Design for manufacturing with directed self-assembly lithography
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In ultra-scaled very-large-scale integration (VLSI), lithography has become the bottleneck in integrated circuit (IC) fabrication. Since the conventional 193nm immersion lithography has reached the resolution limit, multiple patterning (MP) is adopted in order to meet the pitch requirement of ultra-scaled design. However, the manufacturing cost also increases dramatically with the growth of number of masks at the same time. Therefore, industries are looking for alternative lithography techniques to extend the 193nm immersion lithography to the sub-7nm nodes. With the continuous delaying of Extreme Ultraviolet (EUV), Directed Self-Assembly (DSA) lithography has emerged as one of the promising alternative lithography techniques due to its low cost, high throughput, and its ability to multiply the pitch of lines and vias. DSA has been intensively explored by both industry and academia in recent years. Memory and the dense via layer in logic might be the first application of DSA lithography in the mainstream IC production. DSA can also be applied on fabrication of cut masks to reduce the overall wire extensions. However, there are still many challenges, such as defectivity, line edge roughness and placement accuracy, which prevent DSA from the high-volume manufacturing. Integrating this technology into the fab flow and designing circuit around it also remain to be problematic. Considering the limitations and constraints of the topologies of DSA, this dissertation investigates and proposes novel algorithms for the DSA-aware design problem in the areas of design for manufacturability and physical design. First, a DSA based cut mask optimization for unidirectional design is proposed. Efficient algorithm is developed to assign DSA guiding template to metal line ends to minimize wire extensions and conflicts. Second, as redundant via insertion has been widely used in the post-routing stage to improve the yield, but the insertion of more vias introduces challenges for DSA patterning. This dissertation proposes a novel approach to perform the DSA aware redundant via insertion to improve the redundant via insertion rate and DSA compatibility. Since both via grouping and DSA guiding template decomposition are the essential problems for DSA aware design, which should be solved concurrently, this dissertation also proposes an efficient algorithm to solve this problem. Considering multiple patterning has already been used in DSA lithography, a coherent work, including single block-copolymer (BCP) and double block-copolymer guiding template assignment, is proposed for DSA and multiple pattering hybrid lithography. In addition, it is also noticed that optimization in the post-routing stage is not enough to eliminate DSA patterning violations, thus this dissertation also proposes the DSA compliant detailed routing algorithm with concurrent double pattering and guiding templates assignment.