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The ability to control structure in molecular glasses has enabled them to play a key role in modern technology; in particular, they are ubiquitous in organic light-emitting diodes. While the interplay between bulk structure and optoelectronic properties has been extensively investigated, few studies have examined molecular orientation near buried interfaces despite its critical role in emergent functionality. Direct, quantitative measurements of buried molecular orientation are inherently challenging, and many methods are insensitive to orientation in amorphous soft matter or lack the necessary spatial resolution. To overcome these challenges, we use polarized resonant soft X-ray reflectivity (p-RSoXR) to measure nanometer-resolved, molecular orientation depth profiles of vapor-deposited thin films of an organic semiconductor Tris(4-carbazoyl-9-ylphenyl)amine (TCTA). Our depth profiling approach characterizes the vertical distribution of molecular orientation and reveals that molecules near the inorganic substrate and free surface have a different, nearly isotropic orientation compared to those of the anisotropic bulk. Comparison of p-RSoXR results with near-edge X-ray absorption fine structure spectroscopy and optical spectroscopies reveals that TCTA molecules away from the interfaces are predominantly planar, which may contribute to their attractive charge transport qualities. Buried interfaces are further investigated in a TCTA bilayer (each layer deposited under separate conditions resulting in different orientations) in which we find a narrow interface between orientationally distinct layers extending across ≈1 nm. Coupling this result with molecular dynamics simulations provides additional insight into the formation of interfacial structure. This study characterizes the local molecular orientation at various types of buried interfaces in vapor-deposited glasses and provides a foundation for future studies to develop critical structure-function relationships.

Interactions between polymers and surfaces can be used to influence properties including mechanical performance in nanocomposites, the glass transition temperature, and the orientation of thin film block copolymers (BCPs). In this work we investigate how specific interactions between the substrate and BCPs with varying substrate affinity impact the interfacial width between polymer components. The interface width is generally assumed to be a function of the BCP properties and independent of the surface affinity or substrate proximity. Using resonant soft X-ray reflectivity the optical constants of the film can be controlled by changing the incident energy, thereby varying the depth sensitivity of the measurement. Resonant soft X-ray reflectivity measurements were conducted on films of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) and PS-b-poly(methyl methacrylate) (PS-b-PMMA), where the thickness of the film was varied from half the periodicity (L0) of the BCP to 5.5 L0. The results of this measurement on the PS-b-P2VP films show a significant expansion of the interface width immediately adjacent to the surface. This is likely caused by the strong adsorption of P2VP to the substrate, which constrains the mobility of the junction points, preventing them from reaching their equilibrium distribution and expanding the observed interface width. The interface width decays toward equilibrium moving away from the substrate, with the decay rate being a function of film thickness below a critical limit. The PMMA block appears to be more mobile, and the BCP interfaces near the substrate match their equilibrium value.

Molecular orientation anisotropy can be critical in functional organic thin films. For instance, it is known that molecular orientation can affect the performance of organic electronic devices such...

Polarity-switching photopatternable guidelines can be directly used to both orient and direct the self-assembly of block copolymers. We report the orientation and alignment of poly(styrene-block-4-...

The challenges of patterning next-generation integrated circuits have driven the semiconductor industry to look outside of traditional lithographic methods in order to continue cost-effective size ...

Bottlebrush polymers consist of a linear backbone with densely grafted side chains which impact the rigidity of the molecule. The persistence length of the bottlebrush backbone in solution is influenced by both the intrinsic structure of the polymer and the local environment, such as the solvent quality and concentration. Increasing the concentration reduces the overall size of the molecule because of the reduction in backbone stiffness. In this study, we map out the size of a bottlebrush polymer as a function of concentration for a single backbone length. Small-angle neutron scattering measurements are conducted on a polynorbornene-based bottlebrush with polystyrene side chains in a good solvent. The data are fit using a model which provides both the long and short axis radius of gyration (R_(g,2) and R_(g,1), respectively), providing a measure for how the conformation changes as a function of concentration. At low concentrations, a highly anisotropic structure is observed (R_(g,2)/R_(g,1) ≈ 4), becoming more isotropic at higher concentrations (R_(g,2)/R_(g,1) ≈ 1.5). The concentration scaling for both R_(g,2) and the overall Rg is evaluated and compared with predictions in the literature. Coarse-grained molecular dynamics simulations were also conducted to probe the impact of concentration on bottlebrush conformation, showing qualitative agreement with the experimental results.

The directed self-assembly (DSA) of block copolymers (BCPs) is a promising low-cost approach to patterning structures with critical dimensions (CDs) which are smaller than can be achieved by traditional photolithography. The CD of contact holes can be reduced by assembling a cylindrical BCP inside a patterned template and utilizing the native size of the cylinder to dictate the reduced dimensions of the hole. This is a particularly promising application of the DSA technique, but in order for this technology to be realized there is a need for three-dimensional metrology of the internal structure of the patterned BCP in order to understand how template properties and processing conditions impact BCP assembly. This is a particularly challenging problem for traditional metrologies owing to the three-dimensional nature of the structure and the buried features. By utilizing small-angle X-ray scattering and changing the angle between the incident beam and sample we can reconstruct the three-dimensional shape profile of the empty template and the residual polymer after self-assembly and removal of one of the phases. A two-dimensional square grid pattern of the holes results in scattering in both in-plane directions, which is simplified by converting to a radial geometry. The shape is then determined by simulating the scattering from a model and iterating that model until the simulated and experimental scattering profiles show a satisfactory match. Samples with two different processing conditions are characterized in order to demonstrate the ability of the technique to evaluate critical features such as residual layer thickness and sidewall height. It was found that the samples had residual layer thicknesses of 15.9 ± 3.2 nm and 4.5 ± 2.2 nm, which were clearly distinguished between the two different DSA processes and in good agreement with focused ion beam scanning transmission electron microscopy (FIBSTEM) observations. The advantage of the X-ray measurements is that FIBSTEM characterizes around ten holes, while there are of the order of 800 000 holes illuminated by the X-ray beam.

