JP4224355B2 - Static eliminator using alpha rays - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a static eliminator that neutralizes static electricity generated on the surface of a product, for example, in the process of manufacturing a semiconductor wafer, a glass substrate for liquid crystal, etc., using an ambient ionization source, and in particular, an α-ray source is an ambient ionization source. It is related with the static elimination apparatus used as.
[0002]
[Prior art]
In the process of manufacturing products such as semiconductor wafers, glass substrates for liquid crystals, substrates for magnetic disks / optical disks, printed boards, various films, etc., it is known that charging (static electricity) occurs on the surface due to friction between parts. Yes. In the case of a semiconductor wafer, the charge generated in this way can be a factor of surface contamination due to element destruction, product performance deterioration, or adhesion of dust (fine particles).
[0003]
Therefore, in recent years, various types of static eliminator using an atmospheric ionization source have been used as such a charge removing device. For example, an atmosphere that is ionized and generated by each atmosphere ionization source, including a shielding box that is closed around leaving an ion emission opening, and one or more atmosphere ionization sources that are accommodated in the shielding box 2. Description of the Related Art There is known a static eliminator that emits ions from an ion emission aperture and irradiates a static elimination object. As the ionization source, a tungsten electrode for corona discharge, a UV lamp for ultraviolet radiation, a soft X-ray discharge tube for soft X-ray irradiation, or the like is used (for example, see Patent Document 1).
[0004]
In a static eliminator using corona discharge, an electric field having a predetermined strength or higher is generated at the tip of the electrode by applying a high voltage to the tungsten electrode. Thereby, ions are generated in the atmosphere, and the charge (charge) on the surface of the object to be neutralized is neutralized by the ions.
[0005]
In addition, the static eliminator that uses ultraviolet rays uses an action of irradiating ultraviolet rays into the atmosphere with a UV lamp and thereby ionizing molecules in the atmosphere. For example, nitrogen gas is used as the atmosphere.
[0006]
Moreover, what uses soft X-rays is what irradiates soft X-rays in atmosphere using a soft X-ray discharge tube, and ionizes the molecule | numerator in atmosphere by this.
[0007]
By the way, among the above-mentioned static eliminators, the static eliminator using corona discharge and ultraviolet rays has a problem that ozone that causes damage to the static elimination target is generated, and corona discharge, ultraviolet rays and soft X-rays. However, it has been pointed out that it is difficult to make use of a neutralization device that uses a tungsten electrode, a UV lamp, a discharge tube, etc., which is troublesome to maintain and has a relatively short life. Recently, static elimination devices using α rays have been proposed.
[0008]
In a static eliminator using α rays, generally, a thin piece of americium or polonium is used as an α ray source. The flakes are irradiated with alpha rays having a flight distance of about 4 cm, whereby ions are ionized and generated in the atmosphere.
[0009]
In this static eliminator using alpha rays, instead of a discharge tube having the disadvantages of complicated maintenance and a relatively short life, an alpha ray source (atmosphere ionization source) with a long half-life (long life) is used. In addition, there is no possibility that ozone is generated, which is advantageous in terms of avoiding contamination of products and ease of maintenance. Recently, various products have been proposed (see, for example, Patent Documents 2 and 3). )
[0010]
[Patent Document 1]
JP 2001-176691 A [Patent Document 2]
JP 7-45397 A [Patent Document 3]
Japanese Patent Laid-Open No. 7-211483
[Problems to be solved by the invention]
However, the following problems (1) and (2) have been pointed out in the static eliminator using α rays.
[0012]
(1) Since the flight distance of α-ray particles is as short as about 4 cm, the distance between the α-ray source and the charge removal object should be kept relatively short in order to efficiently bring the ionized and generated atmospheric ions into contact with the charge removal object. I have to ask. In such a case, the case where α-rays are directly irradiated to the object to be neutralized is likely to occur, and this is a factor such as product deterioration of the non-static object.
