Due to the increasing availability of Multi Beam Mask Writers (MBMW) and the associated wafer lithography benefits, efficient handling of curvilinear mask shapes in the post tape-out flow becomes increasingly important. The presence of complex curvilinear mask shapes generated by Inverse Lithography Technology (ILT), or similar techniques requires new features and algorithms, especially in the context of applying Mask Process Correction (MPC). This paper discusses the status of Curvilinear Mask Process Correction (CLMPC) and gives a brief outlook into the near future of handling curvilinear mask shapes in the post tape-out flow. A summary of MRC requirements for incoming data and implications for mask inspection are included as well to put CLMPC into the right context. Further, approaches for CLMPC file size compaction along with new methods of data representation based on native curve formats are also discussed.
Photomasks for the semiconductor chip production are typically written with either laser- or e-beam writers. Laser tools have the advantage of fast writing speeds and are overall more cost effective than e-beam writers. On the other hand, ebeam writers achieve significantly better mask accuracy in terms of minimum Critical Dimension (CD) and CD uniformity. Despite the accuracy disadvantage of laser writers, on average, they account for approximately 70% of all masks delivered by the mask industry, during the years between 2018 and 2020. The widespread use of laser writers and their technical limitations make them excellent candidates for Mask Process Corrections (MPC). This work investigates the feasibility of using MPC, developed for e-beam writers, with minor modifications to laser writers. It will be shown that adding an anisotropic component to the models used for e-beam lithography is sufficient for simulating the laser tool signature. With such models, MPC provides an opportunity to expand the application space of laser tools into CD ranges, not possible without MPC and enables tool signature matching between mask writers similar to that used for e-beam writers.
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