Using the CODE Technique to Print Complex Two-Dimensional Structures in a 90nm Ground Rule Process
In a previous paper, we have proposed the CODE (Complementary Double Exposure) technique. A new manufacturable Reticle Enhancement Technique (RET) using two binary masks. We have demonstrated the printability of 80nm dense (300nm pitch), semi-dense and isolated lines using the CODE technique and showed good printing results using a 0.63NA ArF scanner. In a more recent article we described all the steps required to develop the CODE application: the binary decomposition and the solutions developed in order to compensate adequately for line end shortening. This study was done based on aerial image simulations only. In this paper, we will give experimental results for printing complex two-dimensional structures for the high performance version of a 90nm ground rule, 240nm minimal pitch process, using the CODE technique. The results of depth of focus (DOF), energy latitude (EL) and mask error enhancement factor (MEEF) through pitch, and end-cap correction will be discussed, for quadrupole and annular illumination using a 193nm 0.70NA exposure tool. The CODE technique, not only because of a lower cost but also because of its performance, could be a good alternative to the alternating PSM technique, having less design penalties and a better mask making cycle time.
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