[0013]
(2) In order to avoid the exposure (direct irradiation) of the object to be neutralized with α rays as described above, the atmospheric ions ionized and generated by the α rays are moved to an ion emission opening separated by a predetermined distance from the α ray source. A method of sending out by blowing is proposed (for example, see Patent Document 1). However, in such a case, the residence time of the atmosphere ions ionized and generated in the α-ray shielding box becomes long, and during that time, recombination between the atmosphere ions occurs, and the necessary and sufficient ions cannot be released. Is known.
[0014]
The present invention has been made paying attention to the above-mentioned problems, and the object of the present invention is to reliably avoid the situation where the α-rays irradiated from the α-ray source are directly irradiated to the static elimination object. Another object of the present invention is to provide a static eliminator using alpha rays that makes it possible to efficiently contact atmospheric ions ionized and generated by alpha ray irradiation with a static elimination object.
[0015]
Other objects and operational effects of the present invention will be easily understood by those skilled in the art by referring to the description of the following specification.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, a static eliminator using α rays according to the present invention includes an α ray shielding box surrounding the α ray source by a shielding surface for shielding α rays and an ion emission opening, and α One or two or more α-ray sources housed in the radiation shielding box, and discharge atmospheric ions ionized and generated by irradiation of α-rays emitted from the respective α-ray sources from the ion emission openings. In this case, the α ray source in the α ray shielding box reaches the position where the charge removal object is installed, and the α ray emitted from each reaches the position where the charge removal object is installed. There is no positioning.
[0017]
The “position where the static elimination target object is installed” is a position where a static elimination target object determined in advance when using the apparatus is to be placed. When the installation position has a certain range, it means the position closest to the static eliminator. This position may coincide with the outer surface of the α-ray shielding box on the side where the ion emission opening is present.
[0018]
Examples of the “α-ray source” include aluminium and polonium.
[0019]
In the case of “alpha rays never reach”, in addition to the case where the α rays collide with the shielding surface and disappear, they do not collide with the shielding surface and interact with surrounding molecules while flying in the atmosphere. It also includes the case where it goes straight while losing kinetic energy and finally disappears. The maximum reachable distance (α ray flight distance) at this time is known from an empirical formula. In the case of α-ray particles having normal kinetic energy of 4 to 7 eMV at atmospheric pressure and in air, it is about 4 cm. It can be considered that α-ray particles themselves do not exist at a point that is more than the α-ray flight distance from the α-ray source.
[0020]
According to the static eliminator using the α-ray of the present invention, it is possible to reliably avoid the situation where the α-ray irradiated from the α-ray source is directly irradiated to the static elimination object. On the other hand, atmospheric ions are favorably generated in the vicinity of the ion emission opening, and the atmospheric ions can be efficiently brought into contact with the static elimination object, so that the static elimination efficiency is improved.
[0021]
Preferably, in the present invention, the outer contour shape of the space where α rays reach is included in the outer contour shape of the α-ray shielding box as viewed from the side where the ion emission opening is provided.
[0022]
According to such a configuration, in a state where the static eliminator is installed with respect to the static eliminator, even if a person's hand may pass around the static eliminator, the static eliminator is also approached. Even if an object is installed, it is safe because it is not directly irradiated with alpha rays.
[0023]
In the present invention, preferably, the α-ray shielding box has an objective shielding surface on a surface on the side of the static elimination object, and the shielding surface is radiated from the α-ray source toward the static elimination object within the α-ray flight distance. Shields alpha rays.
[0024]
According to such a configuration, the neutralization object is brought closer to the neutralization distance than the α-ray flight distance with respect to the neutralization device using the alpha ray while reliably avoiding the situation where the alpha radiation is directly irradiated to the neutralization object. Can be arranged. At this time, since atmospheric ions are also generated near the static elimination object, the number of ions that disappear due to recombination before reaching the static elimination object is reduced, and the static elimination efficiency is increased.
[0025]
In the present invention, it is more preferable that the α-ray shielding box is located on the side away from the flight distance of the α-ray in the direction of the α-ray emitted from the α-ray source along the opening surface of the ion emission opening. It has a shielding surface.