Polymer chains are attached to nanoparticle surfaces for many purposes, including altering solubility, influencing aggregation, dispersion, and even tailoring immune responses in drug delivery. The most unique structural motif of polymer-grafted nanoparticles (PGNs) is the high-density region in the corona where polymer chains are stretched under significant confinement, but orientation of these chains has never been measured because conventional nanoscale-resolved measurements lack sensitivity to polymer orientation in amorphous regions. Here, we directly measure local chain orientation in polystyrene grafted gold nanoparticles using polarized resonant soft X-ray scattering (P-RSoXS). Using a computational scattering pattern simulation approach, we measure the thickness of the anisotropic region of the corona and extent of chain orientation within it. These results demonstrate the power of P-RSoXS to discover and quantify orientational aspects of structure in amorphous soft materials and provide a framework for applying this emerging technique to more complex, chemically heterogeneous systems in the future., The orientation of polymer chains in the corona of polymer-grafted nanoparticles has never been measured. Here, the authors use polarized resonant soft X-ray scattering to measure local chain orientation in polystyrene grafted gold nanoparticles and quantify the thickness of the anisotropic region of the corona as well as the extent of chain orientation within it.

Bottlebrush block copolymers (BBCPs) are intriguing architectural variations on linear BCPs with highly tunable structure. Confinement can have a significant impact on polymer assembly, giving rise to changes in morphology, assembly kinetics, and properties like the glass transition. Given that confinement leads to significant changes in the persistence length of bottlebrush homopolymers, it is reasonable to expect that BBCPs will see significant changes in their structure and periodicity relative to the bulk morphology. Understanding how confinement influences assembly will be important for designing BBCPs for thin film applications including membranes, integrated photonic structures, and potentially BCP lithography. In order to study the effects of confinement on BBCP conformation and morphology, a blade coating was used to prepare films with continuous variation in film thickness. Unlike thin films of linear BCPs, islands/holes were not observed, and instead mixtures of parallel and perpendicular morphologies emerge after annealing. The lamellar periodicity (L0) of the morphologies is found to be thickness dependent, increasing L0 with decreasing film thickness for blade coated films. Films coated out of tetrahydrofuran (THF) resulted in a single well-defined lamellar periodicity, verified through atomic force microscopy (AFM) and grazing incidence small-angle X-ray scattering (GISAXS), which increases dramatically from the bulk value (30.6 nm) and continues to increase as the film thickness decreases. The largest observed L0 was 65.5 nm, and this closely approaches the estimated upper limit of 67 nm corresponding to a fully extended backbone in a bilayer arrangement. Films coated out of propylene glycol methyl ether acetate (PGMEA) resulted in a mixture of perpendicular lamellae and a smaller, likely cylindrical morphology. The lamellar portion of the film shows the same thickness dependence as the lamellae observed in the THF coated films. The scaling of the lamellar L0 with respect to film thickness follows predictions for confined semiflexible polymers with weak excluded volume interactions and can be related to models for confinement of DNA. Spin coated films shows the same reduction in periodicity, although at very different film thicknesses. This result suggests that the material has shallow free-energy barriers to transitioning between different L0 and morphologies, a property that could be taken advantage of for patterning diverse structures with a single material.

Small-angle scattering measurements of complex macromolecules in solution are used to establish relationships between chemical structure and conformational properties. Interpretation of the scattering data requires an inverse approach where a model is chosen and the simulated scattering intensity from that model is iterated to match the experimental scattering intensity. This raises challenges in the case where the model is an imperfect approximation of the underlying structure, or where there are significant correlations between model parameters. We examine three bottlebrush polymers (consisting of polynorbornene backbone and polystyrene side chains) in a good solvent using a model commonly applied to this class of polymers: the flexible cylinder model. Applying a series of constrained Monte-Carlo Markov Chain analyses demonstrates the severity of the correlations between key parameters and the presence of multiple close minima in the goodness of fit space. We demonstrate that a shape-agnostic model can fit the scattering with significantly reduced parameter correlations and less potential for complex, multimodal parameter spaces. We provide recommendations to improve the analysis of complex macromolecules in solution, highlighting the value of Bayesian methods. This approach provides richer information for understanding parameter sensitivity compared to methods which produce a single, best fit.

The challenges of patterning next generation integrated circuits have driven the semiconductor industry to look outside of traditional lithographic methods in order to continue cost effective size scaling. The directed self-assembly (DSA) of block copolymers (BCPs) is a nanofabrication technique used to reduce the periodicity of patterns prepared with traditional optical methods. BCPs with large interaction parameters (χ(eff)), provide access to smaller pitches and reduced interface widths. Larger χ(eff) is also expected to be correlated with reduced line edge roughness (LER), a critical performance parameter in integrated circuits. One approach to increasing χ(eff) is blending the BCP with a phase selective additive, such as an Ionic liquid (IL). The IL does not impact the etching rates of either phase, and this enables a direct interrogation of whether the change in interface width driven by higher χ(eff) translates into lower LER. The effect of the IL on the layer thickness and interface width of a BCP are examined, along with the corresponding changes in LER in a DSA patterned sample. The results demonstrate that increased χ(eff) through additive blending will not necessarily translate to a lower LER, clarifying an important design criterion for future material systems.

