New placement estimator for contact hole printed with DSA

摘要

Recent industrial results around directed self-assembly (DSA) of block copolymers (BCP) have demonstrated the high potential of such technique. One of the main advantages of this method is the reduction of lithographic steps thus leading to cost reduction. At the same time, the associated correction for mask creation must account for the introduction of this new technique maintaining a high level of accuracy and reliability. In order to create a Vertical Interconnect Layer (VIA) layer, graphoepitaxy DSA is the main candidate. The technique relies on the creation of a confinement guide where the BCP can separate into distinct regions and the resulting patterns are etched in order to obtain an ordered contact layer. The printing of the guiding pattern requires a classical lithography and optical proximity correction (OPC) to obtain the best suited guiding pattern for a specific target. Thus it is necessary to perform simulations of the BCP behavior in order to correctly determine contact hole placement. However, most existing models which simulates the BCP phase segregation have a computational cost that is too high and cannot be used to efficiently correct a full layout. In this study, we propose an original compact model that resolves this issue. The model is based on the calculation of the density probability of PMMA (Polymethyl Methacrylate) domain centers. It is compared with both rigorous simulations (based on the Otha-Kawasaki model) and experiments. For this analysis, test cases are contact shrink and contact multiplication. The number of PMMA domains inside a structure is also discussed and an analytic formula is derived and compared to experiments. The overall consistency of the compact model is presented.