[0026]
The “direction of α rays emitted along the opening surface” may be at least one direction, and need not be all directions.
[0027]
The “side shielding surface” means a shielding surface on the side when the surface with the ion emission opening of the α-ray shielding box is the front.
[0028]
According to such a configuration, the α rays emitted in the direction along the opening surface of the ion emission opening are not shielded by the shielding surface at a distance shorter than the α ray flight distance. A maximum amount of ionized ions can be generated each time.
[0029]
In the present invention, more preferably, the α-ray source is arranged so that the shielding surface of the α-ray shielding box is located ahead of all the α-ray direct directions assumed from the position of the α-ray source.
[0030]
In atmospheric pressure air, the flight distance of α-ray particles is about 4 cm, but depending on the pressure and the type of atmospheric gas, all α-ray particles may not disappear at locations exceeding this flight distance. is there. Therefore, if the α-ray source is arranged so that the wall shielding surface of the α-ray shielding box is located at the front of all α-ray direct directions assumed from the position of the α-ray source, under any use condition However, the possibility of external leakage of α-ray particles can be completely eliminated. In addition, according to such a configuration, since the α-ray source is installed at a position that cannot be seen from the outside, that is, at a deep position, the human body exposure due to inadvertent contact with the α-ray source is good. Can be prevented.
[0031]
In the present invention, it is more preferable that a pair of α-ray sources arranged opposite to each other in the α-ray shielding box so as to sandwich a region where atmospheric ions are ionized and generated by irradiation of α-rays are employed as the α-ray source.
[0032]
According to such a configuration, generation of atmospheric ions can be promoted by a pair of α-ray sources.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a preferred embodiment of a static eliminator using α rays according to the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are merely examples of the present invention, and needless to say, the gist of the present invention is defined only by the claims.
[0034]
The configuration of a static eliminator using α rays in the present embodiment (hereinafter referred to as “α ray neutralizer”) is shown in an internal perspective view of FIG.
[0035]
As shown in the figure, this α-ray static elimination device 1 is formed by affixing a thin piece 12 of americium as an α-ray source to the inner wall surface of a substantially rectangular parallelepiped hollow α-ray shielding box 10. In this example, aluminum is used as the material of the α-ray shielding box. Moreover, in this example, two americium slices 12a and 12b are used, and are pasted on both side walls (10b-1 and 10b-2) along the longitudinal direction of the α-ray shielding box 10 so as to face each other. Yes. In the americium flakes 12 shown in this example, the radiation emitted from each is 3.7 MBq or less, which is not subject to legal regulations.
[0036]
In the central portion of the upper wall surface 10 a of the α-ray shielding box 10, an ion emission opening 11 is provided along the longitudinal direction of the α-ray shielding box 10. In the static eliminator 1, atmospheric ions are constantly ionized and generated by the action of α rays irradiated from the respective americium slices 12, and the atmospheric ions are discharged from the ion emission opening 11 to come into contact with the static elimination object. Let Examples of the static elimination object include a semiconductor wafer, a liquid crystal glass substrate, a magnetic disk / optical disk substrate, a printed circuit board, and various films. The object to be neutralized moves immediately above the ion emission opening 11 in the direction indicated by the arrow X in FIG. 1 (the direction orthogonal to the longitudinal direction of the α-ray shielding box 10, hereinafter referred to as a pass line). (Scanned). Through this scanning, atmospheric ions leaking from the ion emission opening are brought into contact with the surface of the static elimination object, and the charge on the surface of the static elimination object is neutralized.
[0037]
The arrangement state of the americium flakes 12 in the α-ray static elimination apparatus 1 is shown in FIG. This figure is also an AA cross-sectional view of the α-ray shielding box 10 shown in FIG.
[0038]
The arrival distance of α-ray particles irradiated from americium is about 4 cm, and it is known that it has a property of being absorbed when it hits a metal body. In FIG. 2, hatched areas indicated by reference signs S1 and S2 indicate α-ray particle arrival areas from the americium flakes 12 predicted from the properties of the α-ray particles.
