All-In-One Etch Scheme to the Fabrication of Metal Hard-Mask Based Cu/Ultra Low-K Interconnects

Abstract

Due to the inherent limitation from overlay shift control, the punch-through scheme coupled with via CD shrink and the definition optimization of metal hard-mask open was proven to be the current-best choice and only feasible way for the enhancement of TDDB performance and gap-fill window of metal hard-mask based ultra low-k dielectric interconnects. The disadvantages of metal hard-mask based all-in-one etch include the potential defect from TixFy and the early copper exposure before liner removal step. The copper exposure time during all-in-one etch needs well controlled to avoid the via/trench bottom roughness and the inter-layer VBD. Stress migration (SM) also attracts special attention in metal hard-mask based process and its performance can be improved from the point of view of WET clean and post etch treatment (PET). RC (resistance/capacitance) curve can be also improved to target by means of PET.