Split ash processes for via formation to suppress damage to low-k layers

Abstract

Split ash processes are disclosed to suppress damage to low-dielectric-constant (low-K) layers during via formation. For one embodiment, ash processes used to remove an organic layer, such as an organic planarization layer (OPL), associated with via formation are split into multiple ash process steps that are separated by intervening process steps. A first ash process is performed to remove a portion of an organic layer after vias have been partially opened to a low-K layer. Subsequently, after the vias are fully opened through the low-K layer, an additional ash process is performed to remove the remaining organic material. Although some damage may still occur on via sidewalls due to this split ash processing, the damage is significantly reduced as compared to prior solutions, and device performance is improved. Target critical dimension (CD) for vias and effective dielectric constants for the low-K layer are achieved.