[0039]
As is clear from the figure, the highest reaching point in the vicinity of the ion emission opening 11 for α rays irradiated from each of the americium slices 12a and 12b is that the upper wall 10a of the α ray shielding box 10 is an α ray shield ( It may be an objective shielding surface), and is present at a position indicated by symbols P1 and P2 in the same figure (a bare position that does not go outside from the ion emission opening 11).
[0040]
In the present embodiment, the americium flakes 12 are arranged in the α-ray shielding box 10 in consideration of such α-ray maximum arrival points P1 and P2. By arranging the americium flakes 12 in this way, it is possible to reliably avoid a situation in which α rays are directly applied to the static elimination object passing through the pass line located immediately above the ion emission opening 11. On the other hand, since α rays reach the ion emission opening 11, atmospheric ions are always ionized and generated near the ion emission opening 11, and the atmospheric ions are emitted from the ion emission opening 11. Thus, the charge on the surface of the static elimination object can be neutralized satisfactorily.
[0041]
The atmospheric ions emitted from the ion emission opening 11 are not only ionized and generated in the vicinity of the ion emission opening 11 but also ionized in the α-ray shielding box 10 (α-ray particle arrival regions S1 and S2). It is thought that all atmosphere ions generated are included. However, it has been pointed out that the atmospheric ions ionized and generated in the α-ray shielding box 10 may cause recombination between positive and negative ions when the existence density is high or the residence time is long. Therefore, in this embodiment, as is apparent from FIG. 2, the shortest distance between the americium flakes 12a and the americium flakes 12b is kept at least twice as long as the arrival distance of the α-ray particles (about 4 cm). Yes. By doing in this way, collision of alpha ray particles irradiated from both americium flakes 12 is avoided, thereby suppressing recombination of positive and negative ions generated by ionization.
[0042]
However, if the possibility of such recombination between positive and negative ions is not taken into consideration, the shortest distance between the americium flakes 12a and the americium flakes 12b should be less than twice the reach of the α-ray particles (about 4 cm). Can do. In this case, since overlapping regions of α-ray particles from both americium flakes are formed, the generation density of atmospheric ions is increased, and as a result, atmospheric ions contributing to static elimination can be obtained more efficiently. .
[0043]
Next, a modification of the present invention is shown in FIG. The difference from the embodiment shown in FIG. 2 is that the americium flakes 12 are arranged on the side closer to the static elimination object M, and thereby the α-ray maximum reach points P1 and P2 are ion emission. It exists in the point located outside the opening 11 for work. With such a configuration, atmospheric ions are generated near the static elimination object M, so that the number of ions that disappear due to recombination before reaching the static elimination object M is reduced, and the static elimination efficiency is increased.
[0044]
Next, the 1st application example of the alpha ray static elimination apparatus which concerns on this invention is shown in FIG.
[0045]
In the first application example, one americium slice 120 and a container 100 as an α-ray shielding box having a U-shaped cross-section with an open upper surface are used. The figure shows a longitudinal sectional view of the container 100. The americium flake 120 is disposed at the center of the bottom wall of the container 100. In the figure, the hatched area indicated by the symbol S is the α-ray arrival area assumed from the arrangement position of the americium slice 120.
[0046]
Also in the first application example, the highest reaching point of the α ray irradiated from the americium flake 120 toward the ion emission opening 110 exists at a position that does not go outside from the ion emission opening 110. For this reason, similarly, a situation in which α rays are directly applied to the charge removal object passing through the pass line located immediately above the ion emission opening 110 is reliably avoided, while the vicinity of the ion emission opening 110 is avoided. In this case, atmospheric ions are always ionized and generated, and the atmospheric ions are discharged from the ion discharge opening 110, so that the charge on the surface of the object to be neutralized can be satisfactorily neutralized.
