Mask Strategy and Layout Decomposition for Self-Aligned Quadruple Patterning

Self-aligned quadruple patterning (SAQP) process is a proven technique for deep nano-scale IC manufacturing, while its mask design and layout decomposition strategy is less intuitive. In this paper, we examine both 2-and 3-mask SAQP process characteristics and develop various decomposition methods to achieve higher feature density and 2-D design flexibility. It is demonstrated that by generating assisting mandrels, SAQP layout decomposition can be degenerated into a SADP decomposition problem for which mature algorithms already exist in our EDA industry. Moreover, a spacer-expansion mask concept is introduced and a grouping/coloring algorithm to assign feature colors is developed for 3-mask SAQP layout decomposition. Finally, several 2-D layouts are successfully decomposed, showing the functionality of the decomposition method we proposed.