The directed self-assembly (DSA) of block copolymers (BCPs) is a promising low-cost approach to patterning structures with critical dimensions (CDs) which are smaller than can be achieved by traditional photolithography. The CD of contact holes can be reduced by assembling a cylindrical BCP inside a patterned template and utilizing the native size of the cylinder to dictate the reduced dimensions of the hole. This is a particularly promising application of the DSA technique, but in order for this technology to be realized there is a need for three-dimensional metrology of the internal structure of the patterned BCP in order to understand how template properties and processing conditions impact BCP assembly. This is a particularly challenging problem for traditional metrologies owing to the three-dimensional nature of the structure and the buried features. By utilizing small-angle X-ray scattering and changing the angle between the incident beam and sample we can reconstruct the three-dimensional shape profile of the empty template and the residual polymer after self-assembly and removal of one of the phases. A two-dimensional square grid pattern of the holes results in scattering in both in-plane directions, which is simplified by converting to a radial geometry. The shape is then determined by simulating the scattering from a model and iterating that model until the simulated and experimental scattering profiles show a satisfactory match. Samples with two different processing conditions are characterized in order to demonstrate the ability of the technique to evaluate critical features such as residual layer thickness and sidewall height. It was found that the samples had residual layer thicknesses of 15.9 ± 3.2 nm and 4.5 ± 2.2 nm, which were clearly distinguished between the two different DSA processes and in good agreement with focused ion beam scanning transmission electron microscopy (FIBSTEM) observations. The advantage of the X-ray measurements is that FIBSTEM characterizes around ten holes, while there are of the order of 800 000 holes illuminated by the X-ray beam.

Optimizing the extraction of information from x-ray measurements while minimizing exposure time is an important area of research in a variety of fields. The semiconductor industry is reaching a point where the traditional optical metrologies need to be augmented in order to better resolve the critical dimensions of structures with feature sizes below 10 nm. Critical dimension small angle x-ray scattering (CDSAXS) is one measurement technique that is capable of characterizing detailed features of periodic nanostructures. As currently implemented, the measurement utilizes the combined scattering from up to 60 different angles. Reducing the number of angles would dramatically improve the feasibility of CDSAXS for implementation in a fabrication setting, but currently there are no clear guidelines as to which angles provide the most information to minimize the uncertainty in the shape of the target structure while maximizing the throughput. In order to develop guidelines for optimizing the angle selection, simulation studies were conducted on a wide variety of structures with subsets of the full angular range to identify which angles minimized the overall shape uncertainty. Analyzing sets of two angle pairs (including all combinations between 0 deg and 60 deg) provides guidance on which angles best constrain the samples. For select samples, higher numbers of angles were included to explore the impact of additional information on the model uncertainty. In general, low angles (

The three-dimensional architectures for field effect transistors (FETs) with vertical stacking of Gate-all-Around Nanowires provide a pathway to increased device density and superior electrical performance. However, the transition from research into manufacturing will only be successful if their feature shape, critical dimensions, and associated electrical performance are repeatable across the integrated circuit, across the wafer, and among multiple wafers. Patterning process control for these structures will require significant advances in metrology. Two techniques that are potential candidates for this purpose are Mueller Matrix Spectroscopic Ellipsometry based Scatterometry (MMSEscatterometry) and Critical Dimension Small Angle X-Ray Scattering (CDSAXS). In this work, we highlight the characterization of the Nanowire Test Structures fabricated from patterned Si/SixGe1-x/Si/SixGe1-x/Si/SixGe1-x/Si structures using CDSAXS. Preliminary experimental data shows sensitivity to the selective etching of subsurface SixGe1- x. CDSAXS diffraction data provides information in reciprocal space about line shape and periodicity as well as the amount of subsurface etching. Side lobes in the Intensity vs. Qz (structure height) data are observed around Qz positions of around 0.15 nm-1 and 0.5 nm-1 and are at the same positions in the measured and the simulated data for different amounts of SixGe1-x etch in the Nanowire Test Structures. This demonstrates its ability for successful measurement of the critical dimensions and 3D profile of the Nanowire Test Structures, which can then be extended to monitor several key process steps for Nanowire/Nanosheet FET fabrication.

A block copolymer self-consistent field theory (SCFT) model is used for direct analysis of experimental X-ray scattering data obtained from thin films of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) made from directed self-assembly. In a departure from traditional approaches, which reconstruct the real space structure using simple geometric shapes, we build on recent work that has relied on physics-based models to determine shape profiles and extract thermodynamic processing information from the scattering data. More specifically, an SCFT model, coupled to a covariance matrix adaptation evolutionary strategy (CMAES), is used to find the set of simulation parameters for the model that best reproduces the scattering data. The SCFT model is detailed enough to capture the essential physics of the copolymer self-assembly, but sufficiently simple to rapidly produce structure profiles needed for interpreting the scattering data. The ability of the model to produce a matching scattering profile is assessed, and several improvements are proposed in order to more accurately recreate the experimental observations. The predicted parameters are compared to those extracted from model fits via additional experimental methods and with predicted parameters from direct particle-based simulations of the same model, which incorporate the effects of fluctuations. The Flory–Huggins interaction parameter for PS-b-PMMA is found to be in agreement with reported ranges for this material. These results serve to strengthen the case for relying on physics-based models for direct analysis of scattering and light signal based experiments.

Advancements in the directed self-assembly of block copolymers (BCPs) have prompted the development of new materials with larger effective interaction parameters (χe). This enables BCP systems with phase separation at increasingly small degrees of polymerization (N). Very often these systems reside near the order–disorder transition and fit between the weak and strong segregation limits where the behavior of BCP systems is not as thoroughly understood. Utilizing resonant soft X-ray reflectivity (RSoXR) enables both the BCP pitch (L0) and interface width (wM) to be determined simultaneously, through a direct characterization of the composition profile of BCP lamellae oriented parallel to a substrate. A series of high χe BCPs with χe ranging from ≈0.04 to 0.25 and χeN from 19 to 70 have been investigated. The L0/wm ratio serves as an important metric for the feasibility of a material for nanopatterning applications; the results of the RSoXR measurement are used to establish a relationship between χe and L0/...

