As the optical lithography advances into the sub-30nm technology node, the various candidates of lithography have
been discussed. Double dipole lithography (DDL) has been a primary lithography candidate due to the advantages of a
simpler process and a lower mask cost compared to the double patterning lithography (DPL). However, new DDL
requirements have been also emerged to improve the process margin and to reduce the mask-enhanced error factor
(MEEF), which is to maximize the resolution and image contrast. There are two approaches in DDL i.e. model basedand
rule based-DDLs. Rule-based DDL, in which the patterns are decomposed by the simple rules such as x- and ydirectional
rules, shows the low process margin in the 2-dimension (2D) patterns, i.e., line-end to line-end, line-end to
bar and semi-isolated bars.
In this paper, we first present various analyses of our new model-based DDL (MBDDL) method. Our goal is to
maximize the process margin of the 2D patterns. Our main contributions are as follows. (1) We generate new 2D test
patterns including various configurations of the metal layer. The new 2D patterns can be used to optimize the parameters
of the MBDDL and to build the good design rules. The purpose of building the good design rules is improving the
process margin of the certain 2D patterns with the low process margin in spite of optimizing the parameters of MBDDL.
(2) We optimize the initial layout decomposition, which is the first step of MBDDL and affects the whole of MBDDL
quality. In addition, the model-based decomposition is applied with the process-window OPC (PWOPC) in terms of the
criteria of edge placement error (EPE) and mask rule checking (MRC) violation. Our new model-based approach
including the newly designed test patterns and optimized decomposition parameters leads to the improved depth of focus
(DOF) and enhanced the exposure latitude (EL). We achieve the 80nm DOF, which is the manufacturable margin for the
metal 1 layer at the sub-30nm node.