Chen Hsuen-Li, Fan Wonder, Wang Tzyy-Jyann, Ko Fu-Hsiung, Zhai Run-Sheng, Hsu Chien-Kui, Chuang Tung-Jung
Department of Material Science and Engineering, National Taiwan University, Taipei, Taiwan.
Appl Opt. 2004 Apr 1;43(10):2141-5. doi: 10.1364/ao.43.002141.
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 F2 excimer lasers for sub-70-nm lithography applications.
