JP2006216853A - Method and apparatus for cleaning substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and an apparatus for cleaning a substrate capable of making the substrate difficult to be charged, and cleaning the surface of the substrate. <P>SOLUTION: The surface of the substrate A transferred by a transferring means 3 is cleaned and made difficult to be charged by an atmospheric pressure plasma treatment means 1, and then the surface of the substrate A is cleaned by spraying dry ice particles on the surface of the substrate A by a dry ice particle spraying means 2. The atmospheric pressure plasma treatment and the dry ice particle spraying are carried out within a chamber 4. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a substrate cleaning method and a substrate cleaning apparatus for cleaning a substrate such as a glass substrate for a liquid crystal display, a wafer, and a printed circuit board for mounting a semiconductor component.

  In general, the surface of a substrate such as a glass substrate to be assembled in a product such as a liquid crystal display usually has an organic foreign matter such as oil and fat and an inorganic foreign matter such as a metal oxide or dust in the manufacturing process or transport process of the substrate. Adheres. Therefore, the substrate is cleaned prior to assembly into the product, and the organic foreign matter and inorganic foreign matter are removed. As a method for removing the organic foreign matter, a method of irradiating ultraviolet rays has been proposed (see Patent Document 1). In addition, as a method for removing inorganic foreign matters, a method of spraying dry ice has been proposed (see Patent Document 2). Furthermore, a method of simultaneously performing the ultraviolet irradiation and the dry ice jet has been proposed (see Patent Document 3).

By the way, when dry ice injection is performed to remove inorganic foreign matters such as dust, the substrate is charged by friction between the dry ice particles and the substrate. If the substrate is charged before being assembled into a product such as the liquid crystal display, dust may adhere to the substrate due to the charging, which may adversely affect the product. Therefore, in the case of performing the dry ice injection, after that, static elimination is performed using a static elimination device or the like.
Japanese Patent Laid-Open No. 3-101223 Japanese Patent Laid-Open No. 3-116832 JP-A-6-349802

  However, since the charge removal does not suppress the chargeability of the substrate, there arises a problem that the substrate is recharged by a work such as a transfer work or an assembly work after the charge removal. That is, on the surface of the substrate, adhesion of dust due to charging cannot be sufficiently suppressed, and it is difficult to maintain a cleaning state.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a substrate cleaning method and a substrate cleaning apparatus that can make a substrate difficult to charge and can clean the surface of the substrate. And

  In order to achieve the above object, the present invention provides a substrate cleaning method for cleaning a substrate surface by causing dry ice particles to collide with the surface of the substrate after cleaning the surface of the substrate with atmospheric pressure plasma and making it difficult to charge. Is the first gist.

  The present invention also provides atmospheric pressure plasma processing means for generating atmospheric pressure plasma, cleaning the surface of the substrate with the atmospheric pressure plasma and making it difficult to charge, and dry ice particle injection for injecting dry ice particles onto the surface of the substrate. Means and a transfer means for transferring the substrate, and the dry ice particle injection means is operated after the atmospheric pressure plasma processing means is operated on the substrate transferred by the transfer means. The substrate cleaning apparatus is a second gist.

  The present inventor has repeatedly studied a method for cleaning a substrate so that the cleaning state is maintained even after the substrate is cleaned. In the course of the research, it was found that when the surface of the substrate was treated with atmospheric pressure plasma, the organic foreign matter adhering to the surface of the substrate was removed and the substrate became difficult to be charged. As a result of further research, when the dry ice particles collide with the surface of the substrate after the atmospheric pressure plasma treatment, the inorganic foreign matter is removed, and the hardly charged property due to the atmospheric pressure plasma treatment is maintained. As a result, the present inventors have reached the present invention.

  The reason why the organic foreign matter is removed by the atmospheric pressure plasma is not clear, but it is assumed that the organic foreign matter is removed by reacting with the atoms in the plasma and gasifying. The reason why the substrate is difficult to be charged by the atmospheric pressure plasma is not clear, but it is presumed that the surface portion of the substrate is modified by the atmospheric pressure plasma and is difficult to be charged. Furthermore, the removal of inorganic foreign matters by dry ice particles is not limited to the physical movement of inorganic foreign matters by collision with dry ice particles. The inorganic foreign matter is blown off by the gas due to sublimation.

