J. Bekaert

imec Belgium, Louvain, Flanders, Belgium

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Publications (59)47.3 Total impact

  • J. Doise · J. Bekaert · B.T. Chan · R. Gronheid · Y. Cao · S. Hong · G. Lin · D. Fishman · Y. Chakk · T. Marzook ·
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    ABSTRACT: A graphoepitaxy directed self-assembly process using cylindrical phase block copolymers is regarded as a promising approach for patterning irregularly distributed contact holes in future integrated circuits. However, control over cylinder profile and open hole rate, among others, needs to be proven before this technique can be implemented in device fabrication. Computational simulation studies predict that selective control over the surface energy of the template bottom and sidewall is crucial for achieving perpendicular cylinders in an adequate range of template dimensions and block copolymer fill levels. This work offers an experimental investigation of the influence of the surface energy on the morphology of the assembly inside the template. For this study, a dedicated surface energy modification is implemented in our process flow. Selective control over the surface energy of the template bottom and sidewall is achieved by using random copolymer brushes. The optimization of surface energy prior to the directed self-assembly allows an improvement of the three-dimensional morphology of the assembly as well as larger process windows in terms of template dimensions and template fill. In addition, a sidewall that has an affinity for the majority block allows for smaller prepattern templates.
    Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics 11/2015; 33(6). DOI:10.1116/1.4929884
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    ABSTRACT: In this paper, we present an optimization methodology for the template designs of sub-resolution contacts using directed self-assembly (DSA) with grapho-epitaxy and immersion lithography. We demonstrate the flow using a 60nm-pitch contact design in doublet with Monte Carlo simulations for DSA. We introduce the notion of Template Error Enhancement Factor (TEEF) to gauge the sensitivity of DSA printing infidelity to template printing infidelity, and evaluate optimized template designs with TEEF metrics. Our data shows that SMO is critical to achieve sub-80nm non- L0 pitches for DSA patterns using 193i.
    Journal of Micro/ Nanolithography, MEMS, and MOEMS 09/2015; 14(3):031216. DOI:10.1117/1.JMM.14.3.031216 · 1.43 Impact Factor
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    ABSTRACT: In recent years major advancements have been made in the directed self-assembly (DSA) of block copolymers (BCP). Insertion of DSA for IC fabrication is seriously considered for the 7nm node. At this node the DSA technology could alleviate costs for double patterning and limit the number of masks that would be required per layer. At imec multiple approaches for inserting DSA into the 7nm node are considered. One of the most straightforward approaches for implementation would be for via patterning through templated DSA (grapho-epitaxy), since hole patterns are readily accessible through templated hole patterning of cylindrical phase BCP materials. Here, the pre-pattern template is first patterned into a spin-on hardmask stack. After optimizing the surface properties of the template the desired hole patterns can be obtained by the BCP DSA process. For implementation of this approach to be implemented for 7nm node via patterning, not only the appropriate process flow needs to be available, but also appropriate metrology (including for pattern placement accuracy) and DSA-aware mask decomposition are required. In this paper the imec approach for 7nm node via patterning will be discussed.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2015; 9423. DOI:10.1117/12.2086090 · 0.20 Impact Factor
  • H. Yi · J. Bekaert · R. Gronheid · G. Vandenberghe · K. Nafus · H.-S.P. Wong ·
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    ABSTRACT: Cylindrical directed self-assembly (DSA) nanostructures is a promising candidate for patterning the contacts and vias in integrated circuits. To match the contact patterns in an IC layout, physical guiding templates have been adopted to generate aperiodic DSA patterns, and templates of different sizes could lead to various DSA patterns. It is found in the experiment that the density of guiding templates has a strong influence on the DSA patterns. At a low template density, templates tend to become overfilled and result in DSA defects. In this paper, we experimentally demonstrate an effective solution to counteract the influence of template pattern density on the quality of DSA using sub-DSA-resolution Assist Features (SDRAFs). We show that SDRAFs can reduce the DSA defects significantly.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2015; 9423. DOI:10.1117/12.2085866 · 0.20 Impact Factor
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    ABSTRACT: Scanning Electron Microscopy (SEM) is widely used to measure Critical Dimensions (CD) in semiconductor lithography processes. Correlation between the CD-SEM metrology and target profile has drawing attention from metrology community [1]. In this paper, we use a recently developed CD-SEM simulator [2-3] to investigate some artifacts of SEM metrology. The simulation consists of two parts. First part is a stochastic resist modeling for lines and spaces through pitch, exposure dose and focus. Second part is CD-SEM simulation. Both CD and LWR extracted from experimental CD-SEM images were used to train the SEM model. Two types of artifacts were found to be metrology dependent: the first artifact is that a CD-SEM measures CD at various heights across pitch for the same SEM threshold. The second artifact is a misleading CD measurement for trenches not fully developed. By overlapping the CD-SEM simulation with 3D lithography simulation, correlation between CD-SEM metrology and target 3D profile is studied. Finally, a Process Window (PW) analysis based on both experiment and simulation is presented, using the simulated features and SEM images to correct the experimental PW.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2015; 9424. DOI:10.1117/12.2087106 · 0.20 Impact Factor
