Photolithography for Thin-Film-Transistor Liquid Crystal Displays

Abstract

The fundamentals of resist materials and chemistry, equipment, and process engineering for thin-film transistor (TFT) liquid crystal display (LCD) photolithography are reviewed with a primary focus on manufacturing technology. The effects of the materials and concentrations of (mainly TFT array) photoresist constituents on the photosensitivity, dissolution behaviors in the developer, contrast, resolution, dark erosion, and stability against plasma etching are presented. Along with the equipment designs and functions, the process engineering to achieve the optimum resolution, better depth of field, higher throughput, and lower cost is explained and discussed. The efforts to address the great difficulty associated with capability/capacity improvement and increasing dimensions and weight of glass substrates and equipment are also reviewed, in response to the rising volume demands of larger displays. Mura issues related to the critical dimension (CD), differential CD, overlay, differential overlay, and total pitch are elucidated and the essential control factors and approaches are concisely introduced. Guided by the continuing, market-driven industry trends, we report the directions and future challenges for photolithography for TFT LCD applications.