Intensive optimization of masks and sources for 22nm lithography

Rosenbluth, Alan E.; Melville, David O. S.; Tian, Kehan; Bagheri, Saeed; Tirapu-Azpiroz, Jaione; Lai, Kafai; Waechter, Andreas; Inoue, Takuya; Ladányi, L.; Barahona, Francisco; Scheinberg, Katya; Sakamoto, Masaharu; Muta, Hidemasa; Gallagher, Emily; Faure, Tom; Hibbs, M.; Tritchkov, Alexander; Granik, Yuri

doi:10.1117/12.814844

Cited by 33 publications

(18 citation statements)

References 24 publications

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“…It offers our mask shop a unique capability for 28nm node and below mask pattern fidelity error analysis and disposition in R&D, as well as in production. This enhanced 2D structure monitoring approach can cover the inadequacy of current 1D measurement in current OPC model, DRC and MRC, especially the masks without source mask optimization (SMO) [6].…”

Section: Summary and Future Workmentioning

confidence: 99%

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Enhanced photomask quality control by 2D structures monitoring using auto image-to-layout method on advanced 28nm technology node or beyond

et al. 2013

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As device features continue to shrink, achieving acceptable yields becomes increasingly challenging. In the photolithography process, mask error is one of the most critical error sources, since any imperfections on a mask will be amplified and transferred onto a wafer due to Mask Error Enhancement Factor (MEEF) [1]. Furthermore，due to complexity of lithography optical proximity effect correction in advanced technology nodes, more and more 2D structures are applied into mask patterns. Furthermore, more 2D pattern configurations are susceptible to pattering failures due to their much high MEEF factor than 1D pattern. As a result, the conventional mask error control mechanisms for 1D [2] [3] [4] only, such as mean-to-target (MTT) and CD uniformity, are no longer adequate to deal with high MEEF 2D structures.In this paper, a novel 2D structure mask error monitoring technique is introduced to prevent fatal wafer printing errors such as CD error, line-end pull back and other pattern distortions to ensure high quality mask manufacturing and to improve wafer yield in advanced technology nodes. We will demonstrate the flow using typical 2D structure test patterns in 28nm technology node design or beyond. The SEM image would be taken and measured by this novel technique are used to monitor mask fidelity performance.This monitoring technique is based on Image-to-layout, as one of Anchor Semiconductor's pattern centric techniques, which can extract contour and convert it into pattern layouts from SEM or optical image of masks. Further pattern signature analysis can be performed on the pattern (inner /outer vertex, space distance and edge distance), so that we can quickly identify target locations for 2D pattern measurements. We monitor the severity of 2D corner rounding on selected 28nm design rule masks by Pattern Fidelity (PF) ratio and correlate them with wafer printing results.2D pattern measurement techniques and PF ratio monitoring system from SEM image is an effective approach to ensure high quality mask making in 28nm and advanced technology nodes. This PF ratio monitoring from 2D pattern SEM images is an effective approach to ensure high quality mask making in advanced 28nm node and beyond, which can overcome the inadequacy of current 1D measurement only method, especially for the masks are generated without source mask optimization (SMO) [6].

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Section: Summary and Future Workmentioning

confidence: 99%

“…This PF ratio monitoring from 2D pattern SEM images is an effective approach to ensure high quality mask making in advanced 28nm node and beyond, which can overcome the inadequacy of current 1D measurement only method, especially for the masks are generated without source mask optimization (SMO) [6].…”

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confidence: 99%

Enhanced photomask quality control by 2D structures monitoring using auto image-to-layout method on advanced 28nm technology node or beyond

et al. 2013

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“…Furthermore, the intensity of every source point is constrained to be either on (=1) or off (=0). The recent advancements in diffractive optical elements (DoEs) and programmable source shapes [1] have enabled the possibility of having much complex source configurations. The resulting source shapes can be parameterized using pixels, which allow arbitrary free-form source definitions along with gray level intensity for every source co-ordinate location.…”

Section: Advanced Source Configurationsmentioning

confidence: 99%

Source mask optimization for advanced lithography nodes

2010

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Source mask optimization is becoming increasingly important for advanced lithography nodes. In this paper, we present several source mask optimization flows, with increasing levels of complexity. The first flow deals with parametric source shapes. Here, for every candidate source, we start by placing model-based assist features using inverse mask technology (IMT). We then perform a co-optimization of the main feature (for OPC) and assist feature (for printability). Finally, we do a statistical analysis of several lithography process metrics to determine the quality of the solution, which can be used as feedback to determine the next candidate source. In the second flow, the parametric source is instead approximated by a pixel based source inverter, providing a fast and efficient way of exploring the source solution space. The final flow consists of pixilated source shapes realizable via DOEs or programmable illumination.

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“…For the soft Quasar pupil in the left-hand diagram, the target CD was 60 nm, and minimum pitch 120 nm. For the freeform pupil in the right-hand diagram (an SMO solution for a 22 nm SRAM cell [4,13]) a target CD of 45 nm and minimum pitch of 90 nm were chosen for the vertical lines, and a target CD of 90 nm for the horizontal lines (since this source shape is very asymmetric). The simulated impact on delta CD is 0.4 nm for the soft Quasar and 0.3 nm for vertical lines or 0.7 nm for horizontal lines respectively for the depicted freeform source shape.…”

Section: Reticle Level or Wafer Levelmentioning

confidence: 99%

“…SRAM cells, the co-optimization of mask layout and illumination pupil, referred to as source mask optimization (SMO) is currently understood as an important enabler for future process development. Source mask optimization has matured significantly over the last years, and clear benefits of optimized freeform source vs. classic source have been predicted for various applications [3][4][5][6][7][8]. In a freeform (or pixelated) source, the intensity is distributed virtually unconstrained within the illumination pupil.…”

Section: Introductionmentioning

confidence: 99%

Generation of arbitrary freeform source shapes using advanced illumination systems in high-NA immersion scanners

et al. 2010

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The application of customized and freeform illumination source shapes is a key enabler for continued shrink using 193 nm water based immersion lithography at the maximum possible NA of 1.35. In this paper we present the capabilities of the DOE based Aerial XP illuminator and the new programmable FlexRay illuminator. Both of these advanced illumination systems support the generation of such arbitrarily shaped illumination sources. We explain how the different parts of the optical column interact in forming the source shape with which the reticle is illuminated. Practical constraints of the systems do not limit the capabilities to utilize the benefit of freeform source shapes vs. classic pupil shapes. Despite a different pupil forming mechanism in the two illuminator types, the resulting pupils are compatible regarding lithographic imaging performance so that processes can be transferred between the two illuminator types. Measured freeform sources can be characterized by applying a parametric fit model, to extract information for optimum pupil setup, and by importing the measured source bitmap into an imaging simulator to directly evaluate its impact on CD and overlay. We compare measured freeform sources from both illuminator types and demonstrate the good matching between measured FlexRay and DOE based freeform source shapes.

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Intensive optimization of masks and sources for 22nm lithography

Cited by 33 publications

References 24 publications

Enhanced photomask quality control by 2D structures monitoring using auto image-to-layout method on advanced 28nm technology node or beyond

Enhanced photomask quality control by 2D structures monitoring using auto image-to-layout method on advanced 28nm technology node or beyond

Source mask optimization for advanced lithography nodes

Generation of arbitrary freeform source shapes using advanced illumination systems in high-NA immersion scanners

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