  • H. Yi · J. Bekaert · R. Gronheid · G. Fenger · K. Nafus · H.-S.P. Wong ·
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    ABSTRACT: Directed Self-Assembly (DSA) of block copolymers (BCP) has attracted increasing attention as the potential next generation lithography technology. One of the most promising applications of DSA is the patterning of contact holes in IC circuits using physical guiding templates. In previous studies, researchers have demonstrated that DSA patterns are determined not only by the size and shape of guiding templates, but the template density as well. However, the influence of the pattern density has not been explored systematically, nor is there a fast inspection methodology to visualize and quantify the influence. In this paper, we introduce the concept of DSA Interaction Range (DSAIR). The influence of template density on the DSA patterns is examined using Gaussian convolution of x with y [say what it is a convolution of]. This approach provides us with a fast and quantitative way to model the influence of template density and predict the location of overfilled conditions.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2015; 9423. DOI:10.1117/12.2085985 · 0.20 Impact Factor
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    ABSTRACT: Directed Self-Assembly (DSA) is one of the leading candidates for next generation patterning in IC manufacturing. With the continued delay of EUV and the increasing costs of evermore complex multipatterning techniques, DSA has the potential to produce small, well-defined features on a tight pitch. The graphoepitaxy DSA approach can be used to form single or multiple uniform contact holes (cylinders) well below the resolution limit of the optical exposure tool in a pre-pattern template. The utility of these patterns in the semiconductor manufacturing process is dependent on the capability of the process to control the size, edge roughness and placement of these DSA structures in the presence of reasonable levels of variation in the DSA material, the processing of that material and the pre-pattern template. In this study, a 3-D Self-Consistent Field Theory (SCFT) model has been developed to describe the behavior of such DSA systems. The utility of the simulator to describe actual physical behavior is explored, by fine tuning the SCFT model input parameters against experimental data for certain pre-pattern configurations and then evaluating the model predictions for other separate pre-pattern shapes. Two separate calibration studies are presented, one with 2-D guide patterns, in which multiple holes are positioned in a 2-D irregular array, and the other with 1-D structures, where the holes are distributed along one direction only. Pattern contours are extracted from CD-SEM images. A metric that measures the CD and placement is used to evaluate the modeled contours against the experimental contours.
  • K. Okabe · H. Yi · M.C. Tung · R. Tiberio · J. Bekaert · R. Gronheid · H.-S.P. Wong ·
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    ABSTRACT: In this paper we address an important topic for the development of block copolymer directed self assembly, which is the lack of the third dimensional information. The three-dimensional shape of the DSA feature directly impacts the ability to transfer the DSA pattern into etched patterns. Through TEM sample preparation by in-situ focused ion beam (FIB) Pt deposition and milling, we show cross-sectional images for the two most elemental building blocks of directed self assembled block copolymers, namely, the single and double-hole (peanut shape) etched in Si structures with great contrast at the interface formed by PS and PMMA. Additionally, a hard-mask single hole structure processed with a different template material is shown as well. Elemental mapping with energy filtered TEM (EFTEM) was shown to assist interpretation of images. 3D reconstruction of the holes formed in the hard-mask sample was performed using dark field (DF) STEM. A reduction in the SOC and SOG thickness was observed post in-situ Pt deposition for the hard mask structure. Further TEM sample preparation improvements will be needed to minimize the compression observed.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2015; 9423. DOI:10.1117/12.2087569 · 0.20 Impact Factor
  • Source
    Boon Teik Chan · Safak Sayan · Joost Bekaert · Jan Doise · Roel Gronheid ·
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    ABSTRACT: For future VLSI technology nodes, directed self-assembly (DSA) using block-copolymer (BCP) is considered as patterning technique alternative or complimentary to Extreme ultra-violet (EUV) lithography. As a consequence, it is essential to develop a cost-effective DSA process using existing lithography infrastructure as guiding template, i.e. 193 immersion-based. Recent progress in DSA focused on the lithography and chemical formulation processes, however, DSA integration into CMOS process flows remains to be demonstrated. Arindam Mallik et al presented the process assumptions for the 10nm (N10) and 7nm (N7) nodes [1]. DSA lithography is perfectly fit into the desired pitch requirement for N7 technology node. Thus, our current research focuses on the CMOS process integration for fin and via contact holes with DSA technology, using relevant film stacks and state-of-the-art integration flow.
