Coating processes – Centrifugal force utilized
Reexamination Certificate
1999-01-18
2001-02-06
Beck, Shrive (Department: 1762)
Coating processes
Centrifugal force utilized
C427S425000, C118S052000, C118S320000
Reexamination Certificate
active
06183810
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a coating film forming method and to a coating apparatus for forming a coating film such as a photoresist film or an anti-reflective coating film by applying a coating solution to a substrate such as a glass substrate for a liquid crystal display (LCD) device.
In the manufacturing process of an LCD device, a photolithography technology is employed as in the manufacturing process of a semiconductor device. In the photolithography employed for the manufacture of an LCD device, a resist coating film is formed on a glass substrate, followed by exposing the coating film to light in a predetermined pattern and subsequently developing the patterned coating film. Further, a semiconductor layer, an insulating layer and an electrode layer formed on the substrate are selectively etched to form a thin film of ITO (indium tin oxide), an electrode pattern, etc.
A so-called spin coating method is employed for coating an LCD substrate with a resist solution. A spin coater disclosed in, for example, U.S. Pat. No. 5,688,322 is employed for performing the spin coating treatment. In the spin coater disclosed in this prior art, an LCD substrate is held by vacuum suction by a spin chuck. Also, a solvent and a resist are supplied to the substrate, and an upper opening of a rotary is closed by a lid. Under this condition, the spin chuck and the rotary cup are rotated in synchronism. In this case, the coating amount of the resist, which is attached to the substrate, is only 10 to 20% of the supplied amount, with the remaining 80 to 90% of the supplied resist being discharged into a drain cup. The discharged resist solution is partly recycled for reuse. However, most of the discharged resolution is discarded.
In recent years, the LCD substrate is enlarged from 650×550 mm to 830×650 mm. If the LCD substrate is further enlarged in future, the consumption of the resist solution is further increased. Since the resist solution is wasted in a large amount in the conventional spin coating method as pointed out above, it is of high importance to decrease the waste of the resist solution.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention to provide a coating film forming method and a coating apparatus which permit decreasing the consumption of a coating solution used for coating a substrate.
Since an LCD substrate is rectangular, it is generally difficult to coat uniformly the entire surface of the LCD substrate with a resist solution. For uniformly coating the LCD substrate with a resist solution, a parallel moving mechanism of a nozzle is operated to permit a linear nozzle to be moved in parallel with a stationary LCD substrate. During the movement, a resist solution is spurted from the linear nozzle onto the substrate. However, since the conventional parallel moving mechanism of a nozzle has a large foot print (occupied floor area), the apparatus provided with the particular mechanism is rendered bulky. As a result of an extensive research made in an attempt to overcome the above-noted difficulties, the present inventors have arrived at the present invention.
According to an aspect of the present invention, there is provided a method of forming a coating film, in which a coating solution is supplied from a linear nozzle onto a substrate held by a spin chuck arranged inside a cup having an opening so as to form a coating film on the substrate, comprising the steps of:
(a) allowing a spin chuck to hold rotatably a substrate; and
(b) moving the linear nozzle and supplying a coating solution from the linear nozzle onto the substrate while rotating the substrate in a moving direction of the linear nozzle.
In the coating method of the present invention, the linear nozzle and the substrate are moved relative to each other to permit the linear nozzle to assume a predetermined posture relative to the substrate. As a result, the substrate is efficiently coated with the coating solution so as to decrease the consumption of the coating solution.
According to another aspect of the present invention, there is provided a coating apparatus, comprising a spin chuck for rotatably holding a substrate, a linear nozzle for supplying a coating solution onto the substrate, a nozzle moving mechanism for rocking the linear nozzle above the substrate, a rotary driving mechanism for rotating the spin chuck, a switching mechanism for allowing the coating solution to be spurted or not to be spurted from the linear nozzle, and a controller for controlling the rotary driving mechanism, the nozzle moving mechanism and the switching mechanism so as to supply the coating solution onto the substrate while rotating the substrate and moving the linear nozzle in a rotating direction of the substrate.
It is desirable for the linear nozzle to have a solution spurting port having a length corresponding to at least the shorter side of the rectangular substrate. Further, the coating apparatus may include a solvent supply source for supplying a solvent into the linear nozzle.
The coating apparatus may further include a shaking mechanism for shaking the linear nozzle to permit the longitudinal direction of the linear nozzle to be made parallel to the shorter side or longer side of the rectangular substrate, and a supporting arm mounted to the nozzle moving mechanism for supporting the linear nozzle. In this case, the shaking mechanism should desirably include a first bevel gear, a stationary frame for swingably supporting the supporting arm, a second bevel gear, a pivot joined to the linear nozzle, and a gear shaft arranged in a hollow portion of the supporting arm and provided with bevel gears engaged with the first and second bevel gears, respectively. Also, it is possible for the shaking mechanism to include a pivot rotatably mounted to the supporting arm and joined to the linear nozzle, and a small motor whose rotary driving shaft is joined directly or indirectly to the pivot and whose operation is controlled by the controller.
The coating apparatus may further include a back-and-forth moving mechanism for moving the linear nozzle forward or backward in the longitudinal direction of the linear nozzle until the solution spurting port of the linear nozzle overlaps with the entire region in the width direction of the rectangular substrate.
Further, the controller controls the operations of the nozzle moving mechanism and the rotary driving mechanism to permit a rocking angle &agr; of the linear nozzle to be made equal to a rotating angle &ggr; of the substrate and to permit a differentiation amount (&agr;′=d&agr;/dt), which is obtained by differentiating the rocking angle a with time, to be made equal to a differentiation amount (&ggr;′=d&ggr;/dt), which is obtained by differentiating the rotating angle &ggr; with time.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 5374312 (1994-12-01), Hasebe et al.
patent: 5571560 (1996-11-01), Lin
patent: 5772764 (1998-06-01), Akimoto
patent: 5945161 (1999-08-01), Hashimoto et al.
patent: 5962070 (1999-10-01), Mitsuhashi et al.
patent: 5972426 (1999-10-01), Kutsuzawa et al.
Beck Shrive
Calcagni Jennifer
Fulbright & Jaworski L.L.P.
Tokyo Electron Limited
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