A Copper-Molybdenum Etchant with Wide Process Window, Long Bath Life and High Stability for Thin Film Transistor Liquid Crystal Display Applications.

Conventional etchants for multi-metal/alloy stacked structures often suffer from nonuniform etching, residual layers, or undercutting, failing to meet high-generation production standards. This study presents a stable copper-molybdenum (Cu-Mo) etchant with extended bath life for thin film transistor liquid crystal display (TFT-LCD) applications, achieved through compositional optimization. Systematic investigations have been conducted on the effects of etching time, copper ion (Cu) loading (bath life) and storage time on the etch performance, alongside evaluations of sudden-eruption point and material compatibility. Results demonstrate that over-etching beyond the "detected endpoint" by 10% to 90% maintains critical dimension (CD) bias and taper angle of MoNiTi(MTD)/Cu/MTD three-layer and Cu/MTD two-layer within process specifications, as well as the difference between the CD bias of the three-layer and two-layer structures at the same over-etch time. The optimized formulation exhibits a 20% broader process window and 20% longer bath life compared to the process-of-record (POR) etchant. Shelf stability exceeds 15 days with minimal performance degradation, while maintaining compatibility with industrial equipment materials. These advancements address key challenges in high-precision etching for advanced TFT-LCD manufacturing, providing a scalable solution for next-generation display production.