[0047]
However, in the first application example, since the container 100 without the upper wall is used, a part of the human body (for example, a finger or the like) accidentally enters from the ion emission opening 110 and touches the americium flake 120 to be exposed to radiation. It also has the disadvantage of being easily affected. From this point, the α-ray shielding box is difficult to directly touch the americium flakes as shown in FIG. 1, FIG. 2, or FIG. It would be preferable to use a closed one.
[0048]
The 2nd application example of the alpha ray static elimination apparatus which concerns on this invention is shown in FIG. This second application example is also a modification of the first application example described above. The difference from the first application example is that the α-ray irradiation region S protrudes outside the ion emission opening 110. However, the outer contour shape of the space where the α rays reach is included in the outer contour shape of the α-ray shielding box viewed from the side where the ion emission opening 110 is provided (inside the virtual line L1 and the virtual line L2). The same applies to the points. According to such a configuration, since atmospheric ions are generated closer to the static elimination object M, the number of ions annihilated by recombination before reaching the static elimination object M is reduced, and the static elimination efficiency is high. can do. On the other hand, in the state where the static eliminator is installed on the object to be neutralized, even if a person's hand may pass around the static eliminator, an object is installed close to the static eliminator. However, α rays are not directly irradiated and it is safe.
[0049]
Next, the 3rd application example of the alpha ray static elimination apparatus which concerns on this invention is shown in FIG.
[0050]
In the third application example, one americium thin piece 120 and an approximately rectangular parallelepiped α-ray shielding box 100 having an upper wall 100a and provided with an ion emission opening 110 on one side are used. The figure is a longitudinal sectional view of the α-ray shielding box 100.
[0051]
In the third application example, the americium flake 120 is disposed on the upper side wall on the left side of the figure. In the figure, the hatched area indicated by the symbol S is the α-ray arrival area assumed from the arrangement position of the americium slice 120. Also, in the figure, a one-dot chain line indicated by a symbol L is an imaginary line connecting the highest α-ray reaching point P in the vicinity of the ion emission opening 110 and the upper end of the americium flake 120 (location closest to the ion emission opening 110). Is a line.
[0052]
Also in the third application example, the highest reaching point P of α rays irradiated from the americium flake 120 toward the ion emission opening 110 is present at the bare minimum position that does not go outside from the ion emission opening 110. A characteristic point is that in the third application example, the shielding surface of the α-ray shielding box is located ahead of all α-ray direct directions (for example, virtual line L) assumed from the position of the americium flake 120. There is in point. By adopting such a configuration, it is possible to completely eliminate the possibility of external leakage of α-ray particles under any use conditions. In addition, according to such a configuration, since the α-ray source is installed at a position that cannot be seen from the outside, that is, at a deep position, the human body exposure due to inadvertent contact with the α-ray source is good. Can be prevented.
[0053]
In addition, in this third application example, the flight distance of α rays (about 4 cm) in the direction of α rays emitted from the americium flake 120 along the opening surface of the ion emission opening 110 (for example, the imaginary line L). It is considered that the side shielding surface 100b is located at a position farther away. With this configuration, α rays emitted in the direction along the opening surface of the ion emission opening 110 are not shielded by the shielding surface at a distance shorter than the α ray flight distance. The maximum amount of ionized ions can be generated for each line.
[0054]
Next, the 4th application example of the alpha ray static elimination apparatus which concerns on this invention is shown in FIG. This example is also a modification of the third application example. The difference from the third application example is that the highest point P1 of the α ray is located outside the ion emission opening 110. With such a configuration, as in the modification shown in FIG. 3, the atmospheric ions are generated closer to the static elimination object M, so that ions that disappear due to recombination before reaching the static elimination object M are obtained. The number can be reduced and the static elimination efficiency can be increased.
[0055]
In the fourth application example, the same applies to the third application example, but the α-ray shielding box 100 has an upper wall 100a functioning as an object shielding surface on the surface of the static elimination object M side. It is set as the structure which has. The upper wall 100a partially blocks α rays radiated from the americium flake 120 toward the static elimination object M. That is, an α ray flight distance range S2 surrounded by a virtual line L2 extending to the original α-line maximum reaching point indicated by reference symbol P2 in FIG. Excluded by the upper wall 100a. For this reason, the static elimination object M can be disposed closer to the static elimination device than the alpha ray flight distance while reliably avoiding the situation where the alpha radiation is directly applied to the static elimination object M. At this time, since atmospheric ions are also generated near the static elimination object, the number of ions that disappear due to recombination before reaching the static elimination object is reduced, and the static elimination efficiency is increased.