There is a need to characterize nanoscale molecular orientation in soft materials, and polarized scattering is a powerful means to measure this property. However, few approaches have been demonstrated that quantitatively relate orientation to scattering. Here, a modeling framework to relate the molecular orientation of nanostructures to polarized resonant soft X-ray scattering measurements is developed. A variable-angle transmission measurement called critical-dimension X-ray scattering enables the characterization of the three-dimensional shape of periodic nanostructures. When this measurement is conducted at resonant soft X-ray energies with different polarizations to measure soft material nanostructures, the scattering contains convolved information about the nanostructure shape and the preferred molecular orientation as a function of position, which is extracted by fitting using inverse iterative algorithms. A computationally efficient Born approximation simulation of the scattering has been developed, with a full tensor treatment of the electric field that takes into account biaxial molecular orientation, and this approach is validated by comparing it with a rigorous coupled wave simulation. The ability of various sample models to generate unique best fit solutions is then analyzed by generating simulated scattering pattern sets and fitting them with an inverse iterative algorithm. The interaction of the measurement geometry and the change in orientation across a periodic repeat unit leads to distinct asymmetry in the scattering pattern which must be considered for an accurate fit of the scattering.

There is considerable interest in developing multimodal characterization frameworks capable of probing critical properties of complex materials by relying on distinct, complementary methods or tools. Any such framework should maximize the amount of information that is extracted from any given experiment and should be sufficiently powerful and efficient to enable on-the-fly analysis of multiple measurements in a self-consistent manner. Such a framework is demonstrated in this work in the context of self-assembling polymeric materials, where theory and simulations provide the language to seamlessly mesh experimental data from two different scattering measurements. Specifically, the samples considered here consist of diblock copolymers (BCP) that are self-assembled on chemically nanopatterned surfaces. The copolymers microphase separate into ordered lamellae with characteristic dimensions on the scale of tens of nanometers that are perfectly aligned by the substrate over macroscopic areas. These aligned lame...

The directed self-assembly (DSA) of block copolymers (BCPs) is a potential solution for patterning critical features for integrated circuits at future technology nodes. For this process to be implemented, there needs to be a better understanding of how the template guides the assembly and induces subsurface changes in the lamellar structure. Using a rotational transmission X-ray scattering measurement coupled with soft X-rays to improve contrast between polymer components, the impact of the ratio of the guiding stripe width (W) to the BCP pitch (L0) was investigated. For W/L0 < 1, continuous vertical lamella were observed, with some fluctuations in the interface profile near the template that smoothed out further up the structure. Near W/L0 ≈ 1.5, the arrangement of the lamella shifted, moving from polystyrene centered on the guiding stripe to poly(methyl methacrylate) centered on the guiding stripe.

Block copolymers (BCPs) have the potential to play a key role in templating materials for nanoscale synthesis. BCP lithography likely will be one of the first examples of BCP-based nanomanufacturing implemented in a production setting. One of the challenges in implementing BCP lithography is that the lamella need to be oriented perpendicular to the substrate. For many systems, this requires control over interfacial energies for both components at the substrate and interface. Top coats can be designed to provide a neutral interface for both blocks on the BCP surface. The preferentiality of the top coat as a function of composition has been determined qualitatively by examining the orientation of a BCP after annealing with a top coat. Measurements of the interfacial width between the top coat and homopolymers allows the interface energy to be quantitatively determined. Resonant soft X-ray reflectivity measurements on top coat/homopolymer pairs were used to extract the Flory-Huggins parameter (χ) and interface energy (γ) as a function of top coat composition. The difference between χ and γ for each top coat/homopolymer pair was minimized at compositions that resulted in the top coat promoting perpendicular orientation. As the composition moved away from the neutral point the difference between χ and γ for each pair grew larger.

The semiconductor industry is in need of new, in-line dimensional metrology methods with higherspatial resolution for characterizing their next generation nanodevices. The purpose of this short course is to train the semiconductor industry on the NIST-developed critical dimension small angle X-ray scattering (CDSAXS) method. The topics will include both data processing and instrumentation. The short course will also provide an opportunity for discussion of the requirements for CDSAXS and the necessary improvements in X-ray source technology. Expected audience include semiconductor manufacturers, equipment manufacturers, and component manufacturers. The presentations were made at “X-ray Metrology for the Semiconductor Industry” short course at the National Institute of Standards and Technology on Aug. 25, 2016.

Block copolymer (BCP) blends offer a facile route toward customizable nanomaterials. To better understand these systems, the thermodynamics of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) and poly(vinylphenol) (PVPH) blends were examined using scattering measurements and self-consistent field theory (SCFT). PVPH hydrogen bonds to the PMMA block, resulting in the selective infusion into the PMMA layer. Measurements on initially disordered blends show that this interaction can induce an order–disorder transition (ODT). The ODT was observed to be a continuous transition, unlike the first-order thermal ODT typically observed in BCPs. Free energy curves extracted from SCFT simulations also observed a lack of a discontinuity in the first-order derivative. Lamellar systems underwent a greater increase in BCP period compared to identical athermal systems due to the extension of the PMMA chains away from the interface. Comparison with the SCFT models finds good agreement in the predicted behavior of the ble...