    Micro and Nano Engineering (MNE), Lausanne, Switzerland; 09/2014
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    ABSTRACT: With the implementation of multi-patterning ArF-immersion for sub 20nm integrated circuits (IC), advances in equipment monitoring and control are needed to support on-wafer yield performance. These in-situ equipment monitoring improvements, along with advanced litho-cell corrections based on on-wafer measurements, enable meeting stringent overlay and CD control requirements for advanced lithography patterning. The importance of light-source performance on lithography pattering (CD and overlay) has been discussed in previous publications.[1-3] Recent developments of Cymer ArF light-source metrology and on-board monitoring enable end-users to detect, for each exposed wafer, changes in the near-field and far-field spatial profiles and polarization performance, [4-6] in addition to the key `optical' scalar parameters, such as bandwidth, wavelength and energy. The major advantage of this capability is that the key performance metrics are sampled at rates matched to wafer performance, e.g. every exposure field across the wafer, which is critical for direct correlation with on-wafer performance for process control and excursion detection.
    Proceedings of SPIE - The International Society for Optical Engineering 03/2014; 9052. DOI:10.1117/12.2047449 · 0.20 Impact Factor
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    ABSTRACT: Directed Self-Assembly (DSA) of Block Co-Polymers (BCP) has become an intense field of study as a potential patterning solution for future generation devices. The most critical challenges that need to be understood and controlled include pattern placement accuracy, achieving low defectivity in DSA patterns and how to make chip designs DSA-friendly. The DSA program at imec includes efforts on these three major topics. Specifically, in this paper the progress in setting up flows for templated DSA within the imec program will be discussed. A process has been implemented based on a hard mask as the template layer. In this paper primarily the impact of local pattern density and BCP film thickness on the templated DSA process are discussed. The open hole rate and the placement accuracy of BCP patterns within the template are the primary figures of merit.
    SPIE Advanced Lithography; 03/2014
  • B. Baylav · C. Maloney · Z. Levinson · J. Bekaert · A. Vaglio Pret · B. Smith ·
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    ABSTRACT: The roughness present on the sidewalls of lithographically defined patterns imposes a very important challenge for advanced technology nodes. It can originate from the aerial image or the photoresist chemistry/processing [1]. The latter remains to be the dominant group in ArF and KrF lithography; however, the roughness originating from the mask transferred to the aerial image is gaining more attention [2-9], especially for the imaging conditions with large mask error enhancement factor (MEEF) values. The mask roughness contribution is usually in the low frequency range, which is particularly detrimental to the device performance by causing variations in electrical device parameters on the same chip [10-12]. This paper explains characteristic differences between pupil plane filtering in amplitude and in phase for the purpose of mitigating mask roughness transfer under interference-like lithography imaging conditions, where onedirectional periodic features are to be printed by partially coherent sources. A white noise edge roughness was used to perturbate the mask features for validating the mitigation.