  In the substrate cleaning method of the present invention, since the dry ice particles collide with the surface of the substrate after the surface of the substrate is treated with atmospheric pressure plasma, the glass substrate can be hardly charged, and the surface of the substrate Organic foreign matters and inorganic foreign matters adhering to the surface can be removed. In addition, it is difficult to charge due to the atmospheric pressure plasma treatment, the adhesion of dust can be suppressed, and the cleaning state can be maintained.

  Further, the substrate cleaning apparatus of the present invention comprises an atmospheric pressure plasma processing means, a dry ice particle ejecting means, and a conveying means for conveying the substrate, and the atmospheric pressure plasma is applied to the substrate conveyed by the conveying means. Since the dry ice particle ejecting means is activated after the processing means is activated, the substrate cleaning method of the present invention can be easily performed, thereby making the substrate difficult to charge and the substrate. The surface can be cleaned.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a first embodiment of a substrate cleaning apparatus of the present invention. The substrate cleaning apparatus cleans the surface of the substrate A by the atmospheric pressure plasma processing unit 1 and makes it difficult to charge with respect to the substrate A transported by the transport unit 3, and then uses the dry ice particle ejecting unit 2 to Dry ice particles are sprayed onto the surface of the substrate A to clean the surface of the substrate A. Further, atmospheric pressure plasma treatment and dry ice particle injection are performed in one chamber 4.

  More specifically, the atmospheric pressure plasma processing means 1 uses a remote type in this embodiment. That is, the chamber 4 is provided with an electrode set including a pair of the high voltage electrode 11 and the low voltage electrode 12 facing each other with a space therebetween. The high voltage electrode 11 is connected to an AC power source, Grounded. In addition, in the space between the high voltage electrode 11 and the low voltage electrode 12, a gas used for atmospheric pressure plasma is supplied from a gas cylinder 13 provided outside the chamber 4 through a pipe 14. And while supplying gas to the space from one end side (the upper end side in FIG. 1) of the space and applying a voltage between the high voltage electrode 11 and the low voltage electrode 12, atmospheric pressure plasma is generated in the space. The atmospheric pressure plasma is blown from the other end side (the lower end side in FIG. 1) of the space and blown to the surface of the substrate A to be transported by the generated gas. From the viewpoint of maintaining the discharge in a stable state, it is preferable to provide a dielectric such as alumina on at least one of the surfaces where the high voltage electrode 11 and the low voltage electrode 12 face each other.

  The dry ice particle ejecting means 2 includes a nozzle 21 for ejecting dry ice particles in the chamber 4. Further, carbon dioxide gas necessary for forming dry ice particles is supplied to the nozzle 21 from a gas cylinder 22 provided outside the chamber 4 through a pipe 23. Furthermore, in this embodiment, as will be described later, low-temperature nitrogen gas is used in combination so that the formed dry ice particles can reach the surface of the substrate A efficiently. The low-temperature nitrogen gas is supplied through a pipe 25 from a gas cylinder 24 provided outside the chamber 4, and the pipe 25 is connected to the carbon dioxide gas pipe 23. The discharge direction of the dry ice particles by the nozzle 21 is not particularly limited because the discharge becomes difficult when the carbon dioxide gas generated by the sublimation of the dry ice particles enters the portion that generates the atmospheric pressure plasma. It is preferable to set the direction so that carbon dioxide gas does not enter the space of the plasma processing step.

  In this embodiment, the conveying means 3 uses a belt conveyor. That is, the belt conveyor includes an endless belt 31 that carries the substrate A and conveys it, and drive rollers (two in FIG. 1) 32 that run the endless belt 31.

  The chamber 4 is formed in a dome shape so as to cover the transfer means 3, and an inlet 41 for introducing the substrate A to be transferred into the chamber 4 is provided on one end side, and on the other end side. Is provided with an outlet 42 for sending the cleaned substrate A out of the chamber 4.

