Coating processes – Centrifugal force utilized
Reexamination Certificate
1998-04-27
2001-03-27
Beck, Shrive (Department: 1762)
Coating processes
Centrifugal force utilized
C427S010000, C427S385500, C427S425000, C118S052000, C118S315000, C118S320000, C118S321000
Reexamination Certificate
active
06207231
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a coating film forming method and a coating apparatus capable of forming a liquefied coating film by virtue of a solvent such as a resist film, for example, on a surface of a liquid crystal display (LCD) substrate or a semi-conductor wafer.
In manufacturing the LCD substrate, for example, circuits can be formed by coating photoresist on the LCD substrate, then transferring circuit patterns onto the photoresist in terms of a photolithography technique, and then developing the photoresist. In these steps, a coating film forming step of supplying a coating liquid on a surface of the substrate is included.
In this case, as a method of forming a resist film, such a method has been known that, for example, a rectangular LCD substrate is loaded and fixed on a loading table provided in a processing vessel, then an opening portion of the processing vessel is closed by a lid member, then the processing vessel and the loading table are rotated together, then a resist liquid (coating liquid) consisting of a solvent and a photosensitive resin is dropped onto a center area of an upper surface of this substrate, and then the resist liquid is spread in a spiral fashion from a center portion of the substrate to a peripheral portion thereof by virtue of a rotating force and a centrifugal force of the substrate to thus be coated on the upper surface.
In this method, the resist liquid can be coated on the substrate by spreading the resist liquid from a center portion of the substrate to a peripheral portion thereof while rotating the substrate, so that a considerable amount of resist liquid has been scattered toward the processing vessel from an outer peripheral portion which has an extremely high peripheral velocity rather than the center portion thereof. In this case, out of the dropped resist liquid, an amount of the resist liquid coated on the substrate has 10 to 20%, and remaining 80 to 90% has scattered toward the processing vessel.
In particular, in the event that the resist liquid is coated on the rectangular LCD substrate, a very large quantity of the resist liquid has been wasted in order to coat the resist liquid on the overall surface of the substrate without surface areas left uncoated. In recent years, an increase in size of the LCD substrate has been progresses and as a result the waste of the resist liquid has been accelerated in the prior art.
BRIEF SUMMARY OF THE INVENTION
It is an object of the present invention to provide a coating film forming method and a coating apparatus which are capable of reducing an amount of to-be-used coating liquid as much as possible.
According to a first aspect of the present invention, there is provided a coating film forming method of forming a coating film by supplying a coating liquid onto a surface of a substrate which is loaded in a processing vessel, comprising the steps of:
(a) coating the coating liquid on the surface of the substrate by spraying the coating liquid onto the surface thereof while not rotating the substrate, to thus form the coating film; and
(b) regulating a film thickness of the coating film while rotating the substrate.
According to a second aspect of the present invention, there is provided a coating film forming method of forming a coating film by supplying a coating liquid onto a surface of a substrate which is loaded in a processing vessel, comprising the steps of:
(A) coating the coating liquid on the surface of the substrate by spraying the coating liquid onto the surface thereof while not rotating the substrate;
(B) forming the coating film by spreading the coating liquid over the surface of the substrate while rotating the substrate at a first revolution speed; and
(C) regulating a film thickness of the coating film while rotating the substrate which is sealed in the processing vessel, at a second revolution speed which is higher than the first revolution speed.
With the above configuration, the coating liquid can be supplied uniformly to the substrate without rotation of the substrate since the coating liquid is supplied to the substrate by spraying the coating liquid upon coating the coating liquid on the substrate and also scattering of the coating liquid due to a centrifugal force generated by the rotation of the substrate can be prevented since the substrate is not rotated. Therefore, an amount of consumed coating liquid can be extremely reduced since an amount of coating liquid necessary for coating the overall surface of the substrate can be reduced and the wasteful coating liquid scattered to the periphery can be lessened. In particular, if a size of the substrate is increased, the centrifugal force due to rotation of the peripheral portion of the substrate is enlarged so that a probability to scatter the coating liquid becomes higher. Hence, from a viewpoint of saving the coating liquid, it is effective that the coating liquid can be sprayed without the rotation of the substrate.
In addition, if the coating liquid is spread on the surface of the substrate by rotating the substrate at the first lower revolution number as in the second aspect, the coating liquid can be coated more firmly on the overall surface of the substrate without uncoated surface area. In this case, since the coating liquid can be supplied onto the substantially entire surface of the substrate by spraying the coating liquid, the large centrifugal force required to coat the coating liquid on the overall surface of the substrate is not needed. Accordingly, scattering of the coating liquid can be suppressed to the lowest minimum rather than the case where the coating liquid is spread on the overall surface of the substrate only by virtue of the rotation of the substrate.
According to a third aspect of the present invention, there is provided a coating film forming method of forming a coating film by supplying a coating liquid onto a surface of a substrate which is loaded in a processing vessel, comprising the steps of:
(1) coating a solvent on the surface of the substrate;
(2) coating the coating liquid onto the surface of the substrate by spraying the coating liquid onto the surface thereof, to thus form the coating film; and
(3) regulating a film thickness of the coating film by rotating the substrate.
According to a fourth aspect of the present invention, there is provided a coating film forming method of forming a coating film by supplying a coating liquid onto a surface of a substrate which is loaded in a processing vessel, comprising the steps of:
(I) coating a solvent on the surface of the substrate;
(II) coating the coating liquid onto the surface of the substrate by spraying the coating liquid onto the surface of the substrate;
(III) forming the coating film by spreading the coating liquid on the surface of the substrate while rotating the substrate at a first revolution speed; and
(IV) regulating a film thickness of the coating film by rotating the substrate which is sealed in the processing vessel, at a second revolution speed which is higher than the first revolution speed.
According to these third and fourth aspects, since the solvent is coated on the surface of the substrate prior to supply of the coating liquid, the coating liquid can be spread over the surface of the substrate via the solvent when the coating liquid is sprayed on the surface of the substrate. Accordingly, the coating liquid can be coated on the overall surface of the substrate without unevenness and an amount of the coating liquid can be reduced much more.
The above coating method further comprises the step of sealing the substrate into the processing vessel by closing the processing vessel by use of the lid member after the coating film has been formed on the surface of the substrate, and then the step of regulating a film thickness is carried out. Therefore, uniformity of the film thickness can be improved.
Further, since at least one of the solvent and the coating liquid is coated on the surface of the substrate while rotating the substrate and the processing vessel at the first revolution n
Beck Shrive
Calcagni Jennifer
Rader Fishman & Grauer
Tokyo Electron Limited
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