satisfy L _E> L _P, the mesh-like body and the electric charge removal Is placed,
The electric field generated when generating positive ions or negative ions by corona discharge is blocked by the network by the electrostatic shield effect of the network, and positive ions and negative ions can reach the object to be discharged from the network. Characteristic corona discharge ionizer. In the corona discharge ionizer according to claim 1,
The corona discharge ionizer is characterized in that the mesh body is a plate-like mesh body. In the corona discharge ionizer according to claim 1,
The mesh body, mesh body der of cylindrical or conical shape that covers the space from the emitter to the neutralization product is, the bottom surface of the mesh body is opposed to the electric charge removal, from the end of the emitter to the bottom surface of the mesh body the distance and L _E, also corona discharge ionizer, characterized in that the distance from the bottom surface of the mesh body to the neutralization product was L _P. In the corona discharge ionizer according to any one of claims 1 to 3,
A blower tube in which the emitter is located in the tube and the tip of the emitter protrudes from the blower port, the blower port is opposed to the counter electrode, and has the same potential as the mesh by grounding;
A blowing means that communicates with the internal flow path of the blower pipe and blows air to the blower pipe;
With
When the inside of the air pipe is pressurized and blown by the air blowing means, the electric field is generated from the air outlet to the object to be discharged through the periphery of the emitter, and the electric field generated from the emitter to the air pipe is electrostatically shielded. A corona discharge ionizer characterized in that the air duct is shielded by the effect .

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