    Proceedings of SPIE - The International Society for Optical Engineering 02/2014; 9052. DOI:10.1117/12.2045668 · 0.20 Impact Factor
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    ABSTRACT: Directed self assembly has become a very attractive technology for Fin and contact/via applications. Some of the issues related to pattern placement error, defectivity rates and process integration are actively being addressed by the industry and have not faced significant roadblocks for contact-hole applications. While many DSA applications have been proposed, deploying DSA for Fin structures competes in cost and variability control with SADP techniques. Given the 1D nature of find structures, it is difficult to control fin placement with accuracy better than 4nm 3 sigma. In addition, a second patterning step is needed to remove the un-wanted sections of the grating and leaving behind only the required fin structures, therefore limiting its adoption. On the other hand, DSA applied to contact/via holes has demonstrated low defectivity rates due to improved polymerization and processing techniques, as well as an adequate control to reduce the placement error due to thermal fluctuations during the annealing and cylinder formation process. For that reason, the results from contact/via layers can extend to the metal cut layer printing with DSA grapho-epitaxy. In this paper, we show that DSA provides a promising cost-effective solution for the technology scaling by reducing mask number from N to N-1. It is shown that pxOPC may provide better guiding patterns than the conventional one. In addition, the practical grouping rules for DSA should avoid 2D grouping, avoid putting more than 3 features in a group with different pitches, and avoid grouping features with different sizes. Our recommendations to designers for DSA technology are the following: if the design is to be decomposed with 2 or more DSA masks, then the design rules should be set up in this way: first the minimum pitch is better to be on DSA material’s own natural pitch; second, for each DSA mask, singletons and bar-like grouping shapes with DSA’s natural pitch should be used as much as possible.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2014; 9231. DOI:10.1117/12.2065508 · 0.20 Impact Factor
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    ABSTRACT: Directed Self Assembly (DSA) of Block Co-Polymers (BCP) has become an intense field of study as a potential patterning solution for future generation devices. The most critical challenges that need to be understood and controlled include pattern placement accuracy, achieving low defectivity in DSA patterns and how to implement this process as a patterning solution. The DSA program at imec includes efforts on these three major topics. Specifically, in this paper the progress for the templated DSA flow within the imec program will be discussed. An experimental assessment is made based on a 37 nm BCP pitch material. In particular, the impact of different process options is illustrated, and data for CD and placement accuracy of the DSA holes in their template is provided.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2014; 9231. DOI:10.1117/12.2066647 · 0.20 Impact Factor
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    ABSTRACT: Significant interest from the integrated circuit (IC) industry has been placed on directed self-assembly (DSA) for sub 10nm nodes. DSA is being considered as a cost reduction complementary process to multiple patterning (MP) and an enabler of new technology nodes. However, to realize the potential of this technology, it is essential to look holistically at the necessary infrastructure from the point of view of materials, hardware, software, process integration and design methodologies which enable its deployment in large volume manufacturing. One key aspect in enabling DSA processes is the ability to mirror functionality of full chip mask synthesis and verification methods of existing tools used in production. One of those critical components is the ability to accurately model the placement of the target phases in the DSA process with a given mask shape, as well as determining the conditions at which unwanted phase transitions start to occur. Self-consistent field theory and Monte Carlo1 simulators have the capability to probe and explore the mechanisms driving the different phases of a diblock copolymer system. While such methods are appropriate to study the nature of the self-assembly process, they are computationally expensive and they cannot be used to perform mask synthesis operations nor full chip verification. The nature of a compact model is to make a series of approximations allowing a simpler description of the problem in a way that the phenomena of interest can be sufficiently captured even if it is at the expense of its generality. In this case we focus our effort in establishing the minimum set of conditions that a compact model for the manufacture of contact holes using a grapho epitaxy process for a PS-PMMA diblock copolymer system needs. The processes uses etched short trenches as guiding patterns in which the vertical DSA cylinders are formed. By focusing in the phase of interest (i.e., cylinder forming conditions), it is possible to reformulate the problem in a phenomenological formulation which accounts for the interaction among cylinders, the volume fraction of the respective co-polymers and the interaction with the confinement walls. As such, a 2D approximation to the 3D environment can be applied to simplify the representation of the DSA process. This enables the use of a 2D contour for compact model training and verification. Further simplification is not recommended due to the nature of the grapho-epitaxy guiding patterns, where a simple CD measurement is not sufficient to capture the 2D environment of post routed contact patterns for sub 10nm nodes. In this paper, we will study the application of the DSA compact model to a via layer of imec's 7nm technology node standard cells. ArF immersion lithography will be used to pattern the guides, and the layout will be DSA compliant to determine the mask complexity as well as the sensitivity of the solution to mask biases for the contact layer.
    Proceedings of SPIE - The International Society for Optical Engineering 01/2014; 9235. DOI:10.1117/12.2069188 · 0.20 Impact Factor
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    ABSTRACT: Line edge roughness (LER) is a common problem to all lithography techniques and is seen as an increasingly important challenge for advanced technology nodes. Contributions to LER can come from the aerial image itself or the resist related processes. Mask roughness belongs to the former group, which can contribute to the low frequency roughness. This paper investigates the mitigating effect of pupil plane filtering on the mask roughness transfer. Experiments were performed using a mask with edge roughness programmed at different periods on 128 nm pitch vertical line/space patterns. A target phase filter was optimized for ArF illumination source and the roughness period of 200 nm. The filter introduces an orientation dependent defocus; hence, reducing the image fidelity in the direction of roughness features without significantly impacting the fidelity of vertical line and space features. Experimental results showed significant reduction in mask roughness transfer for the target roughness period.