[0056]
As is clear from the above description, according to the present embodiment, it is possible to reliably avoid the situation where the α-ray particles irradiated from the americium flakes are directly irradiated (exposed) to the static elimination object. On the other hand, since the atmospheric ions ionized and generated by the α-ray irradiation can be efficiently brought into contact with the static elimination object, a static elimination device with high static elimination efficiency is realized. In addition, by grounding the bottom wall surface of the α-ray shielding box with a conductor, the charge removal efficiency of the charge removal object can be further improved.
[0057]
In the above description, americium flakes are used as the α-ray source, but polonium may be used as the α-ray source.
[0058]
【The invention's effect】
As is clear from the above description, according to the static eliminator of the present invention, the ionization by α-ray irradiation is performed while reliably avoiding the situation where the α-ray irradiated from the α-ray source is directly irradiated to the static elimination object. The generated atmospheric ions can be efficiently brought into contact with the static elimination object.
[Brief description of the drawings]
FIG. 1 is an internal perspective view showing the configuration of an α-ray static elimination apparatus according to the present invention.
FIG. 2 is a diagram showing in detail an arrangement state of americium flakes in the α-ray static elimination apparatus according to the present invention.
FIG. 3 is a diagram showing a modification of the present invention.
FIG. 4 is a diagram (No. 1) showing an α-ray static eliminator to which the present invention is applied.
FIG. 5 is a diagram (No. 2) showing an α-ray static eliminator to which the present invention is applied.
FIG. 6 is a diagram (part 3) illustrating an α-ray static eliminator to which the present invention is applied;
FIG. 7 is a diagram (part 4) illustrating an α-ray static eliminator to which the present invention is applied;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 alpha ray static elimination apparatus 10 alpha ray shielding box 11 ion emission opening 12 americium flake M neutralization object S alpha ray arrival area P alpha ray highest arrival point X path line (static discharge object moving direction)

Claims (6)

an α-ray shielding box surrounding the α-ray source by a shielding surface for shielding α-rays and an ion emission opening; and one or more α-ray sources accommodated in the α-ray shielding box , A neutralization device using alpha rays that discharges atmospheric ions ionized and generated by irradiation of alpha rays emitted from each alpha ray source from an ion emission opening and contacts the static elimination object;
The α-ray source in the α-ray shielding box is such that the α-rays emitted from each do not reach the position where the object to be neutralized is installed, and atmospheric ions are ionized and generated at the position facing the ion emission opening. Thus, the static eliminator using the alpha rays characterized by being positioned. The α ray according to claim 1, wherein the outer shape of the α ray shielding box viewed from the side where the ion emission opening is provided includes the outer shape of the space where the α ray reaches. There was a static eliminator. The α-ray shielding box has an objective shielding surface on the surface on the static elimination object side, and the shielding surface shields α rays emitted from the α-ray source toward the static elimination object within the α-ray flight distance. The static eliminator using the alpha rays of Claim 1 characterized by the above-mentioned. The α-ray shielding box has a side shielding surface at a position farther than the flight distance of the α-ray in the direction of the α-ray emitted from the α-ray source along the opening surface of the ion emission opening. The α-ray static elimination apparatus according to claim 3. 5. The α according to claim 3, wherein a shielding surface of the α-ray shielding box is located ahead of all α-ray direct directions assumed from the position of the α-ray source. Static eliminator using wires. The pair of α-ray sources arranged opposite to each other in the α-ray shielding box so as to sandwich a region in which atmospheric ions are ionized and generated by irradiation with α-rays are adopted as the α-ray source. The static elimination apparatus using the alpha ray in any one of 3 or 4.

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