Sub-90nm pitch Cu low-k interconnect etch solution using RF pulsing technology

Self-aligned via (SAV) schemes are commonly used for back-end-of-line (BEOL) interconnect structures that have scaled to <; 90nm BEOL pitch [1]. In one implementation of this scheme, a TiN metal hard mask (MHM) is used for trench pattern definition, while the interconnect vias are patterned using a tri-layer resist mask such that the vias are self-aligned to the underlayer trench lines [2]. In this work, we describe a SAV etch process using RF pulsing in a capacitively coupled etch reactor that provides a solution to both via distortion / striation and critical dimension (CD) bias loading. Electrical results will be discussed.