JPH0521131A - Ionizer for clean room - Google Patents

Abstract

PURPOSE:To provide an ionizer for a clean room which reduces contamination within the clean room due to scattered heavy metals, and also prevents electrodes from being worn without lowering electricity-eliminating performance lowered even when discharge is induced with high voltage applied to the electrodes. CONSTITUTION:Each needle electrode 2 of an ionizer 1 for a clean room is formed into a laminated structure where a nickel layer 3 is laminated by means of plating and the like. By this constitution, the wear resistance of nickel is enhanced, the wear rate of each electrode is thereby reduced to a great extent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to improvements in ionizers used to remove static electricity generated in clean rooms.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor manufacturing clean room, a relative humidity in which static electricity is easily generated is about 40%, and a plastic container having a high electric resistance for transporting wafers and semiconductor elements is used. Static electricity is easily generated due to the heavy use of.
This static electricity causes dust to adhere to the surface of the wafer, destroys ICs and semiconductor elements on the wafer, and reduces the yield of products. Moreover, with the recent increase in the density of semiconductor elements, it is desired to make the clean room ultra-clean, and the electrostatic resistance of the semiconductor elements is also lowered, and such production failures due to static electricity are becoming more and more problems.

Therefore, conventionally, an ionizer has been used as a measure for removing static electricity in a clean room. In this ionizer, a high voltage is applied to the electrodes provided on the ionizer to cause corona discharge, and the ions generated at that time neutralize the charge on the charged body to remove the charge.

[0004]

However, in the above-mentioned ionizer, each time the high voltage is applied to the ion generating electrode to cause corona discharge, the electrode is worn and the worn electrode material is scattered. become. Since the electrode material is composed of heavy metal, heavy metal contamination is caused.

Therefore, a part of the electrode is covered with a quartz tube which is hard to wear to prevent scattering of heavy metals. The quartz tube acts as a dielectric, and when a high voltage is applied to the metal electrode in the quartz tube, the quartz tube covering the metal is polarized and electric charges are induced on the surface of the quartz tube, resulting in high charge density. Corona discharge occurs at the part. However, in discharging from the dielectric, the surface of the dielectric remains charged (polarized state) without discharging all charges. Therefore, even if a voltage whose polarity does not change is applied to the electrode covered with the polarized quartz tube, the charge density on the surface of the quartz tube does not increase, and stable discharge cannot be performed.

Further, in order to cause corona discharge in the dielectric on the electrode surface, it is difficult to stably and constantly generate ions with a power source whose polarity does not change, such as a DC power source or a pulse DC power source. That is, in order to cause corona discharge in the quartz tube, it is limited to the AC power source.
However, it is well known that an ionizer using an AC power supply is inferior in static elimination performance to those using a DC power supply or a pulse DC power supply. That is, in the AC power supply, unlike the method of applying using a DC or pulsed DC power supply, since there is no diffusion of ions due to a spatial electric field, the effective range of the ionizer is narrow and the amount of ions that can be effectively used is small. Therefore, the static elimination performance of the ionizer is deteriorated.

The present invention has been provided in order to solve the above-mentioned problems of the prior art, and its object is to limit the type of power supply when a high voltage is applied to electrodes to cause discharge. It is also an object of the present invention to provide an ionizer for a clean room, which is capable of preventing abrasion of the electrodes and reducing heavy metal contamination in the clean room due to scattering of the electrode material without lowering the charge removal performance.

[0008]

The ionizer for a clean room according to claim 1 of the present invention is an ionizer for a clean room for removing static electricity, in which a metal other than the constituent material of the main body is superposed on the surface to generate ions. It is characterized by having electrodes.

A clean room ionizer according to a second aspect is characterized in that the surface layer of the electrode according to the first aspect is made of nickel.

[0010]

In the ionizer for a clean room according to claim 1 of the present invention having the above-mentioned structure, the ion generating electrode has a layered structure in which metals having different properties are superposed by plating or the like, so that the abrasion resistance of the electrode surface layer is improved. Is improved and wear of the electrodes can be prevented. Therefore, heavy metal contamination in the clean room due to scattering of the electrode material is reduced.

In the clean room ionizer according to the second aspect of the present invention, since nickel is superposed on the electrodes to form a laminated structure, the ionizer has more wear resistance than nickel electrodes, and wear of the electrodes can be prevented. Therefore, heavy metal contamination in the clean room due to scattering of the electrode material is reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the clean room ionizer of the present invention will be described below with reference to FIGS.

That is, the clean room ionizer 1 is
As shown in FIG. 1, a pair of positive and negative needle electrodes 2 is attached. The electrode 2 has a laminated structure in which a coating 3 made of nickel is provided on the surface of a tungsten electrode 2a by plating.

In order to investigate the wear rate of the electrode 2 coated with nickel as described above, the ionizer 1 for a clean room provided with this electrode is used as a clean room 4 as shown in FIG.
Installed in.

That is, in this clean room 4, a high performance filter 5 for supplying purified air into the clean room 4 is provided on the ceiling, and the clean room ionizer 1 of this embodiment is installed below the high performance filter 5. Inside the clean room 4, a charged body 12 having an electrostatic charge +,-on the upper part.
Is provided. In addition, inside the clean room 4,
A cleaning device for supplying highly clean air to the electrode 2 of the ionizer 1 is provided. In this device, an air pump 9, a fine particle deposition device 10 equipped with an ionizer, and a membrane filter 11 are provided on a pipe of an air supply passage 6 having an intake port 7 inside the chamber and a supply port near the electrode 2 of the ionizer 1. ing. By such a cleaning device, the needle electrode 2 is supplied from the supply port 8 with highly clean air in which ultrafine particles of less than about 0.005 μm are also controlled. That is, since there are no ultrafine particles in the atmosphere around the electrode 2, it is possible to check the wear rate of the electrode without any influence such as adhesion of the fine particles to the electrode.

