Complementary Double Exposure Technique (CODE), solutions for the two dimensional structures of the 90nm node

In a recent paper [1], we proposed a new manufacturable Reticule Enhancement Technique (RET) using two binary masks, called CODE (Complementary Double Exposure). We demonstrated the printability of 80nm dense (300nm pitch), semi-dense and isolated lines using this technique and showed good performance using an ArF 0.63NA scanner. To be able to use the CODE RET in production, we must be able to handle complex two-dimensional.-structures as well. In this paper we study the representative two-dimensional complex structures of a circuit in order to have a complete overview of this technique. We analyze the impact of the asymmetrical apertures and the impact of the 2nd mask overlap to the 1st mask. We show that asymmetrical apertures impact the line width of the non-critical lines. We also show that the 2nd mask has not only the role of protecting the exposed part. It also contributes strongly to the printability of the complex structures by correcting the defects of the 1st exposure. Finally, we show the results of CODE technique applied to a portion of a real circuit using all the developed rules.