PROCEEDINGS ARTICLE | May 14, 2004
Proc. SPIE. 5376, Advances in Resist Technology and Processing XXI
KEYWORDS: Lithography, Scanners, Diffusion, Scatterometry, Photomasks, Critical dimension metrology, Line edge roughness, Photoresist processing, Semiconducting wafers, Temperature metrology
ArF lithography has been successfully implemented for the development of sub-90nm DRAM devices. Line width control for the ArF lithography is becoming increasingly challenging as design rules shrink. Many works have been performed on the mask, exposure tools, and tracks to obtain better critical dimension (CD) uniformity, however in-field uniformity, in-wafer uniformity, and wafer-to-wafer uniformity from resist itself was not considered thoroughly. In this experiment, resist parameters that contributes to line width variation were considered in resist perspective. For the in-field uniformity, mask CD uniformity is very important. However, the mask error enhancement factor (MEEF) was different ranging from 3.27 to 5.12 depending on the resists in the k1 0.35 processes even though the screened resists met all the required resolution, depth of focus (DOF), exposure latitude (EL), line edge roughness (LER), and profile. For the resists having good MEEF, the in-filed uniformities of the critical layers were highly improved. The PEB sensitivities of the screened resists were evaluated again in terms of post exposure bake (PEB) sensitivity, which were quite higher than those of KrF resists. They ranged from 4.0 to 11.3 nm/°C. In-wafer uniformity was evaluated and compared using the resists having different PEB sensitivity. The resist with better PEB sensitivity showed better result in in-wafer uniformity. Finally, the wafer-to-wafer uniformities of the resists were evaluated. There was different delay after exposure depending on the sequence of the loaded wafers because it was not easy to control the delay time at the interface of a scanner and a track. The CD increased depending on the sequence, and it coincided well with the delay time of the wafers after exposure. The wafer-to-wafer CD variations were improved using the resists having strong resistance to the delay.
