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Templated DSA vias in sub-7 nm circuits: Design strategy and DSA-aware via decomposition
Book Contribution - Book Chapter Conference Contribution
Directed self-assembly (DSA) of block co-polymers (BCP) is a promising candidate for frequency multiplication below 20nm half-pitch. In this study we will focus on the generation of holes using cylindrical phase BCP materials. This is done by means of grapho-epitaxy where physical confinement is used. Conventional lithography (ArF or EUV) is used to create a pre-pattern. After surface energy modification, the BCP is deposited in the pre-patterned holes and annealed at elevated temperature. During the anneal the polymer phase separates and forms the desired cylindrical patterns. The primary concerns of this technique are placement accuracy and dimensional variability of the contact holes. This problem is complicated by the fact that the metrology for pattern placement accuracy determination for DSA is not fully developed. Current methods depend on simultaneous observation of the pre-pattern and the BCP structure. Contours are often impacted by the BCP processing, resulting in increased metrology noise for measuring the pre-pattern position. Other parameters that need to be controlled for high fidelity pattern formation include the geometry and substrate surface energy of the pre-pattern, the impact of BCP material related properties, and the impact of processing conditions. In this work the impact of EUV pre-patterns on the DSA process is investigated. Using EUV is expected to give a placement improvement due to the higher resolution and shape control induced of the pre-pattern. Pre-shaping of the template (e.g. in peanut shapes) is expected to decrease placement errors. In addition Local CD uniformity (LCDU) of low dose patterns caused by stochastic effects is a well-known issue for EUV. In DSA the CD is defined through the BCP composition is therefore expected to be able to repair LCDU of EUV pre-patterns showing that EUV+DSA can be used as complementary techniques.
Book: Proc. DSA2016
Pages: 1 - 1