  The substrate A can be cleaned as follows, for example. That is, first, a single substrate A is placed on one end of the transfer means (belt conveyor) 3, and the substrate A is fed into the chamber 4. Next, the gas used for the atmospheric pressure plasma is supplied to the space between the high pressure electrode 11 and the low pressure electrode 12 in synchronism with the transfer of the substrate A to the position below the electrode set of the atmospheric pressure plasma processing means 1. At the same time, a voltage is applied between the high voltage electrode 11 and the low voltage electrode 12 to generate atmospheric pressure plasma. Then, the atmospheric pressure plasma is sprayed onto the surface of the substrate A being conveyed with the momentum of the supplied gas. This removes organic foreign matters such as fats and oils adhering to the surface of the substrate A, and the surface portion of the substrate A is modified so that the substrate A is hardly charged. Thereafter, carbon dioxide gas and nitrogen gas are supplied to the nozzle 21 in synchronization with the substrate A being transported to a position below the nozzle 21 of the dry ice particle ejection means 2. Thereby, dry ice particles are ejected from the nozzle 21 and collide with the surface of the substrate A. Thereby, inorganic foreign matters such as metal oxides and dust attached to the surface of the substrate A are removed. At this time, the low chargeability of the substrate A by the atmospheric pressure plasma treatment is maintained, and the substrate A is difficult to be charged even when the dry ice particles are cleaned. In this way, the substrate A is cleaned.

  Thereafter, the substrate A is sent out from an outlet 42 provided in the chamber 4 by the transfer means (belt conveyor) 3. The substrate A thus obtained has a surface portion modified by atmospheric pressure plasma treatment so that it is difficult to be charged, and the hard chargeability is maintained thereafter. For this reason, the board | substrate A can suppress adhesion of dust, and can maintain a washing | cleaning state.

  Note that the gas used for the atmospheric pressure plasma, carbon dioxide and nitrogen gas sublimated with dry ice particles are discharged from the inlet 41 and the outlet 42 for the substrate A provided in the chamber 4. In the present invention, “atmospheric pressure” of “atmospheric pressure plasma” means that the inside of the chamber 4 is depressurized using a depressurizing device such as a pump or pressurized using a pressurizing device in order to generate plasma. This means that the atmospheric pressure inside the chamber 4 is not necessarily the same as the atmospheric pressure outside the chamber 4.

Here, the reason why low-temperature nitrogen gas is used in addition to carbon dioxide gas when forming dry ice particles in the above embodiment will be described. That is, when dry ice particles are formed only with carbon dioxide gas, most of them (about 70%) sublimate until they reach the surface of the substrate A, and cleaning with dry ice particles cannot be performed efficiently. Therefore, in the above embodiment, by using a low-temperature nitrogen gas in combination, sublimation of the dry ice particles ejected from the nozzle 21 is suppressed, and the cleaning efficiency with the dry ice particles is improved. For this reason, the low temperature nitrogen gas is supplied so that the temperature of the low temperature nitrogen gas is lower than the sublimation temperature of the dry ice particles (−78.5 ° C. at an absolute pressure of 1 atm) in the vicinity of the nozzle 21. Is done. Further, when used in combination as described above, the volume ratio of carbon dioxide gas and the low-temperature nitrogen gas (CO ₂ / N ₂₎ is set to a range of 1 / 1-1 / 1000.

The combined use of the carbon dioxide gas and the low-temperature nitrogen gas is performed, for example, as follows. That is, as shown in FIG. 2A, a throttle portion 25a is formed in a pipe 25 through which low-temperature nitrogen gas flows, and carbon dioxide gas is mixed in the vicinity of the outlet of the throttle portion 25a. If it does in this way, pressure reduction is carried out by the flow of low-temperature nitrogen gas near the exit of throttle part 25a, and the mixed carbon dioxide gas expands by the pressure reduction, and it becomes dry ice particles. And even after spraying from the nozzle 21, sublimation is suppressed by the low-temperature nitrogen gas. Incidentally, the inner diameter D ₁ of the said diaphragm portion 25a is set to about 40 to 75% of the targeted non part D ₂ internal diameter. Further, as shown in FIG. 2B, the pipe may have a concentric double structure, and carbon dioxide gas may flow through the inner pipe 26 and low-temperature nitrogen gas may flow through the outer pipe 27. Conversely, low temperature nitrogen gas may be flowed through the inner pipe 26 and carbon dioxide gas may be flowed through the outer pipe 27.