Composite materials consisting of nanoparticles dispersed in a polymer matrix have potential applications in a wide range of fields. Grafting polymer chains to nanoparticles is a key strategy for controlling the distribution of those nanoparticles throughout the matrix material. The particle distribution is controlled by the relative length of the matrix chains (P) to the graft chains (N) and the density of the graft chains (σ) for particles of a given radius (R). Using differential scanning calorimetry (DSC) and bulk rheological measurements, we examine the interactions between the graft and matrix chains as a function of the three key parameters: σ, P, and N. The results of these measurements are compared to ultrasmall-angle X-ray scattering (USAXS) measurements [Macromolecules 2012, 45, 4007−4011], which were used to determine the phase behavior of the particles. DSC results indicate that the matrix chains must be completely expelled from the graft layer for the autophobic transition to occur. Similar ...

Advancements in the directed self-assembly of block copolymers (BCPs) have prompted the development of new materials with larger effective interaction parameters (χe). This enables BCP systems with phase separation at increasingly small degrees of polymerization (N). Very often these systems reside near the order–disorder transition and fit between the weak and strong segregation limits where the behavior of BCP systems is not as thoroughly understood. Utilizing resonant soft X-ray reflectivity (RSoXR) enables both the BCP pitch (L0) and interface width (wM) to be determined simultaneously, through a direct characterization of the composition profile of BCP lamellae oriented parallel to a substrate. A series of high χe BCPs with χe ranging from ≈0.04 to 0.25 and χeN from 19 to 70 have been investigated. The L0/wm ratio serves as an important metric for the feasibility of a material for nanopatterning applications; the results of the RSoXR measurement are used to establish a relationship between χe and L0/wm. The results of this analysis are correlated with experimentally established limits for the functionality of BCPs in nanopatterning applications. These results also provide guidance for the magnitude of χe needed to achieve small interface width for samples with sub-10 nm L0.

Densely patterned contact holes form a key component of integrated circuits, but there are significant challenges to patterning holes with a sub 10-nm radius. The directed self-assembly (DSA) of block copolymers offers a potential solution, where a larger hole is initially patterned and a cylinder forming block copolymer (BCP) is assembled inside. The radius of the inner BCP cylinder can now be used to template the hole radius. It can be particularly challenging to characterize the internal structure of the DSA patterned contact hole, particularly for features such as the residual layer, which may adversely impact the etching process. The high aspect ratio of these features makes top-down characterization nearly impossible, forcing the use of challenging cross-section based approaches. Critical Dimension small angle X-ray scattering (CDSAXS) offers the possibility of characterizing the internal structure of DSA patterned contact holes. CDSAXS is a variable angle scattering technique which combines measurements from different sample angles to reconstruct the three-dimensional structure of the sample. In this case the scattering yields a two-dimensional pattern, where the off-axis peaks contain additional information about the structure. A model based inverse analysis is then used to fit the scattering and evaluate the structure of the measured target. Contact holes were prepared with a variety of radii and surface treatments in order to evaluate which conditions resulted in optimal assembly of the BCP inside the template. The results demonstrate a correlation between hole radius, surface treatment and residual layer thickness.

With the advent of high brightness sources and fast detectors, there is a possibility for combining fast X-ray acquisition with high-speed data treatment to reach the timescale for an effective in-line characterization method. We will highlight two recent developments using Small Angle X-ray Scattering on nanoscale etched patterns: the first is the inclusion of a CD-SAXS tool, allowing the data treatment and simulations to reconstruct the form-factor, inside the Xi-cam framework; the second is the development of a high performance Grazing Incidence approach to reconstruct the shape of line profile. This study also shows the comparison between the line profiles reconstructed from both techniques as well as the profile extracted from cross-section SEM.

Polyamide nanomembranes are at the heart of water desalination, a process which plays a critical role in clean water production. Improving their efficiency requires a better understanding of the relationship between chemistry, network structure, and performance but few techniques afford compositional information in ultrathin films (

Bottlebrush block copolymers offer rich opportunities for the design of complex hierarchical materials. As consequences of the densely grafted molecular architecture, bottlebrush polymers can adopt highly extended backbone conformations and exhibit unique physical properties. A recent report has described the unusual phase behavior of ABC bottlebrush triblock terpolymers bearing grafted poly((D,L)-lactide) (PLA), polystyrene (PS), and poly(ethylene oxide) (PEO) blocks (LSO). In this work, a combination of resonant soft X-ray reflectivity (RSoXR), near edge X-ray absorption fine structure spectroscopy (NEXAFS), and self-consistent field theory (SCFT) was used to provide insight into the phase behavior of LSO and underlying backbone chain conformations. Consistent with SCFT calculations, RSoXR measurements confirm a unique mesoscopic ACBC domain connectivity and decreasing lamellar periods (d(0)) with increasing backbone length of the PEO block. RSoXR and NEXAFS demonstrate an additional unusual feature of brush LSO thin films: when the overall film thickness is ~3.25d(0), the film-air interface is majority PS (>80%). Since PS is the midblock, the triblocks must adopt looping configurations at the surface, despite the preference for the backbone to be extended. This result is supported by backbone concentrations calculated through SCFT, which suggest that looping midblocks are present throughout the film. Collectively, this work provides evidence for the flexibility of the bottlebrush backbone and the consequences of low-χ block copolymer design. We propose that PEO blocks localize at the PS/PLA domain interfaces in order to screen the highest-χ contacts in the system, driving the formation of loops. These insights introduce a potential route to overcome the intrinsic penalties to interfacial curvature imposed by the bottlebrush architecture, enabling the design of unique self-assembled materials.

