Optimized reticle alignment structures for minimizing aberration sensitivities and pattern shifts

With the continued shrinks in production structures to 38 nm and below for hyper-NA lithographic tools, there is an opportunity to further optimize these reticle alignment structures to reduce overlay numbers and improve yield. This opportunity is especially relevant for Dual Patterning applications where pattern shifts under different imaging conditions become critical. In this paper, we will present a proposal for improved reticle alignment structures to minimize the sensitivities for lens aberrations and thereby to minimize the contribution of reticle alignment to pattern shifts. Some alternatives will also be addressed. Full compatibility of the proposed alignment structures with older machines as well as continued compatibility of older reticles on the new lithographic tools will be discussed.