Sequential infiltration synthesis (SIS) has emerged in the past decade as a powerful technique for growth of inorganic materials within polymers through atomic layer deposition (ALD) chemistry. In SIS, ALD precursors diffuse into the polymer, leading to growth of nanoscale inorganic materials within the polymer volume. This growth enables direct transformation of lithographic patterns and block copolymers (BCP) to inorganic patterns, adding additional degrees of freedom for pattern design and improving pattern transfer. Here, I will present our recent research in the field of SIS. We shed light on the atomic growth of metal oxide clusters and particles within polymers using high-resolution transmission electron microscopy and x-ray absorption spectroscopy. We follow SIS growth from the nanoscale to the macroscale, expanding our understanding of SIS mechanism and the role of polymer chemistry and reversible polymer-precursor interactions on SIS growth. These insights are then applied in nanofabrication-by-design of homopolymer and block copolymer-templated 3D nanostructures. Importantly, we demonstrate 3D heterostructure fabrication, leading to vertical sub-features patterning, using a single SIS process. In this simple SIS process, we grow, simultaneously but spatially-controlled, two metal oxides within BCP templates by controlling the diffusion time of the two metalorganic precursors. This approach can enable multi-material SIS processes and pave the pathway for 3D patterning.
KEYWORDS: 3D metrology, Scanning electron microscopy, Scanning transmission electron microscopy, Tomography, Line edge roughness, Sensors, 3D image processing, Metrology, Calibration, Transmission electron microscopy
The semiconductor industry continuously moves toward smaller features and more complex, three-dimensional (3D) structures to enable next-generation devices. Thus there is a high need for 3D metrology techniques that would provide feedback to the advancing nanoscale fabrication processes. We introduce an approach for evaluating, calibrating, and developing new metrology of nanopatterns through comparing the new metrology data to 3D ground truth data, obtained by accurate scanning transmission electron microscopy (STEM) tomography 3D characterization. We demonstrate this approach by evaluating 3D height maps of sub-20-nm patterns obtained using multi-secondary electron detector scanning electron microscopy (multi-perspective SEM) and photometric stereo algorithm. We demonstrate the importance of full 3D characterization, including cross-sectional structure, height fluctuations, and line edge roughness to truly probe the pattern’s average structures and their 3D variations. Although STEM tomography is a high-resolution and accurate method, it is considered demanding in terms of sample preparation and cannot be used as an efficient in-line metrology method. However, we show that it can be used as a reliable 3D characterization technique to obtain the necessary 3D data for the development of new 3D metrology tools and demonstrate this approach by evaluating the accessible, in-line, multi-perspective SEM.
KEYWORDS: Directed self assembly, Polymethylmethacrylate, Picosecond phenomena, Tomography, System on a chip, Chemistry, Scanning transmission electron microscopy, Transmission electron microscopy, Semiconducting wafers, 3D image processing
Acquiring three-dimensional (3-D) information becomes increasingly important for the development of block copolymer (BCP) directed self-assembly (DSA) lithography, as two-dimensional imaging is no longer sufficient to describe the 3-D nature of DSA morphology and probe hidden structures under the surface. Using the post-DSA membrane fabrication technique and scanning transmission electron microscopy tomography, we were able to characterize the 3-D structures of BCP in graphoepitaxial DSA hole shrink process. Different DSA structures of singlets formed in templated holes with different surface chemistry and geometry were successfully captured and their 3-D shapes were reconstructed from tomography data. The results reveal that strong polystyrene-preferential sidewalls are necessary to create vertical DSA cylinders and that template size outside of process window could result in defective DSA results in 3-D. Our study as well as the established 3-D metrology would greatly help to develop a fundamental understanding of the key DSA factors for optimizing the graphoepitaxial hole shrink process.
KEYWORDS: Polymethylmethacrylate, Picosecond phenomena, Directed self assembly, Tomography, Transmission electron microscopy, System on a chip, Chemistry, Semiconducting wafers, 3D metrology, Scanning transmission electron microscopy
Acquiring three-dimensional information becomes increasingly important for the development of block copolymer (BCP) directed self-assembly (DSA) lithography, as 2D imaging is no longer sufficient to describe the 3D nature of DSA morphology and probe hidden structures under the surface. In this study, using post-DSA membrane fabrication technique and STEM (scanning transmission electron microscopy) tomography we were able to characterize the 3D structures of BCP in graphoepitaxial DSA hole shrink process. Different DSA structures of singlets formed in templated holes with different surface chemistry and geometry were successfully captured and their 3D shapes were reconstructed from tomography data. The results reveal that strong PS-preferential sidewalls are necessary to create vertical DSA cylinders and that template size outside of process window could result in defective DSA results in three dimensions. Our study as well as the established 3D metrology would greatly help to develop a fundamental understanding of the key DSA factors for optimization of the graphoepitaxial hole shrink process.
Directed self-assembly (DSA) of block copolymers (BCPs) is a rising technique for sub-20 nm patterning. To fully harness DSA capabilities for patterning, a detailed understanding of the three dimensional (3D) structure of BCPs is needed. By combining sequential infiltration synthesis (SIS) and scanning transmission electron microscopy (STEM) tomography, we have characterized the 3D structure of self-assembled and DSA BCPs films with high precision and resolution. SIS is an emerging technique for enhancing pattern transfer in BCPs through the selective growth of inorganic material in polar BCP domains. Here, Al2O3 SIS was used to enhance the imaging contrast and enable tomographic characterization of BCPs with high fidelity. Moreover, by utilizing SIS for both 3D characterization and hard mask fabrication, we were able to characterize the BCP morphology as well as the alumina nanostructures that would be used for pattern transfer.
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