The semiconductor industry is exploring new metrology techniques capable of meeting the future requirement to characterize three-dimensional structure where the critical dimensions are less than 10 nm. X-ray scattering techniques are one candidate owing to the sub-Å wavelengths which are sensitive to internal changes in electron density. Critical-dimension small-angle X-ray scattering (CDSAXS) has been shown to be capable of determining the average shape of a line grating. Here it is used to study a set of line gratings patternedviaa self-aligned multiple patterning process, which resulted in a set of mirrored lines, where the individual line shapes were asymmetric. The spacing between lines was systematically varied by sub-nm shifts. The model used to simulate the scattering was developed in stages of increasing complexity in order to justify the large number of parameters included. Comparisons between the models at different stages of development demonstrate that the measurement can determine differences in line shapes within the superlattice. The shape and spacing between lines within a given set were determined to sub-nm accuracy. This demonstrates the potential for CDSAXS as a high-resolution nanostructure metrology tool.

Block copolymer directed self-assembly (BCP) with chemical epitaxy is a promising lithographic solution for patterning features with critical dimensions under 20 nm. In this work, we study the extent to which lamellae-forming poly(styrene-b-methyl methacrylate) can be directed with chemical contrast patterns when the pitch of the block copolymer is slightly compressed or stretched compared to the equilibrium pitch observed in unpatterned films. Critical dimension small angle X-ray scattering complemented with SEM analysis was used to quantify the shape and roughness of the line/space features. It was found that the BCP was more lenient to pitch compression than to pitch stretching, tolerating at least 4.9% pitch compression, but only 2.5% pitch stretching before disrupting into dislocation or disclination defects. The more tolerant range of pitch compression is explained by considering the change in free energy with template mismatch, which suggests a larger penalty for pitch stretching than compressing. Additionally, the effect of width mismatch between chemical contrast pattern and BCP is considered for two different pattern transfer techniques. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 595–603

There is a need to design new materials to achieve smaller pitches and reduced interfacial widths for block copolymer (BCP) lithography. One option is the use of blends, where the addition of a homopolymer which selectively associates to one of the blocks results in the increase in the Flory–Huggins interaction parameter (χ) between the two phases. In order to explore the effect of this approach on the interfacial width between BCP components, poly(vinylphenol) (PVPH) was added to polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA). Multilayers of this blend were characterized using resonant soft X-ray reflectivity (RSoXR), a measurement that allows the contrast between PS, PMMA, and PVPH to be selectively tuned by varying the beam energy. RSoXR measurements confirmed that PVPH is uniformly distributed throughout the PMMA block. The interfacial width of the block was reduced by 20% upon the addition of a mass fraction of 8% PVPH. The interfacial width of homopolymer bilayers was also investigated in order...

The semiconductor industry is evaluating a variety of approaches for the cost efficient production of future processing and memory generations. Amongst the technologies being explored are multiple patterning steps, extreme ultraviolet (EUV) lithography, multiple-beam electron beam lithography and the directed self-assembly (DSA) of block copolymers (BCPs). BCP DSA utilizes a chemical or topographical template to induce long range order in a thin film of BCP which enhances the resolution of the original pattern. The characterization of buried structure within a DSA BCP film is challenging due to the lack of contrast between the organic materials. Critical-dimension small angle x-ray scattering (CDSAXS) measurements were performed on DSA BCP films, using soft X-rays to tune the contrast, in order to understand the relationship between template structure and film morphology.1 The results of these measurements show that as the width of the guiding stripe widens the arrangement of the BCP on the guiding stripe inverts, shifting from the A block being centered on the guiding stripe to the B block being centered on the guiding stripe. The initial results of integration of mean field simulations into the analysis of scattering data will also be discussed. In addition to examining the BCP structure with CDSAXS, soft X-ray reflectivity2 measurements were performed on BCP to better understand the relationship between interface width for systems with alternative architectures (triblocks) and additives (polymers/ionic liquids). The addition of a selectively associating additive increases the interaction parameter between the two blocks, resulting in the reduction of the interface width and access to smaller pitches. The use of soft X-ray reflectivity allows the evaluation of the distribution of the additive. (1) Sunday, D. F.; Hammond, M. R.; Wang, C.; Wu, W.; Delongchamp, D. M.; Tjio, M.; Cheng, J. Y.; Kline, R. J.; Pitera, J. W. Determination of the Internal Morphology of Nanostructures Patterned by Directed Self Assembly. ACS Nano 2014, 8, 8426–8437. (2) Sunday, D. F.; Kline, R. J. Reducing Block Copolymer Interfacial Widths through Polymer Additives. Macromolecules 2015, 48, 679–686.

New critical dimension metrology methods such as critical dimension small angle X-ray scattering (CDSAXS) are being developed to meet the measurement challenges of next generation devices. Two key requirements for any new CD metrology method are non-destructiveness and the measurement speed. We will report on a study of beam damage and scattering strength of two model photoresist systems, HSQ and PMMA. We also will report on the status and initial results from NIST’s upgraded lab CDSAXS system. 50 nm pitch line gratings were fabricated in HSQ and PMMA films using EUV interference lithography at the Swiss Light Source. The lines were about 30 nm tall and 20-30 nm wide. The 17 keV CDSAXS exposure time was varied from 0.1 s to 60 s to determine the minimum X-ray exposure required to obtain a satisfactory fit. Normal incident measurements separated by a blanket X-ray exposure were repeated to measure the decrease in scattering intensity with X-ray dose. The PMMA scattering signal was found to decrease by about 80 % before stabilizing at around 15 % of the original scattering intensity. The HSQ scattering signal decreased much less and stabilized at about 80 % of the original scattering intensity. We also conducted a series of variable-angle CDSAXS measurements as a function of blanket X-ray exposure to determine how the shape of the photoresist lines changed during X-ray exposure. For PMMA, we found the line width to remain constant and the line height to decrease from 25 nm to 10 nm during the exposure series. The exposures that damaged the samples corresponded to several hours of exposure to the synchrotron beam in a 100 µm spot and were much longer than what was required to characterize the line gratings. Smaller targets result in a larger dose and could potentially damage the resist in the time required to make a CDSAXS measurement. The large differences in beam damage between PMMA and HSQ show that resist damage from CDSAXS will depend on the particular resist chemistries and target size.

