Dust collection method

Abstract

To provide a dust collection method that can stably collect particles in a vacuum chamber.SOLUTION: A conveyed object Gs for dust collection is one in which at least the surface is covered with an insulating material, the surface of an object to be transported for dust collection is charged to a positive or negative potential using an ionizer in the air. At this time, the charging potential is set to a potential lower than the discharge starting potential determined by Paschen's law (charging step). The charged object to be transported for dust collection is transported to a vacuum chamber Lc, Pc1 to Pc3 in a vacuum atmosphere, and the particles existing inside the object are attached to the object to be transported for dust collection (dust collection step).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a dust collection method, and more particularly to a method capable of efficiently collecting particles within a vacuum processing chamber that constitutes a vacuum processing apparatus. [Background technology]

[0002] In the manufacturing process of flat panel displays, semiconductor devices, and the like, vacuum processing apparatuses are widely used that can consistently perform various vacuum processes, such as film formation, heat treatment, and etching, in a vacuum atmosphere on objects to be processed, such as glass substrates and silicon wafers (hereinafter simply referred to as "substrates"). Such vacuum processing apparatuses generally have a load lock chamber and at least one vacuum processing chamber. Then, the substrate is carried into the load lock chamber in an atmospheric atmosphere while being isolated from other chambers, and after the load lock chamber is evacuated to a predetermined pressure, the substrate is transferred to the vacuum processing chamber in a vacuum atmosphere, and each vacuum processing can be performed on the substrate. The substrate that has been subjected to various vacuum processing is transferred again to the load lock chamber, and, while being isolated from other chambers, the substrate is returned to the atmospheric atmosphere by introducing, for example, nitrogen gas (or so-called dry air) as an inert gas through a vent line, and then is collected from the load lock chamber.

[0003] Incidentally, after the initial installation of a vacuum processing apparatus or after the vacuum processing apparatus is restarted due to maintenance or the like, fine particles are often found floating in the vacuum processing chamber. In addition, during operation of the vacuum processing apparatus, particles such as peeled material from the surfaces of parts such as adhesion prevention plates present in the vacuum processing chamber and abrasion powder generated with the operation of movable parts such as gate valves may be floating in the air. Such particles are a factor in reducing product yields, and therefore need to be removed as quickly as possible.

[0004] Such a method of collecting particles is known, for example, in Patent Document 1. In this method, a glass substrate having an adhesive layer on its surface is used as a dust collection transport object, and the dust collection transport object is charged before being transported to a vacuum processing chamber, and the charged object is transported into the vacuum processing chamber, so that floating particles are attached to the adhesive layer and collected. In order to efficiently collect particles floating in the vacuum processing chamber, it is preferable that the dust collection transport object is charged to as high a potential as possible. However, it has been found that even if a dust collection transport object previously charged in the air atmosphere is transported and set in a load lock chamber, and the load lock chamber is evacuated to a predetermined pressure and then transported to the vacuum processing chamber (hereinafter, the path along which the substrate and the dust collection transport object are transported in this manner is referred to as the "transport path"), there are cases in which the particles are not efficiently collected.

[0005] Therefore, the present inventors have conducted extensive research and have come to the following findings. That is, for example, a substrate stage is generally provided in a load lock chamber or each vacuum processing chamber for a transfer robot to receive and hold a substrate during processing, and not only are there components that function as electrodes during processing around the substrate stage, but the walls of the load lock chamber or each vacuum processing chamber also function as electrodes by usually being grounded. In addition, with the miniaturization of vacuum processing apparatuses, there are also locations on the transport path where a substrate is transported in close proximity to components that can function as electrodes, such as chamber walls and gate valve components. Moreover, even if the load lock chamber is evacuated to a predetermined pressure, the pressure at the start of transporting the charged dust collection transport object is not necessarily constant at all times. For this reason, the present inventors have come to the findings that, depending on the potential when the dust collection transport object is charged, a spark discharge occurs during the transport path until the dust collection transport object is transported along the transport path, and the charge amount after the charge is removed is not stable. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-126092 A Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made based on the above findings, and an object of the present invention is to provide a dust collection method capable of stably collecting particles inside a vacuum chamber. [Means for solving the problem]

