Actinic review of EUV masks: performance data and status of the AIMS EUV System

Hellweg, Dirk; Perlitz, Sascha; Magnusson, Krister; Capelli, Renzo; Koch, Markus; Malloy, Matthew

doi:10.1117/12.2219247

Cited by 5 publications

(4 citation statements)

References 8 publications

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“…Since EUV lithography is nowadays adopted for high volume manufacturing (HVM) in the semiconductor industry, it becomes relevant to address various technical and technological challenges on its roadmap [1]. One of the crucial concerns is mask defectivity [2]. While the technology matures and the technical advancements pave the way towards the printability of increasingly fine features, defects of smaller sizes may also become printable.…”

Section: Introductionmentioning

confidence: 99%

Improved ptychographic inspection of EUV reticles via inclusion of prior information

2020

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The development of actinic mask metrology tools represents one of the major challenges to be addressed on the roadmap of extreme ultra violet (EUV) lithography. Technological advancements in EUV lithography result in the possibility to print increasingly fine and highly resolved structures on a silicon wafer, however the presence of fine-scale defects, interspersed in the printable mask layout, may lead to defective wafer prints. Hence the development of actinic methods for review of potential defect sites becomes paramount. Here, we report on a ptychographic algorithm that makes use of prior information about the object to be retrieved, generated by means of rigorous computations, to improve the detectability of defects whose dimensions are of the order of the wavelength. The comprehensive study demonstrates that the inclusion of prior information as a regularizer in the ptychographic optimization problem results in a higher reconstruction quality and an improved robustness to noise with respect to the standard ptychographic iterative engine (PIE). We show that the proposed method decreases the number of scan positions necessary to retrieve an high quality image and relaxes requirements in terms of signal to noise ratio (SNR). The results are further compared with the state-of-art total variation based ptychographic imaging.

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Section: Introductionmentioning

confidence: 99%

Improved ptychographic inspection of EUV reticles via inclusion of prior information

2020

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“…Defects embedded deep in the multilayer reflective coatings or on the mask substrate, are not accessible to a SEM or deep ultraviolet microscopy or defects on the patterned mask which are either elusive or falsely detected by these, make it neccessary for actinitic metrology solutions. 5 In the last decade, several tool development programs were carried out for actinic blank inspection, 6 aerial imaging 7,8 and repair of the patterned masks, 8 which are presently supporting EUV mask shops. A missing gap in the EUV mask ecosystem has been an actinic inspection tool for fast defect detection towards generating a full mask defect map.…”

Section: Introductionmentioning

confidence: 99%

Towards a stand-alone high-throughput EUV actinic photomask inspection tool: RESCAN

et al. 2017

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With extreme ultraviolet (EUV) lithography getting ready to enter high volume manufacturing, there is an imminent need to address EUV mask metrology infrastructure. Actinic defect inspection of patterned EUV photomasks has been identified as an essential step for mask qualification, but there is no commercial tool available right now. We address this gap with the RESCAN tool, a defect inspection platform being built at Paul Scherrer Institut (PSI), co-developed in collaboration with Nuflare Inc, Japan. RESCAN uses Scanning Scattering Contrast Microscopy (SSCM) and Scanning Coherent Diffraction Imaging (SCDI) for fast defect detection and fine defect localization. The development of a stand-alone tool based on these techniques relies on the availability of (1) a bright coherent EUV source with a small footprint and (2) a high frame-rate pixel detector with extended dynamic range and high quantum efficiency for EUV. We present two in-house projects at PSI addressing the development of these components: COSAMI and JUNGFRAU. COSAMI (COmpact Source for Actinic Mask Inspection), is a high-brightness EUV source optimized for EUV photons with a relatively small footprint. JUNGFRAU (adJUstiNg Gain detector FoR the Aramis User station) is a silicon-based hybrid pixel detector, developed in house at PSI and prototyped for EUV. With a high frame rate and dynamic range at 13.5 nm, this sensor solution is an ideal candidate for the RESCAN platform. We believe that these ongoing source and sensor programs will pave the way towards a comprehensive solution for actinic patterned mask inspection bridging the gap of actinic defect detection and identification on EUV reticles.

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“…It is a very powerful research tool for mask review which has significant contributions to EUV mask research. The AIMS prototype, developed by Carl Zeiss, is currently the only actinic review tool commercially available [7].…”

Section: Introductionmentioning

confidence: 99%

Scanning coherent scattering methods for actinic EUV mask inspection

et al. 2016

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Actinic mask inspection for EUV lithography with targeted specifications of resolution, sensitivity, and throughput remains a big hurdle for the successful insertion of EUVL into high volume manufacturing and effective solutions are needed to address this. We present a method for actinic mask inspection based on scanning coherent scattering microscopy. In this method, the mask is scanned with an EUV beam of relatively small spot size and the scattered light is recorded with a pixel detector. Customized algorithms reconstruct the aerial image by iteratively solving the phaseproblem using over-determined diffraction data gathered by scanning across the specimen with a finite illumination. This approach provides both phase and amplitude of actinic aerial images of the mask with high resolution without the need to use high NA (numerical aperture) lenses. Futher, we describe a reflective mode EUV mask scanning lensless imaging tool (RESCAN), which was installed at the XIL-II beamline and later at the SIM beamline of the Swiss Light Source and show reconstructed aerial images down to 10 nm (on-wafer) resolution. As a complementary method, the a-priori knowledge of the sample is employed to identify potential defect sites by analyzing the diffraction patterns. In this method, the recorded diffraction patterns are compared with the die or database data (i.e. previously measured or calculated diffraction data from the defect-free mask layout respectively) and their difference is interpreted as the defect signal. Dynamic software filtering helps to suppress the strong diffraction from defect-free structures and allows registration of faint defects with high sensitivity. Here, we discuss the basic principles of these Fourier domain techniques and its potential for actinic mask inspection with high signal-to-noise ratio and high throughput.

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Actinic review of EUV masks: performance data and status of the AIMS EUV System

Cited by 5 publications

References 8 publications

Improved ptychographic inspection of EUV reticles via inclusion of prior information

Improved ptychographic inspection of EUV reticles via inclusion of prior information

Towards a stand-alone high-throughput EUV actinic photomask inspection tool: RESCAN

Scanning coherent scattering methods for actinic EUV mask inspection

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