Anti-reflection strategies for sub-0.18-mu m dual damascene structure patterning in KrF 248nm lithography

Abstract

Finding high performance and low cost anti-reflection strategies is a common goal for all photolithographers. This task is getting tough for dual damascene process than the metal-etch process because the oxide thickness variation enhances the thin film interference effect. In this paper, different ARC strategies using organic and inorganic material were examined to compare their CD control performance in sub-0.18 mu m dual damascene structure for KrF 248nm lithography. The organic bottom ARC (BARC) achieves reflectivity control through modulating its thickness. The first and second minimal points in BARC swing curve were chosen as the film thickness to be evaluated. The inorganic ARC, which referred to dielectric ARC (DARC) using PECVD silicon oxynitride (SiOxNy) in this article, was investigated with single layer and double layer structures. The double-layer DARC structure consists of two layers with different extinction coefficient K values. The optimal refractive index (N, K) and thickness of each ARC structure were calculated from some available photolithography simulators. A PECVD process for DARC growth chat provides easily tunable range of refractive index and thickness was established to meet the DW process requirement fr om simulation. The performances of each ARC structure were evaluated on patterning 0.18 mu m trench and 0.20 mu m via in back-end-of-line (BEOL) dual damascene process. It showed that the double-layer DARC provided the most effective CD control ability among these ARC structures. The double-layer DARC should be one of the most potential candidates for sub-0.18 mu m dual damascene process.