[0008] In order to solve the above problems, a vacuum processing apparatus has a load lock chamber and a vacuum processing chamber, and can carry a processing object into the load lock chamber in an atmospheric atmosphere, and after the load lock chamber is turned into a vacuum atmosphere, the processing object is transported to the vacuum processing chamber in a vacuum atmosphere, and a dust collection method of the present invention for collecting particles present in the vacuum processing chamber in a vacuum atmosphere includes the steps of: carrying an object to be collected, the object having at least a surface covered with an insulating material, and transporting the object in the atmospheric atmosphere; in the load lock chamber or before loading into the air load lock chamber The dust-collecting transport object is charged to a positive or negative potential, and the charged potential is set to a potential lower than the discharge start potential determined by Paschen's law in nitrogen gas. ±500V and a dust collection process in which the load lock chamber and the vacuum processing chamber are evacuated to a predetermined pressure at which the charged potential when the dust collection transport object is positively or negatively charged in the charging process is maintained, and then the dust collection transport object is transported from the load lock chamber to the vacuum processing chamber in a state in which no gas is introduced, and particles present inside the vacuum processing chamber are attached to the dust collection transport object.

[0009] Here, the inventors have conducted extensive research focusing on Paschen's law for a specific gas species (nitrogen gas), and have found that since the spark voltage V (discharge start potential) at which a spark discharge occurs is expressed as a function V=f(pd) of the product of the gas pressure p(Pa) and the electrode distance d(m), if a configuration is adopted in which the dust collection transport object is charged in the atmosphere to a positive or negative potential lower than the discharge start potential (spark voltage V) determined by Paschen's law based on the pressure in the transport path and the electrode distance between the dust collection transport object and the electrode in this transport path, the dust collection object is transported to the vacuum processing chamber in a vacuum atmosphere while maintaining its charged potential, without being discharged by spark discharge occurring during the transport. This makes it possible to stably collect particles in the vacuum chamber.

[0010] In addition, regarding the potential when charging the transport object for dust collection, if it is set to a potential slightly lower than the lower limit of the discharge start potential in Paschen's law for nitrogen gas, which is the main component of the atmosphere, for example, it is advantageous that the particles can be transported to the vacuum processing chamber while maintaining the charged potential, regardless of the configuration of the vacuum processing apparatus from which the particles are to be collected (i.e., the pressure in the transport path and the distance between the electrodes), and the particles can be collected stably and efficiently. In addition, when various vacuum processes are performed in the vacuum processing chamber, rare gases such as argon gas and helium are sometimes used, but with this type of gas, the discharge start potential determined by Paschen's law is extremely low, and depending on the partial pressure of the rare gas in the vacuum processing chamber in the vacuum atmosphere, a spark discharge may occur immediately. For this reason, in the present invention, it is preferable to keep a state in which no gas is introduced into each chamber of the vacuum processing apparatus during the dust collection process.

[0011] In the present invention, the dust collection transport object is charged to either a positive or negative potential in the charging step, and is designated as a first transport object, and the dust collection transport object is charged to the other of either a positive or negative potential in the charging step, and is designated as a second transport object. Repeat the alternating transport several times.It is preferable to further include a step of: According to this, for example, by transporting the first transported object charged with a positive potential, particles having a negative potential such as C (carbon), O (oxygen), F (fluorine), AlOx (aluminum oxide), and Fe (iron compound) can be collected, while by transporting the second transported object charged with a negative potential, particles having a positive potential such as Si (silicon and glass material) and SUS (stainless steel) can be collected, so that particles can be collected more efficiently. Note that, according to the intensive research of the present inventors, there are cases where particles having a negative potential originally become positively charged or particles having a positive potential originally become negatively charged due to some factor, so that by adopting the above-mentioned configuration for transporting the first transported object and the second transported object, particles can be collected more stably and effectively, which is advantageous.

