We demonstrate an optical-gradient bottom antireflective coating (BARC) film, which can be easily prepared by treating a silicon nitride film with oxygen plasma. The oxygen composition is gradually decreased inside the silicon nitride film. The optical constants of the silicon nitride film are also changed gradually. A reflectance of less than 1% for various highly reflective substrates with high thickness-controlled tolerance has been achieved. The optical-gradient film is also shown to have high thermal stability during the postexposure bake procedure. Results indicate that the optical-gradient-type BARC is suitable in both ArF and F<sub>2</sub> excimer lasers for sub-70-nm lithography applications.
© 2004 Optical Society of America
(220.3740) Optical design and fabrication : Lithography
(310.1210) Thin films : Antireflection coatings
(310.1860) Thin films : Deposition and fabrication
(310.3840) Thin films : Materials and process characterization
Hsuen-Li Chen, Wonder Fan, Tzyy-Jyann Wang, Fu-Hsiung Ko, Run-Sheng Zhai, Chien-Kui Hsu, and Tung-Jung Chuang, "Optical-Gradient Antireflective Coatings for 157-nm Optical Lithography Applications," Appl. Opt. 43, 2141-2145 (2004)