  Further, the spray range (spray angle) of the dry ice particles from the nozzle 21 is appropriately set according to the shape of the substrate A to be cleaned. For example, when cleaning the disk-shaped substrate A, it is preferable that the injection range be circular. Further, when cleaning a wide substrate A, it is preferable that the spray is fan-shaped so that the spray range is a long line in the width direction of the substrate A. It is preferable to provide a plurality of nozzles 21 for spraying in the width direction of the substrate A. Moreover, it is preferable to make the average particle diameter of dry ice particles into the range of 0.01-1000 micrometers from a viewpoint from which detergency becomes favorable.

  Also in the atmospheric pressure plasma processing, the range in which the atmospheric pressure plasma is sprayed is appropriately set depending on the shape of the substrate A to be cleaned. For example, when the wide substrate A is cleaned, the range to be sprayed is the width direction of the substrate A. It is preferable to form a long line.

  The gas used for the atmospheric pressure plasma is not particularly limited as long as the atmospheric pressure plasma is generated. Usually, helium, neon, argon, krypton, xenon, nitrogen, and the like can be used. Used in combination with more than seeds. Especially, it is preferable to mix at least one of oxygen gas and hydrogen gas with the above-mentioned gas from the viewpoint of improving the antistatic property of the substrate. When the oxygen gas or the like is mixed, the mixing ratio is preferably set to 20% by volume or less of the entire mixed gas. This is because if it exceeds 20% by volume, the hard-to-charge property of the substrate tends to be weakened. The amount of gas used for the atmospheric pressure plasma is determined by the volume of the chamber 4 and the area of the substrate A to be cleaned, and is not particularly limited. It is set in the range of 1 to 1000 liters / min.

  Further, in the generation of the atmospheric pressure plasma, the voltage applied between the high voltage electrode 11 and the low voltage electrode 12 is not particularly limited as long as the atmospheric pressure plasma is generated, but is usually in the range of 1 kV to 10 kV. is there. Further, the frequency of the power source is not particularly limited as long as atmospheric pressure plasma is generated, but is usually in a range of 1 kHz to 150 MHz. Note that a higher GHz band may be used. However, the range of 1 kHz to 500 kHz is preferable in consideration of the influence of heat of the workpiece.

  And the conveyance speed of the board | substrate A is determined by the time which washing | cleaning requires, and although it does not specifically limit, Usually, it sets to the range of 0.1-10 m / min.

  FIG. 3 shows a second embodiment of the substrate cleaning apparatus of the present invention. In the substrate cleaning apparatus, the atmospheric pressure plasma processing means 1 is a direct system in the first embodiment shown in FIG. That is, the high voltage electrode 11 is provided above the endless belt 31 on which the substrate A is placed and conveyed, and the low voltage electrode 12 is provided below the endless belt 31 so as to face the high voltage electrode 11. The substrate A passes through the space between the electrodes 12. And the atmospheric pressure plasma process is carried out at the time of the passage. Moreover, the gas used for atmospheric pressure plasma is supplied so that the whole space of an atmospheric pressure plasma processing process may become the gas atmosphere. In this embodiment, the space in the atmospheric pressure plasma treatment process and the space in the dry ice particle injection process are such that the carbon dioxide gas diffused in the space in the dry ice particle injection process is less likely to diffuse into the space in the atmospheric pressure plasma treatment process. A partition wall 4a is provided. The rest is the same as in the first embodiment shown in FIG. 1, and the same reference numerals are given to the same parts. This embodiment also has the same operations and effects as the first embodiment.

  Note that, as in the first and second embodiments, when cleaning by dry ice particle injection is performed after cleaning by atmospheric pressure plasma processing, each cleaning may be performed in a separate chamber.

  In the present invention, as the substrate A to be cleaned, glass substrates for displays used for liquid crystal displays, organic EL displays, plasma displays, glass substrates for designs used for buildings, furniture, etc., wafers, substrates for forming thin film transistors And semiconductor component mounting printed boards, circuit boards, hybrid IC boards, and the like. In addition to glass, materials for the substrate A include ceramics, silicon, various compounds, and the like.