[0012] However, when vacuum processing is performed on a substrate in a vacuum processing chamber, if a substrate (used in production) charged with a positive or negative potential is transported into the vacuum processing chamber, a problem occurs in that particles in the vacuum processing chamber are electrostatically attracted to the substrate. For this reason, it is common to provide a charge removing means such as an ionizer, and after performing charge removing processing on the substrate, transport the substrate into a load lock chamber. In the present invention, it is preferable to use an ionizer disposed in the load lock chamber to charge the dust collection transport object, and to spray positive ions or negative ions from the ionizer onto the surface of the dust collection transport object to charge the dust collection transport object. According to this, since the ionizer provided for removing charge from the substrate can be used for charging the dust collection transport object, it is advantageous that a conventional vacuum processing device can be used as it is without providing a separate device for charging. [Brief description of the drawings]

[0013] [Figure 1] 1 is a plan view of a vacuum processing apparatus in which a dust collection method according to the present invention is carried out; [Diagram 2] 1 is a cross-sectional view of a vacuum processing apparatus in which a dust collecting method of the present invention is carried out. [Diagram 3] 6 is a graph illustrating the setting of potential when charging the dust-collection transport object. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, with reference to the drawings, an embodiment will be described in which the processing object is a glass substrate (hereinafter, simply referred to as "substrate Gs"), the dust collection transport object is a glass dummy substrate Dm not used for production, and the vacuum processing for the substrate Gs is a film formation process by a sputtering method, and the dust collection method of the present invention is applied to a vacuum processing apparatus. In the following, the terms indicating directions such as "upper" and "lower" will be described based on FIG. 2.

[0015] 1, Cm is a so-called cluster tool type vacuum processing apparatus to which the dust collection method of the present invention can be applied. The vacuum processing apparatus Cm includes a transfer chamber Tc in which a vacuum transfer robot R1 is disposed, and a load lock chamber Lc and vacuum processing chambers Pc1, Pc2, and Pc3, which are disposed so as to surround the transfer chamber Tc via gate valves Gv1 to Gv4. As the vacuum transfer robot R1, for example, a known so-called frog leg type having a robot arm 10a and a robot hand 10b provided at the tip of the robot arm 10a and holding a substrate Gs can be used, and as the gate valves Gv1 to Gv4, known valve bodies stored in a valve box can be used, so detailed description is omitted here.

[0016] The transfer chamber Tc, the load lock chamber Lc, and each of the vacuum processing chambers Pc1, Pc2, and Pc3 are connected to an exhaust pipe leading to a vacuum pump unit (not shown), and a vent valve (not shown) is attached, so that, for example, nitrogen gas can be introduced to return the atmosphere to the atmospheric environment. An opening / closing door Dr is provided on the outer wall surface of the relatively small-volume load lock chamber Lc, and through the opening / closing door Dr, an atmospheric transfer robot R2 having a robot hand 11 can carry a substrate Gs into the load lock chamber Lc in an atmospheric atmosphere with the processing surface facing upward, or carry a processed substrate Gs out of the load lock chamber Lc.

[0017] As shown in Fig. 2, an ionizer In is provided on the outer wall surface of the load lock chamber Lc, facing the substrate Gs transported by the atmospheric transport robot R2. The ionizer In discharges electricity from the substrate Gs by irradiating the substrate Gs with positive ions or negative ions, and is also used to charge a dummy substrate Dm, which will be described later. As the ionizer In, a known one can be used, and therefore a detailed description thereof will be omitted here. The installation position of the ionizer In is not limited thereto, and for example, the ionizer In can be installed inside the load lock chamber Lc.

[0018] Each of the vacuum processing chambers Pc1, Pc2, and Pc3 is a component of a sputtering apparatus. Although not specifically illustrated or described, a cathode unit having a target is disposed on the upper wall of each of the vacuum processing chambers Pc1, Pc2, and Pc3, and a gas introduction means is provided for introducing a reactive gas such as a rare gas such as argon gas or nitrogen gas. By sputtering the target, sputtered particles scattered from the target can be attached and deposited on the film formation surface of the substrate Gs to form a predetermined thin film.

[0019] When the vacuum processing is performed on the substrate Gs by the vacuum processing device Cm, the substrate Gs is transferred by the atmospheric transfer robot R2 into the load lock chamber Lc in the atmospheric environment with the processing surface facing upward. At this time, the transfer chamber Tc and each of the vacuum processing chambers Pc1, Pc2, and Pc3, which are isolated from each other, are maintained at a predetermined pressure (for example, 1×10 -5 The load lock chamber Lc is evacuated to a predetermined pressure (Pa). When the load lock chamber Lc is evacuated to a predetermined pressure, the gate valve Gv1 is opened and the vacuum transfer robot R1 receives the substrate Gs from the load lock chamber Lc, transfers it to the first vacuum processing chamber Pc1 where a first thin film is formed on the substrate Gs, and places it on the stage St. In this state, the gate valve Gv2 is closed and the first vacuum processing chamber Pc1 reaches a predetermined pressure, and the first thin film is formed on the substrate Gs by sputtering.

