The Magnitude of Potential Exposure-Tool-Induced Critical Dimension and Overlay Errors in Double Dipole Lithography for the 65-nm and 45-nm Technology Nodes
Authors: Chiou Tsann-Bim , Chen Alek C. , Tseng Shih-En , Eurlings Mark , Hendrickx Eric , Hsu Stephen 
Published: February 2005

Double dipole lithography (DDL, DDL is a trademark of ASML Masktools.) is a viable imaging solution for the 65-nm and 45-nm technology nodes, when using ArF exposure tools. By taking advantage of the extreme off-axis illumination of the dipole, the demonstrated, small critical dimension (CD) can be resolved with a good process window. In this case k1 will be 0.31 when applying formula k1 = (minimum half pitch) × (wavelength, λ)/(numerical aperture, NA), the Rayleigh's resolution equation with minimum half pitch of 80 nm as well as wavelength and NA of 193 nm and 0.75, respectively. The detailed CD measurement data and process window analysis can be seen. The ability of the dipole to resolve this CD, however, applies only to structures that are perpendicular to the orientation of the dipole; i.e., the x-dipole (or horizontal dipole) resolves small, vertical lines and spaces [S. Hsu, N. Corcoran, M. Eurlings, W. Knose, T. Laidig, K. E. Wampler, S. Roy, X. Shi, M. Hsu, J. F. Chen, J. Finders, R. J. Socha and M. Dusa: SPIE 4691 (2002), 476]. The use of the pattern decomposition [S. Hsu, N. Corcoran, M. Eurlings, W. Knose, T. Laidig, K. E. Wampler, S. Roy, X. Shi, M. Hsu, J. F. Chen, J. Finders, R. J. Socha and M. Dusa: SPIE 4691 (2002) 476, S. Hsu, J. F. Chen, N. Cororan, W. Knose, D. J. Van Den Broeke, T. Laidig, K. E. Wampler, X. Shi, M. Hsu, M. Eurlings, J. Finders, T. B. Chiou, R. J. Socha, W. Conley, Y. W. Hsieh, S. Tuan and F. Hsieh: SPIE 5040 (2003) 215] and double exposure of the x-dipole and the y-dipole respectively, make it possible to image an arbitrary device pattern. DDL allows integrated circuit (IC) manufacturers to maintain their roadmaps for shrinking device technology, while extending the use of ArF technology. Compared with other low-k1 imaging solutions, DDL has the advantage of using standard mask technologies, such as binary masks or 6% attenuated phase shift masks (PSMs). Because of the lower cost and faster turn-around time of these masks, DDL has the potential to become the imaging solution of choice for small-volume IC products, such as many application specific IC devices (ASICs). The imaging performance of DDL and the pattern decomposition algorithm are discussed elsewhere [M. Eurlings, E. van Setten, J. A. Torres, M. Dusa, R. Socha, L. Capodieci and J. Finders: SPIE 4404 (2001) 266, S. Hsu, N. Corcoran, M. Eurlings, W. Knose, T. Laidig, K. E. Wampler, S. Roy, X. Shi, M. Hsu, J. F. Chen, J. Finders, R. J. Socha and M. Dusa: SPIE 4691 (2002) 476, S. Hsu, J. F. Chen, N. Cororan, W. Knose, D. J. Van Den Broeke, T. Laidig, K. E. Wampler, X. Shi, M. Hsu, M. Eurlings, J. Finders, T. B. Chiou, R. J. Socha, W. Conley, Y. W. Hsieh, S. Tuan and F. Hsieh: SPIE 5040 (2003) 215]. In this paper, we investigate the CD and overlay (OL) errors caused by exposure tools, such as the illuminator imperfections, for example; these errors include the error caused by the pole intensity imbalance (PIB), aberration induced CD errors, and image placement errors (IPEs). During our research, we carried out extensive simulations of 1-dimensional and 2-dimensional mask-pattern CD errors and IPEs as a function of the PIB, pole size, pole center location, and aberration sensitivity. Simulation results show that the magnitude of the IPE depends on the control of PIB, dipole telecentricity, and the pattern structures. We present an IPE and focus control budget to describe the necessary tool-control requirements, considering the device patterns that satisfy 65-nm and 45-nm technology nodes respectively. The available results show that we can control the sources of the exposure-tool errors, enabling DDL imaging technology to satisfy the requirements of the 65-nm and 45-nm technology nodes.