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Metal Hard Mask (MHM)-All In One (AIO) technology has been widely used in the process flow of copper inter-connect since 28 nm technology node and below. This is because AF immersion exposure technology reaches its limitation for line edge roughness control, photoresist (PR) thickness and profile control. In this paper, we described the issues and the solutions in the development of 28 nm node MHM etch process, including selectivity improvement for photoresist, optimization of line edge roughness (LER), and optimization of TiN profile & CD uniformity. Base on fundamental etch theory, several experiments were conducted, and we successfully achieved TiN with desired profile and CD with good uniformity for 28nm MHM process. |