[0020] Next, the substrate Gs is transferred by the vacuum transfer robot R1 to the second and third vacuum processing chambers Pc2 and Pc3 in order to form the second and third thin films, and then transferred to the load lock chamber Lc. Finally, the inside of the load lock chamber Lc is returned to the atmospheric atmosphere, and the processed substrate Gs is collected by the atmospheric transfer robot R2. Thus, in this embodiment, there is a path (transfer path) along which the substrate Gs is transferred by the vacuum transfer robot R1 between the load lock chamber Lc and each vacuum processing chamber Pc1, Pc2, and Pc3 via the transfer chamber Tc, or between each vacuum processing chamber Pc1, Pc2, and Pc3. At this time, for example, when the substrate Gs passes through the inside of the valve box of the gate valve Gv1 to Gv4, the substrate Gs passes in close proximity to parts that can function as electrodes, such as the valve box inner wall surface and the valve body.

[0021] Incidentally, after the initial installation of the vacuum processing apparatus Cm, or after the vacuum processing apparatus Cm is restarted due to maintenance such as replacement of the target or the adhesion protection plate (not shown), fine particles are often floating in each vacuum processing chamber Pc1, Pc2, Pc3. In addition, during operation of the vacuum processing apparatus Cm, particles such as peeled off from the surface of components such as the adhesion protection plate (not shown) present in each vacuum processing chamber Pc1, Pc2, Pc3, and abrasion powder generated with the operation of movable components such as the gate valves Gv1 to Gv4 may float. For this reason, prior to performing a film formation process on multiple substrates Gs, or during performing a vacuum process on multiple substrates Gs, the particles are removed. Below, a dust collection method of this embodiment in which particles present in each vacuum processing chamber Pc1, Pc2, Pc3 in the vacuum atmosphere of the vacuum processing apparatus Cm are collected by attaching them to a dummy substrate Dm will be specifically described.

[0022] A dummy substrate Dm, which is an insulating glass substrate, is prepared. The dummy substrate Dm is not limited to the above, as long as at least the upper surface can be charged to a positive or negative potential by the ionizer In, and for example, a substrate having an insulating material formed on its surface can be used. The open / close door Dr of the load lock chamber Lc in an atmospheric atmosphere, which is isolated from the transfer chamber Tc, is opened, and the dummy substrate Dm is transferred into the load lock chamber Lc by the atmospheric transfer robot R2 with its insulating surface facing up. When the dummy substrate Dm passes under the ionizer In, for example, positive ions are sprayed by the ionizer In over the entire upper surface of the dummy substrate Dm. As a result, the upper surface of the dummy substrate Dm is charged to a predetermined positive or negative potential (charging process).

[0023] Here, nitrogen gas is used to open the load lock chamber Lc to the atmosphere, so the inside of the load lock chamber Lc, which is in an atmospheric environment, is usually in a nitrogen-rich state. Based on this, Paschen's law for nitrogen gas shows that the discharge inception potential (spark voltage V) is expressed as a function V=f(pd) of the product of the gas pressure p(Pa) and the electrode distance d(m), and the Paschen curve Cp is as shown in Figure 3. At this time, with the Paschen curve Cp as the boundary, the region E1 located above the Paschen curve Cp is the "spark discharge region," and the region E2 located below the Paschen curve Cp is the "non-spark discharge region," and the inflection point of the spark voltage with respect to the product of the gas pressure and the electrode distance is the lower limit (Lp) of the discharge inception potential (±500V).

[0024] Therefore, the potential when charging the dummy substrate Dm is set as follows. That is, the charged potential of the dummy substrate Dm is set so that it is always within the region E2 and as close as possible to the Paschen curve Cp, taking into consideration the type of the dummy substrate Dm, the pressure when the load lock chamber Lc in the atmospheric air is evacuated (i.e., the set pressure when the transfer of the dummy substrate Dm from the load lock chamber Lc to each vacuum processing chamber Pc1, Pc2, Pc3 is started), the pressure in the transfer path of the vacuum processing device Cm, such as the pressure in each vacuum processing chamber Pc1, Pc2, Pc3 during the dust collection process, and the inter-electrode distance between the dummy substrate Dm and the electrode in the transfer path. In this embodiment, the dummy substrate Dm is charged to a positive potential (+500V) slightly lower than the lower limit value (Lp) of the discharge start potential so that it can be applied to any configuration of the vacuum processing device Cm.