By the way, in such an ionizer 1, ± 13
When a direct current voltage of ± 20 kV is applied at intervals of 1 to 11 seconds, positive ions + and negative ions − are alternately generated from the positive and negative needle electrodes 2. The generated positive and negative ions + and − are transported to the charging body 12 by a circulating air flow in a fixed direction. As a result, the electrostatic charges − and + on the charged body 12 are neutralized by the ions of opposite polarities + and −, respectively, and the charge is removed.

In the clean room 4 as described above, a high voltage is applied to the needle-shaped electrode 2 for a certain period of time to cause discharge,
Stereomicroscope (Nikon SMZ-2T, magnification: 8
0), partial scanning electron microscope (JSM-8 manufactured by JEOL Ltd.)
The electrode was photographed at 40, magnification: 200). The wear amount (volume) of the electrode was geometrically calculated from the image. Since the wear amount of the electrode is proportional to the application time of the high voltage, the wear amount (wear rate) per unit time was used to evaluate the wear resistance of the electrode. At this time, for comparison, thorium
Tungsten alloy (W-Th) electrode, aluminum (A
The amount of wear was similarly measured for the l) electrode, the nickel (Ni) electrode, the titanium (Ti) electrode, and the niobium (Nb) electrode. In addition, the wear rate at this time is standardized by the wear rate of the thorium-tungsten alloy (W-Th) electrode that has been conventionally used for clean rooms.
The wear rate of the Th electrode is expressed as 1.

From the above measurement, the results shown in FIG. 3 were obtained. That is, the wear rate of the Ni electrode containing only nickel is higher than that of the conventional W-Th electrode, but the wear rate of the Ni-coated electrode in which nickel is coated on tungsten is significantly lower than that of other various electrode materials. It was This value is reduced to about 1/100 of that of the conventional W-Th electrode. By the way, it is well known that the wear rate of the electrode containing only tungsten is higher than that of the conventional W-Th electrode, which is not shown in the figure. Therefore, both the Ni electrode and the tungsten electrode alone have a larger wear rate than the conventional W-Th electrode, but the wear rate is significantly reduced by using a laminated structure of two metal materials and compensating for the defects of the metal of the surface layer. Has been done.

According to the ionizer for a clean room of the present embodiment as described above, wear due to electric discharge cannot be avoided with various conventional electrode materials, but nickel is plated on these electrodes to form a laminated structure. , Can compensate for the defects of nickel in the surface layer and make it wear resistant,
The wear of the electrodes can be significantly reduced.

Moreover, the wear rate of this embodiment was measured with an ionizer of the DC pulse voltage application system. However, even in the case of each of the DC voltage application electrode and the AC voltage application electrode, since the electrode surface is a metal, the same result is obtained. The effect can be obtained.

Further, since the ions can be stably and constantly generated, the static elimination performance is not impaired.

The present invention is not limited to the above-mentioned embodiments, and the specific shapes of the respective members, or the mounting positions and methods of the respective members can be appropriately changed.

For example, the types of the electrode material and the surface metal are not limited. That is, wear due to discharge cannot be avoided with only a single metal, but by forming a laminated structure by stacking with another metal by plating or the like, the defects of the metal of the surface layer can be compensated and wear resistance can be obtained. The method of applying a high voltage to the electrodes is not limited, and the wear of the electrodes can be significantly reduced without impairing the static elimination performance.

The method of forming a laminated structure is not limited to plating, and a laminated structure can be formed by a thin film forming method such as sputtering.

The wear rate was measured in a clean room equipped with a cleaning device. According to the present invention, however, the wear rate of the electrode is significantly increased regardless of the presence or absence of the cleaning device and the structure of the clean room. Can be reduced to

[0026]

According to the ionizer for a clean room of the present invention, another metal is laminated on the electrode of the ionizer so as to have a laminated structure, and the defect of the metal of the surface layer is compensated to make it wear resistant, so that a high voltage is applied to the electrode. When generating a discharge, the type of power source is not limited, the charge removal performance is not reduced, and further, the wear of the electrode is prevented, and the heavy metal contamination in the clean room due to the scattering of the electrode material can be reduced. it can.

[Brief description of drawings]

FIG. 1 is a side view showing an embodiment of a clean room ionizer of the present invention and an enlarged sectional view of a main part.

FIG. 2 is a structural explanatory view of a clean room to which the clean room ionizer of FIG. 1 is attached.

FIG. 3 is a graph showing the wear rates of various electrode materials normalized by the wear rate of W-Th electrodes.

[Explanation of symbols]

1 Ionizer for clean room 2 needle electrodes 3 Nickel coating 4 clean room 5 High-performance filter 6 air supply path 7 Intake port 8 supply ports 9 Air pump 10 Fine particle deposition equipment 11 Membrane filter 12 Charged body

Claims (2)

[Claims] 1. An ionizer for a clean room for removing static electricity, comprising an ion generating electrode having a laminated structure in which a metal other than a constituent material of the main body is superposed on a surface thereof. 2. The clean room ionizer according to claim 1, wherein the surface layer is made of nickel.