Cleaning and liquid contact with solids – Processes – Including work heating or contact with combustion products
Reexamination Certificate
1998-06-15
2001-01-30
El-Arini, Zeinab (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including work heating or contact with combustion products
Reexamination Certificate
active
06179930
ABSTRACT:
TECHNICAL FIELD
The present invention broadly relates to a pull-up drying method and apparatus, and, more particularly, to a drying technique suitable for drying a member, such as a semiconductor device substrate, liquid crystal panel substrate, or the like, that must satisfy a strict standard of cleanliness.
BACKGROUND ART
Conventionally, when, for example, a semiconductor device substrate or a liquid crystal panel substrate is moist after the cleaning process, dirt remains on the substrate, bacteria multiply on the substrate, or the like. Thus, in order to completely remove the moisture of the substrate, the substrate must be dried after the cleaning process.
Methods of drying a substrate include a spin dryer drying method in which moisture is removed from the substrate by making use of centrifugal force produced as a result of rotating a spinner at a high speed; a steam drying method in which water, which has clung onto the substrate due to isopropyl alcohol (IPA) steam having excellent compatibility with respect to water, is removed by substituting the water on the substrate with IPA; and an air knife drying method in which moisture of the substrate is removed by high-pressure air.
Of the aforementioned conventional drying methods, the spin dryer drying method and the air knife drying method have the problem that the once-removed water droplets turn into mist, which clings onto the substrate again due to circulating current in the apparatus. When mist is produced, contaminants may get mixed in the mist due to wind pressure, and the resulting contaminated mist may cling onto the substrate, thereby contaminating it. In addition, when these methods are used, the substrate may get electrically charged due to high-speed rotation and high-pressure air.
In addition, when the spin dryer drying method is used, the center portion of the substrate may become negatively charged as a result of high-speed rotation, and thus attract outside air, which contaminates the center portion of the substrate.
The steam drying method requires a facility for controlling IPA which is a flammable solvent, a coolant recovery facility, a facility for maintaining the purity of the IPA, or the like, so that facility costs are increased, and a larger area is required for setting the facilities.
When the air knife drying method is performed, the substrates must be dried one at a time, so that a plurality of substrates cannot be dried all at once in batches, resulting in poor drying efficiency. In addition, the air knife drying method requires a conveyance mechanism and a maintenance mechanism, which may produce dust that contaminates the substrates.
Accordingly, in view of the above-described problems, it is an object of the present invention to provide a new drying method and apparatus capable of reducing the possibility of contamination during drying, reducing facility costs and the setting area, and drying substrates in batches.
DISCLOSURE OF THE INVENTION
To this end, according to one aspect of the present invention, there is provided a pull-up drying method in which water in a water bath is heated to a predetermined temperature, and with the water surface kept still, a member to be dried is placed in the water once, and then pulled up at a predetermined speed.
According to this method, when the member in the water heated to a predetermined temperature is pulled up from a still water surface, water droplets can be completely removed from the surface of the member as a result of surface tension and natural evaporation of the water, so that the member can be gently dried, using an apparatus having a simple structure, instead of performing high-speed rotation, using a solvent, or making use of high-pressure air currents.
In a preferred form of the present invention, air currents may be generated so as to flow downward from above the water bath, while the member is being pulled up.
According to this form of the present invention, removal of water from the surface of the member due to surface tension is assisted by the downwardly-flowing air currents, and the downwardly-flowing air currents speed up natural evaporation, thereby allowing the member to be dried much more easily.
In still another preferred form of the present invention, the predetermined temperature may be in the range of not less than about 60° C. to less than the boiling point. In still another preferred form of the present invention, the predetermined speed may be not more than about 200 mm/min.
In these forms of the present invention, when the water temperature is set at a rather high value, or the pull-up speed is set at a low value, it is possible to reliably prevent water droplets from clinging onto the surface of the member.
In still another preferred form of the present invention, when the member is a polygonal plate member, the member, whose plate surface is set parallel to a direction in which the member is pulled up, may have a lower side of the plate surface tilted with respect to the water surface in order to pull up the member in a tilted posture.
In this form of the present invention, the member is pulled up by tilting the lower side of the plate surface of the member, making it possible to prevent water droplets from remaining on the lower side of the member.
According to another aspect of the present invention, there is provided a pull-up drying apparatus comprising a pull-up bath having an overflow portion on at least part of the upper end of the pull-up bath so as to allow water to overflow from the interior of the pull-up bath; a drainage bath having a drainage opening at the outer side of the overflow portion of the pull-up bath; water-supply means for supplying water into the pull-up bath from below the water surface; a member pull-up mechanism for pulling up the member to be dried from below the water surface at a predetermined speed; and water temperature control means for controlling the water temperature in the pull-up bath.
The structure of the apparatus includes water supply means for supplying water from below the water surface, and allows water to overflow from the overflow portion of the pull-up bath, so that the apparatus, in addition to providing the above-described effects, is capable of continuously and constantly supplying water, without moving the water surface, and thus capable of maintaining its water-removing capability and cleanliness.
In a preferred form of the present invention, the water temperature control means may include a heater disposed in the pull-up bath, a heater cover for covering the heater from above the heater, an exhaust tube for allowing gas within the heater cover to escape out of the bath, and a heating control device for controlling the heating by the heater.
According to this form of the present invention, even if air bubbles are produced in the vicinity of the heater, these air bubbles are kept within the heater cover and discharged from the exhaust tubes, so that although the heater is placed directly in the pull-up bath, the air bubbles do not rise towards the water surface, making it possible to keep the water surface still. Thus, there are less water droplets on the member.
In another preferred form of the present invention, the heater cover may be shaped like a lampshade in cross section, and include a center portion for collecting gas produced in the vicinity of the heater, and the exhaust tube may include an exhaust opening disposed at the center portion.
According to this form of the present invention, since the heater cover is shaped like a lampshade, gas is more effectively kept at the center portion of the heater cover.
In still another preferred form of the present invention, the pull-up bath may have a pair of the overflow portions that oppose each other.
According to this form of the present invention, a pair of opposing overflow portions are provided, allowing the direction of water flow to be maintained in the direction of the overflow portions at all times. Therefore, a plurality of members can be placed in a direction perpendicular to the direction of flow of t
Ide Katsuya
Kitagawa Yasuhiro
Oike Kazuo
El-Arini Zeinab
Harness & Dickey & Pierce P.L.C.
Seiko Epson Corporation
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