[0025] When the dummy substrate Dm charged to the positive potential is carried into the load lock chamber Lc (hereinafter, the dummy substrate Dm carried in first is referred to as the first transported article), the open / close door Dr is closed, and the inside of the load lock chamber Lc is evacuated to a predetermined pressure (for example, 1 Pa) by a vacuum pump (not shown). At this time, since the dummy substrate Dm is charged to a positive potential (+500 V) slightly lower than the lower limit value (Lp) of the discharge start potential, there is no problem such as discharging. When the inside of the load lock chamber Lc is evacuated to a predetermined pressure, the gate valve Gv1 is opened, and the dummy substrate Dm in the load lock chamber Lc is received by the vacuum transport robot R1, transported to the first vacuum processing chamber Pc1, and temporarily placed on the stage St. In this state, the gate valve Gv2 is closed and left for a predetermined time. As a result, particles mainly negatively charged floating in the first vacuum processing chamber Pc1 are attached to the surface of the dummy substrate Dm and collected. After being transferred to the first vacuum processing chamber Pc1, the substrate may be transferred to the second vacuum processing chamber Pc2 without being temporarily placed on the stage St.

[0026] Next, the gate valves Gv2 and Gv3 are opened, and the dummy substrate Dm in the first vacuum processing chamber Pc1 is received by the vacuum transfer robot R1, and is transferred to the second vacuum processing chamber Pc2 and temporarily placed on the stage St. In this state, the gate valves Gv2 and Gv3 are closed and left for a predetermined time, and similarly, particles mainly negatively charged floating in the second vacuum processing chamber Pc2 are attached to the surface of the dummy substrate Dm and collected (dust collection process). This series of operations is repeated, and the dummy substrate Dm is transported to the load lock chamber Lc. Finally, after the inside of the load lock chamber Lc is returned to the atmospheric atmosphere, the dummy substrate Dm is collected by the atmospheric transfer robot R2. At this time, when the dummy substrate Dm passes under the ionizer In, for example, negative ions may be sprayed by the ionizer In over the entire surface of the upper surface of the dummy substrate Dm to neutralize the charge on the upper surface of the dummy substrate Dm. Moreover, the dummy substrate Dm collected by the atmospheric transfer robot R2 can be reused as the dummy substrate Dm after cleaning, or can be used as the dummy substrate Dm for pre-sputtering.

[0027] After the dummy substrate Dm as the first transfer object is transferred to the first vacuum processing chamber Pc1, the load lock chamber Lc is returned to the atmospheric atmosphere, and the door Dr is opened, and the next dummy substrate Dm is transferred into the load lock chamber Lc by the atmospheric transfer robot R2 with its insulating surface facing up. When the dummy substrate Dm passes under the ionizer In, the ionizer In blows negative ions onto the entire upper surface of the dummy substrate Dm so that the dummy substrate Dm is charged to a potential opposite to that of the first transfer object (this is referred to as the "second transfer object"). Then, when the dummy substrate Dm as the second transfer object is transferred, the door Dr is closed, and the inside of the load lock chamber Lc is evacuated to a predetermined pressure by a vacuum pump (not shown), and the dummy substrate Dm as the second transfer object is transferred to each of the first to third vacuum processing chambers Pc1 to Pc3 in sequence. As a result, particles that are mainly positively charged and floating in each of the first to third vacuum processing chambers Pc1 to Pc3 adhere to the surface of the dummy substrate Dm and are collected (dust collection process). The transportation of the dummy substrate Dm as the first transported item and the second transported item can be repeated multiple times.

