Meeting the CD (Critical Dimension) linearity and uniformity targets for high-NA EUV photomasks, requires tight control of a wide range of effects contributing to the distortion of the CD signature. So far, many of the factors degrading CD signature have been optimized independently, in particular the compensation of short- and long-range scattering and etch bias effects. Such independent optimization, however, limits the overall mask CD linearity and uniformity results achievable with co-optimization of the different components.
In this work, we discuss the co-optimization of short- and long-range corrections on the e-beam writer and through MPC (Mask Process Correction).
The use of Inverse Lithography (ILT) in semiconductor manufacturing has been driving the need for curvilinear (CL) mask shapes. Complex CL mask shapes lead to an explosion in the vertex density (vertices/um^2) and file size at the mask shop vs. Manhattan corrections. This talk will review mask SEM CD and AIMS measurements from EUV and DUV masks made with end-to-end CL corrections (OPC, MPC and other mask CD corrections) at Intel mask operations (IMO). A path for significant file size reduction with the new MULTIGON record extension to the P39 OASIS file format will be reviewed. MULTIGON insertion involves significant changes in the mask making ecosystem that includes electronic tool design (EDA) tools, MBM writers and inspection tools. The talk will review the status of MULTIGON readiness and insertion at Intel.
The use of Inverse Lithography (ILT) in semiconductor manufacturing has been driving the need for curvilinear (CL) mask shapes. CL shapes improve wafer critical dimension (CD) process window through focus, reduce mask error enhancement factor (MEEF) and enable fully utilizing mask rule checker (MRC) specs to guarantee the best OPC correction on challenging corner-to-corner (CTC) and end-to-end (ETE) 2D geometries. The insertion of Multibeam (MBM) writers in mask high volume manufacturing (HVM) enables patterning complex ILT shapes with high CD control and mask fidelity. Additionally, the MBM tool’s capability to use high dose on low sensitivity resist to improve resolution without any write time penalty enables realizing the complex mask shapes from the optical proximity correction (OPC) tool with high accuracy. However more complex CL mask shapes lead to an explosion in the vertex density (vertices/um^2) and file size at the mask shop vs. Manhattan corrections. This talk will review the benefits from CL corrections and present data collected at Intel mask operations (IMO) that outline challenges in processing CL masks through different modules including mask data prep (MDP), beam fracture, inspection and CD Metrology. A path for significant file size reduction with the new MULTIGON record extension to the P39 OASIS file format will be reviewed. MULTIGON insertion involves significant changes in the mask making ecosystem that includes electronic tool design (EDA) tools, MBM writers and inspection tools. A timeline for MULTIGON insertion aligned with the vendors would be reviewed with a goal of enabling MULTIGON in HVM in 2024.
The introduction of the multi-beam mask writer has made it possible to introduce non-Manhattan shapes on photomasks with no write-time penalty compared to the standard rectilinear mask shapes. While it has been known for some time that removing the Manhattan restriction on OPC output not only allows for improved process window, more recently it has also been demonstrated that it improves mask CD uniformity (CDU). When crucial mask rules are followed, most notably a minimum allowable curvature, we assess the CDU changes at the mask level for an MRC-constrained correction, as compared to either Manhattan or unconstrained corrections. An AIMS analysis was performed to estimate the effect at the optical plane. Lastly, we contrast differences in the CDU as transferred to resist in EUV lithography. We conclude with a view as to the challenges left to enabling high-volume manufacturing of all-angle shapes.
In the last year, the AIMS® EUV has been extended to applications beyond the native defectivity review, such as the metrology of EUV Phase Shift Masks (PSM).
The technology developed for the AIMS® EUV Phase metrology application enables the measurement of the phase difference between the absorber reflected light relative to the light reflected by the multilayer. A reliable information over the mask phase is important for process control in the mask production chain, as well as for the optimization of the wafer exposure process on the scanner.
In this paper we will describe the challenges of enabling a precise metrology for the mask phase and will investigate the advantages of employing EUV phase metrology capability as process of record in the mask shop for different engineering and production steps: etch control, imaging optimization and wafer process window enhancement.
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