1. Field of the Invention
The present invention relates to a coating applicator and a coating application method as well as to an electronic device manufactured by the above coating applicator or according to the above coating application method. The coating applicator operates as follows. While rotating a coating object retained on a turntable, a coating nozzle is placed above the coating object. As moved relative to the coating object in a direction intersecting a rotational direction of the coating object, the coating nozzle discharges a coating solution from a nozzle end orifice thereof, thereby applying the coating solution to the surface of the coating object. Particularly, in regard to applying the coating solution to the surface of the coating object being rotated, as described above, the coating nozzle is characterized as being capable of evenly applying the coating solution to form a coat of a uniform thickness on the surface of the coating object.
2. Description of the Related Arts
In the manufacture of the electronic devices such as semiconductor devices, it has been a general practice to apply the coating solution to the surface of the coating object such as a semiconductor wafer by means of the coating applicator.
As disclosed in patent documents 1 to 3, the following apparatus is used as one of such coating applicators. In this apparatus, the coating object retained in horizontal position is rotated while a cylindrical coating nozzle is placed above this coating object. The coating nozzle discharges the coating solution from the end thereof as moved over this rotating object in a radial direction thereof whereby the coating solution is applied to the surface of the coating object.
In regard to applying the coating solution to the surface of the coating object as described above, the above coating nozzle may be tapered at the end as disclosed in Japanese Patent Application No. 3776745 and Japanese Unexamined Patent Publication No. 2001-310155. Alternatively, the coating nozzle may be shaped like a cylinder having a flattened end as disclosed in Japanese Unexamined Patent Publication No. 2003-117477.
As shown in FIG. 1, the following problem is encountered in a case where a coating nozzle 1 having a tapered end is used to apply a coating solution 2 to a surface of a coating object 3 being rotated. This coating nozzle 1 has such a small flattened area at the end thereof that the coating nozzle 1 feeding the coating solution 2 through a nozzle end orifice 1a thereof fails to form a fully flat coat on the surface of the coating object 3 being rotated. The coating solution 2 so applied to the surface of the coating object 3 forms a coat varied in thickness, width and the like.
As shown in FIG. 2, on the other hand, the following advantage is obtained in a case where a coating nozzle 1 shaped like a cylinder having a flattened end is used to apply the coating solution 2 to the surface of the coating object 3 being rotated. This coating nozzle 1 has such a large flattened area at the end thereof that the coating nozzle 1 feeding the coating solution 2 through the nozzle end orifice 1a thereof forms a flat coat on the surface of the coating object 3 being rotated.
However, the following problem occurs in the case where the coating nozzle 1 shaped like the cylinder having the flattened end is used. As shown in FIG. 2, a part of the coating solution 2 fed to the surface of the coating object 3 through the nozzle end orifice 1a of the coating nozzle 1 is shifted to an upstream portion of the end of the coating nozzle 1, or upstream from a position to feed the coating solution 2 to the coating object 3. Because of the effect of surface tension and the like, the shifted coating solution accumulates on the end of the coating nozzle 1, forming a bump upstream from the position to feed the coating solution 2 to the coating object 3.
The coating solution 2 accumulated into bump runs down onto the coating object 3, resulting in fragmentary bumps 2a of coating solution 2 distributed on the coating object 3, as shown in FIG. 2 and FIG. 3. As shown in FIG. 4, the coating object 3, which is coated with the coating solution 2, suffers from the distributed fragmentary bumps 2a of coating solution 2. That is, it is difficult for the coating nozzle 1 to evenly apply the coating solution 2 to the surface of the coating object 3.