[0028] According to the above embodiment, while each dummy substrate Dm is transported along the transport path, no spark discharge occurs, and each dummy substrate Dm is transported into each vacuum processing chamber Pc1, Pc2, Pc3 while maintaining the initial charged potential. In other words, the dummy substrate Dm is neutralized along the transport path, and the amount of neutralization does not change, so that particles floating in each of the first to third vacuum processing chambers Pc1 to Pc3 can be stably and efficiently collected. In addition, by alternately transporting the first transport object and the second transport object having different polarities at least once, for example, by transporting the first transport object charged to a positive potential, particles having a negative potential such as C (carbon), O (oxygen), F (fluorine), AlOx (aluminum oxide), and Fe (iron compound) can be collected. On the other hand, by transporting the second transport object charged to a negative potential, particles having a positive potential such as Si (silicon or glass material) or SUS (stainless steel) can be collected, and particles can be collected more efficiently. Moreover, by using the ionizer In disposed in the load lock chamber Lc to charge the dummy substrate Dm, it is possible to use a conventional vacuum processing apparatus as is without providing a separate device for charging, which is advantageous.

[0029] Next, the following experiment was carried out to confirm the above effect. In this experiment, although not shown or described, a vacuum chamber of a specified volume was used, and a metallic charged plate supported by an insulator was placed on the bottom surface of the vacuum chamber. Then, the surface of the charged plate was charged to +1000V by an ionizer in the vacuum chamber in the air atmosphere, and then the vacuum chamber was evacuated to a pressure of about 1 Pa. When the potential of the charged plate surface was monitored at this time, the potential was reduced to about 400V. Next, nitrogen gas was introduced into the vacuum chamber, and the vacuum chamber was returned to the air atmosphere, and then the vacuum chamber was evacuated to a pressure of 1 Pa. During this time, when the potential of the charged plate surface was monitored, it was confirmed that no significant change in potential was observed. From this, it was confirmed that if the charged plate was charged to a potential lower than the discharge start potential determined by Paschen's law, the charged potential could be maintained without the occurrence of spark discharge and the charge being removed. This was also the case when the charged plate surface was charged to -1000V.

[0030] Next, the surface of the charged plate was charged to +1000V by an ionizer in a vacuum chamber in an atmospheric atmosphere, and then the vacuum chamber was evacuated to a pressure even lower than that of the above experiment. When the potential of the surface of the charged plate was monitored at this time, it was confirmed that the potential dropped to a level even lower than 400V. This confirmed that the amount of charge after neutralization was not stable depending on the pressure at which the chamber was evacuated. In addition, when the vacuum chamber was evacuated to a pressure of about 1 Pa and argon gas was introduced into the vacuum chamber at a constant flow rate, the surface of the charged plate was neutralized in a few seconds. This shows that it is preferable not to introduce any gas into the vacuum chamber when collecting dust. [Explanation of symbols]

[0031] Cm: vacuum processing device, In: ionizer, Lc: load lock chamber, Pc1 to Pc3: vacuum processing chamber, Gs: substrate (object to be processed), Dm: dummy substrate (object to be transported for dust collection), Cp: Paschen curve.

Claims

1. 1. A method for collecting particles present in a vacuum processing apparatus having a load lock chamber and a vacuum processing chamber, the method comprising: carrying a processing object into the load lock chamber in an air atmosphere; converting the load lock chamber into a vacuum atmosphere; carrying the processing object to the vacuum processing chamber in a vacuum atmosphere; and subjecting the processing object to vacuum processing, the method comprising the steps of: a charging step of charging the dust-collecting transport object, at least the surface of which is covered with an insulating material, to a positive or negative potential in a load lock chamber in an atmospheric environment or before being carried into the load lock chamber in an atmospheric environment, and setting the charging potential at this time to ±500 V, which is a potential lower than the discharge start potential in nitrogen gas as determined by Paschen's law; a dust collection step of evacuating the load lock chamber and the vacuum processing chamber to a predetermined pressure at which the charged potential when the dust collection transport object is positively or negatively charged in the charging step is maintained, and then transporting the dust collection transport object from the load lock chamber to the vacuum processing chamber without introducing any gas, and causing particles present inside the vacuum processing chamber to adhere to the dust collection transport object.

2. 2. The dust collection method according to claim 1, further comprising a step of charging the dust collection object to either a positive or negative potential in the charging step to form a first object and charging the dust collection object to the other of either a positive or negative potential to form a second object, and repeating alternating transport of the first object and the second object multiple times in the dust collection step.

3. 3. The dust collection method according to claim 1, wherein an ionizer disposed in a load lock chamber is used to charge the dust collection transport object, and positive ions or negative ions are sprayed onto the surface of the dust collection transport object by the ionizer to charge the surface.

Images