    Journal of vacuum science & technology. B, Microelectronics and nanometer structures: processing, measurement, and phenomena: an official journal of the American Vacuum Society 11/2013; 31(6):06F801-06F801-6. DOI:10.1116/1.4825102 · 1.46 Impact Factor
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    ABSTRACT: Reducing lithography pattern variability has become a critical enabler of ArF immersion scaling and is required to ensure consistent lithography process yield for sub-30nm device technologies. As DUV multi-patterning requirements continue to shrink, it is imperative that all sources of lithography variability are controlled throughout the product life-cycle, from technology development to high volume manufacturing. Recent developments of new ArF light-source metrology and monitoring capabilities have been introduced in order to improve lithography patterning control.[1] These technologies enable performance monitoring of new light-source properties, relating to illumination stability, and enable new reporting and analysis of in-line performance.
    SPIE Advanced Lithography; 04/2013
  • Monica Kempsell Sears · Joost Bekaert · Bruce W Smith ·
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    ABSTRACT: As semiconductor optical lithography is pushed to smaller dimensions, resolution enhancement techniques have been required to maintain process yields. For some time, the customization of illumination coherence at the source plane has allowed for the control of diffraction order distribution across the projection lens pupil. Phase shifting at the photomask plane has allowed for some phase control as well. Geometries smaller than the imaging wavelength introduce complex wavefront effects that cannot be corrected at source or mask planes. Three-dimensional photomask topography effects can cause a loss of both focal depth and exposure latitude across geometry of varying density. Wavefront manipulation at the lens pupil plane becomes necessary to provide the degrees of freedom needed to correct for such effects. The focus of this research is the compensation of the wavefront phase error introduced by the topographical photomask structures of high resolution phase shift masking combined with off-axis illumination. The compensation is realized through phase manipulation of the lens pupil plane, specifically in the form of spherical aberration. Subwavelength resolution optimization and imaging is presented showing how phase pupil filtering can measurably improve the depth of focus for several photomask structures and types.
    Applied Optics 01/2013; 52(3):314-22. DOI:10.1364/AO.52.000314 · 1.78 Impact Factor
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    ABSTRACT: In recent years Directed Self-Assembly (DSA) has come up as a strong candidate technology for advanced lithography. DSA is a complementary technology that is used to enhance established projection lithography. In this paper, an overview is given of activities at imec that are driving towards readying DSA technology for implementation into semi-conductor manufacturing. Flows for line/space and contact hole pattern formation based on chemo- as well as grapho-epitaxy are available and used for understanding process sensitivities, evaluation of defect densities and the demonstration of integration approaches. The state-of-the-art of the various process flows is discussed along with the primary outstanding issues.
    Journal of Photopolymer Science and Technology 01/2013; 26(6):779-791. DOI:10.2494/photopolymer.26.779 · 1.06 Impact Factor
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    ABSTRACT: We studied the potential of optical scatterometry to measure the full 3D profile of features representative to real circuit design topology. The features were selected and printed under conditions to improve the measurability of the features by scatterometry without any loss of information content for litho monitoring and control applications. The impact of the scatterometry recipe and settings was evaluated and optimal settings were determined. We have applied this strategy on a variety of structures and gathered results using the YieldStar angular reflection based scatterometer. The reported results show that we obtained effective decoupling of the measurement of the 3 dimensions of the features. The results match with predictions by calibrated lithographic simulations. As a verification we have successfully performed a scanner matching experiment using computational Pattern Matcher (cPM) in combination with YieldStar as a metrology tool to characterize the difference between the scanners and verify the matching. The results thus obtained were better than using CD-SEM for matching and verification.
    Proceedings of SPIE - The International Society for Optical Engineering 03/2012; 8324:26-. DOI:10.1117/12.919050 · 0.20 Impact Factor

Publication Stats

546 Citations
47.30 Total Impact Points


  • 2003-2014
    • imec Belgium
      • Smart Systems and Energy Technology
      Louvain, Flanders, Belgium
  • 1999-2003
    • University of Leuven
      • Section of Nuclear and Radiation Physics (IKS)
      Louvain, Flanders, Belgium
  • 2002
    • Université de Montréal
      Montréal, Quebec, Canada