Drying apparatus and drying method

Details Drying apparatus and drying method Drying apparatus and drying method

2000-03-17

2002-07-02

Stinson, Frankie L. (Department: 1746)

Cleaning and liquid contact with solids

Apparatus

With plural means for supplying or applying different fluids...

C134S108000, C134S902000, C134S102100, C034S469000, C034S443000

Reexamination Certificate

active

06412501

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-183469, filed Jun. 29, 1999; and No.
2000-033504
, filed Feb. 10, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a drying apparatus and a drying method for drying to-be-dried objects, such as cleaned wafers of semiconductors, substrates for liquid crystal displays, substrates for recording disks, substrates for masking, and other substrates.
Generally known are drying apparatuses for drying to-be-dried objects such as semiconductor wafers that are subjected to a cleaning process, rinse process, etc. As a typical drying apparatus, there is a so-called vapor drying apparatus that uses a vapor of an organic solvent. In the vapor drying apparatus, the organic solvent on the surface of a to-be-dried object is evaporated in a short time after a treatment liquid, such as pure water, adhering to the object surface is replaced with the organic solvent.
The vapor drying apparatus comprises an apparatus body that constitutes its outer hull, a support mechanism for supporting a wafer, a liquid recovery section, etc. The apparatus body is provided with a drying vessel that is stored with the organic solvent. Isopropyl alcohol (IPA) is used as an example of the organic solvent. A heating device is provided at the bottom of the drying vessel. The heating device produces an organic solvent vapor by heating the organic solvent. The support mechanism has a function to load into or unload the wafer, as an example of the to-be-dried object, from the drying vessel and to support the wafer in the drying vessel. The liquid recovery section discharges the treatment liquid (e.g., pure water), which flows down from the surface the wafer, to the outside of the apparatus.
Before the wafer is loaded into the drying vessel, it is cleaned with a cleaning fluid, such as hydrogen fluoride or pure water, in the cleaning process. The wafer is rinsed with the treatment liquid, such as pure water, in the rinse process after the cleaning process. Before it is inserted into the drying vessel, therefore, the wafer has the treatment liquid on its surface.
The wafer, having the treatment liquid such as pure water thereon, is inserted into the drying vessel by means of the support mechanism, and exposed to the vapor of the organic solvent such as IPA. The vapor is condensed on the surface of the wafer, and the organic solvent adheres to the wafer surface. The treatment liquid having so far been adhering to the wafer surface flows down by being replaced with the organic solvent, and is recovered by means of the liquid recovery section. The organic solvent on the wafer surface is evaporated in a short time, whereupon the wafer is dried. As the treatment liquid flows down from the surface of the wafer, particles on the wafer surface flows down together with the liquid.
If the treatment liquid contains particles in the rinse process, the particles sometimes may adhere to the rinsed wafer surface. If the wafer having the particles thereon is treated by means of the vapor drying apparatus, the particles on the wafer surface may possibly flow down together with the cleaning fluid and unfavorably remain in the drying vessel.
The wafer rinsed with the treatment liquid, e.g., pure water, is at a low temperature immediately after it is inserted into the drying vessel. Therefore, the vapor in the drying vessel is rapidly reduced as the organic solvent is quickly condensed in plenty on the wafer surface immediately after the wafer is loaded into the drying vessel. If the vapor quantity is reduced, a part of the wafer may possibly be exposed to air. Since the heating device goes on heating the organic solvent, the organic solvent vapor continues to be produced. In some cases, however, it takes scores of seconds, for example, to allow the wafer to be covered entire again.
A part of the wafer is left to dry naturally before the wafer is covered entire with the vapor. As this is done, natural oxide films or spots called watermarks inevitably develop along the respective contours of drops of the treatment liquid having been adhering to the wafer. In the case where the wafer is cleaned with hydrogen fluoride or the like in the cleaning process, in particular, the surface of the wafer is hydrophobic and activated, so that watermarks are liable to develop.
Immediately after the wafer is inserted into the drying vessel, as mentioned before, a relatively large quantity of the organic solvent is condensed in a moment on the wafer surface. Accordingly, the organic solvent should never fail to be heated in plenty to produce the vapor, so that a drying process entails high cost. Further, the conventional vapor drying apparatus requires use of a large quantity of organic solvent vapor in the drying process. In drying a large-diameter wafer, therefore, it is hard to secure sufficient organic solvent vapor to be replaced with pure water on the wafer.
BRIEF SUMMARY OF THE INVENTION
Accordingly, a first object of the present invention is to provide a drying apparatus capable of securely removing particles from the surface of a to-be-dried object, such as a wafer, and preventing watermarks from developing on the surface of the to-be-dried object. A second object of the invention is to provide a drying apparatus capable of lowering the cost of a drying process.
In order to achieve the first object described above, a drying apparatus according to the present invention comprises a drying vessel for storing a to-be-dried object, a treatment liquid feeder-discharger capable of feeding a treatment liquid into the drying vessel and discharging the treatment liquid in the drying vessel from the bottom side thereof, a heated organic solvent supplier for feeding a heated organic solvent onto the treatment liquid in the drying vessel, and a vapor supplier for feeding an organic solvent vapor into the drying vessel. Preferably, the treatment liquid feeder-discharger includes an inlet-outlet port opening in the base portion of the drying vessel, an inlet-outlet pipe connected to the inlet-outlet port, a valve, and a treatment liquid source.
In the drying apparatus of the invention, the interior of the drying vessel can be cleaned by feeding the treatment liquid such as pure water into the drying vessel by means of treatment liquid feeder-discharger and causing the pure water to overflow the top of the drying vessel. Particles can be removed from the drying vessel as the treatment liquid is discharged from the base portion of the drying vessel after the vessel is cleaned. The space over the treatment liquid in the drying vessel is filled with the vapor. The to-be-dried object is immersed in the treatment liquid. The organic solvent is condensed on the surface of the object as the object is exposed above the level of the treatment liquid. In this case, at least the lower part of the to-be-dried object is immersed in the treatment liquid before the organic solvent is condensed over the whole surface of the object, so that the temperature of the object is kept lower than that of the vapor. Thus, the organic solvent can be securely condensed on the whole surface of the object.
The drying apparatus of the invention may comprise a first inert gas supplier for introducing an inert gas into the drying vessel through the top portion thereof. Since this inert gas supplier feeds an inert gas such as nitrogen into the drying vessel, the space over the treatment liquid is filled with the organic solvent vapor and the inert gas. Since the to-be-dried object in the drying vessel is covered with the inert gas, in this case, it is restrained from touch oxygen, so that watermarks can be restrained from developing on the surface of the to-be-dried object.
In the drying apparatus of the invention, moreover, the vapor supplier may include an organic solvent tank for storing the organic solvent, heating means for heating the organic solvent in t

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