Optimizing the extraction of information from x-ray measurements while minimizing exposure time is an important area of research in a variety of fields. The semiconductor industry is reaching a point where the traditional optical metrologies need to be augmented in order to better resolve the critical dimensions of structures with feature sizes below 10 nm. Critical dimension small angle x-ray scattering (CDSAXS) is one measurement technique that is capable of characterizing detailed features of periodic nanostructures. As currently implemented, the measurement utilizes the combined scattering from up to 60 different angles. Reducing the number of angles would dramatically improve the feasibility of CDSAXS for implementation in a fabrication setting, but currently there are no clear guidelines as to which angles provide the most information to minimize the uncertainty in the shape of the target structure while maximizing the throughput. In order to develop guidelines for optimizing the angle selection, simulation studies were conducted on a wide variety of structures with subsets of the full angular range to identify which angles minimized the overall shape uncertainty. Analyzing sets of two angle pairs (including all combinations between 0 deg and 60 deg) provides guidance on which angles best constrain the samples. For select samples, higher numbers of angles were included to explore the impact of additional information on the model uncertainty. In general, low angles (

The semiconductor industry needs new metrology methods to continue their current path to next generation integrated circuits. X-ray-based methods hold great promise, but are too slow with commercial compact X-ray sources. Improvements of several orders of magnitude in brightness will enable these new metrology tools. We will discuss the measurements and the compact X-ray source requirements for semiconductor applications.

Using atom transfer radical polymerization (ATRP), we synthesized hybrid organic/inorganic nanoparticles consisting of a silica core and a polystyrene brush. The brushes were grafted from the nanop...

In this chapter, we present an overview on the use of X-rays for the characterization of block copolymer (BCP) systems with a focus on the application to directed self-assembly. The use of small-angle X-ray scattering to characterize both the morphology and thermodynamics of BCP systems is presented. This is accompanied by the development of a newer technique—resonant critical dimension small-angle X-ray scattering. This technique uses soft X-rays to characterize the internal morphology of thin polymer films patterned by a chemical or topographical template. Reflection geometries are also discussed, including the application of grazing incidence small-angle X-ray scattering to determine the orientation of thin film BCPs and specular reflectivity for depth profiling.

Semiconductor devices continue to shrink in size with every generation. These ever smaller structures are challenging the resolution limits of current analytical and inline metrology tools. We will discuss the results of a study of critical dimension small angle x-ray scattering (CDSAXS) comparing the measured intensity from a laboratory source and a synchrotron to determine the improvements in compact x-ray source technology necessary to make CDSAXS a high throughput metrology method. We investigated finFET test structures with and without a high-k gate dielectric coating. The HfO2-based high-k gate dielectric substantially increased the scattering intensity. We found that single-angle laboratory source measurements of 15 min from HfO2-coated finFETs had sufficient scattering intensity to measure the higher order peaks necessary for obtaining high-resolution dimensional fits. Identical bare silicon finFETs required at least 2 h of exposure time for equivalent data quality. Using these structures, we measured the scattering efficiency and determined the required photon flux for next generation x-ray sources to make an inline CDSAXS tool high throughput.

The width and shape of 10 nm to 12 nm wide lithographically patterned SiO2 lines were measured in the scanning electron microscope by fitting the measured intensity vs. position to a physics-based model in which the lines' widths and shapes are parameters. The approximately 32 nm pitch sample was patterned at Intel using a state-of-the-art pitch quartering process. Their narrow widths and asymmetrical shapes are representative of near-future generation transistor gates. These pose a challenge: the narrowness because electrons landing near one edge may scatter out of the other, so that the intensity profile at each edge becomes width-dependent, and the asymmetry because the shape requires more parameters to describe and measure. Modeling was performed by JMONSEL (Java Monte Carlo Simulation of Secondary Electrons), which produces a predicted yield vs. position for a given sample shape and composition. The simulator produces a library of predicted profiles for varying sample geometry. Shape parameter values are adjusted until interpolation of the library with those values best matches the measured image. Profiles thereby determined agreed with those determined by transmission electron microscopy and critical dimension small-angle x-ray scattering to better than 1 nm.

The directed self-assembly (DSA) of block copolymers (BCP) is an emerging resolution enhancement tool that can multiply or subdivide the pitch of a lithographically defined chemical or topological pattern and is a resolution enhancement candidate to augment conventional lithography for patterning sub-20 nm features. Continuing the development of this technology will require an improved understanding of the polymer physics involved as well as experimental confirmation of the simulations used to guide the design process. Both of these endeavors would be greatly facilitated by a metrology, which is capable of probing the internal morphology of a DSA film. We have developed a new measurement technique, resonant critical-dimension small-angle X-ray scattering (res-CDSAXS), to evaluate the 3D buried features inside the film. This is an X-ray scattering measurement where the sample angle is varied to probe the 3D structure of the film, while resonant soft X-rays are used to enhance the scattering contrast. By measuring the same sample with both res-CDSAXS and traditional CDSAXS (with hard X-rays), we are able to demonstrate the dramatic improvement in scattering obtained through the use of resonant soft X-rays. Analysis of the reciprocal space map constructed from the res-CDSAXS measurements allowed us to reconstruct the complex buried features in DSA BCP films. We studied a series of DSA BCP films with varying template widths, and the internal morphologies for these samples were compared to the results of single chain in mean-field simulations. The measurements revealed a range of morphologies that occur with changing template width, including results that suggest the presence of mixed morphologies composed of both whole and necking lamella. The development of res-CDSAXS will enable a better understanding of the fundamental physics behind the formation of buried features in DSA BCP films.

