DUV LITHOGRAPHY (KrF) FOR 130 nm USING OFF-AXIS ILLUMINATION AND ASSISTING FEATURES

To meet the industry’s timing for 130 nm production, different optical lithography solutions are being considered. Due to the maturity of the resists and optical materials, the application of high NA (≤ 0.70) KrF excimer laser exposure tools, together with resolution enhancement techniques, is an attractive solution. There are two main enhancement techniques to extend KrF lithography. The first utilizes alternating phase shift masks. This technique works for both dense lines and isolated lines. The second method involves the use of off-axis illumination such as annular and quadrupole. Off-axis illumination is a very effective enhancement technique for dense lines. However, it is not applicable to fully-isolated lines because of the inherent differences in diffraction pattern. Applying scattering bars (also called assisting features) to an isolated line modifies the diffraction pattern. This diffraction pattern is similar to that generated by dense lines. In this way off-axis illumination can be applied to enhance the depth of focus and exposure latitude of fully-isolated lines in the same manner as dense lines. In this paper, we will show the lithographic performance of a high NA KrF Step & Scan system (PAS 5500/700) when used to image 130 nm lines. Results will be shown with both annular and QUASARTM off-axis illumination techniques applied to enhance the process windows of both dense lines, and isolated lines with scattering bars.