Alternative Lithographic Methods for Variable Aspect Ratio Vias

The foundation of semiconductor industry has historically been driven by scaling. Device size reduction is enabled by increased pattern density, enhancing functionality and effectively reducing cost per chip. Aggressive reductions in memory cell size have resulted in systems with diminishing area between parallel bit/word lines. This affords an even greater challenge in the patterning of contact level features that are inherently difficult to resolve because of their relatively small area, a product of their two domain critical dimension image. To accommodate these trends there has been a shift toward the implementation of elliptical contact features. This empowers designers to maximize the use of free space between bit/word lines and gate stacks while preserving contact area; effectively reducing the minor via axis dimension while maintaining a patternable threshold in increasingly dense circuitry. It is therefore critical to provide methods that enhance the resolving capacity of varying aspect ratio vias for implementation in electronic design systems. This work separately investigates two unique, non-traditional lithographic techniques in the integration of an optical vortex mask as well as a polymer assembly system as means to augment ellipticity while facilitating contact feature scaling. This document affords a fundamental overview of imaging theory, details previous literature as to the technological trends enabling the resolving of contact features and demonstrates simulated & empirical evidence that the described methods have great potential to extend the resolution of variable aspect ratio vias using lithographic technologies

DSA-aware multiple patterning for the manufacturing of vias: Connections to graph coloring problems, IP formulations, and numerical experiments

In this paper, we investigate the manufacturing of vias in integrated circuits with a new technology combining lithography and Directed Self Assembly (DSA). Optimizing the production time and costs in this new process entails minimizing the number of lithography steps, which constitutes a generalization of graph coloring. We develop integer programming formulations for several variants of interest in the industry, and then study the computational performance of our formulations on true industrial instances. We show that the best integer programming formulation achieves good computational performance, and indicate potential directions to further speed-up computational time and develop exact approaches feasible for production

Probing and tuning the electronic properties of low dimensional van der Waals materials

177 p.The investigation on the physical properties of new materials is of fundamental importance to gain understanding and knowledge on systems and phenomena which one day may be exploited for revolutionary technological applications. In this regard, probing and tuning the electronic transport properties of low-dimensional materials might represent one of the routes that can satisfy the requirements of modern electronics/spintronics advancements. Following the common thread of investigating and manipulating the transport properties of low dimensional and low symmetrical systems, this thesis will be divided in two main parts. In the first part molecular functionalization is exploited to tune the intrinsic physical properties of two van der Waals materials: a superconductor and a ferromagnet. The second part focuses on the study of the charge to spin interconversion mechanisms in low symmetry systems. In particular, the study of the magnetoelectrical properties of Tellurium nanowires revealed a tight relationship between spin related phenomena and the symmetry breaking in such a chiral system

Index to 1981 NASA Tech Briefs, volume 6, numbers 1-4

Short announcements of new technology derived from the R&D activities of NASA are presented. These briefs emphasize information considered likely to be transferrable across industrial, regional, or disciplinary lines and are issued to encourage commercial application. This index for 1981 Tech Briefs contains abstracts and four indexes: subject, personal author, originating center, and Tech Brief Number. The following areas are covered: electronic components and circuits, electronic systems, physical sciences, materials, life sciences, mechanics, machinery, fabrication technology, and mathematics and information sciences

In Vivo Selection of a Computationally Designed SCHEMA AAV Library Yields a Novel Variant for Infection of Adult Neural Stem Cells in the SVZ

Directed evolution continues to expand the capabilities of complex biomolecules for a range of applications, such as adeno-associated virus vectors for gene therapy; however, advances in library design and selection strategies are key to develop variants that overcome barriers to clinical translation. To address this need, we applied structure-guided SCHEMA recombination of the multimeric adeno-associated virus (AAV) capsid to generate a highly diversified chimeric library with minimal structural disruption. A stringent in vivo Cre-dependent selection strategy was implemented to identify variants that transduce adult neural stem cells (NSCs) in the subventricular zone. A novel variant, SCH9, infected 60% of NSCs and mediated 24-fold higher GFP expression and a 12-fold greater transduction volume than AAV9. SCH9 utilizes both galactose and heparan sulfate as cell surface receptors and exhibits increased resistance to neutralizing antibodies. These results establish the SCHEMA library as a valuable tool for directed evolution and SCH9 as an effective gene delivery vector to investigate subventricular NSCs

Development of a Wireless MEMS Multifunction Sensor System and Field Demonstration of Embedded Sensors for Monitoring Concrete Pavements, Volume II

This two-pronged study evaluated the performance of commercial off-the-shelf (COTS) micro-electromechanical sensors and systems (MEMS) embedded in concrete pavement (Final Report Volume I) and developed a wireless MEMS multifunctional sensor system for health monitoring of pavement systems (Final Report Volume II). The Volume I report focused on the evaluation of COTS MEMS sensors embedded in concrete pavement sections. The Volume II report covers the set of MEMS sensors that were developed as single-sensing units for measuring moisture, temperature, strain, and pressure. These included the following sensors: (1) nanofiber-based moisture sensors, (2) graphene oxide (GO)–based moisture sensors, (3) flexible graphene strain sensors with liquid metal, (4) graphene strain and pressure sensors, (5) three-dimensional (3D) planar and helical structured graphene strain sensors, (6) temperature sensors, and (7) water content sensors. In addition, the MEMS temperature sensors and the MEMS water content sensors were integrated into one sensing unit as a multifunctional sensor. A wireless signal transmission system was built for MEMS sensor signal readings. Characterization of the sensors was conducted and sensor responses were analyzed using different applications. The sensors developed were installed and tested inside concrete. The results demonstrated the capability to detect sensor response changes at the installed locations