Integrated Circuits and Materials

Silicon oxynitride DARC has been broadly used for DUV lithography due to its tunable refractive index and high etch selectivity to resist. [1] Figure 2313a shows a schematic diagram of the double-DARC layers. The top DARC layer with high k value serves as an absorption media followed by a bottom DARC layer which is designed as a destructive interference media optimized for minimum reflectance in the resist. The optimized n, k, and thickness of each DARC layer were initially chosen based on reflectance simulations and subsequently adjusted based on empirical reflectance measurements. [2]

Figure 2313a. Schematics of the double-DARC layer design. [2]

Dielectric anti-reflection coating films can be deposited using a conventional RF PECVD chamber with SiH₄/N₂O/He chemistry. Helium is used here as dilute gas instead of nitrogen to minimize the incorporation of N-H bonds on the surface of the film. [2] The SiH₄/N₂O ratio was changed to adjust n and k values, while deposition time was used for thickness control. CHF₃, CF₄, O₂ and Ar gases were used for the DARC etch.

[1] T. Ogawa, H. Nakano, T. Gocho, T. Tsumori, SPIE Vol. 2197, 722-732 (1994).
[2] G.Y .Lee, Z.G.Lu, D.M.Dobuzinsky, X. J.Ning, and G. Costrini, Dielectric anti-reflection coating application in a 0.175 /spl mu/m dual-damascene process, Proceedings of the IEEE 1998 International Interconnect Technology Conference, DOI: 10.1109/IITC.1998.704759, 1998.