Method for Reduction of Resist Poisoning in Via-First Trench-Last Dual Damascene Process

摘要

Fabrication of interconnects in integrated circuits (ICs) use low-k dielectric materials, nitrogen containing dielectric materials, copper metal lines, dual damascene processing and amplified photoresists to build features smaller than 100 nm. Regions of an IC with low via density are subject to nitrogen diffusion from nitrogen containing dielectric materials into low-k dielectric material, and subsequent interference with forming patterns in amplified photoresists, a phenomenon known as resist poisoning, which results in defective interconnects. Attempts to solve this problem cause lower IC circuit performance or higher fabrication process cost and complexity. This invention comprises a dummy via and a method of placing dummy vias in a manner that reduces resist poisoning without impairing circuit performance or increasing fabrication process cost or complexity.