Stitching for High NA: new insights and path forward

Davydova, Natalia; Wiaux, Vincent; Bekaert, Joost; Timmermans, Frank; Slachter, Bram; Kovalevich, Tatiana; Setten, Eelco van; Beckers, M.; Gorp, Simon van; Zhao, Rongkuo; Sun, De‐Zheng; Tien, Ming-Chun; Ser, Hoon; Bruin, Diederik de; Hsu, Stephen; Carpaij, Rene

doi:10.1117/12.2653388

Cited by 10 publications

(15 citation statements)

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“…Thus, stitching will be required to achieve the same exposure field as previous scanner generations. [2,3] Previous studies have shown that the formation of the black border region causes deformation of the multi-layer mirror, which can cause pattern placement errors. This necessitates the use of an image border in the double exposure region.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of field stitching optimization for robust manufacturing with high-NA EUVL

Levinson

Dam

Pfaeffli

et al. 2023

DTCO and Computational Patterning II

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The first high-NA EUVL scanner will have an 0.55 NA and will use anamorphic magnification. Therefore, the standard 10×13 cm lithography mask will be imaged into a 2.6×1.65 cm rectangle on the wafer due to the increased reduction factor of the lens’ vertical direction. Layers exposed on high-NA anamorphic scanners will require two stitched halffields to achieve the equivalent exposure area of previous-generation scanners. Stitching strategies will depend on the product type being manufactured. For chips with a large die area, it will be necessary to stitch fields across the die. For smaller chips, it may be advantageous to use three stitched exposures depending on the die size. In any case, the stray light from neighboring fields and black border proximity effects cause challenges for robust manufacturing. Some recent studies have shown that the CD may vary significantly as a function of the proximity to the black border edge due to multilayer stresses. In addition, stitching through a die has increased optical proximity effects which will need to be corrected to achieve the desired wafer CD. In this paper we examine the effects relevant to designing a stitched process, quantify manufacturing tolerances, and show how these effects can be corrected with EDA. More specifically, we examine the optical and mechanical properties of the multi-layer black border etch and optimization of sub-resolution gratings to reduce reflectivity with phase shifting absorber materials. Ultimately, we will show that for a well designed stitch, the effects of stitching can be corrected without impact to process window.

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Section: Introductionmentioning

confidence: 99%

Evaluation of field stitching optimization for robust manufacturing with high-NA EUVL

Levinson

Dam

Pfaeffli

et al. 2023

DTCO and Computational Patterning II

View full text Add to dashboard Cite

show abstract

“…Absorber reflection impact on imaging structures was shown in multiple publications, e.g. [4], [2] and was considered originally in the context of the black border development and keeping minimal distance between fields on wafer.…”

Section: Impact Of Absorber Reflection On Imaging (Tantalum-based Abs...mentioning

confidence: 99%

“…In order to reduce this effect a mitigation mechanism was proposed which turns the phase-shifting properties of the mask to its advantage in this case. Namely, a so-called sub-resolution grating (SRG) concept was introduced [2]. The working principle is illustrated in Figure 9:…”

Section: Mitigation Of Absorber Reflection For Low-n Maskmentioning

confidence: 99%

“…The transition from the absorber area to the black order is not sudden, there is a certain transition area. The transition was measured on NXE:3400B at imec using P44 lines / spaces, large conventional illumination, dark field mask and CAR (these results were also published in [2]). The reticle had thin 55 nm absorber with the absolute reflectance of ~2.7%.…”

Section: Absorber To Black Border Transitionmentioning

confidence: 99%

“…In the past [1], [2] we have considered stitching of relatively large pitches (P44 of line / spaces and P48 of contact holes).…”

Section: Stitching Experiments On Nxe:3400b (Imec)mentioning

confidence: 99%

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Overview of stitching for high NA: imaging and overlay experimental and simulation results

Davydova¹,

Look²,

Wiaux³

et al. 2023

Optical and EUV Nanolithography XXXVI

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An increased interest to stitching for High NA EUVL is observed; this is driven by expected higher demand of larger size chips for various applications. In the past a recommendation was published [1] to have 1-5 um band where no critical structures of a High NA layer would be allowed. In [2], we have introduced new insights on at-resolution stitching. In this publication, we present new experimental results obtained on NXE:3400B scanner. In the past we showed NXE feasibility results of vertical lines and contact holes stitching at relaxed resolution (40-48 nm pitch) in a single wafer location. In this study we evaluate stitching behavior through slit at more aggressive resolutions (P36 and P24 lines / spaces).We provide an overview of interactions in the stitching area such as aerial image interactions, absorber reflection, absorber to black border transition, black border vicinity impact and show corresponding experimental and simulations results. We formulate initial requirements for black border edge placement control and show performance of new masks. For stitching with low-n masks, we discuss using sub-resolution gratings to suppress the elevated mask reflectivity. We show rigorous simulations of stitched images, its sensitivity to overlay errors and propose mitigation mechanisms for OPC. Finally, an overview of stitching enablers will be described: from improved reticle black border position accuracy and absorber reflectivity control to mask resolution and OPC requirements.

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Computational lithography solutions to support EUV high-NA patterning

Zhao¹,

Zhang²,

Tang³

et al. 2023

DTCO and Computational Patterning II

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The EUV High-NA scanner brings innovative design changes to projection optics, such as introducing center obscuration and the anamorphic projection optical system in the projection optics box (POB) to improve the system transmission while the NA is improved1 . These design changes need to be accounted for in the computational lithography software solutions, to ensure accurate modeling and optimization of the High-NA system performance on wafer. In this paper, we will systematically investigate the benefits of Source Mask Optimization (SMO) and mask only optimization to explore EUV High-NA full chip patterning solutions, where mask 3D effects (M3D) are captured in the optical modeling. The paper will focus on assessing the performance (including process window, depth of focus, normalized image log slope) of through-pitch 1D Line/space (L/S) patterns and 2D Contact/Hole (CH) patterns after aforementioned optimizations and demonstrate the impact of center obscuration on imaging. In addition, we will investigate the effect of sub-resolution assistant feature (SRAF) on High-NA patterning via comparing the optimized lithographic performance with and without SRAF. These findings will help determine the most optimal patterning solutions for EUV High-NA as we move towards the first High NA EUV insertion. The paper will also discuss the anamorphic SMO where MRC and mask description needs to change from wafer plane (1x1) to scaled reticle plane (1x2). The interfield stitching will also be briefly discussed in this paper.

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Stitching for High NA: new insights and path forward

Cited by 10 publications

References 0 publications

Evaluation of field stitching optimization for robust manufacturing with high-NA EUVL

Evaluation of field stitching optimization for robust manufacturing with high-NA EUVL

Overview of stitching for high NA: imaging and overlay experimental and simulation results

Computational lithography solutions to support EUV high-NA patterning

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