Development of Multilayer Resist Technology for Halftone Mask in Liquid Crystal Display Manufacturing

Abstract

A halftone mask was used in a lithography process to reduce the number of steps required in liquid crystal display (LCD) manufacturing. Three thicknesses of resist films were produced using the halftone mask. Since the resist is exposed in the area where the sensitivity curve rises, a problem arises in that the thickness of the resist film fluctuates drastically when the exposure dose to the resist fluctuates slightly. We tried to stabilize the film thickness using two kinds of resists having different sensitivities. We used a low-sensitivity resist as a lower layer and a high-sensitivity resist as an upper layer. However, it was not possible to produce a stable film thickness because the two resists blended at the interface. Therefore, we added an aqueous polymer solution as an intermediate layer between the resists which were dissolved in a solvent. This solved the blending problem and a stable film thickness was obtained.