59.1: Mura Inspection for Coated Resist Layer

Abstract

A method to detect mura on a coated photoresist layer in the manufacturing line of display devices is reported. The mura is irregular nonuniformity of transmittance or reflectance on a uniformly manufactured surface. The display devices are manufactured by a series of photolithographic processes, each of which requires uniformly coated layer. The detection of the mura on the film is required in order to keep the device quality high. The mura on the film has been visually inspected by tilting the glass under a single wavelength light such as a sodium lamp, which alters the contrast of the interference light. However the recent growing of glass size has made the manual tilting of the glass impossible. Rather than tilting the glass, we have developed an apparatus which illuminates the glass via a set of narrow bandpass filtered light of different wavelength. The intensity of the reflected light from the film is a periodical function of the layer thickness by the interference of the surface and bottom reflection of the layer, therefore detection sensitivity of the mura which is local variation of the thickness changes. The apparatus enabled to detect the thickness variation of several nanometers by developing a compensation method.