Research
The Center for Hierarchical Manufacturing is focused on the discovery, development and platforming of methodologies and processes that yield well-defined nanostructured materials and elements essential for the manufacturing of next generation devices to enhance computing and information processing, energy conversion and human health. The emphasis is on versatile tools and high-rate processes for well-defined nanostructures that can be systematically integrated into existing manufacturing flows, an objective that requires the bridging of bottom-up techniques to yield sub-30 nm structures with top-down techniques to yield device elements at larger length scales. These processes are based on recognized CHM research strengths that comprise core technologies within the center.
The essential research structure of the CHM consists of three Technical Research Groups (TRGs) and system level test beds in which the key scientific barriers to the manufacturing of device nanostructures using the CHM platform tools are identified, systematically addressed, and resolved. The TRGs provide multi-disciplinary collaborative structure to enable high-impact fundamental research and new discoveries that drive innovation.
- Nanoscale Materials and Processes (TRG 1) addresses the materials and processes necessary for high-reliability nanofabrication and supports fundamental research on the CHM’s core technologies. It is closely coupled to and directly feeds the process platform test beds.
- Nanoelectronics (TRG 2) supports fundamental studies in magnetics, photonics and device design to generate proof-of-concept prototypes that can be assembled using the CHM’s process platforms.
- Bio-Directed Assemblies and Devices (TRG 3) supports new efforts in the area of bio-directed assembly using DNA constructs that can potentially contribute new levels of nanoarchitecture specification, and supports fundamental work on sensor design.
The test beds are the heart of process and platform development where promising concepts transition from laboratory results into reliable, rapid, high-yield and transferable methodologies for nanostructure fabrication. CHM partnerships with commercial fabrication tool and process suppliers provide a mechanism by which these techniques may be widely distributed for use by the broader nanomanufacturing community.
Figure 1: Vision and Systems-Level Organization
The CHM's vision for the development of nanomanufacturing platform technologies and their applications is presented in Figure 1.
Platform Technologies
The unifying theme of the CHM is an integrated processing platform that spans the new technologies for nanofabrication and conventional process tools for device fabrication. In Figure 1, the six process areas within TRG 1 represent core CHM technologies for nanofabrication. The process platforms in blue represent manufacturing technologies into which the nanofabrication technologies must be integrated. The test beds serve as practical vehicles to realize and demonstrate this integration. Beginning from the left, strategic challenges that must be addressed include:
- Fabrication of Nanostructures (Structure Generation). In the definition of sub-30 nm device elements, the challenge is to identify techniques that are reliable, massively-parallel, cost-effective and that provide exceptional control over the size, shape and long range order, and addressability of the nanoscopic domains. These challenges will be met using UMass Amherst strengths in directed self-assembly of synthetic polymers and organic molecules, nanoimprint lithography, and over the long term bio-directed assembly using DNA constructs. For directed assembly the fundamental challenges include eradication of defects, increasing the strength of segregation to reduce domain size, and developing highly ordered systems from low cost components that can be implemented in large scale commodity applications. For nanoimprint lithography, the fundamental challenges include minimization of feature size, creation of function materials and resists and understanding adhesion and release for defect management. The DNA constructs are a seed effort. The fundamental challenges include precise registration folded 3-D DNA structures on surfaces and non-destructive functionalization of the constructs to yield functional materials.
- Functionalization of Nanostructures. While the nanostructure discussed above can serve as substrates or templates, their use in devices requires their functionalization via incorporation of metal, metal oxide, semiconductor or biological elements. These challenges will be met using:
- 3-D replication techniques in which structure of a self assembled block copolymer of NIL generated template can be transformed via phase selective reactions to yield high fidelity replicas in metal oxide materials
- Incorporation of functional additives including semiconductor nanoparticles and nanorods via cooperative assembly within self-assembled templates and nanoscale deposition techniques that yield conformal films within confined geometries.
For the 3-D replication techniques the fundamental challenges include maintaining order and template fidelity during the chemistry, developing new template materials by NIL and establishing techniques to pattern multiple length scales simultaneously. For functional additives, the fundamental challenges are tailoring surface chemistry and size such that the additives partition to the desired domain and assist with, rather than frustrate, self-assembly. For nanoscale deposition techniques the fundamental challenges include scale up and development of new chemistries.
- Integration with Top-Down Processes. High-volume production requires integration of the fabrication and functionalization of nanostructures with high-volume manufacturing. The CHM platform technologies are compatible with Si wafer based technologies and with roll-to-roll processing. Integration is not purely sequential and in many cases patterns generated at the device scale can direct assemble at the nanoscale; in some cases pattern generation at multiple length scales is accomplished simultaneously. Integration presents several crosscutting challenges. These include developing materials and systems that self assemble and anneal on time scales compatible with typical wafer cycle times or roll-to-roll platforms, establishing addressability of individual domains, stabilizing the self-assembled structures for further possessing and establishing proper metrology and quality control, and adapting the fabrication scheme for process-friendly solvents. The development process includes a first-level analysis of the environmental, health and safety considerations of the test bed processes. In addition, tool platforms must be developed for technology transfer. For silicon wafer platforms, the CHM works with leading industry partners such as SRC, IBM, Novellus Systems, and Seagate Technology. For roll-to-roll processing, the CHM collaborates with the Center for Advanced Microelectronics Manufacturing Processing at Binghamton University.
Practical realization of the nanofabrication platform requires system-level test beds demonstrating nanomanufacturing process technologies. The CHM currently focuses on the following test beds:
- Test Bed 1: Self Assembled Polymer Templates for Device Applications
- Test Bed 2: Hierarchical Metal Oxide Films.
New test beds such as rapid imprinting and capillary force lithography via roll-to-roll processing will be considered as TRG efforts mature and solve critical barriers.
Applications Development: TRGs 2 and 3
The Center’s aim with TRGs 2 and 3 is ultimately to build proof-of-concept prototype devices exploiting CHM platform technologies that can be realized using the test bed methodologies.
- TRG 2, Nanoelectronics, focuses on ultrahigh density data storage based on arrays of nanomagnets; design, simulation and fabrication of NASIC circuits and architectures; nanostructured device development for photonic applications in energy conversion and light manipulation; and development of nanomanufacturing standard operating procedures (SOPs) and advanced methods of characterization.
- TRG 3, Bio-Directed Assemblies and Devices, combines expertise in self-assembly, soft materials research, and biomolecular recognition to address fundamentals and applications in bio-directed assembly and sensors. This TRG supports the fundamental work in DNA-cased constructs for materials and device fabrication, and is developing sensor technology that exploits the well-defined architectures produced via the CHM’s core technologies.
