LESAR: A dynamic line-end spacing aware detailed router

As the VLSI technology scales down, 193nm optical lithography reaches the limit and one-dimensional (1D) unidirectional style lithography technique emerges as one of the most promising solutions for coming advanced technology nodes. The 1D process first generates unidirectional dense metal lines and then use line-end cutting to form the target patterns with cut masks. If cuts are too close, they will lead to conflicts. Line-end spacing rules become dynamic rather than static because of cut mask and also now need to be followed strictly. Line-end spacing check between two line-end pairs in the same mask has also been regarded as compulsory line-end spacing constraints that have not discussed in previous works yet. Complying with these rules during APR has become a new bottleneck. In this work, we propose to make the router aware of the dynamic line-end spacing rules, including end-end spacing and parity spacing constraints. Experimental results of our proposed router demonstrates that it can effectively expel all end-end spacing violations as well as 75% of parity spacing violations in a reasonable runtime increase of 14%.