Solution applying apparatus

Abstract

A solution applying apparatus has inner and outer cups each having an upper opening, the inner cup being rotatably disposed in the outer cup. The inner cup houses a planar workpiece such as a glass substrate therein which is to be coated with a coating solution such as a resist solution. The solution applying apparatus also has a lid assembly having an outer cup lid for closing the upper opening of the outer cup and an inner cup lid for closing the upper opening of the inner cup, the inner cup lid being rotatable with respect to the outer cup lid. The inner cup has drain holes defined in an outer circumferential portion thereof for providing communication between a space within the inner cup and a space outside of the inner cup to drain an excessive coating solution from the inner cup. The outer cup has an annular collection passage defined therein along the outer circumferential portion of the inner cup, the drain holes opening into the annular collection passage. The lid assembly includes a self-centering valve body that can be vertically movable into and out of snugly fitting relation to a through hole defined in the inner cup lid and a lost motion mechanism for moving the valve body to an open position thereof while the first and second cup lids remain closed and for opening the outer cup lid while the inner cup lid remains closed. After the workpiece has been coated with the coating solution, the valve body is lifted out of the through hole to smoothly eliminate a vacuum developed in the inner cup, and then the inner cup is opened.