Proximity effects of alternating phase-shift masks

Maurer, Wilhelm; Friedrich, Christoph; Mader, L.; Thiele, Joerg

doi:10.1117/12.373330

Cited by 5 publications

(3 citation statements)

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“…Such dimensional parameters to be controlled include line width (often synonymously named as critical dimension, CD), CD uniformity (CDU), pitch, height, sidewall angle, line edge/width roughness (LER/LWR). Furthermore, as high-resolution electron beam lithography (EBL) is usually applied in photomask manufacturing, it often suffers from, e.g., proximity effect [3] and fogging effect. For quality-management purposes, usually a kind of photomask standard is applied in photomask fabs, which serves as a "reference" for traceability of CD measurements.…”

Section: Introductionmentioning

confidence: 99%

Comparison of EUV Photomask Metrology Between CD-AFM and TEM

et al. 2022

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Accurate metrology of extreme ultraviolet (EUV) photomask is a crucial task. In this paper, two different methods for reference EUV photomask metrology are compared. One is the critical dimension atomic force microscopy (CD-AFM). In the measurements, the contribution of its AFM tip geometry is usually the dominant error source, as measured AFM images are the dilated results of measured structures by the AFM tip geometry. To solve this problem, a bottom-up approach has been applied in calibrating the (effective) AFM tip geometry where the result is traceably calibrated to the lattice constant of silicon crystals. The other is transmission electron microscopy (TEM). For achieving measurement traceability, structure features are measured in pairs in TEM images; thus the distance between the structure pair calibrated by a metrological AFM in prior can be applied to determine the magnification of the TEM image. In this study, selected photomask structures are calibrated by the CD-AFM, and then sample prepared and measured by high-resolution TEM nearly at the same location. The results are then compared. Of six feature groups compared, the results agree well within the measurement uncertainty, indicating excellent performance of the developed methodology. This research supports the development of a photomask standard, which is applied as a “reference ruler” with improved low measurement uncertainty in photomask fabs.

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Section: Introductionmentioning

confidence: 99%

Comparison of EUV Photomask Metrology Between CD-AFM and TEM

et al. 2022

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“…One effect which causes a changed phase is the so called effective phase. Three dimensional simulations and 2D investigations have shown that the effective phase of a structure is also influenced by the lateral size and not only by the vertical profile 4 . The other possibility is that the MPM-248 measurement error for structures smaller than 1,5µm leads to the observed effect.…”

Section: Shifter Width [µM] Measured Phase [°]mentioning

confidence: 99%

Balancing of alternating phase-shifting masks for practical application: modeling and experimental verification

et al. 2001

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Alternating phase shifting masks have proven their capability to enhance the process window and to reduce the mask error enhancement factor effectively. The application of this mask type requires additional mask-properties compared to binary masks or halftone PSM. In this paper two of these mask-properties, the intensity and the phase balancing, are investigated experimentally for 4X and 5X masks at DUV and compared with simulations applying the T-Mask configuration of the SOLID-CM™ program. In a first part the experimentally determined balancing results are discussed. For the measurements two independent methods are compared: Balancing measurements with an AIMS-system (MSM100) and direct optical phase and transmission measurements using a MPM-248 system. The T-Mask as a 3D Maxwell solver allows the simulation of real 3D mask topography. We compare the results of simulations with measured AIMS data. All available mask data like depth of trenches, thickness and composition of chromium/Cr x O y layers, etc. are taken as input for the simulations. The comparison enables an assessment of the possibilities and limitations of 3D masksimulation. Based on 3D mask simulations CD-sensitivity of the different balancing methods was investigated also taking the influence of proximity into account. The simulations allow an assessment of the CD-sensitivity for four analyzed mask types for feature sizes below 150nm on the wafer.

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“…One consequence of this however is, that OPc needs not only to take into account the phase structures on the mask, but also needs to change the width of these phase structures in order to correct successfully for proximity effects. This complication has already been tackled [10]. 6 …”

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confidence: 96%

<title>Mask error enhancement factor</title>

Maurer

2000

SPIE Proceedings

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Optical lithography at the limit of resolution is a highly non-linear pattern transfer process. One consequence of this is an apparent magnification of mask errors. The paper first demonstrates early experimental evidence of this effect. Then it assesses the influence of pattern geometry, of the lithography tool setup, and of different optical enhancement techniques on the MEEF using primarily simulation data. The correspondence of MEEF as an effect of mask linewidth variations to the increased printability of mask defects is illustrated. Strategies to minimize the MEEF -like alternating phase shift masks -are presented. Because the MEEF describes conveniently the concerted action of all components on the whole lithographic pattern transfer process, it is proposed to use the MEEF as a new yardstick to characterize the degree of difficulty of a given lithographic process.

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Proximity effects of alternating phase-shift masks

Cited by 5 publications

References 0 publications

Comparison of EUV Photomask Metrology Between CD-AFM and TEM

Comparison of EUV Photomask Metrology Between CD-AFM and TEM

Balancing of alternating phase-shifting masks for practical application: modeling and experimental verification

<title>Mask error enhancement factor</title>

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