Impact of mask topography and multilayer stack on high NA imaging of EUV masks

Ruoff, Johannes

doi:10.1117/12.864120

Cited by 19 publications

(16 citation statements)

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“…The broad band mask reflectivity depends on illumination angle. It can be represented as a map in the pupil plane as shown in Figure 4 (see also [2] ). Average broad band reflectivity over the angles of incidence is determined by the particular illumination type.…”

Section: Figurementioning

confidence: 99%

Mask aspects of EUVL imaging at 27nm node and below

Davydova

Setten

Han³

et al. 2011

SPIE Proceedings

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EUVL requires the use of reflective optics including a reflective mask. The mask consists of an absorber layer pattern on top of a reflecting multilayer, tuned for 13.53 nm. The EUVL mask is a complex optical element with many parameters contributing the final wafer image quality. Specifically, the oblique incidence of light, in combination with the small ratio of wavelength to mask topography, causes a number of effects which are unique to EUV, such as an HV CD offset. These so-called shadowing effects can be corrected by means of OPC, but also need to be considered in the mask stack design. In this paper we will present an overview of the mask contributors to imaging performance at the 27 nm node and below, such as CD uniformity, multilayer and absorber stack composition, thickness and reflectivity. We will consider basic OPC and resulting MEEF and contrast. These parameters will be reviewed in the context of real-life scanner parameters both for the NXE:3100 and NXE:3300 system configurations. The predictions will be compared to exposure results on NXE:3100 tools, with NA=0.25 for different masks. Using this comparison we will extrapolate the predictions to NXE:3300, with NA=0.33. Based on the lithographic investigation, expected requirements for EUV mask parameters will be proposed for 22 nm node EUV lithography, to provide guidance for mask manufacturers to support the introduction of EUV High Volume Manufacturing.

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Section: Figurementioning

confidence: 99%

Mask aspects of EUVL imaging at 27nm node and below

Davydova

Setten

Han³

et al. 2011

SPIE Proceedings

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“…The Hopkins method used in the simulations of the last section is inaccurate for EUV lithography simulation because it does not take into account the strong dependence of the diffraction orders on the angle of incidence on the EUV mask [5]. This is illustrated in a dramatic way by considering the effect of focus induced image shift discussed next.…”

Section: Enhanced Hopkins Methodsmentioning

confidence: 96%

Etched multilayer mask in EUV lithography for 16 nm node and below

et al. 2014

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Etched multilayer masks in EUV lithography for 16 nm node and below are better than conventional binary masks due to their higher image intensities and image slopes. However, aerial-image simulation of etched multilayer masks requires special care in order to obtain accurate results. In this paper, we first show that the usual Hopkins method for partial coherence simulation gives very inaccurate results when off-axis illumination is used. We then discuss an enhanced Hopkins method which provides far greater accuracy. Simulation results are presented to demonstrate the importance of using the enhanced Hopkins method for EUV lithography simulation.

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“…The exposure system operates with a certain NA allowing light rays to interact with the photomask over wider range of angles of incidence. Since reflectivity is angle dependent this will result in mask-induced apodization in the entrance pupil of the projection optics resulting in non-telecentricity of the system and overlay impact [1] .…”

Section: Euv Mask Challengesmentioning

confidence: 99%

EUVL mask performance and optimization

et al. 2012

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d Toppan Photomasks inc., 131 Old Settlers Boulevard, Round Rock, TX 78664 USA EUV lithography requires an exposure system with complex reflective optics and an equally complex EUV dedicated reflective mask. The required high level of reflectivity is obtained by using multilayers. The multilayer of the system optics and the mask are tuned to each other. The mask is equipped with an additional patterned absorber layer.The EUV mask is an optical element with many parameters that contribute to the final image and overlay quality on the wafer and the productivity of the system. Several of these parameters can be tuned for optimal overlay, imaging and productivity results. This should be done with care because of possible interaction between parameters.We will present an overview of the EUV mask contributors to the imaging, overlay and productivity performance for the 27 nm node and below, such as multilayer and absorber stack composition, reflectivity and reflectivity uniformity. These parameters will be reviewed in the context of real-life scanner parameters for the ASML NXE:3100 and NXE:3300 system configurations. The predictions will be compared to actual exposure results on NXE:3100 systems (NA=0.25) for various masks and extrapolated to the NXE:3300 (NA=0.33).In particular, we will present extensive multilayer and absorber actinic spectral reflectance measurements of a state-ofthe art EUV mask over a range of incidence angles corresponding to an NA of 0.33 at multiple positions within the image field. The ML measurements allow calibrating ML stack for imaging simulations. It allows also the estimation of mask-induced apodization effects having impact on overlay.In general, the reflectivity measurements will give detailed variations over the image field of mask parameters such as ML centroid wavelength and absorber reflectivity which contribute to CD uniformity. Such a relation will be established by means of rigorous full stack imaging simulations taking into account optical properties of the coming NXE:3300 system.Based on this investigation we will propose optimal EUV mask parameters for the 22 nm node EUV lithography and below, to provide guidance for mask manufacturers to support the introduction of EUV High Volume Manufacturing.

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Impact of mask topography and multilayer stack on high NA imaging of EUV masks

Cited by 19 publications

References 0 publications

Mask aspects of EUVL imaging at 27nm node and below

Mask aspects of EUVL imaging at 27nm node and below

Etched multilayer mask in EUV lithography for 16 nm node and below

EUVL mask performance and optimization

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