Imaging enhancement by reduction of mask topography induced phase aberrations for horizontal 1D spaces under D90Y illumination

Last, Thorsten; Winter, Laurens de; Finders, Jo

doi:10.1117/12.2196800

Cited by 9 publications

(4 citation statements)

References 5 publications

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“…More precisely, the current Ta-based absorber is at its limit for imaging extendibility. Thinning down below 50nm Ta-based absorber thickness will reduce the amount of absorbed light, reduce the NILS and increase best focus variation through pitch [10,11]. Although the current Ta-based mask has proven benefits from mask technology point, the imaging performance towards next technology nodes can benefit from mask optimization.…”

Section: Introductionmentioning

confidence: 99%

Novel EUV mask absorber evaluation in support of next-generation EUV imaging

Philipsen¹,

Luong

Opsomer³

et al. 2018

Photomask Technology 2018

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In next-generation EUV imaging for foundry N5 dimensions and beyond, inherent pitch-and orientation-dependent effects on wafer level will consume a significant part of the lithography budget using the current Ta-based mask. Mask absorber optimization can mitigate these so-called mask 3D effects. Thin metal absorbers like Ni and Co have been experimentally investigated due to their high EUV absorption, but they pose challenges on the current technology of subtractive mask patterning [1]. A simulation study of attenuated EUV phase shift masks has identified through multiobjective optimization superior imaging solutions for specific use cases and illumination conditions [2]. Evaluating novel EUV mask absorbers evolves on two levels, demonstrating (1) improvements from lithographic perspective and (2) compatibility with the full mask supply chain including material deposition, absorber patterning, scanner environment compatibility and mask lifetime. On the lithographic level, we have identified regions based on the material optical properties and their gain in imaging performance compared to the reference Ta-based absorber. Within each improvement region we engineered mask absorber materials to achieve both the required imaging capabilities, as well as the technical requirements for an EUV mask absorber. We discuss the material development of Te-based alloys and Ag-based layered structures, because of their high EUV extinction. For the attenuated phase shift materials, we start from a Ru-base material, due to its low refractive index, and construct Ru-alloys. On the experimental level, we examined our novel mask absorber materials against an initial mask absorber requirement list using an experimental test flow. Candidate materials are evaluated on film morphology and stability through thermal, hydrogen, EUV loading, and chemical cleaning, for their EUV optical constants by EUV reflectometry, as well as preliminary for selective dry etch. The careful mask absorber evaluation, combining imaging simulations and experimental material tests, allowed us to narrow down to promising combinations for novel EUV mask absorbers.

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Section: Introductionmentioning

confidence: 99%

Novel EUV mask absorber evaluation in support of next-generation EUV imaging

Philipsen¹,

Luong

Opsomer³

et al. 2018

Photomask Technology 2018

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show abstract

“…[1][2][3][4][5] As the 3D structure modulates the EUV reflection phase, focus and pattern shifts are generated. [6][7][8][9] These phase modulations on the mask behave similarly to an aberration. Thus, the development of the EUV microscope that can observe both the intensity and phase images is strongly required to control this aberration.…”

Section: Introductionmentioning

confidence: 94%

Imaging performance improvement of coherent extreme-ultraviolet scatterometry microscope with high-harmonic-generation extreme-ultraviolet source

Mamezaki¹,

Harada²,

Nagata³

et al. 2017

Jpn. J. Appl. Phys.

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In extreme-ultraviolet (EUV) lithography, the development of a review apparatus for the EUV mask pattern at an exposure wavelength of 13.5 nm is required. The EUV mask is composed of an absorber pattern and a Mo/Si multilayer on a glass substrate. This mask pattern has a three-dimensional (3D) structure. The 3D structure would modulate the EUV reflection phase, which would cause focus and pattern shifts. Thus, the review of the EUV phase image is also important. We have developed a coherent EUV scatterometry microscope (CSM), which is a simple microscope without objective optics. The EUV phase and intensity images were reconstructed with diffraction images by ptychography. For a standalone mask review, the high-harmonic-generation (HHG) EUV source was employed. In this study, we updated the sample stage, pump-laser reduction system, and gas-pressure control system to reconstruct the image. As a result, an 88 nm line-and-space pattern and a cross-line pattern were reconstructed. In addition, a particle defect of 2 µm diameter was well reconstructed. This demonstrated the high capability of the standalone CSM, which can hence be used in factories, such as mask shops and semiconductor fabrication plants.

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“…4(a), it can be deduced that by further thinning down the current Ta-based material, the M3D effects cannot be fully mitigated, and this is also supported by literature. 16,17 Figure 4(b) shows the two options to manipulate the nearfield to minimize M3D effects. By reducing the absorber thickness and thereby ensuring similar or higher EUV absorption, we will reduce the shadowing effect.…”

Section: Materials Screeningmentioning

confidence: 99%

Reducing extreme ultraviolet mask three-dimensional effects by alternative metal absorbers

Philipsen

Luong

Souriau

et al. 2017

J. Micro/Nanolith. MEMS MOEMS

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Over the recent years, extreme ultraviolet (EUV) lithography has demonstrated the patterning of ever-shrinking feature sizes (enabling the N7 technology node and below), whereas the EUV mask has remained unaltered, using a 70-nm tantalum (Ta)-based absorber. This has led to experimentally observed mask three-dimensional (M3D) effects at the wafer level, which are induced by the interaction between the oblique incident EUV light and the patterned absorber with typical thickness values on the order of several wavelengths. We exploit the optical properties of the absorber material of the EUV mask as an M3D mitigation strategy. Using rigorous lithographic simulations, we screen potential single-element absorber materials for their optical properties and optimal thickness for minimum best focus variation through pitch at the wafer level. In addition, the M3D mitigation by absorber material is evaluated by process window comparison of foundry N5-specific logic clips. To valid ate the rigorous simulation predictions and test the processing feasibility of the alternative absorber materials, we have selected the candidate single elements nickel and cobalt for an experimental evaluation on wafer substrates. We present the film characterization as well as the first patterning tests of these single-element candidate absorber materials

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Imaging enhancement by reduction of mask topography induced phase aberrations for horizontal 1D spaces under D90Y illumination

Cited by 9 publications

References 5 publications

Novel EUV mask absorber evaluation in support of next-generation EUV imaging

Novel EUV mask absorber evaluation in support of next-generation EUV imaging

Imaging performance improvement of coherent extreme-ultraviolet scatterometry microscope with high-harmonic-generation extreme-ultraviolet source

Reducing extreme ultraviolet mask three-dimensional effects by alternative metal absorbers

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