Complementary double exposure technique (CODE): a way to print 80nm gate level using a double exposure binary mask approach

To follow the accelerating ITRS roadmap, microprocessor and DRAM manufacturers have introduced the Alternating Phase shift mask (Alt.PSM) resolution enhancement technique (RET) in order to be able to print the gate level on sub 130nm devices. This is done at very high mask costs, a long cycle time and poor guarantee to get defect free masks. S. Nakao(1) has proposed a new RET. He showed that sub 0.1 mum features could be printed with good process latitudes using a double binary mask printing technique. This solution is very interesting, but is applicable to isolated structures only. To overcome this limitation, we have developed an extension to this technique called CODE. This combines Nakao's technique and the use of assist features removed in a second subsequent exposure. This new solution enables us to print isolated as well as dense features on advanced devices using two binary masks. This paper will describe all the steps required to develop the CODE application. Determination of the optimal optical settings Determination of optimal assist feature size and placement Layout rules generation Application of the layout rules to a complex layout, using the Mentor Graphics Calibre environment Experimental verification using a 193nm 0.63NA scanner.