Advances in resist pattern transfer process using 157-nm lithography

The bilayer process we developed for 157-nm lithography uses a fluorine-containing silsesquioxane-type resist (F-SSQ). Gate fabrication is done by using a F-SSQ(90 nm)/organic film(200 nm)/poly-Si(150 nm)/SiO 2 (10 nm)/Si structure. The organic film works well as an anti-reflecting layer. Using a microstepper with a numerical aperture of 0.90 and optimizing the resist thickness, we made a 50-nm 1:1 line-and-space (L/S) pattern by using an alternative phase-shifting mask and made a 45-nm SRAM by using a chromeless phase lithography mask. Neither resist pattern footing nor undercutting was observed on the organic film. The reactive ion etching (RIE) selectivity between the F-SSQ and the organic film was sufficient (about 7), the resist pattern was transferred to the underlayer, and both 50-nm 1:1 L/S and 45-nm SRAM gate patterns were made using the organic film as an etching mask. Contact hole (C/H) fabrication is done by using a F-SSQ(105 nm)/organic film(400 nm)/tetraethyl orthosilicate (TEOS)-SiO 2 (1200 nm)/Si structure, and we made a 75-nm 1:1 C/H pattern by using the microstepper with a binary mask. The RIE selectivity was sufficient (about 15) for making high-aspect-ratio contact holes, and we made a 75-nm 1:1 C/H pattern in 1200-nm-thick TEOS. This bilayer process is thus promising for making 65-nm-node semiconductor devices.