Based on the record for reasonable throughput, 19x nm wavelength inspection is one of the strongest candidates available today for the initial EUV (Extreme Ultraviolet) mask inspection approach until high-throughput E-Beam or actinic inspection is ready. However, there are several key challenges with 19x nm optical inspection of EUV masks. In the previous study, it was demonstrated that a 19x nm inspection system was capable of detecting programmed 15nm edge defects and 7nm CD errors on the programmed defect mask (PDM) containing EUV device designs, and inspected at maximum sensitivity. However, in that study, the inspectability on the product mask was not considered. In this study, EUV product mask inspection with a 19x nm inspection system is demonstrated, with special attention paid to defect sensitivity and inspectability on the product mask. In our results, we discuss whether inspection conditions, such as focus, can be employed to create a trade-off between defect sensitivity and inspectability. In addition, we discuss how defect measurement definitions affect the programmed defect size and the printability on EUV AIMS.
EUV (Extreme Ultraviolet) lithography is one of the key enabling techniques for imaging 7-nm node and beyond wafer technologies. To ensure mask quality levels will support High Volume Manufacturing (HVM), all “defects that matter”, must be identified and screened out before shipment to the wafer fab. Mask defects that matter are the ones that print during exposure at 13.5 nm wavelength. To support EUV development and production schedules, mask defectivity must be reduced to be at or near the optical defect levels. This task is complicated by the fact that actinic EUV mask inspectors are not currently available. In the absence of these EUV inspection tools, all available methods for detecting and characterizing defects must be deployed. Based on extensive deployment and on its record for reasonable throughput, 19x nm wavelength inspection is one of the strongest candidates available today for the initial EUV mask inspection approach. However, there are several key challenges with 19x nm optical inspection of EUV masks. Aside from the documented challenges of using a non-actinic wavelength, a key challenge is that the defect sensitivity varies based on pattern sizes and defect types and therefore, a wide range of pattern sizes and defect types need to be used to optimize inspection sensitivity. Through a variety of evaluations on simple test patterns, it has been confirmed that a combination of multiple focus offsets and polarization settings enables adequate sensitivity to meet early sensitivity requirements for 7 nm EUV production masks. As the result, focus offsets and polarization settings could be optimized to successfully develop new inspection recipes that could meet a target defect criteria with multi-pass inspection.  In this study, we will show inspection results of programmed defect macros (PDMs) based on actual EUV device constructs. Then, it will be discussed whether a combination of multiple focus offsets and polarizations is an effective approach to increase defect sensitivity on device patterns through the analysis of PDMs. We will demonstrate how inspection parameter optimization can be done to tailor 19x nm inspection to EUV device designs and what defect sizes and types are detectable with a 19x nm inspection system to assess capability for meeting the 7nm node development and production requirements.  Kazunori Seki et al., “Minimizing “Tone Reversal” during 19x nm Mask Inspection,” PMJ2018 6-2
Over time mask makers have been driven to low sensitivity e-beam resist materials to meet lithographic
patterning needs. For 7-nm logic node, resolution enhancement techniques continue to evolve bringing
more complexity on mask and additional mask builds per layer. As demonstrated in literature, low
sensitivity materials are needed for low line edge roughness (LER) but impact write tool through put. In
characterizing resist sensitivity for 7-nm, we explore more broadly what advantages and disadvantages
moving to lower sensitivity resist materials brings, where LER, critical dimension uniformity, resolution,
fogging, image placement, and write time results and trends are presented. In this paper, resist material
performance are reported for sensitivities ranging from 20 to 130 μC/cm2 at 50% proximity effect
correction, where the exposure will be using a single beam platform. Materials examined include negative
tone resist types with chemical amplification and positive tone without chemical amplification focusing on
overall trends for 7-nm e-beam resist performance.
In this paper we will describe the development of a new 12% high transmission phase shift mask technology for use
with the 10 nm logic node. The primary motivation for this work was to improve the lithographic process window for
10 nm node via hole patterning by reducing the MEEF and improving the depth of focus (DOF). First, the simulated
MEEF and DOF data will be compared between the 6% and high T PSM masks with the transmission of high T mask
blank varying from 12% to 20%. This resulted in selection of a 12% transmission phase shift mask. As part of this
work a new 12% attenuated phase shift mask blank was developed. A detailed description and results of the key
performance metrics of the new mask blank including radiation durability, dry etch properties, film thickness, defect
repair, and defect inspection will be shared. In addition, typical mask critical dimension uniformity and mask minimum
feature size performance for 10 nm logic node via level mask patterns will be shown. Furthermore, the results of work
to optimize the chrome hard mask film properties to meet the final mask minimum feature size requirements will be
shared. Lastly, the key results of detailed lithographic performance comparisons of the process of record 6% and new
12% phase shift masks on wafer will be described. The 12% High T blank shows significantly better MEEF and larger
DOF than those of 6% PSM mask blank, which is consistent with our simulation data.
In this paper, we discuss the lithographic qualification of high transmission (High T) mask for Via and contact hole applications in 10nm node and beyond. First, the simulated MEEF and depth of focus (DoF) data are compared between the 6% and High T attnPSM masks with the transmission of High T mask blank varying from 12% to 20%. The 12% High T blank shows significantly better MEEF and larger DoF than those of 6% attnPSM mask blank, which are consistent with our wafer data. However, the simulations show no obvious advantage in MEEF and DoF when the blank transmittance is larger than 12%. From our wafer data, it has been seen that the common process window from High T mask is 40nm bigger than that from the 6% attnPSM mask. In the elongated bar structure with smaller aspect ratio, 1.26, the 12% High T mask shows significantly less develop CD pull back in the major direction. Compared to the High T mask, the optimized new illumination condition for 6% attnPSM shows limited improvement in MEEF and the DoF through pitch. In addition, by using the High T mask blank, we have also investigated the SRAF printing, side lobe printing and the resist profile through cross sections, and no patterning risk has been found for manufacturing. As part of this work new 12% High T mask blank materials and processes were developed, and a brief overview of key mask technology development results have been shared. Overall, it is concluded that the High T mask, 12% transmission, provides the most robust and extendable lithographic solution for 10nm node and beyond.