There has been significant interest in hybrid metrology as a novel method for reducing overall measurement uncertainty and optimizing measurement throughput (speed) through rigorous combinations of two or more different measurement techniques into a single result. This approach is essential for advanced 3-D metrology when performing model-based critical dimension measurements. However, a number of fundamental challenges present themselves with regard to consistent noise and measurement uncertainty models across hardware platforms, and the need for a standardized set of model parameters. This is of paramount concern when the various techniques have substantially different models and underlying physics. In this paper we present realistic examples using scanning electron microscopy, atomic force microscopy, and optical critical dimension (CD) methods applied to sub-20 nm dense feature sets. We will show reduced measurement uncertainties using hybrid metrology on 15 nm CD features and evaluate approaches to adapt quantitative hybrid metrology into a high volume manufacturing environment.

We have demonstrated that transmission critical dimension small angle X-ray scattering (CD-SAXS) provides high accuracy and precision CD measurements on advanced 3D microelectronic architectures. The competitive advantage of CD-SAXS over current 3D metrology methods such as optical scatterometry is that CD-SAXS is able to decouple and fit cross-section parameters without any significant parameter cross-correlations. As the industry aggressively scales beyond the 22 nm node, CD-SAXS can be used to quantitatively measure nanoscale deviations in the average crosssections of FinFETs and high-aspect ratio (HAR) memory devices. Fitting the average cross-section of 18:1 isolated HAR contact holes with an effective trapezoid model yielded an average pitch of 796.9 ± 0.4 nm, top diameter of 70.3 ± 0.9 nm, height of 1088 ± 4 nm, and sidewall angle below 0.1°. Simulations of dense 40:1 HAR contact holes and FinFET fin-gate crossbar structures have been analyzed using CD-SAXS to inquire the theoretical precision of the technique to measure important process parameters such as fin CD, height, and sidewall angle; BOX etch recess, thickness of hafnium oxide and titanium nitride layers; gate CD, height, and sidewall angle; and hafnium oxide and titanium nitride etch recess. The simulations of HAR and FinFET structures mimic the characteristics of experimental data collected at a synchrotron x-ray source. Using the CD-SAXS simulator, we estimate the measurement capabilities for smaller similar structures expected at future nodes to predict the applicability of this technique to fulfill important CD metrology needs.

In this paper, we present a comparison of profile measurements of vertical field effect transistor (FinFET) fin arrays by optical critical dimension (OCD) metrology and critical dimension small angle X-ray scattering (CD-SAXS) metrology. Spectroscopic Muller matrix elements measurements were performed at various azimuthal angles for OCD, and X-ray diffraction intensities were collected for different incident angles in CD-SAXS measurements. A common trapezoidal model was used to compute the OCD and CD-SAXS signatures, using rigorous coupled wave (RCW) analysis and a 2D Fourier transform, respectively. Profile parameters, some material parameters, and instruments parameters were adjusted by a non-linear fitting procedure of the data. Results from both measurement techniques were compared and found in reasonable agreement with one another, although some of the parameters have differences that exceed the estimated uncertainties.

We quantified the impact of the carbon spacer length (CSL) of immobilized alkoxysilanes initiators on grafting poly(methyl methacrylate) (PMMA) from the surfaces of monodisperse silica nanoparticles. PMMA was grafted using surface-initiated atom transfer radical polymerization (SI-ATRP), a facile technique to produce well-controlled polymer brushes. The polymerizations were carried out in environmentally friendly 4:1 (v/v) methanol-water solutions at room temperature. Monoethoxysilane initiators of 3, 11, and 15 carbon spacer lengths were synthesized and characterized with (1)H NMR and (13)C NMR. The initiators were then used to modify the surfaces of monodisperse silica nanoparticles in methyl isobutyl ketone, producing dense initiator monolayers with site densities between 1.8-3.6 initiators/nm(2). PMMA was subsequently grafted from the functionalized nanoparticles using both CuCl and CuBr catalysts. We found that polymerizations performed with CuBr were uncontrolled, whereas those with CuCl were controlled. PMMA graft densities ranged between 0.10-0.43 polymers/nm(2), which increased with the initiator carbon spacer length (CSL). Interestingly, longer CSLs make nanoparticle surfaces hydrophobic, causing nanoparticle aggregation in methanol-water solutions. Our results indicate that surface hydrophobicity correlates to increases in PMMA graft density through the adsorption of hydrophobic MMA monomers on initiators with longer CSLs. Thus, to augment PMMA graft densities, a subtle balance must be struck between enabling particle stability and increasing MMA adsorption in methanol-water solutions.

We report on the development of a new measurement method, resonant critical-dimension small-angle x-ray scattering (res-CDSAXS), for the characterization of the buried structure of block copolymers (BCP) used in directed self assembly (DSA). We use resonant scattering at the carbon edge to enhance the contrast between the two polymer blocks and allow the determination of the three-dimensional shape of the native lamella in a line-space pattern by CDSAXS. We demonstrate the method by comparing the results from conventional CDSAXS to res- CDSAXS on a 1:1 DSA BCP sample with a nominal 50-nm pitch. The res- CDSAXS method provides substantially improved uncertainty in the fit of the line shape and allows the determination of the buried structure. © 2013 Society of Photo-Optical Instrumentation Engineers (SPIE) (DOI: 10.1117/1.JMM.12.3.031103)