  Next, examples will be described together with comparative examples.

  In the same manner as in the first embodiment (see FIG. 1), after the glass substrate for liquid crystal display [340 mm × 470 mm × 0.7 mm (thickness)] was cleaned with atmospheric pressure plasma as follows, Washed by spraying dry ice particles. At this time, the substrate was transported at a speed of 1 m / min.

[Atmospheric pressure plasma treatment]
Only argon was used as the gas used for the atmospheric pressure plasma. The high voltage electrode and the low voltage electrode are obtained by coating a 1 mm thick alumina (dielectric) on a rectangular plate made of SUS316L, and the size of both is 75 mm × 420 mm, and the distance between the electrodes is 5 mm. Set to. Then, an AC power source having a frequency of 5 kHz was used as a power source, and a voltage of 5 kV was applied between the high voltage electrode and the low voltage electrode. The amount of power (irradiation energy) was 260 mW · min / cm ² .

[Dry ice particle injection]
The volume ratio (CO ₂ / N ₂ ) between carbon dioxide gas and low-temperature nitrogen gas was set to 1/10, and dry ice particles were injected. The spray range of the dry ice particles was a linear shape that was long in the width direction of the substrate. The average particle size of the dry ice particles was 100 μm.

  In Example 1 described above, the atmospheric gas used for the atmospheric pressure plasma was a mixed gas of argon (99% by volume) and oxygen (1% by volume). Other than that, it was the same as in Example 1 above.

  In Example 1, the atmospheric gas used for the atmospheric pressure plasma was a mixed gas of argon (80% by volume) and oxygen (20% by volume). Other than that, it was the same as in Example 1 above.

  In Example 1, the atmospheric gas used for atmospheric pressure plasma was a mixed gas of argon (99% by volume) and hydrogen (1% by volume). Other than that, it was the same as in Example 1 above.

  In Example 1, the atmospheric gas used for atmospheric pressure plasma was a mixed gas of argon (90% by volume) and hydrogen (10% by volume). Other than that was carried out similarly to the said Example 1.

  In Example 1 described above, the atmospheric gas used for the atmospheric pressure plasma was a mixed gas of argon (80% by volume), hydrogen (10% by volume), and oxygen (10% by volume). Other than that, it was the same as in Example 1 above.

[Comparative Example 1]
In Example 1 described above, cleaning by spraying dry ice particles was performed without performing atmospheric pressure plasma treatment.

[Slightly chargeable]
Thus, the charge amount of the glass substrate of Examples 1-6 obtained and the glass substrate of the comparative example 1 was measured using the static electricity measuring device (The Simco Japan company make, FMX-002). The results are also shown in Table 1 below.

  From the results in Table 1 above, it can be seen that the glass substrates of Examples 1 to 6 are less likely to be charged as compared with the glass substrate of Comparative Example 1.

  In each of the above examples, even when helium, neon, krypton, xenon, or nitrogen was used in place of argon, the same results as in the above examples were obtained.

It is explanatory drawing which shows typically 1st Embodiment of the substrate cleaning apparatus and substrate cleaning method of this invention. (A), (b) is explanatory drawing which shows typically the pipe used when using together a carbon dioxide gas and low-temperature nitrogen gas. It is explanatory drawing which shows typically 2nd Embodiment of the substrate cleaning apparatus and substrate cleaning method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Atmospheric pressure plasma processing means 2 Dry ice particle injection means 3 Conveyance means A Substrate

Claims (2)

  A substrate cleaning method, comprising: cleaning a surface of a substrate with atmospheric pressure plasma and making it difficult to charge, and then cleaning the surface of the substrate by causing dry ice particles to collide with the surface of the substrate.   An atmospheric pressure plasma processing means for generating atmospheric pressure plasma, cleaning the surface of the substrate with the atmospheric pressure plasma and making it difficult to charge, dry ice particle injection means for injecting dry ice particles onto the surface of the substrate, and the substrate A substrate transporting means for transporting the substrate, wherein the dry ice particle ejecting unit is operated after the atmospheric pressure plasma processing unit is operated on the substrate transported by the transporting unit. Cleaning device.

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